Journal articles: 'Optimum Replacement Fraction'

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Ntlokotsi, S., M. F. Moshesh, P. Mntla, O. A. Towobola, and M. A. Mogale. "Optimum INR intensity and therapeutic INR control in patients with mechanical heart valve prosthesis on warfarin oral anticoagulation at Dr George Mukhari academic hospital: a three-year retrospective study." South African Family Practice 60, no. 6 (November 30, 2018): 40. http://dx.doi.org/10.4102/safp.v60i6.4927.

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Background: Available evidence suggest that the optimum prothrombin time-international normalised ratio (PT-INR) intensities recommended for anticoagulation of patients with mechanical heart valve prosthesis may not apply to all race groups. Optimal PT-INR target ranges and effectiveness of warfarin oral anticoagulation were determined among black South African patients fitted with St Jude bileaflet mechanical heart valve prosthesis (SJBMHVP) at Dr George Mukhari Academic Hospital (DGMAH). Methods: A convenience sample of 95 medical records of patients fitted with SJBMHVP from 1994 until 2013 was reviewed. Optimum PT-INR target ranges were estimated using two different methods: the classical two PT-INR target level method and the alternative, PT-INR specific incident rate method. The quality of warfarin anticoagulation was assessed using the fraction in therapeutic range method.Results: Optimum PT-INR target ranges for all participants fitted with SJBMHVP in the aortic position was estimated to be 2.0–3.5 and 2.6–3.5, respectively, by the classical and alternative methods. That of the patients with mitral valve replacement was estimated to be in the range 2.6–3.5 by the classical method and that of patients with double heart valve replacement was estimated to be 3.5 by both methods. The quality of warfarin anticoagulation of participants with SJBMHVP replacement was found to be inadequate as indicated by percentage time in treatment range (TTR) of 49.7% for all study participants compared with the ideal TTR of 70% and above.Conclusion: Optimum Caucasian-based PT-INR intensities recommended for oral anticoagulation of patients fitted with mechanical heart valve prosthesis are applicable to black patients fitted with SJBMHVP at DGMAH.

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Joseph, Aneeta Mary, Stijn Matthys, and Nele De Belie. "Properties of Concrete with Recycled Aggregates Giving a Second Life to Municipal Solid Waste Incineration Bottom Ash Concrete." Sustainability 14, no. 8 (April 13, 2022): 4679. http://dx.doi.org/10.3390/su14084679.

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Economic and environmental factors call for increased resource productivity. Partial or full replacement of Portland cement by wastes and by-products, and natural aggregates by construction and demolition wastes, are two prominent routes of achieving circular economy in construction and related industries. Municipal solid waste incineration (MSWI) bottom ashes have been found to be suitable to be used as a supplementary cementitious material (SCM) after various treatments. This paper reports a brief literature review on optimum use of recycled aggregates in concrete and an experimental study using replacement of natural aggregate by demolished concrete having MSWI bottom ash as partial replacement of Portland cement, and compares its properties to that of completely natural aggregate concrete. Additional water was added as a compensation for the water absorption by the recycled aggregate during the first 30 min of water contact during concrete mixing. Also the fine fraction of crushed concrete (<250 µm) was removed to reduce the ill-effects of using recycled aggregate. The replacement of aggregates was limited to 23% by weight of natural aggregate. The results prove environmentally safe and comparable performance of concrete including recycled aggregate with bottom ash to that of natural aggregate concrete.

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Shaker, Khubab, Muhammad Adnan, Yasir Nawab, Muhammad Umair, Madeha Jabbar, Amna Siddique, and Ahsan Ahmad. "Mechanical Performance of Glass/Epoxy Composites Loaded with Silane-Treated Aluminum Hydroxide Fillers." Polymers 15, no. 17 (August 23, 2023): 3514. http://dx.doi.org/10.3390/polym15173514.

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This study investigates the influence of silane-treated aluminum hydroxide on the mechanical performance of flame-retardant composites. These composites have potential applications for luggage bags, as a replacement for conventional plastics, offering more durability and lighter weight. Glass fabric was used as the reinforcement, while epoxy was used as the matrix material. To impart flame retardancy, aluminum hydroxide nanoparticles were used as fillers in different weight % age (5%, 10% and 15%). As these are inorganic particles and have compatibility issues with the matrix material, silane-coupling agents (Dynasylan® 6490 and Dynasylan Glymo) were used to treat these filler particles. Both the silane-coupling agents fraction used for treatment and the fillers fraction added to the composites were varied to determine the most optimum combination. The mechanical properties of the developed composites such as tensile, flexural, and short beam shear strength were investigated. The best results were exhibited by 10% aluminum hydroxide fillers treated with 1% (by weight) coupling agent (Dynasylan Glymo).

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Bondar, V. O., and R. R. Akhmednabiyev. "DURABILITY OF HEAVY CONCRETE USING BOILER SLAGS WITH CIRCULATING FLUIDIZED BED." ACADEMIC JOURNAL Series: Industrial Machine Building, Civil Engineering 1, no. 50 (April 11, 2018): 97–103. http://dx.doi.org/10.26906/znp.2018.50.1064.

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The results of studying the influence of boiler ash slags with a circulating fluidized bed on the freeze-thaw resistance of heavy concretes are presented. The following materials were used in the studies: Portland cement PPC 500 N, sand with the fineness modulus Mf =1.05, crushed granite fraction 5-10 mm, boiler ashes with circulating fluidized bed, hyperplasticizer «Fluid Premia-196». The study was performed using mathematical planning of the experiment. It is proved that with the replacement of sand with ashes, the freeze-thaw resistance is somewhat reduced, but the hyperplasticizer compensates the reduction of freeze-thaw resistance by reducing the W/C ratio, resulting in the formation of super-fine pore structure of concrete. Fine pores in the concrete structure compensate the ice formation stress at low ambient temperatures. The optimal cement consumption has been established in terms of freeze-thaw resistance, both at full and partial replacement of sand with ash. It was also determined that the optimum should be considered the consumption of a hyperplasticizer in the amount of 1.2-1.4% of the cement mass.

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Zhou, Jinghai, Tianbei Kang, and Fengchi Wang. "Pore structure and strength of waste fiber recycled concrete." Journal of Engineered Fibers and Fabrics 14 (January 2019): 155892501987470. http://dx.doi.org/10.1177/1558925019874701.

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The pore structure is one of the major factors affecting the mechanical properties of waste fiber recycled concrete. In this article, the pore structure and strength performance of waste fiber recycled concrete are experimentally studied. The design variables are water–cement ratio, recycled aggregate replacement rate, waste fiber length, and volume fraction of waste fibers. The pore structure characteristic parameters of waste fiber recycled concrete are investigated using mercury intrusion porosimetry test and fractal theory. The complex distribution of pore structure in space is quantitatively described by fractal dimension, and the pore structure is comprehensively evaluated. The results show that the water–cement ratio has the largest influence on the pore structure, and the fiber length has the least influence. The optimum volume fraction of waste fibers is 0.12%. There is an obvious linear relationship between the pore volume fractal dimension and strength. With the increase in the fractal dimensions, the compressive and splitting tensile strengths increase. Macroscopic mechanical properties of waste fiber recycled concrete can be predicted by the pore structure.

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Mičicová, Z., S. Božeková, M. Pajtášová, and D. Ondrušová. "Curing characteristics and rheological properties of bentonite- filled rubber blends." IOP Conference Series: Materials Science and Engineering 1199, no. 1 (November 1, 2021): 012037. http://dx.doi.org/10.1088/1757-899x/1199/1/012037.

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Abstract The study deals with the examination of the rheological behaviour of rubber blends which were filled with bentonite. The filler - polymer as well as the filler - filler interactions were studied and determined from the frequency sweep and strain sweep rheological measurements. The used natural bentonite was extracted from the locality called Jelsovy Potok. The natural bentonite had a fine fraction with a particle size of 15μm a 45 μm and it was added into rubber blends as a partial replacement of commonly used filler. The rubber blends were characterised on the basis of curing characteristics (minimum torque ML, maximum torque MH, optimum time of cure t(c90), processing safety of blend ts,). Moreover, the complex viscosity and Payne effect were also specified. The required measurements were done by using PRPA 2000.

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Siva Prasad Raju, V., Gorla Jayasri, V. Srinivasa Reddy, and A. Naga Sai Baba. "Flexural behaviour of hybrid fibre reinforced concrete beams made with various packing factors and fine to total aggregate ratio." E3S Web of Conferences 309 (2021): 01060. http://dx.doi.org/10.1051/e3sconf/202130901060.

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The objective of this study is to investigate the flexural behavior of M30 grade PSCC, GFRSCC, SFRSCC and HFRSCC beams made with PF=1.12 and s/a=0.53 and PF=1.14 and s/a=0.57 to understand the effect of copper slag as partial replacement of fine aggregate on its deflection characteristics and cracking behaviour. The yield and ultimate load taken by HFRSCC beams made with optimum PF and s/a ratios are higher than the conventional RCC beam elements. The deflections at centre at failure in HFRSCC beams made with optimum PF and s/a ratios were more than that of conventional beams. This shows improvement in ductility of HFRSCC beams. First crack formation was delayed in M30 grade HFRSCC beams due to dense micro structure with low pore fraction and reduced pore size due to which fatigue strength is increased which in turn increases the time taken for first crack occurrence and thereby increasing the load carrying capacity. The deflection at the mid span decreased in HFRSCC beams which shows that the flexural stiffness of the elements increases thereby reducing the structural member’s deformability, increasing strength and hence controlling deflection.

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Kim, Nae-Hyun. "Application of the Natural Refrigerant Mixture R-290/DME to a Soft Ice Cream Refrigerator." International Journal of Air-Conditioning and Refrigeration 24, no. 04 (December 2016): 1650027. http://dx.doi.org/10.1142/s2010132516500279.

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Due to the ozone depletion issue, R-502, which had long been used as the refrigerant of an ice cream refrigerator, has been replaced by R-404A. However, global warming potential (GWP) of R-404A is high, and thus, a replacement refrigerant is necessary in the long term. Natural refrigerants, such as R-290 or DME (dimethylether), could be a choice. In this study, an ice cream refrigerator cycle was optimized using R-290/DME mixture (mass fraction 65/35). The optimization was accomplished through a search for the proper refrigerant charge amount and the opening of the expansion valve. For the present ice cream refrigerator having 2.8[Formula: see text]L freezer volume, the optimum charge amount was 900[Formula: see text]g, and the optimum valve opening was [Formula: see text]120[Formula: see text]. At this configuration, the ice cream formation time was 3[Formula: see text] 6[Formula: see text] and COP was 2.0. The ice cream formation time was much shorter than when R-404A was used, and the COP was increased by more than 100%. For actual usage of the refrigerant, however, the flammability issue of the R-290/DME mixture should be cleared.

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Mandal, Paranjayee, Ares Gomez-Gallegos, Diego Gonzalez, Hosam Elrakayby, and Paul Blackwell. "Superplastic Behaviour of Ti54M and Ti64." MATEC Web of Conferences 321 (2020): 04028. http://dx.doi.org/10.1051/matecconf/202032104028.

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Even though TIMETAL-54M (Ti-5Al-4V-0.6Mo-0.4Fe or Ti54M) has been commercially available for over 10 years, further study of its superplastic properties is still required in order to assess its applicability within the aerospace industry as a potential replacement for other commercial titanium alloys such as Ti-6Al-4V (Ti64). Ti54M is expected to obtain superplastic characteristics at a lower temperature than Ti64 due to its lower beta-transus temperature. The superplastic forming (SPF) capability of alloys that can be formed at lower temperatures has always attracted the interest of industry as it reduces the grain growth and alpha-case formation, leading to longer life for costly high temperature resistant forming tools. In this work, the SPF characteristics of both Ti54M and Ti64 have been examined by conducting tensile tests according to the ASTM E2448 standard within a range of temperatures and strain values at a fixed strain rate of 1 × 10-4/S. A high strain rate sensitivity and uniform deformation at high strains are key indicators in selecting the optimum superplastic temperature. This was observed at 815˚C and 925˚C for Ti54M and Ti64 respectively. The tensile samples were water quenched to freeze their respective microstructure evolution following superplastic deformation and SEM images were captured for grain size and volume fraction of alpha-phase analyses. A slightly higher alpha-grain growth rate was observed during superplastic deformation of Ti64. The initial fine-grain microstructure of Ti54M (~1.6 micron) resulted in a final microstructure with an average grain size of ~3.4 micron and optimum the alpha/beta ratio. Both the fine-grained microstructure and increased amount of beta-volume fraction promotes the superplastic behaviour of Ti54M by grain boundary sliding (GBS). Thus superplastic properties were observed for Ti54M at a lower temperature (~100˚C) than for Ti64.

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Hameed, A. Abdul, and G. Kalaiyarasan. "Study on the Strength of Glass Fiber Reinforcement Concrete with Fragmentary Replacement of Cement with Fly Ash." International Journal for Research in Applied Science and Engineering Technology 10, no. 12 (December 31, 2022): 1806–9. http://dx.doi.org/10.22214/ijraset.2022.48318.

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Abstract: Concrete is one of the most widely used construction material in today’s world. Cement being one of the essential constituent of the concrete. Environmental issues are also playing a vital role in today’s world, the production of cement one of the major constituent of concrete leads to release the of significant amount of carbon dioxide a greenhouse gas contributing 7% of greenhouse gas emission to the earth atmosphere, beside deforestation and burning of fossil fuels. Safe disposal of glass waste generated in day to day life due to limited life span and after use it is either stock piled or sent to land fill is also a challenging task. There is now a significant world-wide interest to solve the environmental problem caused by industrial waste and other material by including such material in the manufacture of concrete. Effort have been made in concrete industry to use waste glass in concrete production not only provide significant environmental benefits but also enhances performances of concrete when used at optimum amounts. Efforts have been made in the concrete industry to use fly ash & waste glass as partial replacement of cement, fine & coarse aggregates. Recently the research has shown that the waste glass can be effectively used in concrete as several alternatives for the constituent of concrete under proper fraction and grade. Waste glass when ground to a very fine powder show pozzolanic properties as it contains high SiO2 and therefore to some extent can replaced cement in concrete and contributes strength development. In this study, glass fibers in different volume fraction with 20%, 30% and 40% replacement of cement by fly ash has been to study the effect on compressive strength, split tensile strength, of concrete and compared it to the conventional concrete. The overall test result shows glass fiber could be utilized in concrete. The result indicates that the maximum strength of concrete occurs at around 20% glass powder. Beyond 20% glass fiber the strength of concrete reduces and is lower than that of the control.

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Yong, Zi Cong, Ming Kun Yew, Ming Chian Yew, and Jing Han Beh. "Strength properties of renewable bio-based lightweight foam concrete incorporating of polypropylene fibre." E3S Web of Conferences 347 (2022): 02003. http://dx.doi.org/10.1051/e3sconf/202234702003.

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This paper investigates the incorporating of renewable lightweight bio-based aggregate (RLWBBA) in lightweight foam concrete (LWFC). The aim of this research is to incorporate different volume fraction (Vf) of polypropylene (PP) fibre into LWFC to determine the optimum compressive strength and splitting tensile strength. Four different mix was designed containing different percentage of PP replacement (0, 0.1, 0.2 and 0.3%). From the results, the compressive strength of the oil palm shell lightweight foamed concrete with 0.3% of macro polypropylene fibre (OPSLWFC/0.3) had showed the highest compressive strength and splitting tensile strength at 28 days, which are recorded at 4.01 MPa and 0.62 MPa respectively. It also showed the lowest density among all the mix design which is 1152 kg/m3 under demoulded condition. The OPSLWFC/0.3 has increased about 23.38% of 28 days compressive strength and 37.78% of splitting tensile strength compared to the control mix, which contains 0% of fibre proportion. Hence, the findings of this research revealed that the development of environmentally friendly lightweight foamed concrete can be used as an alternative solution for traditional lightweight concrete.

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Nguyen, Duc Vinh Quang, Olga V. Aleksandrova, and Yuriy M. Bazhenov. "Effect of quartz powder and mineral admixtures on the properties of high-performance concrete." Vestnik MGSU, no. 1 (January 2019): 102–17. http://dx.doi.org/10.22227/1997-0935.2019.1.102-117.

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Introduction. This study focuses on the use of silica fume partially replacing cement with 0, 5, 7.5, 10, 12.5 and 30 % constant replacement of fly ash by weight of cement in concrete. Concrete is probably the most extensively used construction material in the world. But the conventional concrete is losing its uses with time and high-performance concrete (HPC) is taking that place. HPC has superior mechanical properties and durability to normal strength concrete. Because of, the microstructure of HPC is more homogeneous than that of normal concrete (NC) due to the physical and chemical contribution of the mineral admixtures as well as it is less porous due to reduced w/c ratio with the addition of a superplasticizer. The inclusion of additives helped in improving the properties of concrete mixes due to the additional reduction in porosity of cement paste and improving the particle packing in the interfacial transition zone (between cement paste and the aggregates).In this experimental investigation the behavior of HPC with silica fume and fly ash with and without quartz powder were studied. The water-binder ratio was kept 0.3 and 20 % quartz flour as partial replacement of fine aggregate for all cases. Materials and methods. Used materials in Vietnam, as follow, Sulfate-resisting Portland cement - PCSR40 (type V) of company Luks Cement (Vietnam) Limited was used in the work. Crushed granite of fraction 9.5…20 mm - as coarse aggregate, Natural sand from Huong river of 0.15…2.5 mm fraction with the fineness modulus of about 3.0 and quartz powder with an average particle size of 5…10 μm were used as fillers; Sika® Viscocrete®-151 is a superplasticizer based on a blend of 3rd generation PCE polymers was used as a plasticizing admixture. The ﬂg ash from Pha Lai thermal power plant and Sika silica Sikacrete® PP1 (particle size < 0.1 μm) was used as a mineral active admixture. The study of strength and technological properties of high-performance concrete was performed by using standard methods. Results. Established by icate that, the workability and strength increase at a certain level and after that, they decline with further increase in the replacement level of silica fume is 12.5 %, on the basis of 30 % FA replacement, the incorporation of 10 % SF showed equivalent or higher mechanical properties and durability compared to the reference samples. Conclusions. HPC consists of mineral admixtures such as silica fume and fly ash use combine quartz powder and superplasticizer helped in improving the strength and durability of concrete mixes due to the additional reduction in porosity of cement paste and an improved interface between it and the aggregate. With 30 % fly ash is optimum dosage used to replacement of cement, incorporation 10 % SF (by weight) and combine of partial replacement of fine aggregate by 20 % quartz powder. On the other hand, a few mathematical equations can be used to derive the durability properties of concrete based on its compressive strength.

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Halfa, Hossam, Asiful H. Seikh, Hany S. Abdo, Ibrahim A. Alnaser, Mahmoud S. Soliman, and Sameh M. Ragab. "Study on the Microstructure of Vanadium-Modified Tungsten High-Speed Steel-Coded SAE-AISI T1 Steel." Advances in Materials Science and Engineering 2022 (December 30, 2022): 1–18. http://dx.doi.org/10.1155/2022/3469305.

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The essential goal of this research is to evaluate the modification process on phase transformation, matrix chemical composition, and precipitated carbide types for modified SAE-AISI T1 steel and their effects on the hardness values after optimum heat treatment conditions. This research adopts the alloying design strategy to enhance one of the most important tools steel coded SAE-AISI T1 (T12001). Therefore, two alloying enhancement processes took place through partial or total tungsten replacement. Investigated steel was modified first through the addition of vanadium and then through the addition of vanadium and carbon. Substitute 5 wt modified SAE-AISI T1 steel. % tungsten with 1 wt. % vanadium, in addition to carbon content, varied from 0 to 1 wt. %. Therefore, to fulfill the goals of this work, Thermo-Calc software was utilized to get the following: (i) thermodynamic equilibrium information, (ii) the expected microstructure, (iii) the constituent volume fraction, and (iv) carbide chemical composition. The chemical composition of the expected phases was confirmed by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray (EDX). In addition, volume fractions of different constituents were estimated by using Thermo-Calc software and authenticated by the imaging analysis process. The experimental findings for the variations in the chemical composition of the matrix and eutectic carbides precipitated, e.g., MC and M6C carbides, agree well with the calculated findings. Tungsten replacement by vanadium with and without extra carbon at traditional SAE-AISI T1 steel encourages MC carbide formation instead of M6C, M23C6, and M7C3 carbides. MC carbide precipitated in vanadium with extra carbon-modified steel contains more carbon, chromium, and tungsten but less vanadium compared with vanadium-modified steel. Vanadium with extra carbon-modified steel precipitated more M6C carbide and gamma-austenite. Hardness measurements emphasized that modified steel is a promising material for its use as a tooling material with low tungsten content and, in turn, produces cutting-tool materials with economical cost.

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Bourekoua, Hayat, Urszula Gawlik-Dziki, Renata Różyło, Mohammed N. Zidoune, and Dariusz Dziki. "Acerola fruit as a natural antioxidant ingredient for gluten-free bread: An approach to improve bread quality." Food Science and Technology International 27, no. 1 (May 25, 2020): 13–21. http://dx.doi.org/10.1177/1082013220929152.

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In this study, we evaluated the effect of enrichment of bread using acerola fruit powder on the physical, sensorial and antioxidant properties of gluten-free breads. We tested different proportions of acerola fruit powder (0–5% w/w) in rice flour. According to the results, loaf volume increased from 423.33 cm3 to 571.67 cm with increasing amount of acerola fruit powder cm3 with increasing amount of acerola fruit powder (from 0 to 5% w/w). Acerola fruit powder improved the structural parameters of the crumb by increasing the size and area fraction of cells. All tested quantities of acerola fruit powder improved textural parameters by decreasing firmness and chewiness and by increasing springiness. In addition, acerola fruit powder positively affected the antioxidant properties of enriched breads. The total phenolic content and antioxidant activity of extracts was found to be increased with the addition of acerola fruit powder. All antioxidant activities were found to be increased with increasing quantities of acerola fruit powder. The sensory attributes of the bread showed that a partial replacement of the rice flour with up to 3% of acerola fruit powder provided satisfactory results. The optimum level of acerola fruit powder for all parameters tested was found to be 3% w/w.

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A. Shubbar, Sawsan D., and Aqeel S. Al-Shadeedi. "UTILIZATION OF WASTE PLASTIC BOTTLES AS FINE AGGREGATE IN CONCRETE." Kufa Journal of Engineering 8, no. 2 (July 17, 2017): 132–46. http://dx.doi.org/10.30572/2018/kje/821171.

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As human communities grow larger and larger, the problem of waste management becomes one of urgent need that should be solved. Recycling and reusing of the waste materials is an efficient measure in management of the waste materials, which in addition to preventing the pollution, it conserves natural resources. Plastic bottles made of polyethylene terephthalate (PET), constitutes a major fraction of household wastes. They are classified as non- biodegradable waste materials which are harmful for public health. So making use of PET in concrete production can be useful method to get rid of plastics solid waste damage on environment. In this research, effect of using waste PET that was converted to granules in concrete has been studied experimentally. Different proportion of sand ranging from 1% to 8%, were replaced by granulated plastic. The resulting concrete was compared with normal concrete without any addition of granulated plastic. Then the specimen were tested at 7 and 28 days after curing, and some engineering properties of the mixtures including slump test, fresh and dry density, compressive, and slip strength have been investigated. Analyzing experimental results of this work indicated that optimum dosage of waste bottles replacement is 2% as fine aggregate- substitution aggregate to get maximum compressive strength and slip strength.

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Wang, D., J. Zhao, J. Garcia-del-Real, and H. Mischo. "The influence of different fly ash-cement replacement ratios on the pressure drop of a horizontal backfilling pipe." IOP Conference Series: Earth and Environmental Science 942, no. 1 (November 1, 2021): 012006. http://dx.doi.org/10.1088/1755-1315/942/1/012006.

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Abstract Fly ash (FA) is a kind of harmful by-product in thermal power generation plants, and finding a way to enhance the utility of fly ash has been widely discussed among civil engineering and mining sectors. To investigate the possible optimal ratios of replacing usually used bind agent namely Portland cement (PC) with fly ash, this paper designed different test groups with varying PC-FA replacement ratio. To identify the physical and chemical characteristics of mixing materials used to produce the backfilling slurries, a rheological experiment and X-ray diffraction test have been conducted. Rheological tests show all these three replacement ratio groups (60%, 65%, 70% respectively) are yield pseudoplastic fluid. Computational fluid dynamics as an efficient and money-saving method also has been introduced in the present research to duplicate the flow behaviors and calculate the pressure drop (PD) in the backfilling pipe circuits. The simulation results suggested that all these three RR categories experience an increasing tendency in pressure drop with increasing flow velocity, but in the velocity range of 2 m/s - 2.4 m/s, the increasing tendency is gentle until flow velocity reaches 2.6 m/s, the PD increase evidently. Furthermore, when the RR = 65%, the pressure drop is significantly lower than that of RR = 60% or RR = 70% at all the corresponding investigated flow particle sizes have significant impact on the pressure drop across a pipe and is dependent on solid fraction and flow rate and velocities. Therefore, we can conclude that a proper dosage of FA in mixing backfilling slurries can reduce pressure drop obviously and thereby decrease the expenses in bind agent. Given the FA’s significant effect on pressure drop, and comprehensive considering the backfilling capacity and backfilling cost, the combination of RR = 65% and velocity = 2.6 m/s is optimum.

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Laksono, Andromeda Dwi, Ika Ismail, and Cahyaningtyas Ratna Ningrum. "Studi Pengaruh Komposisi Pengisi Serat Alam Kayu Galam (Melalueca Leucadendra) Bentuk Serutan pada Sifat Mekanik dan Mikrostruktur Komposit Poliester Sebagai Material Untuk Aplikasi Bilah Kincir Angin." JURNAL SAINTIS 19, no. 1 (April 30, 2019): 9–14. http://dx.doi.org/10.25299/saintis.2019.vol19(1).2629.

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[ID] Sebagai alternatif sumber energi konvensional, energi angin merupakan salah satu energi alternatif yang banyak dikembangkan. Pemanfaatan energi ini tidak lepas dari alat pengonversinya, kincir angin. Salah satu komponen kincir angin yang cukup penting adalah bilah. Bilah sering mengalami masalah berupa pengikisan pada bagian permukaannya akibat benturan dengan oleh partikel yang terbawa oleh angin yang dapat mengakibatkan fungsi bilah tidak optimal. Sehingga, dibutuhkan material pengganti yang lebih kuat tetapi ringan, yakni komposit. Komposit yang digunakan adalah komposit serat alam (serat Melaleuca leucadendra-poliester). Dalam penelitian ini akan dianalisa pengaruh fraksi volume serat berbentuk serutan terhadap kekuatan tarik, kelenturan dan ketangguhan. Pembuatan komposit serat alam Kayu Galam (Melaleuca leucadendra)-poliester dengan cara mencampurkan resin, katalis dan serat Kayu Galam yang berbentuk serutan kemudian dicetak didalam cetakan yang telah dilapisi alumunium foil. Sampel kemudian dilakukan pengujian kekuatan tarik dengan standar ASTM D 638, pengujian tekuk dengan standar ASTM D 790 serta pengujian impak dengan standar ASTM D 6110. Metode yang digunakan dalam pembuatan adalah metode hand lay-up. Hasil dari penelitian ini adalah nilai optimum yang dicapai yaitu 70% serat pada semua uji mekanik. Didapatkan nilai kekuatan tarik berada sebesar 13,07 MPa, kekuatan tekuk optimum 36,8 MPa dan nilai optimum dari kekuatan impak sebesar 590,39 MPa. [EN] As an alternative to conventional energy sources, wind energy is one of the many alternative energies that have been developed. The utilization of this energy is inseparable from its conversion tool, windmills. One component of the windmill that is quite important is the blade. Blades often experience problems in the form of erosion on the surface due to collisions by particles carried by the wind which can cause the blade function to be not optimal. So, it takes a replacement material that is stronger but lighter, namely composite. The composites used were natural fiber composites (Melaleuca leucadendra-polyester fibers). In this study, the effect of the volume fraction of fiber in the form of shavings on tensile strength, flexibility, and toughness will be investigated. The making of natural fiber composites of Galam Wood (Melaleuca leucadendra) -polyester by mixing resin, catalyst, and Galam Wood fiber in the form of shavings is then printed in a mold that has been coated with aluminum foil. Samples were then tested for tensile strength with ASTM D 638 standard, bending test with ASTM D 790 standard and impact testing under ASTM D 6110 standard. The method used in manufacturing was the hand lay-up method. The result of this study is the optimum value achieved is 70% fiber in all mechanical tests. Obtained tensile strength values of 13.07 MPa, the optimum bending strength of 36.8 MPa and the optimum value of impact strength of 590.39 MPa.

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Aleksenskii, Aleksander, Marcus Bleuel, Alexei Bosak, Alexandra Chumakova, Artur Dideikin, Marc Dubois, Ekaterina Korobkina, et al. "Effect of Particle Sizes on the Efficiency of Fluorinated Nanodiamond Neutron Reflectors." Nanomaterials 11, no. 11 (November 14, 2021): 3067. http://dx.doi.org/10.3390/nano11113067.

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Over a decade ago, it was confirmed that detonation nanodiamond (DND) powders reflect very cold neutrons (VCNs) diffusively at any incidence angle and that they reflect cold neutrons quasi-specularly at small incidence angles. In the present publication, we report the results of a study on the effect of particle sizes on the overall efficiency of neutron reflectors made of DNDs. To perform this study, we separated, by centrifugation, the fraction of finer DND nanoparticles (which are referred to as S-DNDs here) from a broad initial size distribution and experimentally and theoretically compared the performance of such a neutron reflector with that from deagglomerated fluorinated DNDs (DF-DNDs). Typical commercially available DNDs with the size of ~4.3 nm are close to the optimum for VCNs with a typical velocity of ~50 m/s, while smaller and larger DNDs are more efficient for faster and slower VCN velocities, respectively. Simulations show that, for a realistic reflector geometry, the replacement of DF-DNDs (a reflector with the best achieved performance) by S-DNDs (with smaller size DNDs) increases the neutron albedo in the velocity range above ~60 m/s. This increase in the albedo results in an increase in the density of faster VCNs in such a reflector cavity of up to ~25% as well as an increase in the upper boundary of the velocities of efficient VCN reflection.

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El-Essawi, Aschraf, Mohammed Morjan, Ingo Breitenbach, Ahmed Bechri, Rene Brouwer, and Wolfgang Harringer. "Modular minimal invasive extracorporeal circuits: another step toward universal applicability?" Perfusion 32, no. 7 (June 3, 2017): 598–605. http://dx.doi.org/10.1177/0267659117712404.

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Introduction: Safety concerns have been one of the main reasons opposing a wider acceptance of minimal invasive extracorporeal circuits (MiECC). Following an extensive experience and a multitude of modifications, we have set out to employ a modular MiECC as a universal extracorporeal circuit. Methods: A total of 129 cardiac surgical procedures were performed by a single surgeon in 2013. Excluding procedures done under circulatory arrest or with the potential need of such, the MiECC was utilized in almost 90% of surgeries. Of sixty-two (simple procedures) patients who underwent coronary artery bypass grafting (CABG), aortic valve replacement (AVR) or CABG + AVR, 82% were non-elective, 10% had a left ventricular ejection fraction (EF) <30% and most had an impaired renal function. Thirty-eight patients had more complex surgeries (complex procedures), 37% of which were urgent, 15% had an EF <30% and the majority had renal dysfunction. Results: The 30-day mortality was 5% in simple procedures and 2.5% in complex procedures. The incidence of postoperative atrial fibrillation was 13% and 16%, respectively. Optimum outcome was defined as a freedom from all complications and blood transfusions and was achieved in 52% and 42%, respectively. Conclusions: This report shows that modular MiECC can be employed with a high safety margin in cardiac surgery. Furthermore, it emphasizes the impact that minimal invasive philosophy could have in improving patient care.

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Köksal, Fuat, Ahmet Beycioğlu, and Magdalena Dobiszewska. "Optimization Based on Toughness and Splitting Tensile Strength of Steel-Fiber-Reinforced Concrete Incorporating Silica Fume Using Response Surface Method." Materials 15, no. 18 (September 7, 2022): 6218. http://dx.doi.org/10.3390/ma15186218.

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The greatest weakness of concrete as a construction material is its brittleness and low fracture energy absorption capacity until failure occurs. In order to improve concrete strength and durability, silica fume SF is introduced into the mixture, which at the same time leads to an increase in the brittleness of concrete. To improve the ductility and toughness of concrete, short steel fibers have been incorporated into concrete. Steel fibers and silica fume are jointly preferred for concrete design in order to obtain concrete with high strength and ductility. It is well-known that silica fume content and fiber properties, such as aspect ratio and volume ratio, directly affect the properties of SFRCs. The mixture design of steel-fiber-reinforced concrete (SFRC) with SF addition is a very important issue in terms of economy and performance. In this study, an experimental design was used to study the toughness and splitting tensile strength of SFRC with the response surface method (RSM). The models established by the RSM were used to optimize the design of SFRC in terms of the usage of optimal silica fume content, and optimal steel fiber volume and aspect ratio. Optimum silica fume content and fiber volume ratio values were determined using the D-optimal design method so that the steel fiber volume ratio was at the minimum and the bending toughness and splitting tensile strength were at the maximum. The amount of silica fume used as a cement replacement, aspect ratio, and volume fraction of steel fiber were chosen as independent variables in the experiment. Experimentally obtained mechanical properties of SFRC such as compression, bending, splitting, modulus of elasticity, toughness, and the toughness index were the dependent variables. A good correlation was observed between the dependent and independent variables included in the model. As a result of the optimization, optimum steel fiber volume was determined as 0.70% and silica fume content was determined as 15% for both aspect ratios.

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Vinotha Jenifer, J., and D. Brindha. "Development of hybrid steel-basalt fiber reinforced concrete – in aspects of flexure, fracture and microstructure." Revista de la construcción 20, no. 1 (2021): 62–90. http://dx.doi.org/10.7764/rdlc.20.1.62.

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The conventional concrete is considered to be critical in various constructional applications due to its setbacks such as service load failures, brittle property, low ductility and low tensile capacity. Apart from the natural bridging mechanism (aggregate bridging), an additional bridging mechanism is necessary to overcome the existing setbacks in plain cement concrete. Thus concrete with one or more types of fibers in suitable combinations can augment the mechanical performance of concrete causing a positive synergy effect. Along with the two control mixes with and without copper slag as partial replacement of fine aggregate, two different groups of hybrid combination of fibers such as steel and basalt were cast with 3 different groups of coarse aggregate proportions of sizes 20 mm and 12.5 mm. The hybridization of fibers is assessed in this study under compression, tension, flexure and fracture. Stress-strain data were recorded under compression to validate the strain capacity of the mixtures. The mechanical properties were analyzed for the positive hybrid effect and the influencing factors were copper slag, hybrid fiber combination and coarse aggregate proportions. The optimum volume fraction of fibers and mix proportions were highlighted based on various behaviors of concrete. Steel as macro fibers and basalt as microfibers were examined under microstructural studies (SEM and EDX). The results from the flexural toughness showcased the potential of hybrid fibers with greater energy absorption capacity ensuring the ductile property of the proposed hybrid fiber reinforced concrete.

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Justo-Reinoso, Ismael, and Mark T. Hernandez. "Use of Sustainable Antimicrobial Aggregates for the In-Situ Inhibition of Biogenic Corrosion on Concrete Sewer Pipes." MRS Advances 4, no. 54 (2019): 2939–49. http://dx.doi.org/10.1557/adv.2020.13.

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ABSTRACTA new generation of cementitious materials is being engineered to selectively inhibit the growth of Acidithiobacillus, which are a key genera of acid-generating bacteria responsible for microbially induced concrete corrosion (MICC). In this context, the substitution of metal-laden granular activated carbon (GAC) particles and/or steel slag for a fraction of the fine aggregates traditionally used in concrete mixture has proven useful. While the antimicrobial properties of specific heavy metals (i.e. copper and cobalt) have been leveraged to inhibit acid-generating bacteria growth on sewer pipes, few studies have researched how biocidal aggregates may affect the microstructural and mechanical properties of cementitious materials. We report here on the effects that these biocidal aggregates substitutions can have on compressive strength, flowability, and setting times of cement-based formulations. Results showed that increases in compressive strength, regardless of the presence or absence of biocidal metals, resulted from the GAC incorporation where sand replacement was 3% by mass or lower, while flowability decreased when percentages higher than 3% of GAC was incorporated in a cement mix. When substituting fine aggregate with steel slag particles in mass ratios between 5% and 40%, compressive strength was not affected, regardless of the presence or absence of copper. Setting times were not affected by the inclusion of GAC or steel slag particles except when substituting GAC particles at 10% of the fine aggregate mass; under this condition both initial and final setting times were decreased. Results suggest that in order to have enhanced inhibition potential against acidophilic microorganisms and equal or improved mechanical properties, a combination of 1% metal-laden GAC and 40% copper-laden steel slag is an optimum fine aggregate substitution scenario.

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Belenkov, Yu N., A. V. Koroteev, and V. Yu Mareev. "Mitral valve replacement and implantation of an extracardial mesh frame in patients with severe heart failure: results of a clinical study and a description of a clinical case 18 years after surgery." Kardiologiia 61, no. 9 (September 30, 2021): 4–10. http://dx.doi.org/10.18087/cardio.2021.9.n1769.

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Aim Dilated cardiomyopathy (DCMP) is a major cause for severe heart failure. Development of a combination (drug and surgery) treatment of this disease is relevant. This prospective observational study was aimed at evaluating short- and long-term results of extracardiac mesh implantation in DCMP patients with heart failure resistant to the optimum drug therapy.Material and methods The extracardiac mesh ACOR-1 was implanted in 15 patients with DCMP. All meshes were produced individually for each patient and made of Gelweave (great Britain) vascular graft strips. The mesh size corresponded to the heart diastolic size, which was measured after achieving a maximum possible clinical improvement for the patient. Long-term results were followed for up to 4 years. Mean age of patients was 43.1±10.8 years (from 28 to 62 years). One patient was followed up for 18 years. Data of that patient were presented as a clinical case report.Results From October, 2003 through October, 2007, 15 DCMP patients received mesh implants. Cases of in-hospital death were absent. In 3 mos. after the surgery, left ventricular volumes decreased (end-diastolic volume decreased from 251.7±80.7 to 229.0±61.3 ml; end-systolic volume decreased from 182.3±73.6 to 167.7±46.2 ml), and the left ventricular pump function improved (ejection fraction increased from 25.2±6.0 to 27.1±5.1 %; cardiac index increased from 2.0±0.5 to 2.4±0.7 ml /min /m2). The functional state of patients improved by one NYHA class, from 3.7±0.3 to 2.8±0.6. In some cases, the left ventricular size and the systolic function completely normalized. There were no episodes of circulatory decompensation in the long term after surgery. Actuarial survival for the observation period was 100%.Conclusion Implantation of extracardiac mesh prevented progression of heart dilatation and, in combination with drug therapy, it may represent an effective method for treatment of DCMP.

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Svensson, Lars G., Brad F. Rosinski, Nicholas J. Tucker, A. Marc Gillinov, Jeevanantham Rajeswaran, Eric E. Roselli, Douglas R. Johnston, Milind Y. Desai, Brian P. Griffin, and Eugene H. Blackstone. "Comparison of Outcomes of Patients Undergoing Reimplantation versus Bentall Root Procedure." AORTA 10, no. 02 (April 2022): 57–68. http://dx.doi.org/10.1055/s-0042-1744135.

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Abstract Background A bioprosthesis- or mechanical-prosthesis–containing polyester graft (composite graft) is standard surgical management for aortic root aneurysms (Bentall procedure), but particularly in the young patient in whom a bioprosthesis is likely to deteriorate and a mechanical prosthesis mandates life-long anticoagulation, valve-sparing procedures have been devised. One such procedure involves reimplantation of the native aortic valve in the polyester graft. With focus on selecting the optimum procedure for young relatively asymptomatic patients, we compared outcomes of reimplantation of the aortic valve versus the Bentall procedure and identified factors influencing outcomes. Methods From January 2000 to January 2017, 643 adults age ≤ 70 with tricuspid aortic valves underwent elective aortic root replacement with either reimplantation (n = 448/70%) or a composite valve graft (Bentall) procedure (n = 195/30%). Outcomes were compared in 100 propensity-matched pairs. Results Patients with fewer symptoms, less aortic regurgitation (AR), higher left ventricular ejection fraction, and smaller cross-sectional aortic area/height ratio had a higher likelihood of valve repair with reimplantation (all p < 0.02) versus receiving a Bentall procedure. Operative mortality was 0.16% (reimplantation, 1/448, 0.22%; Bentall 0/195, 0%). After reimplantation, 8-year freedom from severe AR was 95% and 10-year freedom from reintervention was 98%. Ten-year survival was 95%. Higher preoperative AR grade (p < 0.0001) but not larger root diameter (p = 0.3) was associated with higher grade of late regurgitation after a reimplantation procedure. Among propensity-matched patients, reimplantation compared with a Bentall was associated with similar 10-year survival (89% vs. 94%), but more late AR (8-year freedom from severe AR: 93% vs. 99.9%) and greater early reduction in, but similar late, left ventricular mass (104 vs. 105 g•m–2 at 8 years). Conclusion Excellent aortic valve reimplantation results versus Bentall lead us to recommend reimplantation more often in patients who present with even moderately severe or severe AR and significantly enlarged aortic roots.

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Svensson, Lars G., Brad F. Rosinski, Nicholas J. Tucker, A. Marc Gillinov, Jeevanantham Rajeswaran, Eric E. Roselli, Douglas R. Johnston, Milind Y. Desai, Brian P. Griffin, and Eugene H. Blackstone. "Comparison of Outcomes of Patients Undergoing Reimplantation versus Bentall Root Procedure." AORTA 10, no. 02 (April 2022): 57–68. http://dx.doi.org/10.1055/s-0042-1744135.

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Abstract Background A bioprosthesis- or mechanical-prosthesis–containing polyester graft (composite graft) is standard surgical management for aortic root aneurysms (Bentall procedure), but particularly in the young patient in whom a bioprosthesis is likely to deteriorate and a mechanical prosthesis mandates life-long anticoagulation, valve-sparing procedures have been devised. One such procedure involves reimplantation of the native aortic valve in the polyester graft. With focus on selecting the optimum procedure for young relatively asymptomatic patients, we compared outcomes of reimplantation of the aortic valve versus the Bentall procedure and identified factors influencing outcomes. Methods From January 2000 to January 2017, 643 adults age ≤ 70 with tricuspid aortic valves underwent elective aortic root replacement with either reimplantation (n = 448/70%) or a composite valve graft (Bentall) procedure (n = 195/30%). Outcomes were compared in 100 propensity-matched pairs. Results Patients with fewer symptoms, less aortic regurgitation (AR), higher left ventricular ejection fraction, and smaller cross-sectional aortic area/height ratio had a higher likelihood of valve repair with reimplantation (all p < 0.02) versus receiving a Bentall procedure. Operative mortality was 0.16% (reimplantation, 1/448, 0.22%; Bentall 0/195, 0%). After reimplantation, 8-year freedom from severe AR was 95% and 10-year freedom from reintervention was 98%. Ten-year survival was 95%. Higher preoperative AR grade (p < 0.0001) but not larger root diameter (p = 0.3) was associated with higher grade of late regurgitation after a reimplantation procedure. Among propensity-matched patients, reimplantation compared with a Bentall was associated with similar 10-year survival (89% vs. 94%), but more late AR (8-year freedom from severe AR: 93% vs. 99.9%) and greater early reduction in, but similar late, left ventricular mass (104 vs. 105 g•m–2 at 8 years). Conclusion Excellent aortic valve reimplantation results versus Bentall lead us to recommend reimplantation more often in patients who present with even moderately severe or severe AR and significantly enlarged aortic roots.

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Neelis, Karen J., Trudi P. Visser, Wati Dimjati, G. Roger Thomas, Paul J. Fielder, Duane Bloedow, Dan L. Eaton, and Gerard Wagemaker. "A Single Dose of Thrombopoietin Shortly After Myelosuppressive Total Body Irradiation Prevents Pancytopenia in Mice by Promoting Short-Term Multilineage Spleen-Repopulating Cells at the Transient Expense of Bone Marrow–Repopulating Cells." Blood 92, no. 5 (September 1, 1998): 1586–97. http://dx.doi.org/10.1182/blood.v92.5.1586.

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Abstract Thrombopoietin (TPO) has been used in preclinical myelosuppression models to evaluate the effect on hematopoietic reconstitution. Here we report the importance of dose and dose scheduling for multilineage reconstitution after myelosuppressive total body irradiation (TBI) in mice. After 6 Gy TBI, a dose of 0.3 μg TPO/mouse (12 μg/kg) intraperitoneally (IP), 0 to 4 hours after TBI, prevented the severe thrombopenia observed in control mice, and in addition stimulated red and white blood cell regeneration. Time course studies showed a gradual decline in efficacy after an optimum within the first hours after TBI, accompanied by a replacement of the multilineage effects by lineage dominant thrombopoietic stimulation. Pharmacokinetic data showed that IP injection resulted in maximum plasma levels 2 hours after administration. On the basis of the data, we inferred that a substantial level of TPO was required at a critical time interval after TBI to induce multilineage stimulation of residual bone marrow cells. A more precise estimate of the effect of dose and dose timing was provided by intravenous administration of TPO, which showed an optimum immediately after TBI and a sharp decline in efficacy between a dose of 0.1 μg/mouse (4 μg/kg; plasma level 60 ng/mL), which was fully effective, and a dose of 0.03 μg/mouse (1.2 μg/kg; plasma level 20 ng/mL), which was largely ineffective. This is consistent with a threshold level of TPO required to overcome initial c-mpl–mediated clearance and to reach sufficient plasma levels for a maximum hematopoietic response. In mice exposed to fractionated TBI (3 × 3 Gy, 24 hours apart), IP administration of 0.3 μg TPO 2 hours after each fraction completely prevented the severe thrombopenia and anemia that occurred in control mice. Using short-term transplantation assays, ie, colony-forming unit–spleen (CFU-S) day 13 (CFU-S-13) and the more immature cells with marrow repopulating ability (MRA), it could be shown that TPO promoted CFU-S-13 and transiently depleted MRA. The initial depletion of MRA in response to TPO was replenished during long-term reconstitution followed for a period of 3 months. Apart from demonstrating again that MRA cells and CFU-S-13 are separate functional entities, the data thus showed that TPO promotes short-term multilineage repopulating cells at the expense of more immature ancestral cells, thereby preventing pancytopenia. The short time interval available after TBI to exert these effects shows that TPO is able to intervene in mechanisms that result in functional depletion of its multilineage target cells shortly after TBI and emphasizes the requirement of dose scheduling of TPO in keeping with these mechanisms to obtain optimal clinical efficacy. © 1998 by The American Society of Hematology.

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Neelis, Karen J., Trudi P. Visser, Wati Dimjati, G. Roger Thomas, Paul J. Fielder, Duane Bloedow, Dan L. Eaton, and Gerard Wagemaker. "A Single Dose of Thrombopoietin Shortly After Myelosuppressive Total Body Irradiation Prevents Pancytopenia in Mice by Promoting Short-Term Multilineage Spleen-Repopulating Cells at the Transient Expense of Bone Marrow–Repopulating Cells." Blood 92, no. 5 (September 1, 1998): 1586–97. http://dx.doi.org/10.1182/blood.v92.5.1586.417a07_1586_1597.

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Thrombopoietin (TPO) has been used in preclinical myelosuppression models to evaluate the effect on hematopoietic reconstitution. Here we report the importance of dose and dose scheduling for multilineage reconstitution after myelosuppressive total body irradiation (TBI) in mice. After 6 Gy TBI, a dose of 0.3 μg TPO/mouse (12 μg/kg) intraperitoneally (IP), 0 to 4 hours after TBI, prevented the severe thrombopenia observed in control mice, and in addition stimulated red and white blood cell regeneration. Time course studies showed a gradual decline in efficacy after an optimum within the first hours after TBI, accompanied by a replacement of the multilineage effects by lineage dominant thrombopoietic stimulation. Pharmacokinetic data showed that IP injection resulted in maximum plasma levels 2 hours after administration. On the basis of the data, we inferred that a substantial level of TPO was required at a critical time interval after TBI to induce multilineage stimulation of residual bone marrow cells. A more precise estimate of the effect of dose and dose timing was provided by intravenous administration of TPO, which showed an optimum immediately after TBI and a sharp decline in efficacy between a dose of 0.1 μg/mouse (4 μg/kg; plasma level 60 ng/mL), which was fully effective, and a dose of 0.03 μg/mouse (1.2 μg/kg; plasma level 20 ng/mL), which was largely ineffective. This is consistent with a threshold level of TPO required to overcome initial c-mpl–mediated clearance and to reach sufficient plasma levels for a maximum hematopoietic response. In mice exposed to fractionated TBI (3 × 3 Gy, 24 hours apart), IP administration of 0.3 μg TPO 2 hours after each fraction completely prevented the severe thrombopenia and anemia that occurred in control mice. Using short-term transplantation assays, ie, colony-forming unit–spleen (CFU-S) day 13 (CFU-S-13) and the more immature cells with marrow repopulating ability (MRA), it could be shown that TPO promoted CFU-S-13 and transiently depleted MRA. The initial depletion of MRA in response to TPO was replenished during long-term reconstitution followed for a period of 3 months. Apart from demonstrating again that MRA cells and CFU-S-13 are separate functional entities, the data thus showed that TPO promotes short-term multilineage repopulating cells at the expense of more immature ancestral cells, thereby preventing pancytopenia. The short time interval available after TBI to exert these effects shows that TPO is able to intervene in mechanisms that result in functional depletion of its multilineage target cells shortly after TBI and emphasizes the requirement of dose scheduling of TPO in keeping with these mechanisms to obtain optimal clinical efficacy. © 1998 by The American Society of Hematology.

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Pearn, W. L., and Ya-Chen Hsu. "Optimal tool replacement for processes with low fraction defective." European Journal of Operational Research 180, no. 3 (August 2007): 1116–29. http://dx.doi.org/10.1016/j.ejor.2006.05.030.

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Lalitha*, G., Dr C. Sashidhar, and Dr C. Ramachandrudu. "Durability Performance of Concrete (M-45) Fine Aggregate Partially Replaced with Crushed Waste Glass." International Journal of Innovative Technology and Exploring Engineering 9, no. 6 (April 30, 2020): 1818–22. http://dx.doi.org/10.35940/ijitee.e2966.049620.

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Durability of concrete is as the ability to resist weathering action, chemical attack, and abrasion while giving the desired engineering properties. Concrete require different degrees of durability depending on the exposure environmental conditions. The retrogression of concrete structures is due to effect of attrition of reinforcing bars which is occurred due to the chloride incursion.so it is necessary to study the concrete durability nature before making its usage in present construction. The present research is focused on studying the effect of using sustainable material in concrete preparation. To know the effective usage of crushed waste glass in concrete and significance in Durability properties for different replacements was studied .The present research work was done using materials like cement, Fine aggregate, coarse aggregate, waste crushed glass, super plasticizer in order to know that at which combination of mix there will be optimum effect on properties of concrete. In this research Waste crushed glass was used as fractions of 10%,20%,30% and 40% by weight of crushed glass used. The durability tests to test resistance against acid environment chloride penetration and abrasion resistance tests are performed. The optimum value of acid resistance was observed when fine aggregate was replaced with 30% of fine aggregate with crushed waste glass, less abrasion loss at 30% replacement and chloride penetration also effective at 30% replacement.

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Ouypornprasert, Winai, Narong Traitruengtatsana, and Kong Kamollertvara. "Optimum Partial Replacement of Cement by Nanosilica, Microsilica and Rice Husk Ash for Mass Production of Concrete." Key Engineering Materials 751 (August 2017): 544–49. http://dx.doi.org/10.4028/www.scientific.net/kem.751.544.

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The objective of this technical paper was to propose the use of optimum partial replacement of cement by pozzolan of high-silica content i.e. nanosilica, silica fume and rice husk ash. Firstly cement hydration, pozzolanic reactions of pozzolan and stoichiometry were reviewed. Then the optimum fractional replacement of cement by pozzolan based on the complete consumption of calcium hydroxide and the strength activity index (SAI) were formulated and proposed. After that the results of a series of tests of cement mortars were shown to verify the proposed concepts. The applicability for the mass concrete production was demonstrated by prediction of mean values of nonnormal distributions from the corresponding specifications.

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STRADI, BENITO, and EMMANUEL HAVEN. "OPTIMAL INVESTMENT STRATEGY VIA INTERVAL ARITHMETIC." International Journal of Theoretical and Applied Finance 08, no. 02 (March 2005): 185–206. http://dx.doi.org/10.1142/s0219024905002962.

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This paper studies the optimal replacement policy of an item that experiences stochastic geometric growth in maintenance costs. The model integrates corporate taxes, tax credits, depreciation, and salvage value. We extend this traditional application to cover the cost of replacement with the payout from two bonds. The two-bond portfolio is passively immunized. The intersections between the continuation and replacement boundaries are computed using the Interval-Newton Generalized-Bisection (IN/GB) method. We allow small fluctuations of the replacement boundary. With these fluctuations, multiple intersections of the two boundaries are determined. The IN/GB method finds all these intersections without the need for initial guesses of the problem variables. This is a major computational improvement over traditional single-root finding implementations that require multiple initial guesses and provide no guarantees of existence or uniqueness. We demonstrate that without fluctuations one would expect to find a single optimal replacement time. However with fluctuations, there are several intersections of the continuation and replacement boundaries and the bond weight fractions may change by more than 200% between intersection points. These large changes in portfolio wealth allocation highlight the fragility of the idealized solution in the realm of fluctuations in replacement costs.

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Johnstone, I. M. "The Optimum Timing and Maximum Impact of Full Rehabilitation of New Zealand Housing Stock." Environment and Planning A: Economy and Space 30, no. 7 (July 1998): 1295–311. http://dx.doi.org/10.1068/a301295.

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The author develops a simulation model to estimate the optimum timing and maximum impact of full rehabilitation of New Zealand housing stock. The model is based on the theories of classical population dynamics. Data used in the model include empirical estimates of the mortality of New Zealand housing stock, assumed schedules of depreciation of dwelling services, and assumed schedules of annual maintenance costs. The dwelling service years provided by dwellings serve as a proxy for benefits of rents or imputed rents (excluding rent for land). The cost to construct one dwelling and fractions thereof serve as a proxy for costs of maintenance, rehabilitation, replacement, and new construction. Optimum timing of rehabilitation can increase the quantity of benefits provided by the housing stock per unit total cost but a reduction in the growth rate of new dwellings has a greater impact in achieving the same objective. A stationary and stable housing stock can provide 45% more dwelling services per unit total cost than a housing stock which doubles in size every 35 years.

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Kenneth Miebaka Oba, Tamunoemi Alu LongJohn, and Kaniyeh Anthony Ijeje. "Suitability of Saw Dust Ash and Quarry Dust as Mineral fillers in Asphalt Concrete." International Journal of Engineering and Management Research 12, no. 2 (April 5, 2022): 24–29. http://dx.doi.org/10.31033/ijemr.12.2.4.

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This study attempts to justify how suitable a conventional mineral filler and a non-conventional mineral filler can replace fractions of the aggregates in an asphalt concrete in order to reduce cost and encourage reuse of waste materials. Asphalt concrete mix proportions were generated with 3% Quarry Dust and 3% Saw Dust Ash replacements of aggregates. The binder contents were 3, 4, 5, 6 and 7% for a 60/70 penetration grade asphalt binder. Briquette specimens were formed using the asphalt concrete mix proportions carried out. Standard laboratory experiments were carried out on the aggregates, Quarry Dust, Saw Dust Ash, bituminous binder and asphalt concrete specimens based on the relevant codes and standards. The Marshall method was used for the asphalt concrete design procedure. The optimum binder content was found to be 4.85% using the standard Marshall curves. At optimum binder content, using 4% design air void for medium traffic and maximum aggregate of 10mm, the Stability, Flow, VMA and VFA were 5.83kN, 15.73(0.25mm), 15.28% and 73.25% respectively. These were within the Asphalt Institute design criteria.

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Elsawy, Mohamed B. D. "Geotechnical Behavior of Stabilized Dunes Sand by Cement." Journal of Civil Engineering and Construction 10, no. 2 (May 15, 2021): 69–74. http://dx.doi.org/10.32732/jcec.2021.10.2.69.

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The dunes sand is wide spread with huge quantities all over the world especially in desert areas near roads. The objective of the current paper is to use dunes sand as a foundation soil under structures instead of utilizing expensive replacement with structural fills. The dunes sand samples were collected from a site outside Tabuk city in the north-west of Saudi Arabia. Several experimental tests were performed on the dunes sand samples such as sieve analysis, standard Proctor compaction, drained direct shear and CBR. The test results indicated that the sand dunes are SP according to USCS. The sand dunes have also low shear strength and CBR value. The bearing ability of the sand dunes became weaker due to water immersion. Therefore, the construction on the non-treated dunes sand is impossible. For the later reason, the dunes sand was stabilized with various ordinary Portland cement fractions ranging from 3% to 15%. Compaction and CBR tests were conducted on the stabilized dunes sand. The maximum dry density increased as the increments of the cement contents accompanying with the decrement of porosity and optimum moisture content. The stabilized dunes sand implied higher CBR values than the non-treated soil. The CBR values of the stabilized soil increased with increasing cement fractions. The stabilized dunes sand induced very high CBR values after longer curing times for all the utilized cement contents. The stabilized dunes sand using only 3% is considered the optimum design achieving good performance under structures and best economic mix.

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Eminov, A. A., Sh S. Namazov, and Z. R. Kadyrova. "Development of optimal dinas ramming masses for lining of thermal units." NOVYE OGNEUPORY (NEW REFRACTORIES) 1, no. 6 (November 26, 2022): 7–10. http://dx.doi.org/10.17073/1683-4518-2022-6-7-10.

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The article presents the results of research on the development of optimal chemical, charge and fractional compositions of dinas ramming masses for lining of thermal units. It has been established that the best results, in terms of material composition and thermo mechanical properties, are dominated by prototypes based on quartzite, with a content of quartz sand and kaolin not higher than 20 wt. %. The possibilities of partial replacement of quartzite with quartz sand in the development of new compositions of dinas ramming masses are shown. Ill. 1. Ref. 15. Tab. 5.

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Sokolov, V. "Adaptive optimal robust stabilization of autoregressive plant under biased external disturbance." Proceedings of the Komi Science Centre of the Ural Division of the Russian Academy of Sciences, no. 5 (December 20, 2022): 20–27. http://dx.doi.org/10.19110/1994-5655-2022-5-20-27.

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This paper addresses the problem of adaptive optimal robust control of a discrete-time plant with unknown parameters of autoregressive nominal model, unknown upper bound and bias of external disturbance, and unknown gains of coprime factor perturbations. The control criterion is the worst-case steady-state upper bound of the output. Solution of the problem is based on an optimal polyhedral estimation of unknown non-identifiable parameters with the control criterion treated as the identification criterion. A replacement of unknown parameters is proposed that modifies the plant model to a model without perturbation in control. This transforms the nonconvex control criterion to a linear fractional one and thus makes possible online computation of optimal estimates.

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Arafa, Dalia F., and Mohamed S. Moawad. "Shear Behavior of Reinforced Fiber Concrete Beam Using Steel Lathe Scrap Waste and End Hooked Steel Fiber." Key Engineering Materials 945 (May 19, 2023): 129–44. http://dx.doi.org/10.4028/p-69d246.

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Shear behavior of reinforced concrete beams using steel lathe scrap waste and end hooked steel fibers as fully or partially web shear reinforcement replacement was studied. Steel lathe scrap waste is generated from industrial steel waste and can be used as recycled fibers offering additional advantages towards environmental pollution reduction. To investigate their effect of reinforced concrete beam under shear behavior, ten reinforced concrete beam specimens with 1200 mm long, 200 mm wide, and 300 mm high were tested under quasi-static loading (two-point loading). The studied parameters in this investigation were types of fibers such as steel lathe waste fiber and traditional hooked steel fiber ratio and the web shear reinforcement ratio are zero% and 50%. Results observed were initial and post-cracking stiffness, maximum capacity load, vertical displacements, modes of failures, and the ductility of the specimens. It was concluded that using of steel lathe scrap waste and hooked steel fibers in concrete are advantageous, they changed the mode of failure of the beam from a brittle to a ductile mode of failure due to the ductility of steel used, whether traditional steel fiber or steel lathe waste fiber. The optimum ratio of the steel lathe scrap waste was found equal 0.5% while the optimum ratio of traditional hooked steel fiber is 1% as fractional volume.

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Ahmed, Wisal, C. W. Lim, and Arslan Akbar. "Influence of Elevated Temperatures on the Mechanical Performance of Sustainable-Fiber-Reinforced Recycled Aggregate Concrete: A Review." Buildings 12, no. 4 (April 14, 2022): 487. http://dx.doi.org/10.3390/buildings12040487.

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In recent times, the applications of fiber-reinforced recycled aggregate concrete (FRAC) in practical engineering have gained greater popularity due to its superior mechanical strength and fracture properties. To apply FRAC in buildings and other infrastructures, a thorough understanding of its residual mechanical properties and durability after exposure to fire is highly important. According to the established research, the properties and volume fractions of reinforcing fiber materials, replacement levels of recycled concrete aggregate (RCA), and heating condition would affect the thermal–mechanical properties of FRAC. This review paper aims to present a thorough and updated review of the mechanical performance at an elevated temperature and post-fire durability of FRAC reinforced with various types of fiber material, specifically steel fiber (SF), polypropylene (PP) fiber, and basalt fiber (BF). More explicitly, in this review article the residual mechanical properties of FRAC, such as compressive strength, splitting tensile capacity, modulus of elasticity, mass loss, spalling, and durability after exposure to elevated temperatures, are discussed. Furthermore, this study also encompasses the relationship among the dosages of fibers, replacement levels of recycled aggregate, and the relative residual mechanical properties of FRAC that would help in the optimum selection of the fiber content. Conclusively, this study elaborately reviews and summarizes the relevant and recent literature on recycled aggregate concrete containing SF, PP fiber, and BF. The study further provides a realistic comparison of these fibers in terms of the residual mechanical performance and durability of FRAC that would help in their future enhancements and applications in practical engineering.

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Gaynullina, L. R., and V. P. Tutubalina. "Research of thermal stability of the VG transformer oil in the presence of individual sulfides." Proceedings of the Voronezh State University of Engineering Technologies 80, no. 3 (December 17, 2018): 336–40. http://dx.doi.org/10.20914/2310-1202-2018-3-336-340.

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In connection with the known negative impact of organosulfur connections on quality of transformer oils and the corresponding rise in price of their production including various ways of cleaning of oil fractions of organosulfur connections re-searches of structural and group structure of oil organosulfur connections and their influence on operational properties of transformer oil have been conducted. Influence of individual sulfides on thermal stability of the brand VG transformer oil in electric field is studied by tension of 30 kV/cm at change of concentration of sulfides in range from 0 to 1,0% from the mass of oil. The research was con-ducted with use of methylbenzylsulfide and a metilfenilsulfide on the basis of the brand VG transformer oil without addition of an ionol. It is established that individual sulfides metilbenzil- and metilfenilsulfide treat the anti-oxidizing additives reducing oil aging speed. For obtaining the maximum thermal stability of transformer oil the optimum concentration of individual sulfides making 0,5% of the mass of oil is defined. The analysis of the inhibiting ability metilbenzil-and a metilfenilsulfida has shown that more effective additive to oil is methylbenzylsulfide which increases thermal stability of oil and reduces amount of the absorbed air more (by 2,2 times) in comparison with the metilfenilsulfide, 0,5% of the mass of oil taken at the optimum concentration equal. The carried-out comparative analysis of a molecular structure of methylbenzylsulfide and metilfenilsulfide has shown that with an identical length of a paraffin chain replacement of a naphthenic cycle by an aromatic kernel leads to decrease in efficiency of individual sulfide as anti-oxidizing additive to oil.

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Kibru, Yisak, Anteneh Geremew, and Biruk Yigezu. "POTENTIAL USE OF 'ENSET' FIBER ASH AS PARTIAL REPLACEMENT OF CONVENTIONAL FILLER MATERIAL IN HOT MIX ASPHALT." Journal of Civil Engineering, Science and Technology 12, no. 2 (September 30, 2021): 91–111. http://dx.doi.org/10.33736/jcest.3973.2021.

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The main problems in road construction and maintance work in Ethiopia availability of a large amount of appropriate quality materials in road construction sites, aggregates in different size fractions are not readily obtainable, necessitating their procurement from long distances, thereby causing an exorbitant increase in construction costs. One of the main problems in constructing the asphalt paving mixture is obtaining a sufficient amount of filler material from crushing fine rock material and low percent using ordinary Portland cement (OPC), hydrated lime (HL) and marble dust. To overcome this problem, it is important to come across alternative filler material to address this gap using naturally available material. Currently, renewed attention has been given to the use of ‘waste’ materials instead of conventional aggregates in pavement construction. This research study investigates the potential use of ‘Enset’ fiber ash as a partial replacement of conventional filler material in hot mix asphalt supported by experimental laboratory investigation. In order to achieve this study, purposive sampling techniques were adopted to select the sample size and location. The study evaluated the potential of ‘Enset’ fiber ash as filler for the design of dense-graded hot mix asphalt by referencing traditional filler control mix procedures based on standard specifications, and a crush rock filler was utilized as a conventional filler material as a control for comparison. The Marshal Stability and Rutting Test (RT) was conducted to determine the HMA specimen's performance. Several HMA specimens were prepared using aggregate blend according to ASTM D 1559 with four different percentages of ‘Enset’ fiber ash (EFA) of 15%, 25%, 35% and 45% filler replacement the total filler weight used in the control mix. Specimens were prepared and tests performed according to EN 12697-22 procedure-B for rutting test. All HMA properties were taken at 4% air void and determined their optimum bitumen content (OBC). Almost the same result with the control mix was observed in the study at 15% and 25% of the ‘Enset’ fiber ash (EFA) replacement. However, higher Marshall Stability, a lower void filled with asphalt, better flow, a good void in mineral were observed at 25% ‘Enset’ fiber ash (EFA) replacement. At this rate, the rutting performance is less than that of the control mix but is within the specifications of 2.78mm and 2.9 mm of rutting depth less than 6mm that satisfies the EN 13108 requirement. As a result, Enset fiber ash filler can replace traditional filler material up to 25% of the total filler weight used in this study. It was recommended to use ‘Enset' fiber ash (EFA) as a filler material as a partial replacement in a bituminous paving mixture up to the specificed percentage by weight replacement.

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Sobuz, Md Habibur Rahman, Ayan Saha, Jannatul Ferdous Anamika, Moustafa Houda, Marc Azab, Abu Sayed Mohammad Akid, and Md Jewel Rana. "Development of Self-Compacting Concrete Incorporating Rice Husk Ash with Waste Galvanized Copper Wire Fiber." Buildings 12, no. 7 (July 15, 2022): 1024. http://dx.doi.org/10.3390/buildings12071024.

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This research work is devoted to the experimental investigation of both rheological and mechanical properties of self-compacting concrete (SCC) produced with waste galvanized copper wire fiber and rice husk ash (RHA). In the study, three different volume fractions of 0.5 p to 0.75 percent, 1 percent of scrap copper wire fiber as reinforcing material, and 2 percent RHA as cement replacement were used. To evaluate the fresh characteristics of SCC, the slump flow, J-ring, and V-funnel experiments were conducted for this investigation. Compressive strength, splitting tensile strength, and flexural strength of the concrete were conducted to assess the hardened properties. The test was carried out to compare each characteristic of plain SCC with this modified SCC mixture, containing RHA as pozzolanic materials and copper fiber as reinforcing material. Incorporating copper fiber in the SCC leads to a drop in fresh properties compared to plain SCC but remains within an acceptable range. On the other hand, the inclusion of 2% RHA makes the SCC more viscous. Although adding 2% RHA and 1% copper wire in SCC provide the highest strength, this mix has an unacceptable passing ability. The SCC mix prepared with 2% RHA and 0.75% copper fiber is suggested to be optimum in terms of the overall performance. According to this study, adding metallic fiber reinforcement like copper wire and mineral admixture like RHA can improve the mechanical properties of SCC up to a certain level.

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Carvalho, G., J. M. Novais, P. A. Vanrolleghem, and H. M. Pinheiro. "Optimal operation for timely adaptation of activated sludge plants to changes in the surfactant composition of wastewater." Water Science and Technology 45, no. 4-5 (February 1, 2002): 345–53. http://dx.doi.org/10.2166/wst.2002.0621.

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The composition of a textile industry wastewater is highly variable, as the industrial process has to follow fashion and season trends. Surfactants represent one of the largest COD fractions in a typical textile wastewater. Therefore, it was the aim of this paper to model the acclimatisation behaviour of an activated sludge system when subjected to composition variations in the surfactant containing feed. The model was based on data obtained in SBR experiments in which a linear alkyl ethoxylate as sole carbon source in the feed was replaced by another with a longer ethoxylate chain. A previously developed model (Fractionated Degradation Model) was applied to each of the 21 SBR cycles carried out in this study. The resulting best-fit parameters were investigated and sub-models were further developed, to create an acclimatisation model, able to predict the sludge acclimatisation level. Using the information given by this model, it was possible to propose an optimal operation scheme to pre-acclimatise the sludge before a surfactant replacement is made in the textile process. A cost analysis was carried out to compare different scenarios, with and without the application of this operation scheme. It was concluded that the proposed pre-acclimatisation process may be cost effective as compared to other scenarios if a cheap surfactant-containing product was employed.

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Amagu, Clement A., Beatrice O. Enya, Jun-ichi Kodama, and Mostafa Sharifzadeh. "Impacts of Addition of Palm Kernel Shells Content on Mechanical Properties of Compacted Shale Used as an Alternative Landfill Liners." Advances in Civil Engineering 2022 (February 21, 2022): 1–13. http://dx.doi.org/10.1155/2022/9772816.

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The design of landfill liners of waste disposal to reduce migration of leachate containment, low swelling, and shrinkage and ensure sufficient shear strength to resist bearing capacity and instability of the landfill has been a major challenging task to landfill engineers. Over the last decade, there has been an increase in research on the stability of substitute materials as liners that are environmentally friendly, cost-effective, and socially beneficial due to the growing cost of traditional landfill liners. In this regard, geotechnical tests were conducted on shale samples treated with 0–12% (increment of 2%) of palm kernel shell ash (PKSA) and pulverized palm kernel shell (PPKS) to evaluate their suitability as alternative landfill liners using West African Standard (WAS) and Modified AASHTO Standard (MAS) for compactive energy. The shale has more percentage of finer fractions, thus classified as poorly graded soil (A-7-5). The Atterberg limit tests show that liquid and plastic limits decrease with an increase in plasticity index as the percentage of addition of PKSA and PPKS content increases. The results also established that the maximum dry density (MDD), volumetric shrinkage strain (VSS), and hydraulic conductivity significantly decrease, while the optimum moisture content (OMC) increases as the content of PKSA and PPKS increases at both compactive efforts. The maximum strengths of 380.30 and 448.70 kPa were obtained at 4% of both stabilizers. From the results, it can therefore be concluded that the treated compacted shale meets the condition of the suitability of landfill liners. Furthermore, with the use of industrial and agricultural wastes such as palm kernel shells as replacement materials with natural soils used as liners, significant social, economic, and environmental impact of landfills and reduction in wastes can be achieved. The research results can provide a reference for similar conditions of landfill liners worldwide.

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Sebastian, Kaule, Pfensig Sylvia, Siewert Stefan, Sylvia Pfensig, Stefan Siewert, Klaus-Peter Schmitz, Michael Stiehm, Kohse Stefanie, Grabow Niels, and Öner Alper. "Influence of leaflet geometry on hydrodynamic performance of transcatheter aortic valve prostheses." Current Directions in Biomedical Engineering 5, no. 1 (September 1, 2019): 473–75. http://dx.doi.org/10.1515/cdbme-2019-0119.

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AbstractThe implantation of transcatheter aortic valve prostheses (TAVP) for therapy of aortic valve stenosis shows more and more clinically non-inferiority results compared to surgical valve replacement in intermediate and low risk patients. Commonly clinically used TAVP are manufactured from chemically fixed xenograft leaflet material, e.g. bovine or porcine pericardium. While the clinical use of TAVP currently extends, challenges concerning valve durability and leaflet calcification have to be addressed. In this regard, artificial leaflet materials represent a promising option for a next generation of TAVP. As a first step for the development of TAVP from polymeric nonwoven, the aim of this study was to determine the influence of leaflet geometry on hydrodynamic performance of TAVP prototypes. Based on a parametric model of the valve leaflets, we varied the curvature of the belly line forming the leaflet coaptation area from an initial, quite concave, leaflet geometry with a value of 0.5° to an almost straight geometry for the leaflets with a value 0.15°. Manufacturing of TAVP prototypes was conducted by means of electrospinning technique with a polycarbonate based silicone elastomer. Hydrodynamic characterization according to ISO 5840-3 standards was performed using a pulse duplicator system with a heart rate of 70 BPM, systolic duration of 35%, mean aortic pressure of 100 mmHg and a stroke volume of 96 ml. Cardiac output as well as mean transaortic pressure gradient, closing volume, leakage volume and regurgitation were measured to compare the different leaflet geometries. To summarize, the curvature of the leaflets’ belly has a crucial impact on TAVP hydrodynamics under physiological test conditions. In particular, the opening and closing behavior is strongly influenced by a steeper curvature leading to larger closing volumes and higher regurgitant fractions. Further studies are planned to identify an optimum with respect to leaflet material selection, leaflet geometry and hydrodynamic properties of TAVP.

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Johnson, R. G. "Past and future ice age initiation: the role of an intrinsic deep-ocean millennial oscillation." Earth System Dynamics Discussions 5, no. 1 (May 20, 2014): 545–84. http://dx.doi.org/10.5194/esdd-5-545-2014.

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Abstract. This paper offers three interdependent contributions to studies of climate variation: (1) the recognition and analysis of an intrinsic millennial oceanic oscillation that affects both Northern and Southern high latitude climates, (2) The recognition of an oceanographic switch to ice-free seas west of Greenland that explains the initiation of the Last Ice Age, and (3) an analysis of the effect of increasing salinity in the seas east of Greenland that suggests the possibility of the initiation of an ice age threshold climate in the near future. In the first contribution the millennial oscillation in the flow of the North Atlantic Drift reported by Bond et al. (1997) is proposed to be part of a 1500 yr intrinsic deep ocean oscillation. This oscillation involves the exchange of North Atlantic intermediate-level deep water (NADW) formed in the seas east of Greenland with Antarctic Bottom Water formed in a shallow-water zone at the edge of the Antarctic continent. The concept of NADW formation is already well known, with details of the sinking water flowing out of the Greenland Sea observed by Smethie et al. (2000) using chlorofluorocarbon tracers. The concept of Antarctic Bottom Water formation is also already well established. However, its modulation by the changing fraction of NADW in the Southern Ocean, which I infer from the analysis of Weyl (1968), has not been previously discussed. The modulated lower-salinity Antarctic Bottom Water that reaches the northern North Atlantic then provides negative feedback for the cyclic variation of NADW formation as proposed here. This causes the 1500 yr bipolar oscillation. The feedback suggests the possible sinusoidal character of the proposed oscillation model. The model is consistent with the cooling of the Little Ice Age (Lamb, 1972, 1995), and it also correctly predicts NASA's observation of today's record maximum area of winter sea ice on the Southern Ocean and the present observed record low rate of Antarctic Bottom Water production cited by Broecker (2000). The sinusoidal form of this conceptual model is therefore reinforced by both old and new data, and provides insights into world-wide climate change. The second contribution of this paper is a hypothesis for the initiation of Pleistocene ice ages, typified by the Last Ice Age that began 120 000 yr BP. Instead of the classical Northern high-latitude summer cooling caused by orbital precession and changes in Earth's axis inclination, this hypothesis proposes the sudden onset of year-round ice-free seas west of Greenland, with greatly increased precipitation in the ice sheet nucleation regions of Baffin Island, northern Quebec, and Labrador. Devon Island ice-core studies by Koerner at al. (1988) and deep-sea sediment data reported by Fillon (1985) support the concept of ice-free seas west of Greenland and imply the initial meteorological conditions that are proposed here. These conditions are consistent with the heavy precipitation inferred by Adkins et al. (1997) from deep-sea sediment data. The changes in northeastern Canada were accompanied by quite cold conditions in northern Europe, inferred by Field et al. (1994) from tree pollen data. The European cooling was probably caused by loss of the recurring Iceland low-pressure system due to the dominant effect of a frequent stronger low-pressure system over the Labrador Sea, as postulated in this paper. The key to ice-free seas west of Greenland is the loss of the near-surface stratification that normally enables sea ice to freeze. Using the high-resolution European Space Agency's ENVISAT system, I have monitored the flows through the Nares Strait and found that the dominant southward flow of lower density polar water into Baffin Bay correlated with the growing area of seasonal sea ice forming early in the winter in the Bay near the southern end of the Strait. This implies that low-salinity polar water was the cause of the stratification. A search for the cause of the stratification loss then became a search for the cause of the loss of the southward flow of polar water. The loss could have occurred if denser and more saline Atlantic water replaced the polar water in-flow. Medieval historical records suggest that an analogous partial replacement probably did occur during the early medieval climatic optimum, with some warmer Atlantic water removing the thick perennial sea ice along Greenland's north coast. The NADW formation rate and the Spitsbergen-Atlantic Current (SAC) flow were then near maximum values. I hypothesize that enough of the thick perennial sea ice along Greenland's north coast was removed by the penetration of the SAC flow into the polar ocean to enable a medieval voyage eastward along the coast in AD 1118. This voyage is implied by an old map record showing Greenland realistically as an island. An even stronger SAC flow associated with a stronger maximum in the 1500 yr intrinsic oscillation of the oceanic system was the likely trigger for the initial conditions of ice-sheet growth when the Last Ice Age began. The third contribution of this paper is the hypothesis that modern society's activities might cause a repetition of the transition to an ice age threshold climate within one or two decades from 2013. This possibility depends on a continuing increase of salinity in the seas east of Greenland, with a corresponding increase of NADW formation and the SAC flow. The increase is currently being driven by the increasing rate of the saline Mediterranean outflow that contributes to the North Atlantic Drift. The rate increase is a consequence of the increasing salinity of the Mediterranean Sea as reported by European oceanographers (Science, 279, 483–484, 1998). The rising salinity of the Mediterranean and its increasing outflow is attributed to the diversion of nearly all the in-flowing rivers for irrigation. A further substantial salinity increase should occur with the loss of all perennial polar sea ice possibly within one or two decades from 2013 if the present trend of loss continues. The trend is displayed on the University of Illinois internet site: http://arctic.atmos.uiuc.edu/cryosphere/. The increasing salinity of the Greenland Sea is now reflected in an increasing northward winter penetration by the SAC flow. According to Lamb (1972), during the early 20th century at the time of maximum extension of sea ice in April, open water normally extended only as far north as the southern cape of Spitsbergen at about 76.6° N. But in Aprils of 2013 and 2014, open water extended 380 km farther northward to the north coast of Spitsbergen. When the SAC was running strongly to replace sinking NADW in February of 2014, I observed open water extending about 730 km north from the cape into the polar ocean to latitude 83° N, where the penetration of the SAC flow was beginning to obstruct the southward flow of polar water. Even greater seasonal extensions of the SAC flow are expected with an additional Greenland Sea salinity increase after the loss of all perennial polar sea ice. This could cut off southward movement of polar water through the Fram Strait during much of the winter, and send annual pulses of the denser Atlantic water of the SAC flow into the sea north of Greenland. If these annual pulses begin to occur and allow enough denser Atlantic water to flow southward through the Nares Strait, the Baffin Bay stratification would be lost and a switch to an ice age threshold would occur. The severity of the resulting cold regional climate might have a disruptive effect on higher-latitude societies.

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Ota, T., DNS Senaratne, NK Preston, F. Ferrara, D. Djikic, O. Villemain, L. Takahashi, et al. "Poster Session 3The imaging examination and quality assessmentP626Value of mitral and tricuspid annular displacement to assess the interventricular systolic relationship in severe aortic valve stenosis : a Pilot studyP627Follow-up echocardiography in asymptomatic valve disease: assessing the potential economic impact of the European and American guidelines in a dedicated valve clinic, compared to standard care.P628The tricuspid valve: identification of optimal view for assessing for prolapseP629Right atrial volume by two-dimensional echocardiography in healthy subjectsP630Disturbance of inter and intra atrial conduction assessed by tissue doppler imaging in patients with medicaly controlled hypertension and prehypertension.P631Liver stiffness by shear wave elastography, new noninvasive and quantitative tool for acute variation estimation of central venous pressure in real-time?P632Weak atrial kick contribution is associated with a risk for heart failure decompensationP633Usefulness of wave intensity analysis in predicting the response to cardiac resynchronization therapyP634Early subclinical left ventricular systolic and diastolic dysfunction in gestational hypertension and preeclampsiaP635Clinical comparison of three different echocardiographic methods for left ventricular ejection fraction and LV end diastolic volume measurementP636Assessment of right ventricular-arterial coupling parameters by 3D echocardiography in patients with pulmonary hypertension receiving specific vasodilator therapyP637Prediction of right ventricular failure after left ventricular assist device implant: assessing usefulness of standard and strain echocardiographyP638Kinematic analysis of diastolic function using the novel freely available software Echo E-waves - feasibility and reproducibilityP639Evaluation of coronary flow velocity by Doppler echocardiography in the treatment of hypertension with the ARB: correlation to the histological cardiac fibrosisP640The clinical significance of limited apical ischaemia and the prognostic value of stress echocardiography - A contemporary study from a high volume centerP641Effects of intermediate stenosis of left anterior descending coronary artery on survival in patients with chronic total occlusion of right coronary arteryP642Left ventricular remodeling after a first myocardial infarction in patients with preserved ejection fraction at dischargeP643Left atrial size and acute coronary syndromes. Let is make simple.P644Influence of STEMI reperfusion strategy on systolic and diastolic functionP645Aortic valve resistance risk-stratifies low-gradient severe aortic stenosisP646Does permanent pacemaker implantation complicate the prognosis of patients after transcatheter aortic valve implantation?P647Influence of metabolic syndrome and diabetes on progression of calcific aortic valve stenosis - The COFRASA - GENERAC StudyP648Low referral for aortic valve replacement accounts for worse long-term outcome in low versus high gradient severe aortic stenosis with preserved ejection fractionP649The impact of right ventricular function from aortic valve replacement: A randomised study comparing minimally invasive aortic valve surgery and conventional open heart surgery." European Heart Journal – Cardiovascular Imaging 17, suppl 2 (December 2016): ii122.1—ii130. http://dx.doi.org/10.1093/ehjci/jew250.

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Haberka, M., A. Garcia Martin, P. Barbier, M. Pellegrino, A. Angelis, PJ Howlett, M. Madeira, et al. "Poster session 1GENERAL PRINCIPLESP194Ultrasound indexes of adipose tissue and lipid goals attainment in high and very high cardiovascular risk patientsTHE IMAGING EXAMINATIONP195Right ventricular global longitudinal strain provides higher prognostic value than right free wall longitudinal strain in patients with left heart diseaseP196Normal values of echocardiographlc left and right cardiac chambers dimensions as multifactorially determined by sex, level of physical activity, age, BMI, systolic blood pressure and heart rateAnatomy and physiology of the heart and great vesselsP197Echocardiographic phenotypes according to levels of oxygen consumption at peak exercise: findings from the EURO(pean) EX(ercise) population-based studyAnatomy and physiology of the heart and great vesselsP198Systemic vascular resistance and central arterial stiffness in relation to left ventricular geometry and diastolic function in essential hypertensionAssessment of diameters, volumes and massP199Left atrial diameter predicts a new diagnosis of paroxysmal atrial fibrillation in a population presenting with palpitationsP200Interventricular septum thickness and acute coronary syndromes: small differences, big prognostic influence?P201Detection of abdominal aortic aneurysm in a population referred for an ultrasonographyAssessments of haemodynamicsP202The ultrasound vector velocity method transverse oscillation validated in a flowrig with constant and pulsatile flow and in-vivo of blood flow in the ascending aortaASSESSMENT OF SYSTOLIC FUNCTIONP203Different types of left ventrical remodeling in children with arterial hypertensionP204Assessment of myocardial performance index in hypertensive patients with or without hyperuricemiaP205Strain echocardiography detects mild impairment of systolic function in patients with frequent premature ventricular contractionsP206Speckle tracking strain correlates better with functional capacity and hemodynamic burden than ejection fraction in patients with severe heart failureP207Prognostic value of 2D and 3D echocardiographic volumes, ejection fraction and strain as markers of abnormal left ventricular performanceP208Long-term prognostic value of left ventricular ejection fraction assessed by echocardiography and magnetic resonance imaging after acute STEMIP209Assessment of left ventricular function after percutaneous coronary intervention of chronic total occluded coronary artery by speckle tracking and cardiac magnetic resonanceP210Physiologic variations of tricuspid annular plane systolic excursion in healthy subjects: clinical and echocardiographic correlatesP211Predictors of incipient ventricular dysfunction with tyrosine kinase inhibitors in metastatic renal cell carcinomaAssessment of diastolic functionP212Disagreement between the American Society of Echocardiography (ASE) and gastroenterology-based guidelines for the diagnosis of diastolic dysfunction among patients with advanced liver diseaseP213Nomograms for mitral inflow doppler and tissue doppler velocities in caucasian childrenP215Diastolic function is impaired in women with angina pectoris and no obstructive coronary artery disease independently of coronary microvascular functionP216Clinical value of myocardial performance index in patients with isolated diastolic dysfunctionIschemic heart diseaseP217Cardiac imaging strategy is clinically more effective and at lower cost than traditional ETT strategy for the diagnosis of stable coronary artery diseaseP218Does the ESC clinical pretest probability score stratify our patients correctly? Validation with stress echocardiographyP219Incremental value of exercise echocardiography over exercise electrocardiography in a chest pain unit: a decision curve analysisP220A bedside echocardiographic score for risk stratification of ST-elevation myocardial infarction patients undergoing primary percutaneous coronary interventionP221Interventricular and intraventricular dyssynchrony in patients with Q-wave acute myocardial infarctionP222Comparison of tagging and tissue tracking for myocardial strain assessment at 1.5T and 3.0T following ST-segment elevation myocardial infarctionP223Left atrial strain rate evaluated by two-dimensional speckle tracking is predictor of left ventricular arrhythmias in STEMI patients treated by primary PCIP224Impact of percutaneous coronary intervention of chronic total oclussion on left ventricular function using speckle tracking and cardiac magnetic resonanceHeart valve DiseasesP225Clinical and echocardiographic characteristics of patients with low flow severe aortic stenosis and preserved ejection fractionP226Ventricular-arterial interplay in patients with severe aortic stenosis: additional role of wave intensity analysisP227Degenerative aortic stenosis: don't forget the vascular componentP228Reclassifying low gradient aortic stenosis with 3D transesophageal echocardiography and global longitudinal strainP229Importance of mitral regurgitation on pre- and postoperative clinical status and echocardiographic findings in patients with severe aortic stenosis admitted for aortic valve replacementsP230Aorto-septal angle and degenerative aortic stenosis: a case-control study stenosisP231Difference of sST2 level in mitral stenosis compare with control subjectsP232Velocity-time integral of aortic regurgitation: a novel echocardiographic marker in the evaluation of aortic regurgitation severityP233Color doppler 3D echocardiography-derived regurgitant volume in primary mitral regurgitation: a comparison of different techniques with magnetic resonanceP234Outcome of surgery for degenerative mitral regurgitationP235Mitral valve repair or replacement for functional regurgitation and left ventricular dysfunction: clinical and echocardiographic outcomeP236Prevalence, characteristics and prognosis of moderate to severe tricuspid regurgitation in patients with precapillary pulmonary hypertensionP237Management of late bioprosthetic mitral valve thrombosisP238Relationship between pulmonary venous flow and prosthetic mitral valve thrombosisP239Transcatheter aortic valve implantation does not reduce acutely valvuloarterial impedance in an elderly population with degenerative calcific aortic valve stenosisP240Influence of type of prosthesis on mitral regurgitation change after transcatheter aortic valve replacement for aortic stenosisP241The prevalence of valve disease in patients undergoing atrial fibrillation ablationCardiomyopathiesP242The prognostic value of lung ultrasound at discharge in heart failureP243Prognostic value of global longitudinal strain in non-ischaemic dilated cardiomyopathyP244Additional effect of high intensity exercise training to cardiac resynchronization in heart failure: the reduction on left venticular massP245Dobutamine-induced changes of longitundinal strain predicts longterm mortality in severe heart failureP246Myocardial fibrosis is not related to two-dimensional longitudinal strain in dilated cardiomyopathyP247Echocardiographic parameters are predictors of positive genetic study in a Portuguese population with hypertrophic cardiomyopathy: a multicentre studyP248Myocardial deformation techniques for the evaluation of the right ventricle in fabry diseaseP249Borderline hypertrophic cardiomyopathy or athlete's heart: what is the role for genetic testing in athletes?P250Isolated papillary muscle hypertrophy. Clinical, electrocardiographic and morphologic characteristicsP251Prognostic value of the assessment of left atrial deformation in hypertrophic cardiomyopathyP252Assessment of subtle echocardiographic changes may improve risk stratification of arrhythmias in early stages of arrhythmogenic right ventricular cardiomyopathy (ARVC)P253Long-term correlation of electrocardiography with structural echocardiography changes in patients with arrhythmogenic right ventricular cardiomyopathyP254Right ventricular strain and dyssynchrony assessment in arrhythmogenic right ventricular cardiomyopathy: a cardiac magnetic resonance feature-tracking studyP255Association of non compaction and hypertrophic cardiomyopathies, Noonan and long QT syndromesP256Predictors of mortality in patients with acute myocarditisP257Clinical characteristics and natural history of acute myocarditisP258One-beat 3dimensional echocardiography for the assessment of right ventricular function in heart transplant recipientsP259Hemodynamically irrelevant, non-surgery related pericardial effusion is a predictor of mortality in heart transplanted patientsSystemic diseases and other conditionsP260Left ventricular function as a cardiac marker of target organ damage in non-diabetic, never treated hypertensive patients: Camparison with microalbuminuriaP261Subclinical myocardial dysfunction in hypertensive patients with hyperuricemiaP262Can deformation indices (strain/strain rate) establish differential diagnosis in infiltrative cardiomyopathies?P263Prevalence and factors associated with inappropriately high left ventricular mass in patients with rheumatoid arthritisP264Echocardiographic evaluation of patients with end-stage liver disease, the importance of follow up after liver transplantationP265Cardiovasclular involvement in asymptomatic juvenile localized scleroderma patientsP267Can the left ventricular mechanics using speckle tracking echocardiography in pregnancy predict the new onset heart failure?P268What causes impaired exercise tolerance in HFpEF? Relative contribution from LV filling pressure and other factorsCongenital heart diseaseP269Pregnancy in patients with Ebsteins anomaly - echocardiographic and clinical studyP270Double aortic arch anomalies in clinical practiceP271Echocardiography as the essential imaging modality in congenital heart disease - first one to begin with and the one who staysMasses, tumors and sources of embolismP272Can the reduction of wall shear stress in diskinetic myocardial wall segments be used to predict trombogenicity?Diseases of the aortaP273The role of modified transoesophageal echocardiography for optimal access decision making for transcatheter aortic valve replacement proceduresStress echocardiographyP274Is aortic valve resistance different in patients with severe aortic stenosis and left ventricular fraction below 40% with low or high gradient?P275Does wall motion score index in dobutamine stress echocardiography predict syntax score in catheterization lab?P276Sex-related differences in peak stress left ventricular global longitudinal strain during dobutamine stress echocardiography in patients with significant coronary artery diseaseP277Exercise stress echocardiography complications: a 4-year single center experienceP278Reduced baseline left ventricular longitudinal systolic function is a marker of inducible myocardial ischemia in patients undergoing exercise echocardiographyP279Estimation of mean pulmonary arterial pressure based on right ventricle systolic pressure observed from exercise echocardiography among non-pulmonary hypertension with systemic sclerosisTransesophageal echocardiographyP280Transoesophageal echocardiography in patients with neuroendocrine tumour and carcinoid symptoms is safe without intravenous octreotideP281The feasibility and the clinical benefit of the cognitive-behavioral intervention for preparing patients for transesophageal echocardiographic studyP282Dynamic changes of mitral annulus shape in different types of mitral valve prolapse. A three-dimensional transoesophageal studyReal-time three-dimensional TEEP283Severe aortic stenosis: evaluation of effective and anatomy valve by 2D transthoracic echocardiography and 3D transesophageal echocardiographyP2843D-transeosphageal echocardiography usefulness for assessment of cardiac output in intensive care unit: an ultrasound versus thermodilution comparative study for patients under mechanical ventilationP285The predictive value of three-dimensional vena-contracta in determining the number of MitraClip devices needed during the procedure in functional mitral regurgitationTissue Doppler and speckle trackingP286Should the septum be included in the assessment of right ventricular longitudinal strain?P287Can machine learning help to identify heart failure with preserved ejection fraction?P288Concordance of atrial function measurement by 3D volumetric echocardiography and speckle tracking deformation imagingP289Heterogonous regional diastolic function revealed by 2D speckle tracking echocardiography identifies patients with ischemic etiology of left ventricular systolic dysfunctionP290The values from Real time 3-dimensional strain is not independent from preload changesP291Risk stratification in hypertrophic cardiomyopathy. a potential role for speckle-tracking parameters by cardiac magnetic resonanceP292Abnormal longitudinal peak systolic strain in asymptomatic patients with type-I diabetes mellitusP294Strain evaluation of subclinical cardiac dysfunction in patients with myotonic dystrophy type 1P295Heart function assessment in perinatal asphyxia; speckle tracking indices from greyscale recordings perform better than from tissue Doppler recordings, fractional shortening and tissue Doppler indicesP297Longitudinal strain assessed by automatic function imaging - a useful tool in significant coronary artery disease detection in patients with low risk anginaP298Global 2-Dimensional strain as a predictor of mortality in heart transplant patients with cardiac allograft vasculopathyP299Two-dimensional longitudinal strain and strain rate in asymptomatic middle-aged patients with type 2 diabetes mellitus - a pilot study resultsP300Limited accuracy of myocardial deformation imaging in diagnosis of left ventricular segmental dysfunction in patients with acute myocardial infarction: is it only a limitation of the strain software?Computed Tomography & Nuclear CardiologyP301Evaluation of the actual prevalence of myocardial ischemia in patients prior to performing a peripheral vascular surgeryP302Prognostic value of myocardial ischemia detected by myocardial perfusion imaging in asymptomatic patients with diabetes type 2P303Economic cost analysis derived by coronary computed tomography angiography inappropriate indications to rule out coronary heart disease." European Heart Journal – Cardiovascular Imaging 16, suppl 2 (December 2015): S15—S42. http://dx.doi.org/10.1093/ehjci/jev263.

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Chukwuma, D. I., E. N. Ikezue, E. O. Onu, and J. O. Ezeugo. "Improvement of the Mechanical Properties of Hibiscus Esculentus (Okra) Fiber Reinforced Polymer Composite." Earthline Journal of Chemical Sciences, September 18, 2019, 249–59. http://dx.doi.org/10.34198/ejcs.2219.249259.

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Abstract:

Natural fiber and their composites are the emerging trends in material science. They are speedily gaining grounds in the replacement of synthetic reinforcements. This is due to their low density, high specific mechanical strength, ultimate availability and disposability and less processing requirements. Most plant based fibers have become centers of research. This work is based on Okra fiber. Okra fiber was used as reinforcement in vinyl ester polymer matrix. Okra fiber was chemically treated using NaOH to clean fiber surface, modify the surface to increase the surface roughness and in general enhance bond strength between fiber and matrix. Reinforcement of the matrix using Okra fiber increases mechanical properties of the composite. But for optimal result, certain parameters were considered and varied. The two parameters considered were: fiber length, and proportion or volume fraction. Different variations of fiber length considered were: 10mm, 30mm and 50mm while the different fiber volume fractions considered are 10%, 30% and 50%. This work has analyzed how these parameters can be best combined for optimum values of tensile properties of the composite. The tensile strength of composite was highest at fiber length of 50mm and volume fraction of 10% at ultimate tensile strength of 214MPa.

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Sugiyanto, Gito. "MARSHALL TEST CHARACTERISTICS OF ASPHALT CONCRETE MIXTURE WITH SCRAPPED TIRE RUBBER AS A FINE AGGREGATE." Jurnal Teknologi 79, no. 2 (January 31, 2017). http://dx.doi.org/10.11113/jt.v79.6965.

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Highways are important transportation infrastructures that influence economy, culture, and security. Most of the highways in Indonesia are flexible pavement that use asphalt as a binder. The use of scrapped tire rubber as a partial replacement of fine aggregates is based on the limited available natural aggregate in nature. Utilization of scrapped tire rubber as a fine aggregate is one of the alternatives for reducing environmental pollution and supporting Clean Development Mechanism program. The aim of this study is to analyze the Marshall test characteristics of asphalt concrete (AC) mixture that use scrapped tire rubber as a partial substitute of fine aggregate and comparing with a standard mixture. Laboratory tests are performed on three different types of mixtures as follows the mix without scrapped tire rubber, mix containing 50%, and 100% substitution of aggregate at fraction of No.50 with scrapped tire rubber. The test, it show that optimum asphalt content for ACStandard mixture is 6.76%, while ACScrapped-tire 50% mixture is 7.04% and ACScrapped-tire 100% mixture is 6.25%. The use of scrapped tire rubber in asphalt concrete mixtures can improve the resistance to permanent deformation and resistance to water. The use of scrapped tire rubber is acceptable as a partial replacement of aggregate in asphalt concrete mixtures.

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Mogadam, Emad, David Shavelle, Jing Liu, Gregory Giesler, Ray Matthews, and Niema M. Pahlevan. "Abstract 16138: Validation of a Non-invasive Approach for the Assessment of Left Ventricular-arterial Coupling Following Transcatheter Aortic Valve Replacement." Circulation 142, Suppl_3 (November 17, 2020). http://dx.doi.org/10.1161/circ.142.suppl_3.16138.

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Abstract:

Introduction: Transcatheter aortic valve replacement (TAVR) is an established treatment for patients with severe, symptomatic aortic stenosis (AS). Ventriculoarterial (LV-arterial) coupling defined as the ratio of total arterial elastance (Ea) to left ventricular end-systolic elastance (Ees) reflects effective cardiac energetics and is a well-accepted index for quantification of LV-arterial coupling. Despite its usefulness, estimating Ees/Ea has technical difficulties. Intrinsic Frequency (IF) method is a noninvasive and single waveform system-based approach for quantification of LV-arterial coupling. The objective of this study was to compare IF variables with Ea/Ees in predicting optimum LV-arterial energetics following TAVR. Method: Twenty-eight patients with severe AS, undergoing TAVR were included. Mean age was 85±4, 53% male with mean ejection fraction 59±6.4. IFs during systole (ω1), diastole (ω2), and total IF variation (Δω=ω1-ω2) were computed from the ascending aortic pressure waveforms at baseline and following TAVR. Ea/Ees was computed using single-beat technique proposed by Takeuchi et al. ( Circulation . 1991;83(1):202-212). Results: There was a significant decrease in Ea/Ees (p<0.001) toward optimum coupling immediately after TAVR (Figure 1a). There was a statistically significant correlation between Ea/Ees and Δω (r= 0.68, p<0.01) (Figure 1b). Conclusion: IF appears to be an accurate and reliable index for quantification of LV-arterial coupling given significant concordance with Ea/Ees. The management of patients with acutely altered hemodynamic states post TAVR can benefit from the assessment of LV-arterial coupling. Since IFs can be measured noninvasively using hand-held devices (e.g. an iPhone), this approach should broaden the clinical applicability of this useful parameter for assessing systolic function, therapeutic response and ventricular-arterial interaction post TAVR.

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Journal articles on the topic 'Optimum Replacement Fraction'

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