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1
Briceño-Ahumada, Zenaida, Alesya Mikhailovskaya und Jennifer A. Staton. „The role of continuous phase rheology on the stabilization of edible foams: A review“. Physics of Fluids 34, Nr. 3 (März 2022): 031302. http://dx.doi.org/10.1063/5.0078851.
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Foams play an essential role in food. They contribute to the texture, aroma, and mouthfeel of a product; potentially reduce calories; and visually inspire the consumer. Understanding factors that control foam structure and bubble lifetimes is, therefore, of considerable interest. This review focuses on the effect of the continuous phase rheology for bubbly systems with an emphasis on edible foams. We review common biopolymers used to alter the rheology of the continuous phase of food foams and discuss potential mechanisms responsible for the production and stabilization of such systems. Variations to the matrix (i.e., foamulsions and oil-based foams) and the addition of gelling particles are also considered. This review emphasizes the necessity for fine control over the mechanical properties of the continuous phase to achieve the desired sensorial attributes and foam stability in food products. However, the dynamics of viscoelastic food foams are poorly understood due to their complex nature. We, therefore, discuss rheological studies on model foams and provide future directions for research that is in keeping with current trends and challenges in the food industry and culinary arts.
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Szekrényesy, T., K. Liktor und N. Sándor. „Characterization of foam stability by the use of foam models 1. Models and derived lifetimes“. Colloids and Surfaces 68, Nr. 4 (November 1992): 267–73. http://dx.doi.org/10.1016/0166-6622(92)80212-k.
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3
Linul, Petrică, Radu Bănică, Oana Grad, Emanoil Linul und Nicolae Vaszilcsin. „Highly Electroconductive Metal-Polymer Hybrid Foams Based on Silver Nanowires: Manufacturing and Characterization“. Polymers 16, Nr. 5 (23.02.2024): 608. http://dx.doi.org/10.3390/polym16050608.
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Due to their electroconductive properties, flexible open-cell polyurethane foam/silver nanowire (PUF/AgNW) structures can provide an alternative for the construction of cheap pressure transducers with limited lifetimes or used as filter media for air conditioning units, presenting bactericidal and antifungal properties. In this paper, highly electroconductive metal-polymer hybrid foams (MPHFs) based on AgNWs were manufactured and characterized. The electrical resistance of MPHFs with various degrees of AgNW coating was measured during repeated compression. For low degrees of AgNW coating, the decrease in electrical resistance during compression occurs in steps and is not reproducible with repeated compression cycles due to the reduced number of electroconductive zones involved in obtaining electrical conductivity. For high AgNW coating degrees, the decrease in resistance is quasi-linear and reproducible after the first compression cycle. However, after compression, cracks appear in the foam cell structure, which increases the electrical resistance and decreases the mechanical strength. It can be considered that PUFs coated with AgNWs have a compression memory effect and can be used as cheap solutions in industrial processes in which high precision is not required, such as exceeding a maximum admissible load or as ohmic seals for product security.
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Arabadzhieva, Dimi, Plamen Tchoukov und Elena Mileva. „Impact of Adsorption Layer Properties on Drainage Behavior of Microscopic Foam Films: The Case of Cationic/Nonionic Surfactant Mixtures“. Colloids and Interfaces 4, Nr. 4 (13.11.2020): 53. http://dx.doi.org/10.3390/colloids4040053.
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Aqueous mixtures of cationic hexadecyltrimethylammonium chloride (CTAC) and nonionic pentaethyleneglycol monododecyl ether (C12E5) are investigated. Adsorption layer properties are systematically studied within a wide concentration range for a 1:1 molar ratio of the surfactants. Surface tension and dilatational rheology measurements are conducted by profile analysis tensiometry. The interfacial data are juxtaposed to drainage kinetics and stability results for microscopic foam films, investigated by microinterferometric thin liquid film instrumentation. The obtained results give experimental evidence of synergistic interactions in the studied solutions, as compared to the corresponding single surfactant systems. Specific runs of dynamic and equilibrium surface tension curves are registered against the total surfactant quantity; the surface dilatational elasticities for the mixtures are systematically higher. A clear correlation is established between adsorption layer performance and foam film characteristics. The maxima of the film lifetimes are well outlined, and the respective values are shifted towards lower overall concentrations. The reported results substantiate the key role of the adsorption layers, and the surface dilatational properties in particular, for foam film drainage kinetics and stability. The well-expressed synergy observed in adsorption layer and foam film properties suggests the substantial benefits of using mixed surfactant systems in the design and fine-tuning of foam systems for innovative applications.
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Czakaj, Agnieszka, Emmanouil Chatzigiannakis, Jan Vermant, Marcel Krzan und Piotr Warszyński. „The Influence of the Surface Chemistry of Cellulose Nanocrystals on Ethyl Lauroyl Arginate Foam Stability“. Polymers 14, Nr. 24 (09.12.2022): 5402. http://dx.doi.org/10.3390/polym14245402.
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Guanidine-based surfactant ethyl lauroyl arginate (LAE) and cellulose nanocrystals (CNCs) form complexes of enhanced surface activity when compared to pure surfactants. The LAE-CNC mixtures show enhanced foaming properties. The dynamic thin-film balance technique (DTFB) was used to study the morphology, drainage and rupture of LAE-CNC thin liquid films under constant driving pressure. A total of three concentrations of surfactant and the corresponding mixtures of LAE with sulfated (sCNC) and carboxylated (cCNC) cellulose nanocrystals were studied. The sCNC and cCNC suspension with LAE formed thin films, with stability increasing with surfactant concentration and with complex rheological properties. In the presence of LAE, the aggregation of CNC was observed. While the sCNC aggregates were preferentially present in the film volume with a small fraction at the surface, the cCNC aggregates, due to their higher hydrophobicity, were preferentially located at film interfaces, forming compact layers. The presence of both types of aggregates decreased the stability of the thin liquid film compared to the one for the LAE solution with the same concentration. The addition of CNC to LAE was critical for foam formation, and foam stability was in qualitative agreement with the thin films’ lifetimes. The foam volume increased with the LAE concentration. However, there was an optimum surfactant concentration to achieve stable foam. In particular, the very resistant foam was obtained with cCNC suspensions that formed the interfaces with a complex structure and rheology. On the other hand, at high LAE concentrations, the aggregates of CNC may exhibit antifoaming properties
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Peralta, Alexander, Frederick Just-Agosto, Basir Shafiq und David Serrano. „Innovative vibration technique applied to polyurethane foam as a viable substitute for conventional fatigue testing“. Journal of the Mechanical Behaviour of Materials 21, Nr. 3-4 (01.12.2012): 61–68. http://dx.doi.org/10.1515/jmbm-2011-0013.
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AbstractLifetime prediction using three-point bending (TPB) can at times be prohibitively time consuming and costly, whereas vibration testing at higher frequency may potentially save time and revenue. A vibration technique that obtains lifetimes that reasonably match those determined under flexural TPB fatigue is developed. The technique designs the specimen with a procedure based on shape optimization and finite element analysis. When the specimen is vibrated in resonance, a stress pattern that mimics the stress pattern observed under conventional TPB fatigue testing is obtained. The proposed approach was verified with polyurethane foam specimens, resulting in an average error of 4.5% when compared with TPB.
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SUN, QICHENG, LIANGHUI TAN und GUANGQIAN WANG. „LIQUID FOAM DRAINAGE: AN OVERVIEW“. International Journal of Modern Physics B 22, Nr. 15 (20.06.2008): 2333–54. http://dx.doi.org/10.1142/s0217979208039514.
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Liquid foams are concentrated dispersions of gas bubbles in a small amount of surfactant solution, which are perpetually out of equilibrium systems. The process of liquid draining through networks of Plateau borders in a fresh foam is so-called foam drainage, as a result of both gravitational and capillary forces, which has great effect on the stability of foams. From the view of foam physics and dynamics, this paper briefly introduces foam structure and major lifetime limiting factors of foam. The substantial progress on the theory of drainage, measuring techniques for liquid fractions, drainage in both one dimension and two dimensions, and drainage in microgravity circumstances are overviewed throughout. Remaining tasks are discussed and a multiscale methodology for foam drainage is proposed for future investigations.
8
AbdelKader, Atef. „The effect of cell boundary on 2D foam“. MATEC Web of Conferences 192 (2018): 01011. http://dx.doi.org/10.1051/matecconf/201819201011.
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We have studied the effect of cell boundary on 2D foam, with particular attention to perfect arrays of identical bubbles, and those containing only a single defect with time. We have also examined the effect of the wetness of the foam, observing the stability of two-dimensional foam comprising bubble rafts constrained to a fixed area of liquid surface. Perfectly six-fold coordinated foam appear to be unstable against loss of cohesion, but the lifetime to breakage of the perfect foam increases systematically with changing the cell boundaries. Foams containing a single defect are stable against such breakage due to the elastic stress fields around it.
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Yilixiati, Subinuer, Ewelina Wojcik, Yiran Zhang und Vivek Sharma. „Spinodal stratification in ultrathin micellar foam films“. Molecular Systems Design & Engineering 4, Nr. 3 (2019): 626–38. http://dx.doi.org/10.1039/c8me00102b.
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We report the discovery and analysis of spinodal stratification, a hitherto unreported mechanism underlying drainage and rupture of micellar foam films, that presents unexplored opportunities for understanding and controlling the stability, lifetime and properties of ubiquitous foams.
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Zimnyakov, Dmitry, Marina Alonova, Ekaterina Ushakova, Olga Ushakova, Anna Isaeva und Elena Isaeva. „Dynamic Light Scattering by Foamed Polymers during Preparation of Scaffold Prototypes: Events Statistics Analysis versus Evaluation of Correlation Time in Data Interpretation“. Photonics 8, Nr. 12 (03.12.2021): 549. http://dx.doi.org/10.3390/photonics8120549.
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Polylactide foaming as the key stage in laboratory preparation of highly porous biocompatible matrices used as scaffold prototypes was monitored based the effect of dynamic light scattering in expanding polylactide foams. Intensity fluctuations of scattered laser radiation in the course of foam expansion were analyzed using ensemble-averaged estimates of the speckle lifetime within a running window in the time domain. It was found that, in contrast to the commonly used correlation time of intensity fluctuations, the values of the average speckle lifetime are invariant with respect to the type of dynamics of phase fluctuations of partial components in scattered radiation. This makes it possible to relate this parameter to microscopic mobility of interphase boundaries in the foam in the absence of a priori information on the law of motion relating these boundaries at the microscopic level. The proposed approach in combination with the developed phenomenological model describing the relationship between the average speckle lifetime and the current values of the foam volume, as well as its first-time derivative made it possible to interpret the features of foam structure formation.
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Gochev, Georgi G., Vamseekrishna Ulaganathan, Inga Retzlaff, Cécile Gehin-Delval, Deniz Z. Gunes, Martin Leser, Ulrich Kulozik, Reinhard Miller und Björn Braunschweig. „β-Lactoglobulin Adsorption Layers at the Water/Air Surface: 4. Impact on the Stability of Foam Films and Foams“. Minerals 10, Nr. 7 (17.07.2020): 636. http://dx.doi.org/10.3390/min10070636.
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The complexity and high sensitivity of proteins to environmental factors give rise to a multitude of variables, which affect the stabilization mechanisms in protein foams. Interfacial and foaming properties of proteins have been widely studied, but the reported unique effect of pH, which can be of great interest to applications, has been investigated to a lesser extent. In this paper, we focus on the impact of pH on the stability of black foam films and corresponding foams obtained from solutions of a model globular protein—the whey β-lactoglobulin (BLG). Foam stability was analyzed utilizing three characteristic parameters (deviation time, transition time and half-lifetime) for monitoring the foam decay, while foam film stability was measured in terms of the critical disjoining pressure of film rupture. We attempt to explain correlations between the macroscopic properties of a foam system and those of its major building blocks (foam films and interfaces), and thus, to identify structure-property relationships in foam. Good correlations were found between the stabilities of black foam films and foams, while relations to the properties of adsorption layers appeared to be intricate. That is because pH-dependent interfacial properties of proteins usually exhibit an extremum around the isoelectric point (pI), but the stability of BLG foam films increases with increasing pH (3–7), which is well reflected in the foam stability. We discuss the possible reasons behind these intriguingly different behaviors on the basis of pH-induced changes in the molecular properties of BLG, which seem to be determining the mechanism of film rupture at the critical disjoining pressure.
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Knotek, Vítězslav, Michal Ďurovič und Irena Kučerová. „The Effect of Synthetic Polymer Foams on Cellulosic Material Degradation“. Materials 16, Nr. 3 (31.01.2023): 1210. http://dx.doi.org/10.3390/ma16031210.
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Polymeric materials are widely used at present as auxiliary materials in the preservation of tangible cultural heritage in museums, galleries, or libraries. The desired properties of such materials include chemical inertness and long lifetime, which are verified by accelerated aging tests. This work has tested three color types of PE foam Plastazote® LD45 (white, grey, and black), which is recommended for use in the field of cultural heritage preservation. The volatile organic compounds released from the foams after artificial aging and their influence on lignocellulosic materials were investigated. The cellulosic materials were artificially aged in close contact with the foams. All foams released organic acids ranging from acetic acid to hexanoic acid. White foam released organic acids to an extent higher by an order of magnitude compared to the grey and black types. A great influence of white foam on the properties of cellulosic materials was observed. There were large differences in the rate of degradation between the types of foams tested, indicating the need to develop a test method in order to determine the suitability for use in the preservation of culture heritage objects.
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Алонова, М. В., С. С. Волчков, Д. А. Зимняков, А. А. Исаева, Е. А. Исаева, Е. В. Ушакова und О. В. Ушакова. „Оптическая диффузионная диагностика эволюционирующих полимерных пен“. Журнал технической физики 93, Nr. 4 (2023): 463. http://dx.doi.org/10.21883/jtf.2023.04.55033.279-22.
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Various approaches to the optical diagnostics of evolving polymer foams formed as a result of a decrease in the external pressure according to a given scenario in the "polymer - supercritical fluid" systems are considered.Formed polymer foams are considered as a material platform for the creation of scaffolds for biomedical applications. Diagnostics of the current state of the foam was carried out by statistical analysis of the spatiotemporal fluctuations of the probe laser radiation,multiple scattered in the volume of the evolving foam, or by analyzing the fluorescent response during foaming of the "polymer-fluorophore" mixture, pumped by laser radiation in the absorption band of the fluorophore. A relationship has been established between the average lifetime of dynamic speckles in scattered laser light and a generalized parameter characterizing the foam expansion dynamics. It was also found that the waveguide effect in the walls of the formed pores has a significant influence on the fluorescent response of the evolving foam, leading to an increase in the characteristic dwell time of fluorescence radiation in the walls and, accordingly, to an increase in the contribution of the induced component to the fluorescent response.
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Taherishargh, Mehdi, Bálint Katona, Thomas Fiedler und Imre Norbert Orbulov. „Fatigue properties of expanded perlite/aluminum syntactic foams“. Journal of Composite Materials 51, Nr. 6 (28.07.2016): 773–81. http://dx.doi.org/10.1177/0021998316654305.
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The main purpose of this paper is to present the basic fatigue properties of metal matrix syntactic foams. The investigated syntactic foams consisting of expanded perlite and A356 aluminum matrix were produced using an inert gas pressure infiltration technique. The obtained foams were subjected to cyclic compressive loading in order to investigate their fatigue properties. The standard procedure for cyclic fatigue testing was slightly modified to account for the variation of porosity and strength which is typical for metallic foam samples. This approach allows the direct comparison of the fatigue test results between all investigated samples. Depending on the applied load level, two different failure mechanisms were identified that resulted in characteristic deformation – loading cycle curves. The failure mechanisms were further investigated on the microstructural scale: traces of fatigue beachmarks and extensive plastic deformation were found. Furthermore, Wöhler-like deformation – lifetime diagrams were created in order to predict the expected lifetime of the properties of metal matrix syntactic foams .
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Zhu, Qing You, Weike Peng, Cheng Ji Deng und Hong Xi Zhu. „The Preparation of Porous Andalusite Refractory by Foaming Method“. Advanced Materials Research 881-883 (Januar 2014): 1026–30. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.1026.
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Andalusite can be used to produce porous refractory with the method of foaming and its properties are very good. The bulk density can be controlled by the quantity of foam easily. The compressive strength can reach almost 9 Mpa (1.0g/cm3). The expansion transmit by pores, the remianing andalusite and the transverse growing of mullite crystal are all good for the stabilization of sample during heating. The agglomeration of foam is bad for foaming slurry while stiring, so one way to well-distribute the pores is enhancing the strength of foams. Andalusite can prolong the lifetime of refractory.
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Du, Changling, David Anthony Fikhman und Mary Beth Browning Monroe. „Shape Memory Polymer Foams with Phenolic Acid-Based Antioxidant Properties“. Antioxidants 11, Nr. 6 (01.06.2022): 1105. http://dx.doi.org/10.3390/antiox11061105.
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Phenolic acids (PAs) are natural antioxidant agents in the plant kingdom that are part of the human diet. The introduction of naturally occurring PAs into the network of synthetic shape memory polymer (SMP) polyurethane (PU) foams during foam fabrication can impart antioxidant properties to the resulting scaffolds. In previous work, PA-containing SMP foams were synthesized to provide materials that retained the desirable shape memory properties of SMP PU foams with additional antimicrobial properties that were derived from PAs. Here, we explore the impact of PA incorporation on SMP foam antioxidant properties. We investigated the antioxidant effects of PA-containing SMP foams in terms of in vitro oxidative degradation resistance and cellular antioxidant activity. The PA foams showed surprising variability; p-coumaric acid (PCA)-based SMP foams exhibited the most potent antioxidant properties in terms of slowing oxidative degradation in H2O2. However, PCA foams did not effectively reduce reactive oxygen species (ROS) in short-term cellular assays. Vanillic acid (VA)- and ferulic acid (FA)-based SMP foams slowed oxidative degradation in H2O2 to lesser extents than the PCA foams, but they demonstrated higher capabilities for scavenging ROS to alter cellular activity. All PA foams exhibited a continuous release of PAs over two weeks. Based on these results, we hypothesize that PAs must be released from SMP foams to provide adequate antioxidant properties; slower release may enable higher resistance to long-term oxidative degradation, and faster release may result in higher cellular antioxidant effects. Overall, PCA, VA, and FA foams provide a new tool for tuning oxidative degradation rates and extending potential foam lifetime in the wound. VA and FA foams induced cellular antioxidant activity that could help promote wound healing by scavenging ROS and protecting cells. This work could contribute a wound dressing material that safely releases antimicrobial and antioxidant PAs into the wound at a continuous rate to ideally improve healing outcomes. Furthermore, this methodology could be applied to other oxidatively degradable biomaterial systems to enhance control over degradation rates and to provide multifunctional scaffolds for healing.
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Alonova M.V., Volchkov S.S., Zimnyakov D.A., Isaeva A.A., Isaeva E.A., Ushakova E.V. und Ushakova O.V. „Optical diffusion diagnostics of evolving polymer foams“. Technical Physics 68, Nr. 4 (2023): 432. http://dx.doi.org/10.21883/tp.2023.04.55933.279-22.
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Various approaches to the optical diagnostics of evolving polymer foams formed as a result of a decrease in the external pressure according to a given scenario in the "polymer-supercritical fluid" systems are considered.Formed polymer foams are considered as a material platform for the creation of scaffolds for biomedical applications. Diagnostics of the current state of the foam was carried out by statistical analysis of the spatiotemporal fluctuations of the probe laser radiation,multiple scattered in the volume of the evolving foam, or by analyzing the fluorescent response during foaming of the "polymer-fluorophore" mixture, pumped by laser radiation in the absorption band of the fluorophore. A relationship has been established between the average lifetime of dynamic speckles in scattered laser light and a generalized parameter characterizing the foam expansion dynamics. It was also found that the waveguide effect in the walls of the formed pores has a significant influence on the fluorescent response of the evolving foam, leading to an increase in the characteristic dwell time of fluorescence radiation in the walls and, accordingly, to an increase in the contribution of the induced component to the fluorescent response. Keywords: fluorescent response, speckle correlometry, polylactide, foaming, supercritical carbon dioxide.
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del Castillo-Santaella, Teresa, Yan Yang, Inmaculada Martínez-González, María José Gálvez-Ruiz, Miguel Ángel Cabrerizo-Vílchez, Juan Antonio Holgado-Terriza, Fernando Selles-Galiana und Julia Maldonado-Valderrama. „Effect of Hyaluronic Acid and Pluronic-F68 on the Surface Properties of Foam as a Delivery System for Polidocanol in Sclerotherapy“. Pharmaceutics 12, Nr. 11 (30.10.2020): 1039. http://dx.doi.org/10.3390/pharmaceutics12111039.
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The use of foams to deliver bioactive agents and drugs is increasing in pharmaceutics. One example is the use of foam as a delivery system for polidocanol (POL) in sclerotherapy, with the addition of bioactive compounds to improve the delivery system being a current subject of study. This work shows the influence of two bioactive additives on the structure and stability of POL foam: hyaluronic acid (HA) and Pluronic-F68 (F68). HA is a natural non-surface-active biopolymer present in the extracellular matrix while F68 is a surface-active poloxamer that is biocompatible with plasma-derived fluids. Both additives increase the bulk viscosity of the sample, improving foam stability. However, HA doubled and F68 quadruplicated the foam half lifetime of POL. HA reduced the size and polydispersity of the bubble size distribution and increased the surface elasticity with respect to POL. Both facts have a positive impact in terms of foam stability. F68 also altered bubble structure and increased surface elasticity, again contributing to the enhancement of foam stability. The surface characterization of these systems is important, as in foam sclerotherapy it is crucial to assure the presence of POL at the surface of the bubbles in order to deliver the sclerosant agent in the target vein.
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Pfalzner, Susanne, Shahrzad Dehghani und Arnaud Michel. „Most Planets Might Have More than 5 Myr of Time to Form“. Astrophysical Journal Letters 939, Nr. 1 (27.10.2022): L10. http://dx.doi.org/10.3847/2041-8213/ac9839.
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Abstract The lifetime of protoplanetary disks is a crucial parameter for planet formation research. Observations of disk fractions in star clusters imply median disk lifetimes of 1–3 Myr. This very short disk lifetime calls for planet formation to occur extremely rapidly. We show that young, distant clusters (≤5 Myr, >200 pc) often dominate these types of studies. Such clusters frequently suffer from limiting magnitudes leading to an over-representation of high-mass stars. As high-mass stars disperse their disks earlier, the derived disk lifetimes apply best to high-mass stars rather than low-mass stars. Including only nearby clusters (<200 pc) minimizes the effect of limiting magnitude. In this case, the median disk lifetime of low-mass stars is with 5–10 Myr, thus much longer than often claimed. The longer timescales provide planets ample time to form. How high-mass stars form planets so much faster than low-mass stars is the next grand challenges.
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Zhang, Zhenyu, Guangyao Shen, Rongbo Li, Lei Yuan, Hongfu Feng, Xiuming Chen, Feng Qiu, Guangyin Yuan und Xiaodong Zhuang. „Long-Service-Life Rigid Polyurethane Foam Fillings for Spent Fuel Transportation Casks“. Polymers 16, Nr. 2 (14.01.2024): 229. http://dx.doi.org/10.3390/polym16020229.
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Soft materials bearing rigid, lightweight, and vibration-dampening properties offer distinct advantages over traditional wooden and metal-based fillings for spent fuel transport casks, due to their low density, tunable structure, excellent mechanical properties, and ease of processing. In this study, a novel type of rigid polyurethane foam is prepared using a conventional polycondensation reaction between isocyanate and hydroxy groups. Moreover, the density and size of the pores in these foams are precisely controlled through simultaneous gas generation. The as-prepared polyurethane exhibits high thermal stability exceeding 185 °C. Lifetime predictions based on thermal testing indicate that these polyurethane foams could last up to over 60 years, which is double the lifetime of conventional materials of about 30 years. Due to their occlusive structure, the mechanical properties of these polymeric materials meet the design standards for spent fuel transport casks, with maximum compression and tensile stresses of 6.89 and 1.37 MPa, respectively, at a testing temperature of −40 °C. In addition, these polymers exhibit effective flame retardancy; combustion ceased within 2 s after removal of the ignition source. All in all, this study provides a simple strategy for preparing rigid polymeric foams, presenting them as promising prospects for application in spent fuel transport casks.
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Arangalage, Mélanie, Jean-Philippe Gingras, Nicolas Passade-Boupat, François Lequeux und Laurence Talini. „Asphaltenes at Oil/Gas Interfaces: Foamability Even with No Significant Surface Activity“. Colloids and Interfaces 3, Nr. 1 (21.12.2018): 2. http://dx.doi.org/10.3390/colloids3010002.
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In the oil industry, oil foams can be found at different steps from the crude oil treatment to the gas stations. Their lifetime can sometimes reach several hours and be much longer than the residence times available for gas/liquid separation. However, the conditions of formation and stability of such foams have been poorly studied in the literature, in contrast to the foamability of aqueous systems. On the fields, it is currently observed that crude oils enriched with asphaltenes form particularly stable foams. In this work, we have studied the influence of asphaltenes on the foamability of oil mixtures. All the experiments were performed on model systems of crude oils, that-is-to-say decane/toluene mixtures containing asphaltenes at concentrations ranging from 0.01 to 5 wt%. We in particular demonstrate that, within the investigated concentration range, asphaltenes from two different wells do not have any significant surface active properties despite their contribution to the foamability of oil mixtures. We show that the formation of an asphaltene layer at the interface with air that has been evidenced in the past results from solvent evaporation. Using a recently developed experiment based on the Marangoni effect with our model oils, we demonstrate that asphaltenes are not surface active in those oils. We further characterize the oil foamability by measuring the lifetime of the foam formed by blowing nitrogen through the liquid in a column. At concentrations larger than 1 wt%, asphaltenes significantly enhance the foamability of the oil mixtures. Moreover, the closer the asphaltenes are to their limit of precipitation the larger the foamability. However, we evidence that the oil mixtures themselves foam and we show the importance to consider that effect on the foamability. In addition, we observe that the foamability of the asphaltenes solutions unexpectedly varies with the initial height of the liquid in the column. We suggest that, although not significantly modifying the surface tension, the asphaltenes could be trapped at the oil/gas interface and thus prevent bubble coalescence.
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Zaharia, Sebastian Marian, Mihai Alin Pop und Răzvan Udroiu. „Reliability and Lifetime Assessment of Glider Wing’s Composite Spar through Accelerated Fatigue Life Testing“. Materials 13, Nr. 10 (17.05.2020): 2310. http://dx.doi.org/10.3390/ma13102310.
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The evaluation of the reliability and the lifetime of aerospace components has become an important segment of the design stage. The aeronautical components are subjected to complex, rigorous tests and have a long test life. The main goal in the field of aviation is to have components with high reliability and quality and to meet the mandatory requirements and regulations. The spars are stiffening components positioned along the wing and which take up most of the load and are tested for fatigue over a long period of time. The spar which was analysed in this study has a sandwich structure with GFRP (glass fiber reinforced plastic) skin and foam core. In this paper, the performances in the static and dynamic conditions of the GFRP-foam sandwich structures cut out of the composite spar of a glider were analysed. Additionally, using accelerated techniques based on the three-point fatigue bending test, the main reliability indicators of the GFRP-foam sandwich structures were determined. Using the statistical processing of the experimental data and the Inverse Power Law–Weibull acceleration model, the mean number of cycles to failure, in normal testing conditions of the GFRP-foam specimens was determined, with a value of 102,814. Using the accelerated testing techniques of the GFRP-foam sandwich structures an important decrease of the test time (8.43 times) was obtained.
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Busahmin, Bashir, und Brij Maini. „A Potential Parameter for A Non-Darcy Form of Two-Phase Flow Behaviour, Compressibility Related“. International Journal of Engineering & Technology 7, Nr. 3.3 (21.06.2018): 126. http://dx.doi.org/10.14419/ijet.v7i3.3.14504.
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Numerous scientists did their studies and conducted various laboratory experiments related to a non-Darcy behavior of a two-phase flow for the past thirty years, and made an effort to clarify the behavior. Non-Darcy flow behavior, phenomena occurred in primary recovery method of reservoirs that have an API degree gravity of less than 20. It was confirmed that it results in greater production. The compressibility of foam fits to be the one of the general fundamental factor that directs the lifetime of a non-Darcy form of two phase flow behavior or also is known as the foamy oil. In the process of usual drive depletion, foamy oil featured of low production GOR and high daily production rate. Foamy oil is more compressible than conventional solution gas due to the oil that gas dispersed in it; as a result, oil formation volume factor is much higher than that in conventional oil. This paper represents a laboratory data followed by some of the analysis related to the properties of non-Darcy form of two phase flow and that is the compressibility parameter. The experimental results showed that at different saturation pressures and at a room temperature, the trends fit the expected behavior above the saturation pressures. Moreover, the measurements of live oil compressibility were also attempted below the saturation pressures. It was concluded that other properties such as the viscosity is added a significant effect rather than compressibility in the behavior of what so called foamy oil compared to the presence or absence of asphaltenes and other polar oil components.
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San, Jingshan, Sai Wang, Jianjia Yu, Ning Liu und Robert Lee. „Nanoparticle-Stabilized Carbon Dioxide Foam Used In Enhanced Oil Recovery: Effect of Different Ions and Temperatures“. SPE Journal 22, Nr. 05 (15.02.2017): 1416–23. http://dx.doi.org/10.2118/179628-pa.
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Summary This paper reports the study of the effect of different ions (monovalent, bivalent, and multiple ions) on nanosilica-stabilized carbon dioxide (CO2) foam generation. CO2 foam was generated by coinjecting CO2/5,000 ppm nanosilica dispersion (dispersed in different concentrations of brine) into a sandstone core under 1,500 psi and at different temperatures. A sapphire observation cell was used to determine the foam texture and foam stability. Pressure drop across the core was measured to estimate the foam mobility. The results indicated that more CO2 foam was generated as the sodium chloride (NaCl) concentration increased from 1.0 to 10%. In addition, the foam bubble became smaller and foam stability improved with the increase in NaCl concentration. The CO2-foam mobility decreased from 13.1 to 2.6 md/cp when the NaCl concentration increased from 1 to 10%. For the bivalent ions, the generated CO2-foam mobility decreased from 19.7 to 4.8 md/cp when CaCl2 concentration increased from 0.1 to 1.0%. Synthetic produced water with total dissolved solids (TDS) of 18,583 ppm was prepared to investigate the effect of multiple ions on foam generation. The results showed that stable CO2 foam was generated as the synthetic produced water and nanosilica dispersion/CO2 flowed through a porous medium. The lifetime of the foam was observed to be more than 2 days as the foam stood at room temperature. Mobility of the foam was calculated as 5.2 md/cp.
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Garciadiego Ortega, Eduardo, und Julian RG Evans. „On the energy required to maintain an ocean mirror using the reflectance of foam“. Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 233, Nr. 1 (02.01.2018): 388–97. http://dx.doi.org/10.1177/1475090217750442.
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Among the various interventions proposed to remediate the health and security effects of climate change by solar radiation protection is the proposal to enhance natural ocean whitecap formation. Compared to other solar protection interventions, this is technically simple and quickly terminated. However, it has a drawback: even if the energy be obtained from wind or wave, the power demand to maintain a foam raft determines the capitalization of equipment. The average power demand is inversely related to foam lifetime which can be prolonged by surfactants preferably derived from ingenerate resources. Here, we estimate the associated energy and power demands by identifying the parameters that can be adjusted to moderate the capital cost of implementation. Before dividing by efficiency factors, the range of power demand for an intermediate areal energy requirement of 5 MJ/km2 of ocean varies from 6 to 30 W/km2 for foam lifetime of 10–2 days. The most likely route to deployment is through merchant ship lubrication using bubbly liquids which both reduces fuel consumption and creates an extended wake and is perhaps an example of technical symbiosis.
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Canto, Gizele Scotti do, Janine Treter, Samanta Yang, Gustavo Luís Borré, Maria Paula Garofo Peixoto und George González Ortega. „Evaluation of foam properties of saponin from Ilex paraguariensis A. St. Hil. (Aquifoliaceae) fruits“. Brazilian Journal of Pharmaceutical Sciences 46, Nr. 2 (Juni 2010): 237–43. http://dx.doi.org/10.1590/s1984-82502010000200010.
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Saponins are natural compounds able to form abundant foam, a desirable quality required in some chemical, foods, cosmetic and pharmaceutical processes. Ilex paraguariensis A. St. Hil. (Aquifoliaceae) known as mate, is a South American widely cultivated specie due to the preparation of a tea-like beverage from its leaves. Moreover, its green fruits are a rich source of non-toxic and very low haemolytic saponins. In this study, mate saponin fraction (MSF) was evaluated as a foam former, focusing on its foamability, foam lifetime, and film drainage in the presence of different electrolytes (ionic strength I = 0.024 M). Sodium dodecyl sulphate (SDS) and polysorbate 80 (Poly-80) were used as reference surfactants. The critical micelle concentration (CMC), the minimum attainable surface tension (γCMC), surface excess concentration (Γ) and cross-section molecular surface (A) values of MSF were comparable to those of Poly-80. The foamability of MSF and both reference surfactants was equivalent. The addition of MgCl2 resulted in a negative effect on MSF foamability. The salts NaCl, KBr, and KNO3 exhibited a negative influence on MSF foam lifetime. Similar behavior was observed for MSF film drainage (order of activity: Na2HPO4 > MgCl2 ≈ NaCl ≈ KNO3 > KBr), where a primary fast film drainage rate was followed by film thinning stabilization after around 5 min. The behavior described above seems to be uncorrelated to the solutions' zeta potential.
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Vilkova, Natalya G., Svetlana I. Mishina und Evgeniy D. Deputatov. „FOAMS STABILIZATION BY HYDROPHOBIZED OXIDES OF VARIOUS CHEMICAL NATURE“. IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 63, Nr. 3 (08.03.2020): 23–29. http://dx.doi.org/10.6060/ivkkt.20206303.6126.
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The properties of foams stabilized by hydrophobized titanium oxide and silica are studied. It was shown that when hexylamine was added to silica suspensions (in an amount of ≥ 10 mmol/l), the values of the hydrogen index corresponded to the alkaline region. Moreover, the stability of such foams increases with the increasing concentration of hexylamine and an increase in the relative degree of hydrophobization to ng = 2.75 mmol/g. However, rapid destruction of disperse systems is possible when a certain degree of hydrophobization is achieved (for example, ng≥3 in aerosil suspensions), which is due to aggregation of particles in the initial suspension. The dependence of the lifetime of these dispersed systems on the hydrogen index (pH) is shown. The most stable disperse systems were formed at the pH value of 5, which is close to the isoelectric point of the oxide. Foams obtained from the suspension of the composition: 20% titanium oxide + 76.6 mmol/l hexylamine remained stable for four days or more at pH = 5 and a change in the relative hydrophobicity of the surface (ng) from 0.383 to 1.27 mmol/g. With a significant increase in the degree of hydrophobization of the surface to 4.6 mmol/g and the same pH value, foaming was insignificant (the layer height (h) was 0.2 cm) and life time t≈10 sec. Probably fixing the particles at the liquid-gas interface is an irreversible process only when a certain degree of hydrophobicity is achieved. To explain the possible causes of change stability of the foam containing the titanium dioxide from the pH we have investigated the distribution of particles according to their sizes by the method of sedimentation analysis. It was found that at pH=10 the fractional composition of the suspension with an average radius of 3 µm was equal to 50%, at the same time the maximum radius was 21 µm; the value of the wetting angle of the particles was equal to 40.8º. In an acidic medium (pH=2-3) and at pH=5, the fraction content with an average particle radius of 5 µm was 29% and 30%, respectively. However, low (14.7º) values of the wetting angle at pH=2 can cause low stability of foams in an acidic environment. Highly stable foams were obtained by changing the viscosity of the dispersion medium in suspensions of hydrophobized titanium oxide. When adding glycerol to the suspension composition: 9.0% titanium dioxide + 0.7% hexylamine, pH=9, gel foam was obtained, which was not destroyed within 10 days. However, in an acidic medium with the addition of the same amount of glycerol, the formation of a stable dispersed system was not observed.
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Wan, Yuntian, Xue Lin, Zhongshuai Chang, Xiaohui Dai und Jiangdong Dai. „Chelation Assembly of Cellulose Nanohydrogel onto Flower-Like Structured Foam with Underwater Superoleophobicity for Highly Efficient Oil–Water Separation“. Nano 16, Nr. 06 (18.05.2021): 2150061. http://dx.doi.org/10.1142/s1793292021500612.
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Currently, with the increasingly serious pollution problem of oily wastewater, it is urgent to develop advanced materials and methods. In this work, a Fe(III)-CMC@Ni(OH)2@Ni composite foam with superhydrophilic and underwater superoleophobicity was fabricated by an in situ growth of flower-like Ni(OH)2 nanoparticles and chelated assembly of Fe(III)-CMC nanohydrogel via a layer-by-layer self assembly using [Formula: see text] ion and carboxymethyl cellulose (CMC). The composite foam could separate various oil/water mixtures and exhibited excellent efficiency over 99%. This foam possessed ultrahigh water flux (220000[Formula: see text]L [Formula: see text] [Formula: see text] and better resistant to penetration pressure (1.3[Formula: see text]kPa). After 30 cycles, the oil–water separation performance reduced only 0.5%, but the foam structure was still stable that guarantees a better lifetime. Besides, this composite foam showed anti-fouling, unique durability and excellent corrosion resistance performance. Taking into account all good properties, Fe(III)-CMC@Ni(OH)2@Ni composite foam was expected to be a potential candidate for responding to all kinds of complex oily wastewater conditions.
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Su, Mingyu, Shengli Zhu, Zhenduo Cui, Zhaoyang Li, Shuilin Wu, Meiqing Guo, Hui Jiang und Yanqin Liang. „A self-supported FeNi layered double hydroxide anode with high activity and long-term stability for efficient oxygen evolution reaction“. Sustainable Energy & Fuels 5, Nr. 12 (2021): 3205–12. http://dx.doi.org/10.1039/d1se00558h.
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The FeNi-layered double hydroxides nanoparticles with high oxygen evolution reaction activity and prominent catalytic lifetime were first self-assembled on FeNi foam. This catalyst has a promising future for large-scale non-precious materials in the industry.
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Callaghan, Adrian H., Grant B. Deane und M. Dale Stokes. „Two Regimes of Laboratory Whitecap Foam Decay: Bubble-Plume Controlled and Surfactant Stabilized“. Journal of Physical Oceanography 43, Nr. 6 (01.06.2013): 1114–26. http://dx.doi.org/10.1175/jpo-d-12-0148.1.
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Abstract A laboratory experiment to quantify whitecap foam decay time in the presence or absence of surface active material is presented. The investigation was carried out in the glass seawater channel at the Hydraulics Facility of Scripps Institution of Oceanography. Whitecaps were generated with focused, breaking wave packets in filtered seawater pumped from La Jolla Shores Beach with and without the addition of the surfactant Triton X-100. Concentrations of Triton X-100 (204 μg L−1) were chosen to correspond to ocean conditions of medium productivity. Whitecap foam and subsurface bubble-plume decay times were determined from digital images for a range of wave scales and wave slopes. The experiment showed that foam lifetime is variable and controlled by subsurface bubble-plume-degassing times, which are a function of wave scale and breaking wave slope. This is true whether or not surfactants are present. However, in the presence of surfactants, whitecap foam is stabilized and persists for roughly a factor of 3 times its clean seawater value. The range of foam decay times observed in the laboratory study lie within the range of values observed in an oceanic dataset obtained off Martha’s Vineyard in 2008.
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MAZARI, FUNDA BUYUK, ADNAN MAZARI, DAVID CIRKL und ANTONIN HAVELKA. „Comparison of different interlining materials of car seat cover under repeated loadings“. Industria Textila 71, Nr. 03 (28.06.2020): 199–203. http://dx.doi.org/10.35530/it.071.03.1704.
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In this article, four most commonly used interlining materials (3D spacer fabric, non-woven felt, reticulated foam, and classic Poly-Urethane foam) are tested for comfort and durability. All four layers are tested initially for the air and moisture permeability, then for water vapour permeability under loading and finally tested for compressibility and durability. The repeated loading equivalent to real human pressure was inserted on the samples for 40,000 times to analyse the effect of repeated compression on the interlining materials. This research work gives a very in-depth knowledge of performance of car seat interlining material related to thermophysiological comfort and durability/lifetime.
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Hofmann, Matthias J., und Hubert Motschmann. „Measurement of the lifetime of individual foam lamellae“. Review of Scientific Instruments 87, Nr. 9 (September 2016): 094101. http://dx.doi.org/10.1063/1.4962404.
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Cho, Jae Ung, Li Yang Xie, Chong Du Cho und Sang Kyo Lee. „Crack Propagation of CCT Foam Specimen under Impact Fatigue“. Advanced Materials Research 118-120 (Juni 2010): 32–36. http://dx.doi.org/10.4028/www.scientific.net/amr.118-120.32.
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The objective of this study is to investigate the effect of the low or high strain rate on the impact fatigue properties of the nickel foam material and to understand the lifetime of this material which is subjected to the repeated impacts at different energy levels. Failures of foam materials under single and repeated impacts analogous to fatigue are essential to designers and users in military and aerospace structures. The material failure induced by repeated impact loading becomes a critical issue because of significant loss of stiffness and compressive strength in the foam material. Testing methods to study impact(that is, high strain rate) fatigue are quite numerous; no single standard testing procedure is defined for studying the impact fatigue property of a material. The increasing application of foam material in aerospace structures, owing to high specific stiffness and strength has attracted a great concern about the high sensitivity to impact damage introduced during manufacture or in service, and the effects of such damage on structural degradation. To investigate this issue, this study sets up an experimental procedure to determine the impact fatigue properties of nickel foam material. This study performs both experimental and numerical investigations to catch the impact fatigue behavior of nickel foam with open type. Design life and probability of failure or survival at specified life can be calculated so that the fatigue life of nickel core material subjected to repeated impact loading is predicted.
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Jeffs, G. M. F., J. D. Rosbotham, B. Mathys und R. Frigo. „Polyurethane Rigid Foam Systems for Metal-Faced Sandwich Panels for the 1990s“. Cellular Polymers 10, Nr. 6 (November 1991): 439–51. http://dx.doi.org/10.1177/026248939101000601.
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Sandwich panels with polyurethane rigid foam cores are important building elements for a wide variety of applications. They are used for the cost effective construction of industrial and commercial buildingsand in many stages of the food chain, including cold storage, cold rooms and refrigerated transport containers and trucks. The blowing agent used in the foam systems has traditionally been CFC-ll. This has contributed to the excellent thermal resistance of the panels but its use will be phased out by the year 2000. Foam systems have been developed based on a wide variety of alternatives. These are designed to suit various national and international CFC phase-out schedules. These include systems based on 100% CO2, HCFC-22, HCFC-123 and HCFC-141b. In all cases the formulations have been based around the particular blowingagent to obtain the best combination of processing, physical and thermal resistance properties. Because the HCFCs are now accepted to be transitional substances with a finite production lifetime, the foam systems based on HCFC-123 and -141b are designed to be “drop-In” replacements for those based on CFC-ll. This means that all changes are incorporated into the foam system rather than into the production process and that thermal resistance with those blowing agents equals that for systems based on CFC-11. These panels have an important structural role to play and, in addition to the retention of foam strength, the adhesion between the foam and facing plays an important role in the overall performance of the panel. The parameters affecting adhesion have been investigated with the alternative systems and optimised processing conditions determined. A family of foam systems has been developed to serve the metal-faced sandwich panel industry through the 1990s.
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Ren, Zheng De, Sheng Qin Zhang, Zhu Bing Gao und Qian Ying Zhang. „Thermodynamics and Dynamics of Nitrogen Increasing in LF Refining Process“. Advanced Materials Research 538-541 (Juni 2012): 2387–91. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.2387.
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Nitrogen is one of harmful elements in liquid steel. Reducing nitrogen quantity is required for making high-grade steel. This paper analyzes the reaction mechanism of nitrogen increasing through the methods of metallurgical thermodynamics and dynamics. In liquid steel dissolved nitrogen and nitrides are the main forms of nitrogen. The factors of influence on nitrogen increasing are temperature, kinds and quantity of the alloying elements in the liquid steel, , the lifetime of foam in foam slag, the quantity of flow of argon and so on. Analytical results of metallurgical thermodynamics and dynamics are verified by measuring nitrogen content in the links of LF refining process of new developed area of Chongqing steel and iron Co.Ltd.
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Gonzalez Viejo, Claudia, Christopher H. Caboche, Edward D. Kerr, Cassandra L. Pegg, Benjamin L. Schulz, Kate Howell und Sigfredo Fuentes. „Development of a Rapid Method to Assess Beer Foamability Based on Relative Protein Content Using RoboBEER and Machine Learning Modeling“. Beverages 6, Nr. 2 (03.05.2020): 28. http://dx.doi.org/10.3390/beverages6020028.
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Foam-related parameters are associated with beer quality and dependent, among others, on the protein content. This study aimed to develop a machine learning (ML) model to predict the pattern and presence of 54 proteins. Triplicates of 24 beer samples were analyzed through proteomics. Furthermore, samples were analyzed using the RoboBEER to evaluate 15 physical parameters (color, foam, and bubbles), and a portable near-infrared (NIR) device. Proteins were grouped according to their molecular weight (MW), and a matrix was developed to assess only the significant correlations (p < 0.05) with the physical parameters. Two ML models were developed using the NIR (Model 1), and RoboBEER (Model 2) data as inputs to predict the relative quantification of 54 proteins. Proteins in the 0–20 kDa group were negatively correlated with the maximum volume of foam (MaxVol; r = −0.57) and total lifetime of foam (TLTF; r = −0.58), while those within 20–40 kDa had a positive correlation with MaxVol (r = 0.47) and TLTF (r = 0.47). Model 1 was not as accurate (testing r = 0.68; overall r = 0.89) as Model 2 (testing r = 0.90; overall r = 0.93), which may serve as a reliable and affordable method to incorporate the relative quantification of important proteins to explain beer quality.
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Mironov, Vladimir, Lukashuk und Dmitriy Ogorelkov. „Two Approaches to the Problem of High-cycle Fatigue of Materials and Structures“. MATEC Web of Conferences 253 (2019): 01004. http://dx.doi.org/10.1051/matecconf/201925301004.
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Creation of new types of materials and development of new methods aimed at extending the lifetime of structures are two interconnected approaches to solve the problem of metallic structures fatigue. The paper considers a method for estimating the efficiency of damping implemented in metallic structures by means of energy-intensive materials. The results of comparative calculation are given on the ultimate number of transverse vibration cycles in bridge girders. The calculation uses a linear hypothesis of fatigue-caused damage summation and a model of cyclic material degradation. Notable increase of the vibration decrement for foam-filled metallic structures is predicted, with the lifetime of products lengthening as a result.
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Journal, Baghdad Science. „Synthesis New Liquid Selective Electrodes of Ciprofloxacin Hydrochloride for Determination Ciprofloxacin in Pure form and Pharmaceuticals Preparation.“ Baghdad Science Journal 14, Nr. 4 (03.12.2017): 787–92. http://dx.doi.org/10.21123/bsj.14.4.787-792.
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New membrane electrodes for determination of ciprofloxacin hydrochloride were prepared depending on ciprofloxacin hydrochloride - phosphotungstic acid (CFH-PT) as an active material and these electrodes were made with three plasticizers: Di-octylphenylphosphonate(DOPH), Di-butyl phosphate (DBP)Tri-n-butyl phosphate(TBP), in PVC matrix. One of the ciprofloxacin electrodes was gave Nernstian slope equal to 57.21 mV/ decade for DOPH membrane with concentration range from 1.5×10-5 to1.0×10-1 M, and detection limit equal to 1.5×10-6 M .Lifetime was 93 days. Non- Nernstian responses equal to 39.40 and 30.70 mV/ decade for membranes DBP, TBP, respectively. These electrodes were gave concentration range from 1.0× 10-5 to 1.0×10-2 and from 4.0×10-5 to 1.0×10-2 M,respectively. Detection limits were 7.0×10-6, and 1.7×10-6M, respectively. Lifetimes were 5,2 days, respectively. Also selectivity, influence of PH and samples analysis of ciprofloxacin in a pharmaceutical preparations were studied.
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Toubia, Elias A., Sadra Emami und Donald Klosterman. „Degradation mechanisms of balsa wood and PVC foam sandwich core composites due to freeze/thaw exposure in saline solution“. Journal of Sandwich Structures & Materials 21, Nr. 3 (28.04.2017): 990–1008. http://dx.doi.org/10.1177/1099636217706895.
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Structural engineers commonly use balsa wood and PVC foam as core materials for sandwich composite structures. These structures are frequently exposed to thermal cycling in sea water. The long-term performance and damage mechanism of these composite sandwich structures under such environmental conditions are still unclear. To simulate these effects, sandwich panels using balsa wood (SB100) and foam core (Airex C70.55) with fiber glass/vinyl ester face sheets were exposed to 100 days of freeze/thaw exposure (−20℃ to 20℃). The freezing and thawing occurred in presence of a saline solution. A total of 150 samples were tested for core shear, core compression, and peel tests. Results confirmed that exposure reduced the balsa wood core shear strength by 14%, compression strength by 36%, and compression modulus by 33%. Interestingly, the PVC foam core shear modulus increased by 25% after exposure, whereas the compression modulus reduced by 12%. Simulated lifetime core shear fatigue curves were developed and evaluated. Additional testing techniques such as scanning electron microscopy, optical microscopy, dynamical mechanical analysis, and X-ray computed tomography were used to rationalize the static and fatigue behavior of the core materials.
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Karalko, Anton, Peter Keša, Frantisek Jelínek, Luděk Šefc, Jan Ježek, Pavel Zemánek und Tomáš Grus. „In Vivo Contrast Imaging of Rat Heart with Carbon Dioxide Foam“. Sensors 22, Nr. 14 (08.07.2022): 5124. http://dx.doi.org/10.3390/s22145124.
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Widely used classical angiography with the use of iodine contrast agents is highly problematic, particularly in patients with diabetes mellitus, cardiac and pulmonary diseases, or degree III or IV renal insufficiency. Some patients may be susceptible to allergic reaction to the iodine contrast substance. The intravenous injection of a bolus of CO2 (negative contrast) is an alternative method, which is, however, currently only used for imaging blood vessels of the lower limbs. The aim of our project was to design and test on an animal model a methodology for injecting the CO2 foam which would minimize the possibility of embolization of the brain tissue and heart infarction, leading to their damage. This is important research for the further promotion of the use of CO2, which is increasingly important for endovascular diagnosis and treatment, because carbon-dioxide-related complications are extremely rare. CO2 foam was prepared by the rapid mixing in a 2:1 ratio of CO2 and fetal bovine serum (FBS)-enriched Dulbecco’s Modified Eagle Medium (DMEM). Freshly prepared CO2 foam was administered into the catheterized rat tail vein or cannulated rat abdominal aorta and inferior vena cava (IVC). CO2 foam was compared with commercially available microbubbles (lipid shell/gas core). The rat heart in its parasternal long axis was imaged in B-Mode and Non-linear Contrast Mode before/during and after the contrast administration. Samples of the brain, heart and lungs were collected and subjected to histological examination. The non-linear contrast imaging method enables the imaging of micron-sized gas microbubbles inside a rat heart. The significantly shorter lifetime of the prepared CO2 foam is a benefit for avoiding the local ischemia of tissues.
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Reichenbach, Michael. „"Our foam materials help to extend the lifetime of batteries"“. ATZ worldwide 124, Nr. 12 (25.11.2022): 22–25. http://dx.doi.org/10.1007/s38311-022-1427-1.
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Treter, Janine, Maria P. G. Peixoto, George G. Ortega und Gizele S. Canto. „Foam-forming properties of Ilex paraguariensis (mate) saponin: foamability and foam lifetime analysis by Weibull equation“. Química Nova 33, Nr. 7 (2010): 1440–43. http://dx.doi.org/10.1590/s0100-40422010000700003.
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Wagner, Martin, Andreas Mösenbacher, Marion Eiber, Martin Hoyer, Marco Riva und Hans-Jürgen Christ. „Thermomechanical Fatigue of Lost Foam Cast Al–Si Cylinder Heads—Assessment of Crack Origin Based on the Evaluation of Pore Distribution“. Metals 9, Nr. 8 (26.07.2019): 821. http://dx.doi.org/10.3390/met9080821.
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In automotive cylinder heads, thermomechanical fatigue (TMF) leads to crack initiation within the critical loaded sections. This effect becomes even more relevant in lost foam cast cylinder heads since its system-dependent porosity shows a significant influence on the lifetime under TMF loading. This work covers the identification of a criterion for crack initiation in order to provide the basis for an effective quality control with improved statistical safety by nondestructive testing. Specimens extracted from lost foam cylinder heads were investigated by uniaxial TMF tests, X-ray micro computer tomography (μCT), and scanning electron microscopy (SEM). Due to pore analyses on a global and local scale, it is concluded that pore networks are crucial for crack initiation. Thus, a tool for computation of pore accumulations from μCT data containing interaction criteria by Murakami was developed in order to assess the crack origin. The consideration of pore accumulations significantly improves the predictive accuracy compared to the consideration of single pores.
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Yin, Zhengyu, Rui He, Huaibin Xue, Jingjian Chen, Yue Wang, Xiaoxiao Ye, Nengneng Xu, Jinli Qiao und Haitao Huang. „A bimetallic-activated MnO2 self-assembly electrode with a dual heterojunction structure for high-performance rechargeable zinc-air batteries“. Energy Materials 2, Nr. 3 (2022): 200021. http://dx.doi.org/10.20517/energymater.2022.17.
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A major challenge in developing zinc-air batteries (ZABs) is to exploit suitable cathodes to efficiently accelerate the key electrocatalytic processes involved. Herein, a bifunctional oxygen catalytic self-supported MnO2-based electrode is designed that displays superior oxygen reduction and evolution reaction performance over noble metal electrodes with a total overpotential of 0.69 V. In addition, the as-synthesized NiCo2O4@MnO2/carbon nanotube (CNT)-Ni foam self-supported electrode can be directly used as an oxygen electrode without externally adding carbon or a binder and shows reasonable battery performance with a high peak power density of 226 mW cm-2 and a long-term charge-discharge cycling lifetime (5 mA for 160 h). As expected, the rapid oxygen catalytic intrinsic kinetics and high battery performance of the NiCo2O4@MnO2/CNTs-Ni foam electrode originates from the unique three-dimensional hierarchical structure, which effectively promotes mass transfer. Furthermore, the CNTs combined with Ni foam form a unique “meridian” conductive structure that enables rapid electron conduction. Finally, the abundant Mn3+ active sites activated by bimetallic ions shorten the oxygen catalytic reaction distance between the active sites and reactant and reduce the surface activity of MnO2 for the O, OH, and OOH species. This work not only offers a high-performance bifunctional self-supported electrode for ZABs but also opens new insights into the activation of Mn-based electrodes.
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Kashchiev, D., und D. Exerowa. „Lifetime of a Foam Bilayer in Contact with an Insoluble Monolayer“. Journal of Colloid and Interface Science 203, Nr. 1 (Juli 1998): 146–52. http://dx.doi.org/10.1006/jcis.1998.5527.
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Figueroa, Evaristo, und Basir Shafiq. „Shift in failure modes in foam core sandwich composites subject to repeated slamming on water“. Journal of the Mechanical Behavior of Materials 22, Nr. 1-2 (01.06.2013): 73–80. http://dx.doi.org/10.1515/jmbm-2013-0012.
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AbstractA test program designed and carried out to mimic the repeated impact of the bow section of fast-moving small boats on the ocean surface provided some unique observations in terms of failure mode transition. Damage progression and modes of failure were evaluated for two types of sandwich composites with comparable global strength and stiffness but different foam density and facesheet strength. Testing was performed on flat rectangular specimens that contained symmetric semi-elliptical edge flaws produced near the end of the specimen held by the rotating cam. Type 1 specimens (softer core/stronger facesheet) consistently failed by interface and through-the-thickness core shear, independent of the flaw size. In contrast, a gradual decrease in flaw size in Type 2 specimens (denser core/weaker facesheet) produced a striking transition in the mode of failure from local buckling in the vicinity of the flaw site along with exponentially increasing lifetime, to interface shear failure at the free end accompanied by a dramatic drop in lifetime. The lifetime of Type 2 specimens was more than two orders of magnitude greater than that of Type 1 specimens.
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de la Paz, Ismael, und Basir Shafiq. „Creep relaxation and fully reversible creep of foam core sandwich composites in seawater“. Journal of the Mechanical Behavior of Materials 24, Nr. 5-6 (01.12.2015): 187–94. http://dx.doi.org/10.1515/jmbm-2015-0019.
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AbstractFoam core sandwich composites were subjected to (i) creep to failure, (ii) cyclic creep-relaxation and (iii) fully reversible cyclic creep loading in seawater in order to mimic an actual ship hull’s service lifetime scenario. The results indicate a strong dependence of lifetime on the mode of loading. A significant reduction in the overall life was observed under cyclic creep as compared with the conventional creep to failure. Creep relaxation (R=1) tests were performed at loading-relaxation periods of 24/24, 24/12, 24/6, 12/12 and 6/6 h, while the fully reversible (R=-1) creep tests were conducted at loading-reversed loading times of 36/36, 24/24, 12/12, 6/6, and 3/3 h. The results suggest that creep-relaxation lifetime characteristics depend predominantly on the relaxation time as opposed to loading times, i.e. longer relaxation periods lead to shorter life. Whereas, fully reversible creep appears to be dependent upon the number of reversals whereby, life is observed to reduce as the number of reversals increase. These significant observations are explained in terms of various possible paths to interface cell wall collapse. Modes of failure were predominantly indentation and core compression in the vicinity of the loading site.
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Feucht, Dominik C., Matthias J. Hofmann und Hubert Motschmann. „Simultaneous measurement of the thickness and the lifetime of a foam lamella“. Review of Scientific Instruments 90, Nr. 12 (01.12.2019): 124102. http://dx.doi.org/10.1063/1.5119192.
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Yang, Xin, und Henry Potter. „A Novel Method to Discriminate Active from Residual Whitecaps Using Particle Image Velocimetry“. Remote Sensing 13, Nr. 20 (11.10.2021): 4051. http://dx.doi.org/10.3390/rs13204051.
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Whitecap foam generated by wind-driven wave breaking is distinguished as either active (stage A) or residual (stage B). Discrimination of whitecap stages is essential to quantify the influence of whitecaps on the physical and chemical processes at the marine boundary layer. This study provides a novel method to identify whitecap stages based on visible imagery using particle image velocimetry (PIV). Data used are from a Gulf of Mexico cruise where collocated infrared (IR) and visible cameras simultaneously recorded whitecaps. IR images were processed by an established thresholding method to determine stage A lifetime from brightness temperature. The visible images were also filtered using a thresholding method and then processed using PIV to estimate the average whitecap velocity. A linear relationship was established between the lifetime of stage A and the timescale of averaged velocity. This novel method allows stage A whitecap lifetime to be determined using whitecap velocity and provides an objective approach to separate whitecap stages. This method paves the way for future research to easily quantify whitecap stages using affordable off-the-shelf video cameras. Results, which include evidence that whitecaps stop advancing before stage A ends and may be an indication of bubble plume degassing, are discussed.
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Sun, Luxi, und Animesh JK Patel. „Outcomes of split vs full-thickness skin grafts in scalp reconstruction in outpatient local anaesthetic theatre“. Scars, Burns & Healing 7 (Januar 2021): 205951312110565. http://dx.doi.org/10.1177/20595131211056542.
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Background Surgical excision remains the cornerstone of simultaneous diagnosis and treatment of suspicious skin lesions, and the scalp is a high-risk area for skin cancers due to increased cumulative lifetime ultraviolet (UV) exposure. Due to the inelasticity of scalp skin, most excisions with predetermined margins require reconstruction with skin grafting. Methods A retrospective single-centre cohort study was performed of all patients undergoing outpatient local anaesthetic scalp skin excision and skin graft reconstruction in the Plastic Surgery Department at Addenbrookes Hospital over a 20-month period between 1 April 2017 and 1 January 2019. In total, 204 graft cases were collected. Graft reconstruction techniques included both full-thickness and split-thickness skin grafts. Statistical analysis using Z tests were used to determine which skin grafting technique achieved better graft take. Results Split-thickness skin grafts had a statistically significant ( P = 0.01) increased average take (90%) compared to full-thickness skin grafts (72%). Using a foam tie-over dressing on the scalp led to a statistically significant ( P = 0.000036) increase in skin graft take, from 38% to 79%. Conclusion In skin graft reconstruction of scalp defects after skin cancer excision surgery, split skin grafts secured with foam tie-over dressings are associated with superior outcomes compared to full-thickness skin grafts or grafts secured with sutures only.