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Статті в журналах з теми "Reactant delivery"
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Clausmeyer, Jan, Alexander Botz, Denis Öhl, and Wolfgang Schuhmann. "The oxygen reduction reaction at the three-phase boundary: nanoelectrodes modified with Ag nanoclusters." Faraday Discussions 193 (2016): 241–50. http://dx.doi.org/10.1039/c6fd00101g.
Повний текст джерелаАнотація:
Silver nanoclusters are deposited on bifunctional Θ-shaped nanoelectrodes consisting of a carbon nanoelectrode combined with a hollow nanopipette. The Θ-nanoelectrodes are used as model systems to study interfacial mass transport in gas diffusion electrodes and in particular oxygen-depolarized cathodes (ODC) for the oxygen reduction reaction (ORR) in chlor-alkali electrolysers. By local delivery of O2 gas to the electroactive Ag nanoclusters through the adjacent nanopipette, enhanced currents for the ORR at the Ag nanoparticles are recorded which are not accountable when considering the low solubility and slow diffusion of O2 in highly alkaline media. Instead, local oversaturation of O2 leads to current enhancement at the Ag nanoclusters. Due to the intrinsic high mass transport rates at the nanometric electrodes accompanied by local delivery of reactants, the method generally allows to study electrochemical reactions at single nanoparticles beyond the limitations induced by slow diffusion and low reactant concentration. Kinetic and mechanistic information, for instance derived from Tafel slopes, can be obtained from kinetic regimes not accessible to standard techniques.
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Shafiq, Kanza, Asif Mahmood, Mounir M. Salem-Bekhit, Rai Muhammad Sarfraz, Alanood S. Algarni, Ehab I. Taha, Ahd A. Mansour, Sami Al Zahrani та Yacine Benguerba. "Development and Optimization of Tamarind Gum-β-Cyclodextrin-g-Poly(Methacrylate) pH-Responsive Hydrogels for Sustained Delivery of Acyclovir". Pharmaceuticals 15, № 12 (8 грудня 2022): 1527. http://dx.doi.org/10.3390/ph15121527.
Повний текст джерелаАнотація:
Acyclovir has a short half-life and offers poor bioavailability. Its daily dose is 200 mg five times a day. A tamarind gum and β-cyclodextrin-based pH-responsive hydrogel network for sustained delivery of acyclovir was developed using the free-radical polymerization technique. Developed networks were characterized by FTIR, DSC, TGA, PXRD, EDX, and SEM. The effect of varying feed ratios of polymers, monomers, and crosslinker on the gel fraction, swelling, and release was also investigated. FTIR findings confirmed the compatibility of the ingredients in a new complex polymer. The thermal stability of acyclovir was increased within the newly synthesized polymer. SEM photomicrographs confirmed the porous texture of hydrogels. The gel fraction was improved (from 90.12% to 98.12%) with increased reactant concentrations. The pH of the dissolution medium and the reactant contents affected swelling dynamics and acyclovir release from the developed carrier system. Based on the R2 value, the best-fit model was zero-order kinetics with non-Fickian diffusion as a release mechanism. The biocompatibility of the developed network was confirmed through hematology, LFT, RFT, lipid profile, and histopathological examinations. No sign of pathology, necrosis, or abrasion was observed. Thus, a pH-responsive and biocompatible polymeric system was developed for sustained delivery of acyclovir to reduce the dosing frequency and improve patient compliance.
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Jahedbozorgan, Tayebeh, Minoo Yaghmaei, and Maryam Naserieh. "Comparison of serum ferritin levels in pregnant women with preterm and term deliveries." Immunopathologia Persa 6, no. 2 (May 9, 2020): e25-e25. http://dx.doi.org/10.34172/ipp.2020.25.
Повний текст джерелаАнотація:
Introduction: Despite high rates of mortality and morbidity due to preterm delivery, none of the diagnostic and biochemical tests could help to accurately identify the cases at risk of preterm delivery. Objectives: Since ferritin is an acute phase reactant, this study aimed to evaluate serum ferritin levels in women with preterm and term delivery. Methods: This study was conducted on 150 women with preterm delivery (50 cases in each of the groups 24-30, 30-34, and 34-37 weeks of pregnancy), 150 women with term delivery, and 150 pregnant women who were between 24-37 weeks of pregnancy (same as preterm delivery groups). Results: The mean ferritin level in all preterm groups was significantly higher than that in the term group, but there was no difference among the preterm groups. In addition, ferritin level in each preterm group was significantly higher than those in the normal pregnancy group at the same gestational age. In preterm deliveries, ferritin levels were significantly higher in cases with prelabor rupture of membranes (PROM) or with a prolonged leakage (longer than 12 hours). In addition, in patients with PROM or prolonged leakage, ferritin levels were significantly higher in preterm deliveries than in term deliveries. A ferritin level of 37.5 ng/mL recognized as the best cut-off for preterm delivery, as compared with term delivery, and its sensitivity, specificity, and diagnostic accuracy was 78.7%, 68.7%, and 73.6%, respectively. Conclusion: The findings of the present study showed that serum ferritin level can be used to find patients at risk of preterm delivery.
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Chadwick, Eric Alexander, Pranay Shrestha, Harsharaj Birendrasingh Parmar, Aimy Bazylak, and Volker Schulz. "Biomimetic Microchannels for the Passive Management of Water in PEM Fuel Cells." ECS Meeting Abstracts MA2022-02, no. 40 (October 9, 2022): 1455. http://dx.doi.org/10.1149/ma2022-02401455mtgabs.
Повний текст джерелаАнотація:
In polymer electrolyte membrane (PEM) fuel cells, the bipolar plates (BPPs) are responsible for the transport of reactants (via embedded flow fields), heat, and electrons, and account for 18-28% of the cost of fuel cell systems1. Thus, there is a great opportunity to improve the energy density of PEM fuel cells by improving the functions of BPPs, such as providing liquid water management, which affects reactant delivery and heat distribution. Previous work has shown that mass transport losses due to liquid water accumulation under the lands and channels of PEM fuel cell flow fields limit the power density of fuel cells2. Previous work has demonstrated that water will preferentially flow in a desired direction by implementing biomimetic wicking structures3; however, such wicking structures have not been previously implemented into a fuel cell. Furthermore, the design of BPPs has not been tailored to target areas of water accumulation. In this work, biomimetic geometries that promote passive unidirectional water wicking were implemented in a PEM fuel cell flow field to enhance liquid water removal and the distribution of reactant gases. The BPPs were characterized via constant current electrochemical testing and electrochemical impendence spectroscopy (EIS) to elucidate the dominant losses observed during operation. Operando synchrotron X-ray radiography was performed during the electrochemical testing in order to quantify the liquid water accumulation on the cathode side of the PEM fuel cell. The spatial distribution of liquid water was combined with EIS characterizations to explain the performance of the designs at high current densities, where mass transport losses typically dominate. The results from this work can be used to further optimize the design of PEM fuel cell bipolar plates in order to produce more efficient fuel cell stacks and drive PEM fuel cells into the global energy market. References Y. Wang, D. F. Ruiz Diaz, K. S. Chen, Z. Wang, and X. C. Adroher, Materials Today, 32, 178–203 (2020). N. Ge et al., Electrochimica Acta, 328, 135001 (2019). J. Feng and J. P. Rothstein, Journal of Colloid and Interface Science, 404, 169–178 (2013).
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GUO, LIN, WENCE DING, and FANDIAN MENG. "FABRICATION AND IN VITRO EVALUATION OF FOLATE-MODIFIED IRON FERRITE NANOPARTICLES WITH HIGH DOXORUBICIN LOADING FOR RECEPTORS-MAGNETIC-GUIDED DRUG DELIVERY." Nano 09, no. 02 (February 2014): 1450021. http://dx.doi.org/10.1142/s1793292014500210.
Повний текст джерелаАнотація:
Folate-modified iron ferrite nanoparticles with high doxorubicin loading (FDMP) were developed for dual targeting of tumor cells. Large quantities of doxorubicin and folate ligand were chemically coupled to the synthesized dual-functional magnetic nanoparticles by using the multihand cross-linker poly-L-glutamic acid. FDMP exhibits high drug loading ability, narrow size distribution and pH sensitivity to drug release. The drug loading ratio and the magnetic response can be adjusted by controlling the reactant ratio. FDMP possesses high magnetic-guided ability and exhibits enhanced uptake by folate receptors expressing tumor cells and increased cancer cell cytotoxicity.
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Lewinski, Krzysztof A., and Andrzej P. Jaworski. "Analysis of Flow Errors and Resulting Stoichiometry Uncertainties while Using a Fuel Cell Stack Test Station for Reactant Delivery and Control." ECS Transactions 5, no. 1 (December 19, 2019): 241–52. http://dx.doi.org/10.1149/1.2729006.
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Tanaka, Hiroki, Tatsunari Takahashi, Manami Konishi, Nae Takata, Masaki Gomi, Daiki Shirane, Ryo Miyama, et al. "Self‐Degradable Lipid‐Like Materials Based on “Hydrolysis accelerated by the intra‐Particle Enrichment of Reactant (HyPER)” for Messenger RNA Delivery." Advanced Functional Materials 30, no. 34 (June 23, 2020): 1910575. http://dx.doi.org/10.1002/adfm.201910575.
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Zhang, Qiang, Yohanes Pramudya, Wolfgang Wenzel, and Christof Wöll. "Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films." Nanomaterials 11, no. 7 (June 22, 2021): 1631. http://dx.doi.org/10.3390/nano11071631.
Повний текст джерелаАнотація:
Metal organic frameworks have emerged as an important new class of materials with many applications, such as sensing, gas separation, drug delivery. In many cases, their performance is limited by structural defects, including vacancies and domain boundaries. In the case of MOF thin films, surface roughness can also have a pronounced influence on MOF-based device properties. Presently, there is little systematic knowledge about optimal growth conditions with regard to optimal morphologies for specific applications. In this work, we simulate the layer-by-layer (LbL) growth of the HKUST-1 MOF as a function of temperature and reactant concentration using a coarse-grained model that permits detailed insights into the growth mechanism. This model helps to understand the morphological features of HKUST-1 grown under different conditions and can be used to predict and optimize the temperature for the purpose of controlling the crystal quality and yield. It was found that reactant concentration affects the mass deposition rate, while its effect on the crystallinity of the generated HKUST-1 film is less pronounced. In addition, the effect of temperature on the surface roughness of the film can be divided into three regimes. Temperatures in the range from 10 to 129 °C allow better control of surface roughness and film thickness, while film growth in the range of 129 to 182 °C is characterized by a lower mass deposition rate per cycle and rougher surfaces. Finally, for T larger than 182 °C, the film grows slower, but in a smooth fashion. Furthermore, the potential effect of temperature on the crystallinity of LbL-grown HKUST-1 was quantified. To obtain high crystallinity, the operating temperature should preferably not exceed 57 °C, with an optimum around 28 °C, which agrees with experimental observations.
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Chen, Xiaolong, Yutong Zheng, Yuzhi Jiang, Yaxiong Ji, Shifeng Wang, and Fujia Yu. "Simple and Rapid High-Yield Synthesis of Sub-100 nm Nano-SiO2·0.5H2O Particles Based on Wollastonite." Coatings 9, no. 10 (October 13, 2019): 662. http://dx.doi.org/10.3390/coatings9100662.
Повний текст джерелаАнотація:
Amorphous nano-SiO2·nH2O particles has drawn much attention in industrial applications because of the features of high purification, low density, large specific surface area, fine decentralization, good optical, and mechanical performances. However, the applications have been hindered by the exorbitant price and the serious agglomeration. In this work, using wollastonite as reactant, H2SO4 as solvent, and adding sodium dodecyl benzene sulfonate (SDBS) as surfactant, sub-100 nm amorphous nano-SiO2·0.5H2O particles with good dispersibility, controllable agglomeration, narrow size distribution, and high yield were prepared by a low-cost and simple chemical method. The prepared sphere-like amorphous nano-SiO2·0.5H2O particles with average diameter of 70 nm were absorbed by the SDBS on the surface. The reaction conditions were systematically studied and the optimal technologic condition of the preparation was also confirmed. The achievement had a great perspective for the industrialization of high-quality nano-SiO2·nH2O particles, which hold great promise for various applications, such as plasmonic and catalytic nanoparticles supporting, polymeric matrices strengthening, drug delivery, and adsorption processes.
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Sumera, Florentino C., Shienna Marie A. Pontillas, Josanelle Angela V. Bilo, and John Marty Mateo. "New Poly(Hydroxylauric-co-Lactic Acid) Liquid Polymer for Dissolving Lipophilic Drugs." KIMIKA 28, no. 1 (July 7, 2017): 20–25. http://dx.doi.org/10.26534/kimika.v28i1.20-25.
Повний текст джерелаАнотація:
A liquid, biocompatible polyester based polymer, which could facilitate injectable formulations by simple mixing with the active substance (drug) is much needed by the pharmaceutical companies. A favourite candidate is polylactic acid (PLA) which is biocompatible and biodegradable. However PLA is solid with high crystallinity. Thus, in this research, hydroxylauric acid (HOLA) was copolymerized with lactic acid (LA) in different ratios by polycondensation technique at 180 °C, without a metal catalyst and avoiding the formation of interfering lactides, to provide a liquid polyester. The copolymers molecular weights were determined by Gel Permeation Chromatography (GPC) and their physical states indicated as solid or liquid were noted. The structures as polyesters were confirmed by FT-IR and 1H NMR spectroscopy. Poly(HOLA:LA) products from reactant ratios 0:100 is solid, while ratios of 20:80, 40:60 are mixed (paste) and 60:40, 80:20 and 100:0 are liquids. Thus, the liquid polyesters from the polycondensation of HOLA and LA without catalyst were picked as potential candidates for dissolving hydrophobic drugs that could be used as injectables in controlled drug delivery experiments.
Дисертації з теми "Reactant delivery"
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GALLO, ANDREA. "Electrokinetic delivery of reagents for groundwater remediation." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2912986.
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Hopp, Tobias. "Harnessing the Selective Effects of Arousal in the Context of Persuasive Message Delivery: Violent Video Games, Reactance, Post-Scroll Messaging, and Anti-Violence Messages." Thesis, University of Oregon, 2014. http://hdl.handle.net/1794/18387.
Повний текст джерелаАнотація:
The present dissertation explored the effectiveness of inserting anti-violence, pro-social messages into violent video games. In light of previous, inconsistent findings relative to the effectiveness of in-game persuasive message placement, this study introduced the notion of "post-scroll" video game messaging (i.e., insertion of a persuasive message immediately after the end of a game level or sequence). The theoretical framework employed in this work suggested that video game play would be associated with heightened levels of arousal. Subsequently, the expectation was that heightened levels of arousal would influence message processing on a conditional basis. The results indeed suggested that the combination of high arousal and low levels of message induced state reactance was associated with a number of favorable message outcomes. The results also suggested that the ability to detect message reactance potential was markedly compromised in highly stimulating media environments. Specifically, the current findings indicated that highly aroused message evaluators may rely on externally provided cues when assessing a message's reactance potential. Taken as a whole, the current work's findings provided initial evidence that post-scroll messaging can be a fruitful means of persuasive message delivery.2016-09-29
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DeRoche, Peter M. "A microjet-based reactant delivery method for PEM fuel cells." 2008. http://etd.lib.fsu.edu/theses/available/etd-07142008-121836.
Повний текст джерелаАнотація:
Thesis (M.S.)--Florida State University, 2008.Advisor: Anjaneyulu Krothapalli, Florida State University, FAMU-FSU College of Engineering, Dept. of Mechanical Engineering. Title and description from dissertation home page (viewed Sept. 17, 2008). Document formatted into pages; contains xi, 95 pages. Includes bibliographical references.
Книги з теми "Reactant delivery"
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Sarkar, B. K., and Reena Singh. Hydrogen Fuel Cell Vehicles Current Status. Namya Press, 2022. http://dx.doi.org/10.56962/9789355451118.
Повний текст джерелаАнотація:
Abstract: The hazardous effects of pollutants from conventional fuel vehicles have caused the scientific world to move towards environmentally friendly energy sources. Though we have various renewable energy sources, the perfect one to use as an energy source for vehicles is hydrogen. Like electricity, hydrogen is an energy carrier that has the ability to deliver incredible amounts of energy. On-board hydrogen storage in vehicles is an important factor that should be considered when designing fuel cell vehicles. In this study, a recent development in hydrogen fuel cell engines is reviewed to scrutinize the feasibility of using hydrogen as a major fuel in transportation systems. A fuel cell is an electrochemical device that can produce electricity by allowing chemical gases and oxidants as reactants. With anodes and electrolytes, the fuel cell splits the cation and the anion in the reactant to produce electricity. Fuel cells use reactants, which are not harmful to the environment and produce water as a product of the chemical reaction. As hydrogen is one of the most efficient energy carriers, the fuel cell can produce direct current (DC) power to run the electric car. By integrating a hydrogen fuel cell with batteries and the control system with strategies, one can produce a sustainable hybrid car.
Частини книг з теми "Reactant delivery"
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Ford, Jr., Lacy K. "Reacting to the Scare." In Deliver Us from Evil, 269–96. Oxford University Press, 2009. http://dx.doi.org/10.1093/acprof:oso/9780195118094.003.0010.
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Clayton, Berwyn, and Hugh B. Guthrie. "Australia's National Work-Integrated Learning Strategy in University Education." In Global Perspectives on Work-Based Learning Initiatives, 114–41. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-6977-0.ch005.
Повний текст джерелаАнотація:
This chapter describes how the development of work-integrated learning (WIL) has become an increasingly important component of both curriculum and pedagogy across a wide range of disciplines in Australia's universities. This has been driven by institutions reacting to government and industry demands for work-relevant degrees and work-ready graduates. The chapter analyzes five of the eight action areas in the National WIL Strategy. A number of barriers to further implementation are identified and discussed, including funding, institutional constraints, assessment challenges, and employer capacity, particularly in smaller companies. Ways forward include developing quality information and the resources to support implementation, growing champions of the process in institutions and employers, and developing alternative approaches to delivery given the pressure placed on industry for work placements by all sectors of Australian education.
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Martinho Simões, José A., and Manuel Minas da Piedade. "Titration Calorimetry." In Molecular Energetics. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780195133196.003.0015.
Повний текст джерелаАнотація:
Titration calorimetry is a method in which one reactant inside a calorimetric vessel is titrated with another delivered from a burette at a controlled rate. This technique has been adapted to a variety of calorimeters, notably of the isoperibol and heat flow types. The output of a titration calorimetric experiment is usually a plot of the temperature change or the heat flow associated with the reaction or physical interaction under study as a function of time or the amount of titrant added. A primary use of titration calorimetry is the determination of enthalpies of reaction in solution. The obtained results may of course lead to enthalpies of formation of compounds in the standard state by using appropriate thermodynamic cycles and auxiliary data, as described in chapter 8 for reaction-solution calorimetry. Moreover, when reactions are not quantitative, both the equilibrium constant and the enthalpy of reaction can often be determined from a single titration run. This also yields the corresponding ΔrGo and ΔrSo through equations 2.54 and 2.55. Extensive use has been made of titration calorimetry as an analytical tool. These applications, which are outside the scope of this book, have been covered in various reviews. The historical development of titration calorimetry has been addressed by Grime. The technique is credited to have been born in 1913, when Bell and Cowell used an apparatus consisting of a 200 cm3 Dewar vessel, a platinum stirrer, a thermometer graduated to tenths of degrees, and a volumetric burette to determine the end point of the titration of citric acid with ammonia from a plot of the observed temperature change against the volume of ammonia added. The capabilities of titration calorimetry have enormously evolved since then, and the accuracy limits of modern titration calorimeters are comparable to those obtained in conventional isoperibol or heat-flow instruments. The titration procedures described in the literature can be classified as continuous or incremental, depending on the mode of titrant addition. In the first case the titrant is continuously introduced in the reaction vessel at a programmed (not necessarily constant) rate during a run.
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Su, Chunming, Robert W. Puls, Thomas A. Krug, Mark T. Watling, Suzanne K. O'Hara, Jacqueline W. Quinn, and Nancy E. Ruiz. "Long-Term Performance Evaluation of Groundwater Chlorinated Solvents Remediation Using Nanoscale Emulsified Zerovalent Iron at a Superfund Site." In Waste Management, 1352–71. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-1210-4.ch061.
Повний текст джерелаАнотація:
This chapter addresses a case study of long-term assessment of a field application of environmental nanotechnology. Dense Non-Aqueous Phase Liquid (DNAPL) contaminants such as Tetrachloroethene (PCE) and Trichloroethene (TCE) are a type of recalcitrant compounds commonly found at contaminated sites. Recent research has focused on their remediation using environmental nanotechnology in which nanomaterials such as nanoscale Emulsified Zerovalent Iron (EZVI) are added to the subsurface environment to enhance contaminant degradation. Such nanoremediation approach may be mostly applicable to the source zone where the contaminant mass is the greatest and source removal is a critical step in controlling the further spreading of the groundwater plume. Compared to micro-scale and granular counterparts, NZVI exhibits greater degradation rates due to its greater surface area and reactivity from its faster corrosion. While NZVI shows promise in both laboratory and field tests, limited information is available about the long-term effectiveness of nanoremediation because previous field tests are mostly less than two years. Here an update is provided for a six-year performance evaluation of EZVI for treating PCE and its daughter products at a Superfund site at Parris Island, South Carolina, USA. The field test consisted of two side-by-side treatment plots to remedy a shallow PCE source zone (less than 6 m below ground surface) using pneumatic injection and direct injection, separately in October 2006. For the pneumatic injections, a two-step injection procedure was used. First, the formation was fluidized by the injection of nitrogen gas alone, followed by injection of the EZVI with nitrogen gas as the carrier. In the pneumatic injection plot, 2,180 liters of EZVI containing 225 kg of iron (Toda RNIP-10DS), 856 kg of corn oil, and 22.5 kg of surfactant were injected to remedy an estimated 38 kg of chlorinated volatile compounds (CVOC)s. Direct injections were performed using a direct push rig. In the direct injection plot, 572 liters of EZVI were injected to treat an estimated 0.155 kg of CVOCs. Visual inspection of collected soil cores before and after EZVI injections shows that the travel distance of EZVI was dependent on the method of delivery with pneumatic injection achieving a greater distance of 2.1 m than did direct injection reaching a distance of 0.89 m. Significant decreases in PCE and TCE concentrations were observed in downgradient wells with corresponding increases in degradation products including significant increases in ethene. In the pneumatic injection plot, there were significant reductions in the downgradient groundwater mass flux values for chlorinated ethenes (>58%) and a significant increase in the mass flux of ethene (628%). There were significant reductions in total CVOCs mass (78%), which was less than an estimated 86% decrease in total CVOCs made at 2.5 years due to variations in soil cores collected for CVOCs extraction and determination; an estimated reduction of 23% (vs.63% at 2.5 years) in the sorbed and dissolved phases and 95% (vs. 93% at 2.5 years) reduction in the PCE DNAPL mass. Significant increases in dissolved sulfide, volatile fatty acids (VFA), and total organic carbon (TOC) were observed and dissolved sulfate and pH decreased in many monitoring wells. The apparent effective destruction of CVOC was accomplished by a combination of abiotic dechlorination by nanoiron and biological reductive dechlorination stimulated by the oil in the emulsion. No adverse effects of EZVI were observed for the microbes. In contrast, populations of dehalococcoides showed an increase up to 10,000 fold after EZVI injection. The dechlorination reactions were sustained for the six-year period from a single EZVI delivery. Repeated EZVI injections four to six years apart may be cost-effective to more completely remove the source zone contaminant mass. Overall, the advantages of the EZVI technology include an effective “one-two punch” of rapid abiotic dechlorination followed by a sustained biodegradation; contaminants are destroyed rather than transferred to another medium; ability to treat both DNAPL source zones and dissolved-phase contaminants to contain plume migration; ability to deliver reactants to targeted zones not readily accessible by conventional permeable reactive barriers; and potential for lower overall costs relative to alternative technologies such as groundwater pump-and-treat with high operation and maintenance costs or thermal technologies with high capital costs. The main limitations of the EZVI technology are difficulty in effectively distributing the viscous EZVI to all areas impacted with DNAPL; potential decrease in hydraulic conductivity due to iron corrosion products buildup or biofouling; potential to adversely impact secondary groundwater quality through mobilization of metals and production of sulfides or methane; injection of EZVI may displace DNAPL away from the injection point; and repeated injections may be required to completely destroy the contaminants.
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Taber, Douglass. "Alkaloid Synthesis: Paliurine F, Lepadiformine, and 7-Deoxypancratistatin." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0057.
Повний текст джерелаАнотація:
The sedative alkaloid paliurine F 7 is a pentapeptide bridged by an arene. Gwilherm Evano of the Université de Versailles took advantage of this in his synthesis (Angew. Chem. Int. Ed. 2007, 46, 572) of 7, although it was necessary to prepare, from serine, one of the amino acid derivatives, the protected 3-hydroxyprolinol 2. The key step in the synthesis was the Cu-catalyzed intramolecular coupling of 5 to give the macrolactam 6. Deprotection and acylation then gave paliurine F 7. Lepadiformine 14, isolated from the tunicate Clavelina lepadiformis, shows moderate cytotoxicity, and is also a K+ channel blocker. The synthesis of 14 (Angew. Chem. Int. Ed. 2007, 46, 2631) by Donald Craig of Imperial College started with the aziridine 8, prepared from the corresponding epoxide. Opening of the protected aziridine with the anion of methyl phenyl sulfone set the stage for condensation of the dianion derived from 9 with the aldehyde 10, to give, with high diastereocontrol, the amine 11. Deprotection followed by cyclization then led to the activated ether 12. While the opening of 12 with an alkyl Grignard reagent proceeded with undesired inversion at the reacting center, opening with the alkynyl Grignard delivered mainly the desired 13. Reduction followed by oxidation, epimerization and reduction then gave lepadiformine 14. The Amaryllidaceae alkaloid 7-deoxypancratistatin 21 has potent antiviral activity. A challenge in the assembly of 21 is that the ring fusion is trans, less stable than the corresponding cis diastereomer. The synthesis of 21 (J. Org. Chem. 2007, 72, 2570) by Albert Padwa of Emory University started with 17, the preparation of which by the combination 15 and 16 he had previously reported in the course of his synthesis of lycoricidine (OHL December 11, 2006). Ester 17 had the desired trans ring fusion, but with an angular ester substituent that had to be removed. While it would be expected from the mechanism that Rh-mediated decarbonylation of an aldehyde would proceed with retention of absolute configuration, and this had been confirmed experimentally, this reaction had not been applied to such a challenging substrate. In the event, the transformation proceeded smoothly, to give the desired trans 19. Dehydration and dihydroxylation of 19 led to the cyclic sulfate 20, selective SN2 opening of which delivered 7-deoxypancratistatin 21.
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Daly, Blánaid, Paul Batchelor, Elizabeth Treasure, and Richard Watt. "Planning dental services." In Essential Dental Public Health. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199679379.003.0028.
Повний текст джерелаАнотація:
Planning is an integral part of dental care provision that can operate at many different levels. At a national level, government NHS policy impacts upon dental services in different ways. For example, in the General Dental Service, patient charge bands in England are currently set by the government. In the future, at the national level, the National Health Service Commissioning Board (NHSCB) will determine national policy and national delivery requirements. The NHSCB will be responsible for commissioning primary dental services and contractual arrangements with dentists. At the Health and Wellbeing Board (HWB) level in England, planners (in conjunction with general medical practioner (GMP) consortia/clinical care commissioning groups (CCGs)) will make decisions over the priorities for local services, and the types and range of services offered locally. Within a dental practice, dental practitioners and their team members may develop a range of practice policies aimed at improving the services provided. Finally, every day clinicians develop treatment plans for individual patient care based upon their oral health needs. All these activities are planning in action. This chapter will examine the basic principles of planning, and review the different steps in the planning process. At the most basic level, planning aims to guide choices so that decisions are made in the best manner to reach the desired outcomes. Planning provides a guide and structure to the process of decision-making to maximize results within the limited resources available. Is planning really necessary when there are so many other demands on practitioners’ time? Planning can be justified for the following reasons: . . . ● It provides an opportunity to be proactive in decision-making rather than constantly reacting to pressures and demands. . . . . . . ● It enables priorities to be set. . . . . . . ● It identifies where resources can be directed to have the greatest impact. . . . Various planning models have been proposed to act as a guide to the different steps in the planning process. The rational planning model provides a basic guide to the process (McCarthy 1982), and involves the following steps: . . . 1 Assessment of need: e.g. identification of the oral health problems and concerns of the population. . . . . . . 2 Identifying priorities: agreeing the target areas for action. . . .
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Lehmann, Susan W. "Psychotherapy." In Psychiatric Aspects of Neurologic Diseases. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780195309430.003.0030.
Повний текст джерелаАнотація:
To nonpsychiatric physicians the term psychotherapy often sounds vague and mysterious. Yet, the art of providing healing through the clinician–patient relationship is as old as medicine itself. Psychotherapy is a form of treatment that uses psychologic techniques within the context of this confiding clinician–patient relationship to treat mental symptoms and relieve emotional distress. Psychotherapy may be the main approach to treatment of identified symptoms, or it may be used as an adjunct to pharmacotherapy. The clinician–patient relationship at the core of psychotherapy can be distinguished from other confiding relationships a person may have with family members, friends, mentors, and advisors. In psychotherapy, there is a clearly identified provider of care and a recipient of that care. The provider is specially trained to deliver the care in a professional and coherent way, using specific psychologic techniques. Both the provider and the patient focus their attention on the patient’s specific problems and work together in partnership to address the elements of psychologic distress and improve the patient’s symptoms. The goal of psychotherapy may differ depending on the patient and his or her situation. Sometimes, the goal of psychotherapy is symptom reduction (eg, to decrease anxiety, improve mood, or reduce friction in an interpersonal relationship). It may be used to help an individual replace unhealthy, counterproductive ways of thinking or reacting with more adaptive ones. In other instances, the goal of psychotherapy may be educational or instructive and involve teaching techniques to expand an individual’s coping abilities or communication skills. All forms of psychotherapy develop an individual’s self-awareness and help bolster appropriate self-esteem. The therapeutic setting between patient and clinician establishes validation that the patient’s concerns are worth addressing and provides a sense of hopefulness that things can improve. As new options are explored and new techniques for dealing with distressing situations are discussed, patients develop an increased sense of mastery and feel less overwhelmed by life circumstances. Psychotherapy may take three main forms of: (1) individual, (2) couples or family, or (3) group. In individual psychotherapy, a single patient and therapist work together, focusing on the patient’s unique attitudes, perceived experiences, and behaviors that are associated with his or her current distress.
Тези доповідей конференцій з теми "Reactant delivery"
1
Greska, Brenton, Peter DeRoche, and Anjaneyulu Krothapalli. "A Novel Reactant Delivery System for PEM Fuel Cells." In ASME 2008 6th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/fuelcell2008-65142.
Повний текст джерелаАнотація:
This paper deals with the use of microjets as a reactant delivery method for a PEM fuel cell. The flow physics of this technique have been adapted such that an even distribution of reactants over the membrane is achieved. A single cell based on this microjet delivery method has been built and tested using the fuel cell test station at SESEC. Polarization curves were obtained for a number of different operating conditions in which the relative humidity and supply pressure of the air supply were varied. Similar operating conditions were used to obtain polarization curves for a similarly sized commercially available fuel cell that utilizes commonly used serpentine flow channels for reactant delivery. Comparison of the polarization curves at similar operating conditions revealed that the microjet-based fuel cell was relatively unaffected by the changes in relative humidity and and positively affected by an increase in supply pressure, which was in stark contrast to what was observed for the commercial fuel cell.
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Islam, Nazmul. "Biased AC Electroosmosis Micropump for Water Management in PEM Fuel Cells." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68906.
Повний текст джерелаАнотація:
Proton exchange membrane (PEM) fuel cells are among the most promising fuel cell technologies. Recent experimental and numerical investigations [1–3] on PEM fuel cells (PEMFC) identified water management as one of the most critical issues for designing robust, high-performance PEM fuel cells. Proper water management within the cell is therefore essential, as dehydration of the membrane or flooding of the cathode result in increasing resistive losses. Flooding reduction in the fuel cell is commonly done by removing water with excessive reactant (H2 or O2) flow rates and elevated gas pressures. This mixture makes air delivery the largest parasitic load on fuel cells. Typically, this type of air delivery consumes more than 20% of the fuel cell power. As an alternative, we have developed a novel biased AC electroosmtic micropump for PEM fuel cell applications that can be fabricated with micro-electro-mechanical-systems (MEMS) compatible semiconductor micro-fabrication. This research paper will experimentally demonstrate the bi-directional pumping action that can prevent flooding, increase power density, and ensure stable performance of fuel cell by removing water from flooded regions and redistributing it to under-saturated regions.
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Penley, Sean, Steven Wozniak, Chris Davis, and Phil Barros. "A Holistic Approach Toward UHP Gas Delivery System Design Reduces Stochastic Variability Of Reactant Distribution In Plasma Etch And Deposition Equipment : EO: Equipment Optimization." In 2021 32nd Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC). IEEE, 2021. http://dx.doi.org/10.1109/asmc51741.2021.9435690.
Повний текст джерела
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Pugh, D., A. Valera-Medina, P. Bowen, A. Giles, B. Goktepe, J. Runyon, S. Morris, S. Hewlett, and R. Marsh. "Emissions Performance of Staged Premixed and Diffusion Combustor Concepts for an NH3/Air Flame With and Without Reactant Humidification." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14953.
Повний текст джерелаАнотація:
Abstract Renewably generated ammonia offers a form of carbon-free chemical energy storage to meet the differences between uncertain renewable supply and fluctuating demand, and has the potential to support future energy requirements as a power-to-X concept. The storage and transportation characteristics of NH3 are favorable compared with H2, however there are significant combustion research challenges to enhance fuel reactivity whilst reducing harmful emissions production. The purpose of the presented work was to evaluate different fuel delivery concepts for a representative GT combustor. An experimental and numerical comparison was made between swirl-stabilized premixed and diffusion NH3-air flames at elevated inlet temperature (473 K). The exhaust NOx and unburned NH3 emissions generated from each concept were quantified to optimize operational combustor performance. High-speed OH* and NH2* chemiluminescence was employed to characterize the change in flame topology with variation in fuel-air equivalence ratio, and the resultant influence on measured emission concentrations. Chemiluminescence intensities were shown to elucidate changes in sampled exhaust emissions, enabling detailed analysis of intermediate chemistry. A comparison was made between experimental data and chemical kinetic simulations with a reactor network model, demonstrating the sensitivity of NOx emissions to premixed fuel-air equivalence ratio. A comparison was also made between exclusive primary airflow, and the staged introduction of secondary air, to quantify the change in NOx production between each configuration and improve fuel burnout. Secondary air loadings were incrementally increased through the combustor, and the change in exhaust emissions mapped. In addition, reactant humidification was employed as a secondary process for NOx reduction, having shown favorable performance with NH3/H2 mixtures to limit thermochemical NO production. The efficacy of humidification was compared for both premixed and diffusion configurations.
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Senn, S. M., and D. Poulikakos. "Porous Materials as Fluid Distributors in Polymer Electrolyte Fuel Cells: A Computational Performance Analysis." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42310.
Повний текст джерелаАнотація:
Commonly used ribbed flow-fields such as parallel and serpentine flow-fields in polymer electrolyte fuel cells (PEFC) exhibit limited mass transfer to the part of the diffusion and catalyst layer which is not covered by flow channels, leading to a considerably reduced reactant concentration and increased overpotential losses under the current collector shoulders. In this study, a novel concept is investigated, according to which the traditional ribbed flow delivery systems are replaced with permeable porous fluid distributors, which circumvent drawbacks such as those mentioned earlier. A complex mathematical model, including the conservation of mass, momentum, energy, species and electric current, using Butler-Volmer kinetics for electrochemical reaction rates, is numerically solved in three dimensions, to investigate the impact of different flow configurations on the performance of hydrogen fuel cells. It is found that cells with porous gas distributors generate substantially higher current densities and therefore are more advantageous with respect to mass transfer. Reduction in stack weight is another strong argument for using porous flow distributors in future applications.
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Bakhtiyarov, Sayavur I., Azizaga Kh Shakhverdiyev, Geilani M. Panakhov, and Eldar M. Abbasov. "Polymer/Surfactant Effects on Generated Volume and Pressure of CO2 in EOR Technology." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37100.
Повний текст джерелаАнотація:
Dense phase gases (carbon dioxide, nitrogen, light hydrocarbons, etc.) are used to develop miscibility with crude oil in enhanced oil recovery processes. Due to the certain reasons, carbon dioxide (CO2) flooding is considered the fastest-growing improved oil recovery method. However, due to the low viscosity of dense CO2, displacement front instabilities and a premature CO2 breakthrough is observed in many cases. An alternative scheme to the traditional methods of oil recovery by injection of carbon dioxide gas is the technology developed by the NMT, IGDFF and IMM, which proposes in-situ CO2 generation as a result of the thermochemical reaction between water solutions of the gas-forming (FG) and gas-yielding (GY) chemical agents injected to the productive horizons. This technique excludes CO2 injection from surface communication systems and does not require expensive delivery equipment. This process allows avoiding many negative consequences of CO2 injection technology. Based on the in-situ CO2 generation concept, several new technological schemes were developed in order to provide an integrative effect on the productive horizons. In this paper we present the results of the experimental studies on effect of polymer and surfactant additives on generated CO2 miscibility. The solutions of gas-yielding (GY) agent with different concentrations of surfactants and polymer additives were used as a reacting agent in these laboratory studies. Within the limits of the experimental conditions stochiometric reactions between gas-yielding (GY) and gas-forming (GF) water solutions were simulated. The tests were conducted on the experimental set up designed and built for these purposes. In the first series of experiments a polyacrylamide was added to the gas-yielding (GY) agent in the concentrations 0.1, 0.25 and 0.5 wt.%. A dynamics of the pressure changes during stoichiometric reaction was recorded. It is shown that the pressure of the generated CO2 gas significantly depends on concentration of the polymer additive and, as a consequence, on viscosity of the water solution. It slightly depends on the concentration of the surfactant added to the GY reactant.
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Steinbrenner, Julie E., Eon Soo Lee, Fu-Min Wang, Chen Fang, Carlos H. Hidrovo, and Kenneth E. Goodson. "Flow Regime Evolution in Long, Serpentine Microchannels With a Porous Carbon Paper Wall." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68447.
Повний текст джерелаАнотація:
An important function of the gas delivery channels in Proton Exchange Membrane (PEM) fuel cells is the evacuation of liquid water created at the cathode. The resulting two-phase flow can become an obstacle to reactant transport and a source of parasitic losses. The present work examines the behavior of two-phase flow in 500 μm × 500 μm × 60 cm channels with distributed water injection through a porous carbon paper wall to gain understanding of the physics of flows relevant to fuel cell water management challenges. Flow regime maps based on local gas and liquid flow rates are constructed for experimental conditions corresponding to current densities between 0.5 and 1 A/cm2 and stoichiometric coefficients from 1 to 4. Flow structures are analyzed along the entire length of the channel. It is observed that slug flow is favored to plug flow at high air flow rates and low liquid flow rates. Stratified flow dominates at high liquid flow rates. Along the axial flow direction, the flow regime consistently transitions from intermittent to wavy to stable stratified flow. This progression is quantified using a parameter of flow progression which characterizes the degree of development of the two-phase flow toward the stable stratified condition. This parameter is discussed in relation to fuel cell operating conditions. It provides a metric for analyzing liquid water removal mechanisms in the cathode channels of PEM fuel cells.
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Horlock, J. H., J. B. Young, and G. Manfrida. "The Rational Efficiency of Fossil-Fuel Power Plants." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0848.
Повний текст джерелаАнотація:
Abstract The definition of open cycle rational efficiency is unequivocally based on the ratio of the actual shaft work output from a power plant to the maximum work that could be obtained in a reversible process between prescribed inlet and outlet states. However, the specification of this ideal process remains a matter for discussion. The “classical” definition specifies the outlet state as a “standard” atmosphere (p0,T0) with a given composition of constituent gases and an exergy of zero. The ideal work output is then the exergy of the fuel supplied, which is the sum of the Gibbs function change in reversible combustion at (p0,T0) and the work of extraction and delivery of the reactant and product species. However, two other ideal processes may be considered in which different outlet states are specified leading to alternative definitions of rational efficiency. In one process all species enter and leave the ideal plant individually at (p0,T0) in thermal and mechanical (but not chemical) equilibrium with the environment. In the other, the exhaust is at (p0,T0) but the gas composition is the same as in the real process. A further complication occurs when water or steam is injected into a gas turbine plant. In such cases the exergy of the added water must be considered within any definition of rational efficiency. The three definitions of rational efficiency are discussed and compared and some illustrative calculations presented.
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Hatfield, Jonathan M., and Richard B. Peterson. "A Catalytically Sustained Microcombustor Burning Propane." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/aes-23634.
Повний текст джерелаАнотація:
Abstract The performance of a catalytically sustained microcombustor was investigated. The reactants for combustion were air and propane, which were mixed together and delivered to the end of a bayonet-style, heat recirculating combustor having a reaction volume measuring approximately 0.25 mm3. Platinum wire in the shape of a coil was used as an active surface to catalyze the exothermic reactions. Measurements of temperature and reactant flow rate were made during the study. Results show that propane can be burned in a self-sustaining fashion in the microcombustor with heat release rates as low as 1.0 Watt.
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Hatfield, Jonathan M., and Richard B. Peterson. "A Catalytically Sustained Microcombustor Burning Propane." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/mems-23923.
Повний текст джерелаАнотація:
Abstract The performance of a catalytically sustained microcombustor was investigated. The reactants for combustion were air and propane, which were mixed together and delivered to the end of a bayonet-style, heat recirculating combustor having a reaction volume measuring approximately 0.25 mm3. Platinum wire in the shape of a coil was used as an active surface to catalyze the exothermic reactions. Measurements of temperature and reactant flow rate were made during the study. Results show that propane can be burned in a self-sustaining fashion in the microcombustor with heat release rates as low as 1.0 Watt.