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Articoli di riviste sul tema "Hydrates transfer Cell":
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Herbst-Gervasoni, Corey J., Michael R. Gau, Michael J. Zdilla e Ann M. Valentine. "Crystal structures of sodium-, lithium-, and ammonium 4,5-dihydroxybenzene-1,3-disulfonate (tiron) hydrates". Acta Crystallographica Section E Crystallographic Communications 74, n. 7 (8 giugno 2018): 918–25. http://dx.doi.org/10.1107/s2056989018008009.
Abstract (sommario):
The solid-state structures of the Na+, Li+, and NH4 + salts of the 4,5-dihydroxybenzene-1,3-disulfonate (tiron) dianion are reported, namely disodium 4,5-dihydroxybenzene-1,3-disulfonate, 2Na+·C6H4O8S2 2−, μ-4,5-dihydroxybenzene-1,3-disulfonato-bis[aqualithium(I)] hemihydrate, [Li2(C6H4O8S2)(H2O)2]·0.5H2O, and diammonium 4,5-dihydroxybenzene-1,3-disulfonate monohydrate, 2NH4 +·C6H4O8S2 2−·H2O. Intermolecular interactions vary with the size of the cation, and the asymmetric unit cell, and the macromolecular features are also affected. The sodium in Na2(tiron) is coordinated in a distorted octahedral environment through the sulfonate oxygen and hydroxyl oxygen donors on tiron, as well as an interstitial water molecule. Lithium, with its smaller ionic radius, is coordinated in a distorted tetrahedral environment by sulfonic and phenolic O atoms, as well as water in Li2(tiron). The surrounding tiron anions coordinating to sodium or lithium in Na2(tiron) and Li2(tiron), respectively, result in a three-dimensional network held together by the coordinate bonds to the alkali metal cations. The formation of such a three-dimensional network for tiron salts is relatively rare and has not been observed with monovalent cations. Finally, (NH4)2(tiron) exhibits extensive hydrogen-bonding arrays between NH4 + and the surrounding tiron anions and interstitial water molecules. This series of structures may be valuable for understanding charge transfer in a putative solid-state fuel cell utilizing tiron.
2
Smith, Graham, e Urs D. Wermuth. "Proton-transfer compounds featuring the unusual 4-arsonoanilinium cation from the reaction of (4-aminophenyl)arsonic acid with strong organic acids". Zeitschrift für Kristallographie - Crystalline Materials 233, n. 2 (23 febbraio 2018): 145–51. http://dx.doi.org/10.1515/zkri-2017-2087.
Abstract (sommario):
AbstractThe crystal structures of the 1:1 proton-transfer compounds of (4-aminophenyl)arsonic acid (p-arsanilic acid) with the strong organic acids, 2,4,6-trinitrophenol (picric acid), 3,5-dinitrosalicylic acid, (3-carboxy-4-hydroxy)benzenesulfonic acid (5-sulfosalicylic acid) and toluene-4-sulfonic acid have been determined at 200 K and their hydrogen–bonding patterns examined. The compounds are, respectively, anhydrous 4-arsonoanilinium 2,4,6-trinitrophenolate (1), the hydrate 4-arsonoanilinium 2-carboxy-4,6-dinitrophenolate monohydrate (2), the hydrate 4-arsonoanilinium (3-carboxy-4-hydroxy)benzenesulfonate monohydrate (3) and the partial solvate 4-arsonoanilinium toluene-4-sulfonate 0.8 hydrate (4). The asymmetric unit of2, a phenolate, comprises two independent but conformationally similar cation-anion pairs and two water molecules of solvation, and in all compounds, extensive inter-species hydrogen–bonding interactions involving arsono O–H···O and anilinium N–H···O hydrogen–bonds generate three-dimensional supramolecular structures. In the cases of1and2, the acceptors include phenolate and nitro O-atom acceptors, with3and4, additionally, sulfonate O-atom acceptors, and with the hydrates2–4, the water molecules of solvation. A feature of the hydrogen–bonding in3is the presence of primary chains extending along (010) through centrosymmetric cyclicR22(8) motifs together with conjoined cyclicR34(12) motifs, which include the water molecule of solvation. The primary hydrogen–bonding in the substructure of4involves homomolecular cation–cation arsono O–H···O interactions forming columns down the crystallographic four-fold axis of the unit cell.
3
Sun, Hong, Mingfu Yu, Zhijie Li e Saif Almheiri. "A Molecular Dynamic Simulation of Hydrated Proton Transfer in Perfluorosulfonate Ionomer Membranes (Nafion 117)". Journal of Chemistry 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/169680.
Abstract (sommario):
A molecular dynamic model based on Lennard-Jones Potential, the interaction force between two particles, molecular diffusion, and radial distribution function (RDF) is presented. The diffusion of the hydrated ion, triggered by both Grotthuss and vehicle mechanisms, is used to study the proton transfer in Nafion 117. The hydrated ion transfer mechanisms and the effects of the temperature, the water content in the membrane, and the electric field on the diffusion of the hydrated ion are analyzed. The molecular dynamic simulation results are in good agreement with those reported in the literature. The modeling results show that when the water content in Nafion 117 is low, H3O+is the main transfer ion among the different hydrated ions. However, at higher water content, the hydrated ion in the form of H+(H2O)2is the main transfer ion. It is also found that the negatively charged sulfonic acid group as the fortified point facilitates the proton transfer in Nafion 117 better than the free water molecule. The diffusion of the hydrated ion can be improved by increasing the cell temperature, the water content in Nafion, and the electric field intensity.
4
Fukumoto, Ayako, Toru Sato, Fumio Kiyono e Shinichiro Hirabayashi. "Estimation of the Formation Rate Constant of Methane Hydrate in Porous Media". SPE Journal 19, n. 02 (17 aprile 2013): 184–90. http://dx.doi.org/10.2118/163097-pa.
Abstract (sommario):
Summary Hydrate formation and the relevant mass and heat transfers were numerically analyzed in a microscopic computational domain in which spherical glass beads, water, and methane gas were distributed separately. A hydrate-formation experiment was also carried out by use of a cylindrical pressure cell. The temperature in the cell was controlled by Peltier devices, which were attached to the outer walls of the cell to imitate the adiabatic boundary condition present in the numerical simulation. By history matching between the experiment and calculation, we first obtained a hydrate-formation rate constant per unit volume of water, assuming homogeneous nucleation. Then, after converting the rate by use of a surface-area model of water in porous media, we noted that the area-based rate constant and activation energy of the hydrate formation were estimated to be 6.33 × 1034 mol·m–2 Pa–1 s–1 and 238 × 103 J/mol, respectively, for temperatures of 1.5 to 3.4°C.
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Stoporev, Andrey, Rail Kadyrov, Tatyana Adamova, Evgeny Statsenko, Thanh Hung Nguyen, Murtazali Yarakhmedov, Anton Semenov e Andrey Manakov. "Three-Dimensional-Printed Polymeric Cores for Methane Hydrate Enhanced Growth". Polymers 15, n. 10 (15 maggio 2023): 2312. http://dx.doi.org/10.3390/polym15102312.
Abstract (sommario):
Polymeric models of the core prepared with a Raise3D Pro2 3D printer were employed for methane hydrate formation. Polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), carbon fiber reinforced (UltraX), thermoplastic polyurethane (PolyFlex), and polycarbonate (ePC) were used for printing. Each plastic core was rescanned using X-ray tomography to identify the effective porosity volumes. It was revealed that the polymer type matters in enhancing methane hydrate formation. All polymer cores except PolyFlex promoted the hydrate growth (up to complete water-to-hydrate conversion with PLA core). At the same time, changing the filling degree of the porous volume with water from partial to complete decreased the efficiency of hydrate growth by two times. Nevertheless, the polymer type variation allowed three main features: (1) managing the hydrate growth direction via water or gas preferential transfer through the effective porosity; (2) the blowing of hydrate crystals into the volume of water; and (3) the growth of hydrate arrays from the steel walls of the cell towards the polymer core due to defects in the hydrate crust, providing an additional contact between water and gas. These features are probably controlled by the hydrophobicity of the pore surface. The proper filament selection allows the hydrate formation mode to be set for specific process requirements.
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Hirota, Yuki, Taiki Tominaga, Takashi Kawabata, Yukinobu Kawakita e Yasumitsu Matsuo. "Differences in Water Dynamics between the Hydrated Chitin and Hydrated Chitosan Determined by Quasi-Elastic Neutron Scattering". Bioengineering 10, n. 5 (22 maggio 2023): 622. http://dx.doi.org/10.3390/bioengineering10050622.
Abstract (sommario):
Recently, it was reported that chitin and chitosan exhibited high-proton conductivity and function as an electrolyte in fuel cells. In particular, it is noteworthy that proton conductivity in the hydrated chitin becomes 30 times higher than that in the hydrated chitosan. Since higher proton conductivity is necessary for the fuel cell electrolyte, it is significantly important to clarify the key factor for the realization of higher proton conduction from a microscopic viewpoint for the future development of fuel cells. Therefore, we have measured proton dynamics in the hydrated chitin using quasi-elastic neutron scattering (QENS) from the microscopic viewpoint and compared the proton conduction mechanism between hydrated chitin and chitosan. QENS results exhibited that a part of hydrogen atoms and hydration water in chitin are mobile even at 238 K, and the mobile hydrogen atoms and their diffusion increase with increasing temperature. It was found that the diffusion constant of mobile protons is two times larger and that the residence time is two times faster in chitin than that in chitosan. In addition, it is revealed from the experimental results that the transition process of dissociable hydrogen atoms between chitin and chitosan is different. To realize proton conduction in the hydrated chitosan, the hydrogen atoms of the hydronium ions (H3O+) should be transferred to another hydration water. By contrast, in hydrated chitin, the hydrogen atoms can transfer directly to the proton acceptors of neighboring chitin. It is deduced that higher proton conductivity in the hydrated chitin compared with that in the hydrated chitosan is yielded by the difference of diffusion constant and the residence time by hydrogen-atom dynamics and the location and number of proton acceptors.
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GLASHEEN, J. S., e STEVEN C. HAND. "Anhydrobiosis in Embryos of the Brine Shrimp Artemia: Characterization of Metabolic Arrest During Reductions in Cell-Associated Water". Journal of Experimental Biology 135, n. 1 (1 marzo 1988): 363–80. http://dx.doi.org/10.1242/jeb.135.1.363.
Abstract (sommario):
Upon entry into the state of anhydrobiosis, trehalose-based energy metabolism is arrested in Artemia embryos (cysts). We have compared changes in the levels of trehalose, glycogen, some glycolytic intermediates and adenylate nucleotides in hydrated embryos observed under conditions of aerobic development with those occurring after transfer to 50moll−1 NaCl. This treatment is known to reduce cellassociated water into a range previously referred to as the ametabolic domain. The trehalose utilization and glycogen synthesis that occur during development of fully hydrated cysts are both blocked during desiccation. Upon return to 0.25 moll−1 NaCl both processes are resumed. Analysis of glycolytic intermediates suggests that the inhibition is localized at the trehalase, hexokinase and phosphofructokinase reactions. ATP level remains constant during the 6-h period of dehydration, as does the adenylate energy charge. An additional dehydration experiment was performed in 5.0moll−1 NaCl containing 50mmoll−1 ammonium chloride (pH9-0). The resulting level of gaseous ammonia in the medium has been shown to maintain an alkaline intracellular pH (pHi) in the embryos. The metabolic response to dehydration under these conditions was very similar to the previous dehydration series. Thus, these results are taken as strong evidence that the metabolic suppression observed during dehydration does not require cellular acidification, in contrast to the pronounced inhibitory role of low pHi during entry of hydrated embryos into the quiescent state of anaerobic dormancy. The arrest of carbohydrate metabolism seen during anhydrobiosis indeed appears to be a strict function of embryo water content.
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Apkarian, Robert P., Stephen Lee e Jason Keiper. "Refining Equipment for High Resolution in-Lens Cryo-Sem". Microscopy and Microanalysis 4, S2 (luglio 1998): 258–59. http://dx.doi.org/10.1017/s1431927600021413.
Abstract (sommario):
Advanced metal coating methods have greatly improved the localization of secondary electrons (SEI) from biological specimens staged in an in-lens field emission SEM. Using these metal coatings, molecular level structural information from cell membranes and isolated bio-molecules have been more accurately recorded from frozen-hydrated samples due to the presence of bound water rather than from chemically fixed and dried samples. Although in-lens cryo-SEM systems have provided images with equivalent resolution to TEM-replicas, several conditions are encountered which require optimizing techniques and hardware.A drop of hydrated Bakers yeast on a gold Balzers carrier was plunge-frozen in ethane at its melting point. Thermal properties of ethane, such as the large difference between melting and boiling points, and its low viscosity increase the heat transfer coefficient during plunging thereby leading to faster cooling of the sample than with other cryogens. Carriers were transferred to the cryo-workstation of the Oxford CT 3500 system.
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McCully, Margaret E., Martin J. Canny, Cheng X. Huang, Celia Miller e Frank Brink. "Cryo-scanning electron microscopy (CSEM) in the advancement of functional plant biology: energy dispersive X-ray microanalysis (CEDX) applications". Functional Plant Biology 37, n. 11 (2010): 1011. http://dx.doi.org/10.1071/fp10095.
Abstract (sommario):
The capacity to make measurements of elemental concentrations at the level of single cells by energy dispersive X-ray microanalysis of cryo-fixed, inherently-hydrated plant parts (CEDX) is changing or extending our understanding of many plant functions. We include in this review a wide-ranging catalogue of studies that have used CEDX which provides access to the literature on elements measured, plants and tissues studied, techniques used, level of quantitation and the significant findings. These findings include new perspectives on the following areas: salt tolerance; xylem maturation and solute content, root pressure and embolism refilling; the contents of intercellular spaces; sequestration of toxic elements; biomineralisation with silicon; movement of tracer homologues of native cations; indirect localisation of molecules with a distinctive element component; transfer of nutrients from vesicular-arbuscular (VA) mycorrhizas; the role of mucilages in protection and in generating mechanical force. In an Appendix we discuss the procedures involved in CEDX: cryo-fixation, specimen planing, etching, elemental quantitation and mapping. Limitations on sample numbers, elements measurable, spatial resolution, sensitivity and threshold concentrations quantifiable are outlined. A brief discussion of the potential of emerging technologies for cell-specific analysis of cryo-fixed, hydrated specimens is included. In the Accessory Publication we list our standard protocol for CEDX.
10
Ma, Jianchun, Lifang Wang, Yezhen Zhang e Jianfeng Jia. "Fabrication of a Molybdenum Dioxide/Multi-Walled Carbon Nanotubes Nanocomposite as an Anodic Modification Material for High-Performance Microbial Fuel Cells". Molecules 29, n. 11 (28 maggio 2024): 2541. http://dx.doi.org/10.3390/molecules29112541.
Abstract (sommario):
A nanocomposite of multi-walled carbon nanotubes (MWCNTs) decorated with molybdenum dioxide (MoO2) nanoparticles is fabricated through the reduction of phosphomolybdic acid hydrate on functionalized MWCNTs in a hydrogen–argon (10%) atmosphere in a tube furnace. The MoO2/MWCNTs composite is proposed as an anodic modification material for microbial fuel cells (MFCs). MWCNTs have outstanding physical and chemical peculiarities, with functionalized MWCNTs having substantially large electroactive areas. In addition, combined with the exceptional properties of MoO2 nanoparticles, the synergistic advantages of functionalized MWCNTs and MoO2 nanoparticles give a MoO2/MWCNTs anode a large electroactive area, excellent electronic conductivity, enhanced extracellular electron transfer capacity, and improved nutrient transfer capability. Finally, the power harvesting of an MFC with the MoO2/MWCNTs anode is improved, with the MFC showing long-term repeatability of voltage and current density outputs. This exploratory research advances the fundamental application of anodic modification to MFCs, simultaneously providing valuable guidance for the use of carbon-based transition metal oxide nanomaterials in high-performance MFCs.
Tesi sul tema "Hydrates transfer Cell":
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Abdallah, Mohamad. "Caractérisation multi-échelles des hydrates de gaz formés en présence d'additifs anti-agglomérants". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0048.
Abstract (sommario):
Dans le cadre de la production pétrolière, la formation d’hydrates de gaz peut conduire à la formation de dépôts, au bouchage des lignes et à l’interruption de la production du pétrole et/ou du gaz. La formation d’hydrate peut donc avoir un impact économique fort. Pour assurer la production sans risque d’arrêt de production, différentes stratégies sont adoptées. Une stratégie courante implique la production hors zone hydrates par injection d’additifs thermodynamiques (THIs) par exemple. Cependant, le déplacement des conditions de stabilité des hydrates par les THIs nécessitent l’injection de doses massives d’additif avec un coût environnemental et économique élevés. Une autre stratégie de production, en zone hydrate, consiste à injecter des additifs dits à faible doses (LDHI) : les inhibiteurs cinétiques (KHIs) ou les anti-agglomérants (AAs). Pour les champs pétroliers sous-marins profonds (deep offshore), seule l’injection d’additifs anti-agglomérants (AAs) est pertinente. Ces additifs ne bloquent pas la formation des hydrates mais évitent leur agglomération et dispersent les cristaux formés dans les fluides de production. Le développement des AAs et la validation de leurs applications sur des champs de production nécessitent une investigation approfondie de leurs impacts sur les systèmes réels de production (dispersion des cristaux dans les conduites, la taille des cristaux dans la phase continue, la transportabilité des suspensions, etc…).êPour apporter une meilleure compréhension de l’impact des additifs anti-agglomérants commerciaux (AAs) sur la formation d’hydrates une approche pluridisciplinaire et multi-échelles a été adoptée. La formation d’hydrates de gaz naturel a tout d’abord été réalisée au laboratoire en reproduisant les conditions de production pétrolière avec des systèmes industriels dans des conditions opérationnelles avec trois AA différents. À l’échelle macroscopique, les suspensions de cristaux réalisées sous agitation dans les réacteurs mettent en évidence des effets dépendants de l’AA utilisé. Ils impactent différemment la cinétique de formation des hydrates, le taux et la vitesse de croissance des cristaux ainsi que leur état de dispersion. Sans agitation, ces additifs AAs affectent la morphologie et contrôlent la croissance des cristaux et la phase dans laquelle ils vont croître. Ensuite, une cellule de transfert d’hydrates a été conçue pour prélever des échantillons de suspensions d’hydrates formés dans les réacteurs dans des conditions proches de la réalité industrielle (avec agitation, pression élevée, faible température). Les suspensions d’hydrates transférées ont ensuite été analysées par microtomographie à rayons X à l’aide d’une méthode développée au cours de ce travail. À l’échelle microscopique, l’état de dispersion des grains d’hydrates a été évalué pour l’ensemble des échantillons transférés et des informations ont été obtenues sur la taille des grains d’hydrates dispersés, leur forme et leur sédimentation dans la phase organique. À l’échelle moléculaire des analyses in-situ ont été réalisées par spectroscopie Raman sur des hydrates de méthane formés en présence des additifs AA. Ces essais ont mis en évidence la distribution des hydrates dans les phases organiques (gaz et condensat). Les observations par microscopie optique révèlent des morphologies d’hydrates comparables à celles obtenues en présence des additifs AAs dans les réacteursIn the context of oil production, the formation of gas hydrates can lead to the formation of deposits, the clogging of lines and the interruption of oil and/or gas production. Hydrate formation can therefore have a strong economic impact. To ensure production without the risk of production shutdown, different strategies are adopted. A common strategy involves the production outside the hydrate zone by injection of thermodynamic additives (THIs), for example. However, the displacement of hydrate stability conditions by THIs requires the injection of massive doses of additive with high environmental and economic costs. Another production strategy, in the hydrate zone, consists of injecting so-called low dose inhibitors (LDHI): kinetic inhibitors (KHIs) or anti-agglomerant additives (AAs). For deep offshore oil fields, only the injection of AAs is relevant. These additives do not block the formation of hydrates but prevent their agglomeration and disperse the crystals formed in the production fluids. The development of AAs and the validation of their applications on production fields require an in-depth investigation of their impacts on real production systems (dispersion of crystals in pipes, the size of crystals in the continuous phase, the transportability of slurries, etc…).êTo provide a better understanding of the impact of commercial AAs on the formation of hydrates, a multidisciplinary and multi-scale approach was adopted. The formation of natural gas hydrates was first carried out in the laboratory by reproducing oil production conditions with industrial systems under operational conditions with three different AAs. On the macroscopic scale, the slurries of crystals produced under stirring in the reactors highlight effects dependent on the AA used. They impact differently the kinetics of hydrate formation, the rate and speed of crystal growth as well as their state of dispersion. Without stirring, these AAs additives affect the morphology and control the growth of crystals and the phase in which they will grow. A hydrate transfer cell was then designed to sample of hydrate slurries formed in the reactors under conditions close to industrial reality (with stirring, high pressure, low temperature). The transferred hydrate slurries were then analyzed by X-ray microtomography using a method developed during this work. On the microscopic scale, the state of dispersion of the hydrate grains was assessed for all transferred samples and information was obtained on the size of the dispersed hydrate grains, their shape and their sedimentation in the organic phase. At the molecular scale, in-situ analyzes were carried out by Raman spectroscopy on methane hydrates formed in the presence of the three AA additives. These tests highlighted the distribution of hydrates in the organic phases (gas and condensate). Observations by optical microscopy reveal hydrate morphologies comparable to those obtained in the presence of AAs additives in the reactors
Capitoli di libri sul tema "Hydrates transfer Cell":
1
Fagan, Melinda Bonnie. "Stem cells". In Routledge Encyclopedia of Philosophy. London: Routledge, 2023. http://dx.doi.org/10.4324/9780415249126-q152-1.
Abstract (sommario):
What is a stem cell? The term is a combination of ‘cell’ and ‘stem’. A cell is a major category of living thing, while a stem is a site of growth and support for something else. In science today, a stem cell is defined as a cell derived from a multicellular organism, which is able to both self-renew (produce more stem cells of the same kind) and differentiate (produce cells corresponding to later developmental stages of the source organism). So the concept of a stem cell is somewhat complex, bearing on questions of biological individuality, relations between cells and organisms, and our understanding of development. Stem cell phenomena range from everyday to extraordinary laboratory products. On the everyday side: hair, skin, and blood cells are shed and replaced by ongoing stem cell activities. Stem cells help maintain organs and tissues in mature multicellular organisms. Regeneration in wound-healing is also, often, stem-cell mediated. The hydra’s mythic regeneration potential is due to its plentiful stem cells; similarly for plants. Looking to earlier developmental stages, embryonic cells also exhibit stem cell capacities. If such cells are removed from an early embryo and grown in artificial cell culture, this produces an embryonic stem cell line – an indefinitely renewable source of cells that can, under appropriate conditions, develop to produce many (even all) cell types found in a mature organism. Other experimental products of stem cells include embryoid bodies, organoids, and embryo-like structures. Stem cells are thus found in living organisms (in vivo) and grown artificially (in vitro). Stem cells raise several important metaphysical questions for philosophers of biology. One concerns biological individuality. Multicellular organisms are paradigmatic biological individuals. There are strong reasons to think cells are individuals. Stem cells are cells that divide and develop into other kinds of cell, tissues, organs, and even analogues of whole organisms. Are stem cells individuals? One way to answer this question is in terms of cell lineages. Complicating matters, stem cells mediate between cell and organismal levels of biological organisation. This raises questions about individuality and development for organisms and constituent cell lineages. Metaphysical theories about the nature of stem cells – natural kinds, causal mechanisms, processes – are also unsettled, as is the science. Different metaphysical theories about the nature of stem cells present a problem of theory choice. Alternatives include: stem cells as entities, stemness as a state, disposition to develop, and cell-environment systems. Our knowledge about stem cells is incomplete, based on many different kinds of experiment. The main ways of identifying stem cells are to find, grow, or make them: cell-sorting, in vitro culture, and reprogramming, respectively. The basic design is to remove cells from an organismal source and place them in an environment where they can self-renew. After measuring cell traits in this environment, some cells are moved to a new environment to encourage differentiation. Cell traits in the new environment are then measured. The results correlate traits of an organismal source, candidate stem cells, and differentiated cells. Collectively, these experiments yield many different varieties of stem cell. Characterisation of these varieties is closely tied to technologies and experimental methods for culturing, visualising, and manipulating cells. Uncertainty is a constant, however. It’s impossible to experimentally show that a single cell is a stem cell; all methods of identifying stem cells require populations of homogeneous stem cells. But homogeneity for cells that by definition transform into other things is a fragile assumption. Consequently, stem cells are identified relative to particular experimental methods. Our knowledge of stem cells accumulates by multiplying experimental contexts and relating their outcomes to one another. In practice, knowledge about stem cells has the form of a proliferating network of models. In vitro stem cells are a prominent example: concrete approximations of early developmental stages of a multicellular organism of a particular species. Other important stem cell-based models are organoids and human-animal chimeras. Different stem cell models complement one another, highlighting different aspects of development. More generally, stem cell biology is replete with abstract and concrete models. Social organisation of experiments and resultant models is important for understanding the epistemology of stem cell research. Abstract models play a less prominent role in stem cell research, although lineage tree models are important representations of stem cells and their potential. Classifying stem cells is an unsettled and messy affair, with many different cross-cutting or overlapping distinctions used in practice. There are many varieties of stem cell, but no single agreed-upon system for classifying them. Lineage tree models offer one prospect for such a system. In popular culture, stem cells are associated with medical promise on the one hand, and embryo destruction on the other. Stem cells are tokens of medical promise and hope; the idea being to use their potential to cure a wide range of injuries and diseases. This promise motivates stem cell ‘clinics’ alongside scientific research. The former peddle cures for many ailments unencumbered by scientific evidence or regulatory approval. The latter challenged by ethical questions about human embryo research. Tension between medical hopes and objections to human embryo research has produced a large bioethics literature. Key ethical debates are about research using human embryos, creating human–animal chimeras, and how to balance hope and hype in regulating and funding stem cell research. Broad anti-science cultural movements encourage proliferation of stem cell ‘clinics’ that market alleged cures directly to consumers, bypassing scientific and medical standards.
Atti di convegni sul tema "Hydrates transfer Cell":
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Acharya, Palash V., Arjang Shahriari, Katherine Carpenter e Vaibhav Bahadur. "Aluminum Foam-Based Ultrafast Electronucleation of Hydrates". In ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ht2017-4812.
Abstract (sommario):
Nucleation of hydrates requires very long induction (wait) times, often ranging from hours to days. Electronucleation, i.e. nucleation stimulated by the presence of an electric field in the precursor solution can reduce the induction time significantly. This work reveals that porous aluminum foams enable near-instantaneous electronucleation at very low voltages. Experiments with tetrahydrofuran hydrate nucleation reveal that open-cell aluminum foam electrodes can trigger nucleation in only tens of seconds. Foam-based electrodes reduce the induction time by as much as 150X, when compared to non-foam electrodes. This work also discusses two mechanisms underlying electronucleation. These include bubble generation (due to electrolysis), and the formation of metal-ion coordination compounds. These mechanisms depend on electrode material and polarity, and affect the induction time to different extents. This work also shows that foams result in more deterministic nucleation (compared to stochastic) when compared with non-foam electrodes. Overall, electronucleation can lead to a new class of technologies for active control of formation of hydrates.
2
Meindinyo, Remi-Erempagamo T., Runar Bøe, Thor Martin Svartås e Silje Bru. "Experimental Study on the Effect of Gas Hydrate Content on Heat Transfer". In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41280.
Abstract (sommario):
Gas hydrates are the foremost flow assurance issue in deep water operations. Since heat transfer is a limiting factor in gas hydrate formation processes, a better understanding of its relation to hydrate formation is important. This work presents findings from experimental study of the effect of gas hydrate content on heat transfer through a cylindrical wall. The experiments were carried out at temperature conditions similar to those encountered in flowlines in deep water conditions. Experiments were conducted on methane hydrate, Tetrahydrofuran hydrate, and ethylene oxide hydrate respectively in stirred cylindrical high pressure autoclave cells. Methane hydrate was formed at 90 bars (pressure), and 8°C, followed by a cooling/heating cycle in the range of 8°C → 4°C → 8°C. Tetrahydrofuran (THF) and ethylene oxide (EO) hydrates were formed at atmospheric pressure and system temperature of 1°C in contact with atmospheric air. This was followed by a heating/cooling cycle within the range of 1°C → 4°C → 1°C, since the hydrate equilibrium temperature of THF hydrate is 4.98°C in contact with air at atmospheric pressure. The experimental conditions of the latter hydrate formers were more controlled, given that both THF and EO are miscible with water. We found in all cases a general trend of decreasing heat transfer coefficient of the cell content with increasing concentration of hydrate in the cell, indicating that hydrate formation creates a heat transfer barrier. The hydrate equilibrium temperature seemed to change with a change in the stoichiometric concentration of THF and EO. While the methane hydrate cooling/heating cycles were performed under quiescent conditions, the effect of stirring was investigated for the latter hydrate formers.
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Wang, Xin, Weizhong Li e Minghao Yu. "Numerical Simulation of Methane Hydrate Dissociation in Glass Micro Channels by Depressurization". In ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/power-icope2017-3447.
Abstract (sommario):
Methane hydrate has been paid considerable attention on how to exploit it by efficient and economical methods. A computer modeling approach was used to obtain more detail information during the process of methane hydrate decomposition. A comprehensive Users’ Defined Subroutine (UDS) was used in the FLUENT code to model the methane hydrate dissociation by depressurization. The kinetic model and equilibrium condition were contained in the UDS. The new UDS can model the heat and mass transfer during the decomposition process of methane hydrate. The behavior of the methane hydrate decomposition process in both laboratory-scale simulation and micro channels simulation was investigated in this paper. The laboratory-scale simulation results were compared with ones of the laboratory-scale system studied by Masuda et al. to verify the UDS. Evolutions of methane gas, water and hydrate in the cross micro channels were obtained. The phenomenon of water freezing was predicted by comparing the water temperature and freezing temperature. The results also showed that the dissociation process of gas hydrates as well as the water freezing phenomenon occur not only in the interface between hydrate layer and production zone, but also deep in the hydrate zone.
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Fopah Lele, Armand, Fréderic Kuznik, Holger Urs Rammelberg, Thomas Schmidt e Wolfgang K. L. Ruck. "Modeling Approach of Thermal Decomposition of Salt-Hydrates for Heat Storage Systems". In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17022.
Abstract (sommario):
Heat storage systems using reversible chemical solid-fluid reactions to store and release thermal energy operates in charging and discharging phases. During last three decades, discussions on thermal decomposition of several salt-hydrates were done (experimentally and numerically) [1,2]. A mathematical model of heat and mass transfer in fixed bed reactor for heat storage is proposed based on a set of partial differential equations (PDEs). Beside the physical phenomena, the chemical reaction is considered via the balances or conservations of mass, extent conversion and energy in the reactor. These PDEs are numerically solved by means of the finite element method using Comsol Multiphysics 4.3a. The objective of this paper is to describe an adaptive modeling approach and establish a correct set of PDEs describing the physical system and appropriate parameters for simulating the thermal decomposition process. In this paper, kinetic behavior as stated by the ICTAC committee [3] to understand transport phenomena and reactions mechanism in gas and solid phases is taking into account using the generalized Prout-Tompkins equation with modifications based on thermal analysis experiments. The model is then applied to two thermochemical materials CaCl2 and MgCl2 with experimental activation energies and a comparison is made with TGA-DSC measurement results.
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Deepan Kumar, Sadhasivam, Vishnu Ramesh Kumar R, Devadoss Dinesh Kumar, R. Manojkumar, Tamilselvan A, Boopathi M e Lokesh C. "Design and Thermal Analysis of Battery Thermal Management System for EV". In International Conference on Advances in Design, Materials, Manufacturing and Surface Engineering for Mobility. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2023. http://dx.doi.org/10.4271/2023-28-0087.
Abstract (sommario):
<div class="section abstract"><div class="htmlview paragraph">Controlling thermal dissipation by operating components in car batteries requires a heat management design that is of utmost importance. As a proactive cooling method, the usage of PCM (Phase Change Materials) to regulate battery module temperature is suggested. Even at lower flow rates, liquid cooling has a heat transfer coefficient that is 1.5–3 times better. The rate of global cell production has increased today from 4,000 to 100,000 cells per day. Future-proof Li (metal) battery chemistry with a 3x increase in energy density. Ineffective thermal management of the battery is the root of the issue. In order to optimise battery modules, it is important to identify likely failure modes and causes. The medium used to carry heat from the battery over its passage duration at various operating temperatures is a variety of phase-change materials. The latent heat is significant, and many vegetable fats derived from fatty acids are more effective than salt hydrates and paraffin. Melting temperatures range between -30 and 150 degrees Celsius. As a result of optimisation, the root mean square temperature between batteries was reduced by 13.3% when compared to the primary battery temperature control system. In our work, we describe techniques for enhancing temperature uniformity and cooling in a simple pack battery. Four distinct battery pack combinations are in the works. In the first concept, an intake plenum is added to a standard battery pack. In the second design, jet inlets are integrated with the inlet plenum, and multiple vortex generators are included with the inlet plenum in the third configuration. Finally, the battery pack in the fourth iteration contains an intake plenum, jet inlets, and many vortex generators. The results reveal that integrating an intake plenum, several vortex generators, and jet inlets in the same design yielded significant improvements. According to the findings, the maximum temperature of the battery pack is reduced by 5%, and the temperature differential between the greatest and lowest temperatures recorded by the battery pack is reduced by 21.5 percent.</div></div>
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Zhao, C. Y., D. Zhou e Z. G. Wu. "Heat Transfer Enhancement of Phase Change Materials (PCMs) in Low and High Temperature Thermal Storage by Using Porous Materials". In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22463.
Abstract (sommario):
In this paper the solid/liquid phase change heat transfer in porous materials (metal foams and expanded graphite) at low and high temperatures is experimentally investigated, in an attempt to examine the feasibility of using metal foams to enhance the heat transfer capability of phase change materials for use with both the low and high temperature thermal energy storage systems. In this research, the organic commercial paraffin wax and inorganic hydrate calcium chloride hydrate salts were employed as the low-temperature materials, while the sodium nitrate is used as the high-temperature PCM in the experiment. The heat transfer characteristics of these PCMs embedded with open-cell metal foams were studied experimentally. The composites of paraffin and expanded graphite with different graphite mass ratios, namely, 3%, 6% and 9%, were also made and the heat transfer performances of these composites were tested and compared with metal foams. Overall metal foams can provide better heat transfer performance than expanded graphite due to their continuous inter-connected structures. But the porous materials can suppress the natural convection effect in liquid zone, particularly for the PCMs with low viscosities, thereby leading to the different heat transfer performance at different regimes (solid, solid/liquid and liquid regions). This implies that the porous materials don’t necessarily mean they can always enhance heat transfer in every regime.
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Mukherjee, Partha P., Devesh Ranjan, Rangachary Mukundan e Rodney L. Borup. "Heat and Water Transport in a Polymer Electrolyte Fuel Cell Electrode". In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22703.
Abstract (sommario):
In the present scenario of a global initiative toward a sustainable energy future, the polymer electrolyte fuel cell (PEFC) has emerged as one of the most promising alternative energy conversion devices for various applications. Despite tremendous progress in recent years, a pivotal performance limitation in the PEFC comes from liquid water transport and the resulting flooding phenomena. Liquid water blocks the open pore space in the electrode and the fibrous diffusion layer leading to hindered oxygen transport. The electrode is also the only component in the entire PEFC sandwich which produces waste heat from the electrochemical reaction. The cathode electrode, being the host to several competing transport mechanisms, plays a crucial role in the overall PEFC performance limitation. In this work, an electrode model is presented in order to elucidate the coupled heat and water transport mechanisms. Two scenarios are specifically considered: (1) conventional, Nafion® impregnated, three-phase electrode with the hydrated polymeric membrane phase as the conveyer of protons where local electro-neutrality prevails; and (2) ultra-thin, two-phase, nano-structured electrode without the presence of ionomeric phase where charge accumulation due to electro-statics in the vicinity of the membrane-CL interface becomes important. The electrode model includes a physical description of heat and water balance along with electrochemical performance analysis in order to study the influence of electro-statics/electro-migration and phase change on the PEFC electrode performance.
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Berning, Torsten, e Shiro Tanaka. "A Study of Multiphase Flow and Heat Transfer in Proton Exchange Membrane Fuel Cells With Perforated Metal Gas Diffusion Layers". In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-4654.
Abstract (sommario):
Abstract A numerical analysis of a proton exchange membrane fuel cell (PEMFC) that contains a perforated metal plate at the cathode side has been conducted. The model utilizes the Eulerian multi-phase approach to predict the occurrence and transport of liquid water inside the cell. The PEMFC that was modelled contained micro-channels at both anode and cathode side. Results suggest that despite the fact that the inlet gases are fully saturated (RH = 100%), the holes in the metal sheet remain in the single phase, and the predicted maximum current densities are accordingly high. The high thermal conductivity of the metal sheets result in only a moderate temperature increase in the cell, and the fuel cell membrane is predicted to be hydrated under all conditions investigated. The fact that the cathode channel and the holes in the metal sheet remain dry is attributed to the high pressure drop inside the flow channel.
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Friess, Brooks R., Samuel C. Yew e Mina Hoorfar. "The Effect of Flow Channel Surface Properties and Structures on Water Removal and Fuel Cell Performance". In ASME 2011 9th International Conference on Fuel Cell Science, Engineering and Technology collocated with ASME 2011 5th International Conference on Energy Sustainability. ASMEDC, 2011. http://dx.doi.org/10.1115/fuelcell2011-54489.
Abstract (sommario):
The polymer electrolyte membrane (PEM) fuel cell is a zero emission power generation system that has long been considered as a replacement for conventional fossil fuel combustion systems. However, before constituting a viable market for commercial use, the fuel cell efficiency and reliability need to be improved significantly. It has been shown that water management has significant effect on the power and reliability of the cell as the electrolyte membrane must be well hydrated to allow for ion transfer while excess water blocks the activation sites on the cathode side. The latter effect is known as flooding which occurs at large current densities and compromises the normal operation of the fuel cell. To enhance water management, a prodigious amount of numerical models and experimental studies have been conducted to optimize the properties and structures of different layers. One of the key results of these studies has been the design of the flow field patterns on relatively hydrophobic surface of a graphite plate which is believed to provide a better mechanism for removing water droplets from the cathode flow channel. However, the wettability gradient between the catalyst layer (i.e., hydrophilic) and the flow channel (which is currently hydrophobic) introduces problems as the water droplets formed at the catalyst layer will not likely detach and hence create a film of liquid that will block the activation sites. If the flow channel is made out of a material that is more hydrophilic than the catalyst layer, water removal and transport will be enhanced as water naturally moves from low surface energy to high surface energy sites. Another major factor in controlling water in the PEM fuel cell is the flow field architecture. There has also been a large amount of research on different types of the flow field architectures. However, there have been no studies on the relative performance gains provided by changing the surface properties and the architecture separately. This paper presents an experimental analysis comparing two different flow fields with different surface properties, i.e., a hydrophilic gold flow channel and a hydrophobic graphite flow channel. The paper will also compare three different hydrophilic flow channel architectures: an open gold parallel flow channel, an aluminum foam filled parallel flow channel, and a woven wick filled parallel flow channel. This work will result in finding the optimum geometry and surface properties for achieving maximum performance in the flooding regime.
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Friess, Brooks R., Samuel C. Yew e Mina Hoorfar. "Effect of the Hydrophilic Compact Aluminum-Foam Filled Flow Channel on Water Removal From the Cathode Catalyst Layer". In ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2011. http://dx.doi.org/10.1115/icnmm2011-58172.
Abstract (sommario):
The polymer electrolyte membrane (PEM) fuel cell is a zero emission power generation system that has long been considered as a replacement for conventional fossil fuel combustion systems. However, before constituting a viable market for commercial use, the fuel cell’s efficiency and reliability need to be improved significantly. It has been shown that water management has a significant effect on the power and reliability of the cell as the electrolyte membrane must be well hydrated to allow for ion transfer while excess water blocks the activation sites on the cathode side. The latter effect is known as flooding which occurs at large current densities and compromises the normal operation of the fuel cell. To enhance water management, a prodigious amount of studies have been conducted to optimize the properties and structures of different layers. One of the key results of these studies has been the design of a flow field pattern on the relatively hydrophobic surface of a graphite plate which is believed to provide a better mechanism for removing water droplets from the cathode flow channel. However, the wettability gradient between the catalyst layer (i.e., hydrophilic) and the flow channel (which is currently more hydrophobic) introduces problems as the water droplets formed at the catalyst layer will not likely detach, and hence create a film of liquid that will block the activation sites. If the flow channel is made out of a material that is more hydrophilic than the catalyst layer, water removal and transport will be enhanced as water naturally moves from low surface energy to high surface energy sites. However, recent numerical studies conducted on simulation of water transport in the channels show that removing the water film formed on the hydrophilic channels is limited due to the pressure of the gas flow in the channels. To resolve this problem, the use of compact aluminum foams in the flow channels is studied in this paper. It is shown that the hydrophilicity of the foam-filled flow channel helps the transport of the water droplets at the catalyst layer to the channel in which a liquid film is formed. This film is then removed due to the increased pressure developed in the porous media of the foam (as opposed to the regular open flow channel). The paper includes the experimental results obtained for the fuel cell performance using the new geometry with and without the gas diffusion layers (GDLs). These results will be compared to a similar flow channel that does not include the compressed aluminum porous structure. This work will result in finding the optimum geometry for achieving maximum performance in the flooding regime.