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991.
Of all materials, silicon has the highest capacity to store lithium, and is being developed as an electrode for lithium-ion batteries. Upon absorbing a large amount of lithium, the electrode swells greatly, with a volumetric change up to 300%. The swelling is inevitably constrained in practice, often leading to stress and fracture. Evidence has accumulated that the swelling-induced stress can be partially relieved by plastic flow, and that electrodes of small feature sizes can survive many cycles of lithiation and delithiation without fracture. Here we simulate a particle of an electrode subject to cyclic lithiation and delithiation. A recently developed theory of concurrent large swelling and finite-strain plasticity is used to co-evolve fields of stress, deformation, concentration of lithium, and chemical potential of lithium. We identify three types of behavior. When the yield strength is high and the charging rate is low, the entire particle deforms elastically in all cycles. When the yield strength is low and the charging rate is high, the particle (or part of it) undergoes cyclic plasticity. Under intermediate conditions, the particle exhibits the shakedown behavior: part of the particle flows plastically in a certain number of initial cycles, and then the entire particle remains elastic in subsequent cycles. We discuss the effect of the three types of behavior on the capacity and the electrochemical efficiency.  相似文献   
992.
993.
Heroult J  Zuliani T  Bueno M  Denaix L  Lespes G 《Talanta》2008,75(2):486-493
The development and validation of a method for organotin analysis in soils, including butyl-, phenyl- and octyl-tins, are described in this study. The influence of pretreatment step based on sample lyophilization was first studied. Different solid-liquid extraction techniques including mechanical stirring (MSAE), accelerated solvent (ASE), microwave (MAE) and ultrasound (UAE), were compared. MSAE gave the best recoveries and repeatability and was thus chosen for OTC extraction from soils. Then, ethylation/extraction step before GC-PFPD analysis was investigated and the best derivatisation conditions were assessed in order to achieve a simple, non-expensive and reliable routine procedure. Finally, the robustness of the method was tested by the analysis of several soils with different organic matter content allowing the validation of developed protocol. The method appears to be reliable and accurate for the OTC determination in a broad range of soils.  相似文献   
994.
The flow around a trailing edge is computed with a new hybrid method designed to more clearly separate the effects of total and sub-grid turbulent stress-modelling on the time-averaged and instantaneous velocity fields, and in turn, mean momentum and kinetic energy balances. These two velocity fields independently define Reynolds averaged and sub-grid-scale viscosities, and distinct stresses, at the same location. In particular, resolved eddies can emerge, or sweep in and out of the Reynolds averaged near wall layer, without being dampened by higher levels of the viscosity in this RANS dominated layer. The two-field hybrid model, first tested on channel flows, gives accurate predictions of mean velocities and stresses for different Reynolds numbers and coarse meshes. For the trailing edge flow the results of the hybrid model are close to the reference fine LES for mean velocity and turbulent content, whereas the DES-SST on the same coarse mesh gives too early separation.  相似文献   
995.
Raman spectroscopy was performed on various mixtures of the ionic liquid salt, 1‐ethyl‐3‐methylimidazolium‐bis(trifluoromethylsulfonyl)imide (EMI‐TFSI). When EMI‐TFSI is used in combination with a lithium salt, it could be a potential electrolyte for lithium‐ion or lithium metal batteries. The Raman spectra of EMI‐TFSI, EMI‐TFSI 0.5 M Li‐TFSI, EMI‐TFSI 0.5 M Li‐TFSI 2 M vinylene carbonate (VC) and EMI‐TFSI 0.5 Li‐TFSI 2 M ethylene carbonate (EC) were collected and compared. A comparison of the peak positions of the δs CF3 mode at 742 cm−1 demonstrates that when carbonate additives are present, the lithium ion is no longer interacting with the TFSI anion. Instead, it is coordinated with the carbon–oxygen double bond of the carbonates. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
996.
Poly(vinylamine), PVA, complexes with cobalt chloride hexahydrate exhibit a 45 °C enhancement in the glass‐transition temperature per mol % of the d‐block metal cation. Poly(ethylene imine), PEI, complexes with CoCl2(H2O)6 exhibit a 20 °C enhancement in Tg per mol % Co2+. Since the basicities of primary and secondary amines are comparable (i.e., pKb,PVA ≈ 3.34 vs. pKb,PEI ≈ 3.27) and the rates at which each polymeric ligand displaces waters of hydration in the coordination sphere of Co2+ are similar, transition metal compatibilization is operative in blends of both polymers with CoCl2(H2O)6. These two polymers are immiscible in the absence of the inorganic component. Infrared spectroscopy suggests that nitrogen lone pairs in PVA and PEI coordinate to Co2+. The stress–strain response of a 75/25 blend of PVA and PEI with 2 mol % Co2+ reveals a decrease in elastic modulus from 4.4 × 109 N/m2 to 5.7 × 107 N/m2, a decrease in fracture stress from 3.7 × 107 N/m2 to 2.0 × 106 N/m2, and an increase in ultimate strain from 1.3 to 12% relative to the 75/25 immiscible polymer–polymer blend. A plausible explanation for this effect is based on the fact that cobalt chloride hexahydrate compatibilizes both polymers by forming a coordination bridge between nitrogen lone pairs in dissimilar chains. Hence, poly(ethylene imine), which is very weak with a Tg near −40 °C, is integrated into a homogeneous structure with poly(vinylamine) and the mechanical properties of the individual polymers are averaged in the compatibilized ternary complex. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 552–561, 2000  相似文献   
997.
A novel self-assembly technique for the growth of insoluble and intractable thin organic films is presently reported. Bifunctional 8,8′-dihydroxy-5,5′-biquinoline (bisquinoline) is reactively self-assembled with diethyl zinc to form a linear coordination polymer. FTIR, UV/VIS spectroscopy, profilometry, and photoluminescence measurements were used to characterize these new multilayer films. The growth of these films on glass substrates was monitored by increasing absorbance at 396.6 nm using UV/VIS spectroscopy and by profilometry. FTIR spectroscopy indicated that the self-assembled films are polymeric in nature. The reduction of end-group hydroxyls and a significant red-shift of the photoluminescence emission spectrum with respect to zinc bisquinoline powder was attributed to an increase in conjugation length.  相似文献   
998.
Tetrahydroisoquinoline (THIQ) alkaloids and their derivatives have a structural similarity to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a well-known neurotoxin. THIQs seem to present a broad range of actions in the brain, critically dependent on their catechol moieties and metabolism. These properties make it reasonable to assume that an acute or chronic exposure to some THIQs might lead to neurodegenerative diseases including essential tremor (ET). We developed a method to search for precursor carbonyl compounds produced during the Maillard reaction in overcooked meats to study their reactivity with endogenous amines and identify the reaction products. Then, we predicted in silico their pharmacokinetic and toxicological properties toward the central nervous system. Finally, their possible neurological effects on a novel in vitro 3D neurosphere model were assessed. The obtained data indicate that meat is an alkaloid precursor, and we identified the alkaloid 1-benzyl-1,2,3,4-tetrahydroisoquinoline-6,7-diol (1-benz-6,7-diol THIQ) as the condensation product of phenylacetaldehyde with dopamine; in silico study of 1-benz-6,7-diol-THIQ reveals modulation of dopamine receptor D1 and D2; and in vitro study of 1-benz-6,7-diol-THIQ for cytotoxicity and oxidative stress induction does not show any difference after 24 h contact for all tested concentrations. To conclude, our in vitro data do not support an eventual neurotoxic effect for 1-benz-6,7-diol-THIQ.  相似文献   
999.
A recent mathematical analysis by Michel Petijean aimed at solving the Barron/Mislow controversy concerning the chirality or otherwise of a non-translating spinning cone concluded that both are right: the controversy is a matter of an arbitrary choice of a conversion factor. This reassessment highlights the different physicochemical properties of a stationary spinning cone and a chiral molecule and concludes that Petitjean's analysis is misleading.  相似文献   
1000.
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