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51.
Somendra M. Bhattacharjee John F. Nagle David A. Huse Michael E. Fisher 《Journal of statistical physics》1983,32(2):361-374
The phase transition behavior of a dimer model on a three-dimensional lattice is studied. This model is of biological interest because of its relevance to the lipid bilayer main phase transition. The model has the same kind of inactive low-temperature behavior as the exactly solvable Kasteleyn dimer model on a two-dimensional honeycomb lattice. Because of low-temperature inactivity, determination of the lowest-lying excited states allows one to locate the critical temperature. In this paper the second-lowest-lying excited states are studied and exact asymptotic results are obtained in the limit of large lattices. These results together with a finite-size scaling ansatz suggest a logarithmic divergence of the specific heat aboveT c for the three-dimensional model. Use of the same ansatz recovers the exact divergence (α=1/2) for the two-dimensional model. 相似文献
52.
Kucerka N Pencer J Sachs JN Nagle JF Katsaras J 《Langmuir : the ACS journal of surfaces and colloids》2007,23(3):1292-1299
High-resolution small-angle X-ray scattering (SAXS), complemented by small-angle neutron scattering (SANS) and dynamic light scattering (DLS) experiments, was used to study the effect of curvature on the bilayer structure of dioleoyl-phosphatidylcholine (DOPC) and dioleoyl-phosphatidylserine (DOPS) unilamellar vesicles (ULVs). Bilayer curvature, as a result of finite vesicle size, was varied as a function of vesicle radius and determined by DLS and SANS measurements. Unilamellarity of large DOPC ULVs was achieved by the addition of small amounts (up to 4 mol %) of the charged lipid, DOPS. A comparison of SANS data over the range of 0.02 < q <0.2 A-1 indicated no change in the overall bilayer thickness as a function of ULV diameter (620 to 1840 A). SANS data were corroborated by high-resolution (0.06 < q <0.6 A-1) SAXS data for the same diameter ULVs and data obtained from planar samples of aligned bilayers. Both the inner and outer leaflets of the bilayer were found to be indistinguishable. This observation agrees well with simple geometric models describing the effect of vesicle curvature. However, 1220-A-diameter pure DOPS ULVs form asymmetric bilayers whose structure can most likely be rationalized in terms of geometrical constraints coupled with electrostatic interactions, rather than curvature alone. 相似文献
53.
Production of runaway electrons during disruptions has been observed in the HT‐7 Tokamak. The runaway current plateaus, which can carry part of the pre‐disruptive current, are observed in lower‐hybrid current drive (LHCD) limiter discharges. It is found that the runaway current can mitigate the disruptions effectively. We can use gas puffing to increase the line‐averaged density to restrain the runaway electrons and rebuild the plasmas after the disruptions. Detailed observations are presented on the runaway electrons generated following disruptions in the HT‐7 tokamak discharges. The results indicate that the magnetic oscillations play a significant role in the loss of runaway electrons in disruptions. There are two important preconditions to rebuild plasmas by runaway electrons after the disruptions. One of them are weak magnetic oscillations; another one are LHWs (lower‐hybrid waves) (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
54.
Moussa Z. Boucaud P. Julien F.H. Lavon Y. Sa'ar A. Berger V. Nagle J. Coron N. 《Electronics letters》1995,31(11):912-913
Mid-infrared intersubband emission is investigated in GaAs/AlGaAs asymmetric coupled quantum wells exhibiting an energy separation between the ground and first excited subbands close to the LO-phonon energy. The authors show that an infrared emission occurs between excited subbands under intersubband optical pumping 相似文献
55.
Computational requirements often discourage, or even prohibit, complete fault simulation of circuit designs having greater than 20000 single stuck-at faults. To circumvent this problem, statistical sampling methods have been proposed that provide fault coverage values within a small, predictable error range by simulating only a fraction of the circuit's total faults and using the result fault coverage value as an estimate of the fault coverage for the total circuit. As an introduction to the application of sampling methods to fault simulation of integrated circuits, the statistical theory behind these sampling methods and proposed augmentations of these methods for improving the precision of the sample fault coverage are presented. Various proposed sampling schemes are applied to example circuit designs, and the results are analyzed 相似文献
56.
Rivard C. J. Rodriguez J. B. Nagle N. J. Self J. R. Kay B. D. Soltanpour P. N. Nieves R. A. 《Applied biochemistry and biotechnology》1995,(1):125-135
Tuna processing wastes (sludges high in fat, oil, and grease [FOG]) and municipal solid waste (MSW) generated on Tutuila Island,
American Samoa, represent an ongoing disposal challenge. The biological conversion of the organic fraction of these wastes
to useful products, including methane and fertilizer-grade residue, through anaerobic high-solids digestion is currently in
scale-up development. The suitability of the anaerobic digestion residues as a soil amendment was evaluated through extensive
chemical analysis and greenhouse studies using corn as an indicator crop. Additionally, native Samoan soil was used to evaluate
the specific application rates for the compost. Experiments established that anaerobic residues increase crop yields in direct
proportion to increases in the application rate. Additionally, nutrient saturation was not demonstrated within the range of
application rates evaluated for the Samoan soil. Beyond nutrient supplementation, organic residue amendment to Samoan soil
imparts enhanced water- and nutrient-binding capacities. 相似文献
57.
A novel method for the mono-N-alkylation of primary amines, diamines, and polyamines was developed using cesium bases in order to prepare secondary amines efficiently. A cesium base not only promoted alkylation of primary amines but also suppressed overalkylations of the produced secondary amines. Various amines, alkyl bromides, and alkyl sulfonates were examined, and the results demonstrated this methodology was highly chemoselective to favor mono-N-alkylation over dialkylation. In particular, use of either sterically demanding substrates or amino acid derivatives afforded the secondary amines exclusively, offering wide applications in peptidomimetic syntheses. 相似文献
58.
Gyurcsányi RE Cristalli A Nagy G Nagy L Corder C Pendley BD Ufer S Nagle HT Neuman MR Lindner E 《Fresenius' Journal of Analytical Chemistry》2001,369(3-4):286-294
The analytical performance of amperometric microcells with different electrode geometries is compared for enzyme activity measurements. The microcells were fabricated with thin film photolithography or thick film screen-printing in four different designs. The cells made with the thin film process used flexible substrate with microelectrode array or a circular, disk-shaped working electrode. The screen-printed working electrodes had semicircle or disk shape on ceramic chips. Putrescine oxidase (PUO) activity measurement was used as a model. The determination of PUO activity is important in the clinical diagnosis of premature rupture of the amniotic membrane. An electropolymerized m-phenylenediamine size-exclusion layer was used to eliminate common interferences. The size exclusion layer revealed also to be advantageous in protecting the electrodes from fouling by putrescine (enzyme substrate). The electrode fouling of bare electrodes was insignificant for screen-printed electrodes, but very severe for electroplated platinum working electrodes. The microelectrode array electrodes demonstrated smaller RSD and higher normalized sensitivities for hydrogen peroxide and PUO activity. All the other electrodes were demonstrating comparable analytical performances. 相似文献
59.
Rivard C. J. Kay B. D. Kerbaugh D. H. Nagle N. J. Himmel M. E. 《Applied biochemistry and biotechnology》1995,51(1):155-162
Applied Biochemistry and Biotechnology - Improved organic loading rates for anaerobic bioconversion of cellulosic feedstocks are possible through high-solids processing. Additionally, the reduction... 相似文献
60.
J F Nagle 《Photochemistry and photobiology》1991,54(6):897-903
A recently developed algorithm for analyzing photocycle kinetics was applied to recently obtained Raman data for the time course of bacteriorhodopsin (bR) and its intermediates, L, M, N and O. The algorithm allows all possible transitions between any of the intermediates in the kinetic model. The best fit to all the Raman data required the transitions L in equilibrium with M in equilibrium with N----O----bR and also the branch L in equilibrium with N. The rates are moderately well determined and smooth as a function of pH. From the ratios of forward and backward rates the differences in free energy of the L, M and N states are no larger than 1.5 kcal. The possibility that only the sum of the L and N concentrations is well determined, but not the individual L and N concentrations, was investigated. The model L in equilibrium with M in equilibrium with N----O----bR satisfactorily fitted condensed L + N data and gave predicted individual L and N concentrations considerably different than those measured individually. The possibility of Raman invisible states, such as two Ms or two Ns was also investigated. Models with two Ns were not successful and it cannot yet confidently be concluded which model with two Ms is best. However, the model, L in equilibrium with M1----M2----N----O----bR plus the branch L----N, fits the data better with the same number of parameters as the best model with only one M intermediate. This provides strong support for two Ms in the bR photocycle. 相似文献