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31.
William Hayden Smith Donald K. Hsu 《Journal of Quantitative Spectroscopy & Radiative Transfer》1979,22(3):223-229
The origins of the predissociations observed by Smith, Brzozowski, and Erman for the A3Πand c1Π states of NH have been investigated via a Franck-Condon analysis. It is shown that the measured variation of the predissociation probability is is proportional to the Franck-Condon densities between the bound rotational levels of the A and c states and the vibrational continuum of a 5Σ- state arising from the ground state asympote. Similar calculations for the X3Σ- ground state vibrational continuum, the only other state with a lower dissociation limit, showed that state to be ineffective in producing the observed predissociation. 相似文献
32.
We present the performance improvements obtained both by scaling the Selectively Compensated Collector (SCC) BJT and by using a modified Current-Mode Logic (CML) gate configuration. Scaling the perimeter parameter by using the (tighter) bitcell design rules results in a ~30% reduction in parasitic capacitances, and a 23% lower power-delay product; reducing it from 48 fJ to 37 fJ. The greatest return comes from using a modified CML gate, which has an n-MOS current source. At a supply voltage of 1.1 V, and at 40 μA switching current, the minimum power-delay product of this CML gate is a silicon-substrate bipolar record 4.5 fJ 相似文献
33.
Guerin S Hayden BE Pletcher D Rendall ME Suchsland JP Williams LJ 《Journal of combinatorial chemistry》2006,8(5):791-798
A high-throughput method for physical vapor deposition has been applied to the synthesis of libraries of supported gold particles on amorphous substoichiometric TiO(x)() and carbon supports. The TiO(x)() substrate stoichiometry can be varied or kept constant across a supporting sample, and subsequent deposition of particle sizes on supports are controlled through the nucleation and growth process. TEM measurements indicate nucleation and growth of Au particles takes place, with the smallest particles initially observed at 1.4 nm with a maximum density of 5.5 x 10(12) cm(-2) on titania, and 2.6 nm with concomitantly lower density on carbon. The 1.4-nm particles on titania exhibit a binding energy shift in the Au(4f) core level of 0.3 eV from bulk gold, and the shift is approximately 0.1 eV by the time particles grow to a mean size of 2.5 nm. These shifts are associated with final state effects, and the supported gold particles are metallic and appear to be relatively stable in air. When combined with appropriate substrates and screening techniques, this method provides a highly controllable method for the high-throughput synthesis of model supported catalyst. 相似文献
34.
Physical vapor deposition method for the high-throughput synthesis of solid-state material libraries
A method that combines co-evaporation of pure elements from multiple finite-size sources on temperature-controlled substrates with independently controlled source shutters has been used for the synthesis of solid-state material combinatorial libraries. The source shutters are positioned to achieve a controlled gradient of the deposited elements across the substrate and are fixed during the course of deposition. Choice of the shutter position and the rate of deposition for each source allow the direct synthesis of continuous and controlled materials of varying composition. There are significant advantages of the method over alternatives which rely on sequential deposition and subsequent heat treatment to produce thin film materials. The parameters governing the creation of gradients have been identified and defined. Simulations and experimental data have been compared in the case of a single source. Results are presented for the synthesis of a ternary alloy library to demonstrate the methodology. 相似文献
35.
This paper presents a combustion-driven thermoelectric power generation system that uses PbSnTe-based thermoelectric modules.
The modules were integrated into a gas-fired furnace with a special burner design. The thermoelectric integrated system could
be applied for self-powered appliances or micro-cogeneration. A mathematical model for the integrated energy system was established
that considered irreversibilities in the thermal-to-electric energy conversion process. The electric power output and electrical
efficiency of the system were simulated using the established model. A prototype system was developed and its performance
was investigated at various operating conditions. Applicability of thermoelectric devices to self-powered heating systems
was demonstrated. The thermoelectric integrated combustion system could provide the consumer with heating system reliability
and a reduction in electric power consumption. The integrated system could also offer other advantages including simplicity,
low noise, clean operation, and low maintenance. 相似文献
36.
Combinatorial library screening offers a rapid process for identifying potential therapies to toxins. Hinge peptide libraries,
which rely on conformational diversity rather than traditional molecular diversity, reduce the need for huge numbers of syntheses
and screening steps and greatly expedite the discovery process of active molecules. Hinge peptide libraries having the structures:
Acetyl-X1–X2–hinge–X3–X4–NH2 (capped) and X1–hinge–X2–X3 (uncapped), where X1 through X4 are near-equimolar mixtures of twelve L-amino acids and hinge = 4-aminobutyric acid, were screened for inhibitory activity in bioassays for botulinum neurotoxins
A and B (BoNT/A, BoNT/B) and saxitoxin. The zinc protease activity of the reduced light chains of BoNT/A and /B was assayed
by measuring the cleavage of synthetic substrates. Saxitoxin activity was measured by the restoration of the viability of
neuroblastoma cells treated with ouabain and veratridine. Deconvolution of libraries was accomplished by fixing one position
at a time beginning with the C-terminus. Primary library subsets in which position 4 was fixed showed moderate levels of inhibition
for BoNT/A. Secondary library subsets showed stronger inhibition in the bioassays. In each of the bioassays, inhibitory potency
was stronger when the second position to be fixed was on the opposite side of the hinge, rather than on the same side with
respect to the C-terminus, suggesting that the hinge facilitates the interaction of side chains. Inhibitors for all three
of the toxins studied were discovered within library subsets, although not necessarily in primary subsets. These studies demonstrate
that (1) the best strategy for deconvoluting hinge peptide libraries is by fixing residues alternately on each side of the
hinge moiety, and (2) it is essential to investigate secondary subsets even when primary subsets are inactive. The present
findings support the concept that the increased flexibility imposed by the inclusion of a central hinge residue in small peptides
increases the opportunity for side chain interactions, providing a distinct advantage for hinge peptide libraries over conventional
peptide libraries. Hinge peptide libraries are a rich source of novel ligands for modulation of biomechanisms. The library
subsets uncovered in this study may possess peptides that will lead to effective therapies to neurotoxin poisoning. 相似文献
37.
Wm. Hayden Smith 《光谱学快报》2013,46(4):181-184
Recently, an emission from molecular benzene has been observed in our electron beam excitation source when benzene vas used as a parent molecule for the C2 molecule1 the primary subject of our study. Due to the discussion in this journal 2,3 concerning emission excited in a benzene system as observed by Robinson and Rosamund4, it was felt that our results should be communicated to dispel any ambiguity that may remain for this emission system. 相似文献
38.
Enolate additions to chiral N-sulfonyloxaziridines providing enantiomerically enriched α-hydroxy carbonyl compounds is a reaction of importance, yet a clear understanding of the factors governing stereoinduction in these transformations remains ambiguous. This is despite, previous computational studies, one by Bach et al. employing truncated model systems exploring oxygen atom transfer to an unsubstituted lithium enolate and another by our own group. In clarifying this reactivity we report here a computational study examining oxygen atom transfer from 1-S-(+)-(10-camphorsulfonyl)oxaziridine, viz., archetypal Davis chiral oxaziridine to substituted Li, Na, K enolates offering improved mechanistic understanding. From this investigation, a revised model is offered revealing the metal cation, chelation effects and sterics as decisive stereocontrolling factors in enolate additions to chiral N-sulfonyloxaziridines affording enantiomerically enriched α-hydroxy carbonyl compounds. 相似文献
39.
40.
The dynamics of dissociative hydrogen adsorption on clean polycrystalline uranium has been studied using temperature programmed desorption and supersonic molecular beams. The initial sticking probability was measured as a function of incident kinetic energy between 3 and 255 meV. Two adsorption channels were observed; a non-activated direct channel was shown to be active over the entire energy range studied and a low energy indirect channel that was characterised by a decrease in sticking probability with increasing beam energy, and an insensitivity to both surface temperature and a range of hydrogen coverages. Together these results suggest the existence of an unaccommodated molecular precursor that has sufficient lifetime and mobility to locate favourable sites and dissociatively adsorb. 相似文献