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51.
We report the synthesis of Ag-Au alloy gradients on stainless steel substrates using bipolar electrodeposition (BP-ED), a technique based on the existence of a potential gradient at the interface of a bipolar electrode (BPE) and an electrolytic solution. The interfacial potential gradient causes the rates of electrodeposition of Ag and Au to vary along the length of the BPE, leading to the electrodeposition of a chemical concentration gradient. The surface morphology of the electrodeposits was characterized using scanning electron microscopy (SEM), and their chemical composition was determined using energy dispersive X-ray spectroscopy (EDX). Self-assembled monolayers of a Raman-active probe molecule (benzene thiol) were allowed to form on the surface of the alloy gradients, and confocal Raman microscopy was employed to determine the alloy composition that resulted in the maximum surface enhanced Raman scattering (SERS) intensity. An alloy composition of ca. 70% Ag/30% Au was found to be optimum for SERS excited using 514.5 nm radiation, and it is explained on the basis of composition-dependent changes in the local surface plasmon resonance (LSPR) of the electrodeposited Ag-Au alloy. 相似文献
52.
Sudarsan Vishnupriya Kamalesh Chaudhari Ramya Jagannathan Thalappil Pradeep 《Particle & Particle Systems Characterization》2013,30(12):1056-1062
Interaction of bacteria with citrate‐reduced silver nanoparticles (AgNPs) of size 25 nm ± 8.5 nm is studied using Raman spectroscopy in conjunction with plasmon resonance imaging of single bacterial cells. Distribution of isolated nanoparticles (NPs) inside Escherichia coli (ATCC 25922; E. coli) is observed by hyperspectral imaging (HSI) as a function of incubation time. Time‐dependent degradation of bacterial DNA upon incubation of AgNPs with E. coli is proven by Raman spectroscopic studies. While attachment of NPs is evident in HSI, molecular changes are evident from the surface‐enhanced Raman spectra of adsorbed DNA and its fragments. Distinct enhancement of DNA features is observed upon interaction of AgNPs and the number of such distinct features increases with incubation time, reaches a maximum, and decreases afterwards. This systematic interaction of DNA with the NPs system and its gradual chemical evolution is proven by investigating isolated plasmid DNA. A comparative Raman study with silver ions has shown that DNA features are observable only when bacteria are incubated with AgNPs. Energetics of interaction examined with microcalorimetry suggests the exothermicity of ?1.547 × 1010 cal mol?1 for the NP–bacteria system. Specific interaction of AgNPs with exocyclic nitrogen present in the bases, adenine, guanine, and cytosine, leads to the changes in DNA. 相似文献
53.
We show, using semiclassical methods, that as a symmetry is broken, the transition between universality classes for the spectral
correlations of quantum chaotic systems is governed by the same parametrization as in the theory of random matrices. The theory
is quantitatively verified for the kicked rotor quantum map. We also provide an explicit substantiation of the random matrix
hypothesis, namely that in the symmetry-adapted basis the symmetry-violating operator is random. 相似文献
54.
Ramakrishna Ramaswamy 《Chemical physics》1984,88(1):7-16
A method of analysing classical trajectory data, based on recently derived scaling principles, is applied to a model atom-triatom collinear collision system. Apart from the utility of the scaling idea in extending trajectory computations, the analysis of the scaling coefficients in terms of transition probabilities increases the scope of the classical scaling theory as a means of obtaining (at the very least) qualitative quantum-mechanical information from classical trajectories. As an useful adjunct, the method of continuous quantization is applied to generate approximate transition probabilities. These results are semiquantitative; thus a combination of classical scaling and continuous quantization affords a powerful means of modeling complex collision cases with a minimum of computational effort. 相似文献
55.
56.
In this work, a two-dimensional thermosolutal convection flow under a sinusoidal gravity modulation (g-jitter) field is studied
to understand the effects of the periodic source on flow field, as well as heat and mass transfer mechanisms. A semi-implicit
projection finite element method is adopted to solve the transient Navier–Stokes, energy and species concentration equations.
The fingering regime and the diffusive regime are explored for a series of gravity modulation frequencies. Two types of flow
evolution, synchronous and subharmonic responses, are obtained for different frequencies. Distribution of unstable responses
for the singly unstable condition is in agreement with the literature predict. The results show that heat and mass transfer
rates are affected by the response type. For a subharmonic variation flow field, the overall Nusellt number and Sherwood number
exhibit larger values. In addition, the augmenting condition in combining thermally driving force and solutally driving force
is analyzed for a practical crystal material and displays a different response distribution from those in the fingering regime
and the diffusive regime.
Received on 19 February 2001 / Published online: 29 November 2001 相似文献
57.
58.
Summary The method described is a simple procedure for separating gas oil boiling range petroleum fraction into its aromatic hydrocarbons of the mono-, di- and trinucleartype. This is accomplished by gradient elution through an alumina adsorption column under established/standardised conditions. Characterisation is performed by UV-absorption. The method can be used also for investigating aromatic hydrocarbon structures from other petroleum fractions.
Einfaches Verfahren zur chromatographischen Trennung und Bestimmung von mono-, di- und tricyclischen aromatischen Kohlenwasserstoffen in schwereren Erdölfraktionen
Zusammenfassung Zur Trennung der Erdölfraktion vom Siedebereich des Gasöls in die ein-, zwei- und dreikernigen aromatischen Bestandteile wird eine Gradientenelution an einer Aluminiumoxidsäule unter standardisierten Bedingungen angewendet. Zur Charakterisierung dienen UV-spektrometrische Messungen. Das Verfahren kann auch zur Untersuchung von Aromaten aus anderen Erdölfraktionen eingesetzt werden.相似文献
59.
S. G. Ravi Kumar P. A. Aswatha Narayana K. N. Seetharamu B. Ramaswamy 《国际流体数值方法杂志》1989,9(9):1165-1177
The velocity correction algorithm is used in the finite element method to solve forced convection problems between parallel plates with a triangular step, for Reynolds numbers up to 1000. Equal-order interpolation functions for velocity, pressure and temperature are used. The solutions show a smooth variation of pressure. The streamfunction, isotherms, isobars and velocity profiles are presented for a typical Reynolds number of 500. The skin friction and heat transfer results are presented for Reynolds numbers up to 1000. 相似文献
60.
It is shown that the constrained-component variation generally suggested by Rosicky and Mark is very fundamental, has consistent
variational features and reproduces, as a special case, earlier variational results for atomic systems obtained by Drake and
Goldman. Numerical merits and demerits of this method are qualitatively assessed. 相似文献