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151.
Wang LL Khare SV Chirita V Johnson DD Rockett AA Frenkel AI Mack NH Nuzzo RG 《Journal of the American Chemical Society》2006,128(1):131-142
We describe a theoretical analysis of the structures of self-organizing nanoparticles formed by Pt and Ru-Pt on carbon support. The calculations provide insights into the nature of these metal particle systems-ones of current interest for use as the electrocatalytic materials of direct oxidation fuel cells-and clarify complex behaviors noted in earlier experimental studies. With clusters deposited via metallo-organic Pt or PtRu(5) complexes, previous experiments [Nashner et al. J. Am. Chem. Soc. 1997, 119, 7760; Nashner et al. J. Am. Chem. Soc. 1998, 120, 8093; Frenkel et al. J. Phys. Chem. B 2001, 105, 12689] showed that the Pt and Pt-Ru based clusters are formed with fcc(111)-stacked cuboctahedral geometry and essentially bulklike metal-metal bond lengths, even for the smallest (few atom) nanoparticles for which the average coordination number is much smaller than that in the bulk, and that Pt in bimetallic [PtRu(5)] clusters segregates to the ambient surface of the supported nanoparticles. We explain these observations and characterize the cluster structures and bond length distributions using density functional theory calculations with graphite as a model for the support. The present study reveals the origin of the observed metal-metal bond length disorder, distinctively different for each system, and demonstrates the profound consequences that result from the cluster/carbon-support interactions and their key role in the structure and electronic properties of supported metallic nanoparticles. 相似文献
152.
We investigate the effect of competing nonlinearities on beam dynamics in PT-symmetric potentials. In particular, we consider the stationary nonlinear Schrödinger equation (NLSE) in one dimension with competing cubic and generalized nonlinearity in the presence of a PT-symmetric potential. Closed form solutions for localized states are obtained. These solitons are shown to be stable over a wide range of potential parameters. The transverse power flow associated with these complex solitons is also examined. 相似文献
153.
The intense Geomagnetic Storms (GMSs) with Dst < −100 nT have been investigated for the period from Jan 1996 to Dec 2006.
Seven GMSs of doublet and four of triplet nature are observed. Firstly, each GMS has been studied separately as if they are
associated with independent Coronal Mass Ejections (CMEs). Secondly, for each doublet and triplet, the accumulated effect
on GMS has been investigated and correlated with Dst index so as to understand the geoeffectiveness of Successive Intense
GMSs. Majority of the successive intense GMSs have occurred during maximum phase of Solar cycle. During the occurrence of
overlapping successive storms Dst falls abruptly. For non-overlapping successive storms, the Dst value falls gradually to
minimum, showing a trend of recovery before the geosphere is hit by another storm. It is observed that the combined effect
on GMSs is due to the Solar Wind (SW) being complex, having a very high value of SW velocity (Vsw) continuously for a very
long period of 2 to 6 days. Further, Bz falls to a much lower value and B rises to a pretty high value for accumulated effect
than for isolated GMS. When the GMSs are considered as separate entity, the correlation coefficient of Interplanetary Magnetic
Field (IMF) parameters B and Bz and further, their products Vsw.B and Vsw.Bz correlated with Dst index are found to be −0.65,
0.72, −0.66 and 0.77 respectively; whereas, the coefficients are much better with the respective values of −0.7, 0.87, −0.78
and 0.90, for the accumulated effect of GMSs. Thus, it is preferable to investigate the accumulated effect of CMEs causing
successive GMSs as compared to their isolated effects. 相似文献
154.
Khare N Eggleston CM Lovelace DM Boese SW 《Journal of colloid and interface science》2006,303(2):404-414
The interaction of metalloproteins with oxides has implications not only for bioanalytical systems and biosensors but also in the areas of biomimetic photovoltaic devices, bioremediation, and bacterial metal reduction. Here, we investigate mitochondrial ferricytochrome c (Cyt c) co-sorption with 0.01 and 0.1 M phosphate on hematite (alpha-Fe2O3) surfaces as a function of pH (2-11). Although Cyt c sorption to hematite in the presence of phosphate is consistent with electrostatic attraction, other forces act upon Cyt c as well. The occurrence of multilayer adsorption, and our AFM observations, suggest that Cyt c aggregates as the pH approaches the Cyt c isoelectric point. In solution, methionine coordination of heme Fe occurs only between pH 3 and 7, but in the presence of phosphate this coordination is retained up to pH 10. Electrochemical evidence for the presence of native Cyt c occurs down to pH 3 and up to pH 10 in the absence of phosphate, and this range is extended to pH 2 and 11 in the presence of phosphate. Cyt c that initially adsorbs to a hematite surface may undergo conformation change and coat the surface with unfolded protein such that subsequently adsorbing protein is more likely to retain the native conformational state. AFM provides evidence for rapid sorption kinetics for Cyt c co-sorbed with 0.01 or 0.1 M phosphate. Cyt c co-sorbed with 0.01 M phosphate appears to unfold on the surface of hematite while Cyt c co-sorbed with 0.1 M phosphate possibly retains native conformation due to aggregation. 相似文献
155.
Chandrashekhar Khare 《Japanese Journal of Mathematics》2010,5(1):103-125
After some generalities about the absolute Galois group of
\mathbb Q\mathbb Q, we present the historical context in which Serre made his modularity conjecture. This was recently proved by Wintenberger
and the author ([22], [23]), with an input of Kisin ([24]). The focus of these notes is on the applications of the conjecture.
Some of the applications are based on the methods used in the proof. 相似文献
156.
Kshitij Sanjay Shinde Philipp Michael Michael Rössle Sven Thiele Wolfgang H. Binder 《Journal of polymer science. Part A, Polymer chemistry》2020,58(20):2864-2874
The incorporation of functional groups into unsaturated polyolefine-polymers often represent a challenging task. Based on the known cyclopropanation of double bonds with diazoesters in the presence of metal-catalysts of low molecular weight compounds, we in this article develop an approach to decorate the polymer backbone of poly(diene)s with ester as well as carboxylic groups via cyclopropanation. Therefore, predominantly cis-1,4-poly(isoprene)s are converted with ethyl or tert-butyl diazoacetate using copper(I) N-heterocyclic carbene (NHC) catalysts, while focusing on the technically relevant cyclohexane as solvent. The application of commercially available NHC-Cu(I) catalysts results in modification degrees of 4–5%, while an increased solvent polarity, like dichloromethane, results in up to 17% modification. The resulting esters were further converted to the corresponding free carboxylic groups by deprotection using trifluoroacetic acid. Thus, an introduction of functional groups along the polymer backbone with a wide variety of application, like ionic interaction or hydrogen bonding motifs, was successfully demonstrated. Its potential for upscaling makes this approach feasible for an application in large-scale production processes, such as for manufacturing of modified synthetic rubbers. 相似文献
157.
Coupled discrete models are ubiquitous in a variety of physical contexts. We provide an extensive set of exact quasiperiodic solutions of a number of coupled discrete models in terms of Lamé polynomials of arbitrary order. The models discussed are: (i) coupled Salerno model, (ii) coupled Ablowitz?CLadik model, (iii) coupled ? 4 model and (iv) coupled ? 6 model. In all these cases we show that the coefficients of the Lamé polynomials are such that the Lamé polynomials can be re-expressed in terms of Chebyshev polynomials of the relevant Jacobi elliptic function. 相似文献
158.
159.
In this article, we focus on adaptive linear regression methods and propose a new technique. The article begins with a review of the online passive aggressive algorithm (OPAA), an adaptive linear regression algorithm from the machine learning literature. We highlight the strengths and weaknesses of OPAA and compare it with other popular adaptive regression techniques such as moving window and recursive least squares, recursive partial least squares, and just‐in‐time or locally weighted regression. Modifications to OPAA are proposed to make it more robust and better suited for industrial soft‐sensor applications. The new algorithm is called smoothed passive aggressive algorithm (SPAA), and like OPAA, it follows a cautious parameter update strategy but is more robust. The trade‐off between SPAA's computation complexity and accuracy can be easily controlled by manipulating just two tuning parameters. We also demonstrate that the SPAA framework is quite flexible and a number of variants are easily formulated. Application of SPAA to estimate the time‐varying parameters of a numerically simulated autoregressive with exogenous terms (ARX) model and to predict the Reid vapor pressure of the bottoms flow from an industrial column demonstrates its superior performance over OPAA and comparable performance with the other popular algorithms. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
160.
A single artificial grain boundary in La0.67Ba0.33MnO3 (LBMO) thin film has been prepared by depositing the film on a bicrystal substrate using laser ablation technique. We investigated the magnetic field dependence of magnetoresistance and conductance-voltage characteristics of the grain boundary at 77 K. A decrease of nonlinearity of current-voltage characteristics was observed upon application of magnetic field. The results are explained by assuming the presence of two different types of parallel conducting channels (metallic and highly resistive) across the grain boundary. The analysis of the results reveals that the application of magnetic field suppresses magnetic disorders at the grain boundary region and increases metallic conduction channels across the grain boundary. The temperature dependence of the conduction noise of the bicrystal grain boundary was measured at 0 and 1.5 kG magnetic field and compared with a microbridge on the LBMO film having no grain boundary. The presence of the grain boundary was found to enhance noise by one order of magnitude. The noise of a bicrystal grain boundary showed a decrease in the presence of 1.5 kG magnetic field for T<210 K. This decrease of noise confirms that the application of a magnetic field induces more metallic channels across the grain boundary. 相似文献