bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of 12 DFT functionals in the study of crystal systems: Al2SiO5 orthosilicates and Al hydroxides as a case study
Authors: Demichelis Raffaella , Civalleri Bartolomeo , D'Arco Philippe , Dovesi Roberto 
Published: May 2010

AbstractThe performance of 12 DFT functionals in describing the equilibrium structure and the relative stability of three Al2SiO5 orthosilicates (kyanite, andalusite and sillimanite) and four Al2O3 · nH2O hydroxides (diaspore, boehmite, gibbsite, and bayerite, with the last three systems being H‐bonded layered structures, HBLs) is assessed. Calculations were performed with the periodic ab initio CRYSTAL code by using all electron Gaussian‐type basis sets. The exchange‐correlation functionals tested are: Two LDA functionals (SVWN and PWLSD), five semilocal GGA functionals, both the standard ones tailored for molecules (PW and PBE) and the newly functionals devised for solids (PBEsol, SOGGA, and WC), and five hybrid functionals (B1WC, WC1LYP, B3LYP, B3PW, and PBE0). We find that recent GGA functionals for solids give similar results that are in between LDA and standard GGA functionals. They reproduce quite well the structure of Al2SiO5 polymorphs but fail for the H‐bonded layered Al hydroxides. The inclusion of HF exchange in the hybrid functionals leads to very good predicted structures for both systems. In particular, the structural parameters related to H atoms (OH and H···O distances, the lattice parameter along which the layers are stacked in HBLs) are remarkably improved with respect to the LDA and GGA functionals. Among the studied polymorphs, the correct order of stability is obtained with LDA and GGA functionals for solids, even if they overstabilize denser phases. Standard GGA and hybrids reduce the range of stability but they are often unsatisfactory in reproducing the correct order of stability. This is particularly relevant for the B3LYP functionals. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Continuum, discrete, and explicit solvation models for describing the low‐lying absorption spectrum of the pterin acid in aqueous environment
Authors: Jaramillo Paula , Coutinho Kaline , Canuto Sylvio 
Published: May 2010

AbstractThe absorption spectrum of the acid form of pterin in water was investigated theoretically. Different procedures using continuum, discrete, and explicit models were used to include the solvation effect on the absorption spectrum, characterized by two bands. The discrete and explicit models used Monte Carlo simulation to generate the liquid structure and time‐dependent density functional theory (B3LYP/6‐31G+(d)) to obtain the excitation energies. The discrete model failed to give the correct qualitative effect on the second absorption band. The continuum model, in turn, has given a correct qualitative picture and a semiquantitative description. The explicit use of 29 solvent molecules, forming a hydration shell of 6 Å, embedded in the electrostatic field of the remaining solvent molecules, gives absorption transitions at 3.67 and 4.59 eV in excellent agreement with the S0–S1 and S0–S2 absorption bands at of 3.66 and 4.59 eV, respectively, that characterize the experimental spectrum of pterin in water environment. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2371–2377, 2010
A DFT study on molecular junction devices with cyclic disulfide anchors: Effect of anchor oxidation on electron transport
Authors: Jang Yun Hee 
Published: May 2010

AbstractA molecular‐scale electronic device can be built with programmable molecular switches sandwiched between two electrodes. A cyclic disulfide, 1,2‐dithiolane, is a promising anchor group for attaching molecules to gold electrodes in such molecular junction devices, since its dithiol–Au linkage (with the disulfide bond broken) can provide added stabilities and reduced current fluctuations. However, operations of the molecular switches under redox conditions might lead to redox processes involving the AuS bonds at the contact. Formation of the disulfide linkage can be induced, and the dithiolate group (AuS) can be converted into disulfoxide (AuSO) or disulfone (AuSO2) groups. Coexistence of these various oxidation states at the contact or the conversion between them can be a potential source of current fluctuation in the junction. However, our nonequilibrium Green's function calculations combined with the density functional theory show that the molecular junctions with different oxidation states of the 1,2‐dithiolane alligator clips to two gold electrodes exhibit essentially the same insulating current–voltage characteristics at moderate bias voltages. Therefore, the robustness of the molecular junctions would not be affected by the state change of the disulfide alligator clips at the contact. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Analytical energy gradients of Coulomb‐attenuated time‐dependent density functional methods for excited states
Authors: Nguyen Kiet A. , Day Paul N. , Pachter Ruth 
Published: May 2010

AbstractWe present an implementation and validation of the analytical energy gradient of time‐dependent density functional theory (TDDFT) using Coulomb‐attenuated (CA) functionals for excited state energies, dipole moments, geometries, and vibrational frequencies. The CA‐TDDFT gradient is based on the previous long‐range corrected TDDFT of (Chiba et al. J Chem Phys 2006, 124, 144106) and the Z‐vector formalism of (Furche and Ahlrichs J Chem Phys 2002, 117, 7433). Geometry optimization using CA‐TDDFT was carried out for molecules (substituted stilbenes and coumarins) having intramolecular charge‐transfer excited states and for a series of small molecules (CO, HCN, CH2O, CH2S, CCl2, C2H2, trans‐(CHO)2). We assess the results of the CA functionals, the long‐range corrected LC‐BLYP functional, and the B3LYP hybrid functional, by comparing to accurate experimental data. The results highlight the applicabilty of different functionals for excited state properties. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Entropy–energy balance in base catalyzed keto‐enol interconversion: A joint theoretical and experimental investigation
Authors: Aschi Massimiliano , Zappacosta Romina , DE Maria Paolo , Siani Gabriella , Fontana Antonella , Amadei Andrea 
Published: May 2010

AbstractThe mechanism of base catalyzed keto‐enol interconversion of aqueous 2‐phenylacetylthiophene has been investigated by a joint application of experimental and computational approaches. Primarily we have focused our attention on the water‐enolate proton transfer representing the rate determining step of the reaction. Computational results, in good agreement with experimental data demonstrate the crucial role exerted by the solvent. In particular, beyond the bulk catalytic effect an explicit assistance of solvent molecules allows the reaction to increase its efficiency. A combination on Molecular Dynamics simulations and Perturbed Matrix Method calculations also highlight the subtle balance between energetic and entropic effects which characterize the mechanistic scenario. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Gödelian structures and self‐organization in biological systems
Authors: Brändas Erkki J. 
Published: May 2010

AbstractIn 1986, Seel and Ladik asked, which role Gödel's incompleteness theorem should have in a basic theory of biology. Recently, the author has tried to collect the conditions, which such a meta‐theory must fulfill. A further argument concerned the deeper connection between classical canonical forms of so‐called (triangular) Jordan blocks in the description of open quantal systems far from equilibrium and those of self‐referential contradictions and paradoxes in philosophy and mathematical logic. Related examples were quoted from the emergence of self‐organization in so‐called dissipative structures with applications to both fundamental‐ and of higher order levels of organization. To bring this analogy closer together, we have developed a quantum logical formalism, describing such a Gödelian situation, via the characterization of a well‐defined “truth matrix.” In this setting, the modus operandi of exploiting self‐referential traits and paradoxical inconsistencies emphasize the possibility of a meta‐code in complicated enough (biological) systems. In conclusion, we will revisit situations were the aforementioned self‐referential property, together with the laws of physics and chemistry will guide our understanding of biology. We will finally consider subsequent implications on the various positions on artificial intelligence. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
The quantum divided basins: A new class of quantum subsystems
Authors: Heidarzadeh Farnaz , Shahbazian Shant 
Published: May 2010

AbstractThe rigorous theory of the quantum divided basins (QDB), the quantum subsystems emerging from the net zero‐flux equation, is considered in this article. This framework, the quantum theory of proper open subsystems, is derived from the extension of the quantum theory of atoms in molecules to encompass the new class of quantum subsystems. It is demonstrated that the regional hypervirial theorem and the associated regional observables as well as the subsystem variational procedure are all expressible for the QDB. The history of QDB is briefly reviewed and the bundles, which were introduced by other researchers, are offered as typical examples whereas new examples of QDB (not yet mentioned in literature) are also presented. Based on some model systems as well as the nitrogen molecule, the regional properties and the morphologies of typical QDB are scrutinized. It is also demonstrated that the QDB may be used to study the fine structure of the electron localization and delocalization. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
A computational study of the absorption spectra of 1‐substituted phenyl‐3,5‐diphenylformazans
Authors: Tezcan Habi̇be , Tokay Nesri̇n 
Published: May 2010

AbstractIn this study, the ground‐state geometries and absorption wavelengths of 1‐substituted (NO2, COOH) phenyl‐3,5‐diphenylformazans have been determined with density functional theory (DFT) and time‐dependent DFT (TD‐DFT) by combining polarizable continuum model. The calculations were carried out by using PBE1PBE functional with four basis sets to determine the λmax of the UV–visible (UV–vis) spectra for the studied formazans. Comparison of experimental and theoretical results showed that λmax of the UV–vis spectra could be reproduced by TD‐DFT. The effects of chemical substitution on the UV–vis spectra were analyzed. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Checking the validity of the vorticity expansion approximation of the current‐density functional theory
Authors: Higuchi Katsuhiko , Miyasita Mitiyasu , Higuchi Masahiko 
Published: May 2010

AbstractFour kinds of asymptotic bounds for the exchange‐correlation (XC) energy functional of the current‐density functional theory (CDFT) are derived by using both the coordinate scaling of electrons and the adiabatic connection. These asymptotic bounds are effectively used to check the validity of the approximate form of the exchange‐correlation energy functional of the CDFT. It is found that the vorticity expansion approximation (VEA) formula, which has recently been proposed by us, exactly satisfies all asymptotic bounds, though the local density approximation of the CDFT does not satisfy two of four asymptotic bounds. The validity of the VEA formula is thus confirmed successfully. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Impact of the ionic forms on the UV–Vis spectra 2‐hydroxybenzylamine. A TD‐DFT study
Authors: Adrover Miquel , Frau Juan , Caldés Catalina , Vilanova Bartolomé , Donoso Josefa , Muñoz Francisco 
Published: May 2010

AbstractPCM‐TD‐DFT computations were used to examine the electronic transitions exhibited by the molecular species of 2‐hydroxybenzylamine (2‐BNZ). The theoretical results thus obtained were found to accurately fit their experimental counterparts and to afford the assignation of the different experimental electronic transitions to 2‐BNZ tautomers present in the solution. Also, the HCTH functional was found to accurately reproduce electronic excitations in the cationic species and neutral tautomer, and the B3LYP functional to provide accurate predictions of the transitions for the anionic species and zwitterionic tautomer. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Preventive doping control screening analysis of prohibited substances in human urine using rapid‐resolution liquid chromatography/high‐resolution time‐of‐flight mass spectrometry
Authors: Vonaparti A. , Lyris E. , Angelis Y. S. , Panderi I. , Koupparis M. , Tsantili‐Kakoulidou A. , Peters R. J. B. , Nielen M.W.F. , Georgakopoulos C. 
Published: May 2010

AbstractUnification of the screening protocols for a wide range of doping agents has become an important issue for doping control laboratories. This study presents the development and validation of a generic liquid chromatography/time‐of‐flight mass spectrometry (LC/TOFMS) screening method of 241 small molecule analytes from various categories of prohibited substances (stimulants, narcotics, diuretics, β2‐agonists, β‐blockers, hormone antagonists and modulators, glucocorticosteroids and anabolic agents). It is based on a single‐step liquid‐liquid extraction of hydrolyzed urine and the use of a rapid‐resolution liquid chromatography/high‐resolution time‐of‐flight mass spectrometric system acquiring continuous full scan data. Electrospray ionization in the positive mode was used. Validation parameters consisted of identification capability, limit of detection, specificity, ion suppression, extraction recovery, repeatability and mass accuracy. Detection criteria were established on the basis of retention time reproducibility and mass accuracy. The suitability of the methodology for doping control was demonstrated with positive urine samples. The preventive role of the method was proved by the case where full scan acquisition with accurate mass measurement allowed the retrospective reprocessing of acquired data from past doping control samples for the detection of a designer drug, the stimulant 4‐methyl‐2‐hexanamine, which resulted in re‐reporting a number of stored samples as positives for this particular substance, when, initially, they had been reported as negatives. Copyright © 2010 John Wiley & Sons, Ltd.
Sparse partial least squares regression for on‐line variable selection with multivariate data streams
Authors: McWilliams Brian , Montana Giovanni 
Published: May 2010

AbstractData streams arise in several domains. For instance, in computational finance, several statistical applications revolve around the real‐time discovery of associations between a very large number of co‐evolving data feeds representing asset prices. The problem we tackle in this paper consists of learning a linear regression function from multivariate input and output streaming data in an incremental fashion while also performing dimensionality reduction and variable selection. When input and output streams are high‐dimensional and correlated, it is plausible to assume the existence of hidden factors that explain a large proportion of the covariance between them. The methods we propose build on recursive partial least squares (PLS) regression. The hidden factors are dynamically inferred and tracked over time and, within each factor, the most important streams are recursively identified by means of sparse matrix decompositions. Moreover, the recursive regression model is able to adapt to sudden changes in the data generating mechanism and also identifies the number of latent factors. Extensive simulation results illustrate how the methods perform and compare with alternative penalized regression models for streaming data. We also apply the algorithm to solve a multivariate version of theenhanced index trackingproblem in computational finance. Copyright © 2010 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 3: 170‐193, 2010
Online training on a budget of support vector machines using twin prototypes
Authors: Wang Zhuang , Vucetic Slobodan 
Published: May 2010

AbstractThis paper proposes twin prototype support vector machine (TVM), a constant space and sublinear time support vector machine (SVM) algorithm for online learning. TVM achieves its favorable scaling by memorizing only a fixed‐size data summary in the form of example prototypes and their associated information during training. In addition, TVM guarantees that the optimal SVM solution is maintained on all prototypes at any time. To maximize the accuracy of TVM, prototypes are constructed to approximate the data distribution near the decision boundary. Given a new training example, TVM is updated in three steps. First, the new example is added as a new prototype if it is near the decision boundary. If this happens, to maintain the budget, either the prototype farthest away from the decision boundary is removed or two near prototypes are selected and merged into a single one. Finally, TVM is updated by incremental and decremental techniques to account for the change. Several methods for prototype merging were proposed and experimentally evaluated. TVM algorithms with hinge loss and ramp loss were implemented and thoroughly tested on 12 large datasets. In most cases, the accuracy of low‐budget TVMs was comparable with the resource‐unconstrained SVMs. Additionally, the TVM accuracy was substantially larger than that of SVM trained on a random sample of the same size. Even larger difference in accuracy was observed when comparing with Forgetron, a popular budgeted kernel perceptron algorithm. As expected, the difference in accuracy between hinge loss and ramp loss TVM was negligible and hinge loss version is preferable due to its lower computational cost. The results illustrate that highly accurate online SVMs could be trained from arbitrary large data streams using devices with severely limited memory budgets. Copyright © 2010 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 3: 149‐169, 2010
Antimony biomethylation in culture media revisited in the light of solubility and chemical speciation considerations
Authors: Filella Montserrat , Williams Peter A. 
Published: May 2010

AbstractLaboratory culture experiments have shown that antimony biomethylation can result from bacterial and fungal activity under both aerobic and anaerobic conditions. However, in the light of our current knowledge of antimony solubility and equilibria, critical analysis of the conditions used in published laboratory studies reveals that solution chemistry was generally overlooked and oversaturated solutions were used. As a result, it is very difficult, if not impossible, to establish reliable observed effect‐concentration relationships in the experiments published. © 2010 Wiley Periodicals, Inc. Environ Toxicol 2010.
Two‐mode limited feedback block‐fading adaptive transmission with minimum guaranteed rate in MIMO channel
Authors: Knize Milan , Sykora Jan 
Published: May 2010

AbstractThis paper develops an adaptive scheme relying on a part‐time availability of the channel state information and supplying the constant minimum rate achievable for an arbitrary fading realization. The two‐mode transmission is investigated with the instantaneous perfect channel state information being known at the transmitter in the limited portion of time. We derived a general procedure for a suitable probabilistic description of the channel under such a scheme. The first mode is without any feedback and it uses a simple uniform symbol energy assignment. The second one is the emergency mode with the perfect instantaneous channel state information. It is implemented by the channel inversion (or eigenmode sub‐space channel inversion) guaranteeing the minimum required rate regardless of the channel observation. The parameters of the transmission are the total available transmitted symbol energy, the portion of time the perfect feedback channel is used, the minimum required rate, and the average symbol energy transmitted in the first and the second mode. For these cases, we have found very essential trade‐off among the system parameters and also we have derived a general procedure how to evaluate long‐term performance. Copyright © 2010 John Wiley & Sons, Ltd.
Computational social science
Authors: Cioffi‐Revilla Claudio 
Published: May 2010

AbstractThe social sciences investigate human and social dynamics and organization at all levels of analysis (consilience), including cognition, decision making, behavior, groups, organizations, societies, and the world system. Computational social science is the integrated, interdisciplinary pursuit of social inquiry with emphasis on information processing and through the medium of advanced computation. The main computational social science areas are automated information extraction systems, social network analysis, social geographic information systems (GIS), complexity modeling, and social simulation models. Just like Galileo exploited the telescope as the key instrument for observing and gaining a deeper and empirically truthful understanding of the physical universe, computational social scientists are learning to exploit the advanced and increasingly powerful instruments of computation to see beyond the visible spectrum of more traditional disciplinary analyses. Copyright © 2010 John Wiley & Sons, Inc.This article is categorized under:Data: Types and Structure > Social Networks
Synthesis, Structure and Magnetic Properties of dimeric Nickel(II) Benzoate with Pyridyl‐substituted Nitronyl Nitroxides
Authors: Zhu Lili , Chen Xiaodan , Zhao Qihua , Li Zhongshu , Zhang Xiangyang , Sun Baiwang 
Published: May 2010

AbstractThe novel heterospin complex [Ni2(PhCOO)4(NITpPy)2]·2CH3CN (1) was synthesized by the reaction of nickel benzoate and 2‐(4‐pyridyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide (NITpPy) in acetonitrile and dichloromethane solutions. The X‐ray structure determination shows that complex 1 consists of a symmetrical dimeric NiII benzoate paddle‐wheel core and pyridyl nitrogen atoms of radical ligands at the apical position, in addition, the temperature (2–300K) dependent magnetic susceptibility measurements indicate that 1 has antiferromagnetic behavior.
Local well‐posedness of the viscous rotating shallow water equations with a term of capillarity
Authors: Wu G. , Zhang B. 
Published: May 2010

AbstractMaking use of the Fourier localization method, we prove the local‐in‐time existence and uniqueness of solutions to the viscous rotating shallow water equations with a term of capillarity under both the low regularity assumption on the initial data and the assumption that the initial height is bounded away from zero.
The rounded triangular cross section – Exact solutions for torsion, flow and heat transfer
Authors: Wang C.Y. 
Published: May 2010

AbstractExact solutions for the torsion of a bar, flow, and heat transfer in a duct, all having rounded triangular cross sections, are presented. The family of shapes has the circle and the equilateral triangle as extreme cases. Geometrical properties, torsional rigidity, flow rates, and Nusselt numbers are determined.