bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comprehensive investigation of the structural properties of ferroelectric PbZr0.2Ti0.8O3 thin films grown by PLD
Authors: Walker David , Thomas Pam A. , Collins Steve P. 
Published: June 2009

AbstractX‐Ray diffraction investigations were made of high‐quality epitaxial thin films of the ferroelectric material lead zirconate titanate, PbZr0.2Ti0.8O3 (PZT), grown by pulsed laser deposition (PLD). Layers from 7 to 200 nm in thickness were studied, deposited on a 30 nm SrRuO3 (SRO) electrode on a [001] oriented SrTiO3 (STO) substrate. The out‐of‐plane lattice parameters of the PZT films were measured by high‐resolution X‐ray diffraction using CuKα1 radiation. A significant enhancement of the c lattice parameter with film thickness was observed, the maximum value of 4.25 Å reached in the 30–50 nm thick films. For film thicknesses greater than 100 nm, the c lattice parameter is relaxed, towards the bulk value of 4.13 Å at this composition. The in‐plane lattice parameters were studied by Grazing incidence X‐ray scattering (GIXS), using 15 keV synchrotron radiation at I16, Diamond. The a lattice parameter of domains with [001] oriented normal to the sample surface was effectively lattice matched to the SRO layer in the 7 nm ultra‐thin film, but relaxed compared to the SRO in thicker films. The tetragonality of the [001] oriented domains decreases with increasing film thickness, approaching the bulk value of 1.05 in the thickest films. Evidence for the presence of [100] oriented a‐domains was found in PZT films as thin as 30 nm, the proportion of which increased with increasing film thickness, suggesting they grow in order to relieve stresses that would prevent the epitaxial growth of thicker PZT films. The a‐domains in the thicker films were found to be located nearer to the PZT/SRO interface than to the top surface of the PZT.
Electronic and optical properties of staggered InGaN/InGaN quantum‐well light‐emitting diodes
Authors: Park Seoung‐Hwan , Ahn Doyeol , Koo Bun‐Hei , Kim Jong‐Wook 
Published: June 2009

AbstractElectronic and optical properties of 440 and 530 nm staggered InGaN/InGaN/GaN quantum‐well (QW) light‐emitting diodes are investigated using the multiband effective‐mass theory. These results are compared with those of conventional InGaN/GaN QW structures. The staggered QW structure requires a slightly larger In composition than the conventional QW structure to obtain a given wavelength. The spontaneous emission is found to be improved with the inclusion of the staggered layer for QW structures with a relatively thick well width and the longer wavelength (λ = 530 nm). On the other hand, in the case of QW structures with a relatively thin well width (Lw = 2 nm), the spontaneous emission peak is almost unaffected by a staggered layer.
Phase transitions and electrical properties of (1−x)(K0.5Na0.5)NbO3−xBiScO3 lead‐free piezoelectric ceramics with a CuO sintering aid
Authors: Li Xuhai , Jiang Meng , Liu Jing , Zhu Jiliang , Zhu Xiaohong , Li Lihua , Zhou Yu , Zhu Jianguo , Xiao Dingquan 
Published: June 2009

Abstract(1−x)(K0.5Na0.5)NbO3−xBiScO3 doped with 1 mol% CuO (KNN‐BS‐Cu‐x) lead‐free piezoelectric ceramics were prepared by the solid state reaction technique. With the CuO doping, all the ceramics can be well sintered at 1090–1150 °C and exhibit a perovskite structure. After the substitution of BiScO3, the polymorphic phase transition (PPT) was shifted to near room temperature; besides, the cubic–tetragonal phase transitions were also shifted to lower temperatures and a relaxor behavior was induced. The ceramic (x = 0.018) with PPT near room temperature exhibited excellent electrical properties (d33 = 224 pC/N, kp = 0.40, and TC = 331 °C). A relatively high mechanical quality factor (288) was also obtained in this particular composition. All these results reveal that KNN‐BS‐Cu‐x ceramics may become promising candidates for lead‐free piezoelectric materials.
Microwave‐assisted preparation of nanocrystalline ZnS in aqueous solutions of [EMIM][EtSO4] as a low‐cost ionic liquid, and its characterization and photocatalytic properties
Authors: Esmaili M. , Habibi‐Yangjeh A. 
Published: June 2009

AbstractA fast and template‐free method is proposed for the preparation of nanocrystalline ZnS in the presence of 1‐ethyl‐3‐methylimidazolium ethylsulphate, [EMIM][EtSO4], a room temperature ionic liquid (RTIL), under microwave irradiation for 4 min. Powder X‐ray diffraction (XRD) studies show that the products are excellently crystallized in a cubic structure. Energy dispersive X‐ray (EDX) spectroscopy investigations reveal that the products are extremely pure. The results obtained from scanning electron microscopy (SEM) demonstrate that nanocrystalline ZnS prepared in the presence of the RTIL are smaller than that of the sample prepared in water and the size of the nanoclusters decreases with increasing RTIL content of the media. Diffuse reflectance spectra (DRS) of the as‐prepared ZnS show a blue shift relative to the bulk ZnS, which can be attributed to quantum confinement effect of nanocrystalline ZnS. A possible formation mechanism of the nanocrystalline ZnS in aqueous solutions of the RTIL is presented. The photocatalytic activity of the nanocrystalline ZnS towards photodegradation of methylene blue (MB) was investigated. The results demonstrate that the photocatalytic properties of the nanocrystalline ZnS prepared in the presence of the RTIL are better than that of the sample prepared in water.
Unique structure of ZnO films deposited by chemical bath deposition
Authors: Chu Dewei , Masuda Yoshitake , Kato Kazumi , Hamada Takahiro 
Published: June 2009

AbstractThe unique structure of ZnO films obtained from aqueous solution method was investigated. Scanning electron microscopy (SEM) and X‐ray powder diffraction (XRD) analyses indicate that unique morphology and structure of the region where precipitation on the substrate may occur in parallel with other regions. This is accompanied by a decrease of the electrical resistivity in the absorbed region. A possible mechanism for the resistivity transformation was discussed.
Fast series resistance imaging for silicon solar cells using electroluminescence
Authors: Haunschild Jonas , Glatthaar Markus , Kasemann Martin , Rein Stefan , Weber Eicke R. 
Published: June 2009

AbstractWe introduce a fast and easy to apply method for determining the local series resistance of standard silicon solar cells. For this method only two electroluminescence images taken at different voltages are needed. From these two images, the local voltage and the local current density through the device can be calculated. Knowing these parameters for each pixel yields the local series resistance. By calculating the cell's dark saturation current from the lower voltage image, the method also works with multicrystalline material. We show images, acquired in only 300 ms and compare them with other luminescence based series resistance images. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of metallic coatings on the photoluminescence properties of ZnO nanowires
Authors: Richters J.‐P. , Dev A. , Müller S. , Niepelt R. , Borschel C. , Ronning C. , Voss T. 
Published: June 2009

AbstractWe report on low‐temperature photoluminescence studies of ZnO nanowires coated with thin metallic films. For all analyzed metals (Al, In, Au, Ni, Cu), we find an increased relative intensity of the green deep‐level emission. This is accompanied by a significant reduction of the relative intensity of the surface exciton band. The observed effects are most likely related to the formation of metal induced gap states in the surface region of the ZnO nanowires. A model for the band structure in the surface region of the metal‐coated nanowires is proposed that successfully explains the changes in the photoluminescence spectra after the coating process. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Neuroprotective effect of parthenocissin A, a natural antioxidant and free radical scavenger, in focal cerebral ischemia of rats
Authors: He Shan , Yang Jiehong , Wu Bin , Pan Yuanjiang , Wan Haitong , Wang Yu , Du Yueguang , Wang Shudong 
Published: June 2009

AbstractNeuroprotective effects of parthenocissin A (PA), a novel antioxidant and free radical scavenger, were studied in a transient middle cerebral artery (MCA) occlusion model in rats for the first time. The animals were treated intraperitoneally with PA at 2.5, 5 or 10 mg/kg, for both 30 min before MCA occlusion and 6 h after reperfusion. The MCA was occluded for 1 h in anesthetized Sprague‐Dawley rats. Compared with vehicle‐treated controls, MCA occluded animals treated with PA showed dose‐dependent reductions in brain infarction size with improved neurological and motor outcome. Biomedical assay showed that the PA treatment suppressed lipid peroxidation and restored superoxide dismutase (SOD) activity in brain tissue. In addition, the ischemia/reperfusion (I/R) induced elevation of nitric oxide (NO) production and nitric oxide synthase (NOS) activity in brain tissue was also inhibited. Thus, PA demonstrated a neuroprotective effect in the I/R model and the beneficial effects of the compound may result from the reduction of oxidative stress and the inhibition of NO production induced by I/R. The neuroprotective effects of PA have highlighted the potential use of stilbene oligomers in stroke therapy. Copyright © 2009 John Wiley & Sons, Ltd.
A Study of CDK2 Inhibitors Using a Novel 3D‐QSAR Method Exploiting Receptor Flexibility
Authors: Mazanetz Michael P. , Withers Ian M. , Laughton Charles A. , Fischer Peter M. 
Published: June 2009

AbstractA new 3D‐QSAR method based on the novel molecular dynamics methodology, Active Site Pressurization (ASP), has been validated using two cyclin‐dependent kinase 2 data sets containing 65 purines and 91 oxindoles. ASP allows the construction of cavity casts that represent the maximal energetically feasible 3D distortion of protein binding sites potentially achievable by induced fit upon binding of ligands. The ASP‐QSAR method entails many components of traditional 3D‐QSAR strategies but additionally correlates the biological activity of ligand sets with features of ASP‐derived binding site cavity casts, thus taking target protein flexibility into account implicitly. Both of the data sets used to validate the ASP‐QSAR method resulted in QSAR models that were of exceptional quality and predictivity. A non‐cross‐validated variance coefficient (R2) between 0.959 and 0.99 and a cross‐validated variance coefficient (Q2) of between 0.927 and 0.929 were obtained for these ASP‐QSAR models.
QSAR Modeling of 1‐(3,3‐Diphenylpropyl)‐Piperidinyl Amides as CCR5 Modulators Using Multivariate Adaptive Regression Spline and Bayesian Regularized Genetic Neural Networks
Authors: Jalali‐Heravi Mehdi , Mani‐Varnosfaderani Ahmad 
Published: June 2009

AbstractThis study deals with developing a quantitative structure‐activity relationship (QSAR) model for describing and predicting the inhibition activity of 1‐(3,3‐diphenylpropyl)‐piperidinyl derivatives as CCR5 modulators. Applying the multiple linear regressions (MLR) and its inability in predicting the inhibition behavior showed that the interaction has no linear characteristics. To assess the nonlinear characteristics of the inhibition activity artificial neural networks (ANN) was used for data modeling. In order to select the variables needed for developing ANNs, three variable selection algorithms were used: Stepwise‐MLR, genetic algorithm‐partial least squares (GA‐PLS), and Bayesian regularized genetic neural networks (BRGNNs). R2 and root mean square error (RMSE) values for training (t) and leave‐one‐out (LOO) procedures revealed that BRGNNs is a robust algorithm for the variable selection and regression method simultaneously. Due to the ‘black box’ limitation of neural networks, multivariate adaptive regression spline (MARS) technique was used for modeling. A prominent advantage of MARS with respect to ANN is its ability in interpreting of the results of the model. Q2LOO and Rt2 (0.982 and 0.947) reveal that MARS can describe and predict inhibition activity of these modulators and is as robust as ANN. Because the MARS model can explain the activity of molecules, it is a useful model for designing novel CCR5 inhibitors.
Computer‐Aided Prediction of Rodent Carcinogenicity by PASS and CISOC‐PSCT
Authors: Lagunin Alexey , Filimonov Dmitrii , Zakharov Alexey , Xie Wei , Huang Ying , Zhu Fucheng , Shen Tianxiang , Yao Jianhua , Poroikov Vladimir 
Published: June 2009

AbstractComputer‐aided prediction of rodent carcinogenicity for the external test set consisting of 293 chemicals was performed by PASS (Prediction of Activity Spectra for Substances) and by CISOC‐PSCT. The set included 64 carcinogens from ISS Carcinogens Data Bank and 229 noncarcinogens from the Prestwick Chemical Library. We calculated the accuracy of carcinogenicity prediction by PASS and CISOC‐PSCT in apart, and by the two programs together (the consensus model). Sensitivity, specificity and accuracy (concordance) were calculated for the external test set by PASS (0.81, 0.74, 0.76), by CISOC‐PSCT (0.36, 0.89, 0.77) and by the consensus model (0.69, 0.86, 0.83). Thus, taking into account the prediction results of two computer programs for rodent carcinogenicity the consensus model increases the accuracy of prediction.
Comparative Investigation of the ATP‐Binding Site of Human and Plasmodial Glycogen Synthase Kinase‐3
Authors: Kruggel Sebastian , Lemcke Thomas 
Published: June 2009

AbstractMalaria is still one of the most problematic infectious diseases besides AIDS and tuberculosis. Plasmodial glycogen synthase kinase‐3 (PfGSK‐3) has been proposed as a potential malaria target before but the plasmodial enzyme is not crystallized yet whereas there are several structures published of the human glycogen synthase kinase‐3 (HsGSK‐3). Here we describe the comparison of different PDB structures of the HsGSK‐3 and corresponding homology models of PfGSK‐3. The differences were investigated with molecular interaction fields and also by a docking study of the known inhibitors kenpaullone and flavopiridol.
Investigating Enzyme Selectivity and Hit Enrichment by Automatically Interfacing Ligand‐ and Structure‐Based Molecular Design
Authors: Nicolotti Orazio , Giangreco Ilenia , Miscioscia Teresa Fabiola , Carotti Angelo 
Published: June 2009

AbstractA new method was implemented in the in‐house program @lic& to rationally combine structure‐ and ligand‐based design through nondeterministic rescoring of docking poses for the automated generation of structural alignments of a series of benzamidine compounds acting as protease inhibitors. Such alignments enable 3D‐QSAR models to explain enzyme selectivity and to retrieve with high sensitivity active hits from a pool of 260 structurally‐related benzamidine derivatives.
Theoretical study of the Michael addition of acetylacetone to methyl vinyl ketone catalyzed by the ionic liquid 1‐butyl‐3‐methylimidazolium hydroxide
Authors: Wei Xiaofeng , Zhang Dongju , Zhang Changqiao , Liu Chengbu 
Published: June 2009

AbstractBy performing density functional theory calculations, we have investigated the Michael addition of acetylacetone to methyl vinyl ketone in the absence and presence of the ionic liquid 1‐butyl‐3‐methylimidazolium hydroxide ([bmIm]OH). In the absence of ionic liquids, acetylacetone is firstly tautomerized to enol form and then takes place Michael addition to methyl vinyl ketone. As in the catalyzed Michael addition reaction, a bmIm+‐OH− ion pair is introduced into the reaction system to model the effect of the ionic liquid environment on the reactivity. The calculated results show that the anion enhances nucleophilic ability of acetylacetone since the OH− anion captures a proton to form an acetylacetone anion‐H2O complex, and the cation improves the electrophilic ability of methyl vinyl ketone by forming intermolecular hydrogen‐bonds. Both the remarkable effects of the cation and anion on the reactivity of reactants promote this reaction, which take place more easily compared with uncatalyzed reaction. The calculated results show that the main product of the Michael addition is in its ketone form. Our study provides a detailed reaction mechanism of Michael addition catalyzed by basic ionic liquid [bmIm]OH and clearly reveal the catalytic role of ionic liquid in important chemical reaction. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Time‐independent and time‐dependent methods for the calculation of the vibrational spectra: H2CN as example
Authors: Carbonniere Philippe , Pouchan Claude 
Published: June 2009

AbstractComputed anharmonic transitions and intensities of H2CN are reported in a spectral range ranging from 900 to 2,900 cm−1. Four vibrational treatments were considered from a B3LYP/6‐31+G(d,p) potential electronic surface: The second order perturbational method, the full configuration interaction, the discrete variable representation method and the vibrational analysis arising from a molecular dynamics trajectory. The four approaches yield basically the same results since the convergence of the values is achieved by about 15–20 cm−1. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Three approximations to the nonlocal and energy‐dependent correlation potential in electron propagator theory
Authors: Flores‐Moreno R. , Melin J. , Dolgounitcheva O. , Zakrzewski V. G. , Ortiz J. V. 
Published: June 2009

AbstractThe historical dilemma that pits accuracy against interpretability in molecular electronic structure calculations may be resolved with electron propagator theory. In the interpretation of electron binding energies, electron propagator theory provides a systematically improvable description of electron correlation while retaining one‐electron concepts, such as Dyson orbitals, of wide‐ranging interpretive facility. The nonlocal, energy‐dependent correlation potential, known as the self‐energy, which occurs in the one‐electron equations of electron propagator theory may be approximated in practical calculations. The partial third‐order approximation has been employed in many calculations on large molecules. Applications to fragments of nucleic acids show how qualitative, orbital‐based insights emerge from calculations that suffice to quantitatively assign photoelectron spectra. A quasiparticle virtual orbital method for improving the efficiency of this method shows considerable promise. Simple perturbative approaches may be combined with renormalizations that incorporate final‐state orbital relaxation effects with the use of reference ensembles that correspond to Slater's transition state method. Such approximations produce useful predictions for core as well as valence electron binding energies. Another approximation that is based on highly correlated reference states and a renormalized treatment of the self‐energy shows considerable flexibility in the accurate prediction of electron binding energies. This method suffices to make definitive assignments of photoelectron spectra of double Rydberg anions, species whose ground state electronic structure requires assignment of electrons to nonvalence orbitals. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
On the nature of copper–hydrogen bonding: AIM and NBO analysis of CuHn(1 ≤n≤ 6) complexes
Authors: Uribe Emilbus A. , Daza Martha C. , Villaveces José L. , Delgado Silvia A. 
Published: June 2009

AbstractAn analysis of copper–hydrogen interactions of six minima and one transition state on the CuHnpotential energy surfaces was done using Atoms in Molecules theory and Natural Bond Orbital approach with UB3LYP/DGDZVP wave functions. We localized one minimum on all CuHnpotential energy surfaces (PESs) with the exception of the PES withn= 3. This PES has two symmetrical minima and one transition state. The CuHncomplexes withn= 1, 3, and 5 have a monohydride fragment. Those with even number of hydrogens have a dihydride fragment. The remaining H atoms are coordinated as (H2) to CuH or to HCuH. The copper–hydrogen interactions were classified asclosed shell(CS) and the HH bonds asshared shellusing the Laplacian of ρ(r). When it was considered the |V(r)|/G(r) ratio, we could split the copper–hydrogen interactions intopure CSandtransit CS. Taking into account the magnitude of theH(r), the transit CS copper–hydrogen interactions can be divided intodativeandmetallic. On the other hand, according to the NBO analysis, the copper–H2interactions can be classified assynergisticanddative H2coordinationtypes. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
A new math library
Authors: Beebe Nelson H. F. 
Published: June 2009

AbstractThe design and development of a new mathematical function library is described. The library extends programming support to decimal, as well as binary, arithmetic, and aims to influence the future evolution of floating‐point support in programming languages, libraries, and hardware. It encourages and facilitates research in new computer‐arithmetic designs, and the analysis and comparison of historical ones. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Cysteine‐capped ZnSe quantum dots as affinity and accelerating probes for microwave enzymatic digestion of proteins via direct matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric analysis
Authors: Shastri Lokesh A. , Kailasa Suresh Kumar , Wu Hui‐Fen 
Published: June 2009

AbstractFluorescent semiconductor quantum dots (QDs) exhibit great potential and capability for many biological and biochemical applications. We report a simple strategy for the synthesis of aqueous stable ZnSe QDs by using cysteine as the capping agent (ZnSe‐Cys QDs). The ZnSe QDs can act as affinity probes to enrich peptides and proteins via direct matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) analysis. This nanoprobe could significantly enhance protein signals (insulin, ubiquitin, cytochrome c, myoglobin and lysozyme) in MALDI‐TOFMS by 2.5–12 times compared with the traditional method. Additionally, the ZnSe‐Cys QDs can be applied as heat absorbers (as accelerating probes) to speed up microwave‐assisted enzymatic digestion reactions and also as affinity probes to enrich lysozyme‐digested products in MALDI‐TOFMS. Furthermore, after the enrichment experiments, the solutions of ZnSe‐Cys QDs mixed with proteins can be directly deposited onto the MALDI plates for rapid analysis. This approach shows a simple, rapid, efficient and straightforward method for direct analysis of proteins or peptides by MALDI‐TOFMS without the requirement for further time‐consuming separation processes, tedious washing steps or laborious purification procedures. The present study has demonstrated that ZnSe‐Cys QDs are reliable and potential materials for rapid, selective separation and enrichment of proteins as well as accelerating probes for microwave‐digested reactions for proteins than the regular MALDI‐MS tools. Additionally, we also believe that this work may also inspire investigations for applications of QDs in the field of MALDI‐MS for proteomics. Copyright © 2009 John Wiley & Sons, Ltd.