bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation between processing conditions, microstructure and mechanical behavior in regenerated silkworm silk fibers
Authors: Plaza Gustavo R. , Corsini Paola , Marsano Enrico , Pérez‐Rigueiro José , Elices Manuel , Riekel Christian , Vendrely Charlotte , Guinea Gustavo V. 
Published: December 2011

AbstractRegenerated silkworm fibers spun through a wet‐spinning process followed by an immersion postspinning drawing step show a work to fracture comparable with that of natural silkworm silk fibers in a wide range of spinning conditions. The mechanical behavior and microstructure of these high performance fibers have been characterized, and compared with those fibers produced through conventional spinning conditions. The comparison reveals that both sets of fibers share a common semicrystalline microstructure, but significant differences are apparent in the amorphous region. Besides, high performance fibers show a ground state and the possibility of tuning their tensile behavior. These properties are characteristic of spider silk and not of natural silkworm silk, despite both regenerated and natural silkworm silk share a common composition different from that of spider silk. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Development of new high transparent hybrid organic–inorganic monoliths with surface engraved diffraction pattern
Authors: Moreira Sandra D. F. C. , Silva Carlos J. R. , Prado Luis A. S. A. , Costa Manuel F. M. , Boev Victor I. , Martín‐Sánchez J. , Gomes M. J. M. 
Published: December 2011

AbstractFlexible hybrid xerogels bringing together high optical transparency up to 96%, low shrinkage down to 5.5%, very smooth surface (average roughness of about 0.3 nm) and thermal stability up to 200 °C were achieved as a result of the optimization of sol‐gel preparative method and a new combination of sol‐gel precursors. Two types of hybrid materials (hereafter referred, respectively, as urea‐silicate and amino‐alcohol‐silicate gels) were synthesized in this work. The shrinkage and the transparency of these materials have been drastically improved by using two different derived siloxanes (3‐isocyanate propyltriethoxysilane and 3‐glycidoxypropyltrimethoxysilane) and two amine‐terminated polyether precursors with different molecular weights. A drying process was implemented to minimize yellowing of prepared samples. Under these conditions, we were able to efficiently reproduce a well‐defined imprinted pattern at materials surface by using an original casting mould. The study of the diffraction characteristics of the obtained grating revealed a good reproducibility of the imprinted grating that shows to be comparable with the original mould. The developed methodology opens the possibility to produce diffraction lenses with a wide range of forms by a simple method based on sol‐gel process. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Individual strings of conducting carbon cones and discs in a polymer matrix: Electric field‐induced alignment and their use as a strain sensor
Authors: Høyer Henrik , Knaapila Matti , Kjelstrup‐Hansen Jakob , Liu Xuhai , Helgesen Geir 
Published: December 2011

AbstractWe demonstrate micromechanical strain sensors with integrated readout based on carbon nanocones and discs (CNCs) which are aligned into a string‐like formation using an alternating electric field and studied by AC impedance spectroscopy and electromechanical methods. The CNC particles are first dispersed into a polymer matrix with a particle fraction of 0.1 vol %. This value is well below the percolation threshold (∼ 2 vol %), which suppresses particle aggregation and facilitates transparency allowing the use of an UV‐curable polymer. Alignment was carried out with a 1 kHz, 4 kV/cm electric field and is a consequence of dielectrophoretic effect. It develops in minutes and makes the initially insulating, nonaligned material conductive. This is followed by UV curing of the polymer matrix, which renders a solid state device. The stretching of the aligned strings in the cured polymer leads to a reversible piezoresistive effect, and a gauge factor of about 50 is observed. This is in a sharp contrast to CNC films with particle fraction above percolation threshold (13 vol %), which are conductive but not sensitive to stretching. The strings are Ohmic in nature and moreover show higher DC conductivity (22–500 S/m) compared to identically prepared carbon black strings (1–22 S/m). © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011
Anion exchange membranes derived from nafion precursor for the alkaline fuel cell
Authors: Salerno Holly L. S. , Beyer Frederick L. , Elabd Yossef A. 
Published: December 2011

AbstractRobust hydroxide conducting membranes are required for long‐lasting, low‐cost solid alkaline fuel cells (AFCs). In this study, we synthesize Nafion‐based anion exchange membranes (AEMs) via amination of the Nafion precursor membrane with 1,4‐dimethylpiperazine. This initial reaction produces an AEM with covalently attached dimethylpiperazinium cations neutralized with fluoride anions, while a subsequent ion exchange reaction produces a hydroxide ion conducting membrane. These AEMs possess high thermal stability and different thermal transition temperatures compared to Nafion, while small‐angle X‐ray scattering reveals a similar ionic morphology. The hydroxide ion conductivity of the Nafion‐based AEM is fivefold lower than the proton conductivity of Nafion at 80 °C and 90% relative humidity. More importantly, the hydroxide conductivity is insensitive to drying and rehydrating the membrane, which is atypical of other AEMs with quaternary ammonium cations. The high chemical and thermal stability of this hydroxide conducting Nafion‐based AEM provides a promising alternative for AFCs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011
Wavelet transform of quantum chemical states
Authors: Song Jun , Fan Hong‐Yi , Yuan Hong‐Chun 
Published: December 2011

AbstractBy using the technique of integral within an ordered product of operators, we recast classical wavelet transform to a matrix element of the squeezing‐displacing operator U(μ,s) between the mother wavelet vector 〈ψ| and the state vector |f〉 to be transformed, i.e., we propose that 〈ψ|U(μ,s)|f〉 can be considered as a new kind of spectrum for analyzing the quantum state |f〉. In this way, we propose the wavelet‐ transform spectrum for quantum chemical states. As an example, we carry out the numerical calculation of wavelet‐transform spectrum for the binomial state. It seems to us that this kind of spectrum can be used to recognize a variety of quantum chemical states. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012
Vibrational mode analysis for the multichannel reaction of CH3Cl + OH
Authors: Shojaie Fahimeh , Dehestani Maryam 
Published: December 2011

AbstractThe recently presented ab initio calculations for the reaction system of CH3Cl + OH (Dehestani and Shojaie, Int J Quantum Chem, in press) are applied to the vibrational mode analysis. Extending previous work, we use the vibrational mode analysis to elucidate the relationships of the reactants, the transition state, the intermediates (IM), and the products. The extensive investigation shows that the reaction mechanism is reliable. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
π‐Electron currents in larger fully aromatic benzenoids
Authors: Randić Milan , Vukičević Damir , Novič Marjana , Plavšić Dejan 
Published: December 2011

AbstractRecently, we have reported on calculation of π‐electron ring currents in several smaller fully benzenoid hydrocarbons having up to eight fused benzene rings and five Clar π‐aromatic sextets. In contrast to early HMO ring current calculations and more recent ab initio calculations of π‐electron density, our current calculations are based on a graph theoretical model in which contributions to ring currents comes from currents associated with individual conjugated circuits. In this contribution, we consider several larger fully benzenoid hydrocarbons having from 9 to 13 fused rings and from six or seven π‐aromatic sextets. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Exploring sequential quantum adiabatic switching across supersymmetric partners for finding the eigenstates of a system
Authors: Kar Susmita , Bhattacharyya S. P. 
Published: December 2011

AbstractWe demonstrate that one can exhaustively determine the n‐bound eigenstates of a Hamiltonian H by constructing a sequence of supersymmetric (SUSY) partner Hamiltonians and invoking a time‐dependent quantum adiabatic switching algorithm for passage from the ground state of one to the other. The ground states of the initial pair H(0) and H(1) are constructed by solving the Riccati equation for the superpotential ϕ(0) for H(0) and adiabatically switching from the ground state Ψ of H(0) to the ground state Ψ of H(1). The charge operator Q is then used to recover the first excited state Ψ of H(0). The procedure is repeated for the ground states of SUSY pairs H(n + 1) and H(n + 2), and appropriate charge operators lead to the excited states Ψ of H(0) with
$n = 0,1,2, \cdots.$, thereby exhausting the full eigenspectrum of H(0). The workability of the proposed method is shown with several well‐known examples. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Water oxidation on N‐Doped TiO2 nanotube arrays
Authors: Xie Qin , Meng Qiang‐Qiang , Zhuang Gui‐Lin , Wang Jian‐Guo , Li Xiao‐Nian 
Published: December 2011

AbstractPhotocatalytic splitting water into hydrogen and oxygen by utilizing solar energy is regarded as an effective strategy to solve oil crisis. By utilizing density functional calculations, we herein present the systemic studies with respect to water splitting mechanism on N‐doped TiO2 nanotube arrays (NTAs), and focus on activation energy, thermodynamic properties, and effects of N‐doping on reaction process. Our results reveal that the impurity 2p states of doped nitrogen effectively change electronic structure of TiO2 NTAs, which act as an electron acceptor and facilitate weakly bound electrons of valence band to be easily excited to acceptor level, as well as enhance the first H2O adsorption and dissociation on the inside wall of N‐doped TiO2 NTAs. Therefore, it is found that the rate‐determining step of water splitting is the formation reaction of HOO* on N‐doped TiO2 NTAs rather than the formation of HO* from the first H2O. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Spectroscopic constants and molecular properties of the X2Π and a4Σ− electronic states of the SiF radical
Authors: Shi De‐Heng , Li Wen‐Tao , Sun Jin‐Feng , Zhu Zun‐Lue , Liu Yu‐Fang 
Published: December 2011

AbstractThe potential energy curves (PECs) of the X2Π and a4Σ− electronic states of the SiF radical have been studied by an ab initio quantum chemical method. The calculations have been made using the complete active space self‐consistent field (CASSCF) method, which is followed by the valence internally contracted multireference configuration interaction (MRCI) approach in combination with several correlation‐consistent basis sets. The effects on the PECs by the core‐valence correlation and relativistic corrections are included. The way to consider the relativistic correction is to use the third‐order Douglas–Kroll Hamiltonian approximation. The relativistic corrections are made at the level of cc‐pV5Z basis set. The core‐valence correlation corrections are performed using the cc‐pCV5Z basis set. To obtain more reliable results, the PECs determined by the MRCI calculations are also corrected for size‐extensivity errors by means of the Davidson modification (MRCI+Q). These PECs are extrapolated to the complete basis set limit by the total‐energy extrapolation scheme. Using these PECs, the spectroscopic parameters are determined and compared with those reported in the literature. With these PECs obtained by the MRCI+Q/CV+DK+56 calculations, the vibrational levels, inertial rotation, and centrifugal distortion constants of the first 20 vibrational state of each electronic state are calculated when the rotational quantum number J equals zero. Comparison with the Rydberg‐Klein‐Rees (RKR) data shows that the present results are reliable and accurate. The molecular constants of the X2Π and a4Σ− electronic states determined by the MRCI+Q/CV+DK+56 calculations should be good prediction for future laboratory experiment. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Quartic lattice interactions, soliton‐like excitations, and electron pairing in one‐dimensional anharmonic crystals
Authors: Velarde M. G. , Brizhik L. , Chetverikov A. P. , Cruzeiro L. , Ebeling W. , Röpke G. 
Published: December 2011

AbstractIn this study, it is shown that two added, excess electrons with opposite spins in one‐dimensional crystal lattices with quartic anharmonicity may form a bisolectron, which is a localized bound state of the paired electrons to a soliton‐like lattice deformation. It is also shown that when the Coulomb repulsion is included, the wave function of the bisolectron has two maxima, and such a state is stable in lattices with strong enough electron (phonon/soliton)–lattice coupling. Furthermore, the energy of the bisolectron is shown to be lower than the energy of the state with two separate, independent electrons, as even with account of the Coulomb repulsion the bisolectron binding energy is positive. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Impurity hamiltonian for transition metal complexes based on the exact exchange for correlated electrons hybrid functional
Authors: Krykunov Mykhaylo 
Published: December 2011

AbstractWe present a theoretical method that combines density functional theory (DFT) and full configuration interaction (CI). Such a combination is based on the impurity model to (i) incorporate the advantages of DFT in description of the dynamic correlation and (ii) reduce the number of the two‐electron integrals. The impurity model has been introduced with the help of a special type of the hybrid functional, namely, the exact exchange for correlated electrons (EECE), and the orthogonal fragment orbitals formalism. The EECE functional, originally based on the formulation of the local density approximation + U (LDA + U) method without the empirical parameter U, has been rewritten in this work in a form that incorporates the projected electron–electron repulsion energy operator. This representation has been compared with other types of nonglobal hybrids: position dependent and range separated hybrids. Further, the obtained Hamiltonian of the generalized Anderson model has been transformed to the form that affords the implementation of the linear scaling density‐matrix renormalization group algorithm. © 2011 Wiley Periodicals, Inc.
Quantum molecular similarity analysis and quantitative definition of catecholamines with respect to biogenic monoamines associated: Scale alpha and beta of quantitative convergence
Authors: Morales‐Bayuelo Alejandro , Torres Juan , Vivas‐Reyes Ricardo 
Published: December 2011

AbstractIn this article, we propose to make a quantitative definition of catecholamines with respect monoamine biogenic associated, this quantification allows define the alpha and beta scales, which expresses mathematically the correlation group of catecholamines with respect to their common fragment (phenylethylamine) and the tyrosine precursor, in addition performed quantum molecular similarity analysis using four descriptors, quantified by: molecular quantum similarity indices of overlap, Coulomb, overlap‐interaction, Coulomb‐interaction, overlap‐distances Euclidian, and Coulomb‐distances Euclidian, using the topo‐geometrical superposition approach as method of alignment, also proposes a methodology for defining individual groups quantitatively, based on quantum similarity descriptors and supporting the interpretations with experimental results of structural path of reaction. Take in account the importance of creating tools that allow the quantification of biological relationships, and allow the creation of scales of group relations, this scales may be useful in organic synthesis of catecholamines for determine similarities, considering the search for experimental conditions as an area of growing scientific interest. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Dispersion coefficients for Li+–H and Li+–He systems with coulomb and screened coulomb potentials
Authors: Kar Sabyasachi , Ho Y. K. 
Published: December 2011

AbstractExploiting powerful computational aspects and highly correlated exponential wave functions for two‐electron atoms, we have investigated the effects of screened Coulomb interaction on the hexadecapole polarizability of Li+(11S), and the dispersion coefficients C6, C8, C10, and C12 for interaction of Li+ with H and He atoms in their ground states. The dispersion coefficients and hexadecapole polarizability for different screening parameters ranging from 0 to 1.0 a are reported. In the unscreened case, the hexadecapole polarizability of Li+, and the dispersion C12 coefficients for Li+–H and Li+–He system are reported for the first time in the literature. The C6, C8, and C10 coefficients for the unscreened cases are comparable with the reported results. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
One‐, two‐, and three‐electron bonding: An “in vitro” theoretical study using noninteger nuclear charges evidences the crucial role of electronegativity in the strength of symmetrical bonds
Authors: Chaquin Patrick , Gutlé Claudine 
Published: December 2011

AbstractFictitious hydrogen atoms H*A of variable nuclear charge 0.5 ≤ ZA ≤ 2 (and thus of variable electronegativity) are used to study the intrinsic dependency of chemical bonding on electronegativity. Dissociation energy and equilibrium distance are reported for symmetrical 1‐, 2‐ and 3‐electron H*AH*A systems and 2‐electron dissymmetrical H*A‐H ones. Dealing with symmetrical systems, the strongest two‐electron bonds are found for ZA ≈ 1.2. Oneelectron and three‐electron strongest bonds occur respectively with low (ca. 0.7) and high (ca. 1.7) ZA values and can become stronger than the corresponding 2‐electron system. Comparison with data on real systems leads to conclude that electronegativity is a prevailing atomic property in the control of the dissociation energy of symmetrical 1‐, 2‐ and 3‐electron bonds. A simplified mathematical model at Hartree‐Fock or Heitler‐London level with a minimal basis set reproduces these trends semi‐quantitatively and provides the overall shape of the dissociation curves. Finally some points are qualitatively discussed from MO analysis, which emphasize the dependence of the bonding/antibonding properties on the nucleus charge ZA and their occupancy number. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Molecular level understanding of the role of aldehyde in vegetable‐aldehyde–collagen cross‐linking reaction
Authors: Pu Shang‐Zhi , Wang Ya‐Nan , He Qiang , Liao Xue‐Pin , Zhang Wen‐Hua , Shi Bi 
Published: December 2011

AbstractThe role of formaldehyde (HCHO) in vegetable‐aldehyde–collagen cross‐linking reaction was investigated at the B3LYP/6‐31+G(d) level, where lysine (LYS) was used as model of collagen and catechin (EC) as model of condensed vegetable tannin. Atomic charge and Frontier molecular orbital analysis show that intermediates formed by HCHO reacting with LYS or EC, that is, MLYS, MEC‐6, and MEC‐8, still have both nucleophilic and electrophilic sites, which are elements to form ternary cross‐linking in vegetable‐aldehyde–collagen system. The analysis of energy gap between HOMO (highest occupied molecular orbit) and LUMO (lowest unoccupied molecular orbit) indicate that the intermediate of HCHO–LYS residues (MLYS) can further react with free HCHO to form product P‐N(CH2OH)2 (P‐N‐represents amino acid residue; N represents nitrogen atom on side chain), but the reaction of intermediate MLYS with free EC is difficult to take place. So, the probability of forming ternary cross‐linking structure of amino acid residue–HCHO–EC is small, if HCHO is added before vegetable tannin in vegetable‐aldehyde–collagen system. However, the reactions of EC–HCHO intermediates (MEC‐6 and MEC‐8) with free amino acids, HCHO–amino acid residue intermediate (MLYS), as well as with other EC–HCHO intermediates (MEC‐6 and MEC‐8), are very easy to take place. The reaction enthalpy also shows that the cross‐linking tendency is favorable in thermodynamics. So, it can be deduced that covalent cross‐linking among amino side chain of collagen and vegetable tannin may take place when aldehyde is added after vegetable tannin. In this way, a multiple point cross‐linking reaction occurs to create a high stabilization of collagen. © 2011 Wiley Periodicals, Inc.
Hydrogen‐bonded complexes of nicotine with simple alcohols
Authors: Senthilkumar Lakshmipathi , Ghanty Tapan K. , Kolandaivel Ponmalai , Ghosh Swapan K. 
Published: December 2011

AbstractAb initioand density functional theory studies have been performed on the hydrogen‐bonded complexes of neutral and protonated nicotine with ethanol, methanol, and trifluromethanol to explore their relative stability in a systematic way. Among all the hydrogen‐bonded nicotine complexes considered here, protonated forms in nicotine–ethanol and nicotine–methanol, and neutral form in nicotine–trifluromethanol complexes have been found to be the most stable. In the former two complexes, the proton attached to the pyrrolidine nitrogen acts as a strong hydrogen bond donor, whereas the pyrrolidine nitrogen atom acts as a hydrogen bond acceptor in the latter case. Neutral complex of nicotine with trifluromethanol has been found to possess a very short hydrogen bond (1.57 Å) and basis set superposition error corrected hydrogen bond energy value of 19 kcal/mol. The nature of the various hydrogen bonds formed has been investigated through topological aspects using Bader's atoms in molecules theory. From the calculated topological results, excellent linear correlation is shown to exist among the hydrogen bond length, electron density, and its Laplacian at the bond critical points for all the complexes considered. The natural bond orbital analysis has been carried out to investigate the charge transfer in the nicotine alcohol complexes. In contrast to the blue shifting behavior that is generally exhibited by other CH···O hydrogen bonds involving sp3carbon atom, the CH···O hydrogen bond in the protonated nicotine–ethanol and methanol complexes has been found to be proper with red shifting in nature. © 2011 Wiley Periodicals, Inc.
Benzene–kaolinite interaction properties
Authors: Castro Elton A. S. , Gargano Ricardo , Martins João B. L. 
Published: December 2011

AbstractIn this work, we present a theoretical study of interaction of benzene with kaolinite and an analysis of the vibrational spectra, electrostatic potential maps, and self consistent field (SCF) orbitals. B3LYP and MP2 benzene–kaolinite results indicate a preferential interaction of benzene on kaolinite octahedral surface. Population analysis indicates that the atoms modified their charges when the monoaromatic molecule and clay mineral are close to tetrahedral and octahedral surface of kaolinite, which suggests that the adsorbed molecule becomes slightly positive. Infrared vibrational data show the reduction in the band frequencies related to the kaolinite external hydroxyls, indicating a weak interaction of benzene with clay mineral. It also was verified, from the potential electrostatic maps, a change in electron density in both benzene and kaolinite. Electron localization function analysis was also carried out for this interaction. © 2011 Wiley Periodicals, Inc.