bluuebunny/crossref_metadata_2025 huggingface dataset:
Amphiphilic gradient copolymers of 2‐methyl‐ and 2‐phenyl‐2‐oxazoline: self‐organization in aqueous media and drug encapsulation
Authors: Milonaki Yanna , Kaditi Eleni , Pispas Stergios , Demetzos Costas
Published: December 2011

Gradient (or pseudo‐diblock) copolymers were synthesized from 2‐methyl‐2‐oxazoline and 2‐phenyl‐2‐oxazoline monomer mixtures via cationic polymerization. The self‐assembling properties of these biocompatible gradient copolymers in aqueous solutions were investigated, in an effort to use the produced nanostructures as nanocarriers for hydrophobic pharmaceutical molecules. Dynamic and static light scattering as well as AFM measurements showed that the copolymers assemble in different supramolecular nanostructures (spherical micelles, vesicles and aggregates) depending on copolymer composition. Fluorescence spectroscopy studies revealed a microenvironment of unusually high polarity inside the nanostructures. This observation is related partly to the gradient structure of the copolymers. The polymeric nanostructures were stable with time. Their structural properties in different aqueous media—PBS buffer, RPMI solution—simulating conditions used in pharmacological/medicinal studies, have been also investigated and a composition dependent behavior was observed. Finally, the hydrophobic drug indomethacin was successfully encapsulated within the gradient copolymer nanostructures and the properties of the mixed aggregates were studied in respect to the initial copolymer assemblies. The produced aggregates encapsulating indomethacin showed a significant increase of their mass and size compared to original purely polymeric ones. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Acid‐promoted double ring‐opening reaction of bicyclobis (γ‐butyrolactone) with alcohol and its application to polyester synthesis
Authors: Ohsawa Sousuke , Barkakaty Balaka , Sudo Atsushi , Endo Takeshi
Published: December 2011

Bicyclobis(γ‐butyrolactone) (BBL) bearing methyl group 1a reacted with benzyl alcohol (BnOH) in the presence of p‐toluenesulfonic acid (p‐TsOH) through the double ring‐opening of the bislactone structure to afford the corresponding adduct 2a bearing carboxyl group. The resulting carboxyl group underwent condensation with BnOH to afford the corresponding diester 3a. The second step was quite slow at ambient temperature; however, it was efficiently accelerated by elevating temperature to 120 °C or performing under reduced pressure at 80 °C to afford 3a in an excellent yield. Based on these results, the reaction of 1a with xylene‐α,α‐diol (XyD) was carried out in chlorobenzene at 120 °C to obtain the corresponding polyester bearing ketone group in the side chain. The condensation reaction in the second step was effectively promoted by simultaneous removal of water under reduced pressure. BBLs 1b and 1c bearing reactive groups, isopropenyl and chloromethyl, respectively, were also employed as monomers efficiently. Their reactions with XyD gave the corresponding reactive polyesters bearing methacryloyl and chloroacetyl moieties, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Aqueous cationic olefin polymerization using tris(pentafluorophenyl)gallium and aluminum
Authors: Mathers Robert T. , Lewis Stewart P.
Published: December 2011

Tris(pentafluorophenyl)gallium (3) and aluminum (7) are active coinitiators for the production of medium‐high molecular weight (MW) polymers of styrene and isobutene (IB) under aqueous reaction conditions. Strong Brønsted acids formed in
situ by reaction of these coinitiators with background moisture present in the monomer droplet (5 and 8, respectively) are believed to be responsible for inducing cationic polymerization of these monomers. Of the two, 7 is the most active for IB polymerization in both aqueous media and anhydrous aliphatic solvents. These results are in contradistinction to tris(pentafluorophenyl)boron (2), which is incapable of polymerizing IB in aqueous or aliphatic media. The MWs of the polyisobutenes (PIBs) produced under aqueous conditions by either coinitiator greatly exceed those formed under similar reaction conditions by the strongly acidic chelating diborane (1,2‐C6F4[B(C6F5)2]2, 1) or diborole (1,2‐C6F4[9‐BC12F8]2, 6). Both 3 and 7 are readily synthesized from the corresponding Group 13 halide compounds in conjunction with bis(pentafluorophenyl)zinc (4). Aqueous polymerization of IB dissolved in aliphatic solvents with 3 or 7 can yield PIBs with relatively narrow polydispersities. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Functionalized block copolymers for preparation of reactive self‐assembled surface patterns
Authors: Stadermann Jan , Riedel Maria , Komber Hartmut , Simon Frank , Voit Brigitte
Published: December 2011

Two phase separating block copolymers equipped with functional groups (acid and alkyne) were synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization. Thin films of these materials were prepared and examined with regard to surface morphology, surface composition, and film stability. Self‐assembled structures with domain sizes of about 40 nm were detected through atomik force microscopy (AFM) analysis while X‐ray photoelectron spectroscopy measurements revealed a balanced surface exposure of the two segregated phases. Thus, reactive groups being present in both phases are specifically provided within nanoscopic surface areas. The films showed good stability on exposure to various solvents but the self‐organized surface patterns were only resistant toward ethanol. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
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

Regenerated 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

Flexible 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

We 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

Robust 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

By 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

The 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

Recently, 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

We 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

Photocatalytic 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

The 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

In 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

We 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

In 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

Exploiting 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

Fictitious 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

The 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

Ab 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

In 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.
Theoretical investigation on the structures, densities, and detonation properties of polynitrotetraazaoctahydroanthracenes
Authors: Zhao Guozheng , Lu Ming
Published: December 2011

The polynitrotetraazaoctahydroanthracenes were optimized to obtain their molecular geometries and electronic structures at density functional theory–B3LYP/6‐31+G(d) level. Detonation velocities (D) and detonation pressures (P) were estimated for this nitramine compounds using Kamlet‐Jacobs equations, based on the theoretical densities (ρ) and heats of formation. It is found that there are good linear relationships between volume, density, detonation velocity, detonation pressure and the number of nitro group. Thermal stability of the compounds was investigated by calculating the bond dissociation energies and energy gap (ΔELUMO–HOMO). The simulation results reveal that molecule H performs similarly to famous explosive RDX. These results provide basic information for molecular design of novel high energetic density compounds. © 2011 Wiley Periodicals, Inc.
A simple method to estimate relative stabilities of polyethers cationized by alkali metal ions
Authors: Kuki Ákos , Nagy Lajos , Shemirani Ghazaleh , Memboeuf Antony , Drahos László , Vékey Károly , Zsuga Miklós , Kéki Sándor
Published: December 2011

Dissociation of doubly cationized polyethers, namely [P + 2X]2+ into [P + X]+ and X+, where P = polyethylene glycol (PEG), polypropylene glycol (PPG) and polytetrahydrofuran (PTHF) and X = Na, K and Cs, was studied by means of energy‐dependent collision‐induced dissociation tandem mass spectrometry. It was observed that the collision voltage necessary to obtain 50% fragmentation (CV50) determined for the doubly cationized polyethers of higher degree of polymerization varied linearly with the number of degrees of freedom (DOF) values. This observation allowed us to correlate these slopes with the corresponding relative gas‐phase dissociation energies for binding of alkali ions to polyethers. The relative dissociation energies determined from the corresponding slopes were found to decrease in the order Na+ > K+ > Cs+ for each polyether studied, and an order PPG ≈ PEG > PTHF can be established for each alkali metal ion. Copyright © 2011 John Wiley & Sons, Ltd.
PCDD, PCDF, AND DL‐PCB analysis in food: performance evaluation of the high‐resolution gas chromatography/low‐resolution tandem mass spectrometry technique using consensus‐based samples
Authors: Ingelido Anna Maria , Brambilla Gianfranco , Abballe Annalisa , di Domenico Alessandro , Fulgenzi Anna Rita , Iacovella Nicola , Valentini Anna Laura Iamiceli, Silvia , Felip Elena De
Published: December 2011

Due to safety concerns regarding dietary exposure to POPs, regulatory bodies are issuing detailed guidelines for testing for polychlorodibenzodioxins (PCDDs) and polychlorodibenzofurans (PCDFs) ('dioxins') and dioxin‐like (DL)‐PCBs in foods of animal origin. Determination of the aforesaid chemicals at regulatory levels requires highly selective and sensitive testing techniques. The new generation of low‐resolution mass spectrometers (triple quadrupoles) allows very low levels of quantification to be reached (in the order of tens of femtograms), thus suggesting a potential for their application in food and feed analysis. The performance of the low‐resolution tandem mass spectrometry (LRMS/MS) approach with triple quadrupoles was assessed on a qualified set of food samples from proficiency tests (PTs) and defense analysis. Accuracy was tested comparing the results with data from high‐resolution mass spectrometry (HRMS) and with consensus values from PTs. The cumulative TEQ results were characterized by deviations not exceeding 15% of PCDD + PCDF, DL‐PCB, and PCDD + PCDF + DL‐PCB (TEQTOT) reference consensus values (sample TEQTOT range, 2.29–25.1 pgWHO‐TEQ97/g fat). Congener analytical variabilities did not influence significantly the WHO‐TEQ97 outcome of the corresponding sample. This preliminary performance evaluation highlights the potential of LRMS/MS as a routine technique for quantitative analysis of PCDDs, PCDFs, and DL‐PCBs in food. Copyright © 2011 John Wiley & Sons, Ltd.
Charge state dependent top‐down characterisation using electron transfer dissociation
Authors: Rožman Marko , Gaskell Simon J.
Published: December 2011

The dissociation of protein ions (5–30 kDa) as a function of charge state has been explored in order to suggest the optimal charge state range for top‐down sequencing. Proteins were generated under denaturing conditions and their charge states were modified via ion/ion proton transfer reactions prior to dissociation. Electron transfer dissociation (ETD) data suggested optimal sequence coverage for charge states in the m/z range from 700 to 950 while limited sequence coverage was noted when the precursor m/z was above 1000. Sequence coverage from ETD data was found to be dependent on protein size, with smaller proteins having better sequence coverage. An observed depletion in sequence‐related information was mainly attributed to limited instrument (ion trap) performance (m/z range and resolution). For a combined ETD/collision‐induced dissociation (CID) approach it is difficult to propose an optimal m/z range since good sequence coverage for CID is at intermediate charge states and the optimal m/z range increases with protein size. When only one charge state can be analysed in a combined ETD/CID approach, a range around 950 m/z is suggested as a starting point. Alternatively, two charge states should be explored, each optimal for either ETD or CID. Overall, these suggestions should be useful to achieve enhanced characterisation of smaller proteins/large protein fragments (generated from denaturing solutions) in minimal analysis times. Copyright © 2011 John Wiley & Sons, Ltd.
MpAssign: a framework for solving the many‐core platform mapping problem
Authors: Bouchebaba Youcef , Ozcan Ali‐Erdem , Paulin Pierre , Nicolescu Gabriela
Published: December 2011

Many‐core platforms, providing large numbers of parallel execution resources, emerge as a response to the increasing computation needs of embedded applications. A major challenge raised by this trend is the efficient mapping of applications on parallel resources. This is a nontrivial problem because of the number of parameters to be considered for characterizing both the applications and the underlying platform architectures. Recently, several authors have proposed to use multi‐objective evolutionary algorithm to solve this problem within the context of mapping applications on network‐on‐chips. However, these proposals have several limitations: (1) only few metaheuristics are explored (mainly Nondominated Sorting Genetic Algorithm II and Strength Pareto Evolutionary Algorithm 2), (2) only few objective functions are provided, and (3) they only deal with a small number of the application and architecture constraints. In this paper, we propose a new framework that avoids all of the problems cited previously. Our framework is implemented on top of the jMetal framework, which offers an extensible environment. Our framework allows designers to (1) explore several new metaheuristics, (2) easily add a new objective function (or to use an existing one), and (3) take into account any number of architecture and application constraints. The paper also presents experiments illustrating how our framework is applied to the problem of mapping streaming applications on an NoC‐based many‐core platform. Our results show that several new metaheuristics outperform the classical multi‐objective metaheuristics such as Nondominated Sorting Genetic Algorithm II and Strength Pareto Evolutionary Algorithm 2. Moreover, a parallel multi‐objective evolutionary algorithm is implemented in our framework in order to increase the explored space of solutions by simultaneously running several metaheuristics. Copyright © 2011 John Wiley & Sons, Ltd.
Implantation Site and Lesion Topology Determine Efficacy of a Human Neural Stem Cell Line in a Rat Model of Chronic Stroke
Authors: Smith Edward J. , Stroemer R. Paul , Gorenkova Natalia , Nakajima Mitsuko , Crum William R. , Tang Ellen , Stevanato Lara , Sinden John D. , Modo Michel
Published: December 2011

Stroke remains one of the most promising targets for cell therapy. Thorough preclinical efficacy testing of human neural stem cell (hNSC) lines in a rat model of stroke (transient middle cerebral artery occlusion) is, however, required for translation into a clinical setting. Magnetic resonance imaging (MRI) here confirmed stroke damage and allowed the targeted injection of 450,000 hNSCs (CTX0E03) into peri-infarct tissue, rather than the lesion cyst. Intraparenchymal cell implants improved sensorimotor dysfunctions (bilateral asymmetry test) and motor deficits (footfault test and rotameter). Importantly, analyses based on lesion topology (striatal vs. striatal + cortical damage) revealed a more significant improvement in animals with a stroke confined to the striatum. However, no improvement in learning and memory (water maze) was evident. An intracerebroventricular injection of cells did not result in any improvement. MRI-based lesion, striatal and cortical volumes were unchanged in treated animals compared to those with stroke that received an intraparenchymal injection of suspension vehicle. Grafted cells only survived after intraparenchymal injection with a striatal + cortical topology resulting in better graft survival (16,026 cells) than in animals with smaller striatal lesions (2,374 cells). Almost 20% of cells differentiated into glial fibrillary acidic protein+ astrocytes, but <2% turned into FOX3+ neurons. These results indicate that CTX0E03 implants robustly recover behavioral dysfunction over a 3-month time frame and that this effect is specific to their site of implantation. Lesion topology is potentially an important factor in the recovery, with a stroke confined to the striatum showing a better outcome compared to a larger area of damage.

Disclosure of potential conflicts of interest is found at the end of this article.
Lymph Node Recurrence in Patients With N1b Papillary Thyroid Carcinoma Who Underwent Unilateral Therapeutic Modified Radical Neck Dissection
Authors: Ito Yasuhiro , Kudo Takumi , Takamura Yuuki , Kobayashi Kaoru , Miya Akihiro , Miyauchi Akira
Published: December 2011

Background

Therapeutic modified radical neck dissection (MND) is a mandatory surgical procedure for patients with papillary thyroid carcinoma (PTC) having clinical lateral node metastasis (N1b). However, N1b PTC is still likely to recur in regional lymph nodes after surgery. We investigated the clinicopathological features predicting recurrence in nodes in previously dissected compartments (ipsilateral lateral compartment or central compartment) and nodes in the contralateral lateral compartment for N1b patients who underwent unilateral therapeutic MND.

Methods

A total of 744 N1b PTC patients who underwent thyroidectomy with unilateral therapeutic MND between 1987 and 2004 were enrolled in the study. The patient ages ranged from 12 to 88 years (average 50.2 years). The average postoperative follow‐up period was 113 months.

Results

To date, 87 (12%) and 49 (7%) patients showed recurrence in previously dissected compartments and the contralateral lateral compartment, respectively. On univariate analysis, age >55 years, node metastasis >3 cm, extranodal tumor extension, and extrathyroid extension affected recurrence in previously dissected compartments. Also, the former two were independent predictors on multivariate analysis (P = 0.0170 and <0.0001, respectively). In contrast, only extrathyroid extension and tumor size >4 cm influenced recurrence in the contralateral lateral compartment on univariate analysis. On multivariate analysis, the former was an independent predictor (P = 0.0015), and the latter was of marginal significance (P = 0.0909). To date, 13% of patients having both of these characteristics showed recurrence in the contralateral lateral compartment.

Conclusions

Extremely careful therapeutic MND is required for N1b patients with age >55 years or node metastasis >3 cm because of the likelihood of recurrence in previously dissected compartments. Bilateral MND (therapeutic for ipsilateral side and prophylactic for contralateral side) may be a therapy option for N1b PTC >4 cm and having extrathyroid extension.
Quantification of iron concentration in the liver by MRI
Authors: Alústiza Echeverría José María , Castiella Agustín , Emparanza José Ignacio
Published: December 2011

Objective

Measurement of liver iron concentration is a key parameter for the management of patients with primary and secondary haemochromatosis. Magnetic resonance imaging (MRI) has already demonstrated high accuracy to quantify liver iron content. To be able to improve the current management of patients that are found to have iron overload, we need a reproducible, standardised method that is, or can easily be made, widely available.

Methods

This article discusses the different MRI techniques and models to quantify liver iron concentration that are currently available and envisaged for the near future from a realistic perspective.

Results

T2 relaxometry methods are more accurate than signal intensity ratio (SIR) methods and they are reproducible but are not yet standardised or widely available. SIR methods, on the other hand, are very specific for all levels of iron overload and, what is more, they are also reproducible, standardised and already widely available.

Conclusions

For these reasons, today, both methods remain necessary while progress is made towards universal standardisation of the relaxometry technique.
Splice blocking of zygotic sox31 leads to developmental arrest shortly after Mid‐Blastula Transition and induces apoptosis in zebrafish
Authors: Hu Sheng-Nan , Yu Hui , Zhang Yun-Bin , Wu Zhi-Li , Yan Yuan-Chang , Li Yi-Xue , Li Yuan-Yuan , Li Yi-Ping
Published: December 2011

Here we report that splice blocking morpholinos (Sb MO) against zebrafish sox31 elicit developmental arrest, likely through creating a series of dominant negative splicing variants. Embryos injected with the Sb MO develop normally before the Mid‐Blastula Transition (MBT); however, they do not initiate epiboly. Microarray analysis of mRNAs collected at the dome stage revealed that the Sb MO impairs activation of a large set of zygotic genes and reduces degradation of maternal mRNA during MBT. Furthermore, an apoptotic response occurs in Sb morphants at about 6 hpf. SoxB1 family genes including sox31 thus play an essential role for early embryos traversing the transitional stage.
Reconstitution of respiratory oxidases in membrane nanodiscs for investigation of proton‐coupled electron transfer
Authors: Näsvik Öjemyr Linda , von Ballmoos Christoph , Gennis Robert B. , Sligar Stephen G. , Brzezinski Peter
Published: December 2011

The function of membrane‐bound transporters is commonly affected by the milieu of the hydrophobic, membrane‐spanning part of the transmembrane protein. Consequently, functional studies of these proteins often involve incorporation into a native‐like bilayer where the lipid components of the membrane can be controlled. The classical approach is to reconstitute the purified protein into liposomes. Even though the use of such liposomes is essential for studies of transmembrane transport processes in general, functional studies of the transporters themselves in liposomes suffer from several disadvantages. For example, transmembrane proteins can adopt two different orientations when reconstituted into liposomes, and one of these populations may be inaccessible to ligands, to changes in pH or ion concentration in the external solution. Furthermore, optical studies of proteins reconstituted in liposomes suffer from significant light scattering, which diminishes the signal‐to‐noise value of the measurements. One attractive approach to circumvent these problems is to use nanodiscs, which are phospholipid bilayers encircled by a stabilizing amphipathic helical membrane scaffold protein. These membrane nanodiscs are stable, soluble in aqueous solution without detergent and do not scatter light significantly. In the present study, we have developed a protocol for reconstitution of the aa
3‐ and ba
3‐type cytochrome c oxidases into nanodiscs. Furthermore, we studied proton‐coupled electron‐transfer reactions in these enzymes with microsecond time resolution. The data show that the nanodisc membrane environment accelerates proton uptake in both oxidases.
Bayesian assessment of the expected data impact on prediction confidence in optimal sampling design
Authors: Leube P. C. , Geiges A. , Nowak W.
Published: December 2011

Incorporating hydro(geo)logical data, such as head and tracer data, into stochastic models of (subsurface) flow and transport helps to reduce prediction uncertainty. Because of financial limitations for investigation campaigns, information needs toward modeling or prediction goals should be satisfied efficiently and rationally. Optimal design techniques find the best one among a set of investigation strategies. They optimize the expected impact of data on prediction confidence or related objectives prior to data collection. We introduce a new optimal design method, called PreDIA(gnosis) (Preposterior Data Impact Assessor). PreDIA derives the relevant probability distributions and measures of data utility within a fully Bayesian, generalized, flexible, and accurate framework. It extends the bootstrap filter (BF) and related frameworks to optimal design by marginalizing utility measures over the yet unknown data values. PreDIA is a strictly formal information‐processing scheme free of linearizations. It works with arbitrary simulation tools, provides full flexibility concerning measurement types (linear, nonlinear, direct, indirect), allows for any desired task‐driven formulations, and can account for various sources of uncertainty (e.g., heterogeneity, geostatistical assumptions, boundary conditions, measurement values, model structure uncertainty, a large class of model errors) via Bayesian geostatistics and model averaging. Existing methods fail to simultaneously provide these crucial advantages, which our method buys at relatively higher‐computational costs. We demonstrate the applicability and advantages of PreDIA over conventional linearized methods in a synthetic example of subsurface transport. In the example, we show that informative data is often invisible for linearized methods that confuse zero correlation with statistical independence. Hence, PreDIA will often lead to substantially better sampling designs. Finally, we extend our example to specifically highlight the consideration of conceptual model uncertainty.