bluuebunny/crossref_metadata_2025_split huggingface dataset:
A theoretical study on three conformational structures of 2,6‐distyrylpyridine
Authors: Melendez F. J. , Urzúa Omar , Percino M. Judith , Chapela Victor M. 
Published: July 2009

AbstractAb initio methods at the levels HF/cc‐pVDZ, HF/6‐31G(d,p), MP2/cc‐pVDZ, and MP2/6‐31G(d,p), as well as methods based on density functional theory (DFT) employing the hybrid functional B3LYP with the basis sets cc‐pVDZ and 6‐31G(d,p), have been applied to study the conformers of 2,6‐distyrylpyridine. Bond distances, bond angles, and dihedral angles have been calculated at the B3LYP level. The calculated values were in good agreement with those measured by X‐ray diffraction analysis of 2,6‐distyrylpyridine. The values calculated using the Hartree‐Fock method and second‐order perturbation theory (MP2) were inconsistent. The optimized lowest‐energy geometries were calculated from the reported X‐ray structural data by the B3LYP/cc‐pVDZ method. Three conformations, A, B, and C, were proposed for 2,6‐distyrylpyridine. Calculations at the three levels of theory indicated that conformation A was the most stable structure, with conformations C and B being higher in energy by 1.10 and 2.57 kcal/mol, respectively, using the same method and basis function. The same trend in the relative energies of the three possible conformations was observed at the two levels of theory and with the different basis sets employed. The reported X‐ray data were utilized to optimize total molecular energy of conformation A at the different calculation levels. The bond lengths, bond angles, and dihedral angles were then obtained from the optimized geometries by ab initio methods and by applying DFT using the two basis functions cc‐pVDZ and 6‐31G(d,p). The values were analyzed and compared. The calculated total energies, the relative energies of the molecular orbitals, the gap between them, and the dipole moment for each conformational structure proposed for 2,6‐distyrylpyridine are also reported. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Orientation of endohedral H2, CO, and LiH inside heptagon‐containing C58 and C58H18
Authors: Sun Lili , Chang Yingfei , Tang Shuwei , Wang Rongshun 
Published: July 2009

AbstractThree H2@C58Hx, six CO@C58Hx, and six LiH@C58Hx (x = 0 and 18) complexes were optimized using B3LYP/6‐31G* method. The results show that both C58 and C58H18 destabilize nonpolar H2 and weakly polar CO, and stabilize strongly polar LiH inside their cages. Three H2@C58Hx (x = 0 and 18) complexes are nearly equivalent in energy, and CO orients the longest direction of cage because of spatial repulsion between them in the most stable CO@C58Hx (x = 0 and 18) isomers. Orientation of LiH inside C58Hx (x = 0 and 18) cages is determined by dipole‐induced dipole attractive interaction between them, and this attraction is especially significant in LiH@C58H18 complexes. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
δ and σ vs. π conflicting aromatic pentagonal ring of tungsten with a planar pentacoordinate carbon at the ring center
Authors: Yamaguchi Wataru 
Published: July 2009

AbstractDensity functional theory calculations have predicted a planar dicationic nanocluster CW consisting of a five‐membered tungsten ring and a planar pentacoordinate carbon atom located at the ring center. Although the regular‐pentagonal tungsten ring has strong aromaticity as a whole in terms of a magnetic criterion, detailed analyses have suggested that it is conflicting d‐orbital aromaticity in which δ‐ and σ‐aromaticity coexist with relatively weak π‐antiaromaticity. The system is unique in that δ‐aromaticity is involved in conflicting aromaticity, as well as being found in a conjugated ring consisting of more than three metal atoms. Although the planar pentagonal cluster ion is not the global minimum on the potential energy surface of CW, molecular dynamics simulations suggest that the planar species is fairly stable under mild conditions. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Superconductivity in cuprates: Details of electron phonon coupling
Authors: Larsson Sven 
Published: July 2009

AbstractThe Bardeen‐Cooper‐Schrieffer (BCS) model explains superconductivity (SC) as due to correlation between electronic momentum and nuclear momentum (phonons) in a free electron gas. The BCS model lacks chemical specificity, however, since the coupling mechanism is left unspecified. After the discovery of high TC superconductivity in 1986 it was concluded that electron–phonon interactions are insufficient to explain electron pairing. A large part of theoretical research has since been aiming at finding another mechanism that would allow us to consider the superconducting system as a gas of charged free bosons. However, there appears to be no reason to assume free electrons in oxides. In this article the free‐electron criterion is therefore replaced by the criterion that a pair of electrons can move freely between sites without resistance, i.e., without activation energy. Electron pair transfer is treated in a many‐electron real space approach using standard mixed‐valence theories. Mott‐Hubbard‐U is strictly defined, its dependence on breathing mode coordinates analyzed, and the connection between U and the energy gap for superconductivity clarified. d‐wave gap anisotropy is found to be consistent with the general atomic level model presented here. Softening of phonon half‐breathing modes in inelastic neutron scattering (INS) is connected to mixed‐valency. The fundamental vibronic interaction between spin density wave (SDW) and charge density wave (CDW) states leads to a new phase with energy gap and electron pair carriers that can only be the superconducting phase. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Benchmark calculations for molecules in the gas phase: State‐of‐the‐art coupled‐cluster computations
Authors: Puzzarini Cristina , Barone Vincenzo 
Published: July 2009

AbstractImplementation of very accurate ab initio methods on the one hand and improvements in computer facilities on the other hand allow the determination of structural, thermochemical, and spectroscopic properties of small‐ to medium‐sized molecules to a very high accuracy. The predictive capabilities have become so high that theoretical calculations can guide, support, and even challenge experimental determinations. Therefore, nowadays ab initio calculations are suitable for benchmarking purposes, even for quite large systems. To perform benchmark calculations, highly correlated methods, such as the coupled cluster ones, should be employed in conjunction with extrapolative and additive techniques to account for basis set and wave function truncation errors as well as to include important corrections, such as those related to core correlation and relativistic effects. Some illustrative examples are presented. The comparison of the computed data with experimental results allows us to show how quantum‐chemical computations are able to either accurately predict experimental data or cast doubts on them. Perspectives for extension of extrapolation techniques to the structures and properties of open‐shell systems with an effectiveness and reliability comparable with that well documented for closed‐shell systems are also discussed. Finally, perspectives for wider application of benchmark calculations are addressed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Hydrogen bonding interaction between 1,4‐dioxane and water
Authors: Chaudhari Ajay 
Published: July 2009

AbstractThis work reports an interaction of 1,4‐dioxane with one, two, and three water molecules using the density functional theory method at B3LYP/6‐311++G* level. Different conformers were studied and the most stable conformer of 1,4‐dioxane‐(water)n (n = 1–3) complex has total energies −384.1964038, −460.6570694, and −537.1032381 hartrees with one, two, and three water molecules, respectively. Corresponding binding energy (BE) for these three most stable structures is 6.23, 16.73, and 18.11 kcal/mol. The hydrogen bonding results in red shift in OO stretching and CC stretching modes of 1,4‐dioxane for the most stable conformer of 1,4‐dioxane with one, two, and three water molecules whereas there was a blue shift in CO symmetric stretching and CO asymmetric stretching modes of 1,4‐dioxane. The hydrogen bonding results in large red shift in bending mode of water and large blue shift in symmetric stretching and asymmetric stretching mode of water. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
A DFT investigation of dissociation of nitrous acid, transformation of its monomeric isomers, their dimeric isomers, and dimerization
Authors: Ruangpornvisuti Vithaya 
Published: July 2009

AbstractThe structure optimization of the monomeric isomers of the nitrous acid HONO, their cyclic dimers (HONO)2, and transition states of their transformations has been carried out using the density functional theory calculations at the B3LYP/6‐311++G(d,p) and B3LYP/aug‐cc‐pVQZ levels of theory. Three monomeric isomers (c, t, and z isomers) and six dimeric isomers (cc, ct, cz, tt, zz, and tz isomers) were found. Dissociation of the most stable of the HONO isomer (t isomer) was investigated and its rate constant was obtained at the UB3LYP/aug‐cc‐pVQZ level. Energetics, thermodynamic properties, rate, and equilibrium constants of the monomeric and dimeric isomerizations of the nitrous acid were obtained. Dimerization energies, enthalpies, and free energies of the dimeric isomers, (HONO)2 were also obtained. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Structural alignment using the generalized Euclidean distance between conformations
Authors: Mohazab Ali R. , Plotkin Steven S. 
Published: July 2009

AbstractThe usual Euclidean distance may be generalized to extended objects such as polymers or membranes. Here, this distance is used for the first time as a cost function to align structures. We examined the alignment of extended strands to idealized beta‐hairpins of various sizes using several cost functions, including RMSD, MRSD, and the minimal distance. We find that using minimal distance as a cost function typically results in an aligned structure that is globally different than that given by an RMSD‐based alignment. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Salt Rejection and Water Transport Through Boron Nitride Nanotubes
Authors: Hilder Tamsyn A. , Gordon Daniel , Chung Shin‐Ho 
Published: July 2009

AbstractNanotube‐based water‐purification devices have the potential to transform the field of desalination and demineralization through their ability to remove salts and heavy metals without significantly affecting the fast flow of water molecules. Boron nitride nanotubes have shown superior water flow properties compared to carbon nanotubes, and are thus expected to provide a more efficient water purification device. Using molecular dynamics simulations it is shown that a (5, 5) boron nitride nanotube embedded in a silicon nitride membrane can, in principle, obtain 100% salt rejection at concentrations as high as 1 M owing to a high energy barrier while still allowing water molecules to flow at a rate as high as 10.7 water molecules per nanosecond (or 0.9268 L m−2 h−1). Furthermore, ions continue to be rejected under the influence of high hydrostatic pressures up to 612 MPa. When the nanotube radius is increased to 4.14 Å the tube becomes cation‐selective, and at 5.52 Å the tube becomes anion‐selective.
C957T polymorphism of dopamine D2 receptor gene affects striatal DRD2 in vivo availability by changing the receptor affinity
Authors: Hirvonen Mika M. , Laakso Aki , Någren Kjell , Rinne Juha O. , Pohjalainen Tiina , Hietala Jarmo 
Published: July 2009

AbstractThe C957T polymorphism of the human dopamine D2 receptor gene (DRD2) regulates DRD2 availability in striatum in vivo. Specifically, the T allele predicts high DRD2 availability in healthy volunteers (T/T>T/C>C/C). However, this finding was unexpected as in vitro the T allele is associated with a decrease inDRD2mRNA stability and synthesis of the receptor through a putative alteration in the receptor mRNA folding. To elucidate further how changes in DRD2 density (Bmax) and affinity (KD) contribute to the differences in DRD2 availability between the C957T genotypes, we studied these parameters separately in a sample of 45 healthy volunteers. The subjects had two PET scans with [11C]raclopride (high and low specific radioactivity scans) for the estimation ofBmaxandKD, and were genotyped for the C957T. Moreover, the role of the related and previously studied functional TaqIA polymorphism of ankyrin repeat and kinase domain containing 1 (ANKK1) gene was reassessed for comparative purposes. The results indicate that the C957T increased binding potential by decreasing DRD2KD(C/C>C/T>T/T), whileBmaxwas not significantly altered. These preliminary findings indicate that the C957T genotype‐dependent changes in DRD2 availability are driven by alterations in receptor affinity and putatively in striatal dopamine levels. This mechanism seems to differ from that observed previously for theANKK1gene TaqIA polymorphism, where the minor allele (A1) affects DRD2 availability predominantly by changingBmax. The hypothesis that the two SNPs may have independent effects on dopamine neurotransmission needs to be further tested. Synapse 63:907–912, 2009. © 2009 Wiley‐Liss, Inc.
Differential effects of topiramate on prefrontal glutamatergic transmission when combined with raclopride or clozapine
Authors: Jardemark Kent E. , Konradsson Åsa , Schilström Björn , Marcus Monica M. , Svensson Torgny H. 
Published: July 2009

AbstractTreatment with topiramate may improve negative symptoms in schizophrenia when added to typical antipsychotic drugs (APDs) but not to clozapine. Both dopaminergic and glutamatergic transmissions in the medial prefrontal cortex (mPFC) are facilitated by atypical, but not typical, APDs, which is thought to improve negative symptoms and cognitive dysfunction in schizophrenia. Our previous results show that topiramate increases prefrontal dopamine (DA) outflow when added to the D2/3receptorantagonist raclopride. Here, using intracellular recording in vitro, we investigated the effects of topiramate on glutamatergic neurotransmission in the rat mPFC, both when given alone and in combination with raclopride or clozapine. Neither topiramate nor raclopride alone had any effect onN‐methyl‐D‐aspartate (NMDA)‐induced currents in pyramidal cells of the mPFC. However, the combination of topiramate and raclopride facilitated the NMDA‐induced currents, and this effect was blocked by the D1receptor antagonist SCH23390. Topiramate also facilitated the effect of a submaximal, but inhibited the effect of a maximal, concentration of clozapine on these currents. The effect of combined topiramate and a submaximal concentration of clozapine could be blocked by SCH23390. In addition, combined topiramate and raclopride facilitated excitatory postsynaptic potentials. In contrast, topiramate inhibited clozapine's facilitating effect on these potentials. These data may help explain the improvement of negative symptoms when topiramate is used as adjunctive therapy in schizophrenic patients receiving typical APDs, but they may also shed light on the observed deterioration of symptoms when topiramate is added to full dose clozapine. Synapse 63:913–920, 2009. © 2009 Wiley‐Liss, Inc.
Inherited disorders in the conversion of methionine to homocysteine
Authors: Barić Ivo 
Published: July 2009

SummaryDuring the last decade much important new information relating to the metabolic pathway from methionine to homocysteine has been gained. Interest has been stimulated by the discovery of two novel disorders, glycine N‐methyltransferase deficiency and S‐adenosylhomocysteine hydrolase deficiency. Another disorder in this pathway, methionine adenosyltransferase deficiency, has been increasingly detected, thanks to the expansion of newborn screening programmes by tandem mass spectrometry technology. These significant steps allow important insight into the pathogenesis of these three disorders, as well as into the mechanisms of damage to various organs (liver, brain, muscle) and point to the relevance of these disorders for crucial biological processes such as methylation, transsulfuration or carcinogenesis in mammals, the pathogenesis of numerous pathological conditions, in particular those associated with hyperhomocysteinaemia, the action and possible toxicity of some drugs or consequences of nutritional variations. This review summarizes current knowledge of three inherited disorders in this metabolic pathway and draws attention to their much broader significance for human health and understanding of important biological processes.
A Collaborative Approach to Genetic Testing: A Community Hospital's Experience
Authors: Cohen Stephanie A. , McIlvried Dawn , Schnieders Julie 
Published: July 2009

AbstractThe field of cancer genetics is evolving rapidly, and much has changed over the past ten years in the way services are being provided and by whom they are being provided. We recount here our experience with the evolution of cancer genetic services in a community setting, focusing on collaboration with non‐genetics providers to offer genetic testing for hereditary cancer. This approach allows for the most effective use of genetic counselors’ expertise for challenging cases, and enables the patient to remain within their community to allow for better access to resources for long‐term follow‐up.
Bread type intake is associated with lifestyle and diet quality transition among Bedouin Arab adults
Authors: Abu-Saad Kathleen , Shai Iris , Kaufman-Shriqui Vered , German Larissa , Vardi Hillel , Fraser Drora 
Published: July 2009

The traditionally semi-nomadic Bedouin Arabs in Israel are undergoing urbanisation with concurrent lifestyle changes, including a shift to using unfortified white-flour bread instead of wholewheat bread as the main dietary staple. We explored associations between the transition from wholewheat to white-flour bread and (1) lifestyle factors, (2) overall diet quality, and (3) health status. We conducted a nutrition survey among 451 Bedouin adults, using a modified 24 h recall questionnaire. Bread intake accounted for 32·7 % of the total energy intake. Those consuming predominantly white bread (PWB) (n 327) were more likely to be urban (OR 2·79; 95 % CI 1·70, 4·58), eating store-bought rather than homemade bread (OR 8·18; 95 % CI 4·34, 15·41) and currently dieting (OR 4·67; 95 % CI 1·28, 17·11) than those consuming predominantly wholewheat bread (PWWB) (n 124). PWB consumption was associated with a lower intake of dietary fibre (23·3 (se 0·6) v. 41·8 (se 1·0) g/d; P ≤ 0·001), a higher intake of saturated fats (26·9 v. 24·6 % of total fat; P = 0·013) and lower intakes of Fe (11·0 (se 0·3) v. 16·7 (se 0·4) mg/d), Mg (262·2 (se 5·9) v. 490·3 (se 9·8) mg/d), vitamin E (6·5 (se 0·2) v. 8·6 (se 0·3) mg/d) and most B vitamins than PWWB consumption (P < 0·001 for all), after adjusting for total energy intake. Among those aged ≥ 40 years, PWB consumption was associated with a 9·85-fold risk (95 % CI 2·64, 36·71; P = 0·001) of having one or more chronic conditions, as compared with PWWB consumption, after controlling for other risk factors. White bread intake was associated with a less traditional lifestyle and poorer diet quality, and may constitute a useful marker for at-risk subgroups to target for nutritional interventions.
A pilot study on the molecular phylogeny of Drepanoidea (Insecta: Lepidoptera) inferred from the nuclear gene EF-1α and the mitochondrial gene COI
Authors: Wu C.G. , Han H.X. , Xue D.Y. 
Published: July 2009

AbstractA molecular phylogenetic study of the Drepanoidea based on the EF-1α sequences and combined EF-1α and COI sequences was carried out in order to infer higher classification at and above the subfamily level. The sample contained 14 taxa representing 13 genera recognized in the Drepanoidea. The results revealed that the Drepaninae, Thyatirinae and Cyclidiinae respectively form monophyletic groups. The sister relationship between the Drepaninae and the Thyatirinae was validated. The monophyly of the Cyclidiinae with the Drepaninae+Thyatirinae was supported robustly.Hypsomadius insignisandOreta vatamawithin the traditional definition of the Drepaninae formed an individual clade with robust support (100%) and constitutes a sister relationship to a clade containing the rest of the Drepaninae in all the topologies, which means that the subfamily Oretinae of the Drepanidae should be restored. The family Drepanidae is divided into four subfamilies: Drepaninae, Oretinae, Thyatirinae and Cyclidiinae in this work. The family Epicopeiidae formed a monophyly with high bootstrap values. The result of combined analysis of EF-1α and COI showed that the Epicopeiidae have a closer phylogenetic relationship with the Geometridae than with the Drepanidae and belong to neither the Drepanoidea nor the Geometroidea.
The Influence of Judicial Uncertainty on Executive Support for Negotiation in Canadian Land Claims Policy
Authors: Scholtz Christa 
Published: July 2009

Abstract.Governments and Indigenous groups bargain under the shadow of the law, and this paper pushes the judicial politics research agenda by examining empirically whether flickers in law's shadow systematically affect the implementation of the Canadian government's negotiation choice in the Indigenous land rights context. Through interviews and a time series analysis of Canada's specific claims policy, I find that judicial uncertainty increases the federal government's propensity to accept specific claims for negotiation. However, there is evidence that Indigenous protest action during the Oka crisis and Elijah Harper's role in scuttling the Meech Lake constitutional accord, more than other factors, greatly impacted the federal budget allocated towards negotiation.Résumé.Les négociations entre les gouvernements et les groupes autochtones se déroulent sous les auspices de la loi, et le présent document examine le programme de recherche sur les politiques légales afin de déterminer de façon empirique si certaines imprécisions dans la loi influent sur les options retenues par le gouvernement du Canada en ce qui concerne les droits sur les terres autochtones. Une analyse statistique de la politique de revendication en vigueur au Canada ainsi qu'un certain nombre d'entrevues m'ont permis de constater l'existence d'un flou juridique qui amène le gouvernement fédéral à accepter d'examiner certaines revendications spécifiques à la table des négociations. Il semble toutefois que certains incidents particuliers, comme les gestes de protestation posés par les autochtones lors de la crise d'Oka, ou le rôle joué par Elijah Harper dans l'échec de l'Accord constitutionnel du lac Meech, aient eu une incidence marquée sur l'importance des sommes allouées par le gouvernement fédéral à ces négociations.