bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infrared Absorption Spectroscopy of Adsorbed CO: New Applications in Nanocatalysis for an Old Approach
Authors: Zaera Francisco 
Published: July 2012

AbstractIn this minireview, the power of using a well‐established approach, CO infrared absorption spectroscopy, as a probe for the characterization of novel nanostructured catalysts is discussed. It is argued that the peak positions of the CO stretching mode in IR spectra can be used not only to differentiate between adsorption on metals catalysts and oxide supports, but also to provide information on the oxidation state of the metal, on the surface planes available for adsorption, and on the adsorption bonding modes possible. Perhaps more basic but more important for nanocatalysis applications is the usefulness of the information provided by CO IR spectroscopy to identify and quantify the sites accessible to reactants in the catalytic surfaces of complex nanoarchitectures. A number of examples are provided here from studies by our group to illustrate these points, including the characterization of catalysts based on dendrimer‐ and mesoporous‐silica‐encapsulated metal nanoparticles and on core@shell and yolk@shell nanostructures.
Atomic Polarizability Dominates the Electronic Properties of Peptide Bonds upon Thioxo or Selenoxo Substitution
Authors: Huang Yun , Jahreis Günther , Fischer Gunter , Lücke Christian 
Published: July 2012

AbstractThe amide bond as peptide linkage plays an important role in protein structure and function. A large number of theoretical and experimental studies have focused on the specific nature of the peptide bond. Little attention, however, has been paid to their chalcogen‐substituted congeners, although experimental data on thioamides revealed inconsistencies with the conventional view of amide resonance theory. Here, we employed thioxo and selenoxo substitution to determine experimentally how heavier chalcogens affect the properties of the peptide bond and adjacent atoms. NMR data revealed pronounced deshielding of heteronuclei within a three‐bond distance to the chalcogen atom; this indicates an enhanced electron‐withdrawing potential of the heavier chalcogens despite their lower electronegativities compared to oxygen. Interestingly, linear correlations were observed between chalcogen atomic polarizability and the chemical shift values of those neighboring heteronuclei as well as several physicochemical properties, such as electronic excitation energy, CN rotation barrier, dipole moment and amide proton dissociation. We conclude that the chalcogen polarizability, which relates to the charge capacity, is the dominant factor that determines the electronic properties of peptide bonds substituted with heavier chalcogens.
Synthesis and Anticoagulant Activity of Bioisosteric Sulfonic‐Acid Analogues of the Antithrombin‐Binding Pentasaccharide Domain of Heparin
Authors: Herczeg Mihály , Lázár László , Bereczky Zsuzsanna , Kövér Katalin E. , Timári István , Kappelmayer János , Lipták András , Antus Sándor , Borbás Anikó 
Published: July 2012

AbstractTwo pentasaccharide sulfonic acids that were related to the antithrombin‐binding domain of heparin were prepared, in which two or three primary sulfate esters were replaced by sodium‐sulfonatomethyl moieties. The sulfonic‐acid groups were formed on a monosaccharide level and the obtained carbohydrate sulfonic‐acid esters were found to be excellent donors and acceptors in the glycosylation reactions. Throughout the synthesis, the hydroxy groups to be methylated were masked in the form of acetates and the hydroxy groups to be sulfated were masked with benzyl groups. The disulfonic‐acid analogue was prepared in a [2+3] block synthesis by using a trisaccharide disulfonic acid as an acceptor and a glucuronide disaccharide as a donor. For the synthesis of the pentasaccharide trisulfonic acid, a more‐efficient approach, which involved elongation of the trisaccharide acceptor with a non‐oxidized precursor of the glucuronic acid followed by post‐glycosidation oxidation at the tetrasaccharide level and a subsequent [1+4] coupling reaction, was elaborated. In vitro evaluation of the anticoagulant activity of these new sulfonic‐acid derivatives revealed that the disulfonate analogue inhibited the blood‐coagulation‐proteinase factor Xa with outstanding efficacy; however, the introduction of the third sulfonic‐acid moiety resulted in a notable decrease in the anti‐Xa activity. The difference in the biological activity of the disulfonic‐ and trisulfonic‐acid counterparts could be explained by the different conformation of their L‐iduronic‐acid residues.
Nanosheet‐Enhanced Enantioselectivity in the Vanadium‐Catalyzed Asymmetric Epoxidation of Allylic Alcohols
Authors: Zhao Li‐Wei , Shi Hui‐Min , Wang Jiu‐Zhao , He Jing 
Published: July 2012

AbstractThe use of suitable chiral ligands is an efficient means of producing highly enantioselective transition‐metal catalysts. Herein, we report a facile, economic, and effective strategy for the design of chiral ligands that demonstrate enhanced enantioselectivity and catalytic efficacy. Our simple strategy employs naturally occurring or synthetic inorganic nanosheets as huge and rigid planar substituents for, but not limited to, naturally available α‐amino‐acid ligands; these ligands were successfully used in the vanadium‐catalyzed asymmetric epoxidation of allylic alcohols. The crucial role of the inorganic nanosheets as planar substituents in improving the enantioselectivity of the reaction was clearly revealed by relating the observed enantiomeric excess with the distribution of the catalytic centers and the accessibility of the substrate molecules to the catalytic sites. DFT calculations indicated that the LDH layer improved the enantioselectivity by influencing the formation and stability of the catalytic transition states, both in terms of steric resistance and H‐bonding interactions.
Enhanced Optical Nonlinearity in Noncovalently Functionalized Amphiphilic Graphene Composites
Authors: He Tingchao , Qi Xiaoying , Chen Rui , Wei Jun , Zhang Hua , Sun Handong 
Published: July 2012

AbstractThe good solubility of graphene‐based materials in various solvents without sacrificing their intrinsic properties is a prerequisite for their further applications. In particular, it is important for application as a practical optical limiter. A comprehensive study was conducted on the nonlinear optical property of a rationally designed amphiphilic graphene composite (PEG‐OPE‐rGO). By taking advantages of the unique energy diagram of this graphene composite, the optical limiting (OL) performances of PEG‐OPE‐rGO, which is either dissolved in solvents with moderate polarity or fabricated into thin solid films, are beyond the reported results for other graphene composites. Importantly, the main factors for the enhanced OL response of PEG‐OPE‐rGO are the multiphoton absorption and Förster resonance energy transfer process, instead of the nonlinear scattering mechanism observed for common nanostructured materials. The excellent OL response of PEG‐OPE‐rGO allows it to be one of the best candidates in practical optical limiters. Moreover, the mechanism analysis provides the deep insight for further optimization of the design of promising OL materials.
The Role of the Board in the Dissemination of Integrated Corporate Social Reporting
Authors: Frias‐Aceituno José V. , Rodriguez‐Ariza Lazaro , Garcia‐Sanchez I.M 
Published: July 2012

ABSTRACTThe stakeholder theory recognizes that, besides shareholders and creditors, there exists a broad range of agents who are interested in companies' attitudes towards sustainability. Through corporate social reporting, the social and environmental effects of companies' economic actions are communicated to interest groups. However, the information contained in financial and social reports tends to be presented quite separately from that in the others, and this may lead to confusion among users. Therefore, several major companies have introduced an integrated reporting system, which coherently summarizes the information available, thus making stakeholders participants in business management.Corporate governance mechanisms such as the Board of Directors play an important role in good practices of corporate social responsibility, implementing policies of stakeholder engagement, including processes to achieve holistic transparency.The aim of this paper is to demonstrate the influence played by certain features of the Board of Directors in the degree of information integration presented by leading non‐financial multinational firms. Specifically, we examined 568 companies from 15 countries, for the period 2008–2010. The results obtained show that growth opportunities, the size of a company and its management bodies, together with gender diversity, are the most important factors in the integrated dissemination of information. This effect has been confirmed for the Anglo‐Saxon, Germanic and Latin models of corporate governance. Copyright © 2012 John Wiley & Sons, Ltd and ERP Environment
Kinetic Resolution in Chiral Phosphoric Acid Catalyzed Aldol Reactions: Enantioselective Robinson‐Type Annulation Reactions
Authors: Yamanaka Masahiro , Hoshino Masaya , Katoh Takuya , Mori Keiji , Akiyama Takahiko 
Published: July 2012

AbstractA remarkable kinetic resolution was achieved in a chiral phosphoric acid catalyzed intramolecular aldol reaction. Its combination with an enantioselective Michael reaction resulted in the formation of cyclohexenone derivatives with excellent enantioselectivities. DFT calculations on the intramolecular aldol reaction revealed the importance of the 3,3′‐substituents of the phosphoric acid for the high enantioselectivity in the kinetic resolution process.
Loss of astrocyte polarization upon transient focal brain ischemia as a possible mechanism to counteract early edema formation
Authors: Steiner Esther , Enzmann Gaby U. , Lin Shuo , Ghavampour Sharang , Hannocks Melanie‐Jane , Zuber Benoît , Rüegg Markus A. , Sorokin Lydia , Engelhardt Britta 
Published: July 2012

AbstractBrain edema is the main cause of death from brain infarction. The polarized expression of the water channel protein aquaporin‐4 (AQP4) on astroglial endfeet surrounding brain microvessels suggests a role in brain water balance. Loss of astrocyte foot process anchoring to the basement membrane (BM) accompanied by the loss of polarized localization of AQP4 to astrocytic endfeet has been shown to be associated with vasogenic/extracellular edema in neuroinflammation. Here, we asked if loss of astrocyte polarity is also observed in cytotoxic/intracellular edema following focal brain ischemia after transient middle cerebral artery occlusion (tMCAO). Upon mild focal brain ischemia, we observed diminished immunostaining for the BM components laminin α4, laminin α2, and the proteoglycan agrin, in the core of the lesion, but not in BMs in the surrounding penumbra. Staining for the astrocyte endfoot anchorage protein β‐dystroglycan (DG) was dramatically reduced in both the lesion core and the penumbra, and AQP4 and Kir4.1 showed a loss of polarized localization to astrocytic endfeet. Interestingly, we observed that mice deficient for agrin expression in the brain lack polarized localization of β‐DG and AQP4 at astrocytic endfeet and do not develop early cytotoxic/intracellular edema following tMCAO. Taken together, these data indicate that the binding of DG to agrin embedded in the subjacent BM promotes polarized localization of AQP4 to astrocyte endfeet. Reduced DG protein levels and redistribution of AQP4 as observed upon tMCAO might therefore counteract early edema formation and reflect a beneficial mechanism operating in the brain to minimize damage upon ischemia. © 2012 Wiley Periodicals, Inc.
Expression patterns of cancer stem cell markers ALDH1 and CD133 correlate with a high risk of malignant transformation of oral leukoplakia
Authors: Liu Wei , Wu Lan , Shen Xue‐Min , Shi Lin‐Jun , Zhang Chen‐Ping , Xu Li‐Qun , Zhou Zeng‐Tong 
Published: July 2012

AbstractMolecular markers for predicting oral cancer development in premalignant oral leukoplakia (OL) are urgently needed. The objective of this study was to examine the expression patterns of cancer stem cell markers ALDH1 and CD133 in samples from patients with OL, and determine their prognostic values for subsequent development of oral cancer. Immunohistochemistry for ALDH1 and CD133 was performed in samples from a cohort of 141 patients with biopsy‐proven OL who received a mean follow‐up of 5.5 years. Patient clinicopathologic and follow‐up data were analyzed. Expression of ALDH1 and CD133 was observed in 54 (38.3%) and 32 (22.7%) of 141 patients with OL, respectively. Kaplan–Meier analysis showed that 48.1% patients with ALDH1‐positivity developed oral cancer compared with 12.6% those with ALDH1‐negativity (p < 0.001). Meanwhile, 59.4% patients with CD133‐positivity developed oral cancer compared with 16.5% those with CD133‐negativity (p < 0.001). Multivariate analysis revealed that ALDH1 and CD133 expression was associated with 4.17‐fold [95% confidence interval (CI), 1.96–8.90; p < 0.001] and 2.86‐fold (95% CI, 1.48‐5.55; p = 0.002) increased risk of OL transformation, respectively. Collectively, these data demonstrated for the first time that the expression of ALDH1 and CD133 correlated with malignant transformation in a large series of patients with OL who received a long‐term follow‐up, which suggests that they may serve as predictors to identify OL with a high risk of oral cancer development.
Ostracod Assemblages in Relation to Littoral Plant Communities of a Shallow Lake (Lake Świdwie, Poland)
Authors: Szlauer‐Łukaszewska Agnieszka 
Published: July 2012

AbstractThe aims of this study included: specifying values of ecological parameters and Ostracoda species characteristic for different types of plant habitats occurring in lake systems, determining the impact of mud presence on the taxonomic structure and density of the ostracods, tracing seasonal changes in the structures of Ostracoda assemblages identifying the species typical of particular seasons. Various types of rushes and underwater meadows were taken into consideration as lake microhabitats. The research was conducted in the shallow Lake Œwidwie (NW Poland). Multivariate (constrained) ordination methods were used to analyse the relationships between species composition and environmental variables. In the lake and its margins 31 species of the Ostracoda were identified. The development of water vegetation during the vegetation season was conducive to growth in ostracod density. The accessibility of mud in plant habitats had a favourable effect on the general density of ostracods. Species which preferred a high mud content in their habitats included: Cypria ophtalmica, C. exsculpta and Physocypria kraepelini. Species typically encountered in underwater meadow habitats were: Cyclocypris ovum and Cypridopsis vidua. Underwater meadows of charophyte were characterized by the highest ostracod density in the whole lake system, with the average of 7860 ind. m–2 and the maximum of 17 470 ind. m–2. Species typically encountered in rush habitats included Notodromas monacha, Dolerocypris fasciata and Metacypris cordata. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluating nonpolarizable nucleic acid force fields: A systematic comparison of the nucleobases hydration free energies and chloroform‐to‐water partition coefficients
Authors: Wolf Maarten G. , Groenhof Gerrit 
Published: July 2012

AbstractNucleic acid force fields have been shown to reproduce structural properties of DNA and RNA very well, but comparative studies with respect to thermodynamic properties are rare. As a test for thermodynamic properties, we have computed hydration free energies and chloroform‐to‐water partition coefficients of nucleobases using the AMBER‐99, AMBER‐gaff, CHARMM‐27, GROMOS‐45a4/53a6 and OPLS‐AA force fields. A mutual force field comparison showed a very large spread in the calculated thermodynamic properties, demonstrating that some of the parameter sets require further optimization. The choice of solvent model used in the simulation does not have a significant effect on the results. Comparing the hydration free energies obtained by the various force fields to the adenine and thymine experimental values showed a very large deviation for the GROMOS and AMBER parameter sets. Validation against experimental partition coefficients showed good agreement for the CHARMM‐27 parameter set. In view of mutation studies, differences in partition coefficient between two bases were also compared, and good agreement between experiments and calculations was found for the AMBER‐99 parameter set. Overall, the CHARMM‐27 parameter set performs best with respect to the thermodynamic properties tested here. © 2012 Wiley Periodicals, Inc.
Binding energies of five molecular pincers calculated by explicit and implicit solvent models
Authors: Kessler Jiří , Jakubek Milan , Dolenský Bohumil , Bouř Petr 
Published: July 2012

AbstractMolecular pincers or tweezers are designed to hold and release the target molecule. Potential applications involve drug distribution in medicine, environment technologies, or microindustrial techniques. Typically, the binding is dominated by van der Waals forces. Modeling of such complexes can significantly enhance their design; yet obtaining accurate complexation energies by theory is difficult. In this study, density functional theory (DFT) computations combined with dielectric continuum solvent model are compared with the potential of mean force approach using umbrella sampling and the weighted histogram analysis method (WHAM) with molecular dynamics (MD) simulations. For DFT, functional and basis set effects are discussed. The computed results are compared to experimental data based on NMR spectroscopic measurements of five synthesized tweezers based on the Tröger's basis. Whereas the DFT computations correctly provided the observed trends in complex stability, they failed to produce realistic magnitudes of complexation energies. Typically, the binding was overestimated by DFT if compared to experiment. The simpler semiempirical PM6‐DH2X scheme proposed lately yielded better magnitudes of the binding energies than DFT but not the right order. The MD‐WHAM simulations provided the most realistic Gibbs binding energies, although the approximate MD force fields were not able to reproduce completely the ordering of relative stabilities of model complexes found by NMR. Yet the modeling provides interesting insight into the complex geometry and flexibility and appears as a useful tool in the tweezers' design. © 2012 Wiley Periodicals, Inc.
Computation of scattering by complex targets using an efficient mixed‐order curved moment method
Authors: Deng Chu‐Qiang , Sheng Xin‐Qing , Song Wei 
Published: July 2012

SUMMARYThe goal of this paper is to develop an efficient and accurate computation scheme based on mixed‐order curved moment method for computing scattering from complex targets. To this end, the numerical performances of different kinds of higher‐order basis functions are presented and compared numerically. The formulae in the improved Duffy method for higher‐order curved moment method are derived and given explicitly. An efficient and accurate computation scheme is presented and implemented on the basis of the optimized triangular hierarchical higher‐order basis function and the improved Duffy method. Numerical experiments are performed to show accuracy and efficiency of the presented computation scheme for complex targets. Copyright © 2012 John Wiley & Sons, Ltd.
Dynamic Light Scattering of Rigid Rods – A Universal Relationship on the Apparent Diffusion Coefficient as Revealed by Numerical Studies and Its Use for Rod Length Determination
Authors: Liu Tao , Xiao Zhiwei 
Published: July 2012

AbstractNumerical simulations are performed to study the diffusion behaviors of rigid rods examined by dynamic light scattering (DLS). It was identified that the apparent diffusion coefficient, Dp, determined by DLS obeys a universal relationship Dp/DG = f(qL) = 1.1804 + 0.1764 × tanh [11.799× tan−1(qL) ‐17.169], where DG, L, and q are the mass‐of‐center diffusion coefficient, length of the rod, and scattering vector, respectively. This relationship delineates the DLS experiments into weak (qL < 4.0), intermediate (4.0 < qL < 20.0), and strong translation–rotation coupling regime (qL > 20.0). In weak (strong) coupling regime, Dp is a measure of DG (D// ‐ longitudinal diffusion coefficient) of the rods. In addition, if DLS is performed in the intermediate coupling regime, the rod length can be determined by solving Dp/DG = f(qL).
Rare Earth Metal‐Mediated Group Transfer Polymerization of Vinylphosphonates
Authors: Salzinger Stephan , Rieger Bernhard 
Published: July 2012

AbstractRecent studies have shown that poly(vinylphosphonate)s are readily accessible by rare earth metal‐mediated group transfer polymerization (GTP). This article highlights the progress in this new field and advantages of GTP in comparison to classical anionic and radical polymerization approaches. Late lanthanide metallocenes proved to be efficient initiators and highly active catalysts for vinylphosphonate polymerization yielding polymers of precise molecular weight and low polydispersity. Using this method, our group has developed a surface‐initiated GTP to prepare poly(vinylphosphonate) brushes. In combination with different ester cleavage strategies, rare earth metal‐mediated GTP is an efficient way to create well‐defined high‐molecular‐weight poly(vinylphosphonic acid).
Fingerprint Kernels for Protein Structure Comparison
Authors: Fober Thomas , Mernberger Marco , Klebe Gerhard , Hüllermeier Eyke 
Published: July 2012

AbstractA key task in structural biology is to define a meaningful similarity measure for the comparison of protein structures. Recently, the use of graphs as modeling tools for molecular data has gained increasing importance. In this context, kernel functions have attracted a lot of attention, especially since they allow for the application of a rich repertoire of methods from the field of kernel‐based machine learning. However, most of the existing graph kernels have been designed for unlabeled and/or unweighted graphs, although proteins are often more naturally and more exactly represented in terms of node‐labeled and edge‐weighted graphs. Here we analyze kernel‐based protein comparison methods and propose extensions to existing graph kernels to exploit node‐labeled and edge‐weighted graphs. Moreover, we propose an instance of the substructure fingerprint kernel suitable for the analysis of protein binding sites. By using fuzzy fingerprints, we solve the problem of discontinuity on bin‐boundaries arising in the case of labeled graphs.
Family Business or Social Problem? The Cost of Unreported Domestic Violence
Authors: Carrell Scott E. , Hoekstra Mark 
Published: July 2012

AbstractSocial interest in problems such as domestic violence is typically motivated by concerns regarding equity, rather than efficiency. However, we document that taking steps to reduce domestic violence by reporting it yields substantial benefits to external parties. Specifically, we find that although children exposed to as‐yet‐unreported domestic violence reduce the achievement of their classroom peers, these costs disappear completely once the parent reports the violence to the court. This suggests that the public has an interest in helping families to overcome their problems in general and to report domestic violence in particular. It also suggests that social and judicial interventions may help combat negative peer effects in schools.