bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlling the Structural and Electrical Properties of Diacid Oligo(Phenylene Ethynylene) Langmuir–Blodgett Films
Authors: Ballesteros Luz Marina , Martín Santiago , Cortés Javier , Marqués‐González Santiago , Higgins Simon J. , Nichols Richard J. , Low Paul J. , Cea Pilar 
Published: February 2013

AbstractThe preparation, characterization and electrical properties of Langmuir–Blodgett (LB) films composed of a symmetrically substituted oligomeric phenylene ethynylene derivative, namely, 4,4′‐[1,4‐phenylenebis(ethyne‐2,1‐diyl)]dibenzoic acid (OPE2A), are described. Analysis of the surface pressure versus area per molecule isotherms and Brewster angle microscopy reveal that good‐quality Langmuir (L) films can be formed both on pure water and a basic subphase. Monolayer L films were transferred onto solid substrates with a transfer ratio of unity to obtain LB films. Both L and LB films prepared on or from a pure water subphase show a red shift in the UV/Vis spectrum of about 14 nm, in contrast to L and LB films prepared from a basic subphase, which show a hypsochromic shift of 15 nm. This result, together with X‐ray photoelectron spectroscopic and quartz crystal microbalance experiments, conclusively demonstrate formation of one‐layer LB films in which OPE2A molecules are chemisorbed onto gold substrates and consequently COOAu junctions are formed. In LB films prepared on a basic subphase the other terminal acid group is also deprotonated and associates with an Na+ counterion. In contrast, LB films prepared from a pure water subphase preserve the protonated acid group, and lateral H‐bonds with neighbouring molecules give rise to a supramolecular structure. STM‐based conductance studies revealed that films prepared from a basic subphase are more conductive than the analogous films prepared from pure water, and the electrical conductance of the deprotonated films also coincides more closely with single‐molecule conductance measurements. This result was interpreted not only in terms of better electron transmission in COOAu molecular junctions, but also in terms of the presence of lateral H‐bonds in the films formed from pure water, which lead to reduced conductance of the molecular junctions.
Synthesis of Luminescent Ethynyl‐Extended Regioisomers of Borate Complexes Based on 2‐(2′‐Hydroxyphenyl)benzoxazole
Authors: Massue Julien , Frath Denis , Retailleau Pascal , Ulrich Gilles , Ziessel Raymond 
Published: February 2013

AbstractA series of thirteen luminescent tetrahedral borate complexes based on the 2‐(2′‐hydroxyphenyl)benzoxazole (HBO) core is presented. Their synthesis includes the incorporation of an ethynyl fragment by Sonogashira cross‐coupling reaction, with the goal of extending the conjugation and consequently redshifting their emission wavelength. Different regioisomers, substituted in the 3‐, 4‐, or 5‐position of the phenolate side of the HBO core, were studied in order to compare their photophysical properties. The complexes were characterized by X‐ray diffraction and NMR, UV/Vis, and emission spectroscopy in solution and in the solid state. In all cases, complexation to boron leads to a donor–acceptor character that impacts their photophysical properties. Complexes with a 3‐ or 5‐substituted fragment display mild to pronounced internal charge transfer (ICT), a feature strengthened by the presence of p‐dibutylaminophenylacetylene in the molecular structure, protonation of the nitrogen atom of which leads to a significant blueshift and an increase in quantum yield. On the contrary, when the ethynyl module is grafted on the 4‐position, narrow, structured, symmetrical absorption/emission bands are observed. Moreover, the fact that protonation has little effect on the emission maximum wavelength reveals singlet excited‐state decay. Solid‐state emission properties reveal a redshift compared to solution, explained by tight packing of the π‐conjugated systems and the high planarity of the dyes. Subsequent connection of these complexes to other photoactive subunits (BODIPY, Boranil) provides dyads in which efficient cascade energy transfer is observed.
Does the Molecular Electrostatic Potential Reflect the Effects of Substituents in Aromatic Systems?
Authors: Galabov Boris , Nikolova Valia , Ilieva Sonia 
Published: February 2013

AbstractA detailed analysis of the molecular electrostatic potential (MEP) at selected positions in molecular space was performed for a series of substituted benzene derivatives. We show that appropriately selected MEP values can quantitatively reflect the regiospecific effects of substituents on the aromatic ring. Theoretically evaluated electrostatic potentials in close proximity to the ring carbon atoms reflect well both through‐space and resonance effects and excellent correlation is established between the MEP values and substituent constants. The best descriptor of the local properties at different ring positions is the electrostatic potential at nuclei (EPN).
Reactions of Group 4 Metallocene Complexes with Mono‐ and Diphenylacetonitrile: Formation of Unusual Four‐ and Six‐Membered Metallacycles
Authors: Becker Lisanne , Burlakov Vladimir V. , Arndt Perdita , Spannenberg Anke , Baumann Wolfgang , Jiao Haijun , Rosenthal Uwe 
Published: February 2013

AbstractReactions of Group 4 metallocene alkyne complexes [Cp′2M(η2‐Me3SiC2SiMe3)] (1: M=Zr, Cp′=Cp*=η5‐pentamethylcyclopentadienyl; 2 a: M=Ti, Cp′=Cp*, and 2 b: M=Ti, Cp′2=rac‐(ebthi)=rac‐1,2‐ethylene‐1,1′‐bis(η5‐tetrahydroindenyl)) with diphenylacetonitrile (Ph2CHCN) and of the seven‐membered zirconacyclocumulene 3 with phenylacetonitrile (PhCH2CN) were investigated. Different compounds were obtained depending on the metal, the cyclopentadienyl ligand and the reaction temperature. In the first step, Ph2CHCN coordinated to 1 to form [Cp*2Zr(η2‐Me3SiC2SiMe3)(NCCHPh2)] (4). Higher temperatures led to elimination of the alkyne, coordination of a second Ph2CHCN and transformation of the nitriles to a keteniminate and an imine ligand in [Cp*2Zr(NC2Ph2)(NCHCHPh2)] (5). The conversion of 4 to 5 was monitored by using 1H NMR spectroscopy. The analogue titanocene complex 2 a eliminated the alkyne first, which led directly to [Cp*2Ti(NC2Ph2)2] (6) with two keteniminate ligands. In contrast, the reaction of 2 b with diphenylacetonitrile involved a formal coupling of the nitriles to obtain the unusual four‐membered titanacycle 7. An unexpected six‐membered fused zirconaheterocycle (8) resulted from the reaction of 3 with PhCH2CN. The molecular structures of complexes 4, 5, 6, 7 and 8 were determined by X‐ray crystallography.
Total Synthesis of theEscherichia coliO111O‐Specific Polysaccharide Repeating Unit
Authors: Calin Oliviana , Eller Steffen , Hahm Heung Sik , Seeberger Peter H. 
Published: February 2013

AbstractThe first total synthesis of theO‐antigen pentasaccharide repeating unit from Gram‐negative bacteriaEscherichia coliO111 was achieved starting from four monosaccharide building blocks. Key to the synthetic approach was a bis‐glycosylation reaction to combine trisaccharide10and colitose5. The colitose building block (5) was obtainedde novofrom non‐carbohydrate precursors. The pentasaccharide was equipped at the reducing end with an amino spacer to provide a handle for subsequent conjugation to a carrier protein in anticipation of immunological studies.
Rhenium–Germanium Triple Bonds: Syntheses and Reactions of the Germylidyne Complexes mer‐[X2(PMe3)3ReGeR] (X=Cl, I, H; R=m‐terphenyl)
Authors: Filippou Alexander C. , Chakraborty Uttam , Schnakenburg Gregor 
Published: February 2013

AbstractA general approach to the first compounds that contain rhenium–germanium triple and double bonds is reported. Heating [ReCl(PMe3)5] (1) with the arylgermanium(II) chloride GeCl(C6H3‐2,6‐Trip2) (2; Trip=2,4,6‐triisopropylphenyl) results in the germylidyne complex mer‐[Cl2(PMe3)3ReGeC6H3‐2,6‐Trip2] (4) upon PMe3 elimination. An equilibrium that is dependent on the PMe3 concentration exists between complexes 1 and 4. Removal of the volatile PMe3 shifts the equilibrium towards complex 4, whereas treatment of 4 with an excess of PMe3 gives a 1:1 mixture of 1 and the PMe3 adduct of 2, GeCl(C6H3‐2,6‐Trip2)(PMe3) (2‐PMe3). Adduct 2‐PMe3 can be selectively obtained by addition of PMe3 to chlorogermylidene 2. The NMR spectroscopic data for 2‐PMe3 indicate an equilibrium between 2‐PMe3 and its dissociation products, 2 and PMe3, which is shifted far towards the adduct site at ambient temperature. NMR spectroscopic monitoring of the reaction of complex 1 with 2 and the reaction of complex 4 with PMe3 revealed the formation of two key intermediates, which were identified to be the chlorogermylidene complexes cis/trans‐[Cl(PMe3)4ReGe(Cl)C6H3‐2,6‐Trip2] (cis/trans‐3) by using NMR spectroscopy. Labile chlorogermylidene complexes cis/trans‐3 can be also generated from trans‐[Cl(PMe3)4ReGeC6H3‐2,6‐Trip2]BPh4 (9) and (nBu4N)Cl at low temperature, and decompose at ambient temperature to give a mixture of complexes 1 and 4. Complex 4 reacts with LiI to give the diiodido derivative mer‐[I2(PMe3)3ReGeC6H3‐2,6‐Trip2] (5), which undergoes a metathetical iodide/hydride exchange with Na(BEt3H) to give the dihydrido germylidyne complex mer‐[H2(PMe3)3ReGeC6H3‐2,6‐Trip2] (6). Carbonylation of 4 induces a chloride migration from rhenium to the germanium atom to afford the chlorogermylidene complex mer‐[Cl(CO)(PMe3)3ReGe(Cl)C6H3‐2,6‐Trip2] (7). Similarly, MeNC converts complex 4 into the methylisocyanide analogue mer‐[Cl(MeNC)(PMe3)3ReGe(Cl)C6H3‐2,6‐Trip2] (8). Chloride abstraction from 4 by NaBPh4 in the presence of PMe3 gives the cationic germylidyne complex trans‐[Cl(PMe3)4ReGeC6H3‐2,6‐Trip2]BPh4 (9). Heating complex 4 with cis‐[Mo(PMe3)4(N2)2] induces a germylidyne ligand transfer from rhenium to molybdenum to afford the germylidyne complex trans‐[Cl(PMe3)4MoGeC6H3‐2,6‐Trip2] (10). All new compounds were fully characterized and their molecular structures studied by X‐ray crystallography, which led to the first experimentally determined ReGe triple‐ and double‐bond lengths.
A Conductive Polypyrrole‐Coated, Sulfur–Carbon Nanotube Composite for Use in Lithium–Sulfur Batteries
Authors: Wang Jiazhao , Lu Lin , Shi Dongqi , Tandiono Richard , Wang Zhaoxiang , Konstantinov Konstantin , Liu Huakun 
Published: February 2013

AbstractA novel ternary composite, polypyrrole (PPy)‐coated sulphur–carbon nanotube (S‐CNT), is synthesised by using an in situ, one‐pot method. Firstly, elemental sulfur is loaded into the CNT network by a solution‐based processing technique. Then conducting PPy is coated on the surface of the S‐CNT composite to form the S‐CNT‐PPy ternary composite by carrying out polymerization of the pyrrole monomer in situ. The ternary composite is tested as a cathode for lithium–sulfur batteries. The results show that PPy coating improves significantly the performance of the binary composites (S‐CNT and S‐PPy). The conducting PPy is believed to serve multiple functions in the composite: as a conducting additive, an active material, and an adsorbent and container to confine the polysulfides and prevent them from dissolving into the electrolyte. As a result, PPy coating on the S‐CNT composite enhances its conductivity, capacity and cycling stability. The capacity of S‐CNT‐PPy is about 600 mAh g−1 after 40 cycles, which is much higher than for the S‐CNT composite (430 mAh g−1)
Dioximate‐ and Bis(salicylaldiminate)‐Bridged Titanium and Zirconium Alkoxides: Structure Elucidation by Mass Spectrometry
Authors: Maurer Christian , Pittenauer Ernst , Puchberger Michael , Allmaier Günter , Schubert Ulrich 
Published: February 2013

AbstractThe treatment of titanium alkoxides with 1,5‐pentanedioxime or 2,5‐hexanedioxime resulted in the formation of complexes [{TiL(OR)2}2] in which the dioximate ligands (L) bridge a dimeric Ti2(μ2‐OR)2 unit. The structures of the complexes were determined by single‐crystal structure analysis, ESI mass spectrometry, and 1D and 2D solution NMR spectroscopy. In contrast, the treatment of titanium alkoxides with dioximes bearing cyclic linkers, such as cyclohexyl or aryl groups, resulted in insoluble polymeric compounds. The treatment of various bis(salicylaldiminates) with titanium and zirconium alkoxides resulted in compounds with the same composition [{TiL(OR)2}2], in which, however, two monomeric Ti(OR)2 units are bridged by the ligands L. The two structural possibilities can be distinguished by low‐energy collision‐induced dissociation owing to their different fragmentation patterns.
Antismoking norm and smokers' antismoking attitudes: The interplay between personal and group‐based self‐esteem
Authors: Falomir‐Pichastor Juan M. , Mugny Gabriel , Berent Jacques , Pereira Andrea , Krasteva Diana 
Published: February 2013

AbstractScientific discoveries about the dangers of smoking and antismoking actions carried out in Western countries over recent decades have progressively helped create an antismoking social norm. Nevertheless, many smokers still refuse to quit. We conducted two studies to investigate smokers' resistance to this norm as a function of their personal self‐esteem (PSE) and group‐based self‐esteem (GBSE). An initial correlational study assessed smokers' perception of the antismoking social norm, their PSE, and their antismoking attitudes. Smokers with low PSE had lower antismoking attitudes than those with high PSE when the antismoking norm was strong. The second study assessed GBSE (i.e., smokers' satisfaction as smokers) and manipulated both the strength of the antismoking norm and PSE (i.e., focus on personal weaknesses or strengths). Smokers with low PSE displayed the lowest antismoking attitudes when the antismoking norm was strong and their GBSE was high. These results show that the antismoking norm can produce paradoxical effects and suggest that the way individuals cope with stigmatization is affected by the interplay between PSE and GBSE. Copyright © 2013 John Wiley & Sons, Ltd.
Voltammetric Response on a Puller‐Made Nanometer‐Sized Electrode
Authors: Li Fei , Hunt Benjamin , Sun Peng 
Published: February 2013

AbstractThe method of fabrication of electrodes by using a laser‐puller is a commonly used method to produce small electrodes. Simulation shows that the taper‐shaped insulation layer of a puller‐made electrode has an obvious effect on its voltammetric response, especially when the electrode has a small RG (the ratio of the insulating sheath radius to the electrode radius). The effect of low‐pass filtering on the voltammetric response of a very small puller‐made electrode has also been studied.
Effects of permeability fields on fluid, heat, and oxygen isotope transport in extensional detachment systems
Authors: Gottardi Raphaël , Kao Po‐Hao , Saar Martin O. , Teyssier Christian 
Published: February 2013

AbstractField studies of Cordilleran metamorphic core complexes indicate that meteoric fluids permeated the upper crust down to the detachment shear zone and interacted with highly deformed and recrystallized (mylonitic) rocks. The presence of fluids in the brittle/ductile transition zone is recorded in the oxygen and hydrogen stable isotope compositions of the mylonites and may play an important role in the thermomechanical evolution of the detachment shear zone. Geochemical data show that fluid flow in the brittle upper crust is primarily controlled by the large‐scale fault‐zone architecture. We conduct continuum‐scale (i.e., large‐scale, partial bounce‐back) lattice‐Boltzman fluid, heat, and oxygen isotope transport simulations of an idealized cross section of a metamorphic core complex. The simulations investigate the effects of crust and fault permeability fields as well as buoyancy‐driven flow on two‐way coupled fluid and heat transfer and resultant exchange of oxygen isotopes between meteoric fluid and rock. Results show that fluid migration to middle to lower crustal levels is fault controlled and depends primarily on the permeability contrast between the fault zone and the crustal rocks. High fault/crust permeability ratios lead to channelized flow in the fault and shear zones, while lower ratios allow leakage of the fluids from the fault into the crust. Buoyancy affects mainly flow patterns (more upward directed) and, to a lesser extent, temperature distributions (disturbance of the geothermal field by ~25°C). Channelized fluid flow in the shear zone leads to strong vertical and horizontal thermal gradients, comparable to field observations. The oxygen isotope results showδ18O depletion concentrated along the fault and shear zones, similar to field data.
Liver stiffness is influenced by a standardized meal in patients with chronic hepatitis C virus at different stages of fibrotic evolution
Authors: Arena Umberto , Platon Monica Lupsor , Stasi Cristina , Moscarella Stefania , Assarat Alì , Bedogni Giorgio , Piazzolla Valeria , Badea Radu , Laffi Giacomo , Marra Fabio , Mangia Alessandra , Pinzani Massimo 
Published: February 2013

Abstract

Transient elastography (TE) is increasingly employed in clinical practice for the noninvasive detection of tissue fibrosis in patients with chronic liver disease (CLD), and particularly chronic hepatitis C virus (HCV)-related hepatitis. The present study was designed to provide a definitive characterization of the “confounding” increase in liver stiffness (LS) following a standardized meal in a consecutive population of 125 patients with chronic HCV infection at different stages of fibrotic evolution. LS values were obtained after overnight fasting and 15, 30, 45, 60, and 120 minutes following the onset of a standardized liquid meal (400 mL, 600 Kcal, 16.7% protein, 53.8% carbohydrates, 29.5% fat). An evident increase in LS values was observed 15 to 45 minutes after the onset of the meal with return to baseline premeal levels within 120 minutes in all patients. The peak postmeal delta increase in LS was progressively more marked with increasing stages of fibrosis (P < 0.001), becoming maximal in patients with cirrhosis. However, the probability of identifying the Metavir stage of fibrosis, the Child-Pugh class, or the presence/absence of esophageal varices with the postmeal delta increase in LS was inferior to that obtained with baseline LS values. Conclusion: The results of the present study provide definitive evidence of the confounding effect of a meal on the accuracy of LS measurements for the prediction of fibrosis stage in patients with chronic HCV hepatitis and suggest that a fasting period of 120 minutes should be observed before the performance of TE. (HEPATOLOGY 2013;)
Influence of local objects on hippocampal representations: Landmark vectors and memory
Authors: Deshmukh Sachin S. , Knierim James J. 
Published: February 2013

AbstractThe hippocampus is thought to represent nonspatial information in the context of spatial information. An animal can derive both spatial information as well as nonspatial information from the objects (landmarks) it encounters as it moves around in an environment. In this article, correlates of both object‐derived spatial as well as nonspatial information in the hippocampus of rats foraging in the presence of objects are demonstrated. A new form of CA1 place cells, called landmark‐vector cells, that encode spatial locations as a vector relationship to local landmarks is described. Such landmark vector relationships can be dynamically encoded. Of the 26 CA1 neurons that developed new fields in the course of a day's recording sessions, in eight cases, the new fields were located at a similar distance and direction from a landmark as the initial field was located relative to a different landmark. In addition, object‐location memory in the hippocampus is also described. When objects were removed from an environment or moved to new locations, a small number of neurons in CA1 and CA3 increased firing at the locations where the objects used to be. In some neurons, this increase occurred only in one location, indicating object + place conjunctive memory; in other neurons, the increase in firing was seen at multiple locations where an object used to be. Taken together, these results demonstrate that the spatially restricted firing of hippocampal neurons encode multiple types of information regarding the relationship between an animal's location and the location of objects in its environment. © 2013 Wiley Periodicals, Inc.
Role of Cytochrome P4502B6 in Methadone Metabolism and Clearance
Authors: Kharasch Evan D. , Stubbert Kristi 
Published: February 2013

AbstractMethadone N‐demethylation in vitro is catalyzed by hepatic cytochrome P4502B6 (CYP2B6) and CYP3A4, but clinical disposition is often attributed to CYP3A4. This investigation tested the hypothesis that CYP2B6 is a prominent CYP isoform responsible for clinical methadone N‐demethylation and clearance, using the in vivo mechanism‐based CYP2B6 inhibitor ticlopidine, given orally for 4 days. A preliminary clinical investigation with the CYP3A4/5 substrate probe alfentanil established that ticlopidine did not inhibit intestinal or hepatic CYP3A4/5. Subjects received intravenous plus oral (deuterium‐labeled) racemic methadone before and after ticlopidine. Ticlopidine significantly and stereoselectively (S > R) inhibited methadone N‐demethylation, decreasing plasma metabolite/methadone area under the curve ratios and metabolite formation clearances. Ticlopidine also significantly increased the dose‐adjusted plasma area under the curve for R‐ and S‐methadone by 20% and 60%, respectively, after both intravenous and oral dosing. CYP2B6 inhibition reduces methadone N‐demethylation and clearance, and alters methadone concentrations, demonstrating an important role for CYP2B6 in clinical methadone disposition.
Detection of multiple viral and bacterial infections in acute exacerbation of chronic obstructive pulmonary disease: A pilot prospective study
Authors: Perotin Jeanne‐Marie , Dury Sandra , Renois Fanny , Deslee Gaëtan , Wolak Aurore , Duval Véronique , De Champs Christophe , Lebargy François , Andreoletti Laurent 
Published: February 2013

AbstractFew studies have evaluated the contribution of multiple virus and bacterial infections in acute exacerbation of chronic obstructive pulmonary disease. This study estimated the burden of multiple viral and bacterial respiratory infections in moderate to very severe chronic obstructive pulmonary disease patients that were prospectively followed‐up during a 12‐month pilot study. Clinical data were collected monthly and sputum was collected at the time of each acute exacerbation event. Classical culture techniques for bacteria and multiplex polymerase chain reaction (PCR) and microarray detection assays were performed to identify viral and atypical bacterial pathogens in the sputum. Overall, 51 patients were included and 45 acute exacerbation events were investigated clinically and microbiologically. Among the 45 acute exacerbation events, 44% had evidence of viral infection involving human rhinovirus (HRV) and metapneumovirus (hMPV) in 20% and 18%, respectively. Intracellular bacteria were not found in sputum by PCR. Common bacterial pathogens were identified in 42% of acute exacerbation patients, most frequently Branhamella catarrhalis, Streptococcus pneumoniae and Haemophilus influenzae. Viral or virus and bacteria co‐infections were detected in 27% of acute exacerbation events (n = 12) with HRV and hMPV involved in 92% of cases. Patients with co‐infections did not present greater clinical severity scores at exacerbation and more recurrence of acute exacerbation events at 3 and 6 months than those with single infections (P > 0.4). These results suggest that HRV and hMPV may be contributors or cofactors of AECOPD. These findings indicate that viral or virus and bacterial co‐infections do not impact significantly on the clinical severity of acute exacerbation of chronic obstructive pulmonary disease and recurrence at 3 and 6 months. J. Med. Virol. 85:866–873, 2013. © 2013 Wiley Periodicals, Inc.