bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biodegradable poly(ester‐ether)s: ring‐opening polymerization of D,L‐3‐methyl‐1,4‐dioxan‐2‐one using various initiator systems
Authors: Lochee Yemanlall , Jhurry Dhanjay , Bhaw‐Luximon Archana , Kalangos Afksendiyos 
Published: June 2010

AbstractThe synthesis and detailed characterization of racemic 3‐methyl‐1,4‐dioxan‐2‐one (3‐MeDX) are reported. The bulk ring‐opening polymerization of 3‐MeDX, to yield a poly(ester‐ether) meant for biomedical applications, in the presence of various initiators such as tin(II) octanoate, tin(II) octanoate/n‐butyl alcohol, aluminium tris‐isopropoxide and an aluminium Schiff base complex (HAPENAlOiPr) under varying experimental conditions is here detailed for the first time. Polymerization kinetics were investigated and compared with those of 1,4‐dioxan‐2‐one. The studies reveal that the rate of polymerization of 3‐MeDX is less than that of 1,4‐dioxan‐2‐one. Experimental conditions to achieve relatively high molar masses have been established. Thermodynamic parameters such as enthalpy and entropy of 3‐MeDX polymerization as well as ceiling temperature have been determined. Poly(D,L‐3‐MeDX) is found to possess a much lower ceiling temperature than poly(1,4‐dioxan‐2‐one). Poly(D,L‐3‐MeDX) was characterized using NMR spectroscopy, matrix‐assisted laser desorption ionization mass spectrometry, size exclusion chromatography and differential scanning calorimetry. This polymer is an amorphous material with a glass transition temperature of about −20 °C. Copyright © 2010 Society of Chemical Industry
Nitrosation of dialkylhydroxylamines, and computational and NMR investigations of the interconversion of conformational isomers of N‐nitroso‐dimethylhydroxylamine
Authors: Crugeiras Juan , Maskill Howard , MacFarlane William , Menneer Iain D. , Rios Ana , Rios Miguel A. 
Published: June 2010

AbstractThe effect of acidity upon the rate of nitrosation of N‐benzyl,O‐methylhydroxylamine (3) in 1:1 (v/v) H2O/MeOH at 25 °C has been investigated. The pseudo‐first‐order rate constant (kobs) for loss of HNO2 as the limiting reagent decreases as [H3O+] increases. This is compatible with two parallel reaction channels (Scheme 2). One involves the direct reaction of the free hydroxylamine with HNO2 (k1 = 1.4 × 102 dm3 mol−1 s−1, 25 °C) and the other involves the reaction of the free hydroxylamine with NO+ (k2 = 5.9 × 109 dm3 mol−1 s−1). In contrast, there is only a very slight increase in kobs with increasing [H3O+] for nitrosation of N,O‐dimethylhydroxylamine (4) in dilute aqueous solution at 25 °C to give N‐nitroso‐dimethylhydroxylamine, 5. This also fits a two‐channel mechanism (Scheme 3). Again, one involves the nitrosation of the free base by NO+ (k2 = 8 × 109 dm3 mol−1 s−1, 25 °C) but the other channel now involves catalysis by chloride (k3 = 1.3 × 108 dm3 mol−1 s−1). Arising from these results, we propose an estimate of pKa ∼ −5 for protonated nitrous acid, (O = NOH), which is appreciably different from the literature value of +1.7.The interconversion of cis and trans conformational isomers of 5 has been investigated by temperature‐dependent NMR spectroscopy in CDCl3, methanol‐d4, toluene‐d8 and dimethyl sulfoxide‐d6. Enthalpies and entropies of reaction and of activation have been determined and compared with computational values obtained at the B3LYP/6‐31G* level of theory. The cis form is slightly more stable at normal temperatures and no solvent effects upon the thermodynamics or kinetics of the conformational equilibrium were predicted computationally or detected experimentally. In addition, key geometric parameters and dipole moments have been calculated for the cis and trans forms, and for the lowest energy transition structure for their interconversion, in the gas phase and in chloroform. These results indicate electronic delocalisation in the ground states of 5 which is lost in the transition structure for their interconversion. Copyright © 2010 John Wiley & Sons, Ltd.
The role of Buergi‐Dunitz interactions in the structural stability of proteins
Authors: Fufezan Christian 
Published: June 2010

AbstractNonbonding interactions are essential for protein stability and maintenance of secondary structure. Their strength, however, is not always experimentally accessible. One example is the stability of collagen, which is in part due to Buergi‐Duntiz or n → π* interactions between the peptide backbone atoms [DeRider et al., J Am Chem Soc 2002;124:2497–2505]. Here, the overall frequency of n → π* interactions in proteins has been investigated. The analysis of a nonredundant set of protein structures showed that 45.1% of all residues have a backbone conformation favoring a n → π* nucleophilic attack between the carbonyl oxygen of residue i − 1 and the carbonyl carbon of residue i. These residues form a substantial fraction of right‐ and left‐handed α helices, 310 helices, π helices, and hydrogen bonded turns. Simulations showed that there are only four regions in Ramachandran space that favor backbone ni−1 → π interactions and these Φ, Ψ combinations are observed with high frequencies in the nonredundant protein structure set. Analysis of carbonyl carbon displacements out of the peptide plane in ultra‐high resolution protein structures indeed reveals the presence of the Buergi‐Dunitz trajectory. The Buergi‐Dunitz interaction thus appears to play an important and general role in protein structure stability that has not hitherto been fully explored. Proteins 2010. © 2010 Wiley‐Liss, Inc.
Dry molten globule intermediates and the mechanism of protein unfolding
Authors: Baldwin Robert L. , Frieden Carl , Rose George D. 
Published: June 2010

AbstractNew experimental results show that either gain or loss of close packing can be observed as a discrete step in protein folding or unfolding reactions. This finding poses a significant challenge to the conventional two‐state model of protein folding. Results of interest involve dry molten globule (DMG) intermediates, an expanded form of the protein that lacks appreciable solvent. When an unfolding protein expands to the DMG state, side chains unlock and gain conformational entropy, while liquid‐like van der Waals interactions persist. Four unrelated proteins are now known to form DMGs as the first step of unfolding, suggesting that such an intermediate may well be commonplace in both folding and unfolding. Data from the literature show that peptide amide protons are protected in the DMG, indicating that backbone structure is intact despite loss of side‐chain close packing. Other complementary evidence shows that secondary structure formation provides a major source of compaction during folding. In our model, the major free‐energy barrier separating unfolded from native states usually occurs during the transition between the unfolded state and the DMG. The absence of close packing at this barrier provides an explanation for why ϕ‐values, derived from a Brønsted‐Leffler plot, depend primarily on structure at the mutational site and not on specific side‐chain interactions. The conventional two‐state folding model breaks down when there are DMG intermediates, a realization that has major implications for future experimental work on the mechanism of protein folding. Proteins 2010. © 2010 Wiley‐Liss, Inc.
Binding of nonsteroidal anti‐inflammatory drugs to Aβ fibril
Authors: Takeda Takako , Chang Wenling E. , Raman E. Prabhu , Klimov Dmitri K. 
Published: June 2010

AbstractNonsteroidal anti‐inflammatory drugs are considered as potential therapeutic agents against Alzheimer's disease. Using replica exchange molecular dynamics and atomistic implicit solvent model, we studied the mechanisms of binding of naproxen and ibuprofen to the Aβ fibril derived from solid‐state NMR measurements. The binding temperature of naproxen is found to be almost 40 K higher than of ibuprofen implicating higher binding affinity of naproxen. The key factor, which enhances naproxen binding, is strong interactions between ligands bound to the surface of the fibril. The naphthalene ring in naproxen appears to provide a dominant contribution to ligand‐ligand interactions. In contrast, ligand‐fibril interactions cannot explain differences in the binding affinities of naproxen and ibuprofen. The concave fibril edge with the groove is identified as the primary binding location for both ligands. We show that confinement of the ligands to the groove facilitates ligand‐ligand interactions that lowers the energy of the ligands bound to the concave edge compared with those bound to the convex edge. Our simulations appear to provide microscopic rationale for the differing binding affinities of naproxen and ibuprofen observed experimentally. Proteins 2010. © 2010 Wiley‐Liss, Inc.
AlGaN/GaN/AlGaN double heterojunction HEMTs on n‐type SiC substrates
Authors: Bahat‐Treidel Eldad , Hilt Oliver , Brunner Frank , Würfl Joachim , Tränkle Günther 
Published: June 2010

AbstractIn this paper, we present a systematic study of AlGaN/GaN/AlGaN double heterojunction high‐electron‐mobility‐transistor devices on n‐type SiC substrate and the dependence of the GaN channel layer thickness. A device breakdown voltage enhancement was achieved by increasing the electron confinement in the transistor channel using an AlGaN back barrier‐layer structure. An optimized electron confinement results in a scaling of breakdown voltage with device geometry, low on‐state resistance and a significantly reduced sub‐threshold drain leakage current. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Static skin effect in the quantum Hall regime for high‐mobility electrons on a cylindrical surface
Authors: Friedland K.‐J. , Hey R. , Riedel A. , Maude D. K. 
Published: June 2010

AbstractWe investigate the quantum Hall effect in a highmobility, two‐dimensional electron gas on a cylindrical surface. Due to the varying filling factor along the current path, the electron transport is characterized by sequential transmission along incompressible stripes and compressible bulk regions. For the compressible regions, we observe an exponential decay of the longitudinal resistances by rotating the sample around the cylinder axis. We adopt the model of the so‐called static skin effect for the conductance in the compressible bulk regions and demonstrate that this behavior can be ascribed to probing the skin channel width by moving the Hall bar terminals along the gradient of the magnetic field along the cylinder periphery. We determine L as the characteristic length for the exponential decay of the skin channel width by moving away from the position where the magnetic field is perpendicular to the surface. The values of L are in the sub‐micrometer range, similarly as for low magnetic fields. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Developing winter flow rating relationships using slope‐area hydraulics
Authors: Beltaos Spyros 
Published: June 2010

AbstractDespite recent advances in instrumentation and modelling methods, accurate determination of river discharge under an ice cover still requires direct measurement. Published flows at hydrometric gauging stations are based on interpolation between a few measurements that are carried out during each winter. The feasibility of using slope‐area hydraulics to develop discharge‐stage rating relationships is explored at two stations, Peace River at Peace Point and Mackenzie River at Arctic Red River. Records at both gauges contain key information for understanding local ice jamming processes, which are known to control the long‐term maintenance of the aquatic ecosystems in the respective deltas. For each site, the variations of reach‐average hydraulic parameters with stage are first determined from several nearby cross‐sections. This information is then used to calculate hydraulic resistance characteristics during the ice season based on archived discharge measurement data, which also include ice cover thickness. The Peace River flow measurements indicate a well‐defined seasonal variation in hydraulic resistance, with the exception of years with large slush deposits under the solid‐ice sheet. Slush effects are negligible at the Mackenzie River gauge site, but the stage‐flow relationship is complicated by a variable water surface slope, a result of downstream control by the Beaufort Sea. This feature is most pronounced during the pre‐breakup period when flows are rising sharply and renders flow estimation uncertain. A nearby water‐level gauge would help quantify the slope and increase confidence in winter flow estimates. Copyright © 2010 in the right of Canada.
The effects of network's structural holes: polycentric institutions, product portfolio, and new venture growth in China and Russia
Authors: Batjargal Bat 
Published: June 2010

AbstractThis study examines the effect of network's structural holes (i.e., the absence of a link between two contacts who are both linked to an actor) on product development and profit growth of software ventures in two different institutional contexts—China and Russia. Using interview data of 159 software entrepreneurs in Beijing and Moscow, the study found that the effect of structural holes is contingent upon country institutional context and venture development stage. Specifically, structural holes have a positive main effect on product portfolio, but a negative main effect on profit growth in the second revenue year (early stage of venture development). Structural holes are more useful in the Russian institutional context compared to the Chinese institutional context due to the polycentricity of institutions. The research implications of the findings are discussed. Copyright © 2010 Strategic Management Society.
Laparoscopic hepatic left lateral sectionectomy using the LaparoEndoscopic Single Site approach: evolution of minimally invasive liver surgery
Authors: Aldrighetti Luca , Guzzetti Eleonora , Ferla Gianfranco 
Published: June 2010

AbstractBackground/purposeLaparoscopic liver surgery is attracting wider interest for the treatment of benign and malignant neoplasms. Laparoscopy is a safe and feasible approach for lesions located in the left liver lobe. As the emphasis on minimizing the technique continues, single‐port access surgery is quickly evolving. We present our initial experience of single‐port laparoscopic liver surgery using a LaparoEndoscopic Single Site (LESS) approach with the TriPort System (ASC; Advanced Surgical Concepts, Bray, Ireland) to perform a left lateral sectionectomy via a single supraumbilical incision.MethodsThe abdomen was approached through a 15 mm supraumbilical incision and a single‐port access device was used to perform a left lateral sectionectomy in a patient with a single colorectal metastasis.ResultsThe total operative time was 145 min, with 50 ml blood loss. Hospital stay was 4 days.ConclusionsSingle‐port laparoscopic left lateral sectionectomy is a feasible procedure, when performed by experienced laparoscopic surgeons. It has to be determined whether or not this approach would offer benefit to patients, except in terms of cosmesis, compared to standard laparoscopic liver resection.
Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)
Authors: KORONEOS A. , POLI G. , CVETKOVIĆ V. , CHRISTOFIDES G. , KRSTIĆ D. , PÉCSKAY Z. 
Published: June 2010

AbstractThe Mt Cer Pluton, Serbia, is a complex laccolith-like intrusion (~ 60 km2), situated along the junction between the southern Pannonian Basin and northern Dinarides. It intrudes Palaeozoic metamorphic rocks causing weak to strong thermal effects. Based on modal and chemical compositions, four rock-types can be distinguished: (1) metaluminous I-type quartz monzonite/quartz monzodiorite (QMZD); (2) peraluminous S-type two-mica granite (TMG), which intrudes QMZD; (3) Stražanica granodiorite/quartz monzonite (GDS); and (4) isolated mafic enclaves (ME), found only in QMZD.40K–39Ar dating and geological constraints indicate that the main quartz monzonite/quartz monzodiorite body of Mt Cer was emplaced not later than 21 Ma, whereas the emplacement ages of the Stražanica granodiorite/quartz monzonite and two-mica granites are estimated at around 18 and 16 Ma, respectively. The Mt Cer pluton is similar to the Mt Bukulja pluton, some 80 km southwestwards. Genesis of QMZD cannot be interpreted by fractional crystallization coupled with mixing or assimilation. It is best explained by a convection–diffusion process between mantle-derived minette/leucominette magmas and GDS-like magmas followed by two end-member magma mixing. The composition of GDS rocks suggests that GDS-like magmas could have formed by melting of lower crustal lithologies similar to amphibolite/metabasalts. The geochemistry of TMG is reproduced by an Assimilation/Fractional Crystallization model with a ratio of rate of assimilation to rate of fractional crystallization of 0.4, using the compositions of the least evolved TMG of the Bukulja pluton and adjacent metamorphic rocks as proxies for the parental magma and contaminant, respectively. The origin and evolution of the Mt Cer and adjacent Mt Bukulja plutons provide new constraints on the Tertiary geodynamics of the northern Dinarides–southern Pannonian region. The quartz monzonite/quartz monzodiorite is interpreted as a result of the Oligocene post-collisional Dinaride orogen-collapse, which included a limited lithosphere delamination, small-scale mantle upwelling, and melting of the lower crust. By contrast, the two-mica granite magmas formed through melting in shallower crustal levels during the extensional collapse in the Pannonian area.
Mitochondrial neurogastrointestinal encephalomyopathy associated with progressive hearing loss
Authors: Hiraki N , Udaka T , Yamamoto H , Kadokawa Y , Ohkubo J , Suzuki H 
Published: June 2010

AbstractObjective:We report a rare case of mitochondrial neurogastrointestinal encephalomyopathy with hearing loss.Case report:A 46-year-old woman presented with a three-year history of progressive, bilateral hearing loss and tinnitus. She had been suffering from unexplained abdominal pain and diarrhoea for 20 years. When first seen, her otoscopic findings were normal, and pure tone audiometry showed mild and moderate hearing loss in her right and left ears, respectively. She also had: bilateral ophthalmoparesis, neck and limb muscle weakness, and hypoactive deep tendon reflexes on neurological examination; diffuse leukoencephalopathy on magnetic resonance imaging of the brain; and markedly reduced leukocyte thymidine phosphorylase activity. On the basis of these findings, the patient was diagnosed with mitochondrial neurogastrointestinal encephalomyopathy.Conclusion:Mitochondrial neurogastrointestinal encephalomyopathy is an autosomal recessive disease caused by mutation of the thymidine phosphorylase gene, and is characterised by ophthalmoparesis, peripheral neuropathy, leukoencephalopathy, gastrointestinal symptoms and abnormal mitochondria in muscle cells. Current advances in genetic research may reveal a higher prevalence of mitochondrial disorders than had previously been thought. Otolaryngologists should be aware of mitochondrial neurogastrointestinal encephalomyopathy and other rare genetic disorders when managing patients with progressive hearing loss.
The WEIRD are even weirder than you think: Diversifying contexts is as important as diversifying samples
Authors: Ceci Stephen J. , Kahan Dan M. , Braman Donald 
Published: June 2010

AbstractWe argue that Henrich et al. do not go far enough in their critique: Sample diversification, while important, will not lead to the detection of generalizable principles. For that it will be necessary to broaden the range of contexts in which data are gathered. We demonstrate the power of contexts to alter results even in the presence of sample diversification.
WEIRD walking: Cross-cultural research on motor development
Authors: Karasik Lana B. , Adolph Karen E. , Tamis-LeMonda Catherine S. , Bornstein Marc H. 
Published: June 2010

AbstractMotor development – traditionally studied in WEIRD populations – falls victim to assumptions of universality similar to other domains described by Henrich et al. However, cross-cultural research illustrates the extraordinary diversity that is normal in motor skill acquisition. Indeed, motor development provides an important domain for evaluating cultural challenges to a general behavioral science.
Responsible behavioral science generalizations and applications require much more than non-WEIRD samples
Authors: Konečni Vladimir J. 
Published: June 2010

AbstractThere are many methodological considerations – some intricately associated with the use of WEIRD samples – that adversely affect external validity as much as, or even more than, unrepresentative sampling does. Among suspect applications, especially worrisome is the incorporation of WEIRD-based findings regarding moral reasoning and retribution into normative expectations, such as might be held by international criminal tribunals in “cognitively distant” war-torn areas.
ODD (observation- and description-deprived) psychological research
Authors: Rai Tage S. , Fiske Alan 
Published: June 2010

AbstractMost psychological research consists of experiments that put people in artificial situations that elicit unnatural behavior whose ecological validity is unknown. Without knowing the psychocultural meaning of experimental situations, we cannot interpret the responses of WEIRD people, let alone people in other cultures. Psychology, like other sciences, needs to be solidly rooted in naturalistic observation and description of people around the world. Theory should be inductively developed and tested against real-world behavior.
A topological embedding of the lexicon for semantic distance computation
Authors: DAVIS N. , GIRAUD-CARRIER C. , JENSEN D. 
Published: June 2010

AbstractWe show how a quantitative context may be established for what is essentially qualitative in nature by topologically embedding a lexicon (here, WordNet) in a complete metric space. This novel transformation establishes a natural connection between the order relation in the lexicon (e.g., hyponymy) and the notion of distance in the metric space, giving rise to effective word-level and document-level lexical semantic distance measures. We provide a formal account of the topological transformation and demonstrate the value of our metrics on several experiments involving information retrieval and document clustering tasks.
WordICA—emergence of linguistic representations for words by independent component analysis
Authors: HONKELA TIMO , HYVÄRINEN AAPO , VÄYRYNEN JAAKKO J. 
Published: June 2010

AbstractWe explore the use of independent component analysis (ICA) for the automatic extraction of linguistic roles or features of words. The extraction is based on the unsupervised analysis of text corpora. We contrast ICA with singular value decomposition (SVD), widely used in statistical text analysis, in general, and specifically in latent semantic analysis (LSA). However, the representations found using the SVD analysis cannot easily be interpreted by humans. In contrast, ICA applied on word context data gives distinct features which reflect linguistic categories. In this paper, we provide justification for our approach called WordICA, present the WordICA method in detail, compare the obtained results with traditional linguistic categories and with the results achieved using an SVD-based method, and discuss the use of the method in practical natural language engineering solutions such as machine translation systems. As the WordICA method is based on unsupervised learning and thus provides a general means for efficient knowledge acquisition, we foresee that the approach has a clear potential for practical applications.