bluuebunny/crossref_metadata_2025_split huggingface dataset:
Probing the dynamics of water in chitosan polymer films by dielectric spectroscopy
Authors: Murugaraj P. , Mainwaring D. E. , Tonkin D. C. , Al Kobaisi M. 
Published: November 2010

AbstractChitosan biopolymers are increasingly being used in advanced biomedical applications, where aqueous interactions profoundly influence their physical properties and also their in vivo biomolecular and cellular activity. Here, hydration of chitosan films is studied by dielectric spectroscopy in a conventional constraining plate configuration and compared with free standing films. Film hydration proceeds by an initial water uptake followed by a spontaneous dehydration (deswelling) even in saturated atmospheres. At water contents above a critical value, ∼ 9.5 wt % a dielectric loss resonance peak (βwet) arises from relaxation of evolving chitosan–water complexes, below this value insufficient interchain space for oscillation of these complexes prevents βwet appearing. The βwet frequency was related to water content by a power law with the frequency changing by ∼ 3 orders of magnitude. Importantly the scaling exponents (slopes) differed significantly for unconstrained (free standing) and volume constrained films indicating the effect of internal stresses in constrained films. Both dielectric and conductivity behavior were influenced by internal constraining stresses affecting both oscillatory motion and charge mobility. In biomedical devices, biopolymers may be free standing, surface adhered, or enclosed structures imposing different internal stresses on polymer chains and the mobility of their segments. Dielectric spectroscopy can examine these influences on dielectric and electrical characteristics, which play a critical role in biomolecular interactions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
On the interesting optical properties of highly transparent, thermally stable, spin‐coated polystyrene/zinc oxide nanocomposite films
Authors: Jeeju P. P. , Jayalekshmi S. 
Published: November 2010

AbstractIn the present work, polystyrene/zinc oxide (PS/ZnO) nanocomposite films are prepared by simple mixing followed by film deposition, using spin‐coating technique. Although there are a few reports on the UV‐shielding properties of PS/ZnO nanocomposite films, these reports deal with rather thick films obtained by solution casting. Spin coating is a more advantageous technique where one can control the film thickness by suitably adjusting the viscosity of the solution and the spinning speed and get homogeneous films with thickness around a few hundreds of nanometers. These aspects provide the motivation for the present work where emphasis is given to investigating the optical properties of PS/ZnO nanocomposite films obtained by spin coating and analyzing the effects of each component of the composite (PS/ZnO) on the properties of the other. The nanocomposite films are found to be highly transparent throughout the visible region and the thermal stability is better compared with PS. The optical absorption of the composite films in the UV region is quite high, and this aspect highlights the prospects of applications of these films in UV shielding. The PS matrix brings about considerable surface modification of ZnO nanoparticles, resulting in the reduction of defect states within ZnO and facilitating sharp, near band edge photoluminescence emission. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Layer‐structured poly(vinyl alcohol)/graphene oxide nanocomposites with improved thermal and mechanical properties
Authors: Yang Xiaoming , Shang Songmin , Li Liang 
Published: November 2010

AbstractLayer‐structured poly(vinyl alcohol)/graphene oxide nanocomposites in the form of films are prepared by simple solution processing. The structure and properties of these nanocomposites are studied using X‐ray diffractions, scanning electron microscopy, Fourier‐transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The results indicate that graphene oxide is dispersed on a molecular scale and aligned in the poly(vinyl alcohol) matrix, and there exists strong interfacial interactions between both components, which are responsible for the significant improvement in the thermal and mechanical properties of the nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Macroalgae in the intertidal zone of Cantabrian Sea: richness, cover of characteristic and opportunistic species
Authors: García Pilar , Pesquera Luis Miguel Gutiérrez , Redondo Eva Zapico 
Published: November 2010

Abstract
Macroalgae are one of the biological parameters considered in the European Water Framework Directive (WFD) for establishing the ecological status of coastal water bodies. In order to test the metric used to assess this element in the Cantabrian coast, the quality of rocky bottoms (CFR) index was applied to 164 transects at 28 sites on the coast of Asturias (northern Spain) in the summers of 2007 and 2008.
At each sampling point, three variables were measured: species richness, cover of characteristic and opportunistic macroalgae, and in 2008 the percentage of the area occupied by each characteristic species was also estimated.
Application of the Shapiro–Wilk test to the variables ‘cover of characteristic macroalgae’ and ‘cover of opportunistic algae’ revealed that the data were not normally distributed (P<0.001). A Kolmogorov–Smirnov test revealed: (a) significant differences (P<0.01) between the exposed and semi‐exposed sites, for the three variables studied; (b) significant differences in cover, for six species depending on the type of exposure; and (c) significant differences (P<0.01) in opportunistic macroalgal cover in relation to the two subtypes of water bodies in the study area. However, no significant differences were observed for overall macroalgal cover or species richness.
According to the results obtained, new reference conditions and class boundaries are proposed for the implementation of the CFR index in Asturian coastal waters. The ranges proposed for the CFR index in the present study provide better discrimination for evaluating the ecological status of the studied area.
The results of SIMPER and MDS analyses reinforced the conclusion that the type of exposure and the degree of human impact are the factors that best explain the degree of similarity between the sites sampled. Copyright © 2010 John Wiley & Sons, Ltd.
Scanning Tunneling Microscopy Investigation of Copper Phthalocyanine and Truxenone Derivative Binary Superstructures on Graphite
Authors: Liu Jia , Wang Dong , Wang Jie‐Yu , Pei Jian , Wan Li‐Jun 
Published: November 2010

AbstractThe binary self‐assembly of copper phthalocyanine (CuPc) and 2,3,7,8,12,13‐hexahexyloxy‐truxenone (TrO23) at the solid/liquid interface of highly oriented pyrolytic graphite (HOPG) was investigated by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Pseduohexagonal and linear patterned superstructures of CuPc are obtained by co‐adsorbing with TrO23. High‐resolution STM images reveal the structural details of the arrangement of TrO23 and CuPc in the binary assembly structures. The molecular ratio between CuPc and TrO23 in the adlayer can be modulated by the CuPc concentration in liquid phase. The electronic properties of CuPc and TrO23 in the co‐adsorbed self‐assembly are investigated by STS. The results presented here are helpful to the design and fabrication of multi‐component functional molecular nanostructures.
Evaluation of procedure-based assessment for assessing trainees' skills in the operating theatre
Authors: Marriott J , Purdie H , Crossley J , Beard J D 
Published: November 2010

Abstract

Background
Procedure-based assessment (PBA) is used within most UK surgical training programmes for assessing trainees' procedural skills in the operating theatre. All postgraduate assessment methods require evidence to support their implementation. The aims were to evaluate the validity, reliability and acceptability of PBA.

Methods
Eighty-one trainees in six surgical specialties were assessed performing common procedures; 749 PBAs were provided across 348 operations by 57 clinical supervisors and four independent assessors.

Results
Construct validity was demonstrated by correlation of PBA scores with measures of surgical training and experience. Reliability (G exceeding 0·8) of the adjusted total item score and global summary score for a given procedure was achieved using four and three assessor judgements respectively; assessing a mix of procedures required more cases/assessors because performance is procedure specific. The acceptability of PBA for assessment and feedback within surgical training was predominantly positive among clinical supervisors and trainees.

Conclusion
PBA demonstrated good overall validity and acceptability, and exceptionally high reliability. Trainees should be assessed adequately for each given procedure.
Systematic review and meta-analysis of the effects of statin therapy on abdominal aortic aneurysms
Authors: Twine C P , Williams I M 
Published: November 2010

Abstract

Background
The aim was to investigate the effects of statin therapy on abdominal aortic aneurysm (AAA) disease.

Methods
PubMed, the Cochrane Library, Embase and ClinicalTrials.gov were searched for all studies on any clinical effect of statin therapy on AAA. Outcomes were selected based on their inclusion in two or more studies: AAA expansion rate, 30-day mortality, and short- and long-term postoperative mortality. The data were subjected to meta-analysis by outcome.

Results
Twelve cohort studies were selected for inclusion involving 11 933 individuals. Meta-analysis of four studies examining all-cause postoperative mortality showed a significant improvement with statin therapy at 1, 2 and 5 years (odds ratio (OR) at 5 years 0·57, 95 per cent confidence interval (c.i.) 0·42 to 0·79; P &lt; 0·001) with minimal heterogeneity between the four included studies. There was no significant difference in 30-day mortality after AAA treatment in patients on statin therapy (OR 0·22, 0·02 to 2·90; P = 0·25). Sensitivity analysis including four high-quality studies examining AAA expansion rates showed no significant difference with statin therapy: standardized mean difference −0·14 (95 per cent c.i. −0·33 to −0·05) mm/year (P = 0·16).

Conclusion
The claim of a reduction in AAA expansion rate with statin therapy is based on low-quality evidence and was not significant on meta-analysis. However, statin therapy did appear to improve all-cause survival after AAA repair.
Biological Evaluation and Structural Determinants of p38α Mitogen‐Activated‐Protein Kinase and c‐Jun‐N‐Terminal Kinase 3 Inhibition by Flavonoids
Authors: Goettert Márcia , Schattel Verena , Koch Pierre , Merfort Irmgard , Laufer Stefan 
Published: November 2010

AbstractA series of 42 naturally occurring flavonoids and one flavonoid glucuronide were tested for their ability to inhibit p38α mitogen‐activated protein kinase (p38α) and c‐Jun‐N‐terminal kinase 3 (JNK3). Potent inhibitors with IC50values in the low micromolar range were identified. Structure–activity relationships were evaluated and the most promising compounds were docked into the ATP binding site of these kinases. Among the different classes of flavonoids, the flavonol group showed better inhibition of p38α. Of this class, kaempferol‐7,4′‐dimethylether was a potent p38α inhibitor, displaying 13‐fold selectivity for p38α over JNK3. The flavone compounds without a 6‐methoxy group preferentially inhibited JNK3. The flavone glycoside, luteolin‐7‐O‐glycoside, was identified as a potent inhibitor with the greatest selectivity toward JNK3. In contrast, the flavanol compounds displayed similar inhibitory activities toward both kinases.
Histone Tails: Ideal Motifs for Probing Epigenetics through Chemical Biology Approaches
Authors: Voigt Philipp , Reinberg Danny 
Published: November 2010

AbstractPost‐translational modifications (PTMs) on histone proteins have emerged as a central theme in the regulation of gene expression and other chromatin‐associated processes. The discovery that certain protein domains can recognize acetylated and methylated lysine residues of histones has spurred efforts to uncover and characterize histone PTM‐binding proteins. In this task, chromatin biology has strongly benefited from synthetic approaches stemming from chemical biology. Peptide‐based techniques have been instrumental in identifying histone mark‐binding proteins and analyzing their binding specificities. To explore how histone PTMs carry out their function in the context of chromatin, reconstituted systems based on recombinant histones carrying defined modifications are increasingly being used. They constitute promising tools to analyze mechanistic aspects of histone PTMs, including their role in transcription and their transmission in replication. In this review, we present strategies that have been used successfully to investigate the role of histone modifications, concepts that have emerged from their application, and their potential to contribute to current developments in the field.
Catalytic Reaction Mechanism of Mn‐Doped Nanoporous Aluminophosphates for the Aerobic Oxidation of Hydrocarbons
Authors: Gómez‐Hortigüela Luis , Corà Furio , Sankar Gopinathan , Zicovich‐Wilson Claudio M. , Catlow C. Richard A. 
Published: November 2010

AbstractIn this work we apply state‐of‐the‐art electronic‐structure‐based computational methods based on hybrid‐exchange density functional theory to study the mechanism of the aerobic oxidation of hydrocarbons catalysed by Mn‐doped nanoporous aluminophosphates (Mn‐AlPOs). We compare our results with available experimental data. We show that the catalytic efficiency of Mn‐AlPOs in oxidation reactions is intrinsically linked to 1) the Mn redox activity, in particular between 2+ and 3+ oxidation states, and 2) the coordinative insaturation of tetrahedral Mn embedded in AlPO frameworks, which facilitates the reaction by stabilising oxo‐type radicals through the formation of Mn complexes. Our mechanism demonstrates the crucial role of both MnIII and MnII in the reaction mechanism: MnIII sites undergo an initial reaction cycle that leads to the production of the alkyl hydroperoxide intermediate, which can only be transformed into the oxidative products (alcohol, aldehyde and acid) by MnII. A preactivation step is required to yield the reduced MnII sites able to decompose the hydroperoxide intermediates; this step takes place through a transformation of the hydrocarbon into the corresponding peroxo‐derivative, stabilised by forming a complex with MnIII and yielding at the same time reduced MnII sites. Both species enter a subsequent propagation cycle in which MnII catalyses the dissociation of the hydroperoxide that proceeds until the formation of the oxidative products by two parallel pathways, through alkoxy‐ or hydroxy‐radical‐like intermediates, whilst the MnIII–peroxo complex enables further production of the hydroperoxide intermediate.
The Iron‐Related Molecular Toxicity Mechanism of Synthetic Asbestos Nanofibres: A Model Study for High‐Aspect‐Ratio Nanoparticles
Authors: Turci Francesco , Tomatis Maura , Lesci Isidoro G. , Roveri Norberto , Fubini Bice 
Published: November 2010

AbstractAsbestos shares with carbon nanotubes some morphological and physico‐chemical features. An asbestos‐like behaviour has been recently reported by some authors, though the mechanism of toxicity may be very different. To identify at the atomic level the source of toxicity in asbestos, the effect of progressive iron loading on a synthetic iron‐free model nanofibre previously found non‐toxic in cellular tests was studied. A set of five synthetic chrysotile nanofibres [(Mg,Fe)3(Si2O5)(OH)4] has been prepared with Fe ranging from 0 to 1.78 wt %. The relationship between fibre‐induced free‐radical generation and the physico‐chemical characteristics of iron active sites was investigated with spin‐trapping techniques on an aqueous suspension of the fibres and Mössbauer and EPR spectroscopies on the solids, respectively. The fully iron‐free fibre was inert, whereas radical activity arose with even the smallest amount of iron. Surprisingly, such activity decreased upon increasing iron loading. Mössbauer and EPR revealed isolated iron ions in octahedral sites that undergo both axial and rhombic distortion and the occurrence of aggregated iron ions and/or extra‐framework clustering. The isolated ions largely prevailed at the lowest loadings. Upon increasing the loading, the amount of isolated iron was reduced and the aggregation increased. A linear relationship between the formation of carbon‐centred radicals and the amount of rhombic‐distorted isolated iron sites was found. Even the smallest iron contamination imparts radical reactivity, hence toxicity, to any chrysotile outcrop, thereby discouraging the search for non‐toxic chrysotile. The use of model solids that only differ in one property at a time appears to be the most successful approach for a molecular understanding of the physico‐chemical determinants of toxicity. Such findings could also be useful in the design of safer nanofibres.
Indoline‐3‐Carboxylic Acid Derived Organocatalysts for the anti‐Mannich Reaction
Authors: Pietruszka Jörg , Simon Robert Christian 
Published: November 2010

AbstractMannich type reactions of a preformed aldimine with various carbonyl compounds were investigated with a series of functionalised indoline derivatives as catalysts: indoline‐3‐carboxylic acid, the diphenylcarbinol analogue and O‐protected silyl ether analogues. All compounds were readily prepared in enantiopure form by using an enzymatic kinetic resolution as a key step (E≫100). The alcohol and ether catalysts failed to induce complete chirality transfer but did afford the Mannich bases in good yields and high diastereomeric ratios, whereas the acid catalyst gave the products in a highly diastereo‐ and enantioselective manner. The absolute configuration of the products was determined by a syn–anti isomerisation protocol, initiated by the sterically demanding base 1,8‐diazabicyclo[5.4.0]undec‐7‐ene.
Oriented Free‐Standing Ammonium Vanadium Oxide Nanobelt Membranes: Highly Selective Absorbent Materials
Authors: Zou Rujia , Zhang Zhenyu , Yu Li , Tian Qiwei , Wu Jianghong , Sun Yangang , Chen Zhigang , Hu Junqing 
Published: November 2010

AbstractHighly selective, absorbent, free‐standing, paper‐like membranes made of ammonium vanadium oxide (NH4V4O14) nanobelts have been engineered by taking advantage of the nanoscaled self‐assembly of architectures that display a mesh structure with an average periodic pore size of about 5 to 10 nm. The NH4V4O14 nanobelts are synthesized by using a simple hydrothermal process, and exhibit the same orientation and assemble into bundles, each about 40 to 80 nm in width, 3 to 5 nm in thickness, and up to several millimeters in length. Importantly, the as‐obtained NH4V4O14 nanobelt membranes can highly selectively absorb a variety of organic solvents, covering both polar and non‐polar solvents, for example, the absorbent capacity of glycol is 28 times as high as the initial weight of the membrane, and it can even separate organic solvents with similar polarities and absorb solid contaminants in organic solvents. These highly selective, absorbent membrane materials can be an ideal candidate for the separation and removal of pollution in industrial and environmental applications.
Anion Recognition and Cation‐Induced Molecular Motion in a Heteroditopic [2]Rotaxane
Authors: Leontiev Alexandre V. , Jemmett Charlotte A. , Beer Paul D. 
Published: November 2010

AbstractA heteroditopic [2]rotaxane consisting of a calix[4]diquinone–isophthalamide macrocycle and 3,5‐bis‐amide pyridinium axle components with the capability of switching between two positional isomers in response to barium cation recognition is synthesised. The anion binding properties of the rotaxane’s interlocked cavity together with Na+, K+, NH4+ and Ba2+ cation recognition capabilities are elucidated by 1H NMR and UV‐visible spectroscopic titration experiments. Upon binding of Ba2+, molecular displacement of the axle’s positively charged pyridinium group from the rotaxane’s macrocyclic cavity occurs, whereas the monovalent cations Na+, K+ and NH4+ are bound without causing significant co‐conformational change. The barium cation induced shuttling motion can be reversed on addition of tetrabutylammonium sulfate.
Selective Multiple Magnesiations of the Thieno[3,2‐b]thiophene Scaffold
Authors: Kunz Thomas , Knochel Paul 
Published: November 2010

AbstractA full functionalization of all four positions of the thieno[3,2‐b]thiophene scaffold was achieved. Starting from 2,5‐dichlorothieno[3,2‐b]thiophene, magnesiation of the 3‐ and 6‐position using tmpMgCl⋅LiCl furnishes, after trapping with various electrophiles, 3,6‐difunctionalized dichlorothieno[3,2‐b]thiophenes. Subsequent dechlorination and regioselective metalation or regioselective magnesium insertion into the CCl bond provides fully functionalized thieno[3,2‐b]thiophenes. Furthermore, new condensed heterocycles and small oligomers of these compounds with potential applications in material chemistry have been prepared.
Discovering the unknown: Detection of emerging pathogens using a label‐free light‐scattering system
Authors: Rajwa Bartek , Dundar M. Murat , Akova Ferit , Bettasso Amanda , Patsekin Valery , Dan Hirleman E. , Bhunia Arun K. , Robinson J. Paul 
Published: November 2010

AbstractA recently introduced technique for pathogen recognition called BARDOT (BActeria Rapid Detection using Optical scattering Technology) belongs to the broad class of optical sensors and relies on forward‐scatter phenotyping (FSP). The specificity of FSP derives from the morphological information that bacterial material encodes on a coherent optical wavefront passing through the colony. The system collects elastically scattered light patterns that, given a constant environment, are unique to each bacterial species and serovar. The notable similarity between FSP technology and spectroscopies is their reliance on statistical machine learning to perform recognition. Currently used methods utilize traditional supervised techniques which assume completeness of training libraries. However, this restrictive assumption is known to be false for most experimental conditions, resulting in unsatisfactory levels of accuracy, poor specificity, and consequently limited overall performance for biodetection and classification tasks. The presented work demonstrates application of the BARDOT system to classify bacteria belonging to the Salmonella class in a nonexhaustive framework, that is, without full knowledge about all the possible classes that can be encountered. Our study uses a Bayesian approach to learning with a nonexhaustive training dataset to allow for the automated detection of unknown bacterial classes. © 2010 International Society for Advancement of Cytometry.