bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combined solid‐phase extraction and gas chromatography–mass spectrometry used for determination of chloropropanols in water
Authors: González Paula , Racamonde Inés , Carro Antonia M. , Lorenzo Rosa A. 
Published: August 2011

AbstractA sensitive and rapid derivatization method for the simultaneous determination of 1,3‐dichloro‐2‐propanol (1,3‐DCP) and 3‐chloropropane‐1,2‐diol (3‐MCPD) in water samples has been developed. The aim was to research the optimal conditions of the derivatization process for two selected reagents. A central composite design was used to determine the influence of derivatization time, derivatization temperature and reagent volume. A global desirability function was applied for multi‐response optimization. The analysis was performed by gas chromatography–mass spectrometry. During the optimization of the extraction procedure, four different types of solid‐phase extraction (SPE) columns were tested. It was demonstrated that the Oasis HLB cartridge produced the best recoveries of the target analytes. The pH value and the salinity were investigated using a Doehlert design. The best results for the SPE of both analytes were obtained with 1.5 g of NaCl and pH 6. The proposed method provides high sensitivity, good linearity (R2≥0.999) and repeatability (relative standard deviations % between 2.9 and 3.4%). Limits of detection and quantification were in the range of 1.4–11.2 ng/mL and 4.8–34.5 ng/mL, respectively. Recoveries obtained for water samples were ca. 100% for 1,3‐DCP and 3‐MCPD. The method has been successfully applied to the analysis of different samples including commercially bottled water, an influent and effluent sewage.
Needle microextraction trap for on‐site analysis of airborne volatile compounds at ultra‐trace levels in gaseous samples
Authors: Alonso Monica , Godayol Anna , Antico Enriqueta , Sanchez Juan M. 
Published: August 2011

AbstractDifferent capillary needle trap (NT) configurations are studied and compared to evaluate the suitability of this methodology for screening in the analysis of volatile organic compounds (VOCs) in air samples at ultra‐trace levels. Totally, 22 gauge needles with side holes give the best performance and results, resulting in good sampling flow reproducibility as well as fast and complete NT conditioning and cleaning. Two different types of sorbent are evaluated: a graphitized carbon (Carbopack X) and a polymeric sorbent (Tenax TA). Optimized experimental conditions were desorption in the GC injector at 300°C, no make‐up gas to help the transport of the desorbed compounds to the GC column, 1 min splitless time for injection/desorption, and leaving the NT in the hot injector for about 20 min. Cross‐contamination is avoided when samples containing high VOC levels (above likely breakthrough values) are evaluated. Neither carryover nor contamination is detected for storage times up to 48 h at 4°C. The method developed is applied for the analysis of indoor air, outdoor air and breath samples. The results obtained are equivalent to those obtained with other thermal desorption devices but have the advantage of using small sample volumes, being simpler, more economical and more robust than conventional methodologies used for VOC analysis in air samples.
In Vivo Biocompatibility of Three Potential Intraperitoneal Implants
Authors: Defrère Sylvie , Mestagdt Mélanie , Riva Raphaël , Krier Fabrice , Van Langendonckt Anne , Drion Pierre , Jérôme Christine , Evrard Brigitte , Dehoux Jean‐Paul , Foidart Jean‐Michel , Donnez Jacques 
Published: August 2011

AbstractThe intraperitoneal biocompatibility of PDMS, polyHEMA and pEVA was investigated in rats, rabbits and rhesus monkeys. No inflammation was evidenced by hematological analyses and measurement of inflammatory markers throughout the experiment and by post‐mortem examination of the pelvic cavity. After 3 or 6 months, histological analysis revealed fibrous tissue encapsulating PDMS and PEVA implants in all species and polyHEMA implants in rabbits and monkeys. Calcium deposits were observed inside polyHEMA implants. The intraperitoneal biocompatibility of all 3 polymers makes them suitable for the design of drug delivery systems, which may be of great interest for pathologies confined to the pelvic cavity.magnified image
Pure, Transparent‐Melting Starch Esters: Synthesis and Characterization
Authors: Liebert Tim , Nagel Matilde C. V. , Jordan Torsten , Heft Andreas , Grünler Bernd , Heinze Thomas 
Published: August 2011

AbstractLong chain starch esters were prepared by a new method using molten imidazole as solvent for the biopolymer. The advantage is the simplicity of the reaction mixture. Imidazole is acting not only as solvent, but also as reagent and base. The reaction succeeds via the imidazolide, which is formed in situ with an acid chloride. It yields highly pure derivatives, as could be shown by NMR spectroscopy and elemental analysis. No hints for desoxychloro substituents or other impurities could be found. The high quality of the products prepared is responsible for the occurrence of colorless melts. Although DSC measurements show a variety of thermal transitions, the formation of melts in the range of 40 to 255 °C could be observed with a hot stage microscope. The melting behavior can be adjusted by the type of ester moiety and the amount of ester functions introduced. In case of starch palmitates completely transparent melts are obtained within two distinct DS regions namely around 1.5 and 2.2 to 3.0. Upon cooling the melts form homogeneous films on different supports including glass. They show good adhesion and should therefore be a suitable basic material for the preparation of composites like laminated glass. magnified image
hNCOcanH pulse sequence and a robust protocol for rapid and unambiguous assignment of backbone (1HN, 15N and 13C′) resonances in 15 N/13C‐labeled proteins
Authors: Kumar Dinesh , Hosur Ramakrishna V. 
Published: August 2011

AbstractA three‐dimensional nuclear magnetic resonance (NMR) pulse sequence named as hNCOcanH has been described to aid rapid sequential assignment of backbone resonances in 15N/13C‐labeled proteins. The experiment has been derived by a simple modification of the previously described HN(C)N pulse sequence [Panchal et al., J. Biomol. NMR 20 (2001) 135–147]; t2 evolution is used to frequency label 13C′ rather than 15N (similar trick has also been used in the design of hNCAnH pulse sequence from hNcaNH [Frueh et al., JACS, 131 (2009) 12880–12881]). The modification results in a spectrum equivalent to HNCO, but in addition to inter‐residue correlation peaks (i.e. Hi, Ci−1), the spectrum also contains additional intra‐residue correlation peaks (i.e. Hi−1, Ci−1) in the direct proton dimension which has maximum resolution. This is the main strength of the experiment and thus, even a small difference in amide 1H chemical shifts (5–6 Hz) can be used for establishing a sequential connectivity. This experiment in combination with the HNN experiment described previously [Panchal et al., J. Biomol. NMR 20 (2001) 135–147] leads to a more robust assignment protocol for backbone resonances (1HN, 15N) than could be derived from the combination of HNN and HN(C)N experiments [Bhavesh et al., Biochemistry, 40 (2001) 14727–14735]. Further, this new protocol enables assignment of 13C′ resonances as well. We believe that the experiment and the protocol presented here will be of immense value for structural—and functional—proteomics research by NMR. Performance of this experiment has been demonstrated using 13C/15N labeled ubiquitin. Copyright © 2011 John Wiley & Sons, Ltd.
Traveling‐wave RF shimming and parallel MRI
Authors: Brunner David O. , Paška Jan , Froehlich Juerg , Pruessmann Klaas P. 
Published: August 2011

AbstractAt sufficiently high Larmor frequencies, traveling electromagnetic waves along a magnet bore can be used for remote magnetic resonance excitation and detection, effectively using the bore as a waveguide. So far, this approach has relied only on the lowest waveguide modes and thus has not supported multiple‐channel operation for radiofrequency shimming and parallel imaging. In this work, this limitation is addressed by establishing a larger number of propagating modes and tapping their spatial field diversity with multiple waveguide ports. The number of available modes is increased by loading with dielectric inserts; the ports are implemented by stub and loop couplers at the end of a waveguide extension. The resulting traveling‐wave array, operated at 298 MHz in a 7T whole‐body magnet, is shown to enable radiofrequency shimming as well as parallel imaging with commonly used acceleration factors. The last part of the study concerns the amount of dielectric loading that is required. For the given Larmor frequency and bore dimensions, it is found that rather few water‐filled inserts, occupying ∼5% of the bore cross‐section, are sufficient for effective parallel imaging. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Symplectic algorithms based on the principle of least action and generating functions
Authors: Gao Q. , Tan S.J. , Zhang H.W. , Zhong W.X. 
Published: August 2011

SUMMARYIn this paper, the principle of least action and generating functions are used to construct symplectic numerical algorithms for finite dimensional autonomous Hamiltonian systems. The approximate action is obtained by approximating the generalized coordinates and momentums by Lagrange polynomials and performing Gaussian quadrature. Based on the principle of least action and the requirements of a canonical transformation, different types of symplectic algorithms have been constructed by choosing different types of independent variables at two ends of the time step. The symmetric property of the four types of symplectic algorithms proposed in this paper is discussed, and the exact linear stability domain for small m, n and g is discussed. The linear stability and precision of different types of symplectic algorithms are tested using numerical examples. Copyright © 2011 John Wiley & Sons, Ltd.
A modified scaled boundary finite element method for three‐dimensional dynamic soil‐structure interaction in layered soil
Authors: Birk C. , Behnke R. 
Published: August 2011

SUMMARYThis paper is devoted to the analysis of elastodynamic problems in 3D‐layered systems which are unbounded in the horizontal direction. For this purpose, a finite element model of the near field is coupled to a scaled boundary finite element model (SBFEM) of the far field. The SBFEM is originally based on describing the geometry of a half‐space or full‐space domain by scaling the geometry of the near field / far field interface using a radial coordinate. A modified form of the SBFEM for waves in a 2D layer is also available. None of these existing formulations can be used to describe a 3D‐layered medium.In this paper, a modified SBFEM for the analysis of 3D‐layered continua is derived. Based on the use of a scaling line instead of a scaling centre, a suitable scaled boundary transformation is proposed. The derivation of the corresponding scaled boundary finite element (SBFE) equations in displacement and stiffness is presented in detail. The latter is a nonlinear differential equation with respect to the radial coordinate, which has to be solved numerically for each excitation frequency considered in the analysis.Various numerical examples demonstrate the accuracy of the new method and its correct implementation. These include rigid circular and square foundations embedded in or resting on the surface of layered homogeneous or inhomogeneous 3D soil deposits over rigid bedrock. Hysteretic damping is assumed in some cases. The dynamic stiffness coefficients calculated using the proposed method are compared with analytical solutions or existing highly accurate numerical results. Copyright © 2011 John Wiley & Sons, Ltd.
Quality improvement methods for hexahedral element meshes adaptively generated using grid‐based algorithm
Authors: Sun Lu , Zhao Guoqun , Ma Xinwu 
Published: August 2011

SUMMARYThe quality of finite element meshes is one of the key factors that affects the accuracy and reliability of numerical simulation results of many science and engineering problems. In order to solve the problem wherein the surface elements of the mesh generated by the grid‐based method have poor quality, this paper studied mesh quality improvement methods, including node position smoothing and topological optimization. A curvature‐based Laplacian scheme was used for smoothing of nodes on the C‐edges, which combined the normal component with the tangential component of the Laplacian operator at the curved boundary. A projection‐based Laplacian algorithm for smoothing the remaining boundary nodes was established. The deviation of the newly smoothed node from the practical surface of the solid model was solved. A node‐ and area‐weighted combination method was proposed for smoothing of interior nodes. Five element‐inserting modes, three element‐collapsing modes and three mixed modes for topological optimization were newly established. The rules for harmonious application and conformity problem of each mode, especially the mixed mode, were provided. Finally, several examples were given to demonstrate the practicability and validity of the mesh quality improvement methods presented in this paper. Copyright © 2011 John Wiley & Sons, Ltd.
Elevated temperature nanoindentation behaviour of polyamide 6
Authors: Seltzer Rocio , Kim Jang‐Kyo , Mai Yiu‐Wing 
Published: August 2011

AbstractIt has been found, in this study, that there is no close correlation between the tensile and nanoindentation moduli of polyamide 6 (PA6) at high temperatures. It is demonstrated that heat modifies the surface of PA6 specimens, but its effect on the nanomechanical properties is minor. The main spurious factor which affects the nanoindentation results is adhesion, especially at low indentation depths. The overestimation in the measured indentation moduli can be corrected by performing indentations with loads high enough so that the modulus is independent of the applied load. It is concluded that the lack of strict correlations between the tensile and indentation moduli (after corrections of adhesion) is caused by the shift in the glass transition temperature of PA6 owing to the hydrostatic stress imposed by the indenter. Further proof is given with two examples on hydrostatic pressure‐dependent polymers: polytetrafluoroethylene and polycarbonate. Copyright © 2011 Society of Chemical Industry
Adaptive detrainment in a convective parametrization
Authors: Derbyshire S. H. , Maidens A. V. , Milton S. F. , Stratton R. A. , Willett M. R. 
Published: August 2011

AbstractMass‐flux convection schemes continue to play key roles in large‐scale atmospheric modelling. Currently, however, the specification of detrainment seems a potential weakness. Using cloud‐resolving model results from the European Cloud Systems (EUROCS) humidity case, we consider how detrainment adapts to its environment and formulate a minimal‐complexity description of partial detrainment in convective cloud fields. This can be viewed as an approximation to the behaviour of a multi‐plume scheme. The algorithm is straightforwardly implemented within the Gregory–Rowntree convection scheme as an extension of its original partial‐detrainment scheme. Numerical weather prediction tests in the Met Office Unified Model show significant benefits in full‐model performance. © 2011 Crown Copyright, the Met Office. Published by JohnWiley & Sons Ltd.
Evaluation of ice cloud representation in the ECMWF and UK Met Office models using CloudSat and CALIPSO data
Authors: Delanoë Julien , Hogan Robin J. , Forbes Richard M. , Bodas‐Salcedo Alejandro , Stein Thorwald H. M. 
Published: August 2011

AbstractIce cloud representation in general circulation models remains a challenging task, due to the lack of accurate observations and the complexity of microphysical processes. In this article, we evaluate the ice water content (IWC) and ice cloud fraction statistical distributions from the numerical weather prediction models of the European Centre for Medium‐Range Weather Forecasts (ECMWF) and the UK Met Office, exploiting the synergy between the CloudSat radar and CALIPSO lidar. Using the last three weeks of July 2006, we analyse the global ice cloud occurrence as a function of temperature and latitude and show that the models capture the main geographical and temperature‐dependent distributions, but overestimate the ice cloud occurrence in the Tropics in the temperature range from −60 °C to −20 °C and in the Antarctic for temperatures higher than −20 °C, but underestimate ice cloud occurrence at very low temperatures. A global statistical comparison of the occurrence of grid‐box mean IWC at different temperatures shows that both the mean and range of IWC increases with increasing temperature. Globally, the models capture most of the IWC variability in the temperature range between −60 °C and −5 °C, and also reproduce the observed latitudinal dependencies in the IWC distribution due to different meteorological regimes. Two versions of the ECMWF model are assessed. The recent operational version with a diagnostic representation of precipitating snow and mixed‐phase ice cloud fails to represent the IWC distribution in the −20 °C to 0 °C range, but a new version with prognostic variables for liquid water, ice and snow is much closer to the observed distribution. The comparison of models and observations provides a much‐needed analysis of the vertical distribution of IWC across the globe, highlighting the ability of the models to reproduce much of the observed variability as well as the deficiencies where further improvements are required. Copyright © 2011 Royal Meteorological Society and British Crown Copyright, the Met Office
Antioxidant Deactivation on Graphenic Nanocarbon Surfaces
Authors: Liu Xinyuan , Sen Sujat , Liu Jingyu , Kulaots Indrek , Geohegan David , Kane Agnes , Puretzky Alex A. , Rouleau Christopher M. , More Karren L. , Palmore G. Tayhas R. , Hurt Robert H. 
Published: August 2011

AbstractThis article reports a direct chemical pathway for antioxidant deactivation on the surfaces of carbon nanomaterials. In the absence of cells, carbon nanotubes are shown to deplete the key physiological antioxidant glutathione (GSH) in a reaction involving dissolved dioxygen that yields the oxidized dimer, GSSG, as the primary product. In both chemical and electrochemical experiments, oxygen is only consumed at a significant steady‐state rate in the presence of both nanotubes and GSH. GSH deactivation occurs for single‐ and multi‐walled nanotubes, graphene oxide, nanohorns, and carbon black at varying rates that are characteristic of the material. The GSH depletion rates can be partially unified by surface area normalization, are accelerated by nitrogen doping, and suppressed by defect annealing or addition of proteins or surfactants. It is proposed that dioxygen reacts with active sites on graphenic carbon surfaces to produce surface‐bound oxygen intermediates that react heterogeneously with glutathione to restore the carbon surface and complete a catalytic cycle. The direct catalytic reaction between nanomaterial surfaces and antioxidants may contribute to oxidative stress pathways in nanotoxicity, and the dependence on surface area and structural defects suggest strategies for safe material design.
Functionally Decoupled Soft Lithography for Patterning Polymer Brushes
Authors: Moran Isaac W. , Ell John R. , Carter Kenneth R. 
Published: August 2011

AbstractEasy soft imprint nanolithography (ESINL) is employed in the patterning of multiple olymer brushes. This new approach to soft lithography is found to be uniquely effective at patterning brushes both prior to and subsequent to grafting of the polymer chains. Silicon substrates are grafted with polystyrene, polymethylmethacrylate, and polyhydroxyethylmethacrylate using surface‐initiated atom transfer radical polymerization assisted by activators generated by electron transfer (ARGET‐ATRP) and characterized by contact angle measurements, infrared spectroscopy, and ellipsometry. Line grating features of 3 cm × 3 cm with critical dimensions in the range of 410–480 nm are imprinted directly over grafted brush layers or over assembled monolayers of initiator molecules and transferred to the active layer by reactive ion etching. In all cases the grating pattern is accurately reproduced in the brush layer as confirmed by atomic force microscopy, demonstrating the capability of the technique to generate large‐area nanoscale patterns on a range of surface types and functionalities.
Membranwirkung von Verbunddecken bei Brand – Experimentelle Untersuchungen
Authors: Mensinger Martin , Stadler Martin 
Published: August 2011

AbstractVerbundträger‐Decken‐Systeme zeigen im Brandfall ein gutmütiges Tragverhalten. Durch große Verformungen können Membrankräfte aktiviert und dadurch größere Spannweiten überbrückt werden. Die Nebenträger innerhalb eines Deckenfeldes werden daher bei hohen Temperaturen nicht benötigt und könnten ungeschützt belassen werden. In Großbritannien und der Schweiz wird die Membranwirkung von Verbunddecken im Brand mit dem Verfahren nach Bailey ([1] bis [5]) bereits genutzt. Um das Verfahren auch in Deutschland anwenden zu können, bedarf es jedoch noch einiger eingehender Untersuchungen. Im Rahmen eines gemeinsamen Forschungsvorhabens des Lehrstuhls für Metallbau der Technischen Universität München und des Instituts für Stahlbau der Leibniz Universität Hannover werden derzeit diesbezüglich Untersuchungen durchgeführt. Das Projekt wird vom DASt und der AiF gefördert. In [6] wurden der Stand der Technik und die Idee der Membranwirkung allgemein bereits vorgestellt. In dieser Arbeit wird auf die experimentellen Untersuchungen im Rahmen des Forschungsprojekts eingegangen.Membrane Action of Composite Slabs in Fire – Experimental Investigation. Composite beam slab systems show a very good behaviour in case of fire. Due to large deformations membrane forces are activated inside the slab and wider spans can be bridged. Secondary beams are not necessary at elevated temperatures and can be left unprotected. In Great Britain and Switzerland membrane action is already used to design slab systems in fire ([1] to [5]). To enable such design rules in Germany further investigations are required. For this reason a research project was initiated by the authors. The project is supported by the DASt and AiF. In [6] the state of research and the idea of membrane action are already described. In this paper the experimental part of the project is presented.