bluuebunny/crossref_metadata_2025 huggingface dataset:
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

The 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

Long 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

A 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

At 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

In 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

This 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

The 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

It 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

Mass‐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

Ice 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
Chemical profiling of bioactive constituents in Sarcandra glabra and its preparations using ultra‐high‐pressure liquid chromatography coupled with LTQ Orbitrap mass spectrometry
Authors: Li Xiong , Zhang Yufeng , Zeng Xing , Yang Liu , Deng Yuanhui
Published: August 2011

In this study, a fast and reliable method based on an ultra‐high‐pressure liquid chromatography coupled with photodiode‐array detection (PDA) and a linear ion trap high‐resolution mass spectrometer (LTQ‐Orbitrap XL) has been developed for the identification of bioactive constituents in the whole plant of Sarcandra glabra and its related four preparations. By accurate mass measurements within 5 ppm error for each molecular ion and subsequent fragment ions in routine analysis, 50 compounds, including organic acids, caffeoyl derivatives, flavonoids, coumarins and terpenoids, were identified or tentatively characterized. Among them, 6,7,8‐trihydroxycoumarin‐O‐rhamnopyranoside (17), (2R)‐naringenin‐6‐C‐B‐D‐glucopyranosyl‐(6→1)‐apiose (25) and (2S)‐naringenin‐6‐C‐B‐D‐glucopyranosyl‐(6→1)‐apiose (27) were tentatively identified as new compounds. Besides, 21 of these compounds were coexisting in four preparations of Sarcandra glabra. Fragmentation behaviors of the four major categories of compounds were also investigated. This established UPLC‐PDA/ESI‐MSn method was reliable and effective for the separation and identification of the major constituents and would be the basis for quality control of Sarcandra glabra and its related preparations. Copyright © 2011 John Wiley & Sons, Ltd.
Protein identification by accurate mass matrix‐assisted laser desorption/ionization imaging of tryptic peptides
Authors: Schober Yvonne , Schramm Thorsten , Spengler Bernhard , Römpp Andreas
Published: August 2011

The spatial distribution of proteins in tissue sections can be used to identify potential markers for pathological processes. Tissue sections are often subjected to enzymatic digestion before matrix‐assisted laser desorption/ionization (MALDI) imaging. This study is targeted at improving the on‐tissue identification of tryptic peptides by accurate mass measurements and complementary off‐line liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) analysis. Two adjacent mouse brain sections were analyzed in parallel. The first section was spotted with trypsin and analyzed by MALDI imaging. Direct on‐tissue MS/MS experiments of this section resulted in the identification of 14 peptides (originating from 4 proteins). The second tissue section was homogenized, fractionated by ultracentrifugation and digested with trypsin prior to LC/ESI‐MS/MS analysis. The number of identified peptides was increased to 153 (corresponding to 106 proteins) by matching imaged mass peaks to peptides which were identified in these LC/ESI‐MS/MS experiments. All results (including MALDI imaging data) were based on accurate mass measurements (RMS <2 ppm) and allow a confident identification of tryptic peptides. Measurements based on lower accuracy would have led to ambiguous or misleading results. MS images of identified peptides were generated with a bin width (mass range used for image generation) of Δm/z = 0.01. The application of accurate mass measurements and additional LC/MS measurements increased both the quality and the number of peptide identifications. The advantages of this approach for the analysis of biological tissue sections are demonstrated and discussed in detail. Results indicate that accurate mass measurements are needed for confident identification and specific image generation of tryptic peptides in tissue sections. Copyright © 2011 John Wiley & Sons, Ltd.
Compound‐specific bromine isotope analysis of methyl bromide using gas chromatography hyphenated with inductively coupled plasma multiple‐collector mass spectrometry
Authors: Horst Axel , Holmstrand Henry , Andersson Per , Andersson August , Carrizo Daniel , Thornton Brett F. , Gustafsson Örjan
Published: August 2011

Methyl bromide is the most important natural bromine contributor to stratospheric ozone depletion, yet there are still large uncertainties regarding quantification of its sources and sinks. The stable bromine isotope composition of CH3Br is potentially a powerful tool to apportion its sources and to study both its transport and its reactive fate. A novel compound‐specific method to measure 81Br/79Br isotope ratios in CH3Br using gas chromatography hyphenated with inductively coupled plasma multiple‐collector mass spectrometry (GC/MCICPMS) was developed. Sample amounts of >40 ng could be measured with a precision of 0.1‰ (1σ, n = 3). The method results are reproducible over the long term as shown with 36 analyses acquired over 3 months, yielding a standard deviation (1σ) better than 0.4‰. This new method demonstrates for the first time Br isotope ratio determination in gaseous brominated samples. It is three orders of magnitude more sensitive than previously existing isotope ratio mass spectrometry methods for Br isotope determination of other organobromines, thus allowing applications towards ambient atmospheric samples. Copyright © 2011 John Wiley & Sons, Ltd.
Quantification of methyl thiocyanate in the headspace of Pseudomonas aeruginosa cultures and in the breath of cystic fibrosis patients by selected ion flow tube mass spectrometry
Authors: Shestivska Violetta , Nemec Alexandr , Dřevínek Pavel , Sovová Kristýna , Dryahina Kseniya , Španěl Patrik
Published: August 2011

Infection by Pseudomonas aeruginosa (PA) is a major cause of morbidity and mortality in patients with cystic fibrosis (CF). Breath analysis could potentially be a useful diagnostic of such infection, and analyses of volatile organic compounds (VOCs) emitted from PA cultures are an important part of the search for volatile breath markers of PA lung infection. Our pilot experiments using solid‐phase microextraction, SPME and gas chromatography/mass spectrometric (GC/MS) analyses of volatile compounds produced by PA strains indicated a clear presence of methyl thiocyanate. This provided a motivation to develop a method for real‐time online quantification of this compound by selected ion flow tube mass spectrometry, SIFT‐MS. The kinetics of reactions of H3O+, NO+ and O2+• with methyl thiocyanate at 300 K were characterized and the characteristic product ions determined (proton transfer for H3O+, rate constant 4.6 × 10–9 cm3 s–1; association for NO+, 1.7 × 10–9 cm3 s–1 and nondissociative charge transfer for O2+•, 4.3 × 10–9 cm3 s–1). The kinetics library was extended by a new entry for methyl thiocyanate accounting for overlaps with isotopologues of hydrated hydronium ions. Solubility of methyl thiocyanate in water (Henry's law constant) was determined using standard reference solutions and the linearity and limits of detection of both SIFT‐MS and SPME‐GC/MS methods were characterized. Thirty‐six strains of PA with distinct genotype were cultivated under identical conditions and 28 of them (all also producing HCN) were found to release methyl thiocyanate in headspace concentrations greater than 6 parts per billion by volume (ppbv). SIFT‐MS was also used to analyze the breath of 28 children with CF and the concentrations of methyl thiocyanate were found to be in the range 2–21 ppbv (median 7 ppbv). Copyright © 2011 John Wiley & Sons, Ltd.
Diagnostic cyclisation reactions which follow phosphate transfer to carboxylate anion centres for energised [M–H]– anions of pTyr‐containing peptides
Authors: Tran T. T. Nha , Wang Tianfang , Hack Sandra , Bowie John H.
Published: August 2011

The low‐energy negative ion phosphoTyr to C‐terminal ‐CO2PO3H2 rearrangement occurs for energised peptide [M–H]– anions even when there are seven amino acid residues between the pTyr and C‐terminal amino acid residues. The rearranged C‐terminal ‐CO2PO2H(O–) group effects characteristic SNi cyclisation/cleavage reactions. The most pronounced of these involves the electrophilic central backbone carbon of the penultimate amino acid residue. This reaction is aided by the intermediacy of an H‐bonded intermediate in which the nucleophilic and electrophilic reaction centres are held in proximity in order for the SNi cyclisation/cleavage to proceed. The ΔGreaction is +184 kJ mol−1 with the barrier to the SNi transition state being +240 kJ mol−1 at the HF/6‐31 + G(d)//AM1 level of theory. A similar phosphate rearrangement from pTyr to side chain CO2– (of Asp or Glu) may also occur for energised peptide [M–H]– anions. The reaction is favourable: ΔGreaction is −44 kJ mol−1 with a maximum barrier of +21 kJ mol−1 (to the initial transition state) when Asp and Tyr are adjacent. The rearranged species R1‐Tyr‐NHCH(CH2CO2PO3H–)COR2 (R1 = CHO; R2 = OCH3) may undergo an SNi six‐centred cyclisation/cleavage reaction to form the product anion R1‐Tyr(NH–). This process has a high energy requirement [ΔGreaction = +224 kJ mol−1, with the barrier to the SNi transition state being +299 kJ mol−1]. Copyright © 2011 John Wiley & Sons, Ltd.
Comparison of stable‐isotope labeling with amino acids in cell culture and spectral counting for relative quantification of protein expression
Authors: Collier Timothy S. , Randall Shan M. , Sarkar Prasenjit , Rao Balaji M. , Dean Ralph A. , Muddiman David C.
Published: August 2011

Protein quantification is one of the principal goals of mass spectrometry (MS)‐based proteomics, and many strategies exist to achieve it. Several approaches involve the incorporation of a stable‐isotope label using either chemical derivatization, enzymatically catalyzed incorporation of 18O, or metabolic labeling in a cell or tissue culture. These techniques can be cost or time prohibitive or not amenable to the biological system of interest. Label‐free techniques including those utilizing integrated ion abundance and spectral counting offer an alternative to stable‐isotope‐based methodologies. Herein, we present the comparison of stable‐isotope labeling of amino acids in cell culture (SILAC) with spectral counting for the quantification of human embryonic stem cells as they differentiate toward the trophectoderm at three time points. Our spectral counting experimental strategy resulted in the identification of 2641 protein groups across three time points with an average sequence coverage of 30.3%, of which 1837 could be quantified with more than five spectral counts. SILAC quantification was able to identify 1369 protein groups with an average coverage of 24.7%, of which 1027 could be quantified across all time points. Within this context we further explore the capacity of each strategy for proteome coverage, variation in quantification, and the relative sensitivity of each technique to the detection of change in relative protein expression. Copyright © 2011 John Wiley & Sons, Ltd.
Implementation of dipolar direct current (DDC) collision‐induced dissociation in storage and transmission modes on a quadrupole/time‐of‐flight tandem mass spectrometer
Authors: Webb Ian K. , Londry Frank A. , McLuckey Scott A.
Published: August 2011

Means for effecting dipolar direct current collision‐induced dissociation (DDC CID) on a quadrupole/time‐of‐flight in a mass spectrometer have been implemented for the broadband dissociation of a wide range of analyte ions. The DDC fragmentation method in electrodynamic storage and transmission devices provides a means for inducing fragmentation of ions over a large mass‐to‐charge range simultaneously. It can be effected within an ion storage step in a quadrupole collision cell that is operated as a linear ion trap or as ions are continuously transmitted through the collision cell. A DDC potential is applied across one pair of rods in the quadrupole collision cell of a QqTOF hybrid mass spectrometer to effect fragmentation. In this study, ions derived from a small drug molecule, a model peptide, a small protein, and an oligonucleotide were subjected to the DDC CID method in either an ion trapping or an ion transmission mode (or both). Several key experimental parameters that affect DDC CID results, such as time, voltage, low mass cutoff, and bath gas pressure, are illustrated with protonated leucine enkephalin. The DDC CID dissociation method gives a readily tunable, broadband tool for probing the primary structures of a wide range of analyte ions. The method provides an alternative to the narrow resonance conditions of conventional ion trap CID and it can access more extensive sequential fragmentation, depending upon conditions. The DDC CID approach constitutes a collision analog to infrared multiphoton dissociation (IRMPD). Copyright © 2011 John Wiley & Sons, Ltd.
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

This 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

Easy 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

Verbundträger‐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.
Querkrafttragfähigkeit von Stockschrauben und Solarbefestigern auf Dächern mit Trapezprofileindeckung
Authors: Krüger Helmut , Misiek Thomas , Ummenhofer Thomas
Published: August 2011

Photovoltaik‐ und Solarthermieelemente werden zur energetischen Nutzung sonnenbestrahlter Dachflächen mit unterschiedlichen Befestigungssystemen auf vorhandenen Dachoberflächen montiert. Bei der Installation auf Trapezprofilen kommen hauptsächlich Stockschrauben, Solarbefestiger und Solarkalotten zum Einsatz. Insbesondere für den rechnerischen Nachweis von Stockschrauben und Solarbefestigern sind bisher nur unzureichende Bemessungsansätze verfügbar. Im Mittelpunkt steht hierbei die Einleitung von Querlasten aus Dachschub, Wind und Schnee in die Unterkonstruktion.

Die im vorliegenden Aufsatz vorgestellten Bemessungsverfahren ermöglichen die Bestimmung der Querkrafttragfähigkeit unter Beachtung des Einflusses exzentrisch eingeleiteter Druckkräfte. Dem bemessenden Ingenieur müssen hierzu die Drehfedersteifigkeit Ca der Einspannung des Verbindungsmittels in der Unterkonstruktion, die Trapezprofilsteifigkeit in Sickenrichtung Kb und das Fließmoment My,Rk des Verbindungsmittels zur Verfügung stehen. Eine konservative Abschätzung kann auch mit der Querkrafttragfähigkeit des Trapezprofils Fb und dem Fließmoment My,Rk unter Vernachlässigung der Einspannwirkung in der Unterkonstruktion erfolgen.

Shear bearing capacity of hanger bolts and solar fasteners on roofs with trapezoidal profiles. For the energetic utilization of sunlit roof areas, photovoltaic and solar thermal plants are installed on the existing roof surface by means of different fastening systems. For the installation on trapezoidal profiles, hanger bolts, solar fasteners and solar calottes are primarily applied. Especially for the application of hanger bolts and solar fasteners, only insufficient design approaches are available up to now. The load bearing behavior due to effects from roof shear, wind and snow loading into the substructure is the main problem.

The methods and equations presented within this article facilitate to determine the shear bearing capacity considering the influences of eccentrically induced compressive forces. For this purpose, the torsion spring stiffness Ca of the fastener in the substructure, the trapezoidal profile stiffness Kb and the yield moment My,Rk of the fastener must be provided for the user. An conservative assessment can also be realized by using the shear bearing capacity of the trapezoidal profile Fb and the yield moment My,Rk neglecting the torsion spring stiffness.
Lineage Specific Methylation of the Elf5 Promoter in Mammary Epithelial Cells
Authors: Lee Heather J. , Hinshelwood Rebecca A. , Bouras Toula , Gallego-Ortega David , Valdés-Mora Fátima , Blazek Katrina , Visvader Jane E. , Clark Susan J. , Ormandy Christopher J.
Published: August 2011

Recent characterization of mammary stem and progenitor cells has improved our understanding of the transcriptional network that coordinates mammary development; however, little is known about the mechanisms that enforce lineage commitment and prevent transdifferentiation in the mammary gland. The E-twenty six transcription factor Elf5 forces the differentiation of mammary luminal progenitor cells to establish the milk producing alveolar lineage. Methylation of the Elf5 promoter has been proposed to act as a lineage gatekeeper during embryonic development. We used bisulphite sequencing to investigate in detail whether Elf5 promoter methylation plays a role in lineage commitment during mammary development. An increase in Elf5 expression was associated with decreasing Elf5 promoter methylation in differentiating HC11 mammary cells. Similarly, purified mammary epithelial cells from mice had increased Elf5 expression and decreased promoter methylation during pregnancy. Finally, analysis of epithelial subpopulations revealed that the Elf5 promoter is methylated and silenced in the basal, stem cell-containing population relative to luminal cells. These results demonstrate that Elf5 promoter methylation is lineage-specific and developmentally regulated in the mammary gland in vivo, and suggest that loss of Elf5 methylation specifies the mammary luminal lineage, while continued Elf5 methylation maintains the stem cell and myoepithelial lineages.
Synthesis of One‐Dimensional Tl2O3 Nanostructures from Thermolyses of a New One‐Dimensional Thallium(I) Coordination Polymer Precursor
Authors: Mohammadi Masoomeh , Morsali Ali
Published: August 2011

A new thallium(I) one‐dimensional coordination polymer, [Tl(2,4,6‐tcp)]n (1) (2,4,6‐tcp– = 2,4,6‐trichlorophenoxide) was synthesized and characterized by elemental analyses and IR spectroscopy. Compound 1 was structurally characterized by single‐crystal X‐ray diffraction and is a one‐dimensional coordination polymer with coordination environment of TlO3. Three different Tl2O3 nano‐structures were prepared by direct calcination, thermal decomposition in oleic acid and sol‐gel method in poly vinyl alcohol (PVA). The nano‐materials were characterized by scanning electron microscopy, X‐ray powder diffraction (XRD), and IR spectroscopy. This study demonstrates the coordination polymers may be suitable precursors for the preparation of nanoscale materials with difference and interesting morphologies.
Ce2[CrN3]: Single Phase Synthesis and Characterization of a Nitridochromate(I)
Authors: Bräunling Daniel , Niewa Rainer
Published: August 2011

The ternary nitridochromate Ce2[CrN3] (orthorhombic Immm, a = 378.56(1) pm, b = 340.88(2) pm, c = 1251.27(4) pm) was synthesized in single phase form from the binary nitrides utilizing the decomposition of CrN to Cr2N. Magnetic susceptibility measurements as well as X‐ray absorption spectroscopy indicate a Ce4+(4f0) electronic state and in turn an oxidation state of +1 for chromium provided –3 for nitrogen.
Topological derivatives for networks of elastic strings
Authors: Leugering G. , Sokolowski J.
Published: August 2011

We consider linear second order differential equations on metric graphs under given boundary and nodal conditions. We are interested in the problem of changing the topology of the underlying graph in that we replace a multiple node by a subgraph or concentrate a subgraph to a single node. We wish to do so in an optimal fashion. More precisely, given a cost function we may look for its sensitivity with respect to these operations in order to find an optimal topology of the graph. Thus, in essence, we are looking for the topological gradient for linear second order problems on metric graphs.
A hyperbolic model for granular flow
Authors: Cattani A. , Colombo R.M. , Guerra G.
Published: August 2011

We present a model that describes the motion of some granular material sliding along a slope. During this movement, both erosion and deposition may take place, depending on the speed of the sliding material. Analytically, this model consists of a hyperbolic system of partial differential equations. In the 1D case, the resulting system of balance laws displays interesting behavior. Its convective part gives rise to a 3 × 3 globally well defined Riemann Problem, in spite of the appearance of vacuum and of the lack of strict hyperbolicity. Several numerical integrations show various features of this model.
Decay estimates for the Brinkman‐Forchheimer equations in a semi‐infinite pipe
Authors: Li Y. , Liu Y. , Luo S. , Lin C.
Published: August 2011

In this paper, we consider the Brinkman‐Forchheimer equations in a semi‐infinite pipe. A second order differential inequality is derived which leads to an exponential decay estimate for the energy E (z,t) defined in (3.1) under appropriate initial and boundary conditions. We also indicate how to establish the explicit bound for the total energy.
Interface delamination of bi‐material structure under time harmonic load. Cohesive behaviour of the interface
Authors: Ivanovna J. , Nikolova G. , Gambin B.
Published: August 2011

The interface cohesive behaviour and interface delamination in a bi‐material structure consisting of two plates and material interface with zero thickness under time harmonic load is studied. Previously, the authors studied the elasto‐brittle interface behaviour, from both sides of a crack, initially normal to the interface, when the elastic‐brittle interface debonding appeared. Now, it is again assumed that the restriction for the ratio of energy release rates of the second plate and interface allowing the occurrence of an interface cohesive delamination before the initiation of the normal crack in the second plate is satisfied. The shear lag model is adopted and applied to find the dynamic response of the considered structure, assuming the cohesive interface behaviour, accompanied before of the elastic‐brittle one. In both cases, the growth of debond length is not considered e.g. at a given loading condition the corresponding single debond length is found. The inertia forces of the already debonded interface elasto‐brittle cracks (mode II) are neglected. The appropriate contact conditions are proposed in order to fit together both elastic and cohesive solutions. The Laplace inverse transform is applied to obtain the original of cohesive debond length by the aid of the already obtained elastic value of debond length at the same loading condition. Parametric analysis of the results obtained is illustrated by examples of the modern ceramic‐metal composite on metal substrate. The influence of frequencies and amplitude fluctuations on the cohesive debond length and the interface shear stress distribution are discussed.
Linear plane wave propagation and normal transmission and reflection at discontinuity surfaces in second gradient 3D continua
Authors: dell'Isola F. , Madeo A. , Placidi L.
Published: August 2011

We study plane waves in second gradient solids and their reflection and transmission at plane displacement discontinuity surfaces. The needed extension of the treatment adopted to study plane wave propagation in Cauchy continua is not straightforward and is developed here. In particular, the balance of mechanical energy valid for second gradient continua is deduced. The presented results may be of interest as many boundary layer phenomena can be accounted for by second gradient models. We prove that second gradient elastic moduli may influence, in a measurable manner, how planar waves behave at discontinuity surfaces: the novel results presented here can be the basis of experimental procedures to estimate some among these moduli. We explicitly remark that reflection and transmission coefficients which we have estimated show a significant dependence on frequency, which indeed makes easier to conceive effective measurement methods.
Providers’ Perceptions and Practices Regarding BRCA1/2 Genetic Counseling and Testing in African American Women
Authors: Graves Kristi D. , Christopher Juleen , Harrison Toni Michelle , Peshkin Beth N. , Isaacs Claudine , Sheppard Vanessa B.
Published: August 2011

We examined healthcare providers’ perceptions of genetic counseling and testing in African American women at moderate to high‐risk of carrying a BRCA1/2 mutation. We conducted 20 in‐depth interviews with genetic counselors (n = 5), medical oncologists (n = 8), obstetrician/gynecologists (n = 2) and surgeons (n = 5). Interviews were audiotaped, transcribed and independently coded by two individuals using a content analysis approach. Seven themes emerged relevant to providers’ perceptions of African American women's use of BRCA1/2 genetic services: access factors, cultural beliefs and preferences, effects of testing, patient motivators for genetic counseling and testing, patient‐provider communication, reasons for provider referral, and reasons for patient refusal. Providers identified individual‐ and system‐level barriers to African American women's use of genetic services, including lack of follow‐up after referrals to genetic specialists and challenges to obtaining financial coverage for under‐ and uninsured high‐risk women. Results have implications for physician and patient education regarding appropriate referrals to and uptake of genetic services in at‐risk African American women.
Uneven Distribution of Ceramides, Sphingomyelins and Glycerophospholipids Between Heads and Tails of Rat Spermatozoa
Authors: Oresti Gerardo M. , Luquez Jessica M. , Furland Natalia E. , Aveldaño Marta I.
Published: August 2011

Previous work showed that rat germ cells and spermatozoa contain ceramides and sphingomyelins with high proportions of nonhydroxy and 2‐hydroxy (2‐OH) polyunsaturated fatty acids (PUFA) with very long chains (VLCPUFA). The aim of this study was to assess how these lipids are distributed between the heads and tails of mature spermatozoa in comparison with other membrane lipid classes. In addition to quantitative differences due to the fact that these gametes have a long, voluminous tail and a minute head, several compositional dissimilarities emerged between these two regions. The total cholesterol/total phospholipid ratio, the choline/ethanolamine glycerophospholipid (ChoGpl/EtnGpl) ratio, and the proportion of plasmalogens within these two classes, were much larger in the head than in the tail. Whereas EtnGpl was rich in 22:5n‐6 in both regions, ChoGpl had plenty of 22:4n‐9, especially in the heads. An important proportion of the head EtnGpl‐ 22:5n‐6 and ChoGpl 22:4n‐9 was in plasmenyl‐ (rather than in phosphatidyl‐) subclasses. The heads concentrated all of the sphingomyelin species with nonhydroxy‐ and 2‐OH VLCPUFA, and the tails most of the saturated fatty acids that are present in total sperm sphingomyelin. Unexpectedly, virtually all of the abundant spermatozoal ceramides, predominantly made up by species with 2‐OH VLCPUFA, was located in the tail. The fact that intact rat spermatozoa constitutively have much more VLCPUFA‐containing ceramide than sphingomyelin is explained by the present findings, since the former are mostly lipids of the large tail while the latter mostly collect in the small head.
Perialveolar bacterial microbiota and bacteraemia after dental alveolitis in adult rats that had been subjected to neonatal malnutrition
Authors: Gonçalves de Araújo Flávia Regina , Machado Barbosa de Castro Célia Maria , Advíncula Rocha Judith , Sampaio Bruno , de Fátima Alves Diniz Maria , Baratella Evêncio Liriane , Ramos Montarroyos Ulisses
Published: August 2011

The aim of the present study was to analyse the bacteriological factors during the process of dental alveolitis, relating it to a higher incidence of bacteraemia in adult rats subjected to neonatal malnutrition. We used forty male Wistar rats, suckled by mothers fed a diet during lactation containing 17 % protein in the nourished group (N) or 8 % protein in the undernourished group (UN). After weaning, the animals were given the Labina standard diet. After 90 d, these animals underwent upper right incisor extraction and induction of alveolitis. The oral microbiota was obtained using a swab and blood culture through venous blood. These procedures were performed before the extraction, 5 min after extraction, on the 21st day after alveolitis for groups N-21 and UN-21 and on the 28th day after alveolitis for groups N-28 and UN-28. Data were expressed as means and standard deviations for parametric data, and as medians and interquartile intervals for non-parametric data. Statistical significance was considered by assuming a critical level of 5 %. Before and after extraction, lower bacterial growth was observed per colony-forming unit (CFU) in the perialveolar region of the upper right incisors of undernourished animals, while the opposite was true after alveolitis, when a larger number of CFU was observed in these animals. The percentage of positive blood cultures obtained after alveolitis was greater in the undernourished animals. The present study thus demonstrated the influence of neonatal malnutrition in the perialveolar microbiota and in the development of bacteraemia after dental alveolitis.