bluuebunny/crossref_metadata_2025 huggingface dataset:
Ecological limit functions relating fish community response to hydrologic departures of the ecological flow regime in the Tennessee River basin, United States
Authors: Knight Rodney R. , Murphy Jennifer C. , Wolfe William J. , Saylor Charles F. , Wales Amy K.
Published: November 2013

Ecological limit functions relating streamflow and aquatic ecosystems remain elusive despite decades of research. We investigated functional relationships between species richness and changes in streamflow characteristics at 662 fish sampling sites in the Tennessee River basin. Our approach included the following: (1) a brief summary of relevant literature on functional relations between fish and streamflow, (2) the development of ecological limit functions that describe the strongest discernible relationships between fish species richness and streamflow characteristics, (3) the evaluation of proposed definitions of hydrologic reference conditions, and (4) an investigation of the internal structures of wedge‐shaped distributions underlying ecological limit functions.

Twenty‐one ecological limit functions were developed across three ecoregions that relate the species richness of 11 fish groups and departures from hydrologic reference conditions using multivariate and quantile regression methods. Each negatively sloped function is described using up to four streamflow characteristics expressed in terms of cumulative departure from hydrologic reference conditions. Negative slopes indicate increased departure results in decreased species richness.

Sites with the highest measured fish species richness generally had near‐reference hydrologic conditions for a given ecoregion. Hydrology did not generally differ between sites with the highest and lowest fish species richness, indicating that other environmental factors likely limit species richness at sites with reference hydrology.

Use of ecological limit functions to make decisions regarding proposed hydrologic regime changes, although commonly presented as a management tool, is not as straightforward or informative as often assumed. We contend that statistical evaluation of the internal wedge structure below limit functions may provide a probabilistic understanding of how aquatic ecology is influenced by altered hydrology and may serve as the basis for evaluating the potential effect of proposed hydrologic changes. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. Ecohydrology published by John Wiley & Sons, Ltd.
Leptin deficiency impairs maturation of dendritic cells and enhances induction of regulatory T and Th17 cells
Authors: Moraes‐Vieira Pedro M.M. , Larocca Rafael A. , Bassi Enio J. , Peron Jean Pierre S. , Andrade‐Oliveira Vinícius , Wasinski Frederick , Araujo Ronaldo , Thornley Thomas , Quintana Francisco J. , Basso Alexandre S. , Strom Terry B. , Câmara Niels O.S.
Published: November 2013

Leptin is an adipose‐secreted hormone that plays an important role in both metabolism and immunity. Leptin has been shown to induce Th1‐cell polarization and inhibit Th2‐cell responses. Additionally, leptin induces Th17‐cell responses, inhibits regulatory T (Treg) cells and modulates autoimmune diseases. Here, we investigated whether leptin mediates its activity on T cells by influencing dendritic cells (DCs) to promote Th17 and Treg‐cell immune responses in mice. We observed that leptin deficiency (i) reduced the expression of DC maturation markers, (ii) decreased DC production of IL‐12, TNF‐α, and IL‐6, (iii) increased DC production of TGF‐β, and (iv) limited the capacity of DCs to induce syngeneic CD4+ T‐cell proliferation. As a consequence of this unique phenotype, DCs generated under leptin‐free conditions induced Treg or TH17 cells more efficiently than DCs generated in the presence of leptin. These data indicate important roles for leptin in DC homeostasis and the initiation and maintenance of inflammatory and regulatory immune responses by DCs.
Neutrophils suppress γδ T‐cell function
Authors: Sabbione Florencia , Gabelloni María L. , Ernst Glenda , Gori María S. , Salamone Gabriela , Oleastro Matías , Trevani Analía , Geffner Jorge , Jancic Carolina C.
Published: November 2013

γδ T cells have been shown to stimulate the recruitment and activation of neutrophils through the release of a range of cytokines and chemokines. Here, we investigated the reverse relationship, showing that human neutrophils suppress the function of human blood γδ T cells. We show that the upregulation of CD25 and CD69 expression, the production of IFN‐γ, and the proliferation of γδ T cells induced by (E)‐1‐hydroxy‐2‐methylbut‐2‐enyl 4‐diphosphate are inhibited by neutrophils. Spontaneous activation of γδ T cells in culture is also suppressed by neutrophils. We show that inhibitors of prostaglandin E2 and arginase I do not exert any effect, although, in contrast, catalase prevents the suppression of γδ T cells induced by neutrophils, suggesting the participation of neutrophil‐derived ROS. We also show that the ROS‐generating system xanthine/xanthine oxidase suppresses γδ T cells in a similar fashion to neutrophils, while neutrophils from chronic granulomatous disease patients only weakly inhibit γδ T cells. Our results reveal a bi‐directional cross‐talk between γδ T cells and neutrophils: while γδ T cells promote the recruitment and the activation of neutrophils to fight invading pathogens, neutrophils in turn suppress the activation of γδ T cells to contribute to the resolution of inflammation.
One‐Pot Microwave Synthesis of Fluorescent Carbogenic Nanoparticles from Triton X‐100 for Cell Imaging
Authors: Rajendran Ramesh , Sohila Subramaniam , Muralidharan Rajalakshmi , Muthamizhchelvan Chellamuthu , Ponnusamy Suruttaiyaudiyar
Published: November 2013

Carbon‐based fluorescent nanoparticles have attracted a lot of attention in the field of bioimaging as a result of their excellent emission properties along with their low toxicity. Fluorescent carbogenic nanoparticles (CNPs) were synthesized by a one‐pot microwave pyrolysis technique by using Triton X‐100 as a carbon source. The CNPs are spherical in shape with an average diameter of 5.5 nm, as characterized by transmission electron microscopy and atomic force microscopy. The as‐synthesized CNPs showed strong blue emission under UV illumination, excitation‐dependent emission properties, and chemical stability under different pH conditions. The graphitic nature of the CNPs was studied by using Raman and X‐ray photoelectron spectroscopy. Moreover, the toxicity of these particles was studied through an MTT assay, which showed no noticeable toxicity. The results suggest that the CNPs can be used as effective fluorescent probes for cellular imaging applications.
Reactivity of Diimido Complexes of Moybdenum and Tungsten towards Lithium Derivatives of Diphosphanes and Triphosphanes
Authors: Grubba Rafał , Wiśniewska Aleksandra , Ponikiewski Łukasz , Caporali Maria , Peruzzini Maurizio , Pikies Jerzy
Published: November 2013

The reaction of R2P–P(SiMe3)Li (R = tBu, iPr) with the diimido molybdenum complex [(ArN)2MoCl2·dme] (Ar = 2,6‐iPr2C6H3; dme = 1,2‐dimethoxyethane) yielded the side‐on‐coordinated phosphanylphosphinidene anionic complexes [(2,6‐iPr2C6H3N)2Mo(Cl)(η2‐P=PR2)]– (7Mo, 8Mo). The thermal decomposition of [(2,6‐iPr2C6H3N)2M(Cl)(η2‐P=PR2)]– [M = Mo (7Mo), W (8W)] to [(2,6‐iPr2C6H3N)2M(Cl)(1,2‐η‐tBu2P=P–PtBu2)] [M = Mo (3Mo), W (3W)] was investigated by 31P{1H} NMR spectroscopy. The reactions of [(ArN)2MCl2·dme] (Ar = 2,6‐iPr2C6H3; M = Mo, W) with tBu2P–P(Li)–PtBu2 gave molybdenum and tungsten complexes [(2,6‐iPr2C6H3N)2M(Cl)(1,2‐η‐tBu2P=P–PtBu2)] (3Mo, 3W) bearing an unusual triphosphorus ligand. The solid‐state structures of [(2,6‐iPr2C6H3N)2Mo(Cl)(η2‐P=PtBu2)]– (7Mo), [(2,6‐iPr2C6H3N)2Mo(Cl)(η2‐P=PiPr2)]– (8Mo), [(2,6‐iPr2C6H3N)2Mo(Cl)(1,2‐η‐tBu2P=P–PtBu2)] (3Mo) and [(2,6‐iPr2C6H3N)2W(Cl)(1,2‐η‐tBu2P=P–PtBu2)] (3W) were established by single‐crystal X‐ray diffraction analysis.
A PVC Membrane Sensor for Potentiometric Determination of Atorvastatin in Biological Samples and Pharmaceutical Preparations
Authors: Saber Amr Lotfy
Published: November 2013

The present article reports for the first time the use of Aliquat 336S‐atorvastatin as an electroactive material in a poly(vinyl chloride) matrix membrane sensor plasticized with ortho‐nitrophenyl‐octylether (o‐NPOE) or dioctylphthalate (DOP) for determination of atorvastatin in biological samples (human plasma) and in pharmaceutical preparations. The sensor shows fast, stable and reproducible response over the concentration range of 1.0×10−7–1.0×10−2 mol L−1 atorvastatin with anionic slopes of 60.94±0.2 and 58.22±0.2 and pH range of 5.0–9.0 for o‐NPOE and DOP plasticized based membrane sensors, respectively. The response time of the sensor is stable and fast (10 s). Results were achieved with average recoveries of 99.5 % and 99.3 % and mean standard deviations of ±1.1 % and ±1.4 % for o‐NPOE and DOP plasticized based membrane sensors, respectively. The sensor exhibits high selectivity towards atorvastatin in the presence of many anions, drug excipients and diluents. Validation of the method according to the quality assurance standards shows suitability of the proposed sensors for use in the quality control assessment of the drug.
Mixed Convection Effect on Melting from a Vertical Plate Embedded in Porous Medium with Soret and Dufour Effects
Authors: Jha Basant K. , Mohammed Umaru
Published: November 2013

The present work analyzed the impact of mixed convection on melting from a vertical flat plate embedded in porous medium in the presence of Dufour and Soret effects. The partial differential equations governing the problem under consideration have been transformed by a similarity transformation into a system of ordinary differential equation which is solved numerically by Runge–Kutta–Gill methods. Dimensionless velocity, temperature, and concentration profiles are presented graphically for various values of the Dufour number (Df), Soret number (Sr), melting parameter (M), and buoyancy parameter (Gr/Re). During the investigation, it was found that the melting phenomenon decreases the local Nusselt number and local Sherwood number at the solid–liquid interface. Also, it is interesting to note that the velocity as well as temperature increases while the concentration decreases with an increase in the Dufour number Df (or simultaneous decrease in the Soret number Sr). © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(7): 667–676, 2014; Published online 3 October 2013 in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21113
Passive sampling methods for contaminated sediments: Scientific rationale supporting use of freely dissolved concentrations
Authors: Mayer Philipp , Parkerton Thomas F , Adams Rachel G , Cargill John G , Gan Jay , Gouin Todd , Gschwend Philip M , Hawthorne Steven B , Helm Paul , Witt Gesine , You Jing , Escher Beate I
Published: November 2013

Passive sampling methods (PSMs) allow the quantification of the freely dissolved concentration (Cfree) of an organic contaminant even in complex matrices such as sediments. Cfree is directly related to a contaminant's chemical activity, which drives spontaneous processes including diffusive uptake into benthic organisms and exchange with the overlying water column. Consequently, Cfree provides a more relevant dose metric than total sediment concentration. Recent developments in PSMs have significantly improved our ability to reliably measure even very low levels of Cfree. Application of PSMs in sediments is preferably conducted in the equilibrium regime, where freely dissolved concentrations in the sediment are well-linked to the measured concentration in the sampler via analyte-specific partition ratios. The equilibrium condition can then be assured by measuring a time series or a single time point using passive samplers with different surface to volume ratios. Sampling in the kinetic regime is also possible and generally involves the application of performance reference compounds for the calibration. Based on previous research on hydrophobic organic contaminants, it is concluded that Cfree allows a direct assessment of 1) contaminant exchange and equilibrium status between sediment and overlying water, 2) benthic bioaccumulation, and 3) potential toxicity to benthic organisms. Thus, the use of PSMs to measure Cfree provides an improved basis for the mechanistic understanding of fate and transport processes in sediments and has the potential to significantly improve risk assessment and management of contaminated sediments. Integr Environ Assess Manag 2014;10:197–209. © 2014 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of SETAC.

Key Points

Passive sampling methods (PSMs) can quantify the freely dissolved concentration (Cfree) of a hydrophobic organic contaminant in sediment. Cfree is directly related to chemical activity, which drives diffusive uptake into benthic organisms and exchange across the sediment-water interface. Cfree and chemical activity offer a well-defined basis for the mechanistic understanding of fate and transport processes in sediments and for predicting adverse effects to benthic organisms. Recent developments in PSMs are advancing practical application to improve risk assessment and management of contaminated sediments.
Ultrasound‐assisted fabrication of a biocompatible magnetic hydroxyapatite
Authors: Zhou Gang , Song Wei , Hou Yongzhao , Li Qing , Deng Xuliang , Fan Yubo
Published: November 2013

This work describes the fabrication and characterization of a biocompatible magnetic hydroxyapatite (HA) using an ultrasound‐assisted co‐precipitation method. X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), and transmission electron microscopy (TEM) were used to characterize the structure and chemical composition of the produced samples. The M–H loops of synthesized materials were traced using a vibrating sample magnetometer (VSM) and the biocompatibility was evaluated by cell culture and MTT (3‐(4,5‐dimethylthiazol‐2‐yl)−2,5‐diphenyltetrazolium bromide) assay. Furthermore, in vivo histopathological examinations were used to evaluate the potential toxicological effects of Fe3O4‐HA composites on kidney of SD rats injected intraperitoneally with Fe3O4‐HA particles. The results showed that magnetic iron oxide particles first replace OH ions of HA, which are parallel to the c axis, and then enter the HA crystal lattice which produces changes in the crystal surface of HA. Chemical bond interaction was observed between PO43− groups of HA and iron ions of Fe3O4. The saturation magnetization (MS) of Fe3O4‐HA composites was 46.36 emu/g obtained from VSM data. Cell culture and MTT assays indicated that HA could affect the growth and proliferation of HEK‐293 cells. This Fe3O4‐HA composite produced no negative effects on cell morphology, viability, and proliferation and exhibited remarkable biocompatibility. Moreover, no inflammatory cell infiltration was observed in kidney histopathology slices. Therefore, this study succeeds to develop a Fe3O4‐HA composite as a prospective biomagnetic material for future applications. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3704–3712, 2014.
Human Variation and Risk Assessment: Microarray and Other Studies Utilizing Human Hepatocytes and Human Liver Subcellular Preparations
Authors: Hodgson Ernest , Wallace Andrew D. , Shah Ruchir R. , Choi Kyoungju , Joo Hyun
Published: November 2013

The new paradigms proposed for human health risk assessment stress the need for the use of human and human‐derived cell lines, and this review summarizes the use of primary human hepatocytes and hepatocyte subcellular preparations for the investigation of the metabolism and metabolic interactions of environmental chemicals. This includes interactions based on inhibition, induction, and activation. The role of cytotoxicity is also considered. The use of hepatocytes and hepatocyte preparations provides especially important information for the investigation of human variation and is summarized. This area is, at present, relatively neglected but will in the future be essential for accurate assessment of human health risk. A detailed summary of an initial attempt to utilize microarray technology for the study of genome‐wide effects is included.
Robert Owen in the History of the Social Sciences: Three Presentist Views
Authors: Pūras Adomas
Published: November 2013

This paper argues that the present‐day disagreements over the right course for sociology and its public role are reflected and paralleled in contemporary historiography of Robert Owen, British social reformer and a self‐described social scientist. Historical accounts, written from the perspectives of public sociology, “pure science” sociology, and anti‐Marxism, interpret Owen's historical role in mutually antithetical and self‐serving ways. Contrasting the three presentist accounts, I engage in an analysis of “techniques of presentism”—history‐structuring concepts, such as “disciplinary founder” and “disciplinary prehistory,” that allow presentist authors to get their effects. Along the way, I elaborate Peter Baehr's classification of sociology's founders.
DWI findings of autoimmune pancreatitis: Comparison between symptomatic and asymptomatic patients
Authors: Oki Hodaka , Hayashida Yoshiko , Oki Haruka , Kakeda Shingo , Aoki Takatoshi , Taguchi Masashi , Harada Masaru , Korogi Yukunori
Published: November 2013

Purpose

To compare the MR findings including diffusion‐weighted imaging (DWI) between symptomatic and asymptomatic patients with autoimmune pancreatitis (AIP) and to determine whether DWI can be used as an objective biomarker for symptomatic AIP, which is considered an indication for steroid therapy.

Materials and Methods

This retrospective study was approved by our institutional review board. MRI scans from 37 patients with AIP (symptomatic, n = 19; asymptomatic, n = 18) were retrospectively evaluated. The imaging studies were performed on a 1.5 Tesla scanner and assessed for parenchymal enlargement, narrowing of the main pancreatic duct, hypointensity on fat‐suppressed T1‐weighted images (FS‐T1WI), a capsule‐like rim, extrapancreatic lesions, and hyperintensity on DWI. The findings were compared by univariate and multivariate logistic regression analysis. Apparent diffusion coefficient (ADC) values were also calculated.

Results

Multivariate analysis showed that hyperintensity on DWI were most significantly associated with the symptoms of AIP (odds ratio = 28.2; P = 0.003). Interobserver agreement for DWI was also high. The ADC values were significantly lower in symptomatic than in asymptomatic patients (0.94 ± 0.17 versus 1.16 ± 0.16 × 10−3 mm2/s, P < 0.001). Receiver operating characteristic curve analysis of the ADC values to differentiate between symptomatic and asymptomatic patients showed that sensitivity was 68.4%, specificity 83.3%, and AUC 0.74.

Conclusion

Signal intensity on DWI and ADC value were well correlated with the active symptoms of AIP patients. DWI may be useful as an objective biomarker for determining the indication for steroid therapy. J. Magn. Reson. Imaging 2015;41:125–131. © 2013 Wiley Periodicals, Inc.
Implementation of two‐dimensional L‐COSY at 7 tesla: An investigation of reproducibility in human brain
Authors: Verma Gaurav , Hariharan Hari , Nagarajan Rajakumar , Nanga Ravi P.R. , Delikatny Edward J. , Albert Thomas M. , Poptani Harish
Published: November 2013

Purpose

To evaluate the utility of two‐dimensional (2D) Localized Correlated Spectroscopy (L‐COSY) in metabolic profiling of the human brain at 7 Tesla (T).

Materials and Methods

The 2D L‐COSY sequence was implemented at 7T and its reliability was assessed by test–retest studies of a metabolite phantom and a healthy volunteer. L‐COSY data were acquired from the occipital lobe of healthy subjects (n = 6; all male; age, 30–72 years) to assess intersubject variability. Additionally, two subjects underwent scans from the parieto‐occipital region, basal ganglia, frontal lobe or dorsolateral prefrontal cortex to test the versatility of L‐COSY in studying differing anatomy. Integral/volume measurements of L‐COSY spectra were used to estimate normalized metabolite‐to‐creatine concentrations.

Results

Phantom test–retest studies revealed coefficients of variation (CVs) of 3–20% for most metabolites. Human 2D L‐COSY spectra permitted detection of several metabolite resonances from multiple locations and inter‐subject variation studies demonstrated CVs of 4–26%. Cross‐peaks from gamma‐aminobutyric acid (GABA), isoleucine (Ile), lysine (Lys) and Ethanolamine (Eth) were quantified, which are not readily resolvable with conventional one‐dimensional (1D) MR spectroscopy.

Conclusion

2D L‐COSY at 7T demonstrated improved sensitivity in detecting additional metabolites with reliability comparable to established techniques at lower fields, which may aid in the metabolic assessment of diseased states. J. Magn. Reson. Imaging 2014;40:1319–1327. © 2013 Wiley Periodicals, Inc.
Dopamine and Cu+/2+ can induce oligomerization of α‐synuclein in the absence of oxygen: Two types of oligomerization mechanisms for α‐synuclein and related cell toxicity studies
Authors: Ha Yonghwang , Yang Aerin , Lee Seyoung , Kim Kibong , Liew Hyunjeong , Lee Sang Hyung , Lee Ju Eun , Lee Hong‐In , Suh Yoo‐Hun , Park Hee‐Sung , Churchill David G.
Published: November 2013

α‐Synuclein oligomers can induce neurotoxicity and are implicated in Parkinson's disease etiology and disease progression. Many studies have reported α‐synuclein oligomerization by dopamine (DA) and transition metal ions, but few studies provide insight into joint influences of DA and Cu2+. In this study, DA and Cu2+ were coadministered aerobically to measure α‐synuclein oligomerization under these conditions. In the presence of oxygen, DA induced α‐synuclein oligomerization in a dose‐dependent manner. Cu+/2+ did not effect oligomerization in such a manner in the presence of DA. By electrophoresis, Cu2+ was found easily to induce oligomerization with DA. This implies that oligomerization invoked by DA is reversible in the presence of Cu2+, which appears to be mediated by noncovalent bond interactions. In the absence of oxygen, DA induced less oligomerization of α‐synuclein, whereas DA/Cu2+ induced aerobic‐level amounts of oligomers, suggesting that DA/Cu2+ induces oligomerization independent of oxygen concentration. Radical species were detected through electron paramagnetic resonance (EPR) spectroscopic analysis arising from coincubation of DA/Cu2+ with α‐synuclein. Redox reactions induced by DA/Cu2+ were observed in multimer regions of α‐synuclein oligomers through NBT assay. Cellular toxicity results confirm that, for normal and hypoxic conditions, copper or DA/Cu2+ can induce cell death, which may arise from copper redox chemistry. From these results, we propose that DA and DA/Cu2+ induce different mechanisms of α‐synuclein oligomerization, cross‐linking with noncovalent (or reversible covalent) bonding vs. likely radical‐mediated covalent modification. © 2013 Wiley Periodicals, Inc.
GC models for separation optimization in pressure‐tunable tandem capillary columns operated isothermally
Authors: Veschetti Enrico , Russo Mario Vincenzo
Published: November 2013

In the previous part of this study, a significant improvement of the fundamental relationships that control GC resolution in a pressure‐tunable assembly operating in isothermal conditions inside a single oven was made. A theoretical approach for the correct choice of the working temperature was proposed for the first time. In this second part of our report, a new interfacing device has been proposed for a rapid and reliable alignment of the two columns at the midpoint junction. Moreover, the results of a series of experimental tests have confirmed the validity of the proposed mathematical models.
Stereoselective Condensation of L‐Lactic Acid in Presence of Heterogeneous Catalysts
Authors: Raase Jennifer Marina , Reichert Karl‐Heinz , Schomäcker Reinhard
Published: November 2013

Melt phase condensation of L‐lactic acid with heterogeneous catalysts was performed at 0.5 mbar and 180 °C for 1 to 5 h, aiming at enantiopure products. The products were characterized by DSC, HPLC,1H‐NMR spectroscopy and GPC. Zirconium sulfate tetrahydrate was found to be a suitable catalyst with respect to its selectivity and activity. The activity of this catalyst depends on the calcination conditions. By supporting the catalyst on an acidic material with a very high specific surface area, the catalytic activity can be strongly increased without losing selectivity. Products with nearly 100 mol% L‐lactic acid units were obtained even at high conversion and catalyst concentration.
Stimuli‐Responsive Hydrogels Synthesis using Free Radical and RAFT Polymerization
Authors: Gonçalves Miguel A. D. , Pinto Virgínia D. , Costa Rita A. S. , Dias Rolando C. S. , Hernándes‐Ortiz Julio C. , Costa Mário Rui P. F. N.
Published: November 2013

Temperature and pH stimuli‐responsive hydrogel particles were synthesized using inverse‐suspension polymerization in batch stirred reactor. Different water soluble co‐monomers were present in the initial mixture (e.g. N‐isopropylacrylamide and acrylic acid) as well as crosslinkers with different functionalities. Different operating conditions such as polymerization temperature, monomers dilution, neutralization and the initial ratios of co‐monomers and monomers/crosslinker were also tried. Hydrogel particles were produced considering classical free‐radical polymerization (FRP) and also RAFT polymerization. Commercially available RAFT agents 4‐cyano‐4‐phenylcarbonothioylthio‐pentanoic acid (CPA), 2‐(dodecylthiocarbonothioylthio)‐2‐methylpropionic acid (DDMAT) and cyanomethyl dodecyl trithiocarbonate (CDT) were alternatively used. Sampling at different polymerization times allowed the study of the kinetics of polymerization through the analysis by SEC of the soluble phase. A tetra‐detector array with simultaneous detection of refractive index, light scattering, intrinsic viscosity and ultra‐violet signals was used in these studies. Usefulness of in‐line FTIR‐ATR monitoring to study the building process of such networks was also assessed. The performance of hydrogel beads was studied through drug delivery tests triggered by changes in the environmental temperature and pH. This research aims to contribute for the elucidation of the connection between the synthesis conditions, molecular architecture and properties/performance of such advanced materials.
Effect of Six Technical Lignins on Thermo‐Mechanical Properties of Novolac type Phenolic Resins
Authors: Martínez Juan D. , Velásquez Jorge A.
Published: November 2013

Lignin has been studied as an alternative to phenol in phenolic resins, due to economic and environmental reasons. The possibility of partially replacing phenol in phenol–formaldehyde (PF) resins by different types of lignins and analyze the lignin functional groups influence on the thermo‐mechanical properties of the resins, has been explored. Novolac phenolic resins were prepared with six lignins: five lignins from black liquor of soda pulping bagasse and a commercial ammonium lignosulphonate from pinus taeda (LSA). These lignins have different percentages of functional groups (OH aromatic carbonyls and methoxyl) and polysaccharides. The kinetic study found that modified resins elaborated with lignin LSA exhibit the highest values of activation energy (148.66 and 148.92 kJ mol−1 in models of Flynn‐Wall‐Osawa and Friedman respectively), resulting to be the most stable of modified resins. Finally, this same resin has the highest value of the modulus of elasticity (MOE) of 8.02 GPa, even higher than unmodified phenolic resins. Therefore, LSA lignin, showed the best results in friction phenolic resins, this would imply the stability is within the bio‐polymer and attributable to the linkage between PF and lignin.
Modelling of Spray Polymerisation Processes
Authors: Säckel Winfried , Nieken Ulrich
Published: November 2013

Spray polymerisation is a technique to carry out polymerisations in a highly efficient manner. As experimental optimisation of process parameters is tedious, simulations of the processes inside a single droplet are desirable. Today's models used in spray polymerisation assume ideal mixing and thus do not resolve the particle state along the radius. In this contribution we derive a single particle model for the case of free radical polymerisation, which spatially resolves the physical and chemical processes. The model allows for predicting inhomogeneity of the polymeric product as a function of drying conditions. The state of the polymer is calculated using the method of moments.
Study of the Segregated Behavior of Anionic Microfluidic Polymerization
Authors: Cortese Bruno , Schulze Simon , de Croon Mart , Hessel Volker , Klemm Elias
Published: November 2013

In order to explain the reasons behind the good performance of a microfluidic reactor for anionic polymerization of a commercial polymer ‐ narrow polydispersity index, PDI, of 1.04 (unpublished results of FP7 COPIRIDE project) ‐ modeling of styrene was selected as test system. A comprehensive model accounting for the changes of all the relevant physical parameters was developed and used to compute the fluid dynamics inside the microreactor. The results show that despite the small characteristic dimension of the system an almost segregated behavior is obtained as a consequence of the reaction. This effect leads to the counterintuitive finding that, despite having a very large residence time distribution in the microreactor, polymers with very low PDIs are obtained in a quality as mentioned above.
Emulsion Polymerization Using Switchable Surfactants: A Route Towards Water Redispersable Latexes
Authors: Su Xin , Fowler Candace , O'Neill Catherine , Pinaud Julien , Kowal Erica , Jessop Philip , Cunningham Michael
Published: November 2013

Colloidal latexes of polystyrene and poly(methyl methacrylate) have been prepared by emulsion polymerization using amidine‐based switchable surfactants. Particles with sizes ranging from 50 nm to 350 nm were obtained. Destabilization of the latexes requires only air and heat which destabilize the latex by removing CO2 from the system. The resulting micron sized particles can be easily filtered to yield a dry polymer powder and a clear aqueous phase. We have also developed a new benign means of reversibly coagulating anionic latexes by using “switchable water”, an aqueous solution of switchable ionic strength. The addition of CO2 and switchable water to an anionic latex can result in aggregation of the latex. Subsequent removal of CO2 by sparging with air allows the aggregated latex to be redispersed and recovered in its original state.
Relationship between raised BMI and sugar sweetened beverage and high fat food consumption among children
Authors: Millar Lynne , Rowland Bosco , Nichols Melanie , Swinburn Boyd , Bennett Catherine , Skouteris Helen , Allender Steven
Published: November 2013

Objective

Longitudinal evidence of relationships between unhealthy diets and BMI in children is crucial for appropriately targeting obesity prevention activities. The objective was to determine the relationship between frequency of consumption of sugar sweetened beverages (SSBs) and high fat foods (HFFs) and body weight in Australian children aged from 4 to 10 years.

Methods

Data from 4,164 children participating in four waves (wave 1, 2004; wave 2, 2006; wave 3, 2008; and wave 4, 2010) of the Longitudinal Study of Australian Children were analyzed. A multi‐level growth model tested relationships between consumption of SSB and HFF and BMI z‐scores.

Results

BMI z‐scores were associated with daily consumption of HFF, SSB and maternal BMI independent of BMI z‐scores at wave 1 (baseline); with each additional occurrence of SSB and HFF consumption intake per day, BMI z‐score increased by 0.015 U (P < 0.01) and 0.014 U (P < 0.001), respectively. With each additional maternal BMI unit, BMI z‐score increased by 0.032 (P < 0.001).

Conclusions

Higher BMI z‐scores were strongly associated with the consumption of SSBs and HFFs. Future efforts to prevent obesity should consider urgent action to address the impact of the consumption of SSBs and HFFs in childhood.
Nanomechanics of Carbon Nanotubes
Authors: Sun Y.W. , Dunstan D.J. , Hartmann M.A. , Holec D.
Published: November 2013

We discuss the mechanical properties of carbon nanotubes, in particular the pressure‐dependence of the Raman modes and the collapse pressure, and their relation to the corresponding mechanical properties of graphite and graphene. The frequencies of the Raman G‐mode and radial breathing mode (RBM), as well as the pressure dependence of the RBM can be largely‐explained in the existing framework of C–C stretching modes and envirionmental effects induced by the pressure medium. The pressure dependence of the G‐mode is still missing such an explanation. The collapse pressure can be understood in terms of the continuum theory for thin‐walled tubes. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromechanical Simulation of the Hall‐Petch Effect with a Crystal Gradient Theory including a Grain Boundary Yield Criterion
Authors: Wulfinghoff Stephan , Bayerschen Eric , Böhlke Thomas
Published: November 2013

A viscoplastic strain gradient crystal plasticity theory based on the gradient of the equivalent plastic strain ∇γeq is proposed. A grain boundary yield condition is introduced. The microstructural explanation of the Hall‐Petch effect, accounting for notch‐like stress concentrations at the grain boundary as a result of discrete slip bands, is reviewed. Periodic tensile test FEM simulation results illustrate the prediction of the numerical model. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelbased Investigations of Gyroscopic Effect on the (Elasto‐)Kinematics of Suspension Systems
Authors: Kohl Sergej , Zuber Armin , Sextro Walter
Published: November 2013

During wheel bumping caused by stochastic road excitation, the wheel performs rotational and translational movements. The bump and rebound wheel velocity leads to significant angular velocities based on the (elasto‐)kinematics of the suspension system. Based on the gyroscopic effect, moments arise about the rotating wheel induced by the angular change while bumping. Therefore it leads to undesirable wheel changes and degrades the tire contact and finally decreases the driving stability. A flexible MBS‐model of the five‐link rear axle system that includes these effects has been built up to allow a detailed investigation of the gyroscopic effect. Using the simulation results, conclusions can be drawn for refining design criteria for the kinematics, elastokinematics and topology of the suspension system to increase the active safety of the vehicle. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computing time investigations for variational multirate integration
Authors: Gail Tobias , Leyendecker Sigrid , Ober‐Blöbaum Sina
Published: November 2013

Consider a mechanical system that contains slow and fast dynamics. Let it be possible, to split the potential energy into a slow and a fast potential and the configuration vector into slow and fast variables. For such systems, multirate schemes simulate the different parts using different time steps with the goal to save computing time. For the proposed multirate scheme, a time grid consisting of micro and macro nodes is used and the integrator is derived from a discrete variational principle. Variational integrators conserve properties like symplecticity and momentum maps and have good energy behavior. To solve the resulting system of coupled nonlinear equations, a Newton‐Raphson iteration with an analytical Jacobian is used. It is demonstrated that the multirate approach leads to less computing time compared to singlerate simulation by means of three example systems, the Fermi‐Pasta‐Ulam problem, a triple spherical pendulum and a simple atomistic model, where the latter two are subject to constraints. Computing times are compared for different numbers of micro and macro nodes for dynamic simulations during a certain time interval. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parametric frequency analysis of oscillatory behavior of mouse Zona Pellucida spherical net model: cases of successful and of unsuccessful fertilization
Authors: Hedrih Andjelka , Lazarevic Mihailo , Mitrovic‐Jovanovic Ana
Published: November 2013

The current paper proposes a model for describing mechanical phenomena that occur during the process of mammal fertilization when spermatozoa impact the surface of Zona Pellucida. Zona pellucida (ZP) is a dynamical 3D matrix that surrounds the mammalian oocyte. In the process of fertilization, sperm cell has to penetrate this structure. To describe impact of sperm cells with velocities that are effective and those that are ineffective relative to the oscillatory behavior of ZP, the discreet continuum model in the form of spherical net model is used. Resultant trajectories of knot mass particles dynamics of mouse ZP spherical net model in the form of generalized Lussajous curves are presented. Using generalized Lussajous curves, parametric frequency analysis of oscillatory behavior of knot material particles in the mouse ZP spherical net model is conducted. The influence of impact angles of sperm cells on corresponding knot mass particle trajectory is discussed. Favorable and unfavorable trajectories of knot mass particle motions are discussed in the context of successful fertilization. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the treatment of active behaviour in continuum muscle mechanics
Authors: Heidlauf Thomas , Röhrle Oliver
Published: November 2013

Two approaches of including active contractile behaviour of muscle tissue written in a continuum‐mechanical formulation are presented. One approach relies on the addition of active and passive stress contributions, while the other approach is based on a multiplicative decomposition of the deformation gradient tensor. Both formulations can be stated in a thermodynamically consistent manner, each with different constraints, and both models can reproduce experimental data of passive and fully active muscle. Different behaviours are observed when comparing the active muscle models at submaximal stimulation rates. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Phase Field Approach for Dynamic Fracture
Authors: Kuhn Charlotte , Schlüter Alexander , Müller Ralf
Published: November 2013

In phase field fracture models cracks are indicated by the value of a scalar field variable which interpolates smoothly between broken and undamaged material. The evolution equation for this crack field is coupled to the mechanical field equations in order to model the mutual interaction between the crack evolution and mechanical quantities. In finite element simulations of crack growth at comparatively slow loading velocities, a quasi‐static phase field model yields reasonable results. However, the simulation of fast loading or the nucleation of new cracks challenges the limits of such a formulation. Here, the quasi‐static phase field model predicts brutal crack extension with an artificially high crack speed. In this work, we analyze to which extend a dynamic formulation of the mechanical part of the phase field model can overcome this paradox created by the quasi‐static formulation. In finite element simulations, the impact of the dynamic effects is studied, and differences between the crack propagation behavior of the quasi‐static model and the dynamic formulation are highlighted. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical modelling of local‐global buckling mode interaction of sandwich struts
Authors: Völlmecke Christina , Müller Wolfgang H.
Published: November 2013

A numerical approach simulating the effects of coupled local‐global mode interaction on the postbuckling of axially compressed sandwich beam columns is presented. The formulation is based on the weak form of the balance of linear momentum whilst large strains are considered. An open source software is used to solve the formulation and results are presented showing good phenomenological agreement with analytically derived solutions. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the folding of plates which buckle before and beyond the elastic limit
Authors: Müller Bernhard , Schagerl Martin , Schöder Kai‐Uwe
Published: November 2013

Simply supported rectangular elasto‐plastic plates which are uniformly compressed buckle either before or beyond the elastic limit. Consequently, the post critical behaviour, the position of first membrane yield and folding mode differ significantly whether buckling happens before or beyond the elastic limit. A distinct folding‐line perpendicular to the loading direction develops only for plates which buckle beyond the elastic limit. This article analysis the post‐buckling behaviour and the folding mode of uniformly compressed plates and points out the correlation to the folding mode of axially crushed profiles. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new method for the connection of non‐conforming NURBS patches in isogeometric analysis
Authors: Dornisch Wolfgang , Klinkel Sven
Published: November 2013

The main objective of isogeometric analysis is the use of one common data set for design and analysis. Geometrical models usually consist of multiple NURBS surface patches with non‐matching parametrizations along common edges. The ability to handle non‐conforming meshes is essential for isogeometric finite element systems to avoid manipulations of the geometry model. In general two possible strategies exist. The first one is to enhance the weak form of the potential with additional terms to constrain the deformations of adjacent edges to be equal, e.g. with the Lagrange Multiplier method. The second one is to establish a relation between the deformations of adjacent patches. Thus, superfluous degrees of freedom are condensated out of the system and the patches are connected naturally by shared degrees of freedom. No alteration of the weak form is necessary which simplifies the implementation in existing finite element systems. For adjacent edges with hierarchic knot vectors an analytical solution exists. In the general case of non‐hierarchic knot vectors it is not possible to find an analytical solution. This contribution presents a new numerical method to establish this relation. A collocation along the connection line links the deformations of adjacent patches. A theoretical derivation of the method is given and the choice of the collocation points is investigated. Numerical studies compare the new method with the Lagrange Multiplier method and show its applicability. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modellierung der Bewegung von Wasserrinnsalen auf Zylinderoberflächen in Interaktion mit der Luftumströmung
Authors: Seidel Christian , Dinkler Dieter
Published: November 2013

Die Beweglichkeit von Wasserrinnsalen auf Zylinderoberflächen besitzt beim hydroaeroelastischen Phänomen der Regen‐Wind induzierten Schwingungen, welches bei geneigten Kabeln und Hängern von Schrägkabelbrücken und Bogenbrücken durch gleichzeitiges Auftreten von Regen und Wind entstehen kann, eine elementare Bedeutung für den Erregermechanismus [1]. Bei der Untersuchung des Schwingungsphänomens ist bei der Modellierung der Rinnsale neben der Beschreibung ihrer Beweglichkeit auch die genaue Kenntnis ihrer Gleichgewichtslagen auf der Zylinderoberfläche wichtig. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constitutive modeling of cyclic stress softening in filled elastomers
Authors: Khiêm Vu Ngoc , Dargazany Roozbeh , Itskov Mikhail
Published: November 2013

Quasi‐static cyclic loading tests on filled rubber‐like materials reveal a significant stress softening in the first cycle. The magnitude of this softening, widely known as the Mullins effect, reduces in the next cycles until it reaches a stabilized value referred to as hysteresis. In this contribution, we associate the hysteresis with the fracture of carbon bonds in the filler network. In order to calculate the cyclic energy dissipation, we modify the classic concept of network decomposition [1, 2] and add a new network considered to be responsible for the breakage and re‐formation of carbon black aggregates during loading and unloading. The proposed model is in‐line with a wide range of experimental observations. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of energy dissipation in visco‐elastic materials at finite deformation
Authors: Behnke Ronny , Kaliske Michael
Published: November 2013

In this contribution, the derivation of the energy dissipation rate in generalized visco‐elastic material models with internal stress‐type variables and linear evolution equations is outlined. The approximated dissipation rate is computed from a positive quadratic form of the nonlinear non‐equilibrium stresses and the inverse of the consistent material tangent tensor. The presented method is used to compute the energy dissipation of visco‐elastic rubber material in a large scale application of a steady state rolling tire structure. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite Element Simulation of Steel Solidification under High Temperature
Authors: Moj Lukas , Ricken Tim , Göhler Klaus
Published: November 2013

Finite element simulation of hot working of steel has gained significant importance in steel industries. The aim of describing such processes using the finite element method is to predict phenomena like shrinkage during solidification. Due to this thermo‐mechanical behaviour residual stresses appear, which cause cracks and the final steel slab loses its required properties as a result. We propose a two‐phase incompressible model based on the Theory of Porous Media (TPM) for a numerical description of steelmaking processes. A thermo‐mechanical coupling is required to model a high temperature‐dependency. In order to consider thermal expansion of solid, a multiplicative decomposition of the deformation gradient into a mechanical and a thermal part has been applied. The Von Mises J2 plasticity with isotropic hardening criterion has been selected for the solid‐phase of the model. Representative numerical examples, as well as the influence of single material parameters on the model will be shown. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Phase Field Approach for Martensitic Transformations in Elastoplastic Materials
Authors: Schmitt Regina , Müller Ralf , Skorupski Robert , Smaga Marek , Eifler Dietmar
Published: November 2013

A multivariant phase field model for martensitic transformations in elastoplastic materials is introduced which is in mathematical terms the regularization of a sharp interface approach. The evolution of microstructure is assumed to follow a time dependent Ginzburg‐Landau equation. The coupled problem of the mechanical balance equation and the evolution equations is solved using finite elements and an implicit time integration scheme. In this work, plasticity is considered for the austenitic phase which influences the martensitic evolution. With aid of the model these interactions are studied in detail. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of a membrane flow interaction by an iteration based on a panel method
Authors: Steinrück Herbert , Müllner Markus
Published: November 2013

A flow structure interaction of a membrane and a fluid is investigated. A conventional segregated numerical algorithm, where the membrane deformation and the flow dynamics are calculated alternately has to fail due to the artificial added mass instability. Thus, a new iteration scheme is proposed. In order to get a good prediction for the deformation of the membrane, the equations describing the membrane are coupled to a potential flow solver (panel method). Then a CFD solver can be used to determine the corrections of the flow field due viscosity and turbulence. An example is presented that this procedure seems to be numerically stable. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)