bluuebunny/crossref_metadata_2025 huggingface dataset:
Micro‐gels for impact protection
Authors: Zhou Chao , Wang Bo , Zhang Fengtao , Xu Kun , Han Changyu , Hu Hong , Liu Yanpin , Wang Pixin , Xin John H.
Published: May 2013

A novel kind of impact protective material, named as impact protective micro‐gel (IPM), was synthesized via a precipitation copolymerization of a compound containing boron and silanol. Diphenylmethane diisocyanate (MDI) was introduced as the chain extender to enhance its impact protective performance. Its rheological properties and morphology were investigated. Three‐dimensional (3D) spacer warp‐knitted fabrics were dip‐coated with the IPM made with and without use of MDI, and the impact protective performance of 3D finished fabrics was assessed by drop impact tests. The results show that the adjustment of the MDI content can adjust the real cross‐linking density of the IPM due to the entanglement of polymer chains, and an appropriate cross‐linking density can endow dilatant properties to the IPM samples. The results also show that the impact protective performance of 3D spacer fabrics finished with the IPM can be significantly improved. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2345–2351, 2013
Differential leaf‐litter processing by native (Gammarus pulex) and invasive (Dikerogammarus villosus) freshwater crustaceans under environmental extremes
Authors: Truhlar Allison M. , Dodd Jennifer A. , Aldridge David C.
Published: May 2013

There is increasing interest in understanding the implications of biological invasions within the context of ecosystem functioning. Non‐native crustaceans are of particular interest within fresh waters because of their important contributions to leaf‐litter processing. The alien amphipod Dikerogammarus villosus is spreading rapidly through Europe where it has displaced native gammarids including Gammarus pulex. The resultant change in shredder communities has considerable implications for the dynamics of resource availability within invaded systems.

The invasive success of D. villosus has been attributed to many characteristics, including its ability to tolerate a wide range of environmental conditions and to exploit a wide feeding niche. These characteristics are thought to give D. villosus an advantage over native species, especially in habitats subject to changing environmental conditions.

The leaf (Salix alba) shredding efficiency, defined as the leaf mass consumed over the 4‐day experiment per amphipod‐day, was measured for D. villosus and G. pulex under extreme temperature and conductivity conditions, in single species and mixed species aquaria.

At high temperatures (25°C), D. villosus shredded significantly more leaves than size‐matched G. pulex. Conductivity extremes had no species effect; overall leaf‐shredding efficiency was significantly greater at low conductivity (250 μS cm‐1) than high conductivity (1870 μS cm‐1).

An inspection of daily leaf disc consumption found that the two species showed significantly different leaf consumption patterns, with D. villosus consuming more leaves earlier in the experiment.

These results suggest that D. villosus invasion could lead to ecosystem‐level changes in leaf processing, such as greater leaf processing earlier in autumn and at higher temperatures, which could alter nutrient dynamics and community assemblages within invaded systems. Such effects may not be reflected in biotic indices used to assess ecological status, as these indices do not currently distinguish between native and invasive species in the same family.

Copyright © 2013 John Wiley & Sons, Ltd.
Facile Synthesis of Aluminum‐Based Metal–Organic Frameworks with Different Morphologies and Structures through an OH−‐Assisted Method
Authors: Lin Yichao , Kong Chunlong , Chen Liang
Published: May 2013

We report the facile synthesis of aluminum‐based metal–organic frameworks (MOFs) with different morphologies and structures by tuning the OH− content in the reaction solution. MIL‐96 crystals with dodecahedral and hexagonal column shapes were successfully synthesized by tuning the OH− ion content of the synthesis solution. When the OH− ion content was further increased, MIL‐110 with a nanorod morphology appeared as the product. For the first time, we obtained pure MIL‐96 and MIL‐110 under basic conditions directly by using the 1,3,5‐benzenetricarboxylic acid (btc) linker. All samples show significant thermal stability, with a decomposition temperature above 300 °C. We found that the gas adsorption properties of MIL‐96 were directly dominated by the crystal morphology. At 0.4 °C and 30 bar, the dodecahedral and hexagonal MIL‐96 samples can adsorb 9.3 and 6.5 mmol g−1 CO2, respectively, although they possess similar surface areas and identical crystalline structures. The MIL‐110 nanorod shows a CO2 adsorption capacity of up to 16 mmol g−1 under the same conditions.
Blinded and unblinded internal pilot study designs for clinical trials with count data
Authors: Schneider Simon , Schmidli Heinz , Friede Tim
Published: May 2013

Internal pilot studies are a popular design feature to address uncertainties in the sample size calculations caused by vague information on nuisance parameters. Despite their popularity, only very recently blinded sample size reestimation procedures for trials with count data were proposed and their properties systematically investigated. Although blinded procedures are favored by regulatory authorities, practical application is somewhat limited by fears that blinded procedures are prone to bias if the treatment effect was misspecified in the planning. Here, we compare unblinded and blinded procedures with respect to bias, error rates, and sample size distribution. We find that both procedures maintain the desired power and that the unblinded procedure is slightly liberal whereas the actual significance level of the blinded procedure is close to the nominal level. Furthermore, we show that in situations where uncertainty about the assumed treatment effect exists, the blinded estimator of the control event rate is biased in contrast to the unblinded estimator, which results in differences in mean sample sizes in favor of the unblinded procedure. However, these differences are rather small compared to the deviations of the mean sample sizes from the sample size required to detect the true, but unknown effect. We demonstrate that the variation of the sample size resulting from the blinded procedure is in many practically relevant situations considerably smaller than the one of the unblinded procedures. The methods are extended to overdispersed counts using a quasi‐likelihood approach and are illustrated by trials in relapsing multiple sclerosis.
Direct CH Bond Arylation of Indoles with Aryl Boronic Acids Catalyzed by Palladium Nanoparticles Encapsulated in Mesoporous Metal–Organic Framework
Authors: Huang Yuanbiao , Ma Tao , Huang Ping , Wu Dongshuang , Lin Zujin , Cao Rong
Published: May 2013

Highly dispersed Pd nanoparticles encapsulated in the mesoporous metal–organic framework MIL‐101 demonstrated high activity and selectivity for the direct C2 arylation of various indoles with aryl boronic acids using O2 or 2,2,6,6‐tetramethylpiperidine N‐oxyradical as an external oxidant in acidic media under mild conditions. The green catalyst is easily recoverable and can be reused six times without leaching and loss of activity.
Phosphate‐Tether‐Mediated Ring‐Closing Metathesis for the Preparation of Complex 1,3‐anti‐Diol‐Containing Subunits
Authors: Chegondi Rambabu , Maitra Soma , Markley Jana L. , Hanson Paul R.
Published: May 2013

An array of examples of diastereoselective, phosphate‐tether‐mediated ring‐closing metathesis reactions, which highlight the importance of product ring size and substrate stereochemical compatibility, as well as complexity, is reported. Studies focus primarily on the formation of bicyclo[n.3.1]phosphates, involving the coupling of C2‐symmetric dienediol subunits with a variety of simple, as well as complex, alcohol partners.
Simultaneously Probing Two Ultrafast Condensed‐Phase Molecular Symmetry Breaking Events by Two‐Dimensional Infrared Spectroscopy
Authors: Yang Fan , Yu Pengyun , Zhao Juan , Wang Jianping
Published: May 2013

In condensed phases, a highly symmetric gas‐phase molecule lowers its symmetry under perturbation of the solvent, which is vital to a variety of structural chemistry related processes. However, the dynamical aspects of solvent‐mediated symmetry‐breaking events remain largely unknown. Herein, direct evidence for two types of solvent‐mediated symmetry‐breaking events that coexist on the picosecond timescale in a highly symmetric anion, namely, hexacyanocobaltate, is presented: 1) an equilibrium symmetry‐breaking event in which a solvent‐bound species having lowered symmetry undergoes a population exchange reaction with the symmetry‐retaining species; 2) a dynamic symmetry‐breaking event that is composed of many dynamic population‐exchange reactions under fluctuating solvent interactions. Ultrafast two‐dimensional infrared spectroscopy is used to simultaneously observe and dynamically characterize these two events. This work opens a new window into molecular symmetry and structural dynamics under equilibrium and non‐equilibrium conditions.
Polyethyleneimine‐Functionalized Polyamide Imide (Torlon) Hollow‐Fiber Sorbents for Post‐Combustion CO2 Capture
Authors: Li Fuyue Stephanie , Qiu Wulin , Lively Ryan P. , Lee Jong Suk , Rownaghi Ali A. , Koros William J.
Published: May 2013

Carbon dioxide emitted from existing coal‐fired power plants is a major environmental concern due to possible links to global climate change. In this study, we expand upon previous work focused on aminosilane‐functionalized polymeric hollow‐fiber sorbents by introducing a new class of polyethyleneimine (PEI)‐functionalized polymeric hollow‐fiber sorbents for post‐combustion carbon dioxide capture. Different molecular weight PEIs (Mn≈600, 1800, 10 000, and 60 000) were studied as functional groups on polyamide imide (PAI, Torlon) hollow fibers. This imide ring‐opening modification introduces two amide functional groups and was confirmed by FTIR attenuated total reflectance spectroscopy. The carbon dioxide equilibrium sorption capacities of PEI‐functionalized Torlon materials were characterized by using both pressure decay and gravimetric sorption methods. For equivalent PEI concentrations, PAI functionalized with lower molecular weight PEI exhibited higher carbon dioxide capacities. The effect of water in the ring‐opening reaction was also studied. Up to a critical value, water in the reaction mixture enhanced the degree of functionalization of PEI to Torlon and resulted in higher carbon dioxide uptake within the functionalized material. Above the critical value, roughly 15 % w/w water, the fiber morphology was lost and the fiber was soluble in the solvent. PEI‐functionalized (Mn≈600) PAI under optimal reaction conditions was observed to have the highest CO2 uptake: 4.9 g CO2 per 100 g of polymer (1.1 mmol g−1) at 0.1 bar and 35 °C with dry 10 % CO2/90 % N2 feed for thermogravimetric analysis. By using water‐saturated feeds (10 % CO2/90 % N2 dry basis), CO2 sorption was observed to increase to 6.0 g CO2 per 100 g of sorbent (1.4 mmol g−1). This material also demonstrated stability in cyclic adsorption–desorption operations, even under wet conditions at which some highly effective sorbents tend to lose performance. Thus, PEI‐functionalized PAI fibers can be considered as promising material for post‐combustion CO2 capture.
Novel translinear differential implementation of rational functions with squared denominators
Authors: Carrasco‐Robles Manuel , Serrano Luis
Published: May 2013

This paper presents a novel generic translinear differential output stage that is useful for the implementation of rational functions with a squared denominator. As a proof of concept, such output stage is used to implement the first derivative of a rational activation function. Simulated results are presented for an implementation on a 0.35 µm CMOS process showing an almost perfect fit with the theoretical expressions. Copyright © 2013 John Wiley & Sons, Ltd.
Synthesis and Pharmacological Evaluation of New Pyridazin‐Based Thioderivatives as Formyl Peptide Receptor (FPR) Agonists
Authors: Crocetti Letizia , Vergelli Claudia , Cilibrizzi Agostino , Graziano Alessia , Khlebnikov Andrei I. , Kirpotina Liliya N. , Schepetkin Igor A. , Quinn Mark T. , Giovannoni Maria Paola
Published: May 2013

Preclinical Research

A new series of pyridazinone‐based thioderivatives and pyridazine analogs was synthesized and tested for their ability to bind to the three human formyl peptide receptor (FPR) isoforms (FPR1, FPR2, and FPR3) and to activate intracellular calcium mobilization and chemotaxis in human neutrophils. Among the pyridazin‐3(2H)‐one derivatives tested, analogs 8b and 8c were mixed FPR1/FPR2 agonists, with median effective concentration values in the micromolar range, and were able to activate chemotaxis and Ca2+ flux in human neutrophils in the low micromolar range. Molecular docking studies showed that interaction of a ligand with Arg205 of FPR1 is important for FPR1 agonist activity. For FPR2, differences in activity between oxygen‐containing compounds and their thio‐analogs were due to steric bulkiness of sulfur‐containing groups.
Developmental trajectories and breakdown in F1 interpopulation hybrids of Tribolium castaneum
Authors: Drury Douglas W. , Ehmke Ross C. , Jideonwo Victoria N. , Wade Michael J.
Published: May 2013

When hybrid inviability is an indirect by‐product of local adaptation, we expect its degree of severity between pairs of populations to vary and to be sensitive to the environment. While complete reciprocal hybrid inviability is the outcome of the gradual process of local adaptation, it is not representative of the process of accumulation of incompatibility. In the flour beetle, Tribolium castaneum, some pairs of populations exhibit complete, reciprocal F1 hybrid incompatibility while other pairs are fully or partially compatible. We characterize this naturally occurring variation in the degree and timing of expression of the hybrid incompatible phenotype to better understand the number of genes or developmental processes contributing to speciation. We assessed the morphological and developmental variation in four Tribolium castaneum populations and their 12 possible F1 hybrids at each life‐history stage from egg to adult. We find that the rate of hybrid larval development is affected in all interpopulation crosses, including those eventually producing viable, fertile adults. Hybrid incompatibility manifests early in development as changes in the duration of instars and diminished success in the transition between instars are relative to the parent populations. Parent populations with similar developmental profiles may produce hybrids with disrupted development. The degree and timing of expression of hybrid inviability depends upon populations crossed, direction of the cross, and environment in which hybrids are raised. Our findings suggest that the coordinated expression of genes involved in transitional periods of development is the underlying cause of hybrid incompatibility in this species.
Development of a new multiplex quantitative real‐time PCR assay for the detection of the mtDNA4977 deletion in coronary artery disease patients: A link with telomere shortening
Authors: Sabatino Laura , Botto Nicoletta , Borghini Andrea , Turchi Stefano , Andreassi Maria Grazia
Published: May 2013

Mitochondrial DNA (mtDNA) and telomere shortening have been proposed as important contributors to vascular disease and atherogenesis. The role of mitochondrial and telomere alterations has been examined frequently, but usually separately. Recently, an integrated model in which DNA damage and metabolic pathways intersect in age‐associated cardiovascular disease has been proposed. In this study we developed a fast and reliable real‐time PCR‐based procedure to investigate relative quantification of the 4,977 bp mitochondrial DNA deletion (also indicated as “mtDNA4977 deletion”), employing TaqMan probes with a multiplex approach. As a validation of the assay, a nested PCR coamplification was performed. Telomere shortening was evaluated by a real‐time monochrome multiplex PCR technique employing a SybrGreen‐based analysis. The study of mtDNA4977 deletion and telomere shortening was carried out in atrial biopsies from 11 patients undergoing coronary artery (n = 5) and valve surgery (n = 6). The relative quantifications showed that the amount of mtDNA4977 deletion was greater in tissue of patients with coronary artery disease (CAD) (P = 0.01) and that telomere length (expressed as telomere length relative to a single copy reference gene) was significantly shorter in tissue of CAD patients, compared to patients without CAD (P = 0.03). Moreover, most conventional risk factors were significantly more frequent in CAD patients, smoking and dyslipidemia having the strongest association with the degree of mtDNA4977deletion and a significant correlation with telomere attrition (P = 0.02 and P = 0.006, respectively). In conclusion, the present study suggests that mtDNA4977 deletion and telomere shortening may represent additional and synergic major risk factors for the pathogenesis of CAD and its complications. Environ. Mol. Mutagen. 54:299–307, 2013. © 2013 Wiley Periodicals, Inc.
On detecting non‐monotonic trends in environmental time series: a fusion of local regression and bootstrap
Authors: Lyubchich Vyacheslav , Gel Yulia R. , El‐Shaarawi Abdel
Published: May 2013

In this paper, we propose a new testing procedure for detecting smooth (non)monotonic trends embedded into a linear noise that possibly does not degenerate to a finite‐dimensional representation or into a conditionally heteroscedastic (autoregressive conditionally heteroscedastic/generalized autoregressive conditionally heteroscedastic (ARCH/GARCH)) noise. The proposed nonparametric trend test is local regression‐based, and we develop a flexible and computationally efficient hybrid bootstrap procedure to approximate its finite sample behavior. Because the proposed trend test does not assume prior knowledge on the dependence structure and probability distribution of the observed process, the new testing procedure is fully data‐driven and robust to misspecification of dependence structure and distributional assumptions, which is of particular importance for noisy environmental measurements. Moreover, because the proposed methodology allows to test for monotonic versus non‐monotonic trends and hence, to assess existence of extremums in the hypothesized trend function, the developed approach may be also employed for preliminary detection of regime shifts and change points in the observed environmental data series. Our simulation studies indicate competitive performance of the proposed nonparametric procedure for detection of (non)monotonic trends against conventional trend tests. Copyright © 2013 John Wiley & Sons, Ltd.
Wind speed modeled as an indexed semi‐Markov process
Authors: D'Amico Guglielmo , Petroni Filippo , Prattico Flavio
Published: May 2013

The production of energy through wind turbines is increasing enormously in the latest years. To better design wind turbines, a good model for wind speed is needed. In a previous paper, we showed that semi‐Markov processes are more appropriate for this purpose than simple Markov processes, but to reach an accurate reproduction of real data features, high order models should be used. In this work, we introduce an indexed semi‐Markov process that is able to reproduce the most important statistical features of wind speed data, namely, the probability density function and the autocorrelation function, without the necessity of higher order models. We downloaded a database, freely available from the Web, of wind speed data taken from Lastem station, Italy and sampled every 10 min. We then generate synthetic time series for wind speed by means of Monte Carlo simulations. The time lagged autocorrelation is then used to compare statistical properties of the proposed model with those of real data and also with a synthetic time series generated though a simple semi‐Markov process. Copyright © 2013 John Wiley & Sons, Ltd.
Use of a watershed hydrologic model to estimate interbasin groundwater flow in a Costa Rican rainforest
Authors: Zanon Carlo , Genereux David P. , Oberbauer Steven F.
Published: May 2013

The watershed hydrologic model TOPMODEL was used to estimate interbasin groundwater flow (IGF) into a small lowland rainforest watershed in Costa Rica. IGF is a common hydrological process but often difficult to quantify. Four‐year simulations (2006–2009) using three different model approaches gave estimates of IGF that were very similar to each other (10.1, 10.2, and 9.8 m/year) and to an earlier estimate (10.0 m/year) based on 1998–2002 data from a budget study that did not use a hydrologic simulation model, providing confidence in the new estimates and suggesting each of the three model approaches is viable. Results show no significant temporal variation in IGF during 2006–2009 (or between this period and the earlier study from 1998–2002). Simulations of the 16 consecutive 3‐month periods in 2006–2009 gave 16 values of IGF rate with a mean (10.1 m/year, standard deviation = 0.6 m/year) very similar to the estimates above from the 4‐year simulations. This suggests the modified version of TOPMODEL can be used to model stream discharge and estimate IGF for sub‐annual time periods during which change in water storage is not necessarily equal to zero. Thus, simple watershed models may be used to estimate IGF based on even relatively short calibration periods, making such models useful tools in the study of this widespread hydrological process that affects water and chemical fluxes and budgets but is often difficult and costly to quantify. Copyright © 2013 John Wiley & Sons, Ltd.
The role of the α7 subunit of the nicotinic acetylcholine receptor on motor coordination in mice treated with methyllycaconitine and anabasine
Authors: Welch K. D. , Pfister J. A. , Gardner D. R. , Green B. T. , Panter K. E.
Published: May 2013

The adverse effects of methyllycaconitine (MLA) have been attributed to competitive antagonism of nicotinic acetylcholine receptors (nAChR). Research has indicated a correlation between the LD50 of MLA and the amount of α7 nAChR in various mouse strains, suggesting that mice with more α7 nAChR require more MLA to be poisoned. However, recent research demonstrated that there was no difference in the acute lethality (LD50) to MLA in mice lacking the α7 nAChR subunit compared with wild‐type mice. The objective of this study was to determine if the α7 nAChR subunit plays a role in motor coordination deficiencies that result from exposure to nAChR antagonists and agonists. We compared the motor function and coordination in wild‐type mice to mice lacking the α7 subunit of the nAChR, after treating them with a non‐lethal dose of MLA or anabasine, using the following tests: balance beam, grip strength, rotarod, open field and tremor monitor. Analysis of the data indicated that overall there was no difference between the wild‐type and knockout mice (P = 0.39 for grip strength; P = 0.21 for rotarod; P = 0.41 for balance beam; P = 0.22 for open field; and P = 0.62 for tremors). Thus results from this study suggest that α7 nAChR does not play an integral role in the acute effects of MLA or anabasine on motor function/coordination. Consequently other subunits of nAChRs found in the neuromuscular junction are likely the primary target for MLA and anabasine resulting in motor coordination deficiencies and acute toxicosis. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
Sclerostin antibody stimulates bone regeneration after experimental periodontitis
Authors: Taut Andrei D , Jin Qiming , Chung Jong-Hyuk , Galindo-Moreno Pablo , Yi Erica S , Sugai James V , Ke Hua Z , Liu Min , Giannobile William V
Published: May 2013

The reconstruction of large osseous defects due to periodontitis is a challenge in regenerative therapy. Sclerostin, secreted by osteocytes, is a key physiological inhibitor of osteogenesis. Pharmacologic inhibition of sclerostin using sclerostin-neutralizing monoclonal antibody (Scl-Ab) thus increases bone formation, bone mass and bone strength in models of osteopenia and fracture repair. This study assessed the therapeutic potential of Scl-Ab to stimulate alveolar bone regeneration following experimental periodontitis (EP). Ligature-induced EP was induced in rats to generate localized alveolar bone defects. Following 4 weeks of disease induction, Scl-Ab (+EP) or vehicle (+/− EP) were systemically delivered, twice weekly for up to 6 wks to determine the ability of Scl-Ab to regenerate bone around tooth-supporting osseous defects. 3 and 6 wks after the initiation of Scl-Ab or vehicle treatment, femur and maxillary jawbones were harvested for histology, histomorphometry, and micro-computed tomography (micro-CT) of linear alveolar bone loss (ABL) and volumetric measures of bone support, including bone volume fraction (BVF) and tissue mineral density (TMD). Serum was analyzed to examine bone turnover markers during disease and regenerative therapy. Vehicle + EP animals exhibited maxillary bone loss (BVF, TMD and ABL) at ligature removal and thereafter. 6 weeks of Scl-Ab significantly improved maxillary bone healing, as measured by BVF, TMD and ABL, when compared to vehicle + EP. After 6 weeks of treatment, BVF and TMD values in the Scl-Ab + EP group were similar to those of healthy controls. Serum analysis demonstrated higher levels of bone formation markers osteocalcin and PINP in Scl-Ab treatment groups. Scl-Ab restored alveolar bone mass following experimental periodontitis. These findings warrant further exploration of Scl-Ab therapy in this and other oral bone defect disease scenarios. © 2013 American Society for Bone and Mineral Research.
Role of Ubiquitin Protein Ligase Ring2 in DNA Damage of Human Bronchial Epithelial Cells Exposed to Benzo[a]pyrene
Authors: Yang Jin , Wang Zhiwu , Chen Wentao , Yin Jinzhu
Published: May 2013

Ubiquitylation of histones plays a pivotal role in DNA repair. The ubiquitin ligase Ring2 was recently shown to be the dominant ubiquitin ligase of histone H2A. In a series of experiments using the human bronchial epithelia cells (16HBE) and small interfering RNA (siRNA)‐Ring2 cells exposed to benzo(a)pyrene (BaP), we measured dynamic changes in the levels of DNA damage, expressions of ubiquitinated histone H2A, and nucleotide excision repair (NER) subunit xeroderma pigmentosum (XP) groups A, C, and F (XPA, XPC, XPF). We found that in vitro exposure to BaP increased DNA damage in a time‐ and dose‐dependent manner in 16HBE and siRNA‐Ring2 cells. The results show that although decrease of Ring2 causes DNA hypersensitivity to BaP, the levels of XPA, XPC, and XPF were not affected. These results indicated that Ring2 may effect the DNA repair through other pathways but not through the expressions of NER protein. © 2013 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:357‐363, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.21497
Improved partition–expansion of two‐center distributions involving slater functions
Authors: López Rafael , Ramírez Guillermo , Ema Ignacio , Rico Jaime Fernández
Published: May 2013

The calculation of the electronic structure of large systems is facilitated by the substitution of the two‐center distributions by their projections on auxiliary basis sets of one‐center functions. An alternative is the partition–expansion method in which one first decides what part of the distribution is assigned to each center, and next expands each part in spherical harmonics times radial factors. The method is exact, requires neither auxiliary basis sets nor projections, and can be applied to Gaussian and Slater basis sets. Two improvements in the partition–expansion method for Slater functions are reported: general expressions valid for arbitrary quantum numbers are derived and the efficiency of the procedure is increased giving analytical solutions to integrals previously computed by numerical quadrature. The efficiency of the new version is assessed in several molecules and the advantages over the projection methods are pointed out. © 2013 Wiley Periodicals, Inc.
Differential geometric analysis of alterations in MH α‐helices
Authors: Hischenhuber Birgit , Havlicek Hans , Todoric Jelena , Höllrigl‐Binder Sonja , Schreiner Wolfgang , Knapp Bernhard
Published: May 2013

Antigen presenting cells present processed peptides via their major histocompatibility (MH) complex to the T cell receptors (TRs) of T cells. If a peptide is immunogenic, a signaling cascade can be triggered within the T cell. However, the binding of different peptides and/or different TRs to MH is also known to influence the spatial arrangement of the MH α‐helices which could itself be an additional level of T cell regulation. In this study, we introduce a new methodology based on differential geometric parameters to describe MH deformations in a detailed and comparable way. For this purpose, we represent MH α‐helices by curves. On the basis of these curves, we calculate in a first step the curvature and torsion to describe each α‐helix independently. In a second step, we calculate the distribution parameter and the conical curvature of the ruled surface to describe the relative orientation of the two α‐helices. On the basis of four different test sets, we show how these differential geometric parameters can be used to describe changes in the spatial arrangement of the MH α‐helices for different biological challenges. In the first test set, we illustrate on the basis of all available crystal structures for (TR)/pMH complexes how the binding of TRs influences the MH helices. In the second test set, we show a cross evaluation of different MH alleles with the same peptide and the same MH allele with different peptides. In the third test set, we present the spatial effects of different TRs on the same peptide/MH complex. In the fourth test set, we illustrate how a severe conformational change in an α‐helix can be described quantitatively. Taken together, we provide a novel structural methodology to numerically describe subtle and severe alterations in MH α‐helices for a broad range of applications. © 2013 Wiley Periodicals, Inc.
Influence of variation of a side chain on the folding equilibrium of a β‐peptide: Limitations of one‐step perturbation
Authors: Lin Zhixiong , van Gunsteren Wilfred F.
Published: May 2013

In a recent study (Lin et al., Helv. Chim. Acta 2011, 94, 597), the one‐step perturbation method was applied to tackle a challenging computational problem, that is, the calculation of the folding free enthalpies ΔGF,U of six hepta‐β‐peptides with different, Ala, Val, Leu, Ile, Ser, or Thr, side chains in the fifth residue. The ΔGF,U values obtained using one‐step perturbation based on a single molecular dynamics simulation of a judiciously chosen reference state with soft‐core atoms in the side chain of the fifth residue showed an overall accuracy of about kBT for the four peptides with nonpolar side chains, but twice as large deviations were observed for the peptides with polar side chains. Here, alternative reference‐state Hamiltonians that better cover the conformational space relevant to these peptides are investigated, and post simulation rotational sampling of the χ1 and χ2 torsional angles of the fifth residue is carried out to sample different orientations of the side chain. A reference state with rather soft atoms yields accurate ΔGF,U values for the peptides with the Ser and Thr side chains, but it failed to correctly predict the folding free enthalpy for one peptide with a nonpolar side chain, that is, Leu. Based on the results and those of earlier studies, possible ways to improve the accuracy of the efficient one‐step perturbation technique to compute free enthalpies of folding are discussed. © 2013 Wiley Periodicals, Inc.
Heavy metals recovery from printed circuit board industry wastewater sludge by thermophilic bioleaching process
Authors: Chen Shen‐Yi , Huang Qiao‐Ying
Published: May 2013

BACKGROUND

A large quantity of heavy metal contaminated wastewater sludge is produced during the treatment of printed circuit board (PCB) manufacturing wastewater. The PCB wastewater sludge containing high concentrations of heavy metals, such as Cu and Zn, increases the potential for metal recycling. Although bioleaching is indicated as a promising technology to remove metals from electronic scrap and waste PCBs, its application for metal recovery from PCB wastewater sludge is still very limited. The purpose of this study was to develop a thermophilic bioleaching process operated in a sequencing batch reactor (SBR) to recover heavy metals from PCB wastewater sludge.

RESULTS

The results show that an increase in sludge solid content from 0.5 to 5% (w/v) decreased the rate of pH reduction during the bioleaching process. It was also found that the efficiency and rate of metal solubilization decreased with increasing sludge solid content. At a sludge solid content of 0.5% (w/v), after four repeated feed/decant cycles with 10 days per cycle (40 days) of SBR operation, the maximum efficiencies of metal solubilization in the treated sludge were 65% and 100% for Cu and Zn, respectively.

CONCLUSION

The solubilization efficiency of heavy metals was lower during SBR operation with a longer 20‐day cycle time. Therefore, a shorter 10‐day cycle time for SBR operation is preferred for the thermophilic bioleaching of PCB wastewater sludge. In the treated sludge, the potential mobility and environmental risks of heavy metals were decreased significantly after the thermophilic bioleaching process. © 2013 Society of Chemical Industry
Removal of bisphenol A and 4‐n‐nonylphenol coupled to nitrate reduction using acclimated activated sludge under anaerobic conditions
Authors: Wang Lin , Zhao Junming , Li Yongmei
Published: May 2013

BACKGROUND

Bisphenol A (BPA) and 4‐n‐nonylphenol (4‐n‐NP) are of significant research interest due to their extensive use and toxicological properties. Batch experiments were conducted to investigate the sorption and degradation behavior of BPA and 4‐n‐NP using acclimated activated sludge either under anoxic conditions in the presence of nitrate or under anaerobic conditions in the absence of nitrate.

RESULTS

Sorption of BPA and 4‐n‐NP on sludge was a spontaneous physical and exothermic process; partitioning played a dominant role. The values of partitioning coefficients of BPA and 4‐n‐NP under different redox conditions follow the order anaerobic > anoxic > aerobic. While BPA was degraded under both anaerobic and anoxic conditions, 4‐n‐NP was degraded only under anoxic conditions. The degradation rate of BPA under anoxic conditions is much greater than that under anaerobic conditions, and they are much greater than the degradation rate of 4‐n‐NP under anoxic conditions. Mixed liquor suspended solid and temperature influenced their sorption and degradation. A suitable COD/NO3‐‐N ratio was 15 for both BPA or 4‐n‐NP elimination, and nitrate reduction.

CONCLUSION

Effective degradation of BPA and 4‐n‐NP under nitrate reducing conditions provides an alternative removal method for refractory endocrine disrupting compounds in wastewater treatment plants. © 2013 Society of Chemical Industry
Characterizing the dayside magnetosheath using energetic neutral atoms: IBEX and THEMIS observations
Authors: Ogasawara K. , Angelopoulos V. , Dayeh M. A. , Fuselier S. A. , Livadiotis G. , McComas D. J. , McFadden J. P.
Published: May 2013

We report on the time evolution of energetic neutral atom (ENA) emissions measured by the Interstellar Boundary Explorer (IBEX) during instances of compressed and expanded dayside magnetosheath. The ENA observations, taken during the passage of a corotating interaction region on 27 and 28 November 2010, are compared with in situ observations from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. IBEX's field of view (6.5° full width at half maximum) covered a wide region of the dayside magnetosheath for several days, providing continuous information from that region. The high sensitivity and high‐energy resolution of IBEX instruments enabled unprecedented remote‐sensing diagnostics of dayside magnetosheath ENA spectra at energies between ~0.1 and ~6 keV, which can be directly compared with various upstream parameters. The inferred plasma spectra from ENA observations showed characteristic suprathermal tails described by kappa distributions that correlate well with the solar wind cone angle and are in agreement with in situ observations, suggesting that the shock angle contributed to magnetosheath particle heating. Simultaneous in situ ion measurements in the dayside magnetosheath provided by THEMIS agree reasonably well with IBEX‐inferred spectra, demonstrating synergy between remote IBEX ENA observations (global) and in situ measurements (local) for studying localized magnetospheric processes.
Coupling of electrons and inertial Alfven waves in the topside ionosphere
Authors: Shi Run , Liu Huixin , Yoshikawa A. , Zhang Beichen , Ni Binbin
Published: May 2013

A one‐dimensional kinetic model is constructed to simulate the electron acceleration by inertial Alfven waves. The electrons are divided into cold and hot electrons and treated separately. Cold components are described by the fluid equation and hot ones by the Vlasov equation, both carrying field‐aligned currents. Intense variation of Alfven speed has been introduced by inclusion of cold electrons. The model results show that the exponential decrease of the plasma density plays a key role, which leads to the sharp gradient of both Alfven velocity and electron inertial length. When Alfven waves encounter this sharp gradient at lower altitudes, the electrons accelerated by the waves become super‐Alfvenic, and the width of burst structures becomes much wider than the electron inertial length. Consequently, the background electrons carry the oppositely field‐aligned current due to plasma oscillation. It is demonstrated that the current carried by the electrons exceeding the wavefront is balanced by the reverse current carried by background electrons. This mechanism can be used to reasonably explain observations of the electron bursts accompanied by little net field‐aligned current. Furthermore, our simulation indicates another type of Alfven wave reflection due to mirror force and wave‐particle interaction.
Cool North European summers and possible links to explosive volcanic eruptions
Authors: Jones P. D , Melvin T. M. , Harpham C. , Grudd H. , Helama S.
Published: May 2013

Exactly dated tree‐ring measurements such as ring width (TRW) and maximum latewood density (MXD), which are sensitive to summer temperatures, can provide possible routes to investigate the occurrence of hemispheric‐wide cool summers that might be linked to explosive tropical volcanic eruptions. These measurements can provide much longer records than the instrumental period, enabling much longer periods to be assessed and offers the potential to look at much larger eruptions than recorded over the last 200 years. This paper looks at TRW evidence from Northern Fennoscandia extending over the last 7500 years, using two independently produced chronologies from northern Sweden and northern Finland. TRW is less responsive than MXD to cool summer temperatures, but MXD is only available for the last 2000 years. Additionally, looking at a relatively small location, compared to the Northern Hemisphere average, adds considerable noise. Progress in this area is likely to be made by developing more millennial‐long TRW series across northern high latitudes or being able to develop MXD series from the sub‐fossil material, which comprises most of the samples prior to the last 1000 years. The three most extreme negative values for the region for the last 2000 years are 1601, 542, and 1837, although the latter is not extreme in a long instrumental record for the region. The most extreme year of all occurred in 330BC. Of the 20 most extreme negative years, nine occurred during the AD years with the remaining 11 occurring during the prior 5500 years.
Instability structures during periods of large Richardson number (Ri > ): Evidence of parametric instability
Authors: Walterscheid R. L. , Gelinas L. J. , Hecht J. H. , Liu A. Z.
Published: May 2013

The commonly used criteria for shear and convective instabilities were developed for steady horizontally uniform background flows. However, the formalism that rigorously addresses the instability of waves on a basic state modulated by a primary wave is Floquet theory in which the basic state includes a wave. A Floquet system supports parametric instabilities when conventional Richardson number (Ri) criteria indicate that the system is stable. In a study of small‐scale instability structures during the Maui MALT campaign, Hecht et al. (2005) noted that there were occurrences of ripple (instability) structure when the conventional criteria indicated stable conditions. We have followed up this work with a detailed survey of the occurrence of ripple structure over Maui during periods that were both stable and unstable according to conventional criteria. Values of Ri were calculated from lidar data. We have found frequent occurrence of ripple structure when Ri > . We have focused on a period when there are clear indications of waves and ripple structure exhibiting two‐dimensional instability structure when Ri ~ 1 or greater. These results are analyzed in terms of Floquet theory and interpreted as parametric instabilities occurring for modest primary wave amplitudes.
A model‐based test of accuracy of seawater oxygen isotope ratio record derived from a coral dual proxy method at southeastern Luzon Island, the Philippines
Authors: Liu Gang , Kojima Keitaro , Yoshimura Kei , Okai Takashi , Suzuki Atsushi , Oki Taikan , Siringan Fernando P. , Yoneda Minoru , Kawahata Hodaka
Published: May 2013

The oxygen isotope ratio in seawater (δ18Osw) is an important indicator of past hydroclimatic conditions in the tropics. In this study, we apply a dual proxy approach using δ18O and Sr/Ca in coral skeletons to estimate δ18Osw. Due to a lack of long‐term continuous observational data for δ18Osw, a simplified one‐dimensional box model of the ocean surface associated with historical surface atmospheric data is used for comparison with coral‐derived δ18Osw record. The atmospheric data consist of the precipitation and evaporation values, together with their δ18O compositions from the global isotope reanalysis data. The model successfully reproduces a multidecadal time series for δ18Osw at southeastern Luzon Island, the Philippines, for the period 1979–2001 (r = 0.57, p < 0.01). The result suggests that the coral records are an accurate indicator of hydrological cycle changes at the site. A discrepancy between the reproduction and the coral record in the wet season (December–February) may be caused by seasonal variation in the depth of the mixed layer and upwelling, since these factors are not accounted for in the model. The reproduction is in good agreement with the coral records in the dry season (April–June), implying that δ18Osw estimated using the coral dual proxy method is more robust at this time of year.
Technical considerations in MR angiography: An image‐based guide
Authors: Morelli John N. , Gerdes Clint M. , Schmitt Peter , Ai Tao , Saettele Megan R. , Runge Val M. , Attenberger Ulrike I.
Published: May 2013

As the complexity of the magnetic resonance angiography (MRA) techniques grows, it becomes more difficult for the practicing radiologist to appreciate the physical principles underlying these studies. Nevertheless, such an understanding is requisite for improving clinical image quality. As radiologists are most accustomed to dealing with medical images in everyday practice, it seems natural that an image‐based approach to teaching MRA physics, rather than complex mathematical equations or pulse sequence diagrams, would be preferable. This article adopts such an approach. Simple ways to improve MRA image quality are emphasized along with new technologies and their physical basis. The ultimate goal of the article is to facilitate the practicing radiologist becoming more aware of the variety of MR techniques available, being more confident in modifying sequence parameters to improve image quality and reduce contrast dose, and understanding the basis behind newer MRA techniques. J. Magn. Reson. Imaging 2013;37:1326–1341. © 2013 Wiley Periodicals, Inc.
Correction of eddy current distortions in high angular resolution diffusion imaging
Authors: Zhuang Jiancheng , Lu Zhong‐Lin , Vidal Christine Bouteiller , Damasio Hanna
Published: May 2013

Purpose:

To correct distortions caused by eddy currents induced by large diffusion gradients during high angular resolution diffusion imaging without any auxiliary reference scans.

Materials and Methods:

Image distortion parameters were obtained by image coregistration, performed only between diffusion‐weighted images with close diffusion gradient orientations. A linear model that describes distortion parameters (translation, scale, and shear) as a function of diffusion gradient directions was numerically computed to allow individualized distortion correction for every diffusion‐weighted image.

Results:

The assumptions of the algorithm were successfully verified in a series of experiments on phantom and human scans. Application of the proposed algorithm in high angular resolution diffusion images markedly reduced eddy current distortions when compared to results obtained with previously published methods.

Conclusion:

The method can correct eddy current artifacts in the high angular resolution diffusion images, and it avoids the problematic procedure of cross‐correlating images with significantly different contrasts resulting from very different gradient orientations or strengths. J. Magn. Reson. Imaging 2013;37:1460–1467. © 2012 Wiley Periodicals, Inc.
Polynomial noise modeling of silicon‐based GaN HEMTs
Authors: Colangeli Sergio , Bentini Andrea , Ciccognani Walter , Limiti Ernesto
Published: May 2013

In the framework of silicon (Si) technology, evolution towards high‐frequency analog applications – which involves innovative solutions such as SiGe BiCMOS and FinFET devices – wide bandgap semiconductors grown on Si substrates are likely to represent a valid option in those cases wherever high‐power handling and low noise figures are required. Although such active devices have been extensively investigated in the last years, much of interest has been devoted in developing nonlinear models for high‐power applications, whereas reliable noise models still lack, in particular, the validity of traditional (i.e. equivalent temperature‐based) approaches for noise modeling of wide bandgap devices has not been sufficiently probed yet.

In this contribution, a quite general, black box noise model of active devices is proposed and applied to a family of gallium nitride‐on‐Si high‐electron‐mobility transistors fabricated by Selex ES. The model is based on a polynomial approximation of the device correlation matrix and does not require that an accurate small‐signal equivalent circuit is available; instead, it can be extracted from multifrequency source pull data. Experimental results demonstrate that a typical behavior of the noise parameters is obtained, both versus frequency and gate periphery. Copyright © 2013 John Wiley & Sons, Ltd.