bluuebunny/crossref_metadata_2025 huggingface dataset:
Current Issues in the Social Psychological Study of ‘Language Attitudes’: Constructionism, Context, and the Attitude–Behavior Link
Authors: Soukup Barbara
Published: March 2012

Quantitative social psychological studies of ‘language attitudes’ (particularly speaker evaluation experiments using the ‘matched‐guise technique’) are a popular area of research. But they have also been the subject of much criticism, especially from the perspective of social constructionism. This article focuses on two central points of debate: the issue of whether or not (language) attitudes should be regarded as stable mental entities, and the issue of the attitude–behavior link. Contrary to what has been suggested, adopting a constructionist perspective on these issues does not entail abandoning all quantitative methodology in favor of qualitative (discourse) analysis. Rather, it means conceptualizing speaker evaluation experiments as contextually situated ‘communicative events’. Under such a recast, experiments can be usefully harnessed for the explication of sociolinguistic behavior such as strategic style‐shifting. More generally, quantitative ‘language attitude’ research needs to take constructionist considerations into account in order to retain its scientific relevance today.
Early bedside detection of ischemia and rejection in liver transplants by microdialysis
Authors: Haugaa Håkon , Thorgersen Ebbe B. , Pharo Anne , Boberg Kirsten M. , Foss Aksel , Line Pål Dag , Sanengen Truls , Almaas Runar , Grindheim Guro , Pischke Soeren Erik , Mollnes Tom Eirik , Tφnnessen Tor Inge
Published: March 2012

This study was performed to explore whether lactate, pyruvate, glucose, and glycerol levels sampled via microdialysis catheters in the transplanted liver could be used to detect ischemia and/or rejection. The metabolites were measured at the bedside every 1 to 2 hours after the operation for a median of 10 days. Twelve grafts with biopsy-proven rejection and 9 grafts with ischemia were compared to a reference group of 39 grafts with uneventful courses. The median lactate level was significantly higher in both the ischemia group [5.8 mM (interquartile range = 4.0–11.1 mM)] and the rejection group [2.1 mM (interquartile range = 1.9–2.4 mM)] versus the reference group [1.5 mM (interquartile range = 1.1–1.9 mM), P < 0.001 for both]. The median pyruvate level was significantly increased only in the rejection group [185 μM (interquartile range = 155–206 μM)] versus the reference group [124 μM (interquartile range = 102–150 μM), P < 0.001], whereas the median lactate/pyruvate ratio and the median glycerol level were increased only in the ischemia group [66.1 (interquartile range = 23.9–156.7) and 138 μM (interquartile range = 26–260 μM)] versus the reference group [11.8 (interquartile range = 10.6–13.6), P < 0.001, and 9 μM (interquartile range = 9–24 μM), P = 0.002]. Ischemia was detected with 100% sensitivity and greater than 90% specificity when a positive test was repeated after 1 hour. In 3 cases of hepatic artery thrombosis, ischemia was detected despite normal blood lactate levels. Consecutive pathological measurements for 6 hours were used to diagnose rejection with greater than 80% sensitivity and specificity at a median of 4 days before the activity of alanine aminotransferase, the concentration of bilirubin in serum, or both increased. In conclusion, bedside measurements of intrahepatic lactate and pyruvate levels were used to detect ischemia and rejection earlier than current standard methods could. Discrimination from an uneventful patient course was achieved. Consequently, intrahepatic graft monitoring with microdialysis may lead to the earlier initiation of graft-saving treatment. Liver Transpl, 2012. © 2012 AASLD.
Anesthesia for liver transplantation in US academic centers: Institutional structure and perioperative care
Authors: Walia Ann , Mandell Susan M. , Mercaldo Nathaniel , Michaels Damon , Robertson Amy , Banerjee Arna , Pai Ramachander , Klinck John , Weinger Matthew , Pandharipande Pratik , Schumann Roman
Published: March 2012

Investigators at a single institution have shown that the organization of the anesthesia team influences patient outcomes after liver transplant surgery. Little is known about how liver transplant anesthesiologists are organized to deliver care throughout the United States. Therefore, we collected quantitative survey data from adult liver transplant programs in good standing with national governing agencies so that we could describe team structure and duties. Information was collected from 2 surveys in a series of quantitative surveys conducted by the Liver Transplant Anesthesia Consortium. All data related to duties, criteria for team membership, interactions/communication with the multidisciplinary team, and service availability were collected and summarized. Thirty-four of 119 registered transplant centers were excluded (21 pediatric centers and 13 centers not certified by national governing agencies). Private practice sites (26) were later excluded because of a poor response rate. There were minimal changes in the compositions of the programs between the 2 surveys. All academic programs had distinct liver transplant anesthesia teams. Most had set criteria for membership and protocols outlining the preoperative evaluation, attended selection committees, and were always available for transplant surgery. Fewer were involved in postoperative care or were available for patients needing subsequent surgery. Most trends were associated with the center volume. In conclusion, some of the variance in team structure and responsibilities is probably related to resources available at the site of practice. However, similarities in specific duties across all teams suggest some degree of self-initiated specialization.
QSPR Prediction of Lipophilicity for Organic Compounds Using Random Forest Technique on the Basis of Simplex Representation of Molecular Structure
Authors: Ognichenko Liudmyla N. , Kuz'min Victor E. , Gorb Leonid , Hill Frances C. , Artemenko Anatoly G. , Polischuk Pavel G. , Leszczynski Jerzy
Published: March 2012

The relationship between the octanol‐water partition coefficient for more than twelve thousand organic compounds and their structures was investigated using a QSPR approach based on Simplex Representation of Molecular Structure (SiRMS). The dataset used in our study included 10973 compounds with experimental values of lipophilicity (LogKow) for different chemical compounds. Random Forest (RF) method was used for statistical modeling at the 2D level of representation of molecular structure. Developed models are adequate and successfully validated with external test sets. Proposed models have clear interpretation due to the use of simplex representation of molecular structure and predict the LogKow values with the accuracy of the best modern models. Thus QSPR models proposed in this study represent powerful and easy‐to use virtual screening tool that can be recommended for prediction of octanol‐water partition coefficient.
QSAR Prediction of Passive Permeability in the LLC‐PK1 Cell Line: Trends in Molecular Properties and Cross‐Prediction of Caco‐2 Permeabilities
Authors: Sherer Edward C. , Verras Andreas , Madeira Maria , Hagmann William K. , Sheridan Robert P. , Roberts Drew , Bleasby Kelly , Cornell Wendy D.
Published: March 2012

A QSAR model for predicting passive permeability (Papp) was derived from Papp values measured in the LLC‐PK1 cell line. The QSAR method and descriptor set that performed best in terms of cross‐validation was random forest with a combination of AP, DP, and MOE_2D descriptors. The QSAR model was used to predict the Caco‐2 cell permeability for 313 compounds described in the literature with good success. We find that passive permeability for different cell lines can be predicted with similar molecular properties and descriptors. It is shown that the variation in experimental measurements of Papp is smaller than the error in QSAR predictions indicating that predictions are not quantitatively perfect, although qualitatively useful. We get better predictions if the training set is large and diverse, rather than smaller and more internally consistent. This is because prediction accuracy falls off quickly with decreasing similarity to the training set and it is therefore better to have as large a training set as possible. While single physical parameters are not as good as a full QSAR model in predicting Papp, logD seems the most important parameter. Intermediate values of logD are associated with higher Papp.
A numerical method to solve a class of linear integro‐differential equations with weakly singular kernel
Authors: Yüzbaşı Şuayip , Sezer Mehmet
Published: March 2012

In this paper, a collocation method based on the Bessel polynomials is introduced for the approximate solution of a class of linear integro‐differential equations with weakly singular kernel under the mixed conditions. The exact solution can be obtained if the exact solution is polynomial. In other cases, increasing number of nodes, a good approximation can be obtained with applicable errors. In addition, the method is presented with error and stability analysis. Copyright © 2012 John Wiley & Sons, Ltd.
On the inherent precision of mcDESPOT
Authors: Lankford Christopher L. , Does Mark D.
Published: March 2012

A statistical analysis of the mcDESPOT protocol for characterizing two exchanging water proton pools—a seven‐dimensional problem that fits to multiple flip angle measurements of both spoiled and refocused gradient echoes—is presented. Theoretical calculations of the Cramér‐Rao lower bounds of the variance of fitted model parameters were made using a variety of model system parameters, meant to mimic those expected in human white matter. The results, validated by Monte Carlo simulations, indicated that mcDESPOT signals acquired at feasibly attainable signal‐to‐noise ratios cannot provide parameter estimates with useful levels of precision. Precision can be greatly improved by constraining solutions with a priori model information, although this will generally lead to biased parameter estimates with less specificity. These results indicate that previous, apparently successful applications of mcDESPOT to human white matter may have used data fitting methods that implicitly constrained parameter solutions, or that the two‐pool model of white matter may not be sufficient to describe the observed water proton signal in mcDESPOT acquisitions. In either case, mcDESPOT‐derived estimates of two‐pool model parameters cannot yet be unambiguously related to specific tissue characteristics. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.
Expression of multiple nebulin isoforms in human skeletal muscle and brain
Authors: Laitila Jenni , Hanif Mubashir , Paetau Anders , Hujanen Sari , Keto Joni , Somervuo Panu , Huovinen Sanna , Udd Bjarne , Wallgren‐Pettersson Carina , Auvinen Petri , Hackman Peter , Pelin Katarina
Published: March 2012

Introduction:

Nebulin is a large actin‐binding protein of the skeletal muscle sarcomere. Multiple isoforms of nebulin are produced from the 183‐exon–containing nebulin gene (NEB). Mutations in NEB cause nemaline myopathy, distal myopathy, and core‐rod myopathy.

Methods:

Nebulin mRNA expression was assessed by microarrays and RT‐PCR in 21 human leg muscle and 2 brain samples. Protein expression was assessed by immunohistochemistry in 5 regions of 1 brain sample.

Results:

Nebulin isoform diversity is as high in brain as in skeletal muscle. Isoforms with more than 22 super repeats seem to be more common than previously anticipated. Immunohistochemistry showed nebulin expression predominantly in the cytoplasm of pyramidal neurons but also in the cytoplasm of mainly subcortical endothelial cells.

Conclusions:

Nebulin, as in skeletal muscle, may have a role as an actin filament stabilizer or length regulator in neurons of the human brain, although patients with NEB mutations usually have normal cognition. Muscle Nerve, 2012
Genetic variability and clinical spectrum of Chinese patients with limb‐girdle muscular dystrophy type 2A
Authors: Luo Su‐Shan , Xi Jian‐Ying , Zhu Wen‐Hua , Zhao Chong‐Bo , Lu Jia‐Hong , Lin Jie , Wang Yin , Lu Jun , Qiao Kai
Published: March 2012

Introduction:

Previous studies of limb‐girdle muscular dystrophy type 2A (LGMD2A) patients in many countries have suggested a heterogeneous genetic and clinical spectrum, but the genotypes and phenotypes of Chinese LGMD2A patients remain unclear.

Methods:

We directly screened calpain‐3 (CAPN3) in 18 Chinese Han subjects who exhibited severely reduced or completely absent calpain‐3 expression, as determined by Western blot analysis. We subsequently analyzed genotype/phenotype correlations.

Results:

Seventeen patients (94.4%) were identified who had at least 1 causative mutation. All 18 mutations were distributed along the entire gene, and 11 of the mutations were novel, including 4 missense mutations, 5 deletions, and 2 splicing mutations. The phenotypes of these Chinese LGMD2A patients varied from severe LGMD to distal myopathy, and even asymptomatic hyper‐CK‐emia.

Conclusions:

No evidential correlation was found between the genotypes and phenotypes of the patients assessed in this study. Western blot analysis is still a useful diagnostic method when genetic analysis is unavailable. Muscle Nerve, 2012
Properties on novel PVDF‐HFP‐based composite polymer electrolyte with vinyltrimethoxylsilane‐modified ZSM‐5
Authors: Xiao Wei , Li Xinhai , Guo Huajun , Wang Zhixing
Published: March 2012

A kind of novel poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP)‐based composite polymer electrolyte doped with vinyltrimethoxylsilane (DB171 silane)‐modified ZSM‐5 is prepared by phase inversion method (denoted as M‐ZSM‐5 membrane). Physical and chemical properties of M‐ZSM‐5 membrane are studied by SEM, FTIR, TG‐DSC, EIS, and LSV. The results show that thermal and electrochemical stability can reach 400°C and 5 V, respectively; temperature dependence of ionic conductivity follows Vogel–Tamman–Fulcher relation and ionic conductivity at room temperature is up to 4.2 mS/cm; the interfacial resistance reaches a stable value about 325 Ω after 5 days storage at room temperature, which suggests that it can be potentially suitable as electrolyte in polymer lithium ion battery. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Optimisation of a Capillary Zone Electrophoresis Methodology for Simultaneous Analysis of Organic Aliphatic Acids in Extracts of Brachiaria brizantha
Authors: Vaz Fernando Antonio Simas , da Silva Patrícia Aparecida , Passos Leônidas Paixão , Heller Melina , Micke Gustavo Amadeu , Costa Ana Carolina Oliveira , de Oliveira Marcone Augusto Leal
Published: March 2012

Introduction

Aluminum toxicity is commonly verified in acidic soils, and poses a severe limitation to plant growth and development. Therefore, Al complexation by the root system mucilage, Al complexation by organic compounds that are exuded by the roots and internal metabolic processes must be monitored by organic acids (OA), since they play a central role in these aluminum tolerance mechanisms.

Objective

To optimise a capillary zone electrophoresis method able to perform simultaneous separation of acetic, citric, formic, lactic, malic, oxalic, pyruvic, succinic, tartaric and aspartic acid in plant extract solutions.

Methodology

Method optimisation was achieved by a chemometric approach through experimental designs. The optimal condition found was: 20 mmol/L phthalic acid buffer; 0.8 mmol/L cetyltrimethyl‐ammonium bromide; pH 3.4 adjusted with tris(hydroxymethyl)aminomethane (around 16 mmol/L); −15 kV of voltage; 25 °C of cartridge temperature; indirect ultraviolet detection at 240 nm; and 25 mbar injection for 2 s, within an analysis time of 4 min.

Results

As a repeatability test of the optimal condition, 30 replicates were carried out with the same working electrolyte, where the relative standard deviation of each peak ranged from 0.081 to 0.36% (for migration time) and from 2.4 to 4.6% (for peak area).

Conclusion

The methodology was successfully applied to simultaneously determine citric, malic and aspartic acid in roots and leaves extract solutions of Brachiaria brizantha, demonstrating its usefulness to study aluminum tolerance. Copyright © 2012 John Wiley & Sons, Ltd.
N‐type solar‐grade silicon purified via the metallurgical route: characterisation and fabrication of solar cells
Authors: Schutz‐Kuchly Thomas , Sanzone Vincent , Veschetti Yannick
Published: March 2012

This study focuses on the characterisation and the fabrication of solar cells using n‐type multicrystalline silicon purified via the metallurgical route. Electrical and chemical analyses were performed on wafers taken from several positions along the crystallised ingot. The impact of the fabrication processing steps was investigated via effective carrier lifetime measurements. Solar cells were processed, and their efficiencies were found to be dependent on the position of the wafer along the ingot height, that is, the wafer's resistivity. A maximum conversion efficiency of 15.0% was obtained on cells from the bottom part of the ingot. In this study, the minimum resistivity value of 0.4 Ω cm resistivity is given in order to reach adequate cell efficiency. Light‐soaking experiments were then performed on the fabricated cells. No significant variations of the cell performances were observed even after 110 h at 60 °C, meaning that the fabricated cells are stable under illumination. Copyright © 2012 John Wiley & Sons, Ltd.
Synthesis of twin‐tail tadpole‐shaped (cyclic polystyrene)‐ block‐[linear poly (tert‐butyl acrylate)]2 by combination of glaser coupling reaction with living anionic polymerization and atom transfer radical polymerization
Authors: Huang Bing , Fan Xiaoshan , Wang Guowei , Zhang Yannan , Huang Junlian
Published: March 2012

The twin‐tail tadpole‐shaped (cyclic polystyrene)‐block‐[linear poly (tert‐butyl acrylate)]2 [(c‐PS)‐b‐(l‐PtBA)2] was synthesized by combination of Glaser coupling reaction with atom transfer radical polymerization (ATRP) and living anionic polymerization (LAP). First, the telechelic PS with an active and an ethoxyethyl‐protected hydroxyl groups at both ends was prepared by LAP of St monomers using lithium naphthalenide as initiator and terminated by 1‐ethoxyethyl glycidyl ether. And the alkyne groups were introduced onto each PS end by selectively reaction of active hydroxy group with propargyl bromide in NaH/tetrahydrofuran (THF) system. Then, the intramolecular cyclization was carried out by Glaser coupling reaction in pyridine/Cu(I)Br system in air atmosphere. Finally, the macroinitiator of c‐PS with two bromine groups at the junction point was synthesized via the cleavage of ethoxyethyl group and the subsequent esterification of the deprotected hydroxyl groups with 2‐bromoisobutyryl bromide. The copolymer of (c‐PS)‐b‐(l‐PtBA)2 was obtained by ATRP of tBA monomers, and the PtBA segment was also hydrolyzed for (cyclic polystyrene)‐block‐(linear polyacrylic acid)2 [(c‐PS)‐b‐(l‐PAA)2]. The target copolymers and all intermediates were well characterized by GPC, MALDI‐TOF MS, and 1H NMR in detail. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Strain‐induced crystallization and mechanical properties of functionalized graphene sheet‐filled natural rubber
Authors: Ozbas Bulent , Toki Shigeyuki , Hsiao Benjamin S. , Chu Benjamin , Register Richard A. , Aksay Ilhan A. , Prud'homme Robert K. , Adamson Douglas H.
Published: March 2012

The effects of functionalized graphene sheets (FGSs) on the mechanical properties and strain‐induced crystallization of natural rubber (NR) are investigated. FGSs are predominantly single sheets of graphene with a lateral size of several hundreds of nanometers and a thickness of 1.5 nm. The effect of FGS and that of carbon black (CB) on the strain‐induced crystallization of NR is compared by coupled tensile tests and X‐ray diffraction experiments. Synchrotron X‐ray scattering enables simultaneous measurements of stress and crystallization of NR in real time during sample stretching. The onset of crystallization occurs at significantly lower strains for FGS‐filled NR samples compared with CB‐filled NR, even at low loadings. Neat‐NR exhibits strain‐induced crystallization around a strain of 2.25, while incorporation of 1 and 4 wt % FGS shifts the crystallization to strains of 1.25 and 0.75, respectively. In contrast, loadings of 16 wt % CB do not significantly shift the critical strain for crystallization. Two‐dimensional (2D) wide angle X‐ray scattering patterns show minor polymer chain alignment during stretching, in accord with previous results for NR. Small angle X‐ray scattering shows that FGS is aligned in the stretching direction, whereas CB does not show alignment or anisotropy. The mechanical properties of filled NR samples are investigated using cyclic tensile and dynamic mechanical measurements above and below the glass transition of NR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
A Permafrost Probability Model for the Southern Yukon and Northern British Columbia, Canada
Authors: Bonnaventure Philip P. , Lewkowicz Antoni G. , Kremer Marian , Sawada Michael C.
Published: March 2012

Permafrost maps are needed for infrastructure planning, climatic change adaptation strategies and northern development but often lack sufficient detail for these purposes. The high‐resolution (30 x 30 m grid cells) probability model for the southern Yukon and northern British Columbia presented in this paper (regional model) is a combination of seven local empirical‐statistical models, each developed from basal temperature of snow measurements in winter and ground‐truthing of frozen‐ground presence in summer. The models were blended using a distance‐decay power approach to generate a map of permafrost probability over an area of almost 500 000 km2 between 59°N and 65°N. The result is broadly similar to previous permafrost maps with an average permafrost probability of 58 per cent for the region as a whole. There are notable differences in detail, however, because the main predictive variable used in the local models is equivalent elevation, which incorporates the effects of gentle or inverted surface lapse rates in the forest zone. Most of the region shows permafrost distribution patterns that are non‐linear, resembling those from continental areas such as Mongolia. Only the southwestern area shows a similar mountain permafrost distribution to that in the European Alps with a well‐defined lower limit and a linear increase in probability with elevation. The results of the modelling can be presented on paper using traditional classifications into permafrost zones but given the level of detail, they will be more useful as an interactive online map. Copyright © 2012 John Wiley & Sons, Ltd.
Robust design and optimization of retroaldol enzymes
Authors: Althoff Eric A. , Wang Ling , Jiang Lin , Giger Lars , Lassila Jonathan K. , Wang Zhizhi , Smith Matthew , Hari Sanjay , Kast Peter , Herschlag Daniel , Hilvert Donald , Baker David
Published: March 2012

Enzyme catalysts of a retroaldol reaction have been generated by computational design using a motif that combines a lysine in a nonpolar environment with water‐mediated stabilization of the carbinolamine hydroxyl and β‐hydroxyl groups. Here, we show that the design process is robust and repeatable, with 33 new active designs constructed on 13 different protein scaffold backbones. The initial activities are not high but are increased through site‐directed mutagenesis and laboratory evolution. Mutational data highlight areas for improvement in design. Different designed catalysts give different borohydride‐reduced reaction intermediates, suggesting a distribution of properties of the designed enzymes that may be further explored and exploited.
Ab initio protein structure assembly using continuous structure fragments and optimized knowledge‐based force field
Authors: Xu Dong , Zhang Yang
Published: March 2012

Ab initio protein folding is one of the major unsolved problems in computational biology owing to the difficulties in force field design and conformational search. We developed a novel program, QUARK, for template‐free protein structure prediction. Query sequences are first broken into fragments of 1–20 residues where multiple fragment structures are retrieved at each position from unrelated experimental structures. Full‐length structure models are then assembled from fragments using replica‐exchange Monte Carlo simulations, which are guided by a composite knowledge‐based force field. A number of novel energy terms and Monte Carlo movements are introduced and the particular contributions to enhancing the efficiency of both force field and search engine are analyzed in detail. QUARK prediction procedure is depicted and tested on the structure modeling of 145 nonhomologous proteins. Although no global templates are used and all fragments from experimental structures with template modeling score >0.5 are excluded, QUARK can successfully construct 3D models of correct folds in one‐third cases of short proteins up to 100 residues. In the ninth community‐wide Critical Assessment of protein Structure Prediction experiment, QUARK server outperformed the second and third best servers by 18 and 47% based on the cumulative Z‐score of global distance test‐total scores in the FM category. Although ab initio protein folding remains a significant challenge, these data demonstrate new progress toward the solution of the most important problem in the field. Proteins 2012; © 2012 Wiley Periodicals, Inc.
Anisotropic strain in α‐plane GaN and polarization dependence of the Raman peaks
Authors: Katsikini M. , Arvanitidis J. , Christofilos D. , Ves S. , Dimitrakopulos G. P. , Tsiakatouras G. , Tsagaraki K. , Georgakilas A.
Published: March 2012

The strain anisotropy of a‐plane GaN epilayers is studied by polarization‐dependent Raman spectroscopy. The intensity dependence of the A1(TO), E1(TO) and $E_{2}^{2} $ Raman peaks for an almost strain‐free epilayer is well explained by using Raman tensors of C6v symmetry. However, the corresponding angular dependence for anisotropically strained GaN with |εxx − εyy|∼6 × 10−3 (where x||a and y||m axes) dictates the use of a perturbation term of C2v symmetry that accounts for the orthorhombic distortion of the hexagonal unit cell. The consideration of this term elucidates the appearance of the $E_{2}^{2} $ mode for such epilayer orientations where it is forbidden by the hexagonal symmetry.
Epitaxial La0.7Sr0.3MnO3 thin films grown on SrTiO3 buffered silicon substrates by reactive molecular‐beam epitaxy
Authors: Méchin L. , Adamo C. , Wu S. , Guillet B. , Lebargy S. , Fur C. , Routoure J.‐M. , Mercone S. , Belmeguenai M. , Schlom D. G.
Published: March 2012

La0.7Sr0.3MnO3 (LSMO) thin films (with a thickness of 10, 20, 60, 75, and 100 nm) were grown on SrTiO3 (STO)‐buffered silicon (001) substrates by reactive molecular‐beam epitaxy. X‐ray diffraction (XRD) revealed the heterostructures to be fully epitaxial with orientation relationship (001) LSMO || (001) STO || (001) Si and [100] LSMO || [100] STO || [110] Si. Root mean square roughness was about 0.5 nm as measured by atomic force microscopy (AFM) for films of 10–75 nm thicknesses, and about 1 nm for the 100 nm thick LSMO film. Normalized Hooge parameters in the (0.95 ± 0.25) × 10−30–(3.41 ± 0.71) × 10−30 m3 range were measured at 300 K, which are comparable to the noise level typically measured in the best LSMO films on (001) STO substrates. Overall these very low noise LSMO films with thicknesses in the 10–100 nm range grown on STO/Si showed properties rivaling those of LSMO films deposited on (001) STO single crystal substrates, thus demonstrating their potential use for LSMO‐based devices on silicon substrates.
Different electronic transport regimes in the quasi‐two‐dimensional organic conductors κ‐(BEDT‐TTF)2X
Authors: Müller Jens , Brandenburg Jens , Schweitzer Dieter , Schlueter John A.
Published: March 2012

We study the low‐frequency dynamical properties of correlated charge carriers in various of the quasi‐two‐dimensional organic charge‐transfer salts κ‐(BEDT‐TTF)2X by means of fluctuation (noise) spectroscopy. Close to the critical endpoint of the Mott metal‐insulator transition, a pronounced increase of the 1/f‐noise level accompanied by a substantial shift of spectral weight to low frequencies indicates a sudden increase of the time scale of the charge fluctuations. For the less correlated, more metallic materials, we find a crossover/transition from hopping transport of more‐or‐less localized carriers at elevated temperatures to a low‐temperature regime, where a metallic coupling of the layers allows for coherent interlayer transport of delocalized electrons.
Crystal structure and band parameters of mixed crystals derived from quantum spin liquid β′‐EtMe3Sb[Pd(dmit)2]2 (dmit = 1,3‐dithiol‐2‐thione‐4,5‐dithiolate)
Authors: Kato Reizo , Fukunaga Takeo , Yamamoto Hiroshi M. , Ueda Kohei , Hengbo Cui
Published: March 2012

A molecular Mott insulator β′‐EtMe3Sb[Pd(dmit)2]2 with a quasi‐triangular lattice of a dimer unit [Pd(dmit)2] exhibits quantum spin liquid (QSL) behavior. We introduced Me4Sb+ or Et2Me2Sb+ to the cation site of this anion radical salt without altering its crystal symmetry. The mixing ratio and lattice parameters of these mixed crystals can be continuously tuned. We calculated intermolecular transfer integrals between highest occupied molecular orbitals (HOMOs) based on structural data. Increasing the number of ethyl groups at the cation site reduces the anisotropy of the triangular lattice, and the dimer units form an almost regular triangular lattice in pure Et2Me2Sb salt. In this process, the Pd(dmit)2 molecule is slightly curved to exhibit a crescent shape. This distortion plays an important role in tuning the interdimer transfer integrals.
Spectroscopic characterization of charge order fluctuations in BEDT‐TTF metals and superconductors
Authors: Girlando A. , Masino M. , Kaiser S. , Sun Y. , Drichko N. , Dressel M. , Mori H.
Published: March 2012

The charge‐fluctuating and charge‐ordered states in metallic, insulating and superconducting bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF) salts are characterized through the analysis of the infrared (IR) spectral region relevant to the CC antisymmetric stretch, b1ν22. This spectral region shows dramatic changes in band intensity and band‐shape by varying the temperature. The observed spectral features can be understood on the basis of an extension of the well‐known Kubo model for the spectral signatures of an equilibrium between two states. The two‐orders of magnitude increase in the IR oscillator strength of the b1ν22 mode upon ionization has also to be taken into account.

magnified image

BEDT‐TTF CC antisymmetric stretch, b1ν22.
Analysis of dose–response in flexible dose titration clinical studies
Authors: Xu Xu (Steven) , Yuan Min , Nandy Partha
Published: March 2012

Assessing dose–response from flexible‐dose clinical trials (e.g., titration or dose escalation studies) is challenging and often problematic due to the selection bias caused by ‘titration‐to‐response’. We investigate the performance of a dynamic linear mixed‐effects (DLME) model and marginal structural model (MSM) in evaluating dose–response from flexible‐dose titration clinical trials via simulations. The simulation results demonstrated that DLME models with previous exposure as a time‐varying covariate may provide an unbiased and efficient estimator to recover exposure–response relationship from flexible‐dose clinical trials. Although the MSM models with independent and exchangeable working correlations appeared to be able to recover the right direction of the dose–response relationship, it tended to over‐correct selection bias and overestimated the underlying true dose–response. The MSM estimators were also associated with large variability in the parameter estimates. Therefore, DLME may be an appropriate modeling option in identifying dose–response when data from fixed‐dose studies are absent or a fixed‐dose design is unethical to be implemented. Copyright © 2012 John Wiley & Sons, Ltd.
Xanthohumol Induces Different Cytotoxicity and Apoptotic Pathways in Malignant and Normal Astrocytes
Authors: Zajc I. , Filipič M. , Lah T. T.
Published: March 2012

Cytotoxicity and the mechanisms of cell death induced by xanthohumol (XN) were compared in normal and cancerous human cells as the differences may be relevant for the potential use of XN in cancer therapy. The cancer cells seemed to be more susceptible to the cytotoxicity of XN than normal cells, but a significant difference was observed only in astrocytic cells. XN induced a higher rate of apoptosis in glioblastoma cells than in normal astrocytes, which was associated with activation of p53 and an elevated Bax/Bcl‐2 ratio in glioblastoma cells, indicating an intrinsic caspase‐dependent apoptotic pathway. In contrast, a reduced Bax/Bcl‐2 ratio was observed in normal human astrocytes. This was also associated with higher expression of the cell cycle inhibitor, p21, in glioblastoma cells than in normal astrocytes. In addition, at a lower, non‐cytotoxic concentration, XN partially inhibited the invasiveness of glioblastoma cells. Due to the selective sensitivity of astrocytic cells to XN, this compound should be studied further as a candidate for adjuvant therapy in the treatment of glioma. Copyright © 2012 John Wiley & Sons, Ltd.
A note on atomic density
Authors: Ramírez Guillermo , López Rafael , Ema Ignacio , Fernández Rico Jaime
Published: March 2012

In atomic systems, electron density has a simple finite expansion in spherical harmonics times radial factors. The difficulties in the calculation of some radial factors are illustrated in the low‐lying states of the carbon atom.

Single‐particle methods such as Hartree–Fock and approximate density functional theory cannot ensure the correct expansion of the density in spherical harmonics. Wave‐function methods are appropriate but, as some expansion terms are entirely due to correlation, these methods only will give correct results for high‐quality variational functions. Using full‐configuration integration (CI), all the terms predicted by the theory appear and are not negligible but the convergence of the term due to correlation toward its correct value is uncertain even for very large CI spaces. © 2012 Wiley Periodicals, Inc.
External source method for Kubo‐transformed quantum correlation functions
Authors: Horikoshi Atsushi
Published: March 2012

We revisit the external source method for Kubo‐transformed quantum correlation functions recently proposed by Krishna and Voth. We derive an exact formula and show that the Krishna–Voth formula can be derived as an approximation of our formula. Some properties of this approximation are clarified through a model calculation of the position autocorrelation function for a one‐dimensional harmonic oscillator. A key observation is that the Krishna–Voth correlation function has a term that behaves as the secular term in perturbation theory. © 2012 Wiley Periodicals, Inc.
Hartree–Fock calculation for excited states
Authors: Tassi M. , Theophilou Iris , Thanos S.
Published: March 2012

The Hartree–Fock (HF) method, widely used for the calculation of ground state properties, in recent years has been extended for calculating excited states. In this article, we develop an approach, which does not require time consuming calculations and can give a good approximation for the excitation energies. The method is based on the fact that the subspaces of the occupied and virtual orbitals are mutually orthogonal. We test the accuracy of our method by evaluating the excited state wavefunctions and the corresponding energies for the Li, N, F, Ne, and Na atoms and for the BeH and CH molecules, and we found good agreement with configuration interaction and experimental results. © 2012 Wiley Periodicals, Inc.
Successful full‐scale enhanced anaerobic dechlorination at a NAPL strength 1,1,1‐TCA source area
Authors: Fam Sami A. , Falatko David M. , McGillicuddy Glenn , Pon George , Burkhardt Louis J. , Hone Jonathan
Published: March 2012

Bioremediation of 1,1,1‐trichloroethane (TCA) is more challenging than bioremediation of other chlorinated solvents, such as tetrachloroethene (PCE) and trichloroethene (TCE). TCA transformation often occurs under methanogenic and sulfate‐reducing conditions and is mediated by Dehalobacter. The source area at the project site contains moderately permeable medium sand with a low hydraulic gradient and is approximately 0.5 acre. TCA contamination generally extended to 35 feet, with the highest concentrations at approximately 20 feet. The concentrations then decreased with depth; several wells contained 300 to 600 mg/L of TCA prior to bioremediation. The area of treatment also contained 2 to 30 mg/L of TCE from an upgradient source. Initial site groundwater conditions indicated minimal biotic dechlorination and the presence of up to 20 mg/L of nitrate and 90 mg/L of sulfate. Microcosm testing indicated that TCA dechlorination was inhibited by the site's relatively low pH (5 to 5.5) and high TCA concentration. After the pH was adjusted and TCA concentrations were reduced to less than 35 mg/L (by dilution with site water), dechlorination proceeded rapidly using whey (or slower with sodium lactate) as an electron donor. Throughout the remediation program, increased resistance to TCA inhibition (from 35 to 200 mg/L) was observed as the microbes adapted to the elevated TCA concentrations. The article presents the results of a full‐scale enhanced anaerobic dechlorination recirculation system and the successful efforts to eliminate TCA‐ and pH‐related inhibition. © 2012 Wiley Periodicals, Inc.
A distribution‐matching method for parameter estimation and model selection in computational biology
Authors: Lillacci Gabriele , Khammash Mustafa
Published: March 2012

The determination of the model parameters is a central challenge in computational modeling of biological systems. Typically, only a fraction of the parameters (such as kinetic rate constants) is experimentally measured, whereas the rest is fitted. The fitting process is usually based on experimental time course measurements of observables, which are used to assign parameter values that minimize some measure of the error between these measurements and the corresponding model prediction. The data, which can come from real‐time polymerase chain reaction (PCR), enzymatic reactions, flow cytometry, etc., tend to be very noisy, but the statistics of the noise can often be inferred by performing calibration procedures. In this paper, we show how the knowledge of the properties of the noise, expressed in terms of its cumulative distribution function, can be used to validate or invalidate the estimates provided by an upstream state observer (a particle filter) and to refine them in case they turn out not to be satisfactory. Furthermore, we show how the same tools can be used to discriminate among alternative models of the same biological process. We demonstrate these ideas on a simple gene expression model, and we show how the proposed method is able to handle estimation problems that cannot be effectively solved by classical techniques such as least‐squares estimation. Copyright © 2012 John Wiley & Sons, Ltd.
Model predictive tracking control for a linear system under time‐varying input constraints
Authors: Wada N. , Tomosugi H. , Saeki M.
Published: March 2012

In this paper, we propose a tracking control law for a linear dynamical system under time‐varying input constraints. The proposed control law consists of a dual‐mode model predictive control (MPC) law and a target recalculation mechanism. As the terminal controller of the dual‐mode MPC, we propose a saturation‐level‐dependent gain‐scheduled feedback control law that ensures closed‐loop stability against arbitrary change of the position limit of the actuators. We also present conditions that guarantee feasibility and stability of the control algorithm under time‐varying input constraints. The control algorithm is reduced to an online optimization problem under linear matrix inequality constraints. Copyright © 2012 John Wiley & Sons, Ltd.
Optimizing the Perceived Benefits and Health Outcomes of Writing about Traumatic Life Events
Authors: Andersson Matthew A. , Conley Colleen S.
Published: March 2012

Expressive writing, which involves disclosing one's deepest thoughts and feelings about a stressful life event by using a first‐person perspective, has been linked to gains in health and well‐being, though effect sizes range widely. Assuming a third‐person perspective is a natural and effective way of coping with highly distressing events. Therefore, the current study examined whether a distanced, third‐person approach to expressive writing might be more beneficial than a traditional, first‐person intervention for high baseline levels of event‐linked intrusive thinking. Randomly assigned participants wrote expressively about traumatic life events by using a first‐person or third‐person‐singular perspective. Linguistic analyses showed that assuming a first‐person perspective is linked to higher levels of in‐text cognitive engagement, whereas a third‐person perspective is linked to lower cognitive engagement. However, in a context of higher levels of intrusive thinking, third‐person expressive writing, relative to a traditional first‐person approach, yielded (1) greater perceived benefits and positive, long‐lasting effects as well as (2) fewer days of activity restriction due to illness. Although more research is needed, these results suggest that third‐person expressive writing may be an especially fitting technique for recovering from traumatic or highly stressful life events. Copyright © 2012 John Wiley & Sons, Ltd.
The psychological costs of pay‐for‐performance: Implications for the strategic compensation of employees
Authors: Larkin Ian , Pierce Lamar , Gino Francesca
Published: March 2012

Most research linking compensation to strategy relies on agency theory economics and focuses on executive pay. We instead focus on the strategic compensation of nonexecutive employees, arguing that while agency theory provides a useful framework for analyzing compensation, it fails to consider several psychological factors that increase costs from performance‐based pay. We examine how psychological costs from social comparison and overconfidence reduce the efficacy of individual performance‐based compensation, building a theoretical framework predicting more prominent use of team‐based, seniority‐based, and flatter compensation. We argue that compensation is strategic not only in motivating and attracting the worker being compensated but also in its impact on peer workers and the firm's complementary activities. The paper discusses empirical implications and possible theoretical extensions of the proposed integrated theory. Copyright © 2012 John Wiley & Sons, Ltd.
Ambidexterity and performance in multiunit contexts: Cross‐level moderating effects of structural and resource attributes
Authors: Jansen Justin J.P. , Simsek Zeki , Cao Qing
Published: March 2012

Research suggests that unit‐level ambidexterity positively impacts subsequent unit performance but theory and testing on this impact remain impoverished. We develop a cross‐level model suggesting that structural and resource attributes of the organizational context significantly shape the relationship between unit ambidexterity and performance. Using multisource and lagged data from 285 organizational units located within 88 autonomous branches, results from hierarchical linear modeling show that this relationship is boosted when the organization is decentralized, more resource munificent, or less resource interdependent. We also find that structural differentiation of the organization does not condition the unit ambidexterity‐performance relationship. Through this cross‐level theory and testing, we develop a richer explanation of the effectiveness of ambidextrous units operating in multiunit contexts. Copyright © 2012 John Wiley & Sons, Ltd.
Comparative analysis of cerebrovascular resistance in fetuses with single‐ventricle congenital heart disease
Authors: Szwast A. , Tian Z. , McCann M. , Soffer D. , Rychik J.
Published: March 2012

Objective

We sought to determine whether the presence or absence of aortic obstruction impacts cerebrovascular resistance in fetuses with single‐ventricle (SV) congenital heart disease (CHD).

Methods

Pulsatility indices (PIs) were recorded for the middle cerebral artery (MCA) and the umbilical artery (UA) from 18 to 40 weeks' gestation in 59 fetuses (163 examinations) with SV‐CHD with unobstructed aortic flow, yet decreased pulmonary flow, in 72 fetuses (170 examinations) with obstructed aortic flow and hypoplastic left heart syndrome (HLHS) and in 92 normal fetuses (92 examinations). The cerebral‐to‐placental resistance (CPR) was calculated as the MCA‐PI/UA‐PI. Z‐scores were generated for the MCA‐PI and the UA‐PI in order to make comparisons independent of gestational age. Statistical analyses were performed using one‐way ANOVA with post‐hoc testing. Trends in these variables over the course of gestation were assessed using linear regression and univariate ANOVA.

Results

The MCA‐PI and the CPR were significantly lower in SV fetuses with aortic obstruction compared with SV fetuses with pulmonary obstruction and with normal fetuses. Moreover, the MCA‐PI decreased significantly for SV fetuses with aortic obstruction over the course of gestation. In contrast, the MCA‐PI was higher over the course of gestation in SV fetuses with pulmonary obstruction compared with normal fetuses.

Conclusion

In fetuses with SV‐CHD, cerebrovascular resistance varies substantially between fetuses with and without aortic obstruction. Compared with normal fetuses, cerebrovascular resistance is decreased in SV fetuses with aortic obstruction, yet increased in SV fetuses with pulmonary obstruction. In fetuses with SV physiology, inherent differences in cerebral blood flow may underlie postnatal neurodevelopmental outcomes. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Theoretical insights into bacterial chemotaxis
Authors: Tindall Marcus J. , Gaffney Eamonn A. , Maini Philip K. , Armitage Judith P.
Published: March 2012

Research into understanding bacterial chemotactic systems has become a paradigm for Systems Biology. Experimental and theoretical researchers have worked hand‐in‐hand for over 40 years to understand the intricate behavior driving bacterial species, in particular how such small creatures, usually not more than 5 µm in length, detect and respond to small changes in their extracellular environment. In this review we highlight the importance that theoretical modeling has played in providing new insight and understanding into bacterial chemotaxis. We begin with an overview of the bacterial chemotaxis sensory response, before reviewing the role of theoretical modeling in understanding elements of the system on the single cell scale and features underpinning multiscale extensions to population models. WIREs Syst Biol Med 2012 doi: 10.1002/wsbm.1168

This article is categorized under:

Models of Systems Properties and Processes > Cellular Models

Biological Mechanisms > Cell Signaling

Models of Systems Properties and Processes > Mechanistic Models