bluuebunny/crossref_metadata_2025 huggingface dataset:
Toward the Assignment of the Manganese Oxidation Pattern in the Water‐Oxidizing Complex of Photosystem II: A Time‐Dependent DFT Study of XANES Energies
Authors: Jaszewski Adrian R. , Petrie Simon , Pace Ronald J. , Stranger Rob
Published: April 2011

Density functional theory (DFT) and time‐dependent DFT (TDDFT) calculations are reported on three sets of isomeric models of the {Mn4/Ca} water‐oxidizing complex of photosystem II (PS II), which share the general formula [CaMn4O4(N2C3H4)(RCOO)6]q⋅(H2O)n (R=H, CH3; q=−1, 0, +1, +2; n=3, 4, 5, 6, 7). Comparison with the full range of available data on Mn K‐edge X‐ray absorption energy values determined for the photosystem allows us to validate the structures that correspond to the particular S states and to determine their Mn oxidation patterns. By using a new TDDFT procedure, it is shown that variations in the absolute K‐edge energy values for a particular S state, reported by different research groups, can be quantitatively explained by different geometries adopted by the Mn cluster, which demonstrates flexibility in the position of the fourth ‘dangling’ Mn atom in relation to a cubane structure created by the Ca atom and the three other Mn atoms. Computational results show that each step of the S cycle occurs by removal of one electron directly from the Mn cluster. This Mn‐centered oxidation still agrees with the small difference observed experimentally between the K‐edge energy values of the S2 and S3 states of the photosystem, thus resolving a controversy as to whether this represents ligand‐centered or metal‐centered oxidation. The overall oxidation state of Mn atoms in the tetramanganese cluster during functional turnover changes from 2.75 for S0, 3.00 for S1, and 3.25 for S2 up to 3.50 for the S3 state, which is systematically 0.50 lower than the previously proposed oxidation states of the cluster. The calculations give insight into why these earlier, purely empirical, assignments of the Mn oxidation levels in PS II could be in error.
Semiclathrates of the Ge–P–Te System: Synthesis and Crystal Structures
Authors: Kirsanova Maria A. , Reshetova Liudmila N. , Olenev Andrei V. , Abakumov Artem M. , Shevelkov Andrei V.
Published: April 2011

Novel compounds [Ge46−xPx]Tey (13.9≤x≤15.6, 5.92≤y≤7.75) with clathrate‐like structures have been prepared and structurally characterized. They crystallize in the space group Fm$\bar 3$ with the unit cell parameter changing from 20.544(2) to 20.698(2) Å (Z=8) on going from x=13.9 to x=15.6. Their crystal structure is composed of a covalently bonded GeP framework that hosts tellurium atoms in the guest positions and can be viewed as a peculiar variant of the type I clathrate superstructure. In contrast to the conventional type I clathrates, [Ge46−xPx]Tey contain tricoordinated (3b) atoms and no vacancies in the framework positions. As a consequence of the transformation of the framework, the majority of the guest tellurium atoms form a single covalent bond with the host framework and thus the title compounds are the first representative of semiclathrates with covalent bonding. A comparison is made with silicon clathrates and the evolution of the crystal structure upon changing the tellurium content is discussed.
UARA in edge routers: an effective approach to user fairness and traffic shaping
Authors: Khosroshahy Masood
Published: April 2011

The ever‐increasing share of the peer‐to‐peer (P2P) traffic flowing in the Internet has unleashed new challenges to the quality of service provisioning. Striving to accommodate the rise of P2P traffic or to curb its growth has led to many schemes being proposed: P2P caches, P2P filters, ALTO mechanisms and re‐ECN. In this paper, we propose a scheme named ‘UARA:textbfUser/Application‐aware RED‐based AQM’ which has a better perspective on the problem: UARA is proposed to be implemented at the edge routers providing real‐time near‐end‐user traffic shaping and congestion avoidance. UARA closes the loopholes exploited by the P2P traffic by bringing under control the P2P users who open and use numerous simultaneous connections. In congestion times, UARA monitors the flows of each user and caps the bandwidth used by ‘power users’ which leads to the fair usage of network resources. While doing so, UARA also prioritizes the real‐time traffic of each user, further enhancing the average user quality of experience (QoE). UARA hence centralizes three important functionalities at the edge routers: (1) congestion avoidance; (2) providing user fairness; (3) prioritizing real‐time traffic. The simulation results indicate that average user QoE is significantly improved in congestion times with UARA at the edge routers. Copyright © 2011 John Wiley & Sons, Ltd.
Synthesis, Crystal Structures and Magnetic Properties of a Phenoxo‐Bridged Dinuclear CuII Complex and a Dicyanamide Bridged Novel Molecular Rectangle Based on It
Authors: Biswas Apurba , Drew Michael G. B. , Ribas Joan , Diaz Carmen , Ghosh Ashutosh
Published: April 2011

The phenoxo‐bridged dinuclear CuII complex [Cu2L2(NCNCN)2] (1) and the dicyanamide‐bridged molecular rectangle [Cu4L4{μ1,5‐(NCNCN)2}]·(ClO4)2(H2O)2 (2) were synthesized using the tridentate reduced Schiff‐base ligand HL {2‐[(2‐dimethylamino‐ethylamino)methyl]phenol}. The complexes were characterized by X‐ray structural analyses and variable‐temperature magnetic susceptibility measurements. Complex 2 was formed through the joining of the phenoxo‐bridged dinuclear Cu2O2 cores of 1 via the μ1,5‐bridging mode of dicyanamide. The structural properties of the Cu2O2 cores in two complexes are significantly different. The geometry of the copper ions is distorted trigonal bipyramid in 1 but is nearly square‐pyramidal in 2. These differences have a marked effect on the magnetic properties of two compounds. Although both are antiferromagnetically coupled, the coupling constants (J = –185.2 and –500.9 cm–1 for 1 and 2, respectively) differ considerably.
Three New Antimicrobial Metabolites from the Endophytic Fungus Phomopsis sp.
Authors: Ahmed Ishtiaq , Hussain Hidayat , Schulz Barbara , Draeger Siegfried , Padula Daniele , Pescitelli Gennaro , van Ree Teunis , Krohn Karsten
Published: April 2011

Two new chromones, phomochromone A and B (1 and 2), and one new natural cyclopentenone derivative, phomotenone (3), together with six known compounds, phomosines A–D (4–7), (1S,2S,4S)‐trihydroxy‐p‐menthane (8), and 5‐methylmellein (9), have been isolated from the endophytic fungus Phomopsis sp. through a bioassay‐guided procedure. The structures of the new compounds were assigned on the basis of the 1H and 13C NMR spectra, DEPT, and 2D COSY, HMQC, HMBC, and NOESY experiments, supported by molecular modelling. The absolute configurations of compounds 1–3 were assigned by TD‐DFT CD calculations and, surprisingly, the two related phomochromones A and B have an opposite configuration at C‐2. Compounds 1–3 show good antifungal (Microbotryum violaceum), antibacterial (Escherichia coli, Bacillus megaterium), and antialgal (Chlorella fusca) activities. Compound 8 shows good antialgal and antibacterial activity.
Water quality monitoring using cluster analysis and linear models
Authors: Gonçalves A. Manuela , Alpuim Teresa
Published: April 2011

The development of statistical methodologies based on spatial and temporal hydrological data is a very important tool in the monitoring of surface water quality in a river basin. This paper uses cluster analysis and linear models to describe hydrological space–time series of quality variables and to detect changes in surface water quality data collected in the River Ave hydrological basin, located in the north‐west region of Portugal. This area receives many untreated effluent discharges from textile industries, which result in extreme pollution. Because of this problematic environmental situation, local authorities installed a network of 20 monitoring sites, producing monthly measurements of quality variables and later began to operate three wastewater treatment plants (WTP) at the end of the 1998 hydrological year. In this work, we propose a two‐step methodology to analyse these data which use cluster analysis to classify the quality monitoring sites into spatial homogeneous groups. Then we adjust linear models to the quality variables associated with the clusters, taking into account the seasonal variations throughout the year, different trends for each period of time (before and after the installation of WTPs), and the hydro‐meteorological factor. Finally, statistical tests are performed to evaluate the effective role of the WTPs' performance. Copyright © 2011 John Wiley & Sons, Ltd.
Pilot study of absorption of NO2 with Na2S aqueous solutions
Authors: Chen Luke , Lin Kun‐Fon , Yang Chen‐Lu
Published: April 2011

A pilot‐scale study of sodium sulfide (Na2S) aqueous solutions for NO2 absorption was conducted to obtain field data for process design and system operations. Considered parameters include Na2S concentrations in the scrubbing solutions, gas mass flow rate, liquid mass flow rate, liquid/gas ratio (L/G), pH, and gas residence time. The effects of these parameters on NO2 absorption in a packed tower were investigated thoroughly. The height of transfer unit of the system was deducted as a function of the tested parameters that can be used for designing a NOx scrubbing system. The absorption of NO2 is not sensitive to the inlet NO2 concentration. However, as expected, the NO2 absorption increases with the increase of L/G ratio. An L/G greater than 2.5 is essential to a practical NO2 scrubbing application. The pilot test suggested that the scrubbing solution is with Na2S concentration greater than 0.0015 M at pH 9. The solution effectively removed more than 90% of the incoming NO2 in the five‐foot height packed bed scrubber. The study also indicates that a gas residence time of 4.5 s is essential to achieve more than 80% NO2 absorption. © 2011 American Institute of Chemical Engineers Environ Prog, 2011.
Katian prelude to the Hirnantian (Late Ordovician) mass extinction: a Baltic perspective
Authors: Kaljo Dimitri , Hints Linda , Hints Olle , Männik Peep , Martma Tõnu , Nõlvak Jaak
Published: April 2011

The diversity of several groups of Late Ordovician fossils in the Baltic is discussed and corresponding curves are presented. The curves are correlated with the latest δ13C trend and probable sea surface temperatures of the equatorial ocean in order to link biodiversity and environmental changes. Most groups of macrofossils and acritarchs showed a high‐level biodiversity in the Sandbian and early Katian during a sea level high stand and optimal temperatures. Conodont diversity peaked in the mid‐Katian, scolecodonts in the late Katian and rugose corals even in the Hirnantian, indicating their different ecological demands and the evolutionary status of each group. The diversity peak close to the Guttenberg δ13C excursion marks a turning point in environmental evolution when a new global cooling began but tropical conditions persisted in Baltica due to its northward drift. Biodiversity fluctuated during the Katian. Two diversity peaks noted in the Katian are followed by low‐diversity episodes showing a general step by step decrease in diversity, and a correlation with variable sea level and episodes of climatic cooling. It suggests that the Hirnantian mass extinction was preceded by a rather prolonged period of biodiversity change here called the Katian prelude. Katian biodiversity curves and their links with different facies parameters show that environmental conditions within the ecosystem were the main drivers of change, not solely temperature or more generally climate, but also sedimentary environments including water dynamics together with depth and substrate conditions. The biotic component is less well known, but also important. Copyright © 2011 John Wiley & Sons, Ltd.
The filtering capacity of a tropical riverine wetland: II. Sediment and nutrient balances
Authors: McJannet David , Wallace Jim , Keen Rex , Hawdon Aaron , Kemei Joseph
Published: April 2011

The ability of wetlands to improve the quality of water has long been recognized and has led to the proliferation of wetlands as a means to treat diffuse and point source pollutants from a range of land uses. However, much of the existing research has been undertaken in temperate climates with a paucity of information on the effectiveness of wetlands, particularly natural wetlands, in tropical regions. This paper contributes to addressing this issue by presenting a comprehensive measurement based assessment of the potential for a naturally occurring tropical riverine wetland to improve the quality of the water entering it. We found small net imports and exports of sediment to/from the wetland in individual years, but over the longer term this kind of wetland is neither a sink nor source of sediment. In contrast, phosphorus was continually removed by the wetland with an overall net reduction of 14%. However, it should be noted that there is no ‘permanent’ gaseous loss mechanism for phosphorus, and its removal from the water column is equal to its accumulation in the wetland soil. We found very little removal of nitrogen by this type of wetland from several analyses including: (i) Surface and groundwater fluxes, (ii) Estimation of water column and soil denitrification rates, (iii) Wetland residence times, and (iv) Hydraulic loading. We also found no clear evidence for transformation of nitrogen to more or less bio‐available forms. Hence, while the benefits of using wetlands to improve water quality in controlled environments have been demonstrated in the literature, these benefits may not always be directly translated to unmanaged natural wetland systems when there is strong seasonality in flows and short residence time during the periods of maximum sediment and nutrient load. Copyright © 2011 John Wiley & Sons, Ltd.
Sp1 is upregulated in human glioma, promotes MMP‐2‐mediated cell invasion and predicts poor clinical outcome
Authors: Guan Hongyu , Cai Junchao , Zhang Nu , Wu Jueheng , Yuan Jie , Li Jun , Li Mengfeng
Published: April 2011

Sp1, the first identified transcription factor, has been reported to be associated with the development and progression of various human cancer types. However, the clinical significance and biological role of Sp1 in glioma are less well understood. In this study, we found that the expression of Sp1 was markedly elevated in glioma cell lines and tissues. Immunohistochemistry analysis revealed that the vast majority of 222 paraffin‐embedded archival glioma specimens tested displayed positive Sp1 expression, and 58.6% exhibited high‐level Sp1 expression. Statistical analysis suggested that the high Sp1 expression was correlated strongly with the WHO grading (p < 0.001) and survival status (p < 0.001) of glioma patients. Patients with lower Sp1 expression had better overall survival than those with higher Sp1 expression. Multivariate analysis suggested that Sp1 expression might be an independent prognostic indicator of the survival of patients with glioma. Furthermore, overexpression of Sp1 in glioma cells was found to increase their invasiveness, and in contrast, silencing Sp1 by siRNA caused an inhibition of cell invasion. Moreover, we demonstrated that the up‐regulation of Sp1 could increase activity and expression of MMP‐2. Collectively, our data suggest that Sp1 might represent a valuable prognostic marker for glioma and is involved in modulation of tumor invasion.
Trends in incidence of anal cancer and high‐grade anal intraepithelial neoplasia in Denmark, 1978–2008
Authors: Nielsen Ann , Munk Christian , Kjaer Susanne K.
Published: April 2011

The aim of the study was to determine the incidences of anal cancer and high‐grade anal intraepithelial neoplasia (AIN2/3) over time in Danish women and men. Describing the burden of anal cancer and AIN may be valuable in future evaluations of the human papillomavirus (HPV) vaccine. We included all anal cancers in the Danish Cancer Register in the period 1978–2008 and all cases of AIN2/3 in the Danish Registry of Pathology. Overall and age‐, period‐ and histology‐specific incidence rates were estimated. During the 30‐year period, 2,187 anal cancers were identified, two thirds of which were in women. Between 1978–1982 and 2003–2008, the age‐standardized incidence rate of anal cancer increased from 0.68 to 1.48 per 100,000 person‐years in women and from 0.45 to 0.80 per 100,000 person‐years in men. Although there is no systematic screening for AIN in Denmark, we nevertheless identified 608 cases of AIN2/3 during the study period. The average annual percentage change of 5% between 1998 and 2008 represents a steep increase in the incidence of AIN in both genders. Furthermore, the incidence rate of HPV‐associated anal cancers increased significantly, whereas that of non‐HPV‐associated histological types levelled out or even declined during the 30 years of observation. In women, the increase in HPV‐associated cancers was more pronounced among those under 60 years of age. Our findings indicate that vaccines against HPV might play an important role in the prevention of anal cancer and its precursor lesions.
Optimization of parameters for molecular dynamics simulation using smooth particle‐mesh Ewald in GROMACS 4.5
Authors: Abraham Mark J. , Gready Jill E.
Published: April 2011

Based on our critique of requirements for performing an efficient molecular dynamics simulation with the particle‐mesh Ewald (PME) implementation in GROMACS 4.5, we present a computational tool to enable the discovery of parameters that produce a given accuracy in the PME approximation of the full electrostatics. Calculations on two parallel computers with different processor and communication structures showed that a given accuracy can be attained over a range of parameter space, and that the attributes of the hardware and simulation system control which parameter sets are optimal. This information can be used to find the fastest available PME parameter sets that achieve a given accuracy. We hope that this tool will stimulate future work to assess the impact of the quality of the PME approximation on simulation outcomes, particularly with regard to the trade‐off between cost and scientific reliability in biomolecular applications. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011
How reliable are GIAO calculations of 1H and 13C NMR chemical shifts? A statistical analysis and empirical corrections at DFT (PBE/3z) level
Authors: Pankratyev Evgeniy Yu. , Tulyabaev Artur R. , Khalilov Leonard M.
Published: April 2011

Reliability of calculated 1H and 13C NMR chemical shifts for various classes of organic compounds obtained with gauge‐invariant atomic orbital (GIAO) approach has been studied at the PBE/3ζ level (as implemented in PRIRODA code) using linear regression analysis with experimental data. Empirical corrections for the calculated chemical shifts δH,calc = δPBE/3ζ − 0.08 ppm (RMS 0.18 ppm, MAD 0.66 ppm) and δC,calc = δPBE/3ζ − 6.35 ppm (RMS 3.09 ppm, MAD 9.42 ppm) have been developed using the sets of 263 and 308 experimental values for 1H and 13C chemical shifts, respectively. The confidence intervals of NMR chemical shifts at 95% confidence probability are δH,calc ± 0.35 ppm for 1H and δC,calc ± 6.05 ppm for 13C. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011
Exchange coupling constants using density functional theory: Long‐range corrected functionals
Authors: Ruiz Eliseo
Published: April 2011

The presence of the self‐interaction error in common exchange correlation functionals is one of the main drawbacks of calculations using methods based on Density Functional Theory. The recently developed asymptotically corrected functionals are an alternative way to solve the erroneous asymptotic behavior that may be at the origin of this error. Some of these functionals have been tested in the calculation of the exchange coupling constants of a number of transition metal dinuclear complexes. Correction of the self‐interaction error is especially important for calculations of this kind. This error leads to the inclusion of some static correlation terms that overestimate the J values. This study shows that some of the long‐range corrected functionals tested give promising results. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011
Metastases to the breast from extramammary malignancies—sonographic features
Authors: Lee Ji Hye , Kim Sung Hun , Kang Bong Joo , Cha Eun Suk , Kim Hyun Suk , Choi Jae Jeong
Published: April 2011

Purpose.

To evaluate the clinical and sonographic (US) features of metastatic tumors from extramammary malignancies to the breast.

Methods.

This study included 23 patients with pathologically proven metastases in the breast. Two radiologists retrospectively analyzed the images from US (n = 23), mammography (n = 11), and MRI (n = 5) examinations according to BIRADS.

Results.

Patients presented with a palpable mass or diffuse breast swelling (21/23) or were asymptomatic (2/23). Eighteen patients had solitary or multiple breast masses on US. The common US finding was an ovoid hypoechoic mass with a noncircumscribed margin. The final assessment categories were BIRADS 3 (probably benign finding) in 6 cases (25%) and BIRADS 4 (suspicious abnormality) in 18 cases (75%). In five patients, US displayed a diffuse infiltrative pattern without a focal lesion, which was categorized as BIRADS 4.

Conclusions.

Metastatic tumors in the breast have a wide range of sonographic appearances, with some resembling benign lesions. Any newly developed mass in a patient with a known history of extramammary malignancy, even with a probably benign US appearance, should undergo biopsy for pathologic confirmation. © 2011 Wiley Periodicals, Inc. J Clin Ultrasound, 2011
Vascular endothelial growth factor in cerebral ischemia
Authors: Ma Yihui , Qu Yan , Fei Zhou
Published: April 2011

Vascular endothelial growth factor (VEGF) is involved in many central nervous system disorders, including stroke, and confers neuroprotection in cerebral ischemia. In this Mini‐Review, we examine in detail the in vitro and in vivo evidence for the role of VEGF in cerebral ischemia. VEGF is a therapeutic mediator for cerebral ischemia because of its angiogenic and neuroprotective effects. However, several studies indicate that the delivery route and the timing of VEGF delivery seem to determine the outcome of VEGF therapy after an ischemic insult. In the acute stage of cerebral ischemia, the effect of VEGF is considered controversial. Therefore, further work is necessary to identify a suitable therapeutic regime prior to phase II/III clinical trials. In addition, recent studies indicate that VEGF enhances neurogenesis after ischemia. Therefore, further investigation is necessary to clarify the exact role of VEGF in neurogenesis. © 2011 Wiley‐Liss, Inc.
Getting organizational improvement off the ground: Using the Cube One framework to learn from the turnaround at Continental Airlines
Authors: Kopelman Richard E. , Chiou Andy Y.
Published: April 2011

Much has been written about the remarkable turnaround at Continental Airlines under Gordon Bethune and Greg Brenneman during the 1990s. But much can still be learned from the experience. This article reviews the general components of the turnaround plan at Continental Airlines; briefly describes the Cube One framework, which makes it possible to interpret and assess an organization's functioning by examining its productivity‐, customer‐, and employee‐directed practices; describes management practices implemented at Continental; and examines evidence pertinent to their effectiveness, comparing results during the five‐year period before Bethune and his team arrived (1990–1994) with the five‐year period afterward (1995–1999). It concludes with a look at Continental's practices in the early twenty‐first century. © 2011 Wiley Periodicals, Inc.
An analysis of corporate social responsibility in the Greek telecommunications sector
Authors: Giannarakis Grigoris , Sariannidis Nikolaos , Litinas Nikolaos
Published: April 2011

In assessing the performance of national and multinational businesses, attention focuses not only on financial performance, but also on such issues as social responsibility, environmental impact, and employment practices. There is a range of guidance and reporting mechanisms that allows firms to assess and communicate their performance in the area of corporate social responsibility (CSR). This study focuses on two such mechanisms, the Global Reporting Initiative (GRI) and the Deloitte Reporting Sustainability Scorecard (DRSS), and examines their use in four Greek telecommunications businesses. The findings reveal gaps in reporting practices in this field and highlight the differences between the two reporting systems and their usefulness for nonfinancial reporting. © 2011 Wiley Periodicals, Inc.
Estrogen reduces cellular aging in human mesenchymal stem cells and chondrocytes
Authors: Breu Anita , Sprinzing Benedikt , Merkl Katharina , Bechmann Volker , Kujat Richard , Jenei‐Lanzl Zsuzsa , Prantl Lukas , Angele Peter
Published: April 2011

Chondrocyte aging is associated with cartilage degeneration and senescence impairs the regenerative potential of mesenchymal stem cells (MSCs). Estrogen exerts profound effects on human physiology including articular cartilage and MSCs. The present study should analyze the effects of pre‐ and postmenopausal estrogen concentrations on chondrogenic cells. Physiologic premenopausal concentrations of 17β‐estradiol (E2) significantly decelerated telomere attrition in MSCs and chondrocytes while postmenopausal E2concentration had no significant effects. The estrogen agonist–antagonist tamoxifen did not affect telomere biology, but inhibited the E2‐stimulated reduction in telomere shortening. E2and tamoxifen did not influence cell proliferation, cell morphology, and β‐galactosidase staining in chondrogenic cells. E2treatment did not affect the telomere‐associated proteins TRF1 and TRF2. E2had no regulatory effects on the expression rates of the cell cycle regulator p21 and the DNA repair proteins SIRT1 and XRCC5. In spite of reducing telomere shortening in aging MSCs and chondrocytes, estrogen is not able to prevent somatic cells from replicative exhaustion and from finally entering senescence. The fade of telomere shortening under pre‐ to postmenopausal estrogen concentrations suggests, at least in part, a senescence‐dependent cause for the onset of osteoarthritis in women after menopause. © 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29: 1563–1571, 2011
Disulfide Core Cross‐Linked PEGylated Polypeptide Nanogel Prepared by a One‐Step Ring Opening Copolymerization of N‐Carboxyanhydrides for Drug Delivery
Authors: Xing Tao , Lai Bin , Ye Xiaodong , Yan Lifeng
Published: April 2011

A novel disulfide core cross‐linked PEGylated polypeptide nanogel has been synthesized by a one‐step ring opening copolymerization of γ‐benzyl L‐glutamate N‐carboxyanhydride and L‐cystine N‐carboxyanhydride using an amino group‐terminated poly(ethylene glycol) methyl ether as initiator. Characterization of products confirms the formation of a core cross‐linked PEGylated nanogel with disulfide linkages with a size of about 250 nm, and these studies also confirm that this nanogel can easily be broken by glutathione. Cell viability experiments show the good biocompatibility of the as‐prepared polymer. Studies relating to loading and controlled release of indomethacin under reduction‐sensitive conditions reveal that the nanogel is a good candidate for drug delivery systems.

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Fast Deswelling Kinetics of Nanostructured Poly(N‐Isopropylacrylamide) Photopolymerized in a Lyotropic Liquid Crystal Template
Authors: Forney Bradley S. , Allan Guymon C.
Published: April 2011

The thermal‐response and mechanical properties of poly(N‐isopropylacrylamide) (PNIPAm) are improved by controlling the polymer nanostructure through photopolymerization in a bicontinuous cubic lyotropic liquid crystal (LLC) template. The bicontinuous cubic nanostructure increases the rate and amount of water expelled from PNIPAm for heating above the lower critical solution temperature (LCST) relative to an isotropic PNIPAm hydrogel while maintaining the mechanical integrity of the polymer. These results could allow development of PNIPAm hydrogels with proper water uptake, deswelling kinetics, volume transition, and mechanical properties required for successful performance in a growing number of advanced biological and industrial applications.

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Supramolecular Architectures Self‐assembled from Asymmetrical Hetero Cyclopeptides
Authors: Qin Si‐Yong , Xu Xiao‐Ding , Chen Chang‐Sheng , Chen Jing‐Xiao , Li Ze‐Yong , Zhuo Ren‐Xi , Zhang Xian‐Zheng
Published: April 2011

In this study, two asymmetrical cyclopeptides (CP1 and CP2) were designed and synthesized. The self‐assembly behaviors of the asymmetrical cyclopeptides at varying pHs were investigated in terms of transmission electron microscopy (TEM), circular dichroism (CD), and Fourier transform infrared (FT‐IR) spectroscopy. It was found that the self‐assembly of CP1 resulted in the formation of nanofibers with α‐helix conformation, while CP2 self‐assembled into well‐ordered nanorods with anti‐parallel β‐sheet conformation. The strategy demonstrated here presents great potential for preparation of well‐defined nanostructures via rationally designing the molecular structures of cyclopeptides.

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Adapting Visual‐Analytical Tools for the Exploration of Structural and Dynamical Features of Polymer Conformations
Authors: Thakur Sidharth , Pasquinelli Melissa A.
Published: April 2011

Conformational analysis of macromolecular structures reveals interesting higher‐order spatial arrangements. Analyzing these features as a function of time provides insights into the dynamical behavior of these systems and the identification of relevant subdomains. We present some visual‐analytic methods that we devised to explore the spatial‐temporal properties from molecular dynamics simulation data. These methods automatically detect common features and connect them to properties of interest. These methods yield physical insights that are not easily obtainable with existing methods for particle simulation data, as illustrated for polyacetylene interacting with a carbon nanotube.

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Botulinum toxin injections reduce associative plasticity in patients with primary dystonia
Authors: Kojovic Maja , Caronni Antonio , Bologna Matteo , Rothwell John C. , Bhatia Kailash P. , Edwards Mark J.
Published: April 2011

Botulinum toxin injections ameliorate dystonic symptoms by blocking the neuromuscular junction and weakening dystonic contractions. We asked if botulinum toxin injections in dystonia patients might also affect the integrity of sensorimotor cortical plasticity, one of the key pathophysiological features of dystonia. We applied a paired associative stimulation protocol, known to induce long‐term potentiation–like changes in the primary motor cortex hand area to 12 patients with cervical dystonia before and 1 and 3 months after botulinum toxin injections to the neck muscles. Primary motor cortex excitability was probed by measuring transcranial magnetic stimulation‐evoked motor evoked potentials before and after paired associative stimulation. We also measured the input–output curve, short‐interval intracortical inhibition, intracortical facilitation, short afferent inhibition, and long afferent inhibition in hand muscles and the clinical severity of dystonia. Before botulinum toxin injections, paired associative stimulation significantly facilitated motor evoked potentials in hand muscles. One month after injections, this effect was abolished, with partial recovery after 3 months. There were significant positive correlations between the facilitation produced by paired associative stimulation and (1) the time elapsed since botulinum toxin injections and (2) the clinical dystonia score. One effect of botulinum toxin injection treatment is to modulate afferent input from the neck. We propose that subsequent reorganization of the motor cortex representation of hand muscles may explain the effect of botulinum toxin on motor cortical plasticity. © The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.
The bias/variance trade‐off when estimating the MR signal magnitude from the complex average of repeated measurements
Authors: Tisdall M. Dylan , Lockhart Richard A. , Atkins M. Stella
Published: April 2011

The signal‐dependent bias of MR images has been considered a hindrance to visual interpretation almost since the beginning of clinical MRI. Over time, a variety of procedures have been suggested to produce less‐biased images from the complex average of repeated measurements. In this work, we re‐evaluate these approaches using first a survey of previous estimators in the MRI literature, then a survey of the methods statisticians employ for our specific problem. Our conclusions are substantially different from much of the previous work: first, removing bias completely is impossible if we demand the estimator have bounded variance; second, reducing bias may not be beneficial to image quality. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.
MRS characterization of central neurocytomas using glycine
Authors: Shah Tariq , Jayasundar Rama , Singh Virendera Paul , Sarkar Chitra
Published: April 2011

This study reports in vivo MRS findings in 11 patients with histologically diagnosed central neurocytomas, which are rare intraventricular tumors of neuronal origin. Single‐voxel 1H MRS was carried out prior to surgery using a point‐resolved spectroscopy sequence with TR = 6 s, TE = 135 ms and 128 scans. In vitro high‐resolution 1H spectroscopy was also carried out on two surgically excised samples. The striking features of the spectra from the central neurocytomas were the presence of high glycine, decreased N‐acetylaspartate, increased choline and alanine. Retrospective, blind analysis of the spectra by two independent observers correctly identified all but one central neurocytoma based on the presence of glycine. The presence of glycine and prominent choline in the 1H MR spectrum is a characteristic feature of the central neurocytomas, and could be used to characterize and differentiate them from other brain tumors. Copyright © 2011 John Wiley & Sons, Ltd.
A mathematical analysis of the R‐MAT random graph generator
Authors: Groër Chris , Sullivan Blair D. , Poole Steve
Published: April 2011

The R‐MAT graph generator introduced by Chakrabarti et al (Int Conf Data Mining, 2004) offers a simple, fast method for generating very large directed graphs. These properties have made it a popular choice as a method of generating graphs for objects of study in a variety of disciplines, from social network analysis to high performance computing. We analyze the graphs generated by R‐MAT and model the generator in terms of occupancy problems to prove results about the degree distributions of these graphs. We prove that the limiting degree distributions can be expressed as a mixture of normal distributions with means and variances that can be easily calculated from the R‐MAT parameters. Additionally, this article offers an efficient computational technique for computing the exact degree distribution and concise expressions for a number of properties of R‐MAT graphs. ©2011 Wiley Periodicals, Inc.*. NETWORKS, 2011
An adaptive finite point method for the shallow water equations
Authors: Ortega Enrique , Oñate Eugenio , Idelsohn Sergio , Buachart Chinapat
Published: April 2011

An adaptive Finite Point Method (FPM) for solving shallow water problems is presented. The numerical methodology we propose, which is based on weighted‐least squares approximations on clouds of points, adopts an upwind‐biased discretization for dealing with the convective terms in the governing equations. The viscous and source terms are discretized in a pointwise manner and the semi‐discrete equations are integrated explicitly in time by means of a multi‐stage scheme. Moreover, with the aim of exploiting meshless capabilities, an adaptive h‐refinement technique is coupled to the described flow solver. The success of this approach in solving typical shallow water flows is illustrated by means of several numerical examples and special emphasis is placed on the adaptive technique performance. This has been assessed by carrying out a numerical simulation of the 26th December 2004 Indian Ocean tsunami with highly encouraging results. Overall, the adaptive FPM is presented as an accurate enough, cost‐effective tool for solving practical shallow water problems. Copyright © 2011 John Wiley & Sons, Ltd.
On the techniques for constructing admissible stress fields in model verification: Performances on engineering examples
Authors: Pled F. , Chamoin L. , Ladevèze P.
Published: April 2011

Robust global/goal‐oriented error estimation is used nowadays to control the approximate finite element (FE) solutions obtained from simulation. In the context of computational mechanics, the construction of admissible stress fields (i.e. stress tensors which verify the equilibrium equations) is required to set up strict and guaranteed error bounds (using residual‐based error estimators) and plays an important role in the quality of the error estimates. This work focuses on the different procedures used in the calculation of admissible stress fields, which is a crucial and technically complicated point. The three main techniques that currently exist, called the element equilibration technique (EET), the star‐patch equilibration technique (SPET), and the element equilibration + star‐patch technique (EESPT), are investigated and compared with respect to three different criteria, namely the quality of associated error estimators, computational cost, and easiness of practical implementation into commercial FE codes.

The numerical results that are presented focus on industrial problems; they highlight the main advantages and drawbacks of the different methods and show that the behavior of the three estimators, which have the same convergence rate as the exact global error, is consistent. 2D and 3D experiments have been carried out in order to compare the performance and the computational cost of the three different approaches. The analysis of the results reveals that the SPET is more accurate than EET and EESPT methods, but the corresponding computational cost is higher. Overall, the numerical tests prove the interest of the hybrid method EESPT and show that it is a correct compromise between the quality of the error estimate, practical implementation and computational cost. Furthermore, the influence of the cost function involved in the EET and the EESPT is studied in order to optimize the estimators. Copyright © 2011 John Wiley & Sons, Ltd.
Investigation of the Negative Ions in Ar/O2 Plasma of Magnetron Sputtering Discharge with Al:Zn Target by Ion Mass Spectrometry
Authors: Pokorný Petr , Mišina Martin , Bulíř Jiří , Lančok Ján , Fitl Přemysl , Musil Jindřich , Novotný Michal
Published: April 2011

The magnetron sputtering discharge used to deposit aluminum‐doped zinc oxide was analyzed by energy‐resolved ion mass spectrometry. The flux of negative ions was measured at three radial positions in the plane of the substrate holder. The oxygen flow $\phi _{{\rm O}_{2} } $ was varied from 0 to 17 sccm to investigate the discharge in all operation modes, i.e., metallic, transition, and oxide mode of sputtering. The existence of negative ions was determined from the energy spectra. Main attention was devoted to the investigation of O−, ${\rm O}_{2}^{{-} } $, AlO−, ${\rm AlO}_{2}^{{-} } $, ZnO−, ${\rm ZnO}_{2}^{{-} } $, and ${\rm AlO}_{3}^{{-} } $ negative ions and correlations of their intensities in the energy spectrum with discharge parameters (cathode voltage, magnetron power, and gas pressure). It was found that (i) intensities of negative ions exhibit maxima in the vicinity of transition between the metallic and transition mode of sputtering and (ii) in the oxide mode intensities of these ions are saturated.

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Effect of acidic pH on antibacterial action of peptide isolated from Korean pen shell (Atrina pectinata)
Authors: Yoo Suyeon , Kim Jin‐Young , Park Seong‐Cheol , Choi Do Young , Seo Chang Ho , Hahm Kyung‐Soo , Park Yoonkyung
Published: April 2011

Recently, the rapid emergence of microbial pathogens which are resistant to currently available antibiotics has triggered considerable interest searching for naturally occuring antimicrobial peptides (AMPs). Because AMPs from food organisms are comparatively nontoxic, a number of them are used as sources, purified in new antibiotics. Herein, an antibacterial peptide (heat‐stable KPS‐1) was isolated from Korean pen shell (Atrina pectinata) by the following procedures: solvent‐extraction, heating, ultrafiltration, and RP‐HPLC. The molecular weight of KPS‐1 (4549.1 Da) was revealed by MALDI‐TOF/MS analysis. Interestingly, KPS‐1 inhibitedin vitrogrowth of Gram‐negative bacteria, includingEscherichia coli, E. coliO157,Pseudomonas aeruginosa, Enterobacter sakazakii, andSalmonella typhimurium,at pH 5.2, rather than at pH 7.2. Its minimal inhibitory concentrations (MICs) were ranged from 20 to 80 µg/ml; however, it was not effective against human red blood cells at a concentration of 500 µg/ml. This suggests that this peptide is useful as a clinical agent for some human organs in an acidic environment. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.
Elastic properties of chemically modified baker's yeast cells studied by AFM
Authors: Suchodolskis Arturas , Feiza Vidmantas , Stirke Arunas , Timonina Ana , Ramanaviciene Almira , Ramanavicius Arunas
Published: April 2011

Chemical pretreatment is widely used to facilitate transformation of living cells when foreign components are introduced into a cell through the cell wall. The influence of appropriate chemicals on the wall properties and mechanism of transformation is still a matter of intensive studies. Saccharomyces cerevisiae cells (also known as baker's yeast) were investigated by atomic force microscopy (AFM). The cell walls were modified by lithium acetate and dithiothreitol. The AFM imaging was performed in liquid water‐based environment. The living cells were fixed by trapping into the holes of a polycarbonate membrane. Mechanical and morphological properties of initial intact cells and treated cells were investigated. The increased stiffness of the chemically treated cells was observed. As deduced from the applied theoretical Hertz‐Sneddon model, the treated cells show completely different response mechanism to applied mechanical pressure in comparison with the intact cells. Also, the increased roughness of the cell wall of the treated yeasts was observed. Copyright © 2011 John Wiley & Sons, Ltd.
Parametric variable selection in generalized partially linear models with an application to assess condom use by HIV‐infected patients
Authors: Leng Chenlei , Liang Hua , Martinson Neil
Published: April 2011

To study significant predictors of condom use in HIV‐infected adults, we propose the use of generalized partially linear models and develop a variable selection procedure incorporating a least squares approximation. Local polynomial regression and spline smoothing techniques are used to estimate the baseline nonparametric function. The asymptotic normality of the resulting estimate is established. We further demonstrate that, with the proper choice of the penalty functions and the regularization parameter, the resulting estimate performs as well as an oracle procedure. Finite sample performance of the proposed inference procedure is assessed by Monte Carlo simulation studies. An application to assess condom use by HIV‐infected patients gains some interesting results, which cannot be obtained when an ordinary logistic model is used. Copyright © 2011 John Wiley & Sons, Ltd.
Separation of Monoester and Diester in the Esterification Product of Polyethylene Glycol and Acrylic Acid by the Weibull Method
Authors: Lei Jia‐Heng , Li Hui , Zhang An‐Fu , Du Xiao‐Di , Lu Qian
Published: April 2011

In the extraction system of ethyl acetate and NaCl aqueous solution, partition coefficients of polyethylene glycol mono‐acrylate (PEGmA) and polyethylene glycol di‐acrylate (PEGdA) varied with temperature and concentration of NaCl solution were studied. The best separation condition of PEGmA and PEGdA was determined on that basis. Results of the testing showed that partition coefficients of PEGmA and PEGdA sharply increased with rising concentration of NaCl solution and temperature. Since the incremental degrees of PEGmA and PEGdA were different from each other, the ratio of partition coefficient (KPEGdA/KPEGmA) reached a maximum under the conditions of 20 °C and 5 mol L−1 NaCl. The best separating condition was as follows: PEGdA was extracted out with ethyl acetate by adding 5 mol L−1 NaCl at 20 °C. After three repetitions, the recovery rate of PEGdA reached 99.8%. The water phase was heated to 50 °C and PEGmA was extracted out with ethyl acetate. The recovery rate of PEGmA amounted to 68.8% by three repetitions. After washing and drying, the purity of PEGmA and PEGdA was 99.7 and 98.7% respectively.
Enzymatic Epoxidation of Corn Oil by Perstearic Acid
Authors: Sun Shangde , Yang Guolong , Bi Yanlan , Liang Hui
Published: April 2011

Epoxidized vegetable oils can be used as renewable biodegradable and non‐toxic lubricants, polymer stabilizers, and as intermediates. In this study, as a renewable resource, corn oil rich in oleic and linoleic acids, which was epoxidized using hydrogen peroxide as an oxygen donor and stearic acid as an active oxygen carrier in the presence of Novozym 435. The process was optimized for the enzymatic epoxidation of corn oil with an epoxy oxygen group content of 5.8 ± 0.2% and a percentage relative conversion to oxirane of 85.3 ± 2.9% under the following conditions: 35 °C, 28% stearic acid load (relative to the weight of corn oil), 2.7:1 mol ratio of H2O2/C=C‐bonds, and 10 h. The influence on the enzymatic epoxidation decreased in the order of stearic acid load > reaction temperature ≈ mole ratio of H2O2/C=C‐bonds >reaction time.
DIFFERENTIAL SUBORDINATIONS FOR CLASSES OF MEROMORPHIC p-VALENT FUNCTIONS DEFINED BY MULTIPLIER TRANSFORMATIONS
Authors: EL-ASHWAH R. M. , AOUF M. K. , BULBOACĂ T.
Published: April 2011

We investigate several inclusion relationships and other interesting properties of certain subclasses of p-valent meromorphic functions, which are defined by using a certain linear operator, involving the generalized multiplier transformations.