bluuebunny/crossref_metadata_2025 huggingface dataset:
Emission of positronium negative ions from Cs deposited W(100) and polycrystalline Fe surfaces
Authors: Nagashima Yasuyuki , Hakodate Toshihide , Miyamoto Ayaka , Michishio Koji , Terabe Hiroki
Published: October 2009

Efficient emission of positronium negative ions from Cs deposited W(100) surface has been observed. The emission efficiency measured over a time interval of 3000 s immediately after the deposition was found to be 1.25% for the target with a 2.2 × 1014 atoms/cm2 Cs layer. The emission from Cs deposited polycrystalline Fe surface has also been observed. The upper limit of the binding energy of the ion has been estimated experimentally. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparative study of transformation of micellar structures in CTAB and TTAB binary systems using Positron Lifetime Spectroscopy
Authors: Yadav R. , Singh K. Chandramani , Choudhary S. R. , Jain P. C.
Published: October 2009

The micellar structures of cetyl‐tri‐methyl ammonium bromide (CTAB) and its homologues have been investigated employing several conventional techniques. However, due to lack of sensitivity inherent in these techniques and the perturbation introduced by the probe, the detailed structures of the aggregates in the so‐called single phase regions of these systems are far from being fully understood. Positron has been found to be a useful non‐destructive probe for investigating micellar structures in surfactant systems [1‐3] The present study is an effort to get a better insight into the micellar structures and their transformations in CTAB and TTAB aqueous binary systems Positron lifetime spectroscopy has been employed to study these systems covering a wide range of surfactant concentrations. A comparative study of the results obtained for the two surfactant systems have been discussed in this paper. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coincident Doppler‐broadening spectroscopy of Si, amorphous SiO2, and α‐quartz using mono‐energetic positrons
Authors: Hugenschmidt C. , Pikart P. , Schreckenbach K.
Published: October 2009

Experiments on oxides and on silicon by coincident Doppler broadening spectroscopy (CDBS) using the mono‐ener‐ getic positron beam at the neutron induced positron source NEPOMUC are presented. Doppler‐broadening spectroscopy (DBS) as a function of positron implantation energy is applied in order to compare the crystalline quartz and single crystalline Si with amorphous quartz. More detailed information about the chemical surrounding at the positron annihilation site is gained by CDBS‐experiments. For this reason, the CDBS‐measurements are performed to detect the signature of positrons annihilating with electrons from oxygen. The comparison of the CDB spectra obtained for the quartz samples and ice with that of the Si surface clearly shows that the surface of single‐crystalline Si is terminated with oxygen. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ageing processes in Al‐Cu‐Mg alloys with different Cu/Mg ratios
Authors: Macchi C. , Somoza A. , Ferragut R. , Dupasquier A. , Polmear I. J.
Published: October 2009

Three age‐hardenable Al‐Cu‐Mg alloys with different Cu/Mg ratios were studied by means of positron annihilation lifetime spectroscopy and Vickers hardness as a function of the artificial ageing time at 175 °C. Complementary information on the decomposition sequence was obtained by means of differential scanning calorimetry. The results are discussed in terms of the different structures that are formed during the precipitation sequence of the supersaturated solid solution. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect characterization of heavily As and P doped Si epilayers
Authors: Kilpeläinen Simo , Kuitunen Katja , Slotte Jonatan , Tuomisto Filip , Borot Gaël , Rubaldo Laurent , Clément L. , Pantel Roland , Dutartre Didier
Published: October 2009

In this paper, positron annihilation spectroscopy in Doppler broadening mode is used to show that inactive As and P atoms causing tensile strain in heavily doped Si epilayers are linked to vacancy‐type defects. In the case of As doping, a clear increase in the average number of impurity atoms per monovacancy is observed as As concentration is increased. The effect of high temperature spike annealing on heavily As doped Si epilayers is also investigated and the vacancy‐impurity complexes are shown to be very stable in most samples. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron lifetime studies of CaSO4: Dy thermoluminescence phosphors
Authors: Annalakshmi O. , Chirayath Varghese Anto , Babu S. Hari , Jose M. T. , Amarendra G.
Published: October 2009

Positron lifetime studies have been carried out on CaSO4:Dy phosphors with and without Teflon binder. The effect of Co‐60 gamma irradiation exposure in these samples has been investigated. Unexposed CaSO4:Dy embedded Teflon discs exhibited four lifetime components viz., 228, 755, 3865 and 77 ps with intensities of 62%, 18%, 14% and 6%, respectively. Since Teflon is used as a binder in these phosphors, the long lived components are understood to arise from this. Upon radiation exposure there is a clear change in these resolved lifetime components. To understand the variation of these lifetime components better, positron lifetime studies was carried out on pure CaSO4:Dy powder (without Teflon) as well as pure Teflon discs exposed to varying radiation doses. The variation of positron lifetime parameters of CaSO4:Dy powder showed systematics, ascribable to SO–4 ion formation due to γ‐ray exposure. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PALS study of point defects in Fe‐Al and Fe‐Al‐Cr alloys
Authors: Kansy Jerzy , Hanc Aneta , Pająk Lucjan , Giebel Dawid
Published: October 2009

The concentrations of quenched‐in vacancies in Fe‐Al and Fe‐Al‐Cr systems after their various thermal treatment were studied by positron lifetime spectroscopy. The experimental data were analyzed with the 2‐state trapping model directly implemented to the code of the computer program (LT‐9 2). The number of quenched‐in vacancies strongly depends on the rate of quenching. For fast quenched samples the atomic concentration is of order of 10–4 and it radically falls after annealing at 500 °C for 0.5 h. A comparison of Fe28Al and Fe28Al5Cr samples, after analogical heat treatment, showed that chromium addition caused a systematical decrease of the resistant vacancy concentrations. In the samples that were slowly cooled after quenching at 1000 °C the positrons are trapped at precipitates of minor alloying elements. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of growth conditions on vacancy defects in MOVPE grown AlN thin layers
Authors: Mäki J.‐M. , Tuomisto F. , Bastek B. , Bertam F. , Christen J. , Dadgar A. , Krost A.
Published: October 2009

In this paper we report preliminary results on the vacancy type defects in thin film aluminum nitride (AlN). We have performed positron beam measurements in 7 thin film AlN layers on silicon grown by metal‐organic vapour phase epitaxy (MOVPE) in varying conditions. The growth temperature, V/III supply ratio of the precursor molecules and the layer thicknesses have been varied. All the samples grown had a high concentration of vacancy type defects, hence it seems that the structural defects and possible strain due to lattice mismatch betweenmaterials has a major role in the vacancy formation. Additionally, the growth conditions were found to have an effect on the vacancy content of the samples. Increasing growth temperatures and decreasing layer thickness seemed to increase the vacancy concentration whereas V/III ratio of the growth gases did not seem to have an effect (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron annihilation studies on chalcone chromophore doped PVA
Authors: Bhajantri R. F. , Ravindrachary V. , Harisha A. , Ismayil  , Ranganathaiah C.
Published: October 2009

A novel organic non‐linear optical material 1‐(4‐methylphenyl)‐3‐(4‐ N, N dimethyl amino phenyl)‐2‐propen‐1‐one (MPDMAPP) chalcone chromophore has been synthesized by standard method. Pure and MPDMAPP doped Poly(vinyl alcohol) films are prepared using solution casting method and characterized using UV‐Visible absorption and Positron Annihilation Lifetime Spectroscopy. The optical spectroscopic study shows three absorption bands, 196‐202 nm assigned to localized n →π * transitions, 205‐320 nm to n →π * inter‐band and 385‐428 nm assigned to π →π * transition and arises due to the charge transfer complex. Using observed UV‐Vis spectra, three optical energy gaps, Eg1 (4.96–4.25 eV), Eg2 (3.47–3.32 eV) and Eg3 (2.33–2.24 eV) have been estimated. The observed change in Eg upon doping is understood based on the formation of charge transfer complex arising from the –HC=CH– structure present in the composite and due to the interactions of dopant and OH group of PVA. The PALS results shows that the o‐Ps lifetime decreases continuously as doping concentration increases and I3 initially increases (from 18.82% to 20.95%) from 0 wt% to 0.05 wt% and then decreases gradually up to 16.76% for higher dopant concentrations with decrease in optical band gaps. The variation of positron data with Eg is understood by correlating the probability of Ps formation with the complex. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
o‐Ps lifetime, free volume and Doppler broadening spectroscopy (DBS) studies of 50 MeV Li3+ ion irradiated polystyrene
Authors: Ali S. Asad , Kumar Rajesh , Nambissan P. M. G. , Singh Fouran , Prasad Rajendra
Published: October 2009

Swift Heavy Ion(SHI) irradiation of polymeric materials results in the change of their free volume properties. Polystyrene films (1 mm) were irradiated with Li3+ ions of energy 50 MeV to the fluences from 5x1010 to 3.5x1013 ions/cm2.The effect of ion irradiation on free volume has been characterized by PALS and DBS. From o‐Ps pick off annihilation lifetime τ3, mean free volume hole radius, average free volume of micro voids and fractional free volume are computed. Free volume values change slowly with ion fluence with a decrease at the highest fluence of 3.5x1013 ions/cm2. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect evolution in steels: Insights from positron studies
Authors: Rajaraman R. , Amarendra G. , Sundar C. S.
Published: October 2009

Positron annihilation studies on austentic and ferritic/martensitic and oxide‐dispersion steels are highlighted so as to emphasize the sensitivity of the technique to defect annealing as well as precipitates. The results obtained on austenitic D9 steels are discussed with a view to emphasize the role of small TiC precipitates in the matrix, which play a critical role in void‐swelling behaviour. Further, the role of Ti/C ratio as well as minor alloying elements on swelling behaviour is discussed. The current focus of research is on the use of nanoclusters in ODS alloys towards the suppression of void formation under irradiation. Recent results on the investigation on nano Yttria particles in Fe – model oxide dispersion ferritic steel, are presented with supporting ab‐initio lifetime calculations. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A conservative Fourier‐finite‐element method for solving partial differential equations on the whole sphere
Authors: Dubos T.
Published: October 2009

Solving transport equations on the whole sphere using an explicit time stepping and an Eulerian formulation on a latitude–longitude grid is relatively straightforward but suffers from the pole problem: due to the increased zonal resolution near the pole, numerical stability requires unacceptably small time steps. Commonly used workarounds such as near‐pole zonal filters affect the qualitative properties of the numerical method. Rigorous solutions based on spherical harmonics have a high computational cost.

The numerical method we propose to avoid this problem is based on a Galerkin formulation in a subspace of a Fourier‐finite‐element spatial discretization. The functional space we construct provides quasi‐uniform resolution and high‐order accuracy, while the Galerkin formalism guarantees the conservation of linear and quadratic invariants. For N2 degrees of freedom, the computational cost is 𝒪(N2logN), dominated by the zonal Fourier transforms. This is more than with a finite‐difference or finite‐volume method, which costs 𝒪(N2), and less than with a spherical harmonics method, which costs 𝒪(N3). Differential operators with latitude‐dependent coefficients are inverted at a cost of 𝒪(N2).

We present experimental results and standard benchmarks demonstrating the accuracy, stability and efficiency of the method applied to the advection of a scalar field by a prescribed velocity field and to the incompressible rotating Navier–Stokes equations. The steps required to extend the method towards compressible flows and the Saint‐Venant equations are described. Copyright © 2009 Royal Meteorological Society
Assimilation of SEVIRI infrared radiances with HIRLAM 4D‐Var
Authors: Stengel M. , Undén P. , Lindskog M. , Dahlgren P. , Gustafsson N. , Bennartz R.
Published: October 2009

Four‐dimensional variational data assimilation (4D‐Var) systems are ideally suited to obtain the best possible initial model state by utilizing information about the dynamical evolution of the atmospheric state from observations, such as satellite measurements, distributed over a certain period of time. In recent years, 4D‐Var systems have been developed for several global and limited‐area models. At the same time, spatially and temporally highly resolved satellite observations, as for example performed by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on board the Meteosat Second Generation satellites, have become available.

Here we demonstrate the benefit of a regional NWP model's analyses and forecasts gained by the assimilation of those radiances. The 4D‐Var system of the HIgh Resolution Limited Area Model (HIRLAM) has been adjusted to utilize three of SEVIRI's infrared channels (located around 6.2 µm, 7.3 µm, and 13.4 µm, respectively) under clear‐sky and low‐level cloud conditions. Extended assimilation and forecast experiments show that the main direct impact of assimilated SEVIRI radiances on the atmospheric analysis were additional tropospheric humidity and wind increments. Forecast verification reveals a positive impact for almost all upper‐air variables throughout the troposphere. Largest improvements are found for humidity and geopotential height in the middle troposphere. The observations in regions of low‐level clouds provide especially beneficial information to the NWP system, which highlights the importance of satellite observations in cloudy areas for further improvements in the accuracy of weather forecasts. Copyright © 2009 Royal Meteorological Society
Isotope pattern vector based tandem mass spectral data calibration for improved peptide and protein identification
Authors: Zhang Jingfen , Xu Dong , Gao Wen , Lin Guohui , He Simin
Published: October 2009

Tandem mass spectra contain noisy peaks which make peak picking for peptide identification difficult. Moreover, all spectral peaks can be shifted due to systematic measurement errors. In this paper, a novel use of anisotope pattern vector(IPV) is proposed for denoising and systematic measurement error prediction. By matching the experimental IPVs with the theoretical IPVs of candidate fragment ions, true ionic peaks can be identified. Furthermore, these identified experimental IPVs and their corresponding theoretical IPVs are used in an optimization process to predict the systematic measurement error associated with the target spectrum. In return, the subsequent spectral data calibration based on the predicted systematic measurement error enhances the data quality. We show that such an integrated denoising and calibration process leads to significantly improved peptide and protein identification. Different from the commonly employed chemical calibration methods, our IPV‐based method is a purely computational method for individual spectra analysis and globally optimizes the use of spectral data. Copyright © 2009 John Wiley & Sons, Ltd.
Analysis of S‐adenosylmethionine and related sulfur metabolites in bacterial isolates of Pseudomonas aeruginosa (BAA‐47) by liquid chromatography/electrospray ionization coupled to a hybrid linear quadrupole ion trap and Fourier transform ion cyclotron resonance mass spectrometry
Authors: Cataldi Tommaso R. I. , Bianco Giuliana , Abate Salvatore , Mattia Daniela
Published: October 2009

A comprehensive and highly selective method for detecting in bacterial supernatants a modified sulfur nucleoside, S‐adenosyl‐L‐methionine (SAM), and its metabolites, i.e., S‐adenosylhomocysteine (SAH), adenosine (Ado), 5′‐deoxy‐5′‐methylthioadenosine (MTA), adenine (Ade), S‐adenosyl‐methioninamine (dcSAM), homocysteine (Hcy) and methionine (Met), was developed. The method is based on reversed‐phase liquid chromatography with positive electrospray ionization (ESI+) coupled to a hybrid linear quadrupole ion trap (LTQ) and 7‐T Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). A gradient elution was employed with a binary solvent of 0.05 M ammonium formate at pH 4 and acetonitrile. The assay involves a simultaneous cleanup of cell‐free bacterial broths by solid‐phase extraction and trace enrichment of metabolites with a 50‐fold concentration factor by using immobilized phenylboronic and anion‐exchange cartridges. While the quantitative determination of SAM was performed using stable‐isotope‐labeled SAM‐d3 as an internal standard, in the case of Met and Ade, Met‐13C and Ade‐15N2 were employed as isotope‐labeled internal standards, respectively. This method enabled the identification of SAM and its metabolites in cell‐free culture of Pseudomonas aeruginosa grown in Davis minimal broth (formulation without sulphur organic compounds), with routine sub‐ppm mass accuracies (−0.27 ± 0.68 ppm). The resulting contents of SCSS‐SAM, SS‐dcSAM, MTA, Ado and Met in the free‐cell supernatant of P. aeruginosa was 56.4 ± 2.1 nM, 32.2 ± 2.2 nM, 0.91 ± 0.10 nM, 19.6 ± 1.2 nM and 1.93 ± 0.02 µM (mean ± SD, n = 4 extractions), respectively. We report also the baseline separation (Rs ≥1.5) of both diastereoisomeric forms of SAM (SCSS and SCRS) and dcSAM (SS and RS), which can be very useful to establish the relationship between the biologically active versus the inactive species, SCSS/SCRS and SS/RS of SAM and dcSAM, respectively. An additional confirmation of SAM‐related metabolites was accomplished by a systematic study of their MS/MS spectra. Copyright © 2009 John Wiley & Sons, Ltd.
Zur Entwicklung und zum Einsatz des Liquid‐V‐Dampers zur Tilgung von vertikalen Brückenschwingungen – Teil 1 – Mechanische Grundlagen und Wirkungsweise
Authors: Fink Josef , Kuss Stefan
Published: October 2009

Die Kenntnis über das dynamische Verhalten von Bauwerken gewinnt immer mehr an Bedeutung. Dies trifft insbesondere auf Brücken zu, die durch den Einsatz von hochfesten Materialien sowie komplexen Computerprogrammen schlanker und leichter denn je geplant und gebaut werden können. Dadurch wird die Berücksichtigung dynamischer Kriterien in der Planung und Bauwerksüberwachung unumgänglich. Eine Möglichkeit der Minimierung der auftretenden Schwingungen ist die Anordnung von Schwingungsdämpfern am Tragwerk, die bis dato hauptsächlich in der Form des Masse‐Feder‐Dämpfers realisiert wurden.

In diesem zweiteiligen Beitrag soll der alternative Einsatz von Flüssigkeitsschwingungstilgern in V‐Form (Liquid‐V‐Damper) gegen vertikale Brückenschwingungen speziell für den Einsatz bei Fachwerkbrücken dargestellt werden. Dabei wird der Schwerpunkt im vorliegenden ersten Teil des Beitrages auf die mechanische Wirkungsweise gelegt, der zweite Teil beschäftigt sich mit den zugehörigen Versuchen sowie der praktischen Anwendung der Tilger. Auf die baupraktische Einsatzmöglichkeit der Liquid‐V‐Damper wird dabei ein besonderes Augenmerk gelegt.

Development and use of the Liquid‐V‐Damper against vertical bridge vibrations. Part 1 – Mechanical basics and mode of operation.

Nowadays the acknowledgment of the dynamical behavior of structures, in special for bridges, becomes more and more important because of the use of high strength materials and complex computer simulations. Due to that reasons these structures can be planed and build more slender and light weighted than ever. So the consideration of dynamical effects in the planning phase and the structure monitoring is indispensable. One possible method to reduce structural vibrations is the arrangement of dampers on the structure. The common type of dampers is the mass‐spring damper.

In this two‐part paper the alternative use of tuned liquid column damper (Liquid‐V‐Damper) against vertical bridge vibrations in special designed for truss bridges is presented. The presented first part concerns with the mechanical mode of operation, the second part will present the corresponding testing series and the practical tuning of the damper. Special attention is paid to the practical use of the Liquid‐V‐Damper.
Hsp20-Engineered Mesenchymal Stem Cells Are Resistant to Oxidative Stress via Enhanced Activation of Akt and Increased Secretion of Growth Factors
Authors: Wang Xiaohong , Zhao Tiemin , Huang Wei , Wang Tao , Qian Jiang , Xu Meifeng , Kranias Evangelia G. , Wang Yigang , Fan Guo-Chang
Published: October 2009

Although heat-shock preconditioning has been shown to promote cell survival under oxidative stress, the nature of heat-shock response from different cells is variable and complex. Therefore, it remains unclear whether mesenchymal stem cells (MSCs) modified with a single heat-shock protein (Hsp) gene are effective in the repair of a damaged heart. In this study, we genetically engineered rat MSCs with Hsp20 gene (Hsp20-MSCs) and examined cell survival, revascularization, and functional improvement in rat left anterior descending ligation (LAD) model via intracardial injection. We observed that overexpression of Hsp20 protected MSCs against cell death triggered by oxidative stress in vitro. The survival of Hsp20-MSCs was increased by approximately twofold by day 4 after transplantation into the infarcted heart, compared with that of vector-MSCs. Furthermore, Hsp20-MSCs improved cardiac function of infarcted myocardium as compared with vector-MSCs, accompanied by reduction of fibrosis and increase in the vascular density. The mechanisms contributing to the beneficial effects of Hsp20 were associated with enhanced Akt activation and increased secretion of growth factors (VEGF, FGF-2, and IGF-1). The paracrine action of Hsp20-MSCs was further validated in vitro by cocultured adult rat cardiomyocytes with a stress-conditioned medium from Hsp20-MSCs. Taken together, these data support the premise that genetic modification of MSCs before transplantation could be salutary for treating myocardial infarction.

Disclosure of potential conflicts of interest is found at the end of this article.
Klf4 Interacts Directly with Oct4 and Sox2 to Promote Reprogramming
Authors: Wei Zong , Yang Yang , Zhang Peilin , Andrianakos Rosemary , Hasegawa Kouichi , Lyu Jungmook , Chen Xi , Bai Gang , Liu Chunming , Pera Martin , Lu Wange
Published: October 2009

Somatic cells can be reprogrammed to induced pluripotent stem (iPS) cells by ectopic expression of specific sets of transcription factors. Oct4, Sox2, and Klf4, factors that share many target genes in embryonic stem (ES) cells, are critical components in various reprogramming protocols. Nevertheless, it remains unclear whether these factors function together or separately in reprogramming. Here we show that Klf4 interacts directly with Oct4 and Sox2 when expressed at levels sufficient to induce iPS cells. Endogenous Klf4 also interacts with Oct4 and Sox2 in iPS cells and in mouse ES cells. The Klf4 C terminus, which contains three tandem zinc fingers, is critical for this interaction and is required for activation of the target gene Nanog. In addition, Klf4 and Oct4 co-occupy the Nanog promoter. A dominant negative mutant of Klf4 can compete with wild-type Klf4 to form defective Oct4/Sox2/Klf4 complexes and strongly inhibit reprogramming. In the absence of Klf4 overexpression, interaction of endogenous Klf4 with Oct4/Sox2 is also required for reprogramming. This study supports the idea that direct interactions between Klf4, Oct4, and Sox2 are critical for somatic cell reprogramming.

Disclosure of potential conflicts of interest is found at the end of this article.
Self-Renewal of the Long-Term Reconstituting Subset of Hematopoietic Stem Cells Is Regulated by Ikaros
Authors: Papathanasiou Peter , Attema Joanne L. , Karsunky Holger , Hosen Naoki , Sontani Yovina , Hoyne Gerard F. , Tunningley Robert , Smale Stephen T. , Weissman Irving L.
Published: October 2009

Hematopoietic stem cells (HSCs) are rare, ancestral cells that underlie the development, homeostasis, aging, and regeneration of the blood. Here we show that the chromatin-associated protein Ikaros is a crucial self-renewal regulator of the long-term (LT) reconstituting subset of HSCs. Ikaros, and associated family member proteins, are highly expressed in self-renewing populations of stem cells. Ikaros point mutant mice initially develop LT-HSCs with the surface phenotype cKit+Thy1.1(lo)Lin(-/lo)Sca1+Flk2-CD150+ during fetal ontogeny but are unable to maintain this pool, rapidly losing it within two days of embryonic development. A synchronous loss of megakaryocyte/erythrocyte progenitors results, along with a fatal, fetal anemia. At this time, mutation of Ikaros exerts a differentiation defect upon common lymphoid progenitors that cannot be rescued with an ectopic Notch signal in vitro, with hematopoietic cells preferentially committing to the NK lineage. Althoughdispensable for the initial embryonic development of blood, Ikaros is clearly needed for maintenance of this tissue. Achieving successful clinical tissue regeneration necessitates understanding degeneration, and these data provide a striking example by a discrete genetic lesion in the cells underpinning tissue integrity during a pivotal timeframe of organogenesis.

Disclosure of potential conflicts of interest is found at the end of this article.
MiR-21 Regulates Adipogenic Differentiation through the Modulation of TGF-β Signaling in Mesenchymal Stem Cells Derived from Human Adipose Tissue
Authors: Kim Yeon Jeong , Hwang Soo Jin , Bae Yong Chan , Jung Jin Sup
Published: October 2009

A better understanding of the molecular mechanisms that govern human adipose tissue-derived mesenchymal stem cells (hASCs) differentiation could improve hASCs-based cell therapy and provide new insights into a number of diseases, including obesity. In this study, we examined the roles of microRNA-21 (miR-21) in adipogenic differentiation of hASCs. We found that miR-21 expression was transiently increased after induction of adipogenic differentiation, peaked at 3 days, and returned to the baseline level 8 days. Lentiviral overexpression of miR-21 enhanced adipogenic differentiation. Overexpression of miR-21 decreased both protein and mRNA levels of TGFBR2. The expression of TGFBR2 was decreased during adipogenic differentiation of hASCs in concordance with an increase in the level of miR-21. In contrast, inhibiting miR-21 with 2′-O-methyl-antisense microRNA increased TGFBR2 protein levels in hASCs, accompanied by decreased adipogenic differentiation. The activity of a luciferase construct containing the miR-21 target site from the TGFBR2 3′UTR was lower in LV-miR21-infected hASCs than in LV-miLacZ infected cells. TGF-β-induced inhibition of adipogenic differentiation was significantly decreased in miR-21 overexpressing cells compared with control lentivirus-transduced cells. RNA interference-mediated downregulation of SMAD3, but not of SMAD2, increased adipogenic differentiation. Overexpression and inhibition of miR-21 altered SMAD3 phosphorylation without affecting total levels of SMAD3 protein. Our data are the first to demonstrate that the role of miR-21 in the adipogenic differentiation of hASCs is mediated through the modulation of TGF-β signaling. This study improves our knowledge of the molecular mechanisms governing hASCs differentiation, which may underlie the development of obesity or other metabolic diseases.

Disclosure of potential conflicts of interest is found at the end of this article.
Joint consideration of energy‐efficiency and coverage‐preservation in microsensor networks
Authors: Amini Navid , Vahdatpour Alireza , Dabiri Foad , Noshadi Hyduke , Sarrafzadeh Majid
Published: October 2009

This paper presents an energy‐efficient and coverage‐preserving communication protocol which distributes a uniform energy load to the sensors in a wireless microsensor network. This protocol, called Distance‐based Segmentation (DBS), is a cluster‐based protocol that divides the entire network into equal‐area segments and applies different clustering policies to each segment to (1) reduce total energy dissipation and (2) balance the energy load among the sensors. Therefore, it prolongs the lifetime of the network and improves the sensing coverage. Moreover, the proposed routing protocol does not need any centralized support from a certain node which is at odds with aiming to establish a scalable communication protocol. Results from extensive simulations on two different network configurations show that by lowering the number of wasteful transmissions in the network, the DBS can achieve as much as a 20% reduction in total dissipated energy as compared with current cluster‐based protocols. In addition, this protocol is able to distribute energy load more evenly among the sensors in the network. Hence, it yields up to a 66% increase in the useful network lifetime. According to the simulation results, the sensing coverage degradation of the DBS is considerably slower than that of the other cluster‐based protocols. Copyright © 2009 John Wiley & Sons, Ltd.
Measuring the performance of movement‐assisted certificate revocation list distribution in VANET
Authors: Chen Jiming , Cao Xianghui , Zhang Yu , Xu Weiqiang , Sun Youxian
Published: October 2009

Vehicular Ad hoc Network (VANET) emerges as a promising technology and has chances of very likely to be deployed in the coming years. The security of vehicular networks will be an important way to facilitate road safety. In this paper, we are concerned with the problem of effective and efficient distribution of the certificate revocation units (RSUs) in vehicular networks. We propose a novel distributed approach by introducing mobile nodes that have public safety. An optimal route for mobile nodes is designed to cover blind areas under both delay and cost constraints. The performances of the movement‐assisted approach are measured and evaluated by extensive experiments in large scale networks for Certificate Revocation List (CRL) distribution in VANET. The results show that the proposed movement‐assisted approach obviously improves the performance. Copyright © 2009 John Wiley & Sons, Ltd.
A survey and challenges in routing and data dissemination in vehicular ad hoc networks
Authors: Chen Wai , Guha Ratul K. , Kwon Taek Jin , Lee John , Hsu Yuan‐Ying
Published: October 2009

In this paper, we survey recent results in vehicular ad hoc networks (VANETs) data dissemination. We describe methods proposed to enforce dissemination scope such as geocast/broadcast and multicast. A growing category consisting of methods designed to achieve disruption tolerance in vehicular networks is presented. We describe the key ideas of representative technologies in each category. In addition, we consider location service and security issues that are crucial for data dissemination in VANET. We conclude by sharing our thoughts on further challenges. Copyright © 2009 John Wiley & Sons, Ltd.
Performance of vehicular delay‐tolerant networks with relay nodes
Authors: Farahmand Farid , Cerutti Isabella , Patel Ankitkumar N. , Jue Jason P. , Rodrigues Joel J. P. C.
Published: October 2009

Delay‐tolerant networking (DTN) is an architecture to enable data communications between isolated or remote regions, where long delays and intermittent connectivity can be tolerated. An emerging class of DTN, called Vehicular DTNs (VDTN), exploits transportation systems as the transport layer to transfer data. In these networks, vehicles (e.g., buses, boats, and trains) act as mobile nodes and carry data messages around. Mobile nodes can exchange data messages using devices called relay nodes. Relay nodes, placed in strategic positions along vehicle routes, have the capability to download, store, and upload the data messages from/to the mobile nodes. An important issue in VDTN is the optimal placement of the relay nodes such that delay‐tolerant connectivity in VDTN is ensured at minimum cost. In this paper we show that the problem of optimal relay node placement is an NP‐hard problem. Other contributions of this paper are the formulation of the relay node placement problem using integer linear programming (ILP) formulation and the proposal of heuristic algorithms solving the optimization problem. Using simulation results, we compare the performance of each algorithm under different network constraints, such as node storage capability and network topology. Copyright © 2009 John Wiley & Sons, Ltd.
Analysis of nutrient concentrations in the diet, serum, and urine of giraffe from surveyed North American zoological institutions
Authors: Sullivan Kathleen , van Heugten Eric , Ange‐van Heugten Kimberly , Poore Matthew H. , Dierenfeld Ellen S. , Wolfe Barbara
Published: October 2009

The objectives of the present research were to conduct a survey to investigate the health history and feeding practices of giraffe in captivity in North America and to obtain samples of hay, concentrate, browse, urine, and serum to compare across zoos, possible factors relating to the development of urolithiasis. Forty‐one out of 98 institutions contacted responded, representing 218 giraffe. All responding zoos fed concentrate and alfalfa hay was the primary forage. Sixty‐five percent of zoos fed browse and 43 different species of browse were listed. Six zoos reported a history of urolithiasis, seven reported wasting syndrome, and 10 reported sudden death. The median daily amount (as fed) of concentrate and hay offered were 5.45 kg (range of 2.73–9.55 kg) and 6.82 kg (range of 2.53–12.50 kg), respectively. The concentrate:hay ratio of the offered diet ranged from 0.22 to 3.47 with a median value of 0.79. Forty‐three percent of the institutions offered a ratio greater than 1:1. Samples of concentrate and hay (six zoos), serum (five zoos), and urine (seven zoos) were obtained for chemical analyses. Analyzed nutrient content of the consumed diet, measured by weighing feed and orts for three consecutive days, met recommendations for giraffe, but was excessive for crude protein and P. Concentrate:hay and serum P were positively correlated (r=0.72; P<0.05). High dietary P content and a high level of concentrate relative to hay may be contributing factors to urolith formation and warrant further investigation. Zoo Biol 29:457–469, 2010. © 2009 Wiley‐Liss, Inc.
Contrafreeloading in grizzly bears: implications for captive foraging enrichment
Authors: McGowan Ragen T. S. , Robbins Charles T. , Alldredge J. Richard , Newberry Ruth C.
Published: October 2009

Although traditional feeding regimens for captive animals were focused on meeting physiological needs to assure good health, more recently emphasis has also been placed on non‐nutritive aspects of feeding. The provision of foraging materials to diversify feeding behavior is a common practice in zoos but selective consumption of foraging enrichment items over more balanced “chow” diets could lead to nutrient imbalance. One alternative is to provide balanced diets in a contrafreeloading paradigm. Contrafreeloading occurs when animals choose resources that require effort to exploit when identical resources are freely available. To investigate contrafreeloading and its potential as a theoretical foundation for foraging enrichment, we conducted two experiments with captive grizzly bears (Ursus arctos horribilis). In Experiment 1, bears were presented with five foraging choices simultaneously: apples, apples in ice, salmon, salmon in ice, and plain ice under two levels of food restriction. Two measures of contrafreeloading were considered: weight of earned food consumed and time spent working for earned food. More free than earned food was eaten, with only two bears consuming food extracted from ice, but all bears spent more time manipulating ice containing salmon or apples than plain ice regardless of level of food restriction. In Experiment 2, food‐restricted bears were presented with three foraging choices simultaneously: apples, apples inside a box, and an empty box. Although they ate more free than earned food, five bears consumed food from boxes and all spent more time manipulating boxes containing apples than empty boxes. Our findings support the provision of contrafreeloading opportunities as a foraging enrichment strategy for captive wildlife. Zoo Biol 29:484–502, 2010. © 2009 Wiley‐Liss, Inc.
GAPs in the study of zoo and wild animal welfare
Authors: Goulart Vinícius D. , Azevedo Pedro G. , van de Schepop Joanna A. , Teixeira Camila P. , Barçante Luciana , Azevedo Cristiano S. , Young Robert J.
Published: October 2009

To investigate the science of animal welfare for zoo and wild animals in the period from 1966 to 2007, we conducted a bibliometric analysis of abstracts downloaded from The Web of Science© database using the keyword combination “Animal welfare, Zoo* and wild” in the topic field. In total we downloaded 1,125 abstracts, which were classified into the following categories: year of publication; environment of the study (e.g., zoo) or theoretical; area of knowledge (e.g., conservation in situ); number of experimental animals used; species; addresses of authors; taxonomic classification; publication language; journal name; number of citations received. Since 1990, there has been a rapid increase in the number of articles published in this area of animal welfare. One worrying result was that published articles were predominately of a theoretical nature (58.65%, N=563). Most of the articles were published by authors either in Europe (47.43%, N=480) or North America (37.65%, N=381) and written in English (87.71%, N=971). The majority of experimental studies were conducted with mammals (75.92%, N=391), and had small sample sizes (N=7 for zoo‐based studies). In terms of impact factor (IF), the journals in this study had a median factor equivalent to that for the area of biological sciences (median IF=1.013). Little knowledge cross‐over from farm animal welfare was found (only four articles) in this study. In conclusion, zoo and wild animal welfare as a science may benefit from a greater interaction with farm animal welfare. Zoo Biol 28:561–573, 2009. © 2009 Wiley‐Liss, Inc.
High Methanol Oxidation Activity of Well-Dispersed Pt Nanoparticles on Carbon Nanotubes Using Nitrogen Doping
Authors: Fang Wei-Chuan
Published: October 2009

Pt nanoparticles (NPs) with the average size of 3.14 nm well dispersed on N-doped carbon nanotubes (CNTs) without any pretreatment have been demonstrated. Structural properties show the characteristic N bonding within CNTs, which provide the good support for uniform distribution of Pt NPs. In electrochemical characteristics, N-doped CNTs covered with Pt NPs show superior current density due to the fact that the so-called N incorporation could give rise to the formation of preferential sites within CNTs accompanied by the low interfacial energy for immobilizing Pt NPs. Therefore, the substantially enhanced methanol oxidation activity performed by N-incorporation technique is highly promising in energy-generation applications.
Legislative Involvement in Parliamentary Systems: Opportunities, Conflict, and Institutional Constraints
Authors: FRANCHINO FABIO , HØYLAND BJØRN
Published: October 2009

In parliamentary systems, the need to preserve the political agreement that sustains the executive often motivates legislative involvement in policymaking. Institutional arrangements regulating executive–legislative relations and ministerial autonomy also structure parliamentary participation. However, empirical evidence of these effects remains limited to a few policies and countries. European Union legislation provides the opportunity to test expectations about legislative involvement for different types of measure across various institutional arrangements, across multiple policy areas, and across time. In this article, we investigate legislative involvement in the transposition of 724 directives in 15 member states from 1978 to 2004. Our results confirm that involvement increases as conflict between the responsible minister and her coalition partners intensifies. The discretionary scope embedded in the directive further inflates this effect. Additionally, parliamentary involvement decreases as the government's institutional advantage over the legislature increases, especially if intracoalitional conflict deepens.
Nonparametric Estimation of the Short Rate Diffusion Process from a Panel of Yields
Authors: Sam Abdoul G. , Jiang George J.
Published: October 2009

In this paper, we propose a nonparametric estimator of the short rate diffusion process using observations of a panel of yields. The proposed estimator can greatly reduce the bias of the nonparametric estimator proposed in Stanton (1997) that uses a single time series of short rate observations. Simulations confirm that the new method significantly attenuates the spurious nonlinearity of the drift function as documented in Chapman and Pearson (2000). We apply the method to estimate the U.S. short rate process using a panel of six Treasury yields. With 42 years’ daily observations of the panel of yields, the proposed drift function estimator achieves the same efficiency as the Stanton (1997) estimator based on 145 years of daily short rate observations. Finally, we show that the proposed estimator also has significant economic implications on the pricing of bonds and interest rate derivatives.
How Did Japanese Investments Influence International Art Prices?
Authors: Hiraki Takato , Ito Akitoshi , Spieth Darius A. , Takezawa Naoya
Published: October 2009

We test the luxury consumption hypothesis of Ait-Sahalia, Parker, and Yogo (2004), using a unique international art price, import/export flow, and stock market data set. We find that the demand for art by Japanese collectors is positively correlated with art prices and Japanese stock prices. This correlation is magnified during the “bubble period” of the Japanese economy (the mid-1980s to the early 1990s) and gains even further strength for works of art typically favored by Japanese collectors. Our results suggest that Japanese investors (or Japanese asset markets) indeed affect international art prices—especially during the bubble period and its aftermath.
Block Ownership, Trading Activity, and Market Liquidity
Authors: Brockman Paul , Chung Dennis Y. , Yan Xuemin (Sterling)
Published: October 2009

We examine the impact of block ownership on the firm’s trading activity and secondary-market liquidity. Our empirical results show that block ownership takes potential trading activity off the table relative to a diffuse ownership structure and impairs the firm’s market liquidity. These adverse liquidity effects disappear, however, once we control for trading activity. Our findings suggest that block ownership is detrimental to the firm’s market liquidity because of its adverse impact on trading activity—a real friction effect. After controlling for this real friction effect, we find little evidence that block ownership has a negative impact on informational friction. Our results suggest that the relative lack of trading, and not the threat of informed trading, explains the inverse relation between block ownership and market liquidity.
Proton-temperature-anisotropy-driven magnetic fields in plasmas with cold and relativistically hot electrons
Authors: SHUKLA NITIN , SHUKLA P. K.
Published: October 2009

We present a dispersion relation for a plane-polarized electromagnetic wave in plasmas composed of cold electrons, relativistically hot electrons and bi-Maxwellian protons. It is shown that the free energy in proton-temperature anisotropy drives purely growing electromagnetic modes in our three-component plasma. Expressions for the growth rates and thresholds of instabilities are presented. The present results are relevant for explaining the origin of spontaneously generated magnetic fields in laboratory and astrophysical plasmas.
A common neural system mediating two different forms of social judgement
Authors: Hall J. , Whalley H. C. , McKirdy J. W. , Sprengelmeyer R. , Santos I. M. , Donaldson D. I. , McGonigle D. J. , Young A. W. , McIntosh A. M. , Johnstone E. C. , Lawrie S. M.
Published: October 2009

Background

A wide range of neuropsychiatric conditions, including schizophrenia and autistic spectrum disorder (ASD), are associated with impairments in social function. Previous studies have shown that individuals with schizophrenia and ASD have deficits in making a wide range of social judgements from faces, including decisions related to threat (such as judgements of approachability) and decisions not related to physical threat (such as judgements of intelligence). We have investigated healthy control participants to see whether there is a common neural system activated during such social decisions, on the basis that deficits in this system may contribute to the impairments seen in these disorders.

Method

We investigated the neural basis of social decision making during judgements of approachability and intelligence from faces in 24 healthy participants using functional magnetic resonance imaging (fMRI). We used conjunction analysis to identify common brain regions activated during both tasks.

Results

Activation of the amygdala, medial prefrontal cortex, inferior prefrontal cortex and cerebellum was seen during performance of both social tasks, compared to simple gender judgements from the same stimuli. Task-specific activations were present in the dorsolateral prefrontal cortex in the intelligence task and in the inferior and middle temporal cortex in the approachability task.

Conclusions

The present study identified a common network of brain regions activated during the performance of two different forms of social judgement from faces. Dysfunction of this network is likely to contribute to the broad-ranging deficits in social function seen in psychiatric disorders such as schizophrenia and ASD.
Genetic contribution to the relationship between personality and depressive symptoms among older women
Authors: Pakkala I. , Read S. , Kaprio J. , Koskenvuo M. , Kauppinen M. , Rantanen T.
Published: October 2009

Background

Prior studies suggest that certain types of personality are at higher risk for developing depressive disorders. This study examined the relationship between old age depressive symptoms and two middle-age personality dimensions, neuroticism and extraversion.

Method

The present study is part of the Finnish Twin Study on Aging, where altogether 409 female twins who had completed the Eysenck Personality Inventory at the age of 38–51 years were studied for depressive symptoms 28 years later using Center for the Epidemiologic Studies Depression Scale. Logistic regression analysis suitable for dependent data and univariate and Cholesky models for decomposing the genetic and environmental factor were used.

Results

Middle age extraversion protected from later depressive symptoms while neuroticism increased the risk. Twin modeling indicated that the association between neuroticism and depressive symptoms resulted from shared genetic risk factors common to both traits. However, a substantial proportion of the genetic vulnerability was specific to old age depressive symptoms and was not shared with neuroticism. Middle age extraversion had no genetic relationship with old age depressive symptoms.

Conclusions

The relationship between middle age neuroticism and old age depressive symptoms is strong but only partly the result of genetic factors that predispose to both neuroticism and depressive symptoms. Extraversion, by contrast, has no genetic relationship with depressive symptoms experienced in old age.