bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining protein stability in cell lysates by pulse proteolysis and Western blotting
Authors: Kim Moon‐Soo , Song Jiao , Park Chiwook
Published: March 2009

Proteins require proper conformational energetics to fold and to function correctly. Despite the importance of having information on conformational energetics, the investigation of thermodynamic stability has been limited to proteins, which can be easily expressed and purified. Many biologically important proteins are not suitable for conventional biophysical investigation because of the difficulty of expression and purification. As an effort to overcome this limitation, we have developed a method to determine the thermodynamic stability of low abundant proteins in cell lysates. Previously, it was demonstrated that protein stability can be determined quantitatively by measuring the fraction of folded proteins with a pulse of proteolysis (Pulse proteolysis). Here, we show that thermodynamic stability of low abundant proteins can be determined reliably in cell lysates by combining pulse proteolysis with quantitative Western blotting (Pulse and Western). To demonstrate the reliability of this method, we determined the thermodynamic stability of recombinant human H‐ras added to lysates of E. coli and human Jurkat T cells. Comparison with the thermodynamic stability determined with pure H‐ras revealed that Pulse and Western is a reliable way to monitor protein stability in cell lysates and the stability of H‐ras is not affected by other proteins present in cell lysates. This method allows the investigation of conformational energetics of proteins in cell lysates without cloning, purification, or labeling.
Thermodynamic characterization of two homologous protein complexes: Associations of the semaphorin receptor plexin‐B1 RhoGTPase binding domain with Rnd1 and active Rac1
Authors: Hota Prasanta K. , Buck Matthias
Published: March 2009

Plexin receptors function in response to semaphorin guidance cues in a variety of developmental processes involving cell motility. Interactions with Rho, as well as Ras family small GTPases are critical events in the cell signaling mechanism. We have recently determined the structure of a cytoplasmic domain (RBD) of plexin‐B1 and mapped its binding interface with several Rho‐GTPases, Rac1, Rnd1, and RhoD. All three GTPases associate with a similar region of this plexin domain, but show different functional behavior in cells. To understand whether thermodynamic properties of the GTPase–RBD interaction contribute to such different behavior, we have examined the interaction at different temperatures, buffer, and pH conditions. Although the binding affinity of both Rnd1 and Rac1 with the plexin‐B1 RBD is similar, the detailed thermodynamic properties of the interactions are considerably different. These data suggest that on Rac1 binding to the plexin‐B1 RBD, the proteins become more rigid in the complex. By contrast, Rnd1 binding is consistent with unchanged or slightly increased flexibility in one or both proteins. Both GTPases show an appreciable reduction in affinity for the dimeric plexin‐B1 RBD indicating that GTPase binding is not cooperative with dimer formation, but that a partial steric hindrance destabilizes the dimer. However, a reduced affinity binding mode to a disulphide stabilized model for the dimeric RBD is also possible. Consistent with cellular studies, the interaction thermodynamics imply that further levels of regulation involving additional binding partners and/or regions outside of the RhoGTPase binding domain are required for receptor activation.
Crystal structures of the Arabidopsis thaliana proliferating cell nuclear antigen 1 and 2 proteins complexed with the human p21 C‐terminal segment
Authors: Strzalka Wojciech , Oyama Takuji , Tori Kazuo , Morikawa Kosuke
Published: March 2009

The proliferating cell nuclear antigen (PCNA) is well recognized as one of the essential cellular components of the DNA replication machinery in all eukaryotic organisms. Despite their prominent importance, very little biochemical and structural information about plant PCNAs is available, in comparison with that obtained from other eukaryotic organisms. We have determined the atomic resolution crystal structures of the two distinct Arabidopsis thaliana PCNAs (AtPCNA), both complexed with the C‐terminal segment of human p21. Both AtPCNAs form homotrimeric ring structures, which are essentially identical to each other, including the major contacts with the p21 peptide. The structure of the amino‐terminal half of the p21 peptide, containing the typical PIP box sequence, is remarkably similar to those observed in the previously reported crystal structures of the human and archaeal PCNA‐PIP box complexes. Meanwhile, the carboxy‐terminal halves of the p21 peptide in the plant PCNA complexes are bound to the protein in a unique manner, most probably because of crystal packing effects. A surface plasmon resonance analysis revealed high affinity between each AtPCNA and the C‐terminal fragment of human p21. This result strongly suggests that the interaction is functionally significant, although no plant homologs of p21 have been identified yet. We also discovered that AtPCNA1 and AtPCNA2 form heterotrimers, implying that hetero‐PCNA rings may play critical roles in cellular signal transduction, particularly in DNA repair.
Gonadotropin releasing hormone analogs induce apoptosis by extrinsic pathway involving p53 phosphorylation in primary cell cultures of human prostatic adenocarcinomas
Authors: Clementi Marisa , Sánchez Catherine , Benitez Dixan A. , Contreras Héctor R. , Huidobro Christian , Cabezas Juan , Acevedo Cristian , Castellón Enrique A.
Published: March 2009

BACKGROUND

Gonadotropin‐releasing‐hormone (GnRH) analogs are widely used to block hypothalamic–pituitary–gonadal axis and inhibit blood androgen levels in patients with prostate cancer (PCa). In addition, GnRH analogs induce proliferation arrest and apoptosis through GnRH receptors expressed on the membrane of PCa cells. Possible molecular mechanisms involved in GnRH‐mediated apoptosis on prostate cancer cells were studied.

METHODS

Primary cultures from PCa and benign prostatic hyperplasia (BPH) (non‐malignant control) were derived from samples provided by our Institutional Hospital. Cell cultures were incubated for 24 hr with 20 ng/ml of GnRH agonist Leuprolide (Lp) or antagonist Cetrorelix (Cx). Apoptosis was evaluated by studying the expression of Bax and Bcl‐2 and the activation of caspase‐9 (intrinsic pathway), caspase‐8 (extrinsic pathway), and caspase‐3. Also, mRNA level, protein expression and phosphorylation of p53 were studied.

RESULTS

Cleaved caspase‐8 and ‐3, but not ‐9, increased in presence of Lp and Cx in PCa cell cultures. Bax and Bcl‐2 mRNA levels showed no changes after GnRH‐analog treatments. Only Bax protein showed an increase after Cx treatment in PCa cell cultures. p53 mRNA level was higher in PCa than in BPH cell cultures. Lp and Cx increased p53 expression and phosphorylation in PCa cell cultures.

CONCLUSIONS

Apoptosis induced by GnRH analogs seems to be mediated by extrinsic pathway involving p53 phosphorylation. Phosphorylated‐p53 might be associated with the increase in apoptotic NGF receptor, p75, previously reported by our laboratory. These findings reinforce the concept of clinical use of GnRH analogs for PCa suggesting that intraprostatic treatment may be more effective. Prostate 69:1025–1033, 2009. © 2009 Wiley‐Liss, Inc.
Time‐dependent insulin oligomer reaction pathway prior to fibril formation: Cooling and seeding
Authors: Sorci Mirco , Grassucci Robert A. , Hahn Ingrid , Frank Joachim , Belfort Georges
Published: March 2009

The difficulty in identifying the toxic agents in all amyloid‐related diseases is likely due to the complicated kinetics and thermodynamics of the nucleation process and subsequent fibril formation. The slow progression of these diseases suggests that the formation, incorporation, and/or action of toxic agents are possibly rate limiting. Candidate toxic agents include precursors (some at very low concentrations), also called oligomers and protofibrils, and the fibrils. Here, we investigate the kinetic and thermodynamic behavior of human insulin oligomers (imaged by cryo‐EM) under fibril‐forming conditions (pH 1.6 and 65°C) by probing the reaction pathway to insulin fibril formation using two different types of experiments—cooling and seeding—and confirm the validity of the nucleation model and its effect on fibril growth. The results from both the cooling and seeding studies confirm the existence of a time‐changing oligomer reaction process prior to fibril formation that likely involves a rate‐limiting nucleation process followed by structural rearrangements of intermediates (into β‐sheet rich entities) to form oligomers that then form fibrils. The latter structural rearrangement step occurs even in the absence of nuclei (i.e., with added heterologous seeds). Nuclei are formed at the fibrillation conditions (pH 1.6 and 65°C) but are also continuously formed during cooling at pH 1.6 and 25°C. Within the time‐scale of the experiments, only after increasing the temperature to 65°C are the trapped insulin nuclei and resultant structures able to induce the structural rearrangement step and overcome the energy barrier to form fibrils. This delay in fibrillation and accumulation of nuclei at low temperature (25°C) result in a decrease in the mean length of the fibers when placed at 65°C. Fits of an empirical model to the data provide quantitative measures of the delay in the lag‐time during the nucleation process and subsequent reduction in fibril growth rate resulting from the cooling. Also, the seeding experiments, within the time‐scale of the measurements, demonstrate that fibers can initiate fast fibrillation with dissolved insulin (fresh or taken during the lag‐period) but not with other fibers. Qualitatively this is explained with a conjectual free‐energy space plot. Proteins 2009. © 2009 Wiley‐Liss, Inc.
Automated scaffold selection for enzyme design
Authors: Malisi Christoph , Kohlbacher Oliver , Höcker Birte
Published: March 2009

A major goal of computational protein design is the construction of novel functions on existing protein scaffolds. There the first question is which scaffold is suitable for a specific reaction. Given a set of catalytic residues and their spatial arrangement, one wants to identify a protein scaffold that can host this active site. Here, we present an algorithm called ScaffoldSelection that is able to rapidly search large sets of protein structures for potential attachment sites of an enzymatic motif. The method consists of two steps; it first identifies pairs of backbone positions in pocket‐like regions. Then, it combines these to complete attachment sites using a graph theoretical approach. Identified matches are assessed for their ability to accommodate the substrate or transition state. A representative set of structures from the Protein Data Bank (∼3500) was searched for backbone geometries that support the catalytic residues for 12 chemical reactions. Recapitulation of native active site geometries is used as a benchmark for the performance of the program. The native motif is identified in all 12 test cases, ranking it in the top percentile in 5 out of 12. The algorithm is fast and efficient, although dependent on the complexity of the motif. Comparisons to other methods show that ScaffoldSelection performs equally well in terms of accuracy and far better in terms of speed. Thus, ScaffoldSelection will aid future computational protein design experiments by preselecting protein scaffolds that are suitable for a specific reaction type and the introduction of a predefined amino acid motif. Proteins 2009. © 2009 Wiley‐Liss, Inc.
X‐ray vs. NMR structures as templates for computational protein design
Authors: Schneider Michael , Fu Xiaoran , Keating Amy E.
Published: March 2009

Certain protein‐design calculations involve using an experimentally determined high‐resolution structure as a template to identify new sequences that can adopt the same fold. This approach has led to the successful design of many novel, well‐folded, native‐like proteins. Although any atomic‐resolution structure can serve as a template in such calculations, most successful designs have used high‐resolution crystal structures. Because there are many proteins for which crystal structures are not available, it is of interest whether nuclear magnetic resonance (NMR) templates are also appropriate. We have analyzed differences between using X‐ray and NMR templates in side‐chain repacking and design calculations. We assembled a database of 29 proteins for which both a high‐resolution X‐ray structure and an ensemble of NMR structures are available. Using these pairs, we compared the rotamericity, χ1‐angle recovery, and native‐sequence recovery of X‐ray and NMR templates. We carried out design using RosettaDesign on both types of templates, and compared the energies and packing qualities of the resulting structures. Overall, the X‐ray structures were better templates for use with Rosetta. However, for ∼20% of proteins, a member of the reported NMR ensemble gave rise to designs with similar properties. Re‐evaluating RosettaDesign structures with other energy functions indicated much smaller differences between the two types of templates. Ultimately, experiments are required to confirm the utility of particular X‐ray and NMR templates. But our data suggest that the lack of a high‐resolution X‐ray structure should not preclude attempts at computational design if an NMR ensemble is available. Proteins 2009. © 2009 Wiley‐Liss, Inc.
Reliability behavior of GaN HEMTs related to Au diffusion at the Schottky interface
Authors: Jung Helmut , Behtash Reza , Thorpe James R. , Riepe Klaus , Bourgeois Franck , Blanck Hervé , Chuvilin Andrey , Kaiser Ute
Published: March 2009

The Schottky contact on GaN HEMT power devices is a key element for high power performance and its long term reliability behavior. Up to now such GaN devices are still suffering very often by a leakage current increase during operation resulting in deteriorated transistor behavior. One reason for this problem is owing to insufficiently stable Schottky contacts based on NiAu metalisation. We analysed GaN HEMTs with different aging behaviors by means of HR‐TEM and EDX investigations. It could be shown that on transistors with increasing leakage current Au was found directly on the Schottky interface which may be responsible for the increase of the leakage current. Furthermore, there are strong indications that such Au is diffusing via the gate foot side wall Ni‐SiN interface towards the Schottky barrier. It is proposed that an additional metallic diffusion barrier may solve this aging problem. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamic dependences of slip length for nanofluidic flows over crystalline surfaces: Predictions of molecular theory of solvation
Authors: Kobryn Alexander E. , Ichiki Kengo , Kovalenko Andriy
Published: March 2009

We study the pressure and temperature dependence of the hydrodynamic slip length for the laminar flow of water near the crystalline surfaces of gold, copper, and nickel by the methods of nonequilibrium statistical mechanics. This study is further development of our previous work on formulation of the molecular theory of hydrodynamic (slip) boundary conditions in nanofluidics. Phenomenological picture relates slip length to viscosity of the liquid, and establishes the direct proportionality among them. Any difference between this phenomenological approach and measurements could not be explained, unless one uses the molecular theory of liquids and an appropriate atomistic model for surface corrugation. To vindicate the anomaly, we refer to the notion of formation and rupture of the hydrogen bond network in water. To verify this hypothesis, we apply the theory and perform calculations in the entire range of temperatures for the stable liquid phase and for pressures up to 100 MPa. The variation found in the slip length is of two orders of magnitude, which is much more than the variation in the viscosity alone. We validate our concept by referring to observable changes in the liquid microscopic structure and relating them with the theory. The information obtained is relevant for rational design of new MEMS/NEMS devices. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Modes of cooperative R&D commercialization by start‐ups
Authors: Aggarwal Vikas A. , Hsu David H.
Published: March 2009

This study empirically examines the determinants of heterogeneous firm‐level cooperative R&D commercialization strategies. While the volume of interfirm collaboration has increased dramatically in recent decades, the determinants of firm‐level choices among alternate modes of such cooperative activity remain relatively understudied. We develop a conceptual model of factors determining collaborative mode choice at the organizational portfolio level. These factors include the firm‐level appropriation environment, in which deal‐level choices have portfolio‐level spillover implications, as well as governance capabilities developed by the firm over time. Using a random sample of innovating biotechnology start‐ups, we assemble a firm‐year panel dataset that aggregates transaction‐level collaboration data to the firm‐year level, allowing us to characterize firms' portfolios of collaborative deals. We find broad empirical support for our model, suggesting that a firm's appropriation environment and governance capabilities strongly influence portfolio‐level collaboration mode choices. In addition, we explore the implications of governance capability development, finding that experience with particular modes, as well as deviations from existing capabilities, impact firm valuation. Copyright © 2009 John Wiley & Sons, Ltd.
Facilitating difficult dialogues at the intersections of religious privilege
Authors: Watt Sherry K.
Published: March 2009

This chapter discusses ways student affairs professionals can use the privileged identity exploration model to facilitate difficult discussions at the intersections of religious privilege. Examples are given and practical suggestions offered on ways to create conditions for productive dialogue.
Changes in mouse mu opioid receptor Exon 7/8‐like immunoreactivity following food restriction and food deprivation in rats
Authors: Hadjimarkou Maria M. , Abbadie Catherine , Kasselman Lora J. , Pan Ying‐xian , Pasternak Gavril W. , Bodnar Richard J.
Published: March 2009

Opioid agonists and antagonists respectively increase and decrease food intake. That selective mu opioid antagonists are more effective than antisense probes directed against the mu opioid receptor (MOR‐1) gene in reducing deprivation‐induced feeding suggests a role for isoforms. Both food restriction and deprivation alter protein and mRNA levels of opioid peptides and receptors. Antisera directed against Exon 4 of the MOR‐1‐like immunoreactivity (LI) (Exon 4) clone or directed against mouse Exons 7/8 (mE7/8‐LI) revealed high levels of immunoreactivity in brain nuclei related to feeding behavior. Therefore, the present study assessed MOR‐1LI and mE7/8‐LI in hypothalamic and extrahypothalamic sites in rats exposed to ad libitum feeding, food restriction (2, 7, 14 days), or food deprivation (24, 48 h). MOR‐1‐LI displayed robust reactivity, but was insensitive to food restriction or deprivation. mE7/8‐LI, both in terms of cell counts and relative optical density, was significantly and selectively increased in the dorsal and ventral parvocellular subdivisions of the hypothalamic paraventricular nucleus in food‐restricted (14 days) rats, but all other restriction or deprivation regimens were ineffective in other hypothalamic nuclei. In contrast, significant and site‐specific decreases in relative optical density in the rostral part of the nucleus tractus solitarius (NTS) were observed in food‐restricted (2, 7 days) or food‐deprived (24, 48 h) animals, but these regimens were ineffective in the other extrahypothalamic sites. This study indicates the sensitivity of this mE7/8‐LI probe in the hypothalamic parvocellular paraventricular nucleus and rostral NTS to food restriction and deprivation in rats. Synapse 63:585–597, 2009. © 2009 Wiley‐Liss, Inc.
The Joule‐Thomson effect on the thermoelectric conductors
Authors: Consiglieri L.
Published: March 2009

The transmission of an electric current in a conductor is a process in which some electrical energy is converted into heat (thermal energy). We deal with a nonlinear boundary value elliptic problem which describes the electrical heating of a solid conductor and the Joule‐Thomson effect is taken into account. The existence of a weak solution is proved under both space and temperature dependence of the electrical and thermal conductivities. When the coefficients are only dependent on their temperature argument, some regularity results are stated.
An Unsupervised, Model-Free, Machine-Learning Combiner for Peptide Identifications from Tandem Mass Spectra
Authors: Edwards Nathan , Wu Xue , Tseng Chau-Wen
Published: March 2009

As the speed of mass spectrometers, sophistication of sample fractionation, and complexity of experimental designs increase, the volume of tandem mass spectra requiring reliable automated analysis continues to grow. Software tools that quickly, effectively, and robustly determine the peptide associated with each spectrum with high confidence are sorely needed. Currently available tools that postprocess the output of sequence-database search engines use three techniques to distinguish the correct peptide identifications from the incorrect: statistical significance re-estimation, supervised machine learning scoring and prediction, and combining or merging of search engine results. We present a unifying framework that encompasses each of these techniques in a single model-free machine-learning framework that can be trained in an unsupervised manner. The predictor is trained on the fly for each new set of search results without user intervention, making it robust for different instruments, search engines, and search engine parameters. We demonstrate the performance of the technique using mixtures of known proteins and by using shuffled databases to estimate false discovery rates, from data acquired on three different instruments with two different ionization technologies. We show that this approach outperforms machine-learning techniques applied to a single search engine’s output, and demonstrate that combining search engine results provides additional benefit. We show that the performance of the commercial Mascot tool can be bested by the machine-learning combination of two open-source tools X!Tandem and OMSSA, but that the use of all three search engines boosts performance further still. The Peptide identification Arbiter by Machine Learning (PepArML) unsupervised, model-free, combining framework can be easily extended to support an arbitrary number of additional searches, search engines, or specialized peptide–spectrum match metrics for each spectrum data set. PepArML is open-source and is available from http://peparml.sourceforge.net.
‘It Got Right to the Spot’ The Patient Experience of Primary Angioplasty: A Qualitative Study
Authors: Radcliffe Emma L. , Harding Geoffrey , Rothman Martin T. , Feder Gene S.
Published: March 2009

Background: Primary angioplasty is becoming an established treatment for myocardial infarction. Yet we have a limited understanding of patients' attitudes toward this treatment and their experiences of receiving it in practice.

Aims: Exploration of patients' experiences and perceptions of primary angioplasty as treatment for their heart attack.

Methods: Qualitative study of a purposive sample of patients admitted to a tertiary cardiology unit in east London, UK. Participants were interviewed either in their own homes or in hospital. Recruitment continued until no new substantial themes emerged. Eleven men and four women aged 35 to 74 years who had sustained a myocardial infarction were interviewed 13 to 90 days after primary angioplasty. We used the framework method of analysis to identify and explore emerging themes.

Results: Informants were expecting open-heart surgery as treatment for their heart attack. They were impressed by the service they actually received. They were generally not engaged in decisions about their treatment in the acute setting and this passivity sometimes persisted after discharge. Expectations of follow up in primary care were not often met.

Conclusions: Patients are satisfied with the primary angioplasty as treatment for acute myocardial infarction but have poor understanding of the management of this condition.
The structural basis of allosteric regulation in proteins
Authors: Laskowski Roman A. , Gerick Fabian , Thornton Janet M.
Published: March 2009

Allosteric regulation of protein function occurs when the regulatory trigger, such as the binding of a small‐molecule effector or inhibitor, takes place some distance from the protein's, or protein complex's, active site. This distance can be a few Å, or tens of Å. Many proteins are regulated in this way and exhibit a variety of allosteric mechanisms. Here we review how analyses of experimentally determined models of protein 3D structures, using either X‐ray crystallography or NMR spectroscopy, have revealed some of the mechanisms involved.
Trans-nasal injection of botulinum toxin
Authors: Hussain A , Thiel G , Shakeel M
Published: March 2009

Introduction:

Office-based laryngeal injection for the treatment of a variety of voice disorders is an established practice. Various methods of delivery to the vocal folds are in practice.

Aim:

We present a simple and repeatable method of injecting botulinum toxin into the larynx.

Method:

Botulinum toxin A (Botox®) was delivered into the larynx using a channelled fibre-optic laryngoscope under local anaesthetic, in an office setting.

Results:

Seven patients received regular botulinum toxin injections, via our preferred method. The treatment intervals and dosage regime varied depending on patient requirements. The procedure was carried out in an office setting, with minimal discomfort and inconvenience to the patient.

Conclusion:

We present a method of botulinum toxin delivery to the larynx which is simple, easily repeatable and simply learnt by the otolaryngologist familiar with fibre-optic laryngoscope usage. This method is also comfortable and convenient for the patient.
A prolonged outbreak ofSalmonellaTyphimurium infection related to an uncommon vehicle: hard cheese made from raw milk
Authors: VAN DUYNHOVEN Y. T. H. P. , ISKEN L. D. , BORGEN K. , BESSELSE M. , SOETHOUDT K. , HAITSMA O. , MULDER B. , NOTERMANS D. W. , De JONGE R. , KOCK P. , VAN PELT W. , STENVERS O. , VAN STEENBERGEN J.
Published: March 2009

In 2006, in The Netherlands, an outbreak ofSalmonellaTyphimurium phage type 561 (STM DT7, corresponding to the rare DT7 in the international typing scheme) was detected, accumulating to over 200 cases. By telephone interviews, data were collected from all laboratory-confirmed cases. In addition, in August 2006, a case-control study was performed in a subset of cases. Environmental and microbiological investigation was performed on a suspected dairy farm. In the case-control study (51 cases, 105 matched controls), hard cheese purchased from a farm, specifically farm X, and from a market stall were found to be associated with infection. The dairy production room of farm X tested STM DT7-positive in August. However, it was only in November, after earlier unsuccessful attempts, that a low-level contamination was confirmed in the hard farmhouse cheese, triggering control measures. A timely and adequate response was hampered during this outbreak for several reasons. Measures for improvement in handling future similar incidents are discussed.
A randomized controlled trial of vitamin D3 supplementation for the prevention of symptomatic upper respiratory tract infections
Authors: LI-NG M. , ALOIA J. F. , POLLACK S. , CUNHA B. A. , MIKHAIL M. , YEH J. , BERBARI N.
Published: March 2009

Vitamin D has been shown to be an important immune system regulator. Vitamin D insufficiency during winter may cause increased susceptibility to upper respiratory tract infections (URIs). To determine whether vitamin D supplementation during the winter season prevents or decreases URI symptoms, 162 adults were randomized to receive 50 μg vitamin D3 (2000 IU) daily or matching placebo for 12 weeks. A bi-weekly questionnaire was used to record the incidence and severity of URI symptoms. There was no difference in the incidence of URIs between the vitamin D and placebo groups (48 URIs vs. 50 URIs, respectively, P=0·57). There was no difference in the duration or severity of URI symptoms between the vitamin D and placebo groups [5·4±4·8 days vs. 5·3±3·1 days, respectively, P=0·86 (95% CI for the difference in duration −1·8 to 2·1)]. The mean 25-hydroxyvitamin D level at baseline was similar in both groups (64·3±25·4 nmol/l in the vitamin D group; 63·0±25·8 nmol/l in the placebo group; n.s.). After 12 weeks, 25-hydroxyvitamin D levels increased significantly to 88·5±23·2 nmol/l in the vitamin D group, whereas there was no change in vitamin D levels in the placebo group. There was no benefit of vitamin D3 supplementation in decreasing the incidence or severity of symptomatic URIs during winter. Further studies are needed to determine the role of vitamin D in infection.
The changing panorama of bacterial enteric infections
Authors: STEIN-ZAMIR C. , SHOOB H. , ABRAMSON N. , ZENTNER G. , AGMON V.
Published: March 2009

We studied the age-specific population-based incidence of bacterial enteric infections caused by Shigella, Salmonella and Campylobacter, in Jerusalem. During 1990–2008, 32 408 cases were reported (incidence rate 232·1/100 000 per annum). The patterns of Shigella (47·4% of cases), Salmonella (34·4%) and Campylobacter (18·2%) infections evolved noticeably. Campylobacter rates increased from 15·0 to 110·8/100 000 per annum. Salmonella rates increased from 74·2 to 199·6/100 000 in 1995 then decreased to 39·4/100 000. Shigella showed an endemic/epidemic pattern ranging between 19·7 and 252·8/100 000. Most patients (75%) were aged <15 years; children aged <5 years comprised 56·4% of cases, despite accounting for only 12·9% of the population. Campylobacter was the predominant organism in infants aged <1 year and Shigella in the 1–4 years group. The hospitalization rates were: Shigella, 1·8%; Campylobacter, 2·3%; Salmonella, 6·9%. Infants were 2·2 times more likely to be hospitalized than children aged 1–14 years (P=0·001). Household transmission occurred in 21·2% of Shigella cases compared with 5% in the other bacteria.
The X-ray stellar population of the LMC
Authors: Nazé Yaël
Published: March 2009

In the study of stars, the high energy domain occupies a place of choice, since it is the only one able to directly probe the most violent phenomena: indeed, young pre-main sequence objects, hot massive stars, or X-ray binaries are best revealed in X-rays. However, previously available X-ray observatories often provided only crude information on individual objects in the Magellanic Clouds. The advent of the highly efficient X-ray facilities XMM-Newton and Chandra has now dramatically increased the sensitivity and the spatial resolution available to X-ray astronomers, thus enabling a fairly easy determination of the properties of individual sources in the LMC.
The star clusters of the Magellanic System
Authors: Santiago Basílio X.
Published: March 2009

More than 50 years have elapsed since the first studies of star clusters in the Magellanic Clouds. The wealth of data accumulated since then has not only revealed a large cluster system, but also a diversified one, filling loci in the age, mass and chemical abundance parameter space which are complementary to Galactic clusters. Catalogs and photometric samples currently available cover most of the cluster mass range. The expectations of relatively long cluster disruption timescales in the Clouds have been confirmed, allowing reliable assessments of the cluster initial mass function and of the cluster formation rate in the Clouds. Due to their proximity to the Galaxy, Magellanic clusters are also well resolved into stars. Analysis of colour—magnitude diagrams (CMDs) of clusters with different ages, masses and metallicities are useful tools to test dynamical effects such as mass loss due to stellar evolution, two-body relaxation, stellar evaporation, cluster interactions and tidal effects. The existence of massive and young Magellanic clusters has provided insight into the physics of cluster formation. The magnitudes and colours of different stellar types are confronted with stellar evolutionary tracks, thus constraining processes such as convective overshooting, stellar mass-loss, rotation and pre main-sequence evolution. Finally, the Magellanic cluster system may contribute with nearby and well studied counterparts of recently proposed types of extragalactic clusters, such as Faint Fuzzies and Diffuse Star Clusters.
Kinematical structure of the Magellanic System
Authors: van der Marel Roeland P. , Kallivayalil Nitya , Besla Gurtina
Published: March 2009

We review our understanding of the kinematics of the LMC and the SMC, and their orbit around the Milky Way. The line-of-sight velocity fields of both the LMC and SMC have been mapped with high accuracy using thousands of discrete traces, as well as H i gas. The LMC is a rotating disk for which the viewing angles have been well established using various methods. The disk is elliptical in its disk plane. The disk thickness varies depending on the tracer population, with V/σ ranging from ~2–10 from the oldest to the youngest population. For the SMC, the old stellar population resides in a spheroidal distribution with considerable line-of-sight depth and low V/σ. Young stars and H i gas reside in a more irregular rotating disk. Mass estimates based on the kinematics indicate that each Cloud is embedded in a dark halo. Proper motion measurements with HST show that both galaxies move significantly more rapidly around the Milky Way than previously believed. This indicates that for a canonical 1012 M⊙ Milky Way the Clouds are only passing by us for the first time. Although a higher Milky Way mass yields a bound orbit, this orbit is still very different from what has been previously assumed in models of the Magellanic Stream. Hence, much of our understanding of the history of the Magellanic System and the formation of the Magellanic Stream may need to be revised. The accuracy of the proper motion data is insufficient to say whether or not the LMC and SMC are bound to each other, but bound orbits do exist within the proper motion error ellipse.
New analysis of the proper motions of the Magellanic Clouds using HST/WFPC2
Authors: Kallivayalil Nitya , van der Marel Roeland P. , Anderson Jay , Besla Gurtina , Alcock Charles
Published: March 2009

In HST Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in the Magellanic Clouds centered on background quasars. We used these data to determine the proper motions of the LMC and SMC to better than 5% and 15% respectively. The results had a number of unexpected implications for the Milky Way-LMC-SMC system. The implied three-dimensional velocities were larger than previously believed and close to the escape velocity in a standard 1012 M⊙ Milky Way dark halo, implying that the Clouds may be on their first passage. Also, the relative velocity between the LMC and SMC was larger than expected, leaving open the possibility that the Clouds may not be bound to each other. To further verify and refine our results we requested an additional epoch of data in Cycle 16 which is being executed with WFPC2/PC due to the failure of ACS. We present the results of an ongoing analysis of these WFPC2 data which indicate good consistency with the two-epoch results.
AKARI near-infrared spectroscopy: Detection of H2O and CO2 ices toward young stellar objects in the Large Magellanic Cloud
Authors: Shimonishi Takashi , Onaka Takashi , Kato Daisuke , Sakon Itsuki , Ita Yoshifusa , Kawamura Akiko , Kaneda Hidehiro
Published: March 2009

We present the first results of the AKARI Infrared Camera near-infrared spectroscopic survey of the Large Magellanic Cloud (LMC). The circumstellar material of young stellar objects (YSOs) are affected by galactic environments such as a metallicity or radiation field. Ices control the chemical balance of circumstellar environments of embedded YSOs. We detected absorption features of the H2O ice 3.05 μm and the CO2 ice 4.27 μm stretching mode toward seven massive YSOs in the LMC. This is the first detection of the 4.27 μm CO2 ice feature toward extragalactic YSOs. The present samples are for the first time spectroscopically confirmed to be YSOs. We used a curve-of-growth method to evaluate the column densities of the ices and derived the CO2/H2O ratio to be 0.45±0.17. This is clearly higher than that seen in Galactic massive YSOs (0.17±0.03). We suggest that the strong ultraviolet radiation field and/or the high dust temperature in the LMC may be responsible for the observed high CO2 ice abundance.
The star formation history in 12 SMC fields
Authors: Noël Noelia E. D. , Aparicio Antonio , Gallart Carme , Hidalgo Sebastián L. , Costa Edgardo , Méndez René A.
Published: March 2009

We present a quantitative analysis of the star formation history (SFH) of 12 fields in the Small Magellanic Cloud (SMC) based on unprecedented deep [(B–R),R] color—magnitude diagrams (CMDs) from Noël et al. (2007). Our fields reach down to the oldest main sequence (MS) turnoff with high photometric accuracy, which is vital for obtaining accurate SFHs. We use the IAC-pop code (Aparicio & Hidalgo 2009) to obtain the SFH, using a single CMD generated using IAC-star (Aparicio & Gallart 2004). We find that there are three main periods of enhancement of star formation: a young one peaked at ~0.2–0.5 Gyr old, only present in the eastern and in the central-most fields; one at intermediate ages, peaked at ~4–5 Gyr old in all fields; and an old one, peaked at ~10 Gyr in all the fields but the western ones, in which this old enhancement splits into two, peaked at ~8 Gyr old and at ~12 Gyr old. This “two-enhancement” zone seems to be a robust feature since it is unaffected when using different stellar evolutionary libraries, implying that stars in the SMC take a Hubble time or more to mix. This indicates that there was a global enhancement in ψ(t) at ~4–5 Gyr ago in the SMC. We also find that the age of the old population is similar at all radii and at all azimuth and we constrain the age of this oldest population to be older than ~11.5 Gyr old. The intermediate-age population, in turn, presents variations with both, radii and azimuth. Theoretical studies based on results from larger spatial areas are needed to understand the origin of the young gradient. This young component is highly affected by interactions between Milky Way/LMC/SMC. We do not find yet a region dominated by an old, Milky Way-like, halo at 4.5 kpc from the SMC center, indicating either that this old stellar halo does not exist in the SMC or that its contribution to the stellar populations, at the galactocentric distances of our outermost field, is negligible.
Metallicity and kinematics of a large sample of LMC and SMC clusters
Authors: Grocholski A. J. , Parisi M. C. , Geisler D. , Sarajedini A. , Cole A. A. , Clariá J. J. , Smith V. V.
Published: March 2009

We have carried out a large-scale investigation of the metallicity and kinematics for a number of LMC and SMC star clusters using Caiitriplet spectra obtained at theVLT. Our sample includes 28 LMC and 16 SMC clusters, covering a wide range of ages and spatial extent of the host galaxy. We determine mean cluster velocities to about 2 km s−1and metallicities to 0.05 dex (random error), from about 7 members per cluster. Herein we present the main results for this study for the cluster metallicity distributions, metallicity gradients, age-metallicity relations and kinematics.
The chemical signatures of the Large Magellanic Cloud globular clusters
Authors: Mucciarelli Alessio
Published: March 2009

We present the first results of a long-term project based on the analysis of high-resolution optical spectra for a sample of Large Magellanic Cloud globular clusters. The final aim is to build a new, reliable metallicity scale for this cluster system and shed some light on the role played by the different chemical contributors (AGB, SN II and SN Ia), in order to understand the chemical enrichment history of the Large Magellanic Cloud. The analysis of 6 young and intermediate-age clusters and 11 field stars, observed with the UVES@FLAMES spectrograph, provides crucial information about the chemical composition of the dominant stellar population of the LMC. All these stars are metal-rich ([Fe/H]~ −0.4 dex), with solar-scaled [α/Fe] ratios, that point toward an enrichment from SN Ia. Moreover, we observed a general depletion for the [Al/Fe] ratio (indication of a chemical enrichment by metal-poor SN II) and a strong enhancement of the [Ba/Y] ratio (likely due to the enrichment by metal-poor AGB stars).
A survey of the most massive stars in the Magellanic Clouds
Authors: Bonanos Alceste Z.
Published: March 2009

Despite the large impact very massive stars (>30 M⊙) have in astrophysics, their fundamental parameters remain uncertain. I present results of a survey aiming to characterize the most massive stars in the Magellanic Clouds. The survey targets the brightest, blue, eclipsing binaries discovered by the OGLE microlensing survey, for which masses and radii are measured to 5%. Such precise data are rare and provide constraints for theories of massive star formation and evolution at low metallicities.
Resolving the dusty torus and the mystery surrounding LMC red supergiant WOH G64
Authors: Ohnaka Keiichi , Driebe Thomas , Hofmann Karl-Heinz , Weigelt Gerd , Wittkowski Markus
Published: March 2009

We present mid-IR long-baseline interferometric observations of the red supergiant WOH G64 in the Large Magellanic Cloud with MIDI at the ESO's Very Large Telescope Interferometer (VLTI). Our MIDI observations of WOH G64 are the first VLTI observations to spatially resolve an individual stellar source in an extragalactic system. Our 2-D radiative transfer modeling reveals the presence of a geometrically and optically thick torus seen nearly pole-on. This model brings WOH G64 in much better agreement with the current evolutionary tracks for a 25 M⊙ star — about a half of the previous estimate of 40 M⊙ — and solves the serious discrepancy between theory and observation which existed for this object.
The Magellanic System: Stars, Gas, and Galaxies
Authors: Bland-Hawthorn Joss , Gallagher Jay S.
Published: March 2009

We provide a brief overview of some key issues that came out of the IAUS 256 symposium on the Magellanic System (http://www.astro.keele.ac.uk/iaus256).
Experimental system level analysis of a concurrent dual-band power amplifier for WiMAX and WCDMA applications
Authors: Cidronali Alessandro , Magrini Iacopo , Giovannelli Niccolò , Mercanti Massimiliano , Manes Gianfranco
Published: March 2009

This paper presents a feasibility study for the implementation of a concurrent dual-band power amplifier (PA) design suitable for 1.98 GHz WCDMA and 3.42 GHz WiMAX digital systems. The proposed PA design was compared with a test bed based on a pair of dedicated single-frequency band PAs. The dual-band PA exhibited simultaneous peak output power levels of 24 and 17 dBm in the lower and in the higher bands to maintain ACPR and EVM requirements below 33 dBc and 5%, respectively. The conclusions drawn in the paper justify the design effort of this innovative solution, which is capable of increasing the PAE for concurrent dual-band operation maintaining the performance of more conventional solutions.
Criteria for the evaluation of linear two-port stability using two geometrically derived parameters
Authors: Meng Chinchun , Wei Hung-Ju , Sun Po-Hsing
Published: March 2009

Two geometrically derived stability parameters, µ′ (or µ) and ν′(or ν), are used to analyze the stability of a two-port network. The magnitudes of both µ′ (or µ) and ν′ (or ν) parameters determine geometrical relations between the stability circle and the unit Smith chart in the ΓS(or ΓL) plane. |µ′| (or |µ|) is defined as the minimum distance from the stability circle to the origin of the unit Smith chart in the ΓS(or ΓL) plane, while |ν′|(or |ν|) is defined as the maximum distance. Moreover, the signs of ν′ (or ν) and µ′ (or µ) parameters determine which region of the stability circle is stable (inside or outside) and whether the stable region includes the origin of the Smith chart, respectively. There are totally 12 situations between the stability circle and the unit Smith chart in the ΓS(or ΓL) plane by using µ′ (or µ) and ν′ (or ν) parameters. This paper classifies 12 situations in the ΓSplane and also presents the corresponding practical two-port networks.
Stress change and effective friction coefficient along the Sumatra‐Andaman‐Sagaing fault system after the 26 December 2004 (Mw= 9.2) and the 28 March 2005 (Mw= 8.7) earthquakes
Authors: Cattin R. , Chamot‐Rooke N. , Pubellier M. , Rabaute A. , Delescluse M. , Vigny C. , Fleitout L. , Dubernet P.
Published: March 2009

The 2004 Aceh and 2005 Nias events are the two greatest earthquakes of the past 40 years with a total rupture of 1700 km long and a coseismic slip reaching up to 25 m. These two earthquakes have caused large stress perturbations which significantly altered seismic activity in the Sumatra‐Andaman region. Using both detailed mapping of failure planes and various slip distributions, we calculate this stress change along the Sumatra‐Andaman‐Sagaing fault system from central Sumatra to southern Myanmar. The static Coulomb stress change ΔCFFand the observed seismic activity are in very good agreement with a Coulomb index ∼ 20% greater than the one obtained for random events. Compared to previous studies, this high Coulomb Index confirms two important issues on the use of static stress change criterion: unsuited to study near‐field aftershocks and only relevant for aftershocks analysis on large and mature faults at a time scale of several months. The calculated ΔCFFdistribution suggests that the 2004 and 2005 earthquakes inhibit failure on the North Andaman rift and on the Sagaing fault, while failure is encouraged along the transform Andaman zone, the central Andaman rift, the West Andaman fault, the Sumatra fault system, and the offshore thrust faults west of Sumatra Island. The maximum value of ∼15–20 bar (1.5–2 MPa) for ΔCFFis reached in the northern part of the Sumatra fault system. This high value together with the lack of major earthquake in the last 170 years result in a high seismic hazard for this region. Our results are also consistent with temporal evolution of both earthquakes’ location and focal mechanism prior to and after the events. In particular, we explain the occurrence and the mechanism of seismic swarms observed in the central Andaman rift and along the west Andaman fault. Finally, our calculations reveal that the seismicity in the Andaman rift zone can only be explained ifμ′ > 0.5. This result leads to two end‐member models: one with a constant and high fault friction and one with spatial variations, for which friction may depend on either the nature of the lithosphere (oceanic versus continental) or the fault type.