bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultimate fast optical switching of a planar microcavity in the telecom wavelength range
Authors: Ctistis Georgios , Yuce Emre , Hartsuiker Alex , Claudon Julien , Bazin Maela , Gérard Jean-Michel , Vos Willem L.
Published: April 2011

We have studied a GaAs–AlAs planar microcavity with a resonance near 1300 nm in the telecom range by ultrafast pump-probe reflectivity. By the judicious choice of pump frequency, we observe an ultimate fast and reversible decrease in the resonance frequency by more than half a linewidth due to the instantaneous electronic Kerr effect. The switch-on and switch-off of the cavity is only limited by the cavity storage time of τcav=0.3 ps and not by intrinsic material parameters. Our results pave the way to supraterahertz switching rates for on-chip data modulation and real-time cavity quantum electrodynamics.
Characterization of a high mechanical-Q fiber laser Lorentz force dc magnetometer
Authors: Cranch G. A. , Askins C. G. , Miller G. A. , Kirkendall C. K.
Published: April 2011

A magnetic field sensor is described based on coupling the field into a time varying strain in a fiber laser strain sensor, through the Lorentzian force. A conducting bridge carries an ac current and oscillates at resonance in the presence of a magnetic field. A fiber laser strain sensor attached to the ribbon measures the deflections. The quality factor is shown to be limited by air damping resulting in a measurement resolution of 704 \documentclass[12pt]{minimal}\begin{document}$\text{pT/Hz}^{1/2} \pm 10 \%$\end{document}pT/Hz1/2±10% at ambient pressure and 360 \documentclass[12pt]{minimal}\begin{document}$\text{pT}/\text{Hz}^{1/2} \pm 10 \%$\end{document}pT/Hz1/2±10% at a reduced pressure of 1700 Pa at 1 Hz and 75 mA (rms).
An incremental mean first passage analysis for a quasistatic model of polymer translocation through a nanopore
Authors: de Haan Hendrick W. , Slater Gary W.
Published: April 2011

For the translocation of a polymer through a nanopore, a quasistatic assumption for the dynamics yields a tractable form for the entropic barrier. Although this is a much simplified model, interesting features such as robust scaling emerge from its application. To explore these details, we present a method of mapping the translocation process as an incremental mean first passage problem. In this approach, the quantity of interest is the average first time t0 at which the polymer achieves a displacement of Δs in the translocation coordinate s. Constructing scenarios with different initial conditions and boundary conditions, analytic and exact numerical approaches are used to resolve the dynamics of translocation in detail and generate new insight into the nature of the entropic barrier.
Apparatus for dimensional characterization of fused silica fibers for the suspensions of advanced gravitational wave detectors
Authors: Cumming A. , Jones R. , Barton M. , Cagnoli G. , Cantley C. A. , Crooks D. R. M. , Hammond G. D. , Heptonstall A. , Hough J. , Rowan S. , Strain K. A.
Published: April 2011

Detection of gravitational waves from astrophysical sources remains one of the most challenging problems faced by experimental physicists. A significant limit to the sensitivity of future long-baseline interferometric gravitational wave detectors is thermal displacement noise of the test mass mirrors and their suspensions. Suspension thermal noise results from mechanical dissipation in the fused silica suspension fibers suspending the test mass mirrors and is therefore an important noise source at operating frequencies between ∼10 and 30 Hz. This dissipation occurs due to a combination of thermoelastic damping, surface and bulk losses. Its effects can be reduced by optimizing the thermoelastic and surface loss, and these parameters are a function of the cross sectional dimensions of the fiber along its length. This paper presents a new apparatus capable of high resolution measurements of the cross sectional dimensions of suspension fibers of both rectangular and circular cross section, suitable for use in advanced detector mirror suspensions.
The effects of alloying element Co on Ni–Mn–Ga ferromagnetic shape memory alloys from first-principles calculations
Authors: Bai Jing , Raulot Jean-Marc , Zhang Yudong , Esling Claude , Zhao Xiang , Zuo Liang
Published: April 2011

The effects of Co addition on the properties of Ni8−xMn4Ga4Cox ferromagnetic shape memory alloys are systematically investigated by first-principles calculations. The formation energy results indicate that the added Co preferentially occupies the Ni sites in Ni2MnGa alloy. The total energy difference between the paramagnetic and the ferromagnetic austenite plays an important role on the Curie transformation. The electronic density of states gives rise to the difference in the magnetic properties.
Calibrated simulation for estimating energy savings by the use of cool roof in five Indian climatic zones
Authors: Bhatia Aviruch , Mathur Jyotirmay , Garg Vishal
Published: April 2011

A calibrated model has been used to estimate the energy savings by cool roof application on buildings located in five different climatic zones. The model has been calibrated as per the measured data in a building located in Hyderabad (India), and the same has been used to project energy savings in different cities located in five different climatic zones of the country. Results show that the maximum reduction in energy consumption is observed in Mumbai (warm and humid climate), followed by Ahmedabad (hot and dry climate), Bangalore (temperate climate), and Delhi (composite climate). Least energy saving is observed in Shillong (cold climate). In all the climates except cold, the financial payback period is acceptable, being less than 3 yr, whereas for cold climate, the investment is getting paid back in 6.69 yr, making the cool roof application not very attractive.
Quadrupole plasmon resonance mode in nanocrescent/nanodisk structure:Local field enhancement and tunability in the visible light region
Authors: Zhang Y. , Jia T. Q. , Feng D. H. , Xu Z. Z.
Published: April 2011

We propose a metallic nanostructure consisting of a nanodisk in a nanocrescent. At the quadrupole plasmon resonance wavelengths of the nanocrescent/nanodisk structures, the local electric field amplitudes at the crescent tips are 15 times higher than those of the single nanocrescents. In addition, the quadrupole resonance wavelengths are tunable in the visible region while the peak widths keep less than 5 nm. We study the mechanisms of the local field enhancement (LFE), and find that the coupling between the quadrupole resonance modes of the nanogap and the nanocrescent result into the high LFE factor.
Selective growth of perovskite oxides on SrTiO3 (001) by control of surface reconstructions
Authors: Phark Soo-hyon , Chang Young Jun , Won Noh Tae
Published: April 2011

We report surface reconstruction (RC)-dependent growths of SrTiO3 and SrVO3 on a SrTiO3 (001) surface with two different coexisting surface RCs, namely, (2×1) and c(6×2). Up to the coverage of several layers, epitaxial growth was forbidden on the c(6×2) RC under the growth conditions that permitted layer-by-layer epitaxial growth on the (2×1) RC. Scanning tunneling microscopy on the lattice structure of the c(6×2) RC revealed that this RC-selective growth mainly originated from the significant structural/stoichiometric dissimilarity between the c(6×2) RC and the cubic perovskite films. On the c(6×2) RC, therefore, formation of perovskite islands was forbidden from the nucleation stage.
Twin-beam optical parametric generation in χ(2) nonlinear photonic crystals
Authors: Gallo Katia , Levenius Martin , Laurell Fredrik , Pasiskevicius Valdas
Published: April 2011

We demonstrate optical parametric generation in two-dimensional purely nonlinear lattices. Experiments performed in hexagonally poled LiTaO3 crystals pumped around 800 nm indicate a coherent contribution to the parametric gain arising from multiple resonances of the lattice, resulting in dual-beam signal outputs in the 1–1.7 μm range.
Physical model for the growth of amorphous carbon nanotubes
Authors: Zhao T. K. , Li G. M. , Liu L. H. , Liu Y. N. , Li T. H.
Published: April 2011

A physical model for the growth mechanism of amorphous carbon nanotubes (ACNTs) (namely, “open tips growth and carbon clusters (Cn,n>6) adding”) has been proposed in this letter. Based on Tersoff–Brenner [Phys. Rev. B 37, 6991 (1988) and Phys. Rev. B 42, 9458 (1990)] and Lennard-Jones potential energy functions, a mathematic relationship for the growth of ACNTs was established. The predicted diameters of ACNTs from this physical model were in the range of 5–25 nm. The predicted values were in agreement with the experimental measurements in the range of 7–20 nm.
Modeling study on pressure dependence of plasma structure and formation in 110 GHz microwave air breakdown
Authors: Zhou Qianhong , Dong Zhiwei
Published: April 2011

Recent experimental studies of 110 GHz microwave air volume breakdown have shown that as pressure is decreased from atmosphere to a few torr, the discharge transitions from a well-defined array to a smeared-out array and finally to a diffuse plasma. In this letter, a two-dimensional model coupling plasma fluid equations and Maxwell equations is used to simulate the pressure dependence of plasma structure and formation under conditions similar to the experiments. The modeling pressure dependence of plasma structures in H plane and E plane is qualitatively consistent with the experimental observation. The quantitative discrepancy between modeling and experimental results is explained. The simulations allow a good understanding of plasma structure at different pressures in microwave volume breakdown.
Schottky barrier height on thermally oxidized InAlN surface evaluated by electrical and optical measurements
Authors: Kováč J. , Šramatý R. , Chvála A. , Sibboni H. , Morvan E. , DiForte-Poisson M. A. , Donoval D. , Kordoš P.
Published: April 2011

Current transport and Schottky barrier height analysis on InAlN/GaN structures with thermally oxidized InAlN surface (800 °C, 1 min) was performed. From the current-voltage characteristics measured at various temperatures (300–820 K) and their approximation by various current mechanisms, it follows that the tunneling current dominates. Extraction of the thermionic emission yielded the Schottky barrier height of 2.43 eV at 300 K and its slight decrease with increased temperature. Optical method (photoemission current vs photon energy) allows direct barrier height evaluation without analyzing current mechanisms. Comparative analysis using optical method yielded the room-temperature barrier height of 2.57 eV. Obtained barrier heights document significant barrier enhancement due an InAlN oxidation. This result confirms the thermal oxidation procedure as a useful tool at the preparation of reliable InAlN-based devices.
Homoeologous shuffling and chromosome compensation maintain genome balance in resynthesized allopolyploid
Brassica napus
Authors: Xiong Zhiyong , Gaeta Robert T. , Pires J. Chris
Published: April 2011

Polyploidy has contributed to the evolution of eukaryotes, particularly flowering plants. The genomic consequences of polyploidy have been extensively studied, but the mechanisms for chromosome stability and diploidization in polyploids remain largely unknown. By using new cytogenetic tools to identify all of the homoeologous chromosomes, we conducted a cytological investigation of 50 resynthesized
Brassica napus
allopolyploids across generations S
0:1
to S
5:6
and in the S
10:11
generation. Changes in copy number of individual chromosomes were detected in the S
0:1
generation and increased in subsequent generations, despite the fact that the mean chromosome number among lines was approximately 38. The chromosome complement of individual plants (segregants) ranged from 36 to 42, with a bias toward the accumulation of extra chromosomes. Karyotype analysis of the S
10:11
generation detected aneuploidy and inter- and intragenomic rearrangements, chromosome breakage and fusion, rDNA changes, and loss of repeat sequences. Chromosome sets with extensive homoeology showed the greatest instability. Dosage balance requirements maintained chromosome numbers at or near the tetraploid level, and the loss and gain of chromosomes frequently involved homoeologous chromosome replacement and compensation. These data indicate that early generations of resynthesized
B. napus
involved aneuploidy and gross chromosomal rearrangements, and that dosage balance mechanisms enforced chromosome number stability. Seed yield and pollen viability were inversely correlated with increasing aneuploidy, and the greatest fertility was observed in two lines that were additive for parental chromosomes. These data on resynthesized
B. napus
and the correlation of fertility with additive karyotypes cast light on the origins and establishment of natural
B. napus
.
Coactivators necessary for transcriptional output of the hypoxia inducible factor, HIF, are directly recruited by ARNT PAS-B
Authors: Partch Carrie L. , Gardner Kevin H.
Published: April 2011

Hypoxia-inducible factor (HIF) is the key transcriptional effector of the hypoxia response in eukaryotes, coordinating the expression of genes involved in oxygen transport, glycolysis, and angiogenesis to promote adaptation to low oxygen levels. HIF is a basic helix-loop-helix (bHLH)-PAS (PER-ARNT-SIM) heterodimer composed of an oxygen-labile HIF-α subunit and a constitutively expressed aryl hydrocarbon receptor nuclear translocator (ARNT) subunit, which dimerize via basic helix–loop–helix and PAS domains, and recruit coactivators via HIF-α C-terminal transactivation domains. Here we demonstrate that the ARNT PAS-B domain provides an additional recruitment site by binding the coactivator transforming acidic coiled-coil 3 (TACC3) in a step necessary for transcriptional responses to hypoxia. Structural insights from NMR spectroscopy illustrate how this PAS domain simultaneously mediates interactions with HIF-α and TACC3. Finally, mutations on ARNT PAS-B modulate coactivator selectivity and target gene induction by HIF in vivo, demonstrating a bifunctional role for transcriptional regulation by PAS domains within bHLH-PAS transcription factors.
Grammatical Gender in German: A Case for Linguistic Relativity?
Authors: Bender Andrea , Beller Sieghard , Klauer Karl Christoph
Published: April 2011

The “principle of linguistic relativity” holds that, by way of grammatical categorization, language affects the conceptual representations of its speakers. Formal gender systems are a case in point, albeit a particularly controversial one: Previous studies obtained broadly diverging data, thus giving rise to conflicting conclusions. To a large extent, this incoherence is related to task differences and methodological problems. Here, a priming design is presented that avoids previous problems, as it prevents participants from employing gender information in a strategic manner. Four experiments with German native speakers show priming effects of the prime's grammatical gender on animate and nonanimate targets, an effect for the prime's biological gender on animate targets, but no effect for the prime's biological gender on nonanimate targets, and thus speak against an effect of language on thought for German gender.
Egypt’s rural–urban income disparity: is the gap diverging?
Authors: Helmy Heba Ezzeldin
Published: April 2011

Although some studies have attempted to assess the rural–urban income gap in the 1960s and 1970s, no study has focused on the evolution of the gap over the past 25 years, let alone the evolution in the real differences in per capita income between the rural sector and the urban one. The objective of this study is to fill the gap in the literature on this topic and to appraise the development in the gap – in nominal and real terms – both on the aggregate per capita rural and urban income levels and in different expenditure size classes from 1981 till 2005, a period which witnessed a revolution in the agricultural policies from intensive government intervention to complete liberalization. The results of the study prove that the gap diverged again from 1994 to 2005 after converging from 1981 to 1994. The study also proves that the gap is more apparent in the middle classes rather than the lower ones. Finally, with respect to food consumption the study concluded that a slight gap may exist in favour of rural – and not urban – Egypt.
The revolutions of the Arab Spring: are democracy, development and modernity at the gates?
Authors: Sakbani Michael
Published: April 2011

The paper places in historical perspective the current Arab uprisings. It argues that the reasons behind them lie in the comprehensive political, social, economic and educational failures of the Arab regimes. It documents these failures statistically and analytically. It goes on to provide analysis of the current developments in Egypt, Tunisia, Libya, Syria, Yemen and the rest of the affected states. It concludes by drawing up the implications on the Arab future of these uprisings.
Pandemic (H1N1) 2009 Influenza in Hospitalized Children in Manitoba: Nosocomial Transmission and Lessons Learned from the First Wave
Authors: Fanella Sergio T. , Pinto Michelle A. , Bridger Natalie A. , Bullard Jared M. P. , Coombs Jennifer M. L. , Crockett Maryanne E. , Olekson Karen L. , Poliquin Philippe G. , Caeseele Paul G. Van , Embree Joanne E.
Published: April 2011

Objective.

To review the experiences at Winnipeg Children's Hospital (WCH) during the 2009 influenza season, with an emphasis on nosocomial transmission and infection prevention and control responses.

Design.

A case series of patients admitted to WCH who had laboratory-confirmed cases of influenza between January 1 and July 31, 2009, with a comparison of patients with seasonal influenza and those with pandemic (H1N1) 2009 influenza; a review of the impact of infection prevention and control modifications on nosocomial transmission.

Patients and Setting.

A total of 104 inpatients with influenza, 81 of whom had pandemic (H1N1) 2009 influenza, were reviewed at a large Canadian pediatric tertiary care center.

Results.

There were no differences in risk factors, presentation, or outcome between patients with seasonal influenza and those with pandemic (H1N1) 2009 influenza. There were 8 nosocomial cases of pandemic (H1N1) 2009 influenza. Excluding patients with nosocomial cases, mean length of hospital stay was significantly shortened to 3.7 days for individuals who had pandemic (H1N1) 2009 influenza and who received empiric oseltamivir on admission to the hospital, compared with 12.0 days for patients for whom treatment was delayed (P = .02). Treatment with oseltamivir of all patients with suspected cases of influenza and prompt modifications to infection control practices, including playroom closures and enhanced education of visitors and staff, terminated nosocomial transmission.

Conclusions.

Infection with pandemic (H1N1) 2009 influenza virus resulted in a substantial number of hospitalizations of pediatric patients in Manitoba, including those with nosocomial cases, thereby stressing the capacity of WCH. Immediate therapy with oseltamivir on admission to the hospital resulted in a significantly reduced length of hospitalization. This, coupled with intensified infection prevention and control practices, halted nosocomial transmission. These strategies should be considered in future pandemic influenza or other respiratory viral outbreaks.
Systematic Review of Measurement and Adjustment for Colonization Pressure in Studies of Methicillin-ResistantStaphylococcus aureus, Vancomycin-Resistant Enterococci, andClostridium difficileAcquisition
Authors: Ajao Adebola O. , Harris Anthony D. , Roghmann Mary-Claire , Johnson J. Kristie , Zhan Min , McGregor Jessina C. , Furuno Jon P.
Published: April 2011

Objective.

Colonization pressure is an important infection control metric. The aim of this study was to describe the definition and measurement of and adjustment for colonization pressure in nosocomial-acquisition risk factor studies of methicillin-resistantStaphylococcus aureus(MRSA), vancomycin-resistant enterococci (VRE), andClostridium difficile.

Methods.

We performed a computerized search of studies of nosocomial MRSA, VRE, andC. difficileacquisition published before July 1, 2009, through MEDLINE. Studies were included if a study outcome was MRSA, VRE, orC. difficileacquisition; the authors identified risk factors associated with MRSA, VRE, orC. difficileacquisition; and the study measured colonization pressure.

Results.

The initial MEDLINE search yielded 505 articles. Sixty-six of these were identified as studies of nosocomial MRSA, VRE, orC. difficileacquisition; of these, 18 (27%) measured colonization pressure and were included in the final review. The definition of colonization pressure varied considerably between studies: the proportion of MRSA- or VRE-positive patients (5 studies), the proportion of MRSA- or VRE-positive patient-days (6 studies), or the total or mean number of MRSA-, VRE-, orC. difficile-positive patients or patient-days (7 studies) in the unit over periods of varying length. In 10 of 13 studies, colonization pressure was independently associated with MRSA, VRE, orC. difficileacquisition.

Conclusion.

There is a need for a simple and consistent method to quantify colonization pressure in both research and routine clinical care to accurately assess the effect of colonization pressure on cross-transmission of antibiotic-resistant bacteria.
Current Strategies for Managing Providers Infected with Bloodborne Pathogens
Authors: Turkel Sarah , Henderson David K.
Published: April 2011

Background.

In 1991 the Centers for Disease Control and Prevention issued guidelines to reduce risks for provider-to-patient transmission of bloodborne pathogens. These guidelines, unchanged since 1991, recommend management strategies for hepatitis B e antigen-positive providers and for providers infected with human immunodeficiency virus; they do not address hepatitis C virus (HCV)-infected providers.

Objective.

We summarized current state practices and surveyed state health departments to determine (1) whether state policies have been modified since 1991; (2) whether state laws require prospective notification of patients and/or expert review panels to manage infected providers; (3) the frequency with which infected-providers issues come to the attention of state health departments; and (4) how state health departments intervene.

Methods.

We reviewed the 50 states' laws and guidelines to determine current practices and conducted a structured telephone survey of all state health departments.

Results.

Whereas only 19 states require infected providers to notify patients of the providers’ bloodborne pathogen infection, these 19 states require notification under highly varied circumstances. Only 10 of 50 state health department officials identified these issues as requiring significant departmental effort. No state law or guideline incorporates information about providers’ viral burdens as part of the risk assessment. Only 3 of 50 states have modified policies or laws since initial passage, and only 1 of 50 discusses the management of HCV-infected providers.

Conclusions.

These results identify a need for incorporating contemporary scientific information into guidelines and also suggest that infected-provider issues are not occurring commonly, are not being detected, or are being managed at levels below the state health department.
Perceptions and Influence of a Hospital Influenza Vaccination Policy
Authors: Daugherty Elizabeth L. , Speck Kathleen A. , Rand Cynthia S. , Perl Trish M.
Published: April 2011

Objective.

Seasonal influenza is a significant cause of morbidity and mortality in the United States each year. Healthcare worker (HCW) influenza vaccination is associated with both decreased absenteeism among employees and improved outcomes among patients. However, HCW influenza vaccine uptake remains suboptimal. The objective of this study was to characterize HCWs' understanding of and response to a stringent vaccination policy.

Design, Setting, and Participants.

A survey of 928 hospital staff at a tertiary academic medical center in Baltimore during the 2008-2009 influenza season.

Results.

Of those surveyed, 75% (n = 695) completed the survey; 623 respondents reported regular patient contact, and 91% of those reported vaccination in the current influenza season. However, only 60% reported consistently receiving the vaccine every year. Of those who were vaccinated, 8% (n = 48) reported being vaccinated for the first time during that influenza season. A significant proportion (42%) of respondents were unaware of the major change in hospital policy regarding vaccination. Influences on the decision to be vaccinated varied significantly between those who are regularly vaccinated and those with inconsistent vaccination habits. Attitudes toward hospital policy varied significantly by race and clinical role.

Conclusions.

Although 91% of respondents with regular patient contact reported being vaccinated for influenza in the 2008–2009 season, only 60% reported consistent annual vaccination. Misinformation regarding hospital policies is widespread. Improvements in vaccination rates will likely require multifaceted, targeted efforts focused on specific influences on less adherent groups. The identified variability in influences on the decision to be vaccinated suggests possible targets for future interventions.
Seasonal Influenza Vaccination of Healthcare Employees: Results of a 4-Year Campaign
Authors: Hirsch Pamela , Hodgson Michael , Davey Victoria
Published: April 2011

Objective.

To document successful substantial increases in healthcare worker influenza vaccination rates and to identify reasons for success and failure.

Design.

(1) Four-year longitudinal characterization of facility vaccination rates, (2) Web-based facility-level questionnaire for influenza coordinators to identify success factors in year 3, and (3) semistructured telephone interviews of influenza coordinators at facilities with substantial increases or declines in year 4.

Setting.

National single-payer hospital (healthcare) system with 153 hospitals in 5 levels of complexity.

Patients.

Facility leadership staff.

Methods.

(1) Vaccination data collected from management sources (doses from pharmacies, denominator data from payrolls); (2) a Web-based survey aligned with a previously administered instrument (Wisconsin Health Department), piloted in-house, modified to reflect national strategies and improvements; and (3) semistructured telephone interviews with influenza coordinators at facilities that improved or worsened by more than 20% between the 2007–2008 and 2008–2009 influenza seasons.

Results.

Vaccination acceptance rates improved from 45% of healthcare workers in 2005–2006 to 66.5% in 2008–2009. Facilities with lower complexity had higher vaccination rates. No individual factors were associated with improved performance.

Conclusions.

Sustained management attention can lead to improvements in healthcare worker influenza vaccination rates. Wavering of attention, though, may lead to rapid loss of effectiveness. Declination statements in this system did not contribute to vaccine acceptance.
Clostridium difficile Infection in a Department of Veterans Affairs Long-Term Care Facility
Authors: Guerrero Dubert M. , Nerandzic Michelle M. , Jury Lucy A. , Chang Shelley , Jump Robin L. , Donskey Curtis J.
Published: April 2011

In a Veterans Affairs medical center, 39% of healthcare facility–onset, healthcare facility-associated Clostridium difficile infections had their onset in the affiliated long-term care facility (LTCF). Eighty-five percent of LTCF-onset patients had been transferred from the hospital within the past month. Delays in diagnosis and treatment were common for LTCF-onset patients.
Temperature-dependent photoluminescence study of InP/ZnS quantum dots
Authors: Pham Thi Thuy , Chi Tran Thi Kim , Nguyen Quang Liem
Published: April 2011

This paper reports on the temperature-dependent photoluminescence of InP/ZnS quantum dots under 532 nm excitation, which is above the InP transition energy but well below that of ZnS. The overall photoluminescence spectra show two spectral components. The higher-energy one (named X) is assigned to originate from the excitonic transition; while the low-energy spectral component (named I) is normally interpreted as resulting from lattice imperfections in the crystalline structure of InP/ZnS quantum dots (QDs). Peak positions of both the X and I emissions vary similarly with increasing temperature and the same as the InP bandgap narrowing with temperature. In the temperature range from 15 to 80 K, the ratio of the integrated intensity from the X and the I emissions decreases gradually and then this ratio increases fast at temperatures higher than 80 K. This could result from a population of charge carriers in the lattice imperfection states at a temperature below 80 K to increase the I emission but then with these charge carriers being released to contribute to the X emission.
The influence of solvents and surfactants on the preparation of copper nanoparticles by a chemical reduction method
Authors: Dung Dang Thi My , Tuyet Le Thi Thu , Fribourg-Blanc Eric , Chien Dang Mau
Published: April 2011

A chemical reduction method for preparing colloidal copper nanoparticles in water and ethylene glycol (EG) is reported. The obtained copper nanoparticles were characterized by powder x-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectrophotometry (UV-vis). Surface plasmon resonance peaks immediately after the synthesis appeared at 579 and 551 nm for the colloidal copper in water and EG, respectively. The stability of colloidal copper in EG was longer than that in water. The color of solution in water changed from light-red to black and the nanoparticles mostly precipitated after 22 days, which is attributed to the oxidation of copper nanoparticles in copper oxide (I), as was confirmed by optical absorption measurements. In EG, copper nanoparticles were red and stable even after 2 months. Ascorbic acid plays a role as antioxidant for colloidal copper, due to its ability to scavenge free radicals and reactive oxygen molecules. Polyvinyl pyrrolidone works both as size controller and polymeric capping agent because it hinders the nuclei from aggregation through the polar groups, which strongly absorb the copper particles on the surface with coordination bonds.
Exploiting prior knowledge and gene distances in the analysis of tumor expression profiles with extended Hidden Markov Models
Authors: Seifert Michael , Strickert Marc , Schliep Alexander , Grosse Ivo
Published: April 2011

Motivation: Changes in gene expression levels play a central role in tumors. Additional information about the distribution of gene expression levels and distances between adjacent genes on chromosomes should be integrated into the analysis of tumor expression profiles.

Results: We use a Hidden Markov Model with distance-scaled transition matrices (DSHMM) to incorporate chromosomal distances of adjacent genes on chromosomes into the identification of differentially expressed genes in breast cancer. We train the DSHMM by integrating prior knowledge about potential distributions of expression levels of differentially expressed and unchanged genes in tumor. We find that especially the combination of these data and to a lesser extent the modeling of distances between adjacent genes contribute to a substantial improvement of the identification of differentially expressed genes in comparison to other existing methods. This performance benefit is also supported by the identification of genes well known to be associated with breast cancer. That suggests applications of DSHMMs for screening of other tumor expression profiles.

Availability: The DSHMM is available as part of the open-source Java library Jstacs (www.jstacs.de/index.php/DSHMM).

Contact:  seifert@ipk-gatersleben.de

Supplementary information:  Supplementary data are available at Bioinformatics online. Supplementary data files are available at the Jstacs's web site.
Risk Factors for Intestinal Gangrene in Children With Small‐bowel Volvulus
Authors: Lin Yu‐Pi , Lee Jung , Chao Hsun‐Chin , Kong Man‐Shan , Lai Ming‐Wei , Chen Chien‐Chang , Chen Shih‐Yen , Luo Chih‐Cheng
Published: April 2011

Objectives:

Pediatric small‐bowel volvulus (SBV) is a surgical emergency, and early diagnosis is difficult. We analyzed the clinical manifestations, imaging findings, and laboratory parameters in children with SBV and attempted to determine the risk factors for bowel gangrene.

Patients and Methods:

Forty‐nine children (35 boys and 14 girls) with SBV who were admitted to the hospital for a period of 13 years were enrolled. Clinical and laboratory parameters and evaluation measures included fever, abdominal pain, vomiting, bloody stool, peritoneal signs, severe dehydration, disease duration, white blood cell counts, sugar, C‐reactive protein (CRP), sodium, potassium, metabolic acidosis, blood urea nitrogen, and creatinine. These parameters were statistically compared between patients with and without bowel gangrene.

Results:

Thirty‐six patients (73.5%) were 5 years old or younger, and nearly half were younger than 1 year old. Abdominal pain and vomiting were 2 major symptoms. Malrotation was the most common cause of SBV. In univariate analysis, nonbilious vomiting, peritoneal signs, severe dehydration, leukocytosis (WBC count >18,000 cells/mm3), elevated CRP (>50 mg/dL), and hyponatremia (<130 mmol/L) were significantly associated with bowel gangrene (P < 0.05). In multivariate analysis, nonbilious vomiting, leukocytosis, and elevated CRP were significantly (P < 0.05) associated with bowel gangrene. The resection rate for bowel gangrene was 44.9%, and no mortality was found. Seven (14.3%) patients had postoperative complications, including short‐bowel syndrome (n = 2), adhesion ileus (n = 3), and intraabdominal abscess (n = 3). Seven experienced failure to thrive in later follow‐up.

Conclusions:

Specific clinical manifestations and laboratory parameters are helpful in the identification of bowel gangrene in children with SBV.
Individually Tailored Treatment of Medication Nonadherence
Authors: Hommel Kevin A. , Herzer Michele , Ingerski Lisa M. , Hente Elizabeth , Denson Lee A.
Published: April 2011

Objective:

Nonadherence is a significant health care issue in pediatric inflammatory bowel disease (IBD) that requires intervention to improve outcomes. This pilot randomized controlled trial was designed to evaluate the feasibility, acceptability, and preliminary efficacy of an individually tailored behavioral treatment for nonadherence in adolescents with IBD.

Patients and Methods:

Fourteen adolescents ages 14.89 ± 2.01 years were randomly assigned to immediate care or wait list control conditions and received a manualized individually tailored behavioral intervention for nonadherence. Medication adherence, measured by pill count, served as the primary endpoint. Parents provided demographic data and ratings of intervention acceptability and patients provided disease‐severity data.

Results:

Feasibility of the treatment was demonstrated by 100% treatment session attendance for all of the patients enrolled in the trial. Both parent and patient acceptability ratings were favorable. Comparison of baseline with posttreatment percent adherence across both conditions demonstrated that treatment resulted in a 4% gain in 6‐mercaptopurine/azathioprine adherence (52% at baseline; 56% at posttreatment; δ = 0.07) and a 25% gain in mesalamine adherence (43% at baseline; 68% at posttreatment; δ = 0.57).

Conclusions:

Individually tailored treatment of nonadherence in adolescents with IBD is feasible and may result in substantial improvement in medication adherence. Differential effect of the intervention on medications requires further investigation, but it may reflect differences in regimen complexity, concerns about medication adverse effects, and/or patient/parent preference to target more complex regimens. Large‐scale testing of this intervention is needed to demonstrate effect on clinical outcomes.
Esophageal pH Monitoring With the BRAVO Capsule
Authors: Cabrera José , Davis Miriam , Horn Debbie , Pfefferkorn Marian , Croffie Joseph M.
Published: April 2011

Aim:

The aim of the present study was to report the global experience with placement, complication rate, and recording of esophageal pH using the BRAVO capsule at our institution.

Patients and Methods:

We recorded the rate of any technical problems and complications during placement in all of the patients (ages 4–22 years) who received this device during a 2‐year period. All of the patients undergoing esophagogastroduodenoscopy with the placement of BRAVO pH capsule were included in this analysis. We also examined the pH data recorded on days 1 and 2 for significant day‐to‐day variability during 2 days of pH monitoring.

Results:

Two hundred eighty‐nine BRAVO pH probes were placed from January 1, 2006 to December 31, 2008. At least 1 day of data was obtained in 278 patients (96.2%). Two days of data were obtained in 274 patients (94.8%). Of all of the reported complications, 1% occurred before deployment of the capsule, 4% occurred during deployment of the capsule, and 9% occurred after successful deployment of the capsule. One patient experienced a superficial esophageal tear that was associated with failure of the capsule to release from the delivery system. No patient requested removal of the capsule and all of the capsules detached within 14 days. In 9.12% of our patients, reflux index was normal on day 1 and abnormal on day 2. There was no statistically significant difference between reflux index recorded on day 1 versus day 2 (P = 0.686).

Conclusions:

The BRAVO pH capsule is easy to place, safe, and well tolerated by children. Performing a 48‐hour study detected abnormal reflux in an additional 9% of our patients.
C-type natriuretic peptide modulates quorum sensing molecule and toxin production in Pseudomonas aeruginosa
Authors: Blier Anne-Sophie , Veron Wilfried , Bazire Alexis , Gerault Eloïse , Taupin Laure , Vieillard Julien , Rehel Karine , Dufour Alain , Le Derf Franck , Orange Nicole , Hulen Christian , Feuilloley Marc G. J. , Lesouhaitier Olivier
Published: April 2011

Pseudomonas aeruginosacoordinates its virulence expression and establishment in the host in response to modification of its environment. During the infectious process, bacteria are exposed to and can detect eukaryotic products including hormones. It has been shown thatP. aeruginosais sensitive to natriuretic peptides, a family of eukaryotic hormones, through a cyclic nucleotide-dependent sensor system that modulates its cytotoxicity. We observed that pre-treatment ofP. aeruginosaPAO1 with C-type natriuretic peptide (CNP) increases the capacity of the bacteria to killCaenorhabditis elegansthrough diffusive toxin production. In contrast, brain natriuretic peptide (BNP) did not affect the capacity of the bacteria to killC. elegans. The bacterial production of hydrogen cyanide (HCN) was enhanced by both BNP and CNP whereas the production of phenazine pyocyanin was strongly inhibited by CNP. The amount of 2-heptyl-4-quinolone (HHQ), a precursor to 2-heptyl-3-hydroxyl-4-quinolone (Pseudomonasquinolone signal; PQS), decreased after CNP treatment. The quantity of 2-nonyl-4-quinolone (HNQ), another quinolone which is synthesized from HHQ, was also reduced after CNP treatment. Conversely, both BNP and CNP significantly enhanced bacterial production of acylhomoserine lactone (AHL) [e.g. 3-oxo-dodecanoyl-homoserine lactone (3OC12-HSL) and butanoylhomoserine lactone (C4-HSL)]. These results correlate with an induction oflasItranscription 1 h after bacterial exposure to BNP or CNP. Concurrently, pre-treatment ofP. aeruginosaPAO1 with either BNP or CNP enhanced PAO1 exotoxin A production, via a highertoxAmRNA level. At the same time, CNP led to elevated amounts ofalgCmRNA, indicating thatalgCis involved inC. eleganskilling. Finally, we observed that in PAO1, Vfr protein is essential to the pro-virulent effect of CNP whereas the regulator PtxR supports only a part of the CNP pro-virulent activity. Taken together, these data reinforce the hypothesis that during infection natriuretic peptides, particularly CNP, could enhance the virulence of PAO1. This activity is relayed by Vfr and PtxR activation, and a general diagram of the virulence activation cascade involving AHL, HCN and exotoxin A is proposed.
Making heads or tails of the HU proteins in the planctomycete Gemmata obscuriglobus
Authors: Yee Benjamin , Sagulenko Evgeny , Fuerst John A.
Published: April 2011

Gemmata obscuriglobus has a highly condensed nucleoid which is implicated in its resistance to radiation. However, the mechanisms by which such compaction is achieved, and the proteins responsible, are still unknown. Here we have examined the genome of G. obscuriglobus for the presence of proteins homologous to those that have been associated with nucleoid condensation. We found two different proteins homologous to the bacterial nucleoid-associated protein HU, one with an N-terminal and one with a C-terminal extension relative to the amino acid sequence of the HU found in Escherichia coli. Sequence analysis revealed that one of these HU homologues represents a novel type with a high number of prolines in its C-terminal extension, whereas the other one has motifs similar to the N terminus of the HU homologue from the radio-resistant bacterium Deinococcus radiodurans. The occurrence of two such HU homologue proteins with these two different terminal extensions in one organism appears to be unique among the Bacteria.
Contribution of the PhoP/Q regulon to survival and replication of Salmonella enterica serovar Typhimurium in macrophages
Authors: Thompson Jessica A. , Liu Mei , Helaine Sophie , Holden David W.
Published: April 2011

The ability of serovars of Salmonella enterica to cause systemic disease is dependent upon their survival and replication within macrophages. To do this, bacteria must withstand or surmount bacteriostatic and bactericidal responses by the host cell, including the delivery of hydrolytic enzymes from lysosomes to the phagosome. The bacterial two-component regulatory system PhoP/Q has been implicated in avoidance of phagolysosomal fusion by S. enterica serovar Typhimurium (S. Typhimurium) in murine macrophages. In this study, the involvement of PhoP/Q-activated genes in avoidance of phagolysosomal fusion was analysed: of all the S. Typhimurium mutant strains tested, only an mgtC mutant strain partially reproduced the phenotype of the phoP mutant strain. As this gene is required for bacterial growth in magnesium-depleted conditions in vitro, the contributions of PhoP/Q to intramacrophage replication and survival were reappraised. Although PhoP/Q was required for both replication and survival of S. Typhimurium within murine macrophages, subsequent analysis of the kinetics of phagolysosomal fusion, taking account of differences in the replication rates of wild-type and phoP mutant strains, provided no evidence for a PhoP/Q-dependent role in this process. PhoP/Q appeared to act subsequent to the process of phagolysosomal avoidance and to promote replication of those bacteria that had already escaped a phagolysosomal fate. Therefore, we conclude that the PhoP/Q regulon enables S. Typhimurium to adapt to intramacrophage stresses other than phagolysosomal fusion.
Blue-light-dependent interaction of cryptochrome 1 with SPA1 defines a dynamic signaling mechanism
Authors: Lian Hong-Li , He Sheng-Bo , Zhang Yan-Chun , Zhu Dan-Meng , Zhang Jing-Yi , Jia Kun-Peng , Sun Shu-Xia , Li Ling , Yang Hong-Quan
Published: April 2011

Cryptochromes (CRYs) are blue-light photoreceptors that mediate various light responses in plants and animals. The signaling mechanism by which CRYs regulate light responses involves their physical interactions with COP1. Here, we report that CRY1 interacts physically with SPA1 in a blue-light-dependent manner. SPA acts genetically downstream from CRYs to regulate light-controlled development. Blue-light activation of CRY1 attenuates the association of COP1 with SPA1 in both yeast and plant cells. These results indicate that the blue-light-triggered CRY1–SPA1 interaction may negatively regulate COP1, at least in part, by promoting the dissociation of COP1 from SPA1. This interaction and consequent dissociation define a dynamic photosensory signaling mechanism.
The neural cell adhesion molecule-derived peptide FGL facilitates long-term plasticity in the dentate gyrus in vivo
Authors: Dallérac Glenn , Zerwas Meike , Novikova Tatiana , Callu Delphine , Leblanc-Veyrac Pascale , Bock Elisabeth , Berezin Vladimir , Rampon Claire , Doyère Valérie
Published: April 2011

The neural cell adhesion molecule (NCAM) is known to play a role in developmental and structural processes but also in synaptic plasticity and memory of the adult animal. Recently, FGL, a NCAM mimetic peptide that binds to the Fibroblast Growth Factor Receptor 1 (FGFR-1), has been shown to have a beneficial impact on normal memory functioning, as well as to rescue some pathological cognitive impairments. Whether its facilitating impact may be mediated through promoting neuronal plasticity is not known. The present study was therefore designed to test whether FGL modulates the induction and maintenance of synaptic plasticity in the dentate gyrus (DG) in vivo. For this, we first assessed the effect of the FGL peptide on synaptic functions at perforant path–dentate gyrus synapses in the anesthetized rat. FGL, or its control inactive peptide, was injected locally 60 min before applying high-frequency stimulation (HFS) to the medial perforant path. The results suggest that although FGL did not alter basal synaptic transmission, it facilitated both the induction and maintenance of LTP. Interestingly, FGL also modified the heterosynaptic plasticity observed at the neighboring lateral perforant path synapses. The second series of experiments, using FGL intracerebroventricular infusion in the awake animal, confirmed its facilitating effect on LTP for up to 24 h. Our data also suggest that FGL could alter neurogenesis associated with LTP. In sum, these results show for the first time that enhancing NCAM functions by mimicking its heterophilic interaction with FGFR facilitates hippocampal synaptic plasticity in the awake, freely moving animal.
Decline of Leaf Hydraulic Conductance with Dehydration: Relationship to Leaf Size and Venation Architecture
Authors: Scoffoni Christine , Rawls Michael , McKown Athena , Cochard Hervé , Sack Lawren
Published: April 2011

Across plant species, leaves vary enormously in their size and their venation architecture, of which one major function is to replace water lost to transpiration. The leaf hydraulic conductance (K  leaf) represents the capacity of the transport system to deliver water, allowing stomata to remain open for photosynthesis. Previous studies showed that K  leaf relates to vein density (vein length per area). Additionally, venation architecture determines the sensitivity of K  leaf to damage; severing the midrib caused K  leaf and gas exchange to decline, with lesser impacts in leaves with higher major vein density that provided more numerous water flow pathways around the damaged vein. Because xylem embolism during dehydration also reduces K  leaf, we hypothesized that higher major vein density would also reduce hydraulic vulnerability. Smaller leaves, which generally have higher major vein density, would thus have lower hydraulic vulnerability. Tests using simulations with a spatially explicit model confirmed that smaller leaves with higher major vein density were more tolerant of major vein embolism. Additionally, for 10 species ranging strongly in drought tolerance, hydraulic vulnerability, determined as the leaf water potential at 50% and 80% loss of K  leaf, was lower with greater major vein density and smaller leaf size (|r| = 0.85–0.90; P < 0.01). These relationships were independent of other aspects of physiological and morphological drought tolerance. These findings point to a new functional role of venation architecture and small leaf size in drought tolerance, potentially contributing to well-known biogeographic trends in leaf size.