bluuebunny/crossref_metadata_2025_split huggingface dataset:
Equilibrium heat‐induced denaturation of chitinase 40 from Streptomyces thermoviolaceus
Authors: Pyrpassopoulos Serapion , Vlassi Metaxia , Tsortos Achilleas , Papanikolau Yannis , Petratos Kyriacos , Vorgias Constantinos E. , Nounesis George 
Published: May 2006

AbstractHigh‐precision differential scanning calorimetry (DSC) and circular dichroism (CD) have been employed to study the thermal unfolding of chitinase 40 (Chi40) from Streptomyces thermoviolaceus. Chi40 belongs to family 18 of glycosyl hydrolase superfamily bearing a catalytic domain with a “TIM barrel”‐like fold, which exhibits deviations from the (β/α)8 fold. The thermal unfolding is reversible at pH = 8.0 and 9.0. The denatured state is characterized by extensive structural changes with respect to the native. The process is characterized by slow relaxation kinetics. Even slower refolding rates are recorded upon cooling. It is shown that the denaturation calorimetric data obtained at slow heating rate (0.17 K/min) are in excellent agreement with equilibrium data obtained by extrapolation of the experimental results to zero scanning rate. Analysis of the DSC results reveals that the experimental data can be successfully fitted using either a nontwo‐state sequential model involving one equilibrium intermediate, or an independent transitions model involving the unfolding of two Chi40 energetic domains to intermediate states. The stability of the native state with respect to the final denatured state is estimated, ΔG = 24.0 kcal/mol at 25°C. The thermal results are in agreement with previous findings from chemical denaturation studies of a wide variety of (β/α)8 barrel proteins, that their unfolding is a nontwo‐state process, always involving at least one unfolding intermediate. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Weak universal critical behaviour of the mixed spin‐(1/2, S ) Ising model on the Union Jack (centered square) lattice: integer versus half‐odd‐integer spin‐S case
Authors: Strečka Jozef , Čanová Lucia , Dely Ján 
Published: May 2006

AbstractThe mixed spin‐(1/2, S ) Ising model on the Union Jack (centered square) lattice is investigated by establishing the mapping relationship with its corresponding eight‐vertex model. An interplay between the nearest‐neighbour interaction, the competing next‐nearest‐neighbour interaction and the single‐ion anisotropy gives rise to a rather complex critical behaviour displayed in the reentrant phase transitions, the weak universal critical behaviour, as well as, a presence of first‐ and second‐order phase transitions. The most interesting finding to emerge from the present study relates to a variation of the weak‐universal critical exponents along the line of bicritical points, which is being twice as large for the mixed spin‐(1/2, S ) systems with the integer spin‐S atoms as for the ones with the half‐odd‐integer spin‐S atoms. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of carrier diffusion length in MOCVD‐grown GaN epilayers on sapphire by optical techniques
Authors: Lutsenko E. V. , Gurskii A. L. , Pavlovskii V. N. , Yablonskii G. P. , Malinauskas T. , Jarašiūnas K. , Schineller B. , Heuken M. 
Published: May 2006

AbstractTwo optical techniques for the determination of a bipolar diffusion length LD of optically excited carriers in GaN epitaxial layers, namely a time‐resolved picosecond four‐wave mixing (FWM) on free carrier grating and time‐integrated photoluminescence (PL) are presented and examined. The PL technique is based on time‐integrated photoluminescence (PL) spectra measurements from the front and back sides of the sample under cw and nanosecond pulsed laser excitation. The another method utilizes time‐resolved picosecond four‐wave mixing (FWM) at various light‐induced grating periods to extract diffusion coefficient and carrier recombination lifetime. The value of the diffusion length derived by means of FWM decreases with GaN layer thickness from LD = 260 nm (for 1.7 μm‐thick layer) to LD = 100 nm (for 0.3 μm‐thick layer). The integral PL measurements give the value of LD = 120‐130 nm for the 620 nm layer under pulsed excitation intensities up to 200 kW/cm2. It increases to 150‐170 nm at the excitation intensity enhancement to 1 MW/cm2. These values are close to the value of the diffusion length equal to 160 nm obtained using FWM for this layer thickness evidencing the compatibility of both methods. The changes in the value of LD are discussed in terms of the defect distribution in the epitaxial GaN layer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microscopic theory of carrier‐carrier scattering in nitride based quantum‐dot systems
Authors: Nielsen T. R. , Seebeck J. , Lorke M. , Gartner P. , Jahnke F. 
Published: May 2006

AbstractA microscopic theory is applied to study carrier‐carrier Coulomb scattering in nitride‐based quantum dots. Kinetic equations for the carrier population are used to define capture and relaxation rates. For the states involved in the scattering processes, the combined influence of the quantum‐confined Stark effect and manybody renormalizations is taken into account. It is shown that the charge separation due to the built‐in field is accompanied with strong Hartree energy shifts, which can increase the scattering efficiency. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlGaN metal‐semiconductor‐metal structure for pressure sensing applications
Authors: Hassan Z. , Lee Y. C. , Ng S. S. , Yam F. K. , Liu Y. , Rang Z. , Kauser M. Z. , Ruden P. P. , Nathan M. I. 
Published: May 2006

AbstractWe report on the effects of hydrostatic pressure on an Alx Ga1–x N metal‐semiconductor‐metal (MSM) structure with Ni Schottky contacts. Structural, optical, and electrical analysis of the Alx Ga1–x N film were carried out using atomic force microscopy (AFM), high resolution X‐ray diffraction (HRXRD), Raman, UV‐visible spectroscopy, and Hall effect measurements. The AlN mole fraction in this film was determined to be about 24%. Current‐voltage (I‐V) measurements of the MSM structure under hydrostatic pressure indicated a linear decrease of current with pressure. The decrease of the current under pressure was attributed to an increase in barrier height, tentatively attributed to a combination of piezoelectric and band structure effects. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
HVPE growth of high quality GaN layers
Authors: Brückner Peter , Habel Frank , Scholz Ferdinand 
Published: May 2006

AbstractThe surface morphology of HVPE layers typically shows a high density of pyramidal structures which makes some polishing step necessary before their subsequent use in the next epitaxial growth. We found that a slight misorientation of the substrate totally suppresses the development of these pyramidal structures. The misorientation angle was varied between 0° and 0.6°. We did not observe any influence of the direction of miscut. Surface roughness measurements exhibited, that these HVPE grown layers on miscut templates had a comparably flat surface to MOVPE grown samples. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Degradation of blue LEDs related to structural disorder
Authors: Kamanin A. V. , Kolmakov A. G. , Kop'ev P. S. , Onushkin G. A. , Sakharov A. V. , Shmidt N. M. , Sizov D. S. , Sitnikova A. A. , Zakgeim A. L. , Zolotareva R. V. , Usikov A. S. 
Published: May 2006

AbstractThe degradation of blue light emitting diodes (LEDs) with different structural disorder based on MQW InGaN/GaN grown by MOCVD on sapphire has been investigated. New approach to analyze the degradation has been used. It takes into account the structural disorder determined by the extended defect system relaxation and related with poor coalescence of the mosaic structure domains. The results obtained leads to assumption that the migration and segregations of Ga on domain dislocation boundaries of the mosaic structure and the change of energy activation of Mg related centers are important reasons of degradation for all types of LEDs The fastest degradation for poor ordered LEDs was observed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three methods for the growth of InGaN nanostructures by MOVPE
Authors: Oliver R. A. , Kappers M. J. , van der Laak N. K. , Humphreys C. J. 
Published: May 2006

AbstractInGaN nanostructures have been grown (i) by a droplet epitaxy route, (ii) by pre‐treatment of the GaN pseudo‐substrate with SiH4 and NH3, and (iii) by annealing an InGaN epilayer under a H2 flux. The various methodologies are discussed in the context of possible device applications and of studies of the physics of single nitride quantum dots. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlGaN/GaN/InGaN/GaN HEMTs with an InGaN‐notch
Authors: Liu J. , Zhou Y. G. , Zhu J. , Lau K. M. , Chen K. J. 
Published: May 2006

AbstractWe report an AlGaN/GaN/InGaN/GaN double heterojunction HEMT (DH‐HEMT) with reduced buffer leakage and high‐mobility two‐dimensional‐electron‐gas (2DEG). A 3‐nm thin InxGa1–xN (x = 0.1) layer was inserted into the conventional AlGaN/GaN HEMT structure. A 2DEG mobility of around 1300 cm2/Vs and a sheet resistance of 480 Ω/sq were obtained at room temperature on this new DH‐HEMT structure grown on sapphire substrate with MOCVD‐grown GaN buffer. A peak transconductance of 230 mS/mm, a peak current gain cutoff frequency (fT ) of 14.5 GHz, and a peak power gain cutoff frequency (fmax ) of 45.4 GHz were achieved on a 1×100 μm device. The off‐state source‐drain leakage current is as low as ∼5 μA/mm at VDS = 10 V and the gate leakage current is about 10 μA/mm at a reverse bias of 20 V. For the devices on sapphire substrate, maximum power density of 3.4 W/mm and PAE of 41% were obtained at 2 GHz. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A CUSUM scheme with variable sample sizes and sampling intervals for monitoring the process mean and variance
Authors: Wu Zhang , Zhang Sheng , Wang Penghui 
Published: May 2006

AbstractThe adaptive control feature and CUSUM chart are two monitoring schemes that are much more effective than the traditional static Shewhart chart in detecting process shifts in mean and variance. However, the designs and analyses of the adaptive CUSUM chart are mathematically intractable and the operation is very laborious. This article proposes a VSSI WLC scheme, which is a weighted‐loss‐function‐based CUSUM (WLC) scheme using variable sample sizes and sampling intervals (VSSI). This scheme detects the two‐sided mean shift $\delta_{\mu}$ and increasing standard deviation shift $\delta_{\sigma}$ based on a single statistic WL (the weighted loss function). Most importantly, the VSSI WLC scheme is much easier to operate and design than a VSSI CCC scheme which comprises three individual CUSUM charts (two of them monitoring the increasing and decreasing mean shifts and one monitoring the increasing variance shift). Overall, the VSSI WLC scheme is much more effective than the static $\bar{X}$&S charts (by 72.36%), the VSSI $\bar {X}$&S charts (by 30.97%) and the static WLC scheme (by 50.94%) for detection. It is even more effective than the complicated VSSI CCC scheme for most cases. Copyright © 2006 John Wiley & Sons, Ltd.
Statistical methods for determining the accuracy of quantitative polymerase chain reaction‐based tests
Authors: Richardson Barbra A. , Hughes James P. , Benki Sarah 
Published: May 2006

AbstractQuantitative polymerase chain reaction (PCR)‐based tests are used in several different scientific fields to determine levels of a target DNA sequence of interest (the target molecule). The accuracy of quantitative PCR‐based tests can be assessed by using the assay to determine the number of copies of the target molecule in a sample with a known concentration of the target molecule. For example, a sample with a known concentration of a target DNA sequence is serially diluted into replicate aliquots and these are tested to determine if the observed quantity of the target is close to the expected quantity (given the concentration in the original sample and the dilution). Statistical methods that are conventionally used to assess the accuracy of these assays do not take into account the variability in the number of target molecules in each aliquot from the original sample. We develop methods that take into account this extra variation and which determine the accuracy of quantitative PCR‐based tests in estimating the number of target molecules based on a set of assays of serial dilutions from an original sample with a known concentration of target molecules. These methods are applied to data from an experiment to test the accuracy of a real‐time PCR assay at low HIV‐1 DNA copy levels. Copyright © 2006 John Wiley & Sons, Ltd.
Relations among three aspects of first‐year college students' epistemologies of science
Authors: Smith Carol L. , Wenk Laura 
Published: May 2006

AbstractAt the start of their first semester, 35 college freshmen were given an interview probing (a) their differentiation of scientists' ideas from evidence, and hypotheses from theories; (b) their understanding of the inherent uncertainty of scientific knowledge; and (c) their reasoning about scientific controversies. The most common responses were in terms of an epistemology in which scientists' ideas and evidence are differentiated, and theories are understood as tested hypotheses (Level 2 in our system based on Carey, Evans, Honda, Jay, & Unger, 1989), although students varied in how consistently they differentiated theories and evidence across all questions. Responses in which theories are understood as broader explanatory frameworks guiding hypothesis testing (Level 3) were virtually nonexistent, but some students gave responses that showed awareness of processes of interpreting and reinterpreting patterns of results (Level 2.5). Responses across the three parts of the interview were significantly related. Consistently differentiating scientists' ideas from evidence was strongly related to appreciating the inherent uncertainty of scientific knowledge and with having a deeper understanding of the reasons for scientific controversies and how to resolve them. © 2006 Wiley Periodicals, Inc. J Res Sci Teach 43: 747–785, 2006
Isolation, screening and identification of endophytic antagonistic bacteria toPotato ring rotbacteria
Authors: Hong-Xian Tian , Rui-Xia Wang , Yin-Fan Li , Xiong Wang , Fu-Zai Sun , Jun Yuan 
Published: May 2006

AbstractTwo hundred and forty bacterial strains were isolated from three potato (Solanum tuberosum) cultivars from eight different sources. On the basis of antagonistic bacteria examinationin vitro, greenhouse and field tests, 22.9% of isolated bacteria were endophytic and antagonistic. Three strains, namely A-10', T3(Bacillussp.) and H1-6 (Pseudomonas fluorescens), were chosen for their suppressive effect on bacterial ring rot (Clavibacter michiganensissubsp.sepedonicus) and their growth promotion. The strain A-10' was an endophytic bacterium with the effects of colonization, plant growth promotion and suppression of the pathogenic bacteria, showing good prospects for commercial use.
LucTrap Vectors Are Tools to Generate Luciferase Fusions for the Quantification of Transcript and Protein Abundance in Vivo
Authors: Calderon-Villalobos Luz Irina A. , Kuhnle Carola , Li Hanbing , Rosso Mario , Weisshaar Bernd , Schwechheimer Claus 
Published: May 2006

Abstract
Proper plant growth and development strongly rely on the plant's ability to respond dynamically to signals and cues from the intra- and extracellular environment. Whereas many of these responses require specific changes at the level of gene expression, in recent years it has become increasingly clear that many plant responses are at least in part also controlled at the level of protein turnover. It is a challenge for signal transduction research to understand how distinct incoming signals are integrated to generate specific changes at the transcript or protein level. The activity of luciferase (LUC) reporters can be detected in nondestructive qualitative and quantitative assays in vivo. Therefore,z LUC reporters are particularly well suited for the detection of changes at the transcript and protein level. To the best of our knowledge, the number of plant transformation vectors for LUC fusions is very limited. In this article, we describe the LucTrap plant transformation vectors that allow generation of targeted and random transcriptional and translational fusions with the modified firefly LUC reporter LUC+. We demonstrate that LucTrap-based fusions can be used to monitor rapid changes in gene expression and protein abundance in vivo.
A comparison of written materials vs. materials and counselling for women with sexual dysfunction and multiple sclerosis
Authors: Christopherson Jeannine Marguerite , Moore Katherine , Foley Frederick W , Warren Kenneth G 
Published: May 2006

Aim.  Evaluate whether symptoms of vaginal dryness, low libido, less intense or delayed orgasm could be improved in women with multiple sclerosis who took part in an education or education plus counselling programme.Background.  Sexual dysfunction, a prevalent symptom in women with multiple sclerosis, can negatively affect quality‐of‐life.Methods.  Women attending a large multiple sclerosis clinic were invited and 62 were randomized into one of two groups. Group 1 received written materials on primary, secondary and tertiary sexual dysfunction in multiple sclerosis as well as additional resources (books, websites, list of local psychologists specializing in sexual counselling). Group 2 received the same written materials as well as three counselling sessions from the clinic nurse, the latter two by telephone. The primary outcome measures were the expanded disability status scale and the multiple sclerosis intimacy and sexuality questionnaire‐19. Repeated‐measures analysis of variance was used to evaluate sexual dysfunction score over time and to compare two groups.Results.  At baseline, total expanded disability status scale scores were not correlated with primary, secondary or tertiary sexual dysfunction. Total multiple sclerosis intimacy and sexuality questionnaire‐19 score was correlated with use of anti‐cholinergic medications [r (54) = 0·28, P < 0·05], but no other medications, alcohol or tobacco use. Both groups had equivalent and significant reductions in primary sexual dysfunction [F (1) = 14·79, P < 0·001] postintervention. There was a trend towards an interaction effect for tertiary sexual dysfunction [F (1) = 2·88, P = 0·096], in the direction of group 2 (education and counselling). Subjectively, women welcomed the opportunity to discuss sexual concerns and noted that the written information allowed a framework for initiating discussion with their spouses.Conclusion.  Relatively straightforward interventions provided by a clinic nurse may help women cope with the symptoms of sexual dysfunction associated with multiple sclerosis. Women who do not benefit from basic interventions could then be referred to an expert sexual dysfunction practitioner.Relevance to clinical practice.  Women with multiple sclerosis experience many disease‐related physical and emotional challenges of which sexuality is only one. Sensitivity to sexual dysfunction and being willing to approach the topic is appreciated by women with multiple sclerosis. Nurses do not require in‐depth expertise to offer some basic suggestions which may significantly improve life quality and assist the woman with multiple sclerosis to talk about or cope with sexuality issues.
The functional repertoire of prokaryote cellulosomes includes the serpin superfamily of serine proteinase inhibitors
Authors: Kang Seungha , Barak Yoav , Lamed Raphael , Bayer Edward A. , Morrison Mark 
Published: May 2006

SummaryMany of the Firmicutes bacteria responsible for plant polysaccharide degradation in Nature produce a multiprotein complex called a cellulosome, which co‐ordinates glycoside hydrolase assembly, bacterial adhesion to substrate and polysaccharide hydrolysis. Cellulosomal proteins possess a dockerin module, which mediates their attachment to the scaffoldin protein via its interaction with cohesin modules, and only glycoside hydrolases and other carbohydrate active enzymes were known to reside within the cellulosome. We show here with Clostridium thermocellum ATCC 27405 that members of the serpin superfamily of serine proteinase inhibitors, which are best recognized for their conformational flexibility and co‐ordination of key regulatory functions in multicellular eukaryotes, also reside within the cellulosome. These studies are the first to expand the cellulosome paradigm of protein complex assembly beyond glycoside hydrolase and carbohydrate active enzymes, and to include a newly identified functionality in the Firmicutes.
Identification of a response regulator gene for catabolite control from a PCB‐degrading β‐proteobacteria, Acidovorax sp. KKS102
Authors: Ohtsubo Yoshiyuki , Goto Hiroyuki , Nagata Yuji , Kudo Toshiaki , Tsuda Masataka 
Published: May 2006

Summary Acidovorax sp. (formally Pseudomonas sp.) strain KKS102 carries a bph operon for the degradation of PCB/biphenyl. Transcription from the pE promoter for the bph operon was found to be under catabolite control, i.e. the promoter activity was at a lower level when succinate, fumarate or acetate was added to the culture. Some mutations in the immediate upstream region of the pE promoter resulted in catabolite‐insensitive and constitutively low promoter activity, suggesting that a transcriptional activator was involved in catabolite control. A genetic screen for a pE promoter activator identified two tandemly arranged genes, bphP and bphQ, that encoded proteins homologous to the sensor kinases and response regulators, respectively, of two‐component regulatory system. In the bphPQ double mutant, pE promoter activity was weak and catabolite‐insensitive, and a supply of the bphQ gene alone led to the restoration of the catabolite response. The mechanism of catabolite repression in KKS102 is explained in terms of inhibition of activation by BphQ. The genes highly similar to bphQ were found from several β‐proteobacteria, such as Burkholderia cenocepacia J2315, B. multivorans ATCC17616, B. xenovorans LB400 and Ralstonia solanacearum RS1085.
Paradoxical effects of NPY in the suprachiasmatic nucleus
Authors: Gamble Karen L. , Paul Ketema N. , Karom Mary C. , Tosini Gianluca , Albers H. Elliott 
Published: May 2006

AbstractThe circadian clock in the suprachiasmatic nucleus (SCN) is synchronized by the 24 h, light : dark cycle, and is reset by photic and non‐photic cues. The acute effects of light in the SCN include the increase of mRNA levels of the circadian clock gene Per1 and a dramatic reduction of pineal melatonin. Neuropeptide Y (NPY), which appears to mediate the phase‐resetting effects of non‐photic stimuli, prevents the ability of light, and stimuli that mimic light, to phase shift the circadian clock when injected into the SCN. The purpose of the present study was to determine if NPY inhibits the ability of light to suppress pineal melatonin. Surprisingly, NPY injected into the SCN of hamsters mimicked the effects of light by suppressing pineal melatonin levels. To confirm that NPY inhibited the effects of light on the induction of Per1 mRNA levels, Per1 mRNA levels in the SCN were measured in these same animals. NPY significantly reduced Per1 mRNA levels induced by the light pulse. The suppression of melatonin by NPY appears to be mediated by the same subtype of NPY receptors in the SCN that mediate the modulation of phase shifts. Injection of Y5 receptor agonists mimicked the effects of NPY on pineal melatonin, while injection of a Y2 agonist did not. Thus, these data are the first to demonstrate the paradoxical effects of NPY within the SCN. NPY mimics the effects of light on pineal melatonin and inhibits the effects of light on the induction of Per1 mRNA.