bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of Nitric Oxide Synthesis in Mouse Macrophage Cells by Feverfew Supercritical Extract
Authors: Aviram Anat , Tsoukias Nikolaos M. , Melnick Steven J. , Resek Anna P. , Ramachandran Cheppail
Published: September 2011

Feverfew is the most commonly used medicinal herb against migraine headache. The antimigraine mechanism of feverfew supercritical extract was investigated in vitro using the mouse macrophage cell line (RAW 264.7). Mouse macrophage cells were treated with lipopolysaccharide in the presence and absence of feverfew extracts. Inhibition of lipopolysaccharide‐induced nitric oxide and TNF‐α synthesis were quantified by ELISA. The mRNA and protein expression of iNOS and eNOS genes were analysed by RT‐PCR and western blot analysis, respectively. The feverfew extract inhibited both nitric oxide (NO) and TNF‐α production in a dose‐dependent manner with complete inhibition of NO occurring at 5 µg/mL of feverfew extract. Both eNOS and iNOS mRNA levels were unchanged with the feverfew treatment. However, eNOS and iNOS proteins were significantly down‐regulated by the feverfew extract. Feverfew inhibition of NO is due to the down‐regulation of both eNOS and iNOS enzymes at the translational and/or post‐translational level. Copyright © 2011 John Wiley & Sons, Ltd.
Review: Current applications and challenges for liquid chromatography coupled to isotope ratio mass spectrometry (LC/IRMS)
Authors: Godin Jean‐Philippe , McCullagh James S. O.
Published: September 2011

High‐precision isotope analysis is recognized as an essential research tool in many fields of study. Until recently, continuous flow isotope ratio mass spectrometry (CF‐IRMS) was available via an elemental analyzer or a gas chromatography inlet system for compound‐specific analysis of light stable isotopes. In 2004, however, an interface that coupled liquid chromatography with IRMS (LC/IRMS) became commercially available for the first time. This brought the capability for new areas of application, in particular enabling compound‐specific δ13C analysis of non‐volatile, aqueous soluble, compounds from complex mixtures. The interface design brought with it several analytical constraints, however, in particular a lack of compatibility with certain types of chromatography as well as limited flow rates and mobile phase compositions. Routine LC/IRMS methods have, however, been established for measuring the δ13C isotopic ratios of underivatized individual compounds for application in archeology, nutrition and physiology, geochemistry, hydrology, soil science and food authenticity. Seven years after its introduction, we review the technical advances and constraints, methodological developments and new applications of liquid chromatography coupled to isotope ratio mass spectrometry. Copyright © 2011 John Wiley & Sons, Ltd.
The role of liquid chromatography and flow injection analyses coupled to isotope ratio mass spectrometry for studying human in vivo glucose metabolism
Authors: Godin Jean‐Philippe , Stellingwerff Trent , Actis‐Goretta Lucas , Mermoud Anne‐France , Kochhar Sunil , Rezzi Serge
Published: September 2011

Under most physiological conditions, glucose, or carbohydrate (CHO), homeostasis is tightly regulated. In order to mechanistically appraise the origin of circulating glucose (e.g. via either gluconeogenesis, glycogenolysis or oral glucose intake), and its regulation and oxidation, the use of stable isotope tracers is now a well‐accepted analytical technique. Methodologically, liquid chromatography coupled to isotope ratio mass spectrometry (LC/IRMS) can replace gas chromatography coupled to combustion‐isotope ratio mass spectrometry (GC/C/IRMS) for carrying out compound‐specific 13C isotopic analysis. The LC/IRMS approach is well suited for studying glucose metabolism, since the plasma glucose concentration is relatively high and the glucose can readily undergo chromatography in an aqueous mobile phase. Herewith, we report two main methodological approaches in a single instrument: (1) the ability to measure the isotopic enrichment of plasma glucose to assess the efficacy of CHO‐based treatment (cocoa‐enriched) during cycling exercise with healthy subjects, and (2) the capacity to carry out bulk isotopic analysis of labeled solutions, which is generally performed with an elemental analyzer coupled to IRMS. For plasma samples measured by LC/IRMS the data show a isotopic precision SD(δ13C) and SD(APE) of 0.7 ‰ and 0.001, respectively, with δ13C and APE values of −25.48 ‰ and 0.06, respectively, being generated before and after tracer administration. For bulk isotopic measurements, the data show that the presence of organic compounds in the blank slightly affects the δ13C values. Despite some analytical limitations, we clearly demonstrate the usefulness of the LC/IRMS especially when 13C‐glucose is required during whole‐body human nutritional studies. Copyright © 2011 John Wiley & Sons, Ltd.
A social constructionist view of issues confronting first‐generation college students
Authors: Coffman Stephen
Published: September 2011

Drawing on interviews with first‐generation college students (FGS), the author argues that the students' culture affects college attendance and success. Although FGS often have a vocational perspective to college, the author found that they seek meaningful work with good pay. The author also suggests that good decision making, academic preparation, and a strong social network (family, friends, teachers, and others) play a crucial role in helping FGS adjust to college.
Proteomic analysis of upregulated proteins in Helicobacter pylori under oxidative stress induced by hydrogen peroxide
Authors: Huang Chun‐Hao , Chiou Shyh‐Horng
Published: September 2011

The development of gastric cancer was suggested to be associated with chronic inflammation as a consequence of Helicobacter pylori infection. Such inflammation‐related oxidative stress induced by reactive oxygen species (ROS) in vivo may exert bidirectional effects on both hosts and H pylori. In this study, ROS‐induced oxidative stress was mimicked by coculture of gastric epithelial cells with H pylori treated with hydrogen peroxide (H2O2). To investigate the effect of H2O2 on the proteome of H pylori, we performed two‐dimensional polyacrylamide gel electrophoresis followed by liquid chromatography coupled with nano‐electrospray ionization‐tandem mass spectrometry (liquid chromatography mass spectrometry) and bioinformatics database analysis. The nine most overexpressed proteins consisted of three virulence factors, including cytotoxin‐associated protein A (CagA), vacuolating cytotoxin (VacA), adherence‐associated protein (AlpA), and two antioxidant enzymes alkylhydroperoxide reductase (AhpC) and catalase (KatA), plus one serine protease (HtrA), aconitate hydratase, and fumarate reductase. We have also confirmed the upregulation of virulence factors and antioxidant proteins in several H pylori strains isolated from patients of different clinical outcomes. Furthermore, it is noted that H pylori was found to decrease in infection rate and increase in proliferation after being exposed to H2O2. We also found that gastric epithelial cells can be protected from oxidative damage by H2O2 in the presence of H pylori. In conclusion, this study lends support to the supposition that ROS containing H2O2 as one of the major oxidative species can induce upregulation of virulence factors and antioxidant enzymes in H pylori, which may aid in the elucidation of inflammation leading to the development of gastric cancer from H pylori infection.
Infinite partitions and Rokhlin towers
Authors: KALIKOW STEVEN
Published: September 2011

We find a countable partition P on a Lebesgue space, labeled {1,2,3,…}, for any non-periodic measure-preserving transformation T such that P generates T and, for the T,P process, if you see an n on time −1 then you only have to look at times −n,1−n,…−1 to know the positive integer i to put at time 0 . We alter that proof to extend every non-periodic T to a uniform martingale (i.e. continuous g function) on an infinite alphabet. If T has positive entropy and the weak Pinsker property, this extension can be made to be an isomorphism. We pose remaining questions on uniform martingales. In the process of proving the uniform martingale result we make a complete analysis of Rokhlin towers which is of interest in and of itself. We also give an example that looks something like an independent identically distributed process on ℤ2 when you read from right to left but where each column determines the next if you read left to right.
On the self-similarity problem for smooth flows on orientable surfaces
Authors: KUŁAGA JOANNA
Published: September 2011

On each compact connected orientable surface of genus greater than one we construct a class of flows without self-similarities.
Rigidity of commutative non-hyperbolic actions by toral automorphisms
Authors: WANG ZHIREN
Published: September 2011

Berend [Multi-invariant sets on tori. Trans. Amer. Math. Soc.280(2) (1983), 509–532] obtained necessary and sufficient conditions on a ℤr-action α on a torus 𝕋d by toral automorphisms in order for every orbit to be either finite or dense. One of these conditions is that for every common eigendirection of the ℤr-action there is an element n∈ℤr such that αn expands this direction. In this paper, we investigate what happens when this condition is removed; more generally, we consider a partial orbit {αn⋅x:n∈Ω} where Ω is a set of elements which acts in an approximately isometric way on a given set of eigendirections. This analysis is used in an essential way in the work of the author with E. Lindenstrauss [Topological self-joinings of Cartan actions by toral automorphisms. Preprint, 2010] classifying topological self-joinings of maximal ℤr-actions on tori for r≥3 .
CALL, the foreign-language undergraduate and the teaching of grammar: a linguistic and political battlefield
Authors: Metcalfe Peter
Published: September 2011

The recent history of the teaching of grammar, both for first- and second-language learning, has produced highly polarised and acrimonious debate. The repercussions have extended beyond the boundaries of linguistics into the social and political domain. The present generation of foreign-language undergraduates has been profoundly (if unknowingly) affected by this debate, as reflected in their approach to the learning of grammar, and any consideration of the methodology of language teaching, including that of CALL, must take account of it.
Taking off with CALL
Authors: McCarthy Brian
Published: September 2011

Over the past two years, the Department of Modern Languages at the University of Wollongong (Australia) has developed a range of software, primarily for use with beginner foreign language students. This article looks at the project from three angles: a brief survey of CALL software produced; discussion of some of the elements which have combined to make the project successful; comments on the integration of CALL into the teaching program.
Survival or Fluency? A General Discussion on the Application of Technology to the Teaching of Foreign Languages
Authors: Walls David
Published: September 2011

The issues relating to the application of technology to the teaching and learning of modern languages are far from simple. Such a wide range of disparate disciplines is involved that appropriate and effective solutions can only result from a cohesive integration of the diverse skills, expertise and experience that they encompass.
Computer information systems and learner independence - a word of caution
Authors: Guillot Marie-Noëlle
Published: September 2011

Both economic pressure - the need to accommodate ever greater numbers of foreign language learners, the increasing demand for distance education - and the educational desirability of self-directed learning have stimulated a great surge of research and practical interest in learner autonomy. And there is little doubt that information technology will be called upon, is already being called upon, to play a major role in the teaching profession's efforts to encourage foreign language learners towards self-reliance and to capitalize on the present appeal of computers. But what do we mean by ‘self-reliance’. What do we mean by ‘autonomy’? And what is the relationship between computer-induced motivation and learning?
On the Socio-Indexicality of a Parisian French Intonation Contour
Authors: STEWART CHRISTOPHER M.
Published: September 2011

This study examines how intonation contours prevalent in a Parisian French urban youth vernacular (Conein and Gadet, 1998; Fagyal 2003, 2005) index sociolinguistic meanings for Parisian French listeners. In a web-based experiment, listeners placed recordings with stress patterns ranging from clearly penultimate (‘non-standard’) to clear phrase-final (‘standard’) in cities whose linguistic correctness they had previously evaluated. Stimuli with the most numerous and strongest cues to penultimate prominence were reliably identified with cities low in linguistic prestige. Sociolinguistic experience was shown to predict stimulus evaluations. The conclusions reached speak to the socio-indexicality of certain Parisian intonation contour types and the methodology used herein may lend itself to future studies of socially sensitive language variation.
WELFARE IMPLICATIONS OF HETEROGENEOUS LABOR MARKETS IN A CURRENCY AREA
Authors: Poilly Céline , Sahuc Jean-Guillaume
Published: September 2011

To identify the labor market reforms that offer the highest payoff, we develop a medium-scale two-country model representing a currency union featuring real and nominal rigidities and heterogeneous labor market frictions. A labor market reform is modeled as a permanent structural change in the labor market institutions. We find that changes in the domestic labor market can have drastic welfare implications for both countries. Welfare improvements are observed when a worker (a firm) is more likely to find a job (a worker) or when jobs are less likely to be destroyed. In addition, labor market heterogeneity has sizeable effects on the level of welfare gains. The more flexible the foreign labor market, the higher its welfare. Finally, we show that (i) the way the monetary authorities conduct their policy has negligible welfare effects and (ii) matching frictions can offset the negative effect of price rigidities in the economy.
Articles Published in EJPA 2009–2010
Authors: Ortner Tuulia M. , Vormittag Isabella
Published: September 2011

With reference to EJPA’s unique and broad scope, the current study analyzed the characteristics of the authors as well as the topics and research aims of the 69 empirical articles published in the years 2009–2010. Results revealed that more than one third of the articles were written by authors affiliated with more than one country. With reference to their research aims, an almost comparable number of articles (1) presented a new measure, (2) dealt with adaptations of measures, or (3) dealt with further research on existing measures. Analyses also revealed that most articles did not address any particular field of application. The second largest group was comprised of articles related to the clinical field, followed by the health-related field of application. The majority of all articles put their focus on investigating questionnaires or rating scales, and only a small number of articles investigated procedures classified as tests or properties of interviews. As to further characteristics of the method(s) used, a majority of EJPA contributions addressed self-report data. Results are discussed with reference to publication demands as well as the current and future challenges and demands of psychological assessment.
Threatening Intergroup Relationships
Authors: Falomir-Pichastor Juan Manuel , Mugny Gabriel
Published: September 2011

Five experiments investigated among nonsmokers with initial antismoking attitudes conformity to a norm of intergroup tolerance and nondiscrimination (i.e., a counterattitudinal norm) as a function of the personal versus categorical referent used in intergroup comparisons (self-categorization level), the motivation to respond without prejudice, and the perceived ingroup threat. Results showed that conformity (i.e., a reduction of support for antismoking actions) was moderated by the ingroup threat in the category-referent condition (i.e., conformity was observed only when the perceived threat was low), but by the internal motivation to respond without prejudice in the personal-referent condition. These findings suggest the existence of different moderators of conformity as a function of the self-categorization level.
Modeling the formation and fate of the near‐surface temperature maximum in the Canadian Basin of the Arctic Ocean
Authors: Steele Michael , Ermold Wendy , Zhang Jinlun
Published: September 2011

A numerical model is used to investigate the time and space extent of the near‐surface temperature maximum (NSTM) of the Canadian Basin of the Arctic Ocean over the years 2000–2009. The NSTM is formed from local summertime absorption of solar radiation which, in some circumstances, descends through the fall and early winter to form a warm subsurface layer just below the winter mixed layer. We find that winter survival of this layer is confined largely to the Beaufort Gyre of the Canadian Basin, where Ekman convergence and downwelling push the summer warm layer down below the winter mixing depth. In recent years, summer stratification has increased, downwelling has accelerated, and the NSTM has warmed as the sea ice cover in the Beaufort Gyre has thinned. The result is a strengthening NSTM which contained enough heat by the end of winter 2007/2008 to melt about 20 cm of sea ice. Northwest of Alaska the model also simulates a second, deeper temperature maximum layer that forms from advection of saltier summer Pacific water. However, this layer is difficult to adequately resolve and maintain given the model's resolution.
The structural diversity in α1‐antitrypsin misfolding
Authors: Bottomley Stephen P
Published: September 2011

The structure of α1‐antitrypsin polymers, which cause a devastating disease, is vigorously debated. Here, the state of the field is discussed in view of a paradigm‐changing structure published in this issue of EMBO reports.
Comparison of histopathological*features of Vibrio cholerae O1 El Tor and*O139 Bengal infections in rabbit intestinal mucosa
Authors: Baig Atif
Published: September 2011

Vibrio cholerae is the causative agent of the infectious disease, cholera. The bacteria adhere to the mucosal membrane and release cholera toxin, leading to watery diarrhea. There are >100 serovars of V. cholerae, but the O1 and O139 serovars are the main causative agents of cholera. The present study aimed to compare the severity of intestinal mucosal infection caused by O1 El Tor and O139 V. cholerae in a rabbit ileal loop model.The results showed that although the fluid accumulation was similar in the loops inoculated with O1 and O139 V. cholerae, the presence of blood was detected only in the loops inoculated with the O139 serovar. Serosal hemorrhage was confirmed by histopathological examination and the loops inoculated with O139 showed massive destruction of villi and loss of intestinal glands.The submucosa and muscularis mucosa of the ileum showed the presence of edema with congested blood vessels, while severe hemorrhage was seen in the muscularis propria layer. The loops inoculated with O1 El Tor showed only minimal damage, with intact intestinal villi and glands. Diffuse colonies of the O139 serovar were seen to have infiltrated deep into the submucosal layer of the intestine. Although the infection caused by the O1 serovar was focal and invasive, it was more superficial than that due to O139, and involved only the villi. These observations were confirmed by immunostaining with O1 and O139 V. cholerae-specific monoclonal antibodies. The peroxidase reaction demonstrated involvement of tissues down to the submucosal layer in O139 V. cholerae infection, while in O1 El Tor infection, the reaction was confined mainly to the villi, and was greatly reduced in the submucosal region. This is the first reported study to clearly demonstrate the histopathological differences between infections caused by the O139 Bengal and O1 El Tor pathogenic serovars of V. cholerae (atif et al., 2009).
Enzyme activities in brown forest soils after introduction of Bacillus thuringiensis-based bioinsecticides
Authors: Movsesyan Hasmik , Sargsyan Arevik , Ghazaryan Naira
Published: September 2011

Much attention in the complex of forest pest control methods nowadays is devoted to the application of biological preparations, especially to bacterial formulations produced on the base of Bacillus thuringiensis (BT) that in addition to their high biological effectiveness against injurious insects are safe for man, homoiоtherms, beneficial insects and fish. As is known only 20-40% of sprayed preparation influences directly on pests while its 60-80% by different ways eventually penetrates into the soil. Taking into account also the fact that usage norm of commercial bacterial preparations makes up to 1-3 kg ha^-1^ and that preparation powder contains 45-100 billion viable spores g^-1^ it becomes evident that as a result of spraying huge quantity of bacterial stimulants introduces into the forest soils. In this connection a goal was set to determine the impact of some separately applied domestic insecticides of BT species (BT кб-1, BT кб-2, BT(SAR)-49, BT(SAR)-54, BT(SAR)-86, BT subsp. thuringiensis) introduced into the brown forest soils after spraying on soil enzymatic activity (invertase, urease) defining its fertility. Studies were conducted in 2010 under laboratory conditions. The results obtained indicate that in soils sprayed and non-sprayed by bioinsecticides the activities of invertase and urease undergo to changes from May to August. Maximal activities in soils were registered in June (25.641mg C~6~H~12~O~6~ g^-1^ for invertase and 12.254 mg NH~3~ g^-1^ for urease) and minimal – in May (20.643 mg C~6~H~12~O~6~ g^-1^ for invertase) and in August (9.297 mg NH~3~ g^-1^ for urease) at the average for all variants. By statistical analysis of study results it has been established that there aren’t any significant differences between indices of enzyme activities in sprayed and non-sprayed by biopesticides soils. Study results have led us to the assumption that tested insecticides don’t influence adversely on enzyme activities of brown forest soils and can be widely used in the field of plant protection.
Structural insights into the peroxidase activity and inactivation of human peroxiredoxin 4
Authors: Wang Xi , Wang Likun , Wang Xi'e , Sun Fei , Wang Chih-chen
Published: September 2011

Prx4 (peroxiredoxin 4) is the only peroxiredoxin located in the ER (endoplasmic reticulum) and a proposed scavenger for H2O2. In the present study, we solved crystal structures of human Prx4 in three different redox forms and characterized the reaction features of Prx4 with H2O2. Prx4 exhibits a toroid-shaped decamer constructed of five catalytic dimers. Structural analysis revealed conformational changes around helix α2 and the C-terminal reigon with a YF (Tyr-Phe) motif from the partner subunit, which are required for interchain disulfide formation between Cys87 and Cys208, a critical step of the catalysis. The structural explanation for the restricting role of the YF motif on the active site dynamics is provided in detail. Prx4 has a high reactivity with H2O2, but is susceptible to overoxidation and consequent inactivation by H2O2. Either deletion of the YF motif or dissociation into dimers decreased the susceptibility of Prx4 to overoxidation by increasing the flexibility of Cys87.
A novel role for protein kinase Gcn2 in yeast tolerance to intracellular acid stress
Authors: Hueso Guillem , Aparicio-Sanchis Rafael , Montesinos Consuelo , Lorenz Silvia , Murguía José R. , Serrano Ramón
Published: September 2011

Intracellular pH conditions many cellular systems, but its mechanisms of regulation and perception are mostly unknown. We have identified two yeast genes important for tolerance to intracellular acidification caused by weak permeable acids. One corresponded to LEU2 and functions by removing the dependency of the leu2 mutant host strain on uptake of extracellular leucine. Leucine transport is inhibited by intracellular acidification, and either leucine oversupplementation or overexpression of the transporter gene BAP2 improved acid growth. Another acid-tolerance gene is GCN2, encoding a protein kinase activated by uncharged tRNAs during amino acid starvation. Gcn2 phosphorylates eIF2α (eukaryotic initiation factor 2α) (Sui2) at Ser51 and this inhibits general translation, but activates that of Gcn4, a transcription factor for amino acid biosynthetic genes. Intracellular acidification activates Gcn2 probably by inhibition of aminoacyl-tRNA synthetases because we observed accumulation of uncharged tRNAleu without leucine depletion. Gcn2 is required for leucine transport and a gcn2-null mutant is sensitive to acid stress if auxotrophic for leucine. Gcn4 is required for neither leucine transport nor acid tolerance, but a S51A sui2 mutant is acid-sensitive. This suggests that Gcn2, by phosphorylating eIF2α, may activate translation of an unknown regulator of amino acid transporters different from Gcn4.
Increasing orthostatic stress impairs neurocognitive functioning in chronic fatigue syndrome with postural tachycardia syndrome
Authors: Ocon Anthony J. , Messer Zachary R. , Medow Marvin S. , Stewart Julian M.
Published: September 2011

CFS (chronic fatigue syndrome) is commonly co-morbid with POTS (postural tachycardia syndrome). Individuals with CFS/POTS experience unrelenting fatigue, tachycardia during orthostatic stress and ill-defined neurocognitive impairment, often described as ‘mental fog’. We hypothesized that orthostatic stress causes neurocognitive impairment in CFS/POTS related to decreased CBFV (cerebral blood flow velocity). A total of 16 CFS/POTS and 20 control subjects underwent graded tilt table testing (at 0, 15, 30, 45, 60 and 75°) with continuous cardiovascular, cerebrovascular, and respiratory monitoring and neurocognitive testing using an n-back task at each angle. The n-back task tests working memory, concentration, attention and information processing. The n-back task imposes increasing cognitive challenge with escalating (0-, 1-, 2-, 3- and 4-back) difficulty levels. Subject dropout due to orthostatic presyncope at each angle was similar between groups. There were no n-back accuracy or RT (reaction time) differences between groups while supine. CFS/POTS subjects responded less correctly during the n-back task test and had greater nRT (normalized RT) at 45, 60 and 75°. Furthermore, at 75° CFS/POTS subjects responded less correctly and had greater nRT than controls during the 2-, 3- and 4-back tests. Changes in CBFV were not different between the groups and were not associated with n-back task test scores. Thus we conclude that increasing orthostatic stress combined with a cognitive challenge impairs the neurocognitive abilities of working memory, accuracy and information processing in CFS/POTS, but that this is not related to changes in CBFV. Individuals with CFS/POTS should be aware that orthostatic stress may impair their neurocognitive abilities.
Monogenic Diabetes in a Family with 2 unknown HNF-4A Gene Mutations
Authors: Motzkau M. , Meyer P. , Mertens P.R. , Klose S.
Published: September 2011

Diabetes mellitus classified as Maturity Onset Diabetes of the Young (MODY) is characterized by autosomal dominant inheritance with insulin secretory disturbances.

In 2 siblings with diabetes mellitus manifestation at age under 25 years, low fasting glucose levels, severely elevated glucose levels upon glucose challenge and absent autoantibodies for IA2 and GAD clarification for MODY was sought. Mutational screening for MODY 1–3 mutations was carried out by direct sequencing followed by multiplex ligation-dependent probe amplification (MLPA).

We identified a mutation within the hepatic nuclear factor 4A (HNF-4A) gene hitherto unreported for MODY-1. A causative role of the mutation is not proven, however in the 2 index patients similar phenotypes are present. These cases underline the necessity to screen for MODY when the medical history and lack of autoantibodies suggest alternative diagnoses beside type 1 diabetes.
Coherent structures in plasma-actuator controlled supersonic jets: Axisymmetric and mixed azimuthal modes
Authors: Gaitonde D. V. , Samimy M.
Published: September 2011

High-fidelity simulations are employed to study the effect of eight localized arc filament plasma actuators placed around the periphery of a Mach 1.3 converging-diverging nozzle exit. Emphasis is placed on understanding the coherent structures generated by axisymmetric (m = 0), flapping or first mixed (m = ±1) and second mixed (m = ±2) modes, which are excited at the jet column-mode frequency corresponding to a Strouhal number based on jet diameter of 0.3. Baseline (no control) and constant excitation (actuators on continuously) cases are also simulated. Comparisons with experimental results indicate that the computational model reproduces the main features induced by the actuators. Furthermore, the mean flow exhibits many similarities with the theoretical predictions of Cohen and Wygnanski [J. Fluid Mech. 176, 221 (1987)]. Overall, the results indicate a complex coherent structure generation, evolution, and disintegration process. For m = ±1, the phase-averaged flow reveals successive distorted elliptic vortex rings with axes in the flapping plane but alternating on either side of the jet axis. This generates a chain of structures each of which interacts with its predecessor on one side of the major plane and its successor on the other. Through self and mutual induction, the leading segment of each loop is pinched and passes through the previous ring before rapidly breaking up. The m = ±2 mode yields elliptic structures with major axes of successive rings being aligned with the two symmetry planes, which are orthogonal to each other. The minor axis side is pulled downstream faster than the rest of the structure because of the higher velocity near the jet centerline and self-induced effects, yielding a horse-shoe shape when viewed in profile. The m = 0 mode exhibits axisymmetric roll-up events, with vortex ribs in the braid regions connecting successive large coherent structures. The constant excitation (with largest energy input) and baseline cases are similar to each other, indicating that the direct effect of heating is negligible.
Multipurpose high-pressure high-temperature diamond-anvil cell with a novel high-precision guiding system and a dual-mode pressurization device
Authors: Pippinger Thomas , Miletich Ronald , Burchard Michael
Published: September 2011

A novel diamond-anvil cell (DAC) design has been constructed and tested for in situ applications at high-pressure (HP) operations and has proved to be suitable even for HP sample environments at non-ambient temperature conditions. The innovative high-precision guiding mechanism, comparable to a dog clutch, consists of perpendicular planar sliding-plane elements and is integrated directly into the base body of the cylindrically shaped DAC. The combination of two force-generating devices, i.e., mechanical screws and an inflatable gas membrane, allows the user to choose independently between, and to apply individually, two different forcing mechanisms for pressure generation. Both mechanisms are basically independent of each other, but can also be operated simultaneously. The modularity of the DAC design allows for an easy exchange of functional core-element groups optimized not only for various analytical in situ methods but also for HP operation with or without high-temperature (HT) application. For HP-HT experiments a liquid cooling circuit inside the specific inner modular groups has been implemented to obtain a controlled and limited heat distribution within the outer DAC body.
High spatial resolution characterization of silicon solar cells using thermoreflectance imaging
Authors: Zhou Qiaoer , Hu Xiaolin , Al-Hemyari Kadhair , McCarthy Kevin , Domash Lawrence , Hudgings Janice A.
Published: September 2011

Thermoreflectance imaging is shown to be a high resolution, non-contact method of quantitatively characterizing device performance and identifying electrical shunts in conventional multicrystalline silicon solar cells. Results are in quantitative agreement with a commercial lock-in infrared thermography system but offer an order of magnitude improvement in spatial resolution. Highly resolved thermoreflectance imaging enables extraction of quantitative, spatially resolved device performance characteristics, including local IV curves and local diode ideality factors, offering detailed physical characterization of performance-limiting defects that cannot be obtained from conventional bulk cell testing. Finally, thermoreflectance maps of heat spreading from a point defect provide a simple means of quantifying thermal parameters such as thermal diffusivity and thermal conductivity, which are key field performance indicators.
Influence of dielectric stiffness, interface, and layer thickness on hysteresis loops of ferroelectric superlattices
Authors: Chew K.-H. , Ong L.-H. , Iwata M.
Published: September 2011

We examined the influence of dielectric stiffness, interface, and layer thickness on the hysteresis loops, including the remanent polarization and coercive field of a superlattice comprising alternate layers of ferroelectric and dielectric, using the Landau-Ginzburg theory. An interface energy term is introduced in the free energy functional to describe the formation of interface “dead” layers that are mutually coupled through polarization (or induced-polarization). Our studies reveal that the hysteresis loop is strongly dependent on the stiffness of the dielectric layer, the strength of the interface coupling and layer thickness. The intrinsic coupling at the interface between two neighboring layers reduces the coercive field, though the corresponding remanent polarization is significantly enhanced by a soft dielectric layer.
Microbubble formation and pinch-off scaling exponent in flow-focusing devices
Authors: van Hoeve Wim , Dollet Benjamin , Versluis Michel , Lohse Detlef
Published: September 2011

We investigate the gas jet breakup and the resulting microbubble formation in a microfluidic flow-focusing device using ultra high-speed imaging at 1 × 106 frames/s. In recent experiments [Dollet et al., Phys. Rev. Lett. 100, 034504 (2008)], it was found that in the final stage of the collapse the radius of the neck scales with time with a 1/3 power-law exponent, which suggested that gas inertia and the Bernoulli suction effect become important. Here, ultra high-speed imaging was used to capture the complete bubble contour and quantify the gas flow through the neck. The high temporal resolution images enable us to approach the final moment of pinch-off to within 1 μs. It revealed that during the collapse, the flow of gas reverses and accelerates towards its maximum velocity at the moment of pinch-off. However, the resulting decrease in pressure, due to Bernoulli suction, is too low to account for the accelerated collapse. We observe two stages of the collapse process. At first, the neck collapses with a scaling exponent of 1/3 which is explained by a “filling effect.” In the final stage, the collapse is characterized by a scaling exponent of 2/5, which can be derived, based on the observation that during the collapse the neck becomes less slender, due to the driving through liquid inertia. However, surface tension forces are still important until the final microsecond before pinch-off.
Angular dependence of ferromagnetic resonance and magnetization configuration of thin film Permalloy nanoellipse arrays
Authors: Pardavi-Horvath M. , Ng B. G. , Castaño F. J. , Körner H. S. , Garcia C. , Ross C. A.
Published: September 2011

In-plane and out-of-plane angular dependence of ferromagnetic resonance (FMR) and magnetization measurements were performed on arrays of 20, 40, and 60 nm thick, 520 nm long, and 250 nm wide elliptical Permalloy elements. Besides the main FMR “volume” mode resonance, a well-defined second FMR mode was observed, which exhibits a very strong angular dependence. This mode originates from localized regions where the magnetization has a strong component perpendicular to the bias field and to the volume magnetization. These regions of nonuniform magnetization may be associated with magnetization canting at the edges of the ellipses, due to the nonuniformity of the demagnetizing tensor elements, and with magnetization vortices, which are predicted by micromagnetic simulation.
Voltage-controlled electron tunneling from a single self-assembled quantum dot embedded in a two-dimensional-electron-gas-based photovoltaic cell
Authors: Mar J. D. , Xu X. L. , Baumberg J. J. , Irvine A. C. , Stanley C. , Williams D. A.
Published: September 2011

We perform high-resolution photocurrent (PC) spectroscopy to investigate resonantly the neutral exciton ground-state (X0) in a single InAs/GaAs self-assembled quantum dot (QD) embedded in the intrinsic region of an n-i-Schottky photodiode based on a two-dimensional electron gas (2DEG), which was formed from a Si δ-doped GaAs layer. Using such a device, a single-QD PC spectrum of X0 is measured by sweeping the bias-dependent X0 transition energy through that of a fixed narrow-bandwidth laser via the quantum-confined Stark effect (QCSE). By repeating such a measurement for a series of laser energies, a precise relationship between the X0 transition energy and bias voltage is then obtained. Taking into account power broadening of the X0 absorption peak, this allows for high-resolution measurements of the X0 homogeneous linewidth and, hence, the electron tunneling rate. The electron tunneling rate is measured as a function of the vertical electric field and described accurately by a theoretical model, yielding information about the electron confinement energy and QD height. We demonstrate that our devices can operate as 2DEG-based QD photovoltaic cells and conclude by proposing two optical spintronic devices that are now feasible.
On the effective plate thickness of monolayer graphene from flexural wave propagation
Authors: Kim Sung Youb , Park Harold S.
Published: September 2011

We utilize classical molecular dynamics to study flexural, or transverse wave propagation in monolayer graphene sheets and compare the resulting dispersion relationships to those expected from continuum thin plate theory. In doing so, we determine that regardless of the chirality for monolayer graphene, transverse waves exhibit a dispersion relationship that corresponds to the lowest order antisymmetric (A0) mode of wave propagation in a thin plate with plate thickness of h=0.104 nm. Finally, we find that the achievable wave speeds in monolayer graphene are found to exceed those reported previously for single walled carbon nanotubes, while the frequency of wave propagation in the graphene monolayer is found to reach the terahertz range, similar to that of carbon nanotubes.
Optical routing and switching of energy flow in nanostructure systems
Authors: Sadeghi S. M.
Published: September 2011

We study optical routing and switching of energy transfer between semiconductor quantum dots and metallic nanostructures. We demonstrate that in the presence of a metallic nanoshell, one can use quantum coherence to direct or switch energy transfer flow from a quantum dot to another quantum dot or to the nanoshell. Our results show that a quantum dot-metallic nanoshell system can act as a bistable energy switch formed via quantum mechanical control of energy transfer processes.
Relativistic effects in the interaction of high intensity ultra-short laser pulse with collisional underdense plasma
Authors: Abedi Samira , Dorranian Davoud , Abari Mehdi Etehadi , Shokri Babak
Published: September 2011

In this paper, the effect of weakly relativistic ponderomotive force in the interaction of intense laser pulse with nonisothermal, underdense, collisional plasma is studied. Ponderomotive force modifies the electron density and temperature distribution. By considering the weakly relativistic effect and ohmic heating of plasma electrons, the nonlinear dielectric permittivity of plasma medium is obtained and the equation of electromagnetic wave propagation in plasma is solved. It is shown that with considering the ohmic heating of electrons and collisions, the effect of ponderomotive force in weakly relativistic regime leads to steepening the electron density profile and increases the temperature of plasma electrons noticeably. Bunches of electrons in plasma become narrower. By increasing the laser pulse strength, the wavelength of density oscillations decreases. In this regime of laser-plasma interaction, electron temperature increases sharply by increasing the intensity of laser pulse. The amplitude of electric and magnetic fields increases by increasing the laser pulse energy while their wavelength decreases and they lost their sinusoidal form.
Examination of gas desorption by B4C resin for use in neutron scattering experiment
Authors: Yokoo T. , Kaneko N. , Itoh S. , Otomo T. , Suzuya K. , Suetsugu Y. , Shirai M.
Published: September 2011

Gas desorption rates for several types of B4C resins were investigated using a throughput method. The investigation was particularly focused on determining the out gas composition, effects of dry air, grain size (density) effects on the gas desorption rates. It is found that water is the main component of out gas and that dry air can effectively reduce gas desorption.
Proton transport in a binary biomimetic solution revealed by molecular dynamics simulation
Authors: Liang Chungwen , Jansen Thomas L. C.
Published: September 2011

We report the simulation results of the proton transport in a binary mixture of amphiphilic tetramethylurea (TMU) molecules and water. We identify different mechanisms that either facilitate or retard the proton transport. The efficiency of these mechanisms depends on the TMU concentration. The overall picture is more complicated than a recent suggestion that the presence of amphiphilic molecules suppresses the proton mobility by slowing down the reorientation of the surrounding water molecules. It has also been suggested that the hydronium ion induces local water orientational order, which results in an ordered region that has to move along with the proton potentially slowing down the proton transport as suggested by experiment. We find that water-wire like structures formed at low amphiphile concentrations facilitate proton transfer, and reduction of the hydrogen bond connectivity induced at high concentrations retards it.
Phase transitions in ferroelectric silicon doped hafnium oxide
Authors: Böscke T. S. , Teichert St. , Bräuhaus D. , Müller J. , Schröder U. , Böttger U. , Mikolajick T.
Published: September 2011

We investigated phase transitions in ferroelectric silicon doped hafnium oxide (FE-Si:HfO2) by temperature dependent polarization and x-ray diffraction measurements. If heated under mechanical confinement, the orthorhombic ferroelectric phase reversibly transforms into a phase with antiferroelectric behavior. Without confinement, a transformation into a monoclinic/tetragonal phase mixture is observed during cooling. These results suggest the existence of a common higher symmetry parent phase to the orthorhombic and monoclinic phases, while transformation between these phases appears to be inhibited by an energy barrier.
Exponential stability of stochastic differential delay systems with delayed impulse effects
Authors: Wu Xiaotai , Yan Litan , Zhang Wenbing , Tang Yang
Published: September 2011

In this paper, we investigate the stability of stochastic delay differential systems with delayed impulses by Razumikhin methods. Some criteria on the pth moment exponential stability are obtained. It is shown that if a stochastic delay differential system is exponentially stable, then under some conditions, its stability is robust or weaken with respect to delayed impulses. Moreover, it is also shown that an unstable stochastic delay system can be successfully stabilized by delayed impulses. The effectiveness of the proposed results is illustrated by three examples.
Quantum-dot-induced optical transition enhancement in InAs quantum-dot-embedded p–i–n GaAs solar cells
Authors: Shang X.-J. , He J.-F. , Li M.-F. , Zhan F. , Ni H.-Q. , Niu Z.-C. , Pettersson H. , Fu Y.
Published: September 2011

Photocurrents (PCs) of three p–i–n GaAs solar cells, sample A with InAs quantum dots (QDs) embedded in the depletion region, B with QDs in the n region, and C without QDs, were studied experimentally and theoretically. Above GaAs bandgap, the PC of A is increased, while B is decreased with respect to C, since in A, the QD-induced reflection of hole wave function increases its overlap with electron wave function so that the optical transition rate is enhanced, while carrier mobility in B is reduced due to QD-induced potential variations. Moreover, A and B have increased PCs in the sub-GaAs-bandgap range due to QD optical absorptions.
Ammonium sulfide vapor passivation of In0.53Ga0.47As and InP surfaces
Authors: Alian Alireza , Brammertz Guy , Merckling Clement , Firrincieli Andrea , Wang Wei-E , Lin H. C , Caymax Matty , Meuris Marc , De Meyer Kristin , Heyns Marc
Published: September 2011

The efficiency of the ammonium sulfide vapor (ASV) treatment, as opposed to the wet treatment in the liquid ammonium sulfide solution, on the performance improvement of the In0.53Ga0.47As surface-channel as well as InP-capped buried-channel metal-oxide-semiconductor field-effect-transistors (MOSFET) was demonstrated for the first time. MOSFETs were fabricated with either HCl or ASV surface treatments prior to the gate oxide deposition. ASV treatment was found to be very efficient in boosting the drive current of the transistors compared to that of the HCl treatment. It was also found that the ASV treatment leads to a lower border trap density and slightly higher oxide/semiconductor interface defect density compared to that of the HCl treatment. X-ray photoelectron spectroscopy (XPS) studies of In0.53Ga0.47As native oxide regrowth after both surface treatments identified indium sub-oxides as a possible cause of the performance degradation of the HCl treated devices. Based on this work, ASV treatment could be an efficient solution to the passivation of III-V surfaces.
Graphene based nickel nanocrystal flash memory
Authors: Zhan Ning , Olmedo Mario , Wang Guoping , Liu Jianlin
Published: September 2011

Graphene based flash memory was demonstrated by using nickel nanocrystals as storage nodes. As-grown graphene films were characterized by transmission electron microscopy and Raman spectroscopy to show good film quality. On/off operation of the transistor memory was acquired by static pulse response measurement. The memory window of the device was found up to be 23.1 V by back gate sweep. This memory effect is attributed to charging/discharging of nanocrystals. Furthermore, excellent retention and endurance performance were achieved.
Electronic depiction of magnetic origin in undoped and Fe doped TiO2−d epitaxial thin films
Authors: Bapna Komal , Choudhary R. J. , Pandey S. K. , Phase D. M. , Sharma S. K. , Knobel M.
Published: September 2011

We have investigated the electronic and magnetic properties of the pulsed laser deposited epitaxial thin films of undoped and Fe doped (4 at. %) anatase TiO2−d by photoemission, magnetization measurements, and ab-initio band structure calculations. These films show room temperature magnetic ordering. It is observed that Fe ions hybridize with the oxygen vacancy induced Ti3+ defect states. Our study reveals the formation of local magnetic moment at Ti and Fe sites to be responsible for magnetic ordering. A finite density of states at the Fermi level in both undoped and Fe doped films is also observed, suggesting their degenerate semiconducting nature.