bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Nitrotyrosine-Modified Proteins in Cerebrospinal Fluid
Authors: Beasley Ashley S. , Anderson Caroline , McArthur Justin , Sacktor Ned , Nath Avindra , Cotter Robert J.
Published: March 2010

Background

HIV-associated neurocognitive disorders (HAND) has been associated with the up-regulation of various oxidative stress pathways. Previous studies have linked the neuronal damage observed in individuals diagnosed with HAND to increased nitrotyrosine modification of neuronal proteins.

Materials and methods

Tyrosine nitration alters protein structure and function, affects biological half-life, and potentially prevents the phosphorylation of key tyrosine residues involved in signal transduction pathways. Therefore, in this study we employed proteomics-based experimental approaches to investigate nitrotyrosine-modified proteins in pooled cerebrospinal fluid (CSF) of individuals diagnosed with HAND. To identify specific nitrotyrosine-modified proteins in the CSF of individuals diagnosed with HAND, affinity purification and high-performance tandem mass spectrometry are utilized in a “bottom-up” proteomics approach.

Results

From tandem mass spectrometric analysis, we identified major proteins that underwent nitration as a result of nitro-oxidative stress in the CSF of individuals diagnosed with HAND. We also utilized analytical and biochemical techniques to characterize the expression and modification site of in vivo nitrated lipocalin-type prostaglandin-D synthase in HAND CSF.
Catastrophizing moderates the effect of exposure in vivo for back pain patients with pain‐related fear
Authors: Flink Ida K. , Boersma Katja , Linton Steven J.
Published: March 2010

This investigation was an initial attempt to explore psychological factors that might help or hinder the effect of exposure in vivo for patients with musculoskeletal pain and pain‐related fear. The study was based on data from a randomized‐controlled trial for patients with non‐specific spinal pain (Linton et al., 2008).

First, catastrophizing, anxiety, and depression were studied as possible treatment moderators. We found evidence that catastrophizing was a moderator of treatment outcome in exposure. When further exploring the nature of the relationship between catastrophizing and outcome, the results showed that the exposure was effective only for patients with low or moderate levels of catastrophizing. High catastrophizers did not improve from the treatment. On the other hand, anxiety was a general predictor of poor outcome, and not a specific moderator of outcome in exposure. In contrast, depression was not significantly related to outcome.

Next, patients were divided into high change participants and low change participants based on their improvement in disability after treatment in order to investigate the change in psychological variables during treatment. Descriptive data indicated that high change participants had large improvements across treatment on depression, anxiety, catastrophizing, and fear‐avoidance beliefs whereas low change participants virtually did not change at all on these variables across treatment.

These findings denote that catastrophizing is a moderator of treatment outcome in exposure whereas several psychological variables might be important for the treatment process.
Reproducibility and validity of a diet quality index for children assessed using a FFQ
Authors: Huybrechts Inge , Vereecken Carine , De Bacquer Dirk , Vandevijvere Stefanie , Van Oyen Herman , Maes Lea , Vanhauwaert Erika , Temme Liesbeth , De Backer Guy , De Henauw Stefaan
Published: March 2010

The diet quality index (DQI) for preschool children is a new index developed to reflect compliance with four main food-based dietary guidelines for preschool children in Flanders. The present study investigates: (1) the validity of this index by comparing DQI scores for preschool children with nutrient intakes, both of which were derived from 3 d estimated diet records; (2) the reproducibility of the DQI for preschoolers based on a parentally reported forty-seven-item FFQ DQI, which was repeated after 5 weeks; (3) the relative validity of the FFQ DQI with 3 d record DQI scores as reference. The study sample included 510 and 58 preschoolers (2·5–6·5 years) for validity and reproducibility analyses, respectively. Increasing 3 d record DQI scores were associated with decreasing consumption of added sugars, and increasing intakes of fibre, water, Ca and many micronutrients. Mean FFQ DQI test–retest scores were not significantly different: 72 (sd11)v.71 (sd10) (P = 0·218) out of a maximum of 100. Mean 3 d record DQI score (66 (sd10)) was significantly lower than mean FFQ DQI (71 (sd10);P < 0·001). The reproducibility correlation was 0·88. Pearsons correlation (adjusted for within-person variability) between FFQ and 3 d record DQI scores was 0·82. Cross-classification analysis of the FFQ and 3 d record DQI classified 60 % of the subjects in the same category and 3 % in extreme tertiles. Cross-classification of repeated administrations classified 62 % of the subjects in the same category and 3 % in extreme categories. The FFQ-based DQI approach compared well with the 3 d record approach, and it can be used to determine diet quality among preschoolers.
Single, subcondylar mandibular osteotomy: a new access route for extensive, benign parapharyngeal neoplasms
Authors: Bianchi B , Ferri A , Ferrari S , Copelli C , Magri A S , Sesenna E
Published: March 2010

Objective:

We report a new approach to benign parapharyngeal space tumours: a single, subcondylar mandibular osteotomy.

Method:

Case report and review of the world literature concerning parapharyngeal space access and the various types of mandibular osteotomy.

Results:

The use of a single, subcondylar mandibular osteotomy achieves good exposure and satisfactory aesthetic and functional results, using a simple, easily performed technique that is fast and has minimal morbidity. In addition, this technique preserves the submandibular gland and avoids lip-splitting and post-operative intermaxillary fixation.

Conclusion:

To our knowledge, this is the first report of this approach to the parapharyngeal space. We propose this approach as the first choice for resection of benign neoplasms of the parapharyngeal space.
Salience of working-memory maintenance and manipulation deficits in schizophrenia
Authors: Hill S. K. , Griffin G. B. , Miura T. Kazuto , Herbener E. S. , Sweeney J. A.
Published: March 2010

Background

Encoding and maintenance of information in working memory, followed by internal manipulation of that information for planning adaptive behavior, are two key components of working-memory systems. Both processes have been reported to be impaired in schizophrenia, but few studies have directly compared the relative severity of these abnormalities, or the degree to which manipulation deficits might be secondary to alterations in maintenance processes.

Method

Clinically stable schizophrenia patients (n=25) and a demographically similar healthy comparison group (n=24) were administered a verbal span task with three levels of working-memory load. Maintenance was assessed using sequential position questions. Manipulation processes were assessed by requiring comparison of the relative sequential position of test items, which entailed simultaneous serial search strategies regarding item order.

Results

Both groups showed reduced accuracy and increased reaction time for manipulation compared with maintenance processing. There were significant patient impairments across working-memory loads. There was no differential deficit in manipulation processing, and effect sizes of relative deficit in the patient group were higher for maintenance than manipulation processing.

Conclusions

The strong correlation for maintenance and manipulation deficits suggest that impairments in the ability to internally manipulate information stored in working-memory systems are not greater than alterations in the encoding and maintaining of information in working memory and that disturbances in maintenance processing may contribute to deficits in higher-order working-memory operations.
Maternal label and gesture use affects acquisition of specific object names
Authors: ZAMMIT MARIA , SCHAFER GRAHAM
Published: March 2010

Ten mothers were observed prospectively, interacting with their infants aged 0 ; 10 in two contexts (picture description and noun description). Maternal communicative behaviours were coded for volubility, gestural production and labelling style. Verbal labelling events were categorized into three exclusive categories: label only; label plus deictic gesture; label plus iconic gesture. We evaluated the predictive relations between maternal communicative style and children's subsequent acquisition of ten target nouns. Strong relations were observed between maternal communicative style and children's acquisition of the target nouns. Further, even controlling for maternal volubility and maternal labelling, maternal use of iconic gestures predicted the timing of acquisition of nouns in comprehension. These results support the proposition that maternal gestural input facilitates linguistic development, and suggest that such facilitation may be a function of gesture type.
Longing, Nostalgia, and Golden Age Politics: The American Jeremiad and the Power of the Past
Authors: Murphy Andrew R.
Published: March 2010

I assess several politically powerful ways of drawing on the past in the search for solutions to problems in the present. To probe these dynamics, I turn to the American jeremiad, a longstanding form of political rhetoric that explicitly invokes the past and laments the nation's falling-away from its virtuous foundations. I begin by focusing on the Christian Right's traditionalist jeremiad, which offers both nostalgic and Golden Age rhetoric in its assessment of the United States' imperiled national promise. I argue that, despite differences in the historical location of their ideals and the significant rhetorical power that they bring to political life, such nostalgic and Golden Age narratives represent a constraining political ideal, one ultimately incapable of doing justice to an increasingly diverse American society. I argue furthermore that there is another strand of the American jeremiad and conclude by sketching a different way of drawing on the past, a progressive jeremiad epitomized by the thought of Abraham Lincoln and Frederick Douglass. Such a jeremiad is also deeply rooted in the American tradition and offers a far more promising contribution to a diverse and pluralistic American future.
Genetic influences on the association between fetal growth and susceptibility to type 2 diabetes
Authors: Shields B. M. , Freathy R. M. , Hattersley A. T.
Published: March 2010

The fetal insulin hypothesis proposes that low birth weight and susceptibility to type 2 diabetes (T2D) could both be two phenotypes of the same genotype. Insulin is a key growth factor in utero, and T2D is characterized by insulin resistance and/or beta-cell dysfunction. Therefore, genetic variants impacting on insulin secretion and action are likely to alter both fetal growth and susceptibility to T2D. There are three lines of evidence in support of this hypothesis. (1) Studies of rare monogenic diabetes have shown mutations in a single gene, such as GCK or KCNJ11, can cause diabetes by reducing insulin secretion, and these mutations are also associated with reduced birth weight. (2) Epidemiological studies have indicated that children born to fathers with diabetes are born smaller. As the father cannot influence the intrauterine environment, this association is likely to reflect genes inherited by the fetus from the father. (3) The most compelling evidence comes from recent genome-wide association studies. Variants in the CDKAL1 and HHEX-IDE genes that predispose to diabetes, if present in the fetus, are associated with reduced birth weight. These data provide evidence for a genetic contribution to the association between low birth weight and susceptibility to T2D. This genetic background is important to take into consideration when investigating the impact of environmental determinants and developing strategies for intervention and prevention.
Simulating low‐probability peak discharges for the Rhine basin using resampled climate modeling data
Authors: te Linde A. H. , Aerts J. C. J. H. , Bakker A. M. R. , Kwadijk J. C. J.
Published: March 2010

Climate change will increase winter precipitation, and in combination with earlier snowmelt it will cause a shift in peak discharge in the Rhine basin from spring to winter. This will probably lead to an increase in the frequency and magnitude of extreme floods. In this paper we aim to enhance the simulation of future low‐probability flood peak events in the Rhine basin using different climate change scenarios, and downscaling methods. We use the output of a regional climate model (RCM) and a weather generator to create long, resampled time series (1000 years) of climate change scenarios as input for hydrological (daily) and hydrodynamic (hourly) modeling. We applied this approach to three parallel modeling chains, where the transformation method from different resampled RCM outputs to the hydrological model varied (delta change approach, direct output, and bias‐corrected output). On the basis of numerous 1000 year model simulations, the results indicate a basin‐wide increase in peak discharge in 2050 of 8%–17% for probabilities between 1/10 and 1/1250 years. Furthermore, the results show that increasing the length of the climate data series using a weather generator reduced the statistical uncertainty when estimating low‐probability flood peak events from 13% to 3%. We further conclude that bias‐corrected direct RCM output is to be preferred over the delta change approach because it provides insight into geographical differences in discharge projections under climate change. Also, bias‐corrected RCM output can simulate changes in the variance of temperature and rainfall and in the number of precipitation days, as changes in temporal structure are expected under climate change. These added values are of major importance when identifying future problem areas due to climate change and when planning potential adaptation measures.
Promoting a Precipitation Database for the Mediterranean Region: MedCLIVAR‐HyMeX‐MedFriends Workshop; Barcelona, Spain, 7 September 2009
Authors: Lionello Piero , Llasat Maria Carmen
Published: March 2010

The recovery and extension of precipitation time series in the Mediterranean region was the focus of a workshop held as a side event during the “11th Plinius Conference on Mediterranean Storms.” The workshop was the first occasion for a joint meeting of three projects—Mediterranean Climate Variability and Predictability (MedCLIVAR), Hydrological Cycle in the Mediterranean Experiment (HyMeX), and Mediterranean Flow Regimes From International Experimental and Network Data (MedFriend)—all of which share an interest in the analysis of precipitation at regional scales. Contributions were also presented by the coordinator of the Mediterranean Experiment (MEDEX) project and the chair of the Mediterranean Climate Data Rescue (MEDARE) project.

The workshop provided a forum for discussing the present state of data recovery initiatives aimed at improving knowledge of the time‐space distribution of precipitation in the Mediterranean region, where rain is simultaneously a crucial resource (rain is scarce over a large fraction of the region) and a risk factor producing floods and resultant loss of life and property.
U.S. National Science Foundation Slated for Large Budget Increase
Authors: Showstack Randy
Published: March 2010

Although the Obama administration has promoted its proposed $3.8 trillion federal budget for fiscal year (FY) 2011 as one that works toward reining in budget deficits and living within the nation's means, research is among the areas slated for increases. The National Science Foundation (NSF) would receive $7.42 billion, an 8% increase above the FY 2010 enacted level of $6.87 billion, which pleases NSF administrators. This proposal would keep the agency on track for doubling its budget between about 2007 and 2017.

“The president sees science as a way to build our economy. It's a way to make the nation strong in the future. It's a way of bringing change in society, and in addressing some of the global challenges that we are facing,” NSF director Arden Bement Jr. explained at a 1 February briefing. Bement, who has been at the helm of the agency for more than 6 years, announced in early February that he is leaving later this year to head up the Global Policy Research Institute at Purdue University.
New Concepts and Tools for Geological Mapping of Mars: Geological Mapping of Mars: A Workshop on New Concepts and Tools; Tuscany, Italy, 12–14 October 2009
Authors: Rossi Angelo Pio , Pondrelli Monica
Published: March 2010

Geological mapping is a key tool for understanding the evolution of any planetary surface. The availability of ever growing data sets (e.g., multispectral and hyperspectral imaging and subsurface radar sounding) requires increasing effort in analyzing, integrating, and exploiting them for mapping purposes.

To discuss these issues, about 80 planetary geoscientists gathered in Italy at a workshop co‐organized by the Italian Space Agency (ASI), the International Research School of Planetary Sciences (IRSPS), and the U.S. Geological Survey (USGS). The workshop focused on both data and concepts and covered a range of scientific and technical topics.
AGU Climate Scientists Offer Question‐and‐Answer Service for Media
Authors: Jackson Stacy
Published: March 2010

In fall 2009, AGU launched a member‐driven pilot project to improve the accuracy of climate science coverage in the media and to improve public understanding of climate science. The project's goal was to increase the accessibility of climate science experts to journalists across the full spectrum of media outlets. As a supplement to the traditional one‐to‐one journalist‐expert relationship model, the project tested the novel approach of providing a question‐and‐answer (Q&A) service with a pool of expert scientists and a Web‐based interface with journalists. Questions were explicitly limited to climate science to maintain a nonadvocacy, nonpartisan perspective.
Insulin dimer dissociation and unfolding revealed by amide I two-dimensional infrared spectroscopy
Authors: Ganim Ziad , Jones Kevin C. , Tokmakoff Andrei
Published: March 2010

A structurally sensitive probe of the monomer/dimer equilibrium of insulin was developed using 2DIR spectroscopy and interpreted using calculated spectra.
Determination of the propagation rate coefficient of acrylonitrile
Authors: Junkers Tanja , Koo Sandy P. S. , Barner-Kowollik Christopher
Published: March 2010

For the first time, accurate propagation rate coefficients for acrylonitrile are determined via the pulsed laser polymerization–size exclusion chromatography technique.
Measuring Word Learning Ability in Sequential Bilingual Children
Authors: Kan Pui Fong
Published: March 2010

The purpose of this article is to look at the word learning skills in sequential bilingual children—children who learn two languages (L1 and L2) at different times in their childhood. Learning a new word is a process of learning a word form and relating this form to a concept. For bilingual children, each concept might need to map onto two word forms (in L1 and in L2). In case studies, I present 3 typically developing Hmong-English bilingual preschoolers' word learning skills in Hmong (L1) and in English (L2) during an 8-week period (4 weeks for each language). The results showed gains in novel-word knowledge in L1 and in L2 when the amount of input is equal for both languages. The individual differences in novel word learning are discussed.
Contemporary Outcomes for Children With Hearing Loss
Authors: Harrison Melody
Published: March 2010

Although outcomes for children with cochlear implants have been the focus of investigation in the past 20 years, children with hearing loss in the mild-to severe range have received much less attention from researchers. This brief article discusses the current state of knowledge regarding children with all degrees of hearing loss.
What Do We Want Them To Be When They Grow Up?
Authors: Robertson Lyn
Published: March 2010

Learning to listen and speak are well-established preludes for reading, writing, and succeeding in mainstream educational settings. Intangibles beyond the ubiquitous test scores that typically serve as markers for progress in children with hearing loss are embedded in descriptions of the educational and social development of four young women. All were diagnosed with severe-to-profound or profound hearing loss as toddlers, and all were fitted with hearing aids and given listening and spoken language therapy. Compiling stories across the life span provides insights into what we can be doing in the lives of young children with hearing loss.
Event-Related Potentials and the Swallow System
Authors: Pitts Teresa , Wheeler-Hegland Karen , Davenport Paul
Published: March 2010

Electroencephalography (EEG) is a methodology that offers information on the processing of afferent information to the cortex and does not require a motor response. This method could be highly beneficial to researchers interested in the upper airway, specifically portions of the upper airway which initiate or modify reflexes (i.e. swallowing, cough, gag, etc). The following is a short description of the methodology, signal processing, signal interpretation, and potential impact on swallowing research.
Strengthening Connections Between University Classrooms and Clinical Settings
Authors: Bailey Rita L.
Published: March 2010

The continued evolution of evidence-based practice in dysphagia is enhanced when connections between university classrooms and clinical settings are strengthened. Suggestions for facilitating improved lines of communication and interaction between these two important entities are provided.
Role of Neurostimulation and Neuroplasticity in the Rehabilitation of Dysphagia After Stroke
Authors: Hamdy Shaheen
Published: March 2010

Swallowing problems are common after brain injury, and can affect as many as 50% of patients in the period immediately after stroke. In some cases this can lead to serious morbidity, in particular malnutrition and pulmonary aspiration. Despite this, swallowing therapies remain controversial, with limited evidence base and little in the way of objective scientific criteria. Moreover, swallowing can recover in some patients to a safe level within weeks, making it an interesting model for understanding brain recovery and cortical plasticity. A better understanding of these adaptive processes as seen in spontaneous recovery therefore may help in developing therapeutic interventions that can drive plasticity and so encourage the recovery process. In this article, I will examine present knowledge about the recovery mechanisms for swallowing after brain injury, particularly from investigations with Transcranial Magnetic Stimulation, and explore what aspects are important for compensating for recovery after damage. In addition, I will describe novel approaches to swallowing therapy, based on objective neurophysiological models that may be useful in speeding up the process of recovery and encouraging cortical plasticity that may form the basis for future clinical trials of dysphagia after brain injury.
Reimbursement for Telespeech
Authors: Brown Janet , Brannon Janice , Romanow Kate
Published: March 2010

The American Speech-Language-Hearing Association (ASHA) supports the use of telespeech (also called telepractice) to expand access to speech-language pathology and audiology services; however, widespread acceptance has been influenced by the reluctance of payers to reimburse this method of service delivery. At the present time, schools are leading the way in implementing telespeech, while adoption in health-care settings lags behind. This article provides a brief background about ASHA's activities with regard to telepractice and discusses the status of reimbursement for telespeech in various settings, including schools, private insurance, Medicare, and Medicaid.
Physics and chemistry of hot-wire chemical vapor deposition from silane: Measuring and modeling the silicon epitaxy deposition rate
Authors: Martin Ina T. , Teplin Charles W. , Doyle James R. , Branz Howard M. , Stradins Paul
Published: March 2010

We measure and successfully model the deposition rate (R) of epitaxial Si by hot-wire chemical vapor deposition (HWCVD) onto (100) silicon over a wide range of growth conditions. A deposition rate model based on the fundamentals of gas-filament and gas-substrate interactions is presented; the results are consistent with the observed dependences of R on gas pressure, flow, and filament area. Gas-phase measurements of silane depletion allow calculation of the average radical sticking coefficient from the film deposition rate. Our findings indicate that the epitaxial deposition rate can be increased sufficiently to enable an economical epitaxial film-silicon photovoltaic tech-nology on low-cost foreign substrates. The model can be simply adapted to apply to the HWCVD of amorphous, nanocrystalline, and polycrystalline Si.
Evolution of electron temperature in low pressure magnetized capacitive plasma
Authors: You S. J. , Park G. Y. , Kwon J. H. , Kim J. H. , Chang H. Y. , Lee J. K. , Seong D. J. , Shin Y. H.
Published: March 2010

The evolution of electron temperature in a low pressure magnetized capacitive discharge was investigated under the collisionless electron heating regime. The results showed that while the electron temperature increases monotonously with the magnetic field in previous study [Turner et al., Phys. Rev. Lett. 76, 2069 (1996)], the electron temperature in our experiment exhibited nonmonotonic evolution behavior with the magnetic field. This nonmonotonic evolution of the electron temperature with the magnetic field was shown to be a combined effect of suppressing electron resonance heating and enhancing collisional heating while increasing the magnetic field.
Doping tunable resonance: Toward electrically tunable mid-infrared metamaterials
Authors: Miao Xiaoyu , Passmore Brandon , Gin Aaron , Langston William , Vangala Shivashankar , Goodhue William , Shaner Eric , Brener Igal
Published: March 2010

We demonstrate metamaterials at the mid-infrared (mid-IR) wavelengths (8–12 μm) that can be widely tuned by doping in adjacent semiconductor epilayers. The metamaterials are based on metallic split ring resonators (SRRs) fabricated on doped indium antimonide (InSb). Finite integral time-domain simulation results and measured transmission data show that the resonance blueshifts when the semiconductor electron carrier concentration is increased while keeping the split ring geometry constant. A resonant wavelength shift of 1.15 μm is achieved by varying the carrier concentration of underlying InSb epilayer from 1×1016 to 2×1018 cm−3. This work represents the first step toward active tunable metamaterials in the mid-IR where the resonance can be tuned in real time by applying an electric bias voltage to control the effective carrier density.
A capacitive probe for measuring the clearance between the piston and the cylinder of a gas piston gauge
Authors: Bowers Walter J. , Olson Douglas A.
Published: March 2010

We used a capacitive technique to determine the radial clearance between the piston and cylinder of a gas piston gauge. This method determines the effective area of a piston gauge pressure standard, independent of calibration against another piston gauge or manometer, as long as the diameter of the piston is dimensionally measured. It also allows an independent determination of piston gauge distortion due to pressure. We have used this technique to measure the clearance and the distortion of six gas piston gauges of the Ruska 2465 type operating in gauge mode. Measurements were made on two gauges each in the low, middle, and high ranges. We describe the capacitance technique and the results of the measurements on the six piston gauges.
Localized exciton emission from ZnO nanocrystalline films
Authors: Xu Zheng , He Haiping , Sun Luwei , Jin Yizheng , Zhao Binghui , Ye Zhizhen
Published: March 2010

ZnO nanocrystalline films were grown using In2O3 nanostructure as template by pulsed laser deposition. A strong emission at 3.372 eV dominates the low temperature photoluminescence (PL) spectra. Combined with annealing and surface passivation process, it is indicated from temperature-dependent PL results that the emission could be attributed to recombination of localized excitons. The low probability that localized excitons decay through nonradiative recombination centers may contribute to the efficient luminescence at low temperature. It was suggested that disorder introduced by grain boundaries is responsible for the exciton localization.
A technique for extending the precision and the range of temperature programmed desorption toward extremely low coverages
Authors: Haegel Stefan , Zecho Thomas , Wehner Stefan
Published: March 2010

In this paper, an improvement of the temperature programmed desorption (TPD) technique is introduced, which facilitates fully automated sampling of TPD spectra with excellent reproducibility, especially useful for extremely low coverages. By averaging many sampled TPD spectra, the range of the TPD technique can be extended toward lower coverages, as well as the quality of the spectra can be improved. This allows for easy extraction of information about the adsorbate-surface bond. A state of the art TPD apparatus with a two chamber setup and a high quality quadrupole mass spectrometer was extended by automated components. These are an automated gas dosing system, ensuring precise dosing of gas, combined with a motor driven sample manipulation unit and a liquid nitrogen cryostat with automatic refilling. In addition all components were controlled by a computer. A large number of TPD cycles could be sampled without the need of interaction of an operator. Here, it is shown for up to more than 400 TPD cycles. This opens a wide range of new interesting applications for the TPD technique, especially in the limit of zero coverage. Here, basic experiments on well known adsorbate systems are shown to view the ability and limit of this approach.
Codoping of magnesium with oxygen in gallium nitride nanowires
Authors: Wang Zhiguo , Li Jingbo , Gao Fei , Weber William J.
Published: March 2010

Codoping of p-type GaN nanowires with Mg and oxygen was investigated using first-principles calculations. The Mg becomes a deep acceptor in GaN nanowires with high ionization energy due to the quantum confinement. The ionization energy of Mg doped GaN nanowires containing passivated Mg–O complex decreases with increasing the diameter, and reduces to 300 meV as the diameter of the GaN nanowire is larger than 2.01 nm, which indicates that Mg–O codoping is suitable for achieving p-type GaN nanowires with larger diameters. The codoping method to reduce the ionization energy can be effectively used in other semiconductor nanostructures.
Three-dimensional modeling of transport phenomena and their effect on the formation of ripples in gas metal arc welding
Authors: Rao Z. H. , Zhou J. , Liao S. M. , Tsai H. L.
Published: March 2010

Distinct, periodic arc-shaped ripples are observed on the surface of the weld bead in almost any welded components which have a significant effect on weld quality. This article presents the complex transport phenomena and their effect on the formation of ripples in three-dimensional moving gas metal arc welding. The transient distributions of the melt flow velocity and temperature in the weld pool, weld pool shape and dynamics, and solidified weld bead are calculated. It is found that the surface ripples are formed by the interplay between the up-and-down weld pool dynamics, caused mainly by the periodic droplet impingements, and the rate of weld pool solidification. The effects of various welding parameters, including the welding current, droplet size, droplet frequency, droplet impinging velocity, and travel speed on the pitch (distance between two ripples) and height of the ripple are investigated. This study provides fundamental understanding to the underlying physics that cause the formation of ripples with different pitches and heights.
Compressibility effects on the vortical flow over a 65° sweep delta wing
Authors: Riou Jacques , Garnier Eric , Basdevant Claude
Published: March 2010

The aim of this study is to investigate numerically the compressibility effects on the vortical flow developing over the VFE-2 delta wing. This wing is equipped with a sharp leading-edge and a sweep angle equal to 65°. The angle of attack is set equal to 25.5°, and two different freestream Mach numbers are considered: M∞=0.4 and M∞=0.8. The simulations are based on a turbulent modeling coupling Delayed Detached Eddy Simulation and Zonal Detached Eddy Simulation approaches, allowing a faster decay of the eddy-viscosity in Large Eddy Simulation regions. Such a method allows a good agreement with available experimental data. These computations highlight a modification of the flow behavior with an increase in the freestream Mach number. Indeed, the leading-edge vortex moves toward the wing and its core is dilated. Moreover, it is demonstrated in this study that the leading-edge vortex interacts with shock wave at midchord. This interaction induces a decay of the Rossby number in the leading-edge region and then an earlier breakdown in the transonic regime than in the subsonic one. Furthermore, several cross-flow shock waves deeply alter the aerodynamic field, in particular, a shock wave sitting beneath the leading-edge vortex. It is shown that this cross-flow shock wave moves in the lateral direction and that the frequency of this shock unsteadiness corresponds to the one classically encountered in shock-induced separation problems. As a result, the probability density function of the lateral location of the vortex core is altered in comparison with the subsonic case.
Interband-cascade infrared photodetectors with superlattice absorbers
Authors: Yang Rui Q. , Tian Zhaobing , Cai Zhihua , Klem J. F. , Johnson Matthew B. , Liu H. C.
Published: March 2010

Interband-cascade infrared photodetectors (ICIPs), composed of discrete superlattice absorbers, are demonstrated at temperatures up to 350 K with a cutoff wavelength near 5 μm at 80 K to beyond 7 μm above room temperature. The peak responsivity exceeds 200 mA/W, higher than the values reported from early interband cascade laser structures, suggesting a significantly enhanced quantum efficiency of the superlattice absorbers. A theoretical model, originally developed for quantum well infrared photodetectors (QWIPs), is applied to ICIPs to analyze their device performance. The Johnson-limited and background-limited detectivities are extracted and indicate that background-limited performance temperatures for two ICIP structures are 126 and 105 K at 5 μm. It is expected that optimized ICIPs will provide improved performance by combining the advantages of conventional photodiodes and the discrete nature of QWIPs and IC lasers.
Spontaneous mode switching in coupled oscillators competing for constant amounts of resources
Authors: Hirata Yoshito , Aono Masashi , Hara Masahiko , Aihara Kazuyuki
Published: March 2010

We propose a widely applicable scheme of coupling that models competitions among dynamical systems for fixed amounts of resources. Two oscillators coupled in this way synchronize in antiphase. Three oscillators coupled circularly show a number of oscillation modes such as rotation and partially in-phase synchronization. Intriguingly, simple oscillators in the model also produce complex behavior such as spontaneous switching among different modes. The dynamics reproduces well the spatiotemporal oscillatory behavior of a true slime mold Physarum, which is capable of computational optimization.
Ab initio thermodynamic model to assess stability of heterostructure nanocrystals
Authors: Sadowski T. , Ramprasad R.
Published: March 2010

The tendency for homogenization of CdSe-CdTe heterostructure semiconductor nanocrystals (NCs) with an abrupt interface has been studied using a phenomenological model with parameters determined by ab initio density functional theory. Results indicate that wurtzite-based CdSe-CdTe heterostructure NCs with sizes greater than ∼1000 Å are the most stable, preferring an abrupt interface below 500 K.
Spatially local parallel tempering for thermal-equilibrium sampling
Authors: Spinney R. E. , Bowler D. R. , Gillan M. J.
Published: March 2010

Parallel tempering (PT) is a set of techniques for accelerating thermal-equilibrium sampling in systems where the exploration of configuration space is hindered by energy barriers. With standard PT algorithms, the computational effort scales unfavorably with system size, so that it is difficult to apply them to large systems. We propose local PT algorithms, for which the computational effort is proportional to the number of degrees of freedom. We demonstrate the effectiveness of the new algorithms on two one-dimensional model systems, showing that results for selected observables are correctly reproduced, and that practical linear scaling is achieved. We show also that the algorithms are readily applied to systems in higher dimensions. We note the prospects for studying large extended systems, including surfaces and interfaces.
Raman scattering from surface optical phonon in diameter modulated AlN nanotips
Authors: Sahoo Satyaprakash , Dhara S. , Arora A. K. , Krishnan R. , Chandramohan P. , Srinivasan M. P.
Published: March 2010

We investigate the optical phonons in AlN nanotips using Raman spectroscopy. Apart from the group theoretically allowed optical phonons, an additional phonon mode at 850 cm−1 has been observed. Furthermore, the peak position has shown a significant redshift and its intensity increases dramatically with the change in dielectric medium. In view of its strong response to change in dielectric medium and good agreement with calculated surface optical phonon frequency in AlN, the observed phonon mode is assigned as surface optical phonon, which could be attributed to the diameter modulation in case of AlN nanotip.
High responsivity and internal gain mechanisms in Au-ZnMgO Schottky photodiodes
Authors: Tabares G. , Hierro A. , Ulloa J. M. , Guzman A. , Muñoz E. , Nakamura A. , Hayashi T. , Temmyo J.
Published: March 2010

Schottky photodiodes based on Au-ZnMgO/sapphire are demonstrated covering the spectral region from 3.35 to 3.48 eV, with UV/VIS rejection ratios up to ∼105 and responsivities as high as 185 A/W. Both the rejection ratio and the responsivity are shown to be largely enhanced by the presence of an internal gain mechanism, by which the compensated films become highly conductive as a result of illumination. This causes a large increase in the tunnel current through the Schottky barrier, yielding internal gains that are a function of the incident photon flux.
Kinetic energy spectra in thermionic emission from small tungsten cluster anions: Evidence for nonclassical electron capture
Authors: Concina Bruno , Baguenard Bruno , Calvo Florent , Bordas Christian
Published: March 2010

The delayed electron emission from small mass-selected anionic tungsten clusters Wn− has been studied for sizes in the range 9≤n≤21. Kinetic energy spectra have been measured for delays of about 100 ns after laser excitation by a velocity-map imaging spectrometer. They are analyzed in the framework of microreversible statistical theories. The low-energy behavior shows some significant deviations with respect to the classical Langevin capture model, which we interpret as possibly due to the influence of quantum dynamical effects such as tunneling through the centrifugal barrier, rather than shape effects. The cluster temperature has been extracted from both the experimental kinetic energy spectrum and the absolute decay rate. Discrepancies between the two approaches suggest that the sticking probability can be as low as a few percent for the smallest clusters.
Acoustic phonon strain induced mixing of the fine structure levels in colloidal CdSe quantum dots observed by a polarization grating technique
Authors: Huxter Vanessa M. , Scholes Gregory D.
Published: March 2010

Acoustic phonon modes in colloidal semiconductor nanocrystals are of significant interest due to their role in dephasing and as the main component of homogeneous line broadening. Despite their importance, these modes have proven elusive and have only recently been experimentally observed. This paper expands on results presented in our earlier paper [V. M. Huxter, A. Lee, S. S. Lo, et al., Nano Lett. 9, 405 (2008)], where a cross polarized heterodyne detected ultrafast transient grating (CPH-3TG) technique was used to observe the acoustic phonon mode. In the present work, we explain the origin of the observed quantum beat in the CPH-3TG signal. Further experiments are presented that show that the observed quantum beat, which arises from a coherent acoustic phonon mode in the nanocrystals, appears in anisotropy-type signals. The action of this mode induces a periodic strain in the nanocrystal that lowers the symmetry of the unit cell, mixing the fine structure states and their transition dipole moments. This mixing is manifested in anisotropy signals as a depolarization, which periodically modifies the rotational averaging factors. Through observation of the acoustic phonon mode using the CPH-3TG optical technique, it is possible to access its microscopic (atomic-level) basis and to use it as a probe to quantify changing macroscopic (whole particle) material parameters.
Quantum transport in graphene nanoribbons patterned by metal masks
Authors: Lian Chuanxin , Tahy Kristof , Fang Tian , Li Guowang , Xing Huili Grace , Jena Debdeep
Published: March 2010

Graphene nanoribbons (GNRs) were fabricated by metal mask lithography and plasma etching. GNRs with width ∼20 nm show field-effect conductance modulation of ∼12 at room temperature and >106 at 4.2 K. Conductance quantization due to quantum confinement in low field transport was observed. Landauer formula was utilized to fit the experimental data and excellent agreement was obtained. The extracted subband energy separation was found to deviate from the predicted values of perfect armchair GNRs. Transmission probability is much smaller than unity due to scattering by GNR edge/bulk disorder and impurities, indicating a mean free path ∼40 nm. High field family I-Vs exhibited current saturation tendency and current density as high as 2 A/mm has been measured at low temperature.
Roles of lattice cooling on local heating in metal-molecule-metal junctions
Authors: Tsutsui Makusu , Taniguchi Masateru , Yokota Kazumichi , Kawai Tomoji
Published: March 2010

We report a quantitative assessment of the efficacy of lattice cooling on mitigating local heating in a current-carrying single molecule wire connected to gold nanoelectrodes by comparative analyses of high-field effective temperatures at different ambient temperatures. We find substantial local heating in benzenedithiol single molecule junctions raising the local temperatures by ∼320 K from the ambient to ∼400 K at 0.85 V. The intense self-heating are attributable to decreased thermal conductance at low temperatures that leads to deteriorated heat transfer at metal-molecule contacts, thereby manifesting a critical role of lattice cooling for alleviating metal-molecule-metal junction overheating.
An efficient, low profile, electrically small, three-dimensional, very high frequency magnetic EZ antenna
Authors: Lin Chia-Ching , Ziolkowski Richard W. , Nielsen Jean A. , Tanielian Minas H. , Holloway Christopher L.
Published: March 2010

A very high frequency version of the electrically small, coax-fed, three-dimensional magnetic EZ antenna was designed and tested. The fabricated antenna was formed by integrating a capacitively loaded loop element with a coaxially-fed, electrically small, semicircular loop antenna. This low profile antenna (height ∼λ/25) had an electrical size that was ka∼0.46 at 105.2 MHz (where a is the radius of the minimum enclosing hemisphere). Nearly complete matching to the 50 Ω source and a high overall efficiency (nearly 95%) were achieved. The numerically predicted and the measured results were in good agreement.
Efficient spin injection into GaAs quantum well across Fe3O4 spin filter
Authors: Wada E. , Watanabe K. , Shirahata Y. , Itoh M. , Yamaguchi M. , Taniyama T.
Published: March 2010

We demonstrate efficient spin injection into GaAs across an Fe3O4 electrode. Spin polarization of electrons injected into a GaAs quantum well becomes significantly large below 120 K, reaching a value of 33% at 10 K. The large spin polarization is likely due to spin filtering effect across the insulating ferrimagnetic Fe3O4 layer at the interface. The results indicate that spin filtering effect across Fe3O4 is a very promising means to enhance the spin injection efficiency into semiconductors.
The transition from smooth modification to nanograting in fused silica
Authors: Liang Feng , Sun Quan , Gingras Daniel , Vallée Réal , Chin See Leang
Published: March 2010

The transition from smooth modification to nanograting was observed during nanograting formation in fused silica. This transition is very sensitive to the input laser intensity. A small deviation from the critical intensity will result in the formation of either smooth modification or nanograting. There is an increase in the width of nanograting zone as compared to the smooth modification zone; the former could be due to the increase of the highly localized nonlinear absorption in the direction perpendicular to the laser polarization. Well-shaped nanograting can be fabricated with intensity slightly higher than the threshold.
Bilayer oscillation of subband effective masses in Pb/Ge(111) thin-film quantum wells
Authors: Tang S.-J. , Lee Chang-Yeh , Huang Chien-Chung , Chang Tay-Rong , Cheng Cheng-Maw , Tsuei Ku-Ding , Jeng H.-T.
Published: March 2010

Subband dispersions of quantum-well states in Pb thin films on Ge(111) have been measured with angle-resolved photoemission spectroscopy. The effective masses at the surface zone center exhibit a bilayer oscillation with thickness, in both magnitude and sign. This behavior is attributed to a strong interaction between Pb quantum-well subbands and the Ge valence maximum near the Fermi level, which occurs about every two monolayers.
Self-assembled Si0.80Ge0.20 nanoripples on Si(1 1 10) substrates
Authors: Chen G. , Wintersberger E. , Vastola G. , Groiss H. , Stangl J. , Jantsch W. , Schäffler F.
Published: March 2010

Si 0.8 Ge 0.2 heteroepitaxy on vicinal Si(1 1 10) substrates leads to the formation of a nanoscale ripple morphology. Atomic force microscopy, and grazing incidence small angle x-ray scattering reveal that these SiGe structures are essentially prisms of triangular cross section bounded by two adjacent {105} facets. Transmission electron microscopy shows the existence of a wetting layer. X-ray diffraction in combination with finite element simulations was performed to extract strain distribution maps. The stabilization of the prism structure is attributed to the strain-dependence of the {105} surface energy.
Efficient low-power terahertz generation via on-chip triply-resonant nonlinear frequency mixing
Authors: Bravo-Abad J. , Rodriguez A. W. , Joannopoulos J. D. , Rakich P. T. , Johnson S. G. , Soljačić M.
Published: March 2010

In this letter, we show theoretically how the light-confining properties of triply-resonant photonic resonators can be tailored to enable dramatic enhancements of the conversion efficiency of terahertz (THz) generation via nonlinear frequency down-conversion processes. Using detailed numerical calculations, we predict that this approach can be used to reduce up to three orders of magnitude the pump powers required to reach quantum-limited conversion efficiency of THz generation in conventional nonlinear optical material systems. Furthermore, we propose a realistic design readily accessible experimentally, both for fabrication and demonstration of optimal THz conversion efficiency at sub-W power levels.