bluuebunny/crossref_metadata_2025 huggingface dataset:
Subjective cognitive impairment: Functional MRI during a divided attention task
Authors: Rodda J. , Dannhauser T. , Cutinha D.J. , Shergill S.S. , Walker Z.
Published: October 2010

Background

Individuals with subjective cognitive impairment (SCI) have persistent memory complaints but normal neurocognitive performance. For some, this may represent a pre-mild cognitive impairment (MCI) stage of Alzheimer's disease (AD). Given that attentional deficits and associated brain activation changes are present early in the course of AD, we aimed to determine whether SCI is associated with brain activation changes during attentional processing.

Methods

Eleven SCI subjects and 10 controls completed a divided attention task during functional magnetic resonance imaging.

Results

SCI and control groups did not differ in sociodemographic, neurocognitive or behavioural measures. When group activation during the divided attention task was compared, the SCI group demonstrated increased activation in left medial temporal lobe, bilateral thalamus, posterior cingulate and caudate.

Conclusion

This pattern of increased activation is similar to the pattern of decreased activation reported during divided attention in AD and may indicate compensatory changes. These findings suggest the presence of early functional changes in SCI; longitudinal studies will help to further elucidate the relationship between SCI and AD.
Hippocampal volume in borderline personality disorder with and without comorbid posttraumatic stress disorder: A meta-analysis
Authors: Rodrigues E. , Wenzel A. , Ribeiro M.P. , Quarantini L.C. , Miranda-Scippa A. , de Sena E.P. , de Oliveira I.R.
Published: October 2010

Background

Several studies have found a reduction in hippocampal volume in borderline personality disorder (BPD) patients.

Methods

In order to investigate the degree to which comorbid posttraumatic stress disorder (PTSD) could account for reduction in hippocampal volume in these patients, we conducted a systematic review and meta-analysis of studies that compared hippocampal volume in BPD patients with and without PTSD relative to healthy controls.

Results

Seven articles, involving 124 patients and 147 controls, were included. We found a statistically significant reduction for the left and right hippocampus. Data from the four studies that discriminated BPD patients with and without PTSD indicate that hippocampal volumes were reduced bilaterally in BPD patients with PTSD, relative to healthy controls, but that results were mixed for BPD patients without PTSD, relative to healthy controls.

Conclusions

Results from this meta-analysis suggest that hippocampal volumes are reduced in patients with BPD, relative to healthy controls, but particularly in cases in which patients are diagnosed with comorbid PTSD.
Temperament profiles, major depression, and response to treatment with SSRIs in psychiatric outpatients
Authors: Kampman O. , Poutanen O. , Illi A. , Setälä-Soikkeli E. , Viikki M. , Nuolivirta T. , Leinonen E.
Published: October 2010

Objective

The Temperament and Character Inventory (TCI) is commonly used in adult populations. Our aim was to explore: (1) if there are specific differences in temperament dimensions related to depression in comparison with general population, (2) if the treatment response during the acute phase of major depressive disorder (MDD) is predictable by TCI temperament dimensions.

Method

Temperament profiles in 98 MDD patients were compared with a Finnish community sample. The patients were treated with serotonin selective reuptake inhibitors (SSRIs) for 6weeks and their temperament profiles were assessed at baseline and endpoint. The harm avoidance (HA) and depression scores at baseline and endpoint were modelled with path analysis. For path modelling, we tested the relationships between different temperament dimensions and depression symptoms and other clinical variables with Mancova model.

Results

The HA scores were significantly higher in patients both at baseline and endpoint compared to the Northern Finland 1966 Birth Cohort (NFBC). The patients, and especially males, had slightly higher reward dependency (RD) scores. HA at endpoint explained moderately the Montgomery Åsberg Depression Rating Scale (MADRS) endpoint score. HA endpoint score was strongly explained by HA baseline score.

Conclusions

HA is associated with risk of and treatment response to depression.
A controlled follow-up study of adolescents exposed to a school shooting – Psychological consequences after four months
Authors: Suomalainen L. , Haravuori H. , Berg N. , Kiviruusu O. , Marttunen M.
Published: October 2010

Background

In November 2007, a student shot eight people and himself at Jokela High School, Finland. This study aims to evaluate the long-term effects of exposure to a school shooting among adolescents.

Method

Associations between psychological outcomes and background factors were analysed and compared with “comparison students” four months after the incident. A questionnaire including Impact of Event Scale (IES) and General Health Questionnaire (GHQ-36) was used.

Results

Half of the females and a third of the males suffered from posttraumatic distress. High level of posttraumatic distress (IES ≥ 35), predicting PTSD, was observed in 27% of the females and 7% of the males. The odds ratio was 6.4 (95% confidence interval 3.5–10.5) for having high levels of posttraumatic distress. Severe or extreme exposure and female gender were found to increase the risk. Forty-two percent of the females and 16% of the males had psychiatric disturbance (GHQ ≥ 9). Severe or extreme exposure, older age and female gender increased the risk. Perceived support from family and friends was found to be protective.

Conclusions

The observed risk and protective factors were similar to earlier studies. Follow-up will be essential in identifying factors predicting persisting trauma-related symptoms in adolescence.
The small RNA expression profile of the developing murine urinary and reproductive systems
Authors: Aguilar Ana Laura Gutierrez , Piskol Robert , Beitzinger Michaela , Zhu Jia Yun , Kruspe Dagmar , Aszodi Attila , Moser Markus , Englert Christoph , Meister Gunter
Published: October 2010

microRNAs (miRNAs) are small non‐coding RNAs with fundamental roles in the regulation of gene expression. miRNAs assemble with Argonaute (Ago) proteins to miRNA‐protein complexes (miRNPs), which interact with distinct binding sites on mRNAs and regulate gene expression. Specific miRNAs are key regulators of tissue and organ development and it has been shown in mammals that miRNAs are also involved in the pathogenesis of many diseases including cancer. Here, we have characterized the miRNA expression profile of the developing murine genitourinary system. Using a computational approach, we have identified several miRNAs that are specific for the analyzed tissues or the developmental stage. Our comprehensive miRNA expression atlas of the developing genitourinary system forms an invaluable basis for further functional in vivo studies.
Ecdysone receptor homologs from mollusks, leeches and a polychaete worm
Authors: Laguerre Michel , Veenstra Jan A.
Published: October 2010

The genomes of the mollusk Lottia gigantea, the leech Helobdella robusta and the polychaete worm Capitella teleta each have a gene encoding an ecdysone receptor homolog. Publicly available genomic and EST sequences also contain evidence for ecdysone receptors in the seahare Aplysia californica, the bobtail squid Euprymna scolopes and the medicinal leech Hirudo medicinalis. Three‐dimensional models of the ligand binding domains of these predicted ecdysone receptor homologs suggest that each of them could potentially bind an ecdysone‐related steroid. Thus, ecdysone receptors are not limited to arthropods and nematodes.
The CBS domain protein MJ0729 of Methanocaldococcus jannaschii binds DNA
Authors: Aguado-Llera David , Oyenarte Iker , Martínez-Cruz Luis Alfonso , Neira José L.
Published: October 2010

The cystathionine beta‐synthase (CBS) domains function as regulatory motifs in several proteins. Elucidating how CBS domains exactly work is relevant because several genetic human diseases have been associated with mutations in those motifs. Here, we show, for the first time, that a CBS domain binds calf‐thymus DNA and E‐boxes recognized by transcription factors. We have carried out the DNA‐binding characterization of the CBS domain protein MJ0729 from Methanocaldococcus jannaschii by biochemical and spectroscopic techniques. Binding induces conformational changes in the protein, and involves the sole tryptophan residue. The apparent dissociation constant for the E‐boxes is ∼10 μM. These results suggest that CBS domains might interact with DNA.
Suppressor of cytokine signalling (SOCS) 1 and 3 enhance cell adhesion and inhibit migration towards the chemokine eotaxin/CCL11
Authors: Stevenson Nigel J. , McFarlane Cheryl , Ong Seow Theng , Nahlik Krystyna , Kelvin Alyson , Addley Mark R. , Long Aideen , Greaves David R. , O'Farrelly Cliona , Johnston James A.
Published: October 2010

Suppressors of cytokine signalling (SOCS) proteins regulate signal transduction, but their role in responses to chemokines remains poorly understood. We report that cells expressing SOCS1 and 3 exhibit enhanced adhesion and reduced migration towards the chemokine CCL11. Focal adhesion kinase (FAK) and the GTPase RhoA, control cell adhesion and migration and we show the presence of SOCS1 or 3 regulates expression and tyrosine phosphorylation of FAK, while also enhancing activation of RhoA. Our novel findings suggest that SOCS1 and 3 may control chemotaxis and adhesion by significantly enhancing both FAK and RhoA activity, thus localizing immune cells to the site of allergic inflammation.
NanoProbeArrays for the Analysis of Ultra-Low-Volume Protein Samples using Piezoelectric Liquid Dispensing Technology
Authors: Nagaraj Vinay Janthakahalli , Eaton Seron , Wiktor Peter
Published: October 2010

Antibody microarrays are gaining popularity as a high-throughput technology to investigate the proteome. However, protein extracts from most body fluid or biopsy samples are available in very small volumes and are often unsuitable for large-scale antibody microarray studies. To demonstrate the potential for protein analysis with as little as a few nanoliters of sample, we have developed a new technology called NanoProbeArrays based on piezoelectric liquid dispensing for non-contact printing and probing of antibody arrays. Instead of flooding the protein sample on the antibody microarray surface, as in conventional microarray screening, a piezoelectric inkjet printer is used to dispense nanoliters of fluorescently labeled proteins over the antibody spots on the array. The ability of NanoProbeArrays to precisely identify and reliably distinguish between test proteins from different sources, without any loss of sensitivity and specificity as compared with conventional antibody microarrays, is illustrated here. The utility of NanoProbeArrays for biomarker identification in a complex biological sample was tested by detecting the cytokine interleukin-4 in serum. The significant reduction in volume of sample during NanoProbeArray analysis, as compared with conventional antibody microarrays, offers new opportunities for basic and applied proteomic research.
Our possessions, our selves: Domains of self‐worth and the possession–self link
Authors: Ferraro Rosellina , Escalas Jennifer Edson , Bettman James R.
Published: October 2010

The extent to which a possession is linked to self is a critical determinant of whether a possession elicits grief if lost. We propose a framework for understanding the formation of the possession–self link, arguing that a possession's ability to represent the important domains on which a person bases her self‐worth affects the possession–self link. We also show that dispositional tendencies to incorporate possessions into the self moderate this relationship, while the monetary value of the possession does not affect the strength of the possession–self link.
Reverse phase protein microarrays advance to use in clinical trials
Authors: Mueller Claudius , Liotta Lance A. , Espina Virginia
Published: October 2010

Individualizing cancer therapy for molecular targeted inhibitors requires a new class of molecular profiling technology that can map the functional state of the cancer cell signal pathways containing the drug targets. Reverse phase protein microarrays (RPMA) are a technology platform designed for quantitative, multiplexed analysis of specific phosphorylated, cleaved, or total (phosphorylated and non‐phosphorylated) forms of cellular proteins from a limited amount of sample. This class of microarray can be used to interrogate tissue samples, cells, serum, or body fluids. RPMA were previously a research tool; now this technology has graduated to use in research clinical trials with clinical grade sensitivity and precision. In this review we describe the application of RPMA for multiplexed signal pathway analysis in therapeutic monitoring, biomarker discovery, and evaluation of pharmaceutical targets, and conclude with a summary of the technical aspects of RPMA construction and analysis.
Tissue proteomics of the human mammary gland: Towards an abridged definition of the molecular phenotypes underlying epithelial normalcy
Authors: Moreira José M.A. , Cabezón Teresa , Gromova Irina , Gromov Pavel , Timmermans-Wielenga Vera , Machado Isidro , Llombart-Bosch Antonio , Kroman Niels , Rank Fritz , Celis Julio E.
Published: October 2010

Our limited understanding of the biological impact of the whole spectrum of early breast lesions together with a lack of accurate molecular‐based risk criteria for the diagnosis and assignment of prognostic significance to biopsy findings presents an important problem in the clinical management of patients harboring precancerous breast lesions. As a result, there is a need to identify biomarkers that can better determine the outcome of early breast lesions by identifying subpopulations of cells in breast premalignant disease that are at high‐risk of progression to invasive disease. A first step towards achieving this goal will be to define the molecular phenotypes of the various cell types and precursors – generated by the stem cell hierarchy – that are present in normal and benign conditions of the breast. To date there have been very few systematic proteomic studies aimed at characterizing the phenotypes of the different cell subpopulations present in normal human mammary tissue, partly due to the formidable heterogeneity of mammary tissue, but also due to limitations of the current proteomic technologies. Work in our laboratories has attempted to address in a systematic fashion some of these limitations and here we present our efforts to search for biomarkers using normal fresh tissue from non‐neoplastic breast samples. From the data generated by the 2D gel‐based proteomic profiling we were able to compile a protein database of normal human breast epithelial tissue that was used to support the biomarker discovery program. We review and present new data on the putative cell‐progenitor marker cytokeratin 15 (CK15), and describe a novel marker, dihydropyriminidase‐related protein 3 (DRP3) that in combination with CK15 and other well known proteins were used to define molecular phenotypes of normal human breast epithelial cells and their progenitors in resting acini, lactating alveoli, and large collecting ducts of the nipple. Preliminary results are also presented concerning DRP3 positive usual ductal hyperplasias (UDHs) and on single cell layer columnar cells (CCCs). At least two bona fide biomarkers of undifferentiated ERα/PgR negative luminal cells emerged from these studies, CK15 and c‐KIT, which in combination with transformation markers may lead to the establishment of a protein signature able to identify breast precancerous at risk of progressing to invasive disease.
The missing link: Gender, immigration policy and the Live-in Caregiver Program in Canada
Authors: Brickner Rachel K , Straehle Christine
Published: October 2010

Temporary labour migration is on the rise in the developed world. In May 2009, Canada's Parliamentary Standing Committee on Citizenship and Immigration issued a report on the state of temporary and undocumented foreign workers in Canada, making a series of recommendations to ensure that labour needs can be met through temporary foreign workers and that those workers are able to successfully integrate into Canadian society. The report highlights one Canadian immigration program, the Live-in Caregivers Program, which offers migrant workers the opportunity to apply for permanent residency after working 24 months as a live-in child or elder care provider. The authors argue that the report errs in holding up the Live-in Caregivers Program as a model for other temporary foreign worker programs. Although the path to permanent residency is an important provision of the Live-in Caregivers Program, a gendered analysis of the program shows that the women who come to Canada as caregivers continue to face vulnerability and exploitation because of key structures of the program, most importantly the live-in requirement. Until policy reform accounts for the results of such a gendered analysis, the Live-in Caregivers Program does not ensure that caregivers will be able to integrate successfully into Canadian society.
Holocene vegetation, fire and climate history of the Sawtooth Range, central Idaho, USA
Authors: Whitlock Cathy , Briles Christy E. , Fernandez Matias C. , Gage Joshua
Published: October 2010

The paucity of low- and middle-elevation paleoecologic records in the Northern Rocky Mountains limits our ability to assess current environmental change in light of past conditions. A 10,500-yr-long vegetation, fire and climate history from Lower Decker Lake in the Sawtooth Range provides information from a new region. Initial forests dominated by pine and Douglas-fir were replaced by open Douglas-fir forest at 8420 cal yr BP, marking the onset of warmer conditions than present. Presence of closed Douglas-fir forest between 6000 and 2650 cal yr BP suggests heightened summer drought in the middle Holocene. Closed lodgepole pine forest developed at 2650 cal yr BP and fires became more frequent after 1450 cal yr BP. This shift from Douglas-fir to lodgepole pine forest was probably facilitated by a combination of cooler summers, cold winters, and more severe fires than before. Five drought episodes, including those at 8200 cal yr BP and during the Medieval Climate Anomaly, were registered by brief intervals of lodgepole pine decline, an increase in fire activity, and mistletoe infestation. The importance of a Holocene perspective when assessing the historical range of variability is illustrated by the striking difference between the modern forest and that which existed 3000 yr ago.
On the anatomy of a chain shift
Authors: DINNSEN DANIEL A. , GREEN CHRISTOPHER R. , GIERUT JUDITH A. , MORRISETTE MICHELE L.
Published: October 2010

Phonological chain shifts have been the focus of many theoretical, developmental, and clinical concerns. This paper considers an overlooked property of the problem by focusing on the typological properties of the widely attested ‘s>θ>f’ chain shift involving the processes of Labialization and Dentalization in early phonological development. Findings are reported from a cross-sectional study of 234 children (ages 3 years; 0 months–7;9) with functional (nonorganic) phonological delays. The results reveal some unexpected gaps in the predicted interactions of these processes and are brought to bear on the evaluation of recent optimality theoretic proposals for the characterization of phonological interactions. A developmental modification to the theory is proposed that has the desired effect of precluding certain early-stage grammars. The proposal is further evaluated against the facts of another widely cited developmental chain shift known as the ‘puzzle>puddle>pickle’ problem (Smith 1973).
Responses of ecosystem carbon dioxide fluxes to soil moisture fluctuations in a moist Kenyan savanna
Authors: Otieno D. O. , K'Otuto G. O. , Maina J. N. , Kuzyakov Y. , Onyango J. C.
Published: October 2010

Measurements were conducted within a fence-exclosure between February 2008 and July 2009 to investigate the influence of soil moisture on ecosystem CO2 fluxes in a Themeda triandra-dominated grassland of a humid Kenyan savanna. Rainout shelters were constructed to reduce ambient rainfall by 0%, 10% and 20% respectively to attain variable soil water content (SWC) during plant growth. SWC within the top 30 cm layer, above-ground biomass, soil and plant nitrogen (N) concentrations were assessed monthly alongside CO2 fluxes. Net ecosystem CO2 exchange (NEE) and ecosystem respiration (Reco) were measured with closed chambers while carbon (C) partitioning during the wet and dry seasons were assessed through pulse 13C labelling. There were significant seasonal and between plot differences in SWC, above-ground biomass, canopy light utilization efficiency (α), CO2 fluxes and C allocation pattern resulting from differences in SWC. The ecosystem was a net C sink during the wet and C neutral during the dry seasons. The study showed strong seasonal fluctuations in ecosystem CO2 fluxes and underscores the significant role of the savanna grasslands in regional C balance due to its expansive nature. The savanna grassland is however vulnerable to low soil moisture, with significant reduction in CO2 uptake during drought.
Distributional lexical semantics: Toward uniform representation paradigms for advanced acquisition and processing tasks
Authors: BASILI R. , PENNACCHIOTTI M.
Published: October 2010

The distributional hypothesis states thatwords with similar distributional properties have similar semantic properties(Harris 1968). This perspective on word semantics, was early discussed in linguistics (Firth 1957; Harris 1968), and then successfully applied to Information Retrieval (Salton, Wong and Yang 1975). In Information Retrieval, distributional notions (e.g. document frequency and word co-occurrence counts) have proved a key factor of success, as opposed to early logic-based approaches to relevance modeling (van Rijsbergen 1986; Chiaramella and Chevallet 1992; van Rijsbergen and Lalmas 1996).
Directional distributional similarity for lexical inference
Authors: KOTLERMAN LILI , DAGAN IDO , SZPEKTOR IDAN , ZHITOMIRSKY-GEFFET MAAYAN
Published: October 2010

Distributional word similarity is most commonly perceived as a symmetric relation. Yet, directional relations are abundant in lexical semantics and in many Natural Language Processing (NLP) settings that require lexical inference, making symmetric similarity measures less suitable for their identification. This paper investigates the nature of directional (asymmetric) similarity measures that aim to quantify distributional feature inclusion. We identify desired properties of such measures for lexical inference, specify a particular measure based on Average Precision that addresses these properties, and demonstrate the empirical benefit of directional measures for two different NLP datasets.
Optimization and uncertainty assessment of strongly nonlinear groundwater models with high parameter dimensionality
Authors: Keating Elizabeth H. , Doherty John , Vrugt Jasper A. , Kang Qinjun
Published: October 2010

Highly parameterized and CPU‐intensive groundwater models are increasingly being used to understand and predict flow and transport through aquifers. Despite their frequent use, these models pose significant challenges for parameter estimation and predictive uncertainty analysis algorithms, particularly global methods which usually require very large numbers of forward runs. Here we present a general methodology for parameter estimation and uncertainty analysis that can be utilized in these situations. Our proposed method includes extraction of a surrogate model that mimics key characteristics of a full process model, followed by testing and implementation of a pragmatic uncertainty analysis technique, called null‐space Monte Carlo (NSMC), that merges the strengths of gradient‐based search and parameter dimensionality reduction. As part of the surrogate model analysis, the results of NSMC are compared with a formal Bayesian approach using the DiffeRential Evolution Adaptive Metropolis (DREAM) algorithm. Such a comparison has never been accomplished before, especially in the context of high parameter dimensionality. Despite the highly nonlinear nature of the inverse problem, the existence of multiple local minima, and the relatively large parameter dimensionality, both methods performed well and results compare favorably with each other. Experiences gained from the surrogate model analysis are then transferred to calibrate the full highly parameterized and CPU intensive groundwater model and to explore predictive uncertainty of predictions made by that model. The methodology presented here is generally applicable to any highly parameterized and CPU‐intensive environmental model, where efficient methods such as NSMC provide the only practical means for conducting predictive uncertainty analysis.
Interaction between inclined current sheets and the heliospheric termination shock
Authors: Giacalone Joe , Burgess David
Published: October 2010

Using two‐dimensional hybrid simulations we study the interaction between the Heliospheric Current Sheet (HCS) and the solar wind termination shock (TS). Hot flow anomalies (HFA) are regions of hot, deflected and disturbed plasma flow which may form at the intersection of a shock and current sheet. We study the role played by the inclination, θCn, of the current sheet relative to the shock normal. As previously found, low values of θCn are associated with HFA formation. We find that as θCn increases the HFA is modified, until at θCn = 60° it disappears completely. Thus, HFAs are unlikely to be formed near the TS since the HCS is highly inclined relative to the radial direction (θCn > 60°). We also find that some suprathermal particles, particularly interstellar pickup ions, are trapped near the intersection point of the shock and current sheet where they gain considerable energy, and subsequently drift along the current sheet upstream of the shock. This process is more effective for larger values of θCn. Thus, we expect that upstream of the TS there are likely to be high‐energy particles (energized pickup ions) associated with crossings of the HCS, but only of the particular magnetic reversal polarity associated with HFAs. This may be relevant to recently reported Voyager observations.
Classification of four and six dimensional Drinfel’d superdoubles
Authors: Eghbali A. , Rezaei-Aghdam A. , Heidarpour F.
Published: October 2010

Using adjoint representation we first classify two and three dimensional Lie superbialgebras obtained from decomposable Lie superalgebras. In this way we complete the classification obtained by Eghbali et al., [J. Math. Phys. 51, 073503 (2010); e-print arXiv:0901.4471 [math-ph]]. Then we classify all four and six dimensional Drinfel’d superdoubles.
Electron cyclotron-electron Bernstein wave emission diagnostics for the COMPASS tokamak
Authors: Zajac J. , Preinhaelter J. , Urban J. , Zacek F. , Sestak D. , Nanobashvili S.
Published: October 2010

The COMPASS tokamak recently started operation at the Institute of Plasma Physics AS CR, v.v.i., Prague. A new 16-channel radiometer, operating alternatively in three frequency bands, has been designed and constructed. The system is prepared for detection of normal electron cyclotron emission (O1 or X2) or oblique electron Bernstein wave emission. The end-to-end calibration method includes all components that influence the antenna radiation pattern. A steady recalibration is possible using a noise generator connected to the radiometer input through a fast waveguide PIN-switch. Measurements of the antenna radiation characteristics (2D electric field) were performed in free space as well as in the tokamak chamber, showing the degradation effect of structures on the Gaussian beam shape. First plasma radiation temperature measurements from low-field circular plasmas are available.
New field programmable gate array-based image-oriented acquisition and real-time processing applied to plasma facing component thermal monitoring
Authors: Martin V. , Dunand G. , Moncada V. , Jouve M. , Travere J.-M.
Published: October 2010

During operation of present fusion devices, the plasma facing components (PFCs) are exposed to high heat fluxes. Understanding and preventing overheating of these components during long pulse discharges is a crucial safety issue for future devices like ITER. Infrared digital cameras interfaced with complex optical systems have become a routine diagnostic to measure surface temperatures in many magnetic fusion devices. Due to the complexity of the observed scenes and the large amount of data produced, the use of high computational performance hardware for real-time image processing is then mandatory to avoid PFC damages. At Tore Supra, we have recently made a major upgrade of our real-time infrared image acquisition and processing board by the use of a new field programmable gate array (FPGA) optimized for image processing. This paper describes the new possibilities offered by this board in terms of image calibration and image interpretation (abnormal thermal events detection) compared to the previous system.
Quasioptical design of integrated Doppler backscattering and correlation electron cyclotron emission systems on the DIII-D tokamak
Authors: Rhodes T. L. , Peebles W. A. , Nguyen X. , Hillesheim J. C. , Schmitz L. , White A. E. , Wang G.
Published: October 2010

The quasioptical design of a new integrated Doppler backscattering (DBS) and correlation electron cyclotron emission (CECE) system is presented. The design provides for simultaneous measurements of intermediate wavenumber density and long wavelength electron temperature turbulence behavior. The Doppler backscattering technique is sensitive to plasma turbulence flow and has been utilized to determine radial electric field, geodesic acoustic modes, zonal flows, and intermediate scale (k∼1–6 cm−1) density turbulence. The correlation ECE system measures a second turbulent field, electron temperature fluctuations, and is sensitive to long poloidal wavelength (k≤1.8 cm−1). The integrated system utilizes a newly installed in-vessel focusing mirror that produces a beam waist diameter of 3.5–5 cm in the plasma depending on the frequency. A single antenna (i.e., monostatic operation) is used for both launch and receive. The DBS wavenumber is selected via an adjustable launch angle and variable probing frequency. Due to the unique system design both positive and negative wavenumbers can be obtained, with a range of low to intermediate wavenumbers possible (approximately −3 to 10 cm−1). A unique feature of the design is the ability to place the DBS and CECE measurements at the same radial and poloidal locations allowing for cross correlation studies (e.g., measurement of nT cross-phase).
Stochastic entangled chain dynamics of dense polymer solutions
Authors: Kivotides Demosthenes , Wilkin S. Louise , Theofanous Theo G.
Published: October 2010

We propose an adjustable-parameter-free, entangled chain dynamics model of dense polymer solutions. The model includes the self-consistent dynamics of molecular chains and solvent by describing the former via coarse-grained polymer dynamics that incorporate hydrodynamic interaction effects, and the latter via the forced Stokes equation. Real chain elasticity is modeled via the inclusion of a Pincus regime in the polymer’s force-extension curve. Excluded volume effects are taken into account via the combined action of coarse-grained intermolecular potentials and explicit geometric tracking of chain entanglements. We demonstrate that entanglements are responsible for a new (compared to phantom chain dynamics), slow relaxation mode whose characteristic time scale agrees very well with experiment. Similarly good agreement between theory and experiment is also obtained for the equilibrium chain size. We develop methods for the solution of the model in periodic flow domains and apply them to the computation of entangled polymer solutions in equilibrium. We show that the number of entanglements Π agrees well with the number of entanglements expected on the basis of tube theory, satisfactorily reproducing the latter’s scaling of Π with the polymer volume fraction ϕ. Our model predicts diminishing chain size with concentration, thus vindicating Flory’s suggestion of excluded volume effects screening in dense solutions. The predicted scaling of chain size with ϕ is consistent with the heuristic, Flory theory based value.
A new double-foil soft x-ray array to measure Te on the MST reversed field pinch
Authors: McGarry M. B. , Franz P. , Den Hartog D. J. , Goetz J. A.
Published: October 2010

A soft x-ray (SXR) diagnostic to measure electron temperature on the Madison Symmetric Torus using two complementary methods is presented. Both methods are based on the double-foil technique, which calculates electron temperature via the ratio of SXR bremsstrahlung emission from the plasma in two different energy ranges. The tomographic emissivity method applies the double-foil technique to a tomographic reconstruction of SXR emissivity, creating a two-dimensional map of temperature throughout the plasma. In contrast, the direct brightness method applies the double-foil technique directly to the measured brightness and generates vertical and horizontal radial profiles. Extensive modeling demonstrates advantages and limitations in both techniques. For example, although the emissivity technique provides a two-dimensional mapping of temperature, its reliance on multiple tomographic inversions introduces some artifacts into the results. On the other hand, the more direct brightness technique avoids these artifacts but is only able to provide a radial profile of electron temperature.
The influence of acoustic damping on the transformation efficiency of capacitive micromachined ultrasonic transducer in air
Authors: Lee Seung-Mok , Cha Bu-sang , Okuyama Masanori
Published: October 2010

Acoustic damping of a capacitive micromachined ultrasonic transducer (CMUT) in air causes mechanical impedance to the membrane vibration, which significantly influences the transformation efficiency of the device. We observed the effect of acoustic damping on the transformation efficiency of a CMUT under various external acoustic pressure and device structure conditions; the results were compared with other factors such as capacitance variations originating from the change in air-hole rate [area ratio (AR)] over the total membrane area. The damping ratio of the perforated membrane plate was computed for each acoustic pressure condition, and the results were introduced into calculations of the membrane displacement using the finite element method to take the squeeze-film damping effect into account. The Q factor and transformation efficiency of the CMUT under various AR for the membrane and dimension conditions of the device were studied; the acoustic damping effect is discussed in terms of design optimization.
Low-noise, high-speed detector development for optical turbulence fluctuation measurements for NSTX
Authors: Schoenbeck N. L. , Ellington S. D. , Fonck R. J. , Jaehnig K. , McKee G. R. , Smith D. , Uzun-Kaymak I. U. , Winz G.
Published: October 2010

A new beam emission spectroscopy (BES) diagnostic is under development. Photon-noise limited measurements of neutral beam emissions are achieved using photoconductive photodiodes with a novel frequency-compensated broadband preamplifier. The new BES system includes a next-generation preamplifier and upgraded optical coupling system. Notable features of the design are surface-mount components, minimized stray capacitance, a wide angular acceptance photodiode, a differential output line driver, reduced input capacitance, doubling of the frequency range, net reduced electronic noise, and elimination of the need for a cryogenic cooling system. The irreducible photon noise dominates the noise up to 800 kHz for a typical input power of 60 nW. This new assembly is being integrated into an upgraded multichannel optical detector assembly for a new BES system on the NSTX experiment.
Variable sensitivity of organic light-emitting diodes to operation-induced chemical degradation: Nature of the antagonistic relationship between lifetime and efficiency
Authors: Kondakov Denis Y. , Young Ralph H.
Published: October 2010

The efficiency of any organic light-emitting diode (OLED) decreases with prolonged operation. In fluorescent OLEDs containing the standard hole-transporting material NPB [N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine], prolonged operation also results in chemical degradation of the NPB. Qualitatively and quantitatively, the extent and location of chemical changes are consistent with the hypothesis that chemical degradation of NPB is largely responsible for the loss of device efficiency and that the degradation is initiated by bond-breaking in excited-state NPB. Blue fluorescent OLEDs with low operating voltages and high luminance efficiencies tend to lose efficiency much faster than OLEDs with higher operating voltages and lower efficiencies. Even so, the two types exhibit approximately the same kind and degree of chemical degradation after operation for equal times at equal current densities. In the low-voltage OLEDs, the electric field in the light-emitting layer is weaker, and the concentration of NPB radical-cations near the emission zone is smaller than in the higher-voltage devices. Apparently for this reason, degradation products impair the luminescent efficiency more severely in the low-voltage OLEDs. Such differing sensitivity of low-voltage and high-voltage OLEDs to the same amount of chemical degradation is further demonstrated by experiments with OLEDs that have been doped intentionally with a contaminant modeling a degradation product at realistic concentrations. It is also supported by a substantial recovery of efficiency after a conversion of a degraded low-voltage device into a high-voltage device by replacement of the cathode and electron-injecting interface.
Thermally induced ultrasound emission from printable semiconductor nanoparticles
Authors: Odagawa Akihiro , Matsushita Akio , Hashimoto Masahiko
Published: October 2010

The thermally induced ultrasound emissions from printable semiconductor nanoparticles produced by the application of input pulses are demonstrated on different substrates. Printing processes that use dispersion liquids containing nanoparticles make it possible to generate ultrasound waves on flexible graphite sheets. We argue that the emission efficiency, which is the ratio of the ultrasound pressure to the input power, is greatly affected by the thermal effusivity of the nanoparticles, especially for the shell material in core-shell structured nanoparticles.
Analysis of terahertz plasma resonances in structures with two-dimensional electron systems periodically modulated by interdigitated gate
Authors: Khmyrova Irina , Yamase Ryosuke , Fukuda Makoto , Watanabe Norikazu
Published: October 2010

Simple analytical model is developed to evaluate spatial distribution of sheet electron density in the channel of the high-electron mobility transistor (HEMT)-like structure periodically modulated by the bias voltages applied to interdigitated gate. Resonant frequencies of plasma oscillations excited in the two-dimensional electron gas (2DEG) channel of such structures are evaluated in the ideal and realistic situations. The realistic model accounts for the ungated regions which due to nonideality of gate contact—2DEG channel system can be also affected by the gate bias voltages. It is shown that plasma resonances in realistic structures with fringed ungated regions deviate from those predicted by the ideal model. The model developed can be used to interpret the terahertz plasmon spectra measured experimentally.
Influence of acoustic pressure amplifier tube on a 300 Hz thermoacoustically driven pulse tube cooler
Authors: Wang Xiaotao , Yu Guoyao , Dai Wei , Luo Ercang , Zhou Yuan
Published: October 2010

High frequency thermoacoustically driven pulse tube coolers (PTCs) have the advantages of high energy density, compact structure, and high reliability. Through a series of improvements, the 300 Hz thermoacoustically driven PTC in this paper achieved a fourfold increase in the cooling power compared with that in our last report. A cooling power of 1.04 W at 80 K and a no-load temperature of 63 K are obtained with 500 W heating power. In the system, the acoustic pressure amplifier tube (APAT) plays an important role in coupling the thermoacoustic engine and the PTC. The effects of APAT on the system performance are investigated here through both numeric simulations and experiments. The simulation indicates that length of the APAT is limited due to impedance match requirement between the PTC and the engine, which is partly evidenced by experiments. Calculation also gives a good agreement between calculated pressure wave amplification ratio and experimental values. APAT with different lengths and diameters are investigated through experiments which indicate that there is an optimum diameter for the system performance.
High-intensity laser-plasma interaction with wedge-shaped-cavity targets
Authors: Theobald W. , Ovchinnikov V. , Ivancic S. , Eichman B. , Nilson P. M. , Delettrez J. A. , Yan R. , Li G. , Marshall F. J. , Meyerhofer D. D. , Myatt J. F. , Ren C. , Sangster T. C. , Stoeckl C. , Zuegel J. D. , Van Woerkom L. , Freeman R. R. , Akli K. U. , Giraldez E. , Stephens R. B.
Published: October 2010

High-intensity, short-pulse laser-interaction experiments with small-mass, wedge-shaped-cavity Cu targets are presented. The diagnostics provided spatially and spectrally resolved measurements of the Cu Kα line emission at 8 keV. The conversion efficiency of short-pulse laser energy into fast electrons was inferred from the x-ray yield for wedge opening angles between 30° and 60° and for s- and p-polarized laser irradiation. Up to 36±7% conversion efficiency was measured for the narrowest wedge with p-polarization. The results are compared with predictions from two-dimensional particle-in-cell simulations.
Many-body interactions and coarse-grained simulations of structure of nanoparticle-polymer melt mixtures
Authors: Khounlavong Landry , Pryamitsyn Victor , Ganesan Venkat
Published: October 2010

We present a computational approach for coarse-grained simulations of nanoparticle-polymer melt mixtures. We first examine the accuracy of an effective one-component approach based on a pair interaction approximation to polymer-mediated interactions, and demonstrate that even at low particle volume fractions, the polymer-mediated many-body interaction effects can prove significant in determining the structural characteristics of mixtures of nanoparticles and polymer melts. The origin of such effects is shown to arise from the extent of polymer perturbations resulting from the presence of the nanoparticles. To account for such effects, we propose a new simulation approach that employs a coarse-grained representation of the polymers to capture the many-body corrections to the polymer-mediated pair interaction potentials. The results of the coarse-grained simulations are shown to be in good quantitative agreement with the reference simulations. The method developed in this article is proposed as a tractable approach to coarse-grain and effect computer simulations of atomistic descriptions of polymer-nanoparticle systems.
Rhombohedral-to-orthorhombic transition and multiferroic properties of Dy-substituted BiFeO3
Authors: Khomchenko V. A. , Karpinsky D. V. , Kholkin A. L. , Sobolev N. A. , Kakazei G. N. , Araujo J. P. , Troyanchuk I. O. , Costa B. F. O. , Paixão J. A.
Published: October 2010

Investigation of crystal structure, ferroelectric, and magnetic properties of polycrystalline Bi1−xDyxFeO3 (0.1≤x≤0.2) samples was carried out. X-ray diffraction study revealed composition-driven rhombohedral-to-orthorhombic R3c→Pnma phase transition at x∼0.15. Both structural phases were found to coexist in a broad concentration range. Piezoresponse force microscopy found suppression of the parent ferroelectric phase upon dysprosium substitution. Magnetometric study confirmed that the A-site doping induces appearance of a weak ferromagnetic behavior. Both the ferroelectric and magnetic properties were shown to correlate with a structural evolution.
Transmission and reflection of internal wave beams
Authors: Gregory Kate D. , Sutherland Bruce R.
Published: October 2010

An existing method for predicting the partial transmission of plane internal gravity waves across a weakly stratified region is adapted so as to predict the transmission of internal wave beams having finite horizontal and vertical extent. The results are compared with laboratory experiments in which internal waves generated by an oscillating cylinder are incident upon a mixed region of varying depth and stratification. The results are in good agreement except when the characteristic frequency of the beam is close to the minimum buoyancy frequency of the weakly stratified mixed region. In this case, the predicted transmission coefficient varies rapidly with frequency and so is sensitive to small measurement errors. Applications of this method to atmospheric and oceanic internal waves are discussed.
Thermodynamic data and modeling of the water and ammonia-water phase diagrams up to 2.2 GPa for planetary geophysics
Authors: Choukroun Mathieu , Grasset Olivier
Published: October 2010

We present new experimental data on the liquidus of ice polymorphs in the H2O–NH3 system under pressure, and use all available data to develop a new thermodynamic model predicting the phase behavior in this system in the ranges (0–2.2 GPa; 175–360 K; 0–33 wt % NH3). Liquidus data have been obtained with a cryogenic optical sapphire-anvil cell coupled to a Raman spectrometer. We improve upon pre-existing thermodynamic formulations for the specific volumes and heat capacities of the solid and liquid phase in the pure H2O phase diagram to ensure applicability of the model in the low-temperature metastable domain down to 175 K. We compute the phase equilibria in the pure H2O system with this new model. Then we develop a pressure-temperature dependent activity model to describe the effect of ammonia on phase transitions. We show that aqueous ammonia solutions behave as regular solutions at low pressures, and as close-to-ideal solutions at pressure above 600 MPa. The computation of phase equilibria in the H2O–NH3 system shows that ice III cannot exist at concentrations above 5–10 wt % NH3 (depending on pressure), and ice V is not expected to form above 25%–27% NH3. We eventually address the applications of this new model for thermal and evolution models of icy satellites.
Photoelectron spectroscopic study of the hydrated nucleoside anions: Uridine−(H2O)n=–2, cytidine−(H2O)n=–2, and thymidine−(H2O)n=,1
Authors: Li Xiang , Wang Haopeng , Bowen Kit H.
Published: October 2010

The hydrated nucleoside anions, uridine−(H2O)n=0–2, cytidine−(H2O)n=0–2, and thymidine−(H2O)n=0,1, have been prepared in beams and studied by anion photoelectron spectroscopy in order to investigate the effects of a microhydrated environment on parent nucleoside anions. Vertical detachment energies (VDEs) were measured for all eight anions, and from these, estimates were made for five sequential anion hydration energies. Excellent agreement was found between our measured VDE value for thymidine−(H2O)1 and its calculated value in the companion article by S. Kim and H. F. Schaefer III.