bluuebunny/crossref_metadata_2025_split huggingface dataset:
NUCLEAR-SPIN-BASED MEASUREMENTS OF QUANTUM HALL SYSTEMS
Authors: HIRAYAMA YOSHIRO 
Published: June 2009

Nuclear magnetic resonance (NMR) is widely used in the physical, chemical, and biological sciences. However, conventional NMR techniques based on induction-detection have drawbacks of low-sensitivity and the need of a relatively large sample. It is not suitable to investigate single or double layers (or their nanostructure), which is essential in studying quantum Hall (QH) effects. In this presentation, I discussed a resistively-detected technique to overcome the low-sensitivity limitation of conventional NMR and its application to QH systems. Resistively-detected nuclear-spin-based measurements rely on enhanced interactions between electron and nuclear spins at the degenerate point of different electron-spin states. For example, at the ν = 2/3 degenerate point in a AlGaAs / GaAs system,1–3 nuclear-spin polarization far beyond the thermal equilibrium is generated using current flow (dynamic nuclear-spin polarization). Moreover, nuclear-spin polarization can be detected as enhanced resistance, which is proportional to the magnetization, Mz, of nuclear spins.2 It should be stressed that the special states of ν = 2/3 are needed for dynamic nuclear-spin polarization and Mz detection, but we can apply NMR spectrum and nuclear-spin relaxation (T1 time) measurements for any state we want to estimate. These nuclear-spin-based measurements were successfully applied to characterize QH systems, especially their electron-spin features, using single and double layer systems where characteristics are controlled electrically by the gate biases. For a single layer, we could clarify skyrmion,2 spin-polarization of composite fermion,4 and enhanced spin-orbit interactions in a strongly asymmetric confinement.5 Exciting phases, like a canted antiferromagnetic phase, were studied in a double layer QH system with a total filling factor of 2 (Refs. 6, 7). The low-frequency mode was sensitively detected by monitoring T1, reflecting correlated electron spin features.7 The clear observations of the characteristics, which are difficult to detect in conventional transport and optical measurements, make nuclear-spin-based measurement combined with resistance-detection a versatile and powerful tool for studying QH physics. Possible extensions of such measurements to semiconductor nanosystems were also discussed. The experiments discussed here were mainly carried out at NTT Basic Research Laboratories in collaboration with K. Muraki, N. Kumada, K. Takashina, K. Hashimoto, S. Watanabe and G. Yusa. Note from Publisher: This article contains the abstract only.
GENERAL OVERVIEW OVER INVESTIGATIONS ON LOW-DIMENSIONAL CARBON-BASED MATERIALS IN MAGNETIC FIELDS ABOVE 50 T
Authors: PORTUGALL OLIVER 
Published: June 2009

Carbon nanotubes have been intensively investigated in pulsed magnetic fields, mainly to identify the effect of a magnetic flux along the tube axis on the energy band structure. Clear manifestations of the Ahoronov-Bohm effect have been observed in near-infrared absorption measurements on suspended tubes1 as well as in single-tube transport experiments.2 Subsequent studies have shed light on the excitonic nature of optical excitations3 and the magnetic-field induced optical activity of such excitons.4,5 Ongoing activities are focussing on the magnetic alignment dynamics of carbon nanotubes in liquid suspension which has the potential to provide valuable information on their magnetic susceptibility. Experimental investigations on graphene in pulsed magnetic fields are far less advanced than those on carbon nanotubes. This is due to various experimental factors such as intrinsically short integration times for optical experiments and the destructive effect of electromagnetic perturbations on insufficiently screened transport samples. First results have nevertheless been obtained in both cases: Previous absorption measurements6 up to 32 T have been extended to higher fields thereby confirming the characteristic B1/2-dependence of energy levels. Transport measurements, on the other hand, have revealed extended plateaus in the two-terminal resistance of graphene.7 In this talk we gave a complete overview over recent and ongoing experimental investigations on carbon nanotubes and graphene in magnetic fields above 50 T. We referred to the work of several international collaborations including groups from Houston, Los Alamos, Berlin, Oxford, Tokyo, Dublin, Grenoble and Toulouse. Note from Publisher: This article contains the abstract only.
NONCONFORMING FINITE ELEMENT METHODS FOR THE THREE-DIMENSIONAL HELMHOLTZ EQUATION: ITERATIVE DOMAIN DECOMPOSITION OR GLOBAL SOLUTION?
Authors: GAUZELLINO PATRICIA M. , ZYSERMAN FABIO I. , SANTOS JUAN E. 
Published: June 2009

Iterative domain decomposition (DD) nonconforming finite element methods for the Helmholtz equation attempt to solve two problems. First, there exists no efficient algorithms able to solve the large sparse linear system arising from the discretization of the equation via the standard finite elements method. Secondly, even when DD methods generally yield small matrices, standard conforming elements, such as Q1 elements, force the transmission of a relatively large amount of data among subdomains.In this paper, we compared performance of global methods and a set of DD techniques to solve the Helmholtz equation in a three-dimensional domain. The efficiency of the algorithms is measured in terms of CPU time usage and memory requirements. The role of domain size and the linear solver type used to solve each local problem within each subdomain was also analyzed. The numerical results show that iterative DD methods perform far better than global methods. In addition, iterative DD methods involving small subdomains work better than those with subdomains involving a large number of elements. Properties of the iterative DD algorithms such as scalability, robustness, and parallel performance are also analyzed.
Observational Study of Wind Channeling within the St. Lawrence River Valley
Authors: Carrera Marco L. , Gyakum John R. , Lin Charles A. 
Published: June 2009

Abstract
The presence of orography can lead to thermally and dynamically induced mesoscale wind fields. The phenomenon of channeling refers to the tendency for the winds within a valley to blow more or less parallel to the valley axis for a variety of wind directions above ridge height. Channeling of surface winds has been observed in several regions of the world, including the upper Rhine Valley of Germany, the mountainous terrain near Basel, Switzerland, and the Tennessee and Hudson River Valleys in the United States. The St. Lawrence River valley (SLRV) is a primary topographic feature of eastern Canada, extending in a southwest–northeast direction from Lake Ontario, past Montreal (YUL) and Quebec City (YQB), and terminating in the Gulf of St. Lawrence. In this study the authors examine the long-term surface wind climatology of the SLRV and Lake Champlain Valley (LCV) as represented by hourly surface winds at Montreal, Quebec City, and Burlington, Vermont (BTV). Surface wind channeling is found to be prominent at all three locations with strong bidirectionalities that vary seasonally. To assess the importance of the various channeling mechanisms the authors compared the joint frequency distributions of surface wind directions versus 925-hPa geostrophic wind directions with those obtained from conceptual models. At YUL, downward momentum transport is important for geostrophic wind directions ranging from 240° to 340°. Pressure-driven channeling is the dominant mechanism producing northeasterly surface winds at YUL. These northeasterlies are most prominent in the winter, spring, and autumn seasons. At YQB, pressure-driven channeling is the dominant physical mechanism producing channeling of surface winds throughout all seasons. Of particular importance, both YUL and YQB exhibit countercurrents whereby the velocity component of the wind within the valley is opposite to the component above the valley. Forced channeling was found to be prominent at BTV, with evidence of diurnal thermal forcing during the summer season. Reasons for the predominance of pressure-driven channeling at YUL and YQB and forced channeling at BTV are discussed.
Spectral Retrieval of Latent Heating Profiles from TRMM PR Data. Part IV: Comparisons of Lookup Tables from Two- and Three-Dimensional Cloud-Resolving Model Simulations
Authors: Shige Shoichi , Takayabu Yukari N. , Kida Satoshi , Tao Wei-Kuo , Zeng Xiping , Yokoyama Chie , L’Ecuyer Tristan 
Published: June 2009

Abstract
The spectral latent heating (SLH) algorithm was developed to estimate latent heating profiles for the Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR). The method uses TRMM PR information (precipitation-top height, precipitation rates at the surface and melting level, and rain type) to select heating profiles from lookup tables (LUTs). LUTs for the three rain types—convective, shallow stratiform, and anvil rain (deep stratiform with a melting level)—were derived from numerical simulations of tropical cloud systems from the Tropical Ocean and Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) using a cloud-resolving model (CRM).
The two-dimensional (2D) CRM was used in previous studies. The availability of exponentially increasing computer capabilities has resulted in three-dimensional (3D) CRM simulations for multiday periods becoming increasingly prevalent. In this study, LUTs from the 2D and 3D simulations are compared. Using the LUTs from 3D simulations results in less agreement between the SLH-retrieved heating and sounding-based heating for the South China Sea Monsoon Experiment (SCSMEX). The level of SLH-estimated maximum heating is lower than that of the sounding-derived maximum heating. This is explained by the fact that using the 3D LUTs results in stronger convective heating and weaker stratiform heating above the melting level than is the case if using the 2D LUTs. More condensate is generated in and carried from the convective region in the 3D model than in the 2D model, and less condensate is produced by the stratiform region’s own upward motion.
Influence of Daily Rainfall Characteristics on Regional Summertime Precipitation over the Southwestern United States
Authors: Anderson Bruce T. , Wang Jingyun , Gopal Suchi , Salvucci Guido 
Published: June 2009

Abstract
The regional variability in the summertime precipitation over the southwestern United States is studied using stochastic chain-dependent models generated from 70 yr of station-based daily precipitation observations. To begin, the spatiotemporal structure of the summertime seasonal mean precipitation over the southwestern United States is analyzed using two independent spatial cluster techniques. Four optimal clusters are identified, and their structures are robust across the techniques used. Next, regional chain-dependent models—comprising a previously dependent occurrence chain, an empirical rainfall coverage distribution, and an empirical rainfall amount distribution—are constructed over each subregime and are integrated to simulate the regional daily precipitation evolution across the summer season. Results indicate that generally less than 50% of the observed interannual variance of seasonal precipitation in a given region lies outside the regional chain-dependent models’ stochastic envelope of variability; this observed variance, which is not captured by the stochastic model, is sometimes referred to as the “potentially predictable” variance. In addition, only a small fraction of observed years (between 10% and 20% over a given subregime) contain seasonal mean precipitation anomalies that contribute to this potentially predictable variance. Further results indicate that year-to-year variations in daily rainfall coverage are the largest contributors to potentially predictable seasonal mean rainfall anomalies in most regions, whereas variations in daily rainfall frequency contribute the least. A brief analysis for one region highlights how the identification of years with potentially predictable precipitation characteristics can be used to better understand large-scale circulation patterns that modulate the underlying daily rainfall processes responsible for year-to-year variations in regional rainfall.
Effects of Climate Variability on Water Storage in the Colorado River Basin
Authors: Hurkmans Ruud , Troch Peter A. , Uijlenhoet Remko , Torfs Paul , Durcik Matej 
Published: June 2009

Abstract
Understanding the long-term (interannual–decadal) variability of water availability in river basins is paramount for water resources management. Here, the authors analyze time series of simulated terrestrial water storage components, observed precipitation, and discharge spanning 74 yr in the Colorado River basin and relate them to climate indices that describe variability of sea surface temperature and sea level pressure in the tropical and extratropical Pacific. El Niño–Southern Oscillation (ENSO) indices in winter [January–March (JFM)] are related to winter precipitation as well as to soil moisture and discharge in the lower Colorado River basin. The low-frequency mode of the Pacific decadal oscillation (PDO) appears to be strongly correlated with deep soil moisture. During the negative PDO phase, saturated storage anomalies tend to be negative and the “amplitudes” (mean absolute anomalies) of shallow soil moisture, snow, and discharge are slightly lower compared to periods of positive PDO phases. Predicting interannual variability, therefore, strongly depends on the capability of predicting PDO regime shifts. If indeed a shift to a cool PDO phase occurred in the mid-1990s, as data suggest, the current dry conditions in the Colorado River basin may persist.
Assessing the Performance of the Dissipation Parameterizations in WAVEWATCH III Using Collocated Altimetry Data
Authors: Kalantzi Georgia D. , Gommenginger Christine , Srokosz Meric 
Published: June 2009

Abstract
Wave-breaking dissipation is one of the least understood processes implemented in contemporary wave models. Significant effort has been put in its parameterization, but it has not proven to be totally satisfactory, either theoretically or practically. In this work, the WAVEWATCH III (version 2.22; Tolman) wave model is used to evaluate the two wind input/dissipation source term packages that it includes: (i) Wave Model (WAM) cycle 3 (WAMDIG) and (ii) Tolman and Chalikov. Global model outputs were obtained under the same wind forcing for the two dissipation formulations and were collocated in space and time in the north Indian Ocean with Ocean Topography Experiment (TOPEX) altimeter data. The performance of the model was assessed by evaluating the statistical behavior of the collocated datasets. The parameters examined were significant wave height, wind speed, wind direction, wave direction, wave height for fully developed seas, and energy loss due to wave breaking. From the results, the behavior of the input/dissipation formulations in specific wind and wave conditions was identified; that is, the results give insight to the way the two source term packages “work” and how they respond to local wind sea or swell. Specifically, both of the packages were unable to perform adequately during a season when the area can be mostly affected by swell. However, the results confirmed that the examination of only integral spectral wave parameters does not give information on the inherent physical characteristics of the formulations. Further study, on the basis of point spectra, is necessary to examine the formulations’ performance across the wave spectrum.
An Examination of WRF 3DVAR Radar Data Assimilation on Its Capability in Retrieving Unobserved Variables and Forecasting Precipitation through Observing System Simulation Experiments
Authors: Sugimoto Soichiro , Crook N. Andrew , Sun Juanzhen , Xiao Qingnong , Barker Dale M. 
Published: June 2009

Abstract
The purpose of this study is to investigate the performance of 3DVAR radar data assimilation in terms of the retrievals of convective fields and their impact on subsequent quantitative precipitation forecasts (QPFs). An assimilation methodology based on the Weather Research and Forecasting (WRF) model three-dimensional variational data assimilation (3DVAR) and a cloud analysis scheme is described. Simulated data from 25 Weather Surveillance Radar-1988 Doppler (WSR-88D) radars are assimilated, and the potential benefits and limitations of the assimilation are quantitatively evaluated through observing system simulation experiments of a dryline that occurred over the southern Great Plains. Results indicate that the 3DVAR system is able to analyze certain mesoscale and convective-scale features through the incorporation of radar observations. The assimilation of all possible data (radial velocity and reflectivity factor data) results in the best performance on short-range precipitation forecasting. The wind retrieval by assimilating radial velocities is of primary importance in the 3DVAR framework and the storm case applied, and the use of multiple-Doppler observations improves the retrieval of the tangential wind component. The reflectivity factor assimilation is also beneficial especially for strong precipitation. It is demonstrated that the improved initial conditions through the 3DVAR analysis lead to improved skills on QPF.
An exploratory study of physical activity and perceived barriers to exercise in ambulant people with neuromuscular disease compared with unaffected controls
Authors: Phillips Margaret , Flemming Nicola , Tsintzas Kostas 
Published: June 2009

Objective: To determine activity patterns and perceived barriers to exercise in ambulant people with neuromuscular disease compared with ambulatory controls. Design: Prospective controlled parallel group design. Setting: Outpatient clinic and community. Subjects: Thirteen ambulatory people with neuromuscular disease and 18 ambulatory controls. Main measures: Heart rates were recorded during sedentary activity and treadmill walking at various speeds to indicate activity threshold (flex heart rate), followed by ambulatory heart rate monitoring over two weekdays and one weekend day. The EPIC-Norfolk Physical Activity Questionnaire-2 and Barriers to Physical Activity and Disability Survey were completed. Results: Participants with neuromuscular disease were less active than controls as estimated by both the EPIC-Norfolk Physical Activity Questionnaire-2, P<0.004, and the flex heart rate method, P<0.05. The number of perceived barriers was greater in the neuromuscular group, a mean of 7 (SD 4.2) barriers, compared with mean 3 (SD 2.1) barriers for controls, P<0.05. Specific barriers differed, with the barriers of `pain', `lack of energy' and `exercise is too difficult' showing the greatest discrepancy and being higher in the neuromuscular disease group. Conclusion: Physical activity, as determined by two different methods, was less and barriers to exercise greater in people with neuromuscular disease compared with healthy controls. Specific barriers were different in the two groups. This information could assist in the design of achievable and effective exercise programmes for people with neuromuscular disease.
The effects of a `home-based' task-oriented exercise programme on motor and balance performance in children with spastic cerebral palsy and severe traumatic brain injury
Authors: Katz-Leurer Michal , Rotem Hemda , Keren Ofer , Meyer Shirley 
Published: June 2009

Objectives: To evaluate the feasibility and the ability to recruit and retain children with severe traumatic brain injury or cerebral palsy, and their families, to a simple home-based exercise programme and to assess the immediate and short-term effects of such intervention on reducing impairment and improving function. Study design: Randomized clinical trial. Participants: Twenty children aged 7—13 years, with traumatic brain injury (N = 10) or cerebral palsy (N = 10) who were independent ambulators. Five children from each group were randomly assigned to a control group — regular daily activities, or to an experimental group — regular daily activities plus a home-based task-oriented exercise programme of sit-to-stand and step-up exercise, for six weeks. Outcome measures: Feasibility: The number of participants who completed the programme protocol. Efficacy: Timed Up and Go Test and Functional Reach Test were used as functional balance tests. Maximal isometric strength was assessed by using a hand-held dynamometer; walking performance was assessed by the 10 m walk test, 2-minute walk test and Energy Expenditure Index. Results: Nine children completed all parts of the training programme. At the end of the intervention period an increase of 3—4 cm in the mean Functional Reach Test and a reduction of 1.6 ± 2.1 seconds in the Timed Up and Go Test were noted (P<0.01) in the experimental group while no changes were noted in the control group. In all other outcomes assessed no significant differences were noted between groups. The positive change in balance performance in the experimental group was maintained during a six-week follow-up period. Conclusions: A home-based task-oriented exercise programme can improve balance performance in children with spastic cerebral palsy or severe traumatic brain injury.
Naturally acquired tolerance and sensitization to minor histocompatibility antigens in healthy family members
Authors: van Halteren Astrid G. S. , Jankowska-Gan Ewa , Joosten Antoinette , Blokland Els , Pool Jos , Brand Anneke , Burlingham William J. , Goulmy Els 
Published: June 2009

Abstract
Bidirectional cell transfer during pregnancy frequently leads to postpartum persistence of allogeneic cells and alloimmune responses in both the mother and in her offspring. The life-long consequences of naturally acquired alloimmune reactivity are probably of importance for the outcome of allogeneic stem cell transplantation. We investigated the presence of CD8pos minor histocompatibility (H) antigen–specific cytotoxic T lymphocytes (TCTL) and CD8pos minor H antigen–specific T regulator cells (TREG) in peripheral blood cells obtained from 17 minor H antigen–disparate mother-offspring pairs. Absence of minor H antigen–specific TREG, as marked by the feasibility to expand TCTL from isolated tetramerpos populations, was observed in 6 mothers and 1 son. The presence of minor H alloantigen–specific TREG was observed in 4 mothers and 5 sons. These TREG were detected within isolated tetramerdim staining fractions and functioned in a CTLA-4–dependent fashion. Our study indicates that both TCTL and TREG mediated alloimmunity against minor H antigens may be present in healthy female and male hematopoietic stem cell donors, potentially influencing graft-versus-host reactivity in different ways.