bluuebunny/crossref_metadata_2025 huggingface dataset:
Fur seals, whales and tourists: a commercial history of Deception Island, Antarctica
Authors: Dibbern J. Stephen
Published: September 2009

Deception Island in the South Shetland Islands was the site of some of the earliest commercial activity to be carried out in the Antarctic with the early 19th century hunting of Antarctic fur seals. Nearly a century later it was the site of the most extensive anchorage for the reconstructed ships and ocean liners used as non-pelagic whale processing factories. Deception was also the site of what is the only successful land based commercial activity in Antarctic history. The Hektor whaling station operated in Whalers Bay from 1912 until 1931. Most of the remains of the station have now been obliterated by the volcanic activity that occurred in the late 1960s and 1970. By the later part of the twentieth century Deception Island had become a regular stop for the growing Antarctic tourist cruise industry. No other place in Antarctica has been so thoroughly identified with commercial activity.
A history of the exploitation of the Ross Sea, Antarctica
Authors: Ainley David G.
Published: September 2009

Recent analyses of anthropogenic impacts on marine systems have shown that the Ross Sea is the least affected stretch of ocean on Earth, although historical effects were not included in those studies. Herein the literature is reviewed in order to quantify the extent of extraction of biological resources from the Ross Sea continental shelf and slope from the start of the 20th century. There was none before that time. An intense extraction of Weddell sealsLeptonychotes weddelliiby the expeditions of the ‘heroic’ period and then by New Zealand to feed sled dogs in the 1950–1980s caused the McMurdo Sound population to decrease permanently. Otherwise no other sealing occurred. Blue whalesBalaenoptera musculus intermediawere extirpated from waters of the shelf break front during the 1920s, and have not reappeared. Minke whalesB. bonaerensisprobably expanded into the blue whale vacated habitat, but were then hunted during the 1970–1980s; their population has since recovered. Some minke whales are now taken in ‘scientific whaling’, twice more from the slope compared to the shelf. Other hunted cetaceans never occurred over the shelf and very few ever occurred in slope waters, and therefore their demise from whaling does not apply to the Ross Sea. No industrial fishing occurred in the Ross Sea until the 1996–1997 summer, when a fishery for Antarctic toothfishDissostichus mawsoniwas initiated, especially along the slope. This fishery has grown since then with effects on the ecosystem recently becoming evident. There is probably no other ocean area where the details of biological exploitation can be so elucidated. It appears that the Ross Sea continental shelf remains the least affected of any on the globe. However the same cannot be said of the slope.
SporadicSalmonella entericaserotype Javiana infections in Georgia and Tennessee: a hypothesis-generating study
Authors: CLARKSON L. S. , TOBIN-D'ANGELO M. , SHULER C. , HANNA S. , BENSON J. , VOETSCH A. C.
Published: September 2009

From 1996 to 2004, the incidence ofSalmonellaJaviana infections increased in FoodNet, the U.S. national active foodborne disease surveillance programme. Contact with amphibians and consumption of tomatoes have been associated with outbreaks ofS. Javiana infection. To generate and test hypotheses about risk factors associated with sporadicS. Javiana infections, we interviewed patients with laboratory-confirmedS. Javiana infection identified in Georgia and Tennessee during August–October 2004. We collected data on food and water consumption, animal contact, and environmental exposure from cases. Responses were compared with population-based survey exposure data. Seventy-two of 117 identifiedS. Javiana case-patients were interviewed. Consumption of well water [adjusted odds ratio (aOR) 4·3, 95% confidence interval (CI) 1·6–11·2] and reptile or amphibian contact (aOR 2·6, 95% CI 0·9–7·1) were associated with infection. Consumption of tomatoes (aOR 0·5, 95% CI 0·3–0·9) and poultry (aOR 0·5, 95% CI 0·2–1·0) were protective. Our study suggests that environmental factors are associated withS. Javiana infections in Georgia and Tennessee.
Dirty hands: bacteria of faecal origin on commuters' hands
Authors: JUDAH G. , DONACHIE P. , COBB E. , SCHMIDT W. , HOLLAND M. , CURTIS V.
Published: September 2009

Although many studies have investigated bacteria on the hands of health-care workers and caregivers, few have looked at microbiological contamination on the hands of the general adult public. This study investigated faecal bacteria on the hands of commuters in five UK cities. Of the 404 people sampled 28% were found to have bacteria of faecal origin on their hands. A breakdown by city showed that the proportion of people with contaminated hands increased the further north the city of investigation (P<0·001), an effect which was due in large part to a significant trend in men but not in women. Bus users were more contaminated than train users. The results of this exploratory study indicate that hand hygiene practices in the UK may be inadequate and that faecal indicator bacteria on hands may be used to monitor the effect of hand-washing promotion campaigns.
Anti-VP6 IgG antibodies against group A and group C rotaviruses in South India
Authors: MUKHOPADHYA I. , ANBU D. , ITURRIZA-GOMARA M. , GRAY J. J. , BROWN D. W. , KAVANAGH O. , ESTES M. K. , KANG G.
Published: September 2009

In an epidemiological survey from South India, 936 serum samples were tested for IgG against recombinant baculovirus-expressed VP6 proteins from human group A and group C rotaviruses. The overall seroprevalence for group A was 100% and for group C was 25·32% (95% CI 22·64–28·21). The lowest seroprevalence for group C was in children aged <10 years (16·79%). An age-related rise in seroprevalence in group C, but not group A, suggests different patterns of exposure. Seroprevalence was similar in rural and urban subjects, unlike the higher prevalence in rural subjects in studies elsewhere.
Individual responsibility for what? – A conceptual framework for exploring the suitability of private financing in a publicly funded health-care system
Authors: Tinghőg Gustav , Carlsson Per , Lyttkens Carl H.
Published: September 2009

Policymakers in publicly funded health-care systems are frequently required to make intricate decisions on which health-care services to include or exclude from the basic health-care package. Although it seems likely that the concept of individual responsibility is an essential feature of such decisions, it is rarely explicitly articulated or evaluated in health policy. This paper presents a tentative conceptual framework for exploring when health-care services contain characteristics that facilitate individual responsibility through private financing. Six attributes for exploring the suitability of private financing for specific health-care commodities are identified: (i) it should enable individuals to value the need and quality both before and after utilization; (ii) it should be targeted toward individuals with a reasonable level of individual autonomy; (iii) it should be associated with low levels of positive externalities; (iv) it should be associated with a demand sufficient to generate a private market; (v) it should be associated with payments affordable for most individuals; and finally, (vi) it should be associated with ‘lifestyle enhancements’ rather than ‘medical necessities’. The tentative framework enables exploration of individual responsibility connected to health care as a heterogeneous group of commodities, and allows policymakers to make decisions on rationing by design rather than default.
On the losses in substrate-integrated waveguides and cavities
Authors: Bozzi Maurizio , Pasian Marco , Perregrini Luca , Wu Ke
Published: September 2009

This paper presents a study of losses in substrate-integrated waveguides (SIWs) and cavities. Three mechanisms of losses are considered and separately investigated, namely radiation leakage, ohmic loss, and dielectric loss. A systematic comparison of waveguides with different geometry, operating at different frequencies, is reported. This study permits to give a physical interpretation of the loss mechanisms and to identify design criteria to minimize losses. A similar analysis is also developed in this work for the case of SIW resonant cavities. For these structures, a different variation of losses with respect to frequency is found, which reduces the effectiveness of the design criteria established for SIWs.
Forecasting of scatterometer‐derived wind fields in the north Indian Ocean with a data‐adaptive approach
Authors: Basu Sujit , Sharma Rashmi , Agarwal Neeraj , Kumar Raj , Sarkar Abhijit
Published: September 2009

A combination of genetic algorithm (GA) and empirical orthogonal function (EOF) analysis has been employed to forecast satellite scatterometer–observed surface winds in the north Indian Ocean. The EOFs are used to compress the major part of the spatial variability into a few eigenmodes. The temporal variability is contained in the corresponding principal components (PC) which have been subjected to singular spectrum analysis for filtering out the random part. Forecast of the deterministic part has been carried out using GA with lead times varying from 1 to 4 days. The entire analysis has been done separately for the zonal and meridional winds. Finally, predicted wind fields have been generated as linear combinations of the spatial eigenmodes weighted by the predicted PCs. Forecast quality has been evaluated by comparing with an independent validation data set as well as with buoy data. The performance of the algorithm has been found to be quite encouraging.
A simple model of convection with memory
Authors: Davies Laura , Plant Robert S. , Derbyshire Stephen H.
Published: September 2009

There are at least three distinct time scales that are relevant for the evolution of atmospheric convection. These are the time scale of the forcing mechanism, the time scale governing the response to a steady forcing, and the time scale of the response to variations in the forcing. The last of these,tmem, is associated with convective life cycles, which provide an element of memory in the system. A highly simplified model of convection is introduced, which allows for investigation of the character of convection as a function of the three time scales. For shorttmem, the convective response is strongly tied to the forcing as in conventional equilibrium parameterization. For longtmem, the convection responds only to the slowly evolving component of forcing, and any fluctuations in the forcing are essentially suppressed. At intermediatetmem, convection becomes less predictable: conventional equilibrium closure breaks down and current levels of convection modify the subsequent response.
New tectonic configuration in NE Iran: Active strike‐slip faulting between the Kopeh Dagh and Binalud mountains
Authors: Shabanian Esmaeil , Bellier Olivier , Siame Lionel , Arnaud Nicolas , Abbassi Mohammad R. , Cochemé Jean‐Jacques
Published: September 2009

In this paper, a combined approach of geomorphic analyses, detailed geological mapping on SPOT 5 satellite images and field surveys, complemented by radiometric dating (40Ar/39Ar) allows proposing a new and consistent tectonic configuration for the northeastern Arabia‐Eurasia collision zone. It favors a simple strike‐slip faulting mechanism in NE Iran accommodating the northward motion of central Iran with respect to Eurasia between the Binalud and Kopeh Dagh mountains. Our results demonstrate that ∼2 mm/a (∼25%) of this northward motion has been transferred from the Binalud to the Kopeh Dagh through the Meshkan Transfer Zone since ∼5 Ma. The modern state of stress deduced from fault kinematics analyses shows N30°E trending maximum stress axis and confirms a dominant strike‐slip faulting mechanism. Combining our geological data with other available data, we conclude that kinematics of deformation can be appropriately described by rigid block faulting in NE Iran; instead, the continuous deformation as it has been thought during the last 3 decades.
Comparison of reflected GPS wind speed retrievals with dropsondes in tropical cyclones
Authors: Katzberg Stephen J. , Dunion Jason
Published: September 2009

In an earlier communication, data were presented that demonstrated that quasi‐specular, L‐Band reflection measurements could be used to infer ocean surface winds. Applying an indirect calibration technique, a mean square slope versus surface wind speed was developed and reported. Retrievals using this calibration showed that the resulting surface wind speeds were comparable with other measurements. This report extends the previous results by presenting direct comparisons between GPS dropwindsonde (dropsonde)‐reported wind speeds and the Bi‐static GPS wind speed retrievals for data sets acquired in 2008. Editing of the Bi‐static GPS data will be discussed that takes into effect overland and inside‐the‐eye winnowing. Data will be presented with a regression line to determine the comparative relationship. It will be shown that good agreement exists between the reflected Bi‐static GPS retrieved winds and those reported by the dropsondes when certain well‐defined types of data are excluded.
Effect of wintertime low‐pressure systems on the Atlantic inflow to the Nordic seas
Authors: Richter K. , Furevik T. , Orvik K. A.
Published: September 2009

The response of the Atlantic inflow to the Nordic seas to a variable wind field is investigated using storm track data and observed current meter data from the three inflowing Iceland, Faroe, and Shetland branches and from the Svinøy section off the west coast of Norway. The Atlantic inflow is found to be anomalously large in the Shetland and Svinøy sections for 4–5 days after a storm passage with maximum response after 2–3 days. No similar inflow response was found in the Iceland and Faroe sections. On the contrary, the Faroe current becomes weaker 2 days after the inflow maxima in the Shetland and Svinøy sections. We speculate that this is a lagged response to increased sea level height north of the Greenland‐Scotland Ridge. For longer timescales, most of the winter anomalies in the volume transports through the Shetland and Svinøy sections are related to cyclone variability, with the number of storms, the residence time, and the intensity of the storms being critical factors.
Identification of aerosol type over the Arabian Sea in the premonsoon season during the Integrated Campaign for Aerosols, Gases and Radiation Budget (ICARB)
Authors: Kalapureddy M. C. R. , Kaskaoutis D. G. , Ernest Raj P. , Devara P. C. S. , Kambezidis H. D. , Kosmopoulos P. G. , Nastos P. T.
Published: September 2009

A discrimination of the different aerosol types over the Arabian Sea (AS) during the Integrated Campaign for Aerosols, Gases and Radiation Budget (ICARB‐06) is made using values of aerosol optical depth (AOD) at 500 nm (AOD500) and Ångström exponent (α) in the spectral band 340–1020 nm (α340–1020). For this purpose, appropriate thresholds for AOD500 and α340–1020 are applied. It is shown that a single aerosol type in a given location over the AS can exist only under specific conditions while the presence of mixed aerosols is the usual situation. Analysis indicates that the dominant aerosol types change significantly in the different regions (coastal, middle, and far) of AS. Thus the urban/industrial aerosols are mainly observed in coastal AS, the desert dust particles occur in the middle and northern AS, while clear maritime conditions mainly occur in far AS. Spectral AOD and Ångström exponent data were analyzed to obtain information about the adequacy of the simple use of the Ångström exponent and spectral variation of α for characterizing the aerosols. Using the least squares method, α is calculated in the spectral interval 340–1020 nm along with the coefficients a1 and a2 of the second‐order polynomial fit to the plotted logarithm of AOD versus the logarithm of wavelength. The results show that the spectral curvature can effectively be used as a tool for their discrimination, since the fine mode aerosols exhibit negative curvature, while the coarse mode particles exhibit positive curvature. The correlation between the coefficients a1 and a2 with the Ångström exponent, and the atmospheric turbidity, is further investigated.
Aeronomy of Ice in the Mesosphere receiver/communication lock analysis: When bad space weather is good
Authors: Baker D. N. , McCollough J. P. , McPherron R. L. , Ryan S. M. , Westfall J. C. , Russell J. M. , Bailey S. M.
Published: September 2009

The Aeronomy of Ice in the Mesosphere (AIM) spacecraft (launched on 25 April 2007) is in low‐Earth polar orbit. Some days after launch, AIM began to exhibit a problem in which it would not always achieve proper receiver uplink communications lock (termed “bitlock” throughout this paper). In this context, we examined solar conditions and geomagnetic activity to search for possible connections with periods of bitlock problems. We have found that higher solar wind speeds often lead to greater geomagnetic activity and this, in turn, seems to lead to improved AIM operations. Here we present analysis of AIM bitlock to show when relative improvements or diminutions in spacecraft operations have occurred. We conclude that the spacecraft bitlock problem is related, in part, to space environment conditions (along with a gradual secular trend toward lower performance). The best indicator of “good lock” state (of all we have evaluated) is associated with a shift from low (or quiet) geomagnetic and solar wind conditions toward more disturbed conditions.
Bone Marrow-Derived Progenitor Cells in the Early Phase of Ischemic Stroke: Relation with Stroke Severity and Discharge Outcome
Authors: Cesari Francesca , Nencini Patrizia , Nesi Mascia , Caporale Roberto , Giusti Betti , Abbate Rosanna , Gori Anna Maria , Inzitari Domenico
Published: September 2009

A limited number of studies suggested that in ischemic stroke patients, the number of bone marrow circulating progenitor cells (CPCs), either endothelial progenitor cells (EPCs) or CPCs, was negatively correlated with the number of infarcts as well as with the outcome. The aim of this study was to simultaneously measure CPCs and EPCs in the acute phase of ischemic stroke, and to establish whether a relationship exists with stroke severity and discharge outcome. In 67 (40 M; 27 F) ischemic stroke patients with a median age of 73 (21 to 91) years, the number of CPCs and EPCs was measured by flow cytometry and analyzed in relation to baseline NIH Stroke Scale score, ischemic stroke syndromes, and discharge outcome. Patients with partial anterior circulation syndrome showed a higher CPCs’ number with respect to patients with total anterior circulation syndrome. Moreover, a negative relationship between National Institutes of Health Stroke Scale score at the admission and CPCs number was observed. When the outcome was considered, patients discharged to home had a higher number of CPCs, but not of EPCs, compared with those moved to a rehabilitation unit. We report an association between the number of CPCs measured in the early phase after stroke presentation, neurologic severity, and discharge outcome.
High-resolution molecular images of rubrene single crystals obtained by frequency modulation atomic force microscopy
Authors: Minato Taketoshi , Aoki Hiroto , Fukidome Hirokazu , Wagner Thorsten , Itaya Kingo
Published: September 2009

Frequency modulation atomic force microscopy (FM-AFM) was employed to study molecular structures of rubrene single crystals in ultrahigh vacuum. Molecularly flat and extraordinarily wide terraces were extended over the width of more than a few micrometers with monomolecular steps. Molecular packing arrangements and internal structures were revealed by FM-AFM. The unit cell determined by FM-AFM was consistent with the lattice parameters of bulk crystal within the experimental error, suggesting that the surface structure of rubrene is not reconstructed.
Thermal stability of lanthanum in hafnium-based gate stacks
Authors: Medina-Montes M. I. , Selvidge M. V. , Herrera-Gomez A. , Aguirre-Tostado F. S. , Quevedo-Lopez M. A. , Wallace R. M.
Published: September 2009

The controlled addition of La to HfxSi1−xO2/SiO2/Si dielectric stacks has been shown to enable the engineering of the work function to appropriate levels when TaN or TiN is employed as the capping metal gate. Work function tuning has been suggested to be controlled by La diffusion into the Hf-based dielectric as a result of further thermal treatments. In this paper, we performed high resolution angle resolved x-ray photoelectron spectroscopy (ARXPS) studies to investigate the chemical depth profile distribution of TaN/La2O3/HfO2/SiO2/Si dielectric stacks exposed to a nitridation treatment by NH3 at 700 °C. The stoichiometry and distribution of the HfO2 and SiO2 layers was examined using a self-consistent ARXPS analysis. This study shows that La diffuses to the SiO2/HfO2 interface, and that subsequent rapid thermal annealing at 1000 °C for 5 s does not significantly change the La distribution.
Spatial variations in local switching parameters of ferroelectric random access memory capacitors
Authors: Wu D. , Kunishima I. , Roberts S. , Gruverman A.
Published: September 2009

Spatially resolved studies of the switching behavior of micrometer scale Pb(Zr,Ti)O3 capacitors have been performed by piezoresponse force microscopy (PFM). PFM spectroscopy and bias-dependent imaging of domain patterns have been used to investigate variability in local switching parameters and address the capacitor scaling effect on switching. It was found that average coercive voltage and imprint bias are independent of capacitor size and are similar to the corresponding parameters obtained by polarization hysteresis measurements. This can be attributed to the slow switching kinetics during quasistatic PFM measurements. The obtained results demonstrate a possibility of testing the submicron capacitors in real devices.
Intersubband selection and sum rules in a patterned inverse quantum dot array
Authors: Verma V. B. , Coleman J. J.
Published: September 2009

We present an analysis of the physics of intersubband transitions in a patterned inverse quantum dot (IQD) array. Numerical techniques for computing the oscillator strength for intersubband transitions are outlined along with the selection and sum rules. It is demonstrated that the polarization dependence of intersubband absorption can be controlled through appropriate design of the IQD array geometry.
Poissonian statistics of excitonic complexes in quantum dots
Authors: Abbarchi M. , Mastrandrea C. , Kuroda T. , Mano T. , Vinattieri A. , Sakoda K. , Gurioli M.
Published: September 2009

We report a detailed experimental investigation of the power dependence of excitonic complexes (neutral exciton, neutral biexciton, and charged exciton) confined in single self-assembled GaAs∕AlGaAs strain-free quantum dots grown by droplet epitaxy. By using the random population theory we show that, under stationary excitation, the power dependence of the excitonic complexes precisely follows the Poissonian statistics. This result allows us to determine with great accuracy the state filling condition of the quantum dots (QDs) and therefore to estimate the capture volume of the QDs.
Optical anisotropy readout in solid-state porphyrins for the detection of volatile compounds
Authors: Bussetti G. , Cirilli S. , Violante A. , Chiaradia P. , Goletti C. , Tortora L. , Paolesse R. , Martinelli E. , D’Amico A. , Di Natale C. , Giancane G. , Valli L.
Published: September 2009

The controlled adsorption of molecules of volatile compounds on Langmuir–Schäfer films of tetraphenylporphyrins produces a modification of the film optical anisotropy, as revealed by reflectance anisotropy spectroscopy (RAS). These experiments allow a better understanding of the molecular package occurring in the film as well as of its alteration upon the interaction with volatile compounds, helping in the comprehension of the mechanisms responsible for the binding of molecules. The results recommend RAS as a potential transducer technique for chemical sensing.
Electron tunneling characteristics on La0.7Sr0.3MnO3 thin-film surfaces at high temperature
Authors: Katsiev Khabiboulakh , Yildiz Bilge , Balasubramaniam Kavaipatti , Salvador Paul A.
Published: September 2009

We report on the electron tunneling characteristics on La0.7Sr0.3MnO3 (LSM) thin-film surfaces up to 580 °C in 10−3 mbar oxygen pressure, using scanning tunneling microscopy/spectroscopy (STM/STS). A thresholdlike drop in the tunneling current was observed at positive bias in STS, which is interpreted as a unique indicator for the activation polarization in cation-oxygen bonding on LSM cathodes. Sr-enrichment was found on the surface at high temperature using Auger electron spectroscopy, and was accompanied by a decrease in tunneling conductance in STS. This suggests that Sr-terminated surfaces are less active for electron transfer in oxygen reduction compared to Mn-terminated surfaces on LSM.
Synthesis, magnetic and electromagnetic wave absorption properties of porous Fe3O4/Fe/SiO2 core/shell nanorods
Authors: Chen Y. J. , Gao P. , Zhu C. L. , Wang R. X. , Wang L. J. , Cao M. S. , Fang X. Y.
Published: September 2009

Porous Fe3O4/Fe/SiO2 core/shell nanorods were fabricated, in which the diameter of the pores was 5–30 nm. The magnetic and electromagnetic properties were investigated. The temperature dependent magnetic measurements showed that these nanorods were ferromagnetic with a Verwey temperature of 129 K. The electromagnetic data indicated that effective complementarities between the dielectric loss and the magnetic loss were realized, suggesting that they have excellent electromagnetic wave absorption properties. Thus the porous core/shell nanorods could be used as a kind of candidate absorber.
Pressure dependence of argon cluster size for different nozzle geometries
Authors: Chen Guanglong , Kim Byunghoon , Ahn Byungnam , Kim Dong Eon
Published: September 2009

We experimentally study Rayleigh scattering from a cluster jet produced by high pressure argon gas expanding into vacuum through four different nozzles (a supersonic slit nozzle, a slit nozzle, a conical nozzle, and a sonic nozzle). The scattering signal intensity and the scattering image are recorded by photomultiplier tube and charge-coupled device camera, respectively. Based on the scattering image, the atom density in the gas flow is estimated. This allows for the comparison of the dependence of average cluster size on argon gas backing pressure between the nozzles. The experimental results show that the planar expansion developed from the supersonic slit and the slit nozzles exhibits the higher atom density than the axisymmetric expansion from the conical and the sonic nozzles. The slit nozzle is shown to have the highest pressure dependence of average cluster size. It is found that the supersonic slit nozzle is more favorable to the large clusters than the slit nozzle under the backing pressure of up to 50 bars, though it has the lower pressure dependence of average cluster size.
Comparison of a hydrogel model to the Poisson–Boltzmann cell model
Authors: Claudio Gil C. , Kremer Kurt , Holm Christian
Published: September 2009

We have investigated a single charged microgel in aqueous solution with a combined simulational model and Poisson–Boltzmann theory. In the simulations we use a coarse-grained charged bead-spring model in a dielectric continuum, with explicit counterions and full electrostatic interactions under periodic and nonperiodic boundary conditions. The Poisson–Boltzmann hydrogel model is that of a single charged colloid confined to a spherical cell where the counterions are allowed to enter the uniformly charged sphere. In order to investigate the origin of the differences these two models may give, we performed a variety of simulations of different hydrogel models which were designed to test for the influence of charge correlations, excluded volume interactions, arrangement of charges along the polymer chains, and thermal fluctuations in the chains of the gel. These intermediate models systematically allow us to connect the Poisson–Boltzmann cell model to the bead-spring model hydrogel model in a stepwise manner thereby testing various approximations. Overall, the simulational results of all these hydrogel models are in good agreement, especially for the number of confined counterions within the gel. Our results support the applicability of the Poisson–Boltzmann cell model to study ionic properties of hydrogels under dilute conditions.
Pressure induced magnetic and magnetocaloric properties in NiCoMnSb Heusler alloy
Authors: Nayak Ajaya K. , Suresh K. G. , Nigam A. K. , Coelho A. A. , Gama S.
Published: September 2009

The effect of pressure on the magnetic and the magnetocaloric (MC) properties around the martensitic transformation temperature in NiCoMnSb Heusler alloy has been studied. The martensitic transition temperature has significantly shifted to higher temperatures with pressure, whereas the trend is opposite with the application of applied magnetic field. The maximum magnetic entropy change around the martensitic transition temperature for Ni45Co5Mn38Sb12 is 41.4 J/kg K at the ambient pressure, whereas it is 33 J/kg K at 8.5 kbar. We find that by adjusting the Co concentration and applying suitable pressure, NiCoMnSb system can be tuned to achieve giant MC effect spread over a large temperature span around the room temperature, thereby making it a potential magnetic refrigerant material for applications.
Control of a high Reynolds number Mach 0.9 heated jet using plasma actuators
Authors: Kearney-Fischer M. , Kim J.-H. , Samimy M.
Published: September 2009

The results of particle image velocimetry (PIV) measurements in a high subsonic, heated, jet forced using localized arc filament plasma actuators (LAFPAs) show that LAFPAs can consistently produce significant mixing enhancement over a wide range of temperatures. These actuators have been used successfully in high Reynolds number, high-speed unheated jets. The facility consists of an axisymmetric jet with different nozzle blocks of exit diameter of 2.54 cm and variable jet temperature in an anechoic chamber. The focus of this paper is on a high subsonic (Mj=0.9) jet. Twelve experiments with various forcing azimuthal modes (m=0, 1, and ±1) and temperatures (To/Ta=1.0, 1.4, and 2.0) at a fixed forcing Strouhal number (StDF=0.3) have been conducted and PIV results compared with the baseline results to characterize the effectiveness of LAFPAs for mixing enhancement. Centerline velocity and turbulent kinetic energy as well as jet width are used for determining the LAFPAs’ effectiveness. The characteristics of large-scale structures are analyzed through the use of Galilean streamlines and swirling strength. Across the range of temperatures collected, the effectiveness of LAFPAs improves as temperature increases. Possible reasons for the increase in effectiveness are discussed.
Atomic resolution protein structure determination by three-dimensional transferred echo double resonance solid-state nuclear magnetic resonance spectroscopy
Authors: Nieuwkoop Andrew J. , Wylie Benjamin J. , Franks W. Trent , Shah Gautam J. , Rienstra Chad M.
Published: September 2009

We show that quantitative internuclear N15–C13 distances can be obtained in sufficient quantity to determine a complete, high-resolution structure of a moderately sized protein by magic-angle spinning solid-state NMR spectroscopy. The three-dimensional ZF-TEDOR pulse sequence is employed in combination with sparse labeling of C13 sites in the β1 domain of the immunoglobulin binding protein G (GB1), as obtained by bacterial expression with 1,3-C13 or 2-C13-glycerol as the C13 source. Quantitative dipolar trajectories are extracted from two-dimensional N15–C13 planes, in which ∼750 cross peaks are resolved. The experimental data are fit to exact theoretical trajectories for spin clusters (consisting of one C13 and several N15 each), yielding quantitative precision as good as 0.1 Å for ∼350 sites, better than 0.3 Å for another 150, and ∼1.0 Å for 150 distances in the range of 5–8 Å. Along with isotropic chemical shift-based (TALOS) dihedral angle restraints, the distance restraints are incorporated into simulated annealing calculations to yield a highly precise structure (backbone RMSD of 0.25±0.09 Å), which also demonstrates excellent agreement with the most closely related crystal structure of GB1 (2QMT, bbRMSD 0.79±0.03 Å). Moreover, side chain heavy atoms are well restrained (0.76±0.06 Å total heavy atom RMSD). These results demonstrate for the first time that quantitative internuclear distances can be measured throughout an entire solid protein to yield an atomic-resolution structure.
Negative capacitance in GaN∕AlGaN heterojunction dual-band detectors
Authors: Byrum L. E. , Ariyawansa G. , Jayasinghe R. C. , Dietz N. , Perera A. G. U. , Matsik S. G. , Ferguson I. T. , Bezinger A. , Liu H. C.
Published: September 2009

A study of trap states in n+-GaN∕AlGaN heterostructures using electrical, thermal, and optical analyses is reported. Capacitance-voltage-frequency measurements showed negative capacitance and dispersion, indicating interface trap states. Infrared spectra identified three impurity related absorption centers attributed to shallow Si-donor (pinned to the AlGaN barrier), N-vacancy/C-donor, and deep Si-donor (pinned to the GaN emitter) impurities with corresponding activation energies of 30.8±0.2, 125±1, and 140±2meV, respectively. The shallow Si-donor impurity had a relaxation time of 155±9μs, while the C-donor/N-vacancy and deep Si-donor impurities appear to behave as a single trap state with a relaxation time of 1.77±0.05μs. Multiple analysis techniques allowed the determination of the activation energies of these impurity related centers and the study of the effects of trap states on the electrical behavior of the detector.
Bipolar resistive switching performance of the nonvolatile memory cells based on (AgI)0.2(Ag2MoO4)0.8 solid electrolyte films
Authors: Yan X. B. , Yin J. , Guo H. X. , Su Y. , Xu B. , Li H. T. , Yan D. W. , Xia Y. D. , Liu Z. G.
Published: September 2009

Resistive switching memory cells with polycrystalline (AgI)0.2(Ag2MoO4)0.8 (AIMO) solid electrolyte films as storage medium were fabricated on SiO2/Pt/Ti/Si substrates by using pulse laser deposition technique and focused ion beam lithography. X-ray diffraction, scanning electron microscopy, and energy dispersive x-ray analysis have been employed to investigate the structure, the surface morphology, and the composition of AIMO thin films. The Ag/AIMO/Pt memory cells with sandwich structure exhibit stable, reproducible, and reliable resistive switching characteristics. The ratio of resistance between high resistance states and low resistance states can reach ∼105. Moreover, the low resistance is ∼500 Ω at a compliance current of 0.5 mA, which is favorable to reduce the power dissipation of the entire circuit. The switching-on mechanism has been discussed and the metallic conduction characteristic has also been verified. The fast response speed and the good retention properties further indicate that polycrystalline AIMO thin film is a potential candidate for the next generation nonvolatile memory.
Influence of morphology on the conductance of single-crystal diamond surfaces measured by atomic force microscopy
Authors: Tranvouez E. , Boer-Duchemin E. , Mayne A. J. , Vanderbruggen T. , Scheele M. , Cartwright R. , Comtet G. , Dujardin G. , Schneegans O. , Chrétien P. , Houzé F.
Published: September 2009

A detailed atomic force microscopy (AFM) study of the conductance of hydrogenated single-crystal diamond (100) surfaces over submicron length scales is presented. The hydrogenation process was found to influence the surface morphology by reducing surface roughness, with the subsequent appearance of small triangular structures (with side lengths of 200 nm). Conducting AFM measurements revealed variations in the current and resistance that were related to the topography. Possible explanations include surface inhomogeneity of the electronic structure or variations in the contact resistance due to the surface roughness.
Theoretical study on the dynamical behaviors of ferroelectric thin films with surface transition layers
Authors: Cui Lian , Lü Tianquan , Xu Xu
Published: September 2009

Using the mean field approximation approach, the dynamical behaviors including damping factor and frequency of soft mode, and the real and imaginary parts of permittivity of a ferroelectric thin film with surface transition layers have been first investigated. The results show that the existence of a surface transition layer plays a crucial role in explaining the dynamical properties of thin films different from those of bulk materials. Our calculational results are in excellent agreement with experimental data.
First critical field measurements of superconducting films by third harmonic analysis
Authors: Lamura G. , Aurino M. , Andreone A. , Villégier J.-C.
Published: September 2009

The temperature behavior of the first critical field (BC1) of superconducting thin film samples can be determined with high accuracy using an inductive and contactless method. Driving a sinusoidal current in a single coil placed in front of the sample, a nonzero third harmonic voltage V3 is induced in it when Abrikosov vortices enter the sample. Conditions to be satisfied for the quantitative evaluation of BC1 using this technique are detailed. As a validation test, different type II superconductors (Nb, NbN, MgB2, and Y1Ba2Cu3O7−d under the form of thin films) have been measured. The comparison between experimental results, data presented in literature, and theoretical predictions is presented and discussed.
Cluster-spin-glass behavior in layered LiNi0.4Mn0.4Co0.2O2
Authors: Du Fei , Bie Xiaofei , Chen Yan , Wei Yingjin , Liu Lina , Wang Chunzhong , Zou Guangtian , Chen Gang
Published: September 2009

Layered LiNi0.4Mn0.4Co0.2O2 has been synthesized by citrate precursor method. Its magnetic properties are investigated by dc magnetization. The high-temperature susceptibility curve follows the Curie–Weiss law with Curie and Weiss constant 1.435(2) emu K/mol Oe and −112(4) K, respectively, larger than those values reported in previous researches, which possibly results from the difference in the synthesis process and sintered temperature. Our dc susceptibility differs from that of the homogeneous spin glass in that below Tirr field cooled (FC) curve continues to rise, while the FC curve is almost flat for homogeneous spin glass. Together with the de Almeida–Thouless line analysis, cluster spin glass is suggested to be the ground state of LiNi0.4Mn0.4Co0.2O2. Frustration parameter |θ|/Tf in this system is estimated to be about four, lower than the value that frustration effect is strong enough to give rise to spin glass state. This fact indicates that the cluster-spin-glass results from the short–range structure disorder rather than the geometrical frustration.
Simultaneous readout of multiple microcantilever arrays with phase-shifting interferometric microscopy
Authors: Kelling Sven , Paoloni François , Huang Juzheng , Ostanin Victor P. , Elliott Stephen R.
Published: September 2009

A complete system for the simultaneous monitoring of multiple cantilever sensors from different sensor arrays has been developed and tested for gas- and liquid-phase applications. The cantilever sensors are operated in static-deflection mode and the readout is achieved with phase-shifting interferometric microscopy (PSIM). In contrast to existing cantilever-sensor readout methods, PSIM is not dependent on alignment and allows the monitoring of the entire displacement profiles of all cantilevers within the field of view, using just one light source. To complement the PSIM readout, we have developed a sample cell, which can hold multiple cantilever-array chips, allows for very fast and reproducible sensor-chip replacement, has very low sample-volume requirements, and allows for individual or common addressing of all chips in the sample cell. We demonstrate the functionality of our microcantilever sensor system with a setup that can monitor eight cantilevers from four different sensor chips simultaneously.
Thermoelectric properties and efficiency measurements under large temperature differences
Authors: Muto A. , Kraemer D. , Hao Q. , Ren Z. F. , Chen G.
Published: September 2009

The maximum efficiency of a thermoelectric generator is determined by the material’s dimensionless figure of merit ZT. Real thermoelectric material properties are highly temperature dependent and are often measured individually using multiple measurement tools on different samples. As a result, reported ZT values have large uncertainties. In this work we present an experimental technique that eliminates some of these uncertainties. We measure the Seebeck coefficient, electrical conductivity, and thermal conductivity of a single element or leg, as well as the conversion efficiency, under a large temperature difference of 2–160 °C. The advantages of this technique include (1) the thermoelectric leg is mounted only once and all measurements are in the same direction and (2) the measured properties are corroborated by efficiency measurements. The directly measured power and efficiency are compared to the values calculated from the measured properties and agree within 0.4% and 2%, respectively. The realistic testing conditions of this technique make it ideal for material characterization prior to implementation in a real thermoelectric generator.
A frequency-domain thermoreflectance method for the characterization of thermal properties
Authors: Schmidt Aaron J. , Cheaito Ramez , Chiesa Matteo
Published: September 2009

A frequency-domain thermoreflectance method for measuring the thermal properties of homogenous materials and submicron thin films is described. The method can simultaneously determine the thermal conductivity and heat capacity of a sample, provided the thermal diffusivity is ≳3×10−6 m2/s, and can also simultaneously measure in-plane and cross-plane thermal conductivities, as well the thermal boundary conductance between material layers. Two implementations are discussed, one based on an ultrafast pulsed laser system and one based on continuous-wave lasers. The theory of the method and an analysis of its sensitivity to various thermal properties are given, along with results from measurements of several standard materials over a wide range of thermal diffusivities. We obtain specific heats and thermal conductivities in good agreement with literature values, and also obtain the in-plane and cross-plane thermal conductivities for crystalline quartz.
Formation of fast shocks by magnetic reconnection in the solar corona
Authors: Hsieh M. H. , Tsai C. L. , Ma Z. W. , Lee L. C.
Published: September 2009

Reconnections of magnetic fields over the solar surface are expected to generate abundant magnetohydrodynamic (MHD) discontinuities and shocks, including slow shocks and rotational discontinuities. However, the generation of fast shocks by magnetic reconnection process is relatively not well studied. In this paper, magnetic reconnection in a current sheet is studied based on two-dimensional resistive MHD numerical simulations. Magnetic reconnections in the current sheet lead to the formation of plasma jets and plasma bulges. It is further found that the plasma bulges, the leading part of plasma jets, in turn lead to the generation of fast shocks on flanks of the bulges. The simulation results show that during the magnetic reconnection process, the plasma forms a series of structures: plasma jets, plasma bulges, and fast shocks. As time increases, the bulges spread out along the current sheet (±z direction) and the fast shocks move just ahead of the bulges. The effects of initial parameters ρs/ρm, β∞, and trec on the fast shock generation are also examined, where ρs/ρm is the ratio of plasma densities on two sides of the initial current sheet, β∞=P∞/(B∞2/2μ0), P∞ is the plasma pressure and B∞ is the magnetic field magnitude far from the current sheet, and trec is the reconnection duration. In the asymmetric case with ρs/ρm=2, β∞=0.01 and trec=1000, the maximum Alfvén Mach number of fast shocks (MA1 max) is MA1 max≅1.1, where MA1=Vn1/VA1, and Vn1 and VA1 are, respectively, the normal upstream fluid velocity and the upstream Alfvén speed in the fast shocks frame. As the density ratio ρs/ρm (=1–8) and plasma beta β∞ (=0.0001–1) increase, MA1 max varies slightly. For the case with a large plasma beta β∞ (=5), the fast shock is very weak. As the reconnection duration trec increases, the bulges lead to generation of fast shocks with a higher MA1 max. The present results can be applied to the mechanism of coronal heating by fast shocks.
Relativistic electron and ion dust charging currents
Authors: Tribeche Mouloud , Boukhalfa Soufiane
Published: September 2009

A first theoretical attempt is made to present a relativistic generalization of the well-known orbit-limited motion theory. The appropriate relativistic (electron and ion) dust charging currents are derived. The nonlinear electrostatic potential is then expressed in terms of the variable dust charge and we take advantage of this new transcendental relation to investigate briefly the effects of relativistic charge carriers. As the relativistic character of the plasma increases, it becomes evident that certain negative values of the dust charge can never be achieved as increasingly larger values of the nonlinear potential are involved. The obtained formulas bring a possibility to build theories of nonlinear collective process in relativistic dusty plasmas.
A new all-round density functional based on spin states and SN2 barriers
Authors: Swart Marcel , Solà Miquel , Bickelhaupt F. Matthias
Published: September 2009

We report here a new empirical density functional that is constructed based on the performance of OPBE and PBE for spin states and SN2 reaction barriers and how these are affected by different regions of the reduced gradient expansion. In a previous study [Swart, Solà, and Bickelhaupt, J. Comput. Methods Sci. Eng. 9, 69 (2009)] we already reported how, by switching between OPBE and PBE, one could obtain both the good performance of OPBE for spin states and reaction barriers and that of PBE for weak interactions within one and the same (SSB-sw) functional. Here we fine tuned this functional and include a portion of the KT functional and Grimme’s dispersion correction to account for π-π stacking. Our new SSB-D functional is found to be a clear improvement and functions very well for biological applications (hydrogen bonding, π-π stacking, spin-state splittings, accuracy of geometries, reaction barriers).
Thermodynamic, dynamic, and structural anomalies for shoulderlike potentials
Authors: Barraz Ney M. , Salcedo Evy , Barbosa Marcia C.
Published: September 2009

Using molecular dynamic simulations we study a family of continuous core-softened potentials consisting of a hard core, a shoulder at closest distances, and an attractive well at further distance. The repulsive shoulder and the well distances represent two length scales. We show that if the first scale, the shoulder, is repulsive or has a small well, the potential has a region in the pressure-temperature phase diagram with density, diffusion, and structural anomalies. However, if the closest scale becomes a deep well, the regions in the pressure-temperature phase diagram where the three anomalies are present shrink and disappear. This result helps in defining two length scales potentials that exhibit anomalies.