bluuebunny/crossref_metadata_2025 huggingface dataset:
40 GW Linear Transformer Driver stage for pulse generators of Mega-ampere range
Authors: Kovalchuk B.M. , Kharlov A.V. , Zherlitsyn A.A. , Kumpjak E.V. , Tsoy N.V. , Vizir V.A. , Smorudov G.V.
Published: June 2009

Linear transformer driver (LTD) technology is actively developed at the Institute of High Current Electronics in Tomsk, Russia. This technology is being examined for use in high current high voltage pulsed accelerators. Recent development of high voltage low inductance capacitors and low inductance switches enabled to achieve ~100 ns rise time of the LTD output pulse. This technique allows one to eliminate intermediate pulse forming sections, used in the present accelerator technology, which would keep the footprint of an LTD accelerator small. LTD based drivers are currently considered for many applications, including future very high current Z-pinch drivers for inertial confinement fusion, medium current drivers with adjustable pulse length for isentropic compression experiments, and finally relatively low current accelerators for radiography and X-pinches. In this article, we present the design and test results for a new LTD stage, that operates at 100 kV charging voltage. Current amplitude up to 850 kA with ~140 ns rise time was obtained on a 0.05 Ω load. Stack of the LTD stages can be easily assembled in series or in parallel, thus providing voltage or current multiplication, respectively. Design of multi-mega-volt and multi-mega-ampere generators becomes straightforward with the LTD technology.
Effect of transition section between the main switch and middle cylinder of Blumlein pulse forming line on the diode voltage of intense electron-beam accelerators
Authors: Cheng X.-B. , Liu J.-L. , Qian B.-L. , Zhang J.-D.
Published: June 2009

The rise-time of the pulse on the diode of the intense electron-beam accelerators (IEBA) is one of the important factors that affect the quality and characteristic of the output beam current of the IEBA. In this paper, effect of the transition section between the main switch and middle cylinder of strip spiral Blumlein line (SSBL) on the diode voltage of IEBA is analyzed in theory, based on the theoretical analysis of the wave propagation along the Blumlein pulse forming line (BPFL), the traveling time of the transition section has a great effect on the rise-time, the plateau-time, and the fall-time of the output voltage at the matching load. Furthermore, the operation of the whole accelerator consisting of the primary energy-storage capacitor, the Tesla transformer, a main switch, the transition section, BPFL, and a resistive load was simulated using a circuit-simulation code called PSpice, and the dependence of the output voltage on the inductance of the main switch and the transition section was obtained. It was found from the wave propagation theory and the circuit simulation using computer results that the wave traveling time of the transition section between the main switch and the middle cylinder of the SSBL influences considerably the rise-time, plateau-time, and fall-time of the voltage waveform at the matching load. In order to get an ideal square pulse voltage waveform at the matching load and to improve the electron beam quality of such an accelerator, the wave traveling time of the transition section should be designed as soon as possible. At last, a couple of contrastive experiments are performed on two kinds of IEBA. The experimental results agree with the theoretical analysis and simulated results.
NONPARAMETRIC FILTERING OF THE REALIZED SPOT VOLATILITY: A KERNEL-BASED APPROACH
Authors: Kristensen Dennis
Published: June 2009

A kernel weighted version of the standard realized integrated volatility estimator is proposed. By different choices of the kernel and bandwidth, the measure allows us to focus on specific characteristics of the volatility process. In particular, as the bandwidth vanishes, an estimator of the realized spot volatility is obtained. We denote this the filtered spot volatility. We show consistency and asymptotic normality of the kernel smoothed realized volatility and the filtered spot volatility. We consider boundary issues and propose two methods to handle these. The choice of bandwidth is discussed and data-driven selection methods are proposed. A simulation study examines the finite sample properties of the estimators.
OPTIMAL BANDWIDTH CHOICE FOR ESTIMATION OF INVERSE CONDITIONAL–DENSITY–WEIGHTED EXPECTATIONS
Authors: Jacho-Chávez David Tomás
Published: June 2009

This paper characterizes the bandwidth value (h) that is optimal for estimating parameters of the form$\eta \, = \,E\left[ {\omega /f_{V|U} \left({V|U} \right)} \right]$, where the conditional density of a scalar continuous random variableV, given a random vectorU,$f_{V|U} $, is replaced by its kernel estimator. That is, the parameterηis the expectation ofωinversely weighted by$f_{V|U} $, and it is the building block of various semiparametric estimators already proposed in the literature such as Lewbel (1998), Lewbel (2000b), Honoré and Lewbel (2002), Khan and Lewbel (2007), and Lewbel (2007). The optimal bandwidth is derived by minimizing the leading terms of a second-order mean squared error expansion of an in-probability approximation of the resulting estimator with respect toh. The expansion also demonstrates that the bandwidth can be chosen on the basis of bias alone, and that a simple “plug-in” estimator for the optimal bandwidth can be constructed. Finally, the small sample performance of our proposed estimator of the optimal bandwidth is assessed by a Monte Carlo experiment.
Prevalence of Burkholderia pseudomallei in Guangxi, China
Authors: MA G. , ZHENG D. , CAI Q. , YUAN Z.
Published: June 2009

Melioidosis, an infectious disease caused by the Gram-negative bacterium Burkholderia pseudomallei, is now recognized as an important public health problem in Southeast Asia and tropical northern Australia. Although B. pseudomallei has been detected in various water and soil samples in southeast China, the enviromental distribution of B. pseudomallei in China is unclear. In the winter months of 2007, 154 and 130 soil and water samples, respectively, were collected from several locations in Guangxi, China. The samples were screened for B. pseudomallei by bacterial culture and identification and confirmed by PCR for species-specific 16S rDNA and flagellin genes. B. pseudomallei was detected in 8·4% of the soil samples but in none of the water samples. All positive samples were confined to a single low-lying region from rice paddy fields. Counts of B. pseudomallei ranged from 23 to 521 c.f.u./g soil. This is the first geographical distribution survey of B. pseudomallei in soil in Guangxi, China, and the data are of importance for further evaluating the impact of this pathogen on melioidosis in this region.
High-power monolithic AlGaN/GaN high electron mobility transistor switches
Authors: Alleva Vincenzo , Bettidi Andrea , Ciccognani Walter , De Dominicis Marco , Ferrari Mauro , Lanzieri Claudio , Limiti Ernesto , Peroni Marco
Published: June 2009

This work presents the design, fabrication, and test of X-band and 2–18 GHz wideband high-power single pole double throw (SPDT) monolithic microwave integrated circuit (MMIC) switches in microstrip gallium nitride (GaN) technology. Such switches have demonstrated state-of-the-art performances and RF fabrication yields better than 65%. In particular, the X-band switch exhibits 1 dB insertion loss, better than 37 dB isolation, and a power handling capability better than 39 dBm at a 1 dB insertion loss compression point; the wideband switch shows an insertion loss lower than 2.2 dB, better than 25 dB isolation, and an insertion loss compression of 1 dB at an input drive higher than 38.5 dBm in the entire bandwidth.
Power amplifier optimization using base band and multiharmonic source/load-pull characterization with digital predistortion
Authors: Abib Ghalid Idir , Bergeault Eric , Bensmida Souheil , Mohellebi Reda
Published: June 2009

In this paper, different techniques are combined in a unique characterization system dedicated to power transistor linearity improvement. Successive optimizations are performed using source-pull/load-pull techniques at fundamental, harmonic, and base-band frequencies associated with an instantaneous memoryless base-band predistortion procedure. Measurement results performed at 1.575 GHz on a metal semiconductor field effect transistor (MESFET) power device biased in class-AB under a quadrature phase shift keying (QPSK)-modulated signal excitation show that fundamental frequency load-pull increases the output power and power-added efficiency (PAE) by 2 dB and 16 percentage points, respectively. The fundamental frequency source-pull measurements lead to an adjacent channel power ratio (ACPR) variation equal to 3 dB. For harmonic load-pull (at 2f0), it has been found that some impedances greatly improve linearity but output power and PAE decrease. Source-pull characterization at the second harmonic frequency allows one to find a trade-off between output power, efficiency, and linearity. Moreover, the influence of base-band impedance on ACPR and error vector magnitude (EVM) is found to be 15 dB and 5.5 percentage points, respectively. Finally, instantaneous memoryless base-band predistortion improves ACPR and EVM values by 5 dB and 1 point, respectively.
Low-cost TRM technologies for phased array radars
Authors: Berg Håkan , Thiesies Heiko , Billström Niklas
Published: June 2009

Low-cost enabling technologies for T/R modules (TRMs) in phased array radars are proposed and analyzed in terms of technology, performance, and cost aspects. Phase and amplitude controlling integrated circuits (ICs) realized in a low-cost standard silicon process are demonstrated. The design of several ICs at the S-, C-, on X-band has shown that silicon germanium is a strong contender for gallium arsenide. This also applies to TRMs suited for military active phased array antenna (AESA) radars. The circuits presented in this paper are manufactured by austriamicrosystems in their 0.35 µm SiGe-BiCMOS process with an fTof around 70 GHz. A TRM packaging concept based on soldered surface-mount technology and organic substrates is also demonstrated. A cost analysis concludes that by using the proposed packaging concept and the SiGe core-chip technology, the TRM production cost can be potentially reduced by 70% compared to traditional ceramic hermetic packaging with core chip in GaAs technology.
Design and performance of multi-channel switched sequential amplifiers
Authors: Lehmann Thomas , Knoechel Reinhard
Published: June 2009

This paper presents switched sequential amplifiers (SSAs) using reconfigurable directional couplers as power splitters and combiners. The SSA concept allows matching the efficiency characteristics to the amplitude probability density distribution of the applied modulated signal. Therefore the back-off efficiency can be increased significantly. A three-channel SSA can e.g. theoretically achieve a −10 dB back-off efficiency exceeding 50%. Design parameters and potential efficiency enhancement are discussed for two- and three-channel SSAs. After a brief introduction of the used switched couplers, the circuit concept for two- and three-channel SSAs is described. Calculations for the possible efficiency enhancement are presented. Also signal distortions by the directional couplers are outlined. The paper closes with experimental results for a two-channel SSA.
A double H-shaped resonator and its use as an isotropic ENG metamaterial
Authors: Blaha Michal , Machac Jan , Rytir Martin
Published: June 2009

This paper presents a new planar particle that shows negative effective permittivity under irradiation by an electromagnetic wave. The mutual coupling between the couples of these particles is studied in particular. The response of this particle sensitive to an electric field is strongly anisotropic. The particle is aimed to be used to compose an isotropic epsilon-negative metamaterial in two forms. First, a unit cell of the metamaterial consists of a cube bearing six particles on its faces, located with specific orientations. The experiments showed that this unit cell is suitable for manufacturing an isotropic epsilon-negative metamaterial obtained by arranging these cells in a 3D cubic periodic system. The second form of an epsilon-negative metamaterial with an isotropic response consists of the planar particles themselves, distributed quasi-randomly, composing a 2D system and/or of particles placed in spherical shells and distributed fully randomly in a hosting material forming a 3D system. The isotropy of these systems was verified by measurements in a rectangular waveguide.
The past as prologue: the development of the ‘direct participation’ exception to civilian immunity
Authors: Camins Emily
Published: June 2009

The ‘direct participation’ exception to the principle of distinction, found in Article 51(3) of Protocol I and Article 13(2) of Protocol II, embodies a long-recognized concept in the laws governing armed conflict. For centuries the broad notion that humanity demands the protection only of those citizens who are harmless has found expression in the rules and norms relating to war. This article traces the historical factors and trends which influenced the development of the ‘direct participation’ exception in its current form, revealing a tendency towards ‘humanizing’ the law in favour of civilians, notwithstanding their increased military value.
Can jus ad bellum override jus in bello? Reaffirming the separation of the two bodies of law
Authors: Moussa Jasmine
Published: June 2009

The theoretical separation of jus ad bellum and jus in bello provides important protection during armed conflict. It guarantees that jus in bello will apply regardless of the cause of a conflict. However, this distinction has been challenged by the view that in some cases a situation of self-defence may be so extreme, and the threat to the survival of the state so great, that violations of jus in bello may be warranted. The situation is compounded by the confusion of the principles of necessity and proportionality under jus ad bellum and jus in bello in both academic writing and the jurisprudence of international courts. The dangers of blurring the distinction will be elucidated by examining how jus ad bellum considerations have affected the application of jus in bello in armed conflicts between states and non-state actors.
The civilianization of armed conflict: trends and implications
Authors: Wenger Andreas , Mason Simon J. A.
Published: June 2009

Civilians play an increasingly important and complex role in armed conflicts, both as victims and as perpetrators. While this overall trend towards ‘civilianization’ encompasses all types of present-day conflicts, it is twofold: it takes on a very different nature in high-technology warfare than in the context of low-technology combats that are typical of many civil wars. This article explores these two trends, shows how they merge in asymmetric warfare and outlines key implications for international stabilization and state-building efforts. The present-day conflict landscape is presented from a security policy point of view, placing the ongoing debates on the civilian participation in hostilities in a broader strategic context.
Foraminiferal assemblage changes over the last 15,000 years on the Mackenzie‐Beaufort Sea Slope and Amundsen Gulf, Canada: Implications for past sea ice conditions
Authors: Scott David B. , Schell Trecia , St‐Onge Guillaume , Rochon André , Blasco Steve
Published: June 2009

Two cores, one from the Beaufort Sea Slope at 1000 m water depth (core 750) and one from the Amundsen Gulf at 426 m (core 124), were collected to help determine paleo–ice cover in the Holocene and late glacial of this area. Site 750 is particularly sensitive to changes in paleo–ice cover because it rests beneath the present ice margin of the permanent Arctic ice pack. Core 124 was sampled just in front of the former glacier that moved out into the Amundsen Gulf and started to recede about 13 ka B.P. Both cores have a strong occurrence of calcareous foraminifera in the upper few centimeters, but these disappear throughout most of the Holocene, suggesting more open water in that time period than present. In the sediments representing the end of the last glacial period (dated at ∼11,500–14,000 calibrated years B.P. (cal B.P.)) a calcareous fauna with an abundant planktic foraminiferal fauna suggests a return to almost permanent ice cover, much like the central Arctic today. Together with the foraminifera there was also abundant ice‐rafted debris (IRD) in both cores between 12,000 cal B.P. and ∼14,000 cal B.P., but those units are of different ages between cores, suggesting different events. The IRD in both cores appears to have the same magnetic and chemical signals, but their origins cannot be determined exactly until clay mineralogy is completed. There is abundant organic debris in both cores below the IRD units: the organics in core 750 are very diffuse and not visually identifiable, but the organic material in core 124 is clearly identifiable with terrestrial root fragments; these are 14C dated at over 37,000 years B.P. This is a marine unit as it also has glacial front foraminifera in the sediment with the organic debris that must have been originating from subglacial streams. The seismic and multibeam data both indicate glaciers did not cross the core 124 site.
Land2Sea database of river drainage basin sizes, annual water discharges, and suspended sediment fluxes
Authors: Peucker‐Ehrenbrink Bernhard
Published: June 2009

The Land2Sea database contains data on the sizes of 1519 exorheic river drainage basins (79% of the exorheic land area), annual suspended sediment fluxes (593 rivers, 63% of the exorheic land area), and water discharges (1272 rivers, 76% of the exorheic land area) that have been compiled from a variety of sources. The database extends earlier compilations, such as GEMS/GLORI. The river basins are grouped into 19 large‐scale drainage regions to investigate the regional variability in freshwater and sediment fluxes to various ocean basins. The annual suspended sediment flux to the coastal ocean (∼18.5 × 109 tons) is dominated by east Asia (6.1 × 109 tons); Arabia, India, and southeast Asia (4.3 × 109 tons); and eastern South America (2.4 × 109 tons). Small topical islands of Oceania support the highest annual sediment fluxes per drainage area (∼9650 t km−2 a−1). Annual freshwater discharge to the coastal ocean (∼38,857 km3) is dominated by runoff from eastern South America (11,199 km3); east Asia (7114 km3); and Arabia, India, and southeast Asia (4384 km3). The empirical data agree well with results from global models (ART and BQART) that have been trained on a subset of the data compiled here.
Interaction between the orography‐induced gravity wave drag and boundary layer processes in a global atmospheric model
Authors: Kim Young‐Joon , Hong Song‐You
Published: June 2009

This study investigates the behavior of the orographic gravity‐wave drag (GWDO) processes induced by sub‐grid scale orography in response to the representation of boundary layer mixing in a global atmospheric model. The sensitivity of simulated climatology to the representation of stable boundary layer (SBL) processes associated with GWDO processes in the modeled atmosphere is investigated using the Kim‐Arakawa GWDO parameterization scheme. It is found that the impact of the boundary layer structure is pronounced in the upper atmospheric circulations above the tropopause through the interaction between the boundary layer mixing and GWDO processes, even though the direct impact of the SBL structure is confined to near surface layer. This finding reinforces the notion that the success of a particular physics parameterization scheme in atmospheric models relies heavily on the interaction of a physical process with another, which should be properly considered in developing physics parameterization schemes for atmospheric models.
Model‐based constraints on interpreting 20th century trends in ice core 10Be
Authors: Field Christy V. , Schmidt Gavin A.
Published: June 2009

Beryllium‐10 ice‐core records are useful for understanding solar magnetic field changes over time, and in particular over the 20th century, during which there are a variety of relevant observations. However, differences between 10Be snow concentration records from different locations complicate the process of developing a coherent understanding of changes in cosmogenic isotope production. We use the Goddard Institute for Space Studies ModelE general circulation model to simulate the production and transport of beryllium isotopes for this time period. We compare our results with surface air observations, and with ice‐core records from Dye 3, Taylor Dome, and South Pole. We find that unforced weather‐related (internal) variability causes modeled trends in 10Be snow concentration to vary from the ensemble mean by 50% and greater at all three ice‐core locations. Lower levels of internal variability at Taylor Dome and South Pole relative to Dye 3 make the simulated 10Be values at these locations better estimates of the ensemble‐mean trend in 10Be snow concentration. In addition, the ensemble mean concentration trend at Dye 3 was significantly different from the expected modeled trend based on applied production changes alone. Overall, the results imply that during the 20th century, 10Be data from multiple cores are likely to be required to make meaningful inferences about 10Be production changes. The model simulations imply that data from Antarctica are likely to be more robust.
African monsoon enhancement during the penultimate glacial period (MIS 6.5 ∼ 170 ka) and its atmospheric impact
Authors: Tisserand Amandine , Malaizé Bruno , Jullien Elsa , Zaragosi Sébastien , Charlier Karine , Grousset Francis
Published: June 2009

A reconstruction of northwest African summer monsoon strength during the cold marine isotopic stage (MIS) 6 indicates a link to the seasonal migration of the Intertropical Convergence Zone (ITCZ). High‐resolution studies of eolian dust supply and sea surface temperature recorded in marine core MD03‐2705, on the Mauritanian margin, provide a better understanding about the penultimate glacial history of northwestern African aridity/humidity and upwelling coastal activity. Today, site MD03‐2705 experiences increased upwelling and dust flux during the winter months, when the ITCZ is in a southerly position. Analyses of foraminifera isotopic composition suggest that during MIS 6.5 (180–168 ka) the average position of the ITCZ migrated north, marked by an increase in the strength of the summer monsoon, which decreased eolian dust transport and the coastal upwelling activity. The northward migration is in phase with a specific orbital combination of a low precessional index with a high obliquity signal. High‐resolution analysis of stable isotopes (δ18O and δ13C) and microscale resolution geochemical (Ti/Al and quartz grain counts) determinations reveal that the transition between monsoonal humid (MIS 6.5) and dry (MIS 6.4) conditions has occurred in less than 1.3 ka. Such rapid changes suggest a nonlinear link between the African monsoonal rainfall system and environmental changes over the continent. This study provides new insights about the influence of vegetation and oceanic temperature feedbacks on the onset of African summer monsoon and demonstrates that, during the penultimate glacial period, changes in tropical dynamics had regional and global impacts.
Nondestructive electromagnetic material characterization using a dual waveguide probe: A full wave solution
Authors: Hyde Milo W. , Stewart James W. , Havrilla Michael J. , Baker William P. , Rothwell Edward J. , Nyquist Dennis P.
Published: June 2009

A nondestructive technique for determining the complex permittivity and permeability of a perfect electric conductor backed magnetic shielding material using a dual waveguide probe is presented. The dual waveguide probe allows for the simultaneous collection of reflection and transmission coefficients which distinguishes it from single probe methods common in the literature. Theoretical development of these coefficients, which is accomplished through a coupled magnetic field integral equations formulation using Love's equivalence principle and solved via the method of moments (MOM), is discussed. Evaluation of the resulting MOM impedance matrix elements is performed using complex plane integration leading to enhanced computational efficiency and physical insight. Comparison of the theoretical and measured reflection and transmission coefficients using a root finding algorithm leads to the desired permittivity and permeability. Measurement results of a magnetic shielding material are presented and compared to traditional methods for the purpose of validating the new technique. The probe's sensitivity to aperture alignment, sample thickness, and flange thickness is also investigated.
Estimation of wet surface evaporation from sensible heat flux measurements
Authors: Vercauteren Nikki , Bou‐Zeid Elie , Huwald Hendrik , Parlange Marc B. , Brutsaert Wilfried
Published: June 2009

A new method is proposed to estimate wet surface evaporation by means of measurements of sensible heat flux and of air temperature, relative humidity, and wind speed at one level only. This formulation is made possible by the linearization of the Bowen ratio, a common assumption in other methods, such as Penman's model and its derivatives. The method will be useful in those cases where the sensible heat flux is more reliably acquired at field scales than the net radiation and the ground heat flux, which are needed in many operational methods because of energy budget considerations. Indeed, the ground heat flux is a notoriously difficult variable to measure on wet surfaces, such as lakes or wetlands, especially at the appropriate length scales, whereas sensible heat flux can be obtained from standard temperature variance methods or other instruments such as scintillometers. The proposed method was tested with field experimental data taken over Lake Geneva in Switzerland, where it showed excellent agreement with evaporation rates measured using eddy covariance techniques.
Streamflow changes in Alaska between the cool phase (1947–1976) and the warm phase (1977–2006) of the Pacific Decadal Oscillation: The influence of glaciers
Authors: Hodgkins Glenn A.
Published: June 2009

Streamflow data from 35 stations in and near Alaska were analyzed for changes between the cool phase (1947–1976) and the warm phase (1977–2006) of the Pacific Decadal Oscillation. Winter, spring, and summer flow changes and maximum annual flow changes were different for glaciated basins (more than 10% glacier‐covered area) than for nonglaciated basins, showing the influence of glaciers on historical streamflow changes. Mean February flows, for example, increased for the median of available stations by 45% for glaciated basins and by 17% for nonglaciated ones.
Exospheric signatures of alkali abundances in Europa's regolith
Authors: Cipriani F. , Leblanc F. , Witasse O. , Johnson R. E.
Published: June 2009

The sodium and potassium exospheres of Europa are described as well as the variations of the Na/K ratio from Europa's surface up to about 20 Europa radii. Observations carried out by M. E. Brown (2001) are used to constrain the Na and K source terms. We find that an average source rates ratio of 17 ± 2 at the surface and loss rates ratio of 26 ± 2 reproduce well the observations. These values are consistent with the conclusions by R. E. Johnson et al. (2002) on its most probable origin. Moreover, we here show that a local increase of the surface Na/K ratio by a factor 2 in a 20° × 30° wide region should induce an observable exospheric signature between 80 and 300 km above the surface. Therefore simultaneous observations of sodium and potassium from an Europa orbiter would allow one to derive important properties of the surface and subsurface of the Galilean moon.
Non‐destructive detection of water stress and estimation of relative water content in maize
Authors: Zygielbaum Arthur I. , Gitelson Anatoly A. , Arkebauer Timothy J. , Rundquist Donald C.
Published: June 2009

Non‐destructive estimation of leaf water content provides vital information about vegetation productivity. We report here on controlled seven day experiments using greenhouse‐grown maize. Fifty plants were randomly assigned to two equal groups: water stressed and well watered. Spectroscopic, relative water content (RWC), and chlorophyll concentration measurements were made daily. Because water molecules absorb radiation in near‐ and middle‐infrared, most efforts to sense water deficit remotely utilize infrared wavelengths. In these experiments, we identified a strong, systematic, and repeatable relationship between photosynthetically active radiation (PAR, 400–700 nm) albedo and leaf RWC. We show that visible spectrum reflectance provides a means to detect early stages of plant stress and estimate leaf RWC.
Trends and solar cycle effects in temperature versus altitude from the Halogen Occultation Experiment for the mesosphere and upper stratosphere
Authors: Remsberg Ellis E.
Published: June 2009

Fourteen‐year time series of mesospheric and upper stratospheric temperature versus altitude or T(z) from the Halogen Occultation Experiment (HALOE) are analyzed and reported. The data have been binned according to 10°‐wide latitude zones from 40°S to 40°N and at 10 altitudes from 43 to 80 km: a total of 90 separate time series. Multiple linear regression analysis techniques have been applied to those time series. This study focuses on resolving their 11‐year solar cycle (SC) (or SC‐like) responses and their linear trend terms. Findings for T(z) from HALOE are compared with published results from ground‐based Rayleigh lidar and from rocketsonde measurements. SC‐like responses from HALOE compare well with those from the lidar station data. The cooling trends from HALOE also agree reasonably well with those from the lidar data at low latitudes for the concurrent decade. Cooling trends of the lower mesosphere from HALOE are not as large as those from rocketsondes and from the lidar station time series of the previous two decades, presumably because the changes in the upper stratospheric ozone are near zero during the HALOE time period and do not contribute to its trends.
Linear polyubiquitination: a new regulator of NF‐κB activation
Authors: Iwai Kazuhiro , Tokunaga Fuminori
Published: June 2009

The ubiquitin‐conjugation system regulates a vast range of biological phenomena by affecting protein function mostly through polyubiquitin conjugation. The type of polyubiquitin chain that is generated seems to determine how conjugated proteins are regulated, as they are recognized specifically by proteins that contain chain‐specific ubiquitin‐binding motifs. An enzyme complex that catalyses the formation of newly described linear polyubiquitin chains—known as linear ubiquitin chain‐assembly complex (LUBAC)—has recently been characterized, as has a particular ubiquitin‐binding domain that specifically recognizes linear chains. Both have been shown to have crucial roles in the canonical nuclear factor‐κB (NF‐κB)‐activation pathway. The ubiquitin system is intimately involved in regulating the NF‐κB pathway, and the regulatory roles of K63‐linked chains have been studied extensively. However, the role of linear chains in this process is only now emerging. This article discusses the possible mechanisms underlying linear polyubiquitin‐mediated activation of NF‐κB, and the different roles that K63‐linked and linear chains have in NF‐κB activation. Future directions for linear polyubiquitin research are also discussed.
The role of nuclear pores in gene regulation, development and disease
Authors: Capelson Maya , Hetzer Martin W
Published: June 2009

Nuclear‐pore complexes (NPCs) are large protein channels that span the nuclear envelope (NE), which is a double membrane that encloses the nuclear genome of eukaryotes. Each of the typically 2,000–4,000 pores in the NE of vertebrate cells is composed of multiple copies of 30 different proteins known as nucleoporins. The evolutionarily conserved NPC proteins have the well‐characterized function of mediating the transport of molecules between the nucleoplasm and the cytoplasm. Mutations in nucleoporins are often linked to specific developmental defects and disease, and the resulting phenotypes are usually interpreted as the consequences of perturbed nuclear transport activity. However, recent evidence suggests that NPCs have additional functions in chromatin organization and gene regulation, some of which might be independent of nuclear transport. Here, we review the transport‐dependent and transport‐independent roles of NPCs in the regulation of nuclear function and gene expression.
Mentoring Asian Graduate Students Who Attend Communication Sciences and Disorders Programs in the United States
Authors: Tsai Meng-Ju , Scherz Julie , DiLollo Anthony
Published: June 2009

This qualitative study provided an overview of American faculty members' perceptions of Asian graduate students who are in Communication Sciences and Disorders (CSD) programs in the United States. American faculty members with experience working with Asian graduate students in CSD programs were interviewed to identify their experiences with Asian graduate students compared to those with American students. Further, faculty members were asked about skills that were most helpful in mentoring Asian graduate students. Results yielded a variety of common themes across participants that were classified into three major categories: characteristics of Asian graduate students, English language skills, and teaching and mentoring changes or modifications. Moreover, four primary mentoring skills were identified, including cultural understanding, person-oriented, support system, and reconfirmation.
Stress/electrical scaling in ferroelectrics
Authors: Guyomar Daniel , Hajjaji Abdelowahed , Sebald Gael , Yuse Kaori
Published: June 2009

The present paper introduces a scaling law correlating three factors of ferroelectric materials in quite simple functions: the polarization (P), the electrical field (E), and the stress (T). The law is based on the physical symmetries of the problem and renders it possible to express the mechanical stress (T) as an electric field equivalent {Eeq=Th[P(E=0,T)]} and, as a consequence, also the relationship between strain (S) and polarization (P). Three materials with various phase structure (tetragonal, rhombohedral, and morphotropic) were used for the verification. It was found that such an approach permitted the prediction of the maximal stress using only purely electrical measurements [i.e., measurements of S(E) and P(E)]. Once this law was validated for the compressive stresses, the mapping could be extended in order to predict the polarization behavior in the tensile stress zone. It was shown that the polarization behaved differently as a function of the compressive and tensile stresses. The scaling law could also predict the piezoelectric constant (d33) under stress using only purely electrical measurements. Reciprocally, the dielectric constant (ε33) under an electrical field can be predicted using only purely mechanical measurements. Comparisons of hysteresis loops were made and a good agreement was found for the polarization versus electric field, compressive stresses, and, albeit to a lesser extent, for the coefficients (ε33) and d33.
Optical and ultrasonic signatures of femtosecond pulse filamentation in fused silica
Authors: Mizeikis Vygantas , Juodkazis Saulius , Balčiūnas Tadas , Misawa Hiroaki , Kudryashov Sergey I. , Zvorykin Vladimir D. , Ionin Andrei A.
Published: June 2009

Millimeter-long filaments and accompanying luminous plasma and defect channels created in fused silica by single, moderately focused femtosecond laser pulses with supercritical powers were probed in situ using optical imaging and contact ultrasonic techniques. Above the threshold pulse energy Eopt=5 μJ corresponding to a few megawatt power, the pulses collapse due to self-focusing and the nonlinear focus moves upstream with increasing pulse energy. Behind the focus, elongated, gradually narrowing awl-shaped channels of electron-hole plasma and luminescent defects are produced. In the channels, whose dimensions generally depend on the pulse energy, supercontinuum emission propagating downstream the channels occurs, although its observation requires elevated pulse energies above 25 μJ in order to compensate energy dissipation in the channels. Ultrasonic side-view imaging of the channels, conducted from a few millimeters distance, reveals predominantly compressive pressure transients. The compressive signals are observed above the same threshold pulse energy Eopt, and their amplitude increases linearly with the laser pulse energy, simultaneously exhibiting significant temporal broadening of the corresponding pulsewidths, reflecting square root dependence of the channel length and sublinear (∝E3/4) dependence of the source pressure on the pulse energy. Altogether, these optical and ultrasonic studies demonstrate filamentary pulse propagation with considerable dissipation (∼10 cm−1) in the awl-shaped subcritical plasma channels rich with generated point defects and optical damage sites.
Effect of high-energy electron beam irradiation on the properties of ZnO thin films prepared by magnetron sputtering
Authors: Yun Eui-Jung , Jung Jin Woo , Han Young Hwan , Kim Min-Wan , Lee Byung Cheol
Published: June 2009

In this work we demonstrate that high-energy electron beam irradiation (HEEBI) performed in air at room temperature affects remarkably the electrical, optical, and structural properties of undoped ZnO films prepared on SiO2 substrates by magnetron sputtering techniques. Hall and photoluminescence measurements revealed that the p-type conductivity was realized in HEEBI treated films with low dose of 1014 electrons/cm2 and converted to n-type conductivity with further increase in the amount of dose. X-ray photoelectron spectroscopy showed that indiffusion of Si from the substrate as well as N from the ambient into the films took place as a result of HEEBI treatment at high and low doses, respectively. X-ray diffraction analysis indicated that all as-grown films were found to have compressive stress, which was relieved to some extent by HEEBI treatment with high dose of 1016 electrons/cm2. It was also found that better crystallinity with a bigger grain size was observed in HEEBI treated ZnO films with a higher dose. Field emission scanning electron microscope showed that HEEBI treated films with low dose had surface morphologies with big rodlike shapes. The major acceptorlike defects were determined to be oxygen interstitial and zinc vacancy. A model was proposed in terms of O, Zn, N, and Si diffusion to explain the observed results.
Magnetoresistance of Fe thin films on faceted Al2O3 substrates
Authors: Mooser S. , Jourdan M.
Published: June 2009

Nanopatterned Fe thin films are prepared by e-beam evaporation on faceted Al2O3 substrates. In situ scanning tunneling microscopy investigations show that the Fe morphology consists of a grain structure which follows the shape of the substrate facets. By four-circle x-ray diffraction we demonstrate that the grains are textured with different but defined alignments. The facet morphology results in a pronounced magnetic anisotropy as shown by magnetization loops measured in a vibrating sample magnetometer. The morphology in conjunction with a conventional anisotropic magnetoresistance effect is the origin of a strongly anisotropic magnetoresistance of the samples.
Kinetics of photodarkening in a-As2Se3 thin films
Authors: Sati Dinesh C. , Kumar R. , Mehra R. M. , Jain H. , Ganjoo Ashtosh
Published: June 2009

We report kinetics of photodarkening of a-As2Se3 films in terms of changes in absorption coefficient and optical band gap. These are estimated by in situ measurements of transmission spectra at intervals of 10 ms under laser illumination. The absorption coefficient increase with increasing time of laser illumination before saturating. The change in optical band gap, estimated from transmission spectra are studied as a function of time and intensity. A theoretical fitting of the change in optical parameters is done using photon-assisted site switching model, yielding the time constants for the changes in optical absorption and optical band gap. The change in absorption coefficient and optical band gap with incident laser intensity is also examined to investigate the saturation phenomenon.
On the electron energy in the high power impulse magnetron sputtering discharge
Authors: Gudmundsson J. T. , Sigurjonsson P. , Larsson P. , Lundin D. , Helmersson U.
Published: June 2009

The temporal variation of the electron energy distribution function (EEDF) was measured with a Langmuir probe in a high power impulse magnetron sputtering (HiPIMS) discharge at 3 and 20 mTorr pressures. In the HiPIMS discharge a high power pulse is applied to a planar magnetron giving a high electron density and highly ionized sputtered vapor. The measured EEDF is Maxwellian-like during the pulse; it is broader for lower discharge pressure and it becomes narrower as the pulse progresses. This indicates that the plasma cools as the pulse progresses, probably due to high metal content of the discharge.
Dehydriding process of α-AlH3 observed by transmission electron microscopy and electron energy-loss spectroscopy
Authors: Muto S. , Tatsumi K. , Ikeda K. , Orimo S.
Published: June 2009

The dehydriding reaction of α-AlH3 induced by high-energy electron irradiation was observed in situ by transmission electron microscopy and associated electron energy-loss spectroscopy (EELS). An α-AlH3 crystal decomposed into fine aluminum particles while retaining its initial external shape because of a thin rigid surface layer that covered the entire particle. EELS revealed that the thin surface layer was amorphous aluminum oxide, which stabilizes α-AlH3 particles at ambient temperature.
Maximum power configuration for multireservoir chemical engines
Authors: Xia Shaojun , Chen Lingen , Sun Fengrui
Published: June 2009

A model of a multireservoir isothermal endoreversible chemical engine is put forward in this paper. Optimal control theory is used to determine the optimal configuration of the multireservoir isothermal endoreversible chemical engine for maximum power output. The optimal cycle consists of two constant chemical potential branches and two instantaneous constant mass-flux branches, which is independent of the number of mass reservoirs and the mass transfer law. The results show that, in order to obtain the maximum power output, some mass reservoirs should never connect to the working fluid in the mass transfer processes. A numerical example is provided for a linear mass transfer law three-mass-reservoir chemical engine. The effects of the potential changes of the intermediate mass reservoir on the optimal configuration of the chemical engine and the performance corresponding to the optimal configuration are analyzed. The obtained results are compared with those obtained for a multireservoir endoreversible heat engine. The object studied in this paper is general, and the results could provide some guidelines for optimal design and operation of real chemical engines.
High-performance ab initio density matrix renormalization group method: Applicability to large-scale multireference problems for metal compounds
Authors: Kurashige Yuki , Yanai Takeshi
Published: June 2009

This article presents an efficient and parallelized implementation of the density matrix renormalization group (DMRG) algorithm for quantum chemistry calculations. The DMRG method as a large-scale multireference electronic structure model is by nature particularly efficient for one-dimensionally correlated systems, while the present development is oriented toward applications for polynuclear transition metal compounds, in which the macroscopic one-dimensional structure of electron correlation is absent. A straightforward extension of the DMRG algorithm is proposed with further improvements and aggressive optimizations to allow its application with large multireference active space, which is often demanded for metal compound calculations. Special efficiency is achieved by making better use of sparsity and symmetry in the operator and wave function representations. By accomplishing computationally intensive DMRG calculations, the authors have found that a large number of renormalized basis states are required to represent high entanglement of the electron correlation for metal compound applications, and it is crucial to adopt auxiliary perturbative correction to the projected density matrix during the DMRG sweep optimization in order to attain proper convergence to the solution. Potential energy curve calculations for the Cr2 molecule near the known equilibrium precisely predicted the full configuration interaction energies with a correlation space of 24 electrons in 30 orbitals [denoted by (24e,30o)]. The energies are demonstrated to be accurate to 0.6mEh (the error from the extrapolated best value) when as many as 10 000 renormalized basis states are employed for the left and right DMRG block representations. The relative energy curves for [Cu2O2]2+ along the isomerization coordinate were obtained from DMRG and other correlated calculations, for which a fairly large orbital space (32e,62o) is modeled as a full correlation space. The DMRG prediction nearly overlaps with the energy curve from the coupled cluster with singles, doubles, and perturbative triple [CCSD(T)] calculations, while the multireference complete active space self-consistent field (CASSCF) calculations with the small reference configuration (8e,8o) are found to overestimate the biradical character of the electronic state of [Cu2O2]2+ according to the one-electron density matrix analysis.
Growth and band alignment of epitaxial Ni metal gate on crystalline LaAlO3 (001) dielectric film
Authors: Mi Y. Y. , Wang S. J. , Zegenhagen J. , Chai J. W. , Pan J. S. , Huan C. H. A. , Feng Y. P. , Ong C. K.
Published: June 2009

An epitaxial Ni thin film is grown on a LaAlO3 single-crystalline thin film on Si (001). The p-type Schottky barrier height at the Ni/LaAlO3 interface is measured to be 2.88 eV by x-ray photoemission spectroscopy. The effective work function of the Ni film on LaAlO3 is determined to be 5.15 eV. Good epitaxial quality and a high effective work function suggest that Ni is a promising gate material integrated with LaAlO3 dielectric films for p-type metal oxide semiconductor field effect transistors.
Efficient single-component light-emitting electrochemical cells with an ion-conducting water-soluble polyfluorene
Authors: Vak Doojin , Oh Seung-Hwan , Kim Dong-Yu
Published: June 2009

Polymer light-emitting diodes (PLEDs) and light-emitting electrochemical cells (LECs) were fabricated using a water-soluble conjugated polymer with ion-conducting side chains. The water-soluble polymer was spin-coated on the emitting layer of a PLED and was used as an electron-injecting layer. The PLED showed enhanced performance with LEC behavior due to both the mobile ions and ion-conducting side groups of the polymer. A single-component and single-layer device was also fabricated, which showed typical LEC behavior with 1.13% maximum external quantum efficiency after complete ion migration.