bluuebunny/crossref_metadata_2025 huggingface dataset:
A deep‐ocean Kelvin‐Helmholtz billow train
Authors: van Haren Hans , Gostiaux Louis
Published: February 2010

Detailed overturning is observed between 0.5 and 50 m above the sloping side of Great Meteor Seamount, Canary Basin, using 100 moored temperature sensors, 1 mK accurate, sampling at 1‐Hz. While previously reported frontal bores of 40‐m amplitude can form with vigorous near‐bottom motions and sediment resuspension at the beginning of the upslope phase of large, e.g., tidal, carrier waves, the downslope phase presented here is more “permanently” turbulent away from the bottom. This turbulence is inferred from high‐resolution temperature space‐time series, which reveal ubiquitous “finger‐like” structures. It occurs during the clear‐water tidal phase, with low amounts of acoustic scatterers. The high‐frequency finger‐like motions σ ≫ N, N the buoyancy frequency, are observed simultaneously with local mode‐2 near‐N inertio‐gravity waves and overall shear ∣S∣ ≈ N. They show large temperature variations, 5–10 m vertical amplitudes and occasionally develop Kelvin‐Helmholtz billows. The typical (Eulerian) period of these firstly observed deep‐ocean billows amounts 50 ± 10 s.
Offshore transport of the Alaska Coastal Current water induced by a cyclonic wind field
Authors: Yankovsky Alexander E. , Maze Grace M. , Weingartner Thomas J.
Published: February 2010

The Alaska Coastal Current (ACC) is driven by multiple sources of coastal freshwater discharge and propagates alongshore over hundreds of kilometers. The ACC is also subject to downwelling‐favorable winds associated with cyclonic wind systems. Spatially‐uniform, downwelling winds trap the buoyant ACC waters nearshore. However, we demonstrate with numerical experiments that spatial wind variations, due either to a stationary or translating cyclone, can enhance the offshore transport of buoyant coastal waters in comparison to no‐wind conditions. A stationary atmospheric cyclone induces a strong convergence in the coastal current at the upstream periphery of the cyclone. This convergence generates an offshore filament of buoyant water, which evolves into detached anticyclone. A transient atmospheric cyclone enhances the offshore spreading of freshwater by intensifying mesoscale variability of the coastal current. Thus, the spatial structure of the wind field represents a potentially important mechanism for cross‐shelf freshwater transport.
Storm time occurrence of relativistic electron microbursts in relation to the plasmapause
Authors: Johnston W. Robert , Anderson Phillip C.
Published: February 2010

Microbursts, or short‐duration bursts of precipitating relativistic electrons observed at low altitudes, are associated with whistler mode chorus and have been proposed as one of the primary mechanisms for storm time depletion of the outer radiation belt. Whistler chorus occurs outside the plasmapause and is generated by wave‐particle interactions involving soft electrons (1–100 keV). We use low‐altitude identifications of the plasmapause from the DMSP satellites and microburst observations from the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite to identify the relationship between the plasmapause and microburst locations. Microbursts move radially inward during geomagnetic storms in concert with plasmapause movement, with the microbursts consistently located outside the plasmapause. Near storm peak, as Dst reaches minimum values, microbursts occur at a given L value within hours of erosion of the plasmasphere. This time delay between erosion of the plasmasphere and the appearance of microbursts is positively correlated with L value. We find the occurrence of relativistic microbursts to be associated with a combination of daily averaged 1.5–6 MeV electron fluxes exceeding about 1 particle s−1 sr−1 cm−2 (observed at SAMPEX altitudes) and the presence of soft electrons from the plasma sheet. These observations are consistent with the suggestion that microbursts are associated with chorus and contribute significantly to storm time radiation belt depletion.
Longitudinal and seasonal variations of the equatorial ionospheric ion density and eastward drift velocity in the dusk sector
Authors: Huang Chao‐Song , Rich Frederick J. , de La Beaujardiere Odile , Heelis Roderick A.
Published: February 2010

The longitudinal and seasonal variations of the plasma density and drift velocity in the evening equatorial ionosphere show complex characteristics. In this paper, we analyze the ionospheric ion density and velocity measured by the Defense Meteorological Satellites Program (DMSP) F13 and F17 satellites at ∼1800 LT. Our analysis focuses on whether the longitudinal structure of the equatorial ionospheric density and velocity has multiple wave number components, how the longitudinal structure of the equatorial ion eastward drift varies with season and year, and what causes the longitudinal variations of the ion density and velocity. We find that the longitudinal structure of the ion density and velocity show a wave‐4 pattern during the equinox months (March, April, September, and October), a wave‐3 pattern in northern summer (May–August), and a wave‐2 pattern in northern winter (November–February). The longitudinal structure of the ion density and velocity becomes significantly different from the wave‐4 pattern in the longitude regions with large magnetic declination in the summer and winter. The variation of the equatorial ionospheric ion density shows an in‐phase correspondence with the ion eastward velocity and an anti‐phase correspondence with the ion upward velocity. We suggest that the enhanced upward drift causes the density decrease through the fountain effect and that the enhanced eastward drift causes the density increase through horizontal transport. The change of the ion eastward velocity with longitude can be as high as 180 m s−1 over a longitudinal range of 120° and is related to the solar activity. The results of this study reveal a number of new characteristics of the equatorial plasma horizontal drift in the east–west direction.
Simulation of in situ ultrafine particle formation in the eastern United States using PMCAMx‐UF
Authors: Jung JaeGun , Fountoukis Christos , Adams Peter J. , Pandis Spyros N.
Published: February 2010

A three‐dimensional chemical transport model has been developed incorporating the Dynamic Model for Aerosol Nucleation for the simulation of aerosol dynamics into the regional model PMCAMx. Using a scaled version of the ternary H2SO4‐NH3‐H2O nucleation theory and the Two Moment Aerosol Sectional algorithm, the new model (PMCAMx‐UF) is used to simulate a summertime period in the eastern United States. The model predicts, in agreement with observations, frequent nucleation events that take place over hundreds to thousands of kilometers, especially in the northeastern United States. Detailed comparison with the observations of the Pittsburgh Air Quality Study suggests that the model reproduces reasonably well the details of the events in this sulfur rich area but has a tendency to overpredict the frequency of the events. Regional nucleation is predicted to increase the total number concentrations by roughly a factor of 2.5 over the whole domain. The corresponding increases for particles larger than 10 nm (N10) and 100 nm (N100) were 75% and 15%, respectively. In the Ohio River Valley the increases are as much as a factor of 10 for total particle number and 40% for N100. Contrary to the total particle concentration, increases of N100 take place often in areas different than those of the nucleation events. Nucleation is predicted to decrease the N100 in some areas even if it increases the total number concentration. The sensitivity of the model to the nucleation rate scaling parameter and the ammonia levels is discussed.
Aerosol size distribution modeling with the Community Multiscale Air Quality modeling system in the Pacific Northwest: 3. Size distribution of particles emitted into a mesoscale model
Authors: Elleman Robert A. , Covert David S.
Published: February 2010

In order to improve the Community Multiscale Air Quality modeling system (CMAQ) performance for ultrafine particle concentrations in the Pacific Northwest, CMAQ v4.4 was modified so that particles are input to the model with an appropriate size distribution. CMAQ's default emission size distributions are based on outdated measurements which underrepresent ultrafine particles. At the same time, the size distribution must represent the results of all processes between the point of emission and the smallest resolvable spatial scale of the model. As a computationally efficient and simple solution, size distributions were compiled from published modern observations for traffic‐dominated urban areas, power plants, and marine sources at the typical mesoscale air quality model spatial resolution of 4–15 km. CMAQ was modified so that all chemical species are input according to the emission size distribution of traffic‐dominated urban areas because this source emits the majority of each aerosol species in the Pacific Northwest. For a summer 2001 case study based around field measurements, CMAQ v4.4 underpredicts the observable aerosol number concentrations by 1–2 orders of magnitude, while CMAQ with new emission size distributions underpredicts by ∼1 order of magnitude. The modeled size distributions have improved properties in terms of more distinct Aitken and accumulation modes and a more prominent Aitken mode. Errors remain, especially in the accumulation mode.
Toward increased utilization of historical hurricane chronologies
Authors: Scheitlin K. N. , Elsner James B. , Malmstadt J. C. , Hodges R. E. , Jagger T. H.
Published: February 2010

The record of past tropical cyclones provides an important means to evaluate the hurricane hazard. Historical chronologies are a source of information about tropical cyclones prior to the modern era. Chenoweth (2006) describes an archive of 383 tropical cyclones occurring during the eighteenth and nineteenth centuries, largely before the official hurricane record. The present study demonstrates a novel way this archive can be used to articulate historical tropical cyclone activity across space. First, an event in the archive is assigned a series of latitude/longitude coordinates approximating the descriptive locations of the cyclone's affect. Second, tropical cyclones from the modern record that approach these locations (modern analogs) are mapped. Third, a probable pathway and a realistic track of the archived event is created by averaging the modern analog tracks. As an example, the procedure is used to generate a map showing the tracks of the Atlantic tropical cyclones of 1766. Sensitivity of the methodology to changes in event location and event timing are considered. The study shows that historical hurricane chronologies when combined with a history of cyclone tracks can provide useful information about the older events that is not directly related to where the original information was gathered. When this information is available for all cyclones it should help climatologists better understand long‐term variations in tropical cyclone activity.
Can climate change cause the Yellow River to dry up?
Authors: Liang S. , Ge S. , Wan L. , Zhang J.
Published: February 2010

The source region of the Yellow River, China, has experienced eco‐environmental deterioration in recent decades. The Yellow River discharge has reduced to zero numerous times since 1960, which has left a devastating impact on water resources and ecosystems downstream. Seeking to understand the causes of drying up, we analyze the records of discharge, temperature, and precipitation and explore the linkages among them. Using wavelet analysis, we show that the Yellow River discharge represents a comprehensive response to climatic variations in temperature and precipitation. We suggest that the discharge is best explained by variations in temperature over a 35–50 year trend and precipitation over periods of less than 10 years. Zero discharge events can be quantitatively correlated to periods of warming and reduced precipitation. Findings of this study may have a broad implication in assessing how water resources respond to climate changes.
Skp2B attenuates p53 function by inhibiting prohibitin
Authors: Chander Harish , Halpern Max , Resnick‐Silverman Lois , Manfredi James J , Germain Doris
Published: February 2010

The F‐box protein Skp2 and its isoform Skp2B are both overexpressed in breast cancers. Skp2 alters the activity of p53 by inhibiting its interaction with p300 and by promoting p300 degradation. Here, we report that Skp2B also attenuates the activity of p53; however, this effect is independent of p300, suggesting that another mechanism might be involved. Prohibitin, a protein reported to activate p53, was isolated in a two‐hybrid screen with the carboxy‐terminal domain unique to Skp2B. We observed that prohibitin is a new substrate of Skp2B and that the degradation of prohibitin is responsible for the attenuated activity of p53 in cells overexpressing Skp2B. Furthermore, we show that the activity of p53 is reduced in the mammary glands of Skp2B transgenic mice. This study indicates that both Skp2 and Skp2B attenuate p53 activity through different pathways, suggesting that amplification of the Skp2 locus represents a powerful mechanism to attenuate p53 function in cancer.
A domesticated transposon mediates the effects of a single‐nucleotide polymorphism responsible for enhanced muscle growth
Authors: Butter Falk , Kappei Dennis , Buchholz Frank , Vermeulen Michiel , Mann Matthias
Published: February 2010

Single‐nucleotide polymorphisms (SNPs) in the regulatory regions of the genome can have a profound impact on phenotype. The G3072A polymorphism in intron 3 of insulin‐like growth factor 2 (IGF2) is implicated in higher muscle content and reduced fat in European pigs and is bound by a putative repressor. Here, we identify this repressor—which we call muscle growth regulator (MGR)—by using a DNA protein interaction screen based on quantitative mass spectrometry. MGR has a bipartite nuclear localization signal, two BED‐type zinc fingers and is highly conserved between placental mammals. Surprisingly, the gene is located in an intron and belongs to the hobo‐Ac‐Tam3 transposase superfamily, suggesting regulatory use of a formerly parasitic element. In transactivation assays, MGR differentially represses the expression of the two SNP variants. Knockdown of MGR in C2C12 myoblast cells upregulates Igf2 expression and mild overexpression retards growth. Thus, MGR is the repressor responsible for enhanced muscle growth in the IGF2 G3072A polymorphism in commercially bred pigs.
Theoretical studies on the pK~a~ values of perfluoroalkyl carboxylic acids
Authors: Rayne Sierra , Forest Kaya
Published: February 2010

Computational studies were conducted using the major levels of semiempirical, ab initio, density functional theory (DFT), and the CBS-Q//B3 method and various solvation models on a homologous series of straight chain perfluoroalkyl carboxylic acids (PFCAs) ranging in chain length from C~1~ (trifluoroacetic acid) to C~9~ (n-perfluorodecanoic acid) as well as the monomethyl branched C~7~ (n-perfluorooctanoic acid; n-PFOA) isomers. Regardless of perfluoroalkyl chain length and theoretical method employed, application of a computational thermodynamic cycle indicated no significant change in the estimated aqueous monomeric pK~a~ values between C~1~ and C~9~, all having a relatively constant pK~a~ of about 0 that is in agreement with earlier predictions and recent experimental evidence. Perfluoroalkyl chain helicity does not appear to result in increased monomeric PFCA pK~a~ values at chain lengths greater than 5. Increasing chain length does not substantially influence the structural or electronic character of the carboxylic acid head group. A MMFF94 conformational search yielded 2915 separate low- through high-energy conformers of n-PFOA. Ranking of these structures gave the 94 lowest MMFF94 energy conformations that were subjected to DFT investigations. Application of a thermodynamic cycle approach, coupled with aqueous and gas phase DFT calculations on the molecular and anionic forms for each of the conformers, gave conformationally averaged pK~a~ values for n-PFOA equal to the global minimum helical conformer pK~a~. The conformational populations under study occupy about 100 percent of the global n-PFOA conformational space, indicating no higher energy/low acidity conformations remain unexamined that could influence the predicted composite aqueous monomeric pK~a~ of zero for this compound.
Modeling Three-Dimensional Spatial Regulation of Bacterial Cell Division (Dissertation)
Authors: Arjunan Satya
Published: February 2010

Many important cellular processes are regulated by reaction-diffusion (RD) of molecules that takes place both in the cytoplasm and on the membrane. To model and analyze such multicompartmental processes, we developed a lattice-based Monte Carlo method, Spatiocyte that supports RD in volume and surface compartments at single molecule resolution. Stochasticity in RD and the excluded volume effect brought by intracellular molecular crowding, both of which can significantly affect RD and thus, cellular processes, are also supported. We verified the method by comparing simulation results of diffusion, irreversible and reversible reactions with the predicted analytical and best available numerical solutions. Moreover, to directly compare the localization patterns of molecules in fluorescence microscopy images with simulation, we devised a visualization method that mimics the microphotography process by showing the trajectory of simulated molecules averaged according to the camera exposure time. In the rod-shaped bacterium Escherichia coli, the division site is suppressed at the cell poles by periodic pole-to-pole oscillations of the Min proteins (MinC, MinD and MinE) arising from carefully orchestrated RD in both cytoplasm and membrane compartments. Using Spatiocyte we could model and reproduce the in vivo MinDE localization dynamics by accounting for the previously reported properties of MinE. Our results suggest that the MinE ring, which is essential in preventing polar septation, is largely composed of MinE that is transiently attached to the membrane independently after recruited by MinD. Overall, Spatiocyte allows simulation and visualization of complex spatial and reaction-diffusion mediated cellular processes in volumes and surfaces. As we showed, it can potentially provide mechanistic insights otherwise difficult to obtain experimentally.
Oxygen transfer rate control in the production of human‐like collagen by recombinant Escherichia coli
Authors: Ma Xiaoxuan , Fan Daidi , Shang Long‐an , Cai Qiang , Chi Lei , Zhu Chenhui , Mi Yu , Luo Yan‐e
Published: February 2010

The effects of different methods for elevating the OTR (oxygen transfer rate) during foreign gene expression and the cell growth of recombinant Escherichia coli BL21 were investigated. Two strategies were introduced to control DO (dissolved oxygen) levels in the fermentation broth: (i) increasing fermentor pressure and (ii) supplying oxygen‐enriched air. These two methods were compared with the glucose feedback model, which acted as the control. By adopting a fed‐batch method of cultivation, the cell yield coefficient (YX/S), accumulation of acetic acid and volumetric product yield (Yp) were measured or estimated. Adoption of these two methods led to an improvement in the OTR. The cell density and volumetric product yield in the cultivation controlled by increasing the fermentor pressure reached 77 g·l−1 (dry cell weight) and 14 g·l−1 respectively, which were much higher than those obtained with the strategy of supplying oxygen‐enriched air (48 and 6 g·l−1 respectively) and in the control (46 and 7 g·l−1 respectively). The results indicate that increasing fermentor pressure is an effective way to enhance the OTR and recombinant protein (human‐like collagen) productivity.
Changes in VEGF expression and DNA synthesis in hepatocytes from hepatectomized and tumour‐bearing mice
Authors: García Marcela N. , Andrini Laura B. , Inda Ana María , Ronderos Jorge R. , Hijano Julio C. , Errecalde Ana Lía
Published: February 2010

Transplanted tumours could modify the intensity and temporal distribution of the cellular proliferation in normal cell populations, and partial hepatectomy alters the serum concentrations of substances involved in cellular proliferation, leading to the compensatory liver hyperplasia. The following experiments were designed in order to study the SI (S‐phase index) and VEGF (vascular endothelial growth factor) expression in regenerating liver (after partial hepatectomy) of adult male mice bearing a hepatocellular carcinoma, throughout one complete circadian cycle. We used adult male C3H/S‐strain mice. After an appropriate period of synchronization, the C3H/S‐histocompatible ES2a hepatocellular carcinoma was grafted into the subcutaneous tissue of each animal's flank. To determine the index of SI and VEGF expression of hepatocytes, we used immunohistochemistry. The animals were divided into two experimental groups: Group I, control, hepatectomized animals; Group II, hepatectomized tumour‐bearing animals. The statistical analysis of SI and VEGF expression was performed using Anova and Tukey as a postcomparison test. The results show that in the second group, the curve of SI changes the time points for maximum and minimum activity, and the peak of VEGF expression appears before the first group. In conclusion, in the hepatectomized mice, the increases of hepatic proliferation, measured by the SI index, may produce a rise in VEGF expression with the object of generating a vascular network for hepatic regeneration. Lastly, as we have mentioned, in hepatectomized and tumour‐bearing mice, the peak of VEGF expression appears before the one of DNA synthesis.
Generation of multicomponent ion beams by a vacuum arc ion source with compound cathode
Authors: Savkin K. P. , Yushkov Yu. G. , Nikolaev A. G. , Oks E. M. , Yushkov G. Yu.
Published: February 2010

This paper presents the results of time-of-flight mass spectrometry studies of the elemental and mass-to-charge state compositions of metal ion beams produced by a vacuum arc ion source with compound cathode (WC–Co0.5, Cu–Cr0.25, Ti–Cu0.1). We found that the ion beam composition agrees well with the stoichiometric composition of the cathode material from which the beam is derived, and the maximum ion charge state of the different plasma components is determined by the ionization capability of electrons within the cathode spot plasma, which is common to all components. The beam mass-to-charge state spectrum from a compound cathode features a greater fraction of multiply charged ions for those materials with lower electron temperature in the vacuum arc cathode spot, and a smaller fraction for those with higher electron temperature within the spot. We propose a potential diagram method for determination of attainable ion charge states for all components of the compound cathodes.
Simulations of negative ion plasma sheaths
Authors: Cavenago M.
Published: February 2010

The need to accurately model beams of negative ions in high current sources makes reasonable to refine the simulation mesh up to fractions of the Debye length λD, which is typically 0.01 mm. Even if simulations were finally possible in two space dimensions, still the role of one-dimensional (1D) model to clarify the physics of sheath and presheath structure and the stability of numerical solvers is fundamental. Here a 1D model with negative ion production from the extraction wall/grid is considered, coupled to a driver plasma which acts as an electron and proton reservoir at a variable plasma potential. A bias voltage between lateral walls and the extraction wall is also included. Particle motion is modeled with diffusion equations, also for protons; electrons are magnetized and Poisson equation is solved everywhere. The inverted sheath formation and the H− forward current result sensitive to bias voltage.
Glow plasma trigger for electron cyclotron resonance ion sources
Authors: Vodopianov A. V. , Golubev S. V. , Izotov I. V. , Nikolaev A. G. , Oks E. M. , Savkin K. P. , Yushkov G. Yu.
Published: February 2010

Electron cyclotron resonance ion sources (ECRISs) are particularly useful for nuclear, atomic, and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in an open magnetic trap heated by pulsed (100 μs and longer) high power (100 kW and higher) high-frequency (greater than 37.5 GHz) microwaves of gyrotrons is promising in the field of research in the development of electron cyclotron resonance sources for high charge state ion beams. Reaching high ion charge states requires a decrease in gas pressure in the magnetic trap, but this method leads to increases in time, in which the microwave discharge develops. The gas breakdown and microwave discharge duration becomes greater than or equal to the microwave pulse duration when the pressure is decreased. This makes reaching the critical plasma density initiate an electron cyclotron resonance (ECR) discharge during pulse of microwave gyrotron radiation with gas pressure lower than a certain threshold. In order to reduce losses of microwave power, it is necessary to shorten the time of development of the ECR discharge. For fast triggering of ECR discharge under low pressure in an ECRIS, we initially propose to fill the magnetic trap with the plasmas of auxiliary pulsed discharges in crossed ExB fields. The glow plasma trigger of ECR based on a Penning or magnetron discharge has made it possible not only to fill the trap with plasma with density of 1012 cm−3, required for a rapid increase in plasma density and finally for ECR discharge ignition, but also to initially heat the plasma electrons to Te≈20 eV.
Bio-Nano ECRIS: An electron cyclotron resonance ion source for new materials production
Authors: Uchida T. , Minezaki H. , Tanaka K. , Muramatsu M. , Asaji T. , Kato Y. , Kitagawa A. , Biri S. , Yoshida Y.
Published: February 2010

We developed an electron cyclotron resonance ion source (ECRIS) for new materials production on nanoscale. Our main target is the endohedral fullerenes, which have potential in medical care, biotechnology, and nanotechnology. In particular, iron-encapsulated fullerene can be applied as a contrast material for magnetic resonance imaging or microwave heat therapy. Thus, our new ECRIS is named the Bio-Nano ECRIS. In this article, the recent progress of the development of the Bio-Nano ECRIS is reported: (i) iron ion beam production using induction heating oven and (ii) optimization of singly charged C60 ion beam production.
Carborane beam from ITEP Bernas ion source for semiconductor implanters
Authors: Seleznev D. , Kropachev G. , Kozlov A. , Kuibeda R. , Koshelev V. , Kulevoy T. , Hershcovitch A. , Jonson B. , Poole J. , Alexeyenko O. , Gurkova E. , Oks E. , Gushenets V. , Polozov S. , Masunov E.
Published: February 2010

A joint research and development of steady state intense boron ion sources for hundreds of electron-volt ion implanters has been in progress for the past 5 years. The difficulties of extraction and transportation of low energy boron beams can be solved by implanting clusters of boron atoms. In Institute for Theoretical and Experimental Physics (ITEP) the Bernas ion source successfully generated the beam of decaborane ions. The carborane (C2B10H12) ion beam is more attractive material due to its better thermal stability. The results of carborane ion beam generation are presented. The result of the beam implantation into the silicon wafer is presented as well.
Measurement of radial and axial high energy x-ray spectra in electron cyclotron resonance ion source plasmas
Authors: Noland J. , Benitez J. Y. , Leitner D. , Lyneis C. , Verboncoeur J.
Published: February 2010

Radial and axial x-ray measurements of electron cyclotron resonance ion sources operating at microwave frequencies of 6.4 and 14 GHz are presented. Results indicate a greater detected photon energy in the radial direction than the axial direction for both the 6.4 GHz source and the 14 GHz source. It is also seen that the 14 GHz source produces x-rays with higher energies, when compared to the 6.4 GHz source, in both radial and axial directions.
Simulation of parameter scaling in electron cyclotron resonance ion source plasmas using the GEM code
Authors: Cluggish B. , Zhao L. , Kim J. S.
Published: February 2010

Although heating power and gas pressure are two of the two of primary experimental “knobs” available to users of electron cyclotron resonance ion sources, there is still no clear understanding of how they interact in order to provide optimal plasma conditions. FAR-TECH, Inc. has performed a series of simulations with its generalized electron cyclotron resonance ion source model in which the power and pressure were varied over a wide range. Analysis of the numerical data produces scaling laws that predict the plasma parameters as a function of the power and pressure. These scaling laws are in general agreement with experimental data.
Characteristics of liquid cluster ion beam for surface treatment
Authors: Ryuto H. , Ozaki R. , Kubo Y. , Takeuchi M. , Takaoka G. H.
Published: February 2010

A liquid cluster ion source, which is an ion source for the cluster beams produced with liquid materials, has been developed for the surface treatment of solid materials. The electrodes were designed for increasing the cluster beam intensity by a computer simulation of beam trajectories. The peaks of the cluster size distributions of the water and ethanol cluster ion beams of 3 atm vapor pressure were approximately at 2.4×103 and 1.6×103 molecules, respectively. The cluster size distributions of ethanol clusters were not sensitive to the variations of the acceleration voltages (Ve) and currents (Ie) of the electrons for ionization when the Ve and Ie were larger than approximately 200 V and 200 mA, respectively.
A compact multipurpose nanomanipulator for use inside a scanning electron microscope
Authors: Heeres E. C. , Katan A. J. , van Es M. H. , Beker A. F. , Hesselberth M. , van der Zalm D. J. , Oosterkamp T. H.
Published: February 2010

A compact, two-stage nanomanipulator was designed and built for use inside a scanning electron microscope. It consists of a fine stage employing piezostacks that provide a 15 μm range in three dimensions and a coarse stage based on commercially available stick-slip motors. Besides the fabrication of enhanced probes for scanning probe microscopy and the enhancement of electron field emitters, other novel manipulation processes were developed, such as locating, picking up, and positioning small nanostructures with an accuracy of ∼10 nm. In combination with in situ I-V experiments, welding, and etching, this results in a multipurpose nanofactory, enabling a new range of experiments.
The NSCL electron beam ion trap for the reacceleration of rare isotopes coming to life: First extraction tests with a high-current electron gun
Authors: Schwarz S. , Bollen G. , Johnson M. , Kester O. , Kostin M. , Ottarson J. , Portillo M. , Wilson C. , López-Urrutia J. R. Crespo , Dilling J.
Published: February 2010

NSCL is currently constructing the ReA3 reaccelerator, which will accelerate rare isotopes obtained from gas stopping of fast-fragment beams to energies of up to 3 MeV/u for uranium and higher for lighter ions. A high-current charge breeder, based on an electron beam ion trap (EBIT), has been chosen as the first step in the acceleration process, as it has the potential to efficiently produce highly charged ions in a single charge state. These ions are fed into a compact linear accelerator consisting of a radio frequency quadrupole structure and superconducting cavities. The NSCL EBIT has been fully designed with most of the parts constructed. The design concept of the EBIT and results from initial commissioning tests of the electron gun and collector with a temporary 0.4 T magnet are presented.
Influence of H− velocity on H− extraction probability from a negative ion source
Authors: Matsumoto Y. , Nishiura M. , Shinto K. , Yamaoka H. , Sasao M. , Wada M.
Published: February 2010

We investigate influence of H− initial transport direction and kinetic energy on H− extraction probability with three-dimensional Monte Carlo calculation. As a result, lower energy H− ions are strongly trapped by the electrical potential structure, so that initial condition of H− transport direction is cancelled by alignment of the electric field; thus, it has lower influence for H− extraction probability. Besides, the potential hill induced by the beam extraction voltage more effectively enhances H− extraction probability for the lower energy H− ions. The correlation between the magnitude of the local plasma potential near the extraction region and the mean velocity of H− ions in the region should determine the H− extraction probability from the ion source.
A self-sputtering ion source: A new approach to quiescent metal ion beams
Authors: Oks Efim , Anders André
Published: February 2010

A new metal ion source is presented based on sustained self-sputtering plasma in a magnetron discharge. Metals exhibiting high self-sputtering yield such as Cu, Ag, Zn, and Bi can be used in a high-power impulse magnetron sputtering discharge such that the plasma almost exclusively contains singly charged metal ions of the target material. The plasma and extracted ion beam are quiescent. The ion beams consist mostly of singly charged ions with a space-charge limited current density which reached about 10 mA/cm2 at an extraction voltage of 45 kV and a first gap spacing of 12 mm.
Enhanced surface production in H− ion sources by introducing a negatively biased secondary electrode
Authors: An YoungHwa , Jung BongKi , Hwang Y. S.
Published: February 2010

A transformer coupled plasma negative hydrogen ion source with an external rf antenna has been developed at SNU, which is capable of continuous operation with long lifetime. A positively biased plasma electrode (PE) has been successfully used for the optimization of H− extraction. With molybdenum-coated stainless steel PE, the enhancement of H− production at the electrode surface was observed at the bias voltage lower than the plasma potential. However, the low bias voltage is unfavorable to H− beam extraction since the negative ions are repelled. A second electrode is inserted in front of the PE to enhance H− production at the electrode surface without impeding beam extraction. By biasing the secondary electrode (SE) more negatively, H− production is clearly enhanced although the SE itself reduces H− beam currents because of suppressed electron transport in front of the PE. In this configuration enhancement of surface productions is most pronounced in tantalum electrode among various electrode materials.
3D modeling of the electron energy distribution function in negative hydrogen ion sources
Authors: Terasaki R. , Fujino I. , Hatayama A. , Mizuno T. , Inoue T.
Published: February 2010

For optimization and accurate prediction of the amount of H-ion production in negative ion sources, analysis of electron energy distribution function (EEDF) is necessary. We are developing a numerical code which analyzes EEDF in the tandem-type arc-discharge source. It is a three-dimensional Monte Carlo simulation code with realistic geometry and magnetic configuration. Coulomb collision between electrons is treated with the “binary collision” model and collisions with hydrogen species are treated with the “null-collision” method. We applied this code to the analysis of the JAEA 10 A negative ion source. The numerical result shows that the obtained EEDF is in good agreement with experimental results.
The effect of impurities on spin-polarized Zeeman bound states in dilute magnetic semiconductor-superconductor hybrids
Authors: Lin Shi-Hsin , Rappoport Tatiana G. , Berciu Mona , Jankó Boldizsár
Published: February 2010

We investigate the effect of single and multiple impurities on the Zeeman-localized, spin-polarized bound states in dilute magnetic semiconductor hybrid system. Such bound states appear whenever a dilute magnetic semiconductor showing giant Zeeman effect is exposed to an external magnetic field showing nanoscale inhomogeneity. We consider the specific example of a superconductor-dilute magnetic semiconductor hybrid, calculate the energy spectrum and the wave functions of the bound states in the presence of a single impurity, and monitor the evolution of the bound state as a function of the impurity strength and impurity location with respect to the center of the Zeeman trapping potential. Our results have important experimental implications as they predict robust spin textures even for ideal samples. We find that for all realistic impurity strengths the Zeeman bound state survives the presence of the impurity. We also investigate the effect of a large number of impurities and perform ensemble averages with respect to the impurity locations. We find that the spin-polarized Zeeman bound states are very robust, and they remain bound to the external field inhomogeneity throughout the experimentally relevant region of impurity concentration and scattering strength.
Note: Lateral force microscope calibration using multiple location pivot loading of rectangular cantilevers
Authors: Chung Koo-Hyun , Reitsma Mark G.
Published: February 2010

This note outlines a calibration method for atomic force microscope friction measurement that uses the “pivot” method of [Bogdanovic et al., Colloids Surf. B 19, 397 (2000)] to generate optical lever sensitivities for known torque applied to rectangular cantilevers. We demonstrate the key calibration parameter to be a linear function of the position at which it is determined along the length of the cantilevers. In this way the optical lever system can be calibrated for cantilever torque by applying loads at locations along the length of a cantilever, away from the integrated tip, so that issues such as tip damage or interference can be avoided.
Scaling consideration and compact model of electron scattering enhancement due to acoustic phonon modulation in an ultrafine free-standing cylindrical semiconductor nanowire
Authors: Hattori Junichi , Uno Shigeyasu , Nakazato Kazuo , Mori Nobuya
Published: February 2010

We theoretically investigate the interaction between modulated acoustic phonons and electrons in a free-standing cylindrical semiconductor nanowire and calculate the electron mobility limited by modulated acoustic phonons in a [001]-oriented silicon nanowire (SiNW) at room temperature. The mobility is smaller than that limited by bulk phonons because form factors increase due to acoustic phonon modulation. By expressing the form factor increase through an analytical formula, we derive a compact formula for mobility that is valid for a nanowire in which most electrons occupy the lowest subband, regardless of the wire material. The compact formula achieves excellent accuracy for a [001]-oriented SiNW with a radius of less than 2nm at an electron density of 2×109m−1, and its applicable radius increases with decreasing electron density
Realization of a phononic crystal operating at gigahertz frequencies
Authors: Su M. F. , Olsson R. H. , Leseman Z. C. , El-Kady I.
Published: February 2010

We report on the experimental realization of a phononic crystal, designed to operate at gigahertz frequencies. Detailed studies of the structure have been performed using finite difference time domain method to determine effects of slab modes in finite-thickness slabs, thus enabling precise guidance of experimental efforts. In particular, we find the slab mode effects mitigated in ultrathin (thickness less than lattice periodicity) and ultrathick (thickness more than ten times lattice periodicity) slabs. Gigahertz-frequency phononic crystals are well poised to find usage as high-Q resonators, waveguides, and coupling elements in a variety of application areas including RF communications.
Investigations of the emittance and brightness of ion beams from an electron beam ion source of the Dresden EBIS type
Authors: Silze Alexandra , Ritter Erik , Zschornack Günter , Schwan Andreas , Ullmann Falk
Published: February 2010

We have characterized ion beams extracted from the Dresden EBIS-A, a compact room-temperature electron beam ion source (EBIS) with a permanent magnet system for electron beam compression, using a pepper-pot emittance meter. The EBIS-A is the precursor to the Dresden EBIS-SC in which the permanent magnets have been replaced by superconducting solenoids for the use of the source in high-ion-current applications such as heavy-ion cancer therapy. Beam emittance and brightness values were calculated from data sets acquired for a variety of source parameters, in leaky as well as pulsed ion extraction mode. With box shaped pulses of C4+ ions at an energy of 39 keV root mean square emittances of 1–4 mm mrad and a brightness of 10 nA mm−2 mrad−2 were achieved. The results meet the expectations for high quality ion beams generated by an electron beam ion source.
A Kähler structure on Finsler spaces with nonzero constant flag curvature
Authors: Peyghan E. , Tayebi A.
Published: February 2010

In this paper, we obtain a Kähler structure on the tangent bundle of a Finsler manifold of positive constant flag curvature. We show that there does not exist any Finsler metric such that this structure became locally symmetric or Einstein manifold. Similar results are obtained on a tube around zero section in the tangent bundle in the case of a Finsler manifold of negative constant flag curvature.
X-ray polarimeter with a transmission multilayer
Authors: Kitamoto Shunji , Murakami Hiroshi , Shishido Youich , Gotoh Norimitsu , Shibata Takuma , Saito Kousuke , Watanabe Takeshi , Kanai Jun’ichi , Takenaka Eri , Nagasaki Kenta , Yoshida Masaki , Takei Dai , Morii Mikio
Published: February 2010

We fabricated a novel x-ray polarimeter with a transmission multilayer and measured its performance with synchrotron radiation. A self standing multilayer with seven Mo/Si bilayers was installed with an incident angle of 45° in front of a back-illuminated CCD. The multilayer can be rotated around the normal direction of the CCD keeping an incident angle of 45°. This polarimeter can be easily installed along the optical axis of x-ray optics. By using the CCD as a photon counting detector with a moderate energy resolution, the polarization of photons in a designed energy band can be measured along with the image. At high photon energies, where the multilayer is transparent, the polarimeter can be used for imaging and spectroscopic observations. We confirmed a modulation factor of 45% with 45% and 17% transmission for P- and S-polarization, respectively.
Proton disorder and the dielectric constant of type II clathrate hydrates
Authors: Rick Steven W. , Freeman David L.
Published: February 2010

Computational studies are presented examining the degree of proton disorder in argon and molecular hydrogen sII clathrate hydrates. Results are presented using a variety of model potentials for the dielectric constant, the proton order parameter, and the molecular volume for the clathrate systems. The dielectric constant for the clathrate systems is found to be lower than the dielectric constant of ice in all models. The ratio of the clathrate to ice dielectric constant correlates well with the ratio of the densities, which is not the case for comparisons to the liquid, so that differences in the dielectric constants between ice and the clathrates are most likely due to differences in densities. Although the computed dielectric constant is a strong function of the model potential used, the ratio of the dielectric constant of ice to that of the clathrates is insensitive to the model potential. For the nonpolar guest molecules used in the current study, the degree proton of disorder is found to depend weakly on the identity of the guest but the dielectric constant does not appear to be sensitive to pressure or the type of guest.
Design considerations for surface plasmon resonance based detection of human blood group in near infrared
Authors: Sharma Anuj K. , Jha Rajan , Pattanaik Himansu S.
Published: February 2010

Surface plasmon resonance based sensor for detection of different human blood groups in near infrared region is proposed. The plasmonic structure is based on fused silica or chalcogenide sulfide glass Ge20Ga5Sb10S65, commonly known as 2S2G. Experimental results describing the wavelength-dependent refractive index variation in multiple samples of different blood groups are considered for theoretical calculations. The angular interrogation method is considered. The sensor’s performance is closely analyzed in terms of its angular shift and curve width in order to predict the design consideration for simple and accurate blood-group identifier. The results are explained in terms of light coupling and plasmon resonance condition. Chalcogenide glass-based SPR structure is able to provide highly precise detection of different blood groups. The proposed low-volume blood sensor can be very useful for simple and reliable blood sample detection in medical application.
Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector
Authors: Smith Richard J. , Light Roger A. , Sharples Steve D. , Johnston Nicholas S. , Pitter Mark C. , Somekh Mike G.
Published: February 2010

This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.
Spectroscopic aspects of front transparent conductive films for a-Si thin film solar cells
Authors: Fan Qi Hua , Chen Changyong , Liao Xianbo , Xiang Xianbi , Cao Xinmin , Ingler William , Adiga Nirupama , Deng Xunming
Published: February 2010

This work demonstrates a method to optimize the indium tin oxide (ITO) thin films as front transparent electrode to maximize the efficiency of substrate type amorphous silicon (a-Si) based thin film solar cells. It shows that the total light intensity absorbed by the a-Si layer can be predicted by combining a multilayer optical simulation with the nonuniform solar spectrum and the spectroscopic response of the absorption coefficient of the a-Si film. Consequently, an optimized ITO film can be identified. The photovoltaic performances of experimentally obtained a-Si single junction solar cells confirm the simulation results, indicating an ITO film about 56 nm thick leads to the highest efficiency. Furthermore, it is shown that the ITO films should be deposited at relatively low temperature around 132 °C to avoid damage to the a-Si top p-layer and p-i-n junction. It is found that introducing a small fraction, ∼0.61% flow ratio, of O2 in the sputtering Ar gas reduces the sheet resistivity of the ITO film and improves its transmittance, leading to higher efficiency a-Si solar cells.
rf linewidth reduction in a quantum dot passively mode-locked laser subject to external optical feedback
Authors: Lin C.-Y. , Grillot F. , Naderi N. A. , Li Y. , Lester L. F.
Published: February 2010

The effect of external optical feedback on an InAs/GaAs quantum dot passively mode-locked laser is investigated. The rf linewidth narrows from 8 KHz in the free-running situation to a value as low as 350 Hz under relatively low feedback. The rf linewidth characterization under resonant feedback at a multiple of the laser cavity length validates the prediction of a previous numerical simulation. It is also confirmed that the integrated rms timing jitter varies as the square root of the rf linewidth. The results are promising for the development of compact, monolithic semiconductor mode-locked lasers as low noise optoelectronic oscillators.