bluuebunny/crossref_metadata_2025 huggingface dataset:
The Variation of CMP Pad Asperity Friction as a Function of Speed and Normal Load
Authors: Levert Joseph A. , Haas David , Korach Chad S. , Lakomcik Nicholas , Peters Edward
Published: June 2009

CMP (chemical mechanical polishing) is a vital IC (integrated circuit) manufacturing process. CMP is performed by rubbing the IC surface with a roughened polyurethane polishing pad in the presence of a chemically active, abrasive containing slurry. Friction is a natural consequence of CMP, and this friction can damage next generation, mechanically weak, porous dielectric materials on the IC surface. Earlier research has been done to characterize this friction, but the data is confounded with hydrodynamic effects. More recent experiments have measured the coefficient of friction with varying slurry characteristics but at low speeds and constant normal load which could decouple hydrodynamic effects. This new research measures the coefficient of friction with varying low speeds and varying loads. The coefficient of friction had a very small, statistically significant decrease with increasing normal load. This effect was attributed to elastic Hertzian pad asperity deflection with friction force being proportional to the asperity contact area. At lower normal loads, there was not statistically significant change in the coefficient as a function of speed. At the highest normal load, there was a very small increase in the coefficient of friction as the speed increased. It is proposed that counter-intuitive trend was a result of the following mechanism. Time dependent surface hydration film reduces the coefficient of friction. This surface film is damaged by rubbing, and the lower speed permitted more time for the film to regenerate.
Sensitivity of Engine-Component Wear to Lubricant-Additive and Contact Conditions Using an Antiwear Film Formation Model
Authors: Wong Victor W. , Liao Kai
Published: June 2009

Traditional engine wear models link wear rates to detailed material and contact conditions. Effects of lubricant and additive characteristics are often described by and lumped in empirical parameters such as wear coefficients. With increased environmental concern that lubricant and additives impact emissions and exhaust treatment catalysts, there is increasing interest in optimizing the lubricant and additive combination while providing adequate protection against engine wear. While the mechanisms of anti-wear film formation have been studied in great detail, engineering models of component wear incorporating lubricant chemistry are just beginning to emerge. These models build on the understanding of anti-wear film mechanisms developed and published over the years on the one hand, and on classical wear models for rough surfaces on the other. One such model has been applied to study the sensitivity of the following effects on component wear: Kinetics of ZDDP, which vary according to type and formulation, surface characteristics, contact loads and temperatures, as well as the replenishment and depletion rates of lubricant-additive to the surface-lubricant interfaces. The calculations are done for several engine components under real-world operating conditions.
A Parametric Study of the Dynamics of a Six-Pocket Hydrostatic Journal Bearing
Authors: Braun Minel J. , Moldovan Stefan I. , Balasoiu Ana M.
Published: June 2009

This paper presents a numerical investigation into the dynamics and pressure distribution of a full hydrostatic bearing with six pockets. The pockets are rectangular and the effects of their depth are investigated by choosing a deep pocket type (0.25in) and a shallow one (0.01in), respectively. Parametric studies are partitioned in operational and geometric. The operational ones include the effects of bearing eccentricity and shaft rotation speeds. The geometric ones are the concentric clearance and the pocket depth. Whether deep or shallow the pockets have the same footprint projected base. It was found that the pocket’s depth causes the pressure to be either uniform across the pocket (deep pocket) or vary (shallow) in a ramp increasing in the direction of rotation. In both cases a Raleigh step effect is observed at the downstream edge of the pocket. More interestingly, in the convergent region the hydrodynamic effect on the lands creates pressures that are significantly higher than those in the hydrostatic pockets when the rotational speeds are high. It was found that for narrow clearance the effect of pocket depth on cross-coupled and direct stiffness is negligible, while for the large clearance the stiffness decreases with the increase in the pocket depth. For either type of pocket the stiffness increases with eccentricity and rotation whether the concentric clearance is large or small.
Coefficients Used in a New Transition Reynolds Equation Model
Authors: Deng D. , Braun M. J.
Published: June 2009

This paper presents a numerical investigation of the coefficients used in the transition Reynolds equation model [1], which is applicable to the transition flow of thin films in long journal bearings. Calculations show that the overall coefficient A1(Reh) increases with the increase of Reynolds number, while the other overall coefficient A2(Reh) decreases with the increase of Reynolds number. A1(Reh) is always positive and A2(Reh) is always negative. The magnitude of both A1(Reh) and A2(Reh) is larger for the larger clearance ratio C/R at the same Reynolds number. The curves of A1(Reh) or A2(Reh) for different clearance ratios tend to collapse to one when Taylor number is used as the abscissa, particularly when Taylor number is less than 70. With these coefficients determined the model presented in [1] is fully usable.
A Mixed-Lubrication Model for Shoe-Floor Friction Applied to Pin-on-Disk Apparatus
Authors: Beschorner K. E. , Lovell M. R. , Higgs C. Fred , Redfern M. S.
Published: June 2009

Despite the serious health concern associated with slip and fall accidents and the numerous slip testing devices that have been developed, few studies have attempted to tribologically model the shoe-floor interface. To this end, a mixed-lubrication model for shoe-floor interfaces is proposed. The model is applied to a pin-on-disk apparatus and uses contact mechanics and hydrodynamic lubrication modeling with iterative methods to solve the mixed lubrication problem. Outputs of the model are load supported by the fluid and load supported by the contacting asperities. Measurable parameters input to the model are: curvature of the shoe material (pin), material properties of the shoe material, roughness of the shoe and floor material, viscosity of the fluid, sliding speed and normal force. COF estimates are generated as a function of the proportional load borne by the fluid and the contacting asperities. The model COF values replicate the experimental data for the two different shoe materials tested. The peak hydrodynamic pressure was found just outside the contact region and peak contact pressure was at the center of the pin. The model represents a first step towards developing a mixed-lubrication model for an entire shoe-floor surface.
Sliding Contact of Elastically Dissimilar Periodic Profiles
Authors: Block Joseph M. , Keer Leon M.
Published: June 2009

Various methods for solving the partial contact of surfaces with regularly periodic profiles—which might arise in analyses of asperity level contact, serrated surfaces or even curved structures—have previously been employed for elastic materials. A new approach based upon the summation of evenly spaced Flamant’s solution is used here to solve periodic problems in plane elasticity for sliding contact with Coulomb friction. The advantage is that solutions are derived in a straightforward manner without requiring extensive experience with advanced mathematical theory.
Local Tool Wear Prediction Using Physics-Based Models
Authors: Olortegui-Yume Jorge A. , Park Kyung-Hee , Kwon Patrick Y.
Published: June 2009

A semi-empirical model based on the physics behind tool wear that can depict the tool wear locally is developed to predict crater profiles of multilayer coated carbides. Dissolution and abrasion relationships are recast into a point-wise or local version to predict directly based on the temperature and pressure profiles from FE simulation. The approach is reasonable to explain the crater profiles observed in multilayer coated carbides. However, the model deviates from the real profiles due to the κ-to-α phase transformation in the middle Al2O3 layer, the change in the friction conditions as each layer is exposed, and the combined wear resistance of multi-layers of the cutting tool.
Nano-Scale Tribological Properties of Silicon Pillars With the Variation in Pitch
Authors: Pham Duc-Cuong , Singh R. Arvind , Kim Jinseok , Yang Sungwook , Yoon Eui-Sung
Published: June 2009

Topographical modification of silicon (100) wafers was performed by the creation of nano-structures that consists of pillars with different pitch. The modified surfaces were investigated for their tribological characteristics at nano-scale in comparison with those of the bare silicon surface. Results showed that the modified surfaces have superior nano-tribological properties, as they reduce adhesion and friction forces significantly when compared to the bare silicon surface. Among the nano-structures, adhesion and friction forces reduce with the pitch. The topographical modification of silicon surfaces provides a promising solution to improve the tribological properties of miniaturized devices such as microelectromechanical systems (MEMS) in which silicon is a typically used material.
Oil Wave Journal Bearing Steady-State Data From a New Test Rig
Authors: Dimofte Florin , Ene Nicoleta M. , Oswald Fred B.
Published: June 2009

An oil lubricated wave bearing has been tested on a new rig for fluid film journal bearings at NASA Glenn Research Center in Cleveland, Ohio, USA. The tests are intended to evaluate the rig possibilities of running without misalignment. Data recorded under steady-state conditions included oil flow rate, input, output and oil supply temperatures, and shaft position. Two sets of data were collected: i) by varying the load to 9000 N at a constant shaft rotation speed of 8,000 RPM and ii) by varying the speed from 9,000 to 12,000 RPM at constant load of 6,700 N. The temperatures of the metal sleeves were also recorded. Vibration levels at four locations were displayed and recorded. These measurements indicated that damping from the wave bearings provides significant attenuation of the vibration generated by the air turbine that drives the rig.
Multi-Phase Modeling of Journal Bearing With Oil and Boric Acid Lubricant
Authors: Terrell Elon J. , Higgs C. Fred
Published: June 2009

Past studies have shown that oil lubricants with boric acid powder additives have the ability to both lubricate and support large amounts of applied load. In order to develop the predictive capability for a journal bearing that is lubricated with an oil/boric acid mixture, a multi-phase simulation was created which used particle dynamics and computational fluid dynamics (CFD) modeling.
Hydraulic Fluid Viscosity Selection for Improved Fuel Economy
Authors: Michael Paul , Herzog Steven N.
Published: June 2009

Fluid properties have a major influence upon the energy efficiency of hydraulic equipment. The relationship between hydraulic fluid viscosity, shear stability and system fuel economy has been studied. New viscosity selection guidelines for hydraulic pumps and motors are proposed. These guidelines provide a means for improving the efficiency of fluid power systems.
H-NS Modulates Multidrug Resistance of
Salmonella enterica
Serovar Typhimurium by Repressing Multidrug Efflux Genes
acrEF
Authors: Nishino Kunihiko , Hayashi-Nishino Mitsuko , Yamaguchi Akihito
Published: June 2009

Screening of
Salmonella
mutants for the ability to increase β-lactam resistance has led to the identification of a mutation in
hns
, which codes for the histone-like nucleoid structuring protein (H-NS). In this study, we report that H-NS modulates multidrug resistance through repression of the genes that encode the AcrEF multidrug efflux pump in
Salmonella enterica
serovar Typhimurium.
Besifloxacin, a Novel Fluoroquinolone, Has Broad-Spectrum In Vitro Activity against Aerobic and Anaerobic Bacteria
Authors: Haas Wolfgang , Pillar Chris M. , Zurenko Gary E. , Lee Jacqueline C. , Brunner Lynne S. , Morris Timothy W.
Published: June 2009

The antibacterial spectrum of besifloxacin, a novel fluoroquinolone recently approved for treatment of ocular infections, was studied using 2,690 clinical isolates representing 40 species. Overall, besifloxacin was the most potent agent tested against gram-positive pathogens and anaerobes and was generally equivalent to comparator fluoroquinolones in activity against most gram-negative pathogens. Besifloxacin demonstrated potent, broad-spectrum activity, which was particularly notable against gram-positive and gram-negative isolates that were resistant to other fluoroquinolones and classes of antibacterial agents.
Evaluation of Artemisone Combinations in
Aotus
Monkeys Infected with
Plasmodium falciparum
Authors: Obaldia Nicanor , Kotecka Barbara M. , Edstein Michael D. , Haynes Richard K. , Fugmann Burkhard , Kyle Dennis E. , Rieckmann Karl H.
Published: June 2009

Artemisone (single oral dose, 10 mg/kg of body weight) cured nonimmune
Aotus
monkeys of their
Plasmodium falciparum
infections when combined with mefloquine (single oral dose, 5 and 10 mg/kg but not 2.5 mg/kg). In combination with amodiaquine (20 mg/kg/day), artemisone (10 mg/kg/day) given orally for 3 days cured all infected monkeys. Three days of treatment with artemisone (30 mg/kg/day) and clindamycin (100 mg/kg/day) was also curative.
Reintroduction of Two Deleted Virulence Loci Restores Full Virulence to the Live Vaccine Strain of
Francisella tularensis
Authors: Salomonsson Emelie , Kuoppa Kerstin , Forslund Anna-Lena , Zingmark Carl , Golovliov Igor , Sjöstedt Anders , Noppa Laila , Forsberg Åke
Published: June 2009

A disadvantage of several old vaccines is that the genetic events resulting in the attenuation are often largely unknown and reversion to virulence cannot be excluded. In the 1950s, a live vaccine strain, LVS, was developed from a type B strain of
Francisella tularensis
, the causative agent of tularemia. LVS, which is highly attenuated for humans but still virulent for mice by some infection routes, has been extensively studied and found to protect staff from laboratory-acquired tularemia. The efforts to improve biopreparedness have identified a demand for a vaccine against tularemia. Recently the rapid progress in genomics of different
Francisella
strains has led to identification of several regions of differences (RDs). Two genes carried within RDs,
pilA
, encoding a putative type IV pilin, and FTT0918, encoding an outer membrane protein, have been linked to virulence. Interestingly, LVS has lost these two genes via direct repeat-mediated deletions. Here we show that reintroduction of the two deleted regions restores virulence of LVS in a mouse infection model to a level indistinguishable from that of virulent type B strains. The identification of the two attenuating deletion events could facilitate the licensing of LVS for use in humans.
Mesenteric Lymph Nodes Confine Dendritic Cell-Mediated Dissemination ofSalmonella entericaSerovar Typhimurium and Limit Systemic Disease in Mice
Authors: Voedisch Sabrina , Koenecke Christian , David Sascha , Herbrand Heike , Förster Reinhold , Rhen Mikael , Pabst Oliver
Published: June 2009

In humans with typhoid fever or in mouse strains susceptible toSalmonella entericaserovar Typhimurium (S. Typhimurium) infection, bacteria gain access to extraintestinal tissues, causing severe systemic disease. Here we show that in the gut-draining mesenteric lymph nodes (MLN), the majority ofS.Typhimurium-carrying cells show dendritic-cell (DC) morphology and express the DC marker CD11c, indicating thatS. Typhimurium bacteria are transported to the MLN by migratory DCs. In vivo FLT-3L-induced expansion of DCs, as well as stimulation of DC migration by Toll-like receptor agonists, results in increased numbers ofS. Typhimurium bacteria reaching the MLN. Conversely, genetically impaired DC migration in chemokine receptor CCR7-deficient mice reduces the number ofS. Typhimurium bacteria reaching the MLN. This indicates that transport ofS. Typhimurium from the intestine into the MLN is limited by the number of migratory DCs carryingS. Typhimurium bacteria. In contrast, modulation of DC migration does not affect the number ofS. Typhimurium bacteria reaching systemic tissues, indicating that DC-bound transport ofS. Typhimurium does not substantially contribute to systemicS. Typhimurium infection. Surgical removal of the MLN results in increased numbers ofS. Typhimurium bacteria reaching systemic sites early after infection, thereby rendering otherwise resistant mice susceptible to fatal systemic disease development. This suggests that the MLN provide a vital barrier shielding systemic compartments from DC-mediated dissemination ofS. Typhimurium. Thus, confinement ofS. Typhimurium in gut-associated lymphoid tissue and MLN delays massive extraintestinal dissemination and at the same time allows for the establishment of protective adaptive immune responses.
The stratigraphy of the Lower Ordovician St. George Group, western Newfoundland: the interaction between eustasy and tectonics
Authors: Knight Ian , James Noel P.
Published: June 2009

The St. George Group is a ~500 m thick sequence of carbonate rock that accumulated during Early and early Middle Ordovician time in a series of shallow subtidal and peritidal environments near the outer edge of a low-latitude continental margin. Lithological variations, in the form of two megacycles, reflect deposition in response to eustatic fluctuations in sea level preceding and during the early stages of Taconic orogenesis.Strata are grouped into four formations of roughly equal thickness. The newly named basal Watts Bight Formation is a lower sequence of peritidal limestones and dolostones and an upper thicker, commonly dolomitized succession of burrowed carbonates distinguished by large digitate thrombolite mounds. The overlying Boat Harbour Formation (new) is a series of muddy, peritidal, shallowing-upward sequences of limestone and dolostone. A widespread subaerial disconformity near the top of the formation, reflecting eustaic sea-level fall and the end of the first megacycle, is marked by breccia, quartz-pebble conglomerate, paleokarst, and (or) extensive dolomitization and is succeeded by higher energy peritidal limestones called the Barbace Cove Member (new). The succeeding, thick, monotonous Catoche Formation (revised) is a succession of fossiliferous subtidal limestones with scattered thrombolite mounds whose upper part is locally affected by extensive, multigeneration dolomitization and Pb–Zn mineralization. The St. George Group is capped by the newly defined Aguathuna Formation, a stack of peritidal dolostones and minor limestones and shales deposited during a period of repeated exposure and synsedimentary faulting. An erosional disconformity, resulting from regional compressional tectonics and eustatic sea-level fall, locally marks the top of the St. George and the second megacycle.
An estimate of rebound potential of the Shaftesbury shales at a damsite in British Columbia
Authors: Hanna A. , Little T. E.
Published: June 2009

The hydraulic structures of the proposed site C hydroelectric project in northeastern British Columbia would require deep excavations in Lower Cretaceous Shaftesbury shales. A significant stress relief would occur over most of the area to be occupied by the structures. Concerns about the magnitude and rate of time-dependent rebound and their impacts on project design, construction, and operation have been addressed. A review was made of several important case histories of other major projects constructed on Prairie shales. The properties of those shales were compared with the Shaftesbury shales. Long-term testing to establish the shale swelling characteristics was performed. Analyses were then made to evaluate potential elastic and time-dependent rebounds of the project area. A procedure for computing stress changes and time-dependent deformations due to the unloading effect of excavation followed by structural loading was developed. The procedure is useful in determining differential rebound that would occur in areas of steep topography or significant variations in the distribution of structural loads. Key words : rebound, shales, dam, swelling properties, swelling pressure, stress relief, deep excavations.
Laboratory tests to study hydraulic fill
Authors: Küpper Angela A. G. , Morgenstern Norbert R. , Sego David C.
Published: June 2009

Laboratory flume deposition tests were carried out to study the physical phenomena associated with the deposition of a sand slurry to form a hydraulic fill. The experimental apparatus was carefully designed to minimize flume-wall effects on the flow and to allow discharge of slurry of constant composition for an indefinite period of time. Slurry concentration and flow rate were varied independently to study their effects on characteristics of the fill such as geometry, grain-size distribution, and density. Three different sands were used to evaluate the influence of the mean grain size. Key words : hydraulic fill, flume tests, sand, profile, slope, density.
Comparison between various flume tests used for hydraulic-fill studies
Authors: Küpper Angela A. G. , Morgenstern Norbert R. , Sego David C.
Published: June 2009

Several flume deposition tests carried out in different parts of the world to study hydraulic fills are compared and discussed. The results of all test programs are coherent and consistent with field observations of hydraulic fills and natural alluvial deposits, which suggests that, at least qualitatively, flume tests are adequate to simulate the physical phenomena associated with hydraulic deposition. Key words : hydraulic fill, flume tests, sand, grain size, profile, slope, density.
Nonlinear stiffness parameters from undrained pressuremeter tests
Authors: Jardine R. J.
Published: June 2009

The paper discusses approaches for interpreting nonlinear stiffness data from undrained pressuremeter tests. An approximate simplified method is proposed for transforming curves of pressuremeter modulus (against cavity strain) into equivalent single element plots. The new approach is illustrated using field data obtained in two quite different clays, with generally good agreement being found between pressuremeter-derived data and high-quality laboratory experiments. However, the results indicate a tendency for the laboratory stiffness curves to plot above the pressuremeter characteristics in clays with a low overconsolidation ratio and vice versa for heavily overconsolidated deposits. The reasons for these discrepancies are explored, and it is concluded that disturbance during installation and initial cavity expansion is the most important factor for the observed differences. Key words : shear stiffness, nonlinearity, pressuremeter, clay.
Difficulties with phase spectrum unwrapping in spectral analysis of surface waves nondestructive testing of pavements
Authors: Al-Hunaidi M. O.
Published: June 2009

Spectral analysis of surface waves (SASW) is a nondestructive and in situ method for determining the stiffness profiles of soil and pavement sites. This method involves the generation and measurement of surface Rayleigh waves. By exploiting the dispersive characteristic of these waves in layered systems, the SASW method provides information on the variation of stiffness with depth. This paper presents the results of a case study for near-surface profiling of a pavement site using the SASW method. In this study, inconsistencies were observed in the dispersion curve of the site when the usual procedure of unfolding the relative phase spectrum was followed. A correction procedure to eliminate these inconsistencies is suggested and discussed. The thickness and wave velocities of the various layers obtained with the SASW method, after applying the correction procedure, matched closely those determined from cored samples and cross-hole tests. Key words : nondestructive testing, pavement, layered media, Rayleigh wave, spectral analysis, shear wave velocity, wave propagation.
Interpretation of the tilt response of two tiltmeters to water injection into a tar sands formation
Authors: Jones F. W. , Pascal F. , Rogers J. S.
Published: June 2009

Near-surface tilt associated with fracture growth caused by water injection into a tar sands formation during an 18-day period was monitored by two biaxial mercury-level borehole tiltmeters. A nonlinear inversion method has been used to determine the fracture dimensions and position of its centre for five data groups from within that time. The inversion is limited by having data from only two tiltmeters, and a horizontal rectangular fracture must be assumed. The fracture expands rapidly initially, and more slowly as time progresses. The area of the fracture increases from approximately 5000 to about 240 000 m2 during the 18 days of injection and its centre migrates approximately 50 m. Key words : tiltmeters, tilt response, enhancement monitoring.
SPIN HALL EFFECTS IN HgTe QUANTUM WELL STRUCTURES
Authors: BUHMANN HARTMUT
Published: June 2009

Due to a strong spin orbit interaction HgTe quantum well structures exhibit an unusual subband structure ordering which leads to some remarkable transport properties depending on the actual carrier density. Especially for quantum wells with an inverted band structure ordering, a strong Rashba-type spin orbit splitting gives rise to a strong spin Hall effect in the metallic regime and in the bulk insulating regime spin polarized edge channel transport leads to the formation of the quantum spin Hall effect. Gated quantum well structures have been used to explore these, the metallic and insulating, transport regimes experimentally.
CRITICAL CURRENTS AND NEW EXPERIMENTS ON EXCITONIC ELECTRON BILAYER SYSTEMS
Authors: TIEMANN LARS , DIETSCHE WERNER , HAUSER MAIK , KLITZING KLAUS v.
Published: June 2009

Pure dc interlayer tunneling experiments have found critical currents Icritical in electron double layers at a total filling factor of one. Below Icritical, the four-terminal interlayer resistance is very small but abruptly increases by many orders of magnitude once I > Icritical. The nearly vanishing 4-terminal interlayer resistance is most likely the direct consequence of the interlayer phase-coherence associated with the Bose condensation of the double layer quasi-excitons at total filling factor one.
EDGE HEAT TRANSPORT IN THE QUANTUM HALL REGIME
Authors: GRANGER GHISLAIN , EISENSTEIN J. P. , RENO J. L.
Published: June 2009

We investigate the transport of heat in the integer quantized Hall regime. We make use of quantum point contacts (QPC's) positioned along the edge of a large quantum Hall droplet to both locally heat and locally detect temperature rises at the edge of the droplet. The detection scheme is thermoelectric, in essence identical to one introduced by Molenkamp, et al.1 in the early 1990's for heat transport experiments at zero magnetic field.

At zero magnetic field we find that heat moves away from the heater QPC more or less isotropically. As expected from the Mott formula, we find a close connection between the detector QPC's thermoelectric response and the derivative, with respect to gate voltage, of its conductance.

At high magnetic field our results show, not surprisingly, that heat transport is chiral in the quantum Hall regime. At total filling factor ν = 1 we inject a hot distribution of electrons into the edge with one of three QPC's. We observe a thermoelectric voltage at the other QPC's only if they are "downstream" from the heater. No signals are detected in the upstream direction. The magnitude of the detected thermal response is dependent upon the distance between the heater and detector QPC's.

Additional measurements, in which a second QPC, between the heater and the detector, is used to drain away a portion of the injected heat, strongly suggest that the chiral heat transport we observe is indeed confined to the edge of the Hall droplet.

Experiments are underway in the fractional quantum Hall regime to search for "upstream" heat propagation. Theory has suggested that such anti-chiral transport should exist at certain fractions, notably ν = 2/3, owing to backward-propagating neutral modes.

Note from Publisher: This article contains the abstract only.
RENORMALIZED LANDAU LEVELS AND PARTICLE-HOLE SYMMETRY IN GRAPHENE
Authors: BARLAS YAFIS , LEE WEI-CHENG , NOMURA KENTATO , MACDONALD ALLAN H.
Published: June 2009

In this proceedings paper we report on a calculation of graphene's Landau levels in a magnetic field. Our calculations are based on a self-consistent Hartree-Fock approximation for graphene's massless-Dirac continuum model. We find that because of graphene's chiral band structure interactions not only shift Landau-level energies, as in a non-relativistic electron gas, but also alter Landau level wavefunctions. We comment on the subtle continuum model regularization procedure necessary to correctly maintain the lattice-model's particle hole symmetry properties.
INTEGER AND FRACTIONAL MAGNETOOSCILLATIONS IN IRRADIATED QUANTUM HALL SYSTEMS
Authors: DMITRIEV I. A. , MIRLIN A. D. , POLYAKOV D. G.
Published: June 2009

Recent results on nonequilibrium magnetotransport of electrons in irradiated quantum Hall systems are reviewed. The phenomena discussed include integer and fractional microwave-induced resistance oscillations as well as quantum magnetooscillations in DC and AC conductivity and in local compressibility of a 2D electron gas.
SPIN DYNAMICS IN III-V/II-VI: Mn HETEROVALENT QUANTUM WELLS
Authors: TOROPOV A. A. , TERENT'EV YA. V. , LEBEDEV A. V. , KOP'EV P. S. , IVANOV S. V. , KOYAMA T. , NISHIBAYASHI K. , MURAYAMA A. , OKA Y.
Published: June 2009

We report on the spectroscopic magnetooptical studies of spin dynamics in diluted magnetic semiconductor (DMS) GaAs / AlGaAs / ZnSe / ZnCdMnSe heterovalent double quantum wells (QW). The transients of circularly polarized photoluminescence in an external magnetic field are detected in the structures with different widths of the GaAs QW. The analysis of the data, performed within the rate-equation model, has allowed separate estimations of the spin relaxation rate of localized electrons and holes. The spin flip of the electrons confined in the DMS ZnCdMnSe QW is faster than 20 ps, whereas the spin flip of the heavy hole localized in the GaAs QW is as long as ~9 ns. The long spin flip of the holes is presumably governed by their strong 3-dimensional localization.
INVESTIGATION OF SPIN TRANSPORT IN SEMICONDUCTORS BY SPATIALLY RESOLVED TWO-COLOR HANLE-MOKE MEASUREMENTS
Authors: OSSAU W. , QUAST J.-H. , ASTAKHOV G. V. , HOFFMANN H. , MOLENKAMP L.
Published: June 2009

We report on a considerable impact of light on spin transport in unstrained n -type GaAs . Increasing the intensity of optical spin pumping results in a significant expansion of spin diffusion. Furthermore, in the regime of strong spin pumping the spin gradient, which can be interpreted in terms of a spin outflow from the injection point is enhanced by application of a weak magnetic field. In addition we report on optical spin pumping of modulation doped CdTe -based quantum wells. Using a two-color Hanle-MOKE technique, we find a spin relaxation time of 34 ns in the nearly unperturbed electron gas. Independent variation of pump and probe energies demonstrates the presence of additional electrons in the quantum well, whose spin relaxation time is substantially shorter.
HIGH MAGNETIC FIELDS AND THE POSSIBLE RE-DEFINITION OF THE KILOGRAM
Authors: BRAUN ERICH F.
Published: June 2009

Up to the eighties of the last century high magnetic fields had been thought to be rather useless for metrology. This opinion changed very abruptly in 1980 after the discovery of the quantum Hall effect. This effect allows the reproduction of quantized resistance values with an extremely low uncertainty which today is of the order of 10-9. Nowadays there is an intensive discussion to re-define the unit of mass, the kilogram, by a definition of the Planck constant h, which can be determined by a so-called watt balance which makes use of the quantum Hall effect and thereby of high magnetic fields.
ELECTRON SPIN COHERENCE IN SINGLY CHARGED QUANTUM DOTS
Authors: YAKOVLEV D. R. , GREILICH A. , BAYER M. , YUGOVA I. A.
Published: June 2009

Electron spin coherence is examined experimentally and theoretically in singly charged ( In , Ga ) As / GaAs quantum dots. Time-resolved pump-probe Faraday rotation technique is used to examine fine structure and Zeeman splitting of excitons and resident electrons. Spin dephasing and spin coherence times of resident electrons have been measured in the regime of mode-locking of spin coherency.
SPIN RESOLVED SUBBAND-LANDAU-LEVEL COUPLING AND ELECTRON-HOLE COUPLING IN InAs/AlGaSbAs QUANTUM WELL
Authors: YOSHIDA TAKAHIDE , OTO KENICHI , ISHIDA SHUICHI , GEKA HIROTAKA , SHIBASAKI ICHIRO
Published: June 2009

We have investigated the magneto-transport properties in InAs / AlGaSbAs quantum well (QW), where the lattice mismatch is less than 0.5%. In tilted magnetic fields, the spin-resolved subband-Landau-level coupling has been clearly observed in the magneto-resistance due to the large g -factor of this QW. An anomaly in the Hall effect has been observed at high magnetic fields of the filling factor being less than unity, which is caused by the coexistence of electrons and holes in the system.
FERROMAGNETIC PRECIPITATES IN OXYGEN CONTAMINATED GaN:Fe
Authors: PRZYBYLIŃSKA H. , HAVLIČEK M. , ŚWIĄTEK K. , JANTSCH W.
Published: June 2009

Ferromagnetic MOCVD grown GaN films doped with about 1% Fe and unintentionally contaminated with oxygen were investigated by electron spin resonance. Simultaneously with the paramagnetic resonance of isolated Fe 3+ on Ga sites numerous ferromagnetic resonance (FMR) signals were detected. The narrow linewidths (below 50 G at the easy magnetization orientation) indicated a well-defined crystallographic structure. In all investigated samples the presence of spheroidal magnetite ( Fe 3 O 4) precipitates was detected. The fact that the easy and hard axes changed direction at 105 K and the FMR signal in X band disappeared exactly below the Vervey transition temperature confirmed the identification unambiguously. Bcc iron particles with dimensions small enough to influence the magnetocrystalline anisotropy constant were also observed, but only in samples less contaminated with oxygen. Precipitates of both phases were arbitrarily oriented with respect to the GaN crystallographic axes. In addition, FMR signals related to two distinctly different hexagonally ordered phases could be distinguished, both with the easy magnetization directions lying in the basal plane. The high uniaxial and small in-plane anisotropy constants of one of them are close to those observed in small diameter hematite (α- Fe 2 O 3) nanoparticles. The other hexagonal phase has a Curie temperature of about 360 K and is, yet, unidentified.
METHODOLOGY FOR DATA CONVERSION FROM XML DOCUMENTS TO RELATIONS USING EXTENSIBLE STYLESHEET LANGUAGE TRANSFORMATION
Authors: FONG JOSEPH , SHIU HERBERT , WONG JENNY
Published: June 2009

Extensible Markup Language (XML) has been used for data-transport and data-transformation while the business sector continues to store critical business data in relational databases. Extracting relational data and formatting it into XML documents, and then converting XML documents back to relational structures, becomes a major daily activity. It is important to have an efficient methodology to handle this conversion between XML documents and relational data. This paper aims to perform data conversion from XML documents into relational databases. It proposes a prototype and algorithms for this conversion process. The pre-process is schema translation using an XML schema definition. The proposed approach is based on the needs of an Order Information System to suggest a methodology to gain the benefits provided by XML technology and relational database management systems. The methodology is a stepwise procedure using XML schema definition and Extensible Stylesheet Language Transformations (XSLT) to ensure that the data constraints are not scarified after data conversion. The implementation of the data conversion is performed by decomposing the XML document of a hierarchical tree model into normalized relations interrelated with their artifact primary keys and foreign keys. The transformation process is performed by XSLT. This paper will also demonstrate the entire conversion process through a detailed case study.
UNIFORM RADIATION CONDITIONS FOR A SOUND PROPAGATION MODEL
Authors: PEPLOW A. T. , FINNVEDEN S.
Published: June 2009

In this work, a new set of uniform radiation boundary conditions for a half-space model are derived and applied to a fundamental problem in outdoor sound propagation. This original approach derived here relies upon a high-order family of local radiation boundary conditions related to plane wave reflection coefficients. Validity of the approximation is carried out by examining sound propagation above an impedance ground using a spectral finite element method. This is followed by computational results verified against an analytic solution for sound propagation over hard ground. Finally, the case of sound propagation above a grass-strip surrounded by rigid ground and a rigid-strip in a grassland environment with atmospheric profiles are studied.
APPLICATION OF DISCONTINUOUS GALERKIN SPECTRAL METHOD ON HEXAHEDRAL ELEMENTS FOR AEROACOUSTIC
Authors: CASTEL N. , COHEN G. , DURUFLÉ M.
Published: June 2009

A discontinuous Galerkin method is developed for linear hyperbolic systems on general hexahedral meshes. The use of hexahedral elements and tensorized quadrature formulas to evaluate the integrals leads to an efficient matrix–vector product. It is shown that for high order approximations, the reduction in computational time can be very important, compared to tetrahedral elements. Two choices of quadrature points are considered, the Gauss points or Gauss–Lobatto points. The method is applied to the aeroacoustic system ("simplified" Linearized Euler Equations). Some 3D numerical experiments show the importance of penalization, and the advantage of using high order.
NUMERICAL SIMULATION ON SEARCHING THE OPTIMUM SOURCE-DEPTH DISTRIBUTION FOR REVERBERATION INVERSION BY SIMULATED ANNEALING
Authors: WU JINRONG , SHAN E. C. , GAO TIANFU , MA LI
Published: June 2009

To extract the intrinsic bottom back-scattering information from the reverberation data in shallow water has been a challenge topic for long time. It is shown that the modal back-scattering matrix (MBSM) is the intrinsic description of the bottom scattering.1 The optimum source-depth distribution for inverting MBSM from the reverberation data has been discussed with a Pekeris waveguide.2 In the present work, we extend the procedure to the general case of non-Pekeris waveguide by using the simulated annealing (SA) approach. Numerical simulated examples on searching the optimum source-depth distribution for MBSM inversion are presented. It is shown that: (1) the SA is an effective approach for searching the optimum source-depth distribution for MBSM inversion (2) the MBSM inverted from the optimal source-depth distribution has the strong stability against noise.
EXISTENCE, UNIQUENESS AND ASYMPTOTIC PROPERTIES OF A CLASS OF NONLINEAR STOCHASTIC DIFFERENTIAL DELAY EQUATIONS WITH MARKOVIAN SWITCHING
Authors: WANG LIN , WU FUKE
Published: June 2009

The main aim of this paper is to give some new conditions under which a class of nonlinear stochastic differential delay equations with Markovian switching admit a unique solution and this solution has nice asymptotic properties, including the moment boundedness and the moment boundedness average in time of this solution. These new conditions show that the coefficients of the nonlinear stochastic differential delay equation with Markovian switching are polynomial or controlled by the polynomial functions or functionals. Two examples are also given for illustration.
Decentralized control of adaptive sampling in wireless sensor networks
Authors: Kho Johnsen , Rogers Alex , Jennings Nicholas R.
Published: June 2009

The efficient allocation of the limited energy resources of a wireless sensor network in a way that maximizes the information value of the data collected is a significant research challenge. Within this context, this article concentrates on adaptive sampling as a means of focusing a sensor's energy consumption on obtaining the most important data. Specifically, we develop a principled information metric based upon Fisher information and Gaussian process regression that allows the information content of a sensor's observations to be expressed. We then use this metric to derive three novel decentralized control algorithms for information-based adaptive sampling which represent a trade-off in computational cost and optimality. These algorithms are evaluated in the context of a deployed sensor network in the domain of flood monitoring. The most computationally efficient of the three is shown to increase the value of information gathered by approximately 83%, 27%, and 8% per day compared to benchmarks that sample in a naïve nonadaptive manner, in a uniform nonadaptive manner, and using a state-of-the-art adaptive sampling heuristic (USAC) correspondingly. Moreover, our algorithm collects information whose total value is approximately 75% of the optimal solution (which requires an exponential, and thus impractical, amount of time to compute).
The Development and Evaluation of Performance-Based Functional Assessment
Authors: Price Kathleen J. , Sears Andrew
Published: June 2009

Understanding and describing the physical capabilities of users with motor impairments is a significant challenge for accessibility researchers and system designers alike. Current practice is to use descriptors such as medical diagnoses to represent a person’s physical capabilities. This solution is not adequate due to similarities in functional capabilities between diagnoses as well as differences in capabilities within a diagnosis. An alternative is user self-reporting or observation by another person, but these solutions can be problematic because they rely on individual interpretations of capabilities and may introduce unwanted bias. The current research focuses on defining an objective, quantifiable, repeatable, and efficient methodology for assessing an individual’s physical capabilities in relation to use of information technologies. Thirty-one users with a range of physical capabilities participated in the evaluation of the proposed performance-based functional assessment methodology. Building on the current standard for such assessments, multiple observers provided independent assessments that served as the gold standard for comparison. Promising metrics produced through the performance-based assessment were identified through comparisons with these observer evaluations. Predictive models were then generated via regression and correlation analysis. The models were validated using a three-fold validation process. Results from this initial research are encouraging, with the resulting models explaining up to 92% of the variance in user capabilities. Directions for future research are discussed.
Laboratory experience for teaching sensory physiology
Authors: Albarracín Ana L. , Farfán Fernando D. , Felice Carmelo J.
Published: June 2009

The major challenge in laboratory teaching is the application of abstract concepts in simple and direct practical lessons. However, students rarely have the opportunity to participate in a laboratory that combines practical learning with a realistic research experience. In the Bioengineering Department, we started an experiential laboratory physiology to teach graduated students some aspects of sensorial physiology and exposes them to laboratory skills in instrumentation and physiological measurements. Students were able to analyze and quantify the effects of activation of mechanoreceptors in multifiber afferent discharges using equipment that was not overly sophisticated. In consequence, this practical laboratory helps students to make connections with physiological concepts acquired in theoretical classes and to introduce them to electrophysiological research.
A peer-led supplemental tutorial project for medical physiology: implementation in a large class
Authors: Kibble Jonathan D.
Published: June 2009

The purpose of this study was to evaluate the practicality of implementing a peer-teaching program in a large class (>350 students) of medical students and whether such a program is beneficial. Case-based problems were developed by faculty members to facilitate student problem solving and discussion. Voluntary student enrollment was available during the first week of a semester. Tutorials took place during out of class time and were facilitated by peers from the previous class. Tutors were selected for their outstanding performance in physiology; they were provided with training in facilitation skills and were given a package of model answers. Sixty-eight students enrolled in this pilot program and were organized into groups of ∼8 students. On average, students attended four of six tutorials. Posttutorial quiz scores were significantly greater than paired pretest scores. Surveys showed that students had high expectations at the outset, which were matched with positive perceptions at the end of the tutorial program; the use of near-peer tutors was especially well received. Tutors also gave high approval ratings for their experiences. In conclusion, the peer tutoring program was logistically straightforward to implement in a large class and was endorsed by the participants.
Glucagon acts in a dominant manner to repress insulin-induced mammalian target of rapamycin complex 1 signaling in perfused rat liver
Authors: Baum Jamie I. , Kimball Scot R. , Jefferson Leonard S.
Published: June 2009

The opposing actions of insulin and glucagon on hepatic carbohydrate metabolism are well documented. In contrast, relatively little is known about how the two hormones interact to regulate hepatic protein metabolism. Previously, we reported that glucagon in the absence of insulin represses signaling through the mammalian target of rapamycin complex 1 (mTORC1). In the present study, we sought to determine whether or not the action of one hormone would dominate over the other in the regulation of mTORC1 signaling. Livers were perfused in situ with medium containing either no added hormones (control), 10 nM insulin, 100 nM glucagon, or a combination of the hormones. Compared with control livers, insulin stimulated Akt phosphorylation and mTORC1 signaling, as assessed by increased phosphorylation of the mTORC1 targets eIF4E-binding protein (4E-BP)1 and ribosomal protein S6 kinase (S6K)1, and promoted assembly of the eIF4G·eIF4E complex. Glucagon alone had no effect on mTORC1 signaling but stimulated the activity of protein kinase A (PKA). In the presence of a combination of insulin and glucagon, Akt and TSC2 phosphorylation and PKA activity were all increased compared with controls. However, mTORC1 signaling was repressed compared with livers perfused with medium containing insulin alone, and this effect was associated with reduced assembly of the mTORC1·eIF3 complex. Overall, the results suggest that glucagon acts in a dominant manner to repress insulin-induced mTORC1 signaling, which is in contrast to previous studies showing a dominant action of insulin in the control of hepatic gluconeogenesis.