bluuebunny/crossref_metadata_2025 huggingface dataset:
South Virgin–White Hills detachment fault system of SE Nevada and NW Arizona: Applying apatite fission track thermochronology to constrain the tectonic evolution of a major continental detachment fault
Authors: Fitzgerald Paul G. , Duebendorfer Ernest M. , Faulds James E. , O'Sullivan Paul
Published: March 2009

The South Virgin–White Hills detachment (SVWHD) in the central Basin and Range province with an along‐strike extent of ∼60 km is a major continental detachment fault system. Displacement on the SVWHD decreases north to south from ∼17 to <6 km. This is accompanied by a change in fault and footwall rock type from mylonite overprinted by cataclasite to chlorite cataclasite and then fault breccia reflecting decreasing fault displacement and footwall exhumation. Apatite fission track (AFT) thermochronology was applied both along‐strike and across‐strike to assess this displacement gradient. The overall thermal history reflects Laramide cooling (∼75 Ma) and then rapid cooling beginning in the late early Miocene. Age patterns reflect some complexity but extension along the SVWHD appears synchronous with rapid cooling initiated at ∼17 Ma due to tectonic exhumation. Slip rate is more rapid (∼8.6 km/Ma) in the north compared to ∼1 km/Ma in the south. The displacement gradient results from penecontemporaneous along‐strike motion and formation of the SVWHD by linkage of originally separate fault segments that have differential displacements and hence differential slip rates. East–west transverse structures likely play a role in linkage of different fault segments. The preextension paleogeothermal gradient is well constrained in the Gold Butte block as 18–20°C/km. We present a new thermochronologic approach to constrain fault dip during slip, treating the vertical exhumation rate and the slip as vectors, with the angle between them used to constrain fault dip during slip through the closure temperature of a particular thermochronometer. AFT data from the western rim of the Colorado Plateau constrain the initiation of timing of cooling associated with the Laramide Orogeny at ∼75 Ma, and a reheating event in the late Eocene/early Oligocene associated with burial by sediments (“rim gravels”) most likely shed from the Kingman High to the west of the plateau.
On topography and geoid from 2‐D stagnant lid convection calculations
Authors: King Scott D.
Published: March 2009

Temperature‐dependent convection in the stagnant lid regime with a Frank‐Kamenetskii and Arrhenius viscosity formulation are compared. When properly scaled, the Nusselt number and root‐mean‐square velocity of the fluid for the two viscosity formulations are similar but the surface stresses and hence predicted dynamic topography and geoid differ significantly. The Arrhenius viscosity formulation results are insensitive to a viscosity cutoff at the high viscosity limit as long as the cutoff is 104 times the basal viscosity. The condition number for stagnant lid convection matrices using a penalty formulation is smaller than the penalty number times viscosity contrast value (a reasonable estimate of the condition number), explaining why large viscosity contrast convection problems with the penalty method agree with other formulations and analytic solutions. The difference in magnitude between the maximum and minimum dynamic topography could be used to constrain the magnitude of the viscosity contrast across the stagnant lid in planetary bodies.
Magnetic hole formation from the perspective of inverse scattering theory
Authors: Hamilton R. L. , Peterson D. A. , Libby S. M.
Published: March 2009

The dynamics of oblique, weakly dispersive nonlinear Alfven waves in the presence of weak resistive damping are investigated numerically through an extension of the derivative nonlinear Schrodinger (DNLS) equation. It is observed numerically that the nonlinear dynamics are organized around the dynamics and allowed interactions of the underlying DNLS soliton families. There are three types of oblique Alfven solitons: the compressive two‐parameter soliton and one‐parameter bright soliton along with the rarefactive one‐parameter dark soliton. The damping of either of these compressive solitons is accompanied by the formation of one or more dark solitons. The implication of these processes is that any initial wave profile containing solitons in its Inverse Scattering Transformation representation, in the presence of weak resistive damping, will result in a leading train of dark solitons. These dark solitons have been identified with magnetic holes, and the results described above are discussed in the context of magnetic hole observations and theory.
Factors influencing magmatism during continental breakup: New insights from a wide‐angle seismic experiment across the conjugate Seychelles‐Indian margins
Authors: Collier J. S. , Minshull T. A. , Hammond J. O. S. , Whitmarsh R. B. , Kendall J.‐M. , Sansom V. , Lane C. I. , Rumpker G.
Published: March 2009

We present a model of the northern Seychelles continental margin derived from controlled source, wide‐angle seismic traveltime inversion and teleseismic receiver functions. This margin has been widely cited as a classic example of rifting in association with a continental flood basalt province, the Deccan Traps. However, we do not find the typical set of geophysical characteristics reported at other margins linked to continental flood basalts, such as those of the north Atlantic. The oceanic crust formed immediately after breakup and throughout the first 3 Ma of seafloor spreading is just 5.2 km thick, less than half that typically seen at other volcanic margins. The continent‐ocean transition zone is narrow and while two packages of seaward‐dipping reflectors are imaged within this transition they are weakly developed. Beneath the thinned continental crust there is an approximately 4 km thick layer of high‐velocity material (7.5–7.8 km/s) that we interpret as mafic material intruded and underplating the lower crust. However, we believe that this underplating most likely happened prior to the breakup. Overall the observations show that the rifting of India from the Seychelles was characterized by modest magmatism. The spatial extent of the Deccan flood basalt province is therefore smaller than previously thought. We speculate that either the lateral flow of Deccan‐related hot material beneath the breakup region was hampered, perhaps as the rifted margins did not intersect the center of the Deccan source, or there was incomplete melt extraction from the wide melting region that formed between the rapidly diverging plates. If the latter explanation is correct, then the rate of plate separation, as indicated by the initial seafloor‐spreading rate, is more important in controlling the volume of magmatism generated during continental rifting than has been previously recognized.
Modeling 3‐D wave propagation and finite slip for the 1998 Balleny Islands earthquake
Authors: Hjörleifsdóttir Vala , Kanamori Hiroo , Tromp Jeroen
Published: March 2009

We simulate surface waves in a 3‐D Earth model using a spectral element method for existing kinematic source models of the MW 8.1, 25 March 1998 Balleny Islands earthquake. The 3‐D model incorporates lateral variations in the crust and mantle on the basis of models Crust2.0 and S20RTS. Our objective is to investigate the fit of the observed and simulated long‐period surface waves in the hope of improving on the existing source models. We modify a body wave model determined by Henry et al. (2000) to improve the fit of long‐period surface waveforms. We demonstrate that adding a smooth component of slip extending over a fault that connects the two subevents determined by Henry et al. (2000), without invoking slip on multiple fault planes or on unconnected fault patches, provides reasonable fits to long‐period surface waves as well as body waves.
Comparison of weekly cycle of NO2 satellite retrievals and NOx emission inventories for the continental United States
Authors: Kaynak B. , Hu Y. , Martin R. V. , Sioris C. E. , Russell A. G.
Published: March 2009

Spatially resolved weekly NO2 variations are obtained from 2003 to 2005 Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) tropospheric NO2 columns for three different types of regions: urban, rural, and rural‐point (rural with significant electricity generation unit (EGU) emissions). Regions are compared for magnitudes and weekly profiles. Rural regions do not show any weekly pattern, whereas urban areas show a distinct decrease on the weekends. Rural regions with EGUs show a slight decrease on Sundays. When compared with estimated mobile and stationary nitrogen oxides (NOx) emissions from the year 2004 for seven cities, the satellite data have greater variation during weekdays (Monday–Friday). Overall comparisons show that SCIAMACHY‐derived NO2 correlate well with estimated NOx emissions for urban and rural but less for rural‐point regions.
Vertical structure and horizontal gradients of aerosol extinction coefficients over coastal India inferred from airborne lidar measurements during the Integrated Campaign for Aerosol, Gases and Radiation Budget (ICARB) field campaign
Authors: Satheesh S. K. , Krishna Moorthy K. , Suresh Babu S. , Vinoj V. , Nair Vijayakumar S. , Naseema Beegum S. , Dutt C. B. S. , Alappattu D. P. , Kunhikrishnan P. K.
Published: March 2009

Quantitative estimates of the vertical structure and the spatial gradients of aerosol extinction coefficients have been made from airborne lidar measurements across the coastline into offshore oceanic regions along the east and west coasts of India. The vertical structure revealed the presence of strong, elevated aerosol layers in the altitude region of ∼2−4 km, well above the atmospheric boundary layer (ABL). Horizontal gradients also showed a vertical structure, being sharp with the e−1 scaling distance (D0H) as small as ∼150 km in the well‐mixed regions mostly under the influence of local source effects. Above the ABL, where local effects are subdued, the gradients were much shallower (∼600–800 km); nevertheless, they were steep compared to the value of ∼1500−2500 km reported for columnar AOD during winter. The gradients of these elevated layers were steeper over the east coast of India than over the west coast. Near‐simultaneous radio sonde (Vaisala, Inc., Finland) ascents made over the northern Bay of Bengal showed the presence of convectively unstable regions, first from surface to ∼750–1000 m and the other extending from 1750 to 3000 m separated by a stable region in between. These can act as a conduit for the advection of aerosols and favor the transport of continental aerosols in the higher levels (>2 km) into the oceans without entering the marine boundary layer below. Large spatial gradient in aerosol optical and hence radiative impacts between the coastal landmass and the adjacent oceans within a short distance of <300 km (even at an altitude of 3 km) during summer and the premonsoon is of significance to the regional climate.
Real‐time Bayesian anomaly detection in streaming environmental data
Authors: Hill David J. , Minsker Barbara S. , Amir Eyal
Published: March 2009

With large volumes of data arriving in near real time from environmental sensors, there is a need for automated detection of anomalous data caused by sensor or transmission errors or by infrequent system behaviors. This study develops and evaluates three automated anomaly detection methods using dynamic Bayesian networks (DBNs), which perform fast, incremental evaluation of data as they become available, scale to large quantities of data, and require no a priori information regarding process variables or types of anomalies that may be encountered. This study investigates these methods' abilities to identify anomalies in eight meteorological data streams from Corpus Christi, Texas. The results indicate that DBN‐based detectors, using either robust Kalman filtering or Rao‐Blackwellized particle filtering, outperform a DBN‐based detector using Kalman filtering, with the former having false positive/negative rates of less than 2%. These methods were successful at identifying data anomalies caused by two real events: a sensor failure and a large storm.
Interaction of Cyanide with Enzymes Containing Vanadium, Manganese, Non-Heme Iron, and Zinc
Authors: Sosa-Torres Martha E. , Kroneck Peter M. H.
Published: March 2009

Since the early discovery of Prussian Blue, cyano transition metal complexes have played a fundamental role in coordination chemistry. They represent important compounds with fascinating chemical and physical properties which turn them into valuable tools for both chemists and biologists. HCN as a precursor in prebiotic chemistry has gained interest in view of its polymers being involved in the formation of amino acids, purines, and orotic acid, a biosynthetic precursor of uracil. Clearly, the rapid formation of adenine by aqueous polymerization of HCN is one of the key discoveries in these experiments. The cyanide anion is usually toxic for most aerobic organisms because of its inhibitory effects on respiratory enzymes, but as a substrate it is an important source of carbon and nitrogen for microorganisms, fungi and plants. Most interestingly, the cyanide anion is a ligand of important metal-dependent biomolecules, such as the hydrogenases and the cobalt site in vitamin B12.
A Synopsis of the Management of Vocal Fold Scar
Authors: Hapner Edie R. , Klein Adam
Published: March 2009

Vocal fold scarring remains one of the greatest therapeutic challenges in laryngology and voice therapy. The loss of superior lamina propria results in a change in the pliability of the vocal folds with changes in glottal configuration, glottal closure, and reduced to absent mucosal wave motion. This results in dysphonia of varying severities including breathiness, roughness, loss of pitch range, and flexibility. The aim of this article is to present a brief review of vocal fold architecture and a discussion of the etiologies of vocal fold scarring. Methods to evaluate vocal fold scarring are presented with examples of findings in laryngoscopic, acoustic, aerodynamic, and perceptual assessments. Medical, surgical, and behavioral treatment for vocal folds scaring including sample therapy tasks are included.
Hands-Free Cough and Speech in Long-Term Tube-Free Tracheostomy
Authors: Milstein Claudio , Akst Lee M. , Eliachar Isaac
Published: March 2009

A surgical technique developed by Dr. Isaac Eliachar in the Section of Laryngotracheal Reconstruction, Cleveland Clinic Department of Otolaryngology, dramatically improves quality of life in patients who require a long-term tracheostoma. This procedure, called “long-term tube-free tracheostomy” (LTTFT), creates a self-sustaining tracheostoma that requires no tracheotomy tubes to maintain patency. The advantages of a tube-free procedure are numerous, and the improvements in quality of life of patients who have successfully undergone this operation are readily noticeable. These benefits include (a) removal of tracheal appliances, such as tracheal tubes, valves, vents, and stents; (b) prevention of tissue damage associated with appliances and a decrease in tissue irritation and formation of granulation tissue; (c) better secretion management, elimination of frequent clogging of tracheal appliances, and need for suction; (d) prevention of aspiration; (e) retention or re-establishment of the functions of sniffing and smelling; and (f) performance of hands-free cough and speech production due to the self-constricting capabilities of the stoma. The purpose of this article is to present the concept of LTTFT as an alternative to standard tracheotomy in select patients. The difference between LTTFT as an alternative to tracheotomy and the impact these differences have upon medical decision-making will be emphasized.
Influence of oxygen level on structure and ferromagnetism in Sn0.95Fe0.05O2 nanoparticles
Authors: Thurber Aaron , Reddy K. M. , Punnoose Alex
Published: March 2009

This report discusses the effect of oxygen concentration at atmospheric pressure on the structural composition and ferromagnetism of nanoparticles of Fe doped SnO2. Sn0.95Fe0.05O2 was annealed under controlled atmospheres with gradually increasing oxygen concentrations (varying O2 from 0 to 106 ppm in N2). Prominent mass changes due to oxygen loss take place in the 0–5000 ppm range and the ferromagnetic properties. Ferromagnetism of Sn0.95Fe0.05O2 is inversely related to the oxygen concentration, which confirms the important role of oxygen vacancies this system. X-ray diffraction, thermogravimetric analysis, transmission electron microscopy, and magnetometry studies confirm that the observed changes in the ferromagnetic properties are due to changes in the oxygen stoichiometry.
Analysis and design of a slotless tubular permanent magnet actuator for high acceleration applications
Authors: Meessen K. J. , Paulides J. J. H. , Lomonova E. A.
Published: March 2009

This paper presents the design of a linear actuator for high acceleration applications. In the analysis, a slotless tubular permanent magnet actuator is modeled by means of semianalytical field solutions. Several slotless topologies are modeled and compared to achieve the highest acceleration. A design has been proposed and built, and measurements are conducted to verify the models.
X-ray source studies for radiography of dense matter
Authors: Brambrink E. , Wei H. G. , Barbrel B. , Audebert P. , Benuzzi-Mounaix A. , Boehly T. , Endo T. , Gregory C. , Kimura T. , Kodama R. , Ozaki N. , Park H.-S. , le Gloahec M. Rabec , Koenig M.
Published: March 2009

Studies of short-pulse laser-generated hard x-ray (18–60 keV) sources, suitable for radiographs of large samples of dense matter, are presented. The spatial and dynamic resolutions for different target types and laser parameters have been investigated. A high quality radiograph with good spatial resolution in two dimensions was demonstrated by irradiating freestanding thin W wires. The influence of the geometry for the quality of the radiograph, which is crucial for the design of experiments probing laser-compressed matter, is reported.
Suppression of stimulated Raman scattering due to localization of electron plasma wave in laser beam filaments
Authors: Sharma Prerana , Sharma R. P.
Published: March 2009

The filamentation of the high power laser beam by taking off-axial contribution is investigated when ponderomotive nonlinearity is taken into account. The splitted profile of the laser beam is obtained due to uneven focusing of the off-axial rays. It is observed that the weak electron plasma wave (EPW) propagating in the z direction is nonlinearly coupled in the modified filamentary regions of the laser beam. The semianalytical solution of the nonlinear coupled EPW equation in the presence of laser beam filaments has been found and it is observed that the nonlinear coupling between these two waves leads to localization of the EPW. Stimulated Raman scattering (SRS) of this EPW is studied and backreflectivity has been calculated. Further, the localization of EPW affects the eigenfrequency and damping of plasma wave. As a result of this, mismatch and modified enhanced Landau damping lead to the disruption of SRS process and a substantial reduction in the backreflectivity. For the typical laser beam and plasma parameters with wavelength (λ=1064 nm), power flux (≈1016 W cm−2), and plasma density (n/ncr)=0.2; the backreflectivity was found to be suppressed by a factor of around 20%.
Effect of current corrugations on the stability of the tearing mode
Authors: Militello F. , Romanelli M. , Hastie R. J. , Loureiro N. F.
Published: March 2009

The generation of zonal magnetic fields in laboratory fusion plasmas is predicted by theoretical and numerical models and was recently observed experimentally. It is shown that the modification of the current density gradient associated with such corrugations can significantly affect the stability of the tearing mode. A simple scaling law is derived that predicts the impact of small stationary current corrugations on the stability parameter Δ′. The described destabilization mechanism can provide an explanation for the trigger of the neoclassical tearing mode in plasmas without significant magnetohydrodynamic activity.
Pulse shaping of transversely excited atmospheric CO2 laser using a simple plasma shutter
Authors: Hurst Noah , Harilal S. S.
Published: March 2009

The pulse from a transversely excited atmospheric CO2 laser consists of a sharp spike followed by a long, drawn out tail region spanning about 2–5 μs caused by the nitrogen gas in the laser cavity. The nitrogen tail is undesirable in many applications because it decreases the average power of the laser pulse. We employ a pinhole plasma shutter for eliminating the nitrogen tail and shortening the pulse width. The pinhole shutter optically triggers plasma at a certain point in time with respect to the temporal profile of the laser pulse. This way, a good portion of the sharp spike is transmitted, while the energy stored in the nitrogen tail is consumed in heating the plasma. This simplistic plasma shutter is easy to build and inexpensive compared to other existing plasma shutter designs.
Discrimination between coupling and anisotropy fields in exchange-biased bilayers
Authors: Geshev J. , Nicolodi S. , da Silva R. B. , Nogués J. , Skumryev V. , Baró M. D.
Published: March 2009

In the framework of models that assume planar domain wall formed at the antiferromagnetic part of the interface of exchange-biased bilayers, one cannot distinguish between the cases of high or low ratios between the coupling and the antiferromagnet’s anisotropy fields by using hysteresis loop measurement, ferromagnetic resonance, anisotropic magnetoresistance, or ac susceptibility techniques applied on one and the same sample. The analysis of the experimental data obtained on a series of FeMn/Co films indicated that once the biasing is established the variation in the coercivity with the FeMn layer thickness could be essential for solving this problem. If the coercivity decreases with the thickness then the interlayer exchange coupling is the parameter that varies while the domain-wall energy of the antiferromagnet remains practically constant.
Enhancement of carrier focusing GaN based vertical cavity surface emitting lasers and polariton lasers
Authors: Petrolati E. , Di Carlo A.
Published: March 2009

We have studied the electron and hole focusing problem observed in gallium nitride (GaN) based microcavity lasers. We outlined the relation between the focusing efficiency and the unbalance between electron and hole mobilities. A new device structure is proposed where the n-layer is on the top of the p-layer, which overcomes the focusing limitation of conventional GaN based vertical cavity surface emitting lasers and polariton lasers.
The Hong–Ou–Mandel interferometer: A new procedure for alignment
Authors: Thomas P. J. , Cheung J. Y. , Chunnilall C. J. , Dunn M. H.
Published: March 2009

Two major requirements in the construction of the Hong–Ou–Mandel interferometer are the alignment and length balancing of two optical paths. A new method is presented for meeting these requirements that requires no custom optics or expensive equipment. Using this method, a two photon interferometer sourced by degenerate noncollinear parametric photon pairs was aligned and the optical paths were balanced to within an average of 11.6 μm, yielding two-photon interference features with visibilities of ∼0.9. The method is applicable to arbitrary noncollinear emission angles, including nondegenerate downconversion situations where the signal and idler emission angles differ.
Piezoresponse force microscopy studies of PbTiO3 thin films grown via layer-by-layer gas phase reaction
Authors: Park Moonkyu , Hong Seungbum , Kim Jiyoon , Kim Yunseok , Bühlmann Simon , Kim Yong Kwan , No Kwangsoo
Published: March 2009

We fabricated 20 nm thick PbTiO3 films via reactive magnetron sputtering and studied the domain switching phenomena and retention properties using piezoresponse force microscopy. We found that multistep deposited PbTiO3 thin films showed 29% smaller rms roughness (2.5 versus 3.5 nm), 28% smaller coercive voltage (1.68 versus 2.32 V), 100% higher d33 value, and improved retention characteristic (89% versus 52% of remained poled domain area in 1280 min after poling) than single-step deposited PbTiO3 thin films. We attribute the improvement to the more complete chemical reaction between PbO and TiO2 during the film growth.
Kinetic ion effect on geodesic acoustic Alfvén modes in tokamaks
Authors: Elfimov A. G.
Published: March 2009

Using a quasitoroidal set of coordinates with coaxial circular magnetic surfaces, the Vlasov equation is solved for collisionless plasmas, and the dielectric tensor is found for large aspect ratio tokamaks in a low frequency band. Taking into account q-profile and charge separation parallel electric field, it is found that the Alfvén wave continuum is deformed by ion geodesic effects producing continuum minimum at the rational magnetic surfaces. Low frequency geodesic ion induced Alfvén waves are found below the continuum minimum where collisionless damping has a gap for Maxwell distribution. In kinetic approach, the ion thermal motion defines the geodesic effect but the mode frequency is strongly corrected due to parallel motion of electrons.
Phase coexistence and high electrical properties in (KxNa0.96−xLi0.04)(Nb0.85Ta0.15)O3 piezoelectric ceramics
Authors: Chang Yunfei , Yang Zupei , Ma Difei , Liu Zonghuai , Wang Zenglin
Published: March 2009

( K x Na 0.96 − x Li 0.04 ) ( Nb 0.85 Ta 0.15 ) O 3 lead-free piezoelectric ceramics were produced by conventional solid-state reaction method. The effects of K/Na ratio on the phase transitional behavior, Raman spectrum, microstructure, and dielectric, piezoelectric, and ferroelectric properties of the ceramics have been investigated. The phase structure of the ceramics undergoes a transition from orthorhombic to tetragonal phase with increasing x. A double-degenerate symmetric O–Nb–O stretching vibration v1 and a triply degenerate symmetric O–Nb–O bending vibration v5 are detected as relatively strong scattering in the Raman spectra. The peak shifts of v5 and v1 modes all have a discontinuity with x between 0.42 and 0.46, which may suggest the coexistence of orthorhombic and tetragonal phases in this range. Properly modifying x reduces the sintering temperature, promotes the grain growth behavior, and improves the density of the ceramics. The polymorphic phase transition (at To-t) is shifted to near room temperature by increasing x to 0.44 (K/Na ratio of about 0.85:1), and the coexistence of orthorhombic and tetragonal phases in the ceramics at x=0.44 results in the optimized electrical properties (d33=291 pC/N, kp=0.54, εr=1167, tan δ=0.018, To-t=35 °C, TC=351 °C, Pr=27.65 μC/cm2, and Ec=8.63 kV/cm). The results show that the equal K/Na ratio is not an essential condition in obtaining optimized electrical properties in (KxNa0.96−xLi0.04)(Nb0.85Ta0.15)O3 ceramics.
The dynamics of microscopic bubbles in viscous insulating liquids
Authors: Jomni F. , Denat A. , Aitken F.
Published: March 2009

The dynamics of microscopic bubbles in low viscosity insulating liquids has been widely investigated. It has been shown that the bubble motion (growth, collapse, and rebounds) in such liquids is governed by inertial forces. In this paper, the results of an experimental study of the dynamics of microscopic bubbles in viscous liquids (μ≥3 mPl) are presented. It is shown that, according to the conditions (injected energy, liquid viscosity, and applied pressure), the bubble motion is greatly modified. For example, no bubble rebound is observed in the higher viscosity liquids (e.g., Napvis XD110, μ=83.5 mPl) and, for a given injected energy, the ratio of the expansion time of the bubble to its implosion time drops with increasing in liquid viscosity. The bubble dynamics are then governed by liquid viscosity. Moreover, the transition of the bubble dynamics from the inertial regime to the viscous one has been experimentally observed (as far as the present authors are aware) for the first time. This transition can be explained by a refined analysis of the Rayleigh–Plesset model of bubble dynamics. The bubble dynamics regime can be deduced from a Reynolds number (ReTp) versus elasticity number (Σ) diagram, where four zones can be distinguished. Each zone corresponds to a particular regime: inertial regime with only one growth and collapse stage, inertial regime with at least one bubble rebound, viscous regime, and finally, a regime where a jet of hot liquid is produced. All experimental results are well distributed into the good part of this diagram.
Imaging photoelectron photoion coincidence spectroscopy with velocity focusing electron optics
Authors: Bodi Andras , Johnson Melanie , Gerber Thomas , Gengeliczki Zsolt , Sztáray Bálint , Baer Tomas
Published: March 2009

An imaging photoelectron photoion coincidence spectrometer at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source is presented and a few initial measurements are reported. Monochromatic synchrotron VUV radiation ionizes the cooled or thermal gas-phase sample. Photoelectrons are velocity focused, with better than 1 meV resolution for threshold electrons, and also act as start signal for the ion time-of-flight analysis. The ions are accelerated in a relatively low, 40–80 V cm−1 field, which enables the direct measurement of rate constants in the 103–107 s−1 range. All electron and ion events are recorded in a triggerless multiple-start/multiple-stop setup, which makes it possible to carry out coincidence experiments at >100 kHz event frequencies. As examples, the threshold photoelectron spectrum of the argon dimer and the breakdown diagrams for hydrogen atom loss in room temperature methane and the chlorine atom loss in cold chlorobenzene are shown and discussed.
Modeling two-dimensional solid-phase epitaxial regrowth using level set methods
Authors: Morarka S. , Rudawski N. G. , Law M. E. , Jones K. S. , Elliman R. G.
Published: March 2009

Modeling the two-dimensional (2D) solid-phase epitaxial regrowth (SPER) of amorphized Si (variously referred to as solid-phase epitaxial growth, solid-phase epitaxy, solid-phase epitaxial crystallization, and solid-phase epitaxial recrystallization) has become important in light of recent studies which have indicated that relative differences in the velocities of regrowth fronts with different crystallographic orientations can lead to the formation of device degrading mask edge defects. Here, a 2D SPER model that uses level set techniques as implemented in the Florida object oriented process simulator to propagate regrowth fronts with variable crystallographic orientation (patterned material) is presented. Apart from the inherent orientation dependence of the SPER velocity, it is established that regrowth interface curvature significantly affects the regrowth velocity. Specifically, by modeling the local SPER velocity as being linearly dependent on the local regrowth interface curvature, data acquired from transmission electron microscopy experiments matches reasonably well with simulations, thus providing a stable model for simulating 2D regrowth and mask edge defect formation in Si.
From supercritical hydrodynamic expansion to explosive phase change: Thermodynamic evolution of water during its interaction with high-intensity infrared nanosecond-pulsed laser
Authors: Wu Benxin
Published: March 2009

A predictive hydrodynamic model has been developed for high-intensity infrared nanosecond laser-water interactions. The model is first tested by comparing with experimental measurements for laser-induced pressure and shock wave propagation. Then the verified predictive model is applied to quantitatively understand the water thermodynamic state evolution, which has not been sufficiently studied in literature. It has been found that for the studied intense infrared nanosecond laser-water interaction, the major phase change process during the early stage is the supercritical hydrodynamic expansion followed by an explosive phase change process that occurs as the water thermodynamic-state curve approaches (from outside the binodal curve) and starts touching the critical point in the phase diagram. The model shows that the explosive phase change occurs at a delay time of ∼150 ns after laser pulse starts, which is quantitatively consistent with previous experimental observations.
Crystal-field split levels of Nd3+ ions in GaN measured by luminescence spectroscopy
Authors: Metcalfe Grace D. , Readinger Eric D. , Shen Hongen , Woodward Nathaniel T. , Dierolf Volkmar , Wraback Michael
Published: March 2009

We present the Stark energy sublevels of Nd3+ ions in GaN grown by plasma-assisted molecular beam epitaxy as determined by luminescence spectra. We correlate the photoluminescence spectra with transitions from the F43/2 excited state to the I49/2, I411/2, and I413/2 multiplets of the Nd3+ ion for above and below bandgap excitation, with the strongest emission occurring at 1.12 eV (1106 nm). We determine a splitting of the F43/2 excited state to be 4.1 meV. From photoluminescence excitation spectra, we also identify the Stark sublevels of the upper states F45/2, H29/2, F47/2, S43/2, G27/2, and G45/2. Photoluminescence excitation spectra reveal an optimal excitation energy of 1.48 eV (836 nm). Site-selective spectroscopy studies using combined excitation-emission spectroscopy with confocal microscopy indicate enhanced substantial doping at the Ga site.
The nonequilibrium Ehrenfest gas: A chaotic model with flat obstacles?
Authors: Bianca Carlo , Rondoni Lamberto
Published: March 2009

It is known that the nonequilibrium version of the Lorentz gas (a billiard with dispersing obstacles [Ya. G. Sinai, Russ. Math. Surv. 25, 137 (1970)], electric field, and Gaussian thermostat) is hyperbolic if the field is small [N. I. Chernov, Ann. Henri Poincare 2, 197 (2001)]. Differently the hyperbolicity of the nonequilibrium Ehrenfest gas constitutes an open problem since its obstacles are rhombi and the techniques so far developed rely on the dispersing nature of the obstacles [M. P. Wojtkowski, J. Math. Pures Appl. 79, 953 (2000)]. We have developed analytical and numerical investigations that support the idea that this model of transport of matter has both chaotic (positive Lyapunov exponent) and nonchaotic steady states with a quite peculiar sensitive dependence on the field and on the geometry, not observed before. The associated transport behavior is correspondingly highly irregular, with features whose understanding is of both theoretical and technological interests.
High hole mobility in boron doped diamond for power device applications
Authors: Volpe Pierre-Nicolas , Pernot Julien , Muret Pierre , Omnès Franck
Published: March 2009

Low boron doped homoepitaxial diamond layers were grown on Ib (100) diamond substrates with oxygen added to the gas mixture. The acceptor density of the samples has been estimated by C(V) and Hall effect to lie close to 1016 cm−3 with a maximum low field Hall mobility value of 1870 cm2/V s at 292 K. The presence of oxygen in the gas phase is shown to be a key parameter to obtain such characteristics. The mobility parameters required to simulate the electrical behavior of devices between 300 K and 500 K are then determined for a wide doping range.
Ultrahigh spontaneous emission extraction efficiency induced by evanescent wave coupling
Authors: Wang X.-L. , Furue S. , Ogura M. , Voliotis V. , Ravaro M. , Enderlin A. , Grousson R.
Published: March 2009

A spontaneous emission extraction efficiency greater than 50% is observed in a GaAs/AlGaAs quantum well structure grown on the subwavelength-sized ridge top facet of a V-grooved substrate by means of photoluminescence study. This is an extraction efficiency about 20 times higher than that of a similar structure grown on a flat substrate. It is demonstrated both experimentally and theoretically that the high extraction efficiency is the result of the efficient conversion of evanescent waves into propagating waves in air through constructive coupling of evanescent waves generated on the two sidewall facets of the V-grooved substrate by total internal reflection.
Fully nonlinear ion-acoustic solitary waves in a plasma with positive-negative ions and nonthermal electrons
Authors: Sabry R. , Moslem W. M. , Shukla P. K.
Published: March 2009

Properties of fully nonlinear ion-acoustic solitary waves in a plasma with positive-negative ions and nonthermal electrons are investigated. For this purpose, the hydrodynamic equations for the positive-negative ions, nonthermal electron density distribution, and the Poisson equation are used to derive the energy integral equation with a new Sagdeev potential. The latter is analyzed to examine the existence regions of the solitary pulses. It is found that the solitary excitations strongly depend on the mass and density ratios of the positive and negative ions as well as the nonthermal electron parameter. Numerical solution of the energy integral equation clears that both positive and negative potentials exist together. It is found that faster solitary pulses are taller and narrower. Furthermore, increasing the electron nonthermality parameter (negative-to-positive ions density ratio) decreases (increases) the localized excitation amplitude but increases (decreases) the pulse width. The present model is used to investigate the solitary excitations in the (H+,O2−) and (H+,H−) plasmas, where they are presented in the D- and F-regions of the Earth’s ionosphere. This investigation should be helpful in understanding the salient features of the fully nonlinear ion-acoustic solitary waves in space and in laboratory plasmas where two distinct groups of ions and non-Boltzmann distributed electrons are present.
Cathodoluminescence study of the properties of stacking faults in 4H-SiC homoepitaxial layers
Authors: Maximenko Serguei I. , Freitas Jaime A. , Klein Paul B. , Shrivastava Amitesh , Sudarshan Tangali S.
Published: March 2009

In-grown stacking faults in n-type 4H-SiC epitaxial layers have been investigated by real-color cathodoluminescence imaging and spectroscopy carried out at room and liquid helium temperatures. Stacking faults with 8H stacking order were observed, as well as double layer and multilayer 3C-SiC structures and a defect with an excitonic band gap at 2.635 eV. It was found that 8H stacking faults and triangular surface defects can be generated from similar nucleation sources. Time-resolved measurements reveal that compared to defect-free regions, the carrier lifetimes are severely reduced by the presence of stacking faults corresponding to triangular surface defects and three-dimensional 3C-SiC inclusions.
Large acoustic impedance mismatch in CdTe/MgTe nanodevices
Authors: Jusserand B. , Ghasemi R. , Dynowska E. , Wiater M. , Karczewski G. , Wojtowicz T.
Published: March 2009

From a Raman scattering investigation of folded longitudinal acoustic phonons in zinc-blende CdTe/MgTe superlattices, we demonstrate that this pair of materials displays a large acoustic impedance mismatch Z1/Z2=1.39, which opens promising perspectives for acoustic phonon engineering in semiconductor nanodevices. The determined MgTe sound velocity s=(3.35±0.15)×103 m/s agrees well with ab initio predictions for the same crystalline form.
High-frequency surface acoustic wave propagation in nanostructures characterized by coherent extreme ultraviolet beams
Authors: Siemens Mark E. , Li Qing , Murnane Margaret M. , Kapteyn Henry C. , Yang Ronggui , Anderson Erik H. , Nelson Keith A.
Published: March 2009

We study ultrahigh frequency surface acoustic wave propagation in nickel-on-sapphire nanostructures. The use of ultrafast, coherent, extreme ultraviolet beams allows us to extend optical measurements of propagation dynamics of surface acoustic waves to frequencies of nearly 50 GHz, corresponding to wavelengths as short as 125 nm. We repeat the measurement on a sequence of nanostructured samples to observe surface acoustic wave dispersion in a nanostructure series. These measurements are critical for accurate characterization of interfaces beneath very thin films using this technique.
Role of interface roughness in the transport and lasing characteristics of quantum-cascade lasers
Authors: Khurgin Jacob B. , Dikmelik Yamac , Liu Peter Q. , Hoffman Anthony J. , Escarra Matthew D. , Franz Kale J. , Gmachl Claire F.
Published: March 2009

A density-matrix based theory of transport and lasing in quantum-cascade lasers reveals that large disparity between luminescent linewidth and broadening of the tunneling transition changes the design guidelines to favor strong coupling between injector and upper laser level. This conclusion is supported by the experimental evidence.
Preservation and transplantation of porcine testis tissue
Authors: Zeng W. , Snedaker A. K. , Megee S. , Rathi R. , Chen F. , Honaramooz A. , Dobrinski I.
Published: March 2009

Grafting of immature mammalian testis tissue to mouse hosts can preserve the male germline. To make this approach applicable to a clinical or field situation, it is imperative that the testis tissue and/or spermatozoa harvested from grafted tissue are preserved successfully. The aim of the present study was to evaluate protocols for the preservation of testis tissue in a porcine model. Testis tissue was stored at 4°C for short-term preservation or cryopreserved by slow-freezing, automated slow-freezing or vitrification for long-term storage. Preserved tissue was transplanted ectopically to mouse hosts and recovered xenografts were analysed histologically. In addition, spermatozoa were harvested from xenografts and cryopreserved. Total cell viability and germ cell viability remained high after tissue preservation. Complete spermatogenesis occurred in xenografts preserved by cooling up to 48 h, whereas spermatogenesis progressed to round spermatids in the xenografts that were frozen–thawed before grafting. Approximately 50% of spermatozoa harvested from xenografts remained viable after freezing and thawing. The in vivo developmental potential of cryopreserved tissue was reduced despite high post-thaw viability. Therefore, it is important to evaluate germ cell differentiation in vivo in addition to cell viability in vitro when optimising freezing protocols for testis tissue.
SRB Reproduction, Fertility and Development Award Lecture 2008. Regulation and manipulation of angiogenesis in the ovary and endometrium
Authors: Fraser Hamish M. , Duncan W. Colin
Published: March 2009

The marked cyclical physiological angiogenesis in the developing follicle, corpus luteum and endometrium implies a critical role in health and disease. Our approach to understanding its regulation has been to localise and quantify the temporal changes in putative angiogenic factors, and their receptors, in human and non-human primate tissue and to use antagonists to dissect their role by specific inhibition at defined periods during the ovulatory cycle in non-human primates in vivo. The course of angiogenesis throughout the cycle and the cellular and molecular effects of inhibitory treatments have been investigated in the marmoset ovary and uterus, whereas consequences on pituitary–ovarian function have been monitored in macaques. Inhibition of vascular endothelial growth factor (VEGF) at the time of follicle recruitment or selection prevents endothelial cell proliferation, leading to inhibition of follicular development. VEGF inhibition during the early luteal phase prevents angiogenesis and restricts development of the luteal microvasculature. Inhibition of angiogenesis at all stages of the cycle leads to profound suppression of ovarian function. Even during the ‘post-angiogenic’ period of the luteal phase, inhibition of VEGF precipitates a suppression of progesterone secretion, pointing to additional roles for VEGF in the ovary. In the endometrium, oestrogen drives endometrial angiogenesis through VEGF. Thus, oestrogen can restore angiogenesis after ovariectomy, but not in the presence of VEGF inhibitors. These investigations enhance our understanding of the regulation of angiogenesis in the ovary and uterus and inform studies on conditions with abnormal vascularisation, such as polycystic ovary syndrome, endometriosis, uterine fibroids and menstrual dysfunction.
Gene expression map of the
Arabidopsis
shoot apical meristem stem cell niche
Authors: Yadav Ram Kishor , Girke Thomas , Pasala Sumana , Xie Mingtang , Reddy G. Venugopala
Published: March 2009

Despite the central importance of stem cells in plant growth and development, the molecular signatures associated with them have not been revealed. Shoot apical meristems (SAMs) harbor a small set of stem cells located at the tip of each plant and they are surrounded by several million differentiating cells. This imposes a major limitation in isolating pure populations of stem cells for genomic analyses. We have developed a system to isolate pure populations of distinct cell types of the SAMs, including stem cells. We have used this system to profile gene expression from 4 different cell samples of SAMs. The cell sample-specific gene expression profiling has resulted in a high-resolution gene expression map to reveal gene expression networks specific to individual spatial domains of SAMs. We demonstrate that the cell sample-specific expression profiling is sensitive in identifying rare transcripts expressed in a few specific subsets of cells of SAMs. Our extensive RNA in situ analysis reveals that the expression map can be used as a predictive tool in analyzing the spatial expression patterns of genes and it has led to the identification of unique gene expression patterns within the SAMs. Furthermore, our work reveals an enrichment of DNA repair and chromatin modification pathways in stem cells suggesting that maintenance of genome stability and flexible chromatin may be crucial for stem cell function. The gene expression map should guide future reverse genetics experiments, high-resolution analyses of cell–cell communication networks and epigenetic modifications.
Illoura™: a software tool for analysis, visualization and semantic querying of cellular and other spatial biological data
Authors: McComb Tim , Cairncross Oliver , Noske Andrew B. , Wood David L. A. , Marsh Brad J. , Ragan Mark A.
Published: March 2009

Summary: New high-resolution approaches for mapping ultrastructure of cells in 3D are leading to unprecedented quantities of spatial data. Here we present Illoura, a software tool for the integrated management, analysis and visualization of these data within a semantic context, and illustrate its capability by analysis of spatial relationships in mammalian beta cells.

Availability:  http://www.visiblecell.com/illoura

Contact:  m.ragan@uq.edu.au

Supplementary information:  Supplementary data are available at Bioinformatics online.
Methods and results of in situ target-strength measurements of Atlantic cod (Gadus morhua) during combined trawl-acoustic surveys
Authors: Ermolchev Viacheslav A.
Published: March 2009

Ermolchev, V. A., 2009. Methods and results of in situ target-strength measurements of Atlantic cod (Gadus morhua) during combined trawl-acoustic surveys. – ICES Journal of Marine Science, 66: 1225–1232. This paper presents methods for collecting acoustic and biological data, including in situ target-strength (TS) estimates of fish, with results presented for Atlantic cod (Gadus morhua) obtained from combined trawl-acoustic surveys. These include fish in the small, average, and maximum length classes, within the range 5–136 cm (total fish length, LT). The investigations were done using Simrad EK500/EK60 echosounders with split-beam transducers and special post-processing software. Based on an analysis of data collected in the Barents Sea during 1998–2007, a relationship TS = 25.2 log10(LT) − 74.8 was obtained for Atlantic cod at 38 kHz, with TS in dB and LT in centimetres. Seasonally, and for depths between 50 and 500 m, the variability in cod TS was 3.1 dB, decreasing with depth. The largest day–night difference in mean TS was in August–September, with changes as large as 1.0–1.7 dB. In the other seasons, the day–night difference was <1.0 dB.