bluuebunny/crossref_metadata_2025 huggingface dataset:
How to identify winter convection in the Greenland Sea from hydrographic summer data
Authors: Ronski S. , Budéus G.
Published: November 2005

The identification of winter convection depths from later field observations is an often required but not trivial task. We show from field measurements that the effects of winter convection in the Greenland Sea can vary enormously, including such opposite changes as an increase or decrease of temperature, salinity, or stability. Also, small‐scale fluctuations in the vertical can grow larger or cease. Commonly used indicators for past convection in the Greenland Sea like overall vertical homogeneity or a freshwater input to deeper layers alone are therefore not reliable to construct a time series of winter convection. We explain this variety of effects with the occurrence of two rather different ventilation scenarios possible in the Greenland Sea. They are exemplified by two winters, using mainly hydrographic observations of the adjoining summers. The observed differences are substantiated by the results of a one‐dimensional model. Out of this a multicriteria catalogue is developed, which can be used to determine unambiguously convection depths in the Greenland Sea. The fulfillment of one of the criteria is sufficient to evidence convection, but the suitable criterion may differ from winter to winter. A straightforward indicator proving the absence of winter convection does not exist.
Modes of active intraplate deformation, Flinders Ranges, Australia
Authors: Célérier Julien , Sandiford Mike , Hansen David Lundbek , Quigley Mark
Published: November 2005

The Flinders Ranges form one of the most seismically active zones within the Australian continent with seismogenic strain rates over the last 30 years of ∼10−16s−1. Active deformation in the region reflects late Neogene increases in stress levels in the Indo‐Australian plate as a response to increased plate boundary forcing from collision zones with the neighboring Asian and Pacific plates. Geological and geophysical observations suggest two modes of active deformation in operation in the Flinders Ranges over the last several million years: (1) low‐amplitude (∼200–500 m), long‐wavelength (∼200 km) lithospheric flexure and (2) active reverse faulting along the range front with fault slip rates of up to ∼50 m Myr−1. Numerical models are developed to explore the contribution of each of these deformation modes to the observed geophysical signals. An elastic mode of deformation is suggested by a distinctive long‐wavelength positive correlation between gravity and topography in which the Flinders Ranges are bordered by anomalous topographic and gravity lows, now occupied by playa‐lake systems, centered some 50 km outboard of range‐bounding faults. Numerical models show that flexural instabilities localized by vertical loads arising from older tectonic structuring produce a first‐order match with observed topography and gravity. Numerical models are also used to illustrate how the localized failure evident in the contemporary seismicity and Quaternary faulting record within the Flinders Ranges reflects thermal weakening associated with extraordinary concentrations of heat producing elements in the crust, as reflected in modern‐day heat flows of ∼90 mW m−2.
Analysis of the October 3–7 2000 GEM storm with the WINDMI model
Authors: Horton W. , Spencer E. , Doxas I. , Kozyra J.
Published: November 2005

The 8 dimensional physics model WINDMI is used to analyze the October 3–7, 2000 geomagnetic storm using solar wind input data from the ACE satellite. This period was chosen because it contains an extended interval of well‐defined and quasi‐periodic auroral activations called sawtooth oscillations, a phenomena whose relationship to substorm processes and to upstream solar wind drivers is still under debate. The question of whether multiple sawtooth oscillations are triggered by periodic upstream solar wind features or by internal magnetospheric processes is addressed. The model predicts both the occurrence of 8 auroral activations identified as sawtooth events during the 24 hour period on the 4th of October, in agreement with the measured AL index, and also an earlier multiple sawtooth interval on the 3rd of October, in agreement with the measured AL index. These intervals occur during steady but moderate solar wind IMF Bz values and the periodicity of the sawtooth events was not directly related to any periodic features in the upstream solar wind. The model also predicts the geomagnetic Dst index through the main and recovery phase of the storm.
Waveform inversion of the S reflector west of Spain: Fine structure of a detachment fault
Authors: Leythaeuser T. , Reston T. J. , Minshull T. A.
Published: November 2005

The S reflection west of Iberia has been interpreted as a low‐angle detachment fault separating crustal fault blocks from partially serpentinized mantle. We apply full waveform inversion to investigate the fine structure of S. Our results confirm that S is largely a step increase in velocity (and density), probably from crustal rocks to partially serpentinized mantle peridotites. A ∼50 m thick low velocity zone above S might represent a main fault zone of highly serpentinized peridotites or hydrofractured and altered crustal rocks above the main fault zone. Both interpretations imply focused fluid flow along S, raising the possibility that low‐angle movement along S was aided by the development of local, transient high fluid pressures.
Buried mass anomalies along the hemispheric dichotomy in eastern Mars: Implications for the origin and evolution of the dichotomy
Authors: Kiefer Walter S.
Published: November 2005

Gravity observations indicate the presence of buried, high‐density material along the hemispheric dichotomy in eastern Mars. This material is unrelated to present‐day topography and is probably the result of localized thinning of the crust. This thinning may be the result of an epoch of edge‐driven convection that occurred shortly after the dichotomy formed. Initiation of edge‐driven convection requires that lateral variations in lithospheric structure be created on a timescale that is shorter than the conductive cooling time for the lithosphere, a few tens of million years at most. This timescale cannot be achieved if the dichotomy boundary is created solely by large‐scale convective flow. Formation or modification of the boundary by large impact basins such as Utopia can create the required lithospheric structure in a geologic instant. This suggests that large impacts were important in shaping the dichotomy, at least on a regional scale.
Mapping exchange and residence time in a model of Willapa Bay, Washington, a branching, macrotidal estuary
Authors: Banas N. S. , Hickey B. M.
Published: November 2005

The numerical model GETM is used to examine transport pathways and residence time in Willapa Bay, Washington, a macrotidal estuary with a complex channel geometry. When the model is run with realistic forcing, it reproduces both tidal velocities and the decrease of the salt intrusion length with increasing river flow with errors of 5–20%. Furthermore, a more stringent test, when the model is run with tidal forcing only, it reproduces the along‐channel profile of the effective horizontal diffusivity K, a direct measure of the strength of subtidal dispersion, which is known from previous empirical estimates. A Lagrangian, particle‐tracking method is used to map subtidal transport pathways at the resolution of the model grid. This analysis reveals an interweaving of coherent lateral exchange flows with discontinuous, small‐scale dispersion as well as tidal residual currents that in some locations, sharpen rather than smooth gradients between water masses. Comparison between these Lagrangian results and an Eulerian salt flux decomposition suggests that along‐channel complexity (channel junctions and channel curvature) is at least as important as cross‐sectional depth variation in shaping the subtidal circulation. Finally, a nonconservative tracer method is used to produce high‐resolution, three‐dimensional maps of residence time. This analysis shows that consistent with previous observational work in Willapa, at all except the highest winter‐storm‐level river flows, river‐ and ocean‐density‐driven exchanges are discernable but secondary to tidal stirring. In all seasons, despite the fact that half the volume of the bay enters and leaves with every tide, average retention times in the upper third of the estuary are 3–5 weeks.
Scaling snow observations from the point to the grid element: Implications for observation network design
Authors: Molotch Noah P. , Bales Roger C.
Published: November 2005

The spatial distribution of snow water equivalent (SWE) within 16‐, 4‐, and 1‐km2 grid elements surrounding six snow telemetry (SNOTEL) stations in the Rio Grande headwaters was characterized using field observations of snowpack properties, satellite data, binary regression tree models, and a spatially distributed net radiation/temperature index snowpack mass balance model. In some cases, SNOTEL SWE values were 200% greater than mean grid element SWE. Analyses designed to identify the optimal location for measuring mean grid element SWE accumulation indicated that only 2.4% of each grid element satisfied the criteria of optimality. Similar analyses for the ablation season showed that point SWE and mean grid element SWE were highly correlated (r = 0.73) in areas with relatively persistent snow cover. These locations did not overlap in space with areas deemed optimal at maximum accumulation; areas with persistent snow cover have relatively high accumulation rates. Therefore future observations may need to be placed with the specific objective of representing either accumulation or ablation season processes. These results have implications for large‐scale studies that require ground observations for updating purposes; we show an example of this utility using the SWE product of the National Operational Hydrologic Remote Sensing Center. Furthermore, the relatively consistent spatial patterns of snow accumulation and melt have implications for future observation network design in that results from short‐term studies (e.g., 2 years) can be used to design long‐term observation networks.
Fractal and Noisy CBV Dynamics in Humans: Influence of Age and Gender
Authors: Eke Andras , Hermán Péter , Hajnal Márton
Published: November 2005

The complexity of spontaneous cerebral blood volume (CBV) fluctuations can emerge from random, fractal, or chaotic processes. Our aims were to define the contribution of these patterns to the observed complexity and to evaluate the effect of age and gender on it. The total hemoglobin content as the measure of CBV was monitored by near-infrared spectroscopy on volunteers (men n = 19, age = 20 to 78 years; women n = 23, age = 21 to 79 years). Random and fractal patterns were distinguished by the spectral index ( β). Chaos was identified by surrogate analysis of the correlation dimension (a static chaotic parameter, the dimension of the correlation integral) and the largest Lyapunov exponent (a dynamic chaotic parameter, the rate of exponential divergence of the system states from a perturbed initial condition over the chaotic attractor). In spontaneous CBV fluctuations, both fast random and slow fractal dynamics are present separately in their spectra by a cutoff frequency, f′. Below f′ the pattern is fractal, in that power rises inversely with frequency as 1/ fβ. f′ decreases with age in men and women alike (F1: up to 0.12 ± 0.06 Hz versus F2: up to 0.05 ± 0.04 Hz at P = 0.015, and M1: up to 0.16 ± 0.05 Hz versus M2: up to 0.11 ± 0.04 Hz at P = 0.044). Neither pre- nor postmenopausal age groups (1 and 2, respectively) showed a low β gender difference. Surrogate analysis showed that CBV dynamics cannot be characterized on the grounds of deterministic chaos. Cerebral blood volume fluctuates in a complex, bimodal manner in humans, in that the fast dynamics has no structure, while the slow dynamics exhibits a self-similar, that is, fractal temporal structure. The range of fluctuation amplitudes produced by fractal dynamics is always larger than that of random fluctuations, and it shrinks with an altered structuring in aging women only.
The Carboxyl-Terminal Domain of Inducible Hsp70 Protects from Ischemic Injury in vivo and in vitro
Authors: Sun Yunjuan , Ouyang Yi-Bing , Xu Lijun , Chow Ari Man-Yi , Anderson Robin , Hecker James G , Giffard Rona G
Published: November 2005

Heat shock protein (Hsp)70 can suppress both necrosis and apoptosis induced by various injuries in vivo and in vitro. However, the relative importance of different functions and binding partners of Hsp70 in ischemic protection is unknown. To explore this question, we tested the ability of Hsp70-K71E, an adenosine triphosphate (ATP)ase-deficient point mutant, and Hsp70-381-640, a deletion mutant lacking the ATPase domain and encoding the carboxyl-terminal portion, to protect against ischemia-like injury in vivo and in vitro. Heat shock protein 70-wild type (-WT), -K71E, −381-640, and control vector plasmid LXSN were expressed in primary murine astrocyte cultures. Astrocytes overexpressing Hsp70-WT, -K71E, or −381-640 were all significantly protected from 4 h combined oxygen-glucose deprivation and 24 h reperfusion when assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay or propidium iodide staining and cell counting ( P < 0.05). Brains of rats were transfected with plasmids encoding Hsp70-WT, -K71E, −381-640, or LXSN 24 h before 2 h middle cerebral artery occlusion followed by 24 h reperfusion. Animals that overexpressed either of the mutant proteins or Hsp70-WT had significantly better neurological scores and smaller infarcts than control animals. Protection by both mutants was associated with reduced protein aggregation, as assessed by ubiquitin immunohistochemistry and reduced nuclear translocation of apoptosisinducing factor. The results show that the carboxyl-terminal portion of Hsp70 is sufficient for neuroprotection. This indicates that neither the ability to fold denatured proteins nor interactions with cochaperones or other proteins that bind the amino-terminal half of Hsp70 are essential to ischemic protection.
Predicting internal protein dynamics from structures using coupled networks of hindered rotators
Authors: Abergel Daniel , Bodenhausen Geoffrey
Published: November 2005

Internal motions in proteins, such as oscillations of internuclear vectors u(NiHiN) of amide bonds about their equilibrium position, can be characterized by a local order parameter. This dynamic parameter can be determined experimentally by measuring the longitudinal and transverse relaxation rates of Ni15 nuclei by suitable NMR methods. In this paper, it is shown that local variations of order parameters Sii2 can be predicted from the knowledge of the structure. To this effect, the diffusive motion of the internuclear vector u(NiHiN) is described in a potential that takes into account the deviations of the angles θij between u(NiHiN) and neighboring vectors u(NjHjN) from their average value and similarly of deviations of the angles subtended between u(NiHiN) and u(XjYj), where Xj and Yj are heavy atoms in the vicinity of the u(NiHiN) vector under investigation. It is shown how the concept of vicinity can be defined by a simple cutoff threshold, i.e., by neglecting vectors u(XjYj) with distances d(Ni,Xj)>7.5Å. The local order parameters Sii2 can be predicted from the structure using a limited set of coordinates of heavy atoms. The inclusion of a larger number of heavy atoms does not improve the predictions. Applications to calmodulin, calbindin, and interleukin 4 illustrate the success and limitations of the predictions.
Photoionization of hot radicals: C2H5,n-C3H7, and i-C3H7
Authors: Fan Haiyan , Pratt S. T.
Published: November 2005

The combination of ion-imaging and vacuum-ultraviolet (vuv) single-photon ionization is used to study the internal energy dependence of the relative photoionization yields of the C2H5,n-C3H7, and i-C3H7 radicals following the 266 nm photodissociation of the corresponding alkyl iodides. The comparison of the ion images obtained by vuv photoionization of the radical with those obtained by two-photon-resonant, three-photon ionization of the complementary IP3∕22 and I*P1∕22 atoms allows the extraction of the internal energy dependence of the cross sections. Factors influencing the appearance of the ion images in the different detection channels are discussed, including the secondary fragmentation of the neutral radicals, Franck-Condon factors for the photoionization process, and the unimolecular fragmentation of the parent photoions.
An invariant variational principle for canonical flows on Lie groups
Authors: Muzsnay Zoltán
Published: November 2005

In this paper we examine the existence of Lie groups, whose canonical geodesic flows are variational with respect to a left-invariant regular—but not necessarily quadratic (i.e., metric)—Lagrange function. We give effective necessary and sufficient conditions for the existence of an invariant variational principle generating the canonical flow. With these results, taken in conjunction with the classification of Lie algebras, we solve the inverse problem of invariant Lagrangian dynamics in dimensions up to four.
Pinning mass-selected Agn clusters on the TiO2(110)−1×1 surface via deposition at high kinetic energy
Authors: Tong Xiao , Benz Lauren , Chrétien Steeve , Kemper Paul , Kolmakov Andrei , Metiu Horia , Bowers Michael T. , Buratto Steven K.
Published: November 2005

We present the first scanning tunneling microscopy (STM) study of the deposition of mass-selected silver clusters (Agn,n=1, 2, 3) on a rutile TiO2(110)−1×1 surface at room temperature under hard-landing conditions. Under hard-landing conditions, only small features are observed on the surface in all cases without sintering or surface damage. This suggests that the high impact energy of the clusters mainly dissipates as thermal energy in the substrate, resulting in the recovery of any initial impact-induced surface damage and the formation of bound clusters on the surface near the impact point. STM images indicate that Ag1 binds on the bridging oxygen rows twice as often as on the Ti rows. Density-functional Theory (DFT) calculations are consistent with Ag1 binding at either bridging oxygen vacancies or with two adjacent bridging oxygen atoms in the same bridging oxygen row. STM images of Ag2 and Ag3 depositions indicate almost exclusive binding centered on the Ti-atom rows. DFT calculations suggest that the Ag2 and Ag3 clusters are bound between two bridging oxygen rows, which is consistent with the STM observations.
Does GaH5 exist?
Authors: Speakman Lucas D. , Turney Justin M. , Schaefer Henry F.
Published: November 2005

The existence or nonexistence of GaH5 has been widely discussed [N. M. Mitzel, Angew. Chem. Int. Ed. 42, 3856 (2003)]. Seven possible structures for gallium pentahydride have been systematically investigated using ab initio electronic structure theory. Structures and vibrational frequencies have been determined employing self-consistent field, coupled cluster including all single and double excitations (CCSD), and CCSD with perturbative triples levels of theory, with at least three correlation-consistent polarized-valence-(cc-pVXZ and aug-cc-pVXZ) type basis sets. The X̃A′1 state for GaH5 is predicted to be weakly bound complex 1 between gallane and molecular hydrogen, with Cs symmetry. The dissociation energy corresponding to GaH5→GaH3+H2 is predicted to be De=2.05kcalmol−1. The H–H stretching fundamental is predicted to be v=4060cm−1, compared to the tentatively assigned experimental feature of Wang and Andrews [J. Phys. Chem. A 107, 11371 (2003)] at 4087cm−1. A second Cs structure 2 with nearly equal energy is predicted to be a transition state, corresponding to a 90° rotation of the H2 bond. Thus the rotation of the hydrogen molecule is essentially free. However, hydrogen scrambling through the C2v structure 3 seems unlikely, as the activation barrier for scrambling is at least 30kcalmol−1 higher in energy than that for the dissociation of GaH5 to GaH3 and H2. Two additional structures consisting of GaH3 with a dihydrogen bond perpendicular to gallane (C3v structure 4) and an in-plane dihydrogen bond [Cs(III) structure 5] were also examined. A C3v symmetry second-order saddle point has nearly the same energy as the GaH3+H2 dissociation limit, while the Cs(III) structure 5 is a transition structure to the C3v structure. The C4v structure 6 and the D3h structure 7 are much higher in energy than GaH3+H2 by 88 and 103kcalmol−1, respectively.
First-order mean-spherical approximation for interfacial phenomena: A unified method from bulk-phase equilibria study
Authors: Tang Yiping
Published: November 2005

The recently proposed first-order mean-spherical approximation (FMSA) [Y. Tang, J. Chem. Phys. 121, 10605 (2004)] for inhomogeneous fluids is extended to the study of interfacial phenomena. Computation is performed for the Lennard-Jones fluid, in which all phase equilibria properties and direct correlation function for density-functional theory are developed consistently and systematically from FMSA. Three functional methods, including fundamental measure theory for the repulsive force, local-density approximation, and square-gradient approximation, are applied in this interfacial investigation. Comparisons with the latest computer simulation data indicate that FMSA is satisfactory in predicting surface tension, density profile, as well as relevant phase equilibria. Furthermore, this work strongly suggests that FMSA is very capable of unifying homogeneous and inhomogeneous fluids, as well as those behaviors outside and inside the critical region within one framework.
Fast and stable recording of birefringence and holographic gratings in an azo-polymethacrylate using a single nanosecond light pulse
Authors: Rodríguez F. J. , Sánchez C. , Villacampa B. , Alcalá R. , Cases R. , Millaruelo M. , Oriol L.
Published: November 2005

Pulsed light-induced recording in azobenzene polymers has recently been studied due to its potential use in optical storage applications. In this paper we study the photoinduced birefringence (Δn) and holographic grating recording in an azobenzene side chain liquid-crystalline polymethacrylate irradiating with a single 4ns light pulse at 532nm. For some irradiation conditions, Δn grows in less than 50ns reaching an essentially stable value of about 10−2. Holographic gratings have been registered using intensity and polarization patterns. Fast response and stability, similar to those of Δn, was observed in the holographic recording process. Both light-induced anisotropy and relief contributions have been found in the case of gratings recorded using intensity patterns, relief being the dominant contribution at high recording energies. Polarization gratings have been recorded using two orthogonally circularly polarized beams. The resultant gratings showed stable efficiencies up to 0.8% (measured at 633nm in 1-μm-thick films) and no measurable relief was observed.
Temperature dependence of magnetocurrent in a magnetic tunnel transistor
Authors: Park B. G. , Banerjee T. , Min B. C. , Sanderink J. G. M. , Lodder J. C. , Jansen R.
Published: November 2005

The temperature dependence of magnetocurrent (MC) and transfer ratio has been investigated in a magnetic tunnel transistor (MTT) with a ferromagnetic (FM) emitter of Co or Ni80Fe20. MTT devices of sizes ranging from 10to100μm in diameter were fabricated using a standard photolithography process and predefined Si substrates. This reduces the edge leakage current across the collector Schottky diode and enables room-temperature operation. For the MTT with both Co and Ni80Fe20 emitter, we obtain a MC of about 80% at room temperature. This corresponds to a tunnel spin polarization of the FM emitter/Al2O3 interface of 29% at 1V, demonstrating that the tunnel current is still spin-polarized at a high bias voltage.
Polarized neutron reflectometry in high magnetic fields
Authors: Fritzsche H.
Published: November 2005

A simple method is described to maintain the polarization of a neutron beam on its way through the large magnetic stray fields produced by a vertical field of a cryomagnet with a split-coil geometry. The two key issues are the proper shielding of the neutron spin flippers and an additional radial field component in order to guide the neutron spin through the region of the null point (i.e., point of reversal for the vertical field component). Calculations of the neutron’s spin rotation as well as polarized neutron reflectometry experiments on an ErFe2∕DyFe2 multilayer show the perfect performance of the used setup. The recently commissioned cryomagnet M5 with a maximum vertical field of up to 7.2T in asymmetric mode for polarized neutrons and 9T in symmetric mode for unpolarized neutrons was used on the C5 spectrometer in reflectometry mode, at the NRU reactor in Chalk River, Canada.
Nonlinear hydromagnetic waves in two-ion-species plasmas
Authors: Chaudhuri Manis , Chakrabarti Nikhil , Pal Rabindranath
Published: November 2005

A theoretical study has been carried out to see the modification of low-density electron-ion plasma dynamics in the presence of heavy third-ion species with positive as well as negative charges. It has been shown that the behavior of such a plasma differs from the behavior of a single-ion-species plasma. The stationary state nonlinear equations were solved in different species with respect to charges and masses, and different plasma profiles have been displayed. The weakly nonlinear case has been discussed to demonstrate the low-amplitude solitons.
Generation of cold low divergent atomic beam of indium by laser ablation
Authors: Alti Kamlesh , Khare Alika
Published: November 2005

The formation of low-energy (below 100m∕s), low divergence (without any collimation optics) pulsed indium atomic beam via ablation of thin film by direct illumination (unfocused) from the rear side with second harmonic of Q-switched Nd:YAG laser under high vacuum (∼10−5Torr) is reported. Angular divergence of an ablated indium beam was measured for the different laser powers. Axial atomic and ionic velocities were studied as a function of laser energy per pulse using a beam deflection setup.
Comment on “Monte Carlo investigation of current voltage and avalanche noise in GaN double-drift impact diodes” [J. Appl. Phys. 97, 043709 (2005)]
Authors: Dash G. N.
Published: November 2005

The avalanche noise behavior of impact avalanche transit-time (IMPATT) diodes has been modeled by Reklaitis and Reggiani [J. Appl. Phys. 97, 043709 (2005)]. They have obtained general agreement of their results with those of McIntyre [IEEE Trans. Electron Devices ED-13, 164 (1966)]. However, McIntyre’s theory predicts the opposite noise behavior from that observed in the IMPATT diode. Hence the applicability of the noise model of Reklaitis and Reggiani to IMPATT diode is questionable.
Raman spectroscopic study of (Pb1−xBax)(Yb1∕2Ta1∕2)O3 ceramics
Authors: Rout Dibyaranjan , Subramanian V. , Hariharan K. , Murthy V. R. K. , Sivasubramanian V.
Published: November 2005

The ordered complex perovskite lead ytterbium tantalate undergoes a change in structural and dielectric properties as the concentration of Ba increases. The x-ray diffraction patterns show a decrease in the intensity of superlattice reflections due to Pb-antiparallel displacement as well as to B-site ordering. The structure approaches cubic symmetry with increase in Ba content. The dielectric response shows a gradual change from antiferroelectric to relaxor ferroelectric and then the relaxor behavior starts decreasing as Ba content increases. Raman-scattering study of the samples shows that some of the modes seen for Pb(Yb0.5Ta0.5)O3 disappear and an additional mode appears at 420cm−1 with increase in Ba concentration. A qualitative analysis of various modes suggests that the substitution of Ba for Pb leads to a decrease in the degree of ordering and occurrence of local distortions in the lattice as evidenced by the broadening of certain peaks in the Raman spectra.
Production efficiencies of Kr*(1s5,1s4) atoms leading to vacuum-ultraviolet emissions in ac plasma display panels with Kr–Ne binary mixtures measured by laser-absorption spectroscopy
Authors: Oh J.-S. , Tachibana K. , Hatanaka H. , Kim Y.-M. , Son S.-H. , Jang S.-H.
Published: November 2005

Ne–Kr gas mixtures with high Kr concentrations were applied to ac plasma display panels. Spatiotemporal behaviors of excited Kr atoms in the 1s5 metastable state and the 1s4 resonance state were measured by microscopic laser-absorption spectroscopy in the binary mixtures with Kr concentrations of 20% and 40%. A systematic comparison was done between the characteristics of Ne–Kr-filled panels and those of conventional Ne–Xe panels with the same structure but with lower Xe concentrations of 5% and 10%. For example, the total number of Kr*(1s5) atoms in a unit cell ranged from 7.4×107 to 2.0×108, at the peak was apparently smaller than the value of Xe*(1s5) atoms. However, when the difference in the decay rate of the excited atoms by three-body collision processes is taken into account, the production efficiency of vacuum-ultraviolet (VUV) emission from Kr2* excimers is as large as that from Xe2* excimers in a usual panel since these processes lead directly to the formation of excimers. From the measured density of Kr*(1s4) atoms, it is estimated that the contribution of the atomic resonance line is smaller than the excimer band at those high Kr concentrations. In any case, by summing up those two contributions to the VUV emission, the overall efficiency in the Ne–Kr(40%) panel is estimated to be comparable to that in the Ne–Xe(10%) one.
Effect of dispersive transport and partial trap filling on thermally stimulated current in conjugated polymers
Authors: Nikitenko V. R. , Kadashchuk A. , Schmechel R. , von Seggern H. , Korosko Yu.
Published: November 2005

Thermally stimulated current (TSC) controlled by thermal release of excess charge carriers (holes) from intrinsic traps in a conjugated polymer poly(9,9-bis(2-ethylhexyl) fluorene-2,7-diyl) has been studied at different readout voltages (VRO) applied during the heating run. We found that the TSC peak measured at low applied electric field is located at somewhat higher temperature then the thermally stimulated luminescence (TSL) detected in this material; however, the TSC peak shifts towards the lower temperature with increasing VRO and at high electric fields approaches the temperature spectra of TSL. We found that the above shift of the TSC peak is not accompanied with a substantial increase of TSC intensity usually observed in the TSC of organic solids, and is considered as an indication that the recombination of liberated charge carriers plays no role. Whereas the observed behavior of the TSC peak is due to the thermally stimulated dispersive transport of holes in the polymer. We formulated a model of dispersive TSC, which considers the partial filling of deep traps. Results of the calculations agree well qualitatively with the experiment. The possible implication of the dispersive character of TSC for evaluation of the energetic distribution and spatial concentration of traps from the TSC data is analysed.
Role of interfacial roughness on bias-dependent magnetoresistance and transport properties in magnetic tunnel junctions
Authors: Huang J. C. A. , Hsu C. Y. , Liao Y. F. , Lin M. Z. , Lee C. H.
Published: November 2005

The effects of metal-insulator interfacial roughness, modulated by Ar+ irradiation, on bias dependence of tunnel magnetoresistance (TMR) and electrical transport of CoFe–AlOx–CoFe magnetic tunnel junctions (MTJs) have been studied. Reduction of TMR ratio and asymmetric TMR falloff curves as a function of dc bias have been observed for Ar+-irradiated MTJs. The results are analyzed by x-ray reflectivity together with complex impedance techniques, indicating interfacial roughness which likely results in a proportional rising trap state density (TSD). Increasing TSD for Ar+-irradiated MTJs increases an unpolarized current which decreases TMR ratio. The asymmetric TMR falloff curves are attributed to the different TSDs of bottom and top CoFe–AlOx interfaces in tunneling process.
Flow visualization of cavitating flows through a rectangular slot micro-orifice ingrained in a microchannel
Authors: Mishra Chandan , Peles Yoav
Published: November 2005

Multifarious hydrodynamic cavitating flow patterns have been detected in the flow of de-ionized water through a 40.5μm wide and 100.8μm deep rectangular slot micro-orifice established inside a 202.6μm wide and 20 000μm long microchannel. This article presents and discusses the flow patterns observed at various stages of cavitation in the aforementioned micrometer-sized silicon device. Cavitation inception occurs with the appearance of inchoate bubbles that emerge from two thin vapor cavities that emanate from the boundaries of the constriction element. A reduction in the cavitation number beyond inception results in the development of twin coherent unsteady large vapor cavities, which appear just downstream of the micro-orifice and engulf the liquid jet. The shedding of both spherical and nonspherical vapor bubbles and their subsequent collapse into vapor plumes downstream of the orifice occurs intermittently. A further reduction in the exit pressure only aids in the elongation of the two coherent cavities and produces two stable vapor pockets. Additionally, interference fringes are clearly observed, showing that the vapor pocket has a curved interface with liquid. At low cavitation numbers, the flow undergoes a flip downstream and the two vapor pockets coalesce and form a single vapor pocket that is encircled by the liquid and extends until the exit of the microchannel. The cavitating flow patterns are unique and are markedly different from those reported for their macroworld counterparts. Evidence of pitting due to cavitation has been observed on the silicon just downstream of the micro-orifice. It is therefore apparent that cavitation will continue to influence/impact the design of high-speed MEMS hydraulic machines, and the pernicious effects of cavitation in terms of erosion, choking, and a reduction in performance will persist in microfluidic systems if apposite hydrodynamic conditions develop.
Magnetic-field-induced grain elongation in a medium carbon steel during its austenitic decomposition
Authors: Zhang Y. D. , Esling C. , Muller J. , He C. S. , Zhao X. , Zuo L.
Published: November 2005

A 12-T magnetic field was applied during the austenitic decomposition in a medium plain carbon steel at a slow cooling rate. The magnetic field applied promotes proeutectoid ferrite grains to grow along the field direction and results in an elongated grain microstructure. The grain elongation is the result of the opposing contributions from the atomic dipolar interaction energy of Fe atoms and the interfacial energy.
Carrier transport and recombination in p-doped and intrinsic 1.3μm InAs∕GaAs quantum-dot lasers
Authors: Marko I. P. , Massé N. F. , Sweeney S. J. , Andreev A. D. , Adams A. R. , Hatori N. , Sugawara M.
Published: November 2005

The radiative and nonradiative components of the threshold current in 1.3μm, p-doped and undoped quantum-dot semiconductor lasers were studied between 20 and 370K. The complex behavior can be explained by simply assuming that the radiative recombination and nonradiative Auger recombination rates are strongly modified by thermal redistribution of carriers between the dots. The large differences between the devices arise due to the trapped holes in the p-doped devices. These both greatly increase Auger recombination involving hole excitation at low temperatures and decrease electron thermal escape due to their Coulombic attraction. The model explains the high T0 values observed near room temperature.
High-frequency surface acoustic wave devices based on LiNbO3∕diamond multilayered structure
Authors: Dogheche E. , Remiens D. , Shikata S. , Hachigo A. , Nakahata H.
Published: November 2005

This research is focused on the development of a new technology for the fabrication of high-frequency surface acoustic wave (SAW) filters based on diamond and lithium niobate (LiNbO3) materials. LiNbO3 films are in situ deposited at 490 °C on polycrystalline diamond substrates by radio-frequency magnetron sputtering; a multistep growth process is proposed to deposit oriented LiNbO3 films with a smooth surface. Conventional interdigital transducers are fabricated on top of the piezoelectric LiNbO3 layer by standard optical lithography. We report experimental results for a SAW bandpass filter operating at a frequency above 2.30 GHz. We have observed that Rayleigh SAW modes are excited within this structure, with extremely high phase velocities (up to 12000m∕s). This latter result illustrates the greatest advantage of using diamond as an acoustic substrate. It allows the fabrication of SAW devices operating in the gigahertz frequency range using standard optical lithography.
Formation and evolution of epitaxial Co5Ge7 film on Ge (001) surface by solid-state reaction in an in situ ultrahigh-vacuum transmission electron microscope
Authors: Sun H. P. , Chen Y. B. , Pan X. Q. , Chi D. Z. , Nath R. , Foo Y. L.
Published: November 2005

A thin metallic cobalt (Co) layer was deposited on a single-crystal Ge (001) surface at room temperature by the electron-beam evaporation of a pure Co metal source in an ultrahigh-vacuum transmission electron microscope. The formation and epitaxial growth of a cobalt germanide Co5Ge7 phase on the Ge (001) surface was studied in situ by gradually heating the sample from room temperature to ∼350°C. The occurrence of an epitaxial hexagonal-close-packed Co and the reaction between Co and Ge were observed at ∼225°C. After annealing at ∼300°C for 26.5 h, a continuous epitaxial Co5Ge7 film formed on the Ge (001) substrate. With further annealing at a higher temperature, the continuous Co5Ge7 layer broke up and formed three-dimensional islands in order to relieve the strain energy in the epitaxial Co5Ge7 layer. Two epitaxial relationships between Co5Ge7 and Ge, i.e., Co5Ge7⟨110⟩(001)∕∕Ge⟨100⟩(001) and Co5Ge7⟨001⟩(110)∕∕Ge⟨100⟩(001) were found by electron diffraction.
Self-integration of aligned cobalt nanoparticles into silica nanotubes
Authors: Ren Lirong , Guo Lin , Wark Michael , Hou Yanglong
Published: November 2005

A methodology for self-integrating cobalt particles (10–70nm) into silica nanotubes has been developed during a simple calcination process. Rhombohedral silica nanotubes serve to guide cobalt nanoparticles into one-dimensional alignment. The Co-silica nanotubes prepared by using [Co(NH3)6](HCO3)(CO3)∙2H2O fibers as structure-directing agents have a size of 100–220nm in diameter and up to 30μm in length. Magnetic study shows that the Co-silica nanocomposite exhibits a ferromagnetic characteristic with a large room temperature coercivity of 520Oe. The formation mechanism of Co particle alignment is discussed.
Gas-phase synthesis of nitrogen-doped TiO2 nanorods by microwave plasma torch at atmospheric pressure
Authors: Hong Yong Cheol , Kim Jong Hun , Bang Chan Uk , Uhm Han Sup
Published: November 2005

Nitrogen (N)-doped titanium dioxide (TiO2) nanorods were directly synthesized via decomposition of gas-phase titanium tetrachloride (TiCl4) by an atmospheric microwave plasma torch. X-ray diffraction, field-emission scanning electron microscope, field-emission transmission electron microscope, and electron-energy-loss spectroscopy (EELS) have been employed to investigate fraction of the anatase and rutile phases, diameter and length, and chemical composition of the nanorods, respectively. The diameters of the nanorods are approximately 30–80 nm and the length is several micrometers. EELS data show that incorporation of N into the O site of TiO2 nanorods was enhanced in N2 gas by the microwave plasma torch. Also, a growth model of the rods was proposed on the basis of vapor-liquid-solid mechanism.
Deep-level emissions influenced by O and Zn implantations in ZnO
Authors: Zhao Q. X. , Klason P. , Willander M. , Zhong H. M. , Lu W. , Yang J. H.
Published: November 2005

A set of bulk ZnO samples implanted with O and Zn at various densities were investigated by photoluminescence. The implantation concentration of O and Zn is varied between 1×1017∕cm3 and 5×1019∕cm3. The samples were thermally treated in an oxygen gas environment after the implantation. The results clearly show the influence of O and Zn implantations on the deep-level emission. By comparing the photoluminescence spectra for the samples with different implantations, we can conclude that the VZn is responsible to the observed deep-level emission. In addition, a novel transition at the emission energy of 3.08eV at 77K appears in the O-implanted sample with 5×1019∕cm3 implantation concentration. The novel emission is tentatively identified as O-antisite OZn.
Nonlinear electromagnetic susceptibilities of unmagnetized plasmas
Authors: Yoon Peter H.
Published: November 2005

Fully electromagnetic nonlinear susceptibilities of unmagnetized plasmas are analyzed in detail. Concrete expressions of the second-order nonlinear susceptibility are found in various forms in the literature, usually in connection with the discussions of various three-wave decay processes, but the third-order susceptibilities are rarely discussed. The second-order susceptibility is pertinent to nonlinear wave-wave interactions (i.e., the decay/coalescence), whereas the third-order susceptibilities affect nonlinear wave-particle interactions (i.e., the induced scattering). In the present article useful approximate analytical expressions of these nonlinear susceptibilities that can be readily utilized in various situations are derived
Stochastization as a possible cause of fast reconnection in the frequently interrupted regime of neoclassical tearing modes
Authors: Dumbrajs O. , Igochine V. , Constantinescu D. , Zohm H. ,   ASDEX Upgrade Team
Published: November 2005

The role of stochastization of magnetic field lines in fast reconnection phenomena occurring in magnetized fusion plasma is analyzed. A mapping technique is applied to trace the field lines of toroidally confined plasma where the perturbation parameter is expressed in terms of experimental perturbation amplitudes determined from the Axially Symmetric Divertor Experiment (ASDEX) Upgrade tokamak [S. Günter, C. Angioni, M. Apostoliceanu et al., Nucl. Fusion 45, S98 (2005)]. It is found that fast reconnection observed during amplitude drops of the neoclassical tearing mode instability in the frequently interrupted regime can be related to stochastization.
Mid-infrared InAs∕AlGaSb superlattice quantum-cascade lasers
Authors: Ohtani K. , Fujita K. , Ohno H.
Published: November 2005

We report on the demonstration of mid-infrared InAs∕AlGaSb superlattice quantum-cascade lasers operating at 10μm. The laser structures are grown on n-InAs (100) substrate by solid-source molecular-beam epitaxy. An InAs∕AlGaSb chirped superlattice structure providing a large oscillator strength and fast carrier depopulation is employed as the active part. The observed minimum threshold current density at 80K is 0.7kA∕cm2, and the maximum operation temperature in pulse mode is 270K. The waveguide loss of an InAs plasmon waveguide is estimated, and the factors that determine the operation temperature are discussed.
Changes in testing methods for genital Chlamydia trachomatis in New South Wales, Australia, 1999 to 2002
Authors: Chen Marcus Y. , Donovan Basil
Published: November 2005

Background: Over the last decade, significant advances have occurred in the area of chlamydia diagnostics. The relative frequency of different testing methods employed in the diagnosis of Chlamydia trachomatis infection in New South Wales has not been previously reported. Methods: Testing methods—both laboratory method and specimen type—employed in the diagnosis of chlamydia cases notified in New South Wales between 1999 and 2002 were collated from Health Department records. Results: During a period of increasing notifications, the proportion of men diagnosed with C. trachomatis using nucleic acid tests (NATs) increased from 36% in 1999 to 90% in 2002. Among women, the proportion diagnosed using NATs increased from 42% in 1999 to 92% in 2002. Urine samples were consistently used in the diagnosis of two-thirds of the men, and one-third of the women. Conclusion: Between 1999 and 2002, a rapid shift towards NATs for genital C. trachomatis took place in New South Wales.
Use of lemon or lime juice douches in women in Jos, Nigeria
Authors: Imade Godwin E. , Sagay Atiene S. , Onwuliri Viola A. , Egah Daniel Z. , Potts Malcolm , Short Roger V.
Published: November 2005

Objective: To describe the use of lemon/lime juice for douching by female sex workers (FSWs) and family planning clients (FPCs) in Jos, Nigeria. Method: A total of 300 sexually active women comprising 200 FSWs and 100 FPCs were interviewed in June 2004 to determine the mode and rationale for the use of lemon/lime juice for sex. Result: Majority of the women 167/300 (55.7%, 95% CI = 50–61%) i.e. 163/200 (81.5%, 95% CI=75–87%) FSWs, 4/100 (4%, 95% CI=1–10%) FPCs used vaginal lemon/lime douches. Lime juice was used by 105/167 (62.8%, 95% CI=55–70%), lemon juice by 30/167 (18%, 95% CI=12–25%) or a mixture by 18/167 (10.8%, 95% CI=7–25%). The juice was used either neat 44/167 (26%, 95% CI=20–34%) or diluted in water 75/167 (45%, 95% CI=37–53%) either before or after sex. Nineteen per cent (32/167) found the juice painful. Over half of the women believed that it protected them from pregnancy and/or sexually transmitted infections; they did not know their HIV status. Eighty-six per cent would recommend it to others, and 71% would be willing to take part in a study to evaluate its safety and efficacy. Conclusion: Lemon and lime juice are widely used for douches among women at high risk of HIV transmission. There is an urgent need to determine whether or not this practice promotes or prevents HIV infection.
Assisted reproduction for HIV-infected couples
Authors: Giles Michelle , Mijch Anne , Garland Suzanne
Published: November 2005

Many HIV-infected individuals are in relationships with HIV-uninfected partners and desire to have children. This review focuses on the issue of reproductive choices for these couples, in particular assisted reproductive technologies, and summarises the published outcome data currently available. The results thus far from assisted reproductive technologies in optimising pregnancy outcomes and reducing heterosexual and perinatal HIV transmission are promising. In the future, it is essential that there is ongoing reporting of outcome data, publication of methodology and follow-up, and reporting of adverse outcomes.