bluuebunny/crossref_metadata_2025 huggingface dataset:
Ship Manoeuvring in Restricted Areas: An Attempt to Quantify Dangerous Situations Using a Probabilistic-Fuzzy Method
Authors: Gucma Lucjan , Pietrzykowski Zbigniew
Published: April 2006

This paper presents a practical application of the probabilistic-fuzzy method for assessment of the safety of a ship manoeuvring in waterways. The method, based on probabilistic risk analysis and elements of fuzzy logic, takes into account situations of threatened navigational safety and situations when a navigator intuitively thinks that the safety of manoeuvring ship is threatened. The probability of grounding a ship manoeuvring in a waterway bend is determined by means of simulation method. Then, with the use of experts' knowledge and tools of fuzzy logic the probability of a dangerous situation is determined. Two different approaches are applied for the determination of that probability. The results are compared.
Navigation Safety Analysis in Taiwanese Ports
Authors: Liu Chung-Ping , Liang Gin-Shuh , Su Yuhling , Chu Ching-Wu
Published: April 2006

Many researchers have studied vessel systems to enhance navigation safety at sea, or analysed the statistics of marine casualties of different flagged vessels as well as the fatalities and injuries in ferry accidents. However, little research has been devoted to port safety and especially navigation safety within Taiwanese territorial waters where over a 10-year period there have been 3428 marine accidents with 548 deaths and 524 vessels sunk. In this paper, we use the Grey Relational Analysis (GRA) to analyse the marine accident records of each of Taiwan's commercial ports from 1992–2003. Then, after interviewing the port authority managers and marine specialists, we discover the concerns felt by these professionals about Taiwanese commercial ports. We provide suggestions to strengthen port navigation safety.
Towards a geography of English scientific culture: provincial identity and literary and philosophical culture in the English county town, 1750–1850
Authors: ELLIOTT PAUL
Published: April 2006

Using case studies of English county towns, this article contributes towards the creation of a geography of scientific culture in England, 1750–1850. It argues that although emulation of the metropolis was important, provincial scientific culture had its own distinctive identity often concentrated through the lens of county town sociability and associations. The second part analyses data on literary and scientific institutions from the 1851 census in order to determine whether county towns continued to retain their importance in scientific culture by the middle of the nineteenth century.
Influence of anthropogenic emissions on tropospheric ozone and its precursors over the Indian tropical region during a monsoon
Authors: Beig Gufran , Brasseur Guy P.
Published: April 2006

An emission inventory of ozone precursors developed for the year 1991 and 2001 is used in a Chemistry‐Transport Model (MOZART) to examine the tropospheric changes in ozone and its precursors that have occurred during the 1990s in the geographical region of India in response to enhanced human activities. The maximum variation in ozone concentration near the surface is found to be around 5–10 ppbv. It reaches 5–7% in the lower part of the free troposphere and 3–5% in the upper troposphere. The maximum decadal increase in CO and NOx is about 50–70 ppbv (10–18%) and 0.5–1.5 ppbv (20–50%), respectively in the boundary layer. However, in most of the troposphere, the relative magnitude reduces with height and becomes less then 5% above 10 km. The variation in some of the volatile organic compounds is found to be significant.
Assessing a land surface model's improvements with GRACE estimates
Authors: Niu Guo‐Yue , Yang Zong‐Liang
Published: April 2006

The Gravity Recovery and Climate Experiment (GRACE) satellites have produced an unprecedented data set of terrestrial water storage (TWS) change in large‐scale river basins. Recent research has found that monthly variations of soil moisture and snow water simulated by land surface models compared favorably with the GRACE‐derived TWS change. Compared to the GRACE data, the standard version of the National Center for Atmospheric Research (NCAR) Community Land Model (CLM) produces a weaker TWS variability in tropical and mid‐latitudes but a stronger TWS variation in high latitudes. However, a modified version of CLM that includes more realistic interception, runoff, and frozen soil processes improves the simulation of TWS change in global river basins of various scales. In addition, the modified CLM improves the modeling of evapotranspiration through the improvements in the modeling of TWS variation and runoff in the Amazon River basin. Along this line of research, this paper shows that such GRACE data can be used as a means of evaluating the hydrological schemes in a land surface model.
P‐wave tomography reveals a westward dipping low velocity zone beneath the Kenya Rift
Authors: Park Yongcheol , Nyblade Andrew A.
Published: April 2006

Three teleseismic P‐wave travel time data sets (KRISP 1985, 1989–1990; Kenya Broadband Seismic Experiment) have been inverted to obtain a new tomographic model of the upper mantle beneath the Kenya Rift. The model shows a 0.5–1.5% low velocity anomaly below the rift extending to about 150 km depth. Below ∼150 km depth, the anomaly broadens to the west toward the Tanzania Craton, suggesting a westward dip to the structure. Tomographic images to the south in Tanzania and to the north in Ethiopia also show westward dipping low velocity anomalies below depths of ∼150–200 km. The presence of westward dipping low velocity structures along much of the East African rift (Ethiopia, Kenya and Tanzania) is difficult to explain with a plume model and is consistent with some models of the African Superplume showing anomalous lower and upper mantle structure connecting at mid‐mantle depths under the western side of East Africa.
Bayesian dynamic modeling for monthly Indian summer monsoon rainfall using El Niño–Southern Oscillation (ENSO) and Equatorial Indian Ocean Oscillation (EQUINOO)
Authors: Maity Rajib , Nagesh Kumar D.
Published: April 2006

There is an established evidence of climatic teleconnection between El Niño–Southern Oscillation (ENSO) and Indian summer monsoon rainfall (ISMR) during June through September. Against the long‐recognized negative correlation between ISMR and ENSO, unusual experiences of some recent years motivate the search for some other causal climatic variable, influencing the rainfall over the Indian subcontinent. Influence of recently identified Equatorial Indian Ocean Oscillation (EQUINOO, atmospheric part of Indian Ocean Dipole mode) is being investigated in this regard. However, the dynamic nature of cause‐effect relationship burdens a robust and consistent prediction. In this study, (1) a Bayesian dynamic linear model (BDLM) is proposed to capture the dynamic relationship between large‐scale circulation indices and monthly variation of ISMR and (2) EQUINOO is used along with ENSO information to establish their concurrent effect on monthly variation of ISMR. This large‐scale circulation information is used in the form of corresponding indices as exogenous input to BDLM, to predict the monthly ISMR. It is shown that the Indian monthly rainfall can be modeled in a better way using these two climatic variables concurrently (correlation coefficient between observed and predicted rainfall is 0.82), especially in those years when negative correlation between ENSO and ISMR is not well reflected (i.e., 1997, 2002, etc.). Apart from the efficacy of capturing the dynamic relationship by BDLM, this study further establishes that monthly variation of ISMR is influenced by the concurrent effects of ENSO and EQUINOO.
Radiative scaling of the nocturnal boundary layer and the diurnal temperature range
Authors: Betts Alan K.
Published: April 2006

A radiative scaling for the warm season nocturnal boundary layer (NBL) is proposed, based on the daily mean surface net longwave radiation flux. Using this scaling, a conceptual model is proposed for the NBL, with parameters estimated from multiple linear regression of model data from the European Centre reanalysis, averaged over river basins from the tropics to high latitudes. A radiative temperature scale, computed from surface net longwave radiation flux and the slope of the Stefan‐Boltzmann law, primarily determines the strength of the NBL and the amplitude of the diurnal temperature range, although the length of the nighttime period and the surface wind stress play important subsidiary roles. A related radiative velocity scale or radiative conductance, the duration of the nighttime period and the ratio of the scaled surface heat flux (which increases with wind stress) to the NBL strength determine the depth of the NBL. From an observational perspective, this suggests that the diurnal temperature range may give a useful estimate of surface net longwave radiation flux. From a modeling perspective, this provides a framework for relating model physical parameterizations, especially the coupling at night between the surface, the ground and the atmosphere, to observables, the diurnal temperature range and the strength and depth of the NBL. The model is then applied to estimate the nocturnal rise in concentration of gases such as CO2 and radon that are emitted at the surface.
Geological evolution of the Tyras Vallis paleolacustrine system, Mars
Authors: Di Achille Gaetano , Marinangeli Lucia , Ori Gian Gabriele , Hauber Ernst , Gwinner Klaus , Reiss Dennis , Neukum Gerhard
Published: April 2006

Using the new High Resolution Stereo Camera (HRSC) data and other Martian data sets, we reconstructed the hydrological history of an unnamed complex crater in the Xanthe Terra region. The crater hosted a lacustrine basin fed by a dense and centripetal drainage system, developed along its inner rim, and by the Tyras Vallis channel. Where the Tyras Vallis opens into the crater, a prominent delta‐like feature is visible, characterized by a central terrace and two small longitudinal scarps. This deposit has been used as sedimentary recorder of the crater lake history and allowed assessment of the overall hydrological evolution. Two major stands of the water level have been inferred at 700 and 550 m above the crater floor, based on the correlation between the morphology and topography of the fan and the crater floor deposits. Our reconstruction reveals a complex sedimentary evolution of the fan, which underwent deltaic and alluvial sedimentation, as a result of the different lake water levels and Tyras Vallis supplies. A dominant erosional evolution of the fan‐delta was determined by the interaction between the fluvial characteristics and basin wave regime. Wave height analysis and morphological comparison with terrestrial analogues support this hypothesis. The lacustrine activity could be chronologically placed between the Late Noachian and the Hesperian. The climatic conditions could have allowed the recharge of the regional groundwater system by precipitation and episodic fluvial activity. However, also heating effects of cratering could have affected the system, rejuvenating or accelerating the recharge of the local aquifer.
A multiple proxy and model study of Cretaceous upper ocean temperatures and atmospheric CO2 concentrations
Authors: Bice Karen L. , Birgel Daniel , Meyers Philip A. , Dahl Kristina A. , Hinrichs Kai‐Uwe , Norris Richard D.
Published: April 2006

We estimate tropical Atlantic upper ocean temperatures using oxygen isotope and Mg/Ca ratios in well‐preserved planktonic foraminifera extracted from Albian through Santonian black shales recovered during Ocean Drilling Program Leg 207 (North Atlantic Demerara Rise). On the basis of a range of plausible assumptions regarding seawater composition at the time the data support temperatures between 33° and 42°C. In our low‐resolution data set spanning ∼84–100 Ma a local temperature maximum occurs in the late Turonian, and a possible minimum occurs in the mid to early late Cenomanian. The relation between single species foraminiferal δ18O and Mg/Ca suggests that the ratio of magnesium to calcium in the Turonian‐Coniacian ocean may have been lower than in the Albian‐Cenomanian ocean, perhaps coincident with an ocean 87Sr/86Sr minimum. The carbon isotopic compositions of distinct marine algal biomarkers were measured in the same sediment samples. The δ13C values of phytane, combined with foraminiferal δ13C and inferred temperatures, were used to estimate atmospheric carbon dioxide concentrations through this interval. Estimates of atmospheric CO2 concentrations range between 600 and 2400 ppmv. Within the uncertainty in the various proxies, there is only a weak overall correspondence between higher (lower) tropical temperatures and more (less) atmospheric CO2. The GENESIS climate model underpredicts tropical Atlantic temperatures inferred from ODP Leg 207 foraminiferal δ18O and Mg/Ca when we specify approximate CO2 concentrations estimated from the biomarker isotopes in the same samples. Possible errors in the temperature and CO2 estimates and possible deficiencies in the model are discussed. The potential for and effects of substantially higher atmospheric methane during Cretaceous anoxic events, perhaps derived from high fluxes from the oxygen minimum zone, are considered in light of recent work that shows a quadratic relation between increased methane flux and atmospheric CH4 concentrations. With 50 ppm CH4, GENESIS sea surface temperatures approximate the minimum upper ocean temperatures inferred from proxy data when CO2 concentrations specified to the model are near those inferred using the phytane δ13C proxy. However, atmospheric CO2 concentrations of 3500 ppm or more are still required in the model in order to reproduce inferred maximum temperatures.
Dual-plane stereo particle image velocimetry measurements of velocity gradient tensor fields in turbulent shear flow. II. Experimental results
Authors: Mullin John A. , Dahm Werner J. A.
Published: April 2006

Results are presented from highly resolved dual-plane stereo particle image velocimetry (DSPIV) measurements for the structure, statistics, similarity, and scaling of all nine simultaneous components of the velocity gradient tensor fields ∂ui∕∂xj on the quasi-universal intermediate and small scales of turbulent shear flows. Measurements were obtained at three combinations of the outer-scale Reynolds number Reδ and the local mean shear rate S in the fully developed self-similar far field of a turbulent jet, and thus reflect the combined effects of the large-scale structure, spatial inhomogeneities, and anisotropies inherent in such a flow. Conditions addressed in this study correspond to local outer-scale Reynolds numbers Reδ=6,000 and 30,000 and local mean shear values Sδ∕uc=0 and 1.7, corresponding to Taylor-scale Reynolds numbers Reλ≈44 and 113 and shear rates Sk∕ε=0 and 2.1. Gradient fields investigated here include the individual velocity gradient component fields, the strain rate component fields and the associated principal strain rates, the vorticity component fields and their orientations with respect to the principal strain axes, the enstrophy and enstrophy production rate fields, and the true kinetic energy dissipation rate field. Results normalized on both inner- and outer-scale variables are presented to allow interpretation relative to the similarity and scaling implied by classical turbulence theory. For both Reδ values at S=0, results show that most aspects of these gradient fields are essentially in agreement with the predictions from homogeneous isotropic turbulence, while for S≠0 there are significant and consistent departures from isotropy. Results also provide direct measurements of the exponential scaling factors in the left and right tails of the velocity gradient distributions, as well as quantification of the inner (viscous) length scales in the enstrophy and dissipation rate fields. In addition, strong evidence for multifractal scale similarity at length scales greater than about twice the viscous length λν is found in both the enstrophy and dissipation rate fields.
Growth dynamics and cell migration in ferroelectric thin films
Authors: Li Yan Rong , Li Jin Long , Jun Zhu , Ying Zhang , Zeng Hui Zhong , Wei Xianhua , Tang Jin Long
Published: April 2006

Growth dynamics and unit cell migration of ferroelectric (Ba,Sr)TiO3 thin films were systematically studied with in situ reflective high-energy electron diffraction and atom force microscopy. By measuring the amplitudes of slow surface recovery oscillations of SrTiO3 film grown on (001) SrTiO3 surface, the activation energy of unit cell surface self-diffusion was surprisingly found to be only 0.29±0.01eV. A “unit-cell migration” model was developed to understand the epitaxial growth dynamics of ferroelectric thin films, which is a critical issue in oxide thin film growth and crucial in controlling the atomic structures.
Ion debris characterization from a z-pinch extreme ultraviolet light source
Authors: Antonsen Erik L. , Thompson Keith C. , Hendricks Matthew R. , Alman Darren A. , Jurczyk Brian E. , Ruzic D. N.
Published: April 2006

An XTREME Technologies XTS 13-35 extreme ultraviolet (EUV) light source creates a xenon z pinch that generates 13.5nm light. Due to the near x-ray nature of light at this wavelength, extremely smooth metal mirrors for photon collection must be employed. These are exposed to the source debris. Dissolution of the z-pinch gas column results in high-energy ion and neutral release throughout the chamber that can have adverse effects on mirror surfaces. The XTREME commercial EUV emission diagnostic chamber was designed to maximize diagnostic access to the light and particulate emissions from the z pinch. The principal investigation is characterization of the debris field and the erosive effects on optics present. Light emission from the z pinch is followed by ejection of multiply charged ions and fast neutral particles that make up an erosive flux to chamber surfaces. Attenuation of this erosive flux to optical surfaces is attempted by inclusion of a debris mitigation tool consisting of foil traps and neutral buffer gas flow. Characterization of the z-pinch ejecta is performed with a spherical sector energy analyzer (ESA) that diagnoses fast ion species by energy-to-charge ratio using ion time-of-flight (ITOF) analysis. This is used to evaluate the debris tool’s ability to divert direct fast ions from impact on optic surfaces. The ITOF-ESA is used to characterize both the energy and angular distribution of the direct fast ions. Xe+ up to Xe+4 ions have been characterized along with Ar+ (the buffer gas used), W+, Mo+, Si+, Fe+, and Ni+. Energy spectra for these species from 0.5 up to 13keV are defined at 20° and 30° from the pinch centerline in the chamber. Results show a drop in ion flux with angular increase. The dominant species is Xe+ which peaks around 8keV. Ion flux measured against buffer gas flow rate suggests that the direct fast ion population is significantly attenuated through increases in buffer gas flow rate. This does not address momentum transfer from scattered ions or fast neutral particles. These results are discussed in the context of other investigations on the effects of total particle flux to normal incidence mirror samples exposed for 1×107 pulses. The samples (Si∕Mo multilayer with Ru capping layer, Au, C, Mo, Pd, Ru, and Si) were exposed to the source plasma with 75% argon flow rate in the debris mitigation tool and surface metrology was performed using x-ray photoelectron spectroscopy, atomic force microscopy, x-ray reflectivity, and scanning electron microscopy to analyze erosion effects on mirrors. These results are compared to the measured direct ion debris field.
Electronic properties of the Zr–ZrO2–SiO2–Si(100) gate stack structure
Authors: Fulton C. C. , Lucovsky G. , Nemanich R. J.
Published: April 2006

The interface electronic structure of a layered Zr–ZrO2–SiO2–Si(100) system was studied with x-ray (hν=1254eV) and ultraviolet (hν=21.2eV) photoemission spectroscopies. In situ growth and characterization allow the structures to be deposited and studied in a stepwise manner without the risk of contamination. This study discusses the electronic properties including electron affinities and work functions, valence band maxima, band bending in the Si, and internal fields in a layered high-κ gate stack. With this information the band alignments can be reconstructed and compared to predictions of the vacuum alignment models (i.e., the Schottky-Mott model for metal-semiconductor interfaces or the electron affinity model for heterojunctions) and the interface induced gap states model. The vacuum alignment models are first order approaches to determine the electronic barrier height for a heterojunction, and interface bonding can contribute to charge transfer across the interface, affecting the dipole contribution and altering the barrier heights. In this study, the band offsets and vacuum levels are independently measured, thereby determining the deviation from the vacuum level alignment models. The valence band offsets at the Si–SiO2, SiO2–ZrO2, and ZrO2–Zr are found to be 4.4±0.1, 0.67±0.24, and 4.9±0.44eV, respectively. For these same interfaces the deviations from the electron affinity or Schottky-Mott model are determined to be 0.2±0.14, −1.43±0.29, and 1.3±0.39eV, respectively.
Competing interactions in two dimensional Coulomb systems: Surface charge heterogeneities in coassembled cationic-anionic incompatible mixtures
Authors: Loverde Sharon M. , Velichko Yury S. , Olvera de la Cruz Monica
Published: April 2006

A binary mixture of oppositely charged components confined to a plane such as cationic and anionic lipid bilayers may exhibit local segregation. The relative strengths of the net short range interactions, which favors macroscopic segregation, and the long range electrostatic interactions, which favors mixing, determine the length scale of the finite size or microphase segregation. The free energy of the system can be examined analytically in two separate regimes, when considering small density fluctuations at high temperatures and when considering the periodic ordering of the system at low temperatures [F. J. Solis, S. I. Stupp, and M. Olvera de la Cruz, J. Chem. Phys. 122, 054905 (2005)]. A simple molecular dynamics simulation of oppositely charged monomers, interacting with a short range Lennard-Jones potential and confined to a two dimensional plane, is examined at different strengths of short and long range interactions. The system exhibits well-defined domains that can be characterized by their periodic length scale as well as the orientational ordering of their interfaces. By adding salt, the ordering of the domains disappears and the mixture macroscopically phase segregates in agreement with analytical predictions.
Thermionic emission perpendicular to bulk and multiquantum AlxGa1−xInP barriers
Authors: Chróinín J. Ní , Morrison A. P.
Published: April 2006

A study on thermally activated currents across the bulk and multiquantum barrier (MQB) AlxGa1−xInP∕GaInP has been carried out and compared to experimental results from a series of n-i-n diodes over a range of temperatures. By considering the true quantum mechanical nature of the barriers, in contrast to the classical Richardson formalism, it is found that the alloy crossover strongly affects the transport properties of the material. The measured prefactor is found to decrease as Al content is increased. When applied to the MQB structures, the existing model fails to capture the experimental results.
Formation of vortex dipoles
Authors: Afanasyev Y. D.
Published: April 2006

Evolution of a two-dimensional flow induced by a jet ejected from a nozzle of finite size is studied experimentally. Vortex dipole forms at the front of the developing flow while a trailing jet establishes behind the dipole. The dynamics of the flow is discussed on the basis of detailed measurements of vorticity and velocity fields which are obtained using particle image velocimetry. It is found that dipoles do not separate (pinch-off) from the trailing jet for values of the stroke ratio up to 15, which fact can be contrasted with the behavior of vortex rings reported previously by other authors. A characteristic time scale that is defined differently from the formation time of vortex rings can be introduced. This time scale (startup time) indicates the moment when the dipole starts translating after an initial period when it mainly grows absorbing the jet from the nozzle. A simple model that considers the competing effects of expansion and translation is developed to obtain an estimate of the dimensionless startup time. The dynamics of a dipole after the formation is characterized by a reduced flux of vorticity from the jet. The dipole moves forward with constant speed such that a value of the ratio of the speed of propagation of the dipole to the mean velocity of the jet is found to be 0.5. A universality of this ratio is explained in the framework of a model based on conservation of mass and momentum for the moving dipole.
The impact of the density and type of reactive sites on the characteristics of the atomic layer deposited WNxCy films
Authors: Martin Hoyas A. , Travaly Y. , Schuhmacher J. , Sajavaara T. , Whelan C. M. , Eyckens B. , Richard O. , Giangrandi S. , Brijs B. , Vandervorst W. , Maex K. , Celis J. P. , Jonas A. M. , Vantomme A.
Published: April 2006

The growth of tungsten nitride carbide (WNxCy) films obtained by atomic layer deposition using triethylboron, tungsten hexafluoride, and ammonia precursors is determined by the density and type of reactive sites. The film properties change as a function of thickness. On silicon dioxide and silicon carbide, growth is initially nonlinear such that the transient regimes are characterized by island formation, as evidenced by a parabolic tungsten growth curve extending to film thicknesses of up to 5nm. Such films have low densities of ∼4–6gcm−3 corresponding to only ∼30%–45% of the bulk density of ∼13.1gcm−3 determined for a WN0.45C0.55 composition. X-ray reflectivity, thermal desorption, and elastic recoil detection spectroscopies reveal surface roughening and compositional and density differences close to the substrate surface. The offset from linear growth in the case of WNxCy films deposited on silicon dioxide is induced by the initial reaction of silanol and siloxane groups with triethylborane resulting in passivating ethylsilyl groups on the surface. A transient regime is not observed for WNxCy growth on hydrogen-terminated silicon with the initial growth being dominated by the reduction of tungsten hexafluoride to tungsten. On silicon nitride a short transient regime is observed relative to the carbide and oxide surfaces attributed to the enhanced binding of the triethylboron precursor.
Raman study of the random ZnTe–BeTe mixed crystal: Percolation model plus multimode decomposition
Authors: Pagès O. , Tite T. , Chafi A. , Bormann D. , Maksimov O. , Tamargo M. C.
Published: April 2006

The Verleur and Barker-like multiphonon description proposed for the refined understanding of the two-mode transverse optical (TO) and longitudinal optical (LO) Raman responses from the stiff∕short Be–Se bond in the percolation range (0.19⩽Be⩽0.81) of the random BeSe–ZnSe mixed crystal [O. Pagès et al., Phys. Rev. B 70, 155319 (2004)] is extended to the similar Be–Te bond in the percolation range of the random BeTe–ZnTe mixed crystal. Moreover this description is shown to remain valid just outside the percolation range, in spite of appearances. We deduce that it is not activated by the close intermixing of the stiff and soft continua at the mesoscopic scale but relies directly on the contrast in the bond properties at the microscopic scale. The whole study is supported by extensive ZnBeTe Raman data, and full contour modeling of the TO and LO Raman line shapes by using our phenomenological 1-bond→2-mode percolation model. Care is taken that our ZnBe(Se,Te) epitaxial layers undergo large substrate-induced residual biaxial strains at the two edges of the percolation range. This generates significant phonon shifts, which have to be taken into account.
Generation of frequency tunable polarization entangled photon pairs
Authors: Yabushita Atsushi , Kobayashi Takayoshi
Published: April 2006

Photon pairs with correlated frequencies from an optical parametric system were generated by a continuous wave pump focused on a type-II nonlinear crystal with polarization entanglement. The polarization entanglement of the frequency resolved photons was measured under several typical configurations. By optimizing a condition, the degree of polarization entanglement was improved substantially. We proposed the application of the system, which can be used as a light source of wavelength division multiplexing quantum key distribution, optimizing the configuration of the photon-pair generation.
Archival-overwrite performance of GeSnSb-based phase-change discs
Authors: van Pieterson L. , Hesselink E. W. , Rijpers J. C. N. , Kaiser M. , Verheijen M. A. , Elfrink R.
Published: April 2006

High-speed rewritable digital versatile discs based on GeSnSb phase-change materials may show poor archival-overwrite performance. We have related this to a decrease in the crystalline reflectivity. Transmission electron microscopy images indicate that this is connected to morphology changes of the material. Materials optimization by addition of dopants such as Se or Te can stabilize the crystalline reflectivity and, as a result, improve the archival-overwrite performance to within the specifications for optical recording.
Temperature dependence of the lowest excitonic transition for an InAs ultrathin quantum well
Authors: Singh S. D. , Porwal S. , Sharma T. K. , Rustagi K. C.
Published: April 2006

Temperature dependent photoluminescence and photoreflectance techniques are used to investigate the lowest excitonic transition of InAs ultrathin quantum well. It is shown that the temperature dependence of the lowest energy transition follows the band gap variation of GaAs barrier, which is well reproduced by calculated results based on the envelope function approximation with significant corrections due to strain and temperature dependences of the confinement potential. A redshift in photoluminescence peak energy compared to photoreflectance is observed at low temperatures. This is interpreted to show that the photoluminescence signal originates from the recombination of carriers occupying the band-tail states below the lowest critical point.
A single-time two-point closure based on fluid particle displacements
Authors: Bos W. J. T. , Bertoglio J.-P.
Published: April 2006

A new single-time two-point closure is proposed, in which the equation for the two-point correlation between the displacement of a fluid particle and the velocity allows one to estimate a Lagrangian timescale. This timescale is used to specify the nonlinear damping of triple correlations in the closure. A closed set of equations is obtained without ad hoc constants. Taking advantage of the analogy between particle displacements and scalar fluctuations in isotropic turbulence subjected to a mean scalar gradient, the model is numerically integrated. Results for the energy spectrum are in agreement with classical scaling predictions. An estimate for the Kolmogorov constant is obtained.
An electrically controllable nanoporous smart system
Authors: Kong Xinguo , Qiao Yu
Published: April 2006

The major problems of conventional intelligent materials include the small output forces and the poor deformability. In this article, we show that by directly utilizing the large specific surface area of a nanoporous material, a high-performance shape memory system can be developed based on the electrocapillary effect. As voltage varies, the pressure in the system can be controlled reversibly. The output energy density and the displacement are much higher than that of piezoelectrics and magnetostrictives.
Collision rates of bidisperse inertial particles in isotropic turbulence
Authors: Zaichik Leonid I. , Simonin Olivier , Alipchenkov Vladimir M.
Published: April 2006

This paper presents two statistical models for predicting collision rates of bidisperse heavy particles suspended in homogeneous isotropic turbulence. One of the models is based on the assumption that the joint fluid-particle velocity distribution function is Gaussian. The other model stems from a kinetic equation for the two-point probability density function of the velocity distributions of two particles. The validity of these models is tested against DNS data by Zhou, Wexler, and Wang [J. Fluid Mech. 433, 77 (2001)]. Comparisons between the model predictions and DNS results demonstrate encouraging agreement.
Thermocapillary structure formation in a falling film: Experiment and calculations
Authors: Frank A. M. , Kabov O. A.
Published: April 2006

The present experimental and numerical study is focused on regular structure formation in a film falling down a vertical plate with a built-in rectangular heater. The data on critical Marangoni number and on the wavelength of the most unstable spanwise mode depending on Reynolds and Weber numbers are obtained. The influence of heating intensity on structure geometry is also investigated. The critical Marangoni number is shown to increase nonlinearly with the increase of Reynolds number. The wavelength of the most unstable spanwise mode appears to depend weakly on Reynolds number and much stronger on Weber number. We obtained that the height of the critical two-dimensional bump is not invariant, but depends almost inversely on Reynolds number. The appearance of a reverse flow in the bump is not a criterium for instability onset. For the different fixed Reynolds number values, the structure width significantly grows with the increase of Marangoni number. Numerical results and experimental data are compared and show good enough agreement.
Observation of donor-acceptor pair spectra in the photoluminescence of H- and Zn-implanted ZnO single crystals
Authors: Reynolds D. C. , Litton C. W. , Collins T. C. , Hoelscher J. E. , Nause J.
Published: April 2006

Donor-acceptor (D-A) pair spectra have been observed in the photoluminescence radiative recombination of selected donor bound exciton complexes in zinc oxide (ZnO) single crystals that have been ion implantation doped with H and Zn atoms and subsequently annealed in a nitrogen (N2) atmosphere at temperatures in the range of 700–800°C. Observations of the D-A pair spectra are explained as the bound states of Hopfield’s bound exciton complex model, in terms of the effective mass approximation of the wurtzitic ZnO energy band structure.
Grain-boundary resistivity versus grain size distribution in three-dimensional polycrystals
Authors: Dezanneau G. , Morata A. , Tarancón A. , Salleras M. , Peiró F. , Morante J. R.
Published: April 2006

We have studied the accuracy of the bricklayer model in the evaluation of the grain-boundary resistivity associated to a real three-dimensional (3D) polycrystal. An impedance network electrically equivalent to the 3D structure has been solved by direct calculation. In order to examine the progressive evolution from the bricklayer model to a completely disordered system, the ideal polycrystal was modified in a controlled way, according to a Voronoï diagram approach. From this, the grain-boundary resistivity of a polycrystal, as deduced from the 3D bricklayer model, is lower than the real value. The upper limit of the error made is around 15% in relation to the real one.
Nanoheteroepitaxial lateral overgrowth of GaN on nanoporous Si(111)
Authors: Zang K. Y. , Wang Y. D. , Chua S. J. , Wang L. S. , Tripathy S. , Thompson C. V.
Published: April 2006

Nanoheteroepitaxial (NHE) lateral overgrowth of GaN on nanoporous Si(111) substrates has been demonstrated. Nanopore arrays in Si(111) surfaces were fabricated using anodized aluminum oxide templates as etch masks, resulting in an average pore diameter and depth of about 60 and 160–180nm, respectively. NHE growth of AlN and GaN was found to result in a significant reduction in the threading dislocation density (<108cm−2) compared to that on flat Si(111). Most dislocations that originate at the Si interface bent to lie in the GaN (0001) basal plane during lateral growth over the pore openings. E2 phonon blueshifts in the Raman spectra indicate a significant relaxation of the tensile stress in the coalesced GaN films, due to three-dimensional stress relaxation mechanisms on porous substrates. Our results show that a single step lateral overgrowth of GaN on nanopatterned Si(111) substrates without a dielectric mask is a simple way to improve the crystalline quality of GaN layers for microelectronic applications.
Magnetization switching by spin torque using subnanosecond current pulses assisted by hard axis magnetic fields
Authors: Devolder T. , Crozat P. , Kim J.-V. , Chappert C. , Ito K. , Katine J. A. , Carey M. J.
Published: April 2006

We have induced magnetization switching by spin transfer in pillar-shaped spin valves using nanosecond-scale current pulses combined with hard axis fields. Switching events requiring 100ps pulses were obtained. In comparison with the switching induced by a single current pulse, biasing the device with a hard axis field decreases the pulse duration needed for error-free switching. The reduction of the cost in pulse amplitude scales with the magnitude of the applied field, and can be quantitatively understood from micromagnetic simulations and macrospin arguments taking into account the thermal fluctuations.
Toward rapid and inexpensive identification of bulk carbon nanotubes
Authors: Gilbert K. E. H. , Lehman J. H. , Dillon A. C. , Blackburn J. L.
Published: April 2006

The volume fraction of metallic and semiconducting carbon single-wall nanotubes (SWNTs) has been estimated for purified laser vaporization SWNTs, from an effective medium approximation and the measured spectral responsivity of a LiTaO3 pyroelectric detector covered with SWNT “bucky” paper. The detector spectral responsivity from 600to2000nm is proportional to the expected absorption coefficient of the SWNTs, and variations near 700, 950, and 1750nm correlate with characteristic interband transitions and proportions of SWNTs consistent with 20% metal and 80% semiconductor materials.
Visible orange photoluminescence in a barium titanosilicate BaTiSi2O7
Authors: Takahashi Yoshihiro , Kitamura Kenji , Iyi Nobuo , Inoue Satoru
Published: April 2006

A visible orange photoluminescence (PL) was observed at room temperature from a barium titanosilicate BaTiSi2O7. The diffuse-reflection spectrum revealed the presence of an oxygen defect in the Ti–O polyhedral unit. The broad PL with the peak at 580nm was observed by ultraviolet (UV) excitation at 321nm as the PL excitation spectrum maximum, being sufficient for a visual confirmation under UV light. It was suggested that its peculiar PL is related to both the absolutely isolated pyramidal TiO5 unit pair and the oxygen defect in the TiO5 unit in the BaTiSi2O7 phase.
Thin germanium-carbon alloy layers grown directly on silicon for metal-oxide-semiconductor device applications
Authors: Kelly D. Q. , Wiedmann I. , Donnelly J. P. , Joshi S. V. , Dey S. , Banerjee S. K. , Garcia-Gutierrez D. I. , José-Yacamán M.
Published: April 2006

We report the growth and characterization of thin (<35nm) germanium-carbon alloy (Ge1−xCx) layers grown directly on Si by ultrahigh-vacuum chemical vapor deposition, with capacitance-voltage and leakage characteristics of the first high-κ/metal gate metal-oxide-semiconductor (MOS) capacitors fabricated on Ge1−xCx. The Ge1−xCx layers have an average C concentration of approximately 1at.% and were obtained using the reaction of CH3GeH3 and GeH4 at a deposition pressure of 5mTorr and growth temperature of 450°C. The Ge1−xCx films were characterized by secondary ion mass spectrometry, atomic force microscopy, x-ray diffraction, and cross-sectional transmission electron microscopy. A modified etch pit technique was used to calculate the threading dislocation density. The x-ray diffraction results showed that the Ge1−xCx layers were partially relaxed. The fabricated MOS capacitors exhibited well-behaved electrical characteristics, demonstrating the feasibility of Ge1−xCx layers on Si for future high-carrier-mobility MOS devices.
Functional characterisation of OsAMT1.1 overexpression lines of rice, Oryza sativa
Authors: Kumar Anshuman , Kaiser Brent N. , Siddiqi M. Yaeesh , Glass Anthony D. M.
Published: April 2006

In rice (Oryza sativa L.) OsAMT1.1 is the most active and / or most N-responsive gene responsible for high-affinity NH4+ transport (HATS) activity. We measured 13NH4+ influx and plant biomass in transgenic overexpression lines and two wild type cultivars of rice, Jarrah and Taipei, with one or more copies of OsAMT1.1. 13NH4+ influx was higher for the overexpression lines of Jarrah line when grown at 10 µm external NH4+ concentration, but not for the overexpression lines of Taipei. For seedlings grown at 2 mm external NH4+ concentration Jarrah lines 77-1 and 75-4 showed an increased influx; however, two overexpression lines of Taipei showed reduced influx rates. The biomasses of the transgenic lines grown at low and high external NH4+ concentrations were either reduced or showed no statistically significant differences compared with wild type lines. While 13NH4+ influx into roots of Jarrah line 75-4 grown at 10 µm external NH4+ concentration was significantly higher than in wild type, measurements of 13NH efflux revealed no differences, and thus net uptake of NH4+ was higher in this overexpression line.
Branch roots of young maize seedlings, their production, growth, and phloem supply from the primary root
Authors: Enns Linda C. , McCully Margaret E. , Canny Martin J.
Published: April 2006

Branch root development on the primary root of maize (Zea mays L.) seedlings was followed for 9 d after planting. This period includes the shift from seedling heterotrophy to autotrophy. Linear density of branches in the basal region ranged from ~38 cm–1 at the base to ~10 cm–1 beyond 10 cm. Branch roots in the first ~8 cm were produced before assimilate was available. Branch length decreased from ~26 mm at 1 cm along the primary root to ~8 mm at 10 cm from the base. Without the cotyledon, branch root density in the basal region was ~10 cm–1 and roots were short (~5 mm). Beyond 8–10 cm both measurements matched those of intact seedlings. Dark-grown seedlings had basal branch root densities higher than those without cotyledons but none beyond 10 cm. There were more and smaller diameter sieve tubes in the basal region of the primary root. These decreased distally in number but had larger diameters where branches formed after assimilate was available. Proliferation of basal branch roots in very young seedlings can have major advantages for successful seedling establishment in the field and could be screened for without difficulty.
Cytoplasmic Lipid Droplets Are Sites of Convergence of Proteasomal and Autophagic Degradation of Apolipoprotein B
Authors: Ohsaki Yuki , Cheng Jinglei , Fujita Akikazu , Tokumoto Toshinobu , Fujimoto Toyoshi
Published: April 2006

Lipid esters stored in cytoplasmic lipid droplets (CLDs) of hepatocytes are used to synthesize very low-density lipoproteins (VLDLs), into which apolipoprotein B (ApoB) is integrated cotranslationally. In the present study, by using Huh7 cells, derived from human hepatoma and competent for VLDL secretion, we found that ApoB is highly concentrated around CLDs to make “ApoB-crescents.” ApoB-crescents were seen in <10% of Huh7 cells under normal conditions, but the ratio increased to nearly 50% after 12 h of proteasomal inhibition by N-acetyl-l-leucinyl-l-leucinyl-l-norleucinal. Electron microscopy showed ApoB to be localized to a cluster of electron-lucent particles 50–100 nm in diameter adhering to CLDs. ApoB, proteasome subunits, and ubiquitinated proteins were detected in the CLD fraction, and this ApoB was ubiquitinated. Interestingly, proteasome inhibition also caused increases in autophagic vacuoles and ApoB in lysosomes. ApoB-crescents began to decrease after 12–24 h of proteasomal inhibition, but the decrease was blocked by an autophagy inhibitor, 3-methyladenine. Inhibition of autophagy alone caused an increase in ApoB-crescents. These observations indicate that both proteasomal and autophagy/lysosomal degradation of ApoB occur around CLDs and that the CLD surface functions as a unique platform for convergence of the two pathways.
Intrinsically disordered C-terminal segments of voltage-activated potassium channels: a possible fishing rod-like mechanism for channel binding to scaffold proteins
Authors: Magidovich Elhanan , Fleishman Sarel J. , Yifrach Ofer
Published: April 2006

Membrane-embedded voltage-activated potassium channels (Kv) bind intracellular scaffold proteins, such as the Post Synaptic Density 95 (PSD-95) protein, using a conserved PDZ-binding motif located at the channels' C-terminal tip. This interaction underlies Kv-channel clustering, and is important for the proper assembly and functioning of the synapse. Here we demonstrate that the C-terminal segments of Kv channels adjacent to the PDZ-binding motif are intrinsically disordered. Phylogenetic analysis of the Kv channel family reveals a cluster of channel sequences belonging to three out of the four main channel families, for which an association is demonstrated between the presence of the consensus terminal PDZ-binding motif and the intrinsically disordered nature of the immediately adjacent C-terminal segment. Our observations, combined with a structural analogy to the N-terminal intra-molecular ball-and-chain mechanism for Kv channel inactivation, suggest that the C-terminal disordered segments of these channel families encode an inter-molecular fishing rod-like mechanism for K+ channel binding to scaffold proteins.

Contact:  ofery@bgu.ac.il

Supplementary information: Supplementary data are available at Bioinformatics online.
GRAST: a new way of genome reduction analysis using comparative genomics
Authors: Toft Christina , Fares Mario A.
Published: April 2006

Motivation: Establishment of intra-cellular life involved a profound re-configuration of the genetic characteristics of bacteria, including genome reduction and rearrangements. Understanding the mechanisms underlying these phenomena will shed light on the genome rearrangements essential for the development of an intra-cellular lifestyle. Comparison of genomes with differences in their sizes poses statistical as well as computational problems. Little efforts have been made to develop flexible computational tools with which to analyse genome reduction and rearrangements.

Results: Investigation of genome reduction and rearrangements in endosymbionts using a novel computational tool (GRAST) identified gathering of genes with similar functions. Conserved clusters of functionally related genes (CGSCs) were detected. Heterogeneous gene and gene cluster non-functionalization/loss are identified between genome regions, functional gene categories and during evolution. Results show that gene non-functionalisation has accelerated during the last 50 MY of Buchnera's evolution while CGSCs have been static.

Availability: Software is available at

Contact:  mario.fares@nuim.ie
Splitting the Difference? Causal Inference and Theories of Split-party Delegations
Authors: Butler Daniel M. , Butler Matthew J.
Published: April 2006

We provide an introduction to the regression discontinuity design (RDD) and use the technique to evaluate models of sequential Senate elections predicting that the winning party for one Senate seat will receive fewer votes in the next election for the other seat. Using data on U.S. Senate elections from 1946 to 2004, we find strong evidence that the outcomes of the elections for the two Senate seats are independent.