bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of ruptures of Andaman fault segments in the 2004 great Sumatra earthquake with coseismic ionospheric disturbances
Authors: Heki Kosuke , Otsuka Yuichi , Choosakul Nithiwatthn , Hemmakorn Narong , Komolmis Tharadol , Maruyama Takashi
Published: September 2006

Near‐field coseismic perturbations of ionospheric total electron content (TEC), caused by direct acoustic waves from focal regions, can be observed with Global Positioning System (GPS). They appear 10–15 min after the earthquake with typical periods of ∼4–5 min and propagate as fast as ∼1 km/s toward directions allowed by ambient geomagnetic fields. Ionospheric disturbance, associated with the 2004 December 26 great Sumatra‐Andaman earthquake, was recorded with nine continuous GPS receiving stations in Indonesia and Thailand. Here we explore the possibility to constrain the rupture process of the earthquake with the observed ionospheric disturbances. We assumed linearly distributed point sources along the zone of coseismic uplift extending ∼1300 km from Sumatra to the Andaman Islands that excited acoustic waves sequentially as the rupture propagate northward by 2.5 km/s. TEC variations for several satellite‐receiver pairs were synthesized by simulating the propagation of acoustic waves from the ground to the ionosphere and by integrating the TEC perturbations at intersections of line of sights and the ray paths. The TEC perturbations from individual point sources were combined using realistic ratios, and the total disturbances were compared with the observed signals. Prescribed ratios based on geodetically inferred coseismic uplifts reproduced the observed signals fairly well. Similar calculation using a rupture propagation speed of 1.7 km/s degraded the fit. Suppression of acoustic waves from the segments north of the Nicobar Islands also resulted in a poor fit, which suggests that ruptures in the northern half of the fault were slow enough to be overlooked in short‐period seismograms but fast enough to excite atmospheric acoustic waves. Coseismic ionospheric disturbance could serve as a new indicator of faulting sensitive to ruptures with timescale up to 4–5 min.
Thermobaric deep convection, baroclinic instability, and their roles in vertical heat transport around Maud Rise in the Weddell Sea
Authors: Akitomo Kazunori
Published: September 2006

Numerical experiments with two‐ and three‐dimensional nonhydrostatic models in a rotating frame have been executed to investigate thermobaric deep convection, subsequent baroclinic instability, and their roles in vertical heat transport, using hydrographic data around Maud Rise in the Weddell Sea, Antarctica. Overturning of the water column due to thermobaric convection is apt to occur on the southern and northern flanks of the rise, and induces upward heat transport. The depth of overturning is two times larger on the northern flank (∼1.5 km) than on the southern flank (∼0.7 km). To the contrary, no overturning occurs over the top of the rise in 90 days. Baroclinic instability develops at a density front formed between the overturned and unoverturned regions since a density contrast at the front is enhanced by thermobaricity. Heat transport due to baroclinic instability is similarly upward, and at peak becomes comparable to that due to the overturning. Applicability of the results to the cooling events previously reported is also discussed.
Dust devils on Earth and Mars
Authors: Balme Matt , Greeley Ronald
Published: September 2006

Dust devils, particle‐loaded vertical convective vortices found on both Earth and Mars, are characterized by high rotating wind speeds, significant electrostatic fields, and reduced pressure and enhanced temperature at their centers. On Earth they are subordinate to boundary layer winds in the dust cycle and, except possibly in arid regions, are only “nuisance‐level” phenomena. On Mars, though, they seem to support the persistent background atmospheric haze, to influence the surface albedo through the formation of “tracks” on the surface, and to possibly endanger future exploration because of their high dust load and large potential gradients. High‐resolution numerical simulations and thermophysical scaling models successfully describe dust devil–like vortices on Mars, but fitting dust devil action into the Martian global dust cycle is still problematic. Reliable parameterizations of their erosional abilities and solid temporal and spatial distribution data are still required to build and test a complete model of dust devil action.
Soil organic carbon storage of paddy soils in China using the 1:1,000,000 soil database and their implications for C sequestration
Authors: Liu Qing‐Hua , Shi Xue‐Zheng , Weindorf D. C. , Yu Dong‐Sheng , Zhao Yong‐Cun , Sun Wei‐Xia , Wang Hong‐Jie
Published: September 2006

Organic carbon storage in agricultural soils plays a key role in the terrestrial ecosystem carbon cycle. Paddy soils support important croplands in many parts of the world, especially in Asia. A thorough understanding of organic carbon storage in Chinese paddy soils would be helpful to both greenhouse gases emission and carbon sequestration studies. This paper examines soil organic carbon density (SOCD) and storage (SOCS) of paddy soils in China using the newly compiled 1:1,000,000 digital soil map of China as well as data from 1490 paddy soil profiles. Results show that paddy soils in China cover about 45.7 M ha, nearly 1.5 times more than the results of other studies. In China, the mean SOCD of paddy soils at a depth of 0–100 cm is 111.4 t C ha−1, with a SOCS of 5.1 Pg. These results are 66–75% higher than studies from other scientists. However, the mean SOCD of paddy soils from 0 to 20 cm is 37.6 t C ha−1, with a SOCS of 1.7 Pg, which is 89% higher than studies from other scientists.
Subsurface ocean argon disequilibrium reveals the equatorial Pacific shadow zone
Authors: Gehrie Eric , Archer David , Emerson Steven , Stump Charles , Henning Cara
Published: September 2006

Surface water in the ocean invades the subsurface vertically, against the density gradient, and along constant‐density surfaces from surface outcrops in high latitudes. We present dissolved argon data that distinguishes a diapycnally ventilated upper thermocline in the equatorial Pacific versus an isopycnally ventilated subtropical location near Hawaii. The lower thermocline is shown to be isopycnally ventilated at both locations, in contrast with theoretical and model predictions.
Effect of parameterized sub‐grid‐scale diffusions on the source‐receptor relationship in the WRF model
Authors: Chen Shu‐Hua , Hsu Hsiao‐ming
Published: September 2006

To provide a quantitative assessment of the source‐receptor relationship in an Eulerian framework, the method of artificially adding oscillatory signals with different frequencies to emission locations for a scalar is evaluated. Two‐dimensional numerical experiments of nonlinear hydrostatic mountain waves with wave breaking were used. The scalar time series were collected at a number of downstream locations and decomposed into frequency space to identify their sources and to investigate the strength of those signals with respect to different diffusion schemes. Six experiments were conducted using three sub‐grid eddy coefficients (a constant, a function of deformation, and a function of turbulence kinetic energy (TKE)) and two environmental wind conditions (shear and no shear). Simulated oscillatory signals were affected by parameterized sub‐grid‐scale diffusions. Signals experiencing more sophisticated eddy coefficients were better preserved than those with the simplest constant ones. The signals were shifted to higher frequencies when using the TKE scheme under a uniform wind environment.
Static grounding lines and dynamic ice streams: Evidence from the Siple Coast, West Antarctica
Authors: Horgan H. J. , Anandakrishnan S.
Published: September 2006

Grounding line dynamics are key to our understanding of marine ice sheets such as the West Antarctic Ice Sheet (WAIS). We present an accurate and rapid method for locating grounding lines using GLAS ICESat laser altimetry data. We then apply this technique to the Siple Coast region of the WAIS. Our technique exploits the high surface slope at the grounding line relative to the adjacent flat ice streams and ice shelf. The technique is validated by ground‐based observations. Comparisons between the current grounding line and earlier measured locations demonstrate that the Siple Coast's grounding line has been largely static over the last two decades. This is important as the ice streams have been undergoing considerable variations over this period. We conclude that ice stream flow speeds can vary while the grounding line remains stable. We suggest that grounding lines may migrate abruptly and then stabilize rather than undergoing continuous retreat.
Wavelet‐based index of magnetic storm activity
Authors: Jach A. , Kokoszka P. , Sojka J. , Zhu L.
Published: September 2006

A wavelet‐based method of computing an index of storm activity is put forward. The new index can be computed automatically using statistical procedures and does not require selecting quiet days and removing the secular component by polynomial fitting. This 1‐min index is designed to facilitate the study of the fine structure of geomagnetic storm events and requires only the most recent magnetogram records, e.g., the 2 months including the storm event of interest. It can thus be computed over a moving window as soon as new magnetogram records become available. Averaged over 1‐hour periods, it is practically indistinguishable from the standard Dst index.
Interplanetary magnetic fluctuation anisotropy in the inertial range
Authors: Smith Charles W. , Vasquez Bernard J. , Hamilton Kathleen
Published: September 2006

We have created a database of interplanetary magnetic field spectra from over 900 separate solar wind intervals at 1 AU using data from the Advanced Composition Explorer (ACE) spacecraft. These intervals embrace a broad range of solar wind conditions including fast and slow wind conditions, rarefaction regions, shocked plasma, and magnetic clouds. Every attempt was made to develop a database that samples the broadest possible range of solar wind conditions without regard for occurrence frequency. We have examined the ratio of magnetic power in the component perpendicular to the mean field to that parallel to the mean field (the so‐called variance anisotropy) as measured in the high‐frequency regime of the inertial range and find it to be strongly correlated to the proton beta. The variance anisotropy may be a proxy for the spectrum of density fluctuations in this region of the spectrum that is unresolved by ACE instruments and that is often unresolved by current flight hardware. The observed correlation with proton beta appears to be in keeping with predictions derived from magnetohydrodynamic turbulence concepts where the compressive component is driven by the incompressible turbulence in the low turbulent Mach number regime. This apparent agreement strongly suggests that the compressive component arises from in situ dynamics and has little if anything to do with solar origins.
Multiscale structure of magnetic fields in the heliosheath
Authors: Burlaga L. F. , Ness N. F. , Acũna M. H.
Published: September 2006

Voyager 1 (V1) crossed the termination shock, leaving the solar wind and entering the heliosheath. This paper analyzes the magnetic field observed in the heliosheath from day of year 1 to 308, 2005. The average of the magnetic field strength B is 0.104 nT, but it is highly variable, and its profile appears filamentary. Some sectors and sector boundaries were observed. The daily and hourly averages of B in the inner heliosheath have Gaussian distributions. The widths of the daily and hourly distributions of B are the same within the uncertainties, consistent with a scale invariance of the distribution of B. The distributions of daily and hourly averages of the azimuthal and elevation angles in the heliosheath resemble those in the solar wind. The magnetic field strength in the inner heliosheath has a multifractal structure on scales from ∼2 to 16 days. The multifractal structure can be described by a binomial multiplicative cascade model. The multifractal spectrum of the magnetic field fluctuations in the heliosheath is narrower than that in the distant solar wind. The intermittency exponent decreases by a factor of 3.4 from 0.072 in the distant solar wind to 0.021 in the heliosheath. We also analyzed the multiscale structure of B(t) using wavelets. On an intermediate scale, the magnetic field of the heliosheath contains a quasiperiodic variation suggesting that the effect of solar rotation was observed in the heliosheath beyond 95 AU.
Thermal pressurization and onset of melting in fault zones
Authors: Rempel Alan W. , Rice James R.
Published: September 2006

We examine how frictional heating drives the evolution of temperature, strength, and fracture energy during earthquake slip. For small slip distances, heat and pore fluid are unable to escape the shearing fault core, and the behavior is well approximated by simple analytical models that neglect any transport. Following large slip distances, the finite width of the shear zone is small compared to the thicknesses of the thermal and hydrological boundary layers, and the fault behavior approaches that predicted for the idealized case of slip on a plane. To evaluate the range in which the predictions of these two sets of approximations are valid, we develop a model that describes how frictional dissipation within a finite shear zone drives heat and mass transport through the surrounding static gouge. With realistic parameter values and slips greater than a few centimeters, the subsequent evolution of strength and fracture energy are approximated well by the planar slip model. However, the temperature evolution is much more sensitive to the finite shear zone thickness, and the ultimate temperature rise tends to be intermediate between that predicted for the two simplified cases. We explore the range of conditions necessary for melting to begin and focus in particular on the potential role of fault zone damage in facilitating fluid transport and promoting larger temperature increases. We discuss how the apparent scarcity of exhumed pseudotachylytes places constraints on some of the more uncertain fault zone parameters.
Tidal evolution of the northwest European shelf seas from the Last Glacial Maximum to the present
Authors: Uehara Katsuto , Scourse James D. , Horsburgh Kevin J. , Lambeck Kurt , Purcell Anthony P.
Published: September 2006

Two‐dimensional paleotidal simulations have been undertaken to investigate tidal and tide‐dependent changes (tidal amplitudes, tidal current velocities, seasonal stratification, peak bed stress vectors) that have occurred in the NW European shelf seas during the last 20 ka. The simulations test the effect of shelf‐wide isostatic changes of sea level by incorporating results from two different crustal rebound models, and the effect of the ocean‐tide variability by setting open boundary values either fixed to the present state or variable according to the results of a global paleotidal model. The use of the different crustal rebound models does not affect the overall changes in tidal patterns, but the timing of the changes is sensitive to the local isostatic effects that differ between the models. The incorporation of ocean‐tide changes greatly augments the amplitude of tides and tidal currents in the Celtic and Malin seas before 10 ka BP, and has a large impact on the distribution of seasonally stratified conditions, magnitude of peak bed stress vectors and tidal dissipation in the shelf seas. The predictions on seasonal stratification are supported by well‐dated evidence on tidal mixing front migration in the Celtic Sea. Additional experiments using the global model suggest that the variability of offshore tides has been caused mainly by changes of eustatic sea level and ice‐sheet extent. In particular, a large decrease observed at 10–8 ka BP is attributed to the opening of Hudson Strait accompanied by the retreat of the Laurentide Ice Sheet.
Sea surface temperature fronts in the California Current System from geostationary satellite observations
Authors: Castelao Renato M. , Mavor Timothy P. , Barth John A. , Breaker Laurence C.
Published: September 2006

Sea surface temperature (SST) fronts are determined for the 2001–2004 time period from Geostationary Operational Environmental Satellites (GOES) data in the California Current System (CCS). The probability of detecting a SST front at an individual pixel location in the CCS is presented as a bi‐monthly climatology. Fronts clearly indicate the seasonal evolution of coastal upwelling, as well as meanders and filaments that are often linked with irregularities in coastline geometry. Winter is characterized by low frontal activity along the entire coast. Fronts first appear close to the coast during spring, particularly south of Cape Blanco, where upwelling favorable winds are already persistent. The area of high frontal activity continues to increase during summer, especially between Monterey Bay and Cape Blanco, extending more than 300 km from the coast. The region with high frontal activity widens at ∼2.6 km day−1. Off northern Baja California, a band with persistent fronts is found close to the coast year‐round, but there is no evidence of a seasonal widening of the area of higher activity. During fall, the weakening of upwelling favorable winds leads to a gradual decrease in frontal activity. An empirical orthogonal function (EOF) decomposition reveals the development of SST fronts associated with seasonal upwelling for locations north of Monterey Bay, with less summer intensification to the south. The first appearance of fronts close to the coast during spring and the occurrence of the fronts offshore later in the season are represented by additional statistically significant EOF modes.
Alkaline volcanic rocks from the Columbia Hills, Gusev crater, Mars
Authors: McSween H. Y. , Ruff S. W. , Morris R. V. , Bell J. F. , Herkenhoff K. , Gellert R. , Stockstill K. R. , Tornabene L. L. , Squyres S. W. , Crisp J. A. , Christensen P. R. , McCoy T. J. , Mittlefehldt D. W. , Schmidt M.
Published: September 2006

Irvine, Backstay, and Wishstone are the type specimens for three classes of fine‐grained or fragmental, relatively unaltered rocks with distinctive thermal emission spectra, found as float on the flanks of the Columbia Hills. Chemical analyses indicate that these rocks are mildly alkaline basalt, trachybasalt, and tephrite, respectively. Their mineralogy consists of Na‐ and K‐rich feldspar(s), low‐ and high‐Ca pyroxenes, ferroan olivine, Fe‐Ti (and possibly Cr) oxides, phosphate, and possibly glass. The texture of Wishstone is consistent with a pyroclastic origin, whereas Irvine and Backstay are lavas or possibly dike rocks. Chemical compositions of these rocks plot on or near liquid lines of descent for most elements calculated for Adirondack class rocks (olivine‐rich basalts from the Gusev plains) at various pressures from 0.1 to 1.0 GPa. We infer that Wishstone‐, Backstay‐, and Irvine‐class magmas may have formed by fractionation of primitive, oxidized basaltic magma similar to Adirondack‐class rocks. The compositions of all these rocks reveal that the Gusev magmatic province is alkaline, distinct from the subalkaline volcanic rocks thought to dominate most of the planet's surface. The fact that differentiated volcanic rocks were not encountered on the plains prior to ascending Husband Hill may suggest a local magma source for volcanism beneath Gusev crater.
Surface and aerodynamic roughness in arid and semiarid areas and their relation to radar backscatter coefficient
Authors: Marticorena Béatrice , Kardous Mouldi , Bergametti Gilles , Callot Yann , Chazette Patrick , Khatteli Houcine , Le Hégarat‐Mascle Sylvie , Maillé Michel , Rajot Jean‐Louis , Vidal‐Madjar Daniel , Zribi Mehrez
Published: September 2006

Surface roughness is a key parameter for surface‐atmosphere exchanges of mass and energy. Only a few field measurements have been performed in arid or semiarid areas where it is an important control of the aeolian erosion threshold. An intensive field campaign was performed in southern Tunisia to measure the lateral cover, Lc, and the aerodynamic roughness length, Z0, over 10 sites with different surface roughnesses. Lc was determined by combining field measurements of the geometry of the roughness elements and simple assumptions on their shapes. Z0 was experimentally determined from high‐precision wind velocity and air temperature profiles. The resulting data were found to be in good agreement with the existing relationships linking the geometric and the aerodynamic roughness. This suggests that for natural surfaces, Z0 can be estimated on the basis of the geometric characteristics of the roughness elements. This data set was then used to investigate the capabilities of radar backscatter coefficients, σ0, to retrieve Lc and/or Z0. Significant relationships were found between σ0 and both Lc and Z0. The SAR/ERS data set is in agreement with the SIR‐C SLR data set from Greeley et al. (1997). On the basis of these two data sets including data from different arid and semiarid areas (North Africa, South Africa, North America), we propose an empirical relationship to retrieve Z0 using radar observations in the C band from operational sensors.
Historical and conceptual background of self‐organization by reactive processes
Authors: Tabony James
Published: September 2006

Order, form, pattern and organization are properties central to much living matter. The physicochemical processes by which an initially homogeneous solution of reacting chemicals or biochemicals might self‐organize is hence a question of fundamental biological importance. In most cases, solutions of reacting chemicals in a test‐tube do not self‐organize. Because of this, for many years, it was not thought possible that reactive processes could result in self‐organization. However, progressively over the last hundred years, it has been shown that this is not always the case, and under certain conditions, the combination of reaction with molecular diffusion can lead to macroscopic self‐organization. In ‘complex’ systems comprised of populations of strongly coupled elements, new ‘emergent’ properties, such as self‐organization, arise by way of the dynamics of the system. Self‐organizing reaction‐diffusion systems form a specific type of complex system. Here, I will give a personal overview of the conceptual and historical background to this approach with an emphasis on biological self‐organization.
Microtubules viewed as molecular ant colonies
Authors: Tabony James
Published: September 2006

Populations of ants and other social insects self‐organize and develop ‘emergent’ properties through stigmergy in which individual ants communicate with one another via chemical trails of pheromones that attract or repulse other ants. In this way, sophisticated properties and functions develop. Under appropriate conditions, in vitro microtubule preparations, initially comprised of only tubulin and GTP, behave in a similar manner. They self‐organize and develop other higher‐level emergent phenomena by a process where individual microtubules are coupled together by the chemical trails they produce by their own reactive growing and shrinking. This behaviour is described and compared with the behaviour of ant colonies. Viewing microtubules as populations of molecular ants may provide new insights as to how the cytoskeleton may spontaneously develop high‐level functions. It is plausible that such processes occur during the early stages of embryogenesis and in cells.
Lithium selectively increases neuronal differentiation of hippocampal neural progenitor cells bothin vitroandin vivo
Authors: Kim Jin Seuk , Chang Mi‐Yoon , Yu In Tag , Kim Ju Hee , Lee Sang‐Hun , Lee Yong‐Sung , Son Hyeon
Published: September 2006

Lithium has been demonstrated to increase neurogenesis in the dentate gyrus of rodent hippocampus. The present study was undertaken to investigate the effects of lithium on the proliferation and differentiation of rat neural progenitor cells in hippocampus bothin vitroandin vivo. Lithium chloride (1–3 mm) produced a significant increase in the number of bromodeoxyuridine (BrdU)‐positive cells in high‐density cultures, but did not increase clonal size in low‐density cultures. Lithium chloride at 1 mm(within the therapeutic range) also increased the number of cells double‐labeled with BrdU antibody and TuJ1 (a class III β‐tubulin antibody) in high‐density cultures and the number of TuJ1‐positive cells in a clone of low‐density cultures, whereas it decreased the number of glial fibrillary acidic protein‐positive cells in both cultures. These results suggest that lithium selectively increased differentiation of neuronal progenitors. These actions of lithium appeared to enhance a neuronal subtype, calbindinD28k‐positive cells, and involved a phosphorylated extracellular signal‐regulated kinase and phosphorylated cyclic AMP response element‐binding protein‐dependent pathway bothin vitroandin vivo. These findings suggest that lithium in therapeutic amounts may elicit its beneficial effects via facilitation of neural progenitor differentiation toward a calbindinD28k‐positive neuronal cell type.
Steroid sulfatase (STS) expression in the human temporal lobe: enzyme activity, mRNA expression and immunohistochemistry study
Authors: Steckelbroeck Stephan , Nassen Alexander , Ugele Bernhard , Ludwig Michael , Watzka Matthias , Reissinger Annette , Clusmann Hans , Lütjohann Dieter , Siekmann Lothar , Klingmüller Dietrich , Hans Volkmar H.
Published: September 2006

Dehydroepiandrosterone (DHEA) and its sulfate (DHEAS) are suggested to be important neurosteroids. We investigated steroid sulfatase (STS) in human temporal lobe biopsies in the context of possible cerebral DHEA(S)de novobiosynthesis. Formation of DHEA(S) in mature human brain tissue has not yet been studied. 17α‐Hydroxylase/C17‐20‐lyase and hydroxysteroid sulfotransferase catalyze the formation of DHEA from pregnenolone and the subsequent sulfoconjugation, respectively. Neither their mRNA nor activity were detected, indicating that DHEA(S) are not produced within the human temporal lobe. Conversely, strong activity and mRNA expression of DHEAS desulfating STS was found, twice as high in cerebral neocortex than in subcortical white matter. Cerebral STS resembled the characteristics of the known placental enzyme. Immunohistochemistry revealed STS in adult cortical neurons as well as in fetal and adult Cajal‐Retzius cells. Organic anion transporting proteins OATP‐A, ‐B, ‐D, and ‐E showed high mRNA expression levels with distinct patterns in cerebral neocortex and subcortical white matter. Although it is not clear whether they are expressed at the blood–brain barrier and facilitate an influx rather than an efflux, they might well be involved in the transport of steroid sulfates from the blood. Therefore, we hypothesize that DHEAS and/or other sulfated 3β‐hydroxysteroids might enter the human temporal lobe from the circulation where they would be readily converted via neuronal STS activity.
An Empirical Investigation into the Utilization-Based Information Technology Success Model: Integrating Task–Performance and Social Influence Perspective
Authors: Kim Changki , Jahng Jungjoo , Lee Jinjoo
Published: September 2006

This paper develops the utilization-based information technology (IT) success model by integrating key variables from IT acceptance and IT success literatures, and empirically validates it. The model shows relations among IT utilization, performance expectancy, social influence, and user satisfaction. A field study was undertaken to evaluate and test the relationships via structural equation modeling using LISREL. The path from performance expectancy and user satisfaction to IT utilization was positive and significant. While the path from implicit social influence to IT utilization was found to be significant, explicit social influence had no significant influence on users’ IT utilization. Implications and future research directions are drawn.
Bulk heterojunction organic photovoltaic devices based on phenyl-cored thiophene dendrimers
Authors: Kopidakis Nikos , Mitchell William J. , van de Lagemaat Jao , Ginley David S. , Rumbles Garry , Shaheen Sean E. , Rance William L.
Published: September 2006

Bulk heterojunction organic photovoltaic devices have been fabricated by blending phenyl-cored thiophene dendrimers with a fullerene derivative. A power conversion efficiency of 1.3% under simulated AM1.5 illumination is obtained for a four-arm dendrimer, despite its large optical band gap of 2.1eV. The devices exhibit an increase in short-circuit current and power conversion efficiency as the length of the arm is increased. The fill factors of the devices studied are characteristically low, which is attributed to overly uniform mixing of the blend.
Clifford-Finsler algebroids and nonholonomic Einstein–Dirac structures
Authors: Vacaru Sergiu I.
Published: September 2006

We propose a new framework for constructing geometric and physical models on nonholonomic manifold provided both with Clifford-Lie algebroid symmetry and nonlinear connection structure. Explicit parametrizations of generic off-diagonal metrics and linear and nonlinear connections define different types of Finsler, Lagrange, and/or Riemann–Cartan spaces. A generalization to spinor fields and Dirac operators on nonholonomic manifolds motivates the theory of Clifford algebroids defined as Clifford bundles, in general, enabled with nonintegrable distributions defining the nonlinear connection. In this work, we elaborate the algebroid spinor differential geometry and formulate the (scalar, Proca, graviton, spinor, and gauge) field equations on Lie algebroids. The paper communicates new developments in geometrical formulation of physical theories and this approach is grounded on a number of previous examples when exact solutions with generic off-diagonal metrics and generalized symmetries in modern gravity define nonholonomic spacetime manifolds with uncompactified extra dimensions.
Strong Bragg gratings in phosphate glass single mode fiber
Authors: Albert J. , Schülzgen A. , Temyanko V. L. , Honkanen S. , Peyghambarian N.
Published: September 2006

Bragg gratings with reflectivities greater than 99% have been fabricated in phosphate glass single mode fibers by irradiating the fibers with 193nm wavelength, high intensity pulses from an ArF excimer laser through a phase mask. Thermal treatment for 1000h at temperatures up to 170°C did not degrade the gratings and resulted in an increase in grating strength. The refractive index modulation amplitudes obtained exceed 10−4.
Analysis of the reduced thermal conductivity in InGaAs∕GaAs quantum dot lasers from chirp characteristics
Authors: Tan Hua , Kamath Kishore K. , Mi Zetian , Bhattacharya Pallab , Klotzkin David
Published: September 2006

The thermal conductivity of self-organized quantum dot (QD) active regions is estimated by measurements of wavelength chirp with injected current as a function of the current pulse duty cycle both below and above threshold. A simple model which separates out thermal and charge carrier chirps is used to estimate the thermal conductivity of the QD active region. With this model, the thermal conductivity of the InGaAs QD active region is estimated to be ∼0.1W∕mK, about two orders of magnitude less than that of the bulk material. This is consistent with theoretical predictions of the reduced thermal conductivity of QD regions.
Improved electrical stability in asymmetric fingered polysilicon thin film transistors
Authors: Cuscunà M. , Mariucci L. , Fortunato G. , Bonfiglietti A. , Pecora A. , Valletta A.
Published: September 2006

The authors studied the electrical stability of the asymmetric fingered polysilicon thin film transistors (AF-TFTs) at different bias-stress conditions by using a new test structure with an additional contact on the n+-floating region. This structure allows to measure the two subchannel TFT (sub-TFT) electrical characteristics before and after bias stressing. The AF-TFTs show a very stable saturation regime, even when bias stressing at very high Vds, where the electrical characteristics of both sub-TFTs are degraded. The authors concluded that stability of the AF-TFTs is related to the specific operation of the device rather than to immunity of this structure to hot carrier effects.
Numerical modeling of type III solar radio bursts in the inhomogeneous solar corona and interplanetary medium
Authors: Li Bo , Robinson Peter A. , Cairns Iver H.
Published: September 2006

The first numerical calculations are presented for type III solar radio bursts in the inhomogeneous solar corona and interplanetary medium that include microscale quasilinear and nonlinear processes, intermediate-scale driven ambient density fluctuations, and large-scale evolution of electron beams, Langmuir and ion-sound waves, and fundamental and harmonic electromagnetic emission. Bidirectional coronal radiation driven by oppositely directed beams is asymmetric between the upward and downward directions due to downward beam narrowing in velocity space, and harmonic emission dominates fundamental emission, consistent with observations and theoretical analysis. In the interplanetary medium, fundamental and/or harmonic emission can be important depending on beam parameters and plasma conditions. Furthermore, Langmuir waves are bursty, ion-sound waves also show some degree of irregularity, while electromagnetic radiations are relatively smooth, all qualitatively consistent with observations. Moreover, the statistics of Langmuir wave energy agree well with the predictions of stochastic growth theory, indicating that the beam-Langmuir wave system evolves to a stochastic growth state.
White emission from liquid-crystalline copolymers containing oxadiazole moieties in the side chain
Authors: Kawamoto Masuki , Tsukamoto Takuji , Kinoshita Motoi , Ikeda Tomiki
Published: September 2006

A liquid-crystalline polymer in the side chain was synthesized through copolymerization of a bipolar carrier-transporting monomer with a liquid-crystalline monomer containing oxadiazole moieties substituted with trifluoromethyl groups. A single-layer light-emitting diode of indium tin oxide (ITO)/copolymer/MgAg emitted white light with a maximum luminous efficiency of 0.1cd∕A. The origin of the white emission in the copolymer is the electroplex between bipolar carrier-transporting moieties and strong electron-withdrawing moieties. Furthermore, a simple multilayer device with configuration of ITO/poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)/copolymer/MgAg device showed white emission with CIE 1931 chromaticity coordinates (x,y): (0.30, 0.33).
Diverse effects of two-dimensional and step flow growth mode induced microstructures on the magnetic anisotropies of SrRuO3 thin films
Authors: Yoo Y. Z. , Chmaissem O. , Kolesnik S. , Ullah A. , Lurio L. B. , Brown D. E. , Brady J. , Dabrowski B. , Kimball C. W. , Haji-Sheikh M. , Genis A. P.
Published: September 2006

Geometrical anisotropy axes of diverse SrRuO3 (SRO) films grown by random and directional two-dimensional and step flow modes are determined and their characteristic angular magnetizations are understood in terms of growth mode induced structural effects. Two-dimensional SRO films possess single-crystal-like structural qualities. Angular magnetization measurements show sharp minima and indicate the films’ easy axis to be in the [310] direction. In contrast, examination of step flow SRO films shows the presence of degenerate multiple in-plane domains and the anisotropy axis in a direction close to [110] even though directional surface steps are clearly visible.
Highly efficient and stable sky blue organic light-emitting devices
Authors: Lin Mei-Fang , Wang Lei , Wong Wai-Kwok , Cheah Kwok-Wai , Tam Hoi-Lam , Lee Meng-Ting , Chen Chin H.
Published: September 2006

A highly efficient and stable sky blue organic light-emitting device doped with a sky blue dopant BUBD-1 has been fabricated, achieving an electroluminescence efficiency of 13.2cd∕A and 6.1lm∕W at 20mA∕cm2 and 6.7V, with Commission Internationale del’Eclairage coordinates of (0.16, 0.30) and a half-decay lifetime of 1815h at an initial brightness of 2640cd∕m2. This performance is one of the best blue devices ever reported without using hole blocking layer or any p or n dopant in hole or electron transport layer.
Spatiality, Built Form, and Creative Industry Development in the Inner City
Authors: Hutton Thomas A
Published: September 2006

Theoretical treatments of new industry formation within the inner city emphasise the significance of agglomeration economies, social relations, institutional factors, and representational (semiotic) features of the landscape. The author contributes to a larger understanding of generative processes of industrial innovation in the urban core by demonstrating through theoretical synthesis and case studies, the critical roles played by ‘material’ (or physical) space and form. First, Soja's idea of the ‘industry-shaping power of spatiality’ in the new economic spaces of the post-Fordist metropolis is interpreted as the boundedness of inner-city space, the intimacy of urban landscapes, and the integrity of urban form. Second, the cogency of Helbrecht's injunction regarding the complementarity of abstractive and ‘concrete’ dimensions of urban space in knowledge-based industry clusters is demonstrated by case-study references situated in London, Vancouver, and Singapore. Third, the author draws on Markus's incisive analysis of principal building types (and ‘durable taxonomies' of building function and social meaning) to link historic and contemporary industrialisation processes, including the comingling of production, housing, and consumption. The nexus of theoretical integration lies in the articulation of three-dimensional industrial landscapes comprised of physical space and form as well as symbolic constructs.
A Complex Network Approach to Urban Growth
Authors: Andersson Claes , Frenken Koen , Hellervik Alexander
Published: September 2006

Economic geography can be viewed as a large and growing network of interacting activities. This fundamental network structure and the large size of such systems makes the complex network approach an attractive model for growth dynamics modeling. In this paper the authors propose the use of complex networks for geographical modeling and demonstrate how such an application can be combined with a cellular model to produce output that is consistent with large-scale regularities such as power laws and fractality. Complex networks can provide a stringent framework for growth dynamic modeling where concepts from, for example, spatial interaction models and multiplicative growth models, can be combined with the flexible representation of land and behaviour found in cellular automata and agent-based models. In addition, there exists a large body of theory for the analysis of complex networks that have direct applications in urban geographic problems. The intended use of such models is twofold: (1) to address the problem of how the empirically observed hierarchical structure of settlements can be explained as a stationary property of a stochastic evolutionary process rather than as equilibrium points in a dynamic process, and, (2) to improve the predictive quality of applied urban modeling.
Urban Development and the Politics of a Creative Class: Evidence from a Study of Artists
Authors: Markusen Ann
Published: September 2006

In this paper I critique the notion of ‘the creative class' and the fuzzy causal logic about its relationship to urban growth. I argue that in the creative class, occupations that exhibit distinctive spatial and political proclivities are bunched together, purely on the basis of educational attainment, and with little demonstrable relationship to creativity. I use a case study of artists, one element of the purported creative class, to probe this phenomenon, demonstrating that the formation, location, urban impact, and politics of this occupation are much more complex and distinctive than has been suggested previously. The spatial distribution of artists is a function of semiautonomous personal migration decisions, local nurturing of artists in dedicated spaces and organizations, and the locus of artist-employing firms. Artists have very high rates of self-employment, boosting regional growth by providing import-substituting consumption activities for residents and through direct export of their work. Their contribution to attracting high-tech activity is ambiguous—causality may work in the opposite direction. Artists play multiple roles in an urban economy—some progressive, some problematic. I argue that artists as a group make important, positive contributions to the diversity and vitality of cities, and their agendas cannot be conflated with neoliberal urban political regimes. I show the potential for artists as a political force to lead in social and urban transformation and the implausibility of their common cause with other members of Florida's ‘creative class’, such as scientists, engineers, managers, and lawyers.
Recruitment of dynein to the Jurkat immunological synapse
Authors: Combs Jeffrey , Kim Soo Jin , Tan Sarah , Ligon Lee A. , Holzbaur Erika L. F. , Kuhn Jeffrey , Poenie Martin
Published: September 2006

Binding of T cells to antigen-presenting cells leads to the formation of the immunological synapse, translocation of the microtubule-organizing center (MTOC) to the synapse, and focused secretion of effector molecules. Here, we show that upon activation of Jurkat cells microtubules project from the MTOC to a ring of the scaffolding protein ADAP, localized at the synapse. Loss of ADAP, but not lymphocyte function-associated antigen 1, leads to a severe defect in MTOC polarization at the immunological synapse. The microtubule motor protein cytoplasmic dynein clusters into a ring at the synapse, colocalizing with the ADAP ring. ADAP coprecipitates with dynein from activated Jurkat cells, and loss of ADAP prevents MTOC translocation and the specific recruitment of dynein to the synapse. These results suggest a mechanism that links signaling through the T cell receptor to translocation of the MTOC, in which the minus end-directed motor cytoplasmic dynein, localized at the synapse through an interaction with ADAP, reels in the MTOC, allowing for directed secretion along the polarized microtubule cytoskeleton.
Sperm competition enhances functional capacity of mammalian spermatozoa
Authors: Gomendio Montserrat , Martin-Coello Juan , Crespo Cristina , Magaña Concepción , Roldan Eduardo R. S.
Published: September 2006

When females mate promiscuously, sperm from rival males compete within the female reproductive tract to fertilize ova. Sperm competition is a powerful selective force that has shaped sexual behavior, sperm production, and sperm morphology. However, nothing is known about the influence of sperm competition on fertilization-related processes, because it has been assumed that sperm competition only involves a race to reach the site of fertilization. We compared four closely related rodent species with different levels of sperm competition to examine whether there are differences in the proportion of spermatozoa that become ready to interact with the ovum (“capacitated”) and in the proportion of spermatozoa that experience the acrosome reaction in response to a natural stimulant. Our results show that differences between species in levels of sperm competition were associated with the proportion of spermatozoa that undergo capacitation and with the proportion of spermatozoa that respond to progesterone, an ovum-associated signal. Sperm competition thus favors a larger population of spermatozoa that are competent to fertilize, and spermatozoa that are more sensitive to the signals emitted by the ovum and that may penetrate the ova vestments more rapidly. These results suggest that, contrary to previous assumptions, competition between spermatozoa from rival males continues at the site of fertilization. These findings may have further evolutionary implications because the enhanced competitiveness of spermatozoa during fertilization may increase the risk of polyspermy to females. This could lead to antagonistic coevolution between the sexes and may contribute to the explanation of the rapid divergence observed in fertilization-related traits.
Tracking of Quantum Dot-labeled CFTR Shows Near Immobilization by C-Terminal PDZ Interactions
Authors: Haggie Peter M. , Kim Jung Kyung , Lukacs Gergely L. , Verkman A. S.
Published: September 2006

Mutations in cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-regulated chloride channel, cause cystic fibrosis. To investigate interactions of CFTR in living cells, we measured the diffusion of quantum dot-labeled CFTR molecules by single particle tracking. In multiple cell lines, including airway epithelia, CFTR diffused little in the plasma membrane, generally not moving beyond 100–200 nm. However, CFTR became mobile over micrometer distances after 1) truncations of the carboxy terminus, which contains a C-terminal PDZ (PSD95/Dlg/ZO-1) binding motif; 2) blocking PDZ binding by C-terminal green fluorescent protein fusion; 3) disrupting CFTR association with actin by expression of a mutant EBP50/NHERF1 lacking its ezrin binding domain; or 4) skeletal disruption by latrunculin. CFTR also became mobile when the cytoskeletal adaptor protein binding capacity was saturated by overexpressing CFTR or its C terminus. Our data demonstrate remarkable and previously unrecognized immobilization of CFTR in the plasma membrane and provide direct evidence that C-terminal coupling to the actin skeleton via EBP50/ezrin is responsible for its immobility.
Muslim Rebels
Authors: Kenney Jeffrey T.
Published: September 2006

The Kharijites were a splinter group that broke away from the main forces of Islam during the formative medieval period, purportedly refusing arbitration and committing bloody outrages against their fellow Muslims. Their influence in the political and theological life of the nascent faith has ensured their place in both critical and religious accounts of early Islamic history. Over the centuries, the Kharijites have repeatedly been invoked whenever militant opposition arose and today the label is frequently applied to extremist Islamic movements. After a brief look at Kharijite origins, this book focuses on contemporary Egypt. The book shows how religious images of the Kharijites have dominated public discussion about political opposition movements, effectively undermining attempts to discuss the real issues generating such movements.
Islamism, State, and Ideology
Authors: Kenney Jeffrey T.
Published: September 2006

This chapter explores the modern context in which Egyptians began to introduce the Kharijites into their political discourse. It argues that Muslims in different historical and political circumstances have engaged in rhetorical accusations of Kharijism, with the early rhetorical context considerably obscured by the shadow of the orthodox tradition. The modern context stands more clearly in view; it covers the process of political and economic modernization begun by the Ottoman governor Muhammad ’Ali in the 19th century, the centralized planning and authoritarian style of President Gamal Abdul Nasser's regime, and the development of Egyptian Islamism.