bluuebunny/crossref_metadata_2025 huggingface dataset:
STOIC COMMUNITARIANISM AND NORMATIVE CITIZENSHIP
Authors: Long Anthony A.
Published: May 2007

This essay argues that Stoicism is the ancient philosophy most
relevant to modern politics and civic education. Its relevance is due not
to the advocacy of any specific political system or public policy but to
its theory that the human good depends primarily on rationality and
excellence of character rather than on material prosperity and
productivity. According to Stoicism, all human beings are related to one
another in virtue of our communal nature as rational animals. Reflection
on the norms of human nature persuaded the Stoics that we all share a
common interest in living just and mutually beneficial lives. This
principle, though it favors an equitable distribution of goods and
services, makes rationality and integrity, rather than material
prosperity, the essential values of community and the measure of normative
citizenship and lawmaking. Our goal as Stoic citizens is to practice the
art of what is always possible or in our power—doing our best to
live mutually beneficial and well-reasoned lives—while recognizing
that the external success we are naturally inclined to aim at may be
frustrated because we live in a world we can never fully control.
Asymmetric generation of oceanic crust at the ultra‐slow spreading Southwest Indian Ridge, 64°E
Authors: Searle R. C. , Bralee A. V.
Published: May 2007

We describe topographic, gravity, magnetic, and sonar data from a Southwest Indian Ridge spreading segment near 64°E, 28°S. We interpret these to reveal crustal structure, spreading history, and volcanic and tectonic processes over the last 12 Myr. We confirm that the crust is some 2 km thicker north of the ridge axis, though it varies along and across axis on scales of ∼10 km and 4 Myr. The plate separation rate remained approximately constant at 13 ± 1 km Myr−1, but half‐spreading rates were up to 40% asymmetric, varying between faster‐to‐the‐north and faster‐to‐the‐south on a 4 Myr timescale. Topography shows a dominant E–W lineation normal to the N–S spreading direction. This is superficially similar to faulted abyssal hill terrain of the Mid‐Atlantic Ridge (MAR), but inferred fault scarps are 3–4 times more widely spaced and have greater offsets. Conjugate pairs of massifs on either plate are interpreted as volcanic constructions similar to the large volcano currently filling the median valley at the segment center. They have temporal spacings of ∼4 Myr and are thought to reflect episodic melt focusing along an otherwise melt‐poor ridge. Additionally, there are places, mainly on the southern plate, where lineated topography is replaced by a much blockier topography and embryonic ocean core complexes similar to those recently reported on the MAR near 13°N. There is generally more extrusive volcanism on the northern plate and more tectonism on the southern one. Extrusive volcanism has propagated westward from the segment center since 2 Ma. The FUJI Dome core complex and adjacent seafloor to its east and west appear to be part of a single coherent block, capped by extrusive rock near the segment center, exposing gabbro via a detachment fault over the Dome and probably exposing deeper crust or upper mantle farther west near the segment end. Magnetic anomalies are continuous along this block. We suggest that at its eastern boundary the detachment is simply welded onto magmatically emplaced crust to the east in a similar way to young crust being welded to the old plate at ridge‐transform intersections.
Increasing stoichiometric imbalance in North America's largest lake: Nitrification in Lake Superior
Authors: Sterner Robert W. , Anagnostou Eleni , Brovold Sandra , Bullerjahn George S. , Finlay Jacques C. , Kumar Sanjeev , McKay R. Michael L. , Sherrell Robert M.
Published: May 2007

Lake Superior has exhibited a continuous, century‐long increase in nitrate whereas phosphate remains at very low levels. Increasing nitrate and low phosphate has led to a present‐day severe stoichiometric imbalance; Lake Superior's deepwater NO3−:PO43− molar ratio is 10,000, more than 600 times the mean requirement ratio for primary producers. We examine the rate of [NO3−] increase relative to budgets for NO3− and fixed N. Nitrate in Lake Superior has continued to rise since 1980, though possibly at a reduced rate. We constructed whole‐lake NO3− and N budgets and found that NO3− must be generated in the lake at significant rates. Stable O isotope results indicate that most NO3− in the lake originated by in‐lake oxidation. Nitrate in the lake is responding not just to NO3− loading but also to oxidation of reduced forms of nitrogen delivered to the lake. The increasing [NO3−]:[PO43−] stoichiometric imbalance in this large lake is largely determined by these in‐situ processes.
Improving the precision of high‐rate GPS
Authors: Larson Kristine M. , Bilich Andria , Axelrad Penina
Published: May 2007

In order to improve the accuracy of high‐rate (1 Hz) displacements for geophysical applications such as seismology it is important to reduce systematic errors at seismic frequencies. One such GPS error source that overlaps with seismic frequencies and is not currently modeled is multipath. This study investigates the frequencies and repetition of multipath in high‐rate GPS time series in order to maximize the effectiveness of techniques relying upon the geometric repeatability of GPS satellite orbits. The implementation of the aspect repeat time adjustment (ARTA) method described here uses GPS position time series to estimate time‐varying and site‐dependent shifts. As demonstrated for high‐rate GPS sites in southern California this technique significantly reduces positioning noise at periods from 20 to 1000 s. For a 12‐hour time series, ARTA methods improve the standard deviation of the north component from 8.2 to 5.1 mm and the east component from 6.3 to 4.0 mm. After applying ARTA corrections, common mode errors are removed by stacking. This method further improves the standard deviations to 3.0 and 2.6 mm for the north and east components, respectively.
Quasiperiodic scintillation and data interpretation: Nongeophysical GPS amplitude fluctuations due to intersatellite interference
Authors: Beach Theodore L. , Baragona Curtis A.
Published: May 2007

Spectrograms of high‐rate Global Positioning System (GPS) power data at the L1 frequency (1.57542 GHz) commonly show patterns of fluctuation frequency with respect to time that resemble quasiperiodic scintillation observations. These fluctuation patterns have probably not been noted in the past because of the low sampling frequencies and coarse quantization of power measurements in most GPS receivers. We demonstrate that the source of these fluctuations is usually not edge‐type diffraction from steep ionospheric gradients, as is often hypothesized for quasiperiodic scintillation, despite some features consistent with ionospheric generation. Instead, in most cases these spectrogram patterns derive from intersatellite signal interference between pairs of coarse/acquisition (C/A) codes broadcast on L1. As evidence of this mechanism, we show that most spectrogram features appear on pairs of satellite tracking channels and that the patterns can be reproduced using a multisatellite GPS simulator. We also model the spectrogram patterns, both with regard to the basic GPS C/A code correlation process and the differential Doppler shift conditions that cause the fluctuations. In this latter respect, the GPS quasiperiodic scintillation observations bear resemblance to a mechanism discussed by L. A. Hajkowicz for traditional satellite beacons. Despite the complex nature of the intersatellite interference phenomenon, we can model when the spectrogram patterns are expected to appear. Thus one can screen out these time‐varying interference patterns to find potential occurrences of actual ionospheric edge diffraction in spectrograms. The intersatellite interference phenomenon is also of general interest to GPS radio engineering.
The Impact of Magnetic Resonance Imaging-Detected White Matter Hyperintensities on Longitudinal Changes in Regional Cerebral Blood Flow
Authors: Kraut Michael A , Beason-Held Lori L , Elkins Wendy D , Resnick Susan M
Published: May 2007

White matter hyperintensities are frequently detected on cranial magnetic resonance imaging (MRI) scans of older adults. Given the presumed ischemic contribution to the etiology of these lesions and the posited import of resting brain activity on cognitive function, we hypothesized that longitudinal changes in MRI-detected white matter disease, and its severity at a given time point, would be associated with changes in regional cerebral blood flow (rCBF) over time. We evaluated MRI scans and resting H215O positron emission tomographic rCBF at baseline and after an average of 7.7-year follow-up in Baltimore Longitudinal Study of Aging participants without dementia. Differences in patterns of rCBF were evident at baseline and at follow-up between the group of subjects showing increased white matter disease over the 8-year interval compared with the group with stable white matter ratings. Furthermore, longitudinal changes over time in rCBF also differed between the two groups. Specifically, the group with progressive white matter abnormalities showed greater increase in the right inferior temporal gyrus/fusiform gyrus, right anterior cingulate, and the rostral aspect of the left superior temporal gyrus. Regions of greater longitudinal decrease in this group were evident in the right inferior parietal lobule and at the right occipital pole. Changes in white matter disease over time and its severity at any given time are associated significantly with both cross-sectional and longitudinal patterns of rCBF. The longitudinal increases may reflect cortical compensation mechanisms for reduced efficacy of interregional neural communications that result from white matter deterioration.
Nrf2 Neh5 domain is differentially utilized in the transactivation of cytoprotective genes
Authors: Zhang Jianyong , Hosoya Tomonori , Maruyama Atsushi , Nishikawa Keizo , Maher Jonathan M. , Ohta Tsutomu , Motohashi Hozumi , Fukamizu Akiyoshi , Shibahara Shigeki , Itoh Ken , Yamamoto Masayuki
Published: May 2007

The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) contains two transcription activation domains, Neh4 (Nrf2 ECH homology 4) and Neh5, which co-ordinately regulate transactivation of cytoprotective genes. In the present study we aimed to clarify the role of the Neh5 domain in Nrf2-mediated gene regulation. Deletion of the complete Neh5 domain reduces expression of endogenous Nrf2 target genes, such as HO-1 (haem oxygenase 1), NQO1 [NAD(P)H:quinone oxidoreductase 1] and GCLM (glutamate cysteine ligase modulatory subunit), in human kidney epithelial cells. Furthermore, the deletion of Neh5 markedly repressed CBP [CREB (cAMP-response-element-binding protein)-binding protein] and BRG1 (Brahma-related gene 1) from associating with Nrf2, diminishing their co-operative enhancement of HO-1 promoter activity. Mutational analysis of the Neh5 domain revealed a motif that shares significant homology with β-actin and ARP1 (actin-related protein 1). Mutagenesis of this motif selectively decreased HO-1, but not NQO1 and GCLM, expression. Taken together, these results indicate that the Neh5 domain has the ability to regulate Nrf2 target gene transcription, yet the role of the Neh5 domain in transcription varies from gene to gene.
Artificially evolved Synechococcus PCC6301 Rubisco variants exhibit improvements in folding and catalytic efficiency
Authors: Greene Dina N. , Whitney Spencer M. , Matsumura Ichiro
Published: May 2007

The photosynthetic CO2-fixing enzyme, Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), is responsible for most of the world's biomass, but is a slow non-specific catalyst. We seek to identify and overcome the chemical and biological constraints that limit the evolutionary potential of Rubisco in Nature. Recently, the horizontal transfer of Calvin cycle genes (rbcL, rbcS and prkA) from cyanobacteria (Synechococcus PCC6301) to γ-proteobacteria (Escherichia coli) was emulated in the laboratory. Three unique Rubisco variants containing single (M259T) and double (M259T/A8S, M259T/F342S) amino acid substitutions in the L (large) subunit were identified after three rounds of random mutagenesis and selection in E. coli. Here we show that the M259T mutation did not increase steady-state levels of rbcL mRNA or L protein. It instead improved the yield of properly folded L subunit in E. coli 4–9-fold by decreasing its natural propensity to misfold in vivo and/or by enhancing its interaction with the GroES–GroEL chaperonins. The addition of osmolites to the growth media enhanced productive folding of the M259T L subunit relative to the wild-type L subunit, while overexpression of the trigger factor and DnaK/DnaJ/GrpE chaperones impeded Rubisco assembly. The evolved enzymes showed improvement in their kinetic properties with the M259T variant showing a 12% increase in carboxylation turnover rate (kccat), a 15% improvement in its KM for CO2 and no change in its KM for ribulose-1,5-bisphosphate or its CO2/O2 selectivity. The results of the present study show that the directed evolution of the Synechococcus Rubisco in E. coli can elicit improvements in folding and catalytic efficiency.
K201 (JTV519) suppresses spontaneous Ca2+ release and [3H]ryanodine binding to RyR2 irrespective of FKBP12.6 association
Authors: Hunt Donald J. , Jones Peter P. , Wang Ruiwu , Chen Wenqian , Bolstad Jeff , Chen Keyun , Shimoni Yakhin , Chen S. R. Wayne
Published: May 2007

K201 (JTV519), a benzothiazepine derivative, has been shown to possess anti-arrhythmic and cardioprotective properties, but the mechanism of its action is both complex and controversial. It is believed to stabilize the closed state of the RyR2 (cardiac ryanodine receptor) by increasing its affinity for the FKBP12.6 (12.6 kDa FK506 binding protein) [Wehrens, Lehnart, Reiken, Deng, Vest, Cervantes, Coromilas, Landry and Marks (2004) Science 304, 292–296]. In the present study, we investigated the effect of K201 on spontaneous Ca2+ release induced by Ca2+ overload in rat ventricular myocytes and in HEK-293 cells (human embryonic kidney cells) expressing RyR2 and the role of FKBP12.6 in the action of K201. We found that K201 abolished spontaneous Ca2+ release in cardiac myocytes in a concentration-dependent manner. Treating ventricular myocytes with FK506 to dissociate FKBP12.6 from RyR2 did not affect the suppression of spontaneous Ca2+ release by K201. Similarly, K201 was able to suppress spontaneous Ca2+ release in FK506-treated HEK-293 cells co-expressing RyR2 and FKBP12.6. Furthermore, K201 suppressed spontaneous Ca2+ release in HEK-293 cells expressing RyR2 alone and in cells co-expressing RyR2 and FKBP12.6 with the same potency. In addition, K201 inhibited [3H]ryanodine binding to RyR2-wt (wild-type) and an RyR2 mutant linked to ventricular tachycardia and sudden death, N4104K, in the absence of FKBP12.6. These observations demonstrate that FKBP12.6 is not involved in the inhibitory action of K201 on spontaneous Ca2+ release. Our results also suggest that suppression of spontaneous Ca2+ release and the activity of RyR2 contributes, at least in part, to the anti-arrhythmic properties of K201.
Tapping Toddlers' Evolving Semantic Representation via Gesture
Authors: Capone Nina C.
Published: May 2007

Purpose

This study presents evidence that gesture is a means to understanding the semantic representations of toddlers.

Method

The data were part of a study of toddlers' word learning conducted by N. C. Capone and K. K. McGregor (2005). The object function probe from that study was administered after 1 exposure and after 3 exposures to objects. Here, toddlers' gestures were described and their gesture–speech combinations were analyzed as a function of instruction and time.

Results

A large proportion of toddlers gestured. Gestures were iconic and deictic, but toddlers produced more iconic gestures than previously reported. Consistent with studies of older children, toddlers produced gesture–speech combinations that reflected their learning state.

Conclusion

Gesture can be both a source of semantic knowledge and an expression of that knowledge. Gesture provides a window onto evolving semantic representations and, therefore, can be 1 method of assessing what a child knows at a time when oral language skills are limited and are, perhaps, an unreliable indicator of what the child knows. Embodied knowledge may underlie the use of gesture. Clinical implications are discussed.
Extreme ultraviolet imaging of wire array z-pinch experiments
Authors: Bland S. N. , Ampleford D. J. , Bott S. C. , Lebedev S. V. , Palmer J. B. A. , Pikuz S. A. , Shelkovenko T. A.
Published: May 2007

A multi-frame extreme ultraviolet imaging system based on four pinhole cameras, each backed by a gated microchannel plate (MCP) detector, was used to analyze plasma formation and dynamics in wire array z-pinch experiments on the MAGPIE generator (1 MA, 240 ns) at Imperial College (London). The use of pinhole size, object, and image distances, and MCP sensitivity to determine the spatial and spectral response of the diagnostic is discussed. A high magnification, high resolution version of the diagnostic has produced important information on wire initiation and plasma ablation in various materials. A low magnification version has allowed direct study of the snowplough sheath during array implosion, and of plasma instabilities during stagnation.
Silicon nanoparticles: Absorption, emission, and the nature of the electronic bandgap
Authors: Meier Cedrik , Gondorf Andreas , Lüttjohann Stephan , Lorke Axel , Wiggers Hartmut
Published: May 2007

Silicon nanoparticles synthesized in the gas phase are studied. From time-resolved photoluminescence measurements we determine, quantitatively, the size-dependence of the oscillator strength of the nanoparticles. We investigate experimentally the absorption and photoluminescence emission of nanoparticle ensembles with a broad size distribution. Using a model which accounts for size-effects in both oscillator strength and quantum-confinement, we are able to calculate absorption and emission spectra of ensemble samples. From these results we have determined, whether silicon nanoparticles should be regarded as indirect or direct semiconductors. Moreover, we systematically study the influence of the particle size-distribution on the optical spectra.
Rapid flow of dry granular materials down inclined chutes impinging on rigid walls
Authors: Pudasaini Shiva P. , Hutter Kolumban , Hsiau Shu-San , Tai Shih-Chang , Wang Yongqi , Katzenbach Rolf
Published: May 2007

We performed laboratory experiments of dry granular chute flows impinging an obstructing wall. The chute consists of a 10cm wide rectangular channel, inclined by 50° relative to the horizontal, which, 2m downslope abruptly changes into a horizontal channel of the same width. 15l of quartz chips are released through a gate with the same width as the chute and a gap of 6cm height, respectively. Experiments are conducted for two positions of the obstructing wall, (i) 2m below the exit gate and perpendicular to the inclined chute, and (ii) 0.63m into the horizontal runout and then vertically oriented. Granular material is continuously released by opening the shutter of the silo. The material then moves rapidly down the chute and impinges on the obstructing wall. This leads to a sudden change in the flow regime from a fast moving supercritical thin layer to a stagnant thick heap with variable thickness and a surface dictated by the angle of repose typical for the material. We conducted particle image velocimetry (PIV) experiments by recording the moving material from the side with charge coupled devices (CCD) cameras. The experiment was also video recorded. From the CCD data velocities were also deduced using the PIV technique. In order to compare the results here we describe the experiments for the same material and the same gap width of the silo gate but for the two positions of the obstructing wall. Analysis of the shock front formation and propagation upslope, evolution of the height of the supercritical flow, impact velocity and momentum are presented and discussed in detail. Computed and derived shock front heights match well.
On the force and torque on systems of rigid bodies: A remark on an integral formula due to Howe
Authors: Ragazzo Clodoaldo Grotta , Tabak Esteban
Published: May 2007

M. S. Howe [J. Fluid Mech. 206, 131 (1989)] presented integral formulas for the force and torque on a rigid body that permit the identification of the separate influences of added mass, normal stresses induced by free vorticity, and viscous skin friction. Here a simple extension of Howe’s formulas is done for systems of several rigid bodies. The goal is to separate these effects on each rigid body. These new formulas may help in understanding the hydrodynamic interaction between bodies. As an example, the interaction forces on a pair of bubbles rising at high Reynolds number side by side are computed.
Cavitation visualization of vorticity bridging during the merger of co-rotating line vortices
Authors: Chang N. A. , Yakushiji R. , Dowling D. R. , Ceccio S. L.
Published: May 2007

The flow of two co-rotating, merging line vortices was visualized with cavitation, and the images reveal the complex flow interactions associated with the vortex merger. While the developed cavitation has an influence on the vortical flow, the basic features of the noncavitating flow can be discerned through the judicious application of different free-stream cavitation numbers. By inducing vapor in the vortex cores, the existence of radial “bridging” vortices in the merger zone was confirmed. These visualizations are consistent with the numerically predicted vortex interactions presented by R. L. Bristol, J. M. Ortega, P. S. Marcus, and O. Savas [J. Fluid Mech. 517, 331 (2004)] and the experimentally inferred flow features are reported by A. L. Chen, J. D. Jacob, and O. Savas [J. Fluid Mech. 382, 155 (1999)] and W. J. Devenport, C. M. Vogel, and J. S. Zsoldos [J. Fluid Mech. 394, 357 (1999)].
Room and low temperature direct three-dimensional-strain measurements by neutron diffraction on as-reacted and prebent CuNb∕Nb3Sn wire
Authors: Oguro H. , Awaji S. , Nishijima G. , Badica P. , Watanabe K. , Shikanai F. , Kamiyama T. , Katagiri K.
Published: May 2007

We measured directly by neutron diffraction the axial and lateral residual strains for the prebent and the as-reacted CuNb∕Nb3Sn wires at room temperature and at 7K, in order to investigate the change of the residual strain with prebending treatment. In the axial direction of the wire, the residual strain was changed with 0.20% to the tensile side when measured at both temperatures, while in the lateral direction, the change was 0.08% and 0.03% to the compressive side for the measurements at RT and 7K, respectively. From the obtained data, we estimated the deviatoric strain. At 7K, the value is 0.40% for the as-reacted wires and it reduces to 0.19% when the prebending is applied with a strain εpb=0.8%. These results suggest that the reduction of the residual strain in the axial direction as well as in the lateral direction, i.e., of the deviatoric strain is responsible for the observed enhancement in the superconducting properties of the prebent Nb3Sn wires. In addition, we succeeded in the quantitative evaluation of the deviatoric strain dependence of the upper critical field for the practical Nb3Sn wire. This is very important for the understanding of the general axial strain dependence of the superconducting properties.
Landau thermodynamic potential for BaTiO3
Authors: Wang Y. L. , Tagantsev A. K. , Damjanovic D. , Setter N. , Yarmarkin V. K. , Sokolov A. I. , Lukyanchuk I. A.
Published: May 2007

In this paper the description of the dielectric and ferroelectric properties of BaTiO3 single crystals using the Landau phenomenological thermodynamic potential was addressed. Our results suggest that when using the sixth-power free energy expansion of the thermodynamic potential, remarkably different values of the fourth-power coefficient, β (the coefficient of Pi4 terms), are required to adequately reproduce the nonlinear dielectric behavior of the paraelectric phase and the electric field induced ferroelectric phase (Eb∥[001]), respectively. In contrast, the eighth-power expansion with a common set of coefficients enables a good description for both phases at the same time. These features, together with the data available in literature, strongly attest to the necessity of the eighth-power terms in Landau thermodynamic potential of BaTiO3. In addition, the fourth-power coefficients, β and ξ (the coefficient of Pi2Pj2 terms), were evaluated from the nonlinear dielectric responses along [001], [011], and [111] orientations in the paraelectric phase. Appreciable temperature dependence was evidenced for both coefficients above TC. Further analysis on the linear dielectric response of the single domain crystal in the tetragonal phase demonstrated that temperature dependent anharmonic coefficients are also necessary for an adequate description of the dielectric behavior in the ferroelectric phase below TC. As a consequence, an eighth-power thermodynamic potential, with some of the anharmonic coefficients being temperature dependent, was proposed and compared with the existing potentials. In general the potential proposed in this work exhibits a higher quality in reproducing the dielectric and ferroelectric properties of this prototypic ferroelectric substance.
Mechanical characterization of solution-derived nanoparticle silver ink thin films
Authors: Greer Julia R. , Street Robert A.
Published: May 2007

Mechanical properties of sintered silver nanoparticles are investigated via substrate curvature and nanoindentation methods. Substrate curvature measurements reveal that permanent microstructural changes occur during initial heating while subsequent annealing results in nearly elastic behavior of the thinner films. Thicker films were found to crack upon thermal treatment. The coefficient of thermal expansion was determined from linear slopes of curvature curves to be 1.9±0.097 ppm∕°C, with elastic modulus and hardness determined via nanoindentation. Accounting for substrate effects, nanoindentation hardness and modulus remained constant for different film thicknesses and did not appear to be a function of annealing conditions. Hardness of 0.91 GPa and modulus of 110 GPa are somewhat lower than expected for a continuous nanocrystalline silver film, most likely due to porosity.
Structure, dielectric and optical properties of Bi1.5ZnNb1.5−xTaxO7 cubic pyrochlores
Authors: Wang Qian , Wang Hong , Yao Xi
Published: May 2007

The crystal structure, dielectric properties, and optical properties of Bi1.5ZnNb1.5−xTaxO7 (BZNT,x=0, 0.5, 1.0, 1.5) pyrochlore ceramics were investigated. The structures of the BZNT ceramics were identified as cubic pyrochlores and the lattice parameters decreased with x increasing. Thermogravimetric analysis were carried out suggesting that there are no Bi and/or Zn volatility at the sintered temperatures. All the samples exhibit low dielectric losses and high resistivities. Substituting Nb5+ by Ta5+ leads to smaller permittivity and temperature coefficient of permittivity. The relaxation behavior of the BZNT ceramics was observed at lower temperatures less than −100 °C. The peaks of the dielectric constant in conjunction with the peaks of dielectric loss shift to lower temperatures with x increasing and frequency decreasing, revealing that the active energy became higher according to Arrhenius law. The bands in Raman spectra were assigned to symmetry species. Ta5+ and Nb5+ with large polarizability induced a distortion of the BO6 octahedra leading to a dynamic disorder. The fundamental absorption edges in the absorption spectra show obvious blueshift when x increasing, suggesting that the band gap energy increases. The four compounds show optical absorption at wavelength shorter than 450 nm. This means that the compounds have the ability to respond to the wavelengths in the visible light region.
Influence of thickness and number of dielectric layers on residual stresses in micromultilayer ceramic capacitors
Authors: Jiang W. G. , Feng X. Q. , Yang G. , Yue Z. X. , Nan C. W.
Published: May 2007

The residual stresses due to high-temperature processing in micromultilayer ceramic capacitors (MLCCs) with various thicknesses and numbers of dielectric ceramic layers were investigated by using a three-dimensional elastoplastic finite element model with temperature-dependent material properties taken into account. For comparison, an explicit analytical solution for the in-plane residual stress in the dielectric ceramic layer was derived. Both the numerical results and the analytical model showed that the thickness ratio of the dielectric layer to electrode layer has a dominant impact on the residual stress states. There exists a critical thickness for the dielectric ceramic layer in MLCCs in the case of a given thickness of the electrode layer, below which both high tensile out-of-plane stresses and high compressive in-plane stresses could cause the cracking of the brittle dielectric layers near the electrode tips and/or the debonding of the electrode/dielectric interface.
Shock-induced behavior in micron-sized water aerosols
Authors: Hanson Thomas C. , Davidson David F. , Hanson Ronald K.
Published: May 2007

We have developed a suite of tools for studying aerosols behind shock waves. A Mie-extinction particle sizing diagnostic and a computational model, along with a specially designed square-section shock tube were developed to study the time-history of micrometer-sized aerosols behind shock waves. These tools are critically needed to pursue the use of shock tubes to study the combustion behavior of low-vapor-pressure fuels. While the facility is designed to study reactive systems, we began by measuring the behavior of water aerosols in the range of 1–10μm behind shock waves with temperatures between 450 and 600K and pressures between 0.64 and 1.1atm. From these data we determined evaporation rates and found a correlation that provides the noncontinuum evaporation rate in terms of the d2 evaporation rate and a correction function.
A low-noise ferrite magnetic shield
Authors: Kornack T. W. , Smullin S. J. , Lee S.-K. , Romalis M. V.
Published: May 2007

Ferrite materials provide magnetic shielding performance similar to commonly used high permeability metals but have lower intrinsic magnetic noise generated by thermal Johnson currents due to their high electrical resistivity. Measurements inside a ferrite shield with a spin-exchange relaxation-free atomic magnetometer reveal a noise level of 0.75fTHz−1∕2, 25 times lower than what would be expected in a comparable μ-metal shield. The authors identify a 1∕f component of the magnetic noise due to magnetization fluctuations and derive general relationships for the Johnson current noise and magnetization noise in cylindrical ferromagnetic shields in terms of their conductivity and complex magnetic permeability.
“Self-concentration” effects on the dynamics of a polychlorinated biphenyl diluted in 1,4-polybutadiene
Authors: Cangialosi D. , Alegría A. , Colmenero J.
Published: May 2007

The mobility of isolated polychlorinated biphenyl (PCB54) in 1,4-polybutadiene (PB) has been investigated by means of broadband dielectric spectroscopy. The aim was to provide new insights about the effect of the environment on the dynamics of PCB54. The authors’ results indicate that PCB54 structural dynamics is neither independent of the PB matrix nor slaved to the matrix itself. The authors interpret these results as a consequence of the limited size of cooperatively rearranging regions (CRRs) involved in PCB54 structural relaxation possessing an effective concentration different from the macroscopic one. This implies a non-negligible influence of “self-concentration,” already proven for the component segmental dynamics in polymer blends, also in the relaxation of binary mixtures involving low molecular weight glass formers. This allowed the evaluation of the size of CRR, which was about 1nm for PCB54 in PB. This means that the cooperativity extends over the first shell around PCB54 molecules.
Comparative study of temperature dependent orientational relaxation in a model thermotropic liquid crystal and in a model supercooled liquid
Authors: Chakrabarti Dwaipayan , Bagchi Biman
Published: May 2007

Recent optical Kerr effect experiments have revealed a power law decay of the measured signal with a temperature independent exponent at short-to-intermediate times for a number of liquid crystals in the isotropic phase near the isotropic-nematic transition and supercooled molecular liquids above the mode coupling theory critical temperature. In this work, the authors investigate the temperature dependence of short-to-intermediate time orientational relaxation in a model thermotropic liquid crystal across the isotropic-nematic transition and in a binary mixture across the supercooled liquid regime in molecular dynamics simulations. The measure of the experimentally observable optical Kerr effect signal is found to follow a power law decay at short-to-intermediate times for both systems in agreement with recent experiments. In addition, the temperature dependence of the power law exponent is found to be rather weak. As the model liquid crystalline system settles into the nematic phase upon cooling, the decay of the single-particle second-rank orientational time correlation function exhibits a pattern that is similar to what has been observed for supercooled liquids.
Hole-versus electron-based operations in SiGe nanocrystal nonvolatile memories
Authors: de Sousa J. S. , Freire V. N. , Leburton J.-P.
Published: May 2007

A comparative study between electron- and hole-based data storage operations in Si1−xGex nanocrystal nonvolatile memories is presented. The authors show that the valence band-edge alignment is ideally suited for holes storage, which allows for extremely long retention times for alloy composition x>0 without affecting the programming performances.
H
2
S
exposure of a (100)Ge surface: Evidences for a (2×1) electrically passivated surface
Authors: Houssa M. , Nelis D. , Hellin D. , Pourtois G. , Conard T. , Paredis K. , Vanormelingen K. , Vantomme A. , Van Bael M. K. , Mullens J. , Caymax M. , Meuris M. , Heyns M. M.
Published: May 2007

The experimental study of the bonding geometry of a (100)Ge surface exposed to H2S in the gas phase at 330°C shows that 1 ML S coverage with (2×1) surface reconstruction can be achieved. The amount of S on the Ge surface and the observed surface periodicity can be explained by the formation of disulfide bridges between Ge–Ge dimers on the surface. First-principles molecular dynamics simulations confirm the preserved (2×1) reconstruction after dissociative adsorption of H2S molecules on a (100)Ge (2×1) surface, and predict the formation of (S–H)–(S–H) inter-Ge dimer bridges, i.e., disulfide bridges interacting via hydrogen bonding. The computed energy band gap of this atomic configuration is shown to be free of surface states, a very important finding for the potential application of Ge in future high performance integrated circuits.
Effects of supercritical CO2 fluid on sputter-deposited hafnium oxide
Authors: Liu Po-Tsun , Tsai Chih-Tsung , Yang Po-Yu
Published: May 2007

Low-temperature supercritical fluid (SCF) technology is employed to improve the dielectric characteristics of metal oxide film deposited at low temperature. In this investigation, hafnium oxide (HfO2) film was sputter deposited at room temperature and post-treated with SCF at 150°C, replacing typical high-temperature annealing process. From Fourier transformation infrared and thermal desorption spectroscopy measurement, the absorption peaks of Hf–O–Hf bonding and the oxygen content in HfO2 film have, respectively, shown apparent raise. The leakage current density of the low-temperature deposited HfO2 film is reduced significantly, and the conduction mechanism is modified from trap-assisted quantum tunneling to thermionic emission process, since SCF treatment effectively reduces the number of traps in HfO2 film.
Optofluidic ring resonator based dye laser
Authors: Shopova Siyka I. , Zhou Hongying , Fan Xudong , Zhang Po
Published: May 2007

The authors demonstrate a microfluidic dye laser using a liquid core optical ring resonator (LCORR). The LCORR is made of a fused silica capillary with a wall thickness of a few microns. The circular cross section of the capillary forms a ring resonator that supports whispering gallery modes (WGMs) and provides an optical feedback for lasers. Due to the high Q factor of the WGM (107), a low lasing threshold is achieved (1μJ∕mm2). In addition, they show that the laser can be coupled out via a tapered fiber in touch with the LCORR, thus providing a mechanism for easy laser delivery.
Excimer laser irradiation induced suppression of off-state leakage current in organic transistors
Authors: Chou Wei-Yang , Lin Shih-Ting , Cheng Horng-Long , Tang Fu-Ching , Lin Yow-Jon , You Chang-Feng , Wang Yu-Wu
Published: May 2007

The authors report the suppression of the off-state leakage current and subthreshold swing (SS) in inkjet-printed poly(3-hexylthiophene) thin-film transistors with asymmetric work function source and drain electrodes. Indium tin oxide (ITO) material was used as source/drain electrodes and the source electrode was irradiated by KrF excimer laser. The dominant mechanisms for the suppressive Ioff could be attributed to the increase in the work function of ITO source irradiated by the excimer laser. Lower trap state density formed on the laser irradiated source electrode. Holes could be easily injected into the channel at small lateral electric field resulting in smaller threshold voltage and SS.
Optical properties of helical Ag nanostructures calculated by discrete dipole approximation method
Authors: Zhang Z.-Y. , Zhao Y.-P.
Published: May 2007

The extinction spectra and field distribution of Ag helical nanostructures have been calculated using the discrete dipole approximation method. The plasmon peak of the Ag helix can be tuned not only by the structural parameters but also by the polarizations of the incident light, especially the circular polarizations. In addition, the polarization direction of the incident light can change the spatial distribution of the maximum E field, which provides a simple way to spatially resolve analyte’s distribution on the nanostructures for sensing applications.
Ni–Cr alloy to enhance single- and double-walled carbon nanotube synthesis for field-effect transistor fabrication
Authors: Yang Tsung-Yeh , Yang Wei-Chang , Tseng Tzu-Chun , Tsai Chung-Min , Yew Tri-Rung
Published: May 2007

Single- and double-walled carbon nanotubes were synthesized between predefined Ti∕Ni∕Cr∕Ti multilayer stacks for field-effect transistor fabrication by thermal chemical vapor deposition at 900°C. The Ni nanoprecipitates were induced from Cr matrix because of phase segregation during high temperature process of carbon nanotube growth. The Ni–Cr catalyst was shown to significantly enhance the synthesis of single- and double-walled carbon nanotubes compared to those using pure Ni catalyst, which was demonstrated by both physical and electrical characteristics of the carbon nanotube field-effect transistor fabricated.
Void nucleation in biaxially strained ultrathin films of face-centered cubic metals
Authors: Kolluri Kedarnath , Gungor M. Rauf , Maroudas Dimitrios
Published: May 2007

We report an analysis of void nucleation as a relaxation mechanism in freestanding biaxially strained ultrathin films of face-centered cubic metals based on large-scale molecular-dynamics simulations. Above a critical strain level, multiple threading dislocations are emitted from the film surface. The surface step traces formed by gliding dislocations on intersecting and on adjacent parallel glide planes lead to formation and growth of surface pits and grooves, while vacancies form due to gliding of jogged dislocations and dislocation intersections. Coalescence of the surface pits with vacancy clusters is the precursor to the formation of a larger void extending across the film.
Infrared detection with silicon nano-field-effect transistors
Authors: Nishiguchi K. , Ono Y. , Fujiwara A. , Yamaguchi H. , Inokawa H. , Takahashi Y.
Published: May 2007

The authors fabricated nanoscale silicon metal-oxide-semiconductor field-effect transistors (MOSFETs) to detect an infrared (IR) signal at room temperature. The IR signal excites conduction-band electrons in an undoped channel of a MOSFET and some of them are injected through an energy barrier into a storage node (SN) electrically formed by the MOSFET. Small signals, originating from electrons, stored in the SN are detected by an electrometer with a single-electron resolution. Additionally, the MOSFET controls the number and energy of electrons injected into the SN. This enables electrical control of the sensitivity and cutoff wavelengths of IR signals, suggesting the possibility of highly functional IR sensors.
Photon enhanced aggregation of single walled carbon nanotube dispersions
Authors: Chaturvedi H. , Poler J. C.
Published: May 2007

The authors describe a photon enhanced aggregation of dispersed single walled carbon nanotubes in the presence of electron transfer reagents. A recently synthesized metallodendrimer strongly and specifically binds to the ends of the nanotubes. Upon optical excitation, of the metal to ligand charge transfer absorption, of various ruthenium complexes, the nanotubes rapidly coagulate. The electron transfer mechanism is consistent with observed photon enhancement process. These results support a directed self-assembly paradigm for nanostructured materials.
Phenomenological Differences between Familiar and Unfamiliar Odours
Authors: Mingo Simon A , Stevenson Richard J
Published: May 2007

Unfamiliar odours are harder to discriminate than familiar odours. We explored the phenomenal basis of this difference. In experiments 1a and 1b, participants profiled odour quality for two sets of familiar and unfamiliar odours. In both cases unfamiliar odours were redolent of more odour qualities than familiar stimuli. In experiment 2, participants received (i) a set of familiar and unfamiliar odours and learnt their names, and (ii) a further set of familiar and unfamiliar odours to which they were exposed. Participants then profiled these stimuli as well as a further unexposed set of familiar and unfamiliar odours. Exposure, but not naming, led to a significantly smaller difference between the familiar and unfamiliar stimuli, in terms of their redolence to other odours, when compared to unexposed control stimuli. Unfamiliar exposed odours were also judged as less redolent than unexposed unfamiliar odours. These observations are consistent with a mnemonic basis for odour-quality perception.
Receptor-mediated activation of nitric oxide synthesis by arginine in endothelial cells
Authors: Joshi Mahesh S. , Ferguson T. Bruce , Johnson Fruzsina K. , Johnson Robert A. , Parthasarathy Sampath , Lancaster Jack R.
Published: May 2007

Arginine contains the guanidinium group and thus has structural similarity to ligands of imidazoline and α-2 adrenoceptors (α-2 AR). Therefore, we investigated the possibility that exogenous arginine may act as a ligand for these receptors in human umbilical vein endothelial cells and activate intracellular nitric oxide (NO) synthesis. Idazoxan, a mixed antagonist of imidazoline and α-2 adrenoceptors, partly inhibitedl-arginine-initiated NO formation as measured by a Griess reaction. Rauwolscine, a highly specific antagonist of α-2 AR, at very low concentrations completely inhibited NO formation. Likel-arginine, agmatine (decarboxylated arginine) also activated NO synthesis, however, at much lower concentrations. We found that dexmedetomidine, a specific agonist of α-2 AR was very potent in activating cellular NO, thus indicating a possible role for α-2 AR inl-arginine-mediated NO synthesis.d-arginine also activated NO production and could be inhibited by imidazoline and α-2 AR antagonists, thus indicating nonsubstrate actions of arginine. Pertussis toxin, an inhibitor of G proteins, attenuatedl-arginine-mediated NO synthesis, thus indicating mediation via G proteins.l-type Ca2+channel blocker nifedipine and phospholipase C inhibitor U73122 inhibited NO formation and thus implicated participation of a second messenger pathway. Finally, in isolated rat gracilis vessels, rauwolscine completely inhibited thel-arginine-initiated vessel relaxation. Taken together, these data provide evidence for binding of arginine to membrane receptor(s), leading to the activation of endothelial NO synthase (eNOS) NO production through a second messenger pathway. These findings provide a previously unrecognized mechanistic explanation for the beneficial effects ofl-arginine in the cardiovascular system and thus provide new potential avenues for therapeutic development.
Purkinje cell dysfunction and alteration of long-term synaptic plasticity in fetal alcohol syndrome
Authors: Servais Laurent , Hourez Raphaël , Bearzatto Bertrand , Gall David , Schiffmann Serge N. , Cheron Guy
Published: May 2007

In cerebellum and other brain regions, neuronal cell death because of ethanol consumption by the mother is thought to be the leading cause of neurological deficits in the offspring. However, little is known about how surviving cells function. We studied cerebellar Purkinje cellsin vivoandin vitroto determine whether function of these cells was altered after prenatal ethanol exposure. We observed that Purkinje cells that were prenatally exposed to ethanol presented decreased voltage-gated calcium currents because of a decreased expression of the γ-isoform of protein kinase C. Long-term depression at the parallel fiber–Purkinje cell synapse in the cerebellum was converted into long-term potentiation. This likely explains the dramatic increase in Purkinje cell firing and the rapid oscillations of local field potential observed in alert fetal alcohol syndrome mice. Our data strongly suggest that reversal of long-term synaptic plasticity and increased firing rates of Purkinje cellsin vivoare major contributors to the ataxia and motor learning deficits observed in fetal alcohol syndrome. Our results show that calcium-related neuronal dysfunction is central to the pathogenesis of the neurological manifestations of fetal alcohol syndrome and suggest new methods for treatment of this disorder.
Dominant factors controlling glacial and interglacial variations in the treeline elevation in tropical Africa
Authors: Wu Haibin , Guiot Joël , Brewer Simon , Guo Zhengtang , Peng Changhui
Published: May 2007

The knowledge of tropical palaeoclimates is crucial for understanding global climate change, because it is a test bench for general circulation models that are ultimately used to predict future global warming. A longstanding issue concerning the last glacial maximum in the tropics is the discrepancy between the decrease in sea-surface temperatures reconstructed from marine proxies and the high-elevation decrease in land temperatures estimated from indicators of treeline elevation. In this study, an improved inverse vegetation modeling approach is used to quantitatively reconstruct palaeoclimate and to estimate the effects of different factors (temperature, precipitation, and atmospheric CO
2
concentration) on changes in treeline elevation based on a set of pollen data covering an altitudinal range from 100 to 3,140 m above sea level in Africa. We show that lowering of the African treeline during the last glacial maximum was primarily triggered by regional drying, especially at upper elevations, and was amplified by decreases in atmospheric CO
2
concentration and perhaps temperature. This contrasts with scenarios for the Holocene and future climates, in which the increase in treeline elevation will be dominated by temperature. Our results suggest that previous temperature changes inferred from tropical treeline shifts may have been overestimated for low-CO
2
glacial periods, because the limiting factors that control changes in treeline elevation differ between glacial and interglacial periods.