bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns of nitrogen fixation along 10°N in the tropical Atlantic
Authors: Voss Maren , Croot Peter , Lochte Karin , Mills Matthew , Peeken Ilka
Published: October 2004

Nitrogen fixation supports new production in the oligotrophic oceans and removes dinitrogen and carbon dioxide from mixed layer waters. N‐fixation rates have been estimated in various ways but measurements are still too rare and factors limiting N‐fixation are not yet fully understood. Here we present data from a transect along 10°N through the tropical Atlantic on the Meteor Cruise 55 where N‐fixation rates between 3.7 and 255 μmol N*m−2*d−1 were recorded. The highest rates occurred off Africa in the eastern tropical North Atlantic (ETNA), and in the Amazon River plume in the West and contributed to 1–12.2% of the N‐demand of primary production. N‐fixation rates correlated with dissolved Fe concentrations, which were 20–280 times greater than the estimated demand. High atmospheric Fe inputs combined with the shallow nutricline make the ETNA a favourable environment for N‐fixers.
Bound and free surface waves in a large wind‐wave tank
Authors: Plant William J. , Dahl Peter H. , Giovanangeli Jean‐Paul , Branger Hubert
Published: October 2004

Microwave and acoustic systems operated in the large wind‐wave tank in Luminy, Marseille, France, show that most small‐scale waves produced at large angles to the wind are products of breaking events bound to longer waves in the tank. These longer waves propagate at the dominant wave phase speed for fetches near 7 m but travel at speeds corresponding to the phase speed of a wave half as long as the dominant wave at fetches near 26 m. The microwave and acoustic systems operated at both 8 mm and 2 cm wavelengths. They were set to look at the same surface spot simultaneously at the same incidence and azimuth angles. Measurements were made at seven wind speeds, five incidence angles, seven azimuth angles, and two nominal fetches. Two peaks were found in either the microwave or acoustic Doppler spectrum when looking upwind or downwind but never in both. The low‐frequency peak is due to Bragg scattering from freely propagating short waves, while the high‐frequency peak is a result of Bragg scattering from short waves bound to longer waves. At azimuth angles not aligned with the wind direction the high‐frequency peak was found to move lower until it merged with the low‐frequency peak at azimuth angles around 60°. Fitting the first moments of these Doppler spectra along with the backscattering cross sections to a model of free wave/bound wave scattering showed that the intensity of bound and free short waves generally decreased with azimuth angle but that free wave spectral densities decreased more rapidly. Differences in microwave and acoustic cross sections confirmed that the bound waves were tilted by their parent waves. Spectral densities of bound and free waves were estimated individually by fitting the data to the model. The sum of these spectral densities, the total short‐wave spectral density, was similar to, but lower than, previous measurements. The nature of millimeter‐length bound waves was found to be different at long fetches than at short fetches, a feature not observed in centimeter‐length bound waves.
5‐HT7 receptor efficacy distribution throughout the canine stomach
Authors: Janssen Pieter , Prins Nicolaas H , Peeters Pieter J , Zuideveld Klaas P , Lefebvre Romain A
Published: October 2004

This study aimed to determine, quantify and explain regional differences in the relaxant response to the selective 5‐HT1 and 5‐HT7 receptor agonist 5‐carboxamidotryptamine (5‐CT) throughout the canine stomach.

Longitudinal muscle strips from eight gastric corpus regions and six antrum regions were mounted for isotonic measurement. The 5‐CT‐induced relaxation was examined on a prostaglandin F2α‐induced submaximal response, expressed as percentage of this response and fitted to the operational model of agonism (OMOA). 5‐HT7 receptor messenger RNA (mRNA) expression was compared by means of quantitative PCR.

5‐CT inhibited PGF2α‐induced tonic contraction (corpus) and increase of phasic contraction amplitude (antrum). The consistent antagonism produced by the selective 5‐HT7 receptor antagonist SB‐269970 (10 nM, pA2 estimates 8.2–8.9) confirmed that in every region, the inhibition by 5‐CT was 5‐HT7 receptor mediated. However, variation in the maximum effect (61–108%) and pEC50 (6.4–8.6) was observed throughout the different regions. The OMOA explained these differences as differences in the efficacy parameter τ (ratio of receptor density and coupling efficiency; log τ estimates ranging from 0.1 to 2.1). The log τ gradient decreases going from the lesser to the greater curvature. A proportional difference (68%) in the relative expression of 5‐HT7 receptor mRNA between the lesser and the greater curvature indicates that differences in receptor density contribute to the observed functional differences.

This study illustrates that 5‐HT7 receptors are present throughout the ventral wall of the canine stomach, but the efficacy (expressed as log τ) is clearly greater close to the lesser curvature. Differences in 5‐HT7 receptor expression at least partially explain the functional differences.

British Journal of Pharmacology (2004) 143, 331–342. doi:10.1038/sj.bjp.0705922
Expression of Rho‐kinase (ROCK‐1 and ROCK‐2) and its substantial role in the contractile activity of the sheep ureter
Authors: Levent Adnan , Büyükafşar Kansu
Published: October 2004

Expression of two isoforms of Rho‐kinase (ROCK) and its functional role in the physiological control of smooth muscle contraction in the sheep ureter were investigated. Helical strips of the ureteric smooth muscle were stimulated by electrical field stimulation (EFS, 60 V, 1 mS, 2, 4, 8, 16 and 32 Hz, for 20 S), KCl (80 mM), carbachol (CCh, 10−8–10−4 M) or phenylephrine (Phe, 10−8–10−4 M).

EFS produced a reproducible contractile activity, which was abolished by tetrodotoxin (3 × 10−6 M), a Na+ channel blocker. A muscarinic receptor antagonist, atropine (2 × 10−6 M), and an adrenergic neuron blocker, guanethidine (10−5 M), significantly suppressed the contraction induced by EFS. However, this contraction was augmented in the presence of NG‐nitro‐L‐arginine (L‐NA, 10−4 M), a nitric oxide synthase inhibitor.

Two Rho‐kinase inhibitors, Y‐27632 (5 × 10−5 M) and fasudil (5 × 10−5 M), markedly attenuated the EFS‐elicited contraction. CCh and Phe produced concentration‐dependent contraction in the sheep ureter. pD2 values for Phe and CCh were 5.04±0.11 and 5.00±0.22, respectively. Y‐27632 (5 × 10−5 M) and fasudil (5 × 10−5 M) also significantly inhibited CCh‐ and Phe‐induced contractions. Moreover, these ROCK inhibitors produced relaxations in the KCl‐elicited contraction in a concentration‐dependent manner. pD2 values for Y‐27632 and fasudil were, respectively, 5.17±0.07 and 4.58±0.08 (P<0.001).

Furthermore, the influences of these agents were also tested on spontaneous phasic contractions of the tissue. Among Y‐27632, fasudil, TTX, L‐NA, guanethidine and atropine, only the ROCK inhibitors (10−6–10−5 M) were able to suppress the spontaneous contractile activity.

Western blot analysis has revealed that both isoforms of Rho‐kinase (ROCK‐1 and ROCK‐2) are expressed in the sheep ureter. Densitometric analysis has indicated that these enzymes are less expressed in the sheep ureter than are in the sheep aorta in a significant manner.

These results show that a contractile enzyme, Rho‐kinase, is expressed, and it mediates agonist‐ and EFS‐induced contractions as well as spontaneous contractile activity of the isolated sheep ureter. Since Y‐27632 and fasudil depressed the contractions, it seems plausible to postulate that Rho‐kinase inhibitors may be beneficial in the treatment of renal colic.

British Journal of Pharmacology (2004) 143, 431–437. doi:10.1038/sj.bjp.0705961
Scintillator probe diagnostic for high energy particles escaped from Large Helical Device
Authors: Nishiura M. , Isobe M. , Saida T. , Sasao M. , Darrow D. S.
Published: October 2004

A scintillator probe for escaping fast ion diagnostics has been developed in the Large Helical Device. This probe is capable of traveling across a divertor leg and sweeping the aperture angle rotationally with respect to the axis of the probe shaft. Pitch angle and gyro radius resolutions are estimated numerically by using a Monte Carlo orbit simulation. The result shows that the detector has sufficient resolution in pitch angle and gyro radius for our target plasmas. Under the neutral beam injected plasma, a signal derived from fast ions was obtained on the scintillator plate and analyzed by using the recorded camera image.
A dynamic flame surface density model for large eddy simulation of turbulent premixed combustion
Authors: Knikker R. , Veynante D. , Meneveau C.
Published: October 2004

A dynamic formulation for a previously developed coupled fractal–similarity model for large eddy simulation of premixed combustion is proposed. In this formulation, the fractal dimension is obtained dynamically from the resolved scales, leaving the inner cutoff scale, representative for the smallest flame structures, as the only parameter to be prescribed. The fractal model provides an accurate estimate for the mean flame surface, whereas the similarity model predicts its spatial distribution.
Charge exchange neutral particle measurements with natural diamond detector under the deuterium–deuterium neutron field on JT-60U tokamak
Authors: Ishikawa M. , Kusama Y. , Takechi M. , Nishitani T. , Morioka A. , Sasao M. , Isobe M. , Krasilnikov A. , Kaschuck Yu. A.
Published: October 2004

A natural diamond detector (NDD) has been installed on the JT-60U tokamak to measure the flux and the energy distribution of charge exchange (CX) fast neutral particles. A NDD has many important advantages to be used as a CX neutral particle analyzer, for example very compact size, high energy resolution, and high radiation hardness etc., while the neutrons and γ rays are a large noise source in the deuterium plasma. The shield was set up around the NDD to reduce those noises. Time-resolved energy distribution of CX neutral particles corresponding to injected beam energy have been successfully obtained under high intensity neutron yield Yn>1015 n/s. Further enhanced neutral particle fluxes during sawtooth oscillation and Alfvén eigenmodes were observed with the NDD. The performance of the NDD as CX neutral particle spectrometer under high intensity neutron yield was demonstrated for the first time on JT-60U in this work.
Electron spin resonance study of GaAs:Er,O grown by organometallic vapor phase epitaxy
Authors: Yoshida Makoto , Hiraka Kensaku , Ohta Hitoshi , Fujiwara Yasufumi , Koizumi Atsushi , Takeda Yoshikazu
Published: October 2004

Electron spin resonance (ESR) measurements of GaAs:Er,O grown by organometallic vapor phase epitaxy have been performed at 9.49GHz from 4.5to13K. Several anisotropic ESR signals (A, B, C, and D) are observed, which is consistent with the previous reports. We reexamined the angular dependence and temperature dependence of the signals in detail. Our ESR results indicate that the direction of alignment of two oxygen atoms or two arsenic atoms for an Er-2O center deviates from the ⟨110⟩ direction in various ways, resulting in the various Er-2O centers. Our ESR results also indicate that the paramagnetic states of the Er centers in GaAs change to a singletlike nonmagnetic state below 8K. The ESR measurements under illumination have been performed to investigate the effect of photoexcitation of the host. This result indicates that the energy transfer efficiency from the host to the B center is especially large. We found that the luminescent Er-2O center B and another Er-2O center C considerably differ in the coupling with the lattice.
Mirrorless lasing from thiophene∕phenylene co-oligomer crystals based on stimulated resonance Raman scattering
Authors: Yanagi Hisao , Yoshiki Atsutoshi , Hotta Shu , Kobayashi Shunsuke
Published: October 2004

Very narrowed light emission was observed from single crystals of various thiophene∕phenylene co-oligomers. Under optical pumping at their resonant absorption wavelengths, all the platelet crystals showed amplified spontaneous emission with a full width at half maximum (FWHM) of 5–7nm. When the pumping wavelengths approached the absorption edges, the crystals emitted further narrowed laserlike lines (FWHM<0.5nm). From their Stokes shift frequencies compared with the off-resonant Raman spectra, we assigned these emission lines to the stimulated resonance Raman scattering. These lines appeared in single or double according to the Raman active modes determined by their different molecular symmetry. The dependence of line intensity on polarized pumping suggested that the stimulated resonance Raman scattering was related to polaritonic phenomena of vibrationally dressed excitons in the uniaxially oriented molecular crystals.
Electromigration failure mechanisms for SnAg3.5 solder bumps on Ti∕Cr-Cu∕Cu and Ni(P)∕Au metallization pads
Authors: Shao T. L. , Chen Y. H. , Chiu S. H. , Chen Chih
Published: October 2004

The electromigration behavior of SnAg3.5 solder bumps is investigated under the current densities of 1×104A∕cm2 and 5×103A∕cm2 at 150°C. Different failure modes were observed for the two stressing conditions. When stressed at 1×104A∕cm2, damage occurred in both the anode/chip side and the cathode/chip side. However, failure happened only in the cathode/chip side under the stressing of 5×103A∕cm2. A three-dimensional simulation of the current-density distribution was performed to provide a better understanding of the current-crowding behavior in the solder bump. The current-crowding effect was found to account for the failure in the cathode/chip side. In addition, both the temperature increase and the thermal gradients were measured during the two stressing conditions. The measured temperature increase due to Joule heating was as high as 54.5°C, and the thermal gradient reached 365°C∕cm when stressed by 1×104A∕cm2. This induced thermal gradient may cause atoms to migrate from the chip side to the substrate side, contributing to the failure in the anode/chip side. Moreover, the formation of intermetallic compounds in the anode/chip side may also be responsible for the failure in the anode/chip side.
Downscattered neutron imaging
Authors: Moran Michael , Haan Steven , Hatchett Stephen , Koch Jeffrey , Barrera Carlos , Morse Edward
Published: October 2004

Images with 14 MeV neutrons of inertial confinement fusion (ICF) D,T fusion show the regions of most intense fusion burn, while images based on lower-energy “downscattered” neutrons can reveal regions of nonburning D,T fuel. The downscattered images can help to understand ICF implosion dynamics. Recording downscattered images is difficult because the images are relatively weak, and because they may be obscured by residual “afterglow” of more intense 14 MeV images. The effect of afterglow can be estimated by adding a sequence of images for neutron energies from 14 MeV down to the downscatteed energy of interest. The images will be subject to decay factors which depend on the time response of the neutron scintillator. Preliminary analyses suggest that afterglow will not prevent the recording of useful downscattered images.
Measurements of the relaxation of ion anisotropic distribution functions in tandem-mirror plasmas
Authors: Numakura T. , Cho T. , Kohagura J. , Hirata M. , Fukai T. , Yokoyama N. , Tomii Y. , Minami R. , Sakamoto K. , Imai T. , Miyoshi S.
Published: October 2004

Our proposed “matrix-type” semiconductor detectors are applied for studying the relaxation of ion anisotropic distribution functions having several keV in the central cell of the tandem mirror GAMMA 10. The matrix-type detector array consists of compactly produced six “rows” having different thicknesses of thin dead layers (SiO2) on its surface. Each row has seven channel units (“columns”) for measuring radiation profiles in the radial direction of plasmas. These various SiO2 layers are, thus, employed as “unbreakable ultrathin radiation–absorption filters” having various thicknesses to analyze x-ray energies and distinguish x rays from neutral particles simultaneously. Development of these detectors along with high power gyrotrons allow us to investigate energy transport analyses between ion-cyclotron heated hot ions and electron-cyclotron heated electrons. An application of the matrix-type detectors reveals detailed behavior of electron and ion relaxation from the perpendicular to parallel ion energies in the central cell.
Prototypes of National Ignition Facility neutron time-of-flight detectors tested on OMEGA
Authors: Glebov V. Yu. , Stoeckl C. , Sangster T. C. , Roberts S. , Schmid G. J. , Lerche R. A. , Moran M. J.
Published: October 2004

Prototypes of several National Ignition Facility (NIF) neutron time-of-flight (nTOF) detectors have been built and tested on OMEGA. One group uses a plastic scintillator coupled with a microchannel plate (MCP) photomultiplier tube (PMT), either a single-stage (gain up to 103) MCP PMT and a two-stage (gain up to 106) MCP PMT. Two ultrafast scintillators—BC-422 and BC-422Q—were used. Another nTOF prototype is based on a synthetic diamond wafer produced by the chemical vapor deposition. The nTOF detectors were tested on DD (2.45 MeV) and DT (14.1 MeV) neutron-producing implosions on OMEGA. Based on the results of these tests, a set of nTOF detectors is proposed for use on the NIF to measure ion temperature and DD and DT neutron yields from 109 to 1019.
Turbulence velocimetry of density fluctuation imaging data
Authors: McKee G. R. , Fonck R. J. , Gupta D. K. , Schlossberg D. J. , Shafer M. W. , Holland C. , Tynan G.
Published: October 2004

Analysis techniques to measure the time-resolved flow field of turbulence are developed and applied to images of density fluctuations obtained with the beam emission spectroscopy diagnostic system on the DIII-D tokamak. Velocimetry applications include measurement of turbulent particle flux, zonal flows, and the Reynolds stress. The flow field of turbulent eddies exhibits quasisteady poloidal flows as well as high-frequency radial and poloidal motion associated with electrostatic potential fluctuations and strongly nonlinear multifield interactions. The orthogonal dynamic programming technique, developed for fluid-based particle and amorphous shape (smoke) flow analysis, is investigated to measure such turbulence flows. Sensitivity and accuracy are assessed and sample results discussed.
β
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δ
phase transition during dropweight impact on cyclotetramethylene-tetranitroamine
Authors: Czerski H. , Greenaway M. W. , Proud W. G. , Field J. E.
Published: October 2004

The secondary explosive cyclotetramethylene-tetranitroamine (HMX) exists in a variety of crystal structures; the most widely used being the β-phase which is stable at room temperature and pressure. On heating, a more impact sensitive form (δ phase) is produced. The nonlinear optical technique of second harmonic generation (SHG) can be used as a probe of phase since δ-phase HMX generates a second harmonic at 532nm when 1064nm laser light is incident upon it. We present high-speed photography of SHG in HMX samples during dropweight impact and show that this technique can provide good spatial information and time resolution. We find evidence for small areas of δ-phase HMX appearing in the period from 13μs before ignition to 10μs afterwards, demonstrating that the heating on impact is sufficient to overcome the loading conditions and cause the phase change.
Losses and transmission in two-dimensional slab photonic crystals
Authors: Kafesaki M. , Soukoulis C. M. , Agio M.
Published: October 2004

Using a three-dimensional finite-difference time-domain method, we present an extensive study of the losses in two-dimensional (2D) photonic crystals patterned in step-index waveguides. We examine the origin of these losses and their dependence on the various system parameters such as the filling ratio, the lattice constant, the shape of the holes, and the propagation direction. Furthermore, we examine the possibility of studying these losses using an approximate 2D model; the validity and limitations of such a model are discussed in detail.
Large eddy simulations of decaying rotating turbulence
Authors: Yang X. , Domaradzki J. Andrzej
Published: October 2004

Large eddy simulations of homogeneous isotropic turbulence subjected to system rotation were performed using the truncated Navier-Stokes method. In the method the Navier-Stokes equations are solved through a sequence of direct numerical simulation runs and a periodic processing of small scales to provide the necessary dissipation. The method is evaluated by comparing simulation results with theoretical analysis, direct numerical simulations, as well as with other large eddy simulation results. Obtained results demonstrate several advantages of the method over traditional large eddy simulations models. The method captures important features of rotating turbulence: the energy decay is inhibited, the energy spectrum departs from the classical k−5/3 form, and initially isotropic turbulence becomes anisotropic. For increasing rotation rate three distinct regimes are observed. At low rotation rates, the influence of rotation is weak and flow behaves like for nonrotating cases. At intermediate rotation rates strong coupling between rotation and nonlinear interactions has a significant influence on turbulence. At high rotation rates viscous effects dominate over nonlinear effects. Furthermore, for high Reynolds numbers, small Rossby numbers, and large elapsed time, the k−3 energy spectrum is observed due to the anisotropy identified by various indicators, rather than the k−2 form found under the assumption of isotropy.
System for evaluation of laser-induced damage performance of optical materials for large aperture lasers
Authors: DeMange P. , Carr C. W. , Radousky H. B. , Demos S. G.
Published: October 2004

The evaluation of optical components in various laser systems, with regard to their resistance to laser-induced damage, has often relied on measuring damage threshold fluences. For large-aperture laser systems a small amount of damage in optics does not impede performance. This necessitates the development of damage testing instrumentation that can directly provide information regarding beam obscuration. The number and size of damage scattering sites for a specific laser fluence, wavelength, and pulse duration determine overall beam losses due to damage. We present a design for rapid quantitative characterization of bulk damage performance of optical materials for use in large-aperture laser systems.
Electron cross-field transport in a low power cylindrical Hall thruster
Authors: Smirnov A. , Raitses Y. , Fisch N. J.
Published: October 2004

Conventional annular Hall thrusters become inefficient when scaled to low power. Cylindrical Hall thrusters, which have lower surface-to-volume ratio, are therefore more promising for scaling down. They presently exhibit performance comparable with conventional annular Hall thrusters. Electron cross-field transport in a 2.6 cm miniaturized cylindrical Hall thruster (100 W power level) has been studied through the analysis of experimental data and Monte Carlo simulations of electron dynamics in the thruster channel. The numerical model takes into account elastic and inelastic electron collisions with atoms, electron-wall collisions, including secondary electron emission, and Bohm diffusion. It is shown that in order to explain the observed discharge current, the electron anomalous collision frequency νB has to be on the order of the Bohm value, νB≈ωc/16. The contribution of electron-wall collisions to cross-field transport is found to be insignificant.
Molecular dynamics simulations of void and helium bubble stability in amorphous silicon during heavy-ion bombardment
Authors: Okuniewski Maria A. , Ashkenazy Yinon , Heuser Brent J. , Averback Robert S.
Published: October 2004

A study of void and helium (He) bubble stability in amorphous silicon (a-Si) subjected to heavy-ion bombardment was conducted with molecular dynamics simulations. The effects of incident ion energy, incident ion direction, and He pressure were investigated. He bubbles with pressures equal to or greater than 0.1kbar were found to be stable during isotropic 2keV xenon (Xe) irradiation. Bubbles with pressures below this limit collapsed completely. On the other hand, voids and bubbles of all pressures were stable following unidirectional 2keV Xe bombardment. In this case, the voids and bubbles became elongated and resisted closure, a phenomenon attributed to the inability of liquid Si to wet the flat, low-curvature internal surfaces of the open-volume defect. The void closure rates varied from 55 to 180Å∕dpa as the Xe projectile energy increased from 0.2keV to 2keV, respectively. An analytical model based on a viscous flow mechanism is presented to describe the behavior associated with the slowest closure rate. The faster rates are attributed to pressure-induced convective flow into the void.
Comment on “Spectra and energy levels of Er3+(4f11) in NaBi(WO4)2” [J. Appl. Phys. 94, 7128 (2003)]
Authors: Cascales C. , Zaldo C.
Published: October 2004

A recent article by Gruber et al. [Gruber, J. Appl. Phys. 94, 7128 (2003)] reports the measurements of the optical absorption and photoluminescence spectra of Er3+ in NaBi(WO4)2 (NBW) and the results of the interpretation and fitting of the observed crystal-field (CF) splitting of Er3+ multiplets with a quasicenter model. In the light of available, previously published information, we argued that these conclusions are not warranted. As a proof, the composition of the Er3+-NBW wave functions and the energy levels derived from the final obtained CF parameters have been checked through the simulation of the temperature-dependent paramagnetic susceptibility χm according to the Van Vleck formalism and, unfortunately, experimental curves of χm versus T, measured in parallel and perpendicular directions to the c axis of the NBW crystal, were not adequately reproduced. The same simulation was carried out with a set of free ions and CF parameters resulting from our previous polarized CF analysis of Er3+ in a NBW crystal, and the agreement with the measured χm versus T curves is a clear indication of the validity and physical meaning of our earlier performed CF analysis.
Effects of compressive epitaxial strain on the magnetotransport properties of single-phase electron-doped La0.7Ce0.3MnO3 films
Authors: Chang W. J. , Hsieh C. C. , Juang J. Y. , Wu K. H. , Uen T. M. , Gou Y. S. , Hsu C. H. , Lin J.-Y.
Published: October 2004

Single-phase electron-doped manganite thin films with nominal composition of La0.7Ce0.3MnO3(LCeMO) have been prepared on SrTiO3(100) substrates by pulsed laser deposition. The conditions for obtaining purely single-phase LCeMO films lie within a very narrow window of substrate temperature (Ts∼720°C) and laser energy density (ED∼2J∕cm2) during deposition. In situ postdeposition annealing, mainly to relax the possible epitaxial in-plane tensile strain between the film and the substrate, leads to an increasing c-axis lattice constant accompanied by the formation of secondary CeO2 phase and higher metal-insulator transition temperature. This is indicative of a strong coupling between the electron and lattice degree of freedom.
Excitation of “monotron” oscillations in klystrons
Authors: Nusinovich Gregory , Read Michael , Song Liqun
Published: October 2004

A general method for calculations of starting currents of modes in klystron cavities is developed. This method allows one to determine the threshold for excitation of so-called monotron oscillations in klystrons having an arbitrary geometry of cavities and an arbitrary cross section of an electron beam. The method is used for evaluating the starting currents of monotron oscillations in a sheet beam, X-band klystron, which is currently in the design state at Calabazas Creek Research Inc.
Defects and morphological changes in nanothin Cu films on Mo(100) studied by thermal helium desorption spectrometry
Authors: Venugopal V. , Seijbel L. J. , van der Pers N. M. , Thijsse B. J.
Published: October 2004

Thermal helium desorption spectrometry has been used for a comprehensive experimental investigation of vacancy-related defects and thermal stability of nanothin Cu films (10–300Å) deposited on a Mo(100) substrate at 300K in UHV. In the helium desorption spectra (300–2000K), a peak is observed that shows that the Cu films are highly unstable. Postdeposition annealing treatments show that this peak is due to the thermally-induced island formation of the copper films. This process is strongly dependent on film thickness; its temperature ranging from 429K for a 10-Å film to 1312K for a 300-Å film, which is not simply due to the considerable change of stress with film thickness. Between 70 and 75Å, there is a distinct narrowing of the peak shape, indicating a change in the kinetics. For a 100-Å film lying in the large thickness range, an activation energy E=1.2±0.1eV was determined. The island-formation process is defect-mediated, as suggested by the fact that the temperature is lowered by an increase of the helium implantation energy and fluence. The island formation during deposition at an elevated substrate temperature occurs at a lower temperature than during postdeposition annealing. The helium released from monovacancies (E=1.8±0.2eV) and vacancy clusters in the Cu films and during high-temperature evaporation of the Cu films from the Mo substrate (Esubl=3.5±0.5eV) is also identified. The x-ray diffraction measurements on 60 and 200-Å films show that they are both fcc Cu(100) films with identical macrostrains; the 200-Å film has a sharper texture than the 60-Å film. The orientation relation between the film and the substrate was found to be (100)[100]fccCu‖(100)[110]bccMo.
InP-based dilute-nitride mid-infrared type-II “W” quantum-well lasers
Authors: Vurgaftman I. , Meyer J. R. , Tansu N. , Mawst L. J.
Published: October 2004

We propose and simulate dilute-nitride midwave-infrared (3–6μm) laser structures, whose type-II “W” active regions (InAsN∕GaAsSb∕InAsN∕GaInP) are designed for growth on InP substrates. Besides taking advantage of the relative maturity of InP-based processing technology, this approach allows the substrate to serve as the bottom optical cladding layer, and for a top InP clad to provide high thermal conductivity for epitaxial-side-down mounting. Band structure and optical analyses project that the proposed lasers should produce nearly as much gain as current type-II W devices on GaSb substrates.
Influence of arsenic during indium deposition on the formation of the wetting layers of InAs quantum dots grown by migration enhanced epitaxy
Authors: Song J. D. , Park Y. M. , Shin J. C. , Lim J. G. , Park Y. J. , Choi W. J. , Han I. K. , Lee J. I. , Kim H. S. , Park C. G.
Published: October 2004

We compared the structural and optical properties of InAs∕GaAs quantum dots grown by migration enhanced epitaxy, with and without arsenic, during indium deposition. The uniformity and size of the quantum dots are enhanced in a sample without arsenic. As a result, narrower and longer wavelength photoluminescence is observed in this sample. Furthermore, the thickness of the wetting layers is reduced by ∼20% in the sample without arsenic, and this result agrees well with the speculation that metallic indium has a smaller driving force for corrugating the InAs wetting layers before they are transformed from two-dimensional to three-dimensional layers. Additionally, the photoluminescence linewidth of the sample without arsenic is insensitive to the cryostat temperature due to two major factors: the reduced thickness of the wetting layers and the enhanced uniformity. In the sample with arsenic, however, the photoluminescence linewidth shows typical anomalies.
Erythropoietin mediates tissue protection through an erythropoietin and common β-subunit heteroreceptor
Authors: Brines Michael , Grasso Giovanni , Fiordaliso Fabio , Sfacteria Alessandra , Ghezzi Pietro , Fratelli Maddalena , Latini Roberto , Xie Qiao-wen , Smart John , Su-Rick Chiao-ju , Pobre Eileen , Diaz Deborah , Gomez Daniel , Hand Carla , Coleman Thomas , Cerami Anthony
Published: September 2004

The cytokine erythropoietin (Epo) is tissue-protective in preclinical models of ischemic, traumatic, toxic, and inflammatory injuries. We have recently characterized Epo derivatives that do not bind to the Epo receptor (EpoR) yet are tissue-protective. For example, carbamylated Epo (CEpo) does not stimulate erythropoiesis, yet it prevents tissue injury in a wide variety ofin vivoandin vitromodels. These observations suggest that another receptor is responsible for the tissue-protective actions of Epo. Notably, prior investigation suggests that EpoR physically interacts with the common β receptor (βcR), the signal-transducing subunit shared by the granulocyte-macrophage colony stimulating factor, and the IL-3 and IL-5 receptors. However, because βcR knockout mice exhibit normal erythrocyte maturation, βcR is not required for erythropoiesis. We hypothesized that βcR in combination with the EpoR expressed by nonhematopoietic cells constitutes a tissue-protective receptor. In support of this hypothesis, membrane proteins prepared from rat brain, heart, liver, or kidney were greatly enriched in EpoR after passage over either Epo or CEpo columns but covalently bound in a complex with βcR. Further, antibodies against EpoR coimmunoprecipitated βcR from membranes prepared from neuronal-like P-19 cells that respond to Epo-induced tissue protection. Immunocytochemical studies of spinal cord neurons and cardiomyocytes protected by Epo demonstrated cellular colocalization of Epo βcR and EpoR. Finally, as predicted by the hypothesis, neither Epo nor CEpo was active in cardiomyocyte or spinal cord injury models performed in the βcR knockout mouse. These data support the concept that EpoR and βcR comprise a tissue-protective heteroreceptor.
Unsupervised Categorization and Category Learning
Authors: Pothos Emmanuel M. , Chater Nick
Published: September 2004

When people categorize a set of items in a certain way they often change their perceptions for these items so that they become more compatible with the learned categorization. In two experiments we examined whether such changes are extensive enough to change the unsupervised categorization for the items—that is, the categorization of the items that is considered more intuitive or natural without any learning. In Experiment 1 we directly employed an unsupervised categorization task; in Experiment 2 we collected similarity ratings for the items and inferred unsupervised categorizations using Pothos and Chater's (2002) model of unsupervised categorization. The unsupervised categorization for the items changed to resemble more the learned one when this was specified by the suppression of a stimulus dimension (both experiments), but less so when it was almost specified by the suppression of a stimulus dimension (Experiment 1, nonsignificant trend in Experiment 2). By contrast, no changes in the unsupervised categorization were observed when participants were taught a classification that was specified by a more fine tuning of the relative salience of the two dimensions.
Evidence for Rule-Based Processes in the Inverse Base-Rate Effect
Authors: Winman Anders , Wennerholm Pia , Juslin Peter , Shanks David R.
Published: September 2004

Three studies provide convergent evidence that the inverse base-rate effect (Medin & Edelson, 1988) is mediated by rule-based cognitive processes. Experiment 1 shows that, in contrast to adults, prior to the formal operational stage most children do not exhibit the inverse base-rate effect. Experiments 2 and 3 demonstrate that an adult sample is a mix of participants relying on associative processes who categorize according to the base-rate and participants relying on rule-based processes who exhibit a strong inverse base-rate effect. The distribution of the effect is bimodal, and removing participants independently classified as prone to rule-based processing effectively eliminates the inverse base-rate effect. The implications for current explanations of the inverse base-rate effect are discussed.
Representing Response Position Relative to Display Location: Influence on Orthogonal Stimulus–Response Compatibility
Authors: Cho Yang Seok , Proctor Robert W.
Published: September 2004

Two types of stimulus–response compatibility (SRC) effect occur with orthogonal stimulus and response sets, an overall up–right/down–left advantage and mapping preferences that vary with response position. Researchers agree that the former type is due to asymmetric coding of the stimulus and response alternatives, but disagree as to whether the latter type requires a different explanation in terms of the properties of the motor system. This issue is examined in three experiments. The location of the stimulus set influenced orthogonal SRC when it varied along the same dimension as the responses (Experiments 1 and 2), with the pattern predicted by the hypothesis that the stimulus set provides a referent relative to which response position is coded. The effect of stimulus-set location on orthogonal SRC was independent of the stimulus onset asynchrony (SOA) for a marker that indicated stimulus-set side and the imperative stimulus. In contrast, a spatial correspondence effect for the irrelevant stimulus-set location and response was a decreasing function of SOA. Experiment 3 showed that the orthogonal SRC effect was determined by response position relative to the stimulus-set location and not the body midline. The results support the view that both types of orthogonal SRC effects are due to asymmetric coding of the stimuli and responses.
C1q Governs Deposition of Circulating Immune Complexes and Leukocyte Fcγ Receptors Mediate Subsequent Neutrophil Recruitment
Authors: Stokol Tracy , O'Donnell Peter , Xiao Ling , Knight Sara , Stavrakis George , Botto Marina , von Andrian Ulrich H. , Mayadas Tanya N.
Published: October 2004

Inflammation induced by circulating immunoglobulin G–immune complexes (ICs) characterizes many immune-mediated diseases. In this work, the molecular requirements for the deposition of circulating ICs and subsequent acute leukocyte recruitment in mice were elucidated. We show that after intravenous injection, preformed soluble ICs are rapidly deposited in the postcapillary venules of the cremaster microcirculation, secondary to increased vascular permeability. This deposition is dependent on complement C1q. IC deposition is associated with leukocyte recruitment. Leukocyte rolling, which is mediated by P-selectin in the exteriorized cremaster muscle, is not further increased in response to ICs. In contrast, leukocyte rolling velocity is significantly decreased and leukocyte adhesion is significantly increased in the presence of ICs. The IC-mediated slow leukocyte rolling velocity and subsequent adhesion and emigration are dependent on Fcγ receptors (FcγRs), particularly FcγRIII, with complement C3 and C5 having no detectable role. These studies suggest a regulatory mechanism of IC deposition and leukocyte trafficking in IC-mediated inflammation requiring C1q and FcγRs in sequential, noninteracting roles.
Genomic Analysis of Stationary-Phase and Exit inSaccharomyces cerevisiae: Gene Expression and Identification of Novel Essential Genes
Authors: Martinez M. Juanita , Roy Sushmita , Archuletta Amanda B. , Wentzell Peter D. , Anna-Arriola Sonia Santa , Rodriguez Angelina L. , Aragon Anthony D. , Quiñones Gabriel A. , Allen Chris , Werner-Washburne Margaret
Published: September 2004

Most cells on earth exist in a quiescent state. In yeast, quiescence is induced by carbon starvation, and exit occurs when a carbon source becomes available. To understand how cells survive in, and exit from this state, mRNA abundance was examined using oligonucleotide-based microarrays and quantitative reverse transcription-polymerase chain reaction. Cells in stationary-phase cultures exhibited a coordinated response within 5–10 min of refeeding. Levels of >1800 mRNAs increased dramatically (≥64-fold), and a smaller group of stationary-phase mRNAs decreased in abundance. Motif analysis of sequences upstream of genes clustered by VxInsight identified an overrepresentation of Rap1p and BUF (RPA) binding sites in genes whose mRNA levels rapidly increased during exit. Examination of 95 strains carrying deletions in stationary-phase genes induced identified 32 genes essential for survival in stationary-phase at 37°C. Analysis of these genes suggests that mitochondrial function is critical for entry into stationary-phase and that posttranslational modifications and protection from oxidative stress become important later. The phylogenetic conservation of stationary-phase genes, and our findings that two-thirds of the essential stationary-phase genes have human homologues and of these, many have human homologues that are disease related, demonstrate that yeast is a bona fide model system for studying the quiescent state of eukaryotic cells.
Construction, Characterization, and Complementation of a Conditional-Lethal DNA Topoisomerase IIα Mutant Human Cell Line
Authors: Carpenter Adam J. , Porter Andrew C.G.
Published: September 2004

DNA Topoisomerase IIα (topoIIα) is a DNA decatenating enzyme, abundant constituent of mammalian mitotic chromosomes, and target of numerous antitumor drugs, but its exact role in chromosome structure and dynamics is unclear. In a powerful new approach to this important problem, with significant advantages over the use of topoII inhibitors or RNA interference, we have generated and characterized a human cell line (HTETOP) in which >99.5% topoIIα expression can be silenced in all cells by the addition of tetracycline. TopoIIα-depleted HTETOP cells enter mitosis and undergo chromosome condensation, albeit with delayed kinetics, but normal anaphases and cytokineses are completely prevented, and all cells die, some becoming polyploid in the process. Cells can be rescued by expression of topoIIα fused to green fluorescent protein (GFP), even when certain phosphorylation sites have been mutated, but not when the catalytic residue Y805 is mutated. Thus, in addition to validating GFP-tagged topoIIα as an indicator for endogenous topoIIα dynamics, our analyses provide new evidence that topoIIα plays a largely redundant role in chromosome condensation, but an essential catalytic role in chromosome segregation that cannot be complemented by topoIIβ and does not require phosphorylation at serine residues 1106, 1247, 1354, or 1393.
The small ubiquitin-like modifier (SUMO) is required for gonadal and uterine-vulval morphogenesis in Caenorhabditis elegans
Authors: Broday Limor , Kolotuev Irina , Didier Christine , Bhoumik Anindita , Gupta Bhagwati P. , Sternberg Paul W. , Podbilewicz Benjamin , Ronai Ze'ev
Published: October 2004

The small ubiquitin-like modifier (SUMO) modification alters the subcellular distribution and function of its substrates. Here we show the major role of SUMO during the development of the Caenorhabditis elegans reproductive system. smo-1 deletion mutants develop into sterile adults with abnormal somatic gonad, germ line, and vulva. SMO-1::GFP reporter is highly expressed in the somatic reproductive system. smo-1 animals lack a vulval-uterine connection as a result of impaired ventral uterine π-cell differentiation and anchor cell fusion. Mutations in the LIN-11 LIM domain transcription factor lead to a uterine phenotype that resembles the smo-1 phenotype. LIN-11 is sumoylated, and its sumoylation is required for its activity during uterine morphogenesis. Expression of a SUMO-modified LIN-11 in the smo-1 background partially rescued π-cell differentiation and retained LIN-11 in nuclear bodies. Thus, our results identify the reproductive system as the major SUMO target during postembryonic development and highlight LIN-11 as a physiological substrate whose sumoylation is associated with the formation of a functional vulval-uterine connection.
Estimating private savings behaviour in Greece
Authors: Hondroyiannis George
Published: September 2004

This paper investigates the long‐ and short‐run determinants of aggregate private savings in Greece employing data over the period 1961‐2000. The long‐run savings function is estimated based on an extended life‐cycle hypothesis taking into account the economic and demographic developments during this period. A long‐run saving function sensitive to fertility changes, old dependency ratio, real interest rate, liquidity and public finances is found to exist and the importance of short‐run deviations is presented using vector error‐correction model estimation. The empirical evidence suggests the existence of a stable long‐run savings function in Greece both in the long‐ and short‐run periods and the policy implications of such a relationship are presented.
DAISY on our desktops? A review of LpPlayer 2.4
Authors: Kimbrough B.T.
Published: September 2004

As the first commercially available software for reading DAISY books on a PC, LpPlayer is an inexpensive vehicle for gaining access to the new format. For this review, several textbooks and standard literary works prepared by Recording for the Blind and Dyslexic were subjected to a broad series of searches and other study‐related tasks. Because of its ability to jump directly to a particular page or chapter beginning, LpPlayer will offer perfectly adequate DAISY access to the casual reader of novels or straightforward nonfiction.
IPR in the ensuing global digital economy
Authors: Subba Rao Siriginidi
Published: September 2004

This article covers the evolution of traditional intellectual property rights (IPR) laws and associated concepts from printed to digital works, and discusses how the characteristics of digital replication pose problems for traditional IPR systems. It highlights international treaties on copyright, including the Universal Copyright Convention, the Berne Convention, the Performers and Phonograms treaty and the Sui‐Generis Protection of Databases. It provides some insight into the Indian software industry by discussing the scope of Indian copyright law, the rights of owner, infringement, penalties, and makes a comparison with US law. The article concludes that judicious participation by all countries in the development of a globalized IPR regime would strengthen the global digital economy.
The way ahead: learning cafés in the academic marketplace
Authors: Boone Morell D.
Published: September 2004

Libraries, like the universities they serve, are faced with the daunting task of reconciling the traditional role as repository and provider of information with the increasing demands of a market‐driven society. Learning cafés can provide a place where these two divergent demands are potentially reconciled. By providing sophisticated technologies within a sociable environment, learning cafés seek to enhance the potential for interactive learning among its users. They have the potential to be hosts for an increasingly diverse array of emerging library services. Before incorporating a learning café within new or existing libraries, however, planners must keep in mind the types of learning best suited for this type of area and maintain a flexible design model so that the café can be adapted to future needs.
Do we practice diversity in business schools?
Authors: Levsen Virginia B. , Goettel Nancy , Chong Frank , Farris Roy
Published: September 2004

Business schools are increasingly emphasizing diversity in their courses as well as in their student populations. Additionally, most schools pay lip‐service to increasing diversity in their faculty compositions. But how well are business schools meeting the goal of a diverse faculty? The purpose of this research was to examine this issue through the analyses of the results of a survey sent to 71 schools of business across the USA. The survey examined ethnic backgrounds, asking for the number of Caucasians, Blacks, Hispanics, Asian‐Pacific peoples, and American‐Indians on faculties. Gender and the position in the school, i.e. dean, associate dean, director, professional, were also collected. Diversity varied between the positions held by faculty but not by the number of years in administrative positions. Significant differences between public and private schools were not evident based on these variables.