bluuebunny/crossref_metadata_2025 huggingface dataset:
Synchronous seismicity changes in and around the northern Japan preceding the 2003 Tokachi‐oki earthquake of M8.0
Authors: Ogata Yosihiko
Published: August 2005

The epidemic‐type aftershock sequence (ETAS) model predicts the normal seismic rate that superposes the empirical laws of decreasing aftershock activity. Anomalies (lowering and enhancement) of the seismic rate from the rate predicted by the ETAS model are found to have occurred concurrently during 1996, in three interplate aftershock sequences and in inland (intraplate) seismicity, in and around northern Japan. Each anomaly is explained by change in Coulomb failure stress, caused by aseismic slip that is assumed to have occurred on the plate interface of the 2003 Tokachi‐oki rupture of M8.0. The slip is also supported by a significant change in the distribution of fault mechanisms of moderate earthquakes before and after 1996 in northern Japan. Using the occurrence data of strong earthquakes of M5.0 or larger for the long period 1926–2003, a similar relative quiescence lasting about 10 years is indicated not only preceding the recent 2003 earthquake but also preceding the 1952 and 1968 great Tokachi‐oki earthquakes.
Constraints on the size of the smallest triggering earthquake from the epidemic‐type aftershock sequence model, Båth's law, and observed aftershock sequences
Authors: Sornette Didier , Werner Maximilian J.
Published: August 2005

The physics of earthquake triggering together with simple assumptions of self‐similarity imply the existence of a minimum magnitude m0 below which earthquakes do not trigger other earthquakes. Noting that the magnitude md of completeness of a seismic catalog is not, in general, the same as the magnitude m0 of the smallest triggering earthquake, we compare observed aftershock sequence parameters with the predictions made by the epidemic‐type aftershock sequence model to constrain the value of m0. In particular, we use quantitative fits to observed aftershock sequences from three previous studies, as well as Båth's law, to obtain four estimates of m0. We show that the branching ratio n (average number of triggered earthquakes per earthquake, also equal to the fraction of aftershocks in a seismic catalog) is the key parameter controlling the estimate of the minimum triggering magnitude m0. Conversely, physical upper bounds for m0 estimated from rate and state friction indicate that at the very least, 55% of all earthquakes are aftershocks.
East‐west SST contrast over the tropical oceans and the post El Niño western North Pacific summer monsoon
Authors: Terao Toru , Kubota Takuji
Published: August 2005

The circulation and SST anomalies during the post El Niño Asian summer monsoon season were examined through data analysis and linear equatorial β plane model calculations. Over the Philippine Sea, a negative precipitation anomaly and low‐level anti‐cyclonic anomaly were found. Over the western equatorial Pacific, a low‐level easterly anomaly prevailed. An east‐west SST anomaly contrast dominated over the tropical Indian and Pacific Oceans, with positive anomalies over the Indian and western Pacific Oceans and negative anomalies over the central to eastern Pacific. The β plane model demonstrated that the anti‐cyclonic anomaly over the Philippine Sea was a Rossby response to the negative precipitation anomaly found in this region. The easterly anomaly along the equator was part of a Kelvin response to the SST anomaly contrast. On the northern side of this anomalous easterly, a negative vorticity anomaly developed. This could induce the moist Rossby wave over the Philippine Sea.
Phase relations in Mg3Al2Si3O12 to 180 GPa: Effect of Al on post‐perovskite phase transition
Authors: Tateno Shigehiko , Hirose Kei , Sata Nagayoshi , Ohishi Yasuo
Published: August 2005

Phase relations in Mg3Al2Si3O12 (MgSiO3 + 25 mol% Al2O3; pyrope garnet composition) were investigated on the basis of in‐situ synchrotron X‐ray diffraction measurements at high‐pressure and ‐temperature in a laser‐heated diamond anvil cell (LHDAC). Results demonstrate that perovskite is solely stable up to 140 GPa and 2200 K, and perovskite and CaIrO3‐type post‐perovskite phase (space group: Cmcm) coexist above 140 GPa and 2200 K. Post‐perovskite is formed as a single phase above 150–170 GPa. Previous study has shown that pure MgSiO3 perovskite transforms to post‐perovskite phase above 125 GPa and 2500 K based on the same pressure standard. These results indicate that addition of Al2O3 expands the stability of MgSiO3 perovskite relative to post‐perovskite.
Subtropical catastrophe: Significant loss of low‐mode tidal energy at 28.9°
Authors: MacKinnon J. A. , Winters K. B.
Published: August 2005

An idealized numerical study of a northward propagating internal tide reveals a dramatic loss of energy to small‐scale subharmonic instabilities near 28.9°N. Inspired by observations of the internal tide radiating northward from the Hawaiian Ridge, a three‐dimensional numerical model is initialized with a northward baroclinic tidal flux of approximately 1.7 kW/m. After an initial spinup period, energy is quickly transferred from the baroclinic tide to subharmonic motions, with half the horizontal tidal wavenumber and small vertical scales, through nonlinear advection of horizontal tidal velocity gradients. Potential oceanic implications are twofold. First, once a steady‐state has been reached, the instability acts as a partial filter of northward tidal flux between 27.5 and 29.5°N, in rough agreement with some altimetric tidal observations. Second, elevated shear of the subharmonic motions suggests the potential for elevated near‐surface dissipation rates near the critical latitude that may be important for upper ocean mixing.
Ocean internal wave spectra inferred from seismic reflection transects
Authors: Holbrook W. Steven , Fer Ilker
Published: August 2005

Internal waves affect many important dynamical processes in the ocean, but in situ observations of internal waves are infrequent and spatially sparse. Here we show that remote sensing of internal waves by marine seismic reflection methods can provide quantitative information on internal wave energy and its spatial variability at high lateral resolution and full ocean depth over large volumes of the ocean. Seismic images of the Norwegian Sea water column show reflections that capture snapshots of finestructure displacements due to internal waves. Horizontal wave number spectra derived from digitized reflection horizons in the open ocean compare favorably to the Garrett‐Munk tow spectrum of oceanic internal wave displacements. Spectra within 10 km laterally and 200 m vertically of the continental slope show enhanced energy likely associated with internal wave‐sloping boundary interactions.
NCAR Sponsors Its First Space Weather Colloquium
Authors: Simpson Sarah
Published: August 2005

Students from the United States, Taiwan, Canada, Chile, Finland, Italy, and Mexico gathered in June at the National Center for Atmospheric Research (NCAR) headquarters in Boulder, Colorado, to immerse themselves in space weather. For 8 intensive days of lectures, labs, and discussions, students expanded their perspectives on the breadth of physical processes and disruptive events that typify the Sun‐Earth realm.
Second European Space Weather Week Set for November
Authors: Simpson Sarah
Published: August 2005

Scientists and applications experts will once again gather in the Netherlands to discuss current activities and future plans in space weather.
Glyceraldehyde 3‐phosphate dehydrogenase serves as an accessory protein of the cardiac sarcolemmal KATP channel
Authors: Jovanović Sofija , Du Qingyou , Crawford Russell M , Budas Grant R , Stagljar Igor , Jovanović Aleksandar
Published: August 2005

Cardiac sarcolemmal ATP‐sensitive K+ (KATP) channels, composed of Kir6.2 and SUR2A subunits, are regulated by intracellular ATP and they couple the metabolic status of the cell with the membrane excitability. On the basis of previous studies, we have suggested that glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) may be a part of the sarcolemmal KATP‐channel protein complex. A polypeptide of ∼42 kDa was immunoprecipitated with an anti‐SUR2A antibody from guinea‐pig cardiac membrane fraction and identified as GAPDH. Immunoprecipitation/western blotting analysis with anti‐Kir6.2, anti‐SUR2A and anti‐GAPDH antibodies showed that GAPDH is a part of the sarcolemmal KATP‐channel protein complex in vivo. Further studies with immunoprecipitation/western blotting and the membrane yeast two‐hybrid system showed that GAPDH associates physically with the Kir6.2 but not the SUR2A subunit. Patch‐clamp electrophysiology showed that GAPDH regulates KATP‐channel activity irrespective of high intracellular ATP, by producing 1,3‐bisphosphoglycerate, a KATP‐channel opener. These results suggest that GAPDH is an integral part of the sarcolemmal KATP‐channel protein complex, where it couples glycolysis with the KATP‐channel activity.
Implications and Outcome of Permanent Coronary Sinus Lead Extraction and Reimplantation
Authors: BURKE MARTIN C. , MORTON JOSEPH , LIN ALBERT C. , TIERNEY SEAN , DESAI ASEEM , HONG THOMAS , KIM SUSAN , SALEM YASSER , ALBERTS MICHAEL , KNIGHT BRADLEY P.
Published: August 2005

Objective: We examined the implications and outcome of coronary sinus (CS) lead removal including the feasibility of laser use within the CS. Background: Cardiac anatomy and lead interactions are more complex with the advent of biventricular pacemakers and atrial cardioverters requiring permanent lead/shocking coil placement in the coronary sinus and its branches. Methods: Fifty‐five permanent cardiac leads were extracted during 2003 in 28 consecutive patients. Our study population included a 10/55 (18%) subset (all males; age 73 ± 6 years; EF = 0.24 ± 0.09) that underwent CS (1/10) or vein branch (9/10) lead extraction. Leads were extracted with an excimer laser sheath (n = 4) or by direct traction (n = 6). Median times between implantation and lead removal were 9.5 months (range 5–59) in the laser group and 3 months (range 3–4) in the direct traction group. Indication for extraction was infection (n = 4), dislodgement (n = 3), diaphragm stimulation (n = 2), and elevated threshold (n = 1). The CS was divided into distal, mid, and proximal segments by venogram. Results: Entry of the laser sheath into the CS was necessary in three of four laser patients. The two distal CS laser cases (left lateral CS coil and anterior‐lateral left ventricular (LV) lead) required both 14‐ and 12‐Fr sheaths, separately. The proximal CS laser case (posterior‐lateral LV lead) required a 12 Fr sheath. The remaining laser patient required a 12‐Fr sheath to pass to the mid SVC. There were no procedural complications as a result of CS lead extraction. Reimplantation of a CS lead was attempted in 7/10 patients at a median of 4 days (range 1–300). CS venograms were available for review in patients before initial implantation (6/10) and after extraction (7/10). The postextraction venograms demonstrated complete occlusion of the vein from which the lead was extracted, and its distal branches, which were unusable in 5/10 (50%). The vein occlusions were present in patients with indwelling leads for greater than 3 months and were independent of extraction method. Conclusions: Laser lead extraction in the coronary sinus appears feasible in carefully selected cases with mandatory indications. However, special intraoperative monitoring and echocardiographic imaging with surgical backup ready is strongly recommended. Target vein selection may be limited for the purpose of reimplantation when leads are indwelling for greater than 3 months.
Transient and steady state CO oxidation kinetics on nanolithographically prepared supported Pd model catalysts: Experiments and simulations
Authors: Laurin M. , Johánek V. , Grant A. W. , Kasemo B. , Libuda J. , Freund H.-J.
Published: August 2005

Applying molecular-beam methods to a nanolithographically prepared planar Pd∕SiO2 model catalyst, we have performed a detailed study of the kinetics of CO oxidation. The model catalyst was prepared by electron-beam lithography, allowing individual control of particle size and position. The sample was structurally characterized by atomic force microscopy and scanning electron microscopy before and after reaction. In the kinetic experiments, the O-rich and CO-rich regimes were investigated systematically with respect to their transient and steady-state behaviors, both under bistable and monostable reaction conditions. Separate molecular beams were used in order to supply the reactants, allowing individual control over the reactant fluxes. The desorbing CO2 was detected by both angle-resolved and angle-integrated mass spectrometries. The experimental results were analyzed using different types of microkinetic models, including a detailed reaction-diffusion model, which takes into account the structural parameters of the catalyst as well as scattering of the reactants from the support. The model quantitatively reproduces the results as a function of the reactant fluxes and the surface temperature. Various kinetic effects observed are discussed in detail on the basis of the model. Specifically, it is shown that under conditions of limited oxygen mobility, the switching behavior between the kinetic regimes is largely driven by the surface mobility of CO.
The importance of vibronic perturbations in ferrocytochrome c spectra: A reevaluation of spectral properties based on low-temperature optical absorption, resonance Raman, and molecular-dynamics simulations
Authors: Levantino Matteo , Huang Qing , Cupane Antonio , Laberge Monique , Hagarman Andrew , Schweitzer-Stenner Reinhard
Published: August 2005

We have measured and analyzed the low-temperature (T=10K) absorption spectrum of reduced horse heart and yeast cytochrome c. Both spectra show split and asymmetric Q0 and Qv bands. The spectra were first decomposed into the individual split vibronic sidebands assignable to B1g (ν15) and A2g (ν19, ν21, and ν22) Herzberg-Teller active modes due to their strong intensity in resonance Raman spectra acquired with Q0 and Qv excitations. The measured band splittings and asymmetries cannot be rationalized solely in terms of electronic perturbations of the heme macrocycle. On the contrary, they clearly point to the importance of considering not only electronic perturbations but vibronic perturbations as well. The former are most likely due to the heterogeneity of the electric field produced by charged side chains in the protein environment, whereas the latter reflect a perturbation potential due to multiple heme-protein interactions, which deform the heme structure in the ground and excited states. Additional information about vibronic perturbations and the associated ground-state deformations are inferred from the depolarization ratios of resonance Raman bands. The results of our analysis indicate that the heme group in yeast cytochrome c is more nonplanar and more distorted along a B2g coordinate than in horse heart cytochrome c. This conclusion is supported by normal structural decomposition calculations performed on the heme extracted from molecular-dynamic simulations of the two investigated proteins. Interestingly, the latter are somewhat different from the respective deformations obtained from the x-ray structures.
Time-dependent pump-probe spectra of NeBr2
Authors: Cabrera Jose A. , Bieler Craig R. , Olbricht Benjamin C. , van der Veer Wytze E. , Janda Kenneth C.
Published: August 2005

Time- and frequency-resolved pump-probe measurements on NeBr2 have been performed to better characterize its fragmentation dynamics on the B electronic state for vibrational levels in the energy region of the transition from direct vibrational predissociation to intramolecular vibrational relaxation dynamics. Above ν′=20 of the Br2 stretching mode, it was observed that the dependence of lifetime on the vibrational quantum number deviates from the energy-gap law by leveling off in the range of 10ps<τ<20ps. In addition to measuring the appearance of Br2 product state levels, we were able to monitor the decay of the initially excited NeBr2 via B→E transitions of the complex. These transitions are shifted 20cm−1 to lower energy from the free Br2 resonances, indicating an E state Ne–Br2 bond energy of 82cm−1. Measurements of NeBr2 vibrational predissociation via the Δν=−2 channel were also performed for ν′=27, 28, and 29. The closing of the Δν=−1 channel leads to an increase in the lifetimes of these vibrational levels. A new Nd:yttrium aluminum garnet pumped dual optical parametric oscillator/optical parametric amplifier system is described that allows us to conveniently record time-delayed pump-probe spectra with 2-cm−1 spectral resolution and 15-ps time resolution.
Studies on the behavior of nanoconfined homopolymers with cyclic chain architecture
Authors: Maury-Evertsz Johnny R. , López Gustavo E.
Published: August 2005

We have performed Monte Carlo simulations to study the effect of cyclic architecture on the behavior of homopolymer chains under several conditions of confinement. The collapse of the rings in two stages, a coil-to-globule and a liquidlike-to-solidlike transition, was observed even at extreme confinement. Both transitions were observed at lower temperatures than for linear chains of the same length, 2%–5% lower for unconfined systems, and 10%–15% lower for wall separations below three bond lengths due to the effect of confinement. When the plates separation approached the two-dimensional regime, the coil-to-globule transition shifted to lower temperatures. The inverse trend was observed when the chain length was increased. In the collapsed state, the average size and conformations of linear and cyclic molecules of same length were similar independently of confinement. At temperatures near the coil-to-globule transition, the radius of gyration of unconfined linear chains, ⟨Rg2⟩linear, became larger than for the cyclic chains, ⟨Rg2⟩cyclic, and this difference increased considerably with confinement. The radius of gyration ratio ⟨Rg2⟩linear∕⟨Rg2⟩cyclic in this region decreased rapidly. The decrease was more pronounced and occurred at lower temperatures for slit width confinements. At higher temperatures, in the coil state, the radius of gyration ratio became nearly constant for a given separation, and varied from 0.56 for unconfined systems to 0.47 when the chain was completely confined between the walls. This reduction was attributed to the higher increase in the average size of linear chains with confinement when compared with cyclic chains, due to architectural restrictions.
Euler angles for G2
Authors: Cacciatori Sergio L. , Cerchiai Bianca L. , Vedova Alberto Della , Ortenzi Giovanni , Scotti Antonio
Published: August 2005

We provide a simple coordinatization for the group G2, which is analogous to the Euler coordinatization for SU(2). We show how to obtain the general element of the group in a form emphasizing the structure of the fibration of G2 with fiber SO(4) and base H, the variety of quaternionic subalgebras of octonions. In particular this allows us to obtain a simple expression for the Haar measure on G2. Moreover, as a by-product it yields a concrete realization and an Einstein metric for H.
Determination of structural parameters for ferrocenecarboxaldehyde using Fourier transform microwave spectroscopy
Authors: Subramanian Ranga , Karunatilaka Chandana , Schock Riley O. , Drouin Brian J. , Cassak Paul A. , Kukolich Stephen G.
Published: August 2005

Gas-phase structural parameters for ferrocenecarboxaldehyde have been determined using Fourier transform microwave spectroscopy. Rotational transitions due to a-, b-, and c-type dipole moments were measured. Eighteen rotational constants were determined by fitting the measured transitions of various isotopomers using a rigid rotor Hamiltonian with centrifugal distortion constants. Least-squares fit and Kraitchman analyses have been used to determine the gas-phase structural parameters and the atomic coordinates of the molecule using the rotational constants for various isotopomers. Structural parameters determined from the least-squares fit are the Fe–C bond lengths to the cyclopentadienyl rings, r(Fe–C)=2.047(4)Å, and the distance between the carbon atoms of the cyclopentadienyl rings, r(C–C)=1.430(2)Å and r(C1–C1′)=1.46(1)Å of ring carbon and aldehyde carbon atom. Structural parameters were also obtained using density-functional theory calculations, and these were quite helpful in resolving ambiguities in the structural fit analysis, and providing some fixed parameters for the structural analysis. The results of the least squares and the calculations indicate that the carbon atoms of the Cp groups for ferrocenecarboxaldehyde are in an eclipsed conformation in the ground vibrational state.
Electron-impact ionization of silicon tetrachloride (SiCl4)
Authors: Basner R. , Gutkin M. , Mahoney J. , Tarnovsky V. , Deutsch H. , Becker K.
Published: August 2005

We measured absolute partial cross sections for the formation of various singly charged and doubly charged positive ions produced by electron impact on silicon tetrachloride (SiCl4) using two different experimental techniques, a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam apparatus. The energy range covered was from the threshold to 900eV in the TOF-MS and to 200eV in the fast-neutral-beam apparatus. The results obtained by the two different experimental techniques were found to agree very well (better than their combined margins of error). The SiCl3+ fragment ion has the largest partial ionization cross section with a maximum value of slightly above 6×10−20m2 at about 100eV. The cross sections for the formation of SiCl4+, SiCl+, and Cl+ have maximum values around 4×10−20m2. Some of the cross-section curves exhibit an unusual energy dependence with a pronounced low-energy maximum at an energy around 30eV followed by a broad second maximum at around 100eV. This is similar to what has been observed by us earlier for another Cl-containing molecule, TiCl4 [R. Basner, M. Schmidt, V. Tamovsky, H. Deutsch, and K. Becker, Thin Solid Films 374 291 (2000)]. The maximum cross-section values for the formation of the doubly charged ions, with the exception of SiCl3++, are 0.05×10−20m2 or less. The experimentally determined total single ionization cross section of SiCl4 is compared with the results of semiempirical calculations.
Double-pulse machining as a technique for the enhancement of material removal rates in laser machining of metals
Authors: Forsman A. C. , Banks P. S. , Perry M. D. , Campbell E. M. , Dodell A. L. , Armas M. S.
Published: August 2005

Several nanosecond 0.53-μm laser pulses separated by several tens of nanoseconds have been shown to significantly enhance (three to ten times) material removal rates while minimizing redeposition and heat-affected zones. Economic, high-quality, high-aspect ratio holes (>10:1) in metals are produced as a result. A phenomenological model whereby the second laser pulse interacts with the ejecta produced by the first laser pulse and in close proximity to the material surface is consistent with the observations. Incident laser wavelengths of 1.05 and 0.35 μm also benefit from this pulse format.
Effects of buffer layer and substrate temperature on the surface morphology, the domain structure and magnetic properties of c-axis-oriented Nd2Fe14B films
Authors: Chen S. L. , Liu W. , Chen C. L. , Zhang Z. D.
Published: August 2005

Anisotropic Nd–Fe–B thin films with c-axis texture are fabricated by dc magnetron sputtering on heated Si substrate. The influence of Ti or Mo buffer layer thickness and substrate temperature on the surface morphology, the domain structure and the magnetic properties are investigated and compared for the Nd–Fe–B films. It is found that the morphology of the surface strongly depends on the thickness of the buffer layer. A rough surface is observed if there is no buffer layer between the substrate and Nd–Fe–B layer or the buffer layer is too thick. Mo shows to be the better candidate for the buffer layer for its perfect lattice match with the Nd–Fe–B layer. The best values for the maximum energy products are 11.9 and 14.8MGOe for the Nd–Fe–B films with Ti and Mo buffer layers, respectively.
Reliability analysis method for low-k interconnect dielectrics breakdown in integrated circuits
Authors: Haase Gaddi S. , Ogawa Ennis T. , McPherson Joe W.
Published: August 2005

The shrinking line-to-line spacing in interconnect systems for advanced integrated circuit technology and the use of lower dielectric constant materials create the need for tools to evaluate the interconnect dielectric reliability. A multi-temperature, dual-ramp-rate voltage-ramp-to-breakdown methodology is presented and used here to extract important dielectric-breakdown parameters accurately for minimum-spaced metal lines. It is demonstrated that correction for the true minimum line-to-line spacing distributions become critically important and that the minimum spacing can be extracted electrically and compares favorably to electron microscopy cross sections. The spacing-corrected breakdown field distributions, at various temperatures, for the organosilicate material tested, indicated a very low apparent zero-field activation energy (0.14±0.02eV) and an apparent field-acceleration parameter γ=4.1±0.3cm∕MV that has little or no temperature dependence. Constant-voltage time-dependent-dielectric-breakdown measurements were found to agree well with these observations.
Displacement sensing using evanescent tunneling between guided resonances in photonic crystal slabs
Authors: Suh Wonjoo , Solgaard Olav , Fan Shanhui
Published: August 2005

Using both analytic theory and first-principles finite-difference time-domain simulations, we introduce a displacement sensing mechanism using photonic crystal slabs coupled in the near-field regime. In this regime, the operating characteristics are completely different from conventional resonant optical sensors, and high sensitivity can be obtained without the use of highly reflecting mirrors. This enables high displacement sensitivity combined with low sensitivity to wavelength and to structural disorders, thereby simplifying operation and fabrication of high-sensitivity displacement sensors.
In situ spectroscopic ellipsometry study of GaN nucleation layer growth and annealing on sapphire in metal-organic vapor-phase epitaxy
Authors: Schmidtling T. , Pohl U. W. , Richter W. , Peters S.
Published: August 2005

Deposition and annealing of GaN nucleation layers (NLs) on sapphire during metal-organic vapor-phase epitaxy were studied using in situ spectroscopic ellipsometry. Growth was found to start with a remarkable delay after precursor switching through the formation of an initial roughness and a subsequent coalescence, which leads to the formation of a dense nucleation layer. The initial growth rate strongly depends on growth environment pretreatment and decreases if the susceptor is coated with GaN from preceding growth runs. The evaluation of the optical properties of as-grown NLs shows that the growth rate strongly affects the crystalline quality of the NL. At decreased growth rate the band gap E0 appears more pronounced with values indicating a predominantly cubic structure. During annealing above 800 °C a structural change is observed: the thickness of the dense part of the NL increases on expense of the rough part, maintaining an almost constant total layer thickness. Simultaneously the formation of the hexagonal phase in the NL occurs. The process is accomplished at about 950 °C and is followed by a desorption of the NL at a rate of 1.4 nm∕s in ammonia and nitrogen ambient at 1060 °C. The observations are confirmed by ex situ atomic force microscopy and scanning electron microscopy measurements.
Fullerenelike arrangements in carbon nitride thin films grown by direct ion beam sputtering
Authors: Gago R. , Abrasonis G. , Mücklich A. , Möller W. , Czigány Zs. , Radnóczi G.
Published: August 2005

Carbon nitride (CNx) thin films were grown by direct N2∕Ar ion beam sputtering of a graphite target at moderate substrate temperatures (300–750K). The resulting microstructure of the films was studied by high-resolution transmission electron microscopy. The images showed the presence of curved basal planes in fullerenelike arrangements. The achievement and evolution of these microstructural features are discussed in terms of nitrogen incorporation, film-forming flux, and ion bombardment effects, thus adding to the understanding of the formation mechanisms of curved graphitic structures in CNx materials.
Resonant Raman study of confined Se single helix and Se8 rings
Authors: Li I. L. , Ruan S. C. , Li Z. M. , Zhai J. P. , Tang Z. K.
Published: August 2005

Electron-phonon coupling in Se species confined in the nanoporous matrix has been investigated by using resonant Raman spectra performed with several different laser lines from deep blue to near infrared. The spectra strongly depend on the energies of the excitation laser lines. The one-phonon symmetric A1 modes for Se single helix and Se8 rings are enhanced in the vicinity of their absorption bands. Detailed analysis shows that the Raman band in the high-frequency range of 450–550cm−1 is composed of three individual second-order Raman bands for the confined Se species. These two-phonon Raman shifts occur at twice the frequency shift of the first-order Raman lines, and their intensities are also enhanced when the excitation laser energy matches an electronic transition in Se nanospecies.
Impact of Ge on integration of HfO2 and metal gate electrodes on strained Si channels
Authors: Lin Yanxia , Öztürk Mehmet C. , Chen Bei , Rhee Se Jong , Lee Jack C. , Misra Veena
Published: August 2005

Tensile-strained Si epitaxial layers (7.5nm–17nm) were grown on relaxed Si0.5Ge0.5 virtual substrates by ultrahigh-vacuum rapid thermal chemical vapor deposition. Metal-oxide-silicon capacitors were fabricated with SiO2 or HfO2 as gate dielectrics and Ru–Ta alloy or TaN as the metal gate electrodes. The results indicate that the interface trap density (Dit) increased as the strained silicon thickness decreased, which was attributed to the presence of Ge in the strained Si layer. Higher Dit was observed with SiO2 which may be due to Si consumption during oxidation, leading to a higher density of Ge at the interface. Leakage current density (Jg) was also observed to increase with increasing strained silicon thickness. This trend of increasing Dit and Jg with decreasing strained silicon thickness did not change after rapid thermal annealing. Both Ru–Ta and TaN gate electrodes were found to exhibit as good a performance on strained Si as on bulk Si.
Surface plasmon enhanced spontaneous emission rate of InGaN∕GaN quantum wells probed by time-resolved photoluminescence spectroscopy
Authors: Okamoto Koichi , Niki Isamu , Scherer Axel , Narukawa Yukio , Mukai Takashi , Kawakami Yoichi
Published: August 2005

We observed a 32-fold increase in the spontaneous emission rate of InGaN/GaN quantum well (QW) at 440 nm by employing surface plasmons (SPs) probed by time-resolved photoluminescence spectroscopy. We explore this remarkable enhancement of the emission rates and intensities resulting from the efficient energy transfer from electron-hole pair recombination in the QW to electron vibrations of SPs at the metal-coated surface of the semiconductor heterostructure. This QW-SP coupling is expected to lead to a new class of super bright and high-speed light-emitting diodes (LEDs) that offer realistic alternatives to conventional fluorescent tubes.
Phonon-like dispersion curves of magnetoinductive waves
Authors: Sydoruk O. , Zhuromskyy O. , Shamonina E. , Solymar L.
Published: August 2005

The dispersion characteristics of magnetoinductive (MI) waves for a one-dimensional array of metamaterial elements are investigated for the case where the element properties vary in a bi-periodic manner. It is shown that, by this means (analogously to acoustic waves in a solid), a variety of dispersion curves can be obtained including those displaying an “optical” branch. The flexibility of the metamaterial design makes it possible to apply this approach for obtaining specified dispersion properties. A design permitting parametric amplification is proposed.
Selective oxidation of AlInN layers for current confinement in III–nitride devices
Authors: Dorsaz J. , Bühlmann H.-J. , Carlin J.-F. , Grandjean N. , Ilegems M.
Published: August 2005

Highly selective oxidation of an AlInN interlayer buried in a GaN matrix is demonstrated. This technique was successfully applied to form current apertures in III-nitride light-emitting diodes (LEDs). GaN LEDs were grown by metal-organic vapor phase epitaxy with a lattice-matched AlInN layer inserted in the n-doped region of the device. Mesas were etched by Cl2∕Ar reactive ion etching to give access to the AlInN sidewalls. The sample was then oxidized anodically in a nitrilotriacetic acid solution. Using this technique, the AlInN layer was oxidized laterally up to 22μm deep while the surrounding GaN layers were kept unaffected. It was subsequently demonstrated that the oxidized AlInN layers are insulating and are therefore suitable for lateral current confinement in optoelectronic devices.
Hyperphosphorylation regulates the activity of SREBP1 during mitosis
Authors: Bengoechea-Alonso Maria T. , Punga Tanel , Ericsson Johan
Published: August 2005

The sterol regulatory element-binding protein (SREBP) family of transcription factors controls the biosynthesis of cholesterol and other lipids, and lipid synthesis is critical for cell growth and proliferation. We were, therefore, interested in the expression and activity of SREBPs during the cell cycle. We found that the expression of a number of SREBP-responsive promoter-reporter genes were induced in a SREBP-dependent manner in cells arrested in G
2
/M. In addition, the mature forms of SREBP1a and SREBP1c were hyperphosphorylated in mitotic cells, giving rise to a phosphoepitope recognized by the mitotic protein monoclonal-2 (MPM-2) antibody. In contrast, SREBP2 was not hyperphosphorylated in mitotic cells and was not recognized by the MPM-2 antibody. The MPM-2 epitope was mapped to the C terminus of mature SREBP1, and the mitosis-specific hyperphosphorylation of SREBP1 depended on this domain of the protein. The transcriptional and DNA-binding activity of SREBP1 was enhanced in cells arrested in G
2
/M, and these effects depended on the C-terminal domain of the protein. In part, these effects could be explained by our observation that mature SREBP1 was stabilized in G
2
/M. In agreement with these observations, we found that the synthesis of cholesterol was increased in G
2
/M-arrested cells. Thus, our results demonstrate that the activity of mature SREBP1 is regulated by phosphorylation during the cell cycle, suggesting that SREBP1 may provide a link between lipid synthesis, proliferation, and cell growth.
Interferon-α and -β differentially regulate osteoclastogenesis: Role of differential induction of chemokine CXCL11 expression
Authors: Coelho Luiz F. Leomil , de Freitas Almeida Gabriel Magno , Mennechet Franck J. D. , Blangy Anne , Uzé Gilles
Published: August 2005

In humans, type I interferon (IFN) is a family of 17 cytokines, among which the α subtypes and the β subtype are differentially expressed. It has been suggested that IFN-β activates a specific signaling cascade in addition to those activated by all type I IFNs. Nevertheless, no true biological relevance for a differential activity of α and β IFN subtypes has been identified so far. Because type I IFNs are critical for the regulation of osteoclastogenesis in mice, we have compared the effect of IFN-α2 and IFN-β on the differentiation of human monocytes into osteoclasts. Primary monocytes undergoing osteoclastic differentiation are highly and equally sensitive to both α2 and β IFNs as determined by measuring the induction levels of several IFN-stimulated genes. However, IFN-β was 100-fold more potent than the α2 subtype at inhibiting osteoclastogenesis. Expression profiling of the genes differentially regulated by IFN-α2 and IFN-β in this cellular system revealed the chemokine
CXCL11
as the only IFN-induced gene differentially up-regulated by IFN-β. We show that recombinant CXCL11 by itself inhibits osteoclastic differentiation. These results indicate that autocrine-acting CXCL11 mediates, at least in part, the regulations of osteoclastogenesis by type I IFNs.
NF-Ya activates multiple hematopoietic stem cell (HSC) regulatory genes and promotes HSC self-renewal
Authors: Zhu Jiang , Zhang Yi , Joe Gerard J. , Pompetti Richard , Emerson Stephen G.
Published: August 2005

Hematopoietic stem cell (HSC) self-renewal and differentiation are influenced through multiple pathways, including homeobox transcription factors, signaling through β-catenin and Notch-1, telomerase, and p27. How these multiple pathways interact and are orchestrated is currently unknown. We now report that NF-Ya, the regulatory and DNA-binding subunit of the trimeric transcription factor NF-Y, plays a central, integrating role in several of these HSC pathways. NF-Ya is preferentially expressed in HSC-enriched bone marrow subpopulations, and NF-Ya mRNA rapidly declines with HSC differentiation. Overexpression of NF-Ya in primitive hematopoietic cells activates the transcription of multiple HOX4 paralogs, as well as Notch-1, LEF-1, and telomerase RNA. HSCs overexpressing NF-Ya are biased toward primitive hematopoiesis
in vitro
and show strikingly increased
in vivo
repopulating abilities after single or sequential bone marrow transplantation. Thus, NF-Ya is a potent cellular regulator of HSC self-renewal.
Protein-folding landscapes in multichain systems
Authors: Cellmer Troy , Bratko Dusan , Prausnitz John M. , Blanch Harvey
Published: August 2005

Computational studies of proteins have significantly improved our understanding of protein folding. These studies are normally carried out by using chains in isolation. However, in many systems of practical interest, proteins fold in the presence of other molecules. To obtain insight into folding in such situations, we compare the thermodynamics of folding for a Miyazawa–Jernigan model 64-mer in isolation to results obtained in the presence of additional chains. The melting temperature falls as the chain concentration increases. In multichain systems, free-energy landscapes for folding show an increased preference for misfolded states. Misfolding is accompanied by an increase in interprotein interactions; however, near the folding temperature, the transition from folded chains to misfolded and associated chains is entropically driven. A majority of the most probable interprotein contacts are also native contacts, suggesting that native topology plays a role in early stages of aggregation.
Arabidopsis
ARGONAUTE1 is an RNA Slicer that selectively recruits microRNAs and short interfering RNAs
Authors: Baumberger N. , Baulcombe D. C.
Published: August 2005

ARGONAUTE (AGO) RNA-binding proteins are involved in RNA silencing. They bind to short interfering RNAs (siRNAs) and microRNAs (miRNAs) through a conserved PAZ domain, and, in animals, they assemble into a multisubunit RNA-induced silencing complex (RISC). The mammalian AGO2, termed Slicer, directs siRNA- and miRNA-mediated cleavage of a target RNA. In
Arabidopsis
, there are 10 members of the
AGO
family, and the
AGO1
protein is potentially the Slicer component in different RNA-silencing pathways. Here, we show that AGO1 selectively recruits certain classes of short silencing-related RNA. AGO1 is physically associated with miRNAs, transacting siRNAs, and transgene-derived siRNAs but excludes virus-derived siRNAs and 24-nt siRNAs involved in chromatin silencing. We also show that AGO1 has Slicer activity. It mediates the
in vitro
cleavage of a
mir165
target RNA in a manner that depends on the sequence identity of amino acid residues in the PIWI domain that are predicted by homology with animal Slicer-competent AGO proteins to constitute the RNase catalytic center. However, unlike animals, we find no evidence that AGO1 Slicer is in a high molecular weight RNA-induced silencing complex. The Slicer activity fractionates as a complex of ≈150 kDa that likely constitutes the AGO1 protein and associated RNA without any other proteins. Based on sequence similarity, we predict that other
Arabidopsis
AGOs might have a similar catalytic activity but recruit different subsets of siRNAs or miRNAs.
Bifurcation discovery tool
Authors: Chickarmane Vijay , Paladugu Sri R. , Bergmann Frank , Sauro Herbert M.
Published: August 2005

Motivation: Biochemical networks often yield interesting behavior such as switching, oscillation and chaotic dynamics. This article describes a tool that is capable of searching for bifurcation points in arbitrary ODE-based reaction networks by directing the user to regions in the parameter space, where such interesting dynamical behavior can be observed.

Results: We have implemented a genetic algorithm that searches for Hopf bifurcations, turning points and bistable switches. The software is implemented as a Systems Biology Workbench (SBW) enabled module and accepts the standard SBML model format. The interface permits a user to choose the parameters to be searched, admissible parameter ranges, and the nature of the bifurcation to be sought. The tool will return the parameter values for the model for which the particular behavior is observed.

Availability: The software, tutorial manual and test models are available for download at the following website: http:/www.sys-bio.org/ under the bifurcation link. The software is an open source and licensed under BSD.

Contact:  vijay_chickarmane@kgi.edu
The sign of the swan in Proust's
A la recherche du temps perdu
Authors: Watt Adam
Published: August 2005

This article takes as its starting point Proust and Mallarmé's shared conception of the associative ‘music’ which connects words when considered as signs in literature. It examines the inscription of this in
A la recherche du temps perdu
, concentrating on the homophonic signifiers ‘cygne’, ‘signe’, ‘Swann’ and the English ‘swan’. By demonstrating the complexity of swan references in the novel, following the work of Gilles Deleuze, this article shows how Proust exploits his readers' desire to find satisfying knots at the end of narrative threads. The swan is a motif whose insistent return suggests a unifying pattern, the existence or validity of which is neither confirmed nor denied by the text. Albertine's depiction as a swan represents a figuring which juggles identity and sexuality with blankness, whiteness and the accessibility of the semiotic ‘si(cy)gne’. Proust's swans lead us to Tchaikovsky, to Mallarmé and to Wagner. Ultimately the focus is on the texture of Proust's prose, the subtle ‘rhythms’ to which one is alerted by the smallest of details, by words and their sound echoes, and the associations that sound throughout the novel like an ‘air ou chant sous le texte’.
From the sacred conspiracy to the unavowable community: Bataille, Blanchot and Laure's
Le sacré
Authors: Sweedler Milo
Published: August 2005

This article analyses the importance of the writings of Laure (pseudonym of Colette Peignot) for Georges Bataille's communitarian projects of the late 1930s and early 1940s and for Maurice Blanchot's interpretation of these projects. Through readings of theoretical essays by Bataille, his annotated edition of Laure's
Le Sacré
(published illegally in 1939, only months after the author's death, and distributed clandestinely to a restricted group of readers), and Blanchot's
La Communauté inavouable
, I argue that Laure's book functions as the literary analogue to two avant-garde communities in which Laure and Bataille were involved — Acéphale and the College of Sociology — and that this same book is at the heart of the unavowable community theorized by Blanchot.

Bataille's justification for publishing Laure's writings echoes the very terms he uses to describe his group projects of the late 1930s: community, communication, the sacred, sacrifice. I argue that, in publishing and distributing her book, Bataille effectively sanctifies Laure, turning her into a martyr for the community. However, in contrast to Acéphale and the College of Sociology, the community founded over Laure's dead body was a virtual community: one based on the members' solitary experiences of reading. Laure becomes the figurehead of an unavowable community, as Blanchot's locution would have it.
Reconstructing Byzantine Constantinople: intercession and illumination at the court of Philippe le Bon
Authors: Devereaux Rima
Published: August 2005

This article discusses three texts produced for Philippe le Bon, Duke of Burgundy, in the years following the fall of Constantinople, capital of the Byzantine Empire, to the Ottoman Turks in 1453. These texts deal with the West's painful experience of the postcolonial frontier between itself and Constantinople in the wake of this event. I look at the theme of intercession in two verse laments, Guillaume Dufay's ‘Lamentatio Sanctae Matris Ecclesiae Constantinopolitanae’ (1454), and Jean Molinet's ‘Complainte de Grèce’ (1464). I compare the use of this theme with the role of illumination in a manuscript produced for the Duke in around 1458 (Paris, Bibliothèque Nationale, fonds français, 9087), and containing Bertrandon de la Broquière's
Voyage d'Outremer
, a prose account of a journey to the Orient. The theme of the Church (
Ecclesia
) as intercessor in the laments, and the representation of manuscript patronage and of the cities of Jerusalem and Constantinople in the miniatures of the
Broquière
compilation, serve to bring the fallen Byzantium to the West in textual form. This reconstruction of Byzantine Constantinople may be viewed in theological terms, or it may point to the recovery of the city through the crusade projects of Philippe le Bon.
Thioredoxin‐like domain of human κ class glutathione transferase reveals sequence homology and structure similarity to the θ class enzyme
Authors: Li Jie , Xia Zongxiang , Ding Jianping
Published: August 2005

Glutathione transferases (GSTs) are a superfamily of enzymes that play a vital functional role in the cellular detoxification process. They catalyze the conjugation of the thiol group of glutathione (GSH) to the electrophilic groups of a wide range of hydrophobic substrates, leading to an easier removal of the latter from the cells. The κ class is the least studied one among various classes within the superfamily. We report here the expression, purification, and crystal structure of human κ class GST (hGSTK), which has been determined by the multiple‐isomorphous replacement method and refined to 1.93 Å resolution. The overall structure of hGSTK is similar to the recently reported structure of κ class GST from rat mitochondrion. Each subunit of the dimeric hGSTK contains a thioredoxin (TRX)‐like domain and a helical domain. A molecule of glutathione sulfinate, an oxidized product of GSH, is found to bind at the G site of each monomer. One oxygen atom of the sulfino group of GSF forms a hydrogen bond with the hydroxyl group of the catalytic residue Ser16. The TRX‐like domain of hGSTK shares 19% sequence identity and structure similarity with human θ class GST, suggesting that the κ class of GST is more closely related to the θ class enzyme within the GST superfamily. The structure of the TRX‐like domain of hGSTK is also similar to that of glutathione peroxidase (GPx), implying an evolutionary relationship between GST and GPx.