bluuebunny/crossref_metadata_2025 huggingface dataset:
Proton exchange and diffusion in LiNbO3 using inductance coupled high density plasma
Authors: Ren Z. , Heard P. J. , Yu S.
Published: August 2007

In this article, the underlying physical mechanisms of proton exchange (PE) in LiNbO3 with inductance coupled plasma (ICP) as proton source have been investigated according to quantitative calculations and simulations. It is shown that a high proton density layer near the sample surface acts as the source for proton diffusion. Experimentally, effects of parameters including working pressure, rf bias power, and ICP power are investigated by measurement of the PE depths with secondary ion mass spectrometry. And the variation of PE results has been linked to fundamental plasma characteristics such as ion density and ion flux through the variation in the measured dc self-bias values. A reproducible proton-exchange efficiency of 660nm∕h has been obtained at a relatively low sample temperature of 170°C and working pressure of 8mTorr, with high sample quality.
Synthesis of carbon nanotubes: Controlled fabrication of intraconnects
Authors: Katz D. , Lee S. W. , Lopez D. , Kornblit A. , Grebel H.
Published: August 2007

The authors have successfully fabricated carbon nanotubes bridges (intraconnects) between predetermined layouts of metal tip electrodes, taking advantage of the tips as leading catalytic points. Overall, the authors have demonstrated a yield of 15%–30% depending on the process parameters and electrode layout. They used two deposition methods: chemical vapor deposition (CVD) and plasma enhanced CVD (PECVD). Bridges could be fabricated with only CVD. The authors used carbon monoxide (CO) for the CVD process; the PECVD, however, required a mixture of CO and H2. Ethanol was successfully used with both deposition methods.
Influence of field emission on agglomerated carbon nanotubes in pastes
Authors: Lee Yang Doo , Lee Hyeon Jae , Lee Yun-Hi , Ju Byeong-Kwon
Published: August 2007

The authors have studied the modification of surface morphologies of screen-printed carbon nanotube (CNT) film by a liquid pretreatment and the agglomeration influence of CNT emitters. Liquid pretreatments before and after heat treatment are efficient as a removal process for organic binders for the improvement of field emission. In addition, this method enables to entangle an emitter to free individual standing CNTs.
Adhesion between template materials and UV-cured nanoimprint resists
Authors: Houle F. A. , Guyer Eric , Miller D. C. , Dauskardt Reinhold
Published: August 2007

Defects in polymeric lithographic stencils fabricated by the UV-cured nanoimprint technique result from fundamental surface interactions between template and resist in addition to the presence of particles and contaminants. Repeated and molecularly clean separations of the template from the cured resist are a requirement for successful application of the imprint method yet little is understood about their dependence on interfacial physics and chemistry. The process of interfacial separation of several model acrylate nanoimprint resist formulations cured in contact with clean (no release treatment) and release-treated silica glass surfaces has been quantitatively investigated. The results show that interfacial fracture energies are resist formulation dependent, that the resist-release layer systems studied are not chemically stable and that the release process is more complex than simple fracture at a glass-organic interface.
Functionalization and characterization of InAs and InP surfaces with hemin
Authors: Garcia Michael A. , Losurdo Maria , Wolter Scott D. , Kim Tong-Ho , Lampert W. V. , Bonaventura Joseph , Bruno Giovanni , Giangregorio Maria , Brown April
Published: August 2007

Chemical functionalization of hemin molecules onto InAs and InP is reported. X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and spectroscopic ellipsometry (SE) analyses are used to characterize the III-V surfaces. One notable feature of the C 1s core level spectra is a peak at ∼284eV observed for the functionalization chemistries, which is attributed to CN bonding within the porphyrin molecule. This is corroborated by the observation of N 1s, Fe 2p, and other distinguishable chemical bonding peaks. For example, in the As 3d and P 2p core levels, –COOH bonding is observed to the As and P anion in the InAs and InP samples, respectively, which implies chemisorption of the functional groups to the material surfaces. Another result of the XPS analysis is the impact of the surface functional group on the electronic state of the surface causing upward band bending of the valence band maximum, indicating surface charge transfer as explored in previous work [Garcia et al., Appl. Phys. Lett. 88, 013506 (2006)]. SE analysis on the functionalization process provides data for the effect of hemin and benzoic acid solution concentrations. The authors discuss the dependence of the band bending, surface coverage, and hemin layer thickness as determined by XPS and SE.
Atomic structure of Si(5512)-2×1: Confirmation of the structural model having two kinds of chains through homoepitaxy at 550°C
Authors: Kim Hidong , Li Huiting , Seo Jae M.
Published: August 2007

Recent empty-state scanning tunneling microscopy (STM) images of Si(5512)-2×1 have shown that this surface consists of four types of one-dimensional structures such as honeycomb (H) chain, π-bonded (π) chain, dimer-adatom (D-A) row, and tetramer (T) row. To confirm this revised structural model of the Si(5512)-2×1 surface, the authors performed homoepitaxy on the reconstructed Si(5 5 12) surface held at 550°C and studied the results by STM. Under equilibrium at 550°C there exists three kinds of phases composed of (225), D(337), T(337), and (112) subunits. These subunits consist of only two commutable rows, D-A and T rows, as well as two commutable chains, H and π chains. Mutual transformations among three phases by means of additional Si atoms are well explained by a new structural model having only two kinds of chains.
Magnetostructure of MnAs on GaAs revisited
Authors: Bauer E. , Belkhou R. , Cherifi S. , Locatelli A. , Pavlovska A. , Rougemaille N.
Published: August 2007

The ferromagnetic to nonferromagnetic (α-β) phase transition in epitaxial MnAs layers on GaAs(100) is studied by x-ray magnetic circular dichroism and x-ray magnetic linear dichroism photoemission electron microscopy in order to elucidate the nature of the controversial nonferromagnetic state of β-MnAs. In the coexistence region of the two phases the β phase shows a clear XMLD signal characteristic of antiferromagnetism. The nature and the possible causes of the elusiveness of this magnetic state are discussed.
Analysis of local carrier modulation in InAs semiconductor nanowire transistors
Authors: Zhou X. , Dayeh S. A. , Wang D. , Yu E. T.
Published: August 2007

The authors have used scanning gate microscopy combined with numerical simulations to analyze local carrier and current modulation effects in InAs semiconductor nanowires grown by metal-organic chemical vapor deposition. Measurements of current flow in the nanowire as a function of probe tip position, at both high and low drain bias, reveal that carrier and current modulation is strongest when the probe tip is near the source and drain nanowire contacts, and decreases at greater tip-contact distances. The measured transconductance is approximately 80% greater near the source contact for high drain bias condition and 120% greater near the drain contact for low drain bias condition, respectively, than at the center of the nanowire. Numerical simulations for different tip positions relative to the metal contact confirm that carrier modulation should be stronger when the tip is closer to the source or drain contact than at the center of the wire, consistent with the experimental measurements.
Atomic ordering and interlayer diffusion of Co2FeSi films grown on GaAs(001) studied by transmission electron microscopy
Authors: Hashimoto M. , Trampert A. , Herfort J. , Ploog K. H.
Published: August 2007

The influence of the growth temperature on the atomic ordering and interlayer diffusion of Heusler alloy Co2FeSi films grown on GaAs(001) substrates has been studied using high-resolution transmission electron microscopy. The Co2FeSi∕GaAs(001) films grown below 200°C show a coexistence of the Heusler-type L21 phase and the disordered B2 phase, which can be seen mainly near the interface, due to the low growth temperature. This phase coexistence can affect the spin polarization of the Co2FeSi layer near the interface. On the other hand, the film grown at an elevated temperature of 300°C shows a uniformly atomically ordered L21 phase, indicating that 300°C is approximately the transition temperature to the atomically ordered L21 structure. The elevation of the growth temperature, however, results in the formations of interfacial compounds above 250°C, which could be detrimental to the efficient electrical spin injection.
Glass nanostructures fabricated by soft thermal nanoimprint
Authors: Peroz C. , Heitz C. , Barthel E. , Søndergård E. , Goletto V.
Published: August 2007

A one-step, fast, and potential low cost process has been developed to fabricate silicalike glass nanostructures by combining sol-gel chemistry and thermal nanoimprint. An inorganic-organic sol-gel thin film is patterned at low pressure and temperature with flexible stamps. Various geometries are achieved with a patterning resolution of about 150nm and pattern aspect ratio higher than 4. To obtain pure silica structures a thermal annealing at high temperatures is required. During this step most of the structures collapse due to fluidization of the sol-gel material. It is shown that if a suitable condensation level is obtained during imprinting, the nanostructures are thermally stable.
Nanoimprint fabrication of polymer cell substrates with combined microscale and nanoscale topography
Authors: Eliason Marcus T. , Charest Joseph L. , Simmons Blake A. , García Andrés J. , King William P.
Published: August 2007

This article reports the fabrication of polymer cell culture substrates with combined microscale and nanoscale topography. The substrates were fabricated using two embossing steps, where the microscale features were formed in the first embossing step and then the nanoscale features were formed in the second. The first embossing produced grooves either 2 or 10μm wide, while the second embossing produced grooves 50nm wide on a 150nm pitch. The 50nm grooves were either parallel to or perpendicular to the microgrooves. Osteoblast-like cells were seeded onto the substrates and cell alignment was analyzed using immunofluorescence and scanning electron microscopy. There was a significant decrease in alignment of cells on substrates with nanogrooves perpendicular to microgrooves as compared to those with parallel nanogrooves. This research enables cell response to be examined to complex combinations of microscale and nanoscale topography.
Capacitive and analytical approaches for the analysis of field emission from carbon nanotubes in a sphere-to-plane diode
Authors: Boscolo I. , Cialdi S. , Fiori A. , Orlanducci S. , Sessa V. , Terranova M. L. , Ciorba A. , Rossi M.
Published: August 2007

In this article the authors present a study of the emitting behavior of carbon nanotube cathodes in a sphere-to-plane field emission diode. A capacitive technique is proposed for the measurement of the anode-cathode distance as well as an innovative analytical procedure for the evaluation of the emitting area. Both anode-cathode distance and emitting area are essential parameters for the analysis of field emission experiments, the interpretation of results, and the extraction of technologically relevant data. Such parameters allow them to find out the values of turn on fields, current density, and field enhancement factor through the measurement of the emitted current versus applied voltage. Emission tests on single wall carbon nanotube samples with different morphologies have been performed in order to test the procedures and to compare data relative to samples with different morphologies.
Conformal metal thin-film coatings in high-aspect-ratio trenches using a self-sputtered rf-driven plasma source
Authors: Ji L. , Kim J.-K. , Ji Q. , Leung K.-N. , Chen Y. , Gough R. A.
Published: August 2007

A thin-film coating system has been developed for the deposition of both conductive and insulating materials. The system employs a radio-frequency (rf)-discharge plasma source with four straight rf antennas, which is made of or covered with the deposition material, thus serving simultaneously as a sputtering target. The average deposition rate of the copper thin film can be as high as 500nm∕min when operated under continuous-wave mode. Film properties under different operating conditions (gas pressure and rf power) have been investigated experimentally. Three thin-film coating schemes have been developed, one of which has been demonstrated to be suitable for conformal deep-trench coating. Conformal coating over trenches of high-aspect ratio (>6:1) has been demonstrated at both micron and submicron scales.
Electrical characterization of Pt∕AlGaN∕GaN Schottky diodes grown using AlN template and their application to hydrogen gas sensors
Authors: Miyoshi Makoto , Kuraoka Yoshitaka , Asai Keiichiro , Shibata Tomohiko , Tanaka Mitsuhiro , Egawa Takashi
Published: August 2007

Pt Schottky diodes were fabricated on high-crystal-quality Al0.2Ga0.8N∕GaN epitaxial films grown using epitaxial AlN/sapphire template (AlN template), and their current transport characteristics were measured and analyzed. It was confirmed that reverse leakage currents in Schottky diodes formed on AlN template were drastically reduced compared with samples on sapphire formed with a low-temperature buffer layer. The current transport characteristics in Schottky diodes formed on AlN template were found to be almost explicable using the thermoionic emission and tunneling current components, unlike with samples formed on sapphire. This indicates that the amount of unintentional impurity levels near the surfaces is extremely small for those high-crystal-quality Schottky diodes. Hydrogen-sensing characteristics were also investigated for a Pt∕AlGaN∕GaN Schottky diode formed on AlN template. The diode sensor exhibited sufficient changes in the reverse current even under exposure to extremely slight H2 concentration of 50ppm and exhibited clear reversible responses. These current changes seemed to be due to the reduction of the Schottky barrier height with H2 exposure.
Dual-metal-gate-integration complementary metal oxide semiconductor process scheme using Ru positive-channel metal oxide semiconductor and TaC negative-channel metal oxide semiconductor gate electrodes
Authors: Chang Wen-Tung , Hsieh Tsung-Eong , Lee Chung-Ju
Published: August 2007

This article presents the development of a wet removal process on the integration of complementary metal oxide semiconductor (CMOS) dual metals with Ru for positive-channel metal oxide semiconductor and TaC for negative-channel metal oxide semiconductor on high-k HfO2 gate dielectric. The integration scheme focused on the wet etching capability for the first metal and the selectivity control on the high-k dielectrics under the metal gate. Using the developed chemical, ceric ammonium nitrate and nitric acid mixture used for Ru metal removal and HfO2 treated with Ar∕O2 plasma by selective diluted hydrofluoric wet etching, a CMOS dual-metal-gate structure was achieved with satisfactory device fabrication.
Field emission from randomly oriented ZnO nanowires
Authors: Chang Yong-Qin , Chen Xi-Hong , Zhang Hong-Zhou , Qiang Wen-Jiang , Long Yi
Published: August 2007

Randomly oriented zinc oxide (ZnO) nanowires with different diameters were synthesized on a large scale on silicon substrates through a simple physical evaporation method. The nanowires exhibit stable and uniform electron field emission, and the turn-on field reduces with the diameter decreasing. The perfect field emission ability of the ZnO nanowires may be related to their rough surface and sharp curvature. Considering the efficient synthesis method and their excellent field emission characteristics, the authors expect that the randomly oriented ZnO nanowire films could have a promising industrial prospect as economic emitters for flat panel displays.
Polymer through-hole membrane fabricated by nanoimprinting using metal molds with high aspect ratios
Authors: Yanagishita Takashi , Nishio Kazuyuki , Masuda Hideki
Published: August 2007

Polymer through-hole membranes were fabricated by nanoimprinting using metal molds with high aspect ratios, which were prepared by a replication process using an anodic porous alumina template. The introduction of a two-layer structure of polymers and the selective removal of underlying polymer layer allows the formation of polymer through-hole membranes. The obtained polymer through-hole membranes will be used for various applications that require highly ordered hole array structures with sufficient chemical stability.
Multiplexed mass spectrometry for real-time sensing in a spatially programmable chemical vapor deposition reactor
Authors: Cai Yuhong , Henn-Lecordier Laurent , Rubloff Gary W. , Sreenivasan Ramaswamy , Choo Jae-Ouk , Adomaitis Raymond A.
Published: August 2007

Mass spectrometry has proven valuable in understanding and controlling chemical processes used in semiconductor fabrication. Given the complexity of spatial distributions of fluid flow, thermal, and chemical parameters in such processes, multipoint chemical sampling would be beneficial. The authors have designed and implemented a multiplexed mass spectrometric gas sampling system for real-time, in situ measurement of gas species concentrations at multiple locations in a spatially programmable chemical vapor deposition (SP-CVD) reactor prototype, where such chemical sensing is essential to achieve the benefits of a new paradigm for reactor design. The spatially programmable reactor, in which across-wafer distributions of reactant are programmable, enables (1) uniformity at any desired process design point, or (2) intentional nonuniformity to accelerate process optimization through combinatorial methods. The application of multiplexed mass spectrometric sensing is well suited to our SP-CVD design, which is unique in effectively segmenting the showerhead gas flows by using exhaust gas pumping through the showerhead for each segment. In turn, mass spectrometric sampling signals for each segment are multiplexed to obtain real-time signatures of reactor spatial behavior. Here the authors report results using inert gases to study the spatial distributions of species, validate SP-CVD reactor models, and lead to an understanding of fundamental phenomena associated with the reactor design. This forms the basis for using real-time mass spectrometry to drive process sensing, metrology, and control in such reactor systems.
Fermi gas energetics in low-dimensional metals of special geometry
Authors: Tavkhelidze Avto , Svanidze Vasiko , Noselidze Irakli
Published: August 2007

Changes in the metal properties caused by periodic indents in the metal surface were studied within the limit of quantum theory of free electrons. The authors show that due to destructive interference of de Broglie waves, some quantum states inside the low-dimensional metal become quantum mechanically forbidden for free electrons. Wave-vector density in k space is reduced dramatically. At the same time the number of free electrons does not change, as the metal remains electrically neutral. Because of the Pauli exclusion principle, some free electrons must occupy quantum states with higher wave numbers. The Fermi vector and Fermi energy of low-dimensional metal increase, and consequently, the work function decreases. In the experiment, the magnitude of the effect is limited by the roughness of the metal surface. A rough surface causes scattering of the de Broglie waves and compromises their interference. Recent experiments demonstrated a reduction of work function in thin metal films having periodic indents in the surface. Experimental results are in good qualitative agreement with the theory. This effect could exist in any quantum system comprising fermions inside a potential-energy box of special geometry.
Current spreading of III-nitride light-emitting diodes using plasma treatment
Authors: Lee Hsin-Ying , Pan Ke-Hao , Lin Chih-Chien , Chang Yun-Chorng , Kao Fu-Jen , Lee Ching-Ting
Published: August 2007

In this study, (CF4+O2) plasma is used to selectively treat the p-type GaN region underneath the bonding pad of the anode electrode of III-nitride light-emitting diodes (LEDs). A more uniform light emission distribution is observed in the far-field pattern of the plasma-treated devices and a 16% enhancement of the output intensity under the same biasing current is obtained. The maximum current that can be applied is also higher for the plasma-treated device. Not only does the plasma treatment of the p-GaN layer lead to a highly insulating region but also it does not degrade the device performance. Results from this study indicate that the plasma treatment is able to improve the current spreading of the III-nitride LEDs.
Enhanced electrical and structural properties of stacked AlON∕HfO2 gate oxides on p-type Si substrates
Authors: Choi Wonjoon , Lee Jonghyun , Yang Jungyup , Kim Juhyung , Hong Jinpyo
Published: August 2007

The authors systematically investigated the stacked HfO2 gate oxides by inserting an ultrathin AlON layer between the amorphous HfO2 gate oxide and the p-type Si substrate. The inserted AlON layer was prepared with a remote rf plasma treatment method in order to reduce the effect of the interfacial layer easily formed between the HfO2 gate oxide and Si substrate while the HfO2 gate oxide was directly deposited on the Si substrate. The combination measurements of x-ray photoemission spectroscopy and high resolution transmission electron microscopy for the AlON∕HfO2 gate oxide clearly confirmed a significant decrease in the thickness of the interfacial layer. This structural improvement of stacked AlON∕HfO2 gate oxides corresponded well to more enhanced electrical characteristics of leakage current density (10−3A∕cm2), C-V hysteresis (20mV), and dielectric constant (20.4) than those of single HfO2 gate oxide (10−2A∕cm2, 40mV, and 14.1) grown directly on Si substrate. Therefore, it is expected that the optimized insertion of an additional ultrathin AlON layer can provide the realization of a high quality channel layer in a metal-oxide-semiconductor field effect transistor.
Plasma-surface interactions of model polymers for advanced photoresists using C4F8∕Ar discharges and energetic ion beams
Authors: Engelmann S. , Bruce R. L. , Kwon T. , Phaneuf R. , Oehrlein G. S. , Bae Y. C. , Andes C. , Graves D. , Nest D. , Hudson E. A. , Lazzeri P. , Iacob E. , Anderle M.
Published: August 2007

Plasma based transfer of photoresist (PR) patterns into underlying films and substrates is basic to micro- and nanofabrication but can suffer from excessive surface and line edge roughness in the photoresist and resulting features. The authors have studied the interaction of a set of adamantyl methacrylate-based model polymers with fluorocarbon∕Ar discharges and energetic Ar+ ion beams. Through systematic variation of the polymer structure, the authors were able to clarify the contributions of several critical polymer components on the chemical and morphological modifications in the plasma environment. Etching rates and surface chemical and morphological changes for the model polymers and fully formulated 193 and 248nm photoresists were determined by ellipsometry, atomic force microscopy, time of flight static secondary ion mass spectrometry, and x-ray photoelectron spectroscopy. The polymer structure in the near surface region (∼10nm) of all materials is destroyed within the first seconds of exposure to a fluorocarbon∕Ar plasma. The plasma-induced changes include destruction of polymeric structure in the near surface region and oxygen and hydrogen loss along with fluorination. For the 193nm PR material, the initial densification of the near surface region was followed by the introduction of pronounced surface roughness. This change was not seen for 248nm PR processed under identical conditions. When comparing the responses of different polymer materials, the authors observed a strong dependence of plasma-induced surface chemical and morphological changes on polymer structure. In particular, the adamantane group of 193nm PR showed poor stability under plasma exposure. On the other hand, the plasma-induced changes for polymer resins with or without the low molecular weight chemicals required to make the photoresist system photoactive did not differ significantly. The behavior of the same materials during energetic argon ion beam bombardment was also investigated. No significant differences in etch yield and surface roughness evolution for the different materials were seen in that case.
Development of certified reference materials of ion-implanted dopants in silicon for calibration of secondary ion mass spectrometers
Authors: Simons D. S. , Downing R. G. , Lamaze G. P. , Lindstrom R. M. , Greenberg R. R. , Paul R. L. , Schiller S. B. , Guthrie W. F.
Published: August 2007

Certified reference materials have been developed for calibration of the concentrations of the most common dopants used in silicon semiconductor technology—boron, arsenic, and phosphorus. These materials consist of a single dopant species that is introduced into a silicon wafer by ion implantation. The certified dose (at.∕cm2) of the dopant species is used for calibration of dopant concentration measurements with secondary ion mass spectrometers. Certification measurements were carried out by nuclear analytical methods—neutron depth profiling for boron, instrumental neutron activation analysis for arsenic, and radiochemical neutron activation analysis for phosphorus. SRM 2137 contains a B10 implant with a certified dose of (1.018×1015±0.035×1015)at.∕cm2; SRM 2134 contains a As75 implant with a certified dose of (7.330×1014±0.028×1014)at.∕cm2; SRM 2133 contains a P31 implant with a certified dose of (9.58×1014±0.16×1014)at.∕cm2. Several examples demonstrate the improved interlaboratory agreement that is achievable in the measurement of unknown dopant concentrations and implanted doses when these reference materials are used for calibration by each laboratory.
EIGENENERGIES FOR THE RAZAVY POTENTIAL V(x) = (ζ cosh 2x-M)2 USING THE ASYMPTOTIC ITERATION METHOD
Authors: SOUS A. J.
Published: August 2007

By using the asymptotic iteration method, we have calculated numerically the eigenenergies En of Razavy potential V(x) = (ζ cosh 2x-M)2. The calculated eigenenergies are identical with known values in the literature. Finally, the non-quasi-exactly solvable eigenenergies of Razavy potential for the highest excited states are numerically determined. Some new results for arbitrary parameter M also presented.
NOTE ON NON-METRIC GRAVITY
Authors: BENGTSSON INGEMAR
Published: August 2007

We discuss a class of alternative gravity theories that are specific to four dimensions, do not introduce new degrees of freedom, and come with a physical motivation. In particular we sketch their Hamiltonian formulation and their relation with some earlier constructions.
EXISTENCE OF BLACK HOLES IN FRIEDMANN–ROBERTSON–WALKER UNIVERSE DOMINATED BY DARK ENERGY
Authors: LI ZHONG-HENG , WANG ANZHONG
Published: August 2007

We study the existence of black holes in a homogeneous and isotropic expanding Friedmann–Robertson–Walker (FRW) universe dominated by dark energy. We show that black holes exist in such a universe by considering some specific McVittie solutions, for which the FRW background satisfies the weak (but not the strong) energy condition.
VALIDITY OF EMPARAN–HOROWITZ-MYERS ARGUMENT IN HAWKING RADIATION INTO MASSLESS SPIN-2 FIELDS
Authors: JUNG EYLEE , PARK D. K.
Published: August 2007

The Hawking radiation for massless spin-2 fields is numerically studied when the spacetime background is (4+n)-dimensional Schwarzschild black hole phase. In order to check the validity of the Emparan–Horowitz–Myers argument, black holes radiate mainly on the brane, we assume that the radial equation for the massless spin-2 fields propagating on the brane obeys the master equation approximately. The transmission coefficient is computed explicitly by making use of the Hawking–Hartle theorem. It is shown that the total emission rates into the bulk are dominant compared to the rates on the visible brane when n ≥ 3. However, the bulk-to-brane relative emissivities per degree of freedom always remain O(1) roughly. The experimental significance of these results in the production of mini-black holes in future colliders is briefly discussed.
THE GLAST MISSION AND OBSERVABILITY OF SUPERNOVAE REMNANTS
Authors:   (ON BEHALF OF THE GLAST-LAT COLLABORATION), TIBOLLA OMAR
Published: August 2007

The Gamma-ray Large Area Space Telescope (GLAST) is a collaboration of several countries: France, Germany, Italy, Japan, Sweden and United States of America. GLAST is a satellite-based observatory that will study the Cosmos in the Energy Range 10 keV–300 GeV and consists of two different instruments: the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The two instruments are ready and are now being tested and integrated with the spacecraft: the launch is scheduled for October 2007. GLAST will improve the knowledge about several astrophysical sources (AGNs, Pulsars, GRBs, etc.). In this paper we will consider the scientific case of gamma-ray emitting Supernovae Remnants (SNRs).
SPHEROIDAL AND TORSIONAL MODES OF QUASISTATIC SHEAR OSCILLATIONS IN THE SOLID GLOBE MODELS OF NUCLEAR PHYSICS AND PULSAR ASTROPHYSICS
Authors: BASTRUKOV SERGEY , CHANG HSIANG-KUANG , MIŞICU ŞERBAN , MOLODTSOVA IRINA , PODGAINY DIMA
Published: August 2007

The past three decades of investigation on nuclear physics and pulsar astrophysics have seen gradual recognition that elastodynamic approach to the continuum mechanics of nuclear matter provides proper account of macroscopic motions of degenerate Fermi-matter constituting interior of the nuclear material objects, the densest of all known today. This paper focuses on one theoretical issue of this development which is concerned with oscillatory behavior of a viscoelastic solid globe in the regime of quasistatic, force-free, noncompressional oscillations less investigated in the literature compared to oscillations in the regime of standing shear waves. We show that in this case the problem of computing frequency and lifetime of spheroidal and torsional modes of nonradial shear vibrations damped by viscosity can be unambiguously resolved by working from the energy balance equation and taking advantage of the Rayleigh's variational method. The efficiency of this method is demonstrated by solid globe models of nuclear physics and pulsar astrophysics dealing with oscillations of a spherical mass of a viscoelastic Fermi-solid with homogeneous and nonhomogeneous profiles of the bulk density, the shear modulus, and the shear viscosity.
A GENERAL METHOD FOR CALCULATING PARTITION FUNCTION OF QCD AT FINITE CHEMICAL POTENTIAL
Authors: SUN WEI-MIN , ZONG HONG-SHI
Published: August 2007

In this paper we propose a general method for calculating the partition function of QCD at finite chemical potential. It is found that the partition function is totally determined by the dressed quark propagator at finite chemical potential up to a multiplicative constant. From this a criterion for the phase transition between the Nambu and the Wigner phase is obtained. This general method are applied to two specific cases: the free quark theory and QCD with a model dressed quark propagator proposed in H . Pagels and S. Stokar, Phys. Rev. D20, 2947 (1979). In the first case, the standard Fermi distribution at T = 0 are reproduced. In the second case, a particular form of baryon number distribution is obtained. It is found that when μ is below a critical value, the baryon number density is identically zero, which agrees with the general conclusion in M. A. Halasz et al., Phys. Rev. D58, 096007 (1998). All the results in the present paper are obtained under the condition T = 0 and μ ≠ 0. However, they can be generalized to the the general situation T ≠ 0 and μ ≠ 0 without fundamental difficulty.
DARBOUX TRANSFORMATIONS FOR N-DIMENSIONAL EFFECTIVE MASS SCHRÖDINGER EQUATIONS WITH HYPERSPHERICAL SYMMETRY
Authors: SCHULZE-HALBERG AXEL
Published: August 2007

We construct Darboux transformations of arbitrary order for stationary Schrödinger equations with effective mass that exhibit spherical symmetry in N dimensions (hyperspherical symmetry). The Darboux transformation and the associated transformed Schrödinger equation are obtained in closed form.
SPARTICLE MASS SPECTRUM IN GRAND UNIFIED THEORIES
Authors: ANANTHANARAYAN B. , PANDITA P. N.
Published: August 2007

We carry out a detailed analysis of sparticle mass spectrum in supersymmetric grand unified theories. We consider the spectroscopy of the squarks and sleptons in SU (5) and SO (10) grand unified theories, and show how the underlying supersymmetry breaking parameters of these theories can be determined from a measurement of different sparticle masses. This analysis is done analytically by integrating the one-loop renormalization group equations with appropriate boundary conditions implied by the underlying grand unified gauge group. We also consider the impact of nonuniversal gaugino masses on the sparticle spectrum, especially the neutralino and chargino masses which arise in supersymmetric grand unified theories with nonminimal gauge kinetic function. In particular, we study the interrelationships between the squark and slepton masses which arise in grand unified theories at the one-loop level, which can be used to distinguish between the different underlying gauge groups and their breaking pattern to the Standard Model gauge group. We also comment on the corrections that can affect these one-loop results.
A Rheic cause for the Acadian deformation in Europe
Authors: WOODCOCK N.H. , SOPER N.J. , STRACHAN R.A.
Published: August 2007

The Acadian (mid-Devonian) deformation in NW Europe has typically been interpreted as the culminating event of the Silurian closure of the Iapetus Ocean. This view has been challenged by the recognition of an intervening early Devonian transtensional event across part of the assembled Laurussian continent. Instead, the Acadian shortening must be driven by a renewed ‘push from the south’, involving subduction of the Rheic Ocean, and either flat-slab subduction or impingement of another Gondwana-derived continental fragment. A problem with either hypothesis is the lack of Acadian deformation or even correlative unconformity in the segment of the Rhenohercynian Zone between the Acadian belt and the Rheic suture. The possibility is explored that this Rhenohercynian segment was juxtaposed with the Acadian belt and the Midland Microcraton only during latest Acadian and/or Variscan tectonics. If so, a major lithospheric suture lies buried just south of the Variscan Front, along the Bristol Channel Fault Zone, and the missing Acadian terranes must now lie elsewhere along the orogen. A case is made that they are related to the allochthonous terranes of NW Iberia. In any case, the Acadian event in Europe should properly be regarded as proto-Variscan rather than late Caledonian.
The impact of 3D seismic data on the understanding of compaction, fluid flow and diagenesis in sedimentary basins
Authors: Cartwright Joe
Published: August 2007

Three-dimensional seismic reflection surveying is one of the most exciting technology-driven developments in the Earth Sciences over the past century. Three-dimensional seismic data present the geoscience community with an extraordinary ability to map structures and stratigraphic features in 3D detail to a resolution of a few metres over thousands of square kilometres. This resolving power has been a major factor in the recent recognition of a number of previously unsuspected phenomena in sedimentary basins and has led to some significant insights in basin analysis. This paper reviews some of the recent advances in basin analysis made using the medium of 3D seismic data, focusing on the broad field of fluid–rock interactions in sedimentary basins. Several recently discovered phenomena are reviewed, including polygonal fault systems and large-scale fluid flow pipes. Three-dimensional seismic data have also been invaluable in documenting the spatial variability of diagenetic fronts. The potential for future developments in this field of geophysical interpretation is considerable, and a number of potential areas for future research are highlighted.
Relative sea-level changes from NE Ireland during the last glacial termination
Authors: McCabe A.M. , Cooper J.A.G. , Kelley J.T.
Published: August 2007

Deglacial sea-level records from NE Ireland between 21 and 11 cal. ka bp record marine transgressions and sensitive lithospheric responses to ice loading. The sawtooth sea-level curve contains four intervals characterized by: (1) strong net uplift, subaerial channelling and a global meltwater pulse (21–19 cal. ka bp); (2) ice loading, isostatic depression and high relative sea level (19–17.5 cal. ka bp); (3) ice loading, renewed isostatic depression and high relative sea level for >1000 years (17–14.5 cal. ka bp); (4) catastrophic ice wastage, rapid uplift and lowstand (14.5–13 cal. ka bp). Geophysical models do not capture these fluctuations.
Palaeoenvironments and palaeoecology of the Early Pennsylvanian Lancaster Formation (‘Fern Ledges’) of Saint John, New Brunswick, Canada
Authors: FALCON-LANG HOWARD J. , MILLER RANDALL F.
Published: August 2007

The Pennsylvanian Lancaster Formation (‘Fern Ledges’) of Saint John, New Brunswick, Canada contains a world-famous fossil biota. Largely unstudied since the works of Hartt, Dawson, Matthew, and Stopes in the mid-nineteenth to early twentieth century, we present new data concerning biostratigraphy, taxonomy, palaeoenvironments, and palaeoecology. Megafloral assemblages suggest a mid- to late Langsettian age for the succession, making it approximately coeval with the classic Joggins Formation of nearby Nova Scotia. Facies analysis suggests deposition on a tectonically influenced coastal plain whose braided channels drained into a shallow brackish gulf. Most of the historical fossil collections are derived from flooding surfaces formed by abrupt subsidence events along the coastline. Three communities are recognized. Phoronids, crustaceans, and xiphosurans lived in brackish coastal waters. A lowland community of gastropods, insects, arachnids, and myriapods inhabited coastal forests. Coastal vegetation was dominated by shrubby cordaitaleans and pteridosperms whereas ferns, sphenopsids, and lycopsids were rare. An upland or dryland community, discernible from allochthonous assemblages, comprised forests of giant cordaitaleans, archaic pteridosperms, and plants of uncertain affinity.
The Energy Spilling Reactions of Bacteria and Other Organisms
Authors: Russell James B.
Published: August 2007

For many years it was assumed that living organisms always utilized ATP in a highly efficient manner, but simple growth studies with bacteria indicated that the efficiency of biomass production was often at least 3-fold lower than the amount that would be predicted from standard biosynthetic pathways. The utilization of energy for maintenance could only explain a small portion of this discrepancy particularly when the growth rate was high. These ideas and thermodynamic arguments indicated that cells might have another avenue of energy utilization. This phenomenon has also been called ‘uncoupling’, ‘spillage’ and ‘overflow metabolism’, but ‘energy spilling’ is probably the most descriptive term. It appears that many bacteria spill energy, and the few that do not can be killed (large and often rapid decrease in viability), if the growth medium is nitrogen-limited and the energy source is in ‘excess’. The lactic acid bacterium, Streptococcus bovis, is an ideal bacterium for the study of energy spilling. Because it only uses substrate level phosphorylation to generate ATP, ATP generation can be calculated with a high degree of certainty. It does not store glucose as glycogen, and its cell membrane can be easily accessed. Comparative analysis of heat production, membrane voltage, ATP production and Ohm’s law indicated that the energy spilling reaction of S. bovis is mediated by a futile cycle of protons through the cell membrane. Less is known about Escherichia coli, but in this bacterium energy spilling could be mediated by a futile cycle of potassium or ammonium ions. Energy spilling is not restricted to prokaryotes and appears to occur in yeasts and in higher organisms. In man, energy spilling may be related to cancer, ageing, ischemia and cardiac failure.
History of the Acetone-Butanol-Ethanol Fermentation Industry in China: Development of Continuous Production Technology
Authors: Chiao Jui-shen , Sun Zhi-hao
Published: August 2007

The acetone-butanol-ethanol (ABE) fermentation industry in China was started in the early 1950s in Shanghai and expanded rapidly thereafter. At its peak, there were about 30 plants all over the country and the total annual production of solvents reached 170,000 tons. This large enterprise was compelled to complete shutdown at the end of the 20th century due to the rapid increase of petrochemicals. The success of the ABE industry in China had special features like the development of a continuous fermentation technology. Its main strategic considerations were as follows: maintaining maximal growth and acid production phase, adoption of multiple stages in the solvent phase to allow gradual adaptation to increasing solvent, and the incorporation of stillage to offer enough nutrients to delay cell degeneration. Due to the tremendous national demand for solvents, China has begun a new round of ABE fermentation research. It is expected that a new era in the ABE industry is on the horizon.
Characterization of the Vibrio alginolyticusfur Gene and Localization of Essential Amino Acid Sites in Fur by Site-Directed Mutagenesis
Authors: Liu Qin , Wang Pengbo , Ma Yue , Zhang Yuanxing
Published: August 2007

The expression of iron-regulated genes in bacteria is typically controlled by the ferric uptake regulator (Fur) protein, a global transcriptional repressor that regulates functions as diverse as iron acquisition, oxidative stress, virulence and acid tolerance. We have identified a fur homologue in Vibrio alginolyticus and shown that it complements an Escherichia coli fur mutant. Reverse transcriptase PCR (RT-PCR) analysis proved that unlike many other fur homologues, V. alginolyticusfur is not under the iron-response Fur autoregulation. Homology modeling of the V. alginolyticus Fur protein with the recently solved crystal structure of Fur from Pseudomonas aeruginosa indicated extensive structural conservation. Based on the highly conserved DNA-binding sites and metal-binding sites in Fur protein, a series of site-directed mutations were respectively introduced into the cloned V. alginolyticus fur gene and resulted in partial or complete loss of Fur repressor function. Mutations in H33 and H90 were associated with complete loss of Fur function, mutations in Y56, R57, H87, C93 and H125 were related to partial loss of Fur function, and mutations in C96 and C133 did not show obvious change of Fur function. Our studies allowed the localization of some essential amino acid sites which may play important structural or functional roles in V. alginolyticus Fur activity.
Diminished Redundancy of Outer Membrane Factor Proteins in Rhizobiales: A nodT Homolog Is Essential for Free-Living Rhizobium etli
Authors: Hernández-Mendoza Armando , Nava Noreide , Santana Olivia , Abreu-Goodger Cei , Tovar Anibal , Quinto Carmen
Published: August 2007

Rhizobium etli is a gram-negative soil bacterium that induces nitrogen-fixing nodules on common bean roots (Phaseolus vulgaris). R. etli encodes two genes homologous to nodT of Rhizobium leguminosarum. nodTch is chromosomal and forms an operon with new genes resembling a multi-drug efflux pump of the resistance-nodulation-cell division (RND) family. nodTch is the last gene of this operon and can also be independently transcribed; the gene product is located in the bacterial outer membrane. Cell survival requires nodTch under all conditions tested. A second nodT gene, nodTpc, is encoded by plasmid c; it is constitutively transcribed but does not complement the essential function encoded by nodTch. NodT proteins belong to the outer membrane efflux proteins of the TolC superfamily. The number of duplications in the tolC gene family positively correlates with genome size in gram-negative bacteria. Nonetheless, some α-proteobacteria, including R. etli, encode fewer outer membrane factor exporters than expected suggesting further roles in addition to detoxification.
The Cold Shock Response of Lactobacillus casei: Relation between HPr Phosphorylation and Resistance to Freeze/Thaw Cycles
Authors: Beaufils Sophie , Sauvageot Nicolas , Mazé Alain , Laplace Jean-Marie , Auffray Yanick , Deutscher Josef , Hartke Axel
Published: August 2007

When carrying out a proteome analysis with a ptsH3 mutant of Lactobacillus casei, we found that the cold shock protein CspA was significantly overproduced compared to the wild-type strain. We also noticed that CspA and CspB of L. casei and CSPs from other organisms exhibit significant sequence similarity to the C-terminal part of EIIAGlc, a glucose-specific component of the phosphoenolpyruvate:sugar phosphotransferase system. This similarity suggested a direct interaction of HPr with CSPs, as histidyl-phosphorylated HPr has been shown to phosphorylate EIIAGlc in its C-terminal part. We therefore compared the cold shock response of several carbon catabolite repression mutants to that of the wild-type strain. Following a shift from 37°C to lower temperatures (20, 15 or 10°C), all mutants showed significantly reduced growth rates. Moreover, glucose-grown mutants unable to form P-Ser-HPr (ptsH1, hprK) exhibited drastically increased sensitivity to freeze/thaw cycles. However, when the same mutants were grown on ribose or maltose, they were similarly resistant to freezing and thawing as the wild-type strain. Although subsequent biochemical and genetic studies did not allow to identify the form of HPr implicated in the resistance to cold and freezing conditions, they strongly suggested a direct interaction of HPr or one of its phospho-derivatives with CspA and/or another, hitherto undetected cold shock protein in L. casei.
The Border Sequence of the Balhimycin Biosynthesis Gene Cluster from Amycolatopsis balhimycina Contains bbr, Encoding a StrR-Like Pathway-Specific Regulator
Authors: Shawky Riham M. , Puk Oliver , Wietzorrek Andreas , Pelzer Stefan , Takano Eriko , Wohlleben Wolfgang , Stegmann Efthimia
Published: August 2007

Balhimycin, produced by the actinomycete Amycolatopsis balhimycina DSM5908, is a glycopeptide antibiotic highly similar to vancomycin, the antibiotic of ‘last resort’ used for the treatment of resistant Gram-positive pathogenic bacteria. Partial sequence of the balhimycin biosynthesis gene cluster was previously reported. In this work, cosmids which overlap the region of the characterized gene cluster were isolated and sequenced. At the ‘left’ end of the cluster, genes were identified which are involved in balhimycin biosynthesis, transport, resistance and regulation. The ‘right’ end border is defined by a putative 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (dahp) gene. The proximate gene is similar to a type I polyketide synthase gene of the rifamycin producer Amycolatopsis mediterranei indicating that another biosynthesis gene cluster might be located directly next to the balhimycin gene cluster. The newly identified StrR-like pathway-specific regulator, Bbr, was characterized to be a DNA-binding protein and may have a role in balhimycin biosynthesis. Purified N-terminally His-tagged Bbr shows specific DNA-binding to five promoter regions within the gene cluster. By in silico analysis and by comparison of the DNA sequences binding Bbr, conserved inverted repeat sequences for the Bbr-binding site are proposed. The putative Bbr consensus sequence differs from that published for StrR.