bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of a responsible promoter region and a key transcription factor, CCAAT/enhancer-binding protein ϵ, for up-regulation of PHGPx in HL60 cells stimulated with TNFα
Authors: Hattori Hiroyuki , Imai Hirotaka , Kirai Nozomu , Furuhama Kazuhisa , Sato Osamu , Konishi Kumiko , Nakagawa Yasuhito
Published: November 2007

In the present study we investigated promoter regions of the PHGPx [phospholipid hydroperoxide GPx (glutathione peroxidase)] gene and transcription factors involved in TNFα (tumour necrosis factor α)-induced up-regulation of PHGPx in non-differentiated HL60 cells. Non-differentiated HL60 cells displayed up-regulation of non-mitochondrial and mitochondrial PHGPx mRNA in response to TNFα stimulation. The promoter activity was up-regulated by TNFα stimulation in cells transfected with a luciferase reporter vector encoding the region from −282 to −123 of the human PHGPx gene compared with the non-stimulated control. The up-regulated promoter activity was effectively abrogated by a mutation in the C/EBP (CCAAT/enhancer-binding protein)-binding sequence in this region. ChIP (chromatin immunoprecipitation) assays demonstrated that C/EBPϵ bound to the −247 to −34 region in HL60 cells, but C/EBPα, β, γ and δ did not. The binding of C/EBPϵ to the promoter region was increased in HL60 cells stimulated with TNFα compared with that of the non-stimulated control. An increased binding of nuclear protein to the C/EBP-binding sequence was observed by EMSA (electrophoretic mobility-shift assay) in cells stimulated with TNFα, and it was inhibited by pre-treatment with an anti-C/EBPϵ antibody, but not with other antibodies. The C/EBPϵ mRNA was expressed in PMNs (polymorphonuclear cells), non-differentiated HL60 cells and neutrophil-like differentiated HL60 cells displaying TNFα-induced up-regulation of PHGPx mRNA, but not in macrophage-like differentiated HL60 cells, HEK-293 cells (human embryonic kidney-293 cells) and other cell lines exhibiting no up-regulation. The up-regulation of PHGPx mRNA, however, was detected in HEK-293 cells overexpressing C/EBPϵ as a result of TNFα stimulation. These results indicate that C/EBPϵ is a critical transcription factor in TNFα-induced up-regulation of PHGPx expression.
Differential regulation of class IA phosphoinositide 3-kinase catalytic subunits p110α and β by protease-activated receptor 2 and β-arrestins
Authors: Wang Ping , Kumar Puneet , Wang Chang , DeFea Kathryn A.
Published: November 2007

PAR-2 (protease-activated receptor 2) is a GPCR (G-protein-coupled receptor) that can elicit both G-protein-dependent and -independent signals. We have shown previously that PAR-2 simultaneously promotes Gαq/Ca2+-dependent activation and β-arrestin-1-dependent inhibition of class IA PI3K (phosphoinositide 3-kinase), and we sought to characterize further the role of β-arrestins in the regulation of PI3K activity. Whereas the ability of β-arrestin-1 to inhibit p110α (PI3K catalytic subunit α) has been demonstrated, the role of β-arrestin-2 in PI3K regulation and possible differences in the regulation of the two catalytic subunits (p110α and p110β) associated with p85α (PI3K regulatory subunit) have not been examined. In the present study we have demonstrated that: (i) PAR-2 increases p110α- and p110β-associated lipid kinase activities, and both p110α and p110β are inhibited by over-expression of either β-arrestin-1 or -2; (ii) both β-arrestin-1 and -2 directly inhibit the p110α catalytic subunit in vitro, whereas only β-arrestin-2 directly inhibited p110β; (iii) examination of upstream pathways revealed that PAR-2-induced PI3K activity required the small GTPase Cdc (cell-division cycle)42, but not tyrosine phosphorylation of p85; and (iv) β-arrestins inhibit PAR-2-induced Cdc42 activation. Taken together, these results indicated that β-arrestins could inhibit PAR-2-stimulated PI3K activity, both directly and through interference with upstream pathways, and that the two β-arrestins differ in their ability to inhibit the p110α and p110β catalytic subunits. These results are particularly important in light of the growing interest in PAR-2 as a pharmacological target, as commonly used biochemical assays that monitor G-protein coupling would not screen for β-arrestin-dependent signalling events.
Regulation of Cidea protein stability by the ubiquitin-mediated proteasomal degradation pathway
Authors: Chan Siu Chiu , Lin Sheng-Cai , Li Peng
Published: November 2007

Cidea, one of three members of the CIDE (cell-death-inducing DNA-fragmentation-factor-45-like effector) family of proteins, is highly enriched in brown adipose tissue, in which it plays a critical role in adaptive thermogenesis and fat accumulation. Cidea-null mice have increased energy expenditure with resistance to high-fat-diet-induced obesity and diabetes. However, little is known as to how the Cidea protein is regulated. In the present study we show that Cidea is a short-lived protein as measured by cycloheximide-based protein chase experiments in different cell lines or in differentiated brown adipocytes. Proteasome inhibitors specifically increased the stability of both transfected and endogenous Cidea protein. Furthermore, Cidea protein was found to be polyubiquitinated when overexpressed in different culture cells as well as in differentiated mature brown adipocytes. Extensive mutational analysis of individual lysine residues revealed that ubiquitinated lysine residues are located in the N-terminal region of Cidea, as alteration of these lysine residues to alanine (N-5KA mutant) renders Cidea much more stable when compared with wild-type or C-terminal lysine-less mutant (C-5KA). Furthermore, K23 (Lys23) within the N-terminus of the Cidea was identified as the major contributor to its polyubiquitination signal and the protein instability. Taken together, the results of our study demonstrated that the ubiquitin–proteasome system confers an important post-translational modification that controls the protein stability of Cidea.
Enzyme substrate recognition in oxygen sensing: how the HIF trap snaps
Authors: Metzen Eric
Published: November 2007

The transcriptional activator HIF (hypoxia-inducible factor) is a focal point of biomedical research because many situations in physiology and in pathology coincide with hypoxia. The effects of HIF activation may be a facet of normal growth, as in embryonic development, they may counterbalance a disease, as seen in the stimulation of erythropoiesis in anaemia, and they may be part of the pathological processes, as exemplified by tumour angiogenesis. The oxygen-sensitive α-subunits of HIF are primarily regulated by the enzymatic hydroxylation that induces rapid proteasomal degradation. The HIFα hydroxylases belong to a superfamily of dioxygenases that require the co-substrates oxygen and 2-oxoglutarate as well as the cofactors Fe2+ and ascorbate. The regulation of enzyme turnover by the concentration of the cosubstrate oxygen constitutes the interface between tissue oxygen level and the activity of HIF. The HIFα prolyl hydroxylases, termed PHDs/EGLNs (prolyl hydroxylase domain proteins/EGL nine homologues), bind to a conserved Leu-Xaa-Xaa-Leu-Ala-Pro motif present in all substrates identified so far. This recognition motif is present twice in HIF1α, which gives rise to a NODD [N-terminal ODD (oxygen-dependent degradation domain)] containing Pro402 of HIF1α and a CODD (C-terminal ODD) where Pro564 is hydroxylated. PHD1/EGLN2 and PHD2/EGLN1 hydroxylate both ODDs with higher activity towards CODD, whereas PHD3/EGLN3 is specific for CODD. The reason for this behaviour has been unclear. In this issue of the Biochemical Journal, Villar and colleagues demonstrate that distinct PHD/EGLN domains, that are remote from the catalytic site, function in substrate discrimination. This elegant study improves our understanding of the interaction of the oxygen-sensing PHDs/EGLNs with their substrates, which include, but are not limited to, the HIFα proteins.
Is the influence of variation in the ACE gene on the prospective risk of Type 2 diabetes in middle-aged men modified by obesity?
Authors: Muthumala Amal , Gable David R. , Palmen Jutta , Cooper Jackie A. , Stephens Jeffrey W. , Miller George J. , Humphries Steve E.
Published: November 2007

There is strong evidence for the presence of a functional renin–angiotensin system in diabetogenic tissues, and ACE (angiotensin-converting enzyme) inhibitors may improve glucose metabolism in those individuals at high risk of developing T2DM (Type 2 diabetes). In the present study, we tested the hypothesis that subjects with genetically lower plasma and tissue ACE activity, because of their ACE [I/D (insertion/deletion)] genotype, would have a lower risk of T2DM in 2642 healthy middle-aged Caucasian men (mean age, 56 years) followed-up for 15 years. Obesity was the strongest predictor of T2DM, with an HR (95% CI) [hazard ratio (95% confidence interval)] of 3.74 (2.66-5.26) (P<0.0001). Overall there was no association between ACE genotype (II homozygotes, n=623; and D allele carriers, n=2019) and risk of T2DM, and although in lean men there was no genotype difference in risk in D allele carriers compared with II homozygotes [adjusted HR=0.75 (95% CI, 0.46–1.22)], in obese (body mass index >30 kg/m2) men the risk of T2DM was higher [adjusted HR=4.26 (95% CI, 1.30–13.93)] with a genotype–obesity interaction of P=0.01. A similar pattern of risk was seen by re-analysis of a previously published case-control study, where D allele carriers had a non-significant 1.30 (0.97–1.74)-fold higher risk of developing T2DM than II homozygotes when non-obese, but a 1.79 (1.17–2.72) (P=0.007)-fold higher risk when obese. Further prospective studies are needed to confirm these findings. The ACE D allele may worsen glucose metabolism, which could raise the prospective T2DM risk in obese men, but not in lean men. In obesity, adipose tissue undergoes inflammatory infiltration and the subsequent higher levels of pro-inflammatory angiotensin II may explain this association.
Adsorption, desorption, and diffusion of nitrogen in a model nanoporous material. I. Surface limited desorption kinetics in amorphous solid water
Authors: Zubkov Tykhon , Smith R. Scott , Engstrom Todd R. , Kay Bruce D.
Published: November 2007

The adsorption and desorption kinetics of N2 on porous amorphous solid water (ASW) films were studied using molecular beam techniques, temperature programed desorption (TPD), and reflection-absorption infrared spectroscopy. The ASW films were grown on Pt(111) at 23K by ballistic deposition from a collimated H2O beam at various incident angles to control the film porosity. The experimental results show that the N2 condensation coefficient is essentially unity until near saturation, independent of the ASW film thickness indicating that N2 transport within the porous films is rapid. The TPD results show that the desorption of a fixed dose of N2 shifts to higher temperature with ASW film thickness. Kinetic analysis of the TPD spectra shows that a film thickness rescaling of the coverage-dependent activation energy curve results in a single master curve. Simulation of the TPD spectra using this master curve results in a quantitative fit to the experiments over a wide range of ASW thicknesses (up to 1000 layers, ∼0.5μm). The success of the rescaling model indicates that N2 transport within the porous film is rapid enough to maintain a uniform distribution throughout the film on a time scale faster than desorption.
Adsorption, desorption, and diffusion of nitrogen in a model nanoporous material. II. Diffusion limited kinetics in amorphous solid water
Authors: Zubkov Tykhon , Smith R. Scott , Engstrom Todd R. , Kay Bruce D.
Published: November 2007

The adsorption, desorption, and diffusion kinetics of N2 on thick (up to ∼9μm) porous films of amorphous solid water (ASW) films were studied using molecular beam techniques and temperature programmed desorption. Porous ASW films were grown on Pt(111) at low temperature (<30K) from a collimated H2O beam at glancing incident angles. In thin films (<1μm), the desorption kinetics are well described by a model that assumes rapid and uniform N2 distribution throughout the film. In thicker films (>1μm), N2 adsorption at 27K results in a nonuniform distribution, where most of N2 is trapped in the outer region of the film. Redistribution of N2 can be induced by thermal annealing. The apparent activation energy for this process is ∼7kJ∕mol, which is approximately half of the desorption activation energy at the corresponding coverage. Preadsorption of Kr preferentially adsorbs onto the highest energy binding sites, thereby preventing N2 from trapping in the outer region of the film which facilitates N2 transport deeper into the porous film. Despite the onset of limited diffusion, the adsorption kinetics are efficient, precursor mediated, and independent of film thickness. An adsorption mechanism is proposed, in which a high-coverage N2 front propagates into a pore by the rapid transport of physisorbed second layer N2 species on top of the first surface bound layer.
NH stretching vibrations of pyrrole clusters studied by infrared cavity ringdown spectroscopy
Authors: Matsumoto Yoshiteru , Honma Kenji
Published: November 2007

The IR spectra for various sizes of pyrrole clusters were measured in the NH stretching vibration region by infrared cavity ringdown spectroscopy. The hydrogen-bonded structures and normal modes of the pyrrole clusters were analyzed by a density functional theory calculation of the B3LYP∕6-311+G(d,p) level. Two types of pulsed nozzles, a slit and a large pinhole, were used to generate different cluster size distributions in a supersonic jet. A rotational contour analysis of the NH stretching vibration for the monomer revealed that the slit nozzle provides a warmer jet condition than the pinhole one. The IR spectra, measured under the warmer condition, showed the intense bands at 3444, 3392, and 3382cm−1, which were assigned to hydrogen-bonded NH stretching vibrations due to the dimer, the trimer, and the tetramer, respectively. On the other hand, the IR spectra measured under a lower temperature condition by a pinhole nozzle showed a broad absorption feature in addition to sharp bands. This broad absorption was reproduced by the sum of two Gaussians peaks at 3400 and 3372cm−1 with widths of 30 and 50cm−1 (FWHM), respectively. Compared with the spectra of the condensed phase, two bands at 3400 and 3372cm−1 were assigned to hydrogen-bonded NH stretching vibrations of larger clusters having liquid-like and solid-like structures, respectively.
Time-resolved polaron dynamics in molten solutions of cesium-doped cesium iodide
Authors: Chandrasekhar N. , Unterreiner A.-N.
Published: November 2007

Temperature-dependent investigations of excess electrons in molten solutions of cesium-doped cesium iodide (Cs–CsI) (mole fraction of Cs∼0.003) were performed applying femtosecond pump-probe absorption spectroscopy. The pulse-limited induced bleach observed at probe wavelengths from 600to1240nm was attributed to the excitation of equilibrated excess electrons which were initially formed by melting a Cs–CsI mixture. The interpretation of the relaxation process is based on strongly localized polarons that constitute the majority of defect states in this melt. As expected, the bipolaron contribution was insignificant. The time constants (τ1) were found to be temperature dependent confirming our earlier findings in Na–NaI melts that ionic diffusion almost exclusively controls the dynamics of excess electrons in high temperature ionic liquids. Apart from this temperature dependence, the relaxation dynamics of excess electrons do not differ irrespective of the excitation regime (blue or red part of the respective stationary spectra).
Direct measurement of effective diffusion coefficients in nanochannels using steady-state dispersion effects
Authors: Durand Nicolas F. Y. , Bertsch Arnaud , Todorova Mina , Renaud Philippe
Published: November 2007

We present a method to measure effective diffusion coefficients of fluorescently labeled molecules inside a nanofluidic system. Molecules with small diffusion coefficients show a larger lateral dispersion than highly diffusive species, which is counterintuitive. We performed measurements with wheat germ agglutinin proteins and obtained an effective diffusion coefficient which is four orders of magnitude lower than its free diffusion coefficient. Our technique which is a direct and relatively simple measurement of the effective diffusion coefficients inside nanochannels of well controlled dimensions could help fundamental studies in membranes and separation sciences.
Structural and electronic properties of ultrathin polycrystalline Si layers on glass prepared by aluminum-induced layer exchange
Authors: Antesberger T. , Jaeger C. , Scholz M. , Stutzmann M.
Published: November 2007

We prepared ultrathin polycrystalline silicon layers (5–100nm) by the aluminum-induced layer exchange process. An Al/oxide/amorphous Si layer stack was annealed at temperatures below 577°C, leading to a layer exchange and the crystallization of the silicon. The process dynamics, structural and electronic properties have been studied. In addition to the well known dependence on the annealing temperature, we found an increase of the nucleation density with layer thickness. Raman spectroscopy shows a good crystalline quality down to a layer thickness of 10nm. Hole concentrations of the p-type layers are between 5×1018 and 9×1019cm−3, depending on layer thickness and annealing temperature.
Magnetohydrodynamic flow layer formation in development of resistive double tearing mode
Authors: Dong J. Q. , Long Y. X. , Mou Z. Z. , Zhang J. H. , Li J. Q.
Published: November 2007

Quasilinear development of double tearing modes induced by plasma resistivity is numerically analyzed. The spatiotemporal characteristics of the modes are analyzed in detail. Magnetohydrodynamic flow layers are demonstrated to merge in the development of the modes. The sheared flows lie just at the boundaries of the magnetic islands in the quasilinear stage. The flows have sufficient levels of shear required for turbulence suppression. Possible correlation between the layer formation and triggering of experimentally observed internal transport barriers, preferentially formed in the proximity of rational flux surfaces of low safety factors, is discussed.
The decomposition of the spinor bundle of Grassmann manifolds
Authors: Klinker Frank
Published: November 2007

The decomposition of the spinor bundle of the spin Grassmann manifolds Gm,n=SO(m+n)∕SO(m)×SO(n) into irreducible representations of so(m)⊕so(n) is presented. A universal construction is developed and the general statement is proven for G2k+1,3, G2k,4, and G2k+1,5 for all k. The decomposition is used to discuss properties of the spectrum and the eigenspaces of the Dirac operator.
Combining multiple optical trapping with microflow manipulation for the rapid bioanalytics on microparticles in a chip
Authors: Boer G. , Johann R. , Rohner J. , Merenda F. , Delacrétaz G. , Renaud Ph. , Salathé R.-P.
Published: November 2007

An array of four independent laser traps is combined with a polydimethylsiloxane microfluidic chip to form a very compact system allowing parallel processing of biological objects. Strong three dimensional trapping allows holding objects such as functionalized beads in flows at speeds near 1mm∕s, enabling rapid processing. By pressure control of the inlet flows, the trapped objects can be put in contact with different solutions for analysis purpose. This setup, including a fluorescence excitation-detection scheme, offers the potential to perform complex biochemical manipulations on an ensemble of microparticles.
Mechanical and electronic properties of hard rhenium diboride of low elastic compressibility studied by first-principles calculation
Authors: Zhang R. F. , Veprek S. , Argon A. S.
Published: November 2007

The mechanical and electronic properties of hcp-ReB2 are calculated by a first-principles approach. The calculated extreme equilibrium mechanical properties are consistent with the available experimental and theoretical data. The calculated elastic moduli suggest that hcp-ReB2 has a low compressibility and is most likely an intrinsically brittle material, but its relatively low ideal shear strength, as compared with c-BN, indicates that it is not intrinsically stronger/harder than c-BN. Based on the calculated electronic density of states and valence charge density distribution, the bonding nature of hcp-ReB2 is examined to obtain a deeper insight into the physical origin of the mechanical properties.
IMPACT: A facility to study the interaction of low-energy intense particle beams with dynamic heterogeneous surfaces
Authors: Allain J. P. , Nieto M. , Hendricks M. R. , Plotkin P. , Harilal S. S. , Hassanein A.
Published: November 2007

The Interaction of Materials with Particles and Components Testing (IMPACT) experimental facility is furnished with multiple ion sources and in situ diagnostics to study the modification of surfaces undergoing physical, chemical, and electronic changes during exposure to energetic particle beams. Ion beams with energies in the range between 20 and 5000eV can bombard samples at flux levels in the range of 1010–1015cm−2s−1; parameters such as ion angle of incidence and exposed area are also controllable during the experiment. IMPACT has diagnostics that allow full characterization of the beam, including a Faraday cup, a beam imaging system, and a retarding field energy analyzer. IMPACT is equipped with multiple diagnostics, such as electron (Auger, photoelectron) and ion scattering spectroscopies that allow different probing depths of the sample to monitor compositional changes in multicomponent and/or layered targets. A unique real-time erosion diagnostic based on a dual quartz crystal microbalance measures deposition from an eroding surface with rates smaller than 0.01nm∕s, which can be converted to a sputter yield measurement. The monitoring crystal can be rotated and placed in the target position so that the deposited material on the quartz crystal oscillator surface can be characterized without transfer outside of the vacuum chamber.
Induced magnetism in Cu nanoparticles embedded in Co
Authors: Swaminathan P. , Rosenberg R. A. , Shenoy G. K. , Palmer J. S. , Weaver J. H.
Published: November 2007

One-dimensionally confined nonferromagnetic layers of Cu grown between ferromagnetic layers of Co have an average induced magnetic moment that decreases with Cu film thickness. We studied the effects of changing the nature of confinement to three dimensions by embedding Cu nanoparticles in a Co matrix and measuring the induced moments using x-ray magnetic circular dichroism. The nanoparticle spin moments were more than twice that of films of comparable thickness due to the three dimensional confinement and greater interfacial area.
A comparative study of the electronic structures of oxygen- and chlorine-treated nitrogenated carbon nanotubes by x-ray absorption and scanning photoelectron microscopy
Authors: Ray S. C. , Pao C. W. , Tsai H. M. , Chiou J. W. , Pong W. F. , Chen C. W. , Tsai M.-H. , Papakonstantinou P. , Chen L. C. , Chen K. H.
Published: November 2007

The electronic structures and bonding properties of oxygen- and chlorine-treated nitrogenated carbon nanotubes (N-CNTs) were studied using x-ray absorption near-edge structure (XANES) and scanning photoelectron microscopy. Features in the C K-edge XANES spectra are shifted by ∼0.3eV toward higher energies and by ∼1.1eV toward lower energies relatively to those of the more symmetrical pyridinelike and graphitelike structured N-CNTs upon chlorination and oxidation, respectively. Increases in N K-edge XANES intensities for both chlorination and oxidation reveal substitution of C–C bonds by C–N bonds consistent with the observed valence-band photoemission spectra of the decrease of the C 2s bond and the increase of the N 2s bond.
The stationary phase method for a wave packet in a semiconductor layered system. The applicability of the method
Authors: Rodríguez-Coppola H. , Diago-Cisneros L. , Pérez-Álvarez R.
Published: November 2007

Using the formal analysis made by Bohm [D. Bohm, Quantum Theory (Dover, New York, 1979)] to calculate approximately the phase time for a transmitted and the reflected wave packets through a potential barrier, we calculate the phase time for a semiconductor system formed by different mesoscopic layers. The transmitted and the reflected wave packets are analyzed and the applicability of this procedure, based on the stationary phase of a wave packet, is considered in different conditions. For the applicability of the stationary phase method an expression is obtained in the case of the transmitted wave depending only on the derivatives of the phase, up to third order. This condition indicates whether the parameters of the system allow us to define the wave packet by its leading term. The case of a multiple barrier systems is shown as an illustration of the results. This formalism includes the use of the transfer matrix to describe the central stratum, whether it is formed by one layer (the single barrier case), or two barriers and an inner well (the double barrier resonant tunneling semiconductor structure system), but one can assume that this stratum can be comprise of any number or any kind of semiconductor layers.
Au-assisted molecular beam epitaxy of InAs nanowires: Growth and theoretical analysis
Authors: Tchernycheva Maria , Travers Laurent , Patriarche Gilles , Glas Frank , Harmand Jean-Christophe , Cirlin George E. , Dubrovskii Vladimir G.
Published: November 2007

The Au-assisted molecular beam epitaxial growth of InAs nanowires is discussed. In situ reflection high-energy electron diffraction observations of phase transitions of the catalyst particles indicate that they can be liquid below the eutectic point of the Au-In alloy. The temperature range where the catalyst can be liquid covers the range where we observed nanowire formation (380–430 °C). The variation of nanowire growth rate with temperature is investigated. Pure axial nanowire growth is observed at high temperature while mixed axial/lateral growth occurs at low temperature. The change of the InAs nanowire shape with growth duration is studied. It is shown that significant lateral growth of the lower part of the nanowire starts when its length exceeds a critical value, so that their shape presents a steplike profile along their axis. A theoretical model is proposed to explain the nanowire morphology as a result of the axial and lateral contributions of the nanowire growth.
Formation and stability of rocksalt ZnO nanocrystals in MgO
Authors: Eijt S. W. H. , de Roode J. , Schut H. , Kooi B. J. , De Hosson J. Th. M.
Published: November 2007

Coimplantation of Zn and O ions into a single crystalline MgO and subsequent thermal annealing were applied in the synthesis of ZnO nanocrystals. Electron microscopy showed that rocksalt instead of wurtzite ZnO stabilizes for relatively large nanocrystals up to ∼15nm, resulting from its small lattice mismatch with MgO of ∼1.7%. The vacancies initially created by implantation induce favorable nanocrystal growth kinetics and are effectively absorbed during the nucleation and growth processes. The optical band edge of the ZnO nanocrystals was detected at ∼2.8eV.
(
1
+
1
)
-dimensional separation of variables
Authors: Pucacco Giuseppe , Rosquist Kjell
Published: November 2007

In this paper we explore general conditions which guarantee that the geodesic flow on a two-dimensional manifold with indefinite signature is locally separable. This is equivalent to showing that a two-dimensional natural Hamiltonian system on the hyperbolic plane possesses a second integral of motion which is a quadratic polynomial in the momenta associated with a secind rank Killing tensor. We examine the possibility that the integral is preserved by the Hamiltonian flow on a given energy hypersurface only (weak integrability) and derive the additional requirement necessary to have conservation at arbitrary values of the Hamiltonian (strong integrability). Using null coordinates, we show that the leading-order coefficients of the invariant are arbitrary functions of one variable in the case of weak integrability. These functions are quadratic polynomials in the coordinates in the case of strong integrability. We show that for (1+1)-dimensional systems, there are three possible types of conformal Killing tensors and, therefore, three distinct separability structures in contrast to the single standard Hamilton-Jacobi-type separation in the positive definite case. One of the new separability structures is the complex∕harmonic type which is characterized by complex separation variables. The other new type is the linear∕null separation which occurs when the conformal Killing tensor has a null eigenvector.
Subwavelength imaging by metallic slab lens with nanoslits
Authors: Xu Ting , Du Cunlei , Wang Changtao , Luo Xiangang
Published: November 2007

A metallic slab lens featured with specially designed nano slits is presented to realize imaging for arbitrary object and image distances. Based on the particular propagation properties of surface plasmon polaritons in nanostructures, slits perforated in silver slab are designed with variant widths to produce desired optical phase retardations. Numerical simulation of an illustrative lens is performed through finite-difference time-domain method and shows that subwavelength imaging is realized at the designed position.
Structural properties and magic structures in hydrogenated finite and infinite silicon nanowires
Authors: Zdetsis A. D. , Koukaras E. N. , Garoufalis C. S.
Published: November 2007

Unusual effects such as bending and “canting,” related with the stability, have been identified by ab initio real-space calculations for hydrogenated silicon nanowires. We have examined in detail the electronic and structural properties of finite and infinite nanowires as a function of length (and width) and have developed stability and bending rules, demonstrating that “magic” wires do not bend. Reconstructed 2×1 nanowires are practically as stable as the magic ones. Our calculations are in good agreement with the experimental data of Ma et al. [Science 299, 1874 (2003).].
Memory effect in a system of zincblende Mn-rich Mn(Ga)As nanoclusters embedded in GaAs
Authors: Wang W. Z. , Deng J. J. , Lu J. , Sun B. Q. , Zhao J. H.
Published: November 2007

Zincblende Mn-rich Mn(Ga)As nanoclusters embedded in GaAs matrices are fabricated by in situ postgrowth annealing diluted magnetic semiconductor (Ga,Mn)As films with Mn concentration ranging from 2.6% to 8% at 650°C. Magnetization measurements show that memory effect and slow magnetic relaxation, the typical characteristics of the spin-glass-like phase, occur below the blocking temperature of 45K in samples with high Mn concentration, while for samples with low Mn concentration, ferromagnetic order remains up to 360K. The behavior of low-temperature spin dynamics can be explained by the hierarchical model.
Evidence for the existence of a metal-insulator-semiconductor junction at the electrode interfaces of CaCu3Ti4O12 thin film capacitors
Authors: Deng Guochu , Yamada Tomoaki , Muralt Paul
Published: November 2007

P -type conductivity has been observed in CaCu3Ti4O12 (CCTO) ceramics and also in thin films deposited by pulsed laser deposition. I-V and C-V relationships of the CCTO thin films showed characteristics typical of a tunnel metal-insulator-semiconductor structure, evidencing its capacitance response as the origin of the high apparent dielectric constant observed in CCTO thin films. The very thin insulating layer on top of the film can be reduced in thickness by treatment in HCl acid, as shown by smaller threshold voltages in the I-V curves. The overall behavior is compatible with a conduction activation energy of ∼80to100meV in the bulk of the film, and a diffusion potential at the interface of 500to800meV. The acceptor concentration is of the order of 1019cm−3.
Faces as Objects of Non-Expertise: Processing of Thatcherised Faces in Congenital Prosopagnosia
Authors: Carbon Claus-Christian , Grüter Thomas , Weber Joachim E , Lueschow Andreas
Published: November 2007

Congenital prosopagnosia (cPA) is a severe disorder in recognising familiar faces, a human characteristic that is presumably innate, without any macro-spatial brain anomalies. Following the idea that cPA is based on deficits of configural face processing, we used a speeded grotesqueness decision task with thatcherised faces, since the Thatcher illusion can serve as a test of configural disruption (Lewis and Johnston, 1997 Perception26 225–227). The time needed to report the grotesqueness of a face in relation to orientation showed dissociate patterns between a group of fourteen people with cPA and a group of matched controls: whereas the RTs of controls followed a strong sigmoid function depending on rotation from the upright orientation, the RTs of people with cPA showed a much weaker sigmoid trend approaching a linear function. The latter result is interpreted as a diagnostic sign of impaired configural processing, being the primary cause of the absence of ‘face expertise’ in prosopagnosia.
Laboratory measurements of electrical resistivity, polarizability and phase angle spectra of sulphide bearing rocks from captains flat N.S.W.
Authors: Newton A.W. , Smith M.J. , McSharry P.J. , Emerson D.W.
Published: November 2007

Measured resistivities of sphalerite – galena – pyrite ores evince an inverse correlation with metallic mineral concentration whereas induced polarization parameters show a positive correlation. The resistivity of massive sulphide ore appears much greater than that of constituent minerals suggesting limited usefulness of geophysical methods which locate electrical conductors. The high polarizability of concentrated ores corroborates the applicability of induced polarization for locating massive sulphide deposits. The low resistivity and high polarizability of zinc rich samples suggest that sphalerite may contribute significantly to the electrical properties of lead–zinc–silver ores. Laboratory measurements of phase angle spectra suggest that this parameter may be of diagnostic value in surface and downhole variable frequency I.P. surveying.
Aeromagnetic survey over lower palaeozoic andesites in the Parkes-Daroobalgie area N.S.W.
Authors: Emerson D.W. , Smith M.J. , Templeton R.J.
Published: November 2007

Detailed and reconnaissance airborne magnetic data over a 150 square mile tract in the Parkes area N.S.W. have been compared and used to investigate the magnetic response and distribution of Ordovician volcanics and metasediments which occur in the area.
Metric conversion and geophysics - further comments
Authors: Brown A.R.
Published: November 2007

The article "Metric Conversion and Geophysics" in your March 1972 issue describes some aspects of the SI system of units. However, the symbols used for some units are not those approved under the SI system. These units and their approved symbols are listed below:- [see full text for table]. Two useful booklets for anyone concerned with metric conversion are provided by the Metric Conversion Board (1971) and Australian Academy of Science (1970). Fairly comprehensive lists of units and symbols are included, Metric conversion of seismic reflection exploration in Australia suffers from a heavy dependence on American technology. Until the U.S.A. itself decides to metricate the difficulties will continue. For example, seismic reflection equipment is manufactured with 24 (or a simple multiple thereof) recording channels, a singularly non-metric number, which results in several non-round metric dimensions in geophone spread geometrics.
Part 4. Plate boundary evolution in the Solomons region: Ophiolite basement complex in a fractured, island chain, Santa Isabel, British Solomon Islands
Authors: Stanton R.L. , Ramsay W.R.H.
Published: November 2007

As part of a continuing programme involving the structural, petrological, and geochemical evolution of the British Solomon Islands, attention has now centred, among other islands, on Santa Isabel, where a well developed basement ophiolite sequence is exposed. Further work in the area will involve the geochemical relationships between the various members of the ophiolite basement. The Solomons lies within Suess's outer 1st Australian Arc, now regarded as the margin between the India and Pacific lithospheric plates (Le Pichon, 1968) and have been termed a composite, fractured island chain (Coleman and Hackman, 1974). The Group comprises a double en echelon chain of islands, which is believed to reflect a system of basins and anticlinal horsts now progressively offset by sinistral shear (Carey, 1968; Krause, 1967; Hackman, 1973). Five Provinces were originally recognised in the region (Coleman, 1965) and these were subsequently amended to four (Hackman, 1973).
Part 6. Present plate boundary seismic, volcanic and kinematic processes: Time variations in recent volcanism and seismicity along convergent plate boundaries of the south Bismarck Sea, Papua New Guinea
Authors: Cooke R.J.S.
Published: November 2007

A striking spatial and temporal clustering of volcanic eruptions has occurred in the Bismarck Volcanic Arc, Papua New Guinea, since late 1972. In the complete arc, six volcanoes have been active during this period, Long Island, Langila, Ulawan, Karkar, Manam, and Ritter Island. Ulawan is located in the eastern (New Britain) half of the arc. The other five are located consecutively in the western half of the arc; no definite historical eruptions are known from any other volcano in the sector containing them. This western half is distinguishable from the eastern half on petrological and geophysical grounds by Johnson (this Symposium). The only western volcanoes with historical eruptions but not active in this present phase, are in the Schouten Islands at the far western end of the arc; this sector is also petrologically distinguishable.
DHEM: the Que-Hellyer volcanics experience
Authors: Silic J. , Eadie E.T.
Published: November 2007

The intermediate volcanic sequence hosting the Que River and Hellyer mines provides an excellent environment for electromagnetics in that the only two strong conductors ever found in them have been developed into mines. Now that the ground has been thoroughly explored by surface EM and the search is by necessity becoming deeper, downhole EM has become an extremely important aspect of the exploration programme. However, even in this ideal environment for EM, there are factors that cause interpretation headaches, although all can be overcome with care and experience. These problems include the overlying moderately conductive black shales, instrumentation responses from the Sirotem unit, responses from culture, and the effect of strong conductors such as the known ore bodies close to the target.
Case history of geophysical surveys over the Golden Cross gold silver deposit
Authors: Collins S.
Published: November 2007

The discovery of the Golden Cross gold-silver deposit was originally aided by an airborne magnetometer survey. It has subsequently proved, however, to be a difficult geophysical target. A variety of geophysical tools have been tried over the deposit, but none has been successful in identifying a clear signature for the main ore zone.
Interactive broadband constrained inversion
Authors: Mansfield G.
Published: November 2007

Conventional algorithms for the inversion of seismic data generally produce inverted traces which are limited in bandwidth to that of the input seismic data. This necessitates that a low-frequency model be added to the inverted traces in order to produce full bandwidth seismic logs. A problem with this method is that there is usually a gap in frequency between the low end of the seismic and the high end of the model spectra. A further problem with conventional inversion methods is that it is difficult to incorporate well or geologic information into the inversion process. To overcome these problems a new broadband constrained inversion method which combines seismic, well, and geologic information is used. This method simultaneously satisfies constraints imposed by the well and geologic information, whilst inverting the seismic data. The output is an optimized broadband acoustic impedance model. In order to combine the diverse data types of seismic amplitudes, well logs, geologic models, and horizon interpretations, an interactive workstation is used. The interactive environment is ideal for this work as it provides the flexibility required to manipulate and display both the varying incoming data types and the output data model.
Extended FK domain migration ? An efficient variable velocity algorithm
Authors: Whiting P.
Published: November 2007

Constant velocity FK domain migration, as developed by Stolt in 1978, has significant performance advantages over all other commercially available migration algorithms.However, even with Stolt's pre-migration time stretching (or psuedo-depth conversion), this algorithm suffers serious accuracy problems in the presence of any significant velocity variations. This paper develops a method of extending the accuracy of FK domain migration to steep dips in arbitrary velocity fields. The basis of the new method is the partitioning of the unmigrated data set into dip ranges and computing unique time stretching factors for each. Stolt's original time stretching is shown to be the zero-dip special case of this more general algorithm. Following the separate migration of the partitions, the data is merged to form a correctly migrated data set. As few as four partitions is shown to produce very significant improvements. Even though Extended FK Domain Migration is a few times slower than conventional FK domain migration, it can still produce accuracy comparable to phase shift migration at a fraction of the cost.
Application of raypath modelling to verify the mapping of Gippsland gas fields
Authors: Megallaa M.
Published: November 2007

One of the Victorian Government's policies in the oil and gas area is to enhance the benefits to the State in the energy sector by assessing the nature and extent of the petroleum resources. To evaluate the production capacity of developed and undeveloped gas fields, a comprehensive study was commissioned by the DITR in 1988. The first step in a study of this type is to check the accuracy of the depth maps, to see if they adequately describe the reservoir geometry. Raypath modelling, using the Advanced Interpretation Mapping System (AIMS ? Version III), was carried out by Geophysical Services International (GSI), Sydney, on a number of selected profiles over the Snapper, Marlin-Turrum, Barracouta, Kipper and Emperor fields for the DITR. Input data for the models were extracted from the operator's maps. The software simulates the normal incidence raypaths (or wave theory solution) for all shotpoints, and from this information it generates gather records and/or synthetic seismic profiles. By comparing the model data with those from data acquisition, processing and interpretation, it was possible to check the validity of the interpretation of the reservoir's geometry. This modelling work showed that the synthetic data were comparable with the acquisition and processing data, confirming that the depth maps (tied to well control) produced by the operator using its proprietary software are adequate and most likely to represent subsurface configuration of the reservoirs.
The use of an active drill bit for inverse VSP measurements
Authors: Rector III J.W. , Marion B.P. , Hardage R.A.
Published: November 2007

Vertical Seismic Profiling (VSP) is often used to provide high resolution seismic images near a wellbore. A new borehole seismic technique, the TOMEX� survey (Rector, et al., 1988), uses the vibrations produced by a drill bit as a downhole seismic energy source to produce inverse VSP data. No downhole instrumentation is required to acquire the data, and the data recording does not interfere with or delay the drilling process. Hence, there is no loss of rig time in performing the survey. These characteristics offer a method to acquire SWD (seismic-while-drilling) borehole seismic surveys. In addition, 3-D imaging around a well can be obtained at significant savings compared to conventional offset VSP imaging. The continuous signals generated by the bit during drilling are monitored with a reference sensor attached to the top of the drillstring, and the reference sensor signals are crosscorrelated with signals from surface-positioned geophones to produce inverse VSP data. Deconvolution and time shifts are then performed to remove the effects of recording the source reference trace at a location that is a considerable distance from the source. Results from tests demonstrate that these processed drill-bit source data are virtually identical to conventional forward VSP data. In using the drill bit as a downhole seismic source for inverse VSP, many of the limitations of conventional VSP are overcome. Several applications for VSP that were previously considered to be prohibitively expensive are now feasible. Furthermore, this seismic-while-drilling technique offers the potential for the explorationist to make real-time drilling decisions at the well site.
Cullen australasicum (syn. Psoralea australasica): a review and some preliminary studies related to its potential as a low rainfall perennial pasture legume
Authors: Dear B. S. , Li G. D. , Hayes R. C. , Hughes S. J. , Charman N. , Ballard R. A.
Published: November 2007

This paper reviews the morphology, establishment, herbage quality, grazing tolerance, palatability, anti-nutritional compounds and rhizobial symbiosis of Cullen australasicum (Schltdl.) J.W. Grimes (syn. Psoralea australasica Schltdl.), a deep-rooted Australian native legume commonly known as tall verbine or native scurf-pea. Its natural distribution and the edaphic and climatic characteristics of germplasm collection sites within Australia are described. It also reports the results of three preliminary studies; two field studies on the establishment, persistence and herbage quality, and a glasshouse study to identify an effective Rhizobium strain for C. australasicum. In the field studies, C. australasicum established readily from seed and demonstrated similar persistence to Medicago sativa L. over a 3-year period in the medium rainfall wheat belt of southern New South Wales. The productivity of C. australasicum in year 3 was similar to M. sativa at one site but inferior at the second site. C. australasicum demonstrated superior persistence and higher herbage yields than Lotus corniculatus L. in year 3 at both sites. The mineral content of the leaves and stems of C. australasicum in these studies were similar to M. sativa and L. corniculatus for most elements except for Mo and Zn, which were significantly higher, and Na which was lower in C. australasicum. Organic matter digestibility of the leaves and stems of C. australasicum ranged from 79 to 89% and 62 to 72%, respectively, compared with 73–79% and 59–73% in M. sativa. Crude protein levels of C. australasicum leaves and stems were 22–28% and 15–27%, respectively, compared with 26–33% and 13–33% in M. sativa. The study of Rhizobium strains isolated from four South Australian soils identified a superior strain (SRDI 483) capable of establishing an effective symbiosis with C. australasicum. The potential of C. australasicum as a drought hardy perennial legume for extensive grazing systems where M. sativa fails to persist because of selective grazing is discussed. Its low palatability to sheep was seen as an advantage in assisting its survival in extensive low-input grazing systems.