bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of thickness and cap layer on the switching behavior of single Co nanowires
Authors: Brands M. , Leven B. , Dumpich G.
Published: May 2005

We have measured the low-temperature magnetoresistance (MR) of single cobalt nanowires of various lengths, thicknesses, and widths prepared by electron-beam lithography. The MR measurements exhibit peaks at the coercive fields Hc where Hc increases with decreasing wire width. From the shape of the peaks different switching mechanisms can be distinguished. While the resistance jumps for platinum-covered Co nanowires are sharp, pure Co nanowires exhibit broadened peaks due to domain-wall pinning at the Co/CoO interface. Covering the Co nanowires with insulating carbon yields a sharp switching behavior while simultaneously offering the possibility to investigate the resistance behavior of pure cobalt. By reducing the thickness of the wires the sharpness of the switching behavior continuously degenerates.
Generalized density functional theories using the k-electron densities: Development of kinetic energy functionals
Authors: Ayers Paul W.
Published: May 2005

Several explicit formulas for the kinetic energy of a many-electron system as a functional of the k-electron density are derived, with emphasis on the electron pair density. The emphasis is on general techniques for deriving approximate kinetic energy functionals and features generalized Weisacker bounds and methods using density-matrix reconstruction. Adapting results from statistical mechanics, a hierarchy of equations is derived that links electron pairs, triplets, quadruplets, etc.; this may be used to derive more accurate approximations. Several methods for defining the exact kinetic energy functional are presented, including the generalizations of the Levy and Lieb formulations of density-functional theory. Together with N-representability constraints on the k-density, this paper provides the basis for “generalized density functional theories” based on the electron pair density. There are also implications for conventional density-functional theory, notably regarding the development of more accurate density functionals for the kinetic energy.
Atomically designed precursors in optical fiber amplifiers: The thermal stability of the heterobimetallic ErAl3(OPri)12 in a solution-coated silica soot
Authors: Engholm M. , Lashgari K. , Edvardsson S. , Westin G. , Norin L.
Published: May 2005

The thermal stability of the bimetallic alkoxide ErAl3(OPri)12 doped in an unsintered silica (soot) has been investigated. Samples have been heated to different temperatures (up to 1500°C and analyzed by using ultraviolet-visible-near infrared absorption spectroscopy, infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, thermal gravimetric analysis, and powder x-ray diffraction. It is seen that the doped samples heated up to 1000°C show broad glasslike absorption spectra, indicating an amorphous structure, while the high-temperature sample shows an ordered crystallinelike structure with sharp characteristic absorption peaks. X-ray diffraction measurements indicate the formation of an ordered structure at temperatures of 1500°C, revealing a crystal phase of silica and phases of erbium and aluminosilicate. A comparison is also made with a sample doped with aqueous ErCl3 and Al(NO3)3. It is concluded that the local structure of the ErAl3 precursor is not preserved at temperatures above 1000°C. Alternative doping procedures are discussed.
Current–voltage characteristics of Schottky barriers with barrier heights larger than the semiconductor band gap: The case of NiGe∕n-(001)Ge contact
Authors: Chi D. Z. , Lee R. T. P. , Chua S. J. , Lee S. J. , Ashok S. , Kwong D.-L.
Published: May 2005

Current–voltage-temperature characterization has been performed on NiGe∕n-(100)Ge Schottky contacts that were formed by the solid-state reaction of Ni with Ge. An effective barrier height of 0.732–0.735eV, which is larger than the band-gap 0.66eV of Ge, was obtained. A physical model describing the current transport mechanism in a Schottky contact with a barrier height larger than the semiconductor band gap is proposed and discussed on the basis of thermionic-field emission as the dominant transport mechanism. The observation of a barrier height larger than the semiconductor band gap should be of technological importance as it suggests that NiGe is an ideal contact and Schottky source/drain material in Ge-based p-metal-oxide-semiconductor field-effect-transistors.
Effects of condensation reactions on the structural, mechanical, and electrical properties of plasma-deposited organosilicon thin films from octamethylcyclotetrasiloxane
Authors: Ross April D. , Gleason Karen K.
Published: May 2005

Organosilicon thin films were deposited from octamethylcyclotetrasiloxane and hydrogen peroxide using pulsed-plasma-enhanced chemical vapor deposition. Fourier transform infrared (FTIR) analysis shows significant organic content as well as hydroxyl and silanol moieties present in the as-deposited materials. Complete removal of the hydroxyl groups after annealing at 400°C for 1h was confirmed by FTIR and indicates that a condensation reaction between proximal hydroxyl groups occurred. This leads to the formation of additional Si–O–Si linkages, also confirmed by FTIR, and these structural changes lead to increased mechanical properties for the film. Mechanical property measurements were in accordance with this hypothesis, as the hardness increased between 46% and 125% after annealing. The structure-hardness relationship was evaluated in the framework of the continuous random network theory, and a percolation of rigidity was observed at a connectivity number of 2.35–2.4. Dielectric constants of the annealed films ranged between 2.78 and 3.20. Film structure and properties were strongly dependent on the feed rate of the oxidant relative to that of the siloxane.
Geometric phase effects in the H+H2 reaction: Quantum wave-packet calculations of integral and differential cross sections
Authors: Juanes-Marcos Juan Carlos , Althorpe Stuart C.
Published: May 2005

We report quantum wave-packet calculations on the H+H2 reaction, aimed at resolving the controversy over whether geometric phase (GP) effects can be observed in this reaction. Two sets of calculations are reported of the state-to-state reaction probabilities, and integral and differential cross sections (ICSs and DCSs). One set includes the GP using the vector potential approach of Mead and Truhlar; the other set neglects the phase. We obtain unequivocal agreement with recent results of Kendrick [J. Phys. Chem. A 107, 6739 (2003)], predicting GP effects in the state-to-state reaction probabilities, which cancel exactly on summing the partial waves to yield the ICS. Our results therefore contradict those of Kuppermann and Wu [Chem. Phys. Lett. 349 537 (2001)], which predicted pronounced GP effects in the cross sections. We also agree with Kendrick in predicting that there are no significant GP effects in the full DCS at energies below 1.8eV, and in the partial (0⩽J⩽10) DCS at energies above this. However, we find that in the full DCS above 1.8eV (which was not reported by Kendrick), there are GP effects, which may be experimentally measurable.
Simulated annealing study of morphological transitions of diblock copolymers in solution
Authors: Sun Pingchuan , Yin Yuhua , Li Baohui , Chen Tiehong , Jin Qinghua , Ding Datong , Shi An-Chang
Published: May 2005

The simulated annealing method was applied to study the self-assembling process of diblock copolymers in selective solvents for one block. The simulation results illustrated that the morphologies of the copolymer aggregates strongly depend on the interactions between the core-forming blocks and the solvents and on the length of the corona-forming blocks. Multiple morphological transitions were observed in one system. The transition sequence (disordered state-spherical micelles-short rodlike micelles-long rodlike micelles-onionlike aggregates) was observed for copolymers with increasing core-solvent interaction. Similar transitions were observed with the decrease of the length of the corona-forming blocks. The mechanisms of these transitions are investigated. The simulation results are compared with experiments and other simulations.
Charge transfer in DNA: Hole charge is confined to a single base pair due to solvation effects
Authors: Voityuk Alexander A.
Published: May 2005

We include solvation effects in tight-binding Hamiltonians for hole states in DNA. The corresponding linear-response parameters are derived from accurate estimates of solvation energy calculated for several hole charge distributions in DNA stacks. Two models are considered: (A) the correction to a diagonal Hamiltonian matrix element depends only on the charge localized on the corresponding site and (B) in addition to this term, the reaction field due to adjacent base pairs is accounted for. We show that both schemes give very similar results. The effects of the polar medium on the hole distribution in DNA are studied. We conclude that the effects of polar surroundings essentially suppress charge delocalization in DNA, and hole states in (GC)n sequences are localized on individual guanines.
Possible experimental test to determine the role of microscopic vortex rings in the λ transition in helium II
Authors: Tomchenko M. D.
Published: May 2005

An experimental test is proposed for determining the role of microscopic vortex rings (MVRs) in the λ transition in helium II. It is assumed that bulk He II contains an ensemble of vortex rings which initiate the λ transition and to a significant degree determine the value of Tλ. However, in very thin films of He II, such that the thickness d of the superfluid layer is less than the size d0 of the smallest MVRs, the rings will not fit, and no MVR ensemble exists in them. Because of this, Tλ(d) curve of helium II films on disordered substrates should have a feature in the form a jump at d≈d0≈6±4 Å. The available experimental data on the heat capacity of thin films of He II are insufficiently complete and precise for drawing conclusions as to the presence of the proposed feature.
A kind of potential permanent magnet film
Authors: Su H. L. , Ji G. B. , Tang S. L. , Chen W. , Li Z. , Gu B. X. , Du Y. W.
Published: May 2005

Fe 48 Co 52 nanowire arrays with various diameters and interpore distances were fabricated by electrochemical deposition. The dependences of the permanent magnetic properties on the diameter and interpore distance of the nanowire were investigated. The magnetic dipolar interaction among nanowires was employed to explain the experimental results. After annealing at 550°C, the excellent permanent magnetic properties were obtained. The coercivity Hc is 3.99kOe, the squareness Mr∕Ms is 0.96, and the maximum energy product of the whole composite film (BH)mf is estimated to be 7.1MGOe, which avails Fe–Co nanowire arrays prospective as a kind of potential permanent magnet film.
Interaction of Abrikosov vortex with grain boundaries near Hc1. II. Magnetic and transport properties of polycrystalline high-Tc superconductors
Authors: Belevtsov L. V.
Published: May 2005

The magnetic and transport characteristics of a polycrystalline superconductor are investigated theoretically starting from the results on the energy distribution of an Abrikosov vortex in the vortex-laminar model [L. V. Belentsov, Low Temp. Phys. 31, 116 (2005)]. It is shown that these properties depend largely on the normalized grain size, the intergrain coupling strength, the anisotropy, and the degree of surface smoothness (“specularity”) of the material. The first vortex entry field Hp, the first critical field Hc1, and the Gibbs free energy are calculated, and also the field dependence of the magnetization M(H), pinning potential Up(H), and critical current density Jc(H) near H∼Hc1. The vortex-vortex interaction energy is found.
Superconductivity in nonadiabatic systems with an “extended” singularity in the electron energy spectrum
Authors: Palistrant M. E.
Published: May 2005

An equation for determining the superconducting transition temperature Tc is obtained in the linear approximation in the nonadiabaticity for a system with a square-root singularity in the electron density of states. The vertex function is calculated and analytical expressions are obtained for Tc in the limiting cases Tc≪μ1 and μ1=0 (μ1 is the singular point) and also an expression for the coefficient of the isotope effect. It is shown that the contribution of nonadiabatic effects to Tc is significant and decreases on approach to the singular point μ1=0, and the smallness of the isotope effect is due to the presence of such a singularity in the electron energy spectrum and the nonadiabaticity of the system.
Frustrated states of the spin-glass type in diluted ferrimagnetic oxides
Authors: Efimova N. N.
Published: May 2005

The results of comprehensive experimental research on two model frustrated systems of dilute ferrimagnetic oxides—the slightly anisotropic cubic spinels Li0.5Fe2.5−xGaxO4 and the highly anisotropic hexagonal BaFe12−xGaxO19—are reviewed and summarized. The concentration x-T phase diagrams constructed for this class of magnets for the first time are discussed, the mechanisms of formation of disordered states of the spin-glass type (with the role of the exchange interaction and anisotropy taken into account) are examined, and the structure of the states and the influence of spatial inhomogeneity of the cluster type are considered. It is shown for the example of the Li–Ga spinels that in this class of anisotropic Heisenberg magnets with short-range exchange the form of the x-T diagram differs from the canonical form for spin-glass systems: in the reentrant region (0.9⩽x⩽1.5) one observes a new cooperative frustrated state and a line of first-order phase transitions T1(x) terminating in a critical point at x=0.8.
On the theory of electromagnetic fields radiated by an elastic wave in a ferromagnet
Authors: Kolesnichenko Yu. A. , Stepanenko D. I.
Published: May 2005

The generation of electromagnetic oscillations by a sound wave in a substance having magnetic order is investigated under conditions of the normal skin effect. The amplitude of the electric field and the phase difference of the electromagnetic and sound waves are calculated as functions of the saturation magnetization, anisotropy energy, magnetostriction constants, and other parameters characterizing the magnetic material.
Magnetic absorption of electromagnetic waves by a small metallic particle of ellipsoidal form
Authors: Grigorchuk N. I. , Tomchuk P. M.
Published: May 2005

The magnetic absorption of electromagnetic waves by a small metallic particle of ellipsoidal form is investigated in frequency regions both higher and lower than the characteristic frequency of the free passage of an electron between walls of the particle. The boundary conditions chosen are diffuse reflection of the electron from the inner surface of the particle. For the case when the thickness of the skin layer is large compared to the characteristic size of the particle, analytical expressions are obtained which permit determination of the dependence of the energy absorbed by a particle on its shape and orientation with respect to the direction of incidence of the radiation. The low-frequency absorption by small metallic particles is analyzed in detail for the first time. For particles in the form of oblate or prolate ellipsoids of revolution it is shown at particle sizes and what initial polarizations of the incident wave that the magnetic absorption becomes dominant over electric absorption.
Isochoric thermal conductivity of solid nitrogen
Authors: Konstantinov V. A. , Manzhelii V. G. , Revyakin V. P. , Sagan V. V.
Published: May 2005

The isochoric thermal conductivity of solid nitrogen is investigated on four samples of different densities in the temperature interval from 20 K to the onset of melting. In α-N2 the isochoric thermal conductivity exhibits a dependence weaker than Λ∝1/T; in β-N2 it increases slightly with temperature. The experimental results are discussed within a model in which the heat is transported by low-frequency phonons or by “diffusive” modes above the mobility edge. The growth of the thermal conductivity in β-N2 is attributed to the decreasing “rotational” component of the total thermal resistance, which occurs as the rotational correlations between the neighboring molecules become weaker.
EPR spectra of deuterated methyl radicals trapped in low temperature matrices
Authors: Dmitriev Yu. A.
Published: May 2005

EPR spectra of CHD2 and CD3 radicals are investigated in low-temperature matrices of H2, D2, and Ne at temperatures of 1.6–4.2 K. A method of condensation from the gas phase on a cold substrate is used. With decreasing sample temperature, a transformation of the shape of the CD3 spectrum in H2, D2, and Ne matrices and CHD2 spectrum in H2 and Ne is observed. This transformation was reversible in the above temperature range. The temperature effects are explained as reflecting a change in the populations of the lowest rotational states of the radicals. The temperature behavior of the EPR spectra for radicals trapped in various matrices are compared on the basis of the present data and known results for deuterated methyl radicals in Ar obtained in photolytic experiments. As a result the existence of a hindering barrier for the radical rotation is suggested.
Hysteretic phenomena in Xe-doped C60 from x-ray diffraction
Authors: Prokhvatilov A. I. , Galtsov N. N. , Legchenkova I. V. , Strzhemechny M. A. , Cassidy D. , Gadd G. E. , Moricca S. , Sundqvist B. , Aksenova N. A.
Published: May 2005

Polycrystalline fullerite C60 intercalated with Xe atoms at 575 K and a pressure of 200 MPa was studied by powder x-ray diffraction. The integrated intensities of a few brighter reflections have been utilized to evaluate the occupancy of the octahedral interstitial sites in C60 crystals, which turned out to be (34±4)%, and in good agreement with another independent estimate. It is found that reflections of the (h00) type become observable in Xe-doped C60. The presence of xenon in the octahedral sites affects both the orientational phase transition as well as the glassification process, decreasing both characteristic temperatures as well as smearing the phase transition over a greater temperature range. Considerable hysteretic phenomena have been observed close to the phase transition and the glassification temperature. The signs of the two hysteresis loops are opposite. There is reliable evidence that at the lowest temperatures studied the thermal expansion of the doped crystal is negative under cool-down.
Low-temperature microhardness of Xe-intercalated fullerite C60
Authors: Fomenko L. S. , Lubenets S. V. , Natsik V. D. , Cassidy D. , Gadd G. E. , Moricca S. , Sundqvist B.
Published: May 2005

The Vickers microhardness of Xe-intercalated polycrystalline fullerite C60 (XexC60, x≃0.35) is measured in a moderately low temperature range of 77 to 300 K. A high increase in the microhardness of the material (by a factor of 2 to 3) as compared to that of pure C60 single crystals is observed. It is shown that the step-like anomaly in the temperature dependences of the microhardness of pure C60 single crystals recorded under the orientational fcc-sc phase transition (Tc≃260 K) is also qualitatively retained for XexC60, but its onset is shifted by 40 K towards lower temperatures and the step becomes less distinct and more smeared. This behavior of H̄V(T) correlates with x-ray diffraction data, the analysis of which revealed a considerable influence of xenon interstitial atoms on the peculiar features of fullerite thermal expansion due to orientational phase transitions (see the paper by A.I. Prokhvatilov et al. in this issue).
Metallic–nonmetallic transition on the conductivity temperature dependence of multiwall carbon nanotubes
Authors: Sun Yong , Miyasato Tatsuro , Kirimoto Kenta , Kusunoki Michiko
Published: May 2005

We applied a noncontacting surface acoustic wave technique to measure the conductivity of aligned multiwall carbon nanotube films. By changing intensities of the parallel and perpendicular electric field components at the surface of the film sample, we observed different temperature dependencies of the conductivity. It was found that the temperature dependence of the conductivity parallel to the tube axis is comparable to that of a single-wall carbon nanotube, namely, there is a metallic–nonmetallic transition at temperature of 280 K. On the other hand, the temperature dependence of the conductivity perpendicular to the tube axis is similar to that of a graphene sheet.
Ion damage effects from negative deflector plate voltages during the plasma-assisted molecular-beam epitaxy growth of dilute nitrides
Authors: Oye Michael M. , Wistey Mark A. , Reifsnider Jason M. , Agarwal Sumit , Mattord Terry J. , Govindaraju Sridhar , Hallock Gary A. , Holmes Archie L. , Bank Seth R. , Yuen Homan B. , Harris James S.
Published: May 2005

We studied the effects of ion damage on the optical properties of dilute nitrides grown by plasma-assisted molecular-beam epitaxy. A dual-grid retarding field ion energy analyzer was used to measure the ion flux and ion energy distribution at the substrate position from an Applied-EPI UniBuilb™ rf plasma cell. These changes were measured as the negative deflector plate voltage varied from 0 to −800V. The largest ion flux resulted with a −100V setting, while the greatest ion energies occurred with −200V. Deflector plate voltages more negative than −300V resulted in a significant reduction in both the ion flux and ion energy. The damage caused by these ions was determined by measuring the pre- and postanneal photoluminescence properties of Ga0.8In0.2N0.01As0.99 quantum wells. Comparable optical properties were possible with various combinations of ion fluxes and ion energies, which demonstrate how the ion flux and ion energy each impart an individual effect on the sample’s optical properties. An awareness of these effects is crucial because the optical properties of dilute nitrides grown with an improper deflector plate voltage setting can lead to a greater degree of ion damage to the sample.
Electrical properties of 0.5 nm thick Hf-silicate top-layer∕HfO2 gate dielectrics by atomic layer deposition
Authors: Kamiyama Satoshi , Miura Takayoshi , Nara Yasuo , Arikado Tsunetoshi
Published: May 2005

The electrical properties have been studied for hafnium (Hf)-based gate stack structures, fabricated using atomic layer deposition (ALD) technology. The very thin ALD Hf-silicate layers on the top of HfO2 gate structures were very important in obtaining good electrical properties, because these surface films prevented a reaction between the polysilicon electrodes and HfO2 films during high temperature activation annealing. From subthreshold characteristic measurements, Ioff values were less than about 10pA∕μm and Ion values at ∣Vg∣=1.1V were greater than 350 and 120μA∕μm for n- and p- metal oxide semiconductor field effect transistors, respectively. The effective mobility curves for the Hf-based gate stack structures were at the same level as those of 1.6 nm SiON reference films at 0.8MV∕cm. Furthermore, the interfacial trap densities were less than 5*1010cm−2 for the Hf-based gate stack structures, achieving the same level as in the 1.6 nm SiON reference films.
Infrared absorption study of hydrogen incorporation in thick nanocrystalline diamond films
Authors: Tang C. J. , Neves A. J. , Carmo M. C.
Published: May 2005

We present an infrared (IR) optical absorbance study of hydrogen incorporation in nanocrystalline diamond films. The thick nanocrystalline diamond films were synthesized by microwave plasma-assisted chemical vapor deposition and a high growth rate about 3.0μm∕h was achieved. The morphology, phase quality, and hydrogen incorporation were assessed by means of scanning electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). Large amount of hydrogen bonded to nanocrystalline diamond is clearly evidenced by the huge CH stretching band in the FTIR spectrum. The mechanism of hydrogen incorporation is discussed in light of the growth mechanism of nanocrystalline diamond. This suggests the potential of nanocrystalline diamond for IR electro-optical device applications.
Generation of terahertz monochromatic acoustic phonon pulses by femtosecond optical excitation of a gallium nitride/aluminium nitride superlattice
Authors: Martinez C. E. , Stanton N. M. , Walker P. M. , Kent A. J. , Novikov S. V. , Foxon C. T.
Published: May 2005

We describe the generation of pulses of monochromatic acoustic phonons by ultrafast laser excitation of a gallium nitride/aluminium nitride superlattice (SL). The SL response to the optical excitation was studied using femtosecond pump-probe measurements. Superconducting bolometers were used to detect the phonons that leak out of the SL and propagate across the substrate. We see that, for excitation wavelengths around 430 nm, a pronounced enhancement in the longitudinal acoustic phonon signal occurs. The results are consistent with similar measurements using GaAs∕AlAs SL’s, where propagating monochromatic phonons were generated under resonant photoexcitation [Appl. Phys. Lett. 81, 3497 (2002)].
Ultraviolet lasing and time-resolved photoluminescence of well-aligned ZnO nanorod arrays
Authors: Han Xinhai , Wang Guanzhong , Wang Qingtao , Cao Li , Liu Ruibin , Zou Bingsuo , Hou J. G.
Published: May 2005

Well-aligned ZnO nanorod arrays were synthesized by thermal evaporation of ZnO powder on ZnO thin films. The nanorods are almost the same length of 5.5μm and well-oriented perpendicular to the substrates. The time-integrated and time-resolved photoluminescence spectra of the nanorod arrays revealed the existence of laser action with the excitation threshold of 130μJ∕cm2 and emission lifetime of less than 30 ps. At the excitation fluence a little below threshold, the decay fits well to a biexponential function with a fast component (∼80ps) and a slower component (∼360ps).
Preparation of highly conductive Mn-doped Fe3O4 thin films with spin polarization at room temperature using a pulsed-laser deposition technique
Authors: Ishikawa Mizue , Tanaka Hidekazu , Kawai Tomoji
Published: May 2005

We report on the preparation of MnxFe3−xO4 (x=0, 0.1, or 0.5) epitaxial thin films using a pulsed-laser deposition technique. Conditions for modified film formation are discussed, in addition to their electrical and magnetic properties in relation to the potential development of room temperature spin electronics devices. The film with x=0.1 could be fabricated at a higher substrate temperature (600°C) than the Fe3O4 thin film without Mn doping. The doped films exhibited low resistivity of about 7.0×10−3(x=0.1)–9.0×10−2(x=0.5)Ωcm at room temperature. Moreover, a spin polarization of the carrier of MnxFe3−xO4 (x=0, 0.1, or 0.5) films was confirmed at room temperature by examination of anomalous Hall coefficient measurements.
Ferromagnetism in nanocrystalline epitaxial Co:TiO2 thin films
Authors: Pradhan A. K. , Hunter D. , Dadson J. B. , Williams T. M. , Zhang Kai , Lord K. , Lasley B. , Rakhimov R. R. , Zhang Jun , Sellmyer D. J. , Roy U. N. , Cui Y. , Burger A. , Hopkins C. , Pearson N. , Wilkerson A. L.
Published: May 2005

We report on the observation of remarkable room-temperature ferromagnetism in nanocrystalline epitaxial Co:TiO2 films grown on sapphire (0001) substrates by a pulsed-laser deposition technique using high-density targets. The films were characterized by x-ray measurements, atomic force microscopy, micro-Raman, electron-paramagnetic resonance, and magnetization studies. The films exhibit three-dimensional islandlike growth that contains nanocrystalline particles. Our experimental results suggest that the remarkable ferromagnetism in Co:TiO2 films is controlled either by the interstitial Co2+ ions or small clusters, which are mainly present at the interface and on the surface of the films. Our work clearly indicates that Co interstitials and nanoclusters cause room-temperature ferromagnetism in Co-doped TiO2.
The Spaces of Home in Chicano and Latino Representations of the San Diego–Tijuana Borderlands (1968–2002)
Authors: Berelowitz Jo-Anne
Published: May 2005

In this paper I examine the ways that artists in the San Diego–Tijuana borderlands have represented the spaces of home from the late 1960s to the present. The historical trajectory is from the agonistic nationalism of the Chicano Movement, which sought to reestablish the homeland of Aztlán, to the Border Art Workshop's more inclusive multiculturalist engagement with ‘the borderlands’, to the flexible combinatorial binationalism that marks the current postborder condition. Works of art characteristic of each phase are discussed.
“You Can Make a Place for it”: Remapping Urban First Nations Spaces of Identity
Authors: Wilson Kathi , Peters Evelyn J
Published: May 2005

Contemporary research on migration, particularly those studies drawing upon theories of transnationalism, demonstrates the ways in which social relations are stretched across spaces, allowing individuals to disrupt boundaries and create identities of belonging to more than one place. This research focuses on the disruption of state boundaries through migration and identity construction. In this paper we utilize elements of transnational theory and stories of First Nations migrants to explore the ways that First Nations urbanization also disrupts boundaries. Colonial perspectives and practices that confined First Nations cultural practices and identities within the physical boundaries of reserves and defined all other spaces as settler spaces created a framework for the construction of the contemporary Canadian nation-state. We present the results of eighteen in-depth interviews conducted with urban First Nations migrants. The interviews focused on understanding how migration to cities shapes relationships to the land (an important element of indigenous identity), the challenges cities present to maintaining connections to the land, and the strategies First Nations migrants use to preserve those connections. By resisting the assignment of First Nations cultures and identities to reserves, First Nations migration to cities challenges the identity of the modern state by disrupting its internal borders and boundaries.
The effect of biosolids on cereals in central New South Wales, Australia. 2. Soil levels and plant uptake of heavy metals and pesticides
Authors: Cooper J. L.
Published: May 2005

Two forms of biosolids, with and without lime, were applied to acid soils at 2 sites growing wheat and triticale in central New South Wales. The forms of biosolids used were dewatered sewage sludge cake, and N-Viro Soil which is a lime-amended sewage sludge. Dewatered sewage sludge cake was applied at rates of 0, 6, 12 and 24 dry Mg/ha, and N-Viro soil at 0, 1.5, 3.0 and 4.5 dry Mg/ha. The soil was sampled and analysed at 2 points in time to determine the effect of the biosolids on heavy metal concentrations. Vegetative plant material and grain were also analysed for heavy metal and organo-chlorine pesticide levels.
Zinc and copper concentrations increased significantly with the addition of biosolids, especially with the highest rates of dewatered sewage sludge cake. However, all soil heavy metals were below the maximum allowable soil contaminant concentrations set by Environment Protection Authority, NSW. Cereal species, the addition of lime, and biosolids each affected heavy metal concentrations in plant material, but the responses differed between sites. Also, the changes in heavy metal concentrations in plant material were smaller and less consistent than the changes in soil heavy metal concentrations. The maximum heavy metal concentrations in grain were all below the maximum permitted concentrations of Food Standards Australia New Zealand. There were no detectable changes in the levels of organo-chlorine pesticides in the grain.
Storage temperature effects on moisture loss and the development of chilling injury in Lanes Late navel orange
Authors: Henriod R. E. , Gibberd M. R. , Treeby M. T.
Published: May 2005

The navel orange cultivar Lanes Late is an important export commodity for the Australian citrus industry with key markets in Asia and the United States of America. Low temperatures during storage and transport are used to extend postharvest life and for the purpose of insect disinfestation, making fruit more prone to chilling injury. The effects of low temperature and storage duration on the development of chilling injury were therefore examined. Cartons of about 100 fruit were stored at 3, 1 or –1°C for 0, 10, 20 or 30 days before transfer to a 22°C post-storage observation room. Fruit were assessed for chilling injury at transfer and every 10 days post-storage for 30 days. At all observation times the main effects of temperature and storage duration on the incidence of chilling injury and chilling injury index were significant with no interaction. The highest incidences of chilling injury were observed for fruit stored at –1°C (21%) and for 30 days (28%). Similarly, the chilling injury index was greatest for fruit stored at –1°C (0.47) for 30 days compared with fruit stored at 3 and 1°C (0.34 and 0.27, respectively). The incidence of chilling injury and the chilling injury index increased 2.1- and 3.0-fold, respectively, between the 10 and 30 day post-storage observations. Moisture loss was positively correlated with the chilling injury index (R2 = 0.53; P<0.001), supporting the hypothesis that moisture loss and time are important determinants of the expression of chilling injury. Based on this study, it is recommended that fruit storage and transit time be kept to ≤20 days and transport temperatures are maintained at ≥1°C. The expression of chilling injury could be minimised by reducing the post-storage handling time when moisture loss is expected to be highest.
Temperature and water availability effects on radiation and water use efficiencies in alfalfa (Medicago sativa L.)
Authors: Collino D. J. , Dardanelli J. L. , De Luca M. J. , Racca R. W.
Published: May 2005

Alfalfa, the most important forage crop in Argentina, shows considerable variability in forage production caused by variations in inter-annual rainfall and intra-annual radiation and temperature regimes. Such variation may affect radiation use efficiency and water use efficiency. This paper seeks to study the effects of temperature and water availability on radiation use efficiency and water use efficiency. We conducted the experiment in Córdoba, Argentina, under irrigated and droughted conditions. Drought was imposed by mobile rainout shelters during 3 consecutive periods. We measured forage, intercepted photosynthetically active radiation and water use to calculate radiation use efficiency and water use efficiency between cuttings. Under irrigation, radiation use efficiency and water use efficiency normalised by daytime vapour pressure deficit, were not limited by mean temperature above 21.3 and 21.9°C, respectively. Below those critical values, both variables decreased consistently with temperature decrements. Under drought, radiation use efficiency tended to decrease and water use efficiency tended to increase. In addition, the relationship between relative dry matter and relative water use was not linear, as reported in previous studies for annual crops.
Source pool geometry and the assembly of continental avifaunas
Authors: Graves Gary R. , Rahbek Carsten
Published: May 2005

Classical niche-assembly models propose that the composition of biotic communities in continental landscapes is determined chiefly by the autecology of species, interspecific competition, and the diversity of resources and habitats within a region. In contrast, stochastic models propose that simulation algorithms can replicate the macroecological patterns, if not the mechanisms, of community assembly. Despite fundamental differences in assumptions, both categories of models assume that species are drawn from regional source pools. We explored the implications of source pool geometry on the assembly of avian communities with an analysis of assemblage dispersion fields, which can be visualized by overlaying the geographic ranges of all species that occur in an assemblage. Contours of species richness surrounding focal quadrats illustrate the decay rate of assemblage similarity with distance and the probable geometry of assemblage source pools. We used a geographic database for 2,891 species of South American birds to characterize dispersion fields for assemblages sampled by 1° latitude-longitude quadrats (n= 1,676). We show that the median range size of dispersion fields varies by an order of magnitude across the continent. Because abundance generally correlates with geographic range size within taxonomic groups, the number of individuals per species in avifaunal source pools must also vary by an order of magnitude. Most significantly, dispersion field geometry was surprisingly asymmetrical and exhibited complex geographical patterns that were associated with the distribution of biomes. These results are broadly consistent with the predictions of niche-assembly models but offer little support for stochastic assembly models.
Gain-swept superradiance applied to the stand-off detection of trace impurities in the atmosphere
Authors: Kocharovsky V. , Cameron S. , Lehmann K. , Lucht R. , Miles R. , Rostovtsev Y. , Warren W. , Welch G. R. , Scully M. O.
Published: May 2005

We show that gain-swept superradiance can be used to detect low (parts per million) concentrations of various gases at distances on the order of kilometers, which is done by using pulse timing to create small regions of gain at positions that sweep toward a detector. The technique is far more sensitive than previous methods such as light detection and ranging or differential absorption light detection and ranging.
Establishing genetic transformation for comparative developmental studies in the crustacean
Parhyale hawaiensis
Authors: Pavlopoulos Anastasios , Averof Michalis
Published: May 2005

The amphipod crustacean
Parhyale hawaiensis
has been put forward as an attractive organism for evolutionary developmental comparisons, and considerable effort is being invested in isolating developmental genes and studying their expression patterns in this species. The scope of these studies could be significantly expanded by establishing means for genetic manipulation that would enable direct studies of gene functions to be carried out in this species. Here, we report the use of the
Minos
transposable element for the genetic transformation of
P. hawaiensis
. Transformed amphipods can be obtained from ≈30% of surviving individuals injected with both a
Minos
element carrying the
3xP3-DsRed
fluorescent marker and with mRNA encoding the
Minos
transposase. Integral copies of the transposon are inserted into the host genome and are stably inherited through successive generations. We have used reporter constructs to identify a muscle-specific regulatory element from
Parhyale
, demonstrating that this transformation vector can be used to test the activity of
cis
-regulatory elements in this species. The relatively high efficiency of this transgenic methodology opens new opportunities for the direct study of
cis
-regulatory elements and gene functions in
Parhyale
, allowing functional studies to be carried out beyond previously established model systems in insects.
The antiretroviral activity of APOBEC3 is inhibited by the foamy virus accessory Bet protein
Authors: Löchelt Martin , Romen Fabian , Bastone Patrizia , Muckenfuss Heide , Kirchner Nadine , Kim Yong-Boum , Truyen Uwe , Rösler Uwe , Battenberg Marion , Saib Ali , Flory Egbert , Cichutek Klaus , Münk Carsten
Published: May 2005

Genome hypermutation of different orthoretroviruses by cellular cytidine deaminases of the APOBEC3 family during reverse transcription has recently been observed. Lentiviruses like HIV-1 have acquired proteins preventing genome editing in the newly infected cell. Here we show that feline foamy virus (FFV), a typical member of the foamy retrovirus subfamily Spumaretrovirinae, is also refractory to genome deamination. APOBEC3-like FFV genome editing in APOBEC3-positive feline CRFK cells only occurs when the accessory FFV Bet protein is functionally inactivated. Editing of
bet
-deficient FFV genomes is paralleled by a strong decrease in FFV titer. In contrast to lentiviruses, cytidine deamination already takes place in APOBEC3-positive FFV-producing cells, because edited proviral DNA genomes are consistently present in released particles. By cloning the feline APOBEC3 orthologue, we found that its homology to the second domain of human APOBEC3F is 48%. Expression of feline APOBEC3 in APOBEC3-negative human 293T cells reproduced the effects seen in homologous CRFK cells: Bet-deficient FFV displayed severely reduced titers, high-level genome editing, reduced particle release, and suppressed Gag processing. Although WT Bet efficiently preserved FFV infectivity and genome integrity, it sustained particle release and Gag processing only when fe3 was moderately expressed. Similar to lentiviral Vif proteins, FFV Bet specifically bound feline APOBEC3. In particles from Bet-deficient FFV, feline APOBEC3 was clearly present, whereas its foamy viral antagonist Bet was undetectable in purified WT particles. This is the first report that, in addition to lentiviruses, the foamy viruses also developed APOBEC3-counter-acting proteins.
A central role forS-nitrosothiols in plant disease resistance
Authors: Feechan Angela , Kwon Eunjung , Yun Byung-Wook , Wang Yiqin , Pallas Jacqueline A. , Loake Gary J.
Published: May 2005

AnimalS-nitrosoglutathione reductase (GSNOR) governs the extent of cellularS-nitrosylation, a key redox-based posttranslational modification. Mutations inAtGSNOR1, anArabidopsis thaliana GSNOR, modulate the extent of cellularS-nitrosothiol (SNO) formation in this model plant species. Loss ofAtGSNOR1function increased SNO levels, disabling plant defense responses conferred by distinct resistance (R) gene subclasses. Furthermore, in the absence ofAtGSNOR1, both basal and nonhost disease resistance are also compromised. Conversely, increased AtGSNOR1 activity reduced SNO formation, enhancing protection against ordinarily virulent microbial pathogens. Here we demonstrate that AtGSNOR1 positively regulates the signaling network controlled by the plant immune system activator, salicylic acid. This contrasts with the function of this enzyme in mice during endotoxic shock, where GSNOR antagonizes inflammatory responses. Our data imply SNO formation and turnover regulate multiple modes of plant disease resistance.
Subtree power analysis and species selection for comparative genomics
Authors: McAuliffe Jon D. , Jordan Michael I. , Pachter Lior
Published: May 2005

Sequence comparison across multiple organisms aids in the detection of regions under selection. However, resource limitations require a prioritization of genomes to be sequenced. This prioritization should be grounded in two considerations: the lineal scope encompassing the biological phenomena of interest, and the optimal species within that scope for detecting functional elements. We introduce a statistical framework for optimal species subset selection, based on maximizing power to detect conserved sites. Analysis of a phylogenetic star topology shows theoretically that the optimal species subset is not in general the most evolutionarily diverged subset. We then demonstrate this finding empirically in a study of vertebrate species. Our results suggest that marsupials are prime sequencing candidates.
MB06322 (CS-917): A potent and selective inhibitor of fructose 1,6-bisphosphatase for controlling gluconeogenesis in type 2 diabetes
Authors: Erion Mark D. , van Poelje Paul D. , Dang Qun , Kasibhatla Srinivas Rao , Potter Scott C. , Reddy M. Rami , Reddy K. Raja , Jiang Tao , Lipscomb William N.
Published: May 2005

In type 2 diabetes, the liver produces excessive amounts of glucose through the gluconeogenesis (GNG) pathway and consequently is partly responsible for the elevated glucose levels characteristic of the disease. In an effort to find safe and efficacious GNG inhibitors, we targeted the AMP binding site of fructose 1,6-bisphosphatase (FBPase). The hydrophilic nature of AMP binding sites and their widespread use for allosteric regulation of enzymes in metabolic pathways has historically made discovery of AMP mimetics suitable for drug development difficult. By using a structure-based drug design strategy, we discovered a series of compounds that mimic AMP but bear little structural resemblance. The lead compound, MB05032, exhibited high potency and specificity for human FBPase. Oral delivery of MB05032 was achieved by using the bisamidate prodrug MB06322 (CS-917), which is converted to MB05032 in two steps through the action of an esterase and a phosphoramidase. MB06322 inhibited glucose production from a variety of GNG substrates in rat hepatocytes and from bicarbonate in male Zucker diabetic fatty rats. Analysis of liver GNG pathway intermediates confirmed FBPase as the site of action. Oral administration of MB06322 to Zucker diabetic fatty rats led to a dose-dependent decrease in plasma glucose levels independent of insulin levels and nutritional status. Glucose lowering occurred without signs of hypoglycemia or significant elevations in plasma lactate or triglyceride levels. The findings suggest that potent and specific FBPase inhibitors represent a drug class with potential to treat type 2 diabetes through inhibition of GNG.
Conserved modular design of an oxygen sensory/signaling network with species-specific output
Authors: Crosson Sean , McGrath Patrick T. , Stephens Craig , McAdams Harley H. , Shapiro Lucy
Published: May 2005

Principles of modular design are evident in signaling networks that detect and integrate a given signal and, depending on the organism in which the network module is present, transduce this signal to affect different metabolic or developmental pathways. Here we report a global transcriptional analysis of an oxygen sensory/signaling network in
Caulobacter crescentus
consisting of the sensor histidine kinase FixL, its cognate response regulator FixJ, the transcriptional regulator FixK, and the kinase inhibitor FixT. It is known that in rhizobial bacteria these proteins form a network that regulates transcription of genes required for symbiotic nitrogen fixation, anaerobic and microaerobic respiration, and hydrogen metabolism under hypoxic conditions. We have identified a positive feedback loop in this network and present evidence that the negative feedback regulator, FixT, acts to inhibit FixL by mimicking a response regulator. Overall, the core circuit topology of the Fix network is conserved between the rhizobia and
C. crescentus
, a free-living aerobe that cannot fix nitrogen, respire anaerobically, or metabolize hydrogen. In
C. crescentus
, the Fix network is required for normal cellular growth during hypoxia and controls expression of genes encoding four distinct aerobic respiratory terminal oxidases and multiple carbon and nitrogen metabolic enzymes. Thus, the Fix network is a conserved sensory/signaling module whose transcriptional output has been adapted to the unique physiologies of
C. crescentus
and the nitrogen-fixing rhizobia.
RETRACTED: Odor maps in the olfactory cortex
Authors: Zou Zhihua , Li Fusheng , Buck Linda B.
Published: May 2005

In the olfactory system, environmental chemicals are deconstructed into neural signals and then reconstructed to form odor perceptions. Much has been learned about odor coding in the olfactory epithelium and bulb, but little is known about how odors are subsequently encoded in the cortex to yield diverse perceptions. Here, we report that the representation of odors by fixed glomeruli in the olfactory bulb is transformed in the cortex into highly distributed and multiplexed odor maps. In the mouse olfactory cortex, individual odorants are represented by subsets of sparsely distributed neurons. Different odorants elicit distinct, but partially overlapping, patterns that are strikingly similar among individuals. With increases in odorant concentration, the representations expand spatially and include additional cortical neurons. Structurally related odorants have highly related representations, suggesting an underlying logic to the mapping of odor identities in the cortex.