bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrating agricultural policies and water policies under water supply and climate uncertainty
Authors: Mejías Patricia , Varela‐Ortega Consuelo , Flichman Guillermo
Published: June 2004

Understanding the interactions of water and agricultural policies is crucial for achieving an efficient management of water resources. In the EU, agricultural and environmental policies are seeking to converge progressively toward mutually compatible objectives and, in this context, the recently reformed Common Agricultural Policy (CAP) and the EU Water Framework Directive constitute the policy framework in which irrigated agriculture and hence water use will evolve. In fact, one of the measures of the European Water Directive is to establish a water pricing policy for improving water use and attaining a more efficient water allocation. The aim of this research is to investigate the irrigators' responses to these changing policy developments in a self‐managed irrigation district in southern Spain. A stochastic programming model has been developed to estimate farmers' response to the application of water pricing policies in different agricultural policy scenarios when water availability is subject to varying climate conditions and water storage capacity in the district's reservoir. Results show that irrigators are price‐responsive, but a similar water‐pricing policy in different agricultural policy options could have distinct effects on water use, farmers' income, and collected revenue by the water authority. Water availability is a critical factor, and pricing policies are less effective for reducing water consumption in drought years. Thus there is a need to integrate the objectives of water policies within the objectives of the CAP programs to avoid distortion effects and to seek synergy between these two policies.
Latitudinal distribution of the deuterium to hydrogen ratio in the atmospheric water vapor retrieved from IMG/ADEOS data
Authors: Zakharov Vyacheslav I. , Imasu Ryoichi , Gribanov Konstantin G. , Hoffmann Georg , Jouzel Jean
Published: June 2004

Latitudinal distribution of the columnar deuterium/hydrogen ratio of atmospheric water vapor, δDvap, was retrieved from high‐resolution infrared spectra. Interferometric Monitor for Greenhouse gases (IMG) sensor aboard the ADvanced Earth Observing Satellite (ADEOS) observed the spectra over the ocean during the operational period from December 1996 through June 1997. The latitudinal mean δDvap was relatively large with values around −100‰ in the tropical region decreasing down to minimal values of −800‰ at high latitudes. For retrieving δDvap, a type of spectral fitting method was adopted using a forward/retrieval calculation code developed by Gribanov et al. [2001]. This method is expected to be applicable for data analyses of future satellite sensors such as IASI and TES.
Transport of cross helicity and radial evolution of Alfvénicity in the solar wind
Authors: Matthaeus W. H. , Minnie J. , Breech B. , Parhi S. , Bieber J. W. , Oughton S.
Published: June 2004

A transport theory including cross helicity, magnetohydrodynamic (MHD) turbulence, and driving by shear and pickup ions, is applied to the radial evolution of the solar wind. The radial decrease of cross helicity observed in the solar wind can be accounted for when sufficient driving is included to overcome the inherent tendency for MHD turbulence to produce Alfvénic states.
Zinc/silicon ratios of sponges: A proxy for carbon export to the seafloor
Authors: Ellwood Michael J. , Kelly Michelle , Nodder Scott D. , Carter Lionel
Published: June 2004

Reconstruction of past carbon export events is difficult. Most proxies for carbon export suffer from problems related to remineralisation and diagenetic effects above, at and below the sediment‐water interface. Here we demonstrate that deep‐sea hexactinellid sponges incorporate zinc (Zn) into their silica skeletons in a direct relationship with the amount of particulate organic carbon (POC) accumulating in sediments. Such a relationship suggests that Zn incorporation into siliceous sponge spicules is from Zn associated with particulate organic matter (POM) ‘raining down’ from overhead waters. The dissolved Zn pool does not appear to be a major Zn source to deep‐ocean sponges. Likewise, water temperature and pressure do not appear to strongly influence Zn incorporation into sponge silica. These results suggest that the Zn to silicon (Si) ratio of deep ocean sponges could serve as a useful proxy for reconstructing past POC burial events.
Observation of the whole process of interaction between barchans by flume experiments
Authors: Endo Noritaka , Taniguchi Keisuke , Katsuki Atsunari
Published: June 2004

Through laboratory experiments generating unidirectional water flows, we examine the process of interaction between two moving barchans (sandy bed configurations in a crescentic plan‐shape), which may take dozens of years for barchan dunes in the nature. Three types of the interaction were observed. The first type was absorption of two barchans into one. The second was that the upstream fast barchan rode on the downstream slow barchan and simultaneously a newly born barchan was ejected from the lee side of the slow barchan. The third was that the downstream slow barchan was split into two before the upstream fast barchan touched the downstream. The type of the interaction was determined by both relative and absolute size of two barchans.
Counterstreaming electrons in magnetic clouds near 5 AU
Authors: Crooker N. U. , Forsyth R. , Rees A. , Gosling J. T. , Kahler S. W.
Published: June 2004

Suprathermal electron pitch angle spectrograms were searched for counterstreaming signatures in 31 magnetic clouds identified in Ulysses data when the spacecraft was located ∼5 AU from the Sun. Under the assumption that counterstreaming indicates closed field lines, that is, field lines attached to the Sun at both ends, we find that the clouds range from 0 to 100% closed, with an average of 55% closed, and that the percentage of closed flux tends to increase with increasing cloud size. The results are similar to those found at 1 AU, implying that the rate at which a cloud opens, presumably by interchange reconnection back at the Sun, slows significantly as its leading edge moves further out into the heliosphere.
Angiotensin II-induced ERK1/ERK2 activation and protein synthesis are redox-dependent in glomerular mesangial cells
Authors: GORIN Yves , RICONO Jill M. , WAGNER Brent , KIM Nam-Ho , BHANDARI Basant , CHOUDHURY Goutam Ghosh , ABBOUD Hanna E.
Published: June 2004

Angiotensin II (Ang II) stimulates hypertrophy of glomerular mesangial cells. The signalling mechanism by which Ang II exerts this effect is not precisely known. Downstream potential targets of Ang II are the extracellular-signal-regulated kinases 1 and 2 (ERK1/ERK2). We demonstrate that Ang II activates ERK1/ERK2 via the AT1 receptor. Arachidonic acid (AA) mimics the action of Ang II on ERK1/ERK2 and phospholipase A2 inhibitors blocked Ang II-induced ERK1/ERK2 activation. The antioxidant N-acetylcysteine as well as the NAD(P)H oxidase inhibitors diphenylene iodonium and phenylarsine oxide abolished both Ang II- and AA-induced ERK1/ERK2 activation. Moreover, dominant-negative Rac1 (N17Rac1) blocks activation of ERK1/ERK2 in response to Ang II and AA, whereas constitutively active Rac1 resulted in an increase in ERK1/ERK2 activity. Antisense oligonucleotides for Nox4 NAD(P)H oxidase significantly reduce activation of ERK1/ERK2 by Ang II and AA. We also show that protein synthesis in response to Ang II and AA is inhibited by N17Rac1 or MEK (mitogen-activated protein kinase/ERK kinase) inhibitor. These results demonstrate that Ang II stimulates ERK1/ERK2 by AA and Nox4-derived reactive oxygen species, suggesting that these molecules act as downstream signal transducers of Ang II in the signalling pathway linking the Ang II receptor AT1 to ERK1/ERK2 activation. This pathway involving AA, Rac1, Nox4, reactive oxygen species and ERK1/ERK2 may play an important role in Ang II-induced mesangial cell hypertrophy.
Regulation of the human involucrin gene promoter by co-activator proteins
Authors: TRAN Nhu Q. , CROWE David L.
Published: June 2004

Stratified squamous epithelial cells undergo an orderly process of terminal differentiation that is characterized by specific molecular and morphological changes, including expression of the cornified envelope protein involucrin. Significant progress has been made in characterizing the upstream regulatory region of the involucrin gene. Binding sites for AP-1 (activator protein 1) and Sp1 transcription factors were shown to be important for involucrin promoter activity and tissue-specific expression. Defective terminal differentiation is often characterized by decreased or lack of involucrin expression. Recently, a dominant-negative construct of the transcriptional co-activator P/CAF [p300/CBP-associated factor, where CBP stands for CREB (cAMP-response-element-binding protein)-binding protein] was shown to inhibit involucrin expression in immortalized keratinocytes [Kawabata, Kawahara, Kanekura, Araya, Daitoku, Hata, Miura, Fukamizu, Kanzaki, Maruyama and Nakajima (2002) J. Biol. Chem. 277, 8099–8105]. Loss of expression or inactivation of other co-activators has also been demonstrated [Suganuma, Kawabata, Ohshima, and Ikeda (2002) Proc. Natl. Acad. Sci. U.S.A. 99, 13073–13078]. In the present study, we re-expressed CBP and P/CAF in immortalized keratinocyte lines that had lost expression of these co-activator proteins. Re-expression of these proteins restored calcium- and RA (retinoic acid)-responsive involucrin expression in these cells. RA and calcium signalling induced exchange of CBP and P/CAF occupancy at the AP-1 sites of the involucrin promoter. CBP and P/CAF inductions of the involucrin expression were not dependent on MEK (mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase), p38, protein kinase C or CaM kinase (calcium/calmodulin-dependent kinase) signalling. Kinase-induced changes in involucrin promoter activity directly resulted from changes in AP-1 protein expression. We concluded that CBP and P/CAF are important regulators of involucrin expression in stratified squamous epithelial cells.
Effect of thyroid hormone binding proteins on insulin receptor binding of B1-thyronine-insulin analogues
Authors: SHOJAEE-MORADIE Fariba , CHAN Michelle P. Y. , TELFER Micayla A. , BRANDENBURG Dietrich , SUNDERMANN Erik , ECKEY Heike , KLEINJUNG Jens , SCHÜTTLER Achim , JONES Richard H.
Published: June 2004

Certain thyronine-insulin analogues, which form non-covalent complexes with plasma proteins, have been shown to act preferentially in the liver. We hypothesized that this property may be dependant on the ability of the analogue to bind to the insulin receptor without prior dissociation from the binding protein. NαB1-L-thyroxyl-insulin, NαB1-3,3′,5′-triiodothyronine-insulin, NαB1-D-thyroxyl-insulin and NαB1-L-thyroxyl-aminolauroyl-insulin were compared with insulin for their capacity to inhibit the binding of [125I]TyrA14-insulin to rat liver plasma membrane in albumin-free buffer. Effective doses at 50% maximum inhibition of binding (ED50) were calculated with and without addition of the thyroid hormone binding proteins transthyretin, thyroxine binding globulin and human serum albumin. The binding of thyronine-insulin analogues to insulin receptors was inhibited in a dose-dependant manner by the addition of thyroid hormone binding proteins at concentrations in the physiological range. Complexes of thyronine-insulin analogues with thyroid hormone binding proteins exhibit impaired insulin receptor binding affinities compared with those of the analogues in their free form. Hepatoselectivity in vivo may not depend on binding of the intact complexes to hepatocytes. These results have implications for the physiological role of hormone binding proteins and the in vivo properties of other insulin analogues which bind to plasma proteins.
Conformational stability and domain coupling in D-glucose/D-galactose-binding protein from Escherichia coli
Authors: PISZCZEK Grzegorz , D'AURIA Sabato , STAIANO Maria , ROSSI Mosè , GINSBURG Ann
Published: June 2004

The monomeric D-glucose/D-galactose-binding protein (GGBP) from Escherichia coli (Mr 33000) is a periplasmic protein that serves as a high-affinity receptor for the active transport and chemotaxis towards both sugars. The effect of D-glucose binding on the thermal unfolding of the GGBP protein at pH 7.0 has been measured by differential scanning calorimetry (DSC), far-UV CD and intrinsic tryptophanyl residue fluorescence (Trp fluorescence). All three techniques reveal reversible, thermal transitions and a midpoint temperature (Tm) increase from 50 to 63 °C produced by 10 mM D-glucose. Both in the absence and presence of D-glucose a single asymmetric endotherm for GGBP is observed in DSC, although each endotherm consists of two transitions about 4 °C apart in Tm values. In the absence of D-glucose, the protein unfolding is best described by two non-ideal transitions, suggesting the presence of unfolding intermediates. In the presence of D-glucose protein, unfolding is more co-operative than in the absence of the ligand, and the experimental data are best fitted to a model that assumes two ideal (two-state) sequential transitions. Thus D-glucose binding changes the character of the GGBP protein folding/unfolding by linking the two domains such that protein unfolding becomes a cooperative, two two-state process. A KA′ value of 5.6×106 M−1 at 63 °C for D-glucose binding is estimated from DSC results. The domain with the lower stability in DSC measurements has been identified as the C-terminal domain of GGBP from thermally induced Trp fluorescence changes.
Instability of phase space structures
Authors: Eremin D. Yu. , Berk H. L.
Published: June 2004

Adiabatic analysis of self-consistent dynamics of a phase space structure surrounded by passing particles under the assumption of a slowly changing amplitude and frequency has revealed that the system can reach a point where adiabatic theory breaks down. Linear perturbative analysis shows that an instability is triggered at precisely these points. Numerical runs were performed to test the adiabatic theory and the instability analysis of a Bernstein–Greene–Kruskal mode for the bump-on-tail problem. First a passing particle distribution function was used that has a constant slope with respect to the action variable. Then a flat passing particle distribution function, which has nearly the same instability criterion and growth rate as the first case was studied and it produces a precise comparison with the results from numerical simulations until instability sets in. Afterwards smaller phase space structures still persist and frequency sweeping continues at a lower rate.
Thickness effect of ferroelectric domain switching in epitaxial PbTiO3 thin films on Pt(001)/MgO(001)
Authors: Kim Yong Kwan , Kim Sang Sub , Shin Hyunjung , Baik Sunggi
Published: June 2004

Epitaxial PbTiO3 thin films of various thicknesses were prepared by pulsed laser deposition on Pt(001)/MgO(001) substrates. Their ferroelectric domain structures and switching behavior were then investigated mainly using scanning force microscopy as a function of film thickness. Direct evidence of a-domain switching was observed under an external electric field, while its contribution to the total piezoelectric response was found negligible. Thinner epitaxial PbTiO3 films with higher c-domain population and larger tetragonality resulted in enhanced d33 piezoelectric coefficients. The results suggest that the key factor determining the piezoelectric response in epitaxial ferroelectric films is not the a-to-c domain switching but apparently the population of c-domains and their tetragonality.
Well-behaved metal–oxide–semiconductor capacitor characteristics of hafnium silicate films deposited in an atomic layer deposition mode by vapor–liquid hybrid deposition process
Authors: Xuan Y. , Hojo D. , Yasuda T.
Published: June 2004

We report electrical properties of hafnium silicate films prepared in an atomic layer deposition mode using Hf(OtC4H9)4 and Si(OC2H5)4 precursors. Film deposition was carried out at room temperature using the vapor–liquid hybrid deposition technique. The C–V curve of the metal–oxide–semiconductor capacitor fabricated by postdeposition anneal and Au electrode evaporation shows good agreement with the theoretical one except for a positive flatband voltage shift of 0.2–0.3 V. The leakage current density was four orders of magnitude lower than SiO2 reference data in the equivalent-oxide-thickness range of <2.5 nm.
Carbon nanotube transistor optimization by chemical control of the nanotube–metal interface
Authors: Auvray S. , Borghetti J. , Goffman M. F. , Filoramo A. , Derycke V. , Bourgoin J. P. , Jost O.
Published: June 2004

Most carbon nanotube transistors work as Schottky barrier transistors. We show that chemical treatment of operational p-type nanotube transistors by trifluoro-acetic acid (TFA) leads to the drastic improvement of all the key device parameters. This effect is due to the highly polar nature of the TFA molecule which, once adsorbed at the metal–nanotube interface, lowers the Schottky barrier for the holes and thus favors their injection.
Observation of 1.5μm photoluminescence and electroluminescence from a holmium organic complex
Authors: Zang F. X. , Li W. L. , Hong Z. R. , Wei H. Z. , Li M. T. , Sun X. Y. , Lee C. S.
Published: June 2004

Electroluminescence (EL) and photoluminescence in both the visible and near-infrared spectral range were observed from a holmium(dibenzoylmethanato)3(bathophenanthroline) [Ho(DBM)3bath]. Five peaks at 580nm, 660nm, 980nm, 1200nm, and 1500nm, respectively, were attributed to the internal 4f electronical transitions of the Ho3+ ions. Except for the emissions of the Ho3+ ions, a broadband exciplex emission from 480nmto670nm appeared in the EL cases. The emission intensity of the exciplex at organic interface showed a tendency to saturation beyond a certain driving voltage, while the emissions of the Ho3+ ions kept increasing. This evolution of visible EL spectra was discussed in terms of the extension of the charge recombination zone. The 1500nm emission corresponding to the F55→I65 transition suggests that the Ho(DBM)3bath is a potential candidate for optical communications.
Heat capacity measurements of two-dimensional self-assembled hexadecanethiol monolayers on polycrystalline gold
Authors: Zhang Z. S. , Wilson O. M. , Efremov M. Yu. , Olson E. A. , Braun P. V. , Senaratne W. , Ober C. K. , Zhang M. , Allen L. H.
Published: June 2004

The melting characteristics of hexadecanethiol two-dimensional self-assembled monolayers (SAMs) grown on polycrystalline Au surfaces are obtained via heat capacity measurements using nanocalorimetry at scanning rates of ∼30 000°C∕s. The analyzed amount of alkanethiol in the form of SAMs is typically in the 10−11 mol range. Melting occurs over a broad (full width on the half height ∼100°C) temperature range with a melting temperature of about 70°C, if the alkanethiol is partially desorbed from the Au surface during thermal treatment. SAMs in their as-deposited state without desorption have melting temperatures above 100°C. The heat of fusion is about 20kJ∕mol. Partial desorption of the alkanethiol is directly observed. The melting characteristics of three-dimensional SAMs on Au nanoparticles are comparable to earlier studies using conventional calorimetry.
Radiation-defect-dependent photoconductivity transients and photoluminescence in semi-insulating GaN
Authors: Gaubas E. , Kazlauskas K. , Tomašiūnas R. , Vaitkus J. , Žukauskas A.
Published: June 2004

Effect of radiation defects on the photoconductivity transients and photoluminescence (PL) spectra have been examined in semi-insulating GaN epitaxial layers grown on bulk n-GaN∕sapphire substrates. Manifestation of defects induced by 10keV x-ray irradiation with the dose of 600Mrad and 100keV neutrons with the fluence of 5×1014cm−2 have been revealed through steady-state and pulsed PL as well as through contact photoconductivity and microwave absorption transients. Synchronous decrease of the PL intensity of yellow, blue, and ultraviolet bands peaked at 2.19, 2.85, and 3.42eV, respectively, with density of radiation-induced defects is observed. The decrease of the PL intensity is accompanied by an increase of asymptotic decay lifetime, which is due to excess-carrier multi-trapping. The decay fits the stretched exponent approximation exp[−(t∕τ)α] with the different factors α in as-grown material (α≈0.7) and irradiated samples (α≈0.3).
Focused-ion-beam directed self-assembly of Cu2O islands on SrTiO3(100)
Authors: Du Y. , Atha S. , Hull R. , Groves J. F. , Lyubinetsky I. , Baer D. R.
Published: June 2004

Nanoscale islands of Cu2O have been synthesized on single-crystal SrTiO3 (100) substrates using oxygen plasma-assisted molecular-beam epitaxy (MBE). Island growth location has been controlled by using an ex situ Ga+ focused ion beam (FIB) to modify the growth surface in discrete locations prior to island synthesis. The FIB modifications have generated surface topography with lateral dimensions of 150–200nm. Ex situ atomic force microscopy study after island growth reveals that certain FIB substrate modification and MBE growth condition combinations lead to directed self-assembly of metal oxide islands at the edges of the FIB modified zones.
Microstructure of heteroepitaxial GaN grown on mesa-patterned 4H-SiC substrates
Authors: Bassim N. D. , Twigg M. E. , Eddy C. R. , Henry R. L. , Holm R. T. , Culbertson J. C. , Stahlbush R. E. , Neudeck P. G. , Trunek A. J. , Powell J. A.
Published: June 2004

Cross-sectional transmission electron microscopy and atomic force microscopy have been used to study the microstructure of a thin heteroeptiaxial GaN film grown on (0001) 4H-SiC mesa surfaces with and without atomic scale steps. Analysis of a mesa that was completely free of atomic-scale surface steps prior to III–N film deposition showed that these GaN layers had a wide variation in island height (1–3μm) and included the presence of pit-like defects on the film surface. This sample had a low dislocation density (5×108∕cm2) as compared to conventionally grown samples on unpatterned (0001) on-axis 4H-SiC (2×109∕cm2), coupled with a 3–5 times increase in grain size. A comparison of a GaN film on the step-free 4H-SiC mesa region with a GaN film on a stepped 4H-SiC mesa region on the same substrate showed that the presence of surface steps reduced the overall grain size of the film from 7–10μm to a grain size of about 2–3μm. Since the GaN films grow via a Volmer–Weber mechanism, a decrease in the number of heterogeneous nucleation sites may allow the growth of large GaN islands before coalescence, thus reducing the number of threading dislocations. These results are promising for the further development of unique, low-dislocation density active regions for GaN device structures on 4H-SiC.
Three-dimensional particle-in-cell simulations of rapid start-up in strapped oven magnetrons due to variation in the insulating magnetic field
Authors: Luginsland J. W. , Lau Y. Y. , Neculaes V. B. , Gilgenbach R. M. , Jones M. C. , Frese M. H. , Watrous J. J.
Published: June 2004

A three-dimensional parallel particle-in-cell code, ICEPIC, is used to simulate the geometry and the magnetic field profiles of the recent low-noise, fast startup magnetron experiments at the University of Michigan. The fast startup, the power levels, and the starting currents that have been observed in these experiments are quantitatively reproduced in the simulations. The tendency for low noise operation has also been reproduced with the use of an azimuthally varying magnetic field.
Coulomb blockade in suspended Si3N4-coated single-walledcarbon nanotubes
Authors: Peng H. B. , Golovchenko J. A.
Published: June 2004

Uniform coaxial coating of suspended single-walled carbon nanotubes with high-quality dielectric silicon nitride has been obtained by low-pressure chemical vapor deposition. A three-terminal device has been demonstrated by coating a suspended metallic nanotube grown directly on contacting metal electrodes with subsequent patterning of a top gate electrode. Large charging energies have been observed in the suspended nanotubes and the conversion factor from gate voltage to the electrostatic potential in the nanotube approaches unity, which can be attributed to the device geometry.
Photonic crystals through holographic lithography: Simple cubic, diamond-like, and gyroid-like structures
Authors: Ullal Chaitanya K. , Maldovan Martin , Thomas Edwin L. , Chen Gang , Han Yong-Jin , Yang Shu
Published: June 2004

We show how to fabricate three basic photonic crystal structures with simple cubic, fcc, and bcc translational symmetry by interference lithography. The structures are fabricable by the interference of beams launched from the same half space. The simple cubic structure is size scalable while the structure with fcc translational symmetry possesses two band gaps. Both these structures are experimentally realized.
Nonlinear transmission properties of a deep-etchedmicrostructured waveguide
Authors: Linden S. , Mondia J. P. , Van Driel H. M. , Kleckner T. C. , Stanley C. R. , Modotto D. , Locatelli A. , De Angelis C. , Morandotti R. , Aitchison J. S.
Published: June 2004

In this letter, we investigate the nonlinear transmission properties of a one-dimensional micro-structured AlGaAs waveguide with a defect in the middle of a deep-etched Bragg grating. The transmitted spectrum depends on the spectral position of the incident pulse spectrum with respect to the defect mode as well as the pulse intensity. These findings are very important for all optical switching applications and can be explained by the interplay between self-phase modulation of the incident 250fs pulses in the waveguide and the filtering properties of the defect mode.
Ball milling sound statistical analysis and its relationship with the mechanical work intensity
Authors: Cuadrado-Laborde C. , Damonte L. C. , Mendoza-Zélis L.
Published: June 2004

In this article we present an attempt to relate the intensity of the mechanical work done in ball milling processes with some characteristics of the sound recorded during these milling runs. In order to reach this purpose the ball milling sound was recorded at several vial frequencies in a broad range from 14 to 40 Hz, with and without a powder charge. This charge was of two distinct types: Al+Fe2O3 or Fe2O3. Two kinds of parameters were proposed to describe quantitatively a milling sound record: total root-mean-square power (dB) and 75 (95) percentile. In order to prove the validity of these results a comparison was made with the rate of energy transfer necessary to reach the displacement reaction between Al and Fe2O3. The reaction ignition was apparently delayed, for milling frequencies in a narrow range around 35 Hz, which can be explained in terms of a decrease in the rate of energy transfer as suggested by the sound parameters aforementioned. There is general consensus, between ball milling researchers, that the energy transfer is a monotonous function of the vial frequency. The results exposed here clearly show that this in fact is not the case. There would be vial frequencies at which reactions slow down for the given experimental conditions. We propose then this technique as a tool to monitor ball milling processes for application in several circumstances. The potential of the method results improve the ability of sound analyzer programs to measure in real time, without further postprocess.
Periodic method: Correction for thermocouple and simultaneous estimation of thermal conductivity and thermal diffusivity
Authors: Ould Lahoucine Cherif , Khellaf Abdallah
Published: June 2004

Difficulty in thermal conductivity determination from temperature data recorded in the quasisteady state using the periodic method is investigated. The reason for the previously resulting big discrepancy comes from the fact that the thermocouple effects have been ignored in earlier models. Taking into account these important effects, a new model is developed and the thermal conductivities for Delrin and 304 stainless steel are determined with high accuracy.
Nanopillar growth mode by vapor-liquid-solid epitaxy
Authors: Taraci J. L. , Dailey J. W. , Clement T. , Smith David J. , Drucker Jeff , Picraux S. T.
Published: June 2004

We report epitaxial growth of Ge nanopillars (NPs) on Si(100) by vapor-liquid-solid (VLS) growth from digermane. This growth morphology is characterized by short, low-aspect-ratio pillars and is markedly different from the long, narrow nanowires (NWs) previously reported for VLS growth. The NP growth mode occurs at low digermane pressures. It is attributed to surface-diffusion-induced lateral growth in combination with an insufficient Ge concentration gradient in the AuGe eutectic to catalyze NW growth. High resolution electron microscopy confirms that the NPs are epitaxial with the Si (100) substrate and are fully relaxed and strain free.
Dielectric relaxation in 91%Pb(Zn1∕3Nb2∕3)O3–9%PbTiO3 single crystal at low temperature
Authors: Bao Peng , Yan Feng , Dai Yurong , Zhu Jingsong , Wang Yening , Luo Haosu
Published: June 2004

The temperature dependent dielectric response of ⟨001⟩-oriented 91%Pb(Zn1∕3Nb2∕3)O3–9%PbTiO3 single crystal has been studied at various frequencies. A dielectric relaxation process with a broad distribution of time constant has been observed below 180K. The peak temperature of the dielectric loss can be fitted well with Volger–Fulcher relation. We assume this relaxation process can be attributed to the freezing of ferroelectric macrodomain walls induced by the pinning of point defects.
Optical properties of Mn4+ ions in GaN:Mn codoped with Mg acceptors
Authors: Han B. , Korotkov R. Y. , Wessels B. W. , Ulmer M. P.
Published: June 2004

The optical properties of Mn–Mg-codoped epitaxial GaN were studied. Addition of Mg acceptors quenches the weak manganese-related photoluminescence (PL) band at 1.3eV in GaN:Mn and a series of sharp PL peaks are observed at 1eV in codoped epilayers. The change in PL spectra indicates that the Mg addition stabilizes the Mn4+ charge state by decreasing the Fermi level. The 1eV PL peaks are tentatively attributed to intracenter transitions involving Mn4+ ions. Spin-allowed 3d-shell T24–T14 transitions and their phonon replicas are involved. The relative intensities of the sharp peaks are strongly dependent on the excitation wavelength, indicating that the optically active Mn4+ centers involved in the separate peaks are different. The temperature dependence of the PL spectrum suggests the presence of at least three distinct Mn4+ complex centers.
X-ray energy spectrum measurements by an annular superconducting tunnel junction with trapped magnetic flux quanta
Authors: Lisitskiy M. P. , Nappi C. , Ejrnaes M. , Cristiano R. , Huber M. , Rottler K. , Jochum J. , von Feilitzsch F. , Barone A.
Published: June 2004

We report on the Fe55 x-ray pulse height spectrum of an annular superconducting tunnel junction (STJ) collected without an external magnetic field. An energy resolution of 100eV was obtained for the Kα line of the top electrode. The Josephson critical current and Fiske resonances were suppressed by the presence of trapped magnetic flux quanta which created a persistent current and self-generated magnetic field. The obtained energy resolution and the stability of the trapped magnetic flux under irradiation demonstrate the capability of an annular STJ device with trapped flux quanta to detect radiation without using the external magnetic field that is required in the conventional detection scheme.
ZnMgO
epilayers and ZnO–ZnMgO quantum wells for optoelectronic applications in the blue and UV spectral region
Authors: Gruber Th. , Kirchner C. , Kling R. , Reuss F. , Waag A.
Published: June 2004

We have investigated the properties of ZnMgO epilayers and ZnO–ZnMgO quantum well structures grown by metalorganic vapor-phase epitaxy. A well-controlled incorporation of magnesium, x⩽0.10, could be confirmed resulting in a blueshift of the photoluminescence emission wavelength of the Zn1−xMgxO layers up to 200meV. Using ZnMgO as barrier material, ZnO–ZnMgO quantum well structures with different well widths have then been fabricated. The confinement effect in the ZnO quantum wells leads to the expected increase of the corresponding quantum well emission energy with decreasing well width. A comparison to calculations also suggests a further enhancement of the exciton binding energy in the quantum wells of up to 90meV.
Characterization of line-defect-waveguide lasers in two-dimensional photonic-crystal slabs
Authors: Sugitatsu Atsushi , Asano Takashi , Noda Susumu
Published: June 2004

Here we investigate a line-defect-waveguide laser in a two-dimensional photonic-crystal slab. The change δλ in lasing wavelength for a change δW in waveguide width is found to be extremely large: δλ∕δW=2. It is two orders of magnitude greater than that for a conventional distributed-feedback laser. An investigation of the electromagnetic-field distribution at the waveguide-mode edge is made, giving an indication of the cavity-mode structure for lasing oscillation. Fourier transform analysis reveals that the extremely large tunability originates from the “zigzag” mode behavior of the line-defect waveguide in the photonic crystal, due to two-dimensional distributed feedback and reflection.
Chemistry-mediated two-dimensional to three-dimensional transition of In thin films
Authors: Wei H. L. , Huang Hanchen , Woo C. H. , Zhang X. X. , Zhou L. G.
Published: June 2004

This letter reports a mechanism of chemistry-mediated two-dimensional to three-dimensional (2D–3D) transition during In thin film deposition, and the corresponding evolution of nanoscale islands. Using magnetron sputtering technique, we deposit In on Au substrate. Despite the fact that In wets on Au, In islands prevail over the uniform film soon after the deposition starts. The 2D–3D transition is found to be a result of the formation of Au3In on the Au substrate. The alloy formation leads to nonwetting of In, thereby the high mobility of In atoms and In clusters, and eventually well-separated In islands. The structures of In and Au are characterized by scanning electron microscopy, transmission electron microscopy, and electron diffraction.
Work-function difference between Al and n-GaN from Al-gated n-GaN∕nitrided-thin-Ga2O3∕SiO2 metal oxide semiconductor structures
Authors: Bae Choelhwyi , Krug Cristiano , Lucovsky Gerald , Chakraborty Arpan , Mishra Umesh
Published: June 2004

In most previous reports on Al-gated n-GaN∕SiO2 metal–oxide–semiconductor (MOS) structures, the work–function difference between Al and n-GaN (ϕms) has been chosen as 0V by assuming that the work function of the Al gate and n-GaN are both 4.1eV. In this letter, ϕms is determined as ∼0.1V using Al-gated n-GaN∕nitrided-thin-Ga2O3∕SiO2 MOS capacitors by measuring flatband voltage as a function of oxide thickness. Formation of an ultrathin (∼0.6-nm-thick) Ga2O3 layer on n-GaN prior to the deposition of SiO2 is important to prevent uncontrolled parasitic oxidation of then-GaN surface and possibly reduces the interface dipole between n-GaN and SiO2.
In situ ultraviolet treatment in an Ar ambient upon p-type hydrogenated amorphous silicon–carbide windows of hydrogenated amorphous silicon based solar cells
Authors: Myong Seung Yeop , Kim Sang Soo , Lim Koeng Su
Published: June 2004

We proposed an in situ postdeposition ultraviolet treatment in an Ar ambient (UTA) to improve the p∕i interface of amorphous silicon based solar cell. We have increased the conversion efficiency by ∼16% by improving the built-in potential and reducing recombination at the p∕i interface. Through spectroscopic ellipsometry and Fourier-transform infrared measurements, it is concluded that the UTA process induces structural modification of the p-type hydrogenated amorphous silicon–carbide (p-a-SiC:H) window layer. An ultrathin p-a-SiC:H contamination layer formed during the UTA process acts as a buffer layer at the interface.
Metalorganic vapor phase epitaxy InSbp+nn+ photodiodes with low dark current
Authors: Paltiel Y. , Sher A. , Raizman A. , Shusterman S. , Katz M. , Zemel A. , Calahorra Z. , Yassen M.
Published: June 2004

Photodiodes of InSb were fabricated on epilayers grown by metalorganic vapor phase epitaxy (MOVPE). Dark reverse current density as low as 1×10−7A∕cm2 at −0.1V bias, and zero-bias-resistance area products as high as 1×106Ωcm2 were measured. These values are comparable to the best values reported for InSb diodes grown by molecular-beam epitaxy. The very good uniformity of the diode dark current implies that MOVPE is a promising growth technique for the fabrication of state-of-the-art focal plane InSb detector arrays.
Single-mode operation of terahertz quantum cascade lasers with distributed feedback resonators
Authors: Mahler Lukas , Köhler Rüdeger , Tredicucci Alessandro , Beltram Fabio , Beere Harvey E. , Linfield Edmund H. , Ritchie David A. , Davies A. Giles
Published: June 2004

Distributed feedback terahertz quantum-cascade lasers emitting at 4.34 and 4.43THz are presented. Mode selection is based on a complex-coupling scheme implemented into the top-contact layer by a combination of wet chemical etching and ohmic-contact deposition. Single-mode emission stable at all injection currents and operating temperatures is shown, with a side-mode suppression ratio exceeding 20dB. Peak output powers of up to 1.8mW are obtained at low temperatures.
Electron field emission from SiC∕Si heterostructures by high temperature carbon implantation into silicon
Authors: Xing Y. M. , Zhang J. H. , Yang W. W. , Yu Y. H. , Song Z. R. , Lin Z. X. , Shen D. S.
Published: June 2004

A high-intensity electron field emission was obtained from a SiC∕Si heterostructure, which was formed by high temperature carbon implantation into silicon. Densely distributed sharp tips were easily obtained at the interface of the SiC∕Si heterostructure by post-implantation etching off the top Si. A low turn-on field of 2.6V∕μm was observed with samples formed by 160keV carbon implantation with a dose of 8.0×1017cm−2. The existence of the densely distributed small protrusions was considered as the main reason for efficient emission.
Frozen magnetoresistance in the magnetization reversal of granular Bi(Pb)-HTSCs
Authors: Sukhanov A. A. , Omelchenko V. I.
Published: June 2004

The frozen magnetoresistance of ceramic Bi(Pb)-HTSC samples is investigated as a function of the fields initiating magnetic flux trapping and the magnetization-reversing fields: Rt(Hi,Hr). It is found that the Rt(Hr) curves are nonmonotonic. The value of the frozen magnetoresistance decreases substantially after application of the first Hr pulse (Hr<Hi) but remains practically unchanged upon subsequent magnetization reversals by pulses of the same magnitude but of either polarity. The influence of the magnetization reversal on the anisotropy of the magnetoresistance and the negative magnetoresistance effect are studied. It is shown that the results are in conflict with models of the critical state for the granules and superconducting loops but are well described quantitatively by the proposed model of granular Bi(Pb)-HTSCs, according to which the magnetic flux trapping occurs in “normal” granules wrapped in superconducting shells, while the resistance of the samples is determined by chains of weak links.
Magnetic and transport properties of La0.7Sr0.3MnO3/Pr0.65Ca0.35MnO3 multilayered films with different microstructure
Authors: Prokhorov V. G. , Flis V. S. , Kaminsky G. G. , Lee Y. P.
Published: June 2004

The magnetic and transport properties of single-crystal and polycrystalline La0.7Sr0.3MnO3/Pr0.65Ca0.35MnO3 multilayered films are investigated in the temperature range 4.2–300 K. It is shown that the transformation from an incoherent to a coherent interface between layers leads to an enhancement of the ferromagnetic coupling, which is accompanied by a modification in the temperature dependence of the resistance and by a grown negative magnetoresistance ratio at room temperature. The influence of grain boundaries on the transport of carriers in the multilayered films is discussed on the basis of modern theoretical approaches.
Low-temperature behavior of disordered magnetic impurities: Distribution of effective Kondo temperatures
Authors: Zvyagin A. A. , Makarova A. V.
Published: June 2004

Several rare-earth compounds, low-dimensional organic conductors, and spin chains exhibit low-temperature divergences of their magnetic susceptibility and specific heat (non-Fermi-liquid behavior). Such divergences are often related to disordered ensembles of magnetic impurities in those systems. In this work the distribution function of the effective characteristic of a single magnetic impurity, the Kondo temperature, is derived. We calculate how the distributions of Kondo temperatures depend on the effective dimensionality of the problem and on the concentration of impurities.
Low-temperature anomalies heat capacity, Ohmic loss in the 0–100 MHz range, and linear dimensions of samples of uranium and some of its compounds
Authors: Dmitriev V. M. , Prentslau N. N. , Gurevich A. M. , Ischenko L. A. , Terekhov A. V. , Suski W. , Troć R.
Published: June 2004

From measurements of the heat capacity and resistivity of α uranium and the compounds UCu5Al, UCu4Al8, UFe4Al8, and U3Ni3Sn4 it is established experimentally for the first time that those properties have anomalies at temperatures near 60 K and in the vicinity of the transitions α1(43 K), α2(37 K), and α3(23 K). It is assumed that these anomalies in compounds containing uranium as a constituent are due specifically to the uranium. It is found that in UCu5Al the temperature dependence of the Ohmic loss changes from being of a semiconductor character at T>TN (TN=20 K) to a metallic character at T<TN. It is discovered that the linear dimensions of α uranium and of the compound UCu5Al suffer a change upon repeated thermocycling from room to low temperatures.
Interaction of acoustic waves with an interface in highly anisotropic layered crystals
Authors: Kosevich A. M. , Minaev P. A. , Syrkin E. S. , Polyakov M. L.
Published: June 2004

The scattering of acoustic waves on a planar defect in the interior of a crystal is studied by the methods of lattice dynamics. The model chosen consists of two semi-infinite, highly anisotropic crystals, the forces of interaction between which are distinct from the interactions within the crystals themselves. The model is used to study the resonant transmission of waves through an impurity monolayer. This resonant transmission effect is due to the weak coupling of the defect to the host lattice and cannot be described in the framework of the standard theory of elasticity, since the displacements of the defect layer and of the closest-lying layers of the host matrix are substantially different. For nongrazing angles of incidence the resonant transmission effect can be illustrated qualitatively by the example of an infinite linear chain containing a point impurity.
Molecular phylogeny of Australasian anopsobiine centipedes (Chilopoda : Lithobiomorpha)
Authors: Edgecombe Gregory D. , Giribet Gonzalo
Published: June 2004

Species assigned to the anopsobiine centipede genera Anopsobius Silvestri, 1899, and Dichelobius Attems, 1911, are widely distributed on fragments of the Gondwanan supercontinent, including temperate and tropical Australia, New Zealand, New Caledonia, the Cape region of South Africa, and southern South America. Phylogenetic relationships between Australasian and other Gondwanan Anopsobiinae are inferred based on parsimony and maximum likelihood analyses (via direct optimisation) of sequence data for five markers: nuclear ribosomal 18S rRNA and 28S rRNA, mitochondrial ribosomal 12S rRNA and 16S RNA, and the mitochondrial protein-coding cytochrome c oxidase subunit I. New molecular data are added for Anopsobius from South Africa and New Zealand, Dichelobius from New Caledonia, and a new species from Queensland, Australia, Dichelobius etnaensis, sp. nov. The new species is based on distinctive morphological and molecular data. The molecular phylogenies indicate that antennal segmentation in the Anopsobiinae is a more reliable taxonomic character than is spiracle distribution. The former character divides the Gondwanan clade into a 17-segmented group (Dichelobius) and a 15-segmented group (Anopsobius). Confinement of the spiracles to segments 3, 10 and 12 has at least two origins in the Gondwanan clade. The area cladogram for Dichelobius (Queensland (Western Australia + New Caledonia)) suggests a relictual distribution pruned by extinction.
A bubble-driven microfluidic transport element for bioengineering
Authors: Marmottant Philippe , Hilgenfeldt Sascha
Published: June 2004

Microfluidics typically uses channels to transport small objects by actuation forces such as an applied pressure difference or thermocapillarity. We propose that acoustic streaming is an alternative means of directional transport at small scales. Microbubbles on a substrate establish well controlled fluid motion on very small scales; combinations (“doublets”) of bubbles and microparticles break the symmetry of the motion and constitute flow transport elements. We demonstrate the principle of doublet streaming and describe the ensuing transport. Devices based on doublet flow elements work without microchannels and are thus potentially cheap and highly parallelizable.
The synaptic vesicle protein SV2A is the binding site for the antiepileptic drug levetiracetam
Authors: Lynch Berkley A. , Lambeng Nathalie , Nocka Karl , Kensel-Hammes Patricia , Bajjalieh Sandra M. , Matagne Alain , Fuks Bruno
Published: June 2004

Here, we show that the synaptic vesicle protein SV2A is the brain binding site of levetiracetam (LEV), a new antiepileptic drug with a unique activity profile in animal models of seizure and epilepsy. The LEV-binding site is enriched in synaptic vesicles, and photoaffinity labeling of purified synaptic vesicles confirms that it has an apparent molecular mass of ≈90 kDa. Brain membranes and purified synaptic vesicles from mice lacking SV2A do not bind a tritiated LEV derivative, indicating that SV2A is necessary for LEV binding. LEV and related compounds bind to SV2A expressed in fibroblasts, indicating that SV2A is sufficient for LEV binding. No binding was observed to the related isoforms SV2B and SV2C. Furthermore, there is a high degree of correlation between binding affinities of a series of LEV derivatives to SV2A in fibroblasts and to the LEV-binding site in brain. Finally, there is a strong correlation between the affinity of a compound for SV2A and its ability to protect against seizures in an audiogenic mouse animal model of epilepsy. These experimental results suggest that SV2A is the binding site of LEV in the brain and that LEV acts by modulating the function of SV2A, supporting previous indications that LEV possesses a mechanism of action distinct from that of other antiepileptic drugs. Further, these results indicate that proteins involved in vesicle exocytosis, and SV2 in particular, are promising targets for the development of new CNS drug therapies.