bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-domain and lock-in rate-window photocarrier radiometric measurements of recombination processes in silicon
Authors: Mandelis Andreas , Pawlak Micha , Wang Chinhua , Delgadillo-Holtfort Isabel , Pelzl Josef
Published: December 2005

Time-domain and lock-in rate-window photocarrier radiometry (PCR) configurations are introduced both experimentally and theoretically to investigate the responses of p- and n-type Si wafers under a repetition-period-scanned square-wave-modulated super-band-gap laser beam which produces free excess photocarriers. The complete asymmetric time-domain carrier diffusion and recombination boundary-value problem with different front- and back-surface recombination velocities was solved in terms of the full spectrum of spatial eigenmodes and used to fit the time-domain data. The accurate measurement of the photocarrier transport properties (bulk lifetime, surface recombination velocities, and ambipolar diffusivity) was found to require the linear superposition of all the effective decay lifetimes associated with the eigenmode spectrum. The effects of the infinite prior pulse train to the current photocarrier radiometric response wave form were quantified and were found to be very important for certain ranges of transport parameters, pulse durations, and repetition periods. The time-domain formalism was further used to develop a theory for lock-in rate-window photocarrier radiometry. The application of the theory to the experimental results shows that they retain the time-domain character of the photocarrier generation and recombination processes, with data quality and signal-to-noise ratio superior to coaddition-averaged transients, especially in the case of samples exhibiting very low time-domain PCR signals.
Quantum transport in chains with noisy off-diagonal couplings
Authors: Pereverzev Andrey , Bittner Eric R.
Published: December 2005

We present a model for conductivity and energy diffusion in a linear chain described by a quadratic Hamiltonian with Gaussian noise. We show that when the correlation matrix is diagonal, the noise-averaged Liouville–von Neumann equation governing the time evolution of the system reduces to the [Lindblad, Commun. Math. Phys. 48, 119 (1976)] equation with Hermitian Lindblad operators. We show that the noise-averaged density matrix for the system expectation values of the energy density and the number density satisfies discrete versions of the heat and diffusion equations. Transport coefficients are given in terms of model Hamiltonian parameters. We discuss conditions on the Hamiltonian under which the noise-averaged expectation value of the total energy remains constant. For chains placed between two heat reservoirs, the gradient of the energy density along the chain is linear.
350 mW high-power He–Ne laser and its application in photodynamic therapy
Authors: Ling Yi-Ming , Wu Si-En
Published: December 2005

A high-power He–Ne laser that has two laser tubes with a flat discharge cross section is designed and made. It can generate the total output power of more than 350 mW. The laser beams can be coupled into a quartz optic fiber using an optical system and the output power from the end of the optic fiber is more than 280 mW. The optic fiber will then pass through the endoscope tube to enter the human body to destroy the cancer for photodynamic therapy (PDT). In 44 clinical cases where the high He–Ne laser is used for PDT, the complete response rate is about 60%. The design of this high-power He–Ne laser and its application are introduced briefly in this article.
X-ray-absorption fine structure measurement with parallel-plate capacitor: Observation of surface electronic states of metals
Authors: Ishii Masashi , Nakao Aiko
Published: December 2005

For surface electronic state analyses of metals, we developed a new x-ray-absorption fine structure (XAFS) measurement technique with a parallel-plate capacitor. Since the capacitance is changed by x-ray-induced photoionization on the metal surface, the surface XAFS spectrum of a metal can be obtained from the capacitance dependent on the x-ray photon energy. We adopted this technique to the Cu metals. The XAFS spectrum at the CuK absorption edge is different from the conventional XAFS spectrum of either Cu or Cu2O. This finding suggests that the XAFS spectrum indicates two-dimensional (2D) electronic states between the Cu bulk and the Cu2O native oxide layer. The 2D electronic states were characterized by degeneration of Cu 4pπ and a blueshift of Cu 4pσ. These characteristics can be explained by hybridization of vertical Cu 4pz with horizontal 4px and 4py in CuO-like structure at the interface.
A double-beam common path laser interferometer for the measurement of electric field-induced strains of piezoelectric thin films
Authors: Huang Z. , Whatmore R. W.
Published: December 2005

We report in this paper the development of a modified Mach-Zehnder-type double-beam common path laser interferometer for the measurement of electric field-induced strain in piezoelectric materials, especially for the thin films. Compared to previous interferometers, this one is simpler and more compact, and the measurement and reference arms share a common path for most of the optical length. Example results have been reported for the quartz, lead zirconate titanate (PZT) ceramic sample, and PZT thin films. Double- and single-beam measurements have been carried out at different frequencies for the same spot of a PZT thin-film sample and it was found that the single-beam values were a few times of the values as obtained from the double-beam technique. This phenomenon is confirmed by the laser scanning vibrometer measurements.
Meteorological radiosonde interface for atmospheric ion production rate measurements
Authors: Harrison R. G.
Published: December 2005

A disposable balloon-carried instrument, interfaced to a commercial meteorological radiosonde for measuring the atmospheric ion production rate, is described. The sensor used is a gamma-sensitive Geiger tube, operated at 550V bias, produced from a lightweight transformerless supply. The supply requires 15Vat10mA, and precision regulation is used to minimize the Geiger tube’s response to bias voltage changes. The supply was stable to 0.1% for supply voltage variations between 15 and 25V, and varied by less than 1% over temperatures from −53to25°C during an atmospheric ascent. A digital counter incremented with each Geiger tube event, and the instantaneous count value was telemetered over a radiolink, time-stamped on reception to obtain the count rate. The derived ion production rate profile agrees with a standard parametrization to 5%.
Anomalous attenuation at low temperatures in high-intensity helium beam sources
Authors: Hedgeland H. , Jardine A. P. , Allison W. , Ellis J.
Published: December 2005

High-intensity supersonic helium beam sources are a critical component in modern thermal energy helium atom scattering apparatuses. In common with sources developed elsewhere, we have observed beam attenuation at low temperature as the helium flow through the nozzle is increased. A detailed analysis of the measurements demonstrates that direct backscattering in the nozzle-skimmer region is likely to be the major attenuation source. A numerical model, which describes the principle sources of scattering in the region between source and skimmer, is shown to provide a good description of the experimental data for a range of flow conditions and for stagnation temperatures between 37 and 300K. The model includes partial accommodation of atoms scattered from surfaces of the skimmer and chamber, together with a realistic scattering potential. We use the model to predict the effect of various geometric alterations, aimed at improving the ultimate beam intensity.
Evaluation of the sensitivity to mechanical vibrations of an IR Fourier spectrometer
Authors: Comolli L. , Saggin B.
Published: December 2005

This article presents an experimental and theoretical investigation of the sensitivity to mechanical disturbances of a Fourier-transform infrared spectrometer, the Planetary Fourier Spectrometer, currently orbiting around Mars onboard ESA Mars Express orbiter. A theoretical analysis has been performed in order to highlight the expected effects of the vibrations, then laboratory tests have been designed and carried out for instrument characterization. The two classical types of disturbance effects were expected in the case of mechanical vibrations: the interfering type, leading to an additive contribution to the interferograms, and the modifying type, which changes the interferometer sensitivity. Both effects have been evidenced in the experimental tests and the instrument sensitivity derived; moreover, the effects on the spectra, which are the Fourier transform of interferograms, are highlighted and characterized. The effects of both harmonic and random broadband spectrum disturbances have been considered. While the broadband disturbances increase uniformly the noise, harmonic disturbances produce localized effects in the spectra and replicas of the spectral features with wave-number shifts proportional to disturbance frequency. It has also been highlighted that, the disturbances from mechanical vibrations being uncorrelated with the interferometric signals, by spectrum averaging, like all the other noise sources, they can be reduced. Methods for spectrum diagnostics and for increasing the signal-to-noise ratio in vibration-affected spectra are proposed as well.
Nanosecond rise time air-core current transformer for long-pulse current measurement in pulsed power
Authors: Shukla R. , Shyam A. , Chaturvedi S. , Kumar R. , Lathi D. , Chaudhary V. , Verma R. , Debnath K. , Sharma S. , Sonara J. , Shah K. , Adhikary B.
Published: December 2005

A slow-wave delay line type air-core (nonmagnetic Nylon former) current transformer fabricated using silver epoxy for the measurement of currents of long pulse durations and few nanoseconds rise times is reported in this article. The advantage of using silver epoxy is that it fills all the voids between coil and shield and enhances the proximity of the coil to the shield, leading to a high value of distributed capacitance. Thus the transit time of the coil increases and it can measure fast current pulses of longer durations. Increasing the inductance of the coil can compensate for the resulting reduction in the sensitivity of the coil for matched termination. An easy experimental technique to find the value of the matched terminating resistor is also reported in this article. We have also done simulations of the slow wave current transformer using PSPICE.
Optical absorption spectrum measurement of films at a low temperature using photothermal bending spectroscopy
Authors: Habuchi Hitoe , Harada Daisuke
Published: December 2005

The optical absorption spectrum of a semiconductor film was obtained at a low temperature using an optical cantilever method called photothermal bending spectroscopy. The film, clamped on one side in a cryostat, was uniformly cooled with nitrogen gas. The product of the measurable optical absorption coefficient and the thickness of the film was better than 1×10−3 at 110K. We demonstrated that the 1.74eV peak in the optical absorption spectrum of a C60 film could not be observed at room temperature, but could be observed at 110K due to a sharpening of the Urbach tail slope.
Interfacial layer formations between Cu(In,Ga)Se2 and InxSy layers
Authors: Abou-Ras D. , Kostorz G. , Strohm A. , Schock H.-W. , Tiwari A. N.
Published: December 2005

Cu ( In , Ga ) Se 2 (CIGS) thin-film solar cells with InxSy buffer layers deposited by physical vapor deposition yield efficiencies of up to 14.8%. For substrate temperatures during the InxSy deposition ranging from 23to200°C, air annealing of the completed solar cells leads to an improvement of the photovoltaic performance. However, at substrate temperatures of 300°C, the efficiencies are practically zero, and air annealing does not improve this value. To understand the effects of substrate temperature and air annealing on the CIGS/InxSy interfaces of the solar cells, these interfaces have been studied by means of bright-field and high-resolution transmission electron microscopy, selected-area electron diffraction (SAED), and energy-dispersive x-ray spectrometry (EDX). It is shown that air annealing leads to a substantial Cu depletion on the CIGS side of the CIGS/InxSy interface, probably inducing the formation of a compositionally graded interface between the buffer and CIGS. For the 300°C sample, CuIn5S8 formed instead of InxSy, as identified by means of SAED and EDX. The large density of vacancies and defects in the spinel-type cubic crystal structure of CuIn5S8 provides a large number of recombination centers at the heterojunction of the solar cell, thus deteriorating considerably its photovoltaic performance.
Compaction processes in granular beds composed of different particle sizes
Authors: Lowe C. A. , Greenaway M. W.
Published: December 2005

A piston impacting a granular bed will cause the material to compact; the strength of a granular bed is significant during weak impact relating to piston speeds of 100m∕s. The strength associated with the granular structure is described as the intergranular stress; this is the resistance of a granular bed to compaction which can be measured by carefully constructing experiments. The compaction process may then be modeled by solving a hyperbolic system of equations that utilizes these data to close the system. The compaction behavior of a porous material is particle-size dependent; to accurately describe the response of two granular beds that may be of different particle sizes and distributions, it is essential that the intergranular stress is derived for each particle bed. This work uses recent compaction experiments to derive intergranular stress curves for prepressed conventional HMX material that is of nonuniform distribution with a mean diameter of 40μm and a microfine HMX of more uniform distribution of mean diameter <5μm. Steady-state compaction waves in the solid material are analyzed: initially the solid is assumed to behave as an incompressible medium. The speed and extent of compaction can be simply determined through the solution of a quadratic equation. Following this, the assumption is relaxed allowing changes in solid-phase density; a complicated equation of state makes the use of numerical methods mandatory. The speed of steady-state waves in HMX due to low impact compaction can be determined within 2% accuracy using the simple closed solution based on solid incompressibility, which is a function of the initial material porosity and density, piston speed, and the intergranular stress of the granular bed. This analysis reveals the difference between the weak impact response of a coarse nonuniform bed and a fine almost uniform granular bed that are initially loaded to 75% of the theoretical maximum density. The fine particle beds have increased resistance to compaction meaning that the extent of compaction is reduced and the speed of compaction waves are faster. The long-term objective of this research is the study of combustion and detonation in granular beds; a two-phase flow capability is required to simulate this type of problem. A multiphase flow model is utilized to simulate the complete low impact response of HMX that includes gas-phase effects. The time-dependent flow rapidly attains steady-state conditions; these solutions agree with the steady-state solutions of the reduced problem described above. Dissipation due to compaction is analyzed and compared with other dissipative processes within the system.
Influence of interfaces on the storage of ion-implanted He in multilayered metallic composites
Authors: Höchbauer T. , Misra A. , Hattar K. , Hoagland R. G.
Published: December 2005

We studied ion beam mixing and He accumulation in Cu∕Nb multilayer thin films after 33keV He implantation at room temperature to a dose of 1.5×1017atoms∕cm2. Multilayered thin films consisting of alternating Cu and Nb layers were produced by magnetron sputtering. Two types of samples, one with an individual layer thickness of 4nm and another with 40nm were examined. The Cu∕Nb samples were analyzed in the as-deposited state, after He ion implantation, as well as after post-implantation annealing. The ion beam mixing of the interface structure was monitored by Rutherford backscattering spectrometry and cross-section transmission electron microscopy imaging. Elastic recoil detection analysis was performed to examine the helium concentration depth distribution. Scanning electron microscopy was employed to investigate He blister formation upon annealing. A comparison of the results deduced from the methods listed above reveals a very high morphological stability of the nanolayered structure. The nanolayered structure of the Cu∕Nb multilayer thin films is retained. He bubbles were observed to reside within the layers but more so at the Cu∕Nb incoherent interfaces.
Temperature control of electromigration to form gold nanogap junctions
Authors: Esen G. , Fuhrer M. S.
Published: December 2005

Controlled electromigration of gold nanowires of different cross-sectional areas to form nanogap junctions is studied using a feedback method. A linear correlation between the cross-sectional area of the gold nanowires and the power dissipated in the junction during electromigration is observed, indicating that the feedback mechanism operates primarily by controlling the temperature of the junction during electromigration. We also show that the role of the external feedback circuit is to prevent thermal runaway; minimization of series resistance allows controlled electromigration to a significant range of junction resistances with a simple voltage ramp.
Structure, twinning behavior, and interface composition of epitaxial Si(111) films on hex-Pr2O3(0001)∕Si(111) support systems
Authors: Schroeder T. , Zaumseil P. , Weidner G. , Lupina G. , Wenger Ch. , Müssig H.-J. , Storck P.
Published: December 2005

The structure of epitaxial Si overlayers on a hexagonal Pr2O3(0001)∕Si(111) substrate system was investigated by a combination of x-ray reflectivity, specular x-ray diffraction, off-specular grazing incidence x-ray diffraction, and transmission electron microscopy. The Pr2O3 film grows on the Si(111) substrate in the (0001)-oriented hexagonal phase matching the in-plane symmetry by aligning the [101¯0] oxide along the bulk [011¯] Si direction. The hexagonal Pr2O3(0001) surface induces the growth of [111]-oriented cubic-Si epilayers exhibiting a microstructure which is composed of two types of domains. The ABC-stacked domains preserve the crystal orientation of the substrate, while the CBA-stacked domains are rotated by 180°. A depth profile of the chemical composition of the epi-Si∕Pr2O3∕Si(111) material stack was recorded by combining ion-beam sputtering techniques with x-ray photoelectron spectroscopy.
Materials aspects of laser-ablation-deposited cuprate∕manganate bilayers for spin-polarized injection devices
Authors: Chakalov R. A. , Passerieux G. , Jones I. P. , Mikheenko P. , Ireland J. , Chakalova R. I. , Colclough M. S. , Muirhead C. M.
Published: December 2005

We report studies of cuprate∕manganate bilayers deposited onto SrTiO3 substrates by laser ablation. A significant difference in the properties of the individual layers is observed depending on the material deposition sequence. The material which is on the bottom of the multilayer shows worse properties, e.g., a critical temperature of ∼60K for YBa2Cu3O7−δ (YBCO) covered by La2∕3Ca1∕3MnO3 (LCMO) as opposed to a value of ∼90K when YBCO is on the top. Similarly, the LCMO film has its metal-insulator transition temperature shifted below the Curie temperature when the YBCO is on top. We argue that the effect is not due to degraded crystal quality, cation substitution, or an electronic interaction, but results from a reduction in the oxygen content of the underlying layer. We find that this reduction is a feature of the complete LCMO layer and is not associated with the constituent elements. We discuss possible explanations for this effect.
Influence of Be and Al on the magnetostrictive behavior of FeGa alloys
Authors: Mungsantisuk Pinai , Corson Robert P. , Guruswamy Sivaraman
Published: December 2005

The rare-earth-free body-centered-cubic FeGa-based alloys have an attractive combination of large low-field magnetostriction at room temperature, good mechanical properties, low hysteresis, and relatively low cost for use in sensor and actuator devices. This paper examines the influence of partially substituting Ga in FeGa alloys with Be and Al on their magnetostrictive behavior. Magnetic and magnetostrictive properties of the various ternary FeGaAl and FeGaBe alloys prepared by directional growth process are presented. It is shown that substitution of Ga with Al and Be can be made in FeGa alloys in certain composition ranges without a significant reduction in magnetostriction. Minimal reductions in magnetostriction when Ga is partially substituted by smaller Be or larger Al atoms in certain composition ranges indicate that local electronic environments are more important and that the effects of Ga and Be are additive.
Analytical interatomic potential for modeling nonequilibrium processes in the W–C–H system
Authors: Juslin N. , Erhart P. , Träskelin P. , Nord J. , Henriksson K. O. E. , Nordlund K. , Salonen E. , Albe K.
Published: December 2005

A reactive interatomic potential based on an analytical bond-order scheme is developed for the ternary system W–C–H. The model combines Brenner’s hydrocarbon potential with parameter sets for W–W, W–C, and W–H interactions and is adjusted to materials properties of reference structures with different local atomic coordinations including tungsten carbide, W–H molecules, as well as H dissolved in bulk W. The potential has been tested in various scenarios, such as surface, defect, and melting properties, none of which were considered in the fitting. The intended area of application is simulations of hydrogen and hydrocarbon interactions with tungsten, which have a crucial role in fusion reactor plasma-wall interactions. Furthermore, this study shows that the angular-dependent bond-order scheme can be extended to second nearest-neighbor interactions, which are relevant in body-centered-cubic metals. Moreover, it provides a possibly general route for modeling metal carbides.
Three-dimensional optical modeling and optimizations of color filter liquid-crystal-on-silicon microdisplays
Authors: Zhang Baolong , Kwok Hoi-Sing , Huang Ho-Chi
Published: December 2005

We have developed a three-dimensional (3D) optical modeling of small color pixels in color filter liquid-crystal-on-silicon (CF-LCOS) microdisplays. The 3D optical modeling includes a LC electromechanical analysis of color LC cells, a calculation of optical reflectance using the extended Jones matrix, and a standard RGB (sRGB) representation of the optical reflectance in the pixel array. The simulated optical reflectance agreed well with the experiments. With this 3D optical analysis as a tool, the relation of the lateral color fringing field with pixel size and thickness of color filter were studied. Minimizations of the fringing field in the CF-LCOS microdisplays were obtained by pixel arrangement, rubbing direction, and LC mode. The color purity of the CF-LCOS microdisplays could attain 63% National Television System Committee (NTSC) level for a typical pixel size of 15μm. With an optimized LC mode, the color purity could still be maintained at 54% NTSC level even when the pixel size was reduced to 9μm. This enabled the feasibility of the CF-LCOS microdisplays for very high-resolution display applications.
Study of Cu diffusion in porous dielectrics using secondary-ion-mass spectrometry
Authors: Rodriguez Oscar R. , Gill William N. , Plawsky Joel L. , Tsui Ting. Y. , Grunow Stephan
Published: December 2005

Secondary-ion-mass spectrometry measurements were used to study Cu diffusion in porous silica. The total concentration of Cu+ decreases with increasing porosity of the dielectric. This behavior is the combined result of both the chemistry and the morphology of the dielectric. The injection of Cu is triggered by outgassing of hydroxyl and water-related species from the dielectric; furthermore, the reduced available cross-sectional area of solid for diffusion, due to porosity, leads to reduced diffusion through the porous film. This suggests that surface diffusion does not play an important role in this process. The Cu+ concentration at the Cu/dielectric interface is on the order of 1023at.∕m3, but decreases with time and exponentially with porosity, which suggests the occurrence of a chemical reaction at the interface. A model of molecular diffusion and ion drift that considers the porosity of the film is developed and the results are consistent with the experimental data.
Electrochemical preparation of a stable accumulation layer on Si: A synchrotron radiation photoelectron spectroscopy study
Authors: Skorupska K. , Lublow M. , Kanis M. , Jungblut H. , Lewerenz H. J.
Published: December 2005

Chronoamperometric conditioning of float zone n-Si(111) in 2M NaOH solution in the potential range negative from open-circuit potential is performed in a combined electrochemistry/ultrahigh-vacuum surface analysis experiment. Synchrotron Radiation Photoelectron Spectroscopy measurements at the U49/2 beamline at Bessy II using the SoLiAs facility show formation of a ultrahigh-vacuum-stable permanent accumulation layer without junction formation. Comparison of the Thomas–Fermi screening potential and the mean inelastic scattering length λesc of photoelectrons at hν=150eV (λesc=4Å) and hν=585eV (λesc=15Å) indicates a surface electron concentration of 3×1018cm−3 for a bulk doping level of 1015cm−3. The observed shift of the Si2p3∕2 and 2p1∕2 core level with photon energy is in excellent agreement with the shifted onset of the x-ray photoelectron spectroscopy valence-band spectrum measured at hν=150eV.
Radiative recombination of charged excitons and multiexcitons in CdSe quantum dots
Authors: Troparevsky M. C. , Franceschetti A.
Published: December 2005

We report semi-empirical pseudopotential calculations of emission spectra of charged excitons and biexcitons in CdSe nanocrystals. We find that the main emission peak of charged multiexcitons—originating from the recombination of an electron in an s-like state with a hole in an s-like state—is blueshifted with respect to the neutral monoexciton. In the case of the negatively charged biexciton, we observe additional emission peaks of lower intensity at higher energy, which we attribute to the recombination of an electron in a p state with a hole in a p state.
Splitting and merging of Görtler vortices
Authors: Mitsudharmadi H. , Winoto S. H. , Shah D. A.
Published: December 2005

The splitting and merging of Görtler vortices are experimentally studied by varying the spacings of vertical wires located 10mm upstream of a concave surface leading edge of 2.0m radius of curvature subjected to a free-stream velocity of 3.0m∕s. The splitting and merging as the result of the linear instability of the vortices with respect to spanwise perturbation (Eckhaus instability), occurred when the wire spacing was set to respectively twice and half of the dominant or most amplified wavelength of Görtler vortices. These show the susceptibility of Görtler vortices to wavelengths greater and smaller than the most amplified wavelength of the vortices. The spectral study shows that the values of the dimensionless frequency parameter for the wire spacings of 7.5, 15.0, and 30.0mm are nearly constant (of about 0.5) for the streamwise locations where the mushroom-like structures dominate the flow. It is also found that the dimensionless wavelength parameter is more sensitive than the Reynolds number of the vertical wires as a threshold identification of transition from one pair to two pairs of vortex configurations.
Direct numerical simulations of shock propagation in bubbly liquids
Authors: Delale C. F. , Nas S. , Tryggvason G.
Published: December 2005

The propagation of a pressure wave in an initially quiescent bubbly liquid of relatively high void fraction contained in a two-dimensional (2D) or three-dimensional (3D) rectangular domain is investigated by direct numerical simulations of the Navier-Stokes equations using a front-tracking/finite-volume method. The gas pressure inside the bubbles is either set equal to a constant or varied by the polytropic relation. Results obtained for 2D and 3D domains show mean shock speeds in agreement with those of one-dimensional homogeneous bubbly liquid theory.
Magnetostatic interactions in mesoscopic Ni80Fe20 ring arrays
Authors: Wang J. , Adeyeye A. O. , Singh N.
Published: December 2005

We investigate, directly using magnetic force microscopy, the effect of magnetostatic interactions in arrays of Ni80Fe20 mesoscopic rings. The rings were fabricated on silicon substrate using deep ultraviolet lithography at 248 nm exposure wavelength. We observed that the transitions from onion-to-vortex and vortex-to-reverse onion magnetic states are strongly dependent on the edge-to-edge-spacing of the rings due to dipolar magnetostatic interaction. For a closely packed ring array, the transition from onion to vortex state occurs at a much lower field due to collective magnetic switching as compared with widely spaced rings. The remanent magnetic state is found to be very sensitive to the orientation of the applied field due to shape anisotropy.
Martensitic transformation and shape memory effect in a ferromagnetic shape memory alloy: Mn2NiGa
Authors: Liu G. D. , Chen J. L. , Liu Z. H. , Dai X. F. , Wu G. H. , Zhang B. , Zhang X. X.
Published: December 2005

Heusler alloy Mn2NiGa has been developed by synthesizing a series of ferromagnetic shape memory alloys Mn25+xNi50−xGa25 (x=0–25). Mn2NiGa exhibits a martensitic transformation around room temperature with a large thermal hysteresis up to 50 K and a lattice distortion as large as 21.3% and has a quite high Curie temperature of 588 K. The martensite shows a high-saturated field up to 2 T. The excellent two-way shape memory behavior with a strain of 1.7% was observed in the single crystal Mn2NiGa. The magnetic-field-controlled effect created a total strain up to 4.0% and changed the sign of the shape deformation effectively.
Electrical-field effect on carbon nanotubes in a twisted nematic liquid crystal cell
Authors: Baik In-Su , Jeon Sang Youn , Lee Seung Hee , Park Kyung Ah , Jeong Seok Ho , An Kay Hyeok , Lee Young Hee
Published: December 2005

We have fabricated twisted nematic cells doped by carbon nanotubes (CNTs). The CNTs with a minute amount of doping did not perturb the liquid crystal orientation in the off and on state. The hysteresis studies of voltage-dependent transmittance and capacitance under ac and dc electric field showed that the residual dc, which is related to an image sticking problem in liquid crystal displays, was greatly reduced due to the ion trapping by CNTs.
Current-induced vortex unbinding in bolometer mixers
Authors: Barends R. , Hajenius M. , Gao J. R. , Klapwijk T. M.
Published: December 2005

We present a description of the current-voltage characteristics of hot electron bolometers in terms of the current-dependent intrinsic resistive transition of NbN films. We find that, by including this current dependence, we can correctly predict the complete current-voltage characteristics, showing excellent agreement with measurements for both low and high bias and for small as well as large devices. It is assumed that the current dependence is due to vortex-antivortex unbinding as described in the Berezinskii–Kosterlitz–Thouless theory. The presented approach will be useful in guiding device optimization for noise and bandwidth.
Nanoimprint pattern transfer quality from specular x-ray reflectivity
Authors: Lee Hae-Jeong , Soles Christopher L. , Ro Hyun Wook , Jones Ronald L. , Lin Eric K. , Wu Wen-li , Hines Daniel R.
Published: December 2005

Specular x-ray reflectivity is used for high precision measurements of the pattern height, residual layer thickness, and the line-to-space ratio for parallel line and space patterns fabricated with nanoimprint lithography. The line-to-space ratio is profiled vertically to reveal relative linewidth variations as a function of the feature height. These relative linewidth variations are quantified through an external measure of the average pitch to fully define the line shape profile or cross section. An excellent fidelity of the nanoimprint pattern transfer process is quantified by comparing the line shape profiles of the mold to the imprinted pattern.
Growth of single conductive nanowires at prescribed loci
Authors: Cheng Chuanding , Haynie Donald T.
Published: December 2005

Conductive 75 nm diameter nanowires have been self-assembled from aqueous solution between 15μm gap electrodes on a SiO2 substrate at predefined locations. Nanowire assembly was initiated by application an electric field, and it occurred along the direction of field lines where the field is strongest. Certain salts of palladium, but not of related metals, yielded nanowires under comparable conditions. The simple and straightforward approach to nanowire assembly outlined here could be used for nano/microscale device interconnection at precise positions at room temperature, important for device development, integration, and packaging.
Generation of terahertz radiation using zinc oxide as photoconductive material excited by ultraviolet pulses
Authors: Ono Shingo , Murakami Hidetoshi , Quema Alex , Diwa Gilbert , Sarukura Nobuhiko , Nagasaka Ryujiro , Ichikawa Yo , Ogino Hiraku , Ohshima Eriko , Yoshikawa Akira , Fukuda Tsuguo
Published: December 2005

Terahertz (THz) radiation generated from photoconductive antenna fabricated on a single crystal zinc oxide (ZnO) is presented. The THz-radiation power is saturated at bias voltages above 800V∕cm and the obtained spectrum extends up to 1 THz. Moreover, ZnO is found to be highly transparent in the visible, near-infrared, mid-infrared and THz frequency regions. The results depicted here will categorically unravel the prospects of using ZnO as a material for integrated active optics.
Light yield of undoped sapphire at low temperature under particle excitation
Authors: Amaré J. , Beltrán B. , Cebrián S. , García E. , Gómez H. , Irastorza I. G. , Luzón G. , Martínez M. , Morales J. , de Solórzano A. Ortiz , Pobes C. , Puimedón J. , Rodríguez A. , Ruz J. , Sarsa M. L. , Torres L. , Villar J. A. , Coron N. , Dambier G. , Leblanc J. , de Marcillac P. , Redon T.
Published: December 2005

In this letter, we report on the performance of scintillating sapphire bolometers developed in the framework of the ROSEBUD (Rare Objects Search with Bolometers UnDerground) Collaboration devoted to dark matter searches. The simultaneous measurement of heat and light allows the discrimination of the type of particle increasing the sensitivity for these searches. A heat versus light negative correlation for gamma events has been observed. Its interpretation, in a simple framework, allows the estimation of the light yield of undoped sapphire at a temperature of about 20 mK under gamma, alpha, and neutron excitation.
Fabrication, structure, magnetic properties of highly ordered cobalt disulfide nanowire arrays
Authors: Yue G. H. , Yan P. X. , Liu J. Z. , Fan X. Y. , Zhuo R. F.
Published: December 2005

Highly ordered arrays of parallel CoS2 nanowires with a diameter of about 50 nm and a length up to about 50μm were synthesized by two electrical fields in an anodized aluminum oxide film. In this letter, fabrication, structure, magnetic properties of highly ordered magnetic cobalt disulfide nanowires arrays were studied. Also, a growth mechanism has been speculated.
Field-modified photoluminescence spectra in coupled quantum dots
Authors: Zhu Jia-Lin , Chu Weidong , Xu Dong , Dai Zhensheng
Published: December 2005

Photoluminescence spectra of an exciton in coupled quantum dots under an electric field have been calculated and investigated, and it has been compared with a recent experiment. For coupled quantum dots, the four s-shell exciton states are dramatically affected by the electric field and the symmetry of the two dots. The electric field can induce anticrossings in the spectra, which are remarkably influenced by the differences between the two dots. The field-modified photoluminescence spectra can be used in the experiment to determine whether the two dots are identical and to obtain some information about electronic and structural parameters of coupled quantum dots.
Self-organized MnAs quantum dots formed during annealing of GaMnAs under arsenic capping
Authors: Sadowski J. , Janik E. , Lusakowska E. , Domagala J. Z. , Kret S. , Dlużewski P. , Adell M. , Kanski J. , Ilver L. , Brucas R. , Hanson M.
Published: December 2005

Formation of MnAs quantum dots in a regular ring-like distribution has been found on molecular beam epitaxy grown (GaMn)As(100) surfaces after low-temperature annealing under As capping. The appearance of the dots depends on the thickness and Mn concentration in the (GaMn)As layer. With 5 at. % substitutional Mn the quantum dots showed up for layers thicker than 100 nm. For thinner layers the surfaces of the annealed samples are smooth and well ordered with 1×2 surface reconstruction, just as for as-grown (GaMn)As. The annealed surfaces are Mn rich, and are well suited for continued epitaxial growth.
1H N.M.R. investigations of the selective intramolecular migration of a platinum(II) complex from methionine sulfur to imidazole N 1 in N-acetylated L-methionyl-L-histidine
Authors: Djuran Milo I. , Milinkovic´ Snezana U.
Published: December 2005

Reactions of two platinum(II) complexes
[Pt(dien)Cl]+ and
[Pt(Gly-Met-S,N,N´)Cl],
in which dien is diethylenetriamine and Gly-Met is the dipeptide
glycyl-L-methionine coordinated through the sulfur and two nitrogen atoms,
with N-acetylated dipeptide L-methionyl-L-histidine
(MeCO-Met-His) have been studied by 1H n.m.r.
spectroscopy. All reactions were carried out in 50 mM phosphate buffer at pD
7.4 and at room temperature. In the initial stages of the reactions both
platinum(II) complexes form a kinetically favoured platinum–peptide
complex with unidentate coordination of MeCO-Met-His through the sulfur atom
of the methionine residue. In the second stages of the reaction an
intramolecular migration of a
[Pt(dien)]2+ unit from the sulfur to the
nitrogen atom of imidazole has been observed. This migration reaction is very
slow and strongly selective to the N 1 atom of the imidazole ring of the
histidine side chain. No migration of the platinum(II) complex was observed in
the reaction between
[Pt(Gly-Met-S,N,N´)Cl]
and the dipeptide MeCO-Met-His. It was found that the latter complex, with a
more sterically hindered Gly-Met ligand, reacts more slowly with
thioether-containing molecules than
[Pt(dien)Cl]+ and forms a more stable
platinum–sulfur bond. This study is an important step in the development
of new platinum(II) complexes for selective covalent modification of peptides
and proteins.
Biomarkers in Marine Organisms: A Practical Approach.
(Eds P. Garrigues, H. Barth, C. H. Walker and J.-F. Narbonne)
Authors: Bowden Bruce F.
Published: December 2005

Biomarkers in Marine Organisms: A Practical Approach

Eds P. Garrigues, H. Barth, C. H. Walker and J.-F. Narbonne
The Synthesis of Sulfur-Containing Spiro Orthocarbonates
Authors: Bromley Mark K. , Gason Samuel J. , Looney Mark G. , Solomon David H.
Published: December 2005

New sulfur-containing spiro orthocarbonates (SOCs) were prepared by using
dichlorodiphenoxymethane. Mercapto alcohols were employed to yield O,S SOCs,
and O,S diphenoxy intermediates in a one-step procedure. By adopting a
two-step synthesis under basic conditions, a range of sulfur-containing
heteroatom SOCs was produced. Preliminary studies indicate that this
methodology is applicable to different ring
sizes.
Experiments Directed Towards the Synthesis of Anthracyclinones. XXXIV Hetero-Diels - Alder Reactions Using Chiral Boron and Titanium Reagents
Authors: Bercich Mark D. , Cambie Richard C. , Rutledge Peter S.
Published: December 2005

Reactions between benzaldehyde or o-anisaldehyde and a
series of silyloxy dienes catalysed by the chiral acyl- oxyborane (CAB)
complex (4) give high yields of enantioselective products from a Mukaiyama
aldol rather than a hetero-Diels–Alder reaction. Attempts to effect a
similar catalytic reaction with anthraquinone aldehydes were unsuccessful but
use of 2 equiv. of the CAB complex (1) followed by cyclization promotes a
formal hetero- Diels–Alder reaction between the aldehyde (7) and the
diene (12) to give the dihydropyrone (24) in 45% yield and with a
79% e.e. in favour of the 2'R enantiomer.
Hetero-Diels–Alder reactions between the aldehyde (7) and the diene (12)
using the chiral titanium complexes
Ti[(R)-BINOL]Cl 2 ,
Ti[(R,R)-TADDOL]Cl
2 and Ti[(R)-BINOL]
2 have been investigated. The first two complexes
promote the reaction at −30 and −78° respectively but with low
induced enantioselectivities.
Preparation and Molecular Structures of FcC ≡ CI and {Co2(CO)6}2(µ:µ-FcC2C2Fc) [Fc = Ferrocenyl, (h-C5H4)Fe(h-C5H5)]
Authors: Bruce Michael I. , Skelton Brian W. , Smith Mark E. , White Allan H.
Published: December 2005

Iodination of FcC ≡ CH with morpholinium iodide gave structurally
characterized iodoethynylferrocene, FcC ≡ CI; its reaction with
Co2(CO)8 affords
{Co2(CO)6}2(µ:µ-FcC2C2Fc),
also characterized by an X-ray structure determination. This compound is
formed by deiodinative coupling of the iodoalkyne and subsequent addition of a
Co2(CO)6 group to each C ≡ C
triple bond in the resulting diyne.
Pigments of Fungi. LVIII. Sinapiquinone and Sinapicolone, Red Pigments from the Toadstool Cortinarius sinapicolor
Authors: Gill Melvyn , Milanovic Nives M.
Published: December 2005

Sinapiquinone (4), only the second natural product that incorporates a
1,2-anthraquinone chromophore, and sinapicolone (6), a
dihydroanthracenone–anthrone ‘tetramer’, are isolated from
the Australasian toadstool Cortinarius sinapicolor and
their structures and absolute stereochemistry are determined by spectroscopic
methods.
Properties and single-crystal X-ray structure of Bis[3,3″-bis(4-methylphenyl)-2,2′:6′,2″-terpyridine]iron(II) hexafluorophosphate - acetonitrile - diisopropyl ether (1/1.5/1)
Authors: Benniston Andrew C. , Farrugia Louis J. , Mackie Philip R. , Mallinson Paul , Clegg William , Teat Simon J.
Published: December 2005

Absorption and electrochemical properties are reported for the iron(II)
complex of the unusually substituted ligand
3,3″-bis(4-methylphenyl)-2,2′:6′,2″-terpyridine, along
with the structure determination of the complex by single-crystal X-ray
crystallography. Crystal data for
C67H64.5F12FeN7.5OP2,
M 1336.6: triclinic, a 12.768(3),
b 15.789(4), c 17.160(4) Å,
α 85.553(6), β 77.756(6), γ 66.754(5)˚,
V 3106.1(12) Å3, space group
P 1, Z 2, ρ 1.43 g
cm–3, µ 0.30 mm-1 for
λ 0.6849 Å, R 0.091 for 4456 observed
(I > 2σ(I) ) reflections,
wR2 0.241, Δρ1.68 e
Å–3. The structural analysis reveals that,
as observed in analogous bisterpyridineiron(II) complexes, the ligands adopt
the preferred meridional binding motif. As a result, the
‘pulling-in’ of the outer pyridine rings forces each pair of
3,3″ substituted tolyl groups to diverge, resulting in an average
distance between the tolyl methyl groups of c. 11.6
Å. The cyclic voltammetery of the complex in MeCN displays upon
oxidative scanning a reversible one-electron wave
(E˚ = + 0.99 V v.
s.c.e.) and three one-electron waves under reducing conditions
(E1˚ = –1.27 V,
E2˚ = –1.51 V,
E3˚ = –1.96 V
v. s.c.e.). The electronic spectrum in acetonitrile
contained an MLCT band centred at 571 nm, with a molar absorption coefficient
of 18210 M–1 cm–1.
When compared to similar phenyl-substituted terpyridine ligand iron(II)
complexes this is a relatively low value and is assigned to reduced electronic
delocalization throughout the terpyridine backbone.
Using zero tillage, fertilisers and legume rotations to maintain productivity and soil fertility in opportunity cropping systems on a shallow Vertosol
Authors: Armstrong R. D. , Millar G. , Halpin N. V. , Reid D. J. , Standley J.
Published: December 2005

The effect of 2 tillage practices (zero v. conventional), fertiliser application (nitrogen, phosphorus and zinc), and pulse–cereal rotation on changes in soil mineral nitrogen, plant-available water in the soil, grain yield and protein, and key soil fertility parameters (total nitrogen, organic carbon) in the Central Highlands of Queensland were examined between 1991 and 1998. Four pasture treatments (perennial legume, perennial grass, annual legume and legume–grass mixes) were included in January 1995, following previously unsuccessful attempts to grow lucerne and annual medics. The experiment was conducted as an opportunity cropping system on an open downs soil at Gindie that is representative of a large proportion (70%) of soils in the Central Highlands. Tillage practice did not affect the amount of mineral nitrate or the plant-available water content of the soil at planting, except in 1991 and 1998 when plant-available water content was higher under conventional tillage than zero tillage. However, zero tillage improved grain yield in 2 of 4 years (wheat in 1992; sorghum in 1996), increased uptake of nitrogen in every crop and produced greater grain protein levels in both wheat crops grown than conventional tillage. There were grain responses to nitrogen + phosphorus fertilisers (wheat in 1991 and sorghum in 1997). Grain protein was increased with applications of nitrogen regardless of whether phosphorus was added in 3 of the 4 crops planted. Sowing a pulse did not significantly increase grain yields in the following crop although it did increase soil mineral nitrogen at planting. Soil nitrate remained low in control (P0N0) plots (<39 kg N/ha) when crops were planted each year but increased significantly (average 84 kg N/ha) following a long fallow of 3.5 years resulting from drought. Plant-available water content of the soil at sowing was lower where chickpeas had been grown the previous season than with wheat. Neither tillage practice nor fertiliser application affected soil organic carbon or soil total nitrogen concentrations in the topsoil. However, all pasture treatments improved soil total nitrogen compared with continuous cropping, and with the exception of annual pasture legumes, also improved soil organic carbon after only 2 seasons. Largest improvements in soil fertility (total nitrogen and organic carbon) occurred with perennial species. It was concluded that zero tillage practices can have beneficial impacts on grain yields as well as minimising environmental degradation such as soil erosion in this region. However, if soil fertility levels are to be maintained, or improved, perennial pasture rotations will need to be used as current levels of fertiliser application or rotations with pulses had no significant beneficial effect.
Prevalence of sclerotinia stem rot of canola in New South Wales
Authors: Hind T. L. , Ash G. J. , Murray G. M.
Published: December 2005

Surveys of petal infestation and stem infection conducted in 1998, 1999 and 2000 indicated that Sclerotinia sclerotiorum poses a threat to the Australian canola industry. Inoculum was present throughout all canola-growing regions of New South Wales and the stem disease was widespread throughout southern New South Wales. Percentage petal infestation increased over the 3 years surveyed with values ranging from 0 to 99.4%. The highest petal infestation values were observed in 2000 (maximum of 99.4%, mean of 82.2%), with lower mean values in 1998 (38.4%) and 1999 (49.6%). Stem infection ranged from 0 to 37.5% and most fields had less than 10% stem infection. Stem rot incidence before harvest did not relate to percentage petal infestation determined during flowering. This indicated that factors other than percentage petal infestation were important in influencing stem rot incidence. While there was no relationship between percentage petal infestation and stem rot incidence, stem infection never occurred without prior petal infestation.