bluuebunny/crossref_metadata_2025 huggingface dataset:
High color purity phosphors of LaAlGe2O7 doped with Tm3+ and Er3+
Authors: Li Yu-Chun , Chang Yen-Hwei , Lin Yu-Feng , Lin Yi-Jing , Chang Yee-Shin
Published: August 2006

Phosphors of LaAlGe2O7 doped with Tm3+ and Er3+ of high color purity, exhibiting a narrow band emission in the blue and green regions, were obtained. (La1−xLnx)AlGe2O7 (Ln=Tm,Er) powders are bright emitters, with chromaticity color coordinates that are comparable to or better than those of standard phosphors for display or lighting devices. The blue emission of the Tm3+-doped phosphor had CIE chromaticity coordinates (0.151, 0.033) with a dominant wavelength of 455nm and a color purity of 94%. The Er3+-doped phosphor had color coordinates (0.249, 0.718), a dominant wavelength of 542nm, and 92% purity.
Field emission from honeycomblike network of vertically aligned AlN nanoplatelets
Authors: Tang Y. B. , Cong H. T. , Cheng H.-M.
Published: August 2006

Honeycomblike network of vertically aligned AlN nanoplatelets was synthesized on etched Si substrate via a simple vapor phase method without catalyst. The nanoplatelets are hexagonal wurtzite AlN and their thickness is 10–100nm. Field emission (FE) measurements showed that this nanostructure has a low turn-on field of 3.2–5.0V∕μm and a threshold field of 7.8–12.1V∕μm at sample-anode distances of 50–100μm. The fluctuation of FE current with density of 10mA∕cm2 over 5h is lower than 3%. The low turn-on and threshold fields and the small fluctuation of current demonstrate that this two-dimensional AlN nanostructure is a promising FE material.
Magnetic anisotropy of (110) Fe∕Co superlattices
Authors: Vas’ko V. A. , Kim Miyoung , Mryasov O. , Sapozhnikov V. , Minor M. K. , Freeman A. J. , Kief M. T.
Published: August 2006

Magnetic anisotropy field of (110) Fe∕Co superlattices was found to be as high as 1T, with an in-plane easy axis. First principles calculations within the local spin density approximation show good agreement with the measurement. Lowering the symmetry by creating artificial superlattice structures leads to a significant increase in magnetic anisotropy energy as compared with any allotropic form of the elemental components and cubic FeCo. Large anisotropy is attributed to the cubic symmetry breaking due to the multilayer artificial atomic arrangement. Dependence of the anisotropy field on the superlattice period is supported by Monte Carlo film growth modeling.
Sharp-line electroluminescence from individual quantum dots by resonant tunneling injection of carriers
Authors: Turyanska L. , Baumgartner A. , Chaggar A. , Patanè A. , Eaves L. , Henini M.
Published: August 2006

We report sharp electroluminescence lines from individual self-assembled InAs quantum dots (QDs) excited by resonant tunneling injection of carriers from the n- and p-doped GaAs layers of a p-i-n diode. Bias-tunable tunneling of carriers into the dots provides a means of controlling injection and light emission from a small number of individual dots within a large ensemble. We also show that the extent of carrier energy relaxation prior to recombination can be controlled by tailoring the morphology of the QD layer.
Moisture-resistant ZnO transparent conductive films with Ga heavy doping
Authors: Nakagawara Osamu , Kishimoto Yutaka , Seto Hiroyuki , Koshido Yoshihiro , Yoshino Yukio , Makino Takahiro
Published: August 2006

Moisture-resistant ZnO transparent conductive films were formed with Ga heavy doping by off-axis-type rf magnetron sputtering. The resistivity of 12.4wt% Ga-doped ZnO is 1.3×10−3Ωcm and changes by less than 3% over a 2000h reliability test at a temperature of 85°C and a humidity of 85%. The crystal structural analysis of the heavily Ga-doped ZnO films indicates that the c axis grows along various directions, which is quite different from the conventional c-axis oriented growth. The effect of heavy doping is discussed based on the crystal structural transformation and carrier compensation by excess Ga segregated in the film.
Large-scale ordering of porous Si using anodic aluminum oxide grown by directed self-assembly
Authors: Zou Jia , Qi Xiaoyuan , Tan Liwen , Stadler Bethanie J. H.
Published: August 2006

Porous Si with perfect long range order (mm2 scale) was obtained using an integrated mask of ordered anodic aluminum oxide (AAO). This represents an increase of many orders of magnitude in the ordered domain size compared with porous Si made with self-assembled AAO masks. Here, master stamps composed of silicon nitride posts (180nm diameter, 400nm spacing) were imprinted into Al films that were grown onto nitride-coated Si wafers. The Al films were then anodized and the resulting ordered, nanoporous pattern was transferred into the Si using reactive ion etching. The stamps could be reused a multitude of times to produce exact replicas.
Chemical synthesis and magnetic properties of dilute magnetic ZnTe:Cr crystals
Authors: Zhao Lijuan , Zhang Bei , Pang Qi , Yang Shihe , Zhang Xixiang , Ge Weikun , Wang Jiannong
Published: August 2006

ZnTe and Cr doped ZnTe crystals have been synthesized using a solvothermal process. The characterizations by x-ray diffraction and transmission electron microscopy show that the synthesized ZnTe:Cr crystals have a cubic structure and Cr is incorporated into ZnTe. The magnetic properties of ZnTe:Cr are investigated. A hysteresis is observed in the magnetization versus magnetic field measurements below 10K. The detailed analyses suggest that the hysteresis possibly originated from the magnetic short-range ordering of Zn1−xCrxTe compounds in the sample.
Phase equilibria and plate-fluid interfacial tensions for associating hard sphere fluids confined in slit pores
Authors: Fu Dong , Li Xiao-Sen
Published: August 2006

The excess Helmholtz free energy functional for associating hard sphere fluid is formulated by using a modified fundamental measure theory [Y. X. Yu and J. Z. Wu, J. Chem. Phys. 117, 10156 (2002)]. Within the framework of density functional theory, the thermodynamic properties including phase equilibria for both molecules and monomers, equilibrium plate-fluid interfacial tensions and isotherms of excess adsorption, average molecule density, average monomer density, and plate-fluid interfacial tension for four-site associating hard sphere fluids confined in slit pores are investigated. The phase equilibria inside the hard slit pores and attractive slit pores are determined according to the requirement that temperature, chemical potential, and grand potential in coexistence phases should be equal and the plate-fluid interfacial tensions at equilibrium states are predicted consequently. The influences of association energy, fluid-solid interaction, and pore width on phase equilibria and equilibrium plate-fluid interfacial tensions are discussed.
Steric effect in the energy transfer reaction of Ar(P23)+N2
Authors: Watanabe D. , Ohoyama H. , Matsumura T. , Kasai T.
Published: August 2006

Steric effect for N2(C,Πu3) formation in the energy transfer reaction of Ar(P23)+N2 was directly measured by using an oriented Ar(P23,MJ=2) beam at a collision energy of 0.06eV. The N2(C,Πu3) chemiluminescence intensity was measured as a function of the magnetic orientation field direction in the collision frame. A significant alignment effect on the energy transfer probability was observed. The relative reactivity for each magnetic substate in the collision frame σ∣MJ′∣ was determined to be σ∣2∣:σ∣1∣:σ0=0.50:0.60:1.00. It is suggested that the observed steric effect is primarily due to the favorable configuration of the 3p orbital for the efficient overlap with the 2σu molecular orbital of N2.
Slow processes in startup scenarios of long-pulse gyrotrons
Authors: Nusinovich G. S. , Sinitsyn O. V. , Antonsen T. M. , Vlasov A. N. , Cauffman S. R. , Felch K. L.
Published: August 2006

A gyrotron startup scenario describes the variation of gyrotron parameters during onset of a pulse. This typically includes variations in beam parameters during the voltage rise, in the course of which the operating mode is excited and then driven to high efficiency operation while suppressing other parasitic modes. For long-pulse gyrotrons, however, additional processes with longer time constants should also be considered as part of the startup scenario. Such slow processes include ion neutralization of the beam space charge, thermal expansion of cavity walls caused by their ohmic heating, and reduction of the beam current due to emission cooling of the cathode. In the present paper, we analyze the importance of these effects on the stability and efficiency of gyrotron operation.
Three-terminal Ge dot/SiGe quantum-well photodetectors for near-infrared light detection
Authors: Elfving A. , Karim A. , Hansson G. V. , Ni W.-X.
Published: August 2006

A three-terminal metal-oxide-semiconductor field-effect transistor type of photodetector has been fabricated with a multiple stack of Ge dot/SiGe quantum-well heterostructures as the active region for light detection at 1.3–1.55μm. Gate-dependent edge incidence photoconductivity measurements at room temperature revealed a strong dependence of the photoresponse on the gate voltage. At positive gate bias, the hole transport from the dots into the wells was improved, resulting in a faster response. The high photoresponsivity at negative VG, measured to be 350mAW−1 at 1.31μm and 30mAW−1 at 1.55μm, was ascribed to the photoconductive gain.
Output properties of C60 field-effect transistor device with Eu source/drain electrodes
Authors: Ochi Kenji , Nagano Takayuki , Ohta Toshio , Nouchi Ryo , Kubozono Yoshihiro , Matsuoka Yukitaka , Shikoh Eiji , Fujiwara Akihiko
Published: August 2006

Field-effect transistor (FET) device with thin films of C60 has been fabricated with Eu electrodes exhibiting small work function. The C60 FET device shows n-channel FET properties with high field-effect mobility, 0.50cm2V−1s−1. Furthermore, nonvanishing drain current, i.e., normally on, is observed in this FET device. This originates from small energy barrier for electron from Eu source electrode to lowest unoccupied molecular orbital of C60.
Retarded boson-fermion interaction in atomic systems
Authors: Datta Sambhu N. , Misra Anirban
Published: August 2006

The retarded interaction between an electron and a spin-0 nucleus is derived from electrodynamical perturbation theory. The contribution of retardation at order v2∕c2 mimics the Breit interaction [Phys. Rev. 34, 553 (1929); 36, 388 (1930); 39, 616 (1932)] with the Dirac matrix α2 being replaced by p2∕m2c where p2 is the linear momentum operator for the nucleus. An effective one-electron retardation operator is obtained in relative coordinates, and this can be used through all orders in perturbation theory without any problem of infinite degeneracy. A few steps of unitary transformation lead to the nonrelativistic limit. The leading terms in retardation corrections to energy are of order (me∕mn)α2Z4(α2mec2). The implications for atomic systems are discussed.
Temperature-dependent thermal conductivity of nanorod-based nanofluids
Authors: Yang B. , Han Z. H.
Published: August 2006

In this work, the temperature dependence of thermal conductivity enhancement in nanofluids containing Bi2Te3 nanorods has been studied. The Bi2Te3 nanorods of average diameter 20nm and length 170nm are synthesized using the sonochemical technique. The 3ω-wire method has been developed to measure the thermal conductivity of nanofluids. The thermal conductivity enhancement in the nanorods-in-FC72 and the nanorods-in-oil nanofluids has been experimentally found to decrease with increasing temperature, in contrast to the trend observed in nanofluids containing spherical nanoparticles. The contrary trend is attributable mainly to the particle aspect ratio.
Excitation wavelength dependence of terahertz emission from semiconductor surface
Authors: Suzuki Masato , Tonouchi Masayoshi , Fujii Ken-ichi , Ohtake Hideyuki , Hirosumi Tomoya
Published: August 2006

The authors have measured terahertz radiation from InSb, InAs, and InGaAs excited by femtosecond optical pulses at wavelengths of 1560, 1050, and 780nm. The amplitude of the terahertz field strongly depends on the pump wavelengths. Among the materials, the InSb emitter shows the largest terahertz emission amplitude at high power 1560nm excitation, whereas 780nm excitation provides the weakest. With increasing photon energy, the increase in emission amplitude from InAs is less as compared to that from InGaAs. The decrease from InSb and InAs originates in low mobilities of L or X valley carriers generated by intervalley scatterings.
Ferroelectric film switching via oblique domain growth observed by cross-sectional nanoscale imaging
Authors: Gysel Roman , Tagantsev Alexander K. , Stolichnov Igor , Setter Nava , Pavius Michaël
Published: August 2006

Different stages of polarization reversal in a Pb(Zr,Ti)O3 ferroelectric film have been directly observed using a technique of cross-sectional piezoelectric force imaging. Analysis of the local piezoelectric response measured across the cross section strongly suggests that polarization reversal occurs via oblique domain growth rather than by growth of domains perpendicular to the film plane. The proposed approach represents a valuable extension to the piezoelectric force microscopy (PFM) and contributes to a better understanding of results observed using more standard techniques. Particularly, oblique domain growth explains the gradual variation of piezoelectric response amplitude commonly observed in planar PFM images.
Trapping and manipulation of microscopic bubbles with a scanning optical tweezer
Authors: Jones P. H. , Stride E. , Saffari N.
Published: August 2006

The authors have demonstrated three-dimensional trapping of ultrasound contrast agent microbubbles using a circularly scanning optical tweezers to confine the microbubble in a time-averaged optical potential. They have measured the maximum transverse drag force that may be applied to the trapped microbubble before it escapes and found that this decreases significantly at small trap radii. They explain this in terms of the relative volumes of the microbubble and the trap and anticipate that this feature will be important in experiments involving the insonation of optically trapped microbubbles.
Observation of enhanced defect emission and excitonic quenching from spherically indented ZnO
Authors: Coleman V. A. , Bradby J. E. , Jagadish C. , Phillips M. R.
Published: August 2006

The influence of spherical nanoindentation on the band edge and deep level emission of single crystal c-axis ZnO has been studied by cathodoluminescence (CL) spectroscopy and monochromatic imaging. Excitonic emission is quenched at the indent site and defect emission in the range of 450–720nm is enhanced. Analysis of CL monochromatic images and spectra suggests that at least two different defect states are responsible for the broad defect emission band. Additionally, the indents result in a strong crystallographic dependence of the defect emission, producing a rosette feature with [112¯0] [21¯1¯0], and [12¯10] orientations that reflect the star-shaped luminescence quenching observed at the excitonic peak (390nm).
Large fluorine-vacancy clusters in Si and their capture efficiency for self-interstitials
Authors: Lopez Giorgia M. , Fiorentini Vincenzo
Published: August 2006

Based on ab initio density-functional energetics for saturated (n=2m+2) fluorine-vacancy clusters FnVm for m up to 4, the authors set up a model showing that (a) fluorine-vacancy (F–V) aggregates in Si can form in any size and concentration for sufficient concentrations of incorporated (e.g., implanted) F, and (b) the F to V ratio in F–V complexes (i.e., the inverse capture efficiency of self-interstitials) is an ensemble average over many cluster sizes. It ranges between 4 and 2, with typical values of 2.2–2.5, consistent with recent experimental estimates.
Observation of transient reorientation of dye-doped liquid crystals by pumped attenuated total reflection
Authors: Lo Kuang-Yao , Huang Chia-Yi
Published: August 2006

A transient reorientation of liquid crystals in azo-dye-doped liquid crystals (ADDLCs) is observed by the improved attenuated total reflection leading a pump light into a coupling prism, namely, pumped ATR experiment. The evanescent wave of the pump light induces the photoexcitation of azo dye at the limited effective depth, and the evanescent wave of the probe light detects the dynamic behavior in real time. The time response of the photoexcitation in ADDLCs in the pumped ATR experiment is less than 2ms and it is believed that the reaction occured in the local region of 100nm.
Alternating current flow in internally flawed conductors: A tomographic analysis
Authors: Saguy H. , Rittel D.
Published: August 2006

The alternating current potential drop technique is a nondestructive testing method that is mostly applied to estimate the depth of surface breaking flaws (e.g., cracks) in metallic conductors. When the flaw is hidden (internal or bottom cracks), other techniques (e.g., radiographic) must be used, which may only provide limited information on the location and dimensions of the hidden flaw. This work presents a detailed numerical analysis of ac flow in internally flawed conductors. The results can be used to reveal and estimate the dimensions and location of hidden flaws.
Intrinsic characteristics of semiconducting oxide nanobelt field-effect transistors
Authors: Cheng Yi , Xiong P. , Fields Lenwood , Zheng J. P. , Yang R. S. , Wang Z. L.
Published: August 2006

Field-effect transistors (FETs) based on individual semiconducting oxide (SnO2 and ZnO) nanobelts with multiterminal electrical contacts have been fabricated and characterized. Simultaneous two-terminal and four-terminal measurements enable direct correlation of the FET characteristics with the nature of the contacts. Devices with high-resistance non-Ohmic contacts exhibit a Schottky barrier FET behavior. In contrast, low-resistance Ohmic contacts on the nanobelt lead to high-performance n-channel depletion mode FETs with well-defined linear and saturation regimes, large “on” current, and an on/off ratio as high as 107. The FET characteristics of such devices show a significant modification by a 0.2% H2 gas flow at room temperature. The excellent intrinsic characteristics of these nanobelt FETs make them ideal candidates as nanoscale biological and chemical sensors based on field-effect modulation of the channel conductance.
Direct measurement of the domain switching contribution to the dynamic piezoelectric response in ferroelectric ceramics
Authors: Jones Jacob L. , Hoffman Mark , Daniels John E. , Studer Andrew J.
Published: August 2006

The dynamic piezoelectric response of ferroelectric ceramics is comprised of both intrinsic (piezoelectric lattice strain) and extrinsic (non-180° domain wall motion) components. Here the authors report direct measurements of non-180° domain wall motion in ceramic lead zirconate titanate during application of subcoercive cyclic driving electric fields using an in situ stroboscopic neutron diffraction technique. During unipolar cycling at 1Hz and half of the coercive field, non-180° domain switching gives rise to approximately 34% of the measured d33 coefficient of 400pm∕V.
Formation of Ru nanocrystals by plasma enhanced atomic layer deposition for nonvolatile memory applications
Authors: Yim Sung-Soo , Lee Moon-Sang , Kim Ki-Su , Kim Ki-Bum
Published: August 2006

The formation of Ru nanocrystals is demonstrated on a SiO2 substrate by plasma enhanced atomic layer deposition using diethylcyclopentadienyl ruthenium and NH3 plasma. The island growth of Ru was observed at the initial stages of the film formation up to a nominal thickness of 11.1nm. A maximum Ru nanocrystal spatial density of 9.7×1011∕cm2 was achieved with an average size of 3.5nm and standard deviation of the size of 20%. Electron charging/discharging effect in the Ru nanocrystals is demonstrated by measuring the flatband voltage shift in the capacitance-voltage measurement of metal-oxide-semiconductor memory capacitor structure.
Rainbow refractometry with a tailored incoherent semiconductor laser source
Authors: Peil Michael , Fischer Ingo , Elsäßer Wolfgang , Bakić Saša , Damaschke Nils , Tropea Cameron , Stry Sandra , Sacher Joachim
Published: August 2006

The authors demonstrate within a metrology experiment the applicability of a recently proposed temporally incoherent semiconductor laser source which relies on nonlinear dynamics. The realized spectrally broadband emission with an output power of 110mW and a coherence length of only 120μm is used in a rainbow refractometry experiment for sizing of liquid droplets, representing an important problem in industrial processes. The observed emission characteristics are attractive for implementation of modern imaging and metrology techniques which are based on the properties of well-directed, temporally incoherent light.
Enhanced spontaneous emission of CdSe quantum dots in monolithic II-VI pillar microcavities
Authors: Lohmeyer H. , Kruse C. , Sebald K. , Gutowski J. , Hommel D.
Published: August 2006

The emission properties of CdSe∕ZnSe quantum dots in ZnSe-based pillar microcavities are studied. All-epitaxial cavities made of ZnSSe and MgS∕ZnCdSe superlattices with a single quantum-dot sheet embedded have been grown by molecular beam epitaxy. Pillar structures with diameters down to 500nm have been realized by focused-ion-beam etching. A pronounced enhancement of the spontaneous emission rate of quantum dots coupling to the fundamental mode of the cavities is found as evidence for the Purcell effect. The enhancement by a factor of up to 3.8 depends systematically on the pillar diameter and thus on the Purcell factor of the individual pillars.
Localization of pointlike scatterers in solids with subwavelength resolution
Authors: Simonetti F.
Published: August 2006

The possibility of improving the resolution of current subsurface imaging technology, based on elastic wave probing, is investigated. It is demonstrated that in the case of pointlike scatterer localization, super-resolution methods developed for scalar wave probing can also be applied to elastic waves. An experiment performed on a steel specimen with two through thickness parallel holes demonstrates a subwavelength resolution which is more than 2.5 times higher than that predicted by the Rayleigh criterion.
Electronic and magnetic properties of the Ag-doped Fe3O4 films studied by x-ray absorption spectroscopy
Authors: Liu S. H. , Tsai H. M. , Pao C. W. , Chiou J. W. , Ling D. C. , Pong W. F. , Tsai M.-H. , Lin H. J. , Jang L. Y. , Lee J. F. , Hsu J. H. , Wang W. J. , Hsu C. J.
Published: August 2006

The electronic and magnetic properties of Ag-doped Fe3O4 films were studied by x-ray absorption near-edge structure (XANES), extended x-ray absorption fine structure (EXAFS), and x-ray magnetic circular dichroism (XMCD) measurements. A comparison between the Ag K-edge EXAFS Fourier transform spectra of Ag-doped Fe3O4 and the Ag metal shows that Ag atoms aggregate into Ag granules. The O K-edge and Ag L3-edge XANES spectra consistently indicate an electron transfer from the Fe3O4 host into Ag granules. The Fe L3,2-edge XMCD spectra and hysteresis measurements reveal that Ag granules reduce the average magnetic moment of Fe ions and the saturation magnetization of Fe3O4.
Do single-electron lithium bonds exist? Prediction and characterization of the H3C⋯Li–Y (Y=H, F, OH, CN, NC, and CCH) complexes
Authors: Li Ying , Wu Di , Li Zhi-Ru , Chen Wei , Sun Chia-Chung
Published: August 2006

A new kind of single-electron lithium bonding complexes H3C⋯LiY (Y=H, F, OH, CN, NC, and CCH) was predicted and characterized in the present paper. Their geometries (C3v) with all real harmonic vibrational frequencies were obtained at the MP2/aug-cc-pVTZ level. For each H3C⋯LiY complex, single-electron Li bond is formed between the unpaired electron of CH3 radical and positively charged Li atom of LiY molecule. Due to the formation of the single-electron Li bond, the C–H bonds of the CH3 radical bend opposite to the LiY molecule and the Li–Y bond elongates. Abnormally, the three H3C⋯LiY (Y=CN, NC, and CCH) complexes exhibit blueshifted Li–Y stretching frequencies along with the elongated Li–Y bonds. Natural bond orbital analyses suggest ca. 0.02 electron transfer from the methyl radical (CH3) to the LiY moiety. In the single occupied molecular orbitals of the H3C⋯LiY complexes, it is also seen that the electron could of the CH3 radical approaches the Li atom. The single-electron Li bond energies are 5.20–6.94kcal∕mol for the H3C⋯LiY complexes at the CCSD(T)∕aug-cc-pVDZ+BF (bond functions) level with counterpoise procedure. By comparisons with some related systems, it is concluded that the single-electron Li bonds are stronger than single-electron H bonds, and weaker than conventional Li bonds and π-Li bonds.
Stranski-Krastanov growth in Mg0.37Zn0.63O∕ZnO heteroepitaxy: Self-organized nanodots and local composition separation
Authors: Matsui Hiroaki , Hasuike Noriyuki , Harima Hiroshi , Tanaka Takanori , Tabata Hitoshi
Published: August 2006

Heteroepitaxy of strained Mg0.37Zn0.63O layers on ZnO (0001) substrates introduces a transition from two-dimensional to Stranski-Krastanov growth accompanying lattice relaxation at a critical thickness, as indicated by the nanodots formation on the growing planar layer. Due to differences in the atomic size of Mg and Zn, the strained layer was compressively distorted at the heterointerface and alloy compositions fluctuated locally. Elastic strain induced by the lattice misfit acted as a driving force for the self-organization of surface nanodots. Moreover, a strained field generated by alloy fluctuation caused local composition separation with a correlation between surface roughening and a lateral Mg segregation.
Resistivity scaling in single-walled carbon nanotube films patterned to submicron dimensions
Authors: Behnam Ashkan , Noriega Leila , Choi Yongho , Wu Zhuangchun , Rinzler Andrew G. , Ural Ant
Published: August 2006

The authors describe efficient patterning of transparent, conductive single-walled carbon nanotube thin films by photolithography and e-beam lithography followed by reactive ion etching, and study the transport characteristics of the films patterned down to 200nm lateral dimensions. The resistivity of the films is independent of device length, while increasing over three orders of magnitude compared to the bulk films, as their width and thickness shrink. This behavior is explained by a geometrical argument. Such “top-down” patterning of nanotube films should permit their integration into submicron device structures; however, the strong resistivity scaling will have to be taken into account.
Enhanced Bragg reflections from size-matched heterostructure photonic crystal thin films prepared by the Langmuir-Blodgett method
Authors: Bardosova M. , Pemble M. E. , Povey I. M. , Tredgold R. H. , Whitehead D. E.
Published: August 2006

The Langmuir-Blodgett method was used to engineer photonic crystal thin films of an AB architecture. Structures were studied by transmittance and reflectance spectroscopies. For an AB structure in which the silica particle diameter B is twice that of A, reflectance features associated with the first order Bragg peak for the “A” domain are only observed when the structure is probed from the A side of the structure. Furthermore, this feature is enhanced in intensity compared to that for a structure consisting solely of A particles. These findings are attributed to a matching of first and second order Bragg processes.
Experimental investigation on pressurized liquid in confining nanoenvironment
Authors: Surani Falgun B. , Han Aijie , Qiao Yu
Published: August 2006

In this letter, the authors report the experimental observations of pressure induced liquid motions in a confining nanoporous gel. As the pressure is sufficiently high, water molecules can move out of the initially energetically favorable gel matrix and enter the hydrophobic nanopores. As the pressure is lowered, this process is irreversible, leading to the pronounced hysteresis of sorption isotherm. This phenomenon is essential to developing advanced energy absorption systems. A first-order thermodynamics analysis is presented.
Mid-infrared electroluminescence at room temperature from InAsSb multi-quantum-well light-emitting diodes
Authors: Krier A. , Stone M. , Zhuang Q. D. , Liu Po-Wei , Tsai G. , Lin H. H.
Published: August 2006

Room-temperature electroluminescence is reported from InAsSb multiple-quantum-well light-emitting diodes. The diodes exhibited emission in the mid-infrared peaking near 4μm. The spectral dependence on injection current at 4K was investigated and two transitions were identified, centered at 4.05 and 3.50μm, which are associated with the eigenstates of the confined holes inside the quantum well. The use of an Sb predeposition and As flux surface exposure during epitaxial growth was observed to have a major effect on the electroluminescence output.
Electronic transport properties of Cs-encapsulated double-walled carbon nanotubes
Authors: Li Y. F. , Hatakeyama R. , Kaneko T. , Izumida T. , Okada T. , Kato T.
Published: August 2006

Electronic transport properties of Cs-encapsulated double-walled carbon nanotubes (DWNTs) synthesized via a plasma irradiation method are investigated by fabricating them as field-effect transistor devices. The authors’ results indicate that Cs-encapsulated DWNTs exhibit a high performance n-type characteristic in contrast to ambipolar behavior of pristine DWNTs. Coulomb blockade oscillations are observed on the Cs-encapsulated DWNTs at low temperatures. In addition, it is found that the semiconducting characteristics of the as-synthesized Cs-encapsulated DWNTs can possibly be controllable by adjusting applied negative dc bias voltages during the plasma synthesis process.
Probing the intrinsic conductivity of multiwalled carbon nanotubes
Authors: Zamkov Mikhail , Alnaser Ali S. , Shan Bing , Chang Zenghu , Richard Patrick
Published: August 2006

The authors report the two-photon electron emission study of quantum transport parameters in multiwalled carbon nanotubes. The present experimental approach is based on measurements of the electron-phonon scattering dynamics and does not employ any electrical contacts, which dramatically reduces the uncertainty in the determination of an electron mean-free path l. It is found that near the Fermi level (<0.1eV) the ballistic travel of electrons averages around 4μm, which is comparable to the nanotube length, whereas in high-current regime (⩾0.3eV) l decreases to less than 1μm.
Theory of the ultrafast nonlinear response of terahertz quantum cascade laser structures
Authors: Weber C. , Banit F. , Butscher S. , Knorr A. , Wacker A.
Published: August 2006

Using density matrix theory, the linear and ultrafast nonlinear optical properties of a recently developed terahertz quantum cascade laser are investigated. All relevant excitation regimes, from coherent Rabi flopping up to the scattering dominated stationary response, are covered by the theory. It is shown that the coherence transfer between different periods is important to describe optical effects.
Light propagation and transmission in hybrid-aligned nematic liquid crystal cells: Geometrical optics calculations
Authors: Mendoza Carlos I. , Reyes J. Adrian
Published: August 2006

The authors present a geometrical approach to calculate the transmission of light in a hybrid-aligned nematic cell under the influence of an applied electric field. Using the framework of geometrical optics they present results for the ray tracing as well as the transmission of light as a function of the applied low frequency voltage. Dispersion effects are included through a wavelength dependent dielectric function. Their results for the transmittance as a function of the applied voltage show oscillations that are in good qualitative agreement with previously obtained experimental measurements.
Effects of grain size on the mosaic tilt and twist in InN films grown on GaN by metal-organic chemical vapor deposition
Authors: Wang H. , Huang Y. , Sun Q. , Chen J. , Wang L. L. , Zhu J. J. , Zhao D. G. , Zhang S. M. , Jiang D. S. , Wang Y. T. , Yang H.
Published: August 2006

The structural property of InN films grown on Ga-face GaN layers by metal-organic chemical vapor deposition has been studied by high-resolution x-ray diffraction. The mosaic tilt and twist are found to be strongly dependent on the surface lateral grain size. The twist decreases with increasing grain size and finally approaches to a constant level. On the other hand, the mosaic tilt increases substantially when the grain size becomes large enough and exceeds the width of step terraces on the GaN surface, showing an important mechanism for the defect generation in the InN∕GaN system with large out-of-plane lattice mismatch.
Efficient Yb3+:Y3Al5O12 ceramic microchip lasers
Authors: Dong Jun , Shirakawa Akira , Ueda Ken-ichi , Yagi Hideki , Yanagitani Takagimi , Kaminskii Alexander A.
Published: August 2006

Low-threshold and highly efficient continuous-wave (cw) Yb3+:Y3Al5O12 (Yb:YAG) ceramic laser with near-diffraction-limited beam quality was demonstrated at room temperature. Dual-wavelength operation at 1030 and 1049nm with 5% transmission of the output coupler was achieved by varying pump power intensity. Slope efficiencies of 79% at 1030nm and 67% at 1049nm were achieved for 1-mm-thick Yb:YAG ceramic plate (CYb=9.8at.%) under cw laser-diode pumping. The effect of pump power on the laser emission spectra of both wavelengths is addressed. Excellent laser performance indicates that Yb:YAG ceramic laser materials could be potentially used in high-power solid-state lasers.
Reduction of ultrasound inertial cavitation threshold using bifrequency excitation
Authors: Gilles Bruno , Béra Jean Christophe , Mestas Jean Louis , Cathignol Dominique
Published: August 2006

Within the scope of an application to transcutaneous ultrasonic thrombolysis, this study compares inertial cavitation thresholds obtained at the focus of a transducer for two types of ultrasonic excitations: a classical one frequency signal and an excitation combining two slightly different frequencies. A cepstral filtering method is used to measure inertial cavitation activity for these signals. A 30% reduction of the threshold is observed when using bifrequency excitation.
In situ transmission electron microscopy study of electric-field-induced 90° domain switching in BaTiO3 single crystals
Authors: Qi X. Y. , Liu H. H. , Duan X. F.
Published: August 2006

The 90° domain switching in single crystalline BaTiO3 under an external static electric field has been investigated by in situ transmission electron microscopy using a special homemade transmission electron microscope stage. With the initial domains gradually disappearing, new domains that are 90° away from the initial ones are observed to occur with polarizations being switched to the direction of the external electric field, and domain boundaries being changed from ⟨101⟩ to ⟨1¯01⟩ in order to maintain a “head-to-tail” arrangement.
Longitudinal DXA measurements demonstrate lifetime differences in lean and fat tissue deposition between boars and barrows under individual and group-penned systems
Authors: Suster D. , Leury B. J. , Kerton D. J. , Borg M. R. , Butler K. L. , Dunshea F. R.
Published: August 2006

Thirty-two Large White × Landrace male pigs were used to determine the relationships between the rates of tissue deposition and age, in boars and barrows under 2 housing systems. A 2 × 2 factorial design was used, with the respective treatments being sex (boar or barrow) and housing condition (individually penned system or group-penned system). Surgical castration was performed at 7 days of age. Individually housed pigs were used to provide an estimate of potential growth and were weaned at 10 days into individual cages and provided with supplemental fermented skim milk for 2 weeks. Group-housed pigs were weaned at 24 days of age and reared in group pens of boars and castrates typical for commercial production. Conventional weaner, grower, and finisher diets were provided ad libitum to all pigs from weaning onwards. A Hologic QDR4500A dual-energy X-ray absorptiometer (DXA) was used to determine lean, fat, and bone composition at 4-weekly intervals from 10 until 150 days of age. Over the 20 weeks of the study, boars deposited less fat than barrows (136 v. 179 g/day, s.e.d. = 6.49, P < 0.001). Over the same time frame, boars deposited more lean tissue than barrows when individually penned (490 v. 444 g/day, s.e.d. = 14.4, P < 0.05) but there was no difference in group-penned pigs (464 v. 443 g/day, s.e.d. = 14.4, P > 0.1). This was more pronounced in the final 4 weeks of growth when individually penned boars deposited 200 g/day more lean than barrows (P < 0.001), with no increase in group-penned animals. However, during this growth phase, group penning further increased the fat deposition margin between boars and barrows where boars deposited 90 g/day less fat when individually penned (P < 0.001), but 140 g/day less fat (P < 0.001) when group penned. The results show that the advantages of boars in terms of growth and lean tissue composition are substantially reduced in group-penned situations. However, because of fat deposition, boars retain some advantage over barrows in group-penned systems at liveweights over about 50 kg. These data may aid in the accurate prediction of the nutrient requirements and optimum slaughter weight for barrows.
Genetics of flight time and other measures of temperament and their value as selection criteria for improving meat quality traits in tropically adapted breeds of beef cattle
Authors: Kadel Meridy J. , Johnston David J. , Burrow Heather M. , Graser Hans-U. , Ferguson Drewe M.
Published: August 2006

Flight time, an objective measure of temperament, was recorded in 3594 Brahman, Belmont Red, and Santa Gertrudis heifers and steers. Two subjective measures of temperament (crush score and flight speed score) were also available for over 2000 of these animals. Temperament measures were recorded post-weaning (average age 8 months) and again at the start of finishing (average age 19 months) on a subset of the animals. Nine meat quality traits were measured on these animals and included measures on 2 different muscles [M. longissimus thoracis et lumborum (LTL) and M. semitendinosus (ST)]. The heritability of flight time measured post-weaning and at the start of finishing was 0.30 and 0.34, respectively, with a repeatability of 0.46 across the measurement times. Heritabilities for scored temperament traits were 0.21, 0.19, and 0.15 for post-weaning flight speed score, post-weaning crush score, and start of finishing crush score, respectively. Genetic correlations across measurement times for flight time were 0.98 and 0.96 for crush score, indicating a strong underlying genetic basis of these temperament measures over time; however, the corresponding phenotypic correlations were lower (0.48 and 0.37, respectively). Longer flight times (i.e. better temperament) were genetically correlated with improved tenderness (i.e. lower shear force and higher tenderness scores), with genetic correlations of –0.42 and 0.33 between LTL shear force, and Meat Standards Australia (MSA) tenderness, respectively. Genetic correlations between post-weaning crush score and the same meat quality traits were 0.39 and –0.47, respectively. However, genetic and phenotypic correlations between measures of temperament and other meat quality traits were generally low, with the exception of crush scores with LTL Minolta a* value (–0.37 and –0.63 for post-weaning and start of finishing measurement time, respectively). Predicted correlated responses of –0.17 kg LTL shear force and 2.6 MSA tenderness points per generation were predicted based on the genetic parameter estimates and a recording regime of both flight time and crush scores. Selection based on the measures of temperament described in this study could be used to improve temperament itself and correlated improvements can also occur in meat tenderness and eating quality traits in tropically adapted breeds of cattle.
Alkaloid production by isolates of the sorghum ergot pathogen (Claviceps africana) from Australia and other countries
Authors: Blaney Barry , Chakraborty Sukumar , Murray Sally-Ann
Published: August 2006

Isolates of Claviceps africana from Australia, Africa, Asia, and America were tested for the production of dihydroergosine (DHES), and its biogenic precursors dihydroelymoclavine (DHEL) and festuclavine (FEST), in culture. Several growth media were evaluated to optimise alkaloid production with little success. The best of these involved 2-stage culturing on high-sucrose substrate. Australian C. africana isolates varied widely and inconsistently in alkaloid production, with DHES concentrations in mycelium ranging from: <0.1 to 9 mg DHES/kg; <0.1 to 1.6 mg DHEL/kg; and <0.1 to 0.4 mg FEST/kg. In a separate experiment using similar culturing techniques, DHES was produced by 2 of 3 Australian isolates, 1 of 3 USA isolates, 1 of 4 Indian isolates, the sole Puerto Rican isolate, the sole Japanese isolate, but not the sole South African isolate. In this experiment, DHES concentrations detected in mycelium of Australian isolates (0.1–1.0 mg DHES/kg) were of similar magnitude to isolates from other countries (0.2–1.8 mg DHES/kg). Three C. africana isolates, including one that produced only traces of alkaloid in culture after 8 weeks, were inoculated onto panicles of sterile male sorghum plants. After 8 weeks, all 3 isolates produced 10–19 mg DHES/kg in the panicles, demonstrating that the growing plant favoured more consistent alkaloid production than culture medium.
Effects of xylanase supplementation on between-bird variation in energy metabolism and the number of Clostridium perfringens in broilers fed a wheat-based diet
Authors: Choct M. , Sinlae M. , Al-Jassim R. A. M. , Pettersson D.
Published: August 2006

Three experiments were conducted to examine: (a) the apparent metabolisable energy (AME) contents, the level of non-starch polysaccharides (NSP), and the extract viscosity value of 9 wheat samples; (b) the efficacy of a xylanase in reducing between-bird variation for AME; and (c) the effect of a xylanase on the number of Clostridium perfringens in broilers fed a low AME wheat diet. Experiment 1 revealed that the AME value of wheat varied from 11.5 to 13.6 MJ/kg dry matter (DM), which negatively correlated with the total NSP level (r = –0.97). Experiment 2 involved a 48-cage individual bird trial, where xylanase increased (P < 0.05) the AME from 12.51 to 13.09 MJ/kg DM and reduced (P < 0.05) its standard deviation from 1.13 to 0.52. The standard deviation for feed conversion ratio, ileal viscosity, and faecal viscosity was also reduced. In this experiment, there was a strong correlation between AME and excreta viscosity (r = –0.81) and the caecal xylanase activity of birds fed the control diet was positively correlated with AME (r = 0.72). In Expt 3, xylanase reduced the number of Clostridium perfringens, the causative agent for necrotic enteritis, to a non-detectable level in the ileum and caeca of broilers fed a low-ME wheat diet.
Seasonal characteristics of the surface mixed layer in the Australasian region: implications for primary production regimes and biogeography
Authors: Condie Scott A. , Dunn Jeff R.
Published: August 2006

The seasonal cycle of physical, chemical, and biological properties of the surface ocean mixed layer in the Australasian region (0 to 50°S, 90 to 180°E) were described on the basis of a range of data products, some of which are described for the first time. They include seasonal fields of temperature, salinity, mixed layer depth, nitrate, phosphate and silicate from the CSIRO Atlas of Regional Seas (CARS), as well as estimates of chlorophyll from SeaWiFS ocean colour data, and a range of supplementary information taken from published studies. Seasonal chlorophyll cycles were interpreted within the context of variability in nutrient concentrations and mixed layer depths. This interpretation included a biogeographical description, which was compared with related regional and global products. Such descriptions provide a baseline for future investigations of interannual variability and long-term trends in mixed layer properties, as well as contributing to the development of spatial frameworks for management of the region’s resources.
Estimating local stream fish assemblage attributes: sampling effort and efficiency at two spatial scales
Authors: Kennard Mark J. , Pusey Bradley J. , Harch Bronwyn D. , Dore Elli , Arthington Angela H.
Published: August 2006

As part of a wider study to develop an ecosystem-health monitoring program for wadeable streams of south-eastern Queensland, Australia, comparisons were made regarding the accuracy, precision and relative efficiency of single-pass backpack electrofishing and multiple-pass electrofishing plus supplementary seine netting to quantify fish assemblage attributes at two spatial scales (within discrete mesohabitat units and within stream reaches consisting of multiple mesohabitat units). The results demonstrate that multiple-pass electrofishing plus seine netting provide more accurate and precise estimates of fish species richness, assemblage composition and species relative abundances in comparison to single-pass electrofishing alone, and that intensive sampling of three mesohabitat units (equivalent to a riffle–run–pool sequence) is a more efficient sampling strategy to estimate reach-scale assemblage attributes than less intensive sampling over larger spatial scales. This intensive sampling protocol was sufficiently sensitive that relatively small differences in assemblage attributes (<20%) could be detected with a high statistical power (1-β > 0.95) and that relatively few stream reaches (<4) need be sampled to accurately estimate assemblage attributes close to the true population means. The merits and potential drawbacks of the intensive sampling strategy are discussed, and it is deemed to be suitable for a range of monitoring and bioassessment objectives.
Recurrent gonorrhoea in South Australia, 1987 - 2003
Authors: D'Onise Katina , Waddell Russell
Published: August 2006

In Australia, it is unclear if individuals are being recurrently infected with gonorrhoea, a proxy for identifying core groups. We reviewed all notified gonococcal (GC) infections in South Australia between 1987 and 2003. A case of repeated GC infection is one in which at least one further episode of GC infection occurred after 30 days and within 365 days of the first infection. There were 253 recurrent infections (7.26%) from 238 individuals. Men who have sex with men (MSM) and Aboriginal and Torres Strait Islanders (ATSI) were significantly more likely to be recurrently infected with gonorrhoea than the rest of the South Australian population. This method of identifying individuals who have recurrent gonococcal infections can be used to target more frequent screening for individuals in a population who are more likely to be a part of the core group.