bluuebunny/crossref_metadata_2025 huggingface dataset:
Production efficiency of thin metal flyers formed by laser ablation
Authors: Cogan S. , Shirman E. , Haas Y.
Published: May 2005

Thin metal plates (flyers) were launched from an aluminum-coated glass support using nanosecond and picosecond Nd: yttrium aluminum garnet laser pulses at 1.06 μm. The velocity of the flyers was measured as a function of incident fluence and of the delay between two consecutive laser pulses using a time-of-flight method. Profilometric scans of the craters formed on the substrate provided an accurate mapping of the crater’s morphology and enabled a realistic estimation of the flyer’s mass. The combination of these measurements allowed the determination of the flyer’s kinetic energy and hence the efficiency of the launching process as a function of the initiating laser’s energy. Threshold fluences of 1.3–2.0J∕cm2 and acceleration efficiencies up to 0.45 were measured under our experimental conditions. The results show that acceleration efficiency rises with the energy of initiating laser and drops when the delay time between two pulses of 10-ns full width at half maximum becomes larger. The acceleration efficiency is also reduced (relative to a 10-ns laser pulse) when the process is initiated by a single 20-ps pulse. On the basis of these data we assume that the launching efficiency may be optimized by using 2-ps laser pulses with a subnanosecond delay time between them.
Electronic properties of a semiconducting oligomer/silicon (111) interface: Influence of silicon doping
Authors: Papaefthimiou V. , Kennou S.
Published: May 2005

The interface formation between a semiconducting oligomer and the p-doped Si(111) surface was investigated by X-ray and ultraviolet photoelectron spectroscopies (UPS) and the results were compared to the same oligomer/Si (n-doped) interface. The position of the energy levels of the bulk oligomer film was identical in both interfaces, while differences appeared at the first steps of the interface formation. The band bending at the interfaces was assessed from X-ray photoelectron spectra while the interfacial dipoles from the UPS results. A ∼0.30eV dipole layer was observed at the oligomer/Si (p-doped) interface whereas the oligomer/Si (n-doped) interface is dipole free. The valence-band offset between silicon and the oligomer was found ∼0.40eV in both cases.
Thin-film encapsulation of organic light-emitting devices
Authors: Ghosh A. P. , Gerenser L. J. , Jarman C. M. , Fornalik J. E.
Published: May 2005

Organic light-emitting devices (OLED) are extremely sensitive to moisture and oxygen. Without high-performance hermetic seals, the life of these devices is limited. Bottom-emitter OLEDs are commonly sealed using epoxy and cover glass with large amounts of desiccant. In top-emitter OLEDs the light passes through the cover glass on which the desiccant typically resides. Thus, transparent thin-film encapsulation without any desiccant is most desirable. This paper reports the results of a robust thin-film encapsulation method that utilizes a layer of aluminum oxide deposited by atomic layer deposition (ALD) process as the primary moisture barrier. More than 1000 h in 85 °C and 85% RH testing has been observed without significant device degradation caused by moisture. Data corroborating this method's superiority over other physical deposition methods for OLED encapsulation are also presented.
Zero-field spin splitting in modulation-doped AlxGa1−xN∕GaN two-dimensional electron systems
Authors: Cho K. S. , Huang Tsai-Yu , Wang Hong-Syuan , Lin Ming-Gu , Chen Tse-Ming , Liang C.-T. , Chen Y. F. , Lo Ikai
Published: May 2005

Low-temperature magnetotransport measurements were performed on AlxGa1−xN∕GaN two-dimensional electron systems. By studying the beating pattern in the Shubnikov–de Haas oscillations in a perpendicular magnetic field, we are able to measure the zero-field spin-splitting energies in our systems. Our experimental results demonstrate that the Rashba term due to structural inversion asymmetry is the dominant mechanism which gives rise to the measured zero-field spin splitting in our wurzite AlGaN∕GaN structures. By utilizing the persistent photoconductivity (PPC) effect, we are able to increase the carrier density n in our AlGaN∕GaN two-dimensional electron system. It is found that the Rashba spin-orbit splitting parameter α decreases with increasing n. We suggest that the formation of long-lived electron-hole pairs induced by the PPC effect decreases the large electric field near the AlGaN∕GaN interface, causing α to decrease with increasing n.
Observation of large electron drift velocities in InN by ultrafast Raman spectroscopy
Authors: Tsen K. T. , Poweleit C. , Ferry D. K. , Lu Hai , Schaff William J.
Published: May 2005

Electron transport in an InN film grown on GaN has been studied by transient Raman spectroscopy at T=300K. Our experimental results demonstrate that under the subpicosecond laser excitation and probing, electron drift velocity of carriers in the Γ valley can exceed its steady-state value by as much as 40%. Electron velocities have been found to cut off at around 2×108cm∕s, significantly larger than those observed for other III-V semiconductors, such as GaAs and InP. These experimental results have been compared with ensemble Monte Carlo simulations and good agreement has been obtained.
Time domain reflectometry of glass beads/magnetite mixtures: A time and frequency domain study
Authors: Mattei Elisabetta , De Santis Alberto , Di Matteo Andrea , Pettinelli Elena , Vannaroni Giuliano
Published: May 2005

The measurements of the time domain reflectometry (TDR) signal propagating along a coaxial probe, filled with dry mixtures of glass beads and magnetite, are analyzed for deriving the attenuation factor α and the bandwidth. Samples with different percentages (5%–25%) of magnetite are considered. The α values are obtained by two different methods: (i) wave amplitude at the second reflection, (ii) electromagnetic parameters and widths of the passing bands. The two methods provide consistent α values within the experimental uncertainties. The agreement supports the possibility of measuring the attenuation factor from the second TDR reflection, for anhydrous samples similar to the investigated mixtures.
Transformation of diamond nanoparticles into onion-like carbon by electron irradiation studied directly inside an ultrahigh-vacuum transmission electron microscope
Authors: Hiraki J. , Mori H. , Taguchi E. , Yasuda H. , Kinoshita H. , Ohmae N.
Published: May 2005

In situ observation of the transformation of diamond nanoparticles (DNP) into onion-like carbon (OLC) was made during electron-beam irradiation inside an ultrahigh-vacuum transmission electron microscope at 300 kV with 8.5×1023e∕m2. 5 nm DNP changed into OLC within about 10 min of irradiation, while 20 nm DNP did not change to OLC but to graphite. Therefore, the size effect is critical to the formation of OLC. The mechanism of formation of OLC from DNP is discussed.
CdTe photoluminescence: Comparison of solar-cell material with surface-modified single crystals
Authors: Corwine C. R. , Sites J. R. , Gessert T. A. , Metzger W. K. , Dippo P. , Li Jingbo , Duda A. , Teeter G.
Published: May 2005

Low-temperature photoluminescence (PL) is used to study defect evolution during Cu diffusion into single-crystal CdTe under various atmospheres. PL reveals a zero-order phonon peak at 1.456 eV when Cu-coated CdTe is annealed at 400 °C in an oxidizing atmosphere, but not under other tested conditions. A similar peak is seen in polycrystalline thin-film CdTe samples, which are known to contain copper and oxygen impurities. First-principles band structure calculations determined the likely defect assignment as a transition between a Cui–OTe donor complex and the valence band.
Electroluminescence from metal/oxide/strained-Si tunneling diodes
Authors: Liao M. H. , Chen M.-J. , Chen T. C. , Wang P.-L. , Liu C. W.
Published: May 2005

The metal-oxide-silicon light-emitting diode under biaxial tensile mechanical strain is studied. The emission line shape of the device can be fitted by the electron-hole-plasma recombination model. The energy gap of strained Si extracted by the light emission spectra at the temperature of 120 K is reduced by 15 meV under 0.13% biaxial tensile strain. The light intensity of the device under 0.13% biaxial tensile strain increases 9% as compared to the relaxed-Si device. The upshift of valence band edge under mechanical strain to increase the majority hole concentration at the oxide∕Si interface may be responsible for this light emission enhancement. The mechanical strain is measured by Raman spectroscopy, strain gauge, and analyzed by the finite element method.
Amplified spontaneous emission in an organic semiconductor multilayer waveguide structure including a highly conductive transparent electrode
Authors: Reufer M. , Feldmann J. , Rudati P. , Ruhl A. , Müller D. , Meerholz K. , Karnutsch C. , Gerken M. , Lemmer U.
Published: May 2005

We demonstrate that the amplified spontaneous emission (ASE) threshold in multilayer waveguide structures suitable for the use in future organic injection lasers can be drastically reduced by inserting a crosslinked hole transport layer (HTL) between a highly conductive indium tin oxide (ITO) electrode and the polymer emission layer. While no ASE is observed when the active layer material is directly spincoated onto the ITO electrode, it can be completely restored upon insertion of a 300-nm-thick HTL. This observation is attributed to reduced attenuation of the waveguided mode enabling the ASE process and is theoretically confirmed by calculations of the mode intensity fraction propagating in the absorptive ITO electrode.
High critical current properties of MgB2 bulks prepared by a diffusion method
Authors: Ueda Shinya , Shimoyama Jun-ichi , Iwayama Isao , Yamamoto Akiyasu , Katsura Yukari , Horii Shigeru , Kishio Kohji
Published: May 2005

Highly dense MgB2 bulks with high purity were synthesized by the newly developed PICT-diffusion method, starting from magnesium and boron which were separately packed in sealed stainless tubes. Critical current density, Jc, systematically improved with a decrease of grain size of the samples. A sample reacted at 800°C for 60h exhibited the highest Jc of ∼0.86MA∕cm2 at 20K in self-field, which was almost three times higher than that of conventional porous MgB2 bulks prepared by the solid-state reaction. Besides an increase of effective current pass, small grains with 30–100nm in size and good grain connectivity resulted in the dramatically enhanced Jc.
Aging effect and origin of deep-level emission in ZnO thin film deposited by pulsed laser deposition
Authors: Shan F. K. , Liu G. X. , Lee W. J. , Lee G. H. , Kim I. S. , Shin B. C.
Published: May 2005

ZnO thin films were deposited on sapphire substrates at 400°C in the pulsed laser deposition (PLD) system. Those thin films showed two emission peaks. One was near band edge emission at around 379nm; the other was deep-level (DL) emission at around 510nm. The aging effect on photoluminescence (PL) of the thin film was observed. It was found that the DL emission decreased with time. Post-annealing processes were carried out to find the origin of the DL emission. The thin films were annealed at 800°C in N2 or O2 ambient gas in a rapid thermal annealing system. An atomic force microscope was used to investigate the surface morphologies of the thin films. The surface roughness of annealed thin film was much smaller than that of the as-deposited one. The transmittance of the annealed thin film decreased much compared with that of the as-deposited thin film. The DL emission of the thin film annealed in N2 increased, and the DL emission of thin film annealed in O2 decreased. The oxygen vacancies instead of zinc interstitials were the main reason for DL emission in ZnO thin films deposited by PLD.
Pressure-induced transient structural change of liquid germanium induced by high-energy picosecond laser pulses
Authors: Chaoui N. , Siegel J. , Wiggins S. M. , Solis J.
Published: May 2005

The temporal evolution of the reflectivity of germanium at 514 nm upon irradiation with single high-energy picosecond laser pulses has been measured using a streak camera. It is found that, for a well-defined high fluence range, the reflectivity of the laser-induced molten phase attains a value of 0.85, considerably above the value reported for liquid Ge in thermal equilibrium (0.75). This behavior is consistent with a strong densification of the liquid phase remaining after the explosive vaporization of a thin surface layer. Within the specified fluence interval, this anomalously high reflectivity state is independent of the fluence and lasts tens of nanoseconds. Both characteristics point to the presence of a pressure-induced transient structural change in liquid germanium.
On the exposure to mobile phone radiation in trains
Authors: Ferrer J. , Fernández-Seivane L. , Hernando J. M. , Castán M. B. , García L. , Vázquez J. M.
Published: May 2005

This report presents theoretical estimates of the power density levels which may be reached inside trains. Two possible sources of high levels of radiation are discussed. The first one arises since the walls of the wagons are metallic and therefore bounce back almost all radiation impinging on them. The second is due to the simultaneous emission of a seemingly large number of nearby telephones. The theoretical study presented here shows that power densities stay at values below reference levels always.
Phonon lifetimes and phonon decay in InN
Authors: Pomeroy J. W. , Kuball M. , Lu H. , Schaff W. J. , Wang X. , Yoshikawa A.
Published: May 2005

We report on the Raman analysis of A1(LO) (longitudinal optical) and E2 phonon lifetimes in InN and their temperature dependence from 80 to 700 K. Our experimental results show that among the various possible decay channels, the A1(LO) phonon decays asymmetrically into a high energy and a low energy phonon, whereas the E2 phonon predominantly decays into three phonons. Possible decay channels of the A1(LO) phonon may involve combinations of transverse optical and acoustic phonons. Phonon lifetimes of 1.3 and 4 ps were measured at 80 K for the A1(LO) and the E2 phonons, respectively. This rather long A1(LO) phonon lifetime suggests that hot phonon effects will play a role in InN for carrier relaxation.
Nucleation of β-FeSi2 nanostructures at pinned step bunches on the Si(111) surface
Authors: Brady R. P. , Sharma A. S. , Giblet R. L. , Cottier R. J. , Golding T. D. , Perez J. M.
Published: May 2005

We report the preferential nucleation and synthesis of β-FeSi2 nanostructures at pinned step bunches on the Si(111) surface. The nanostructures are synthesized by depositing Fe on Si at room temperature and subsequent annealing. The surface topography is studied using scanning tunneling microscopy and atomic force microscopy. The size, shape and orientation of the nanostructures indicate that the phase is the semiconducting β-FeSi2 phase.
Critical precipitate size revisited and implications for oxygen precipitation in silicon
Authors: Vanhellemont Jan , De Gryse Olivier , Clauws Paul
Published: May 2005

A generalized expression is derived describing the impact of intrinsic point defects and strain on the critical size of spheroidal incoherent precipitates. An important phenomenon that has been neglected so far is the incorporation of intrinsic point defects of the host matrix in the precipitate itself. It is shown that this can have an important impact both on the critical precipitate size, on the amount of emitted intrinsic point defects, and on the precipitated phase itself. The theoretical results are illustrated for the case of oxygen precipitation in silicon.
Proton irradiation effect on single-wall carbon nanotubes in a poly(3-octylthiophene) matrix
Authors: Neupane P. P. , Manasreh M. O. , Weaver B. D. , Rafaelle R. P. , Landi B. J.
Published: May 2005

Proton irradiation effects on interband transitions in single-wall carbon nanotubes matrixed in poly(3-octylthiophene) were investigated. The interband transitions were measured using an optical absorption technique. Two interband transitions were observed, at 0.71 and 1.28 eV in a sample that was subject to 2 MeV proton irradiation to fluences ranging between 5.0×1010cm−2 and 5.6×1015cm−2. The optical absorption spectra were collected after cooling the sample to 10 K. The total integrated areas of the two transitions were monitored as a function of proton fluence. The results indicate that proton irradiation to fluences as high as 5.6×1015cm−2 has little effect on the interband transitions in carbon nanotubes. However, small radiation-related degradation has been observed as judged by the broadening of the interband transition spectra and by the reduction of the radial breathing mode intensity observed by Raman scattering.
Photoluminescence characterization of excitonic centers in ZnO epitaxial films
Authors: Watanabe M. , Sakai M. , Shibata H. , Tampo H. , Fons P. , Iwata K. , Yamada A. , Matsubara K. , Sakurai K. , Ishizuka S. , Niki S. , Nakahara K. , Takasu H.
Published: May 2005

Photoluminescence properties of nominally undoped ZnO thin films grown by radical-source molecular-beam epitaxy have been investigated as a function of (i) sample growth conditions, (ii) excitation laser power density, and (iii) measurement temperatures. Altogether four excitonic emission peaks were observed at photon energy of 3.3646, 3.3606, 3.3572, and 3.3331 eV, which are tentatively denoted as emission peaks A, D, F, and G, respectively. We have classified the defect types responsible for the emission peaks into the following two groups; (i) D and F, whose responsible defect types are suggested to be residual impurities such as aluminum and indium, respectively, and (ii) A and G, whose responsible defect types are suggested to be intrinsic defects such as oxygen vacancies, interstitial zinc, and extended structural defects particularly for G.
Phonons in strained In1−xGaxAs∕InP epilayers characterized by infrared reflectance
Authors: Yu G. , Rowell N. L. , Lockwood D. J. , Poole P. J.
Published: May 2005

Strained In1−xGaxAs epilayers over a wide range of x values from 0.252 to 0.762 have been grown by chemical beam epitaxy on heavily doped InP(100) substrates. The infrared p-polarized reflectivity of these samples has been measured and the first derivative of the reflectance has been analyzed using a specially developed fitting technique. Expressions for the variation of the phonon frequencies with Ga fraction for the InAs-like and GaAs-like modes have been obtained. The present results substantially improve on earlier results obtained from epilayers on semi-insulating substrates having a narrower concentration range around x=0.468 where In1−xGaxAs is lattice matched to InP.
Spin-selective optical absorption of singly charged excitons in a quantum dot
Authors: Högele Alexander , Kroner Martin , Seidl Stefan , Karrai Khaled , Atatüre Mete , Dreiser Jan , Imamoğlu Atac , Warburton Richard J. , Badolato Antonio , Gerardot Brian D. , Petroff Pierre M.
Published: May 2005

We report high resolution laser absorption spectroscopy of a single InGaAs∕GaAs self-assembled quantum dot embedded in a field-effect structure. We show experimentally that the interband optical absorption to the lower Zeeman branch of the singly charged exciton is strongly inhibited due to spin (Pauli) blockade of the optical transition. At high magnetic fields the optical absorption to the upper Zeeman branch dominates the absorption spectrum. We find, however, that the spin blockade is not complete and a 10% leakage remains at high magnetic fields. Applying a gate voltage to empty the dot of its resident electron turns the spin blockade off. This effect is observed at 1.5 K and up to 9 T.
Spatially resolved cathodoluminescence of GaN nanostructures fabricated by photoelectrochemical etching
Authors: Díaz-Guerra C. , Piqueras J. , Popa V. , Cojocaru A. , Tiginyanu I. M.
Published: May 2005

The emission properties of GaN nanostructures created by photoelectrochemical etching have been investigated by cathodoluminescence (CL) in the scanning electron microscope. Columnar structures with diameters of 150–250 nm formed near the surface of the as-grown GaN layers branch into nanowires with diameters of 20–60 nm, while islands with coral-like relief were observed at the bottom of the etched areas. CL emission of the observed nanostructures is dominated by free electron to acceptor transitions. Local CL spectra provide direct evidence of the existence of either compressive or tensile stress in different nanostructures. No free exciton luminescence was observed in GaN nanowires, supporting their relation to threading dislocations.
Highly sensitive optical response of optical fiber long period gratings to nanometer-thick ionic self-assembled multilayers
Authors: Wang Zhiyong , Heflin J. R. , Stolen Rogers H. , Ramachandran Siddharth
Published: May 2005

Ionic self-assembled multilayers deposited on long period fiber gratings (LPGs) yield dramatic resonant-wavelength shifts, even with nanometer-thick films. Fine control of the refractive index and the thickness of these films was achieved by altering the relative fraction of the anionic and cationic materials combined with layer-by-layer deposition. We demonstrate the feasibility of this highly controllable deposition technique for fine-tuning grating properties. In addition a variety of biological and chemical sensing agents can easily be incorporated into these films, which makes this an attractive platform for realization of high-performance LPG-based sensors.
p
-ZnO/n-GaN heterostructure ZnO light-emitting diodes
Authors: Hwang Dae-Kue , Kang Soon-Hyung , Lim Jae-Hong , Yang Eun-Jeong , Oh Jin-Yong , Yang Jin-Ho , Park Seong-Ju
Published: May 2005

We report on the characteristics of a ZnO light-emitting diode (LED) comprised of a heterostructure of p-ZnO/n-GaN. The LED structure consisted of a phosphorus doped p-ZnO film with a hole concentration of 6.68×1017cm−3 and a Si-doped n-GaN film with an electron concentration of 1.1×1018cm−3. The I–V of the LED showed a threshold voltage of 5.4 V and an electroluminescence (EL) emission of 409 nm at room temperature. The EL emission peak at 409 nm was attributed to the band gap of p-ZnO which was reduced as the result of the band offset at the interface of p-ZnO and n-GaN.
Amorphous carbon film growth on Si: Correlation between stress and generation of defects into the substrate
Authors: Brusa R. S. , Macchi C. , Mariazzi S. , Karwasz G. P. , Laidani N. , Bartali R. , Anderle M.
Published: May 2005

Amorphous carbon films of several thicknesses were prepared by graphite sputtering on crystalline silicon substrate. The samples were depth profiled with positron annihilation spectroscopy for open-volume measurements and characterized for their residual internal stress. It was found that after film growth the substrate presents vacancy-like defects decorated by oxygen in a layer extending in the substrate by several tens of nanometers beyond the film/Si interface. The width of the defected layer and the decoration of vacancy-like defects are directly and inversely proportional to the measured intensity of the residual stress, respectively. These findings indicate the existence of a relaxation mechanism of the stress in the films that involves deeply the substrate. The decorated vacancy-like defects are suggested to be bounded to dislocations induced in the substrate by the stress relaxation.
Optimized energy window of He beams for accurate determination of depth in channeling Rutherford backscattering spectrometry
Authors: Shao Lin , Wang Y. Q. , Zhang X. , Wetteland C. J. , Nastasi M. , Thompson P. E. , Mayer J. W.
Published: May 2005

We propose a method to improve accurate determination of damage/impurity depth profiles by channeling Rutherford backscattering by using He+4 beams in an energy window of 400–800 keV. This is based on the study of the stopping power of He+4 ions as a function of incident energy along the Si ⟨100⟩ axis, which shows that the channeling stopping power within the above energy window is close to the random stopping power. Experiments on 100 nm deep Sb-doped Si superlattices show that the approach significantly reduces the error in determining the depth location of Sb, for example, from 8% by using 2-MeV He+4 to 1% by using 600-keV He+4 ions.
Gold film with gold nitride—A conductor but harder than gold
Authors: Šiller L. , Peltekis N. , Krishnamurthy S. , Chao Y. , Bull S. J. , Hunt M. R. C.
Published: May 2005

The formation of surface nitrides on gold films is a particularly attractive proposition, addressing the need to produce harder, but still conductive, gold coatings which reduce wear but avoid the pollution associated with conventional additives. Here we report production of large area gold nitride films on silicon substrates, using reactive ion sputtering and plasma etching, without the need for ultrahigh vacuum. Nanoindentation data show that gold nitride films have a hardness ∼50% greater than that of pure gold. These results are important for large-scale applications of gold nitride in coatings and electronics.
A Heat-driven thermoacoustic cooler capable of reaching liquid nitrogen temperature
Authors: Dai Wei , Luo Ercang , Hu Jianying , Ling Hong
Published: May 2005

This article introduces a heat-driven thermoacoustic cooler capable of reaching liquid nitrogen temperature with no moving parts. The thermoacoustic cooler consists of a traveling wave thermoacoustic prime mover and a pulse tube cooler. By using a tapered resonance tube, the prime mover can provide a pressure ratio higher than 1.26. By using a long thin tube, a reservoir is no longer needed in the pulse tube cooler. After preliminary optimizations, the lowest temperature reaches 68.8 K. This result shows the potential to achieve cryogenic temperatures lower than 70 K by applying thermoacoustic technology, which is simply realized through combinations of tubes and solid materials without the need of any moving parts.
Nanostructured tungsten carbide catalysts for polymer electrolyte fuel cells
Authors: Yang X. G. , Wang C. Y.
Published: May 2005

In this study, high current densities (i.e., 0.9A∕cm2) have been obtained in a hydrogen∕air polymer electrolyte fuel cell using nanoscale tungsten carbide as the anode catalyst and carbon supported platinum as the cathode catalyst under normal operating conditions of 80 °C and 3 atm. These results show a possibility of replacing precious metal anode catalysts with transition metal compounds for hydrogen oxidation, thereby creating a fundamental technology to reduce the cost of future fuel cell engines. The tungsten carbide-based catalysts were synthesized by means of chemically reduced mechanical alloying. The high electrocatalytic activity toward hydrogen oxidation reaction is attributed to the inherent W–C valence and the unique nanostructure of synthesized carbides. These properties were confirmed by x-ray diffraction and transmission electron microscopy.
Enhanced magnetic and bolometric sensitivity of La0.7Ce0.3MnO3 thin films due to 200 MeV Ag ion irradiation
Authors: Choudhary R. J. , Kumar Ravi , Patil S. I. , Husain Shahid , Srivastava J. P. , Malik S. K.
Published: May 2005

The parameters for bolometric performance [temperature coefficient of resistance (TCR) and noise value] and magnetic sensitivity of pulsed-laser-deposited thin films of La0.7Ce0.3MnO3 and their dependence on the 200 MeV Ag ions irradiation are studied. It is observed that the TCR value and magnetic sensitivity can be tuned in different temperature regime by controlling the irradiation fluence value. It turns out that irradiation with a fluence value of 5×1010ions∕cm2 changes the TCR value in a positive direction and enhances magnetic sensitivity at room temperature, while irradiation with a fluence value of 1×1012ions∕cm2 enhances these parameters at 200 K. The observations are explained on the basis of structural and electrical transport modifications induced by the 200 MeV Ag ion irradiation.
High-mobility nanocrystalline silicon thin-film transistors fabricated by plasma-enhanced chemical vapor deposition
Authors: Lee Czang-Ho , Sazonov Andrei , Nathan Arokia
Published: May 2005

Hydrogenated nanocrystalline silicon (nc-Si:H) films were deposited by using 13.56MHz plasma-enhanced chemical vapor deposition at 260°C by means of a silane (SiH4) plasma heavily diluted with hydrogen (H2). The high-quality nc-Si:H film showed an oxygen concentration (CO) of ∼1.5×1017at.∕cm3 and a dark conductivity (σd) of ∼10−6S∕cm, while the Raman crystalline volume fraction (Xc) was over 80%. Top-gate nc-Si:H thin-film transistors employing an optimized ∼100nm nc-Si:H channel layer exhibited a field-effect mobility (μFE) of ∼150cm2∕Vs, a threshold voltage (VT) of ∼2V, a subthreshold slope (S) of ∼0.25V∕dec, and an ON∕OFF current ratio of ∼106.
Speaker Variations Influence Speechreading Speed for Dynamic Faces
Authors: Kaufmann Jürgen M , Schweinberger Stefan R
Published: May 2005

We investigated the influence of task-irrelevant speaker variations on speechreading performance. In three experiments with video digitised faces presented either in dynamic, static-sequential, or static mode, participants performed speeded classifications on vowel utterances (German vowels /u/ and /i/). A Garner interference paradigm was used, in which speaker identity was task-irrelevant but could be either correlated, constant, or orthogonal to the vowel uttered. Reaction times for facial speech classifications were slowed by task-irrelevant speaker variations for dynamic stimuli. The results are discussed with reference to distributed models of face perception (Haxby et al, 2000 Trends in Cognitive Sciences4 223–233) and the relevance of both dynamic information and speaker characteristics for speechreading.
Effects of the Degree of Fluctuation on Subjective Preference for a 1 Hz Flickering Light
Authors: Soeta Yoshiharu , Mizuma Kazunobu , Okamoto Yosuke , Ando Yoichi
Published: May 2005

Humans are believed to have a preferred amount of stimulus variation in their perceptual environment. Here, paired comparison tests were conducted to examine whether the fluctuation of a flickering light improves subjective preference. Sine-wave and bandpass noise acted as the light source. We have previously shown that the preferred temporal frequency of a flickering light without any fluctuation is approximately 1 Hz (Soeta et al 2002 Journal of the Optical Society of America A19 289 – 294). This was used as the center frequency of the light source. The bandwidth was set at 1, 2, 4, 8, and 16 Hz, to control the amplitude of the first peak of the autocorrelation function, ø1 Results show that the preferred ø1 of a flickering light is 0.46.
Geometric and Perceptual Effects of the Location of the Observer Vantage Point for Linear-Perspective Images
Authors: Todorović Dejan
Published: May 2005

New geometric analyses are presented of three impressive examples of the effects of location of the vantage point on virtual 3-D spaces conveyed by linear-perspective images. In the ‘egocentric-road’ effect, the perceived direction of the depicted road is always pointed towards the observer, for any position of the vantage point. It is shown that perspective images of real-observer-aimed roads are characterised by a specific, simple pattern of projected side lines. Given that pattern, the position of the observer, and certain assumptions and perspective arguments, the perceived direction of the virtual road towards the observer can be predicted. In the ‘skewed balcony’ and the ‘collapsing ceiling’ effects, the position of the vantage point affects the impression of alignment of the virtual architecture conveyed by large-scale illusionistic paintings and the real architecture surrounding them. It is shown that the dislocation of the vantage point away from the viewing position prescribed by the perspective construction induces a mismatch between the painted vanishing point of elements in the picture and the real vanishing point of corresponding elements of the actual architecture. This mismatch of vanishing points provides visual information that the elements of the two architectures are not mutually parallel.
Is Synaesthesia an X-Linked Dominant Trait with Lethality in Males?
Authors: Ward Jamie , Simner Julia
Published: May 2005

In previous research the inheritance patterns of synaesthesia (eg experiencing colours from graphemes) has been studied and it was concluded that synaesthesia is most likely to be the outcome of a single gene passed on the X chromosome in a dominant fashion. In addition, it has been reported that the female – male ratio of synaesthetes is as high as 6: 1 and the families of synaesthetes contain more female than male members. This raises the possibility that the gene may be associated with lethality in males. In this study we replicate and extend previous research by investigating the female – male ratio and inheritance patterns in a large sample of synaesthetic families ( N = 85). We were able to verify the authenticity of grapheme – colour associates in at least one proband from each family using internal consistency. As before, our results show a female – male bias and are broadly consistent with an X-linked dominant mode of inheritance. However, there was no evidence of male lethality (eg synaesthetes are just as likely to give birth to sons as to daughters). Moreover, our female – male ratio of synaesthetes within families was 2: 1 —considerably lower than previous estimates. We speculate that men may be more reluctant to disclose synaesthesia than women (indeed, our female – male ratio based on self-referral was 3.7: 1). Finally, we discuss how the genotype may give rise to the phenotype in terms of changes in synaptogenesis or plasticity extending into childhood, to be subsequently shaped by the environment.
Global versus Local Image Expansion in Estimating Time-to-Contact from Complex Optic Flow
Authors: Giachritsis Christos D , Harris Mike G
Published: May 2005

Previous work (Harris and Giachritsis 2000, Vision Research40 601–611) has shown that, when global and local image expansion are placed in conflict, estimates of time-to-contact (TTC) are based almost exclusively upon global expansion. Here we extend this finding by demonstrating that global image expansion continues to predominate even under conditions that seem more favourable to a local analysis. We added a global rotation to the stimulus so that the global pattern of expansion was distorted while leaving the local expansion unaffected. Even under relatively high rotation rates (30° s−1), local expansion continued to have little systematic effect upon estimates of TTC.
Two Reference Frames for Visual Perception in Two Gravity Conditions
Authors: Lipshits Mark , Bengoetxea Ana , Cheron Guy , McIntyre Joseph
Published: May 2005

The processing and storage of visual information concerning the orientation of objects in space is carried out in anisotropic reference frames in which all orientations are not treated equally. The perceptual anisotropies, and the implicit reference frames that they define, are evidenced by the observation of ‘oblique effects’ in which performance on a given perceptual task is better for horizontally and vertically oriented stimuli. The question remains how the preferred horizontal and vertical reference frames are defined. In these experiments cosmonaut subjects reproduced the remembered orientation of a visual stimulus in 1g (on the ground) and in 0g, both attached to a chair and while free-floating within the International Space Station. Results show that while the remembered orientation of a visual stimulus may be stored in a multimodal reference frame that includes gravity, an egocentric reference is sufficient to elicit the oblique effect when all gravitational and haptic cues are absent.
Remote Effects of Highlights on Gloss Perception
Authors: Berzhanskaya Julia , Swaminathan Gurumurthy , Beck Jacob , Mingolla Ennio
Published: May 2005

The perception of a glossy surface in a static monochromatic image can occur when a bright highlight is embedded in a compatible context of shading and a bounding contour. Some images naturally give rise to the impression that a surface has a uniform reflectance, characteristic of a shiny object, even though the highlight may only cover a small portion of the surface. Nonetheless, an observer's impression of gloss may be partial and nonuniform at image regions outside of a highlight. A rating scale and small probe points indicating image locations were used to investigate the differential perception of gloss within a single object. Gloss ratings given by observers were not uniform across a surface, but decreased as a function of distance from a highlight. When, by design, the distance from a highlight was uncoupled from the luminance value at corresponding probe points, the decrease in rated gloss correlated more with distance than with luminance change. Experiments also indicated that gloss ratings may change as a function of estimated surface distance, rather than as a function of image distance. Surface continuity affected gloss ratings, suggesting that surface and gloss processing are closely related.
White's Effect: Removing the Junctions but Preserving the Strength of the Illusion
Authors: Howe Piers D L
Published: May 2005

White's effect (also known as the Munker-White effect) is a lightness illusion in which, contrary to expectations based on simultaneous contrast and Wallach's rule, a gray rectangle predominantly surrounded by white appears lighter than an identical rectangle that is mainly surrounded by black. The illusion is often explained in terms of T-junctions that are formed by the three-way intersection of the gray rectangle, a black stripe, and a white stripe. I present a circular variant of White's effect in which all the junctions have been removed without significantly affecting the strength of the illusion, suggesting that junctions are not an important consideration in all versions of White's effect.
Eragrostis curvula (Schrad.) Nees. complex pastures in southern New South Wales, Australia: a comparison with Medicago sativa L. and Phalaris aquatica L. pastures under rotational grazing
Authors: Johnston W. H. , Cornish P. S. , Shoemark V. F.
Published: May 2005

A grazing experiment conducted in Wagga Wagga (New South Wales) from September 1993 to September 1998 compared the productivity of pastures containing 3 palatable types of summer-active Eragrostis curvula complex, with pastures containing either Medicago sativa or Phalaris aquatica. Issues relating to the management of E. curvula pastures were also investigated. Herbage growth rates of the P. aquatica and M. sativa pastures were highest in winter and spring; E. curvula pastures were most productive in summer and autumn. Stocking rates equivalent to 30–40 dry sheep were carried by the pastures during their growing seasons. Throughout the study, the pastures were dominated by their respective sown perennial species, however, a suite of desirable and undesirable annual grasses and annual legumes usually contributed >20% of total herbage mass in spring. The P. aquatica pasture contained a higher proportion of weedy species than the other pastures, especially C4 grasses and broadleafed species, and towards the end of the experiment it was also invaded by several native perennial grasses. Overall, the wool yield from the M. sativa pasture was 0.5–1.0 kg/animal.year higher than the other pastures. Management to minimise herbage accumulation on the E. curvula pastures was a key issue, and provided that pastures were grazed heavily, this was achieved by the rotational grazing strategy used in the experiment. It was concluded that palatable varieties of E. curvula have a useful and complementary role as perennial pastures in southern Australia. By increasing herbage availability in summer and autumn, E. curvula may improve management flexibility for a wide range of pastures that are commonly grown on farms.
Biophysical and sociological impacts of farmyard manure and its potential role in meeting crop nutrient needs: a farmers
Authors: Reddy K. S. , Kumar N. , Sharma A. K. , Acharya C. L. , Dalal R. C.
Published: May 2005

Cropping in Madhya Pradesh, Central India, experiences an overall nutrient deficit of about 1 Mt of nitrogen (N), phosphorus (P) and potassium (K) annually. In addition to increasing the supply of inorganic fertilisers, the balance between inputs and losses must also be met by indigenous organic sources such as farmyard manure. Although large amounts of animal dung are produced in India, less than 50% of this is currently used to produce farmyard manure. With the objective of increasing manure production and manure nutrient use in cropping, we surveyed 100 farmers from 4 randomly selected villages in Madhya Pradesh to: record perceptions and attitudes towards farmyard manure use for crop production; estimate nutrient balances; and test fields for concentrations of soil organic carbon (C), nitrogen, and available nutrients.
All farmers’ field soils were low in organic C and available N, although available P, zinc and iron occurred in low to medium concentrations. However, the majority of farmers under-fertilised their crops, resulting in a negative nutrient balance; 0.9 Mt of NPK in 1997–98, which is predicted to increase to 1.8 Mt by 2020 over a 19 × 106 ha cropped area in Madhya Pradesh. All of the farmers surveyed believed that added farmyard manure improved their soil productivity and the majority also believed that farmyard manure increased crop yields; favourably affecting soil physical conditions and water-holding capacity. However, most farmers were not aware of the contribution of farmyard manure to plant nutrients.
The major constraint listed by all the surveyed farmers was the insufficient quantity of farmyard manure available for field application. Its production was restricted by the competitive use of about 50% of cattle dung as a domestic fuel. The marginal farmers (<0.9 ha farm size) expressed their unwillingness to shift to other fuel sources, presumably due to limited cash flow from the farm, however 58–85% of farmers with larger holdings (0.9–25 ha) were receptive to using alternative fuel sources such as liquid petroleum gas. Although the nutrient content of farmyard manure was found to be relatively low (about 7.6 kg N/t dry farmyard manure), use of all animal dung for manure should be encouraged by introducing liquid petroleum gas supply in villages. This would help to reverse the negative nutrient balance in Madhya Pradesh soils via an integrated nutrient management approach (utilisation of all nutrient sources and optimisation of crop nutrient requirements).
The effect of applied nitrogen on the growth and nutrient concentration of Kalonji (Nigella sativa)
Authors: Ashraf M. , Ali Q. , Rha E. S.
Published: May 2005

Growth and nutrient accumulation in Kalonji (Nigella sativa L.) under varying levels of nitrogen, were examined in a field experiment. Sixty-three-day-old plants were supplied with varying levels of nitrogen of 0, 30, 60 and 90 kg N/ha soil. Maximum biomass and seed yield were recorded at 30 and 60 kg N/ha. The soil nitrogen level, 90 kg/ha, proved to be ineffective in promoting growth of Kalonji. Accumulation of nitrogen, potassium and phosphorus in both shoots and roots of Kalonj increased consistently with increase in soil nitrogen. However, this pattern of increase in the levels of 3 nutrients in plant tissues had a negative association with the growth of the crop, particularly at the supra-optimal nitrogen levels (60 and 90 kg N/ha).
Ontogeny and the effects of corticosteroid pretreatment on aquaporin water channels in the ovine cerebral cortex
Authors: Ron Nitin P. , Kazianis John A. , Padbury James F. , Brown Courtney M. , McGonnigal Bethany G. , Sysyn Gregory D. , Sadowska Grazyna B. , Stonestreet Barbara S.
Published: May 2005

The aim of the present study was to determine the ontogeny and effects of corticosteroid pretreatment on aquaporin 4 (AQP4) channel mRNA and protein expression in the cerebral cortex of sheep during development. A portion of the cerebral cortex was snap-frozen from fetuses of dexamethasone- and placebo-treated ewes at 60%, 80% and 90% of gestation, dexamethasone- and placebo-treated newborn lambs and adult sheep. Cerebral cortical samples were obtained 18 h after the last of four 6 mg dexamethasone or placebo injections were given over 48 h to the ewes and adult sheep. Lambs were treated with 0.01 mg kg−1 dexamethasone or placebo in the same schedule as the ewes and adult sheep. Amplification of an ovine AQP4 cDNA fragment was accomplished by reverse transcription–polymerase chain reaction using primers based on a homologous bovine sequence. The resulting cDNA was used to determine AQP4 channel mRNA expression by Northern hybridisation using phosphorimaging. The relative abundance of AQP4 mRNA was normalised to the ovine ribosomal gene L32. A portion of the frontal cortex was also analysed for AQP4 protein expression by Western immunoblot. Densitometry was performed and the results expressed as a ratio to an adult brain pool. Aquaporin 4 channel mRNA and protein were detectable as early as at 60% gestation. There were no changes in AQP4 mRNA expression among the fetal, newborn and adult groups or after dexamethasone pretreatment in any age group. The expression of the AQP4 protein was higher (P < 0.05) in fetuses at 80% and 90% of gestation (2.9- and 3.3-fold, respectively), in lambs (3.2-fold) and in adult sheep (3.8-fold) compared with fetuses at 60% of gestation, as well as in adult sheep (1.3-fold) compared with fetuses at 80% of gestation. Dexamethasone pretreatment resulted in decreases (P < 0.05) in AQP4 protein expression in the lambs and adult sheep, but not in the fetal groups. We conclude that: (1) AQP4 mRNA and protein were expressed early in fetal and throughout ovine development; (2) protein, but not mRNA, expression increased between 60% and 80% of gestation and did not differ from adult levels by 90% of gestation; and (3) dexamethasone pretreatment resulted in decreases in AQP4 protein expression in lambs and adult sheep, but not in fetuses. The maturational increases in AQP4 protein expression and dexamethasone-related decreases in expression were post-transcriptional, because changes in AQP4 mRNA expression were not observed.