bluuebunny/crossref_metadata_2025 huggingface dataset:
Metal nanoparticle precipitation in periodic arrays in Au2O-doped glass by two interfered femtosecond laser pulses
Authors: Qu Shiliang , Qiu Jianrong , Zhao Chongjun , Jiang Xiongwei , Zeng Huidan , Zhu Congshan , Hirao K.
Published: March 2004

We report on the precipitation control of Au nanoparticles in periodic arrays in silicate glass. Au2O-doped glass samples were first irradiated by two 800 nm interfered femtosecond laser pulses at room temperature and then heat treated at 550 °C for the Au nanoparticle precipitation in the laser irradiation areas. One-dimensional periodic arrays of the Au nanoparticles were controlled by changing the pulse energy and the incident angle between the interfered laser pulses. The smallest dimension in the obtained arrays was a width of 300 nm. The mechanism of the metal nanoparticle precipitation by this technique was discussed. Only two pulses are required to encode these periodic microstructures, which are applicable to emerging nanostructure devices such as optical memory with ultrahigh storage density, micrograting with high diffractive efficiency and integrative micro-optical switches.
Simulation of terahertz pulse propagation in biological systems
Authors: Pickwell E. , Cole B. E. , Fitzgerald A. J. , Wallace V. P. , Pepper M.
Published: March 2004

Studies in terahertz (THz) imaging have revealed a significant difference between skin cancer (basal cell carcinoma) and healthy tissue. Since water has strong absorptions at THz frequencies and tumor affects the water content of tissue, a likely contrast mechanism is variation in water content. Modeling the propagation of a THz pulse through water is the first step toward understanding the origin of contrast in terahertz pulsed images of skin cancer. In this letter, we develop a finite-difference-time-domain simulation to model the propagation of a THz pulse and incorporate double Debye theory to model the behavior of water subject to THz radiation. Furthermore, we apply this model to skin.
Unidirectional magnetostrictive Terfenol/epoxy composite
Authors: Kim Jong Chul , Kwon Oh Yeoul , Lee Zin Hyoung
Published: March 2004

We have developed a unidirectional composite for improving magnetostrictive properties and mechanical properties of giant magnetostrictive composite. The composite consists of bulk RFe2 dendrites with a preferred orientation of 〈112〉 and an electrically insulated binder between the dendrites, which is analogous to a lamination pattern. We investigated the magnetostrictive properties of composites by varying the volume fraction of RFe2 phase in the range of 60%–80%. The results demonstrated that the unidirectional composites had much higher strain and d33 than a monolithic Terfenol-D at the same volume fraction of RFe2 phase and these results were compared with the model for uniform strain.
Systematic design of photonic crystal structures using topology optimization: Low-loss waveguide bends
Authors: Jensen Jakob S. , Sigmund Ole
Published: March 2004

Topology optimization is a promising method for systematic design of optical devices. As an example, we demonstrate how the method can be used to design a 90° bend in a two-dimensional photonic crystal waveguide with a transmission loss of less than 0.3% in almost the entire frequency range of the guided mode. The method can directly be applied to the design of other optical devices, e.g., multiplexers and wave splitters, with optimized performance.
Giant magnetostriction on Fe85Ga15 stacked ribbon samples
Authors: Liu G. D. , Liu L. B. , Liu Z. H. , Zhang M. , Chen J. L. , Li J. Q. , Wu G. H. , Li Y. X. , Qu J. P. , Chin T. S.
Published: March 2004

Large magnetostrictions of −1300 and +1100 ppm related in the different directions have been obtained in our stacked Fe85Ga15 ribbon samples. In the case of non-180° domain magnetization in the high anisotropic samples, the magnetostrictions are mainly attributed to the existence of Ga clusters which preferentially orient with the ribbon normal due to the ribbon grain texturing. Forming the modified DO3 structure, the Ga–Ga atom pairs distribute in the matrix and cause the x-ray diffraction peak split in melt-spun ribbons. As a special micromorphology, Ga clusters highly condensed in some nanoscale dots have also been experimentally observed.
Picosecond response of gallium-nitride metal–semiconductor–metal photodetectors
Authors: Li Jianliang , Xu Ying , Hsiang T. Y. , Donaldson W. R.
Published: March 2004

Metal–semiconductor–metal ultraviolet photodiodes fabricated on GaN were tested in the picosecond regime with an electro-optic sampling system. A device with a feature size of 1 μm showed a response with 1.4 ps rise time and 3.5 ps full width at half maximum. The derived electron velocity, 1.43×107 cm/s, is in good agreement with independent photoexcitation measurements. A slower impulse response was observed in a device with smaller feature size of 0.5 μm.
Dielectric behavior of electroactive fluorinate-based terpolymers
Authors: Ang Chen , Yu Zhi
Published: March 2004

The dielectric and ferroelectric properties of the poly(vinylidene fluoride–trifluoroethylene–chlorotrifluoroethylene) terpolymers are studied in the temperature range 160–380 K. More attention was given to the dielectric loss in the dielectric spectra and the following results were obtained: (1) there are two dielectric polarization mechanisms, modes A and B, contributing to the majority of the dielectric permittivity; (2) by using the Cole–Cole plot method, precise relaxation rates of mode B can be obtained, which follow the Vogel–Fulcher relation with reasonable parameters, TVF=∼160±2 K, UVF=∼0.16±0.01 eV, ν0=1×1012 Hz. The temperature where mode A occurs does not shift with the variation of frequency and a well-developed hysteresis loop is observed, indicating the existence of a normal “paraelectric–ferroelectric” transition in the terpolymer.
Photonic switching based on the photoinduced birefringence in bacteriorhodopsin films
Authors: Huang Yuhua , Wu Shin-Tson , Zhao Youyuan
Published: March 2004

Photoinduced birefringence in bacteriorhodopsin films was investigated using pump–probe method and its application for photonic switching explored. A diode-pumped second-harmonic YAG laser was used as a pumping beam and a diode laser at λ=660 nm was used as a probing beam. The pump and probe beams overlap at the sample. Without the pumping beam, the probing light cannot transmit the analyzer to the detector. However, due to the photoinduced anisotropy, a portion of the probing light is detected when the pumping beam is present. Since λ=660 nm is far from the absorption peak (∼570 nm) of the ground state, the photoinduced birefringence predominates. Using the intensity-dependent photoinduced birefringence in a bacteriorhodopsin film, we have demonstrated a photonic switch with ∼1000:1 contrast ratio, ∼0.6 s rise time and ∼1.5 s decay time.
Excitation and recording of morphology-dependent resonances in spherical microresonators by hollow light guiding fibers
Authors: Nürenberg Alexandra , Schweiger Gustav
Published: March 2004

We report the excitation and simultaneous recording of morphology-dependent resonances in dye-doped microresonators by a single hollow fiber. The spherical microresonator was plugged in the tapered end of a light guiding flexible hollow fiber. Light from a frequency-doubled Nd:YVO4 laser was coupled via a beam splitter into one end of the hollow fiber and transported to the resonator mounted on the tapered end of the fiber. Fluorescence was excited in the resonator. This fluorescence was partly coupled in the hollow fiber and guided back to the untapered end. Here, the fluorescence was separated from the laser light by a beam splitter and analyzed spectroscopically. The tapered fiber was prepared by heating with a CO2 laser.
Generation and detection of terahertz pulses using post-process bonding of low-temperature-grown GaAs and AlGaAs
Authors: Desplanque L. , Lampin J. F. , Mollot F.
Published: March 2004

We present an electro-optical method to measure very high frequency characteristics of planar electronic devices. This method allows one to generate and detect subpicosecond electrical pulses on a coplanar stripline using photoconduction and electroabsorption sampling in transferred low-temperature-grown epitaxial layers. The epitaxial lifted-off films are directly van der Waals bonded on the transmission line under test. Good switching efficiency and short electrical rise time (<490 fs) are measured. A bandwidth of 2.5 THz with 60 dB of dynamic range is obtained. This confers to the technique a large field of applications in ultrahigh-speed electronic measurements.
Electron-doped infinite-layer thin films with TC over 40 K grown on DyScO3 substrates
Authors: Karimoto Shin-ichi , Naito Michio
Published: March 2004

We report high-quality electron-doped infinite-layer superconducting thin films with a TC of over 40 K grown on lattice-matched DyScO3 substrates by molecular-beam epitaxy. The optimally doped film seems to be free from strain, thus leading to a low resistivity of 75 μΩ cm at room temperature and 15 μΩ cm just above TC.
Superprism effect in bidimensional rectangular photonic crystals
Authors: Căbuz A. I. , Centeno E. , Cassagne D.
Published: March 2004

In this letter, we show that photonic crystals with geometries of lower symmetry, such as the rectangular geometry, are uniquely suited for applications involving the superprism effect. The extra degree of freedom provided by the anisotropy of the unit cell allows more freedom in searching for suitable iso-frequency curves. Also, the appearance of multiple orders of diffraction allows more than one incident plane wave to couple to the same Bloch mode. This extra degree of freedom is decisive when trying to optimize the transmission. We illustrate these ideas on a particular rectangular configuration which ensures a strong angular superprism effect, a well collimated transmitted beam, and power transmissions of up to 80%.
High detectivity InGaAs/InGaP quantum-dot infrared photodetectors grown by low pressure metalorganic chemical vapor deposition
Authors: Jiang J. , Tsao S. , O’Sullivan T. , Zhang W. , Lim H. , Sills T. , Mi K. , Razeghi M. , Brown G. J. , Tidrow M. Z.
Published: March 2004

We report a high detectivity middle-wavelength infrared quantum dot infrared photodetector (QDIP). The InGaAs quantum dots were grown by self-assembly on an InGaP matrix via low pressure metalorganic chemical vapor deposition. Photoresponse was observed at temperatures above 200 K with a peak wavelength of 4.7 μm and cutoff wavelength of 5.2 μm. The background limited performance temperature was 140 K, and this was attributed to the super low dark current observed in this QDIP. A detectivity of 3.6×1010 cm Hz1/2/W, which is comparable to the state-of-the-art quantum well infrared photodetectors in a similar wavelength range, was obtained for this InGaAs/InGaP QDIP at both T=77 K and T=95 K at biases of −1.6 and −1.4 V, respectively.
Red–green–blue generation from a lone dual-wavelength GdAl3(BO3)4:Nd3+ laser
Authors: Brenier Alain , Tu Chaoyang , Zhu Zhaojie , Wu Baichang
Published: March 2004

We demonstrate the simultaneous generation of the three basal red–green–blue colors from a lone GdAl3(BO3)4:Nd3+ bi-functional laser and optical nonlinear crystal. The laser works in a dual-wavelength operation in the two F3/24→I11/24 (near 1062 nm) and F3/24→I13/24 (near 1338 nm) channels, under a fixed wavelength pumping (at 744.7 nm) and with a fixed crystal orientation. Red and green results from self-frequency doubling of the two laser channels, blue results of self-sum frequency mixing of the pump and the 1338 nm laser.
Three-photon-excited fluorescence of Al2O3-SiO2 glass containing Eu3+ ions by femtosecond laser irradiation
Authors: You Hongpeng , Nogami Masayuki
Published: March 2004

Near-infrared to visible upconverted fluorescence was observed in the Al2O3–SiO2 glass containing Eu3+ ions during femtosecond laser irradiation. The dependence of the intensity of the Eu3+ emission on the pump power reveals that the three-photon excitation is dominant in the upconversion process from near-infrared into the visible fluorescence. The analysis of the upconversion mechanism indicates that upconversion fluorescence comes from the three-photon simultaneous absorption that leads to the population of the 4f levels via the excitation of the charge transfer state of the Eu3+ ions.
High-resolution mapping of nonuniform carrier transport at contacts to polycrystalline CdTe/CdS solar cells
Authors: Sutter P. , Sutter E. , Ohno T. R.
Published: March 2004

We demonstrate a spectroscopic technique based on scanning tunneling microscopy that provides high-resolution maps of local carrier transport across contacts to polycrystalline thin-film solar cells. Using this technique, preferential transport channels across a p+-ZnTe/p-CdTe back contact of a p-CdTe/n-CdS solar cell are imaged with 20 nm spatial resolution. Transport across this contact is highly nonuniform. Large areas of high resistance coexist with nanoscale low-resistance regions that are strongly correlated with grain boundaries in the CdTe absorber. These results suggest an important role of grain boundaries as near-contact conducting channels.
Electrical conductivity of hollow polyaniline microspheres synthesized by a self-assembly method
Authors: Long Yunze , Chen Zhaojia , Ma Yongjun , Zhang Ze , Jin Aizi , Gu Changzhi , Zhang Lijuan , Wei Zhixiang , Wan Meixiang
Published: March 2004

In this letter, we report the electrical properties of hollow polyaniline (PANI) microspheres. β-naphthalene sulfonic acid (NSA) and salicylic acid (SA) doped PANI microspheres were synthesized by a self-assembly method. The room-temperature conductivity is 8.6×10−2 S/cm for PANI–NSA microspheres (0.8–2 μm in outer diameter) and 5.6×10−4 S/cm for PANI–SA microspheres (3–7 μm in outer diameter). The conductivity of an individual PANI–SA microsphere is measured directly by a two-probe technique, about 8×10−2 S/cm (which is two orders of magnitude higher than that of a PANI–SA microsphere’s pellet). The measurements of conductivity, I–V curve, and magnetoresistance demonstrate that the electrical properties of PANI microspheres are dominated by the intersphere contacts due to the sample’s microscopic inhomogeneity.
Photoinduced charge-density-wave dynamics in K0.3MoO3
Authors: Ren Yuhang , Lüpke Gunter , Xu Zhu’an
Published: March 2004

We report on time-resolved spectroscopy from the ultraviolet to mid-infrared spectrum of low-frequency collective excitations: dispersion and anisotropy of amplitude mode and phase mode in quasi-one-dimensional charge-density wave conductors, K0.3MoO3 and K0.33MoO3. Our results show that the time-resolved optical technique provides momentum resolution of collective modes.
Effects of hydrostatic and uniaxial stress on the Schottky barrier heights of Ga-polarity and N-polarity n-GaN
Authors: Liu Y. , Kauser M. Z. , Nathan M. I. , Ruden P. P. , Dogan S. , Morkoç H. , Park S. S. , Lee K. Y.
Published: March 2004

We report measurements of the Schottky barrier heights of Ni/Au contacts on Ga-polarity and N-polarity n-GaN under hydrostatic pressure and applied in-plane uniaxial stress. Under hydrostatic pressure the two different polarities of GaN yield significantly different rates of Schottky barrier height increase with increasing pressure. Uniaxial stress parallel to the surface affects the Schottky barrier height only minimally. The observed changes in barrier height under stress are attributed to a combination of band structure and piezoelectric effects.
Domain structure of epitaxial CaHfO3 gate insulator films on SrTiO3
Authors: Shibuya Keisuke , Ohnishi Tsuyoshi , Lippmaa Mikk , Kawasaki Masashi , Koinuma Hideomi
Published: March 2004

Thin CaHfO3 films were grown on (100) and (110)-oriented SrTiO3 surfaces with the aim of obtaining an insulator film for epitaxial oxide device design. We show that films grown on the (100) surface of SrTiO3 have a multidomain structure, which increases film roughness and decreases the maximum breakdown field of the insulator. Single-domain films were obtained on the SrTiO3 (110) surface. These films had a breakdown field of 5 MV/cm and a dielectric constant of εr=16 to 17 at room temperature.
Near-field optical nanopatterning of crystalline silicon
Authors: Wysocki G. , Heitz J. , Bäuerle D.
Published: March 2004

Nanoscale photochemical and photophysical etching of Si in Cl2 atmosphere is demonstrated by means of an optical near-field setup. With 351 nm Ar+-laser radiation and low intensities, the etching mechanism is purely photochemical. In this regime, the width of patterns—which is about 115 nm at full width at half maximum (FWHM)—corresponds, approximately, to the diameter of the fiber tip. The vertical etch rate is of the order of 1 nm/s. With 514.5 nm Ar+-laser light etching is observed only at significantly higher laser-light intensities. Patterns with width down to about 30 nm at FWHM have been achieved. Here, the lateral resolution corresponds to about 1/18 of the laser wavelength employed.
Field emission properties of heavily Si-doped AlN in triode-type display structure
Authors: Taniyasu Yoshitaka , Kasu Makoto , Makimoto Toshiki
Published: March 2004

Using heavily Si-doped AlN, a triode-type field emission display is demonstrated. The device consists of the heavily Si-doped AlN field emitter, mesh grid, and phosphor-coated anode screen. The device exhibits a low turn-on electric field of 11 V/μm, and the field emission current exponentially increases as the grid voltage increases. The field emission current reaches 9.5 μA at an electric field strength of 23 V/μm. Luminescence from the phosphor excited by the field-emitted electrons is uniform over the anode screen and is intense enough for the display application. The field emission current is stable over time.
Optical measurement of rolling and spinning of half-coated nanoparticles
Authors: Choi Jaehyuck , Lo Y.-H.
Published: March 2004

A technique of detecting the rolling and spinning of half-coated nanoparticles using interference ring patterns of the fluorescence has been demonstrated. Using the unique ability to measure nanoparticle rotations in multiple degrees of freedom, we are able to determine the orientation of a moving nanoparticle in real time. Ultimately, the detailed knowledge of the rotational behavior of half-coated nanoparticles is expected to produce physical insight of nano biomechanical systems.
Mapping In concentration, strain, and internal electric field in InGaN/GaN quantum well structure
Authors: Takeguchi M. , McCartney M. R. , Smith David J.
Published: March 2004

Quantitative comparisons have been made of the In concentration, strain, and internal electric field present in a pseudomorphic InGaN/GaN quantum well. Z-contrast scanning transmission electron microscopy was used for mapping In concentration with atomic resolution, variations of the c-lattice parameter of the InGaN layer were measured from (0001) lattice fringes in high-resolution transmission electron micrographs, and the internal electric fields were determined by differentiating phase images obtained by electron holography. Based on these measurements, it was concluded that local fluctuations of In concentration caused inhomogeneities in the internal electric field across the quantum well. The band structure of the quantum well would thus be altered not only by quantum dot effects but also by the additional modulation of the internal electric field, leading to further broadening of the light emission.
Room-temperature silicon light-emitting diodes based on dislocation luminescence
Authors: Kveder V. , Badylevich M. , Steinman E. , Izotov A. , Seibt M. , Schröter W.
Published: March 2004

We demonstrate electroluminescence (EL) with an external efficiency of more than 0.1% at room temperature from glide dislocations in silicon. The key to this achievement is a considerable reduction of nonradiative carrier recombination at dislocations due to impurities and core defects by impurity gettering and hydrogen passivation, respectively, which is shown by means of deep-level transient spectroscopy. Time-resolved EL measurements reveal a response time below 1.8 μs, which is much faster, compared to the band-to-band luminescence of bulk silicon.
Out-of-plane mosaic of single-wall carbon nanotube films
Authors: Zhou W. , Winey K. I. , Fischer J. E. , Sreekumar T. V. , Kumar S. , Kataura H.
Published: March 2004

For single-wall carbon nanotube (SWNT) films deposited from suspension onto filter membranes, or by drop casting or spin coating onto flat substrates, the tube axes lie preferentially in the film plane. Using x-ray scattering and a two-dimensional detector, we show that this out-of-plane mosaic spread can be easily and accurately quantified. It varies significantly with deposition conditions, and the aligning effects of deposition and external force in the film plane (e.g., magnetic field) are additive. Films from well-dispersed tubes show better alignment than from poor dispersions. The finite out-of-plane mosaic in C60@SWNT films enables quantitative separation of one-dimensional diffraction (chains of C60 peas) from the 2D rope lattice diffraction.
Capping-layer-induced magnetic coupling in a two-dimensional nanostructured system
Authors: Navarro E. , Huttel Y. , Clavero C. , Armelles G. , Cebollada A.
Published: March 2004

The magnetic polarization of a Pt capping layer leads to an increase of the interisland magnetic coupling in a two-dimensional array of Fe islands. For small superparamagnetic islands, Pt deposition leads to a superparamagnetic–ferromagnetic transition. For larger ferromagnetic but weakly coupled islands, Pt deposition produces a stronger interisland coupling. Polar Kerr spectroscopy measurements and simulations evidence the magnetic polarization of Pt in contact with Fe. The described effects and their interpretation are supported by the use of a nonpolarizable Al capping, where both the superparamagnetic-to-ferromagnetic transition and the increase of the interisland coupling are absent.
Effects of dielectric structure of HfO2 on carrier generation rate in Si substrate and channel mobility
Authors: Kang Chang Yong , Cho Hag-Ju , Choi Rino , Kang Chang Seok , Kim Young Hee , Rhee Se Jong , Choi Chang Hwan , Akbar Shahriar M. , Lee Jack C.
Published: March 2004

This letter presents the effects of surface preparation for hafnium-based dielectrics on the bulk carrier generation rates and the carrier mobility. Different surface preparations result in different interfacial layers. Nitrogen-incorporated layers effectively block impurity penetration from hafnium oxide, and lead to the increase of bulk carrier generation lifetime. However, nitrogen-incorporated interface layers increase interface state density and degrade channel mobility, even though bulk carrier generation lifetime is increased. Thus, mobility degradation is preliminarily caused by fixed charge and interface states of the high-k dielectrics.
Biexciton luminescence from AlxGa1−xN epitaxial layers
Authors: Yamada Yoichi , Ueki Yusuke , Nakamura Kohzo , Taguchi Tsunemasa , Kawaguchi Yasutoshi , Ishibashi Akihiko , Yokogawa Toshiya
Published: March 2004

Excitonic optical properties of Ga-rich AlxGa1−xN ternary alloy epitaxial layers (x=0.019, 0.038, 0.057, 0.077, and 0.092) have been studied by means of photoluminescence (PL) and time-resolved PL spectroscopy. The luminescence line due to radiative recombination of biexcitons was clearly observed for all of the five ternary alloy epitaxial layers with different Al compositions. The energy separation between exciton luminescence and biexciton luminescence increased with increasing Al composition, which indicated the increase in the binding energy of biexcitons in ternary alloys.
Mapping the potential within a nanoscale undoped GaAs region using a scanning electron microscope
Authors: Kaestner B. , Schönjahn C. , Humphreys C. J.
Published: March 2004

Semiconductor dopant profiling using secondary electron imaging in a scanning electron microscope has been developed in recent years. In this letter, we show that the mechanism behind it also allows mapping of the electric potential of undoped regions. By using an unbiased GaAs/AlGaAs heterostructure, this letter demonstrates the direct observation of the electrostatic potential variation inside a 90-nm-wide undoped GaAs channel surrounded by ionized dopants. The secondary electron emission intensities are compared with two-dimensional numerical solutions of the electric potential.
A miniature x-ray tube
Authors: Haga A. , Senda S. , Sakai Y. , Mizuta Y. , Kita S. , Okuyama F.
Published: March 2004

A miniature x-ray tube is described. The tube is made of Kovar, inside which a grounded target is located close to a field-electron emitter consisting of aligned carbon nanofibers, which continues to work for around 100 h in the 10−6 Pa region unless arcing is induced between the electrodes. The resolution of the contact x-ray images provided by the tube would be impossible using the existing techniques of conventional x-ray radiography, whether the sample is biological or nonbiological.
Analyses of Facial Attractiveness on Feminised and Juvenilised Faces
Authors: Ishi Hanae , Gyoba Jiro , Kamachi Miyuki , Mukaida Shigeru , Akamatsu Shigeru
Published: March 2004

We conducted two experiments to investigate the psychological factors affecting the attractiveness of composite faces. Feminised or juvenilised Japanese faces were created by morphing between average male and female adult faces or between average male (female) adult and boy (girl) faces. In experiment 1, we asked the participants to rank the attractiveness of these faces. The results showed moderately juvenilised faces to be highly attractive. In experiment 2, we analysed the impressions the participants had of the composite faces by the semantic-differential method and determined the factors that largely affected attractiveness. On the basis of the factor scores, we plotted the faces in factor spaces and analysed the locations of attractive faces. We found that most of the attractive juvenilised faces involved impressions corresponding to an augmentation of femininity, characterised by the factors of ‘elegance’, ‘mildness’, and ‘youthfulness’, which the attractive faces potentially had.
Familiarity Breeds Attraction: Effects of Exposure on the Attractiveness of Typical and Distinctive Faces
Authors: Peskin Melissa , Newell Fiona N
Published: March 2004

Several studies have shown that facial attractiveness is positively correlated with both familiarity and typicality. Here we manipulated the familiarity of typical and distinctive faces to measure the effect on attractiveness. In our first experiment, we collected ratings of attractiveness, distinctiveness, and familiarity using three different groups of participants. Our stimuli included 84 images of female faces, presented in a full-face view. We replicated the finding that attractiveness ratings negatively correlate with distinctiveness ratings. In addition, we showed that attractiveness ratings were positively correlated with familiarity ratings. In our second experiment, we demonstrated that increasing exposure to faces increases their attractiveness, although there was no differential effect of exposure on typical and distinctive faces. Our results suggest that episodic familiarity affects attractiveness ratings independently of general or structural familiarity. The implications of our findings for the ‘face-space’ model are discussed.
Ethnic Categorisation of Faces is Not Independent of Face Identity
Authors: Bruyer Raymond , Leclere Stéphanie , Quinet Pascal
Published: March 2004

Is the extraction of a visually derived semantic code from faces (ethnicity) affected by face identity (familiarity) or not? The traditional view considers that this operation is made independently of face identity, and in parallel with the recognition of identity. However, some recent studies cast doubt on this parallel thesis regarding other visually derived semantic codes, namely: facial expression, facial speech, apparent age, and gender. Twenty-eight Caucasian participants were enrolled in an ‘ethnic-decision’ task on morphed faces made of an Asiatic source face and a Caucasian source face, in the proportion of 70%–30%. Half of the original faces were previously made familiar by a learning procedure (associating the face, surname, occupation, and city of residence of the person displayed), while the remaining half were unfamiliar. The results showed clearly that ethnic decision was affected by face familiarity. This adds support to the thesis according to which the identification of identity and the extraction of visually derived semantic codes are not made independently from each other and that the ‘parallel-route’ hypothesis becomes weakly supported.
Revisiting Snodgrass and Vanderwart's Object Pictorial Set: The Role of Surface Detail in Basic-Level Object Recognition
Authors: Rossion Bruno , Pourtois Gilles
Published: March 2004

Theories of object recognition differ to the extent that they consider object representations as being mediated only by the shape of the object, or shape and surface details, if surface details are part of the representation. In particular, it has been suggested that color information may be helpful at recognizing objects only in very special cases, but not during basic-level object recognition in good viewing conditions. In this study, we collected normative data (naming agreement, familiarity, complexity, and imagery judgments) for Snodgrass and Vanderwart's object database of 260 black-and-white line drawings, and then compared the data to exactly the same shapes but with added gray-level texture and surface details (set 2), and color (set 3). Naming latencies were also recorded. Whereas the addition of texture and shading without color only slightly improved naming agreement scores for the objects, the addition of color information unambiguously improved naming accuracy and speeded correct response times. As shown in previous studies, the advantage provided by color was larger for objects with a diagnostic color, and structurally similar shapes, such as fruits and vegetables, but was also observed for man-made objects with and without a single diagnostic color. These observations show that basic-level ‘everyday’ object recognition in normal conditions is facilitated by the presence of color information, and support a ‘shape + surface’ model of object recognition, for which color is an integral part of the object representation. In addition, the new stimuli (sets 2 and 3) and the corresponding normative data provide valuable materials for a wide range of experimental and clinical studies of object recognition.
The Influence of Object Size and Surface Shape on Shape Constancy from Stereo
Authors: Champion Rebecca A , Simmons David R , Mamassian Pascal
Published: March 2004

The failure of shape constancy from stereoscopic information is widely reported in the literature. In this study we investigate how shape constancy is influenced by the size of the object and by the shape of the object's surface. Participants performed a shape-judgment task on objects of five sizes with three different surface shapes. The shapes used were: a frontoparallel rectangle, a triangular ridge surface, and a cylindrical surface, all of which contained the same maximum depth information, but different variations in depth across the surface. The results showed that, generally, small objects appear stretched and large objects appear squashed along the depth dimension. We also found a larger variance in shape judgments for rectangular stimuli than for cylindrical and ridge-shaped stimuli, suggesting that, when performing shape judgments with cylindrical and ridge-shaped stimuli, observers rely on a higher-order shape representation.
Orientation-Selective Adaptation during Motion-Induced Blindness
Authors: Montaser-Kouhsari Leila , Moradi Farshad , Zandvakili Amin , Esteky Hossein
Published: March 2004

When a global moving pattern is superimposed on high-contrast stationary or slowly moving stimuli, the latter occasionally disappear for periods of several seconds (motion-induced blindness, MIB). Here, an adaptation paradigm was used to determine if orientation-selective adaptation still occurs for the stimulus that is no longer visible. Two slowly drifting high-contrast Gabor patches were presented to observers. As soon as both patches disappeared, one was eliminated from the screen. After 2 s, two low-contrast Gabor patches were presented as tests at the same locations and observers were asked to report their orientations. The observers' performance was significantly higher when the orientation of the low-contrast test patch was orthogonal to the orientation of the high-contrast adapting patch ( p < 0.0001) for the location where the patch was present during MIB, even though it was perceptually invisible. The observers' performance was not significantly different at the adjacent control location where the stimulus was absent during the MIB. Although no stimulus was visible at either location, orientation-selective adaptation was preserved only for the location at which the patch remained present. Since orientation information is processed in low-level visual areas such as the primary visual cortex (V1), we conclude that MIB originates in an area higher than V1.
Immune response of the tammar wallaby (Macropus eugenii) to sperm antigens
Authors: Kay D. J. , Kitchener A. L.
Published: March 2004

In the present study, male and female tammar wallabies were immunised with whole tammar wallaby sperm in adjuvant. An assay for sperm antibodies using a live sperm ELISA has been developed to detect sperm surface antigens and used to validate an assay using a 3-[(3-cholamidopropyl) dimethylammonio]-1 propanesulfonate (CHAPS) membrane extract of whole tammar wallaby sperm. The tests were used to monitor the immune response to whole sperm in both male and female tammar wallabies. Antisera with a limited array of specificities were generated, with those locating to the midpiece region of the sperm appearing the most likely candidates for targets for fertility perturbation based on immunofluorescence of fixed and non-fixed sperm. These systemically generated antibodies were demonstrated to have access to both the female and male tammar reproductive tracts and were found on ejaculated sperm and antibodies from female sera and follicular fluid-labelled fresh ejaculated sperm from non-immunised males. Preliminary sequencing of these proteins has identified some possibilities for further investigation.
Interferon-α-like biological activity in human seminal plasma, follicular fluid, embryo culture medium, amniotic fluid and fetal blood
Authors: Lepej Snježana Židovec , Vujisić Sanja , Stipoljev Feodora , Mažuran Renata
Published: March 2004

Interferons (IFNs) are a group of cytokines exhibiting antiviral, antiproliferative and immunoregulatory properties. The principal stimulus for the synthesis of IFNs is the presence of viral double-stranded RNA, although rare examples of constitutive synthesis have also been described. The aim of the present study was to determine IFN-α-like biological activity in the seminal plasma, follicular and amniotic fluid, embryo culture medium, and fetal blood obtained from patients without apparent viral or bacterial infections. Interferon-α-like biological activity was determined by a standard cytopathic effect inhibition bioassay. The study included two groups of patients. The first group consisted of 30 married couples participating in the programme for assisted reproduction and the second group consisted of 23 patients scheduled for prenatal diagnosis (15 for amniocentesis and eight for cordocentesis). The seminal plasma of infertile men (asthenozoospermia, oligoasthenozoospermia) contained a high titre of IFN-α-like antiviral activity. Asthenozoospermia was diagnosed in men with a normal sperm concentration but less than 50% progressively motile sperm and oligoasthenozoospermia was diagnosed in men with a sperm count less than 1 × 106 mL−1. Despite slightly higher antiviral titres in the seminal plasma obtained from asthenozoospermic patients, no clear association between IFN-α-like biological activity and sperm concentration was found. Interferon-α-like biological activity was found in all samples of follicular and amniotic fluid and in fetal blood of patients with intrauterine growth retardation and trisomy 18. Antiviral titres from seminal plasma and follicular fluids were significantly higher compared with amniotic fluids and fetal blood. Embryo culture medium did not contain IFN-α-like biological activity. Our results demonstrate that IFN-α-like activity in biological fluids is relevant for reproduction, even in the absence of infection.
Ultrastructural localisation of calcium deposits in the mouse ovary
Authors: Sedmíková M. , Rajmon R. , Petr J. , Vaňková M. , Rozinek J. , Řehák D. , Jílek F.
Published: March 2004

Follicle-enclosed mouse oocytes contain numerous calcium deposits. The ultrastructural distribution of calcium deposits in the nuclei, mitochondria and cytoplasm of mouse oocytes and granulosa cells of primary, secondary and antral follicles was examined using the combined oxalate–pyroantimonate method. The mitochondria of oocytes from all types of follicles had the highest levels of calcium deposits of all oocyte compartments, with the exception of primary follicles, in which oocyte nuclei contained the same level of calcium deposits as the mitochondria. Calcium deposits in the cytoplasm of oocytes from primary follicles were significantly lower than those in the cytoplasm of oocytes from secondary and antral follicles. Calcium deposits in the cytoplasm of granulosa cells were significantly lower than calcium deposits in the mitochondria of granulosa cells and this difference persisted throughout all categories of follicles. Calcium deposits in the nuclei of granulosa cells did not differ from levels in the mitochondria in primary and secondary follicles. In contrast, the nuclei of granulosa cells from antral follicles had lower levels of calcium deposits than the mitochondria. The differences observed in calcium deposits in various cellular compartments in oocytes and granulosa cells in the follicles of ovaries of adult mice can be attributed to their acquisition of meiotic competence and follicular development.
Effect of a gonadotrophin-releasing hormone antagonist on luteinising hormone secretion and early pregnancy in gilts
Authors: Virolainen J. V. , Love R. J. , Tast A. , Peltoniemi O. A. T.
Published: March 2004

The aims of the present study were: (1) to determine the duration of suppression of luteinising hormone (LH) following a single treatment with a gonadotrophin-releasing hormone (GnRH) antagonist (BIM-21009; Biomeasure) at a dose of 100 μg kg−1; (2) to block LH pulses only for certain days of pregnancy; and (3) to determine the period of early pregnancy most susceptible to suppression of LH. Three groups of gilts were injected with 100 μg kg−1 on Day 16 (n = 5), 14 (n = 6) or 19 (n = 4) of pregnancy. Blood for LH analysis was collected at 20-min intervals for 12 h on the day before treatment and during varying stages of early pregnancy. Blood for progesterone analysis was collected daily and development of pregnancy was followed using real-time ultrasound. Prior to treatment, gilts had 2.6 ± 0.7 LH pulses per 12 h. The GnRH antagonist abolished LH pulses for a period of 2.7 ± 1.8 days and, thereafter, suppressed the resumed LH pulses (P < 0.05). Pregnancy was disrupted in three pigs (20%) with a mean treatment-to-abortion period of 4.7 days concurrent with a mean treatment-to-progesterone decline interval of 4.3 days. In a proportion of pigs, short-term LH suppression may cause early disruption of pregnancy.
Fertility of mice following receipt of ovaries slow cooled in dimethyl sulphoxide or ethylene glycol is largely independent of cryopreservation equilibration time and temperature
Authors: Snow M. , Cox S.-L. , Jenkin G. , Shaw J.
Published: March 2004

Cryopreservation procedures generally depend on both the cryoprotectant used and the equilibration conditions to which the material is exposed. The aim of the present study was to examine the effect of cryoprotectants (dimethyl sulphoxide (DMSO) and ethylene glycol (EG)) and equilibration conditions (0, 30 or 120 min at 0°C or 120 min at room temperature) on the fertility of mice receiving cryopreserved mouse ovaries. The study compared the fertility of cryopreserved Day 14 mouse pup ovaries following grafting to adult recipient mice for 4 months. There was no effect of the cryoprotectant or equilibration condition used on the interval to the first plugging/mating or on the interval to the birth of the first litter, the size of litters, the number of litters produced or the total number of offspring produced. Despite this, when compared with control females (untreated, sham and fresh transplant) the cryopreservation and transplantation procedures delayed fertility. However, the size of litters was equivalent for all cryopreserved and control groups (P > 0.05). The results show that, for the equilibration conditions examined, DMSO and EG are equally efficient cryoprotective agents for mouse ovarian tissue.
Development of in-vitro-derived bovine embryos in protein-free media: effects of amino acids, glucose, pyruvate, lactate, phosphate and osmotic pressure
Authors: Wirtu G. , Pope C. E. , Damiani P. , Miller F. , Dresser B. L. , Short C. R. , Godke R. A. , Bavister B. D.
Published: March 2004

In experiment 1, the effects of a group of either 20 (i.e. glutamine + essential + non-essential) or 11 (i.e. hamster embryo culture medium (HECM)-6) amino acids were evaluated in modified potassium simplex optimised medium (mKSOM) or basic medium (BM)-3. In experiment 2, the effects of glucose, pyruvate, lactate, phosphate or all four substrates were evaluated in low- or high-osmotic pressure BM-3 (255 and 275 mOsmol respectively) containing 20 amino acids (BM-3-20aa). In experiment 1, mKSOM containing 20 amino acids (mKSOM-20aa) supported the highest frequency of total, expanded (Days 7, 8 and 9) and hatched blastocysts. In experiment 2, supplement type affected the frequency of development to at least the morula stage (Day 7), expanded (Day 8), hatched (Day 9) or total blastocysts and cell number per blastocyst. Osmotic pressure affected the frequency of expanded blastocysts (Day 7) and blastocyst cell number. Regardless of the osmotic pressure, BM-3-20aa containing glucose (0.2 mm) supported the highest frequency of blastocyst development. The interaction between supplement type and osmotic pressure was not significant; however, treatment mean differences were more marked in high- than in low-osmotic pressure medium. In conclusion, the beneficial effects of amino acids on in vitro embryo development are influenced by the base medium. Moreover, glucose-containing media supported a higher frequency of embryonic development than pyruvate- and/or phosphate-supplemented media, indicating that glucose plays more important roles in non-energy generating pathways.
Temporal aspects of feeding events in tammar (Macropus eugenii) and parma (Macropus parma) wallabies. I. Food acquisition and oral processing
Authors: Lentle R. G. , Hume I. D. , Stafford K. J. , Kennedy M. , Springett B. P. , Browne R. , Haslett S.
Published: March 2004

We studied parameters that influence the efficiency of food acquisition and oral processing in the tammar wallaby (a grazer) and the parma wallaby (a grazer/browser), both in captivity and under free range on Kawau Island, New Zealand.In captivity, both species spent less time feeding per gram of dry matter intake when browsing than when grazing, and there were no significant differences between the species with respect to the rates of feeding per gram of dry matter intake of a given food. However, under free-ranging conditions, tammar wallabies spent longer feeding than did parma wallabies, so it was likely that tammar wallabies spent more time grazing than browsing. Differences in the relationships between feeding event and inter-feed interval duration in captive and free-ranging wallabies indicated that feeding behaviour was influenced by different factors in the two situations.Microtemporal analysis of the chewing sounds of free-ranging tammar and parma wallabies showed that the interval between the first and second sounds in a 'run' of chewing sounds was longer than that between subsequent intervals, indicating that there was a time cost associated with food aquisition. However, as there were no significant differences between the two wallaby species, either in the mean duration of 'runs' of chewing sounds within feeding events or in the mean duration of whole feeding events, this cost was similar for grazing and browsing. Chewing characteristics differed from those of larger (eutherian) herbivores in that the numbers of chews in a run were not randomly distributed, both species having a preponderance of runs with seven chews. Whilst, the intervals between the second and subsequent chewing sounds in a run did not vary in a periodic manner, such as would occur in batch processing of food, they were more prolonged in runs with more chewing sounds and were significantly longer in tammar wallabies than in parma wallabies. Thus, the slower rate of oral processing of grass was likely due to a generally slower rate of chewing when grazing than when browsing.
Biogeography of the ant fauna of the Tiwi Islands, in northern Australia's monsoonal tropics
Authors: Andersen Alan N. , Woinarski John C. Z. , Hoffmann Ben D.
Published: March 2004

This paper describes the biogeography at the species level of ants from the Tiwi Islands, and represents the first such analysis for any region in Australia. The Tiwi Islands are located 20 km off the mainland coast near Darwin in northern Northern Territory, and include Australia's second largest insular landmass after Tasmania. The islands receive the highest mean annual rainfall (up to 2000 mm) in monsoonal northern Australia, and they are the closest part of the Australian landmass to south-east Asia. On the basis of ~1300 species records, we list 154 species (including nine introduced) from 34 genera. The richest genera are Polyrhachis (20 species), Monomorium (15), Camponotus (14), Pheidole (12), and Iridomyrmex (11). In all, 66% of the native Tiwi species belong to Torresian (tropical) species groups, which is considerably higher than the 44% for Australia's monsoonal ant fauna as a whole. Fifteen Tiwi ant species are not known from mainland Australia. These include a species of Anonychomyrma, which is the only record of the genus in monsoonal Australia, Polyrhachis debilis, the only representative of the sub-genus Cyrtomyrma known from north-western Australia, and the only species of the araneoides group of Rhytidoponera known from the Northern Territory. Unfortunately, the Tiwi ant fauna also includes the exotic invasive species Pheidole megacephala, which represents a serious conservation threat.