bluuebunny/crossref_metadata_2025 huggingface dataset:
Short wavelength electron temperature gradient instability in toroidal plasmas
Authors: Gao Zhe , Sanuki H. , Itoh K. , Dong J. Q.
Published: January 2005

The electron temperature gradient (ETG) driven mode in the very short wavelength region k⊥ρe>1 is identified with a gyrokinetic integral equation code in toroidal plasmas. This “double-humped” growth rate of the conventional ETG and short wavelength ETG modes is attributed to the toroidal drift resonance mechanism and the nonmonotonic behavior of normalized real frequency as the poloidal wavelength varies. This instability provides a possibility existence of a kind of turbulence source with very small size of cells. However, the wavelength of the short wavelength ETG mode is too short and induced transport may be small unless there are inverse cascade effects. In addition, the critical threshold of electron temperature gradient (R∕LTe)c for the short wavelength ETG mode is higher than that for the conventional ETG mode.
Combination of time of flight direct recoiled spectroscopy and ion scattering trajectory simulations of (Ga,Mn)N growth by chemical beam epitaxy
Authors: Carreño Luz Angela , Bensaoula Abdelhak
Published: January 2005

In situ direct recoiled spectroscopy combined with scattering-recoiling trajectory simulations were applied to characterization of (Ga,Mn)N thin films grown by chemical beam epitaxy. Relative intensities of the scattering and recoiling signals recorded as a function of the sample azimuthal rotation allowed determination of the surface composition and periodicity. Models locating the Mn atoms at Ga sites and interstitial positions and the presence of N vacancies at percent levels were simulated. We find that most Mn atoms are located at Ga sites with a nonnegligible level going to interstitial positions; inclusion of N vacancies is also necessary to duplicate some experimental features. This agrees with the samples free carrier concentrations and photoluminescence measurements.
Inexpensive multichannel digital data acquisition system for a meteorological radiosonde
Authors: Harrison R. G.
Published: January 2005

Meteorological radiosondes are launched routinely to obtain lower troposphere soundings of temperature, relative humidity, pressure, and wind parameters. The ability to carry extra sensors considerably extends the usefulness and cost-effectiveness of each sounding, permitting research into other properties of the lower atmosphere such as ozone, radioactivity, and electric field. An inexpensive four-channel digital data acquisition system is described which fits within the Vaisala RS80-15L radiosonde, for integration with other sensors. Using a 12-bit analog to digital conversion, a microcontroller formats the voltage measurements obtained for serial transmission over the radiosonde’s UHF radio link at 300baud. Maximum sampling rate on one channel is 10Hz, which is reduced if multiple channels are sampled. The standard meteorological data telemetry is unaffected. During an entire flight in which the equipment experienced atmospheric temperatures from 4°Cto−55°C, the absolute error on a 5V fsd range was less than 15mV.
Convective oscillations in multilayer systems under the combined action of buoyancy and thermocapillary effect
Authors: Nepomnyashchy A. , Simanovskii I. , Braverman L.
Published: January 2005

The joint action of buoyancy and thermocapillary effect on the convection in a multilayer system is investigated. It is found that the competition between buoyancy and thermocapillarity may lead to the appearance of a specific type of oscillations. Predictions of the linear stability theory are justified by nonlinear simulations. The nonlinear development of the oscillatory instability is studied.
Direct evidence of nanocluster-induced luminescence in InGaN epifilms
Authors: Chang H. J. , Chen C. H. , Chen Y. F. , Lin T. Y. , Chen L. C. , Chen K. H. , Lan Z. H.
Published: January 2005

x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectrometry, and cathodoluminescence measurements have been employed to study the correlation between optical and structural properties in InGaN epitaxial films. In-rich quantum dots were found to be dispersed throughout the film. By the combination of these measurements, we clearly identify that brighter luminescence arises from In-rich regions while dimmer luminescence corresponds to the Ga-rich matrix regions.
Acoustical technique for Lagrangian velocity measurement
Authors: Mordant Nicolas , Metz Pascal , Pinton Jean-François , Michel Olivier
Published: January 2005

Ultrasonic transducers array can be used to track solid particles advected by a turbulent flow. The simultaneous use of four linear antennas of transducers gives the 3D position of the particles. The extraction of the Doppler frequency shift gives a precise estimation of velocity components. We describe the principle of the technique, the signal conditioning and the acquisition schemes. We show briefly the performances of the technique applied to a turbulent flow at high Reynolds number. The dynamical range of the measurement is over 55dB and the frequency response spans over 2decades. These performances allow us to investigate the inertial time scales of Lagrangian turbulence.
Finite-element study of strain distribution in transistor with silicon–germanium source and drain regions
Authors: Yeo Yee-Chia , Sun Jisong
Published: January 2005

The strain field in the silicon channel of a metal–oxide–semiconductor transistor with silicon–germanium (Si1−yGey) source and drain regions was evaluated using a finite-element method. The physical origin of the vertical and lateral strain components in the transistor channel region was explained. The magnitude and distribution of the strain components, and their dependence on device design parameters such as the spacing L between the Si1−yGey stressors and the Ge mole fraction y in the stressors were investigated. Reducing the interstressor spacing L or increasing the Ge mole fraction y in the stressors increases the magnitude of the vertical tensile strain and the lateral compressive strain in the portion of the channel region where the inversion charge resides. This is beneficial for improving the hole mobility in p-channel metal–oxide–semiconductor transistors.
Spatially resolved diagnosis of stress-induced breakdown in oxide dots by in situ conducting atomic force microscopy
Authors: Xie X. N. , Chung H. J. , Sow C. H. , Wee A. T. S.
Published: January 2005

We report an investigation on the stress-induced breakdown (BD) in ultrathin oxide grown by atomic force microscopy (AFM oxide). A conducting atomic force microscopy (c-AFM) technique was employed to stress the AFM oxide and examine its BD behavior. It was found that thermal annealing has a strong impact on the dielectric strength of AFM oxide. The stress-induced trap generation probability, Pt, could be reduced by ∼50% after annealing the oxide at elevated temperatures. Such a thermal effect is related to the local structural relaxation and trap state minimization in AFM oxide upon annealing. The spatially resolved current images allow a microscopic diagnosis of the distribution of BD sites: isolated single BD spots and laterally propagated BD areas were observed in an oxide dot. Soft and hard breakdown sites were also distinguished on the current images.
Microscopic simulation of the percolation of manganites
Authors: Dong Shuai , Zhu Han , Wu X. , Liu J.-M.
Published: January 2005

The one-orbital double exchange model is studied using the METROPOLIS Monte Carlo method and the microscopic resistor network. The phase competition and percolation are displayed microscopically. As far as the resistivity is concerned, the metal–insulator transition is described by the competition between a fraction p of metallic resistors and a fraction 1−p of insulating resistors. p can be obtained as a function of temperature T, doping percentage x, and external field H. In the present model, systems with different x, T, and H can be unified into a single class of percolation, which is different from the standard picture.
Microfluidic interferometer
Authors: Domachuk P. , Grillet C. , Ta’eed V. , Mägi E. , Bolger J. , Eggleton B. J. , Rodd L. E. , Cooper-White J.
Published: January 2005

We present a class of compact, fluid-based, interferometric, tunable optical components: the single-beam microfluidic Mach–Zender interferometer. Phase delay is achieved through light propagation across a fluid–air interface (meniscus). The effect of meniscus curvature on the device transmission is considered using the three-dimensional beam propagation method and shown to be an important device parameter. We engineer the meniscus curvature using monomer surface chemistry, rendering it flat, and find that the experimental response corresponds well with simulation. The device has a resonance at 1.3μm with a 25dB extinction ratio; the latter can be adjusted by shifting the meniscus position.
Enhancement of the electroabsorption in multiple quantum well structures containing a nipi delta-doping superlattice
Authors: Tribuzy C. V-B. , Areiza M. C. L. , Landi S. M. , Borgstrom M. , Pires M. P. , Souza P. L.
Published: January 2005

Transmission measurements as a function of applied reverse voltage, together with a fit procedure, demonstrate that the introduction of a nipi delta-doping superlattice in a GaAs∕AlGaAs multiple-quantum-well structure, for application in amplitude modulation, enhances the change in absorption with applied electric field, leading to an improvement of the device performance.
InGaN nano-ring structures for high-efficiency light emitting diodes
Authors: Choi H. W. , Jeon C. W. , Liu C. , Watson I. M. , Dawson M. D. , Edwards P. R. , Martin R. W. , Tripathy S. , Chua S. J.
Published: January 2005

A technique based on the Fresnel diffraction effect for the fabrication of nano-scale site-controlled ring structures in InGaN/GaN multi-quantum well structures has been demonstrated. The ring structures have an internal diameter of 500 nm and a wall width of 300 nm. A 1cm−1 Raman shift has been measured, signifying substantial strain relaxation from the fabricated structure. The 9 nm blueshift observed in the cathodoluminescence spectra can be attributed to band filling and/or screening of the piezoelectric field. A light emitting diode based on this geometry has been demonstrated.
Lowered dislocation densities in uniform GaN layers grown on step-free (0001) 4H-SiC mesa surfaces
Authors: Bassim N. D. , Twigg M. E. , Eddy C. R. , Culbertson J. C. , Mastro M. A. , Henry R. L. , Holm R. T. , Neudeck P. G. , Trunek A. J. , Powell J. A.
Published: January 2005

We report that very low threading dislocation densities (8×107∕cm2) were achieved in uniform GaN layers grown by metalorganic chemical vapor deposition on (0001) 4H-SiC mesa surfaces 50μm×50μm in area that were completely free of steps. Transmission electron microscopy (TEM) indicated that all observable GaN film threading dislocations were of edge type. TEM analysis of the defect structure of the nucleation layer (aluminum nitride, AlN) revealed a lack of c-component dislocations, and the clean annihilation of lateral, a-type dislocations within the first 200 nm of growth, with no lateral dislocations developing threading arms. These results indicate that the elimination of steps on the initial (0001) 4H-SiC growth surface may play an important role in the removal of mixed and c-type dislocations in subsequently grown AlN and GaN heteroepitaxial layers.
Synthesis of carbon nanotube peapods directly on Si substrates
Authors: Ohno Y. , Kurokawa Y. , Kishimoto S. , Mizutani T. , Shimada T. , Ishida M. , Okazaki T. , Shinohara H. , Murakami Y. , Maruyama S. , Sakai A. , Hiraga K.
Published: January 2005

Carbon nanotubes encapsulating fullerenes, peapods, have been synthesized directly on Si substrates. High-density and high-quality singe-walled carbon nanotubes (SWNTs) were grown on a SiO2∕Si substrate by dip-coating of metal acetate solution and alcohol chemical vapor deposition technique. The caps of SWNTs were opened by annealing in dry air. Then, fullerene doping into the SWNTs was performed by vapor phase doping technique. Encapsulations of C60 and Gd@C82 were confirmed by transmission electron microscopy. Raman scattering spectroscopy was performed for synthesized peapods. From Raman scattering spectroscopy of synthesized peapods, the smallest diameters of the SWNTs capable of fullerene encapsulation were estimated to be 1.28 nm for C60 and 1.43 nm for Gd@C82.
Optical trapping of colloidal particles and measurement of the defect line tension and colloidal forces in a thermotropic nematic liquid crystal
Authors: Smalyukh I. I. , Kuzmin A. N. , Kachynski A. V. , Prasad P. N. , Lavrentovich O. D.
Published: January 2005

We demonstrate optical trapping and manipulation of transparent microparticles suspended in a thermotropic nematic liquid crystal with low birefringence. We employ the particle manipulation to measure line tension of a topologically stable disclination line and to determine colloidal interaction of particles with perpendicular surface anchoring of the director. The three-dimensional director fields and positions of the particles manipulated by laser tweezers are visualized by fluorescence confocal polarizing microscopy.
Self-assembled FePt nanodot arrays with mono-dispersion and -orientation
Authors: Gai Zheng , Howe J. Y. , Guo Jiandong , Blom D. A. , Plummer E. W. , Shen J.
Published: January 2005

For self-assembled nanodots, the ultimate dream is to simultaneously achieve tunable uniformity in size, spatial distribution, chemical composition, and crystallographic orientation. By utilizing the Volmer–Weber growth mode in thin film epitaxy, we have grown self-assembled two-dimensional arrays of FePt alloy nanodots that are uniform in size, chemical composition, and are all crystallgraphically aligned. These dot assemblies are ferromagnetic at room temperature and can be easily transferred onto other templates without destroying the size and orientation uniformity.
Synthesis and optical properties of germanium nanorod array fabricated on porous anodic alumina and Si-based templates
Authors: Mei Y. F. , Li Z. M. , Chu R. M. , Tang Z. K. , Siu G. G. , Fu Ricky K. Y. , Chu Paul K. , Wu W. W. , Cheah K. W.
Published: January 2005

A large quantity of monocrystalline germanium nanorods and their arrays were produced on a porous anodic alumina (PAA) template utilizing saturated vapor adsorption, during which the Ge gas pressure was saturated at a high temperature in an airtight quartz tube. Raman scattering and photoluminescence (PL) results were acquired from the Ge nanorod array and discussed in details. Using Si-based PAA template with 25 nm nanopores, Si-based Ge nanorod array with a large area (larger than 1×1cm2) was obtained and the quantum confinement effect is demonstrated in Raman spectrum.
Effect of annealing atmosphere on the structure and luminescence of Sn-implanted SiO2 layers
Authors: Lopes J. M. J. , Zawislak F. C. , Fichtner P. F. P. , Lovey F. C. , Condó A. M.
Published: January 2005

Sn nanoclusters are synthesized in 180 nm SiO2 layers after ion implantation and heat treatment. Annealings in N2 ambient at high temperatures (T⩾700°C) lead to the formation of Sn nanoclusters of different sizes in metallic and in oxidized phases. High-resolution transmission electron microscopy (TEM) analyses revealed that the formed larger nanoparticles are composed by a Sn metallic core and a SnOx shell. The corresponding blue-violet photoluminescence (PL) presents low intensity. However, for heat treatments in vacuum, the PL intensity is increased by a factor of 5 and the TEM data show a homogeneous size distribution of Sn nanoclusters. The low intensity of PL for the N2 annealed samples is associated with Sn oxidation.
Controlled n-type doping of AlN:Si films grown on 6H-SiC(0001) by plasma-assisted molecular beam epitaxy
Authors: Ive Tommy , Brandt Oliver , Kostial Helmar , Friedland Klaus J. , Däweritz Lutz , Ploog Klaus H.
Published: January 2005

We study the properties of Si-doped AlN films grown on 6H-SiC(0001) by plasma-assisted molecular beam epitaxy. Whereas nominally undoped AlN films are invariably insulating in nature, Si-doped films are found to be semiconducting with an electron concentration up to 7.4×1017cm−3, and a resistivity approaching 1 Ω cm at room temperature. Even heavy Si-doping (1×1020cm−3) does not degrade the structural properties of the AlN films. The morphology of these films is characterized by Si-induced step-bunching, but remains smooth with a rms roughness of about 1 nm.
Lasing characteristics of InGaAs∕InGaAsP multiple-quantum-well waveguide-type depleted optical thyristor with vertical window
Authors: Choi Woon Kyung , Kim Doo Gun , Choi Young Wan , Lee Seok , Woo Deok Ha , Kim Sun Ho
Published: January 2005

This study demonstrates the lasing characteristics of InGaAs∕InGaAsP multiple-quantum-well waveguide-type depleted optical thyristor using the vertical window. The measured switching voltage and current are 3.36V and 10μA, respectively. The lasing threshold current is 131mA at 25°C. The output peak wavelength is 1570nm at a bias current of 1.22 Ith and there is no input signal. The vertically injected depleted optical thyristor shows very good isolation between input and output signals.
Magnetic shape memory effect in an antiferromagnetic γ-Mn-Fe(Cu) alloy
Authors: Zhang J. H. , Peng W. Y. , Chen Shipu , Hsu (Xu Zaoyao) T. Y.
Published: January 2005

A magnetic shape memory effect occurring in a polycrystalline antiferromagnetic Mn85.5Fe9.5Cu5.0 (at. %) alloy is reported. The results show that because of a strong coupling between the antiferromagnetic transition and the fcc→fct martensitic transformation with (101) twinning in the alloy, its martensitic transformation start temperature (MS) and reverse transformation temperature (Af) are close to each other and almost coincide with the antiferromagnetic transition temperature (TN). Being driven by an applied magnetic field of ∼10kOe, the recoverable magnetic-field-induced strains reach to −4.8×10−4(ε‖) and +3.0×10−4(ε⊥) in the directions parallel and transverse to the field, respectively, indicating a type of magnetic shape memory material, based on a Mn-rich Mn-Fe composition, which is different from existing ferromagnetic alloys.
Hot-electron transport in 4H–SiC
Authors: Ardaravičius L. , Matulionis A. , Kiprijanovic O. , Liberis J. , Cha H.-Y. , Eastman L. F. , Spencer M. G.
Published: January 2005

Nanosecond-pulsed technique is used to study hot-electron transport in donor-doped 4H–SiC (n=2×1017cm−3) biased parallel to the basal plane. The measurements of current with 1ns voltage pulses are carried out at average electric fields up to 570kV∕cm. A region with a negative differential conductance is observed for the range of fields exceeding 280kV∕cm, followed by a sharp increase in the current at fields over 345kV∕cm. The dependence of drift velocity on electric field is deduced for the field range below the onset of the negative differential conductance to appear: the value of the saturation velocity is estimated as 1.4×107cm∕s at room temperature.
Reversible change of birefringence sign by optical and thermal processes in an azobenzene polymethacrylate
Authors: Rodríguez F. J. , Sánchez C. , Villacampa B. , Alcalá R. , Cases R. , Millaruelo M. , Oriol L.
Published: January 2005

Birefringence (Δn) induced in an azobenzene polymethacrylate by combination of biphotonic and thermotropic processes has subsequently been changed in sign by room temperature illumination with linearly polarized blue light. The sign of Δn can be reversed again, by simply heating up the film to 100°C. This change of Δn between positive and negative values can be repeated several times. Besides, by appropriate choice of film thickness and blue light irradiation conditions the same absolute value for positive and negative Δn values can be obtained.
Inverted co-flow diffusion flame for producing soot
Authors: Stipe Christopher B. , Higgins Brian S. , Lucas Donald , Koshland Catherine P. , Sawyer Robert F.
Published: January 2005

We developed an inverted, co-flow, methane∕air∕nitrogen burner that generates a wide range of soot particles sizes and concentrations. By adjusting the flow rates of air, methane, and nitrogen in the fuel, the mean electric mobility diameter and number concentration are varied. Additional dilution downstream of the flame allows us to generate particle concentrations spanning those produced by spark-ignited and diesel engines: particles with mean diameters between 50 and 250nm and number concentrations from 4.7∙104to107cm−3. The range of achievable number concentrations, and therefore volume concentrations, can be increased by a factor of 30 by reducing the dilution ratio. These operating conditions make this burner valuable for developing and calibrating diagnostics as well as for other studies involving soot particles.
Self-poled Pb(Zr,Ti)O3 films with improved pyroelectric properties via the use of (La0.8Sr0.2)MnO3/metal substrate heterostructures
Authors: Es-Souni M. , Kuhnke M. , Iakovlev S. , Solterbeck C.-H. , Piorra A.
Published: January 2005

Pb ( Zr , Ti ) O 3 (PZT) thin films were deposited on different substrate heterostructures including platinized silicon, stainless steel and Ni-based alloy foils. A buffer layer of (La0.8Sr0.2)MnO3 (LSMO) between PZT and substrate was used. The pyroelectric coefficients were determined using low frequency sinusoidal temperature waves. It is demonstrated that PZT films deposited on metallic foils exhibit high pyroelectric coefficients of up to 760μC∕Km2 in the unpoled state, whereas the films deposited on platinized substrates were found to have pyroelectric coefficients in the range of 30μC∕Km2. These results are explained in terms of elemental diffusion from the substrate together with stressed states of the films.
Interwall support in double-walled carbon nanotubes studied by scanning tunneling microscopy
Authors: Park Min Hwan , Jang Jae Won , Lee Cheol Eui , Lee Cheol Jin
Published: January 2005

Atomically resolved room temperature scanning tunneling microscopy images of carbon nanotubes were obtained, and actual values of the nanotube dimensions were estimated from a line profile fitting analysis. It was found that the cross sectional deformation induced by the van der Waals forces between the CNTs and the substrate is much smaller in the double-walled carbon nanotubes than in the single-walled nanotubes.
The shear-layer instability of a circular cylinder wake
Authors: Thompson Mark C. , Hourigan Kerry
Published: January 2005

A reinterpretation is made of previously published data concerning the frequency of the instability waves in the separated shear layer from a circular cylinder for Reynolds numbers in the range 103–105. An accurate fit to the observed variation can be achieved using a piecewise fit based on theoretical and empirical arguments. A logical conclusion is that the ratio of the frequency of the instability waves to the Kármán vortex shedding frequency is indeed determined by the boundary-layer properties at separation, as suggested by Bloor.
Interfacial reactions during GaN and AiN epitaxy on 4H– and 6H–SiC(0001)
Authors: Losurdo Maria , Capezzuto Pio , Bruno Giovanni , Brown April , Kim Tong-Ho , Yi Changhyun , Zakharov D. N. , Liliental-Weber Z.
Published: January 2005

Thin layers of AlN and GaN have been grown by plasma-assisted molecular beam epitaxy on Si-face 4H– and 6H–SiC(0001)Si substrates. The impact of the SiC surface preparation and oxide removal via a Ga deposition and desorption process on the chemistry and structure of the GaN/SiC and AlN/SiC interfaces, and on the GaN/SiC subsurface reactivity is characterized. We also investigate the impact of this process on growth mode evolution.
Magnetic suppression of secondary electrons in plasma immersion ion implantation
Authors: Tan Ing Hwie , Ueda Mario , Dallaqua Renato S. , Rossi Jose O.
Published: January 2005

In this work, magnetic suppression of secondary electrons in plasma immersion ion implantation is demonstrated experimentally in a vacuum arc system. Secondary electrons emitted normally to a copper sample surface were detected by a Faraday cup, whose signal exhibited large negative spikes coincident with high voltage pulses when aluminum ions of an unmagnetized plasma were implanted. When a 12.5 mT magnetic field parallel to the sample’s surface is applied, these spikes are not seen, showing that secondary electrons were magnetically suppressed. Another cup, oriented to detect electrons that flow along the field lines, does not exhibit such negative spikes in either unmagnetized or magnetized plasmas, indicating that a virtual cathode was formed by the trapped secondary electrons.
Nanoindentation and photoreflectance study on polycrystalline ternary Al–C–N thin films
Authors: Ji A. L. , Ma L. B. , Liu C. , Zheng P. , Li C. R. , Cao Z. X.
Published: January 2005

Berkovich hardness and optical gap were determined by nanoindentation and photoreflectance measurement for ternary Al–C–N thin films of various compositions along with structural characterization. The deposits were fabricated by reactive magnetron sputtering of aluminum target onto Si(100) substrates, with the mixture of argon, nitrogen, and methane as precursor. High-resolution transmission electron microscopy and selected-area electron diffraction revealed a polycrystalline structure with rich defects in the film, and x-ray diffraction displays only one reflection at 2θ≈36° from the basal planes. The hardness is over 26GPa for all the deposits, it measures 53.4GPa in the sample Al47C20N33. The optical gap, defined as the photon energy where (1∕R)(dR∕dE) maximizes, R is the photoreflectance, lies within 5.2to5.6eV. These results indicate the wide-gap nature of aluminum carbonitrides, implying diverse potential applications of their thin films as protective coating of an ultraviolet detector, dielectric barrier layer in electronics, etc.
Optical bistability and stationary patterns in photonic-crystal vertical-cavity surface-emitting lasers
Authors: Dabbicco Maurizio , Maggipinto Tommaso , Brambilla Massimo
Published: January 2005

We report the experimental observation of optical bistability and coherent transverse pattern formation in optically injected, photonic-crystal vertical-cavity surface-emitting lasers, electrically biased below threshold. For injected frequency blueshifted with respect to the cavity resonance, the system exhibits optical bistability and the injected uniform plane-wave breaks up, giving rise to honeycomb- and rolls-like transverse patterns. By comparison with numerical simulations we associate the observed phenomena with the onset of a modulational instability, and discuss the application of this device as an optical memory based on the cavity soliton concept.
Template-induced crystallization of amorphous SiO2 and its effects on the mechanical properties of TiN∕SiO2 nanomultilayers
Authors: Wei Lun , Mei Fanghua , Shao Nan , Kong Ming , Li Geyang , Li Jianguo
Published: January 2005

Ti N ∕ Si O 2 nanomultilayers with various thicknesses of the SiO2 layer have been prepared by multi-target magnetron sputtering. Studies show that amorphous SiO2, which is more favorable under sputtering condition, crystallizes at smaller layer thickness (0.45–0.9nm) due to the template effect of TiN layers. Correspondingly, multilayers exhibit coherent epitaxial growth with intensive (111) texture, and show significant hardness enhancement with maximum hardness of 44.5GPa. Further increase in the SiO2 layer thickness (≳1nm) leads to the formation of amorphous SiO2 which blocks the coherent growth of the films, and thus decreases the multilayer hardness gradually.
Discovery of a free-living chlorophyll
d
-producing cyanobacterium with a hybrid proteobacterial/cyanobacterial small-subunit rRNA gene
Authors: Miller Scott R. , Augustine Sunny , Olson Tien Le , Blankenship Robert E. , Selker Jeanne , Wood A. Michelle
Published: January 2005

Chlorophyll
d
-producing cyanobacteria are a recently described group of phototrophic bacteria that is a major focus of photosynthesis research, previously known only from marine environments in symbiosis with eukaryotes. We have discovered a free-living member of this group from a eutrophic hypersaline lake. Phylogenetic analyses indicated these strains are closely related to each other but not to prochlorophyte cyanobacteria that also use an alternative form of chlorophyll as the major light-harvesting pigment. We have also demonstrated that these bacteria acquired a fragment of the small-subunit rRNA gene encoding a conserved hairpin in the bacterial ribosome from a proteobacterial donor at least 10 million years before the present. Thus, our most widely used phylogenetic marker can be a mosaic of sequence fragments with widely divergent evolutionary histories.
Deranged aortic intima‐media thickness, plasma triglycerides and granulopoiesis in Sl/Sld mice
Authors: Dileepan Kottarappat N. , Johnston Thomas P. , Li Yuai , Tawfik Ossama , Stechschulte Daniel J.
Published: January 2005

STUDIES were carried out to evaluate the impact of a high‐fat dietary regimen on aortic wall thickness, peripheral blood leukocyte profile, and plasma cholesterol and triglyceride levels in the mast cell‐deficient Sl/Sld mouse. The results demonstrated that the mean aortic wall thickness of Sl/Sld mice was significantly higher than their normal littermates, and were increased in both genotypes after a 17‐day high‐fat regimen. In comparison with normal littermates, Sl/Sld genotypes had elevated levels of plasma triglycerides with normal levels of plasma cholesterol, and the high‐fat diet markedly lowered the triglyceride levels. Total peripheral blood leukocytes, the monocyte and granulocyte counts, and hemoglobin levels were significantly lower in Sl/Sld mice, although the number of lymphocytes, eosinophils and basophils were the same in both genotypes. Interestingly, the high‐fat diet regimen elevated leukocyte counts and the number of monocytes and granulocytes in Sl/Sld mice.
Suppression of matrix metalloproteinase‐9 production from neutrophils by a macrolide antibiotic, roxithromycin, in vitro
Authors: Kanai Ken-Ichi , Asano Kazuhito , Hisamitsu Tadashi , Suzaki Harumi
Published: January 2005

BACKGROUND: Macrolide antibiotics such as erythromycin and roxithromycin (RXM) have an anti‐inflammatory effect that may account for their clinical benefit in the treatment of chronic airway inflammatory diseases. However, the precise mechanism of this anti‐inflammatory effect is not well understood.

Purpose: The influence of RXM on matrix metalloproteinase (MMP)‐9 production from neutrophils in response to lipopolysaccharide (LPS) stimulation was examined in vitro.

Methods: Neutrophils prepared from normal human peripheral blood (1×105 cells/ml) were treated with various concentrations of RXM for 1 h, and then stimulated with 1.0 μg/ml of LPS in the presence of the agent for 24 h. MMP‐9 and tissue inhibitor of metalloproteinase (TIMP)‐1 levels in culture supernatants were examined by enzyme‐linked immunosorbent assay.

Results: Addition of RXM at more than 5.0 μg/ml into cell cultures caused significant suppression of MMP‐9 production, which was increased by LPS stimulation. However, the ability of cells to produce TIMP‐1 was not affected by RXM treatment, even when the cells were cultured in the presence of agent at 10.0 μg/ml. We then examined the influence of RXM on transcriptional factor, nuclear factor‐κB and activator protein (AP)‐1 activation by LPS stimulation. RXM exerted suppressive action on NF‐κB (P50 and P65) activation when the cells were cultured for 4 h at more than 5.0 μg/ml of the agent. RXM at more than 2.5 μg/ml also suppressed AP‐1 (Fra 1 and Jun B) activation in 4‐h cultured cells. We finally examined the influence of RXM on MMP‐9 mRNA expression in neutrophils. Addition of RXM into cell cultures at more than 5.0 μg/ml caused significant inhibition of mRNA expression, which was enhanced by LPS stimulation for 12 h.

Conclusion: These results strongly suggest that RXM inhibits neutrophil transmigration into inflammatory sites and results in favorable modification of the clinical status of inflammatory diseases.
The three-dimensional flight of red-footed boobies: adaptations to foraging in a tropical environment?
Authors: Weimerskirch H. , Le Corre M. , Ropert-Coudert Y. , Kato A. , Marsac F.
Published: January 2005

In seabirds a broad variety of morphologies, flight styles and feeding methods exist as an adaptation to optimal foraging in contrasted marine environments for a wide variety of prey types. Because of the low productivity of tropical waters it is expected that specific flight and foraging techniques have been selected there, but very few data are available. By using five different types of high-precision miniaturized logger (global positioning systems, accelerometers, time depth recorders, activity recorders, altimeters) we studied the way a seabird is foraging over tropical waters. Red-footed boobies are foraging in the day, never foraging at night, probably as a result of predation risks. They make extensive use of wind conditions, flying preferentially with crosswinds at median speed of 38 km h
�'1
, reaching highest speeds with tail winds. They spent 66% of the foraging trip in flight, using a flap-glide flight, and gliding 68% of the flight. Travelling at low costs was regularly interrupted by extremely active foraging periods where birds are very frequently touching water for landing, plunge diving or surface diving (30 landings h
-1
). Dives were shallow (maximum 2.4 m) but frequent (4.5 dives h
-1
), most being plunge dives. While chasing for very mobile prey like flying fishes, boobies have adopted a very active and specific hunting behaviour, but the use of wind allows them to reduce travelling cost by their extensive use of gliding. During the foraging and travelling phases birds climb regularly to altitudes of 20-50 m to spot prey or congeners. During the final phase of the flight, they climb to high altitudes, up to 500 m, probably to avoid attacks by frigatebirds along the coasts. This study demonstrates the use by boobies of a series of very specific flight and activity patterns that have probably been selected as adaptations to the conditions of tropical waters.
X-ray diffraction studies of the contractile mechanism in single muscle fibres
Authors: Holmes K. C. , Trentham D. R. , Simmons R. , Lombardi Vincenzo , Piazzesi Gabriella , Reconditi Massimo , Linari Marco , Lucii Leonardo , Stewart Alex , Sun Yin-Biao , Boesecke Peter , Narayanan Theyencheri , Irving Tom , Irving Malcolm
Published: January 2005

The molecular mechanism of muscle contraction was investigated in intact muscle fibres by X–ray diffraction. Changes in the intensities of the axial X–ray reflections produced by imposing rapid changes in fibre length establish the average conformation of the myosin heads during active isometric contraction, and show that the heads tilt during the elastic response to a change in fibre length and during the elementary force generating process: the working stroke. X–ray interference between the two arrays of myosin heads in each filament allows the axial motions of the heads following a sudden drop in force from the isometric level to be measured
in situ
with unprecedented precision. At low load, the average working stroke is 12 nm, which is consistent with crystallographic studies. The working stroke is smaller and slower at a higher load. The compliance of the actin and myosin filaments was also determined from the change in the axial spacings of the X–ray reflections following a force step, and shown to be responsible for most of the sarcomere compliance. The mechanical properties of the sarcomere depend on both the motor actions of the myosin heads and the compliance of the myosin and actin filaments.
Nuclear insertions help and hinder inference of the evolutionary history of gorilla mtDNA
Authors: THALMANN O. , SERRE D. , HOFREITER M. , LUKAS D. , ERIKSSON J. , VIGILANT L.
Published: January 2005

Numts are fragments of mitochondrial DNA (mtDNA) that have been translocated to the nucleus, where they can persist while their mitochondrial counterparts continue to rapidly evolve. Thus, numts represent ‘molecular fossils’ useful for comparison with mitochondrial variation, and are particularly suited for studies of the fast‐evolving hypervariable segment of the mitochondrial control region (HV1). Here we used information from numts found in western gorillas (Gorilla gorilla) and eastern gorillas (Gorilla beringei) to estimate that these two species diverged about 1.3 million years ago (Ma), an estimate similar to recent calculations for the divergence of chimpanzee and bonobo. We also describe the sequence of a gorilla numt still possessing a segment lost from all contemporary gorilla mtDNAs. In contrast to that sequence, many numts of the HV1 are highly similar to authentic mitochondrial organellar sequences, making it difficult to determine whether purported mitochondrial sequences truly derive from that genome. We used all available organellar HV1 and corresponding numt sequences from gorillas in a phylogenetic analysis aimed at distinguishing these two types of sequences. Numts were found in several clades in the tree. This, in combination with the fact that only a limited amount of the extant variation in gorillas has been sampled, suggests that categorization of new sequences by the indirect means of phylogenetic comparison would be prone to uncertainty. We conclude that for taxa such as gorillas that contain numerous numts, direct approaches to the authentication of HV1 sequences, such as amplification strategies relying upon the circularity of the mtDNA molecule, remain necessary.
Pleistocene refugia and recolonization routes in the southern Andes: insights from Hypochaeris palustris (Asteraceae, Lactuceae)
Authors: MUELLNER A. N. , TREMETSBERGER K. , STUESSY T. , BAEZA C. M.
Published: January 2005

Hypochaeris palustris (Phil.) De Wild. is a species growing in the southern Andean chain. To elucidate potential Pleistocene refugia and recolonization routes in the southern Andes, we analysed amplified fragment length polymorphisms (AFLPs) in 206 individuals in 21 populations of H. palustris from the coastal Cordillera, the central, northern, and eastern ranges of the southern Andes, and Patagonia. Populations from the coastal Cordillera harboured more private AFLP fragments, and exhibited a higher frequency of polymorphic fragments as well as higher Shannon diversity than all other areas investigated. The comparison among pooled AFLP profiles of each region revealed that the central Andean ranges shared most fragments with populations from the margins of the distributional area in the Andes, in the N, E, and S (Patagonia). Phenetic analysis indicated close relationships among populations of the central ranges. Populations of the coastal Cordillera were shown to be highly differentiated from the Andean populations. It is very likely therefore that (1) H. palustris recolonized the central ranges of the southern Andes from nearby refugia, possibly unglaciated areas N, E, and/or S of its present distributional area; (2) the postglacial spread of H. palustris in the central ranges of the southern Andes occurred rapidly; and (3) the coastal Cordillera served as a refugium for H. palustris, but these populations did not contribute to the recolonization of the central Andean ranges.
Evidence for emergence of an amphibian iridoviral disease because of human‐enhanced spread
Authors: JANCOVICH J. K. , DAVIDSON E. W. , PARAMESWARAN N. , MAO J. , CHINCHAR V. G. , COLLINS J. P. , JACOBS B. L. , STORFER A.
Published: January 2005

Our understanding of origins and spread of emerging infectious diseases has increased dramatically because of recent applications of phylogenetic theory. Iridoviruses are emerging pathogens that cause global amphibian epizootics, including tiger salamander (Ambystoma tigrinum) die‐offs throughout western North America. To explain phylogeographical relationships and potential causes for emergence of western North American salamander iridovirus strains, we sequenced major capsid protein and DNA methyltransferase genes, as well as two noncoding regions from 18 geographically widespread isolates. Phylogenetic analyses of sequence data from the capsid protein gene showed shallow genetic divergence (< 1%) among salamander iridovirus strains and monophyly relative to available fish, reptile, and other amphibian iridovirus strains from the genus Ranavirus, suggesting a single introduction and radiation. Analysis of capsid protein sequences also provided support for a closer relationship of tiger salamander virus strains to those isolated from sport fish (e.g. rainbow trout) than other amphibian isolates. Despite monophyly based on capsid protein sequences, there was low genetic divergence among all strains (< 1.1%) based on a supergene analysis of the capsid protein and the two noncoding regions. These analyses also showed polyphyly of strains from Arizona and Colorado, suggesting recent spread. Nested clade analyses indicated both range expansion and long‐distance colonization in clades containing virus strains isolated from bait salamanders and the Indiana University axolotl (Ambystoma mexicanum) colony. Human enhancement of viral movement is a mechanism consistent with these results. These findings suggest North American salamander ranaviruses cause emerging disease, as evidenced by apparent recent spread over a broad geographical area.
Genetic exchange across a hybrid zone within the Iberian endemic golden‐striped salamander,Chioglossa lusitanica
Authors: SEQUEIRA F. , ALEXANDRINO J. , ROCHA S. , ARNTZEN J. W. , FERRAND N.
Published: January 2005

The study of hybrid zones resulting from Pleistocene vicariance is central in examining the potential of genetically diverged evolutionary units either to introgress and merge or to proceed with further isolation. The hybrid zone between two mitochondrial lineages ofChioglossa lusitanicais located near the Mondego River in Central Portugal. We used mitochondrial and nuclear diagnostic markers to conduct a formal statistical analysis of theChioglossahybrid zone in the context of tension zone theory. Key results are: (i) cline centres are not coincident for all markers, with average widths ofca. 2–15 km; (ii) heterozygote deficit was not observed across loci near the transect centre; (iii) associations of parental allele combinations (‘linkage disequilibrium’R) were not detected either across loci or across the transect. These observations suggest that theChioglossahybrid zone is not a tension zone with strong selection against hybrids but instead one shaped mostly by neutral mixing. The patterns uncovered suggest a complex history of populations over a small scale that may be common in southern Pleistocene refugia.
Seeing ghosts: the effect of unsampled populations on migration rates estimated for sampled populations
Authors: SLATKIN MONTGOMERY
Published: January 2005

In 2004, the term ‘ghost population’ was introduced to summarize the effect of unsampled subpopulations that exchange migrants with other subpopulations that have been sampled. Estimated long‐term migration rates among populations sampled will be affected by ghost populations. Although it would be convenient to be able to define an apparent migration matrix among sampled populations that incorporate the exchange of migrants with ghost populations, no such matrix can be defined in a way that predicts all features of the coalescent process for the true migration matrix. This paper shows that if the underlying migration matrix is symmetric, it is possible to define an apparent migration matrix among sampled subpopulations that predicts the same within‐population and between‐population homozygosities among sampled populations as is predicted by the true migration matrix. Application of this method shows that there is no simple relationship between true and apparent migration rates, nor is there a way to place an upper bound on the effect of ghost populations. In general, ghost populations can create the appearance of migration between subpopulations that do not actually exchange migrants. Comparison with published results from the application of the program, migrate, shows that the apparent migration rates inferred with that program in a three‐subpopulation model differ from those based on pairwise homozygosities. The apparent migration matrix determined by the method described in this paper probably represents the upper bound on the effect of ghost populations.
Association between major histocompatibility complex class II DRB alleles and parasite load in the hairy‐footed gerbil, Gerbillurus paeba, in the southern Kalahari
Authors: HARF R. , SOMMER S.
Published: January 2005

We investigated the importance of the MHC‐constitution (major histocompatibility complex‐constitution) on the endoparasite load in free‐range hairy‐footed gerbils (Gerbillurus paeba) in the southern Kalahari Desert. While the number of alleles of the duplicated DRB exon 2 gene had no significant effects on the individual status of being ‘not infected’ or ‘infected’ and on the number of helminth morphotype infections per individual, it significantly affected the faecal egg count values. One allele (Gepa‐DRB*15) was only found in uninfected mice. Our results support the hypotheses that MHC polymorphism in G. paeba is maintained by pathogen‐driven selection. The present study is the first investigation on associations between duplicated DRB gene loci and the parasite load in mammals.
Annotation: Understanding the development of psychopathy
Authors: Viding Essi
Published: January 2005

Background:  Psychopaths are not only antisocial, but also have a callous and unemotional personality profile. This article selectively reviews evidence that psychopathic personality traits are an important factor in understanding and predicting the development of persistent antisocial conduct. Cognitive neuroscience research and more tentative genetic work on psychopathy will be discussed, especially as they relate to possible developmental trajectories to psychopathy.

Results:  A personality‐based approach has been successful in clarifying the conceptual boundaries of psychopathy and delineating a group of antisocial individuals with a distinct profile of offending and clear neurocognitive markers indicating problems in processing distress in others and punishment directed to oneself. These markers are also present in children with psychopathic tendencies, suggesting that psychopathy may be a developmental disorder. The neurocognitive profile relates to the callous and unemotional personality traits at the core of psychopathy and may index particular vulnerability to persistent antisocial conduct. Preliminary twin studies suggest that personality traits at the core of psychopathy are much more highly heritable than other personality traits. There are as yet no molecular genetic studies of psychopathy.

Conclusions:  It is argued that an interdisciplinary approach that integrates cognitive neuroscience and genetics will enhance understanding of the development of psychopathy.