bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of single-domain anatase TiO2(001)-(1×4) islands on SrTiO3(001) after thermal annealing
Authors: Silly Fabien , Castell Martin R.
Published: October 2004

Scanning tunneling microscopy is used to investigate the appearance of nanoscale islands on the SrTiO3(001) surface following cycles of repetitive annealing. Atomic-resolution images reveal that the surface of the islands is covered by features typical of the anatase TiO2(001) surface reconstruction. Small islands display a mixed (1×4) and (1×5) reconstruction, whereas only the single-domain (1×4) reconstruction is observed on large islands. These results reveal a simple process for the creation of single-domain anatase nanoislands.
In situ transmission electron microscopy study of the electric field-induced transformation of incommensurate modulations in a Sn-modified lead zirconate titanate ceramic
Authors: He H. , Tan X.
Published: October 2004

Electric field-induced transformation of incommensurate modulations in a Sn-modified lead zirconate titanate ceramic was investigated with an electric field in situ transmission electron microscopy technique. It is found that the spacing between the (1∕x){110} satellite spots and the fundamental reflections do not change with external electric field, indicating that the modulation wavelength stays constant under applied field. The intensity of these satellites starts to decrease when the field level reaches a critical value. Further increase in the field strength eventually leads to the complete disappearance of the satellite reflections. In addition, the 12{111}-type superlattice reflections showed no response to electrical stimuli.
Ge metal-insulator-semiconductor structures with Ge3N4 dielectrics by direct nitridation of Ge substrates
Authors: Maeda Tatsuro , Yasuda Tetsuji , Nishizawa Masayasu , Miyata Noriyuki , Morita Yukinori , Takagi Shinichi
Published: October 2004

We have fabricated Ge metal-insulator-semiconductor structures with ultrathin pure germanium nitride (Ge3N4) films by the direct nitridation of germanium (Ge) substrates. The plasma-enhanced nitridation technique was used with dc plasma source at low temperatures. Capacitance–voltage characteristics with no hysteresis and capacitance equivalent thickness of 1.23 nm have been achieved.
Threshold voltage instability characteristics under positive dynamic stress in ultrathin HfO2 metal-oxide-semiconductor field-effect transistors
Authors: Rhee Se Jong , Kang Chang Yong , Kang Chang Seok , Choi Chang Hwan , Choi Rino , Akbar Mohammad S. , Lee Jack C.
Published: October 2004

The characteristics of threshold voltage instability of HfO2 metal-oxide-semiconductor field-effect transistors under positive dynamic stress were investigated. Compared to constant stress, a smaller threshold voltage shift was observed at higher frequency and lower duty cycle under unipolar pulse stress. Similarly, the degradation of maximum transconductance was also reduced with unipolar stress conditions. However, the change of subthreshold swing was found to be negligible and fairly independent of stress frequencies and duty cycles. The traps in the bulk of the HfO2 dielectric are believed to be the primary factor for the larger change in threshold voltage. Compared to the result under constant voltage stress, unipolar stress allowed higher ten-year lifetime operating voltage.
Cofabrication of superconducting YBa2Cu3O7−δ and semiconducting devices on (100) Si substrates
Authors: Méchin Laurence , Huot Guillaume , Bloyet Daniel
Published: October 2004

We report the process technology for the modular integration of YBa2Cu3O7−δ (YBCO) and p-type metal-oxide-semiconductor (p-MOS) devices on the same silicon substrate. Basic test structures consisting of single p-MOS field-effect transistors with a Pt-based metallization and YBCO bridges were fabricated. After completion of the p-MOS fabrication, highly c-axis-oriented YBCO films showing a critical temperature of 86 K were grown on a free silicon surface. The electrical characteristics at 77 K of the p-MOS transistors were comparable to those of this technology with Al metallization. This means that no fatal degradation was introduced into the p-MOS process by the YBCO one. The cofabrication on the same silicon substrate of devices using such disparate technologies as YBCO and MOS is a very promising starting point for a new generation of monolithic integrated circuits combining the advantages of oxide and semiconductor properties.
Fast gas chromatography with luminol chemiluminescence detection for the simultaneous determination of nitrogen dioxide and peroxyacetyl nitrate in the atmosphere
Authors: Marley Nancy A. , Gaffney Jeffrey S. , White Robert V. , Rodriguez-Cuadra Luis , Herndon Scott E. , Dunlea Ed , Volkamer Rainer M. , Molina Luisa T. , Molina Mario J.
Published: October 2004

An instrument has been designed and constructed for the simultaneous determination of nitrogen dioxide (NO2) and peroxyacetyl nitrate (PAN) in atmospheric samples. The instrument’s design is based on separation by fast gas chromatography (GC) with a 30 ft capillary column (DB-1) followed by detection by luminol chemiluminescence. The chemiluminescent reaction between NO2 or PAN and luminol takes place at the gas–liquid interface on the surface of a solid support. The chemiluminescent emission at 425 nm is detected with a photon counting module. The instrument is controlled by a 1.8 GHz Notebook computer with a WINDOWS 2000 operating system and a custom software application programmed in LABVIEW. Detection limits are in the low parts per trillion (ppt) with a time resolution of 30 s to 1 min. The instrument was operated during the Mexico City Metropolitan Area/Mexico City Megacity 2003 collaborative air quality study. Results for NO2 from this fast GC method were compared with results from a co-located differential optical absorption spectrometer (DOAS) and a tunable diode laser absorption spectromenter (TDLAS). The results support the application of the new luminol-based instrument for atmospheric measurements.
Surface potential measurements by the dissipative force modulation method
Authors: Fukuma Takeshi , Kobayashi Kei , Yamada Hirofumi , Matsushige Kazumi
Published: October 2004

In this study, we propose a novel surface property measurement technique using noncontact atomic force microscopy (NC-AFM), which is referred to as the “dissipative force modulation (DM) method.” NC-AFM-based surface property measurements have mostly utilized conservative tip-sample interaction forces, which induce a frequency shift of cantilever resonance without dissipating cantilever vibration energy. In the DM method, local surface properties are measured by detecting a modulated dissipative tip–sample interaction force which dissipates cantilever vibration energy and hence induces an amplitude variation in cantilever vibration. Since the force sensitivity to dissipative interactions obtained in a typical NC-AFM setup is much higher than that to conservative ones, the DM method can improve the sensitivities of conventional NC-AFM-based techniques that utilize conservative interactions. Combining this method with Kelvin-probe force microscopy, we present the first quantitative surface potential measurement through dissipative tip–sample interactions.
Near-stoichiometric LiNbO3 optical waveguides fabricated using vapor transport equilibration and Ti co-diffusion
Authors: Zhang De-Long , Wong W. H. , Pun E. Y. B.
Published: October 2004

Near-stoichiometric planar and strip LiNbO3 optical waveguides were demonstrated using vapor transport equilibrium process and co-diffusion of titanium metal. Optical confinement is better in z-cut substrates than in x-cut substrates, and the waveguides were characterized optically. Spectral measurements, such as OH− absorption, optical absorption near the fundamental edge, and Raman scattering, were carried out to examine the Li-composition and crystalline phase inside and outside the guiding layer. The results have shown that the vapor transport equilibration process has brought these waveguides toward stoichiometric composition, the Li content inside and outside the waveguide layer is essentially identical, and the LiNbO3 phase is still retained within the waveguide layer.
Charge trapping and interface characteristics of thermally evaporated HfO2
Authors: Chowdhury N. A. , Garg R. , Misra D.
Published: October 2004

Charge trapping and interface characteristics of hafnium oxide (HfO2) films, grown by standard thermal evaporation, were investigated. High frequency capacitance–voltage and conductance measurements were carried out at various temperatures on aluminum gate metal–oxide–semiconductor capacitors, annealed at 450°C. A hysteresis below 30mV was observed. Electrical data show, that charge trapping in HfO2 initially increases with decrease in temperature while it shows a turnaround phenomenon when the temperature is decreased further. Interface state density distribution observed at low temperatures suggests that charge-trapping behavior of these films is mostly due to shallow traps at the interface.
Subpicosecond photocarrier lifetimes in GaSb∕ErSb nanoparticle superlattices at 1.55μm
Authors: Hanson M. P. , Driscoll D. C. , Zimmerman J. D. , Gossard A. C. , Brown E. R.
Published: October 2004

We demonstrate subpicosecond photocarrier lifetimes at 1.55μm in GaSb∕ErSb nanoparticle superlattices grown by molecular beam epitaxy. Pump–probe measurements were made with a 1.55μm mode-locked laser in transmission geometry to determine the photocarrier lifetime. The lifetime is found to be dependent on the size of the ErSb particles, amount of ErSb, and the distance between layers of particles. Through manipulation of these three parameters the photocarrier lifetime can be tuned down to less than 300fs, the temporal limit of our experiment.
Thermal conductivity measurement under hydrostatic pressure using the 3ω method
Authors: Chen Feng , Shulman Jason , Xue Yuyi , Chu C. W. , Nolas George S.
Published: October 2004

We have designed and modeled new techniques, based on the 3ω method, to measure thermal conductivity of liquids (κl) and solids (κs) under hydrostatic pressure (P). The system involves a solid sample immersed in a liquid pressure medium, both of which have unknown thermal properties. The temperature (T) and P dependance of κl are first determined through the use of a modified 3ω technique. This method uses a conducting wire (Pt, in this work), which is immersed in the pressure medium, as the heater/sensor. In addition to κl, this allows for the accurate determination of the specific heat per volume of the liquid and Pt, (ρC)l and (ρC)Pt, respectively. The information of κl and (ρC)l can then be used to make corrections to measurements of κs, in which the sample is immersed in the pressure medium, and a metal strip acts as the heater/sensor. We present the T and P dependence of κl and (ρC)l for the widely used pressure medium 3M Fluorinert FC77 up to 0.8 GPa. The measurement of κs for a thermoelectric clathrate material, Sr8Ga16Ge30, in FC77 is analyzed in detail, and the refined data achieves an accuracy of 1%. The setup can be modified to measure κ and ρC up to 3.5 GPa.
Alfvén continuum and Alfvén eigenmodes in the National Compact Stellarator Experiment
Authors: Fesenyuk O. P. , Kolesnichenko Ya. I. , Lutsenko V. V. , White R. B. , Yakovenko Yu. V.
Published: October 2004

The Alfvén continuum (AC) in the National Compact Stellarator Experiment (NCSX) [G. H. Neilson et al., in Fusion Energy 2002, 19th Conference Proceedings, Lyon, 2002 (International Atomic Energy Agency, Vienna, 2003), Report IAEA-CN-94/IC-1] is investigated with the AC code COBRA [Ya. I. Kolesnichenko et al., Phys. Plasmas 8, 491 (2001)]. The resonant interaction of Alfvén eigenmodes and the fast ions produced by neutral beam injection is analyzed. Alfvén eigenmodes residing in one of the widest gap of the NCSX AC, the ellipticity-induced gap, are studied with the code BOA-E [V. V. Lutsenko et al., in Fusion Energy 2002, 19th Conference Proceedings, Lyon, 2002 (International Atomic Energy Agency, Vienna, 2003), Report IAEA-CN-94-TH/P3-16].
Kink effect in short-channel polycrystalline silicon thin-film transistors
Authors: Valletta A. , Gaucci P. , Mariucci L. , Fortunato G. , Brotherton S. D.
Published: October 2004

Excess current, induced by impact ionization (kink effect) has been investigated in short-channel polysilicon thin-film transistors (TFTs). We have shown, both experimentally and by using two-dimensional (2-D) numerical simulations, that the output characteristics are substantially degraded by the kink effect as the channel length is reduced. In particular, we have shown that the excess current, triggered by the impact ionization and enhanced by the parasitic bipolar transistor action, scales nearly as L−2, thus making very difficult the downscaling of polysilicon TFTs. Such L dependence has been clarified through a detailed analysis of the current components obtained from 2-D numerical simulations. The analysis demonstrates that there are fundamental issues with the output characteristics, and it appears that the introduction of appropriate drain field relief structures will be necessary for the fabrication of short-channel polysilicon TFTs with high output impedance.
Photocurrent detection from photochromic diarylethene film
Authors: Tsujioka Tsuyoshi , Masui Kyoko , Otoshi Fumio
Published: October 2004

The photocurrent characteristics of a diarylethene (DAE) film were investigated. The photocurrents were attributed to the dissociation of electric carriers from the excited molecules in the DAE film. We demonstrated the on-off property of the photocurrent according to the isomerization state. Results reveal that the short-wavelength light corresponding to the high-energy absorption band of the colored DAE film generated higher carrier∕photon efficiency than did the long-wavelength light corresponding to the low-energy absorption band.
Room-temperature synthesis of ultraviolet-emitting nanocrystalline GaN films using photochemical vapor deposition
Authors: Yamazaki Shunsuke , Yatsui Takashi , Ohtsu Motoichi , Kim Taw-Won , Fujioka Hiroshi
Published: October 2004

We fabricated UV-emitting nanocrystalline gallium nitride (GaN) films at room temperature using photochemical vapor deposition (PCVD). For the samples synthesized at room temperature with V/III ratios exceeding 5.0×104, strong photoluminescence peaks at 3.365 and 3.310eV, which can be ascribed to transitions in a mixed phase of cubic and hexagonal GaN, were observed at 5K. A UV emission spectrum with a full width at half-maximum of 100meV was observed, even at room temperature. In addition, x-ray photoelectron spectroscopy measurement revealed that the film deposited by PCVD at room temperature was well nitridized.
Impact of HfO2 buffer layers on data retention characteristics of ferroelectric-gate field-effect transistors
Authors: Aizawa Koji , Park Byung-Eun , Kawashima Yoshihito , Takahashi Kazuhiro , Ishiwara Hiroshi
Published: October 2004

Electrical properties of the p-channel metal-ferroelectric-insulator-silicon field-effect transistors (MFISFETs) using Pt∕SrBi2Ta2O9(SBT)∕HfO2∕Si and Pt∕(Bi,La)4Ti3O12(BLT)∕HfO2∕Si gate structures were investigated. Sol-gel-derived 400-nm-thick SBT and BLT films were deposited on an HfO2 film of approximately 10 nm in thickness. The channel width and channel length of the fabricated MFISFETs were 50 and 5 μm, respectively. The significant drain current on∕off ratios were retained for over 10 days at room temperature. The fabricated MFISFETs using a Pt∕SBT∕HfO2∕Si gate structure exhibited a drain current on∕off ratio of about 105 even after 15.9 days had elapsed. It was also found in the fabricated MFISFETs that a write pulse width as short as 20 ns was enough for obtaining the significant drain current on∕off ratio. It is concluded from these results that HfO2 is one of the best buffer layer materials for realizing MFISFETs with long data retention and high operation speed.
Improved supercooling in transient thermoelectrics
Authors: Thonhauser T. , Mahan G. D. , Zikatanov L. , Roe J.
Published: October 2004

We present calculations for the supercooling of a thermoelectric material during a transient current pulse. At room temperature, a standard steady-state cooler produces a maximum temperature drop of 82 K. During a current pulse, this value can be increase to about 108 K. While prior calculations focused on the optimization of the current pulse with respect to length and height, we investigate the influence of the pulse shape upon the cooling mechanism. Our results show that using a quadratic pulse form, the supercooling effect can be improved and a maximum temperature drop of 116 K can be achieved, exceeding all previously reported results by 8 K. The mechanism increases the ratio of ZTeff∕ZT from the previous value of 1.76 to a maximum of 2.01. The optimized pulse shape requires less energy and, therefore, prevents extensive heating of the material after the minimum temperature is reached, resulting in an increase of efficiency by approximately a factor of 2.
High-resolution diffuse x-ray scattering from threading dislocations in heteroepitaxial layers
Authors: Daniš S. , Holý V. , Zhong Z. , Bauer G. , Ambacher O.
Published: October 2004

Diffuse x-ray scattering from epitaxial layers with screw dislocations perpendicular to the surface is calculated assuming correlated dislocation positions. The resulting intensity distribution was compared with a reciprocal-space map measured in a symmetric diffraction from a hexagonal GaN(0001) layer, and a good correspondence was achieved. From the fit, both the dislocation density and their correlation length were determined.
Scanning tunneling microscopy on ultrathin silicon on insulator (100)
Authors: Sutter P. , Ernst W. , Sutter E.
Published: October 2004

(100)-oriented ultrathin silicon-on-insulator (SOI) with Si template thickness at or below 10nm, normally fully depleted due to carrier trapping in surface states, can be made conducting by terminating the surface with monolayer amounts of Ge. With this modification, which preserves the morphology of the surface, imaging with atomic resolution by scanning tunneling microscopy (STM) becomes possible. STM imaging is used to demonstrate surface smoothing by a thin (few monolayers) Si buffer at high temperature. Tunneling spectroscopy shows a high sheet resistance of the SOI sample, caused by a partial dewetting of the oxide supported Si template during thermal surface cleaning. High-resolution imaging and spectroscopy by STM will enable studies, at the atomic scale, of technologically relevant processes on ultrathin SOI.
La
2
Hf
2
O
7
high-κ gate dielectric grown directly on Si(001) by molecular-beam epitaxy
Authors: Dimoulas A. , Vellianitis G. , Mavrou G. , Apostolopoulos G. , Travlos A. , Wiemer C. , Fanciulli M. , Rittersma Z. M.
Published: October 2004

We show that at deposition temperature in the 750–770°C range, the La2Hf2O7 (LHO) compound can be grown crystalline on Si(001). The predominant orientation is (001)LHO∕∕(001)Si and [110]LHO∕∕[110]Si and results in ultimately clean interfaces, indicating a strong tendency for cube-on-cube epitaxy. The ordered pyrochlore and random fluorite phases coexist in the dielectric. Acceptable gate leakage current, negligible hysteresis and high dielectric permittivity κ∼23 were obtained from electrical characterization of metal–insulator–semiconductor capacitors. The quality of interfaces and the good electrical characteristics make crystalline LHO a promising high-κ candidate for the replacement of SiO2 in the gate of future aggressively scaled transistors.
Submonolayer InGaAs∕GaAs quantum-dot lasers with high modal gain and zero-linewidth enhancement factor
Authors: Xu Zhangcheng , Birkedal Dan , Juhl Michael , Hvam Jørn M.
Published: October 2004

The gain spectra of a submonolayer (SML) InGaAs∕GaAs quantum dot (QD) laser working at 30°C were measured using the Hakki–Paoli method. It is found that the maximum modal gain of QD ground states is as high as 44cm−1 and no gain saturation occurs below the threshold at the lasing wavelength of 964.1nm. When the injection current is about 0.98 times the threshold, the gain spectrum becomes symmetric with respect to the lasing wavelength, and zero-linewidth enhancement factor is observed. These properties are attributed to the high density and the high uniformity of SML QDs in our laser diode.
The LEAF picosecond pulse radiolysis facility at Brookhaven National Laboratory
Authors: Wishart James F. , Cook Andrew R. , Miller John R.
Published: October 2004

The BNL Laser-Electron Accelerator Facility (LEAF) uses a laser-pulsed photocathode, radio-frequency electron gun to generate ⩾7 ps pulses of 8.7 MeV electrons for pulse radiolysis experiments. The compact and operationally simple accelerator system includes synchronized laser pulses that can be used to probe or excite the electron-pulsed samples to examine the dynamics and reactivity of chemical species on the picosecond time scale.
Ion species control in high flux deuterium plasma beams produced by a linear plasma generator
Authors: Luo G.-N. , Shu W. M. , Nakamura H. , O’Hira S. , Nishi M.
Published: October 2004

The ion species ratios in low energy high flux deuterium plasma beams formed in a linear plasma generator were measured by a quadrupole mass spectrometer. And the species control in the plasma generator was evaluated by changing the operational parameters like neutral pressure, arc current, and axial magnetic confinement to the plasma column. The measurements reveal that the lower pressures prefer to form more D+ ions, and the medium magnetic confinement at the higher pressures results in production of more D2+, while the stronger confinement and/or larger arc current are helpful to D2+ conversion into D3+. Therefore, the ion species can be controlled by adjusting the operational parameters of the plasma generator. With suitable adjustment, we can achieve plasma beams highly enriched with a single species of D+, D2+, or D3+, to a ratio over 80%. It has been found that the axial magnetic configuration played a significant role in the formation of D3+ within the experimental pressure range.
A digital sedimentator for measuring erythrocyte sedimentation rate using a linear image sensor
Authors: Yoshikoshi Akio , Sakanishi Akio , Toyama Yoshiharu
Published: October 2004

A digital apparatus was fabricated to determine accurately the erythrocyte sedimentation rate (ESR) using a linear image sensor. Currently, ESR is utilized for clinical diagnosis, and in the laboratory as one of the many rheological properties of blood through the settling of red blood cells (RBCs). In this work, we aimed to measure ESR automatically using a small amount of a sample and without moving parts. The linear image sensor was placed behind a microhematocrit tube containing 36 μl of RBC suspension on a holder plate; the holder plate was fixed on an optical bench together with a tungsten lamp and an opal glass placed in front. RBC suspensions were prepared in autologous plasma with hematocrit H from 25% to 44%. The intensity profiles of transmitted light in 36 μl of RBC suspension were detected using the linear image sensor and sent to a personal computer every minute. ESR was observed at the settling interface between the plasma and RBC suspension in the profile in 1024 pixels (25 μm/pixel) along a microhematocrit tube of 25.6 mm total length for 1 h at a temperature of 37.0±0.1 °C. First, we determined the initial pixel position of the sample at the boundary with air. The boundary and the interface were defined by inflection points in the profile with 25 μm resolution. We obtained sedimentation curves that were determined by the RBC settling distance l(t) at the time t from the difference between pixel locations at the boundary and the interface. The sedimentation curves were well fitted to an empirical equation [Puccini et al., Biorheol. 14, 43 (1977)] from which we calculated the maximum sedimentation velocity smax at the time tmax. We reached tmax within 30 min at any H, and smax linearly related to the settling distance l(60) at 60 min after the start of sedimentation from 30% to 44% H with the correlation coefficient r=0.993. Thus, we may estimate conventional ESR at 1 h from smax more quickly and accurately with less effort.
Characterization of multiple Si∕SiO2 interfaces in silicon-on-insulator materials via second-harmonic generation
Authors: Jun B. , White Y. V. , Schrimpf R. D. , Fleetwood D. M. , Brunier F. , Bresson N. , Cristoloveanu S. , Tolk N. H.
Published: October 2004

Charge generation, transport, and recombination processes in UNIBOND® silicon-on-insulator wafers are studied via an optical second-harmonic generation (SHG) technique. The electric fields at the interfaces vary with time due to charge trapping. The presence of a thin native oxide layer on the top Si film contributes significantly to the SH intensity due to the strong time-dependent electric field generated by electrons transported to the surface. For the thick buried oxide, the electric field is primarily due to carrier trapping at the interface, and it varies with time weakly. The SHG signals depend strongly on the externally applied electric field, which can differentiate the contribution of each interface to the total SH signal.
Structural properties and spin–phonon coupling effect of La1−xTexMnO3 thin films
Authors: Guo Haizhong , Chen Zhenghao , Liu Lifeng , Ding Shuo , Zhou Yueliang , Lu Huibin , Jin Kuijuan , Cheng Bolin
Published: October 2004

Electron-doped La1−xTexMnO3 thin films epitaxially grown on MgO substrates by laser molecular-beam epitaxy are studied. The samples have smooth surfaces, are single crystalline, and c-oriented. Spin–glass behavior of the films is observed at low temperature. Raman spectra of the samples show a significant change in the spin–glass phase. A softening of the 615cm−1 stretching mode is observed near and below the magnetic ordering temperature. This behavior may be ascribed to magnetic interactions due to spin–phonon coupling terms.
Origin of the green photoluminescence from zinc sulfide nanobelts
Authors: Ye Changhui , Fang Xiaosheng , Li Guanghai , Zhang Lide
Published: October 2004

ZnS nanobelts with a pure wurtzite phase have been synthesized by a thermal evaporation method with the assistance of H2S in an Ar atmosphere. Photoluminescence band centered at about 535nm has been observed under excitation in the range of 250–480nm with decay rate as short as 860ps. The origin of this intense photoluminescence is related to elemental sulfur species on the surface of the ZnS nanobelts. This assignment is substantiated by structural analysis by high-resolution electron microscopy, x-ray photoelectron spectroscopy, and photoluminescence and excitation technique. ZnS nanobelts with intense surface photoluminescence could be used as effective green light emitters, humid sensors, and UV light detectors.
Generation of relativistic electron mirrors and frequency upconversion in laser–plasma interactions
Authors: Kulagin Victor V. , Cherepenin Vladimir A. , Suk Hyyong
Published: October 2004

It is shown analytically and by computer simulation that relativistic electron mirrors (bunches with extremely short length) can be generated by an ultra-intense nonadiabatic laser pulse (pulse with a sharp rising edge) incident normally upon a thin rarefied plasma layer provided the cross dimensions of laser beam are large enough. Due to Coulomb forces, the electron mirror is a transient structure that exists as a single whole only during a limited time at the beginning of the laser–plasma interaction. Frequency upconversion of the probe laser pulse into the single, ultrashort, and coherent hard x-ray pulse due to backscattering off such a relativistic electron mirror is also considered and the spectrum of upshifted radiation is investigated.
Enhanced nonconservative forces between polarizable nanoparticles in a time-dependent electric field
Authors: Fuchs R. , Claro F.
Published: October 2004

We find the time-averaged force between two polarizable particles in a uniform oscillating electric field. The force is in general noncentral, and if the dielectric function is dissipative, nonconservative. When dielectric surface modes are excited, the magnitude of the force is enhanced and its direction changes in such a way that the lines of force can spiral toward a fixed point, where the force is zero.
Structural, magnetic, and electrical properties of NiMnSb thin films grown on InSb by pulsed-laser deposition
Authors: Gardelis S. , Androulakis J. , Giapintzakis J. , Monnereau O. , Buckle P. D.
Published: October 2004

We report the growth of single-phase, stoichiometric polycrystalline thin films of the half-Heusler ferromagnet NiMnSb, predicted to be half-metallic, on single crystal InSb (100) substrates heated at 200°C by pulsed laser deposition. The films exhibit saturation magnetization of 4μB∕formula unit at 5K and coercive fields of 2Oe at 300K indicative of their good structural quality. At low temperatures (T<200K) the system behaves like a Heisenberg ferromagnet as expected for a half-metal, while at T>200K it behaves like an itinerant ferromagnet. The resistivity of the film at 5K is 6μΩcm.
Random shearing by zonal flows and transport reduction
Authors: Kim Eun-jin , Diamond P. H.
Published: October 2004

The physics of random shearing by zonal flows and the consequent reduction of scalar field transport are studied. In contrast to mean shear flows, zonal flows have a finite autocorrelation time and can exhibit complex spatial structure. A random zonal flow with a finite correlation time τZF decorrelates two nearby fluid elements less efficiently than a mean shear flow does. The decorrelation time is τD=(τη/τZFΩrms2)1/2 (τη is the turbulent scattering time, and Ωrms is the rms shear), leading to larger scalar field amplitude with a slightly different scaling (∝τD/Ωrms), as compared to the case of coherent shearing. In the strong shear limit, the flux scales as ∝Ωrms−1.
Apparatus for measuring static electric field effects in photoexcitation experiments of gas-phase atoms and molecules using synchrotron radiation
Authors: Harries James R. , Azuma Yoshiro
Published: October 2004

We have developed an apparatus for performing photoexcitation experiments at a synchrotron radiation beamline in a static electric field of up to 100 kV cm−1. The design allows for the simultaneous detection of photoions, visible-ultraviolet fluorescent photons, and long-lived excited neutral particles produced during the decay of the excited states. In this article we describe the design of the electrodes which create the field (one of which incorporates a slit to allow the detection of photoions), modeling of the field-spread across the interaction regions, and methods for calibrating the observed effective field strength. We present sample spectra and calibration data obtained at the Photon Factory (Tsukuba, Japan) and the Advanced Light Source (Berkeley, CA).
Fast CCD camera for x-ray photon correlation spectroscopy and time-resolved x-ray scattering and imaging
Authors: Falus P. , Borthwick M. A. , Mochrie S. G. J.
Published: October 2004

A new, fast x-ray detector system is presented for high-throughput, high-sensitivity, time-resolved, x-ray scattering and imaging experiments, most especially x-ray photon correlation spectroscopy (XPCS). After a review of the architectures of different CCD chips and a critical examination of their suitability for use in a fast x-ray detector, the new detector hardware is described. In brief, its principal component is an inexpensive, commercial camera—the SMD1M60—originally designed for optical applications, and modified for use as a direct-illumination x-ray detector. The remainder of the system consists of two Coreco Imaging PC-DIG frame grabber boards, located inside a Dell Power-edge 6400 server. Each frame grabber sits on its own PCI bus and handles data from 2 of the CCD’s 4 taps. The SMD1M60 is based on a fast, frame-transfer, 4-tap CCD chip, read out at12-bit resolution at frame rates of up to 62 Hz for full frame readout and up to 500 Hz for one-sixteenth frame readout. Experiments to characterize the camera’s suitability for XPCS and small-angle x-ray scattering (SAXS) are presented. These experiments show that single photon events are readily identified, and localized to within a pixel index or so. This is a sufficiently fine spatial resolution to maintain the speckle contrast at an acceptable value for XPCS measurements. The detective quantum efficiency of the SMD1M60 is 49% for directly-detected 6.3 keV x rays. The effects of data acquisition strategies that permit near-real-time data compression are also determined and discussed. Overall, the SMD1M60 detector system represents a major improvement in the technology for time-resolved x-ray experiments, that require an area detector with time-resolutions in few-milliseconds-to-few-seconds range, and it should have wide applications, extending beyond XPCS.
Relativistic effects on the Weibel instability of circularly polarized microwave produced plasmas
Authors: Shokri B. , Ghorbanalilu M.
Published: October 2004

Analyzing the production of a weakly relativistic plasma produced by microwave fields with circular polarization in the adiabatic approximation, the electron distribution function is obtained, which is nonequilibrium and anisotropic. Furthermore, it is shown that the produced plasma is accelerated in the direction of propagating microwave electric fields. The electron velocity in this direction strongly depends on electron origination phase, electric field phase, and amplitude of the microwave electric field. Making use of the dielectric tensor obtained for this plasma, it is shown that the Weibel instability develops due to the anisotropic property of the distribution function. It is shown that the growth rate in the relativistic case is higher than that obtained for the nonrelativistic case by a factor depending on the electric field strength and plasma frequency.
Reflections in gyrotrons with radial output: Consequences for the ITER coaxial gyrotron
Authors: Dumbrajs O. , Nusinovich G. S. , Piosczyk B.
Published: October 2004

A theory describing the influence of reflections on operation of gyrotrons with radial output is presented. The theory is used for evaluating the effect of reflections on the operation of the 170 GHz ITER coaxial cavity gyrotron, which is under development in cooperation between EUROATOM Associations (CRPP Lausanne, FZK Karlsruhe, and HUT Helsinki) together with European tube industry (Thales Electron Devices, Velizy, France). It is shown that for optimally chosen external magnetic field value and electron beam radius, possible reflections do not change the final steady-state operation, which corresponds to generation of a 2.2 MW millimeter-wave power. The effect of deviation of the magnetic field and the beam radius from optimal values on the device operation is also studied.
Thermal density fluctuations and correlations in homogeneous plasmas
Authors: Hazeltine R. D. , Mahajan S. M.
Published: October 2004

The spatial correlation function for thermal plasma density fluctuations is computed from the plasma entropy. The method is demonstrated by three examples: a Maxwellian plasma, a strongly magnetized plasma, and a plasma dominated by Coulomb collisions. In each case the entropy is computed from the one-particle distribution function and then, following the Einstein method, used to construct the probability distribution for density fluctuation.
Helium line intensity ratio in microwave-generated plasmas
Authors: Podder N. K. , Johnson J. A. , Raynor C. T. , Loch S. D. , Ballance C. P. , Pindzola M. S.
Published: October 2004

The line intensity ratio method provides a nonintrusive diagnostic for the measurement of electron temperature in microwave-generated plasmas. For optically thin plasmas of low density, a line intensity method using He I lines can often be used, and is based on the fact that the electron impact excitation rate coefficients for helium singlet and triplet states are insensitive to electron density but differ as a function of the electron temperature. Line intensity measurements are presented from microwave-generated helium plasmas. Both steady-state corona and collision-radiative theoretical models are used to evaluate the ground and excited state populations. The line ratio versus electron temperature obtained from both of these methods are compared with the results from measurements. However, it is not possible to diagnose the electron temperature from the line ratios alone due to the presence of significant opacity and nonnegligible 1s2s 3S metastable fraction in the plasma.
Muellerina flexialabastra (Loranthaceae): a new species of mistletoe from south-eastern Australia
Authors: Downey Paul O. , Wilson Carol A.
Published: October 2004

A new species of mistletoe, Muellerina flexialabastra Downey & C.A. Wilson (Loranthaceae), from south-eastern Australia is described. The description of this new species is based on morphological and nuclear DNA sequence differences between it and the other four species of the genus: Muellerina celastroides, M.�eucalyptoides, M.�bidwillii and M.�myrtifolia. Several morphological attributes that separate this new species from its relatives: (i) the shape of the corolla, (ii) the direction flowers open in relation to the floral triad axis, (iii)�the shape of the flower umbel, (iv) leaf size, (v) location of epicortical runners and (vi) the host species. In addition, nuclear DNA analysis revealed 11 unique nucleotide base changes in this new species supporting its species status.
A revision of Cassinia (Asteraceae: Gnaphalieae) in Australia. 1. Introduction and generic and infrageneric considerations
Authors: Orchard A. E.
Published: October 2004

The nomenclatural and taxonomic history of Cassinia R.Br. is reviewed, particularly in relation to its close relative Ozothamnus R.Br. Current concepts of Ozothamnus are shown to be unsatisfactory, with that genus consisting of a 'core' of approximately 25 species (including the type species O.�rosmarinifolius R.Br.) which are defined by their possession of inner phyllaries with radiating tips and no paleae (or only very few) between the florets, and other characters. The other 25 species (approximate) of 'Ozothamnus' need re-examination and probable placement elsewhere (but not in Cassinia). Cassinia can be satisfactorily defined as a genus distinct from 'core' Ozothamnus. As a precursor to a series of papers describing the species of Cassinia (including a large number of new taxa), Cassinia is divided into two subgenera, seven sections and two series. New taxa described are Cassinia copensis Orchard, Cassinia subg. Achromolaena (Cass.) Orchard, Cassinia sect. Complanatae Orchard, Cassinia sect. Venustae Orchard, Cassinia sect. Leptocephalae Orchard, Cassinia sect. Costatae Orchard, Cassinia sect. Arcuatae Orchard, Cassinia (sect. Cassinia) ser. Cassinia and Cassinia (sect. Cassinia) ser. Longifoliae Orchard.
β-caryophyllene in the skin secretion of the Australian green tree frog, Litoria caerulea: an investigation of dietary sources
Authors: Smith Benjamin P. C. , Hayasaka Yoji , Tyler Michael J. , Williams Brian D.
Published: October 2004

Uptake of noxious and toxic compounds from the diet and their subsequent concentration in integumentary glands is an important step in the defence strategy of many frog species. In this study we show that the Australian green tree frog, Litoria caerulea White, is capable of sequestering β-caryophyllene (a prominent component of the parotoid gland secretion of wild frogs), and most probably other terpenes, from its diet. Animals fed caryophyllene-dosed crickets rapidly acquired the compound in high quantities after only one feeding. Furthermore, dietary analysis of wild-caught animals identified a major source of caryophyllene (the spur-throated grasshopper) in the frogs' diet. Although the ecological significance of this uptake system has not been clarified, the presence of terpenes in the parotoid gland secretions of L. caerulea is interesting when viewed in terms of their wide spectrum of bioactivity and abundance in the environment.
Kinematics, maximal metabolic rate, sprint and endurance for a slow-moving lizard, the thorny devil (Moloch horridus)
Authors: Clemente Christofer J. , Thompson Graham G. , Withers Philip C. , Lloyd David
Published: October 2004

Metabolic physiology, morphology, activity patterns, performance traits and movement kinematics are thought to have coevolved in lizards. We examined links between these parameters for the thorny devil (Moloch horridus), a morphologically and ecologically specialised agamid lizard (body mass ~30 g). It has a maximum sustainable metabolic rate (VO2max) of 0.99 mL O2 g–1 h–1 while running at a velocity of 0.11�m�sec–1 at 35°C. This VO2 is typical of that for other lizards (except varanids), but its burst speed (1.21�m�sec–1) is slower than for a typical agamid (e.g. Ctenophorus ornatus at 3.59 m sec–1) and its endurance is appreciably higher. The kinematic pattern of hind-limb movement for M. horridus is different to that of a 'typical' similar-sized agamid, Ctenophorus ornatus, which is a fast-moving lizard that shelters in rock crevices. It is also different to the ecologically equivalent Phrynosoma platyrhinos. The slow and erratic ventilation of M. horridus (2.3 breaths min–1) at its maximum sustainable aerobic running speed occurs when it stops running. This might be a consequence of the hypaxial muscles being used for both lung ventilation and locomotion, which might be impairing pulmonary ventilation when running, but might also contribute to its high endurance. M. horridus is metabolically typical of agamids, but its body shape, movement patterns and locomotory performance traits are different, and might have coevolved with its specialisation for eating ants.
OPA1 requires mitofusin 1 to promote mitochondrial fusion
Authors: Cipolat Sara , de Brito Olga Martins , Dal Zilio Barbara , Scorrano Luca
Published: October 2004

The regulated equilibrium between mitochondrial fusion and fission is essential to maintain integrity of the organelle. Mechanisms of mitochondrial fusion are largely uncharacterized in mammalian cells. It is unclear whether OPA1, a dynamin-related protein of the inner membrane mutated in autosomal dominant optic atrophy, participates in fusion or fission. OPA1 promoted the formation of a branched network of elongated mitochondria, requiring the integrity of both its GTPase and C-terminal coiled-coil domain. Stable reduction of OPA1 levels by RNA interference resulted in small, fragmented, and scattered mitochondria. Levels of OPA1 did not affect mitochondrial docking, but they correlated with the extent of fusion as measured by polyethylene glycol mitochondrial fusion assays. A genetic analysis proved that OPA1 was unable to tubulate and fuse mitochondria lacking the outer membrane mitofusin 1 but not mitofusin 2. Our data show that OPA1 functionally requires mitofusin 1 to regulate mitochondrial fusion and reveal a specific functional difference between mitofusin 1 and 2.
Satellite of the Congress of the Society of the Study of Ingestive Behaviour, Maastricht, The Netherlands: Control of food intake in man
Authors: Westerterp-Plantenga Margriet S. , Bellisle France , Yeomans Martin
Published: October 2004

The Society for the Study of Ingestive Behaviour meets each year to discuss and highlight recent developments in our understanding of all aspects of controls of eating and drinking. The aim of this satellite was to focus on key issues in human food intake control: palatability, central and peripheral signalling, dietary restraint, macronutrients, energy density, heritability and the significance of animal models for research in man, and to bring together researchers approaching these issues from different perspectives. The presentations including live discussions are reflected in the following papers.
Does dieting make you fat?
Authors: Hill Andrew J.
Published: October 2004

Dieting Makes You Fat, the title of a 1980s book on weight control, is a popularised paradox, conveying a conclusion that is consistent with personal experience and the reported failure of most dietary approaches in the treatment of obesity. Few studies have been designed specifically to test this association. Yet there are prospective data showing that baseline dieting or dietary restraint increases the risk of weight gain, especially in women. Metabolic adaptations and the disinhibited eating of restrained eaters have been the most commonly cited explanations for such weight gain. Dietary restraint has also been implicated in the development and persistence of binge eating. The present paper critically evaluates the evidence supporting this paradox and reaches a rather different conclusion.
Dieting: really harmful, merely ineffective or actually helpful?
Authors: Lowe Michael R. , Timko C. Alix
Published: October 2004

Dieting has developed a negative reputation among many researchers and health care professionals. However, ‘dieting’ can refer to a variety of behavioural patterns that are associated with different effects on eating and body weight. The wisdom of dieting depends on what kind of dieting is involved, who is doing it, and why. Thus, depending on what one means by the term, dieting can be quite harmful, merely ineffective or actually beneficial. The present paper considers examples of all three. In particular, we argue that judgements about the desirability of dieting should consider the likely consequences to particular individuals of engaging in, or not engaging in, dieting behaviour.
Effects of alcohol on food and energy intake in human subjects: evidence for passive and active over-consumption of energy
Authors: Yeomans Martin R.
Published: October 2004

The effects of alcohol on food and energy intake in human subjects have been the subject of a number of controlled studies recently. Unlike the evidence for other macronutrients, there is minimal evidence for any compensatory reduction in food intake in response to energy ingested as alcohol. In contrast, all studies testing intake within 1 h of preload ingestion report a higher intake of food following alcohol relative to energy-matched controls, although this short-term stimulatory effect is not evident if the test meal is delayed beyond 1 h. This time-course suggests that short-term stimulation of appetite may be mediated by the pharmacological action of alcohol on the appetite control system, either through enhanced orosensory reward or impaired satiety. In the long term, energy ingested as alcohol is additive to energy from other sources, suggesting that moderate alcohol consumption results in long-term passive over-consumption alongside short-term active over-consumption of energy through appetite stimulation. Despite the consistency of enhanced energy intake after moderate alcohol, evidence of an association between alcohol in the diet and obesity remains contentious, although the most recent results suggest that alcohol intake correlates with BMI. Future research needs to address this issue and clarify the mechanisms underlying appetite stimulation by alcohol.
The utility of animal models of human energy homeostasis
Authors: Thibault Louise , Woods Stephen C. , Westerterp-Plantenga Margriet S.
Published: October 2004

The prevalence of obesity among adults and children has increased steadily over the last few years worldwide, reaching epidemic proportions. Particularly alarming is the link between obesity and the development of chronic disorders such as heart disease, type 2 diabetes, hypertension and some cancers (Bjorntorp, 1997). Environmental causes of obesity are thought to include a sedentary lifestyle and an abundance of highly palatable energy-dense foods (Hillet al.2003). Genetic factors also contribute to susceptibility to obesity, although the genetic basis of most human obesities is thought to be polygenic (Comuzzie & Allison, 1998; Barshet al.2000). The present paper considers some of the animal models used to infer aspects of human obesity, with an emphasis upon their usefulness.