bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for recombination XUV lasing at 52.0 nm and 49.8 nm in a fast, compact Z-pinch discharge
Authors: Wagner T. , Eberl E. , Hoffmann D.H.H.
Published: March 2009

Evidence of gain in a recombining Z-pinch plasma has been obtained at 52 and 49.8 nm. The amplified XUV radiation originated from the 4f-3d and the 4d-3p transitions of Lilike oxygen, OVI. The plasmas were generated in a small diameter Z-pinch discharge with moderate currents of 40 kA. The gain coefficient was determined by variation of the pinch tube length, leading to a gain-length product of 2.5 (4f-3d) and of 2.2 (4d-3p) for a length of 9 cm.
Excimer laser plasma to control laser pulse duration
Authors: Lou Qihong
Published: March 2009

An injection-locking excimer laser beam with a pulse duration of 25 ns is focused on the surface of a polymide film. The laser beam that passes through the etching film is shorter than the original one. By optimizing the thickness of the film and the beam powerdensity, a pulse with a 3-ns pulse duration can be obtained using this switch technology.
Beam smoothing and temporal effects:Optimized preparation of laser beams for direct-drive inertial confinement fusion
Authors: Boreham B.W. , Hora H. , Aydin M. , Eliezer S. , Goldsworthy M.P. , Min Gu , Gahatak A.K. , Lalousis P. , Stening R.J. , Szichman H. , Hora H. , Aydin M. , Eliezer S. , Goldsworthy M.P. , Min Gu , Gahatak A.K. , Lalousis P. , Szichman H. , Maddever R.A.M. , Luther-Davies B. , Baldwin K.G.H. , Maddever R.A.M. , Rode A.V.
Published: March 2009

Direct-drive laser fusion received a number of setbacks from the experimental observation in the 1960s and 1970s of very complex interactions in laser plasma experiments caused by a number of nonlinear and anomalous phenomena. Although smoothing methods were introduced intuitively or empirically–succeeding in reducing these difficulties–it was not until a few years ago that the 20-ps stochastic pulsation mechanism was discovered. We assume here that this 20-ps stochastic pulsation may be the major obstacle to achieving direct-drive fusion, even though it is now generally assumed that the major challenge to the achievement of direct-drive fusion is the Rayleigh-Taylor instability. While we do not discount the importance of the Rayleigh-Taylor mechanisms, we concentrate here on the analysis of the pulsation process. A method of analysis was developed, using time-dependent real-time computations employing a genuine two-fluid model, which includes the interior electric fields and the very large amplitude longitudinal plasma oscillations that are driven by the laser field. These mechanisms, which were first suggested in 1974, reveal themselves now as self-generated von-Laue gratings, preventing the propagation of laser radiation through the outermost plasma corona and preventing energy deposition by temporal interruption caused by thermal relaxation and the subsequent reestablishment of these gratings, and so on. The abolition of this pulsation by broad-band laser irradiation or other smoothing methods is now well understood. A synopsis of these developments is presented here, consistent with Rubbia's proposition of using the MJ drivers for laser fusion, the technology for which is now available.
Studies on laser-driven shocks using a Nd:glass laser
Authors: Dhareshwar L.J. , Gopi N. , Murali C.G. , Narayan B.S. , Chatterjee U.K.
Published: March 2009

A review of work done on laser generated shocks in solids using a high-peak-power Nd:glass laser in the Laser and Plasma Technology Division of the Bhabha Atomic Research Centre is presented in this paper. The 20-J/5-ns Nd:glass laser used in the experiments is able to produce focused laser intensities in the range of 5 × 1011-1013 W/cm2 and a shock pressure in the range of 0.1–5 Mbar. A l-J/100-ps Nd:glass laser is also being developed for laser shock studies, details of which are presented. Several diagnostics have been developed for laser shock studies of which the main diagnostics are optical shadowgraphy, optical interferometry, and laser velocity interferometry for particle velocity measurement. The measurement of ablation pressure in various types of targets, the scaling of ablation pressure with laser intensity, the effect of laser beam nonuniformity on shockfront or ablation pressure uniformity, the smoothing of shockfront and pressure profiles in high-Z coated and high-Z doped targets, and so on, are the various experimental studies conducted. We have tried to study X-ray driven ablation in aluminum and plastic targets using gold and copper as X-ray producing targets. Uniform pressure of about 0.1 Mbar has been generated over an area of 4 mm2
High-power Nd3+:glass laser system in KAIST (Sinmyung I)
Authors: Kong H.J. , Lee S.S. , Kim H.S. , Han K.G. , Kim N.S. , Um K.Y. , Park J.R. , Lee J.Y.
Published: March 2009

A high-power Nd3+:glass laser system has been constructed and tested. This system consists of a master oscillator, a four-pass amplifier for preamplification, and five-stage amplifiers. The system has been demonstrated in excess of 80 J (2 TW) at 40-ps pulse duration. Final laser beam quality was quite good due to the compensation of the polarization distortion in the four-pass preamplifier, the minimization of the diffraction effect by the image relaying, and the elimination of high spatial frequency components by the spatial filtering. This enables us to obtain high laser output power without any severe spatial spiking effects. Gains and spatial profiles of output pulses were measured after each amplifier stage.
Experimental study into the asymptotic stage of the separation of the turbulized mixtures in gravitationally stable mode
Authors: Kucherenko Yu.A. , Pylaev A.P. , Murzakov V.D. , Popov V.N. , Komarov O.R. , Saveľev V.E. , Cherret R. , Haas J.F.
Published: March 2009

An experimental investigation into the asymptotic stage of the separation of the turbulized mixtures of two fluids with densities ratio n = 3 has been carried out. The turbulized mixtures resulted from Rayleigh–Taylor instability when the contact boundary between two fluids was moved under an acceleration. At a certain instant of time, the system changes from the gravitationally unstable mode to the gravitationally stable one by the way of changing of the acceleration sign. During the ampoule motion with the investigated fluids at the gravitationally stable mode, the depth of penetration of the heavy fluid into the light one was registered with the photographic method. The length of the ampoule way at the gravitationally stable mode has been fixed so that the final (asymptotic) stage of the separation could be registered. At the result of themeasurements, it has been determined the separation process at the asymptotic stage has the same dimensionless velocity asat the initial stage.
Possibility of low-dense magnetized DT plasma ignition threshold achievement in a MAGO system
Authors: Buyko A.M. , Garanin S.F. , Mokhov V.N. , Yakubov V.B.
Published: March 2009

The MAGO concept using the thermonuclear target with DT gas preliminary heating up to kiloelectronvolt range temperatures, which sufficiently enables the reduction of requirements of the compression rate (to 10 km/s) and the compression degree (to several hundreds) of the target, is investigated. The MAGO chamber with the Laval supersonic annular nozzle is used for plasma preheating. In this chamber magnetized plasma is accelerated up to 1000-km/s velocities and heated by collisionless shock waves. Systems with liner and magnetic compression are considered for the subsequent plasma compression. Energizing of a real-size system can be supplied by the magnetic flux compression generators with energy 100−500 MJ. Experiments close to the threshold of ignition can be conducted proportionally in 2−3 times reduced systems. Then the energy required will be 10–30 times less than in a real-size system.
Changing mass liner system for generation of soft X rays
Authors: Buyko A.M. , Burenkov O.M. , Chernyshev V.K. , Garanin S.F. , Kuznetsov S.D. , Kuzyayev A.I. , Mokhov V.N. , Morozov I.V. , Pavlovsky E.S. , Petrukhin À.À. , Startsev A.I. , Yakubov V.B. , Anderson B.G. , Ekdahl C.A. , Kammerdiner J. , Lindemuth I.R. , Reinovsky R.E. , Rodriguez P. , Sheehey P.J. , Veeser L.R. , Younger S.M. , Zerwekh B.
Published: March 2009

Powerful pulse installations are usually used to produce large yields of X-ray radiation. With an increase of the stored energy up to 100 MJ, the costof a single experiment on these installations becomes comparable to the cost of a shot with explosive magnetic generators (EMG), according to expert estimates. The physical scheme of a device with a changeable mass liner forlarge soft X-ray (in the range of 0.3 to 0.5 keV) yields eneration is investigated. The scheme investigated is substantially free from difficulties connected with high precision liners and fast switches for current pulse sharpening.
Coherence in Compton scattering at large angles
Authors: Giordano G. , Matone G. , Luccio A. , Miceli L.
Published: March 2009

Compton scattering of laser light by an electron beam at large angles, in particular at 90°, produces coherent hard radiation if the density of the electron beam is high enough. In this case, the intensity of the scattered radiation is greatly enhanced in a small cone around the forward direction of propagation of the electron beam. As an example, the production of 1-KeV coherent X rays is discussed.
Interaction physics of the fast ignitor concept
Authors: Deutsch C. , Furukawa H. , Mima K. , Murakami M. , Nishihara K.
Published: March 2009

The interaction of relativistic electrons produced by ultrafast lasers and focussing them on strongly precompressed thermonuclear fuel is analytically modelled. Energy loss to target electrons is treated through binary collisions and Langmuir wave excitation. The overall penetration depth is determined by quasielastic and multiple scattering on target ions. Thus, it appears possible to ignite efficient hot spots in a target with density larger than 300 g/cc.
Modification of stimulated Brillouin scattering due to magnetic anisotropy in laser–plasma interaction
Authors: Khan M. , Sarkar S. , Desai T. , Pant H.C.
Published: March 2009

Laser plasma experiments reveal rich interplay between laser plasma instabilities. The growth of stimulated Brillouin scattering (SBS) is one of the most significant constraints of laser fusion experiments. In this paper, a mechanism of stabilization of SBS process due to magnetic anisotropy has been presented. Magnetic anisotropy induced by the temporally exponentially growing nonoscillating magnetic moment from inverse Faraday effect (IFE) has been studied.It has been shown that for interaction of Nd laser (λ = 1.06 μm) on solid deuterium target the SBS growth rate (y) ∼ 3.45 ps and the phase velocities of the incident and scattered electromagnetic (EM) waves have been shown to decay exponentially (∼e∼λ1) in this SBS process resulting in wave-number mismatch.
Synchrotron acceleration of transparent charged macroparticles by a laser beam
Authors: Pozwolski Alexandre
Published: March 2009

The acceleration of transparent charged macroparticles by the repeated radiation pressure of a laser beam is considered. A radial electric field allows a motion along a closed path, on a stable orbit. For macroparticles made out of carborundum, of radiusr= 0.5 μm, velocities above 100 km/s look feasible, allowing the production of high densities of energy.
Microwave excitation and applications of an elliptical excimer lamp
Authors: He Ziming , Prelas Mark A. , Meese Jon M. , Lin Li-Te
Published: March 2009

The concept and experimental results of a microwave-excited elliptical excimer lamp are presented in this paper. The plasma excimer photons are excited at one focus, and the absorber is placed at the second focus. Two elliptical microwave cavities with different eccentricities were tested to study the excitation and characteristics of such an elliptical excimer lamp. The results show that it can be a high-efficiency, narrow-band incoherent vacuum–ultraviolet (VUV)-to-near-infrared photon source. The potential applications of such an excimer lamp, especially with tunable vibronic solid-state and diamond thin film growth, are discussed.
Proton–boron-11 fusion reactions induced by heat-detonation burning waves
Authors: Eliezer S. , Martínez-Val J. M.
Published: March 2009

Proton-boron-11 is the clean fusion reactionpar excellence, but it is very difficult to exploit it because of the very high ignition temperature of this reaction and its moderate fusion yield. In this paper, a proposal is made to induce these reactions by a heat-detonation wave that expands across a compressed target. The front of the wave has a double-layer structure, with a first front driven by electron heat conduction and a second front heated by α-particle energy deposition. Both fronts create a hot plasma where the stopping power is dominated by ions. The wave is originated by an ignitor triggered by an ultraintense lightning beam. This beam can be made of photons (laser), plasma (ramjets), or ions (proton beams, borane clusters). Proton beam shots of 1022. W/cm2and several GA for some picoseconds would be needed for this purpose. The supersonic propagation of the fusion wave and the ignitor requirements are analyzed in this paper. The main conclusion is that the burning wave can only propagate if a substantial fraction of the radiation losses from the already burning fuel is reabsorbed in the colder fuel. It is calculated that for densities larger than few thousands g/cm3most of the bremsstrahlung radiation created in the hot plasma can be reabsorbed by the Compton effect in a region of 1 g/cm2optical thickness of the surrounding compressed and cold fuel.
Solid state heat capacity disk laser
Authors: Albrecht G.F. , Sutton S.B. , George E.V. , Sooy W.R. , Krupke W.F.
Published: March 2009

This paper describes a solid state laser concept that scales to MW levels of burst power and MJ of burst energy and burst durations measured in seconds. During lasing action, waste heat is purposely stored in the heat capacity of the active medium. The paper outlines the principal scaling laws of key operational features and arrives at a conceptual design example of the laser head as well as a mobile laser system.
Isometric immersions into a homogeneous Lorentzian Heisenberg group and rigidity
Authors: LODOVICI SINUÊ DAYAN BARBERO , MANFIO FERNANDO
Published: March 2009

In this paper we prove an existence result for local and global isometric immersions of semi-Riemannian surfaces into the three dimensional Heisenberg group endowed with a homogeneous left–invariant Lorentzian metric. As a corollary, we prove a rigidity result for such immersions.
Effects of Human Race and Face Inversion on the N170
Authors: Gajewski Patrick D. , Schlegel Katrin , Stoerig Petra
Published: March 2009

To learn whether the N170 would be differentially affected by orientation inversion of same- and other-race faces, we recorded event-related brain potentials (ERPs) in Caucasian and locally resident Asian subjects viewing upright and upside-down front-view photographs of African, Asian, and Caucasian faces. Results show that the time-to-peak was significantly delayed for inverted Caucasian faces in both subject groups. The same-race N170 peaked later than either other-race N170 in the Caucasian, but showed no significant difference between Caucasian and Asian faces in the Asian participants. Inversion, therefore, appears to affect the N170’s latency predominantly for faces of familiar races. This conclusion gains support from a positive correlation between the latency of the N170 evoked by both upright and inverted Caucasian faces and the amount of time that the Asian participants had lived in Europe. The N170’s race- and inversion-dependent latency increase may, thus, express an impairment of processing that emphasizes individuation of familiar-race faces, and develops during familiarization.
Heart Rate Response to Music
Authors: Riganello F. , Quintieri M. , Candelieri A. , Conforti D. , Dolce G.
Published: March 2009

Background and rationale: Investigation of the brain’s emotional response to music is limited by methodological problems mainly related to the characterization of the emotions and concomitant brain conditions. In this study, artificial intelligence procedures were applied to identify significant music-induced changes in heart rate variability and to classify autonomic reactions to stimuli requiring complex brain operations. Both healthy subjects and traumatic brain-injury (TBI) patients were studied in order to test the method’s validity. Methods: 16 TBI patents and 26 healthy subjects were requested to listen to selected music samples while the heart beat was continuously recorded. The parametric and nonparametric frequency spectra were computed on the heart rate and the spectra descriptors were entered into a 1-R rules (very simple classification rules) data-mining procedure. Data-mining procedures independently classified the heart-rate spectral patterns and the emotions reported by subjects as positive, indifferent, or negative. Results and conclusions: The data-mining procedures sorted the nu_LF descriptor as the spectral parameter that allowed clustering the emotions reported by the subjects as positive and negative. Classification by nu_LF was comparable to that by self-reported emotions, with an overall correct classification by author in 76.0% of controls and 70% of patients. The identification of negative and positive emotions was correct in 81.3% and 68.9% of controls and in 65% and 74% of TBI patients, without significant differences between healthy subjects and TBI patients. This observation suggests that autonomic concomitants of emotions are detectable in response to complex emotional stimuli.
Match and Mismatch of Taste, Odor, and Color is Reflected by Electrical Activity in the Human Brain
Authors: Skrandies Wolfgang , Reuther Nicole
Published: March 2009

We aimed at elucidating the relationship between odor, taste, color, and food stimuli where subjects were studied either with questionnaires or in electrophysiological experiments. First, a total of 144 word pairs were rated by 660 subjects who determined whether the first stimulus (odor or taste word) matched the second one (color or food word). In an electrophysiological experiment, EEG was recorded from 30 electrodes in 24 healthy adults while clearly matching, or nonmatching, word pairs were presented on a monitor. Evoked potentials were computed for different stimulus classes (matching or nonmatching combinations of odor or taste and color or food words). Six components were identified and compared between conditions. For most components, field strength (GFP) was lower for nonmatching than for matching word pairs. In addition to late effects, electrical brain activity was influenced by experimental conditions as early as at 100 ms latency. Most effects observed were in the time range between 100 and 250 ms. Our data show how color and food words are differently affected when paired with odor or taste words. Complex interactions between stimulus modality (taste/odor) and different target words (color/food) occurred depending on whether the pairs were seen by the subjects as appropriate or inappropriate. Topographical effects indicated that different neural populations were activated in different conditions. Most interestingly, there were many cognitive effects occurring quite early (on the order of 100 ms) after stimulus presentation, and our results suggest rapid cognitive processing of information on odor, taste, color, and food items. This is an important prerequisite for the preconscious and fast choice of food items in everyday behavior, and the data confirm earlier findings on rapid and preconscious semantic processing in the visual cortex.
Startle Reactivity and Peritraumatic Dissociations in Acute Stress Disorder
Authors: Elsesser Karin , Freyth Claudia , Lohrmann Thomas , Sartory Gudrun
Published: March 2009

Startle reactions and their relationship to dissociative symptoms were assessed in acute stress disorder (ASD) patients. Electromyographic (EMG) responses, heart-rate reactions (HRR), and skin conductance responses (SCR) to startle stimuli were compared between victims of mixed traumatic events (n = 31) and healthy controls without trauma exposure (n = 20). All ASD patients met criteria for acute stress disorder (although 12 of them did not demonstrate the required number of dissociative symptoms). Compared to controls, ASD patients showed increased HRR and slower habituation, as well as increased SCRs to the startle stimuli. There were no significant group differences in relation to EMG responses. In ASD patients, reported intensity of peritraumatic dissociations was related to lower EMG startle magnitude and more rapid EMG habituation, suggesting a protective mechanism of dissociative symptoms that may come into effect in response to arousing situations and stimuli.
Functional Connectivity During Auditory Processing in Huntington’s Disease
Authors: Beste Christian , Schüttke Anne , Konrad Carsten , Saft Carsten , Andrich Jürgen , Pfleiderer Bettina
Published: March 2009

Huntington’s disease (HD) is a neurogenetic disorder accompanied by structural alterations of the basal ganglia. In a recent study we investigated auditory processing in symptomatic and presymptomatic HD. Increased activation intensities were found for the symptomatic-HD group compared to controls, which were assumed to reflect an ability to maintain functioning. However, altered functional connectivities may also give this appearance. In this study we evaluated (1) if functional connections and, hence, the organization between brain areas is also altered and (2) how intensity of activation in a brain region relates to functional connectivities of that brain region. Functional connectivity analysis was applied to the data, including the Heschl gyrus, mediodorsal thalamic nucleus, caudate nucleus, putamen, and, as a control, a region of interest (ROI) in the occipital cortex. The symptomatic group presented higher functional connectivity than the pre-HD and control groups between thalamic nuclei bilaterally, and between the left caudate and left thalamic nucleus, respectively. The pre-HD group showed no altered patterns of functional connectivity compared to controls. Moreover, functional connectivity was inversely related to activation intensity of the corresponding brain region. The results suggest that alterations in functional connectivity in HD possibly relate to the degree of neuropathology and are sensitive to hemisphere-dependent differences in neuropathology. The inverse relation of functional connectivity and activation intensity suggests that they may alternative strategies that can be used to maintain brain function in the neurodegenerative advanced stage in HD patients. Since functional connectivity was not altered until the symptomatic stage, the results indicate that functional connectivity is a robust measure, since it does not alter until late stages of disease, when neuropathology becomes more severe.
Modeling all exceedances above a threshold using an extremal dependence structure: Inferences on several flood characteristics
Authors: Ribatet M. , Ouarda T. B. M. J. , Sauquet E. , Gresillon J.‐M.
Published: March 2009

Flood quantile estimation is of great importance for several types of engineering studies and policy decisions. However, practitioners must often deal with the limited availability of data and with short‐length observation series. Thus, the information must be used optimally. During the last decades, to make better use of available data, inferential methodology has evolved from annual maxima modeling to peaks over a threshold. To mitigate the lack of data, peaks over a threshold are sometimes combined with additional information, mostly regional or historical information. However, the most important information for the practitioner remains the data available at the target site. In this study, a model that allows inference on the whole time series is introduced. In particular, the proposed model takes into account the dependence between successive extreme observations using an appropriate extremal dependence structure. Results show that this model leads to more accurate flood peak quantile estimates than conventional estimators. In addition, as the time dependence is taken into account, inferences on other flood characteristics can be performed. An illustration is given with flood duration data. Our analysis shows that the accuracy of the proposed models to estimate flood duration is related to specific catchment characteristics. Some suggestions to increase the flood duration predictions are presented.
Coronal magnetic field analysis with Faraday rotation observations of Alfven waves
Authors: Jensen E. A. , Russell C. T.
Published: March 2009

Faraday rotation observations of an Alfven wave at 4 solar radii during the January 9, 1983 superior conjunction of the Helios spacecraft were simultaneously obtained in Goldstone, California and Canberra, Australia allowing the measurement of the Alfven wave speed. We find that the T. Hoeksema et al. (1982) potential field source surface model performs better than the M. Paetzold et al. (1987) magnetic field magnitude model for predicting the magnitude of the magnetic field in the region based on the observed Alfven speed. Assuming the Alfven wave is monochromatic, coherent, and radially propagating, we determine the minimum magnetic field fluctuation required to reproduce the observations. We use the minimum magnetic field fluctuation to calculate the minimum Alfven wave energy flux of 6 × 1019 W; this is approximately 20% of the wave energy required to accelerate the solar wind.
On the incompatibility of Richards' equation and finger‐like infiltration in unsaturated homogeneous porous media
Authors: Fürst Tomáš , Vodák Rostislav , Šír Miloslav , Bíl Michal
Published: March 2009

It is demonstrated by means of a mathematical proof that Richards' equation, in principle, cannot admit finger‐like solutions for three‐dimensional homogeneous unsaturated porous media flow, subject to monotone boundary conditions. This is demonstrated for any reasonable type of homogeneous porous material; the result is not dependent on any particular form of the hydraulic conductivity or the retention curve. Moreover, it is explained why hysteresis of the retention curve does not play any role in the proof. Consequently, the proof is true for any type of hysteretic behavior of the retention curve. An alternative approach to finger flow modeling is discussed which uses the ideas of cellular automata.
Inelastic tunneling spectra of MgO barrier magnetic tunneling junctions showing large magnon contribution
Authors: Bang Do , Nozaki T. , Djayaprawira D. D. , Shiraishi M. , Suzuki Y. , Fukushima A. , Kubota H. , Nagahama T. , Yuasa S. , Maehara H. , Tsunekawa K. , Nagamine Y. , Watanabe N. , Itoh H.
Published: March 2009

We investigated bias-voltage and temperature dependence of conductivity arising from the magnon contribution in MgO-based magnetic tunneling junctions (MTJs) with different ferromagnetic electrodes. Second derivative conductance curves showed broad peak structure, which extends from 5 to 200 mV, accompanied by additional peaks at around 23, 54, and 85 mV. The peak intensities were larger for antiparallel configuration than for parallel configuration except that at 85 mV. This difference in the peak intensity was observed to be larger for the MTJs having higher tunneling magnetoresistance ratio, indicating a magnetic origin of these peaks. Abrupt increase in the second derivative conductance at very low biasing voltage in the antiparallel configuration suggests the important role of the surface magnon excitation.
Synthesis of SmFeAsO by an easy and versatile route and its physical property characterization
Authors: Awana V. P. S. , Pal Anand , Vajpayee Arpita , Kishan H. , Alvarez G. A. , Yamaura K. , Takayama-Muromachi E.
Published: March 2009

We report synthesis, structure, electrical transport, and heat capacity of SmFeAsO. The title compound is synthesized by one-step encapsulation of stoichiometric FeAs, Sm, and Sm2O3 in an evacuated (10−5 Torr) quartz tube by prolong (72 h) annealing at 1100 °C. The as-synthesized compound is crystallized in tetragonal structure with P4/nmm space group having lattice parameters a=3.937 26(33) A and c=8.498 02(07) A. The resistance (R-T) measurements on the compound exhibited ground state spin-density-wave (SDW)-like metallic steps below 140 K. Heat capacity CP(T) measurements on the title compound, showed an anomaly at around 140 K, which is reminiscent of the SDW ordering of the compound. At lower temperatures the CP(T) shows a clear peak at around 4.5 K. At lower temperature below 20 K, Cp(T) is also measured under an applied field of 7 T. It is concluded that the CP(T) peak at 4.5 K is due to the antiferromagnetic ordering of Sm3+ spins. These results are in confirmation with ordering of Sm in Sm2−xCexCuO4.
Deep levels in GaTe and GaTe:In crystals investigated by deep-level transient spectroscopy and photoluminescence
Authors: Cui Yunlong , Caudel David D. , Bhattacharya Pijush , Burger Arnold , Mandal Krishna C. , Johnstone D. , Payne S. A.
Published: March 2009

Deep levels of undoped GaTe and indium-doped GaTe crystals are reported for samples grown by the vertical Bridgman technique. Schottky diodes of GaTe and GaTe:In have been fabricated and characterized using current-voltage, capacitance-voltage, and deep-level transient spectroscopy (DLTS). Three deep levels at 0.40, 0.59, and 0.67 eV above the valence band were found in undoped GaTe crystals. The level at 0.40 eV is associated with the complex consisting of gallium vacancy and gallium interstitial (VGa-Gai), the level at 0.59 eV is identified as the tellurium-on-gallium antisite (TeGa), and the last one is tentatively assigned to be the doubly ionized gallium vacancy (VGa∗). Indium isoelectronic doping is found to have noticeable impacts on reducing the Schottky saturation current and suppressing the densities of TeGa and VGa∗ defects. The peak which dominated the DLTS spectrum of GaTe:In is assigned to be the defect complex consisting of VGa and indium interstitial (Ini). Low-temperature photoluminescence (PL) spectroscopy measurements were performed on GaTe and GaTe:In crystals. A shallow acceptor level at 140 meV corresponding to VGa was measured in undoped GaTe. Two shallow acceptor levels at 123 and 74 meV corresponding to VGa and indium-on-gallium antisite InGa were observed in GaTe:In samples. The PL results suggested that the indium atoms could occupy gallium vacant sites during GaTe crystal growth period and thereby change the electrical and optical properties of GaTe crystal.
A general framework to quantify the effect of restricted diffusion on the NMR signal with applications to double pulsed field gradient NMR experiments
Authors: Özarslan Evren , Shemesh Noam , Basser Peter J.
Published: March 2009

Based on a description introduced by Robertson, Grebenkov recently introduced a powerful formalism to represent the diffusion-attenuated NMR signal for simple pore geometries such as slabs, cylinders, and spheres analytically. In this work, we extend this multiple correlation function formalism by allowing for possible variations in the direction of the magnetic field gradient waveform. This extension is necessary, for example, to incorporate the effects of imaging gradients in diffusion-weighted NMR imaging scans and in characterizing anisotropy at different length scales via double pulsed field gradient (PFG) experiments. In cylindrical and spherical pores, respectively, two- and three-dimensional vector operators are employed whose form is deduced from Grebenkov’s results via elementary operator algebra for the case of cylinders and the Wigner–Eckart theorem for the case of spheres. The theory was validated by comparison with known findings and with experimental double-PFG data obtained from water-filled microcapillaries.
Three-dimensional pattern formation of magnetically labeled microgel beads for biological tissue engineering
Authors: Kawamoto H. , Inoue H. , Nakamura M.
Published: March 2009

We commenced basic research on the three-dimensional (3D) pattern formation of microgel beads for applications in biological tissue engineering. In this new technique, microgel beads are premagnetized by doping them with magnetic nanoparticles. Living cells will be included in the beads for actual use. If a nonuniform magnetic field is applied to a solution containing these magnetized beads, the beads will align, contact, and form a 3D structure. The structure is controlled by the seed pattern of the magnetic particles plugged in a substrate and the profile of the magnetic field distribution. We constructed tubes, which imitate blood vessels, for demonstration using gel beads whose diameters are of the order of several tens of micrometers. The diameter of the demonstrated tube was less than 0.5 mm and its length was 6.6 mm, although living cells were not included in the beads. Numerical calculations by using the discrete element method were conducted to confirm the formation of the tube and to predict the effect of centrifugal force, which will be applied to fill cells in the space between magnetically patterned beads. Although this unique technology is in the nascent stage, this 3D pattern formation technique by the control of the magnetic field has potential to be one of the effective engineering technologies for manufacturing 3D patterned biological tissues in the future.
Self-separated hydrothermal lead zirconate titanate thick films for high frequency transducer applications
Authors: Zhu B. P. , Zhou Q. F. , Shi J. , Shung K. K. , Irisawa S. , Takeuchi S.
Published: March 2009

Using a simple rapid heating process, Pb(Zr0.52Ti0.48)O3 (PZT) thick films prepared by hydrothermal method were separated from a Ti substrate. Scanning electron microscopy (SEM) revealed that the self-separated films were crack-free. After solution infiltration and high temperature annealing, the PZT thick films were shown to possess good electric properties. At 1 kHz, the dielectric constant and the loss were 593 and 0.05, respectively. The remnant polarization was 30.0 μC/cm2 at room temperature. A high frequency single element ultrasound transducer fabricated with these films showed a bandwidth at −6 dB of 73% at a center frequency of 67 MHz.
Characterization of archeological human bone tissue by enhanced backscattering of light
Authors: Leonetti M. , Capuani S. , Peccianti M. , Ruocco G. , Conti C.
Published: March 2009

Enhanced backscattering of light is used to detect microarchitectural changes in human archeological bones. Measurements on tibia cortical and trabecular tissue demonstrate the high sensitivity of the cone width and enhancement factor to the different morphologies. The approach allows to unveil the presence of periostitic lesions, thus addressing its feasibility for anthropological studies.
Practical enhancement of photoluminescence by metal nanoparticles
Authors: Sun G. , Khurgin J. B. , Soref R. A.
Published: March 2009

We develop a simple yet rigorous theory of the photoluminescence (PL) enhancement in the vicinity of metal nanoparticles. The enhancement takes place during both optical excitation and emission. The strong dependence on the nanoparticle size enables optimization for maximum PL efficiency. Using the example of InGaN quantum dots (QDs) positioned near Ag nanospheres embedded in GaN, we show that strong enhancement can be obtained only for those QDs, atoms, or molecules that are originally inefficient in absorbing as well as in emitting optical energy. We then discuss practical implications for sensor technology.
Candicidin-producing
Streptomyces
support leaf-cutting ants to protect their fungus garden against the pathogenic fungus
Escovopsis
Authors: Haeder Susanne , Wirth Rainer , Herz Hubert , Spiteller Dieter
Published: March 2009

Leaf-cutting ants such as
Acromyrmex octospinosus
live in obligate symbiosis with fungi of the genus
Leucoagaricus
, which they grow with harvested leaf material. The symbiotic fungi, in turn, serve as a major food source for the ants. This mutualistic relation is disturbed by the specialized pathogenic fungus
Escovopsis
sp., which can overcome
Leucoagaricus
sp. and thus destroy the ant colony. Microbial symbionts of leaf-cutting ants have been suggested to protect the fungus garden against
Escovopsis
by producing antifungal compounds [Currie CR, Scott JA, Summerbell RC, Malloch D (1999) Fungus-growing ants use antibiotic-producing bacteria to control garden parasites.
Nature
398:701–704.]. To date, however, the chemical nature of these compounds has remained elusive. We characterized 19 leaf-cutting ant–associated microorganisms (5
Pseudonocardia
, 1
Dermacoccus
, and 13
Streptomyces
) from 3
Acromyrmex
species,
A. octospinosus
,
A. echinatior
, and
A. volcanus
, using 16
S
-rDNA analysis. Because the strain
Streptomyces
sp. Ao10 proved highly active against the pathogen
Escovopsis
, we identified the molecular basis of its antifungal activity. Using bioassay-guided fractionation, high-resolution electrospray mass spectrometry (HR-ESI-MS), and UV spectroscopy, and comparing the results with an authentic standard, we were able identify candicidin macrolides. Candicidin macrolides are highly active against
Escovopsis
but do not significantly affect the growth of the symbiotic fungus. At least one of the microbial isolates from each of the 3 leaf-cutting ant species analyzed produced candicidin macrolides. This suggests that candicidins play an important role in protecting the fungus gardens of leaf-cutting ants against pathogenic fungi.
Postthymic maturation influences the CD8 T cell response to antigen
Authors: Makaroff Lydia E. , Hendricks Deborah W. , Niec Rachel E. , Fink Pamela J.
Published: March 2009

Complete T cell development requires postthymic maturation, and we investigated the influence of this ontological period on the CD8 T cell response to infection by comparing responses of mature CD8 T cells with those of recent thymic emigrants (RTEs). When activated with a noninflammatory stimulus or a bacterial or viral pathogen, CD8 RTEs generated a lower proportion of cytokine-producing effector cells and long-lived memory precursors compared with their mature counterparts. Although peripheral T cell maturation is complete within several weeks after thymic egress, RTE-derived memory cells continued to express inappropriate levels of memory cell markers and display an altered pattern of cytokine production, even 8 weeks after infection. When rechallenged, RTE-derived memory cells generated secondary effector cells that were phenotypically and functionally equivalent to those generated by their mature counterparts. The defects at the effector and memory stages were not associated with differences in the expression of T cell receptor-, costimulation-, or activation-associated cell surface markers yet were associated with lower Ly6C expression levels at the effector stage. This work demonstrates that the stage of postthymic maturation influences cell fate decisions and cytokine profiles of stimulated CD8 T cells, with repercussions that are apparent long after cells have progressed from the RTE compartment.
A mouse model for nonsyndromic deafness (DFNB12) links hearing loss to defects in tip links of mechanosensory hair cells
Authors: Schwander Martin , Xiong Wei , Tokita Joshua , Lelli Andrea , Elledge Heather M. , Kazmierczak Piotr , Sczaniecka Anna , Kolatkar Anand , Wiltshire Tim , Kuhn Peter , Holt Jeffrey R. , Kachar Bechara , Tarantino Lisa , Müller Ulrich
Published: March 2009

Deafness is the most common form of sensory impairment in humans and is frequently caused by single gene mutations. Interestingly, different mutations in a gene can cause syndromic and nonsyndromic forms of deafness, as well as progressive and age-related hearing loss. We provide here an explanation for the phenotypic variability associated with mutations in the cadherin 23 gene (
CDH23
).
CDH23
null alleles cause deaf-blindness (Usher syndrome type 1D; USH1D), whereas missense mutations cause nonsyndromic deafness (DFNB12). In a forward genetic screen, we have identified
salsa
mice, which suffer from hearing loss due to a
Cdh23
missense mutation modeling DFNB12. In contrast to
waltzer
mice, which carry a CDH23 null allele mimicking USH1D, hair cell development is unaffected in
salsa
mice. Instead, tip links, which are thought to gate mechanotransduction channels in hair cells, are progressively lost. Our findings suggest that DFNB12 belongs to a new class of disorder that is caused by defects in tip links. We propose that mutations in other genes that cause USH1 and nonsyndromic deafness may also have distinct effects on hair cell development and function.
Contextualized self: When the self runs into social dilemmas
Authors: Liu Chang‐Jiang , Li Shu
Published: March 2009

Research on the construction of self and of others has indicated that the way that individuals construe themselves and others exerts an important influence on their cognition, emotion, and even behavior. The present study extends this line of research to mixed‐motive situations in which short‐term individual and long‐term collective interests are at odds. In addition, this study associates the importance of context interdependence, and specifically its interaction with independent self‐construal, with an individual's cooperative behavior. We used a priming task to manipulate the level of self‐construal and also manipulated the degree of interdependent context by giving participants a chance to assign rewards either to their group members or to themselves alone. The results showed that when participants received interdependent (as opposed to independent) self‐construal priming, they consistently contributed highly, regardless of context manipulation. In contrast, those primed with an independent self‐construal contributed less in the investment game, but only when placed in a context where group members were encouraged to think about their individual (versus mutual) fate. In this situation they contributed the least to the group in the game. These findings indicate that independent self‐construal in a low interdependence context produces the most competitive behavior. The results also showed that how participants felt about their interaction with other group members mediated the effect of context interdependence on cooperative behavior, and possibly that was especially the case for independent self‐construal. The results demonstrate that the self can be contextualized and embedded in the social contexts and symbolic systems within which people live.
Shape effect of the outermost flux surface on effective helical ripple and zonal flow response in an L = 2 heliotron
Authors: Yamagishi Osamu , Murakami Sadayoshi
Published: March 2009

We calculate two indicators for neoclassical and anomalous transport in the low collisional regime, effective helical ripple εeff and zonal flow response
, in an L = 2 heliotron with various shapes of the outermost flux surface. The εeff has a minimum as a function of a parameter representing plasma column twisting, δb. The time average of the damped zonal flow,
, shows a similar dependence on δb. We can thus find the optimum configuration for both these indicators in an arbitrary L = 2 heliotron, by choosing the optimum value of δb, together with inherent toroidicity and main helicity of the outermost flux surface. The existence of the optimum is due to the most effective cancellation of the radial drifts of the particles trapped in each helical ripple, rather than the magnetic field symmetry in a whole surface.
Physics of non-diffusive turbulent transport of momentum and the origins of spontaneous rotation in tokamaks
Authors: Diamond P.H. , McDevitt C.J. , Gürcan Ö.D. , Hahm T.S. , Wang W. X. , Yoon E.S. , Holod I. , Lin Z. , Naulin V. , Singh R.
Published: March 2009

Recent results in the theory of turbulent momentum transport and the origins of intrinsic rotation are summarized. Special attention is focused on aspects of momentum transport critical to intrinsic rotation, namely the residual stress and the edge toroidal flow velocity pinch. Novel results include a systematic decomposition of the physical processes which drive intrinsic rotation, a calculation of the critical external torque necessary to hold the plasma stationary against the intrinsic residual stress, a simple model of net velocity scaling which recovers the salient features of the experimental trends and the elucidation of the impact of the particle flux on the net toroidal velocity pinch. Specific suggestions for future experiments are offered.
Development of an in situ ellipsometer for deposition and erosion studies at the first wall of a tokamak
Authors: Dittmar T. , Kreter A. , von Keudell A.
Published: March 2009

An in situ, real-time ellipsometer has been developed to be integrated in the first wall of a tokamak. This ellipsometer allows one to measure deposition and erosion of test surfaces exposed to the tokamak plasma. The design is optimized for resistance against high heat loads and large magnetic fields. The instrument is separated into two compartments, one at atmospheric pressure and water-cooled, housing electronic components and devices to generate and detect polarized light, and one at vacuum, holding the sample to be exposed to the tokamak plasma. The ellipsometer has been calibrated and tested in laboratory plasmas and its integration in the TEXTOR tokamak has been demonstrated.
RNATOPS-W: a web server for RNA structure searches of genomes
Authors: Wang Yingfeng , Huang Zhibin , Wu Yong , Malmberg Russell L. , Cai Liming
Published: March 2009

Summary: RNATOPS-W is a web server to search sequences for RNA secondary structures including pseudoknots. The server accepts an annotated RNA multiple structural alignment as a structural profile and genomic or other sequences to search. It is built upon RNATOPS, a command line C++software package for the same purpose, in which filters to speed up search are manually selected. RNATOPS-W improves upon RNATOPS by adding the function of automatic selection of a hidden Markov model (HMM) filter and also a friendly user interface for selection of a substructure filter by the user. In addition, RNATOPS-W complements existing RNA secondary structure search web servers that either use built-in structure profiles or are not able to detect pseudoknots. RNATOPS-W inherits the efficiency of RNATOPS in detecting large, complex RNA structures.

Availability: The web server RNATOPS-W is available at the web site www.uga.edu/RNA-Informatics/?f=software&p=RNATOPS-w. The underlying search program RNATOPS can be downloaded at www.uga.edu/RNA-Informatics/?f=software&p=RNATOPS.

Contact:  cai@cs.uga.edu

Supplementary information:  Supplementary data are available at Bioinformatics online.
PADRE: a package for analyzing and displaying reticulate evolution
Authors: Lott Martin , Spillner Andreas , Huber Katharina T. , Moulton Vincent
Published: March 2009

Summary: Recent advances in gene sequencing for polyploid species, coupled with standard phylogenetic tree reconstruction, leads to gene trees in which the same species can label several leaves. Such multi-labeled trees are then used to reconstruct the evolutionary history of the polyploid species in question. However, this reconstruction process requires new techniques that are not available in current phylogenetic software packages. Here, we describe the software package PADRE (Package for Analyzing and Displaying Reticulate Evolution) that implements such techniques, allowing the reconstruction of complex evolutionary histories for polyploids in the form of phylogenetic networks.

Availability: PADRE is an open-source Java program freely available from http://www.uea.ac.uk/cmp/research/cmpbio/PADRE.

Contact:  martin.lott@uea.ac.uk