bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating tropical cyclone‐climate feedbacks using the TRMM Microwave Imager and the Quick Scatterometer
Authors: Sriver Ryan L. , Huber Matthew , Nusbaumer Jesse
Published: September 2008

Sea surface temperature (SST) and near‐surface winds from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and the Quick Scatterometer (QuikScat) are used to calculate globally integrated tropical cyclone‐induced SST anomalies and power dissipation (PD). We estimate tropical cyclone‐induced upper ocean cooling to be ∼35% higher than our previous estimates based on reanalyzed ERA40 and NCEP surface data. Annually averaged, global PD estimates from TMI are ∼5 × 1019 J for the years 1998 to 2006 (roughly 30% greater than ERA40 PD for overlapping years). QuikScat PD is estimated to be ∼1.7 × 1020 J for the years 2000 to 2006. On the basis of these results, we conclude that the cyclone‐induced cooling signal appears to be underrepresented in ERA40 and NCEP reanalysis, as postulated in recent observational and modeling studies. Furthermore, we observe a strong positive relationship between PD and ocean surface cooling, providing further evidence for the likelihood of cyclone‐induced climatic feedbacks. These results support the hypothesis that tropical cyclones play an active role in the tropical surface ocean heat budget by cooling the tropical upper oceans through enhanced vertical mixing, which likely represents a net warming beneath the oceanic mixed layer. Thus, to the degree that vertical mixing is important for regulating the ocean's meridional overturning circulation and poleward heat transport, tropical cyclones may be an important contributor to Earth's climate system. This further confirms the results of Emanuel (2001, 2002) and Sriver and Huber (2007b) that possible future changes in integrated cyclone intensity associated with warmer SST may provide possible climatic feedbacks through enhanced vertical mixing and increased ocean heat transport, thus buffering the tropics to increased temperatures while amplifying the warming at higher latitudes.
Gravity above subduction zones and forces controlling plate motions
Authors: Krien Y. , Fleitout L.
Published: September 2008

Short‐ and intermediate‐wavelength gravity and geoid anomalies are used to provide constraints on the mechanical structure of subduction zones and on the forces involved. This study is based on 2D Cartesian dynamically self‐consistent models with Newtonian or power law rheologies. We show that both strong decoupling of the two convergent plates (shear stresses of the order of 107 Pa) and weakened bending lithosphere are necessary to reproduce the observed geoid and gravity data. Good fits are found for relatively low failure stresses (≈30–50 MPa). For all models providing reasonable predictions of gravity, only a small fraction of the downgoing slab weight is transmitted to the surface plates. About 10% of the energy is dissipated in the contact zone between the two plates, 10% to 20% in the bending region, and more than 70% in the sublithospheric mantle. The basal tractions (on the order of ≈1−4 × 1012 N/m) induce a net motion of the plates, with the subducting lithosphere moving faster than predicted by the no‐net‐motion principle. A marked positive geoid anomaly is predicted above subduction zones at intermediate wavelength (λ = 2000–4000 km) in the case of pure whole mantle convection. Such large geoid highs are not observed. Introducing “partial layering” (i.e., mass anomalies hampering mantle flow through the transition zone) is necessary to reconcile model predictions and observations for these wavelengths.
Fissural volcanism, polygenetic volcanic fields, and crustal thickness in the Payen Volcanic Complex on the central Andes foreland (Mendoza, Argentina)
Authors: Mazzarini F. , Fornaciai A. , Bistacchi A. , Pasquarè F. A.
Published: September 2008

Shield volcanoes, caldera‐bearing stratovolcanoes, and monogenetic cones compose the large fissural Payen Volcanic Complex, located in the Andes foreland between latitude 35°S and 38°S. The late Pliocene‐Pleistocene and recent volcanic activity along E‐W trending eruptive fissures produced basaltic lavas showing a within‐plate geochemical signature. The spatial distribution of fractures and monogenetic vents is characterized by self‐similar clustering with well defined power law distributions. Vents have average spacing of 1.27 km and fractal exponent D = 1.33 defined in the range 0.7–49.3 km. The fractal exponent of fractures is 1.62 in the range 1.5–48.1 km. The upper cutoffs of fractures and vent fractal distributions (about 48–49 km) scale to the crustal thickness in the area, as derived from geophysical data. This analysis determines fractured media (crust) thickness associated with basaltic retroarc eruptions. We propose that the Payen Volcanic Complex was and is still active under an E‐W crustal shortening regime.
Paleointensity determination using continuous thermal measurements by a high‐temperature vibrating thermomagnetometer
Authors: Dunlop David J.
Published: September 2008

A vibrating thermomagnetometer which measures magnetization M continuously at high temperature is used to test a new method of paleointensity determination involving single rather than double heatings. Loss of natural remanent magnetization (NRM) is recorded by the average of 20–25 measurements at the peak temperature T achieved in a zero‐field heating step. Partial thermoremanent magnetization (pTRM) is calculated from the average M after in‐field cooling to room temperature T0. For comparison with data taken at T0, values of M measured at T are multiplied by Ms(T0)/Ms(T), with the aid of the thermomagnetic or Ms(T) curve measured on a chip of the sample. NRM versus pTRM results from 11 heating‐cooling steps on a diabase containing both single‐domain magnetite inclusions in plagioclase and coarser multidomain magnetite grains reproduce the features of Thellier double‐heating paleointensity results for samples from the same site. The NRM – pTRM plot is nonlinear, with convex‐down curvature. For a stringent validation of the single‐heating method, a truly single‐domain sample needs to be tested.
Petrology of some oceanic island basalts: PRIMELT2.XLS software for primary magma calculation
Authors: Herzberg C. , Asimow P. D.
Published: September 2008

PRIMELT2.XLS software is introduced for calculating primary magma composition and mantle potential temperature (TP) from an observed lava composition. It is an upgrade over a previous version in that it includes garnet peridotite melting and it detects complexities that can lead to overestimates in TP by >100°C. These are variations in source lithology, source volatile content, source oxidation state, and clinopyroxene fractionation. Nevertheless, application of PRIMELT2.XLS to lavas from a wide range of oceanic islands reveals no evidence that volatile‐enrichment and source fertility are sufficient to produce them. All are associated with thermal anomalies, and this appears to be a prerequisite for their formation. For the ocean islands considered in this work, TP maxima are typically ∼1450–1500°C in the Atlantic and 1500–1600°C in the Pacific, substantially greater than ∼1350°C for ambient mantle. Lavas from the Galápagos Islands and Hawaii record in their geochemistry high TP maxima and large ranges in both TP and melt fraction over short horizontal distances, a result that is predicted by the mantle plume model.
Discrepancies between observed and ocean general circulation model–simulated anomalies in recent SSTs of the tropical Indian Ocean caused by apparent trends in atmospheric reanalysis data
Authors: Yamanaka Goro
Published: September 2008

We investigated the discrepancy between observed and ocean general circulation model (OGCM)‐simulated anomalies in recent sea surface temperatures (SSTs) of the tropical Indian Ocean. Observed SSTs show a warming beginning in the late 1990s, whereas simulated SSTs show a cooling over the same period. Examination of surface heat fluxes in the OGCM showed that the simulated SST cooling was caused primarily by a decreasing trend in the reanalyzed solar radiation used as the surface boundary condition. In the atmospheric reanalysis, the decrease in solar radiation was attributed to an increase in cloud cover, deduced from precipitation data, and in part responding to observed local warming of the Indian Ocean SSTs prescribed as the lower boundary condition. Observation‐based estimates of precipitation, however, show no significant increasing trend, so no increase in cloud cover is indicated. Caution is needed when atmospheric reanalysis data are used for surface boundary conditions for OGCMs.
Weaker solar wind from the polar coronal holes and the whole Sun
Authors: McComas D. J. , Ebert R. W. , Elliott H. A. , Goldstein B. E. , Gosling J. T. , Schwadron N. A. , Skoug R. M.
Published: September 2008

Observations of solar wind from both large polar coronal holes (PCHs) during Ulysses' third orbit showed that the fast solar wind was slightly slower, significantly less dense, cooler, and had less mass and momentum flux than during the previous solar minimum (first) orbit. In addition, while much more variable, measurements in the slower, in‐ecliptic wind match quantitatively with Ulysses and show essentially identical trends. Thus, these combined observations indicate significant, long‐term variations in solar wind output from the entire Sun. The significant, long‐term trend to lower dynamic pressures means that the heliosphere has been shrinking and the heliopause must be moving inward toward the Voyager spacecraft. In addition, our observations suggest a significant and global reduction in the mass and energy fed in below the sonic point in the corona. The lower supply of mass and energy may result naturally from a reduction of open magnetic flux during this period.
Whistler mode waves from lightning on Venus: Magnetic control of ionospheric access
Authors: Russell C. T. , Zhang T. L. , Wei H. Y.
Published: September 2008

The fluxgate magnetometer on Venus Express samples the magnetic field near periapsis at 128 Hz. Bursts of plane‐polarized magnetic waves in the vicinity of 100 Hz are observed propagating at small angles to the magnetic field. The magnetic field is generally horizontal in the region around periapsis, located at high northern latitudes. When the magnetic field remains within 15° of horizontal during the 2‐min periapsis pass, no such waves are observed; but when there are brief periods during which the local magnetic field dips into the atmosphere by more than 15°, the bursts begin to appear. Such radial excursions of the magnetic field occur 25% of the time in the region around periapsis. The bursts are seen only on passes with these excursions. We interpret this magnetic control in terms of the coupling between the electromagnetic wave from lightning discharges refracted vertically by the increasing electron density and the nearly horizontal ionospheric magnetic field along which the energy is guided to the spacecraft. The inferred rate of electric discharges in the Venus atmosphere is about 20% of that seen in the Earth's atmosphere.
Importance of predicting the dose temporal profile for large solar energetic particle events
Authors: Neal John S. , Nichols Theodore F. , Townsend Lawrence W.
Published: September 2008

It has been proposed that proton intensities on the stream‐limited plateau present a minimal radiation hazard to astronauts, and hazardous intensities occur upon coronal‐mass‐ejection‐driven shock arrival at the spacecraft. Forecasts then need only predict the arrival time and severity of the shock prior to its arrival at the spacecraft. We evaluated dose to the bone marrow, eye, and skin for the largest events since 1996, in terms of the >10 MeV proton flux, prior to and after shock arrival. Doses at shock arrival were compared to the space‐permissible exposure limits (SPELs), and for five of the seven events, limits were exceeded for aluminum shielding thicknesses up to 3 g cm−2 prior to the arrival of the shocks. The 30‐d SPELs have been exceeded as early as 9 h after event initiation, but more generally, sometime between 20 and 50 h after event initiation. These results suggest that one cannot simply predict the arrival time and intensity of a shock if exceeding the 30‐d SPELs is to be avoided. Similarly, waiting for the shock to arrive at a sentinel spacecraft such as the Advanced Composition Explorer to provide a 1‐h warning of shock intensity may not prevent one from exceeding the 30‐d SPELs. In order to predict when 30‐d SPELs will be exceeded for a given event, one must forecast the dose temporal profile associated with that event.
Reprint: Good Laboratory Practice: Preventing Introduction of Bias at the Bench
Authors: Macleod Malcolm R , Fisher Marc , O'Collins Victoria , Sena Emily S , Dirnagl Ulrich , Bath Philip MW , Buchan Alistair , van der Worp H Bart , Traystman Richard J , Minematsu Kazuo , Donnan Geoffrey A , Howells David W
Published: September 2008

As a research community, we have failed to show that drugs, which show substantial efficacy in animal models of cerebral ischemia, can also improve outcome in human stroke. Accumulating evidence suggests this may be due, at least in part, to problems in the design, conduct, and reporting of animal experiments which create a systematic bias resulting in the overstatement of neuroprotective efficacy. Here, we set out a series of measures to reduce bias in the design, conduct and reporting of animal experiments modeling human stroke.
Evaluation of the Novel 5-HT4Receptor PET Ligand [11C]SB207145 in the Göttingen Minipig
Authors: Kornum Birgitte R , Lind Nanna M , Gillings Nic , Marner Lisbeth , Andersen Flemming , Knudsen Gitte M
Published: September 2008

This study investigates 5-hydroxytryptamine 4 (5-HT4) receptor binding in the minipig brain with positron emission tomography (PET), tissue homogenate-binding assays, and autoradiography in vitro. The cerebral uptake and binding of the novel 5-HT4receptor radioligand [11C]SB207145 in vivo was modelled and the outcome compared with postmortem receptor binding. Different models for quantification of [11C]SB207145 binding were evaluated: One-tissue and two-tissue compartment kinetic modelling, Logan arterial input, and three different reference tissue models. We report that the pig autoradiographic 5-HT4receptor distribution resembles the human 5-HT4receptor distribution with the highest binding in the striatum and no detectable binding in the cerebellum. We found that in the minipig brain [11C]SB207145 follows one-tissue compartment kinetics, and the simplified reference tissue model provides stable and precise estimates of the binding potential in all regions. The binding potentials calculated for striatum, midbrain, and cortex from the PET data were highly correlated with 5-HT4receptor concentrations determined in brain homogenates from the same regions, except for hippocampus where PET-measurements significantly underestimate the 5-HT4receptor binding, probably because of partial volume effects. This study validates the use of [11C]SB207145 as a promising PET radioligand for in vivo brain imaging of the 5-HT4receptor in humans.
Grapevines (Vitis spp.) as Components of the *North American Prairie Biomass Economy:** High-Value Phytochemicals, Platform Chemicals, and Bioenergy
Authors: Rayne Sierra
Published: September 2008

Grapevines (Vitis spp.) offer the potential for contributing to the North American prairie biomass based economy. While these regions are too cold for the traditional V. vinifera wine grape species, they are well-suited for more cold hardy varietals. The grapevines provide opportunities for high-value phytochemicals and platform chemicals (primarily stilbene based) as well as bioenergy production from resulting lignocellulosic residues. In a biorefinery concept, the 'front-end' high-value phytochemicals could help subsidize the lower-value bioenergy production.
Microstructural properties of phosphorus-doped p-type ZnO grown by radio-frequency magnetron sputtering
Authors: Oh Min-Suk , Hwang Dae-Kue , Choi Yong-Seok , Kang Jang-Won , Park Seong-Ju , Hwang Chi-Sun , Cho Kyoung Ik
Published: September 2008

Phosphorus (P)-doped ZnO thin films were grown by radio-frequency magnetron sputtering to study the microstructural properties of p-type ZnO. As-grown P-doped ZnO, a semi-insulator, was converted to p-type ZnO after being annealed at 800°C in an N2 ambient. X-ray diffraction, secondary-ion-mass spectrometry, and Hall effect measurements indicated that P2O5 phases in as-grown P-doped ZnO disappeared after thermal annealing to form a substitutional P at an O lattice site, which acts as an acceptor in P-doped ZnO. Transmission electron microscopy showed that the formation of stacking faults was facilitated to release the strain in P-doped ZnO during post-thermal annealing.
Amorphization-decomposition behavior of HfW2O8 at high pressure
Authors: Sakuntala T. , Rao Rekha , Garg Alka B. , Achary S. N. , Tyagi A. K.
Published: September 2008

Structural stability of HfW2O8 is investigated at high pressure using Raman spectroscopy. Irreversible amorphization is found to occur when pressurized to above 3 GPa under hydrostatic conditions. The Raman spectrum of the pressure-amorphized sample closely resembles that of amorphous WO3. On the other hand, spectrum of the recovered sample subjected to uniaxial compression of about 5 GPa showed bands characteristic of crystalline HfO2 besides the parent cubic phase and amorphous phase. Ex situ x-ray diffraction measurements on the pressure-cycled samples also indicated the presence of monoclinic HfO2. These results suggest that the observed pressure-induced amorphization (PIA) under hydrostatic compression is indeed due to hindered decomposition, which is facilitated under uniaxial compression. Thus, the behavior of HfW2O8 appears to be different from that of ZrW2O8, which exhibited only PIA and not pressure-induced decomposition at ambient temperature.
LABVIEW graphical user interface for precision multichannel alignment of Raman lidar at Jet Propulsion Laboratory, Table Mountain Facility
Authors: Aspey R. A. , McDermid I. S. , Leblanc T. , Howe J. W. , Walsh T. D.
Published: September 2008

The Jet Propulsion Laboratory operates lidar systems at Table Mountain Facility (TMF), California (34.4°N, 117.7°W) and Mauna Loa Observatory, Hawaii (19.5°N, 155.6°W) under the framework of the Network for the Detection of Atmospheric Composition Change. To complement these systems a new Raman lidar has been developed at TMF with particular attention given to optimizing water vapor profile measurements up to the tropopause and lower stratosphere. The lidar has been designed for accuracies of 5% up to 12 km in the free troposphere and a detection capability of <5 ppmv. One important feature of the lidar is a precision alignment system using range resolved data from eight Licel transient recorders, allowing fully configurable alignment via a LABVIEW/C++ graphical user interface (GUI). This allows the lidar to be aligned on any channel while simultaneously displaying signals from other channels at configurable altitude/bin combinations. The general lidar instrumental setup and the details of the alignment control system, data acquisition, and GUI alignment software are described. Preliminary validation results using radiosonde and lidar intercomparisons are briefly presented.
Transport properties of Ti-Zr-Ni quasicrystalline and glassy alloys
Authors: Kuo Y. K. , Kaurav N. , Syu W. K. , Sivakumar K. M. , Shan U. T. , Lin S. T. , Wang Q. , Dong C.
Published: September 2008

We report on measurements of the temperature dependence of the electrical resistivity (ρ), thermopower (S), and thermal conductivity (κ) of Ti-Zr-Ni alloys between 10 and 300 K. A series of Ti-Zr-Ni quasicrystals (QCs) Ti40Zr40Ni20, Ti45Zr35Ni20, and Ti50Zr30Ni20 and metallic glasses Ti35Zr45Ni20 and Ti40Zr40Ni20 was prepared to systematically study the compositional and structural dependences of their transport properties. The resistivity of all these alloys was found to be very weakly temperature dependent with a negative temperature coefficient of resistance. Further, the observed increase in electrical resistivity with increasing Ti/Zr ratio is most likely due to the increase in disorder. The S/T against temperature curves exhibited a maximum between 20 and 50 K and a noticeable deviation from the expected linear behavior in S(T) at higher temperatures. Such observations in the thermopower of QCs have been attributed to the electron-phonon enhancement and phonon drag effect. The measured thermal conductivities were analyzed by separating the electronic and phonon contributions that provide a reasonable explanation for plateau-type feature in κ(T) of QCs. Our present results suggest that the transport properties of glassy phase are influenced by the same mechanisms as those of quasicrystalline phase.
Optically induced relaxation of anisotropically strained M-plane GaN films on LiAlO2
Authors: Flissikowski T. , Brandt O. , Misra P. , Grahn H. T.
Published: September 2008

We study the anisotropic in-plane strain in M-plane GaN films on LiAlO2 by using photoreflectance, photoluminescence, Raman, and time-resolved pump-and-probe spectroscopy. We find a partial and anisotropic relaxation of these highly strained films under intense optical pumping. The strain relaxation is observed as a redshift of the E2-Raman line and as a redshift of the fundamental interband transition energies in the photoreflectance spectra. The photoluminescence intensity in the exposed areas of the sample is significantly reduced compared to the one for unexposed areas. This observation suggests that the strain relaxation is probably due to the introduction of defects, which act as nonradiative recombination centers.
Evaluation of the strains in charge-ordered Pr1−xCaxMnO3 thin films using Raman spectroscopy
Authors: Antonakos A. , Palles D. , Liarokapis E. , Filippi M. , Prellier W.
Published: September 2008

Thin films of Pr1−xCaxMnO3 (x=0.5,0.6) deposited on LaAlO3 and SrTiO3 substrates have been studied by Raman spectroscopy at low temperatures in order to investigate the effect of strains from the Ca doping or the substrate. A detailed assignment of the observed bands is suggested based on the present observations and published results on manganites. We assign the low frequency bands to modes involving only displacements of the A-site ions from their mass dependence by the Ca substitution for Pr (Pr/Ca–O modes). The Ag(2) mode, which is related to the tilting angle of the MnO6 octahedra, appears strongly coupled with the carriers and is very sensitive to the strain effects. Based on the Raman data obtained from the film cross sectional area, we extract the strain distribution across the film. Besides, we calculate in the pseudocubic approximation the phonon deformation potentials, the Grüneisen parameter, and the bulk modulus of the film, which are in good agreement with the ultrasonic measurements.
Quantum confinement observed in the x-ray absorption spectrum of size distributed meteoritic nanodiamonds
Authors: Berg Thomas , Marosits Edit , Maul Jochen , Nagel Peter , Ott Ulrich , Schertz Florian , Schuppler Stefan , Sudek Christa , Schönhense Gerd
Published: September 2008

We present a near edge x-ray absorption fine structure study of artificial chemical vapor deposition diamonds with sizes in the micron range and of size distributed nanodiamonds extracted from the Murchison meteorite. The modified peak shape in the case of the nanodiamond sample is explained by the interplay between the size distribution of the nanodiamonds and quantum confinement effects within a quantitative analysis based on the effective mass approximation theory.
Impact of magnetron configuration on plasma and film properties of sputtered aluminum nitride thin films
Authors: Duquenne C. , Tessier P. Y. , Besland M. P. , Angleraud B. , Jouan P. Y. , Aubry R. , Delage S. , Djouadi M. A.
Published: September 2008

We have investigated the growth of the c-axis oriented aluminum nitride (AlN) thin films on (100) silicon by reactive dc magnetron sputtering at low temperature, considering the effect of the magnet configuration on plasma and film properties. It appears that a magnet modification can significantly modify both the plasma characteristics and the film properties. Electrical and optical characterizations of the plasma phase highlight that depending on the magnet configuration, two very different types of deposition process can be involved in the same deposition chamber. On the one hand, with a balanced magnetron (type 1), the deposition process enhances the production of AlN dimers in the plasma phase and enables to synthesize AlN films with different preferential orientations (100, 002, and even 101). On the other hand, a strongly unbalanced magnetron (type 2) provides a limited production of AlN species in the plasma phase and a strong increase in the ratio of ions to metal atom flux on the growing films. In the latter case, the ion energy provided by the ion flux to the growing film is typically in the 20–30 eV range. Thus, dense (002) oriented films with high crystalline quality are obtained without any substrate heating.
Interband and intersubband optical characterization of semipolar (112¯2)-oriented GaN/AlN multiple-quantum-well structures
Authors: Lahourcade L. , Kandaswamy P. K. , Renard J. , Ruterana P. , Machhadani H. , Tchernycheva M. , Julien F. H. , Gayral B. , Monroy E.
Published: September 2008

We report on semipolar GaN/AlN multiple-quantum-well structures grown on m-plane sapphire by plasma-assisted molecular-beam epitaxy. Optical investigation confirms a significant reduction in the quantum-confined Stark effect, in agreement with theoretical calculations, which predict an internal electric field between 0.6 and −0.55 MV/cm in the quantum wells, depending on the strain state. With respect to polar materials, the reduction in the internal electric field results in a substantial redshift of the intersubband energy.
Reliability study of tunable ferroelectric capacitors
Authors: Sherman Vladimir O. , Czarnecki Piotr , De Wolf Ingrid , Yamada Tomoaki , Setter Nava , Malic Barbara , Vukadinovic Miso , Kosec Marija
Published: September 2008

In this paper, the reliability of tunable ferroelectric thin film capacitors has been addressed. The long term stability of tunable capacitors based on Ba0.3Sr0.7TiO3 films deposited by chemical solution deposition onto an alumina substrate was investigated by monitoring their tunable performance as a function of the number of ON-OFF switching cycles and as a function of time. The conditions of civil aeronautic applications were chosen to plan the lifetime experiments. More than 300×106 of switching cycles with an amplitude of 150 V and frequency of 1 kHz were successfully applied to the investigated capacitors without damaging them. Moreover, no degradation in the C-V characteristic was observed after the application of 150 V dc voltage during 15 h. Additionally, the effect of illumination of the ferroelectric film by ultraviolet light on the tunable performance of the capacitors has been investigated. A positive effect of such illumination on the C-V characteristics of ferroelectric capacitor has been found.
Surface reformation and electro-optical characteristics of liquid crystal alignment layers using ion beam irradiation
Authors: Oh Byeong-Yun , Lee Kang-Min , Kim Byoung-Yong , Kim Young-Hwan , Han Jin-Woo , Han Jeong-Min , Lee Sang-Keuk , Seo Dae-Shik
Published: September 2008

The surface modification characteristics of liquid crystal (LC) alignment layers irradiated with various argon (Ar) ion beam (IB) energies were investigated as a substitute for rubbing technology. Various pretilt angles were created on the IB-irradiated polyimide (PI) surfaces after IB irradiation, but the Ar ions did not alter the morphology on the PI surface, indicating that the pretilt angle was not due to microgrooves. The chemical bonding states of the IB-irradiated PI surfaces were analyzed in detail by x-ray photoelectron spectroscopy to verify the compositional behavior for the LC alignment. Chemical structure analysis showed that the alignment ability of LCs was due to the preferential reorientation of the carbon network due to the breaking of C=O double bonds in the imide ring parallel to the incident IB direction. The potential of applying nonrubbing technology to display devices was further supported by the superior electro-optical characteristics compared to rubbed PI.
Metamorphic high electron mobility Te-doped AlInSb/GaInSb heterostructures on InP (001)
Authors: Delhaye G. , Desplanque L. , Wallart X.
Published: September 2008

This work reports on the Te δ-doping of high electron mobility AlInSb/GaInSb heterostructures grown by molecular beam epitaxy on InP(001) substrates with a metamorphic approach. The combination of atomic force microscopy and van der Pauw measurements is used to investigate and explain the influence of the buffer layers on the electron mobility and sheet density in the heterostructure. Furthermore, a significant increase in the electron sheet density is reached when the δ-doping plane is incorporated in a thin AlSb layer introduced in the barrier. This improvement is explained by the lower dopant activation energy in the AlSb layer. AlInSb/GaInSb heterostructures with an electron mobility of 18 000 cm2/V s and sheet density of 2.2×1012 cm−2 at room temperature are demonstrated.
Anisotropic etching in inductive plasma source with no rf biasing
Authors: Park Wontaek
Published: September 2008

An inductive plasma source driven with phase shifted antenna coils at 2 MHz has been developed to accelerate ions for semiconductor etching process. The experiment was carried out in SF6/O2/Ar gas mixtures in the pressure range between 0.3 and 0.9 mTorr and rf power between 0.6 and 1.5 kW. Measurement of the ion energy spectra behind the wafer has shown high energy ions (up to 70 eV). An anisotropic etching (without rf biasing) of a polysilicon film has been demonstrated in this experiment. The acceleration of the electrons was numerically studied based on the fluid theory. The numerical results show that electrons affected by Lorentz force and thermal pressure gradient make axial electron currents, which contribute to form axial electric fields and ion acceleration.
Cascade of Y-shaped spin filters in InGaAs/InAs/InGaAs quantum wells
Authors: Cummings A. W. , Akis R. , Ferry D. K. , Jacob J. , Matsuyama T. , Merkt U. , Meier G.
Published: September 2008

An all-electrical semiconductor device for generating and detecting spin-polarized currents with a two-stage cascade of three-terminal spin filters is discussed, where the first stage serves as the spin polarizer and the second stage serves as the detector. Transport simulations show imbalanced output conductance for higher-order subbands, independent of the spin-orbit coupling strength. However, when only the lowest subband is occupied the simulations show that the conductance asymmetry is spin-orbit dependent. Therefore, the conductance asymmetry of the lowest subband can be used to indicate spin polarization. Based on the simulations an experimental device to measure the spin-dependent conductance asymmetry is proposed.
A surface-sensitive UHV dielectric spectrometer for studies of nanoscale molecular systems on a planar surface
Authors: Underwood Jason M. , Price John C.
Published: September 2008

We describe an apparatus for dielectric spectroscopy (DS) experiments on ultrathin (<100 nm) molecular films in an ultrahigh vacuum (UHV) environment. The apparatus is capable of measurements of ex situ prepared films, as well as in situ physisorbed or chemisorbed layers. Pressures of 5×10−10 Torr are typical, and the audiofrequency DS measurements can be performed over a range of temperatures 7–500 K, using a continuous-flow cold finger. The combination of turbomolecular pump, differentially pumped quick-access door, and backfilling with dry N2 affords vent-exchange-pump cycle times under an hour. The system pressure returns to the 10−9 Torr scale within 48 h, without a high-temperature bake. Since the cold finger is mounted on a long-stroke translation stage, the apparatus can be attached to other analytical UHV equipment, and the sample may be transferred for additional in situ measurements. Film dielectric properties are probed via coplanar interdigital electrode capacitors, which are microfabricated on fused SiO2 wafers. Besides permitting the usual equilibrium dielectric measurements, the system also provides a novel way to study adsorption/desorption phenomena and film growth.
Implementation of maskless laser lithography using a Raman spectroscopy microprobe
Authors: Codan Barbara , Sergo Valter
Published: September 2008

A new use of a Raman spectroscopy microprobe is described. This kind of instrument uses an intense light source, usually a laser, to obtain chemical information from the scattered light sent to the sample through a microscope objective lens. A Raman microprobe is most often equipped with a motorized stage. The coupling of a focused laser light with the possibility of moving the stage under the very same light can be used to perform maskless photolithography as a laser writer. The versatility and resolution of this application are tested and described, producing different arrays of holes on photoresist. Holes as small as 1 μm are produced, thus demonstrating a lateral resolution sufficient for several applications. As an example of application, a pattern of a human protein, fibronectin, has been produced on a gold surface, which can then be used for the study of cell adhesion.
Vertically well-aligned epitaxial Ni31Si12 nanowire arrays with excellent field emission properties
Authors: Lee Chung-Yang , Lu Ming-Pei , Liao Kao-Feng , Wu Wen-Wei , Chen Lih-Juann
Published: September 2008

Vertically well-aligned single crystal Ni31Si12 nanowire (NW) arrays were epitaxially grown on Ni31Si12 films preferentially formed on Ni foil substrates with a simple vapor phase deposition method in one step. The Ni31Si12 NWs are several micrometers in length and 50–80 nm in diameter. The resistivities of the Ni31Si12 NWs were measured to be 51 μΩ cm by four-terminal electrical measurement. The NWs can carry very high currents and possess excellent field emission properties. The growth of vertically well-aligned Ni31Si12 NW arrays shall lead to significant advantages in the fabrication of vertical Si nanodevices.
Temperature-dependent quantitative 3ω scanning thermal microscopy: Local thermal conductivity changes in NiTi microstructures induced by martensite-austenite phase transition
Authors: Chirtoc M. , Gibkes J. , Wernhardt R. , Pelzl J. , Wieck A.
Published: September 2008

We develop the theoretical description of 3ω signals from the resistive Wollaston thermal probe (ThP) of a scanning thermal microscope (SThM) in terms of an equivalent low-pass filter. The normalized amplitude and phase frequency spectra are completely characterized by a single parameter, the crossover frequency fc(k) depending on the sample thermal conductivity k. The application concerns polycrystalline NiTi shape memory alloy microstructured by focused Ga ion beam milling and implantation. The calibration of the ThP combined with a novel two-step normalization procedure allowed quantitative exploitation of 3ω signal variations as small as −1.75% in amplitude and 0.60° in phase upon heating the sample from room temperature to 100 °C. This corresponds to k increase of 23.9% that is consistent with the expected thermal conductivity variation due to martensite-austenite structural phase transition. To our knowledge this is for the first time that SThM 3ω phase information is used quantitatively as well. The static, calibrated 3ω measurements are complementary to 3ω SThM images of the patterned sample surface. The local SThM measurement of temperature-dependent thermal conductivity opens the possibility to imaging structural phase transitions at submicron scale.
Room temperature continuous-wave operation of InAs∕InP(100) quantum dot lasers grown by gas-source molecular-beam epitaxy
Authors: Li S. G. , Gong Q. , Lao Y. F. , He K. , Li J. , Zhang Y. G. , Feng S. L. , Wang H. L.
Published: September 2008

We report on the InAs quantum dots (QDs) laser in the 1.55μm wavelength region grown by gas source molecular-beam epitaxy. The active region of the laser structure consists of fivefold-stacked InAs QD layers embedded in the InGaAsP layer. Ridge waveguide lasers were processed and continuous-wave mode operation was achieved between 20 and 70°C, with characteristic temperature of 69K. High internal quantum efficiency (56%) and low infinite length threshold current density (128A∕cm2 per QD layer) was obtained for the as-cleaved devices at room temperature. The lasing wavelength range between 1.556 and 1.605μm can be covered by varying the laser cavity length.
Characteristics of GaN-based photonic crystal surface emitting lasers
Authors: Lu Tien-chang , Chen Shih-Wei , Kao Tsung-Ting , Liu Tzu-Wei
Published: September 2008

Characteristics of GaN-based photonic crystal surface emitting lasers (PCSELs) were investigated and analyzed. The GaN-based PCSEL emits a blue wavelength at 401.8 nm with a linewidth of 1.6 Å and shows a threshold energy density about 2.7 mJ/cm2 under the optical pumping at room temperature. The lasing wavelength emitted from PCSELs with different lattice constants occurs at the calculated band edges showing different polarization angles due to the light diffracted in specific directions, corresponding exactly to Γ, K, and M directions in the K-space. Furthermore, the PCSEL also shows a spontaneous emission coupling efficiency β of about 5×10−3 and a characteristic temperature of 148 K.
Ultrahigh-Q two-dimensional photonic crystal slab nanocavities in very thin barriers
Authors: Kuramochi Eiichi , Taniyama Hideaki , Tanabe Takasumi , Shinya Akihiko , Notomi Masaya
Published: September 2008

We demonstrate that width-modulated line-defect nanocavities in photonic crystals with long air slots on either side can maintain an ultrahigh Q even with very thin in-plane photonic crystal (only several rows of air holes). Although it is commonly believed that high-Q photonic crystal nanocavities require relatively thick in-plane barriers, surprisingly these nanocavities fabricated in silicon photonic crystals exhibit an ultrahigh Q (>106) even with very thin barriers. This design may be useful for various nanocavity applications.
Lorentz-type relationship of the temperature dependent dielectric permittivity in ferroelectrics with diffuse phase transition
Authors: Ke Shanming , Fan Huiqing , Huang Haitao , Chan H. L. W.
Published: September 2008

The temperature dependence of the dielectric permittivity of perovskite Ba(ZrxTi1−x)O3 solid solutions, PbMg1/3Nb2/3O3 relaxor, and BaTiO3 ferroelectric ceramics was measured. It is found that a Lorentz-type law can be used to describe the dielectric permittivity of either the normal ferroelectrics with or without diffuse phase transitions (DPT) or the typical ferroelectric relaxors. The ferroelectric DPT can be well described by just one fitting process using the Lorentz-type law, while the relaxor ferroelectric transition needs two independent fitting processes. The Lorentz-type law fails at the low temperature side of the dielectric maximum of a first-order ferroelectric phase transition. Above the transition temperature, the dielectric curves of all the studied materials can be well described by a Lorentz-type law.
Near-infrared absorption of germanium thin films on silicon
Authors: Sorianello V. , Perna A. , Colace L. , Assanto G. , Luan H. C. , Kimerling L. C.
Published: September 2008

Using differential optical absorption spectroscopy of germanium thin films epitaxially grown on silicon, we accurately evaluate the near-infrared absorption versus wavelength and temperature. The results allow for optimized design and realization of Ge-on-Si photodetectors.
Monkeypox virus evades antiviral CD4
+
and CD8
+
T cell responses by suppressing cognate T cell activation
Authors: Hammarlund Erika , Dasgupta Anindya , Pinilla Clemencia , Norori Patricia , Früh Klaus , Slifka Mark K.
Published: September 2008

Monkeypox virus (MPV) is a virulent human pathogen that has gained increased attention because of its potential use as a bioterrorism agent and inadvertent introduction into North America in 2003. The US outbreak also provided an important opportunity to study MPV-specific T cell immunity. Although MPV-specific CD4
+
and CD8
+
T cells could recognize vaccinia virus (VV)-infected monocytes and produce inflammatory cytokines such as IFNγ and TNFα, they were largely incapable of responding to autologous MPV-infected cells. Further analysis revealed that, unlike cowpox virus (CPV), MPV did not interfere with MHC expression or intracellular transport of MHC molecules. Instead, MPV-infected cells were capable of preventing T cell receptor (TcR)-mediated T cell activation
in trans
. The ability to trigger a state of nonresponsiveness represents a unique MHC-independent mechanism for blocking antiviral T cell activation and inflammatory cytokine production and is likely an important attribute involved with viral dissemination in the infected host.
Image interpretation by a single bottom-up top-down cycle
Authors: Epshtein Boris , Lifshitz Ita , Ullman Shimon
Published: September 2008

The human visual system recognizes objects and their constituent parts rapidly and with high accuracy. Standard models of recognition by the visual cortex use feed-forward processing, in which an object's parts are detected before the complete object. However, parts are often ambiguous on their own and require the prior detection and localization of the entire object. We show how a cortical-like hierarchy obtains recognition and localization of objects and parts at multiple levels nearly simultaneously by a single feed-forward sweep from low to high levels of the hierarchy, followed by a feedback sweep from high- to low-level areas.
Rapid enhancement of two-step wiring plasticity by estrogen and NMDA receptor activity
Authors: Srivastava Deepak P. , Woolfrey Kevin M. , Jones Kelly A. , Shum Cassandra Y. , Lash L. Leanne , Swanson Geoffrey T. , Penzes Peter
Published: September 2008

Cortical information storage requires combined changes in connectivity and synaptic strength between neurons, but the signaling mechanisms underlying this two-step wiring plasticity are unknown. Because acute 17β-estradiol (E2) modulates cortical memory, we examined its effects on spine morphogenesis, AMPA receptor trafficking, and GTPase signaling in cortical neurons. Acute E2 application resulted in a rapid, transient increase in spine density, accompanied by temporary formation of silent synapses through reduced surface GluR1. These rapid effects of E2 were dependent on a Rap/AF-6/ERK1/2 pathway. Intriguingly, NMDA receptor (NMDAR) activation after E2 treatment potentiated silent synapses and elevated spine density for as long as 24 h. Hence, we show that E2 transiently increases neuronal connectivity by inducing dynamic nascent spines that “sample” the surrounding neuropil and that subsequent NMDAR activity is sufficient to stabilize or “hold” E2-mediated effects. This work describes a form of two-step wiring plasticity relevant for cortical memory and identifies targets that may facilitate recovery from brain injuries.
Epigallocatechin-3-gallate inhibits IL-6 synthesis and suppresses transsignaling by enhancing soluble gp130 production
Authors: Ahmed Salahuddin , Marotte Hubert , Kwan Kevin , Ruth Jeffrey H. , Campbell Phillip L. , Rabquer Bradley J. , Pakozdi Angela , Koch Alisa E.
Published: September 2008

Regulation of IL-6 transsignaling by the administration of soluble gp130 (sgp130) receptor to capture the IL-6/soluble IL-6R complex has shown promise for the treatment of rheumatoid arthritis (RA). However, enhancing endogenous sgp130 via alternative splicing of the gp130 gene has not yet been tested. We found that epigallocatechin-3-gallate (EGCG), an anti-inflammatory compound found in green tea, inhibits IL-1β–induced IL-6 production and transsignaling in RA synovial fibroblasts by inducing alternative splicing of gp130 mRNA, resulting in enhanced sgp130 production. Results from
in vivo
studies using a rat adjuvant-induced arthritis model showed specific inhibition of IL-6 levels in the serum and joints of EGCG-treated rats by 28% and 40%, respectively, with concomitant amelioration of rat adjuvant-induced arthritis. We also observed a marked decrease in membrane-bound gp130 protein expression in the joint homogenates of the EGCG-treated group. In contrast, quantitative RT-PCR showed that the gp130/IL-6Rα mRNA ratio increased by ∼2-fold, suggesting a possible mechanism of sgp130 activation by EGCG. Gelatin zymography results showed EGCG inhibits IL-6/soluble IL-6R–induced matrix metalloproteinase-2 activity in RA synovial fibroblasts and in joint homogenates, possibly via up-regulation of sgp130 synthesis. The results of these studies provide previously undescribed evidence of IL-6 synthesis and transsignaling inhibition by EGCG with a unique mechanism of sgp130 up-regulation, and thus hold promise as a potential therapeutic agent for RA.
Direct characterization of amyloidogenic oligomers by single-molecule fluorescence
Authors: Orte Angel , Birkett Neil R. , Clarke Richard W. , Devlin Glyn L. , Dobson Christopher M. , Klenerman David
Published: September 2008

A key issue in understanding the pathogenic conditions associated with the aberrant aggregation of misfolded proteins is the identification and characterization of species formed during the aggregation process. Probing the nature of such species has, however, proved to be extremely challenging to conventional techniques because of their transient and heterogeneous character. We describe here the application of a two-color single-molecule fluorescence technique to examine the assembly of oligomeric species formed during the aggregation of the SH3 domain of PI3 kinase. The single-molecule experiments show that the species formed at the stage of the reaction where aggregates have previously been found to be maximally cytotoxic are a heterogeneous ensemble of oligomers with a median size of 38 ± 10 molecules. This number is remarkably similar to estimates from bulk measurements of the critical size of species observed to seed ordered fibril formation and of the most infective form of prion particles. Moreover, although the size distribution of the SH3 oligomers remains virtually constant as the time of aggregation increases, their stability increases substantially. These findings together provide direct evidence for a general mechanism of amyloid aggregation in which the stable cross-β structure emerges via internal reorganization of disordered oligomers formed during the lag phase of the self-assembly reaction.
Pragmatic factors in the development of a switch-adjective language
Authors: Koloskova Yulia , Ohori Toshio
Published: September 2008

The Miyako-Hirara dialect of Ryukyuan is a switch-adjective language, i.e. it employs both nominal and verbal strategies for its adjectival roots. The choice of the encoding option in the predicative position depends on the information structure of the sentence. If a predicative adjective is in the focus domain, the nominal strategies (adjectival root + munu, reduplicated forms) are used. If a predicative adjective belongs to the presupposition, the verbal strategy (-kaɨ forms) is employed. We argue that Miyako-Hirara employs a switch-adjective encoding in order to retain the functional distinction between the predicates in focus and those in the domain of presupposition, in the absence of other means of morphological marking for the informational status of constituents.