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A disruption database characterizing the current quench of disruptions with ITER-like tungsten divertor has been developed on EAST. It provides a large number of plasma parameters describing the predisruptive plasma, current quench time, eddy current, and mitigation by massive impurity injection, which shows that the current quench time strongly depends on magnetic energy and post-disruption electron temperature. Further, the energy balance and magnetic energy dissipation during the current quench phase has been well analysed. Magnetic energy is also demonstrated to be dissipated mainly by ohmic reheating and inductive coupling, and both of the two channels have great effects on current quench time. Also, massive gas injection is an efficient method to speed up the current quench and increase the fraction of impurity radiation.
Diet has a major influence on the composition and metabolic output of the gut microbiome. Higher-protein diets are often recommended for older consumers; however, the effect of high-protein diets on the gut microbiota and faecal volatile organic compounds (VOC) of elderly participants is unknown. The purpose of the study was to establish if the faecal microbiota composition and VOC in older men are different after a diet containing the recommended dietary intake (RDA) of protein compared with a diet containing twice the RDA (2RDA). Healthy males (74⋅2 (sd 3⋅6) years; n 28) were randomised to consume the RDA of protein (0⋅8 g protein/kg body weight per d) or 2RDA, for 10 weeks. Dietary protein was provided via whole foods rather than supplementation or fortification. The diets were matched for dietary fibre from fruit and vegetables. Faecal samples were collected pre- and post-intervention for microbiota profiling by 16S ribosomal RNA amplicon sequencing and VOC analysis by head space/solid-phase microextraction/GC-MS. After correcting for multiple comparisons, no significant differences in the abundance of faecal microbiota or VOC associated with protein fermentation were evident between the RDA and 2RDA diets. Therefore, in the present study, a twofold difference in dietary protein intake did not alter gut microbiota or VOC indicative of altered protein fermentation.
Some fire ants of the genus Solenopsis have become invasive species in the southern United States displacing native species by competition. Although the displacement pattern seems clear, the mechanisms underlying competitive advantage remain unclear. The ability of ant workers to produce relatively larger amount of alarm pheromone may correspond to relative greater fitness among sympatric fire ant species. Here we report on quantitative intra-specific (i.e. inter-caste) and inter-specific differences of alarm pheromone component, 2-ethyl-3,6-dimethylpyrazine (2E36DMP), for several fire ant species. The alarm pheromone component was extracted by soaking ants in hexane for 48 h and subsequently quantified by gas chromatography-mass spectrometry at single ion monitoring mode. Solenopsis invicta workers had more 2E36DMP than male or female alates by relative weight; individual workers, however, contained significantly less pyrazine. We thus believe that alarm pheromones may serve additional roles in alates. Workers of Solenopsis richteri, S. invicta, and hybrid (S. richteri × S. invicta) had significantly more 2E36DMP than a native fire ant species, Solenopsis geminata. The hybrid fire ant had significantly less 2E36DMP than the two parent species, S. richteri and S. invicta. It seems likely that higher alarm pheromone content may have favored invasion success of exotic fire ants over native species. We discuss the potential role of inter-specific variation in pyrazine content for the relationship between the observed shifts in the spatial distributions of the three exotic fire ant species in southern United States and the displacement of native fire ant species.
Based on the analysis of data from the numerous dedicated experiments on plasma disruptions in the TEXTOR tokamak the mechanisms of the formation of runaway electron (RE) beams and their losses are proposed. The plasma disruption is caused by a strong stochastic magnetic field formed due to nonlinearly excited low-mode-number magneto-hydro-dynamics (MHD) modes. It is hypothesized that the RE beam is formed in the central plasma region confined by an intact magnetic surface due to the acceleration of electrons by the inductive toroidal electric field. In the case of plasmas with the safety factor
the most stable RE beams are formed by the outermost intact magnetic surface located between the magnetic surface
and the closest low-order rational surface
. The thermal quench (TQ) time caused by the fast electron transport in a stochastic magnetic field is calculated using the collisional transport model. The current quench (CQ) stage is due to the particle transport in a stochastic magnetic field. The RE beam current is modelled as a sum of a toroidally symmetric part and a small-amplitude helical current with a predominant
component. The REs are lost due to two effects: (i) by outward drift of electrons in a toroidal electric field until they touch the wall and (ii) by the formation of a stochastic layer of REs at the beam edge. Such a stochastic layer for high-energy REs is formed in the presence of the
MHD mode. It has a mixed topological structure with a stochastic region open to the wall. The effect of external resonant magnetic perturbations on RE loss is discussed. A possible cause of the sudden MHD signals accompanied by RE bursts is explained by the redistribution of runaway current during the resonant interaction of high-energetic electron orbits with the
Electronic medical records (EMR) provide a unique opportunity for efficient, large-scale clinical investigation in psychiatry. However, such studies will require development of tools to define treatment outcome.
Natural language processing (NLP) was applied to classify notes from 127 504 patients with a billing diagnosis of major depressive disorder, drawn from out-patient psychiatry practices affiliated with multiple, large New England hospitals. Classifications were compared with results using billing data (ICD-9 codes) alone and to a clinical gold standard based on chart review by a panel of senior clinicians. These cross-sectional classifications were then used to define longitudinal treatment outcomes, which were compared with a clinician-rated gold standard.
Models incorporating NLP were superior to those relying on billing data alone for classifying current mood state (area under receiver operating characteristic curve of 0.85–0.88 v. 0.54–0.55). When these cross-sectional visits were integrated to define longitudinal outcomes and incorporate treatment data, 15% of the cohort remitted with a single antidepressant treatment, while 13% were identified as failing to remit despite at least two antidepressant trials. Non-remitting patients were more likely to be non-Caucasian (p<0.001).
The application of bioinformatics tools such as NLP should enable accurate and efficient determination of longitudinal outcomes, enabling existing EMR data to be applied to clinical research, including biomarker investigations. Continued development will be required to better address moderators of outcome such as adherence and co-morbidity.
A brief overview of the research activities at the Thermionic Energy Conversion (TEC) Center is given. The goal is to achieve direct thermal to electric energy conversion with >20% efficiency and >1W/cm2 power density at a hot side temperature of 300–650C. Thermionic emission in both vacuum and solid-state devices is investigated. In the case of solid-state devices, hot electron filtering using heterostructure barriers is used to increase the thermoelectric power factor. In order to study electron transport above the barriers and lateral momentum conservation in thermionic emission process, the current-voltage characteristic of ballistic transistor structures is investigated. Embedded ErAs nanoparticles and metal/semiconductor multilayers are used to reduce the lattice thermal conductivity. Cross-plane thermoelectric properties and the effective ZT of the thin film are analyzed using the transient Harman technique. Integrated circuit fabrication techniques are used to transfer the n- and p-type thin films on AlN substrates and make power generation modules with hundreds of thin film elements. For vacuum devices, nitrogen-doped diamond and carbon nanotubes are studied for emitters. Sb-doped highly oriented diamond and low electron affinity AlGaN are investigated for collectors. Work functions below 1.6eV and vacuum thermionic power generation at temperatures below 700C have been demonstrated.
Die-on-wafer and wafer-level three-dimensional (3D) integrations of heterogeneous IC technologies are briefly described, emphasizing a specific 3D hyper-integration platform using dielectric adhesive wafer bonding and Cu damascene inter-wafer interconnects to provide a perspective on wafer-level 3D technology processing. Wafer-level 3D partitioning of high Q passive components, analog-to-digital (A/D) converters, RF transceivers, digital processors, and memory is discussed for high-performance RF-microwave-millimeter applications, especially where high manufacturing quantities are anticipated. Design and simulation results of 3D heterogeneous integration are presented. This 3D technology is applicable to smart wireless terminals, millimeter phased array radars, and smart imagers.
Intermetallic compound (IMC) growth during solid-state aging at 125, 150, and 170 °C up to 1500 h for four solder alloys (eutectic SnPb, Sn–3.5Ag, Sn–3.8Ag–0.7Cu, and Sn–0.7Cu) on Cu under bump metallization was investigated. The samples were reflowed before aging. During the reflow, the solders were in the molten state and the formation of the IMC Cu6Sn5 in the cases of eutectic SnPb and Sn–3.5Ag had a round scallop-type morphology, but in Sn–0.7Cu and Sn–3.8Ag–0.7Cu the scallops of Cu6Sn5 were faceted. In solid-state aging, all these scallops changed to a layered-type morphology. In addition to the layered Cu6Sn5, the IMC Cu3Sn also grew as a layer and was as thick as the Cu6Sn5. The activation energy of intermetallic growth in solid-state aging is 0.94 eV for eutectic SnPb and about 1.05 eV for the Pb-free solders. The rate of intermetallic growth in solid-state aging is about 4 orders of magnitude slower than that during reflow. Ternary phase diagrams of Sn–Pb–Cu and Sn–Ag–Cu are used to discuss the reactions. These diagrams predict the first phase of IMC formation in the wetting reaction and the other phases formed in solid-state aging. Yet, the morphological change and the large difference in growth rates between the wetting reaction and solid-state aging cannot be predicted.
Polystyrene (PS) clay nanocomposites were synthesized and used to prepare foams in both batch and continuous extrusion process. It was found that the addition of a small amount of clay could greatly reduce cell size and increase cell density. Once exfoliated, the nanocomposite foam exhibits the highest cell density and the smallest cell size at the same particle concentration. Exfoliated microcellular nanocomposite foams with good surface quality was successfully produced using supercritical carbon dioxide.
We have developed a solution delivery technique for performing copper CVD using the reduction of Cu(hfac)2 [where H(hfac) = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionel. We have obtained deposition rates of up to 3.6 mg cm−2 hr−1 (ca. 60 nm min−1) for a deposition temperature of 300 °C and reactor conditions of 40 Torr H2, 12 Torr isopropanol, and 1 Torr Cu(hfac)2. The increased rates are several times faster than growth rates observed using conventional Cu(hfac)2 sublimation with pure H2 as the carrier gas. We compare growth rates and film microstructure using TiN- and WNx-coated substrates. We also give preliminary results showing how the partial pressures of H2, i-PrOH, and Cu(hfac)2 each influence the deposition rate.
Transmission electron microscopy (TEM) in both cross sectional and plan view is used to study the effect of annealing Ag-Ti bilayers deposited on SiO2/Si substrates in an NH3 ambient. The resulting structure, texture and grain size are investigated. Comparisons are made between films annealed at 400, 500 and 600 °C. Silver films show increasingly strong <111> texture with annealing temperature while exhibiting a bamboo-like grain structure at 600 °C. Considerable grain growth with lateral grain sizes of up to 5 times the thickness of the Ag film is observed at 600 °C. The grains typically extend through the Ag film thickness. The Ti/SiO2 interface uniformity and the absence of voids at the substrate surface are positive indicators of the role of titanium as a good adhesion promoter. At 600 °C, a uniform TiN encapsulation layer is observed on the Ag surface.
The texture in polycrystalline Ag thin films prepared by e-beam evaporation has been characterized by an x-ray diffraction technique as a function of underlayers and encapsulation temperatures. The Ag films deposited on Ti layers showed a strong <111> fiber texture with a fiber axis parallel to the film normal, whereas an almost random orientation was observed in the Ag films on Cr layers. This underlayer dependence of texture is associated with the lattice match between Ag and underlayer metal. In addition to <111> texture, the Ag films on Ti also exhibited a <511> texture component, which is the result of twinning of <111> -oriented grains. After the encapsulation process, the <111> texture in the Ag films on Ti was significantly improved, as evidenced by an increased (111) diffraction intensity and a slightly narrower space distribution of the texture along the fiber axis. The highly textured Ag films are expected to exhibit an improved electromigration resistance.
The stress state of evaporated Ag films prepared on Ti underlayers before and after encapsulation process has been studied by x-ray diffraction using a “sin2ψ” technique. A low tensile stress of approximately 61 MPa was measured in the as-deposited Ag films. The stress was caused by nonequilibrium growth during film deposition and resulted in a lattice tension state in the film plane and a lattice compression state along the film normal. Thermal mismatch stress was produced by the encapsulation process at 600 °C, but most of this stress relaxed during the cooling stage, and a residual tensile stress of ∼ 320 MPa in the film plane was determined.
An array of microdisks with diameter of about 9 μm and spacing of 50 μm has been fabricated by dry etching from a 50 Å/50 Å GaN/AlxGa1-xN (x∼ 0.07) multiple quantum well (MQW) structure grown by reactive molecular beam epitaxy. The as-grown MQWs and the microdisk structures have been studied by picosecond time-resolved photoluminescence (PL) spectroscopy. PL emission spectra and decay dynamics were measured at various temperatures and pump intensities. With respect to the original MQWs, we observe strong enhancement of the transition intensity and lifetime for both the intrinsic and barrier transitions. The intrinsic transition is excitonic at low temperatures and exhibits an approximate 10 fold increase in both lifetime and PL intensity upon formation of the microdisks. The exciton transition magnitude diminishes rapidly with increased temperature however, while the enhanced lifetime shows little change. At room temperature the dominant GaN well transition is found to be band-to-band in nature as evidenced by effective band gap shrinkage and band-filling effects seen within the PL spectrum. The implications of our results to III-Nitride microdisk lasers are discussed.
In this work the normal reflectance, R, at a planar silica aerogel interface and the normal transmittance, T, of a silica aerogel slab were measured using a Fourier Transform Infrared Spectrometer. Two procedures were used to obtain the effective optical constants, i.e., the refractive index n and the absorption index κ, of silica aerogel. One procedure determined κ from the measured transmittance T and then determined n from the results for κ and from the measured reflectance R using the Kramers–Kronig relation; the other procedure determined n and κ of silica aerogel from n and κ of fully dense silica glass by using the Clausius–Mossotti equation, Maxwell Garnett formula, and Bruggeman formula. The first procedure has a relatively large error due to the inaccuracy of the transmission and reflection measurements. The second procedure, especially the Clausius–Mossotti equation, yields values of n that are consistent with experiments and may be used for the calculation of the effective optical constants and the extinction coefficient of silica aerogel.
Dislocations in LiB3O5(LBO) single crystal were investigated by white-beam synchrotron radiation topography(WBSRT). The WBSRT revealed that the grown-in dislocations are mainly pure screw or edge types with the Burgers vectors in the low index directions on (010) lattice plane. Based on the structure analysis, the formation cause of dislocations can be interpreted in terms of the loose packing of B-O rings and the low density of Li+ on (010) lattice plane.
Reduction of MCln, n = 3 for M = Cr, Mo, n = 4 for W with LiBEt3H in THF results in formation of nanometer-sized crystalline metal carbide, M2C particles whereas the same reduction reaction in toluene results in formation of the corresponding metal particles. As an example of this methodology, the reduction of MoC13(THF)3 and WC14 in THF by Li/C10H8 is described in detail. Reduction of MoC13(THF)3 in THF by Li/C10H8 resulted in formation of a black suspension from which black powder can be isolated. Electron diffraction and X-ray powder diffraction data showed the black powder is amorphous. Energy dispersive spectroscopy confirmed the presence of molybdenum, and no chlorine was detected. Ex-situ variable temperature X-ray powder diffraction experiments showed the presence of fec Mo2C which upon further heating underwent a phase transformation to hexagonal Mo2C. Crystalline molybdenum was also observed after heating to 750°C for 3 hours. Reduction of WC14 in THF by Li/C10H8 results in formation of a black powder which on heating underwent phase transitions from amorphous to fcc W2C to hexagonal W2C as determined by X-ray powder diffraction.
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