75 research outputs found

    A Study of Low Energy Ar+ Ion Bombardment Induced Lattice Damage in (100) n-GaAs by Channeling

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    It has been found that sputter cleaning of GaAs single crystals results in damage or loss of crystallinity in the first few tens of nanometers of the crystal. The damage is a result of both - energetic Ar ions impinging on and being incorporated in the GaAs surface and the resultant preferential sputtering of As from the GaAs lattice. A study of this damage which was done at room temperature and at -110 °C was made by the use of Selected Area Electron Channeling Patterns. The relationship between the degree of surface disorder, as shown by the pattern degradation, and sputtering parameters (ion beam voltage and ion beam dose) was experimentally obtained. The energy regime investigated was 0.5 to 5 keV with sputtering times from 5 to 20 minutes. The results showed increasing contrast degradation in the selected area channeling patterns (SACPs) with increasing incident ion energies from 0.5 to 4 keV, a maxima in contrast degradation for a sputtering time of 10 minutes and greater contrast degradation at room temperature than at -110 °C

    Notions and subnotions in information structure

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    Three dimensions can be distinguished in a cross-linguistic account of information structure. First, there is the definition of the focus constituent, the part of the linguistic expression which is subject to some focus meaning. Second and third, there are the focus meanings and the array of structural devices that encode them. In a given language, the expression of focus is facilitated as well as constrained by the grammar within which the focus devices operate. The prevalence of focus ambiguity, the structural inability to make focus distinctions, will thus vary across languages, and within a language, across focus meanings

    Fermi Surface as a Driver for the Shape-Memory Effect in AuZn

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    Martensites are materials that undergo diffusionless, solid-state transitions. The martensitic transition yields properties that depend on the history of the material and may allow it to recover its previous shape after plastic deformation. This is known as the shape-memory effect (SME). We have succeeded in identifying the primary electronic mechanism responsible for the martensitic transition in the shape-memory alloy AuZn by using Fermi-surface measurements (de Haas-van Alphen oscillations) and band-structure calculations. This strongly suggests that electronic band structure is an important consideration in the design of future SME alloys

    Temporary use of shape memory spinal rod in the treatment of scoliosis

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    NiTinol shape memory alloy is characterized by its malleability at low temperatures and its ability to return to a preconfigured shape above its activation temperature. This process can be utilized to assist in scoliosis correction. The goal of this retrospective study was to evaluate the clinical and radiographic results of intraoperative use of shape memory alloy rod in the correction of scoliosis. From May 2002 to September 2006, 38 scoliosis patients (ranging from 50° to 120°; 22 cases over 70°) who underwent shape memory alloy-assisted correction in our institute were reviewed. During the operation, a shape memory alloy rod served as a temporary correction tool. Following correction, the rod was replaced by a rigid rod. The mean blood loss at surgery was 680 ± 584 ml; the mean operative time was 278 ± 62 min. The major Cobb angle improved from an average 78.4° preoperatively to 24.3° postoperatively (total percent correction 71.4%). In 16 patients with a major curve <70° and flexibility of 52.7%, the deformity improved from 58.4° preoperatively to 12.3° postoperatively (percent correction, 78.9%). In 22 patients with a major curve >70° and flexibility of 25.6%, the deformity improved from 94.1° preoperatively to 30.1° postoperatively (percent correction, 68.1%). Only one case had a deep infection. There were no neurologic, vascular or correction-related complications such as screw pullout or metal fracture. The study shows that the intraoperative use of a shape memory rod is a safe and effective method to correct scoliosis

    Curbside Recycling in the U.S.a.: Convenience and Mandatory Participation

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    This research examines the relationship between the success of a residential curbside recycling program (RCRP), measured as material recovery rate (MRR), and two program factors: (1) whether or not participation is mandated; and (2) convenience, measured by container provision, collection frequency and collection day relative to municipal solid waste collection day. Residential curbside recycling programs, with correct strategies and program design, can be an important part of solid waste management plans world-wide. While residential curbside recycling programs are growing in popularity, many basic design questions lie unanswered and successful program strategies are not always obvious. Data from 357 residential curbside recycling programs in the United States are used to test the hypotheses. Mandatory participation residential curbside recycling programs are seen to collect more material than voluntary participation residential curbside recycling programs. Container provision appears effective for voluntary, but not mandatory, residential curbside recycling programs. Increasing collection frequency appears to have a small positive effect on residential curbside recycling program success, while collection day has little effect on material recovery rate.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

    TOI-1268b: The youngest hot Saturn-mass transiting exoplanet

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    We report the discovery of TOI-1268b, a transiting Saturn-mass planet from the TESS space mission. With an age of less than 1 Gyr, derived from various age indicators, TOI-1268b is the youngest Saturn-mass planet known to date; it contributes to the small sample of well-characterised young planets. It has an orbital period of P = 8.1577080 \ub1 0.0000044 days, and transits an early K-dwarf star with a mass of M∗ = 0.96 \ub1 0.04 M+, a radius of R∗ = 0.92 \ub1 0.06 R+, an effective temperature of Teff = 5300 \ub1 100 K, and a metallicity of 0.36 \ub1 0.06 dex. By combining TESS photometry with high-resolution spectra acquired with the Tull spectrograph at the McDonald Observatory, and the high-resolution spectrographs at the Tautenburg and OndR ejov Observatories, we measured a planetary mass of Mp = 96.4 \ub1 8.3 Mp and a radius of Rp = 9.1 \ub1 0.6 Rp. TOI-1268 is an ideal system for studying the role of star-planet tidal interactions for non-inflated Saturn-mass planets. We used system parameters derived in this paper to constrain the planeta\u27s tidal quality factor to the range of 104.5-5.3. When compared with the sample of other non-inflated Saturn-mass planets, TOI-1268b is one of the best candidates for transmission spectroscopy studies

    Ionospheric gas dynamics of satellites and diagnostic probes

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    The gas dynamics of interactions of a tenuous ionosphere with moving satellites and probes that have bearings on the diagnostics of the ionosphere are discussed. Emphasis is on the cases where the body is moving at mesothermal speeds, namely intermediate between the thermal speeds of ions and electrons of the ambient ionosphere. Methods of collision-free plasma kinetics with self-consistent field are used. The development of the topics for discussion starts with stationary Langmuir probe which entails the basic mechanism of body-plasma interaction that becomes further intricated as the body moves at a higher and higher speed. Applications of the theory of plasma interaction to meteors which move in the ionosphere are also presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43801/1/11214_2004_Article_BF00212707.pd
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