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This study examines the effect of online community's recognition on continued participation in idea competitions, and how personal winning record moderates such an influence. We reason that the motivating role of community recognition might either be reinforced or substituted by personal winning record, depending upon whether relational motives (psychological and social bonding) or individualistic motives (personal benefits, such as status and career enhancement) are the primary behavior driver. Through an event history analysis of data obtained from a platform of creative design contests, we find that although community recognition exerts a positive effect on the rate of continued participation for designers who are yet to win any competitions, this effect increasingly turns negative for designers who have won. Such findings indicate that the motivating role of community recognition might be substituted instead of reinforced by personal winning record, lending support to the individualistic view while rejecting the relational view. Although virtual social spaces represent an important means for modern competition platforms to attract and motivate participants, our study informs practitioners about online community's limitation in retaining “star” participants.

The original online version of this article was revised because a number of authors had the wrong affiliation number next to their names. © 2021, Springer Nature B.V.

Endovascular treatment for acute ischemic stroke has evolved in the past years. The current development of stent-retriever thrombectomy is a landmark in the clinical treatment and study results of acute ischemic stroke. This review summarizes the recent study results, elucidates the shortcomings of endovascular stroke treatment, and takes the opportunity for an outlook on the role of stroke interventions in the future.

著者人数: 23名, Accepted: 2006-01-05

Background: People who inject drugs are the group at greatest risk of hepatitis C virus (HCV) infection. The advent of new direct-acting antiviral (DAA) treatment provides opportunities for increased uptake of therapy. Methods: We conducted in-depth interviews with thirty HCV positive participants from the SuperMIX cohort study. Interviews were transcribed, coded, and analysed for emerging themes and similarities between participants. General descriptions and critical interpretation of themes were generated and selective quotes extracted verbatim to best illustrate the critical themes. Results: Participants described their experiences of living with HCV, their knowledge of HCV treatment accessibility, and information on the types of support ain themes: Understanding the need for treatment; Knowledge and framing of treatment access; and Support during treatment. Conclusion: The new, highly effective DAAs for the treatment of HCV are heralded as the potential beginning of HCV elimination, especially in settings where scale up is high. Our data from active PWID show that the availability of DAA medications in and of themselves is likely not to be enough to ensure that PWID will come forward for HCV treatment in sufficient numbers to drive elimination.

We present a surface constitutes arrays of periodic patches, which may serve as the metasurface to synthesize the Luneburg lens. The main purpose is by using different sizes of patches to achieve different refractive index at each stage, and get the proper function of Luneburg lens., QC 20160525

著者人数: 43名, Accepted: 2010-04-28

We present an alternate interpretation of recent STEREO/STE observations that were originally attributed to energetic neutral atoms (ENA) from the heliosheath. The signal attributed to the diffuse ENA source instead shows the characteristics of a point source. We point out that the peak intensity seen by STEREO/STE is centered at the ecliptic longitude of the bright X-ray source Sco X-1. The observed energy spectrum and intensity are also consistent with the X-rays from Sco X-1. The problem of energy dissipation at the solar wind termination shock remains unsolved while current understanding of the interaction between the solar wind and interstellar wind awaits future observations., Comment: Accepted by ApJL

We present an alternate interpretation of recent STEREO/STE observations that were originally attributed to energetic neutral atoms (ENA) from the heliosheath. The signal attributed to the diffuse ENA source instead shows the characteristics of a point source. We point out that the peak intensity seen by STEREO/STE is centered at the ecliptic longitude of the bright X-ray source Sco X-1. The observed energy spectrum and intensity are also consistent with the X-rays from Sco X-1. The problem of energy dissipation at the solar wind termination shock remains unsolved while current understanding of the interaction between the solar wind and interstellar wind awaits future observations., Comment: Accepted by ApJL

Infrared sensing in the two wavelength ranges (3-5 micrometers and 8-12 micrometers) has important military applications. Most commonly used detecting materials and devices are HgCdTe-based detectors and quantum-well infrared photodetectors (QWIP). Antimonide-based III-V materials also have potentials. To further realize a multi-wavelength imaging device, however, requires the integration of infrared photodetector array consisting of materials having different bandgap energies (usually having different lattice dimensions too). A major challenge arises - to obtain high-quality low-defect heteropitaxial layers.

The research program consists of formation of a strain-modulated amorphous template and selective area template with a strain-absorbing buried oxide layer formed by lateral oxidation, then develop a two-wavelength infrared imaging array in the 3-8 micron range by integrating InAs(x)Sb(1-x) PINs with GaAs driving electronic circuits.

Random walks on state space partitions provide an abstract generic picture for the description of macroscopic fluctuations in complex systems like proteins. We first determine the average residence probability and the average distribution of residence times in a particular macroscopic state for the ensemble of random partitions of a one-dimensional state space. We then extend our study to the Bethe lattice and also the 2-, 3- and higher dimensional lattices. Our treatment involves both extensive analytical and numerical analyses. Finally, we compare the solution of our model on the Bethe lattice with the experimental data and find excellent agreement.

Since the beginning of this project (10+ years ago) we have been concerned with quantum well heterostructures (QWHs) and their use in advanced forms of lasers, light emitting diodes (LEDs), and more generally in optoelectronics. This has led us into a wide range of studies and discoveries, including the commercially important process (patented) of impurity-induced layer disordering (which can be employed to change a QWH, in whatever pattern desired, from QW lower gap to bulk-crystal higher energy band gap).

Measurements of the hole density in heavily carbon-doped GaAs and A1x,Gal-xAs as a function of the annealing temperature are presented. It is shown that the hole density increases and the hole mobility decreases after annealing at low temperatures (T < 550 deg C). However, higher annealing temperatures (T > 600 deg C) result in a reduction of the hole concentration reaching a maximum carrier concentration of = 5 x 1019 cm-3. These changes observed in the electrical properties can be explained by two mechanisms: (1) the passivation of carbon acceptors by hydrogen incorporated during growth; and (2) the change in the lattice site location of carbon atoms, which is dependent on the total carbon concentration.

For some time interests have been aroused by the III-V quantum well heterostructures (QWHs) and superlattices (SLs) and, in addition to fundamental effects, the special opportunities QWHs and SLs afford in making possible improved forms of lasers, not to mention other devices and optoelectronic systems. In this report, studies have been made of: (1) Al(x)Ga(1-x)As-GaAs lasers on Si, (2) impurity induced layer disordering (which is an especially advantageous phenomenon in QWHs and SLs), (3) phonon-assisted laser operation and its unambiguous identification by control of the cavity Q of QWH samples, (4) the use of cavity Q to fill the recombination spectrum of QWHs, and (5) hydrolization and reliability of Al(x)Ga(1-x)As-GaAs QWHs and SLs, and (6) various other laser problems associated with higher gap crystals such as In(y) (Al(x)Ga(1-x)(1-y)P. Keywords: Lasers; Silicon; Semiconductors.

Interior ballistic performance of unslotted single-perforated stick propellants in a large-caliber gun could be influenced significantly by the erosive burning effect. To analyze erosive burning phenomena, a comprehensive model, with special emphasis on the interaction of turbulence and combustion, has been formulated. Experimentally, a test rig using a center-perforated cylindrical propellant grain with large web thickness (approx. 1.0 cm) was designed, constructed, and tested. The location of the instantaneous propellant burning surface was determined by the use of real time X-ray radiography. Based upon X-ray images, the instantaneous burning rate of NOSOL-363 stick propellant was found to be much higher (up to 3.2 times) than the strand burning rate under strong cross-flow conditions. Keywords: Erosive burning, Stick propellant, Theoretical modeling, Experimental measurements, k-epsilon turbulent closure, Two-variable joint probability density function, Real-time x-ray radiography.

A comprehensive theoretical model has been formulated for studying the degree of vulnerability of various solid propellants being heated by hot spall fragments. The model stimulates the hot fragment conductive ignition (HFCI) processes caused by direct contact of hot inert particles with solid propellant samples. The model describes the heat transfer and displacement of the hot particle, the generation of the melt (or foam) layer caused by the liquefaction, pyrolysis, and decompression of the propellant, and the regression of the propellant as well as the time variation of its temperature distributions. To partially validate the theoretical model in the absence of the necessary chemical kinetic data, an ice-melting and evaporation experiment was designed and conducted. These experiments provide features of the conductive heating, melting, and evaporating process. Calculated results compare well with experimental data in temperature-time traces, spall particles-sinking velocity, and displacement.

Although an ultimate goal of this work is to achieve long term reliable laser operation of Al(x)Ga(1-x)As-GaAs quantum well heterostructures (QWH's), or similar III-V QWH's, grown on Si, this has proven to be a formidable enough problem that to the best of our knowledge no one has exceeded the results we reported in 1987 and 1988. This problem is of such dimensions that it may not be solved for as much as 10 years, or even more All we know so far is that continuous (cw) 300 K Al(x)Ga(1-x)As-GaAs QWH lasers can be grown on Si, and that, indeed, the heat sinking of an Al(x)Ga(1-x)As-GaAs QWH laser on Si is better than a similar laser on a GaAs substrate. Nevertheless, the problem of growing better versions of these devices (i.e., long-lived high performance cw 300 K lasers on Si) has run into the fundamental issue of the large GaAs-Si lattice and thermal expansion mismatch, and hence the built-in difficulty in reducing the defects guaranteed by mismatch. Accordingly, and as much as we have worked further on the problem of Al(x)Ga(1-x)As-GaAs QWH lasers on Si, we have worked as hard on other QWH laser problems, as well as a impurity-induced layer disordering (or layer intermixing, IILD) and its application in laser devices. We briefly describe this work below and append the titles and abstracts of the papers we have published on laser studies and IILD. (RH)

The research goal is to further develop quantum well heterostructure (QWH) lasers and to realize reliable Al(x)Ga(1-x)As-GaAs QWH lasers on Si. In spite of the significant lattice and thermal expansion mismatch between GaAs and Si, the idea of splicing III-V semiconductor technology, i.e., optoelectronics and photonics, onto Si has obvious appeal. Adding to this is the fact, as shown earlier in this work, that cw 300 K Al(x)Ga(1-x)As-GaAs QWH lasers can be grown on Si, and that the Si substrate serves as a better heat sink than GaAs. This makes possible the right-side-up heat sinking needed for electronic-photonic integrated circuits. This report contains research results on quantum well heterostructures on Si, impurity-induced layer disordering, phonon-assisted laser operations and other laser studies. (jhd)

Progress is reported on research in molecular physics involving electron-bombardment molecular dissociation. The velocity distribution of metastable and ionic fragments are measured using a pulsed electron beam and a time-of-flight technique. During the past year, experiments involving detection of ionic fragments from the hydrogen halides and acytelene have been underway. The velocity spectrum of protons resulting from dissociation of the hydrogen halides show several distinct features, and attempts are presently being made to assign these features to particular molecular states. Measurements to determine electron bombardment threshold energies for these features have been made and should help in confirming such assignments. Several different ionic fragments have been detected from the dissociation of acytelene. A mass filter is used in these experiments to obtain velocity spectra of each mass species separately. (Author)

This study addressed the problem of water vapor production and distribution in comet P/Halley, based upon interpretation of observational data obtained during the recent 1985-86 apparition. The data was acquired using the Lunar and Planetary Laboratory charge-coupled device (CCD) on the 154-cm Catalina telescope of the University of Arizona Observatories. Our data acquisition system was employed in two modes. The long-slit (∼200") spectroscopy mode covered the wavelength range 5200-10400 Å at a spectral resolution ∼14 Å. The narrow band filter imaging mode allowed two-dimensional mapping of selected cometary emission features, as well as the continuum, with a field of view of roughly 10 arc-min. Both neutral and ionized (H₂O⁺) water species were studied, with emphasis on the ion distribution. This involved comparing long-slit spatial profiles obtained ∼UT 1986 March 05.5, as well as cuts across filter images (∼ March 06.5) centered on the H₂O⁺ 0,8,0-band emission, with the Vega-1 spacecraft in situ ion density measurements (∼ March 06.3). Our March 05 spectroscopic data revealed a central dip, of order 30% relative to the profile peak, in H₂O⁺ column density in the inner coma (inside ∼ 2 x 10⁴ km from the nucleus), which filled in farther tailward. Similarly the BD - 3 plasma detector aboard Vega-1 measured a decrease in local ion density, of roughly 60% at the closest approach distance (∼ 9000 km sunward of the nucleus), relative to the inbound maximum density at R ≃ 12000 km from the nucleus. These results suggest a bimodal flow of ions out of the coma and/or an extended region over which the H₂0 molecules were being ionized. Our imaging data showed that, while the falloff in ion density was relatively rapid sunward of the nucleus, it was much more gradual in the anti-solar direction. This is due to the solar wind sweeping ions from the head of the comet into the plasma tail, whose width was of order 10⁵ km in the inner coma, diverging slowly and breaking up into

A two fluid hydrodynamical model describing the modification of a stellar wind flow due to its interaction with galactic cosmic-rays is investigated. The two fluids consist of the thermal stellar wind gas and the galactic cosmic-rays. A polytropic one fluid model is used to describe the stellar wind gas, and the cosmic-rays modify the wind via their pressure gradient. The cosmic-rays are considered to be a hot low density gas of negligible mass flux, but with a significant pressure and energy flux compared to the thermal gas. The equations used are essentially those employed in two fluid hydrodynamical models of cosmic-ray shock acceleration by the first order Fermi mechanism, but suitably modified to apply in a spherical geometry and including the effects of gravity on the flow. The stellar wind consists of a transonic flow with a termination shock, and subsonic flow outside the shock. The model shows the deceleration of the wind upstream of the shock by the positive galactic cosmic-ray pressure gradient. The dissertation first discusses the fluid polytropic stellar winds and how to insert shocks in the flow. The hydrodynamical equations governing cosmic-ray modified winds are then introduced followed by a discussion of the physics of the interaction between the thermal stellar wind and the cosmic-rays. A description of the singularities of the equations is also presented. The system of equations is first solved by a finite difference method in the test particle approximation in which the cosmic-rays do not modify the flow, with appropriate boundary conditions applied at infinity, at the wind termination shock, and at the star. A perturbation scheme to determine the modification of the wind by the cosmic-rays is then developed. This scheme applies when the modification of the wind by the cosmic-rays is sufficiently small. Finally a numerical iteration is employed to exactly solve the equations. This latter method has the advantage that it can be applied when there

Endovascular treatment for acute ischemic stroke has evolved in the past years. The current development of stent-retriever thrombectomy is a landmark in the clinical treatment and study results of acute ischemic stroke. This review summarizes the recent study results, elucidates the shortcomings of endovascular stroke treatment, and takes the opportunity for an outlook on the role of stroke interventions in the future.