3,839 research outputs found
Theoretical Problems in High Resolution Solar Physics, 2
The Science Working Group for the High Resolution Solar Observatory (HRSO) laid plans beginning in 1984 for a series of workshops designed to stimulate a broadbased input from the scientific community to the HRSO mission. These workshops have the dual objectives of encouraging an early start on the difficult theoretical problems in radiative transfer, magnetohydrodynamics, and plasma physics that will be posed by the HRSO data, and maintaining current discussions of results in high resolution solar studies. This workshop was the second in the series. The workshop format presented invited review papers during the formal sessions and contributed poster papers for discussions during open periods. Both are presented
A comparison of channel morphology, marsh elevation, and biological processes in natural and dredged tidal salt marshes in Louisiana
Channel networks in tidal marshes serve as conduits for the exchange of water between the estuary and the marsh surface and form the spatial structure that regulates the flow of organisms, materials, and energy throughout the marsh system. Canal dredging creates channels with distinct linear shapes, and the artificial levee created from the dredged material creates ‘spoil banks’ along either side of the channel edge. Differences in morphology and adjacent marsh surface elevation between natural and dredged channel systems have not been well quantified, but may have important implications for the functioning of tidal channels as habitat for marsh-dependent species. I used GIS methods commonly applied to terrestrial landscape patterns, Light Detection and Ranging (LiDAR) data, and aerial orthophotographs to examine differences in the shape complexity of natural and dredged channel networks and to compare the elevation of the marsh adjacent to natural and dredged channels and productive and non-productive oil and gas wells in a tidal salt marsh in Louisiana. I examined the distribution of Spartina alterniflora, Geukensia demissa demissa, and Littoraria irrorata in relation to channel morphology, soil properties and elevation of the marsh edge at natural creeks, dredged canals, and open bay edges in order to correlate landscape patterns with ecological processes. Dredged canal networks were significantly less complex in shape. The elevation of the marsh within 30 m of the channel edge was highest along dredged channels. The marsh at distances greater than 30 m from dredged canals appears to be more broken up, but not lower in elevation than in natural systems. Densities of S. alterniflora and G. demissa were lower, and soil and leaf nitrogen were less in marsh adjacent to dredged canals. The age distribution of G. demissa populations provided evidence that structural differences between natural creeks and dredged canal systems influence the recruitment, growth, and mortality of mussels. This work demonstrates that landscape scale changes to tidal marshes have the potential to alter ecological processes at the microhabitat scale. Dredged canals may reduce the growth and productivity of plants and animals that are critical to maintaining coastal Louisianans marshes
Rotator Cable Strain and the Abduction Force after Transection of the Cable Insertions
The goal of this study was to assess the functionality of the rotator cable in stress-shielding the rotator crescent region. The hypothesis was that releasing the rotator cable would significantly increase strain in the rotator crescent and significantly decrease abduction force.
Surface strain and abduction force were measured for 8 cadaveric specimens for three different states of the rotator cable: intact, anterior or posterior insertion released, and both anterior and posterior insertions released. A custom-built shoulder simulator applied a physiological loading pattern to the rotator cuff muscles to simulate abduction. For each cable state, the specimen was fixed in place at both 0 and 30 degrees of abduction. Four specific regions were analyzed for strain: two areas towards the center of the rotator crescent and an area on both the supraspinatus and infraspinatus tendons. Statistical analysis was performed with anterior and posterior separated and with the two groups combined comparing the intact state to the fully released state.
No significant change was found in major principal strain across any of the four regions or two abduction angles when analyzing both the anterior and posterior groups separated and combined. A significant increase in abduction force was found at 0 degrees of abduction when the groups were combined. No other significant changes in abduction force were found.
The increase in abduction force indicates that the rotator crescent area is a better abductor than the rotator cable and is not stress-shielded by the cable. The results of the strain analysis also demonstrate this by showing no significant change upon cable release. Therefore, the rotator cable should not be relied upon to shield tears in the rotator crescent, and these tears should be surgically repaired
Community Norms and Organizational Practices: The Legitimization of Wage Arrears in Russia, 1992-1999
What role do community norms play in the diffusion and persistence of new organizational practices? We explore this question through an examination of the widespread practice of wage arrears, the late and nonpayment of wages, in Russia during the 1990s. Existing research on wage arrears most often examines this practice as a means of flexible wage adjustment under difficult economic conditions. We develop an alternative theory that explains wage arrears through their acceptance as a legitimate form of organizational behavior within local communities. Our empirical analysis finds some support for the neoclassical position that wage arrears reflect adjustment to negative shocks, but this perspective fails to account for a number of important facts, including a high level of arrears among apparently successful firms. In contrast, our results find strong support for the institutional perspective. The statistical analysis demonstrates powerful and robust community effects both in firm adoption of this practice, controlling for firm performance, liquidity, and fixed firm effects, and in workers’ reaction to arrears, through their quit (exit) and strike (voice) behavior.institutions, norms, legitimacy, arrears, organizational practices, sociology, Russia
Community Norms and Organizational Practices: The Legitimization of Wage Arrears in Russia, 1992-1999
What role do community norms play in the diffusion and persistence of new organizational practices? We explore this question through an examination of the widespread practice of wage arrears, the late and nonpayment of wages, in Russia during the 1990s. Existing research on wage arrears most often examines this practice as a means of flexible wage adjustment under difficult economic conditions. We develop an alternative theory that explains wage arrears through their acceptance as a legitimate form of organizational behavior within local communities. Our empirical analysis finds some support for the neoclassical position that wage arrears reflect adjustment to negative shocks, but this perspective fails to account for a number of important facts, including a high level of arrears among apparently successful firms. In contrast, our results find strong support for the institutional perspective. The statistical analysis demonstrates powerful and robust community effects both in firm adoption of this practice, controlling for firm performance, liquidity, and fixed firm effects, and in workers' reaction to arrears, through their quit (exit) and strike (voice) behavior.institutions, norms, legitimacy, arrears, organizational practices, sociology, Russia
On the theory of coronal heating mechanisms
Theoretical models describing solar coronal heating mechanisms are reviewed in some detail. The requirements of chromospheric and coronal heating are discussed in the context of the fundamental constraints encountered in modelling the outer solar atmosphere. Heating by acoustic processes in the 'nonmagnetic' parts of the atmosphere is examined with particular emphasis on the shock wave theory. Also discussed are theories of heating by electrodynamic processes in the magnetic regions of the corona, either magnetohydrodynamic waves or current heating in the regions with large electric current densities (flare type heating). Problems associated with each of the models are addressed
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