3,951 research outputs found
Recommended from our members
Vendor and Professional Certification Where is it Headed?
Trade journals and magazines define three categories of computer certification: professional, industry, and vendor. The purpose of this study was to compare Information Systems IS) professionals\u27 value of professional and vendor certification types in relation to technical and management positions in IS. It appears that IS professionals value both certification types equally when not considering job position. Findings suggest technical and managerial IS professionals value the two types of certifications differently when job position is considered. Future research is warranted to determine why the respondents considered these two certifications differently for both technical (programmers and analysts) and managerial positions
Magnetic Braking and Viscous Damping of Differential Rotation in Cylindrical Stars
Differential rotation in stars generates toroidal magnetic fields whenever an
initial seed poloidal field is present. The resulting magnetic stresses, along
with viscosity, drive the star toward uniform rotation. This magnetic braking
has important dynamical consequences in many astrophysical contexts. For
example, merging binary neutron stars can form "hypermassive" remnants
supported against collapse by differential rotation. The removal of this
support by magnetic braking induces radial fluid motion, which can lead to
delayed collapse of the remnant to a black hole. We explore the effects of
magnetic braking and viscosity on the structure of a differentially rotating,
compressible star, generalizing our earlier calculations for incompressible
configurations. The star is idealized as a differentially rotating, infinite
cylinder supported initially by a polytropic equation of state. The gas is
assumed to be infinitely conducting and our calculations are performed in
Newtonian gravitation. Though highly idealized, our model allows for the
incorporation of magnetic fields, viscosity, compressibility, and shocks with
minimal computational resources in a 1+1 dimensional Lagrangian MHD code. Our
evolution calculations show that magnetic braking can lead to significant
structural changes in a star, including quasistatic contraction of the core and
ejection of matter in the outermost regions to form a wind or an ambient disk.
These calculations serve as a prelude and a guide to more realistic MHD
simulations in full 3+1 general relativity.Comment: 20 pages, 19 figures, 3 tables, AASTeX, accepted by Ap
Non-symmetric liquid crystal dimer containing a carbohydrate-based moiety
Peer reviewedPublisher PD
Recommended from our members
Internet Technology in 2010: The Issue of IPv6 Adoption in the U.S.A.
Computer industry literature suggests that IPv4 Internet addresses are likely to have been depleted by the year 2010, and at least Asia and Europe will be using the new IPv6 Internet addresses. Literature also suggests that the U.S.A. is lagging behind Asia and Europe with the implementation of IPv6. Empirical data supporting the fact that the U.S.A. is lagging behind is not available in the literature. This paper presents the issues regarding IPv6, reasons why Asia and Europe are implementing IPv6, and why the U.S.A. is lagging behind. Empirical data is presented to support the literatureâs suggestion that the U.S.A. is lagging behind. The consequences of this inactivity regarding the implementation of IPv6 by the U.S.A. are discussed
Structure and Dynamics of Metalloproteins in Live Cells
X-ray absorption spectroscopy (XAS) has emerged as one of the premier tools for investigating the structure and dynamic properties of metals in cells and in metal containing biomolecules. Utilizing the high flux and broad energy range of X-rays supplied by synchrotron light sources, one can selectively excite core electronic transitions in each metal. Spectroscopic signals from these electronic transitions can be used to dissect the chemical architecture of metals in cells, in cellular components and in biomolecules at varying degrees of structural resolution. With the development of ever-brighter X-ray sources, X-ray methods have grown into applications that can be utilized to provide both a cellular image of relative distribution of metals throughout the cell as well as a high-resolution picture of the structure of the metal. As these techniques continue to grow in their capabilities and ease of use, so to does the demand for their application by chemists and biochemists interested in studying the structure and dynamics of metals in cells, in cellular organelles and in metalloproteins
What is the location and extent of pathology in surgical cases of chronic biceps tendinopathy undergoing subpectoral bicep tenodesis?
The proximal aspect of the long head of the biceps brachii (LHBB) has long been implicated as a pain generator in the shoulder. Biceps tenodesis is one surgical treatment option for refractory biceps tendonitis. The purpose of this study was to examine the tendinopathic changes in the intra-articular segment of long head of the biceps tendon as well as all three zones of the bicipital tunnel in a cohort of patients with chronic refractory biceps symptoms
Recommended from our members
A comparison of times series approaches for dendroecological reconstructions of past canopy disturbance events
Time series analysis can identify outliers in tree-ring widths that may not only indicate past disturbances, but may also estimate the subsequent effects of these disturbances on tree growth. Finding a way to isolate these disturbance signals from tree-ring time series could have broad applications in forest ecology and management. Time series outliers may be expressed as pulse, step, or trend interventions, but few dendroecological studies have explored how well these different types of interventions express the response of tree-ring widths to a canopy disturbance resulting in a release event. This study addresses that question by comparing two different time series approaches for detecting release events: a pulse intervention approach and a new combined step and trend (CST) intervention approach. These methods are tested against tree-ring collections with known historical canopy disturbance events: northern red oaks (Quercus rubra) in New York released by the chestnut blight during the early 1920s, eastern hemlocks (Tsuga canadensis) in Pennsylvania released by adjacent selective logging in 1910, and northern red oaks and chestnut oaks (Quercus montana) in West Virginia released through an experimental thinning in 1982. Clusters of CST interventions, but not pulse interventions, were detected for all three collections during and immediately after the known disturbance events, showing that a CST intervention approach consistently reconstructs these release events. In addition, a CST intervention approach isolated canopy disturbance signals from tree-ring widths as disturbance-growth indices. Detrending disturbances from tree-ring widths provides an alternative approach to reconstruct climate in closed-canopy forests; however, just as importantly, disturbance-growth indices created through this method can also reconstruct changes in tree growth rates, biomass, or carbon resulting from a past disturbance event or forest thinning
- âŠ