6,035 research outputs found
Discussion of the selection and use of teaching aids and standard materials in the lower school at Perkins School for the Blind
Thesis (Ed.M.)--Boston Universit
Stress condensation in crushed elastic manifolds
We discuss an M-dimensional phantom elastic manifold of linear size L crushed
into a small sphere of radius R << L in N-dimensional space. We investigate the
low elastic energy states of 2-sheets (M=2) and 3-sheets (M=3) using analytic
methods and lattice simulations. When N \geq 2M the curvature energy is
uniformly distributed in the sheet and the strain energy is negligible. But
when N=M+1 and M>1, both energies appear to be condensed into a network of
narrow M-1 dimensional ridges. The ridges appear straight over distances
comparable to the confining radius R.Comment: 4 pages, RevTeX + epsf, 4 figures, Submitted to Phys. Rev. Let
Molecular line mapping of the giant molecular cloud associated with RCW 106 - II. Column density and dynamical state of the clumps
We present a fully sampled C^{18}O (1-0) map towards the southern giant
molecular cloud (GMC) associated with the HII region RCW 106, and use it in
combination with previous ^{13}CO (1-0) mapping to estimate the gas column
density as a function of position and velocity. We find localized regions of
significant ^{13}CO optical depth in the northern part of the cloud, with
several of the high-opacity clouds in this region likely associated with a
limb-brightened shell around the HII region G333.6-0.2. Optical depth
corrections broaden the distribution of column densities in the cloud, yielding
a log-normal distribution as predicted by simulations of turbulence.
Decomposing the ^{13}CO and C^{18}O data cubes into clumps, we find relatively
weak correlations between size and linewidth, and a more sensitive dependence
of luminosity on size than would be predicted by a constant average column
density. The clump mass spectrum has a slope near -1.7, consistent with
previous studies. The most massive clumps appear to have gravitational binding
energies well in excess of virial equilibrium; we discuss possible
explanations, which include magnetic support and neglect of time-varying
surface terms in the virial theorem. Unlike molecular clouds as a whole, the
clumps within the RCW 106 GMC, while elongated, appear to show random
orientations with respect to the Galactic plane.Comment: 17 pages, to appear in MNRA
On Pair Production in the Crab Pulsar
We consider the widespread assumption that coherent pulsar radio emission is
based on extended pair production leading to plasma densities highly exceeding
the Goldreich-Julian density. We show as an example that the observed low
frequency (160 MHz) emission of the Crab pulsar is incompatible to the model of
extended pair production. Our results rule out significant pair production if a
plasma process is responsible for coherence and the radio emission originates
from inside the light cylinder.Comment: accepted for publication in ApJ Letters; 4 pages, no figure
Business Warehouse Modeling Using SAP: Simulating A Business Case To Apply Strategic Enterprise Management To Accounting
The goal of this research project is to develop a simulation model specifically for the Management Accounting Information Systems course – an SAP enabled course for junior Accounting majors at Saint Joseph's University. The purpose of this simulation is to present students with a set of business scenarios, and have the students make a knowledgeable decision using SAP Business Warehouse software. The scenarios will act as a simplified replication of the business environment; thus, they will provide the students with an integrated learning experience. They will make business decisions to ensure the profitability and cash flow of a corporation. While making these decisions, students participate in the application and analysis provided by PC4YOU, which is a simulated company within SAP for demonstration and education purposes. Eventually, the students will need to justify the existence of their strategic plans by evaluating benefits of the system using the reporting tools available within SAP. To provide a “learning by doing” experience, the scenarios will be used to demonstrate the reporting functionality within PC4YOU, the simulated company integrated into the SAP SEM system. Today’s global economy is putting a premium on the ability of students to evaluate a broad range of decisions in collaboration with adaptive supply chains. A critical component of the evolving accounting curriculum lies in the ability to extend students beyond the numbers to evaluate the effective and efficient delivery of these supply chains
Discrimination of Vaccinated and infected Pigs by Salmonella-specific IGa antibodies
Isotype switching from IgM to IgG or IgA leads to generation of high affinity antibodies during the immune response. This phenomenon can be applied for differentiation of early and late infection stages. The purpose of this study was to evaluate the applicability of a newly developed Ig-isotype specific Salmonella antibody ELISA for discrimination between vaccinated and infected pigs. Using this novel ELISA we were able to detect different patterns of Salmonella-specific IgM, IgG and IgA antibodies following immunization with a S. Typhimurium live vaccine or after experimental infection with a nalidixic-acid resistant wild-type strain of S. Typhimurium. Interestingly, Salmonella-specific IgA antibodies represented an excellent tool for the recognition of fresh infection in vaccinated pigs. Under SPF conditions, we were able to discriminate between naive, vaccinated, experimentally infected nonvaccinated, and experimentally infected vaccinated animals. However, the highest specific IgA levels were detected in challenged vaccinated pigs. Preliminary results from field trials support the findings from experiments using SPF animals
G_2 Perfect-Fluid Cosmologies with a proper conformal Killing vector
We study the Einstein field equations for spacetimes admitting a maximal
two-dimensional abelian group of isometries acting orthogonally transitively on
spacelike surfaces and, in addition, with at least one conformal Killing
vector. The three-dimensional conformal group is restricted to the case when
the two-dimensional abelian isometry subalgebra is an ideal and it is also
assumed to act on non-null hypersurfaces (both, spacelike and timelike cases
are studied). We consider both, diagonal and non-diagonal metrics and find all
the perfect-fluid solutions under these assumptions (except those already
known). We find four families of solutions, each one containing arbitrary
parameters for which no differential equations remain to be integrated. We
write the line-elements in a simplified form and perform a detailed study for
each of these solutions, giving the kinematical quantities of the fluid
velocity vector, the energy-density and pressure, values of the parameters for
which the energy conditions are fulfilled everywhere, the Petrov type, the
singularities in the spacetimes and the Friedmann-Lemaitre-Robertson-Walker
metrics contained in each family.Comment: Latex, no figure
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