5,493 research outputs found
Sequence distribution studies of dichloroprotoanemonin-methyl methacrylate copolymers
Chloride elimination and ultraviolet bands in dichloroprotoanemonin/methyl methacrylate copolymer
Diagnostic procedures for antenna hydraulic drive systems
Diagnostic, testing, and maintenance procedures for hydraulic drive systems for large steerable antenna
Physical Capital and Capital Service Costs in U.S. Colleges and Universities: 1993
Physical capital represents an important input to the production of higher education--the essential services of buildings, equipment, and land--for which we have only highly inadequate measures. This paper has three objectives: to report estimates of the value of the capital stocks used by 3,148 colleges and universities in the US in 1993 (virtually all of them), to give a sense of the distribution of that physical capital and of capital service costs among different kinds of institutions, and to make these estimates available to other students of higher education in the form of FoxPro or Excel files.Education
Optimal Scheduling Using Branch and Bound with SPIN 4.0
The use of model checkers to solve discrete optimisation problems is appealing. A model checker can first be used to verify that the model of the problem is correct. Subsequently, the same model can be used to find an optimal solution for the problem. This paper describes how to apply the new PROMELA primitives of SPIN 4.0 to search effectively for the optimal solution. We show how Branch-and-Bound techniques can be added to the LTL property that is used to find the solution. The LTL property is dynamically changed during the verification. We also show how the syntactical reordering of statements and/or processes in the PROMELA model can improve the search even further. The techniques are illustrated using two running examples: the Travelling Salesman Problem and a job-shop scheduling problem
Satellite laser ranging work at the Goddard Space Flight Center
Laser ranging systems, their range and accuracy capabilities, and planned improvements for future systems are discussed, the systems include one fixed and two mobile lasers ranging systems. They have demonstrated better than 10 cm accuracy both on a carefully surveyed ground range and in regular satellite ranging operations. They are capable of ranging to all currently launched retroreflector equipped satellites with the exception of Timation III. A third mobile system is discussed which will be accurate to better than 5 cm and will be capable of ranging to distant satellites such as Timation III and LAGEOS
Spitzer Observations of NGC 1333: A Study of Structure and Evolution in a Nearby Embedded Cluster
We present a comprehensive analysis of structure in the young, embedded
cluster, NGC 1333 using members identified with Spitzer and 2MASS photometry
based on their IR-excess emission. In total, 137 members are identified in this
way, composed of 39 protostars and 98 more evolved pre-main sequence stars with
disks. Of the latter class, four are transition/debris disk candidates. The
fraction of exposed pre-main sequence stars with disks is 83% +/- 11%, showing
that there is a measurable diskless pre-main sequence population. The sources
in each of the Class I and Class II evolutionary states are shown to have very
different spatial distributions relative to the distribution of the dense gas
in their natal cloud. However, the distribution of nearest neighbor spacings
among these two groups of sources are found to be quite similar, with a strong
peak at spacings of 0.045 pc. Radial and azimuthal density profiles and surface
density maps computed from the identified YSOs show that NGC 1333 is elongated
and not strongly centrally concentrated, confirming previous claims in the
literature. We interpret these new results as signs of a low velocity
dispersion, extremely young cluster that is not in virial equilibrium.Comment: 59 pages, 20 figures, accepted to ApJ, verion with full resolution
figures available at
http://www.cfa.harvard.edu/~rgutermuth/preprints/gutermuth_ngc1333.pdf .
Updated to fix astro-ph figure garblin
Creation and Reproduction of Model Cells with Semipermeable Membrane
A high activity of reactions can be confined in a model cell with a
semipermeable membrane in the Schl\"ogl model. It is interpreted as a model of
primitive metabolism in a cell. We study two generalized models to understand
the creation of primitive cell systems conceptually from the view point of the
nonlinear-nonequilibrium physics. In the first model, a single-cell system with
a highly active state confined by a semipermeable membrane is spontaneously
created from an inactive homogeneous state by a stochastic jump process. In the
second model, many cell structures are reproduced from a single cell, and a
multicellular system is created.Comment: 11 pages, 7 figure
Background independence in a nutshell
We study how physical information can be extracted from a background
independent quantum system. We use an extremely simple `minimalist' system that
models a finite region of 3d euclidean quantum spacetime with a single
equilateral tetrahedron. We show that the physical information can be expressed
as a boundary amplitude. We illustrate how the notions of "evolution" in a
boundary proper-time and "vacuum" can be extracted from the background
independent dynamics.Comment: 19 pages, 19 figure
The Properties of X-ray Luminous Young Stellar Objects in the NGC 1333 and Serpens Embedded Clusters
We present Chandra X-ray data of the NGC 1333 embedded cluster, combining
these data with existing Chandra data, Sptizer photometry and ground based
spectroscopy of both the NGC 1333 & Serpens North clusters to perform a
detailed study of the X-ray properties of two of the nearest embedded clusters
to the Sun. In NGC 1333, a total of 95 cluster members are detected in X-rays,
of which 54 were previously identified with Spitzer. Of the Spitzer sources, we
detect 23% of the Class I protostars, 53% of the Flat Spectrum sources, 52% of
the Class II, and 50% of the Transition Disk YSOs. Forty-one Class III members
of the cluster are identified, bringing the total identified YSO population to
178. The X-ray Luminosity Functions (XLFs) of the NGC 1333 and Serpens clusters
are compared to each other and the Orion Nebula Cluster. Based on this
comparison, we obtain a new distance for the Serpens cluster of 360+22/-13 pc.
The X-ray luminosity was found to depend on the bolometric luminosity as in
previous studies of other clusters, and that Lx depends primarily on the
stellar surface area. In the NGC 1333 cluster, the Class III sources have a
somewhat higher X-ray luminosity for a given surface area. We also find
evidence in NGC 1333 for a jump in the X-ray luminosity between spectral types
of M0 and K7, we speculate that this may result from the presence of radiative
zones in the K-stars. The gas column density vs. extinction in the NGC 1333 was
found to be N_H = 0.89 +/- 0.13 x 10^22 A_K, this is lower than expected of the
standard ISM but similar to that found previously in the Serpens Cloud Core.Comment: 58 pages, 14 figures, accepted by A
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