12,108 research outputs found
Post-operative cranial pressure monitoring system
System for monitoring of fluidic pressures in cranial cavity uses a miniaturized pressure sensing transducer, combined with suitable amplification means, a meter with scale calibrated in terms of pressures between minus 100 and plus 900 millimeters of water, and a miniaturized chart recorder covering similar range of pressures
Studies of molecular properties of polymeric materials
Aerospace environment effects (high energy electrons, thermal cycling, atomic oxygen, and aircraft fluids) on polymeric and composite materials considered for structural use in spacecraft and advanced aircraft are examined. These materials include Mylar, Ultem, and Kapton. In addition to providing information on the behavior of the materials, attempts are made to relate the measurements to the molecular processes occurring in the material. A summary and overview of the technical aspects are given along with a list of the papers that resulted from the studies. The actual papers are included in the appendices and a glossary of technical terms and definitions is included in the front matter
Remote sensing of aquatic plants
Various sensors were tested in terms of their ability to detect and discriminate among noxious aquatic macrophytes. A survey of researchers currently studying the problem and a brief summary of their work is included. Results indicated that the sensor types best suited to assessment of the aquatic environment are color, color infrared, and black-and-white infrared film, which furnish consistently high contrasts between aquatic plants and their surroundings
Absorbed dose thresholds and absorbed dose rate limitations for studies of electron radiation effects on polyetherimides
The threshold values of total absorbed dose for causing changes in tensile properties of a polyetherimide film and the limitations of the absorbed dose rate for accelerated-exposure evaluation of the effects of electron radiation in geosynchronous orbit were studied. Total absorbed doses from 1 kGy to 100 MGy and absorbed dose rates from 0.01 MGy/hr to 100 MGy/hr were investigated, where 1 Gy equals 100 rads. Total doses less than 2.5 MGy did not significantly change the tensile properties of the film whereas doses higher than 2.5 MGy significantly reduced elongation-to-failure. There was no measurable effect of the dose rate on the tensile properties for accelerated electron exposures
Recent results and new hardware developments for protein crystal growth in microactivity
Protein crystal growth experiments have been performed on 16 space shuttle missions since April, 1985. The initial experiments utilized vapor diffusion crystallization techniques similar to those used in laboratories for earth-based experiments. More recent experiments have utilized temperature induced crystallization as an alternative method for growing high quality protein crystals in microgravity. Results from both vapor diffusion and temperature induced crystallization experiments indicate that proteins grown in microgravity may be larger, display more uniform morphologies, and yield diffraction data to significantly higher resolutions than the best crystals of these proteins grown on earth
Early stage morphology of quench condensed Ag, Pb and Pb/Ag hybrid films
Scanning Tunneling Microscopy (STM) has been used to study the morphology of
Ag, Pb and Pb/Ag bilayer films fabricated by quench condensation of the
elements onto cold (T=77K), inert and atomically flat Highly Oriented Pyrolytic
Graphite (HOPG) substrates. All films are thinner than 10 nm and show a
granular structure that is consistent with earlier studies of QC films. The
average lateral diameter, , of the Ag grains, however, depends on
whether the Ag is deposited directly on HOPG ( = 13 nm) or on a Pb
film consisting of a single layer of Pb grains ( = 26.8 nm). In
addition, the critical thickness for electrical conduction () of Pb/Ag
films on inert glass substrates is substantially larger than for pure Ag films.
These results are evidence that the structure of the underlying substrate
exerts an influence on the size of the grains in QC films. We propose a
qualitative explanation for this previously unencountered phenomenon.Comment: 11 pages, 3 figures and one tabl
A procedure for the change point problem in parametric models based on phi-divergence test-statistics
This paper studies the change point problem for a general parametric,
univariate or multivariate family of distributions. An information theoretic
procedure is developed which is based on general divergence measures for
testing the hypothesis of the existence of a change. For comparing the accuracy
of the new test-statistic a simulation study is performed for the special case
of a univariate discrete model. Finally, the procedure proposed in this paper
is illustrated through a classical change-point example
SDSS J092455.87+021924.9: an Interesting Gravitationally Lensed Quasar from the Sloan Digital Sky Survey
We report the discovery of a new gravitationally lensed quasar from the Sloan
Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was
selected from among known SDSS quasars by an algorithm that was designed to
select another known SDSS lensed quasar (SDSS 1226-0006A,B). Five separate
components, three of which are unresolved, are identified in photometric
follow-up observations obtained with the Magellan Consortium's 6.5m Walter
Baade telescope at Las Campanas Observatory. Two of the unresolved components
(designated A and B) are confirmed to be quasars with z=1.524; the velocity
difference is less than 100 km sec^{-1} according to spectra taken with the W.
M. Keck Observatory's Keck II telescope on Mauna Kea. A third stellar
component, designated C, has the colors of a quasar with redshift similar to
components A and B. The maximum separation of the point sources is 1.78". The
other two sources, designated G and D, are resolved. Component G appears to be
the best candidate for the lensing galaxy. Although component D is near the
expected position of the fourth lensed component in a four image lens system,
its properties are not consistent with being the image of a quasar at z~1.5.
Nevertheless, the identical redshifts of components A and B and the presence of
component C strongly suggest that this object is a gravitational lens. Our
observations support the idea that a foreground object reddens the fourth
lensed component and that another unmodeled effect (such as micro- or
milli-lensing) demagnificates it, but we cannot rule out the possibility that
SDSS0924+0219 is an example of the relatively rare class of ``three component''
lens systems.Comment: 24 pages, 6 figures, accepted by A
Annual Survey of Virginia Law: Property Law
While the Supreme Court of Virginia handed down decisions of significance dealing with the ownership and operation of real property in the Commonwealth during the past year, in most cases the court was content to apply well-settled law in new fact situations, or to extend the boundaries of such law gently into new territory. The General Assembly, for its part, spent most of its energy clarifying existing legislation or repairing portions of statutes which, either in operation or in prospect, needed relatively minor modifications. The foregoing statements are not intended to belittle the cases which were decided and the legislation which was enacted during the past year, the most significant parts of which are discussed in this article
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