6,453 research outputs found
Fluid injection device for high-pressure systems
Screw activated device, consisting of a compressor, shielded replaceable ampules, a multiple-element rubber gland, and a specially constructed fluid line fitting, injects measured amounts of fluids into a pressurized system. It is sturdy and easily manipulated
Gravitational instantons, extra dimensions and form fields
A broad class of higher dimensional instanton solutions are found for a
theory which contains gravity, a scalar field and antisymmetric tensor fields
of arbitrary rank. The metric used, a warp product of an arbitrary number of
any compact Einstein manifolds, includes many of great interest in particle
physics and cosmology. For example 4D FRW universes with additional dimensions
compactified on a Calabi-Yau three fold, a torus, a compact hyperbolic manifold
or a sphere are all included. It is shown that the solution of this form which
dominates the Hartle Hawking path integral is always a higher dimensional
generalisation of a Hawking Turok instanton when the potential of the scalar
field is such that these instantons can exist. On continuation to Lorentzian
signature such instantons give rise to a spacetime in which all of the spatial
dimensions are of equal size and where the spatial topology is that of a
sphere. The extra dimensions are thus not hidden. In the case where the
potential for the scalar field is generated solely by a dilatonic coupling to
the form fields we find no integrable instantons at all. In particular we find
no integrable solutions of the type under consideration for the supergravity
theories which are the low energy effective field theories of superstrings.Comment: 11 pages, 4 figure
How is a Closed String Loop like a Black Hole?
We demonstrate that under plausible assumptions the entropy and temperature
associated with the small oscillations on a circular loop of radius and a
black hole of mass are identical.Comment: 6 pages, uses harvma
Salt stabilizer for preventing chlorine depletion and increasing shelf-life of potable water - A concept
Proposed concept, based on law of mass action uses addition of salt to increase chlorine ions produced in sodium hydrochlorite solutions, thereby increasing solution shelf-life. This technique is not costly. Usefulness will be determined by acceptability of salt in product undergoing long shelf-life
Constraining the quintessence equation of state with SnIa data and CMB peaks
Quintessence has been introduced as an alternative to the cosmological
constant scenario to account for the current acceleration of the universe. This
new dark energy component allows values of the equation of state parameter
, and in principle measurements of cosmological distances to
Type Ia supernovae can be used to distinguish between these two types of
models. Assuming a flat universe, we use the supernovae data and measurements
of the position of the acoustic peaks in the Cosmic Microwave Background (CMB)
spectra to constrain a rather general class of Quintessence potentials,
including inverse power law models and recently proposed Supergravity inspired
potentials. In particular we use a likelihood analysis, marginalizing over the
dark energy density , the physical baryon density
and the scalar spectral index , to constrain the slopes of our Quintessence
potential. Considering only the first Doppler peak the best fit in our range of
models gives . However, including the SnIa data and the three
peaks, we find an upper limit on the present value of the equation of state
parameter, at , a result that appears to
rule out a class of recently proposed potentials.Comment: Accepted for pubblication in PRD, 7 pages, 6 figures. New revised
analysi
Environmental test planning, selection and standardization aids available
Requirements for instrumentation, equipment, and methods to be used in conducting environmental tests on components intended for use by a wide variety of technical personnel of different educational backgrounds, experience, and interests is announced
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