35,449 research outputs found
Passively regulated water electrolysis rocket engine Patent
Water electrolysis rocket engine with self- regulating stoichiometric fuel mixing regulato
Fluid flow meter with comparator reference means Patent
Photometric flow meter with comparator reference mean
Precision thrust gage Patent
Development of temperature compensated thrust measuring gage for measuring forces as function of time in environment with varying temperatur
Electromechanical flowmeter accurately monitors fluid flow
Electromechanical flowmeter remotely and accurately monitors the flow rate and total volume of a transparent liquid discharged from a dispensing system. A dual dispensing tube system provides a relative reference level which permits compensation for temperature variations
Jumping bristletail (Insecta: Apterygota: Microcoryphia) records in the southeastern United States
Few records of Microcoryphia exist for the southeastern United States, with named species being reported only from Arkansas, Tennessee, and the mid-Atlantic states, and with an unnamed species being reported from Georgia. Records are here provided from 291 specimens housed in the Mississippi Entomological Museum, including ten new species-level state records. This is also the first published report of the order Microcoryphia from Alabama and Mississippi. Species include the machilids Pedetontoides atlanticus Mendes in Alabama, Arkansas, Georgia, Mississippi, and North Carolina; Pedetontus cf. atlanticus in Kentucky; Pedetontus (Verhoeffilis) gershneri Allen in Arkansas; and Pedetontus (Pedetontus) saltator Wygodzinsky and Schmidt in Mississippi and North Carolina; and the meinertellid Machiloides banksi (Silvestri) in Alabama, Arkansas, Mississippi, and North Carolina
Lsdiff M and the Einstein Equations
We give a formulation of the vacuum Einstein equations in terms of a set of
volume-preserving vector fields on a four-manifold . These vectors
satisfy a set of equations which are a generalisation of the Yang-Mills
equations for a constant connection on flat spacetime.Comment: 5 pages, no figures, Latex, uses amsfonts, amssym.def and amssym.tex.
Note added on more direct connection with Yang-Mills equation
Cosmic Strings and Chronology Protection
A space consisting of two rapidly moving cosmic strings has recently been
constructed by Gott that contains closed timelike curves. The global structure
of this space is analysed and is found that, away from the strings, the space
is identical to a generalised Misner space. The vacuum expectation value of the
energy momentum tensor for a conformally coupled scalar field is calculated on
this generalised Misner space. It is found to diverge very weakly on the
Chronology horizon, but more strongly on the polarised hypersurfaces. The
divergence on the polarised hypersurfaces is strong enough that when the proper
geodesic interval around any polarised hypersurface is of order the Planck
length squared, the perturbation to the metric caused by the backreaction will
be of order one. Thus we expect the structure of the space will be radically
altered by the backreaction before quantum gravitational effects become
important. This suggests that Hawking's `Chronology Protection Conjecture'
holds for spaces with non-compactly generated Chronology horizon.Comment: 15 pages, plain TeX, 2 figures (not included), DAMTP-R92/3
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