3,206 research outputs found
Mass spectrometric determination of the composition of the Venus clouds
The instrumentation is analyzed for determining the composition of the clouds on Venus. Direct analysis of the gas phase atmosphere, and the detection of ferrous chloride with a mass spectrometer are dicussed along with the mass analyzer, and the pre-separation of cloud particles from the ambient atmosphere
Lunar lander mass spectrometer Final report
Sputter ion source for lunar lander mass spectromete
Sputtering ion source Final report, 29 Mar. - 30 Sep. 1963
Modified sputtering ion source analyses of solid
Mass spectrometer analysis of solid materials with the ion-microprobe sputter source
Sputter ion source mass spectrometer for analysis of solid material
The 10Be contents of SNC meteorites
Several authors have explored the possibility that the Shergottites, Nakhlites, and Chassigny (SNC) came from Mars. The spallogenic gas contents of the SNC meteorites have been used to: constrain the sizes of the SNC's during the last few million years; to establish groupings independent of the geochemical ones; and to estimate the likelihood of certain entries in the catalog of all conceivable passages from Mars to Earth. The particular shielding dependence of Be-10 makes the isotope a good probe of the irradiation conditions experienced by the SNC meteorites. The Be-10 contents of nine members of the group were measured using the technique of accelerator mass spectrometry. The Be-10 contents of Nakhla, Governador Valadares, Chassigny, and probably Lafayette, about 20 dpm/kg, exceed the values expected from irradiation of the surface of a large body. The Be-10 data therfore do not support scenario III of Bogard et al., one in which most of the Be-10 in the SNC meteorites would have formed on the Martian surface; they resemble rather the Be-10 contents found in many ordinary chondrites subjected to 4 Pi exposures. The uncertainties of the Be-10 contents lead to appreciable errors in the Be-10 ages, t(1) = -1/lambda ln(1 Be-10/Be-10). Nonetheless, the Be-10 ages are consistent with the Ne-21 ages calculated assuming conventional, small-body production rates and short terrestrial ages for the finds. It is believed that this concordance strengthens the case for at least 3 different irradiation ages for the SNC meteorites. Given the similar half-thicknesses of the Be-10 and Ne-21 production rates, the ratios of the Be-10 and Ne-21 contents do not appear consistent with common ages for any of the groups. In view of the general agreement between the Be-10 and Ne-21 ages it does not seem useful at this time to construct multiple-stage irradiation histories for the SNC meteorites
Betti numbers for numerical semigroup rings
We survey results related to the magnitude of the Betti numbers of numerical
semigroup rings and of their tangent cones.Comment: 22 pages; v2: updated references. To appear in Multigraded Algebra
and Applications (V. Ene, E. Miller Eds.
Gauge/Gravity Duality and Warped Resolved Conifold
We study supergravity backgrounds encoded through the gauge/string
correspondence by the SU(N) \times SU(N) theory arising on N D3-branes on the
conifold. As discussed in hep-th/9905104, the dynamics of this theory describes
warped versions of both the singular and the resolved conifolds through
different (symmetry breaking) vacua. We construct these supergravity solutions
explicitly and match them with the gauge theory with different sets of vacuum
expectation values of the bi-fundamental fields A_1, A_2, B_1, B_2. For the
resolved conifold, we find a non-singular SU(2)\times U(1)\times U(1) symmetric
warped solution produced by a stack of D3-branes localized at a point on the
blown-up 2-sphere. It describes a smooth RG flow from AdS_5 \times T^{1,1} in
the UV to AdS_5 \times S^5 in the IR, produced by giving a VEV to just one
field, e.g. B_2. The presence of a condensate of baryonic operator det B_2 is
confirmed using a Euclidean D3-brane wrapping a 4-cycle inside the resolved
conifold. The Green's functions on the singular and resolved conifolds are
central to our calculations and are discussed in some detail.Comment: 22 pages, 2 figures, v2 added note on wrapped euclidean D3 brane,
other minor correction
Diffusion in an Expanding Plasma using AdS/CFT
We consider the diffusion of a non-relativistic heavy quark of fixed mass M,
in a one-dimensionally expanding and strongly coupled plasma using the AdS/CFT
duality. The Green's function constructed around a static string embedded in a
background with a moving horizon, is identified with the noise correlation
function in a Langevin approach. The (electric) noise decorrelation is of order
1/T(\tau) while the velocity de-correlation is of order MD(\tau)/T(\tau). For
MD>1, the diffusion regime is segregated and the energy loss is Langevin-like.
The time dependent diffusion constant D(\tau) asymptotes its adiabatic limit
2/\pi\sqrt{\lambda} T(\tau) when \tau/\tau_0=(1/3\eta_0\tau_0)^3 where \eta_0
is the drag coefficient at the initial proper time \tau_0.Comment: 19 pages, 2 figures, minor corrections, version to appear in JHE
Correlations in a Confined gas of Harmonically Interacting Spin-Polarized Fermions
For a fermion gas with equally spaced energy levels, the density and the pair
correlation function are obtained. The derivation is based on the path integral
approach for identical particles and the inversion of the generating functions
for both static responses. The density and the pair correlation function are
evaluated explicitly in the ground state of a confined fermion system with a
number of particles ranging from 1 to 220 and filling the Fermi level
completely.Comment: 11 REVTEX pages, 3 postscript figures. Accepted for publication in
Phys. Rev. E, Vol. 58 (August 1, 1998
Stability of the non-extremal enhancon solution I: perturbation equations
We consider the stability of the two branches of non-extremal enhancon
solutions. We argue that one would expect a transition between the two branches
at some value of the non-extremality, which should manifest itself in some
instability. We study small perturbations of these solutions, constructing a
sufficiently general ansatz for linearised perturbations of the non-extremal
solutions, and show that the linearised equations are consistent. We show that
the simplest kind of perturbation does not lead to any instability. We reduce
the problem of studying the more general spherically symmetric perturbation to
solving a set of three coupled second-order differential equations.Comment: 20 pages, 1 figure, references added, typos fixed, version to appear
in PR
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