12,041 research outputs found
Development of a flash, bang, and smoke simulation of a shell burst
A large number of experiments (cue test firings) were performed in the definition of the cue concepts and packaging configurations. A total of 344 of these experiments were recorded with instrumentation photography to allow a quantitative analysis of the smoke cloud to be made as a function of time. These analyses were predominantly made using a short test site. Supplementary long range visibility tests were conducted to insure the required 3 kilometer visibility of the smoke signature
Reply to comments by A. Douglas, J. B. Young, and N. S. Lyman and a note on the revised moments for Pahute Mesa tectonic release
In two earlier papers (Wallace et al., 1983, 1985), we discussed the evidence for tectonic release from underground nuclear explosions on Pahute Mesa at the Nevada
Test Site (NTS) as observed in long-period body waves. It has been shown for some time that the nonisotropic component of the surface waves from most of these events could be explained by an equivalent double-couple source; namely strike-slip motion on north-striking faults
On the accuracy of the melting curves drawn from modelling a solid as an elastic medium
An ongoing problem in the study of a classical many-body system is the
characterization of its equilibrium behaviour by theory or numerical
simulation. For purely repulsive particles, locating the melting line in the
pressure-temperature plane can be especially hard if the interparticle
potential has a softened core or contains some adjustable parameters. A method
is hereby presented that yields reliable melting-curve topologies with
negligible computational effort. It is obtained by combining the Lindemann
melting criterion with a description of the solid phase as an elastic
continuum. A number of examples are given in order to illustrate the scope of
the method and possible shortcomings. For a two-body repulsion of Gaussian
shape, the outcome of the present approach compares favourably with the more
accurate but also more computationally demanding self-consistent harmonic
approximation.Comment: 25 pages, 7 figure
The Virulence in the Guinea-pig of Tubercle Bacilli Isolated before Treatment from South Indian Patients with Pulmonary Tuberculosis 3. Virulence related to Pretreatment Status of Disease and to Response to Chemotherapy
This is the last of a series of three reports from the Tuberculosis Chemotherapy Centre
Madras, on a study undertaken with the object of finding out whether differences in the
virulence in the guinea-pig of tubercle bacilli isolated from South Indian tuberculous patients
before the start of chemotherapy are related to the severity of the patients’ disease on
admission to treatment and to the subsequent response to chemotherapy. The 281 patients in
this study were drawn from the patients admitted to a l-year comparison of four domiciliary
chemotherapeutic regimens : (a) 3.9-5.5 mg/kg isoniazid plus 0.2-0.3 g/kg sodium PAS daily,
divided into two doses (PH series) ; (b) 7.8-9.6 mg/kg isoniazid alone daily in one dose
(HI-I series) ; (c) 7.8-9.6 mg/kg isoniazid alone daily, divided into two doses (HI-2 series) ;
(d) 3.9-5.5 mg/kg isoniazid alone daily, divided into two doses (H series).
No evidence was found of an association between the virulence of the organisms and
any pretreatment condition of known prognostic importance. There was no association
between pretreatment virulence and progress during treatment in the PH series (the most
effective regimen). In the other series, however, the progress was more satisfactory in
patients infected with organisms of low virulence than in those infected with organisms of
high virulence, the association between virulence and progress attaining statistical significance
in the combined HI-2 and H series (the least effective regimens) and only just
failing to do so in the smaller HI-1 series.
Possible explanations are put forward both for the absence of an association between
virulence and severity of disease on admission and for the presence of an association
between virulence and response in the patients treated with isoniazid alone
A Search for Ultraviolet Emission from LINERs
We have obtained Hubble Space Telescope WFPC2 2200 A and optical V-band
images of 20 low-luminosity active galactic nuclei, most of which are
spectroscopically classified as LINERs, in order to search for a possible
photoionizing continuum. Six (30%) of the galaxies are detected in the UV. Two
of the detected galaxies (NGC 3642 and NGC 4203) have compact, unresolved
nuclear UV sources, while the remaining four UV sources (in NGC 4569, NGC 5005,
NGC 6500, and NGC 7743) are spatially extended. Combining our sample with that
of Maoz et al. (1995), we find that the probability of detection of a nuclear
UV source is greatest for galaxies having low internal reddening and low
inclination, and we conclude that dust obscuration is the dominant factor
determining whether or not a UV source is detected. Large emission-line
equivalent widths and the presence of broad-line emission also increase the
likelihood of detection of nuclear UV emission. Our results suggest that the
majority of LINERs harbor obscured nuclear UV sources, which may be either
accretion-powered active nuclei or young star clusters. Under the assumption
that the compact UV sources in NGC 3642 and NGC 4203 have nonstellar power-law
spectra extending into the extreme ultraviolet, the extrapolated ionizing
fluxes are sufficiently strong to photoionize the narrow-line regions of these
objects. The V-band images of many galaxies in our sample reveal remarkably
strong dust lanes which may be responsible for obscuring some UV sources.Comment: 25 pages, 4 figures, 3 tables, LaTeX, AASTeX v4.0 style file,
accepted for publication in The Astrophysical Journal, additional figures
available at http://astro.berkeley.edu/~barth/papers/u
Fermi point in graphene as a monopole in momentum space
We consider the effective field theory of graphene monolayer with the Coulomb
interaction between fermions taken into account. The gauge field in momentum
space is introduced. The position of the Fermi point coincides with the
position of the corresponding monopole. The procedure of extracting such
monopoles during lattice simulations is suggested.Comment: Latex, 12 page
Evidence for a Black Hole and Accretion Disk in the LINER NGC 4203
We present spectroscopic observations from the Hubble Space Telescope that
reveal for the first time the presence of a broad pedestal of Balmer-line
emission in the LINER galaxy NGC 4203. The emission-line profile is suggestive
of a relativistic accretion disk, and is reminiscent of double-peaked transient
Balmer emission observed in a handful of other LINERs. The very broad line
emission thus constitutes clear qualitative evidence for a black hole, and
spatially resolved narrow-line emission in NGC 4203 can be used to constrain
its mass, with M_BH less than 6 x 10^6 solar masses at 99.7% confidence. This
value implies a ratio of black-hole mass to bulge mass of less than
approximately 7 x 10^-4 in NGC 4203, which is less by a factor of ~3 - 9 than
the mean ratio obtained for other galaxies. The availability of an independent
constraint on central black-hole mass makes NGC4203 an important testbed for
probing the physics of weak active galactic nuclei. Assuming M_BH near the
detection limit, the ratio of observed luminosity to the Eddington luminosity
is approximately 10^-4. This value is consistent with advection-dominated
accretion, and hence with scenarios in which an ion torus irradiates an outer
accretion disk that produces the observed double-peaked line emission.
Follow-up observations will make it possible to improve the black-hole mass
estimate and study variability in the nuclear emission.Comment: 10 pages (LaTeX, AASTeX v4.0), 2 postscript figures, accepted for
publication in The Astrophysical Journal Letter
Dynamics of monatomic liquids
We present a theory of the dynamics of monatomic liquids built on two basic
ideas: (1) The potential surface of the liquid contains three classes of
intersecting nearly-harmonic valleys, one of which (the ``random'' class)
vastly outnumbers the others and all whose members have the same depth and
normal mode spectrum; and (2) the motion of particles in the liquid can be
decomposed into oscillations in a single many-body valley, and nearly
instantaneous inter-valley transitions called transits. We review the
thermodynamic data which led to the theory, and we discuss the results of
molecular dynamics (MD) simulations of sodium and Lennard-Jones argon which
support the theory in more detail. Then we apply the theory to problems in
equilibrium and nonequilibrium statistical mechanics, and we compare the
results to experimental data and MD simulations. We also discuss our work in
comparison with the QNM and INM research programs and suggest directions for
future research.Comment: 53 pages, 16 figures. Differs from published version in using
American English spelling and grammar (published version uses British
English
Arrays of Cooper Pair Boxes Coupled to a Superconducting Reservoir: `Superradiance' and `Revival.'
We consider an array of Cooper Pair Boxes, each of which is coupled to a
superconducting reservoir by a capacitive tunnel junction. We discuss two
effects that probe not just the quantum nature of the islands, but also of the
superconducting reservoir coupled to them. These are analogues to the
well-known quantum optical effects `superradiance,' and `revival.' When revival
is extended to multiple systems, we find that `entanglement revival' can also
be observed. In order to study the above effects, we utilise a highly
simplified model for these systems in which all the single-electron energy
eigenvalues are set to be the same (the strong coupling limit), as are the
charging energies of the Cooper Pair Boxes, allowing the whole system to be
represented by two large coupled quantum spins. Although this simplification is
drastic, the model retains the main features necessary to capture the phenomena
of interest. Given the progress in superconducting box experiments over recent
years, it is possible that experiments to investigate both of these interesting
quantum coherent phenomena could be performed in the forseeable future.Comment: 23 pages, 5 figures Clarifications made as recommended by refere
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