6,367 research outputs found
A multidegree-of-freedom vibrational apparatus
Apparatus uses prestressed cables to support vibrational table. Cables are durable, do not require frequent servicing, and provide increased safety. Because much weight rests on these cables, vibration actuating pistons can provide longer service. In event of structural failure of other supporting components, they will support entire weight of vibrational table
Young open clusters in the Milky Way and Small Magellanic Cloud
NGC6611, Trumpler 14, Trumpler 15, Trumpler 16, Collinder 232 are very young
open clusters located in star-formation regions of the Eagle Nebula or the
Carina in the MW, and NGC346 in the SMC. With different instrumentations and
techniques, it was possible to detect and classify new Herbig Ae/Be stars,
classical Be stars and to provide new tests / comparisons about the Be stars
appearance models. Special stars (He-strong) of these star-formation regions
are also presented.Comment: Proceedings IAUS266 at the IAU-GA 200
Water ice in the Kuiper belt
We examine a large collection of low-resolution near-infrared spectra of Kuiper Belt objects (KBOs) and centaurs in an attempt to understand the presence of water ice in the Kuiper Belt. We find that water ice on the surface of these objects occurs in three separate manners: (1) Haumea family members uniquely show surfaces of nearly pure water ice, presumably a consequence of the fragmentation of the icy mantle of a larger differentiated proto-Haumea; (2) large objects with absolute magnitudes of H < 3 (and a limited number to H = 4.5) have surface coverings of water iceâperhaps mixed with ammoniaâthat appears to be related to possibly ancient cryovolcanism on these large objects; and (3) smaller KBOs and centaurs which are neither Haumea family members nor cold-classical KBOs appear to divide into two families (which we refer to as "neutral" and "red"), each of which is a mixture of a common nearly neutral component and either a slightly red or very red component that also includes water ice. A model suggesting that the difference between neutral and red objects due to formation in an early compact solar system either inside or outside, respectively, of the ~20 AU methanol evaporation line is supported by the observation that methanol is only detected on the reddest objects, which are those which would be expected to have the most of the methanol containing mixture
Analytical study of the fracture of liquid- filled tanks impacted by hypervelocity particles
Shock waves in water and stress waves in tank walls of water-filled fuel tanks impacted by hypervelocity particle
O stars effective temperature and HII regions ionization parameter gradients in the Galaxy
Extensive photoionization model grids are computed for single star HII
regions using stellar atmosphere models from the WM-basic code. Mid-IR emission
line intensities are predicted and diagnostic diagrams of [NeIII]/[NeII] and
[SIV]/[SIII] excitation ratio are build, taking into account the metallicities
of both the star and the HII region. The diagrams are used in conjunction with
galactic HII region observations obtained with the ISO Observatory to determine
the effective temperature Teff of the exciting O stars and the mean ionization
parameter U. Teff and U are found to increase and decrease, respectively, with
the metallicity of the HII region represented by the [Ne/Ne_sol] ratio. No
evidence is found for gradients of Teff or U with galactocentric distance Rgal.
The observed excitation sequence with Rgal is mainly due to the effect of the
metallicity gradient on the spectral ionizing shape, upon which the effect of
an increase in Teff with Z is superimposed. We show that not taking properly
into account the effect of metallicity on the ionizing shape of the stellar
atmosphere would lead to an apparent decrease of Teff with Z and an increase of
Teff with Rgal.Comment: Accepted in Ap
WZW-Poisson manifolds
We observe that a term of the WZW-type can be added to the Lagrangian of the
Poisson Sigma model in such a way that the algebra of the first class
constraints remains closed. This leads to a natural generalization of the
concept of Poisson geometry. The resulting "WZW-Poisson" manifold M is
characterized by a bivector Pi and by a closed three-form H such that
[Pi,Pi]_Schouten = .Comment: 4 pages; v2: a reference adde
Classical and Quantum Gravity in 1+1 Dimensions, Part III: Solutions of Arbitrary Topology
All global solutions of arbitrary topology of the most general 1+1
dimensional dilaton gravity models are obtained. We show that for a generic
model there are globally smooth solutions on any non-compact 2-surface. The
solution space is parametrized explicitly and the geometrical significance of
continuous and discrete labels is elucidated. As a corollary we gain insight
into the (in general non-trivial) topology of the reduced phase space.
The classification covers basically all 2D metrics of Lorentzian signature
with a (local) Killing symmetry.Comment: 39 pages, 22 figures, uses AMSTeX, extended version of former chapter
7 (Gravitational Kinks) now available as gr-qc/9707053, problem with figure 6
fixe
Identification of human papillomavirus DNA in cutaneous lesions of Cowden syndrome
Background: Cowden syndrome (CS) or multiple hamartoma syndrome is a cancer-associated genodermatosis inherited in an autosomal dominant pattern. One of the diagnostic criteria is facial papules which are felt to be trichilemmomas, benign hair follicle tumors, which some consider to be induced by human papillomavirus (HPV). Objective: To search for HPV in skin tumors, especially trichilemmomas, from patients with CS. Methods: Skin lesions from patients with CS were classified histologically. Each tumor was then analyzed for HPV DNA by polymerase chain reaction with different primer sets; positive amplicons were typed by direct sequencing. Results: Twenty-nine biopsies from 7 patients with CS were investigated. Only 2 of 29 tumors clinically suspected of being trichilemmomas were confirmed histologically. In addition, 3 sclerotic fibromas, also typical of CS, were found, as well as 1 sebaceous hyperplasia. The other 23 lesions showed histological features of HPV-induced tumors in various stages of development. HPV DNA was found in 19 of 29 cutaneous lesions. Tumors without any histological signs of HPV induction were negative for HPV DNA. Two tumors which were histologically classified as common warts contained HPV types 27 and 28. All the 17 other HPV types belong to the group of epidermodysplasia-verruciformis-associated types. Conclusions: The majority of cutaneous lesions in CS contain HPV DNA. They may have a variety of histological patterns. Trichilemmomas are not clinically distinctive and can be difficult to identify in CS patients. Copyright (C) 2003 S. Karger AG, Basel
Lie Algebroid Yang Mills with Matter Fields
Lie algebroid Yang-Mills theories are a generalization of Yang-Mills gauge
theories, replacing the structural Lie algebra by a Lie algebroid E. In this
note we relax the conditions on the fiber metric of E for gauge invariance of
the action functional. Coupling to scalar fields requires possibly nonlinear
representations of Lie algebroids. In all cases, gauge invariance is seen to
lead to a condition of covariant constancy on the respective fiber metric in
question with respect to an appropriate Lie algebroid connection.
The presentation is kept in part explicit so as to be accessible also to a
less mathematically oriented audience.Comment: 24 pages, accepted for publication in J. Geom. Phy
- âŠ