9,607 research outputs found
Gas chromatograph injection system
An injection system for a gas chromatograph is described which uses a small injector chamber (available in various configurations). The sample is placed in the chamber while the chamber is not under pressure and is not heated, and there is no chance of leakage caused by either pressure or heat. It is injected into the apparatus by changing the position of a valve and heating the chamber, and is volatilized and swept by a carrier gas into the analysis apparatus
Euler number of Instanton Moduli space and Seiberg-Witten invariants
We show that a partition function of topological twisted N=4 Yang-Mills
theory is given by Seiberg-Witten invariants on a Riemannian four manifolds
under the condition that the sum of Euler number and signature of the four
manifolds vanish. The partition function is the sum of Euler number of
instanton moduli space when it is possible to apply the vanishing theorem. And
we get a relation of Euler number labeled by the instanton number with
Seiberg-Witten invariants, too. All calculation in this paper is done without
assuming duality.Comment: LaTeX, 34 page
N=2 Topological Yang-Mills Theory on Compact K\"{a}hler Surfaces
We study a topological Yang-Mills theory with fermionic symmetry. Our
formalism is a field theoretical interpretation of the Donaldson polynomial
invariants on compact K\"{a}hler surfaces. We also study an analogous theory on
compact oriented Riemann surfaces and briefly discuss a possible application of
the Witten's non-Abelian localization formula to the problems in the case of
compact K\"{a}hler surfaces.Comment: ESENAT-93-01 & YUMS-93-10, 34pages: [Final Version] to appear in
Comm. Math. Phy
Exotic Smoothness and Physics
The essential role played by differentiable structures in physics is reviewed
in light of recent mathematical discoveries that topologically trivial
space-time models, especially the simplest one, , possess a rich
multiplicity of such structures, no two of which are diffeomorphic to each
other and thus to the standard one. This means that physics has available to it
a new panoply of structures available for space-time models. These can be
thought of as source of new global, but not properly topological, features.
This paper reviews some background differential topology together with a
discussion of the role which a differentiable structure necessarily plays in
the statement of any physical theory, recalling that diffeomorphisms are at the
heart of the principle of general relativity. Some of the history of the
discovery of exotic, i.e., non-standard, differentiable structures is reviewed.
Some new results suggesting the spatial localization of such exotic structures
are described and speculations are made on the possible opportunities that such
structures present for the further development of physical theories.Comment: 13 pages, LaTe
Enhancing Existing Isolated Underpasses with Fencing Reduces Wildlife Crashes and Connects Habitat
The impact of wildlifeâvehicle collisions on drivers and wildlife populations has been gaining attention in the United States. Given the established success of wildlife crossings with fencing in reducing wildlife crashes and connecting habitat, information is needed on cost-effective means of implementation for departments of transportation. When wildlife crossings are constructed, they are often built into new road projects as a series of 2 or more underpasses and/or overpass structures connected by exclusionary fencing. Given limited transportation budgets and the prevalence of maintenance activities more so than new construction in many states, enhancing existing underpasses on previously constructed roads has been recognized as a cost-effective mitigation opportunity. More research is needed, however, on the effects of adding fencing to existing underpasses, particularly those that are too far from one another to be connected with contiguous fencing. In this study, we evaluated the effectiveness of this measure when applied to isolated underpasses. Approximately 1.6 km of 2.4-m-high wildlife fencing was added to each of 2 existing underpasses, a large bridge underpass and a large box culvert, situated approximately 8 km apart from one another on Interstate 64 in Virginia, USA. We conducted a 2-year post-fencing camera monitoring study and compared the findings from a 2-year pre-fencing study with regard to collision frequencies with white-tailed deer (Odocoileus virginianus) and black bears (Ursus americanus); the use of the underpasses by wildlife; and roadside deer activity. We also evaluated deer activity data to compare different fence end designs applied at the study sites. After fencing installation, deerâvehicle collisions (DVCs) were reduced by 96.5% and 88% at the box culvert and bridge underpass, respectively, and there were no increases in DVCs within 1.6 km of the fence ends. Deer crossings increased 410% at the box culvert and 71% at the bridge underpass. Use of the culvert and bridge underpasses by other mammals increased 81% and 165%, respectively. Although deer use of the underpasses was much greater than their activity at any of the fence ends, there was relatively high deer activity at the fence ends that did not tie into a feature such as right-of-way fencing. Our study found that the addition of wildlife fencing to certain existing isolated underpasses can be a highly cost-effective means of increasing driver safety and enhancing habitat connectivity for wildlife. The benefits from crash reduction exceeded the fencing costs in 1.8 years, and fencing resulted in an average saving of \u3e$2.3 million per site over the 25-year lifetime of the fencing. The results add to the growing body of knowledge about effective ways we can use existing infrastructure to connect wildlife habitat and increase driver safety
On non- solutions to the Seiberg-Witten equations
We show that a previous paper of Freund describing a solution to the
Seiberg-Witten equations has a sign error rendering it a solution to a related
but different set of equations. The non- nature of Freund's solution is
discussed and clarified and we also construct a whole class of solutions to the
Seiberg-Witten equations.Comment: 8 pages, Te
On the radio and NIR jet of PKS 2155-304 and its close environment
PKS 2155-304 is one of the brightest BL Lac object in the sky and a very well
studied target from radio to TeV bands. We report on high-resolution (~ 0.12
arcsec) direct imaging of the field of PKS 2155-304 using adaptive optics
near-IR observations in J and Ks bands obtained with the ESO multi-conjugate
adaptive optic demonstrator (MAD) at the Very Large Telescope. These data are
complemented with archival VLA images at various frequencies to investigate the
properties of the close environment of the source. We characterized the faint
galaxies that form the poor group associated to the target. No radio emission
is present for these galaxies, while an old radio jet at ~ 20 kpc from the
nucleus of PKS 2155-304 and a jet-like structure of ~ 2 kpc (~ 1 arcsec) in the
eastern direction are revealed. No counterparts of these radio jets are found
in the NIR or in archival Chandra observations.Comment: 10 pages, 7 figures, accepted for publication in The Astronomical
Journa
S-duality and Topological Strings
In this paper we show how S-duality of type IIB superstrings leads to an
S-duality relating A and B model topological strings on the same Calabi-Yau as
had been conjectured recently: D-instantons of the B-model correspond to
A-model perturbative amplitudes and D-instantons of the A-model capture
perturbative B-model amplitudes.
Moreover this confirms the existence of new branes in the two models.
As an application we explain the recent results concerning A-model
topological strings on Calabi-Yau and its equivalence to the statistical
mechanical model of melting crystal.Comment: 13 page
MAD Adaptive Optics Imaging of High Luminosity Quasars: A Pilot Project
We present near-IR images of five luminous quasars at z~2 and one at z~4
obtained with an experimental adaptive optics instrument at the ESO Very Large
Telescope. The observations are part of a program aimed at demonstrating the
capabilities of multi-conjugated adaptive optics imaging combined with the use
of natural guide stars for high spatial resolution studies on large telescopes.
The observations were mostly obtained under poor seeing conditions but in two
cases. In spite of these non optimal conditions, the resulting images of point
sources have cores of FWHM ~0.2 arcsec. We are able to characterize the host
galaxy properties for 2 sources and set stringent upper limits to the galaxy
luminosity for the others. We also report on the expected capabilities for
investigating the host galaxies of distant quasars with adaptive optics systems
coupled with future Extremely Large Telescopes. Detailed simulations show that
it will be possible to characterize compact (2-3 kpc) quasar host galaxies for
QSOs at z = 2 with nucleus K-magnitude spanning from 15 to 20 (corresponding to
absolute magnitude -31 to -26) and host galaxies that are 4 mag fainter than
their nuclei.Comment: 19 pages, 12 figures, accepted for pubblication in The Astronomical
Journa
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