5,004 research outputs found
Towards a Continuous Record of the Sky
It is currently feasible to start a continuous digital record of the entire
sky sensitive to any visual magnitude brighter than 15 each night. Such a
record could be created with a modest array of small telescopes, which
collectively generate no more than a few Gigabytes of data daily.
Alternatively, a few small telescopes could continually re-point to scan and
reco rd the entire sky down to any visual magnitude brighter than 15 with a
recurrence epoch of at most a few weeks, again always generating less than one
Gigabyte of data each night. These estimates derive from CCD ability and
budgets typical of university research projects. As a prototype, we have
developed and are utilizing an inexpensive single-telescope system that obtains
optical data from about 1500 square degrees. We discuss the general case of
creating and storing data from a both an epochal survey, where a small number
of telescopes continually scan the sky, and a continuous survey, composed of a
constellation of telescopes dedicated each continually inspect a designated
section of the sky. We compute specific limitations of canonical surveys in
visible light, and estimate that all-sky continuous visual light surveys could
be sensitive to magnitude 20 in a single night by about 2010. Possible
scientific returns of continuous and epochal sky surveys include continued
monitoring of most known variable stars, establishing case histories for
variables of future interest, uncovering new forms of stellar variability,
discovering the brightest cases of microlensing, discovering new novae and
supernovae, discovering new counterparts to gamma-ray bursts, monitoring known
Solar System objects, discovering new Solar System objects, and discovering
objects that might strike the Earth.Comment: 38 pages, 9 postscript figures, 2 gif images. Revised and new section
added. Accepted to PASP. Source code submitted to ASCL.ne
Metal-Insulator transition in the Generalized Hubbard model
We present the exact ground-state wave function and energy of the generalized
Hubbard model, subjected to the condition that the number of double occupied
sites is conserved, for a wide, physically relevant range of parameters. For
one hole and one double occupied site the existence of the ferromagnetic
ground-state is proved which allow one to determine the critical value of the
on-site repulsion corresponding to the point of metal-insulator transition. For
the one dimensional model the exact solution for special values of the
parameters is obtained.Comment: 20 pages, LaTex. Mod.Phys.Lett.B 7 (1993) 1397; Journal of Physics:
Condensed Matter (to appear
TASS Mark IV Photometric Survey of the Northern Sky
The Amateur Sky Survey (TASS) is a loose confederation of amateur and
professional astronomers. We describe the design and construction of our Mark
IV systems, a set of wide-field telescopes with CCD cameras which take
simultaneous images in the and passbands. We explain our
observational procedures and the pipeline which processes and reduces the
images into lists of stellar positions and magnitudes. We have compiled a large
database of measurements for stars in the northern celestial hemisphere with
-band magnitudes in the range 7 < V < 13. This paper describes data taken
over the four-year period starting November, 2001. One of our results is a
catalog of repeated measurements on the Johnson-Cousins system for over 4.3
million stars.Comment: Accepted for publication in December, 2006, issue of PASP. 44 pages
including 20 figures. Patches catalog available at
http://spiff.rit.edu/tass/patches
Distinguishing cancerous from non-cancerous cells through analysis of electrical noise
Since 1984, electric cell-substrate impedance sensing (ECIS) has been used to
monitor cell behavior in tissue culture and has proven sensitive to cell
morphological changes and cell motility. We have taken ECIS measurements on
several cultures of non-cancerous (HOSE) and cancerous (SKOV) human ovarian
surface epithelial cells. By analyzing the noise in real and imaginary
electrical impedance, we demonstrate that it is possible to distinguish the two
cell types purely from signatures of their electrical noise. Our measures
include power-spectral exponents, Hurst and detrended fluctuation analysis, and
estimates of correlation time; principal-component analysis combines all the
measures. The noise from both cancerous and non-cancerous cultures shows
correlations on many time scales, but these correlations are stronger for the
non-cancerous cells.Comment: 8 pages, 4 figures; submitted to PR
Suburban Deer Management: A Matter of Perspective
Many metropolitan areas in the eastern United States are experiencing management conflicts associated with overabundant deer (Odocoileus virginianus) populations. Sometimes these deer populations exceed the biological carrying capacity of available habitat and wildlife acceptance capacity (Decker and Purdy 1988) of local residents. For nearly 2 decades, a deer management controversy has been developing in Durand Eastman Park and the Town of Irondequoit, located in the greater Rochester metropolitan area, Monroe County, New York. Three local citizen organizations concerned about deer are described, and each has promoted various nonhunting alternatives to reduce human-deer problems. For 15 years, the New York State Department of Environmental Conservation (DEC) has promoted liberal archery seasons as the preferred alternative for reducing deer numbers, although the discharge of bow and arrows is prohibited within the Town of Irondequoit and Durand Eastman Park by local laws. During 1992, DEC and Cornell Cooperative Extension (CCE) organized a Citizen Task Force (CTF) in an attempt to resolve this controversy and reach consensus with community leaders concerning future deer management objectives and alternatives. CTF members exhibited a wide range of values and attitudes concerning suburban deer management. A deer management plan was developed and implemented based on CTF recommendations. This case study emphasizes the need for integrating both the biological and human dimensions to resolve suburban wildlife management issues
A zeta function approach to the relation between the numbers of symmetry planes and axes of a polytope
A derivation of the Ces\`aro-Fedorov relation from the Selberg trace formula
on an orbifolded 2-sphere is elaborated and extended to higher dimensions using
the known heat-kernel coefficients for manifolds with piecewise-linear
boundaries. Several results are obtained that relate the coefficients, ,
in the Shephard-Todd polynomial to the geometry of the fundamental domain. For
the 3-sphere we show that is given by the ratio of the volume of the
fundamental tetrahedron to its Schl\"afli reciprocal.Comment: Plain TeX, 26 pages (eqn. (86) corrected
Sensitivity of Second Harmonic Generation to Space Charge Effects at Si(111)/Electrolyte and Si(111)/SiO\u3csub\u3e2\u3c/sub\u3e/Electrolyte Interfaces
The potential dependence in the surface second harmonic response from hydrogen terminated n‐Si(111) and oxidized n‐Si(111) surfaces has been examined in aqueous NH4F and H2SO4 solutions. The relative phase of the nonlinear response as measured by rotational anisotropy experiments is found to be highly sensitive to the presence of the oxide and the field applied across the Si(111)/oxide/electrolyte interface. These observations are attributed to field effects within the space–charge region of the semiconductor which vary with the presence and thickness of the insulating oxide layer on the Si(111) surface
Human Dimensions of Contraception in Wildlife Management
Wildlife damage management was so much simpler in the good old days. If deer (Odocoileus virginianus), beaver (Castor canadensis), or other animals were a problem in a particular situation, people simply had them shot, trapped, or poisoned. Not many years ago, most people would go along with this approach, and those who didn\u27t like it were marginalized as the radical fringe. Not so today. Greater and more diverse segments of the public want a say in what professionals decide to do with their wildlife. The public wants to participate in setting objectives for management and in approving the methods for accomplishing those objectives. Kania and Conover (1991) emphasized that wildlife agencies should respond to these societal changes rather than resist them, thereby enhancing the value of the wildlife resource for all people. Changes in sociopolitical values have resulted in more stakeholder groups who want to be included in wildlife management decisions today than at any other time since the advent of applied wildlife management in North America (Curtis and Richmond 1992)
Random Planar Lattices and Integrated SuperBrownian Excursion
In this paper, a surprising connection is described between a specific brand
of random lattices, namely planar quadrangulations, and Aldous' Integrated
SuperBrownian Excursion (ISE). As a consequence, the radius r_n of a random
quadrangulation with n faces is shown to converge, up to scaling, to the width
r=R-L of the support of the one-dimensional ISE. More generally the
distribution of distances to a random vertex in a random quadrangulation is
described in its scaled limit by the random measure ISE shifted to set the
minimum of its support in zero.
The first combinatorial ingredient is an encoding of quadrangulations by
trees embedded in the positive half-line, reminiscent of Cori and Vauquelin's
well labelled trees. The second step relates these trees to embedded (discrete)
trees in the sense of Aldous, via the conjugation of tree principle, an
analogue for trees of Vervaat's construction of the Brownian excursion from the
bridge.
From probability theory, we need a new result of independent interest: the
weak convergence of the encoding of a random embedded plane tree by two contour
walks to the Brownian snake description of ISE.
Our results suggest the existence of a Continuum Random Map describing in
term of ISE the scaled limit of the dynamical triangulations considered in
two-dimensional pure quantum gravity.Comment: 44 pages, 22 figures. Slides and extended abstract version are
available at http://www.loria.fr/~schaeffe/Pub/Diameter/ and
http://www.iecn.u-nancy.fr/~chassain
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