6,843 research outputs found
Potential time-cost benefits from use of orbital-height photographic data in cartographic programs
Cost effectiveness of mapping using satellite- borne photograph
Mean-Field Spin Glass models from the Cavity--ROSt Perspective
The Sherrington-Kirkpatrick spin glass model has been studied as a source of
insight into the statistical mechanics of systems with highly diversified
collections of competing low energy states. The goal of this summary is to
present some of the ideas which have emerged in the mathematical study of its
free energy. In particular, we highlight the perspective of the cavity
dynamics, and the related variational principle. These are expressed in terms
of Random Overlap Structures (ROSt), which are used to describe the possible
states of the reservoir in the cavity step. The Parisi solution is presented as
reflecting the ansatz that it suffices to restrict the variation to hierarchal
structures which are discussed here in some detail. While the Parisi solution
was proven to be correct, through recent works of F. Guerra and M. Talagrand,
the reasons for the effectiveness of the Parisi ansatz still remain to be
elucidated. We question whether this could be related to the quasi-stationarity
of the special subclass of ROSts given by Ruelle's hierarchal `random
probability cascades' (also known as GREM).Comment: Based on talks given at `Young Res. Symp.', Lisbon 2003, and `Math.
Phys. of Spin Glasses', Cortona 200
On the dynamics of interfaces in the ferromagnetic XXZ chain under weak perturbations
We study the time evolution of interfaces of the ferromagnetic XXZ chain in a
magnetic field. A scaling limit is introduced where the strength of the
magnetic field tends to zero and the microscopic time to infinity while keeping
their product constant. The leading term and its first correction are
determined and further analyzed in more detail for the case of a uniform
magnetic field.Comment: 20 pages, 2 figures, uses conm-p-l.cls. 1 reference adde
Measurements of ozone in the Antarctic region during August and September of 1987
Mixing ratios are presented for ozone in the austral polar atmosphere during Aug. and Sept. of 1987. Since the mid-1970's, there has been a continuing decrease in the total column abundance of ozone over Antarctica during the late winter and early spring. This reduction now amounts to about one-half of the historical October mean. The results presented are derived from an ultraviolet ozone photometer. The ER-2 aircraft carrying 14 instruments participated in a major effort to penetrate the region of depletion. Data were gathered between altitudes of 53 deg and 72 deg S at pressure altitudes up to 21 km in a series of 12 flights. Additional data were obtained between latitudes of 37 deg N and 53 deg S on the 3 flight legs required to reach Punta Arenas from Moffett Field, CA, and on the same return legs to Moffett Field. The observed ozone mixing ratios indicate the effects of chemistry as well as the effects of the stratospheric polar vortex. Examples of the distributions of ozone mixing ratios as a function of altitude, latitude, or a time and the relationships to temperature and other trace gases are presented
Some Observations for Mean-Field Spin Glass Models
We obtain bounds to show that the pressure of a two-body, mean-field spin
glass is a Lipschitz function of the underlying distribution of the random
coupling constants, with respect to a particular semi-norm. This allows us to
re-derive a result of Carmona and Hu, on the universality of the SK model, by a
different proof, and to generalize this result to the Viana-Bray model. We also
prove another bound, suitable when the coupling constants are not independent,
which is what is necessary if one wants to consider ``canonical'' instead of
``grand canonical'' versions of the SK and Viana-Bray models. Finally, we
review Viana-Bray type models, using the language of L\'evy processes, which is
natural in this context.Comment: 15 pages, minor revision
Higher Dimensional Lattice Chains and Delannoy Numbers
Fix nonnegative integers n1 , . . ., nd, and let L denote the lattice of points (a1 , . . ., ad) ∈ ℤd that satisfy 0 ≤ ai ≤ ni for 1 ≤ i ≤ d. Let L be partially ordered by the usual dominance ordering. In this paper we use elementary combinatorial arguments to derive new expressions for the number of chains and the number of Delannoy paths in L. Setting ni = n (for all i) in these expressions yields a new proof of a recent result of Duichi and Sulanke [9] relating the total number of chains to the central Delannoy numbers. We also give a novel derivation of the generating functions for these numbers in arbitrary dimension
Survey for ants on the island of Maui, Hawaii, with emphasis on the little fire ant (Wasmannia auropunctata)
Reports were scanned in black and white at a resolution of 600 dots per inch and were converted to text using Adobe Paper Capture Plug-in.The little fire ant (LFA), Wasmannia auropunctata, is an aggressive pest ant with a painful sting that has spread to many parts of the world through human commerce. In the State of Hawaii, LFA had been intercepted previously as early as 1930, but only recently, in 1999, were established populations found in the Puna District, on the island of Hawaii (Big Island), occupying residential and agricultural sites, such as fruit orchards and plant nurseries. A single population was found on Kauai in 1999, but it has been contained and nearly eradicated. However, on Hawaii island, LFA is now well established in the Puna/Hilo area, with at least 50 sites covering at least several hundred acres. Even though nursery shipments leaving Hilo are checked for LFA by inspectors of the Hawaii Department of Agriculture, it is likely that LFA-infested shipments have reached Maui. This study surveyed portions of the island of Maui for ants, with a main goal of finding populations of LFA. Since much of the nursery material sent from Hawaii to Maui is promptly planted in new developments, searches were focused on newly developed/landscaped areas. During the survey, over 18,000 ants were collected on 4,300 peanut butter baited chopsticks at 360 sites, resulting in 823 locations with 23 ant species but no LFA. The big-headed ant (Pheidole megacephala) was by far the most abundant ant encountered in the survey and present at 55% of the sampling sites. However, since not all ant species are equally attracted to the peanut butter bait used in this survey, the relative abundance of ant species encountered may be biased, and 12 species of ants previously recorded for Maui were not collected in the survey.Primary funding for the study was from the U.S. Fish and Wildlife Service. Funding was also received from the US Geological Survey, Invasive Species Program
Spirocerca Lupi
Spirocerca lupi is commonly known as the esophageal worm of the dog. It occurs in the walls of the esophagus and larger arteries of the dog, fox, wolf and jackal. It is very common throughout the South, particularly in Alabama, Georgia, Florida, Mississippi and probably other states, constituting a formidable menace to the dog
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