3,964 research outputs found
Ohio's statewide land use inventory: An operational approach for applying LANDSAT data to state, regional and local planning programs
The programmatic, technical, user application, and cost factors associated with the development of an operational, statewide land use inventory from LANDSAT data are described. The LANDSAT multispectral data are subjected to geometrical and categorical processing to produce map files for each of the 200 fifteen (15) minute quads covering Ohio. Computer compatible tapes are rescanned to produce inventory tapes which identify eight (8) Level I land use categories and a variety of Level II categories. The inventory tapes are processed through a series of ten (10) software programs developed by the State of Ohio. The net result is a computerized inventory which can be displayed in map or tabular form for various geographic units, at a variety of scales and for selected categories of usage. The computerized inventory data files are applied to technical programs developed by the various state agencies to be used in state, regional, and local planning programs
Phenotypes of the ovarian follicular basal lamina predict developmental competence of oocytes
BACKGROUND: The ovarian follicular basal lamina underlies the epithelial membrana granulosa and maintains the avascular intra-follicular compartment. Additional layers of basal lamina occur in a number of pathologies, including pili annulati and diabetes. We previously found additional layers of follicular basal lamina in a significant percentage of healthy bovine follicles. We wished to determine if this phenomenon existed in humans, and if it was related to oocyte function in the bovine. METHODS: AND RESULTS: We examined follicles from human ovaries (n = 18) by electron microscopy and found that many follicles had additional layers of basal lamina. Oocytes (n = 222) from bovine follicles with normal or unusual basal laminas were isolated and their ability to undergo in vitro maturation, fertilization and culture to blastocyst was compared. Healthy bovine follicles with a single layer of basal lamina had oocytes with significantly (P < 0.01) greater developmental competence than healthy follicles with additional layers of follicular basal lamina (65 versus 28). CONCLUSIONS: These findings provide direct evidence that the phenotype of the follicular basal lamina is related to oocyte competence
Norm-dependent Random Matrix Ensembles in External Field and Supersymmetry
The class of norm-dependent Random Matrix Ensembles is studied in the
presence of an external field. The probability density in those ensembles
depends on the trace of the squared random matrices, but is otherwise
arbitrary. An exact mapping to superspace is performed. A transformation
formula is derived which gives the probability density in superspace as a
single integral over the probability density in ordinary space. This is done
for orthogonal, unitary and symplectic symmetry. In the case of unitary
symmetry, some explicit results for the correlation functions are derived.Comment: 19 page
A coarse grained model of granular compaction and relaxation
We introduce a theoretical model for the compaction of granular materials by discrete vibrations which is expected to hold when the intensity of vibration is low. The dynamical unit is taken to be clusters of granules that belong to the same collective structure. We rigourously construct the model from first principles and show that numerical solutions compare favourably with a range of experimental results. This includes the logarithmic relaxation towards a statistical steady state, the effect of varying the intensity of vibration resulting in a so-called `annealing' curve, and the power spectrum of density fluctuations in the steady state itself. A mean-field version of the model is introduced which shares many features with the exact model and is open to quantitative analysi
The Chemical Compositions of the Type II Cepheids -- The BL Her and W Vir Variables
Abundance analyses from high-resolution optical spectra are presented for 19
Type II Cepheids in the Galactic field. The sample includes both short-period
(BL Her) and long-period (W Vir) stars. This is the first extensive abundance
analysis of these variables. The C, N, and O abundances with similar spreads
for the BL Her and W Vir show evidence for an atmosphere contaminated with
-process and CN-cycling products. A notable anomaly of the BL Her
stars is an overabundance of Na by a factor of about five relative to their
presumed initial abundances. This overabundance is not seen in the W Vir stars.
The abundance anomalies running from mild to extreme in W Vir stars but not
seen in the BL Her stars are attributed to dust-gas separation that provides an
atmosphere deficient in elements of high condensation temperature, notably Al,
Ca, Sc, Ti, and -process elements. Such anomalies have previously been seen
among RV Tau stars which represent a long-period extension of the variability
enjoyed by the Type II Cepheids. Comments are offered on how the contrasting
abundance anomalies of BL Her and W Vir stars may be explained in terms of the
stars' evolution from the blue horizontal branch.Comment: 41 pages including 11 figures and 4 tables; Accepted for publication
in Ap
The Southern Galactic Plane Survey: The Test Region
The Southern Galactic Plane Survey (SGPS) is a project to image the HI line
emission and 1.4 GHz continuum in the fourth quadrant of the Milky Way at high
resolution using the Australia Telescope Compact Array (ATCA) and the Parkes
Radio Telescope. In this paper we describe the survey details and goals,
present lambda 21-cm continuum data, and discuss HI absorption and emission
characteristics of the SGPS Test Region (325.5 deg < l < 333.5 deg; -0.5 deg <
b < +3.5 deg). We explore the effects of massive stars on the interstellar
medium (ISM) through a study of HI shells and the HI environments of HII
regions and supernova remnants. We find an HI shell surrounding the HII region
RCW 94 which indicates that the region is embedded in a molecular cloud. We
give lower limits for the kinematic distances to SNRs G327.4+0.4 and G330.2+1.0
of 4.3 kpc and 4.9 kpc, respectively. We find evidence of interaction with the
surrounding HI for both of these remnants. We also present images of a possible
new SNR G328.6-0.0. Additionally, we have discovered two small HI shells with
no counterparts in continuum emission.Comment: 17 pages, 7 embedded EPS figures, 10 low-res jpeg figures, uses
emulateapj5.sty. Accepted for publication in the Astrophysical Journal.
Version with all full resolution figures embedded is available at
http://www.astro.umn.edu/~naomi/sgps/papers/SGPS.ps.g
Interim Report
Author: F. R. Rodgers for N. H. Taylor for Sage Improvement CommitteeReason: C. W. Farr reviewing for declassificationMemo regarding 1956 interim repor
The Flux Variability of Markarian 501 in Very High Energy Gamma Rays
The BL Lacertae object Markarian 501 was identified as a source of gamma-ray
emission at the Whipple Observatory in March 1995. Here we present a flux
variability analysis on several times-scales of the 233 hour data set
accumulated over 213 nights (from March 1995 to July 1998) with the Whipple
Observatory 10 m atmospheric Cherenkov imaging telescope. In 1995, with the
exception of a single night, the flux from Markarian 501 was constant on daily
and monthly time-scales and had an average flux of only 10% that of the Crab
Nebula, making it the weakest VHE source detected to date. In 1996, the average
flux was approximately twice the 1995 flux and showed significant
month-to-month variability. No significant day-scale variations were detected.
The average gamma-ray flux above ~350 GeV in the 1997 observing season rose to
1.4 times that of the Crab Nebula -- 14 times the 1995 discovery level --
allowing a search for variability on time-scales shorter than one day.
Significant hour-scale variability was present in the 1997 data, with the
shortest, observed on MJD 50607, having a doubling time of ~2 hours. In 1998
the average emission level decreased considerably from that of 1997 (to ~20% of
the Crab Nebula flux) but two significant flaring events were observed. Thus,
the emission from Markarian 501 shows large amplitude and rapid flux
variability at very high energies as does Markarian 421. It also shows large
mean flux level variations on year-to-year time-scales, behaviour which has not
been seen from Markarian 421 so far.Comment: 19 pages, 3 figures, to appear in ApJ, June 20, 1999, Vol. 518 #
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