180,964 research outputs found
Censusing manatees: a report on the feasibility of using aerial surveys and mark and recapture techniques to conduct a population survey of the West Indian Manatee
This report results from an invitation to review the needs and
prospects for capture-recapture and aerial census studies of the
manatee (Trichechus manatus) in Florida. Three aerial reconnaissance flights provided a
first hand view of manatee habitats, as follows: May 3, Suwannee
River to Kings Bay and Crystal River (Rathbun, Eberhardt), May 4,
Vero Beach to Ft. Lauderdale and Ft. Myers by way of Whitewater Bay
(Rose, Percival, Eberhardt), and May 5, Cape Canaveral to Jacksonville,
St. Johns River and Blue Spring (Rose, Kinnaird, Eberhardt). (24 page document
UBVI CCD photometry and star counts in 9 inner disk Galactic star clusters
We present and discuss new CCD-based photometric material in the UBVI
pass-bands for nine Galactic star clusters located inside the solar ring, for
which no CCD data are currently available. They are: IC 2714, NGC 4052,
ESO131SC09, NGC 5284, NGC 5316, NGC 5715, VdB-Hagen ~164, NGC 6268, and Czernik
38. We first perform star counts by combining our optical photometry wi th
2MASS, and derive cluster sizes and radial density profiles. The fundamental
parameters - age, reddening and distance- are then inferred from the analysis
of the star distribution in color-color and color-magnitude diagrams of only
the spatially selected likely members. Our analysis shows that ESO131SC09, NGC
5284, and VdB-Hagen 164 are most probably not clusters, but random enhancements
of a few bright stars along the line of sight, with prop erties much similar to
open cluster remnants. The remaining clusters are physical groups, and are all
younger than about 1 Gyr . We use the newly derived set of parameters, in
particular distance and reddening, to investigate their position in the Galaxy
in the context of the spiral structure of the Milky Way. We find that the
youngest clusters (IC 2714, NGC 5316, and NGC 6268) are located close to or
inside the Carina-Sagittarius arm, and are therefore {\i t bona fide} spiral
structure tracers. On the other hand, the oldest (Czernik 38, NGC 4052, and NGC
5715) are floating in the inter-arm space between the Carina-Sagittarius and
the more distant Scutum-Crux arm. Interestingly enough, the oldest clusters of
this sample - Czernik 38 and NGC 5715- are among the few known open clusters to
be older or as old as the Hyades in the inner Galactic disk, where star
clusters are not expected to survive for a long time, because of the strong
tidal field and the higher probability of close encounters .Comment: 17 pages, 11 eps figures, in press in MNRA
Larvae of Nearshore Fishes in Oceanic Waters near Oahu, Hawaii
Larvae of over 50 families of nearshore fishes were taken in oceanic waters about 13 km offshore of the leeward (southwest) coast of Oahu, Hawaii during 1977-78, The five most frequently taken families (Labridae, Parapercidae, Serranidae, Gobiidae, and Carangidae) made up over 50% of the total nearshore larvae. Most other families were taken very infrequently. Comparison of catch data from three types of nets indicated that 1.25-m diameter bongo nets often sampled larvae as well or better than a 3-m Isaacs-Kidd trawl and that smaller, 70-cm diameter bongo nets were often as effective as the larger nets for certain abundant taxa. Only a few taxa showed evidence of seasonal patterns in abundance. Irregular temporal variability in abundance of some taxa may have been related to occasional recent influxes of surface water from closer to shore. Most larvae taken were late preflexion stage or older. Densities of even the most abundant taxa were rarely greater than 0.001 m-3. The nearshore fish larvae were not dominated by taxa with large larvae or with larvae possessing apparent specializations to pelagic existence, Most taxa taken were pelagic spawners as adults, but larvae of demersal spawners were roughly as well represented as demersal spawners are among the nearshore fish fauna. Previous studies of waters
closer to shore probably sampled insufficient volumes for any but a few exceptionally abundant taxa. Sampling with volumes filtered of the order of 104-105 m3 will be necessary to determine if the dominant taxa taken by the present study are ever more abundant closer to shore, (PDF file contains 23 pages.
Identification of Candidate Millisecond Pulsars from Fermi LAT Observations II
Following our work presented in Dai et al. (2016), we report our detailed
data analysis for another 38 Fermi gamma-ray un-associated sources. These
sources are selected from the Fermi Large Area Telescope (LAT) third source
catalog on the basis of the properties of known gamma-ray millisecond pulsars
(MSPs) and for the purpose of finding likely candidate MSPs. From our analysis
of the LAT data, we identify that among the 38 sources, 28 of them are single
point-like sources with clean background and their spectra show significant
curvature. We also conduct analysis of archival X-ray data available for 24 of
the 28 sources. In the fields of 10 sources, there are at least one X-ray
object, and in those of the other 14 sources, no X-ray object is detected but
probably due to the X-ray observations being short. We discuss the possible MSP
nature for these sources. Six of them(J0514.6-4406, J1035.7-6720, J1624.2-4041,
J1744.1-7619, J1946.4-5403, and J2039.6-5618) are most likely associated with
pulsars because of multi-wavelength identifications including direct radio or
gamma-ray detection of pulsations. To firmly establish the associations or
verify the MSP nature for other sources, deep X-ray and/or optical observations
are needed.Comment: 18 pages, 4 figure
Conductance statistics from a large array of sub-10 nm molecular junctions
Devices made of few molecules constitute the miniaturization limit that both
inorganic and organic-based electronics aspire to reach. However, integration
of millions of molecular junctions with less than 100 molecules each has been a
long technological challenge requiring well controlled nanometric electrodes.
Here we report molecular junctions fabricated on a large array of sub-10 nm
single crystal Au nanodots electrodes, a new approach that allows us to measure
the conductance of up to a million of junctions in a single conducting Atomic
Force Microscope (C-AFM) image. We observe two peaks of conductance for
alkylthiol molecules. Tunneling decay constant (beta) for alkanethiols, is in
the same range as previous studies. Energy position of molecular orbitals,
obtained by transient voltage spectroscopy, varies from peak to peak, in
correlation with conductance values.Comment: ACS Nano (in press
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