11,892 research outputs found
Evaluation of ERTS data for certain oceanographic uses
The author has identified the following significant results. (1) Sunglint effects over water can be expected in ERTS-1 images whenever solar elevations exceed 55 deg. (2) Upwellings were viewed coincidently by ERTS-1 and NOAA-2 in Lake Michigan on two occasions during August 1973. (3) A large oil slick was identified 100 km off the Maryland coast in the Atlantic Ocean. Volume of the oil was estimated to be least 200,000 liters (50,000 gallons). (4) ERTS-1 observations of turbidity patterns in Lake St. Clair provide circulation information that correlates well with physical model studies made 10 years ago. (5) Good correlation has been established between ERTS-1 water color densities and NOAA-2 thermal infrared surface temperature measurements. Initial comparisons have been made in Lake Erie during March 1973
Evaluation of ERTS data for certain oceanographic uses
The author has identified the following significant results. Upwelling along the eastern shore of Lake Michigan was occurring during the 3 and 21 August 1973 visits by ERTS-1. The NOAA-2 VHRR thermal-IR data are being digitized for comparison. Early indications are that these upwellings induced a calcium carbonate precipitate to form in the surface waters. It is most pronounced in the MSS-4 channel. On the lake bottom this jell-like sediment is known as marl and adds to the eutrophication of the lake. This phenomenon may help to explain the varve-like nature of bottom cores that have been observed in the Great Lakes
Gamma-ray emission from the solar halo and disk: a study with EGRET data
Context: The Sun has recently been predicted to be an extended source of
gamma-ray emission, produced by inverse-Compton (IC) scattering of cosmic-ray
(CR) electrons on the solar radiation field. The emission was predicted to be
extended and a confusing foreground for the diffuse extragalactic background
even at large angular distances from the Sun. The solar disk is also expected
to be a steady gamma-ray source. While these emissions are expected to be
readily detectable in the future by GLAST, the situation for available EGRET
data is more challenging. Aims: The theory of gamma-ray emission from IC
scattering on the solar radiation field by Galactic CR electrons is given in
detail. This is used as the basis for detection and model verification using
EGRET data. Methods: We present a detailed study of the solar emission using
the EGRET database, accounting for the effect of the emission from 3C 279, the
moon, and other sources, which interfere with the solar emission. The analysis
was performed for 2 energy ranges, above 300 MeV and for 100-300 MeV, as well
as for the combination to improve the detection statistics. The technique was
tested on the moon signal, with our results consistent with previous work.
Results: Analyzing the EGRET database, we find evidence of emission from the
solar disk and its halo. The observations are compared with our model for the
extended emission. The spectrum of the solar disk emission and the spectrum of
the extended emission have been obtained. The spectrum of the moon is also
given. Conclusions: The observed intensity distribution and the flux are
consistent with the predicted model of IC gamma-rays from the halo around the
Sun.Comment: Corrected typos, added acknowledgements. A&A in pres
Atomistic Hydrodynamics and the Dynamical Hydrophobic Effect in Porous Graphene
Mirroring their role in electrical and optical physics, two-dimensional
crystals are emerging as novel platforms for fluid separations and water
desalination, which are hydrodynamic processes that occur in nanoscale
environments. For numerical simulation to play a predictive and descriptive
role, one must have theoretically sound methods that span orders of magnitude
in physical scales, from the atomistic motions of particles inside the channels
to the large-scale hydrodynamic gradients that drive transport. Here, we use
constraint dynamics to derive a nonequilibrium molecular dynamics method for
simulating steady-state mass flow of a fluid moving through the nanoscopic
spaces of a porous solid. After validating our method on a model system, we use
it to study the hydrophobic effect of water moving through pores of
electrically doped single-layer graphene. The trend in permeability that we
calculate does not follow the hydrophobicity of the membrane, but is instead
governed by a crossover between two competing molecular transport mechanisms.Comment: 6 pages, 3 figure
Multi-wavelength Signatures of Cosmic Rays in the Milky Way
Cosmic rays (CRs) propagate in the Milky Way and interact with the
interstellar medium and magnetic fields. These interactions produce emissions
that span the electromagnetic spectrum, and are an invaluable tool for
understanding the intensities and spectra of CRs in distant regions, far beyond
those probed by direct CR measurements. We present updates on the study of CR
properties by combining multi-frequency observations of the interstellar
emission and latest CR direct measurements with propagation models.Comment: 8 pages, 4 figures. Proceedings of the 35th International Cosmic Ray
Conference, ICRC201
GALPROP WebRun: an internet-based service for calculating galactic cosmic ray propagation and associated photon emissions
GALPROP is a numerical code for calculating the galactic propagation of
relativistic charged particles and the diffuse emissions produced during their
propagation. The code incorporates as much realistic astrophysical input as
possible together with latest theoretical developments and has become a de
facto standard in astrophysics of cosmic rays. We present GALPROP WebRun, a
service to the scientific community enabling easy use of the freely available
GALPROP code via web browsers. In addition, we introduce the latest GALPROP
version 54, available through this service.Comment: Accepted for publication in Computer Physics Communications. Version
2 includes improvements suggested by the referee. Metadata completed in
version 3 (no changes to the manuscript
Surface circulation in the Great Lakes as observed by LANDSAT-1 August 1972 - December 1973: Southern Lake Michigan
The surface current circulation patterns of southern Lake Michigan were charted for all cardinal and subcardinal wind directions, employing LANDSAT-1 observations of the distribution of natural tracing material borne in the surface waters. These colorants consist chiefly of river discharges composed of suspended sediments, pollutants, and algae; extensive chemical precipitations proved valuable for areas farther from shore. Comparison of the satellite-derived surface current charts with previous theoretical and empirical studies shows good agreement
Chemical Bonds in the First Year Course
Author Institution: Department of Chemistry, Earlham College, Richmond, Indian
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