29,840 research outputs found
GMRT Low Frequency Observations of Extrasolar Planetary Systems
Extrasolar planets are expected to emit detectable low frequency radio
emission. In this paper we present results from new low frequency observations
of two extrasolar planetary systems (Epsilon Eridani and HD 128311) taken at
150 MHz with the Giant Metrewave Radio Telescope (GMRT). These two systems have
been chosen because the stars are young (with ages < 1 Gyr) and are likely to
have strong stellar winds, which will increase the expected radio flux. The
planets are massive (presumably) gas giant planets in longer period orbits, and
hence will not be tidally locked to their host star (as is likely to be the
case for short period planets) and we would expect them to have a strong
planetary dynamo and magnetic field. We do not detect either system, but are
able to place tight upper limits on their low frequency radio emission, at
levels comparable to the theoretical predictions for these systems. From these
observations we have a 2.5sigma limit of 7.8 mJy for Epsilon Eri and 15.5 mJy
for HD 128311. In addition, these upper limits also provide limits on the low
frequency radio emission from the stars themselves. These results are discussed
and also the prospects for the future detection of radio emission from
extrasolar planets.Comment: 6 pages, 2 figures, accepted for publication in MNRA
Patterns in Illinois Educational School Data
We examine Illinois educational data from standardized exams and analyze
primary factors affecting the achievement of public school students. We focus
on the simplest possible models: representation of data through visualizations
and regressions on single variables. Exam scores are shown to depend on school
type, location, and poverty concentration. For most schools in Illinois,
student test scores decline linearly with poverty concentration. However
Chicago must be treated separately. Selective schools in Chicago, as well as
some traditional and charter schools, deviate from this pattern based on
poverty. For any poverty level, Chicago schools perform better than those in
the rest of Illinois. Selective programs for gifted students show high
performance at each grade level, most notably at the high school level, when
compared to other Illinois school types. The case of Chicago charter schools is
more complex. In the last six years, their students' scores overtook those of
students in traditional Chicago high schools.Comment: 9 pages, 6 figure
Thin Film Formation During Splashing of Viscous Liquids
After impact onto a smooth dry surface, a drop of viscous liquid initially
spreads in the form of a thick lamella. If the drop splashes, it first emits a
thin fluid sheet that can ultimately break up into droplets causing the splash.
Ambient gas is crucial for creating this thin sheet. The time for sheet
ejection, , depends on impact velocity, liquid viscosity, gas pressure
and molecular weight. A central air bubble is trapped below the drop at
pressures even below that necessary for this sheet formation. In addition, air
bubbles are entrained underneath the spreading lamella when the ejected sheet
is present. Air entrainment ceases at a lamella velocity that is independent of
drop impact velocity as well as ambient gas pressure.Comment: 8 pages, 11 figure
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Trace gas transport in the subsurface of Mars
The ExoMars Trace Gas Orbiter (TGO) will have the capability of detecting and characterizing a broad suite of trace gases in the atmosphere of Mars. Interpreting the results of this mission will require an understanding of how these trace gases are transported from their sources, which may be deep underground, to the atmosphere. Here we present results of modeling designed to measure the timescales of release from putative subsurface methane sources. These transport timescales are far longer than mixing times in the atmosphere and could be up to 10 million years
Development of a floating tidal energy system suitable for use in shallow water
A proposal is made for the use of a traditional streamwaterwheel suspended between two floating catamaranNPL series demi-hulls as means of generating electricalpower. Two prototype devices, of lengths 1.6m and 4.5m,have been developed, constructed and tested. It was foundthat the concept is sound although greater investment isrequired with regards to the materials and bothhydrodynamic and aerodynamic design of the waterwheelto ensure an economically viable system. The workpresented concentrates on practical aspects associated withdesign, construction and trial testing in Southampton waterof the 4.5m prototype. The relatively low cost, ease ofdeployment, and the fact that conventional boat mooringsystems are effective, combine to make this an attractivealternative energy solution for remote communities
A theoretical study of the aerodynamic characteristics of lifting-body entry vehicles Summary report, Mar. 1965 - Mar. 1966
Aerodynamic characteristics of lifting-body entry vehicle
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New Early Miocene Formation and Vertebrate Local Fauna, Big Bend National Park, Brewster County, Texas
Contents: Abstract -- Introduction -- Acknowledgments -- Localities -- Synopsis of Fauna -- Part I: Geology -- Part II: Systematic Descriptions, Excluding Lagomorpha -- Part III: Systematic Descriptions, Lagomorpha -- Part IV: Age and Interpretation of the Castolon Local Fauna -- Literatrue CitedThe early Miocene Delaho (new) Formation is a locally derived sequence of basin fill sediments now severely deformed by later Tertiary normal faulting. These sediments contain the Castolon local fauna comprising seventeen mammalian taxa. Three genera are new. Age of the Castolon local fauna is considered middle Arikareean, and differences between it and other Arikareean faunas are caused in part by ecological bias.Texas Memorial Museu
Creation of prompt and thin-sheet splashing by varying surface roughness or increasing air pressure
A liquid drop impacting a solid surface may splash by emitting a thin liquid
sheet that subsequently breaks apart or by promptly ejecting droplets from the
advancing liquid-solid contact line. Using high-speed imaging, we show that air
pressure and surface roughness influence both splash mechanisms. Roughness
increases prompt splashing at the advancing contact line but inhibits the
formation of the thin sheet. If the air pressure is lowered, droplet ejection
is suppressed not only during thin-sheet formation but for prompt splashing as
well. The threshold pressure depends on impact velocity, liquid viscosity and
surface roughness
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