21,307 research outputs found
An algorithm for correcting CoRoT raw light curves
We introduce the CoRoT detrend algorithm (CDA) for detrending CoRoT stellar
light curves. The algorithm CDA has the capability to remove random jumps and
systematic trends encountered in typical CoRoT data in a fully automatic
fashion. Since enormous jumps in flux can destroy the information content of a
light curve, such an algorithm is essential. From a study of 1030 light curves
in the CoRoT IRa01 field, we developed three simple assumptions which upon CDA
is based. We describe the algorithm analytically and provide some examples of
how it works. We demonstrate the functionality of the algorithm in the cases of
CoRoT0102702789, CoRoT0102874481, CoRoT0102741994, and CoRoT0102729260. Using
CDA in the specific case of CoRoT0102729260, we detect a candidate exoplanet
around the host star of spectral type G5, which remains undetected in the raw
light curve, and estimate the planetary parameters to be Rp=6.27Re and P=1.6986
days.Comment: 8 pages, 13 figure
Notes on the Trematode Subfamily Loimoinae (Monogenea), with a Description of a New Genus
The subfamily Loimoinae was named by Price (1936) for a peculiar monogenetic trematode, Loimos salpinggoides MacCal lum, 1917, from the gills of a dusky shark, Carcharias obscurus (Lesueur), at Woods Hole, Massachusetts, USA. Price (1938) redescribed this trematode, correcting several errors made by MacCallum. Manter (1938) described Tricotyle scoliodoni from a shark, Scoliodon terrae-novae (Richardson), from Beaufort, North Carolina, USA. He noted some similarities between Tricotyle and Loimos. The redescription of Loimos by Price increased these similarities
Crystal water induced switching of magnetically active orbitals in CuCl2
The dehydration of CuCl2*2(H2O) to CuCl2 leads to a dramatic change in
magnetic behavior and ground state. Combining density functional electronic
structure and model calculations with thermodynamical measurements we reveal
the microscopic origin of this unexpected incident -- a crystal water driven
switching of the magnetically active orbitals. This switching results in a
fundamental change of the coupling regime from a three-dimensional
antiferromagnet to a quasi one-dimensional behavior. CuCl2 can be well
described as a frustrated J1-J2 Heisenberg chain with ferromagnetic exchange J1
and J2/J1 ~ -1.5 for which a helical ground state is predicted.Comment: 6 pages, 5 figures, 1 table (PRB, accepted
Intensity Thresholds and the Statistics of the Temporal Occurrence of Solar Flares
Introducing thresholds to analyze time series of emission from the Sun
enables a new and simple definition of solar flare events, and their
interoccurrence times. Rescaling time by the rate of events, the waiting and
quiet time distributions both conform to scaling functions that are independent
of the intensity threshold over a wide range. The scaling functions are well
described by a two parameter function, with parameters that depend on the phase
of the solar cycle. For flares identified according to the current, standard
definition, similar behavior is found.Comment: 5 pages, 4 figures, revtex
Bulk, rare earth and other trace elements in Apollo 14 and 15 and Luna 16 samples
The chemical abundances were measured by instrumental and radiochemical neutron activation analysis in a variety of lunar specimens. Apollo 14 soils are characterized by significant enrichments of Al2O3, Na2O and K2O and depletions of TiO2, FeO, MnO and Cr2O3 relative to Apollo 11 and to most of Apollo 12 soils. The uniform abundances in 14230 core tube soils and three other Apollo 14 soils indicate that the regolith is uniform to at least 22 cm depth and within approximately 200 m from the lunar module. Two Luna 16 breccias are similar in composition to Luna 16 soils. Four Apollo 15 soils (LM, STA 4, 9, and 9a) have variable compositions. Interelement correlations between MnO-FeO, Sc-FeO, V-Cr2O3 and K2O-Hf negate the hypothesis that howardite achondrites may be primitive lunar matter, argue against the fission hypothesis for the origin of the moon, and precludes any selective large scale volatilization of alkalies during lunar magmatic events
Long Term Surface Salinity Measurements
Our long-term goal is to establish a reliable system for monitoring surface salinity around the global ocean. Salinity is a strong indicator of the freshwater cycle and has a great influence on upper ocean stratification. Global salinity measurements have potential to improve climate forecasts if an observation system can be developed. This project is developing a new internal field conductivity cell that can be protected from biological fouling for two years. Combined with a temperature sensor, this foul-proof cell can be deployed widely on surface drifters. A reliable in-situ network of surface salinity sensors will be an important adjunct to the salinity sensing satellite AQUARIUS to be deployed by NASA in 2009. A new internal-field conductivity cell has been developed by N Brown, along with new electronics. This sensor system has been combined with a temperature sensor to make a conductivity - temperature (UT) sensor suitable for deployment on drifters. The basic sensor concepts have been proven on a high resolution CTD. A simpler (lower cost) circuit has been built for this application. A protection mechanism for the conductivity cell that includes antifouling protection has also been designed and built. Mr. A.Walsh of our commercial partner E-Paint has designed and delivered time-release formulations of antifoulants for our application. Mr. G. Williams of partner Clearwater Instrumentation advised on power and communication issues and supplied surface drifters for testing
The Homogeneous Nucleation Of Nonane
The homogeneous nucleation rate of n-nonane has been measured as a function of temperature and supersaturation ratio in a precision fast-expansion chamber. The measured nucleation rate ranges from 102 to 105 drops/cm3 over the temperature range 215-270 K. The results have been compared to the classical theory and to the classical theory with the RKC replacement factor. The RKC theory functional form is the basis for an empirical rate equation to fit the data. A full listing of the thermodynamic constants used for the reduction of the data is given. © 1984 American Institute of Physics
Homogeneous Nucleation Of Toluene
The authors have used a fast expansion chamber to measure the homogeneous nucleation rate of toluene as a function of temperature and supersaturation. The measured nucleation rate ranges from 102 to 105 drops/cm3 s over a temperature range of 215-267 K. The measurements are compared with the classical nucleation theory and with the RKC theory. The inclusion of the RKC replacement factor brings the data into good agreement with theory using physically realistic values of the surface tension and the sticking coefficient. An empirical curve fit to the data is presented as well as a full listing of the thermodynamic constants used for the calculations. © 1983 American Institute of Physics
Homogeneous Nucleation Of Ethanol
The authors have used an expansion cloud chamber to measure homogeneous nucleation rate as a function of temperature and supersaturation in ethanol. Nucleation rates from 102 to 105 drops/cm3 sec were measured in the temperature range 252-272 °K. An empirical functional fit to the data is used to extrapolate for comparison with other data in the literature at a nucleation rate of 1 drop/cm3 sec and to compare with the predictions of the classical Becker-Doring homogeneous nucleation theory. A full listing of the data and thermodynamics constants used in the reduction of the data is given in an appendix. © 1982 American Institute of Physics
Lifetime predictions for the Solar Maximum Mission (SMM) and San Marco spacecraft
Lifetime prediction techniques developed by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) are described. These techniques were developed to predict the Solar Maximum Mission (SMM) spacecraft orbit, which is decaying due to atmospheric drag, with reentry predicted to occur before the end of 1989. Lifetime predictions were also performed for the Long Duration Exposure Facility (LDEF), which was deployed on the 1984 SMM repair mission and is scheduled for retrieval on another Space Transportation System (STS) mission later this year. Concepts used in the lifetime predictions were tested on the San Marco spacecraft, which reentered the Earth's atmosphere on December 6, 1988. Ephemerides predicting the orbit evolution of the San Marco spacecraft until reentry were generated over the final 90 days of the mission when the altitude was less than 380 kilometers. The errors in the predicted ephemerides are due to errors in the prediction of atmospheric density variations over the lifetime of the satellite. To model the time dependence of the atmospheric densities, predictions of the solar flux at the 10.7-centimeter wavelength were used in conjunction with Harris-Priester (HP) atmospheric density tables. Orbital state vectors, together with the spacecraft mass and area, are used as input to the Goddard Trajectory Determination System (GTDS). Propagations proceed in monthly segments, with the nominal atmospheric drag model scaled for each month according to the predicted monthly average value of F10.7. Calibration propagations are performed over a period of known orbital decay to obtain the effective ballistic coefficient. Progagations using plus or minus 2 sigma solar flux predictions are also generated to estimate the despersion in expected reentry dates. Definitive orbits are compared with these predictions as time expases. As updated vectors are received, these are also propagated to reentryto continually update the lifetime predictions
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