1,827 research outputs found
Design study for LANDSAT D attitude control system
A design and performance evaluation is presented for the LANDSAT D attitude control system (ACS). Control and configuration of the gimballed Ku-band antenna system for communication with the tracking and data relay satellite (TDRS). Control of the solar array drive considered part of the ACS is also addressed
Design study for LANDSAT-D attitude control system
The gimballed Ku-band antenna system for communication with TDRS was studied. By means of an error analysis it was demonstrated that the antenna cannot be open loop pointed to TDRS by an onboard programmer, but that an autotrack system was required. After some tradeoffs, a two-axis, azimuth-elevation type gimbal configuration was recommended for the antenna. It is shown that gimbal lock only occurs when LANDSAT-D is over water where a temporary loss of the communication link to TDRS is of no consequence. A preliminary gimbal control system design is also presented. A digital computer program was written that computes antenna gimbal angle profiles, assesses percent antenna beam interference with the solar array, and determines whether the spacecraft is over land or water, a lighted earth or a dark earth, and whether the spacecraft is in eclipse
Sulphur-bearing molecules in diffuse molecular clouds: new results from SOFIA/GREAT and the IRAM 30 m telescope
We have observed five sulphur-bearing molecules in foreground diffuse
molecular clouds lying along the sight-lines to five bright continuum sources.
We have used the GREAT instrument on SOFIA to observe the 1383 GHz transitions of SH towards the star-forming regions W31C,
G29.96-0.02, G34.3+0.1, W49N and W51, detecting foreground absorption towards
all five sources; and the EMIR receivers on the IRAM 30m telescope at Pico
Veleta to detect the HS 1(10)-1(01), CS J=2-1 and SO 3(2)-2(1) transitions.
In nine foreground absorption components detected towards these sources, the
inferred column densities of the four detected molecules showed relatively
constant ratios, with N(SH)/N(HS) in the range 1.1 - 3.0, N(CS)/N(HS)
in the range 0.32 - 0.61, and N(SO)/N(HS) in the range 0.08 - 0.30. The
observed SH/H ratios - in the range (0.5-2.6) - indicate
that SH (and other sulphur-bearing molecules) account for << 1% of the
gas-phase sulphur nuclei. The observed abundances of sulphur-bearing molecules,
however, greatly exceed those predicted by standard models of cold diffuse
molecular clouds, providing further evidence for the enhancement of endothermic
reaction rates by elevated temperatures or ion-neutral drift. We have
considered the observed abundance ratios in the context of shock and turbulent
dissipation region (TDR) models. Using the TDR model, we find that the
turbulent energy available at large scale in the diffuse ISM is sufficient to
explain the observed column densities of SH and CS. Standard shock and TDR
models, however, fail to reproduce the column densities of HS and SO by a
factor of about 10; more elaborate shock models - in which account is taken of
the velocity drift, relative to H, of SH molecules produced by the
dissociative recombination of HS - reduce this discrepancy to a factor
~ 3.Comment: 30 pages, accepted for publication in A&
Alteraciones de las carnes congeladas y enfriadas : Medios para evitarlas
Primera parte (por Juan E. Richelet): Mohosidades. Slime. Mould. Moisissnres. Brown o Black Spot. Cómo se pueden evitar las mohosidades de las carnes.
Segunda parte (por Juan E. Richelet): Bone Stink. Bola hedionda. Hediondez de huesos. Procedimientos
adoptados por las empresas de los frigorÃficos establecidos en el paÃs para evitar el Bone Stink. Operación que se realiza en los frigorÃficos antes de embarcar carnes, para cerciorarse si están atacadas de esta alteración. Medidas a tomarse.
Tercera parte (por el Dr. Desiderio Bernier): Onchocerca Gibsoni. Onchocerciasis. Familia de los Filarideos. Comprobación del parásito y medidas tomadas. Consideraciones sobre el parásito y los nódulos. Distribución geográfica del parásito. Descripción del parásito. Caracteres. Nomenclatura. Acción patológica del parásito. Conclusiones.Facultad de Ciencias Agrarias y Forestale
Kinetically Inhibited Order in a Diamond-Lattice Antiferromagnet
Frustrated magnetic systems exhibit highly degenerate ground states and
strong fluctuations, often leading to new physics. An intriguing example of
current interest is the antiferromagnet on a diamond lattice, realized
physically in A-site spinel materials. This is a prototypical system in three
dimensions where frustration arises from competing interactions rather than
purely geometric constraints, and theory suggests the possibility of unusual
magnetic order at low temperature. Here we present a comprehensive
single-crystal neutron scattering study of CoAl2O4, a highly frustrated A-site
spinel. We observe strong diffuse scattering that peaks at wavevectors
associated with Neel ordering. Below the temperature T*=6.5 K, there is a
dramatic change in the elastic scattering lineshape accompanied by the
emergence of well-defined spin-wave excitations. T* had previously been
associated with the onset of glassy behavior. Our new results suggest instead
that T* signifies a first-order phase transition, but with true long-range
order inhibited by the kinetic freezing of domain walls. This scenario might be
expected to occur widely in frustrated systems containing first-order phase
transitions and is a natural explanation for existing reports of anomalous
glassy behavior in other materials.Comment: 40 pages, 9 figures, Introduction and discussion altered and
expanded. Additional section and figure added to Supplementary Informatio
Management of radiation dermatitis in patients receiving cetuximab and radiotherapy for locally advanced squamous cell carcinoma of the head and neck: proposals for a revised grading system and consensus management guidelines
Background: Radiation dermatitis developing in patients receiving cetuximab concomitantly with radiotherapy for locally advanced squamous cell carcinoma of the head and neck (LA SCCHN) is now recognized to have different pathophysiological and clinical characteristics to the radiation dermatitis associated with radiotherapy or concomitant chemotherapy and radiotherapy. Current grading tools were not designed to grade this type of radiation dermatitis; their use may lead to misclassification of reactions and inappropriate management strategies, potentially compromising cancer treatment. Patients and methods: An advisory board of seven leading European specialists (three medical oncologists, three radiation oncologists and a dermatologist) with extensive experience of the use of cetuximab plus radiotherapy produced consensus guidelines for the grading and management of radiation dermatitis in patients receiving cetuximab plus radiotherapy. Results: Modifications to the current, commonly used National Cancer Institute—Common Terminology Criteria for Adverse Events version 4.3 for grading radiation dermatitis were proposed. Updated management guidelines, building on previously published guidelines from 2008, were also proposed. Conclusions: The proposed revisions to the grading system and updated management guidelines described here represent important developments toward the more appropriate grading and effective management of radiation dermatitis in patients receiving cetuximab plus radiotherapy for LA SCCH
Controlling suction by vapour equilibrium technique at different temperatures, application to the determination of the water retention properties of MX80 clay
Problems related to unsaturated soils are frequently encountered in
geotechnical or environmental engineering works. In most cases, for the purpose
of simplicity, the problems are studied by considering the suction effects on
volume change or shear strength under isothermal conditions. Under isothermal
condition, very often, a temperature independent water retention curve is
considered in the analysis, which is obviously a simplification. When the
temperature changes are too significant to be neglected, it is necessary to
account for the thermal effects. In this paper, a method for controlling
suction using the vapour equilibrium technique at different temperatures is
presented. First, calibration of various saturated saline solutions was carried
out from temperature of 20 degrees C to 60 degrees C. A mirror psychrometer was
used for the measurement of relative humidity generated by saturated saline
solutions at different temperatures. The results obtained are in good agreement
with the data from the literature. This information was then used to determine
the water retention properties of MX80 clay, which showed that the retention
curve is shifting down with increasing of temperature
Science results from the imaging Fourier transform spectrometer SpIOMM
SpIOMM is an imaging Fourier transform spectrometer designed to obtain the
visible range (350 to 850 nm) spectrum of every light source in a circular
field of view of 12 arcminutes in diameter. It is attached to the 1.6-m
telescope of the Observatoire du Mont Megantic in southern Quebec. We present
here some results of three successful observing runs in 2007, which highlight
SpIOMMs capabilities to map emission line objects over a very wide field of
view and a broad spectral range. In particular, we discuss data cubes from the
planetary nebula M27, the supernova remnants NGC 6992 and M1, the barred spiral
galaxy NGC7479, as well as Stephans quintet, an interacting group of galaxies.Comment: 10 pages, 7 figures, to appear in "Ground-based and Airborne
Instrumentation for Astronomy II", SPIE conference, Marseille, 23-28 June
200
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