36,996 research outputs found
The Colour Changes In Lizards, Particularly In Phrynosoma
The activities of the melanophore system of Phrynosoma in comparison with that of Chamaeleo may be stated categorically in the following way.
I. The blanching of Phrynosoma blainvillii is due
(1) to the action of its concentrating nerve-fibres on its melanophores,
(2) to the action of a hydrohumour, probably adrenalin, on the same cells,
(3) to the direct response of these cells to darkness, and
(4) to high temperatures.
II. The blanching of Chamaeleo is due to the first, third, and fourth of these factors. Whether the second factor is effective in this lizard is not yet determined.
III. The darkening of Phrynosoma is due
(5) to the action of a pituitary neurohumour on its melanophores,
(6) to the direct response of these cells to strong light, and
(7) usually, to low temperatures.
There are no dispersing nerve-fibres known in Phrynosoma.
IV. The darkening of Chamaeleo is due to the sixth and probably to the seventh of these factors. This lizard presents strong indications of possessing dispersing nerve-fibres. Whether it darkens from a pituitary neurohumour or not is unknown
Forest and range mapping in the Houston area with ERTS-1
ERTS-1 data acquired over the Houston area has been analyzed for applications to forest and range mapping. In the field of forestry the Sam Houston National Forest (Texas) was chosen as a test site, (Scene ID 1037-16244). Conventional imagery interpretation as well as computer processing methods were used to make classification maps of timber species, condition and land-use. The results were compared with timber stand maps which were obtained from aircraft imagery and checked in the field. The preliminary investigations show that conventional interpretation techniques indicated an accuracy in classification of 63 percent. The computer-aided interpretations made by a clustering technique gave 70 percent accuracy. Computer-aided and conventional multispectral analysis techniques were applied to range vegetation type mapping in the gulf coast marsh. Two species of salt marsh grasses were mapped
Thomas-Fermi versus one- and two-dimensional regimes of a trapped dipolar Bose-Einstein condensate
We derive the criteria for the Thomas-Fermi regime of a dipolar Bose-Einstein
condensate in cigar, pancake and spherical geometries. This also naturally
gives the criteria for the mean-field one- and two-dimensional regimes. Our
predictions, including the Thomas-Fermi density profiles, are shown to be in
excellent agreement with numerical solutions. Importantly, the anisotropy of
the interactions has a profound effect on the Thomas-Fermi/low-dimensional
criteria.Comment: 5 pages, 2 figure
Design considerations and test facilities for accelerated radiation effects testing
Test design parameters for accelerated dose rate radiation effects tests for spacecraft parts and subsystems used in long term mission (years) are detailed. A facility for use in long term accelerated and unaccelerated testing is described
Jupiters radiation belts and their effects on spacecraft
The effects of electron and proton radiation on spacecraft which will operate in the trapped radiation belts of the planet Jupiter are described, and the techniques and results of the testing and simulation used in the radiation effects program are discussed. Available data from the Pioneer 10 encounter of Jupiter are compared with pre-encounter models of the Jupiter radiation belts. The implications that the measured Jovian radiation belts have for future missions are considered
Design studies of continuously variable transmissions for electric vehicles
Preliminary design studies were performed on four continuously variable transmission (CVT) concepts for use with a flywheel equipped electric vehicle of 1700 kg gross weight. Requirements of the CVT's were a maximum torque of 450 N-m (330 lb-ft), a maximum output power of 75 kW (100 hp), and a flywheel speed range of 28,000 to 14,000 rpm. Efficiency, size, weight, cost, reliability, maintainability, and controls were evaluated for each of the four concepts which included a steel V-belt type, a flat rubber belt type, a toroidal traction type, and a cone roller traction type. All CVT's exhibited relatively high calculated efficiencies (68 percent to 97 percent) over a broad range of vehicle operating conditions. Estimated weight and size of these transmissions were comparable to or less than equivalent automatic transmission. The design of each concept was carried through the design layout stage
Inflation, Renormalization, and CMB Anisotropies
In single-field, slow-roll inflationary models, scalar and tensorial
(Gaussian) perturbations are both characterized by a zero mean and a non-zero
variance. In position space, the corresponding variance of those fields
diverges in the ultraviolet. The requirement of a finite variance in position
space forces its regularization via quantum field renormalization in an
expanding universe. This has an important impact on the predicted scalar and
tensorial power spectra for wavelengths that today are at observable scales. In
particular, we find a non-trivial change in the consistency condition that
relates the tensor-to-scalar ratio "r" to the spectral indices. For instance,
an exact scale-invariant tensorial power spectrum, n_t=0, is now compatible
with a non-zero ratio r= 0.12 +/- 0.06, which is forbidden by the standard
prediction (r=-8n_t). Forthcoming observations of the influence of relic
gravitational waves on the CMB will offer a non-trivial test of the new
predictions.Comment: 4 pages, jpconf.cls, to appear in the Proceedings of Spanish
Relativity Meeting 2009 (ERE 09), Bilbao (Spain
Some gamma-ray shielding measurements made at altitudes greater than 115000 feet using large Ge(Li) detectors
A series of balloon-flight experiments at altitudes greater than 115,000 feet were conducted to gain information relative to the use of composite shields (passive and/or active) for shielding large-volume, lithium-drifted, germanium (Ge(Li)) detectors used in gamma-ray spectrometers. Data showing the pulse-height spectra of the environmental gamma radiation as measured at 5.3 and 3.8 gms sq cm residual atmosphere with an unshielded diode detector are also presented
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