92 research outputs found
Absorption and Screening in Phycomyces
In vivo absorption measurements were made through the photosensitive zones of Phycomyces sporangiophores and absorption spectra are presented for various growth media and for wavelengths between 400 and 580 mµ. As in mycelia, ß-carotene was the major pigment ordinarily found. The addition of diphenylamine to the growth media caused a decrease in ß-carotene and an increase in certain other carotenoids. Growth in the dark substantially reduced the amount of ß-carotene in the photosensitive zone; however, growth on a lactate medium failed to suppress ß-carotene in the growing zone although the mycelia appeared almost colorless. Also when diphenylamine was added to the medium the absorption in the growing zone at 460 mµ was not diminished although the colored carotenoids in the bulk of the sporangiophore were drastically reduced. Absorption which is characteristic of the action spectra was not found. Sporangiophores immersed in fluids with a critical refractive index show neither positive nor negative tropism. Measurements were made of the critical refractive indices for light at 495 and 510 mµ. The critical indices differed only slightly. Assuming primary photoreceptors at the cell wall, the change in screening due to absorption appears too large to be counterbalanced solely by a simple effect of the focusing change. The possibility is therefore advanced that the receptors are internal to most of the cytoplasm; i.e., near the vacuole
Relativistic Effect on Low-Energy Nucleon-Deuteron Scattering
The relativistic effect on differential cross sections, nucleon-to-nucleon
and nucleon-to-deuteron polarization transfer coefficients, and the spin
correlation function, of nucleon-deuteron elastic scattering is investigated
employing several three-dimensional relativistic three-body equations and
several nucleon-nucleon potentials. The polarization transfer coefficients are
found to be sensitive to the details of the nucleon-nucleon potentials and the
relativistic dynamics employed, and prefer trinucleon models with the correct
triton binding energy. (To appear in Phys. Rev. C)Comment: pages: 21, LaTex text + 7 ps-figures at the en
Proton-Deuteron Elastic Scattering from 2.5 to 22.5 MeV
We present the results of a calculation of differential cross sections and
polarization observables for proton-deuteron elastic scattering, for proton
laboratory energies from 2.5 to 22.5 MeV. The Paris potential parametrisation
of the nuclear force is used. As solution method for the charged-composite
particle equations the 'screening and renormalisation approach' is adopted
which allows to correctly take into account the Coulomb repulsion between the
two protons. Comparison is made with the precise experimental data of Sagara et
al. [Phys. Rev. C 50, 576 (1994)] and of Sperison et al. [Nucl. Phys. A422, 81
(1984)].Comment: 24 pages, 8 eps figures, uses REVTe
Collisions in a parallel atomic beam
A calculation is given for the collision frequency and the angular distribution of particles scattered from a well collimated atomic beam. It is assumed that their total number is small. Results are plotted for the flow from a supersonic nozzle with the Mach-number varying from 0 to 8. (2 refs)
Generator of a dense atomic gas curtain (for use in Intersecting Storage Rings)
A supersonic beam source is described which continuously generates a gas curtain for the proton beam profile observation in the Intersecting Storage Rings at CERN. Its maximum intensity is 10/sup 20 / atoms/sr s. A commonly used theoretical model for the determination of the intensity downstream of the source is discussed. Some results about the condensation behaviour of sodium vapour on metallic substrate surfaces are reported. (8 refs)
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