964 resultados para Melanosome photo-dispersion
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Référence bibliographique : Rol, 58716
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Référence bibliographique : Rol, 59494
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Référence bibliographique : Rol, 59495
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Référence bibliographique : Rol, 59496
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Référence bibliographique : Rol, 59497
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Référence bibliographique : Rol, 59498
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Référence bibliographique : Rol, 59499
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Michael Snow's 'Photo Essay' that adorns a wall in A Block.
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The atomic mean square displacement (MSD) and the phonon dispersion curves (PDC's) of a number of face-centred cubic (fcc) and body-centred cubic (bcc) materials have been calclllated from the quasiharmonic (QH) theory, the lowest order (A2 ) perturbation theory (PT) and a recently proposed Green's function (GF) method by Shukla and Hiibschle. The latter method includes certain anharmonic effects to all orders of anharmonicity. In order to determine the effect of the range of the interatomic interaction upon the anharmonic contributions to the MSD we have carried out our calculations for a Lennard-Jones (L-J) solid in the nearest-neighbour (NN) and next-nearest neighbour (NNN) approximations. These results can be presented in dimensionless units but if the NN and NNN results are to be compared with each other they must be converted to that of a real solid. When this is done for Xe, the QH MSD for the NN and NNN approximations are found to differ from each other by about 2%. For the A2 and GF results this difference amounts to 8% and 7% respectively. For the NN case we have also compared our PT results, which have been calculated exactly, with PT results calculated using a frequency-shift approximation. We conclude that this frequency-shift approximation is a poor approximation. We have calculated the MSD of five alkali metals, five bcc transition metals and seven fcc transition metals. The model potentials we have used include the Morse, modified Morse, and Rydberg potentials. In general the results obtained from the Green's function method are in the best agreement with experiment. However, this improvement is mostly qualitative and the values of MSD calculated from the Green's function method are not in much better agreement with the experimental data than those calculated from the QH theory. We have calculated the phonon dispersion curves (PDC's) of Na and Cu, using the 4 parameter modified Morse potential. In the case of Na, our results for the PDC's are in poor agreement with experiment. In the case of eu, the agreement between the tlleory and experiment is much better and in addition the results for the PDC's calclliated from the GF method are in better agreement with experiment that those obtained from the QH theory.
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On cover: Niagara Falls.
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Photosynthetic state transitions were investigated in the cyanobacterium Synechococcus sp. PCC 6301 by studying fluorescence emission, heat loss, and PS I activity in intact cells brought to state 1 and state 2. 77K fluorescence emission spectra were modelled with a sum of 6 components corresponding to PBS, PS II, and PS I emissions. The modelled data showed a large decrease in PS II fluorescence accompanied with a small increase in the PS I fluorescence upon transition to state 2 for excitation wavelengths absorbed by both PBS and ChI ll.. The fluorescence changes seen with ChI .a. excitations do not support the predictions of the mobile PBS model of state transition in PBS-containing organisms. Measurements of heat loss from intact cells in the two states were similar for both ChI it. and PBS excitations over three orders of magnitude of laser flash intensity. This suggests that the PBS does not become decoupled from PS II in state 2 as proposed by the PBS detachment model of state transition in PBS-containing organisms. PS I activity measurements done on intact cells showed no difference in the two states, in contrast with the predictions of all of the existing models of state transitions. Based on these results a model for state transition In PBScontaining organisms is proposed, with a PS II photoprotectory function.
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This photograph was taken on the wedding day of Richard Nelson Bell and Iris Sloman in 1939. Pictured in the photograph, from left, are: Charles Bell, father of Richard Nelson Bell; Josephine Sloman, mother of Iris; Richard Nelson Bell; Iris Sloman Bell; Mary Bell, mother of Richard Nelson Bell; and Albert Sloman, father of Iris. This family photo was in the possession of Rick Bell, of St. Catharines, Ontario. The Sloman - Bell ancestry includes escaped Black slaves from the United States.
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A black and white photograph taken in 1939 on the occasion of the marriage of Richard Nelson Bell to Iris Sloman. Pictured in the photograph, from left to right, are: Bert Sloman; Richard Nelson Bell; Iris Sloman Bell; and Helen Beatty Sloman. This photograph was in the possession of Rick Bell, the son of Richard Nelson and Iris Bell. The Bell - Sloman family descends from former Black slaves from the United States.Bert Sloman (Albert Edward Sloman) passed away in 1986 at Kitchener-Waterloo, Ontario. His wife Vera Matilda Sloman passed away January 4, 2011 at Cambridge Memorial Hospital. They had a son, Ron Sloman.
