M2 Decrease Research Articles

Intra-pulse decrease of M2 of a copper vapor laser beam

The temporal behavior of the beam divergence of a copper vapor laser (CVL) equipped with on- or off-axis unstable resonators at 510.6 nm has been investigated experimentally and theoretically. The temporal change of the beam divergence is measured using a streak camera and is evaluated by the M 2 factor. Narrowing of the beam divergence during the pulse is observed. Also is found that the difference of the narrowing ratio between the on-axis and off-axis unstable resonators resulted from the near-field pattern of the laser beam.

1H-NMR studies on thermochromism Ni(ii) complexes with N,N-diethylethylenediamine

The temperature dependence of the second moment (M2) of 1H NMR absorptions was measured in solid thermochromic bis(N,N-diethylethylenediamine)Ni(II) complexes. Perchlorate and tetrafluoroborate having a thermochromic phase transition at Ttr = 383 and 367 K, respectively, showed a discontinuous M2 change at Ttrr indicating that a marked change of the chelate-ring motions takes place at the transition. A small M2 value of ca. 8 G2 observed above the respective Ttr could be explained by the excitation of the chelate-ring puckering together with a large-amplitude librations of the whole complex ions. A gradual M2 decrease upon heating from 100 to 400 K was observed in bromide and iodide exhibiting continuous thermochromism. These M2 changes and the reported visible electron absorption maxima showed a quite analogous temperature dependence. This suggests that some kind of chelate-ring motion such as the puckering also takes place in the continuous thermochromism complexes.

Pyruvate kinase synthesis and degradation by normal and pathologic cells during erythroid maturation

Mature erythrocytes contain a specific isozyme of pyruvate kinase (R- PK) while immature erythroblasts coexpress R-PK and another isozyme, M2- PK. To determine what roles degradation and decreasing of synthesis played in the disappearance of M2-PK during erythroid maturation, M2-PK and R-PK synthesis and degradation were studied in erythroblasts from fetal liver and blood BFU-E-derived erythroblasts from healthy subjects, an erythroleukemic patient, and a patient with an erythrocyte PK hyperactivity associated with M2-PK persistence in mature erythrocytes. In normal erythroblasts, R-PK synthesis was constant throughout erythroid maturation, whereas M2-PK synthesis decreased to the point of becoming undetectable. R-PK degradation was very low, while M2-PK degradation was more pronounced and steady during erythroid maturation. In leukemic erythroblasts, total protein turnover was higher than in normal cells, but the M2-PK degradation rate was lower. In erythroblasts from the patient with M2-PK persistence in mature erythrocytes, M2-PK synthesis did not decline with cell maturation. In conclusion, our results emphasize the importance of the decrease of M2- PK synthesis in the disappearance of M2-PK during erythroid maturation. Further studies of patients with pathologic persistence of M2-PK synthesis will help in the understanding of this event involved in erythroid maturation.

1H and 19F NMR Studies on the Motion of Ammonium Ions in Solid Ammonium Tetrafluoroaluminate(III)

The temperature dependences of the NMR second moment, M2, and of the spin-lattice relaxation time, T1, of 1H and 19F nulcei were observed for NH4AIF4. With increasing temperature a decrease of M2(1H ), attributable to the onset of cationic reorientation, was observed between 77 and 150 K. This was confirmed by measurements of T1(1H) observed at two Larmor frequencies. Nonexponential magnetization recovery was detected in the T1 measurement of both 1H and 19F, especially below 150 K, indicating strong magnetic coupling between both systems. Therefore, in such cases T1 was determined from the initial slope of the magnetization recovery curve. The motional parameters of the cation were evaluated from the T1, data. The log T1 vs. T-1 curves of both nuclei showed a discontinuity around 143 K, indicating a phase transition which has already been suggested by other workers.

Experimental and molecular dynamics study of depolarized Rayleigh scattering by O2

Collision-induced effects on depolarized Rayleigh scattering (DRS) in gaseous oxygen at 300 K in the pressure range from 10 to 3000 bar have been studied experimentally. DRS spectra for four thermodynamic states at this temperature and in the pressure range from 130 to 3000 bar have also been obtained from molecular dynamics (MD) simulation. Molecular trajectories were calculated using the Lennard-Jones atom–atom potential and the system polarizability was modeled using the first order dipole–induced dipole approximation. The frequency dependence of DRS band shapes is well reproduced by the MD results, which predict that the orientational contribution dominates the overall band shape. The agreement between experimental and calculated second, fourth, and sixth spectral moments is very good. The observed density dependence of the spectral moments is analyzed in terms of contributions from the collision-induced (CI) polarizability component and orientational pair correlations. The second spectral moment, M2, is found to decrease with increasing density at low densities and to increase at higher densities. The MD results indicate that the initial decrease in M2 is due primarily to slow relaxation of the CI polarizability at low densities. The increase in M2 at higher densities is found to be mainly due to the contribution from orientational-CI cross correlations. MD results as well as analytical calculations, carried out for the low density limit, predict that the CI contribution to the total DRS intensity remains relatively small (≤4%) throughout the entire density range. The observed density dependence of the intensity is not consistent with these calculations. Possible sources of this disagreement are discussed.