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In order to study the dependence of the secondary electron emission yield γ on the defect states of the MgO surface in plasma display panels, cathodoluminescence (CL) spectra of MgO films, which were deposited at oxygen partial pressures of 0, 4.0×10−4, and 1.2×10−5 Torr, were measured. The CL intensities from the F (oxygen ion vacancy+one electron) and F+ (oxygen ion vacancy+one electron) centers of the MgO film that was deposited at high oxygen partial pressure (1.2×10−4 Torr), significantly increased with aging during discharge. Assuming that the probabilities of transitions are proportional to the measured CL intensities from the F and F+ bands of the MgO films, the γi values of MgO films for Ne and Xe ions, which include the F and F+ bands, were calculated. The tendencies of the breakdown voltages calculated using these γi values were consistent with those of the measured voltages of the MgO films. These calculated results suggested that the influence of the F and F+ bands on the γi values for Xe ions is large compared with that for Ne ions, and that the γi value of the MgO film for Xe ions increases with increasing numerical densities of the F and F+ centers, especially for F+ centers.

Radiochlmica Actaculty. Our results, which can be observed in the Fig. 3 and 4, have some interesting consequences. In the zone of the maximal yield -(I _ /Thyr ratio approximately equal to 2) -the iodination degree is 1.7. In these conditions, a 50% of the radioactivity of the hydrolysed product correspond to diiodinated tyrosine; thus, considering that thyrotrophin ha» 10 tyrosine residues, it can be calculated that 4.25 % of those residues bear two iodine atoms. The same type of calculation shows that for a (I~/Thyr) ratio of 15.8 (the maximal ratio in our experiments), this value increases to 23.4%. On the other hand, bearing in mind that such a relatively high proportion of diiodinated tyrosine residues may eventually alter the behaviour of the labeled hormone, it seems advisable to make a compromise between the yield of the labeling process and the proportion of diiodinated tyrosine residues. In this sense, it can be calculated that, for a fairly high yield such as 70%, which has been obtained with a (I~/Thyr) ratio of 0.34, the iodination degree is 0.24 and only 0.2% of the tyrosine residues bear two iodine atoms. Thus, we think that these last conditions allow the obtention of a labeled hormone which is better suited for its subsequent utilization.From the foregoing discussion, it can be deduced also that the optimum ratio between the number of the iodide atoms which are present and the number of molecules of the polypeptide is independent of the relative proportion of Na 131 I in the total quantity of iodide. Thus, the conclusions of the present work are also valid for labeling with higher specific activities. Even though we studied only two molecules, the size and complexity of which are quite different, it should be mentioned that in some preliminary experiments we observed that in the labeling of human seroalbumin (molecular weight approximately equal to 69,000), it is possible to find a similar effect as that demonstrated in the case of thyrotrophin. These facts induce us to think that these phenomena may occur generally in any la-beling process of a polypeptide or a protein. For this reason we believe that similar studies as those reported here should be carried out for every particular polypeptide. This study should include basically the following points: 1. The determination of the optimum ratio between the number of iodide atoms and the number of polypeptidic molecules which are present in the reaction.2. The determination of the relative proportion of MIT and DIT residues with respect to the total number of polypeptidic molecules. This value is interesting because, as has been shown in the case of angiotensin [2], the presence of two iodine atoms in the same tyrosine residue, determines a significant decrease of the biological activity of the molecule. It seems possible that similar effects may be observed in other polypeptides having a given biological activity. Our results demonstrate also that it should be born in mind that the sole obtention of a high labeling yield is not a sufficient guara...

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A numerical simulation method using a one-dimensional fluid model under the local field approximation is presented in order to understand pulsed-dc discharge in He–Xe gas mixture in a cell of a full-color plasma display panel. Spatiotemporal behaviors of the electric field and number densities of twelve independent particles, including electrons and four kinds of ions, were calculated self-consistently at a gas pressure of 200 Torr (27 kPa) and an electrode distance of 0.02 cm. The imprisonment of 147-nm-resonance radiation, the excitation source of phosphors, was also taken into account. Calculated results of the discharge current and voltage are consistent with those of experiment. The waveform of 147-nm-resonance radiation agreed well with experiment, although that of the discharge current showed some difference, probably due to the local field approximation.

The surface voltage and charge on the dielectric barrier in a plasma display panel (PDP)-like microdischarge have been measured using an electrooptic crystal. The initiation of discharge starts the accumulation of surface charges and the charges spread uniformly over the entire region of the electrode surface under the condition of a time resolution of 0.1 ms. For the case of a gas mixture of Ne+Xe (10%), the plasma light emission at the cathode side is much stronger than that at the anode, however, the quantity of surface charges accumulated at both electrodes are the same. The surface charges at various gas pressures are also measured as functions of externally applied voltage and total charge flowing in an external circuit estimated from the discharge current. These characteristics for the microdischarge are compared with the results obtained for macrodischarge. It is found that the voltage difference on the barrier surface between the ground and high-voltage electrodes, caused by the accumulated charges, is an important factor in determining the barrier discharge.

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