Proposed New Method for Separating Isotopes
RECENTLY1 a double mercury discharge vessel was used (Fig. 1), in which a large current running in the outer vessel irradiated the small current discharge in the inner vessel with 2537 Å resonance radiation. This irradiation caused the running voltage and electron temperature in the inner discharge to be reduced appreciably over the non-irradiated mode of operation. The explanation offered was that the neutral Hg atoms in the inner vessel absorbed the resonance radiation and entered the 63P1 state (see Fig. 2), and from this level the atom was ionized by electron impact. In addition the 63P0 and 63P2 metastable levels are populated from the 63P1 level by electron collisions and by cumulative absorption and radiative decay of higher levels. Because the radiation field is doing approximately half the ionization work, the electron temperature drops correspondingly.
Immunoglobulin g lymphocytotoxic antibodies in clinical liver transplantation: Studies toward further defining their significance
Twenty‐two consecutive liver allograft recipients, who tested positive for immunoglobulin G (IgG) lympho‐cytotoxicity were subjected to pretransplantion and posttransplantation immunologic monitoring of antidonor IgG lymphocytotoxic antibody titers, total hemolytic complement activity (CH100), circulating immune complexes (CIC), and platelet counts in an effort to improve our understanding of the preformed antibody state in clinical hepatic transplantation. Ten contemporaneous liver transplant recipients whose crossmatch results were negative and who experienced severe hepatocellular damage early after transplantation were included as controls. Crossmatch test results were negative 1 day after transplantation and during the 1 month follow‐up remained negative in 14 of 22 (64%) sensitized recipients, most of whom had relatively low (≦ 1:16) antidonor IgG antibody titers before transplantation. After transplantation, this group and the control group experienced no thrombocytopenia, no increase of CIC, and a gradual increase in CH100 activity that reached normal levels within 1 week. A strong negative correlation between prothrombin time (PT) and CH100 activity in these groups of patients suggested that changes in CH100 activity (P < 0.0005) were tightly linked to liver synthetic function. In contrast, the crossmatch test results remained positive after transplantation in 8 of 22 (36%) sensitized recipients, all of whom had relatively high (> 1:32 to 1024) pretransplantation titers of antidonor IgG antibodies. After transplantation these patients developed a syndrome that was characterized by decreased CH100 activity and increased CIC compared with pretransplantation levels and refractory thrombocytopenia that was associated with a 50% allograft failure rate because of biopsy‐proven humoral and acute (cellular) rejection. Moreover, the lack of a strong negative correlation between PT and CH100 activity (P = 0.1) in this group of patients suggested that the hypocomplementemia was not tightly linked to liver synthetic function. Before transplantation, determination of anti—donor antibody class (IgG) and titer alone showed a strong negative predictive value (100%) but less than optimal positive predictive value (67%) for identifying patients who experienced the posttransplantation syndrome described above. Therefore, evaluation of platelet counts, CH100 activity, CIC, persistence of anti‐donor antibodies and results of a liver biopsy performed after transplantation assisted in identifying sensitized liver allograft recipients who suffered the adverse consequences of the preformed antibody state.
Electron Attachment in Sulfur Hexafluoride Using Monoenergetic Electrons
Electron attachment leading to the formation of SF6— and SF5— in sulfur hexafluoride has been investigated using nearly‐monoenergetic electrons of established energies of less than 2 ev. The dissociative attachment process leading to the formation of SF5— maximizes at less than 0.1 ev and then decreases to zero at approximately 1.5 ev. In the case of resonance capture leading to the formation of SF6—, the capture process occurs at less than 0.1 ev and only over an energy range estimated to be not larger than 0.05 ev. This leads to an estimated cross section for this resonance capture process of 10—15 cm2. A discussion is given of the method used in the establishment of the electron energy scale at such low energies and the use of the resonance capture process for measuring electron energy distributions.