Metastable anions of dinitrobenzene: resonances for electron attachment and kinetic energy release.

Attachment of free, low-energy electrons to dinitrobenzene (DNB) in the gas phase leads to DNB(-) as well as several fragment anions. DNB(-), (DNB-H)(-), (DNB-NO)(-), (DNB-2NO)(-), and (DNB-NO(2))(-) are found to undergo metastable (unimolecular) dissociation. A rich pattern of resonances in the yield of these metastable reactions versus electron energy is observed; some resonances are highly isomer-specific. Most metastable reactions are accompanied by large average kinetic energy releases (KER) that range from 0.5 to 1.32 eV, typical of complex rearrangement reactions, but (1,3-DNB-H)(-) features a resonance with a KER of only 0.06 eV for loss of NO. (1,3-DNB-NO)(-) offers a rare example of a sequential metastable reaction, namely, loss of NO followed by loss of CO to yield C(5)H(4)O(-) with a large KER of 1.32 eV. The G4(MP2) method is applied to compute adiabatic electron affinities and reaction energies for several of the observed metastable channels.

Low-energy electron attachment to the dichlorodifluoromethane (CCl2F2) molecule.

Results from a joint experimental study of electron attachment to dichlorodifluoromethane (CCl(2)F(2)) molecules in the gas phase are reported. In a high resolution electron beam experiment involving two versions of the laser photoelectron attachment method, the relative cross section for formation of the dominant anion Cl(-) was measured over the energy range 0.001-1.8 eV at the gas temperature T(G) = 300 K. It exhibits cusp structure at thresholds for vibrational excitation of the nu(3)(a(1)) mode due to interaction with the attachment channels. With reference to the thermal attachment rate coefficient k(T = 300 K) = 2.2(8) x 10(-9) cm(3) s(-1) (fitted average from several data), a new highly resolved absolute attachment cross section for T(G) = 300 K was determined. Partial cross sections for formation of the anions Cl(-), Cl(2)(-), F(-), ClF(-), and CCl(2)F(-) were measured over the range 0-12 eV, using three different electron beam experiments of medium energy resolution. The dependence of the attachment rate coefficient k(T(e);T(G) = 300 K) on electron temperature T(e) was calculated over the range 50-15 000 K, based on a newly constructed total cross section for anion formation at T(G) = 300 K. R-matrix calculations for Cl(-) production have been carried out for comparison with the experimental data. The R-matrix results are in line with the main experimental observations and predict the dependence of the DEA cross section on the initial vibrational level nu(3)() and on the vibrational temperature. Furthermore, the cross section for vibrational excitation of the nu(3) mode has been computed.

Fragmentation of metastable SF(6)(-*) ions with microsecond lifetimes in competition with autodetachment.

Fragmentation of metastable SF(6)(-*) ions formed in low energy electron attachment to SF(6) has been investigated. The dissociation reaction SF(6)(-*)-->SF(5) (-)+F has been observed approximately 1.5-3.4 micros and approximately 17-32 micros after electron attachment in a time-of-flight and a double focusing two sector field mass spectrometer, respectively. Metastable dissociation is observed with maximum intensity at approximately 0.3 eV between the SF(6)(-*) peak at zero and the SF(5)(-) peak at approximately 0.4 eV. The kinetic energy released in dissociation is low, with a most probable value of 18 meV. The lifetime of SF(6)(-*) decreases as the electron energy increases, but it is not possible to fit this decrease with statistical Rice-Ramsperger-Kassel/quasiequilibrium theory. Metastable dissociation of SF(6)(-*) appears to compete with autodetachment of the electron at all electron energies.

Pathogenetic significance of venous hyperoxaemia in retinopathy of prematurity.

Ten underweight newborns with severe retinopathy of prematurity (ROP) and 18 newborns with slight changes in the sense of ROP were compared with 66 healthy infants. The distribution of 13 possibly pathogenetically effective features in these 3 groups of patients was studied by means of variance analysis. The greatest significance resulted for multiple blood transfusions and exchange transfusions. From this it was concluded that the toxic oxygen effect on the immature retina was probably more dependent on the venous PO2 (determined by Hb concentration, O2-affinity, arterial PO2, and blood flow) than on the isolated arterial PO2.

[Vascular complications in primary hyperlipoproteinemias (HLP) with special reference to changes in the eye fundus]. / Gefässkomplikationen bei primären Hyperlipoproteinämien (HLP) unter besonderer Berücksichtigung von Augenhintergrundsveränderungen.

The distribution of the types of hyperlipoproteinaemias revealed 2 peaks of frequency, i. e. in the types IIa and IIb corresponding 41% and in the types IV and V corresponding 55%. Weight indices and disturbed glucose tolerance are in the types III-V significantly higher than in the types IIa and IIb. The risk factor hypertension was registered in 34% in the investigation material. The highest prevalence rates for myocardial infarctions were in the patients of the types IIb and III, for PAD in the type III. The addition of hypertension and diabetes mellitus to hyperlipoproteinaemia reveals an exacerbation of the vascular risk. Changes of the fundus oculi, which correspond to the picture of a fundus hypertonicus cause to think of the presence of a hyperlipoproteinaemia in all patients with normotension.

[Concentration course of lithium in liquor and aqueous humor after single oral application in man]. / Konzentrationsverlauf von Lithium im Liquor und Augenkammerwasser nach einmaliger oraler Applikation beim Menchen

Kinetic examinations of lithium concentrations in the aqueous humour and in the liquor in man were carried out. The passage of lithium into both extravascular compartments took place in different manners. Lithium - liquor concentrations seem to be only of a rather limited positive evidence as to the concentrations at the spot of action; the possible causes for this fact are discussed.

[The influence of centrally acting drugs on flicker fusion frequency]. / Beeinflussung der Flimmerverschmelzungsfrequenz durch zentralwirksame Pharmaka.

From the research results given we may conclude that the flicker fusion frequency is reduced not only by tranquillisers but also by neuroleptic drugs. The records obtained of the effect of the dosage can be seen as a measure of the efficiency of this method. It should be established by means of similar experiments, by including additional substances, in which regions of the cortico-retinal system the site of action should be presumed to be.

Cell kinetic studies in mixed leukocyte cultures: an in vitro model of homograft reactivity.

The recognition phase of homograft immunity can be studied in vitro in the mixed leukocyte culture reaction. In this reaction, at the end of seven days, up to 30 per cent of the lymphocytes in culture "respond" to a single allogeneic cell stimulus. This paper presents evidence that the lymphocytes responding in culture divide with the generation time of 18-21 hours, with some asynchrony, and that a large percentage of the cells found at the end of the culture period may be the products by division of a small number of cells initially responding. Two estimates are made of the frequency of the initially responding unit (the cell(s) responsible for initiating the response). These are probably minimum estimates and are in the range of 1 in 200 to 1 in 2000 cells which can initially respond. This very high frequency of responding units as compared with the responding units in immediate type hypersensitivity (antibody production) is discussed.