Authors:Frederic Poineau, Charles Yeamans, G. Silva, Gary Cerefice, Alfred Sattelberger, and Kenneth Czerwinski
Uranium mononitride (UN), sesquinitride (U2N3) and dinitride (UN2) were characterized by extended X-Ray absorption fine structure spectroscopy. Analysis on UN indicate the presence of three
uranium shells at distances of 3.46(3), 4.89(5) and 6.01(6) Å and a nitrogen shell at a distance of 2.46(2) Å. For U2N3, two absorbing uranium atoms at different crystallographic positions are present in the structure. One of the uranium atoms
is surrounded by nitrogen atoms at 2.28(2) Å and by uranium atoms at 3.66(4) and 3.95(4) Å. The second type of uranium atom
is surrounded by nitrogen atoms at 2.33(2) and 2.64(3) Å and by uranium atoms at 3.66(4), 3.95(4) and 5.31(5) Å. Results on
UN2 indicate two uranium shells at 3.71(4) and 5.32(5) Å and two nitrogen shells at 2.28(2) and 4.34(4) Å. The lattice parameters
of UN, U2N3 and UN2 unit cells were respectively determined to be 4.89(5), 10.62(10) and 5.32(5) Å. Those results are well in agreement with
those obtained by X-Ray diffraction analysis.
Several isomorphic groups of micas: Muscovite-Phengite-Muscovite-Li-Muscovite; Biotite-Zinnwaldite-Lepidolite and Biotite-Phlogopite
were investigated by DTA, TG and DTG. Octehedral vacancies and the sites of octahedral cationic occupancy were determined
from IR-spectra of the hydroxyls. The influence of a composition and fine structure of the micas on the shape of the thermal
curves was discussed. A one to one correspondence between the isomorphic series members and individual thermal curves makes
it possible to determine the chemical composition of a mica sample. The combination of thermal and IR-spectra of hydroxyl
analyses permits to link the Order-Disorder data with thermal properties of mica.
Revelation of details which are hidden in a backscattering spectrum due to finite apparatus resolution demands the numerical
solution of a linear Fredholm integral equation of the first kind with only approximately known and near-singular kernel.
Unphysical oscillations of the solution are largely avoided by properly chosen smoothness conditions. Adequate algebraization
of the problem is achieved by approximation of the solution by a cubic spline function. Reliability of the approach is studied
by mathematical experiments with realistic kernels.
Authors:Katalin Halasy, Balázs Szőke, and Gergely Janzsó
The nitrergic neuron population and certain aspects of their connectivity (peptidergic inputs, co-localization with GABA, synaptic target distribution) were studied in the medial septum of the rat brain. The histochemical localization of NADPH diaphorase and immunohistochemical identification of nNOS at light and electron microscopic level was applied. Double-labeling experiments with galanin and leucine enkephalin, moreover the postembedding GABA immunogold staining was also carried out. NADPH diaphorase- and nNOS-immunopositive neurons could be identified inside the borders of medial septum. Out of their peptidergic inputs galanin- and leucine enkephaline-immunopositive varicose fibers were found in close apposition with nNOS-immunopositive neurons. Based on fine structural characteristics (large indented nucleus, thin cytoplasmic rim, lack of axosomatic synapses) the nitrergic neurons are suggested to be identical with the septal cholinergic nerve cells. Their boutons established asymmetrical synapses mainly on dendritic shafts and spines, some of which were also nNOS-immunopositive. A lower amount of nNOS-immunopositive boutons of presumably extrinsic origin were found to be GABAergic.
Studies of finer details in mass and charge distribution fission leads to a better understanding of the fission process. Experimental determination of independent and cumulative yields using radiochemical techniques as well as mass spectrometers and fission product recoil separators form the basis of such studies. It has been established that closed shells as well as an even number of nucleons influence both mass and charge distributions. The magnitudes of these effects may be estimated from existing experimental yield data and various fission models. Using our measurements of several fission yields and those existing in the literature we have calculated even-odd proton and neutron effects for various low energy fissioning systems. Where enough data existed, direct calculations were made, whereas for other cases the Zp-model of WAHL has been used. It is found that the even-odd proton effect is well established and pronounced in thermal neutron fission of235U and233U. Lesser effects were found for reactor neutron induced fission of232Th, thermal neutron fission of239Pu and spontaneous fission of245Cm and249Cf. No effect seems to exist in the thermal neutron fission of241Pu and the spontaneous fission of252Cf. The even-odd neutron effect is found to be much lower than the corresponding proton effect in235U and233U fissions and is nonexistent in the rest of the fissioning systems.
Authors:C. L. Frank, Szabina J. Czirok, Csilla Vincze, G. Rácz, Á. Szél, and B. Vígh
In earlier works we have found that in the mammalian pineal organ, a part of autonomic nerves - generally thought to mediate light information from the retina - form vasomotor endings on smooth muscle cells of vessels. We supposed that they serve the vascular support for circadian and circannual periodic changes in the metabolic activity of the pineal tissue. In the present work, we investigated whether peripheral nerves present in the photoreceptive pineal organs of submammalians form similar terminals on microvessels. In the cyclostome, fish, amphibian, reptile and bird species investigated, autonomic nerves accompany vessels entering the arachnoidal capsule and interfollicular meningeal septa of the pineal organ. The autonomic nerves do not enter the pineal tissue proper but remain in the perivasal meningeal septa isolated by basal lamina. They are composed of unmyelinated and myelinated fibers and form terminals around arterioles, veins and capillaries. The terminals contain synaptic and granular vesicles. Comparing various vertebrates, more perivasal terminals were found in reptiles and birds than in the cyclostome, fish and amphibian pineal organs. Earlier, autonomic nerves of the pineal organs were predominantly investigated in connection with the innervation of pineal tissue. The perivasal terminals found in various submammalians show that a part of the pineal autonomic fibers are vasomotoric in nature, but the vasosensor function of some fibers cannot be excluded. We suppose that the vasomotor regulation of the pineal microvessels in the photosensory submamalian pineal - like in mammals - may serve the vascular support for circadian and circannual periodic changes in the metabolic activity of the pineal tissue. The higher number of perivasal terminals in reptiles and birds may correspond to the higher metabolic activity of the tissues in more differentiated species.
Authors:Andrea B. Merlo, Virginia Vetere, José M. Ramallo-López, Félix G. Requejo, and Mónica L. Casella
in a cell with kapton windows in order to avoid contact with air. Both X-ray absorption near edge structure (XANES) and extended X-ray absorption finestructure (EXAFS) experiments were performed at the Pt L 3 and Ge K edges. Three ion chambers were