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The GALLEX collaboration aims at the detection of solar neutrinos in a radiochemical experiment employing 30 tons of Gallium in form of concentrated aqueous Gallium-chloride solution. The detector is primarily sensitive to the otherwise inaccessible pp-neutrinos. Details of the experiment have been repeatedly described before [1-7]. Here we report the present status of implementation in the Laboratori Nazionali del Gran Sasso (Italy). So far, 12.2 tons of Gallium are at hand. The present status of development allows to start the first full scale run at the time when 30 tons of Gallium become available. This date is expected to be January, 1990.
We have used thermal desorption spectroscopy to carry out a comparative study of potassium adsorption on Al(111) and on the fivefold Al-Pd-Mn surface. Potassium adsorption on the quasicrystal was found to be different than on Al(111). The potassium monolayer desorbed from fivefold Al-Pd-Mn at lower temperatures than from Al(111). Potassium is known to form a dense monolayer on Al(111), with an ideal coverage of 0.33, but for the monolayer on fivefold Al Pd Mn we find that the saturation coverage is only one twelfth.
A model proposed for the atomic structure of the new hexagonal Al-Fe(V)-Si phase which was found in rapidly solidified Al-Fe(V)-Si alloys is discussed in terms of relation this phase to approximants. The structure of this new phase was described as hexagonal packing of double Mackay icosahedral units similar to those of which the cubic α-(AlFeSi) approximant phase is built up. On the basis of this model the experimental high resolution electron microscopic (HREM) images of the hexagonal phase were successfully interpreted. Like the á phase this structure is characterized by the local icosahedral ordering and can be regarded as an approximant.
Icosahedral quasicrystals Al71.5Pd20.3Mn8.2, Al70.7Pd21.34Re7.96, Al62.5Cu25.5Fe12.5, and α-Al68.31Mn21.21Si10.48 1/1- approximant were investigated by using a monoenergetic slow positron beam. The structural vacancy densities in the first three samples were determined to be 5.0×1020, 7.7×1020, and 4.7×1020 cm−3, respectively, by analyzing the measured S-parameter.
Formation of defects during Zn diffusion into undoped and Fe-doped InP single crystals at 700°C has been observed by transmission electron microscopy for various diffusion conditions. The observations are correlated with Zn concentration profiles obtained by electron microprobe measurements and secondary-ion mass spectrometry. The results allow the conclusion that indiffusing interstitial Zn can occupy In sublattice sites via a kick-out reaction. Under appropriate diffusion conditions supersaturations of In self-interstitial atoms result leading to defect formation. Observations in Fe-doped InP suggest that Zn also replaces Fe on In sublattice sites leading to redistribution and to precipitation of Fe.
Non-local damping was investigated by Ferromagnetic Resonance (FMR) using ultrathin magnetic single and double layer structures prepared by Molecular Beam Epitaxy (MBE). The double layer structures show magnetic damping which is caused by spin transport across a normal metal spacer (N). In double layer structures a thin Fe layer, F1, was separated from a thick Fe layer, F2, by a Au(001) spacer. The interface magnetic anisotropies separated the FMR fields of F1 and F2 by a big margin allowing one to investigate FMR in F1 while F2 had a negligible angle of precession, and vice versa. The Fe films in magnetic double layers acquire non-local interface Gilbert damping. It will be shown that the precessing magnetic moments act as spin pumps and spin sinks. This concept was tested by investigating the FMR linewidth around an accidental crossover of the resonance fields for the layers F1 and F2. There is another possible mechanism for non-local damping which is based on a “breathing Fermi surface” of the spacer. The temperature dependence of the non-local damping indicates that this mechanism is weak in Au spacers. Surprisingly the Au spacer acts as an additional impedance for the spin pump mechanism. Finally, it will be shown that electron-electron correlations in a Pd spacer can lead to a significant enhancement of the non-local damping.
The oxidation behavior of i-A163Cu25Fe12 at 800°C in air was investigated by means of TGA, XRD, SEM and TEM. In the beginning a homogeneous oxide layer is formed by the subsequent growth of metastable γ-Al2O3 and Θ-Al2O3. Nucleation of the thermodynamical stable α-Al2O3 occurs at the interface oxide/quasicrystal. The following growth of α-Al2O3 through the oxide layer leads to the formation of oxide nodules. The high growth rate of the α-Al2O3 can be explained by the incorporation of copper ions. The oxidation resistance of the quasicrystal is insufficient at high temperatures, because no protective oxide layer is formed. The high temperature oxidation behavior of Al-Cu-Fe quasicrystal and the aluminides β-FeAl and β-NiAl is compared regarding the oxidation rate, the oxide phases and the concentration changes in the material due to selective oxidation of aluminum.
A continuation of this WG was voted for at the IAU GA 2006 in Prague. The International Celestial Reference Frame (ICRF) is defined by the positions of 212 distant quasars at radio wavelengths. The primary, optical reference frame is the Hipparcos Celestial Reference Frame (HCRF), which is the Hipparcos Catalog without astrometric ‘problem’ stars (in: H. Rickman (ed.) 2001, Proceedings IAU XXIV General Assembly, Transactions IAU XXIVB (San Francisco: ASP), Resolution B1.2). The Tycho-2 catalog with its 2.5 million brightest stars forms the first step in the densification of the optical reference frame. However, the limiting magnitude of about V = 12 of the Tycho-2 catalog is not sufficient for most applications in astronomy and the goal of this IAU Working Group is to further extend the grid of highly accurate positions and motions toward more and fainter stars. The web site of this WG is at <ad.usno.navy.mil/dens_wg/>.
We examined cells from the nucleus pulposus and annulus
fibrosus of adult bovine intervertebral discs, using
confocal laser scanning microscopy on living unfixed tissue. These
cells were visualised using chloromethyl
fluorescein diacetate, a membrane-impermeant fluorescent dye. The
organisation of cells from the outer
annulus was also determined using confocal microscopy after fixation
and staining the actin-filaments with
FITC-phalloidin. We found that cellular processes were a dominant
feature of cells from all regions of the
disc including the cells of the nucleus pulposus and inner annulus.
These processes were also visible in
histological sections of disc examined both at the light and electron
microscope level, even though cells from
the nucleus and inner annulus appeared chondrocyte-like, being rounded
and enclosed in a capsule. The
function of these processes is at present unknown. We suggest that they
may serve to sense mechanical strain.
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