Male reproductive health has deteriorated in many countries during the last few decades. In the 1990s, declining semen quality has been reported from Belgium, Denmark, France, and Great Britain. The incidence of testicular cancer has increased during the same time. Incidences of hypospadias and cryptorchidism also appear to be increasing. Similar reproductive problems occur in many wildlife species. There are marked geographic differences in the prevalence of male reproductive disorders. While the reasons for these differences are currently unknown, both clinical and laboratory research suggest that the adverse changes may be inter-related and have a common origin in fetal life or childhood. Exposure of the male fetus to supranormal levels of estrogens, such as diethlylstilbestrol, can result in the above-mentioned reproductive defects. The growing number of reports demonstrating that common environmental contaminants and natural factors possess estrogenic activity presents the working hypothesis that the adverse trends in male reproductive health may be, at least in part, associated with exposure to estrogenic or other hormonally active (e.g., antiandrogenic) environmental chemicals during fetal and childhood development. An extensive research program is needed to understand the extent of the problem, its underlying etiology, and the development of a strategy for prevention and intervention. Environ Health Perspect 104(Suppl 4): 741-803 (1996)

The structure of the Au(110) surface was investigated in the temperature range between 60 and 1250 K by the ion channeling and blocking method using an electrostatic energy analyzer. An anomalous temperature dependence of the blocking pattern was found around 680 K which may be caused by a roughening transition. Above 770 K the number of visible atom layers increases faster with increasing temperature, as expected from the temperature dependence of the mean vibration amplitude.The number of observed disordered (110) layers follows a logarithmic growth law as predicted by the premelting theory and molecular dynamics simulations.

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The growth quality ofYBaCuO thin films deposited by sputtering on different substrates (AlzOs, MgO, SrTiOs, Zr(Y)Oz) has been studied by X-ray diffraction and channeling experiments as a function ofthe deposition temperature. Besides the substrate orientation, the substrate temperature is the parameter determining whether films grow in c-, a-, (110) or mixed directions. Epitaxial growth correlates with high critical current values in the films ofup to 5.5 x 106 AJcm2 at 77 K. Ultrathin films with thicknesses down to 2 nm were grown revealing threedimensional superconducting behaviour. Films on (100) SrTiOs of9 nm thickness and below are partially strained indicating commensurate growth. From the analysis of the surface disorder 1 displaced Ba atom per Baz Y row was obtained indicating that the disordered layer thickness is about 0.6 nm. Tunnel junctions fabricated on these films reveal gap-like structures near ±16m V and ±30m V.Epitaktisches Wachsturn und Eigenschaften dünner Schichten des Hochtemperatur-Supraleiters YBaCuO ZUSAMMENFASSUNG Das Verfahren der Magnetron-Kathodenzerstäubung wurde zur Abscheidung dünner YBaCuO-Schichten auf verschiedenen Substraten (AlzOs, MgO, SrTiOs, Zr(Y)Oz) optimiert. Die Wachstumsrichtung und die kristalline Güte der Schichten wurde in Abhängigkeit von der Substrat-Oberflächengüte, der Orientierung und der Temperatur mittels Ionenchanneling und Röntgendiffraktion untersucht. Der Grad der Epitaxie und die Mosaik-Verbreiterung bestimmen den kritischen Transportstrom mit Werten bis zu 5.5 ·106 Ä/cm2 bei 77 K. Selbst in ultradünnen Schichten mit einer minimalen Dicke von bis zu 2 nm zeigt das supraleitende Verhalten 3-dimensionalen Charakter. Schichten auf (100) SrTiOs mit Dicken kleiner etwa 9 nm sind teilweise zur Unterlage verspannt, was auf kommensurables Wachstum hinweist. Die Channeling-Analyse der Schichtoberfläche ergibt in günstigen Fällen eine Verlagerung von nur 1 Ba-Atom pro Baz YKette, was einer maximalen Dicke der gestörten Oberfläche von etwa 0.6 nm entspricht. Auf diesen Schichten präparierte Tunneldioden zeigen Strukturen mit einer Energielücke inderNähe von ±16m V und ±30m V.--I --

C -axis oriented YBa2Cu3O7−x (YBCO) thin films were deposited on polycrystalline metallic tapes buffered with yttria stabilized zirconia (YSZ). The in-plane alignment of the YSZ layers achieved by simultaneous ion bombardment of the growing film (ion beam assisted deposition) and of the postdeposited YBCO thin films was studied by x-ray diffraction as a function of the buffer layer thickness. A significant improvement of the in-plane texture, achieved for buffer layers exceeding a thickness of about 1.5 μm, resulted in high critical current densities above 106 A/cm2 of the YBCO films.

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