Atomic relocations in a two-layer Al/Ni system bombarded with ions having energies close to the sputtering threshold

Collision cascades developed at 300 K in a Ni single crystal and in a system comprising a monolayer of Al atoms on the Ni(100) single crystal face bombarded at normal incidence by 25-and 50-eV Ar and Xe atoms were simulated by method of molecular dynamics. It was found that the number of atoms relocated through the Al-Ni interface markedly exceeds the number of analogous relocations in the nickel single crystal.     

Insulin receptors and signal transduction proteins in the hypothalamo-hypophyseal system: a review on morphological findings and functional implications

Receptors for insulin are widely distributed in the brain and pituitary. The current hypothesis on receptor function in these regions points to a role of insulin as a mediator in the communication of the peripheral endocrine system with the brain via various steps of the neuroendocrine axis. Recent data demonstrate that receptor-positive neurons in the brain, i.e. in the hypothalamus, and secretory cells in the anterior pituitary gland possess specific proteins that are thought to be involved in key steps of post receptor signal transduction, in particular insulin receptor substrate-1 and phosphatidylinositol 3'-kinase (PI3k). PI3k is a critical enzyme of the intracellular signaling pathway that is activated by a number of receptor tyrosine kinases, including receptors for insulin and IGF-1. This information further completes the framework indicating in vivo activity of insulin receptors in central neuroendocrine cells and their involvement in one branch of several physiological mechanisms that control body metabolism and nutritional behaviour.     

Glycine-receptor activation is required for receptor clustering in spinal neurons

The ability of nerve cells to receive up to several thousands of synaptic inputs from other neurons provides the anatomical basis for information processing in the vertebrate brain. The formation of functional synapses involves selective clustering of neurotransmitter receptors at presumptive postsynaptic regions of the neuronal plasma membrane. Receptor-associated proteins are believed to be crucial for this process. In spinal neurons, synaptic targeting of the inhibitory glycine receptor (GlyR) depends on the expression of the anchoring protein gephyrin. Here we show that the competitive GlyR antagonist strychnine and L-type Ca2+-channel blockers inhibit the accumulation of GlyR and gephyrin at postsynaptic membrane areas in cultured rat spinal neurons. Our data are consistent with a model in which GlyR activation that results in Ca2+ influx is required for the clustering of gephyrin and GlyR at developing postsynaptic sites. Similar activity-driven mechanisms may be of general importance in synaptogenesis.     

Primary sclerosing cholangitis--an ulcerative colitis-associated illness with surgical consequences

Primary sclerosing cholangitis (PSC) is generally associated with ulcerative colitis (UC). The disease typically progresses slowly, but ultimately, and leads to cirrhosis, liver failure or bile duct cancer. PSC patients with simultaneous ulcerative colitis are also at higher risk for colorectal cancer. At the present time, there is no effective treatment for PSC, although preliminary data show encouraging results after treatment with ursodeoxycholic acid. However, there are no data concerning the delay or prevention of progress of the disease with this drug, because follow-up time is not yet long enough. Isolated bile duct strictures should be treated endoscopically. The possible effect of proctocolectomy on the course of PSC is controversial. Liver transplantation is the therapy of choice for PSC in its final stage. The 5-year survival rate (89%) is significantly better than after transplantation for other indications. Patients with ulcerative colitis have to be followed up by lifelong colonoscopy. Although the course of UC after transplantation is mostly asymptomatic, these patients are at higher risk for colorectal cancer.     

Zur Bewertung von Schutzschichten gegen Heißgaskorrosion an Gasturbinenschaufeln

On the Assessment of Protective Coatings to combat Hot Gas Corrosion on Gas Turbine Blades . Turbine blades of aero-engines are normally protected from hot gas corrosion by means of aluminium diffusion coatings. The inherent negative results of these coatings – the resistance to corrosion gains with the growing thickness of the coating, but the strength generally suffers – calls for an optimum balance between resistance to hot gas corrosion and resistance to mechanical stresses for a maximally long life of the blades. Conventional criteria – chiefly that of the progress of corrosion – not being adequate for a reliable assessment of the potential gain, it is recommended that creep and fatigue tests using simultaneously superimposed corrosion be employed for evaluating protective coatings. Tests conducted at faithfully simulated service conditions on samples and blades in cast nickel material IN 100 show how increasing thickness will cause the fatigue strength and the ductility of the coating to be reduced at a more or less rapid rate. The tests suggest the conclusion that conventional coating parameters still need improving if the optimum balance between resistance to hot gas corrosion and resistance to mechanical stresses shall be gained. The still small number of tests conducted cannot provide conclusive evidence. This paper is nevertheless published in the hope that it will invite in-depth studies of the problem of high temperature protective coatings under the additional aspect of true-to-life mechanical stresses.     

Polymere Procyanidine, die pr?genden Bestandteile der Mandel-Samenschale

Zusammenfassung Die Samenschale der Mandel (Prunus amygdalus Batsch) besteht neben fettem Öl, Lignin, Polysacchariden und Cutin zu ca. 30% aus Procyanidinen der verschiedensten Polymerisationsgrade. Monomer-Einheiten der Dimere bis Tetracosamere sind (–)-Epicatechin und (+)-Catechin. Prodelphinidine waren nicht nachzuweisen. Die Dimere B-1, B-3, B-4, Trimere und Oligomere sind in Aceton/Wasser löslich. Der Hauptanteil ist hochpolymer und wird in Thioglykolsäure durch Thiolyse gespalten. Die hochpolymeren Procyanidine prägen Struktur und Eigenschaften der Samenschale.

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Procyanidin polymers crucial to the structure of the almond seedcoat

Summary The seedcoat of almond (Prunus amygdalus Batsch) contains up to 30% procyanidins with different degrees of polymerisation and, in addition, fatty oils, lignin, polysaccharides and cutin. Monomer units of dimers to tetracosamers are (–)-epicatechin and (+)-catechin. Prodelphinidins could not be detected. The dimers B-1, B-3, B-4, trimers and oligomers are soluble in acetone/water. The bulk material is large polymer, that is only soluble, by thiolysis, in thioglycolic acid. The large polymer procyanidins are crucial to the structure and attributes of the seedcoat.

     

Einfluß der Versuchsparameter auf die Abschreckgeschwindigkeiten beim Laseroberflächenumschmelzen am Beispiel ledeburitischer Stähle

Influence of the Process Parameters on Quenching Rates in Laser Melting of Ledeburitic Steels On quenching, surface melted ledeburitic steels solidify dendritically. The secondary arm separation can be used to estimate the cooling rate and hence enables the effect of the operating conditions on the cooling rate to be assessed. In general, the residual melt solidifies as an eutectic or as chromium carbide or a mixture of chromium carbide and iron. The resultant carbide net and the resultant grain refinement change the hardness of the surface. The hardness can be controlled by varying the quenching rate in surface melting and if necessary a subsequent heat treatment.