Objective To determine the sensitivity of 4 strains of Oxalobacter formigenes (OxF) found in humans, HC1, Va3, CC13, and OxK, to varying concentrations of commonly-prescribed antibiotics. OxF gut colonization has been associated with a decreased risk of forming recurrent calcium oxalate kidney stones. Methods For each strain and each antibiotic concentration, 100 μL of an overnight culture and 100 μL of the appropriate antibiotic were added to a 7 mL vial of oxalate culture media containing 20 mM oxalate. On the fourth day, vials were visually examined for growth, and a calcium oxalate precipitation test was performed to determine whether OxF grew in the presence of the antibiotic. Results All 4 OxF strains were resistant to amoxicillin, amoxicillin/clavulanate, ceftriaxone, cephalexin, and vancomycin while they were all sensitive to azithromycin, ciprofloxacin, clarithromycin, clindamycin, doxycycline, gentamicin, levofloxacin, metronidazole, and tetracycline. One strain, CC13, was resistant to nitrofurantoin while the others were sensitive. Differences in minimum inhibitory concentration between strains were demonstrated. Conclusions Four human strains of OxF are sensitive to a number of antibiotics commonly utilized in clinical practice; however, minimum inhibitory concentrations differ between strains.

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Au metalization schemes were deposited on AlGaN/ GaN heterostructures. The dependence of the specific contact resistance on the annealing conditions and the V:Al thickness ratio was shown. For an optimized electrode stack, a low specific contact resistance of 8.9 Â 10 À6 X cm 2 was achieved at an annealing temperature of 650 C. Compared to the conventional Ti/Al/Ni/Au contact, this is a reduction of 150 K. The microstructure and contact formation at the AlGaN/metal interface were investigated by transmission electron microscopy including high-resolution micrographs and energy dispersive X-ray analysis. It was shown that for low-resistive contacts, the resistivity of the metalization has to be taken into account. The V:Al thickness ratio has an impact on the formation of different intermetallic phases and thus is crucial for establishing ohmic contacts at reduced annealing temperatures. V

Neurodegenerative diseases represent a challenge for biomedical research due to their high prevalence and lack of mechanism-based treatments. Because of the complex pathology of neurodegenerative disorders, multifunctional drugs have been increasingly recognized as potential treatments. We identified homobivalent γ-carbolinium salts as potent inihitors of both cholinesterases, N-methyl-D-aspartate receptors, and monoamine oxidases. Homobivalent γ-carbolines displayed similar structure-activity relationships on all tested targets and may present promising designed multiple ligands for the treatment of neurodegenerative disorders.

Reduotion der Ester von Thioealfoneiiuren mit einwerthigen und sweiwerthigen Alkylen duroh Sohwefelwaseerstoff.(Aue dem chemischen Laboratorium der technischen Hochschule zu Braunschweig.)[Eingegangen am 30. Juni.]