Eine absolute Axiomatik der Geometrie in einer begrenzten Ebene

Ohne ZusammenfassungMit dem Wort absolut wollen wir andeuten, daß es eine metrische Axiomatik betrifft, wobei nicht von vornherein in den Axiomen festgelegt ist, ob die Geometrie eine hyperbolische, parabolische oder elliptische ist.     

An efficient synthesis of the taxane-derived anticancer agent ABT-271

ABT-271, 1, has been identified as a promising anticancer agent. ABT-271 is a novel taxane possessing a C9-(R)-hydroxyl group as opposed to a C9-ketone which is present in Taxol and Taxotere. To further evaluate ABT-271 as a potential anticancer agent, an efficient synthesis was developed which allows the large scale synthesis of ABT-271. Ketalization of the 7,9-diol of 9-DHAB-III, 2, allows selective removal of the C13-acetate with phenyllithium. The resulting C13-hydroxyl group is then acylated using LiHMDS and beta-lactam 22 to give ABT-271 in protected form. The protecting groups were removed first by acidic hydrolysis followed by basic hydrolysis to provide ABT-271. Application of this synthetic sequence provided over 600 g of ABT-271, 1.     

An Approach to the Synthesis of Four Rhodomicrobium Vannielii Lipid a Analogues

Abstract

The preparation of four Rh. Vannielii Lipid A analogues (i.e. compounds 22, 23, 30 and 33) is described. Non-neighbouring group supported introduction of the β-glycosidic linkages was performed by coupling the mannopyranosyl bromide 2 and the 2-azido-2-deoxy-glucopyranosyl bromides 10 and 13 with the suitably protected glycosyl acceptors 3, 4 and 5 in the presence of a heterogeneous silver catalyst, to give compounds 6, 7, 14 and 24, respectively. Selective removal of the ally1 group and reduction of the azido functions followed by several O,N-acylation steps afforded, after complete deblocking, the tri-and disaccharide Rh. Vannielii Lipid A analogues 22, 23, 30 and 33.     

Innovative technique for the direct determination of proteins in calcified aortic valves

Aortal valve mineralization very frequently causes a genesis of aortic stenosis, which is the most often surgically treated heart disease. Hydroxyapatite deposits have been identified as one of the causes leading to the loss of elasticity of the aortic valves. It is known that phosphates/calcium is accumulated in valve tissues during mineralization, but the mechanism of this process remains unclear. The work is focused mainly on the study of protein composition of mineralized aortic valves by nano-liquid chromatography electrospray ionization in a quadrupole orthogonal acceleration time-of-flight mass spectrometry. New methodological approach based on direct enzymatic digestion of proteins contained in hydroxyapatite deposits was developed for the study of pathological processes connected with osteogenesis. Our objectives were to simplify the traditional analytical protocols of sample preparation and to analyze the organic components of the explanted aortic valves for significant degenerative aortic stenosis. The study of aortic valve mineralization on the molecular level should contribute to understanding this process, which should consequently lead to effective prevention as well as to new ways of treatment of this grave disease.

The use of matrix-specific calibrations for oxygen in analytical glow discharge spectrometry

The performance of glow discharge optical emission spectroscopy and mass spectrometry for oxygen determination is investigated using a set of new conductive samples containing oxygen in the percent range in three different matrices (Al, Mg, and Cu) prepared by a sintering process. The sputtering rate corrected calibrations obtained at standard conditions for the 4 mm anode (700 V, 20 mA) in GD-OES are matrix independent for Mg and Al but not for Cu. The importance of a “blue shifted” line of oxygen at 130.22 nm (first reported by Köster) for quantitative analyses by GD-OES is confirmed. Matrix-specific calibrations for oxygen in GD-MS are presented. Two source concepts—fast flow (ELEMENT GD) and low gas flow (VG9000)—are evaluated obtaining higher sensitivity with the static flow source. Additional experiments using Ar-He mixtures or μs pulsed GD are carried out in ELEMENT GD aiming to improve the oxygen sensitivity.     

On plane geometric spanners: A survey and open problems

Given a weighted graph $G=(V,E)$ and a real number $t?1$, a t-spanner of G is a spanning subgraph $G^{\prime }$ with the property that for every edge xy in G, there exists a path between x and y in $G^{\prime }$ whose weight is no more than t times the weight of the edge xy. We review results and present open problems on different variants of the problem of constructing plane geometric t-spanners.     

Direct analysis of psychoactive tryptamine and harmala alkaloids in the Amazonian botanical medicine ayahuasca by liquid chromatography–electrospray ionization-tandem mass spectrometry

A direct injection/liquid chromatography–electrospray ionization-tandem mass spectrometry procedure has been developed for the simultaneous quantitation of 11 compounds potentially found in the increasingly popular Amazonian botanical medicine and religious sacrament ayahuasca. The method utilizes a deuterated internal standard for quantitation and affords rapid detection of the alkaloids by a simple dilution assay, requiring no extraction procedures. Further, the method demonstrates a high degree of specificity for the compounds in question, as well as low limits of detection and quantitation despite using samples for analysis that had been diluted up to 200:1. This approach also appears to eliminate potential matrix effects. Method bias for each compound, examined over a range of concentrations, was also determined as was inter- and intra-assay variation. Its application to the analysis of three different ayahuasca preparations is also described. This method should prove useful in the study of ayahuasca in clinical and ethnobotanical research as well as in forensic examinations of ayahuasca preparations.     

An Improved Design and Versatile New Lamination Fabrication Method for Twin Electrode Thin Layer Cells Utilizing Track‐etch Membranes

Reported here are laminated membrane electrodes, an improved design and more advantageous method of fabrication for previously reported thin layer cell electrode systems developed on track‐etch membranes. The laminated membrane approach potentially further improves flow resistance by dramatically reducing the surface area to volume ratio, but also produces a cohesive device that can be more readily applied to a broad range of applications. In addition, this new fabrication method was implemented in a scalable, commercial process and resulting product demonstrations indicate that volume manufacturing is feasible. Characterization of laminated membrane electrodes reveal redox cycling amplification factors as high as 30 with linear responses to variable concentrations of redox couple. These performance characteristics are shown to be comparable to similar generator‐collector systems fabricated through much more laborious laboratory methods. This combination of added versatility, cost‐reduced fabrication and exceptional performance clearly reveals unrealized potential of track‐etch membrane approaches and boosts their candidacy as powerful new options for generator‐collector electrode systems.     

Fast algorithms for collision and proximity problems involving moving geometric objects

Consider a set of geometric objects, such as points, line segments, or axes-parallel hyperrectangles in ^d, that move with constant but possibly different velocities along linear trajectories. Efficient algorithms are presented for several problems defined on such objects, such as determining whether any two objects ever collide and computing the minimum interpoint separation or minimum diameter that ever occurs. In particular, two open problems from the literature are solved: deciding in o(n²) time if there is a collision in a set of n moving points in ², where the points move at constant but possibly different velocities, and the analogous problem for detecting a red-blue collision between sets of red and blue moving points. The strategy used involves reducing the given problem on moving objects to a different problem on a set of static objects, and then solving the latter problem using techniques based on sweeping, orthogonal range searching, simplex composition, and parametric search.