Beiträge zur Chemie der Pyrrolpigmente, 13. Mitt. Die thermische Stabilität der geometrischen Isomeren von Arylmethylidenpyrrolinonen

From kinetic studies and the investigation of several model compounds it has been deduced that the interconversion of (E)- and (Z)-arylmethylidenepyrrolinones proceeds via a thermal accessible dipolar (singlet) state thus being analogous to the many known thermal (Z)—(E)-isomerizations. There is a pronounced dependence of this reaction on the solvent and the substitution of the aryl part of the molecule; the equilibrium position between (Z)- and (E)-isomers is determined by the substituent in position 4 of the pyrrolinone ring.

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12. Mitt.:H. Falk undJ. M. Ribó, Mh. Chem.107, 307 (1976).     

Mass spectra of substances ionized by fission fragment induced desorption

The mass spectra of substances of physiological and pharmaceutical interest such as steroids, alkaloids, sugars, glycosides and similar, obtained by fission fragment induced desorption as first applied by Macfarlane are presented. The behaviour of organic and inorganic salts is also discussed, including that of mixtures of salts and organic substances. Comparison is made with field desorption data, where available, and electron impact data for those substances of sufficient volatility.     

New Pyrrolo[1,2-a]azepine Type Alkaloids from Stemona and Stichoneuron (Stemonaceae)

Three new pyrroloazepine type alkaloids, stichoneurines A and B and 6-hydroxycroomine were isolated from the lipophilic root extracts of Stichoneuron caudatum and Stemona tuberosa collected in Thailand together with the already known croomine, tuberostemonine, and tuberostemonine A. The structures were elucidated by spectroscopic methods including H/H-COSY, HMQC, and HMBC. Information on the relative stereochemistries and conformational behaviour was obtained by analysis of the NOESY spectra. The formation of pyrroloazepine alkaloids in the genus Stichoneuron is reported for the first time and supports its affiliation to the family Stemonaceae. The occurrence of two different types of alkaloids, of the tuberostemonine and croomine series, in different geographical provenances of Stemona tuberosa is of special chemosystematic interest and may contribute to a more natural species delimitation within that complex group.     

Co- and homocyclotrimerization reactions of protected 1-alkynyl-2-deoxyribofuranose. Synthesis of C-nucleosides, C-di- and C-trisaccharide analogues

Cyclotrimerization of β- or α-ethynyl-3,5-di-O-toluoyl-2-deoxy-d-ribofuranose with α,ω-diynes proceeded smoothly under Rh-catalysis to afford the corresponding β- or α-benzene C-nucleoside derivatives. Analogous co-cyclotrimerization of α- or β-propynyl- and -phenylethynyl-3,5-di-O-toluoyl-2-deoxy-d-ribofuranose with α,ω-diynes gave the corresponding arene derivatives only under microwave irradiation in the presence of a Rh-catalyst in moderate yields. Attempted homocyclotrimerization of β- or α-ethynyl-3,5-di-O-toluoyl-2-deoxy-d-ribofuranose under Rh-catalysis led only to enynes while the use of Ru-catalyst gave the desired 1,2,4- and 1,3,5-tri-(2-deoxyribofuranose-1-yl)benzene.     

Cardiac phosphorus-31 two-dimensional chemical shift imaging in patients with hereditary hemochromatosis

Hemochromatosis is a hereditary iron overload syndrome characterized by increased iron storage, followed by liver cirrhosis and is often associated with restrictive cardiomyopathy. The purpose of this study was to detect alterations of cardiac high-energy phosphate metabolism in patients with hereditary hemochromatosis (HHC) prior to the development of structural heart diseases. Therefore cardiac phosphorus-31 two-dimensional chemical shift imaging ((31)P 2D CSI) was employed. Twenty-four male patients (mean age 47.2 +/- 12 years) homozygous for the C282Y mutation in the hemochromatosis associated HFE gene and twenty-four male healthy volunteers (mean age 47 +/- 11 years) as age-matched controls were included in this study. Using a 1.5-Tesla whole-body magnetic resonance scanner, electrocardiograph-triggered transversal 31P 2D CSI was performed. Left ventricle mean phosphocreatine (PCr) to beta-adenosine triphosphate (beta-ATP) ratios of patients with HHC (1.60 +/- 0.41) were significantly decreased in comparison to healthy volunteers (1.93 +/- 0.36; p = 0.004). Furthermore, we detected moderate, negative correlations between left ventricular PCr to beta-ATP ratios and transferrin saturation, cholesterol, low-density lipoprotein as well as triglyceride. This study shows that 31P 2D CSI permits the detection of alterations of cardiac high-energy phosphate metabolism in patients with HHC, but without any evidence for heart disease. The decreased PCr to beta-ATP ratios in HHC might be caused by mitochondrial impairment due to cardiac iron overload.     

NMR investigation of defect properties in single crystal SrTiO3

Abstract

⁴⁹Ti and ⁸⁷Sr nuclear magnetic resonance measurements were performed in single crystalline SrTiO₃ between 90 K and 1800 K at various oxygen partical pressures. The NMR lines are found to be shifted with rising temperature due to oxygen vacancies acting as donors. Furthermore, three distinct motion-induced nuclear spin relaxation rates could be observed. The corresponding jump rates are attributed to the following processes: translational jumps of charged oxygen vacancies between oxygen sites, localized motion of oxygen vacancies in Fe-vacancy complexes, self diffusion of Sr²⁺.     

Necessary and sufficient conditions for linear convergence of ℓ1‐regularization

Motivated by the theoretical and practical results in compressed sensing, efforts have been undertaken by the inverse problems community to derive analogous results, for instance linear convergence rates, for Tikhonov regularization with ℓ¹‐penalty term for the solution of ill‐posed equations. Conceptually, the main difference between these two fields is that regularization in general is an uncon strained optimization problem, while in compressed sensing a constrained one is used. Since the two methods have been developed in two different communities, the theoretical approaches to them appear to be rather different: In compressed sensing, the restricted isometry property seems to be central for proving linear convergence rates, whereas in regularization theory range or source conditions are imposed. The paper gives a common meaning to the seemingly different conditions and puts them into perspective with the conditions from the respective other community. A particularly important observation is that the range condition together with an injectivity condition is weaker than the restricted isometry property. Under the weaker conditions, linear convergence rates can be proven for compressed sensing and for Tikhonov regularization. Thus existing results from the literature can be improved based on a unified analysis. In particular, the range condition is shown to be the weakest possible condition that permits the derivation of linear convergence rates for Tikhonov regularization with a priori parameter choice. © 2010 Wiley Periodicals, Inc.     

The residual method for regularizing ill-posed problems

Although the residual method, or constrained regularization, is frequently used in applications, a detailed study of its properties is still missing. This sharply contrasts the progress of the theory of Tikhonov regularization, where a series of new results for regularization in Banach spaces has been published in the recent years. The present paper intends to bridge the gap between the existing theories as far as possible. We develop a stability and convergence theory for the residual method in general topological spaces. In addition, we prove convergence rates in terms of (generalized) Bregman distances, which can also be applied to non-convex regularization functionals.We provide three examples that show the applicability of our theory. The first example is the regularized solution of linear operator equations on L^p-spaces, where we show that the results of Tikhonov regularization generalize unchanged to the residual method. As a second example, we consider the problem of density estimation from a finite number of sampling points, using the Wasserstein distance as a fidelity term and an entropy measure as regularization term. It is shown that the densities obtained in this way depend continuously on the location of the sampled points and that the underlying density can be recovered as the number of sampling points tends to infinity. Finally, we apply our theory to compressed sensing. Here, we show the well-posedness of the method and derive convergence rates both for convex and non-convex regularization under rather weak conditions.     

Development of a usability scale based on the three ISO 9241-11 categories “effectiveness,” “efficacy” and “satisfaction”: a technical note

Accreditation and Quality Assurance - An emerging intervention in the area of dementia therapy is serious gaming. Serious gaming is understood as any meaningful use of computerized game whose chief...