2-Hydroxy-4-methoxy-trans-cinnamic acid as a precursor of herniarin inArtemisia dracunculus

The isolation of (E)-2-hydroxy-4-methoxycinnamic acid (1) fromArtemisia dracunculus L. supports strongly the assumption that this compound is an intermediate in the biosynthesis of 7-methoxycoumarin (herniarin,3). The structure of the UV-unstable compound1 was derived from¹H-NMR data and by comparison of the stable dimethylated derivative with synthetic (E)-2,4-dimethoxycinnamic acid methyl ester (2).Dedicated to Prof. Dr.Kurt L. Komarek on the occasion of his 60th birthday.     

Gross spaces

A Gross space is a vector space of infinite dimension over some field , which is endowed with a symmetric bilinear form and has the property that every infinite dimensional subspace satisfies dim dim. Gross spaces over uncountable fields exist (in certain dimensions). The existence of a Gross space over countable or finite fields (in a fixed dimension not above the continuum) is independent of the axioms of ZFC. Here we continue the investigation of Gross spaces. Among other things, we show that if the cardinal invariant b equals , a Gross space in dimension exists over every infinite field, and that it is consistent that Gross spaces exist over every infinite field but not over any finite field. We also generalize the notion of a Gross space and construct generalized Gross spaces in ZFC.

     

Comparison of the Phenolic Compound Profile and Antioxidant Potential of Achillea atrata L. and Achillea millefolium L.

In the present study, Achillea atrata L. and A. millefolium L. were compared for the first time with regard to their phenolic compound profile and antioxidant activity by applying the 2,2-diphenyl-picryl hydrazyl radical assay. For this purpose, aerial plant parts were consecutively extracted with solvents of increasing polarity (dichloromethane, n-butanol, ethyl acetate), revealing that the A. atrata ethyl acetate fraction showed the highest antioxidant activity with an IC₅₀ value of 12.2 ± 0.29 µg/mL compared to 17.0 ± 0.26 µg/mL for A. millefolium. Both species revealed the presence of luteolin, apigenin, centaureidin, and nevadensin exclusively in this most polar fraction, which are known as effective 2,2-diphenyl-picryl hydrazyl radical scavengers. The antioxidant capacity of the aforementioned fractions strikingly correlated with their total phenolic contents, which was highest in the ethyl acetate fraction of A. atrata. Characterization of the metabolite profiles of both Achillea species showed only marginal differences in the presence of key compounds, whereas the concentrations of individual compounds appeared to be species-specific. Our results suggest that A. atrata, based on its compound pattern and bioactivity characteristics, has similar qualities for phytotherapy as A. millefolium.     

Uncommon temperature dependence of the rotational motion of OH− centers in NaCl

Abstract

The correlation time τ_D of the rotational motion of OH^? centers in NaCl was studied for two different OH^?-concentrations (44 ppm and 220 ppm) between 0.5 K and 16 K by ²³Na nuclear spin relaxation measurements. The correlation time in the sample containing 44 ppm OH^? is given by phonon-assisted tunneling of isolated defects, whereas the OH^?-motion in the sample containing 220 ppm can be described by a coupled ensemble of quantum mechanical hindered rotators below a critical temperature which is determined by the strength of the interaction between the OH^? dipoles.     

In-situ study of deformation-enhanced atomic diffusion in NaCl by nuclear magnetic resonance

Abstract

Enhancements in atomic diffusion during deformation are investigated by ²³Na rotating frame nuclear spin relaxation measurements on pure NaCl single crystals. The enhanced diffusion is shown to arise from deformation-induced excess concentration of vacancies. Evaluation of the data yields the concentration of these vacancies as a function of temperature and strain rate.     

On the codimension of modules over skew power series rings with applications to Iwasawa algebras

The first purpose of this paper is to set up a general notion of skew power series rings S over a coefficient ring R, which are then studied by filtered ring techniques. The second goal is the investigation of the class of S-modules which are finitely generated as R-modules. In the case that S and R are Auslander regular we show in particular that the codimension of M as S-module is one higher than the codimension of M as R-module. Furthermore its class in the Grothendieck group of S-modules of codimension at most one less vanishes, which is in the spirit of the Gersten conjecture for commutative regular local rings. Finally we apply these results to Iwasawa algebras of p-adic Lie groups.     

Numerical Simulation of Crack Growth in Polyethylene Composites by Means of the Cohesive Zone Model

Summary: The cohesive zone model is used for the numerical simulation of crack growth in homogeneous specimens made of two different grades of polyethylene (PE) as well as in PE-bimaterials. The material data and the shapes of the cohesive function are deduced from experimental data by Ivankovic et al., Eng. Fract. Mech. 71, 2004, 657–668 and Ting et al., Polym. Eng. Sci. 46, 2006, 763–777. Fracture toughness parameters are evaluated from the simulated load versus displacement curves. The results show a significant influence of the arrangement of the two PE-grades in the bimaterial specimens, caused by both the different material properties and the different characteristic parameters of the cohesive function.     

Photoacoustic imaging in attenuating acoustic media based on strongly causal models

In this paper, we derive time reversal imaging functionals for two strongly causal acoustic attenuation models, which have been proposed recently. The time reversal techniques are based on recently proposed ideas of Ammari et al. for the thermo‐viscous wave equation. Here and there, an asymptotic analysis provides reconstruction functionals from first order corrections for the attenuating effect. In addition, we present a novel approach for higher order corrections. Copyright © 2013 John Wiley & Sons, Ltd.     

Beiträge zur Chemie der Pyrrolpigmente, 11. Mitt.: Die Lichtabsorption geometrisch isomerer Arylmethyliden-pyrrolinone —Konformationsanalytische Studien

By investigation of the geometrical isomers of several substituted arylmethylidene-pyrrolinones using lanthanide induced shift experiments in connection with a computer program, the ring current model,PPP—SCF—LCAO—MO—CI calculations and UV spectroscopy the following conclusions could be drawn: The light absorptions ofZ- andE-isomers vary only in the case of different dihedral angles at the arylmethine bond. The dihedral angles in theE-isomers are determined by the substituent in 4-position of the lactam ring. Hydrogen makes no difference whereas methyl leads to a more twistedE-structure which therefore shows a marked hypsochromic shift of the intense long wavelength absorption band, as compared to the correspondingZ-isomer.     

Beiträge zur Chemie der Pyrrolpigmente, 8. Mitt.: ZumBrunings—Corwin-Effekt bei Pyrromethenderivaten

TheBrunings—Corwin-effect of pyrromethene derivatives is discussed on the basis of thePPP-SCF-LCAO-MO-CI method. To this end the electron absorption spectra of pyrromethenes and their corresponding positively charged ions were calculated for several torsional angles of the methine bridge. In the case of the free base the calculation predicts a weak hypsochromic effect and decreasing intensity of the first transition with increasing torsion. The cations are predicted to exhibit a strong bathochromic shift and decreasing intensity. The latter result is in excellent qualitative and quantitative agreement with the experimental results, assuming a torsional angle of approximately 30° for both methine bridge bonds.