The (F*F) 1/4-method for the transmission problem in two-dimensional linear elasticity

In this article we present an inversion algorithm for the determination of the shape of a two-dimensional penetrable obstacle from knowledge of the elastic field generated by an incident plane compressional and shear wave. In particular, Kirsch's improved variant of the linear sampling method, the so called (F ^* F?)^1/4-method is extended to the elastic case. A mathematical analysis that reveals the compactness and normality of the far-field operator is presented. Finally, numerical results are presented showing the robustness of the (F ^* F?)^1/4-method with respect to noise.     

What's the probability of a rational ratio being irreducible?

We determine the probability that any given rational ratio is irreducible.     

Urinary Metabolomics Study of Patients with Bicuspid Aortic Valve Disease

Bicuspid aortic valve (BAV) is the most common congenital heart defect responsible for valvular and aortic complications in affected patients. Causes and mechanisms of this pathology are still elusive and thus the lack of early detection biomarkers leads to challenges in its diagnosis and prevention of associated cardiovascular anomalies. The aim of this study was to explore the potential use of urine Nuclear Magnetic Resonance (NMR) metabolomics to evaluate a molecular fingerprint of BAV. Both multivariate and univariate statistical analyses were performed to compare the urinary metabolome of 20 patients with BAV with that of 24 matched controls. Orthogonal partial least squared discriminant analysis (OPLS-DA) showed statistically significant discrimination between cases and controls, suggesting seven metabolites (3-hydroxybutyrate, alanine, betaine, creatine, glycine, hippurate, and taurine) as potential biomarkers. Among these, glycine, hippurate and taurine individually displayed medium sensitivity and specificity by receiver operating characteristic (ROC) analysis. Pathway analysis indicated two metabolic pathways likely perturbed in BAV subjects. Possible contributions of gut microbiota activity and energy imbalance are also discussed. These results constitute encouraging preliminary findings in favor of the use of urine-based metabolomics for early diagnosis of BAV.     

Evaluation of the activity of the sponge metabolites avarol and avarone and their synthetic derivatives against fouling micro- and macroorganisms

The sesquiterpene hydroquinone avarol (1) was isolated from the marine sponge Dysidea avara, whereas the corresponding quinone, avarone (2), was obtained by oxidation of avarol, and the significantly more lipophilic compounds [3'-(p-chloro-phenyl)avarone (3), 3',4'-ethylenedithioavarone (4), 4'-isopropylthioavarone (5), 4'-tert-butylthioavarone (6), 4'-propylthioavarone (7), 4'-octylthioavarone (8)] were obtained by nucleophilic addition of thiols or p-chloroaniline to avarone. All these compounds were tested, at concentrations ranging from 0.5 to 50 microg/mL, for their effect on the settlement of the cyprid stage of Balanus amphitrite, for toxicity to both nauplii and cyprids and for their growth inhibitory activity on marine bacteria (Cobetia marina, Marinobacterium stanieri, Vibrio fischeri and Pseudoalteromonas haloplanktis) and marine fungi (Halosphaeriopsis mediosetigera, Asteromyces cruciatus, Lulworthia uniseptata and Monodictys pelagica).     

A unified framework for the numerical solution of general quadratic matrix equations

^** Email: vassilios.tsachouridis{at}ieee.org^*** Email: N.karcanias{at}city.ac.uk^**** Email: ixp{at}le.ac.uk Algebraic quadratic equations are special cases of a singlegeneralized algebraic quadratic matrix equation (GQME). Thispaper focuses on the numerical solution of the GQME using probability-1homotopy methods. A synoptic review of these methods and theirapplication to algebraic matrix equations is provided as background.A large variety of analysis and design problems in systems andcontrol are reported as special cases of the presented frameworkand some of them are illustrated via numerical examples fromthe literature.     

A large [Mn10Na]4 loop of four linked Mn10 loops

A large [Mn10Na]4 loop-of-loops aggregate was prepared from the use of 1,3-propanediol (pdH2) in manganese carboxylate chemistry. It is constructed from four [Mn10(mu3-O)2(O2CMe)13(pd)6(py)2]- loops linked through Na+ ions and exhibits a saddlelike topology. Magnetic characterization showed that the Mn10 loop has an S approximately 4 ground-state spin and displays frequency-dependent in-phase and out-of-phase alternating current signals and also hysteresis loops that, however, are not typical of single-molecule magnets because of the existence of intermolecular interactions between the Mn10 units.     

Second harmonic imaging of chloroplasts using the two-photon laser scanning microscope

BackgroundSecond harmonic information reveals information about the structure of spatially oriented structures with an asymmetry. We study the second harmonic images of the grana and intergranal parts of chloroplasts in the leaves of the shade moss Plagiomnium affine.ResultsA two-photon microscope with blocking filters to suppress fluorescence generated both forward and backward second harmonic illumination to be captured. In the starch free chloroplasts of the single cell layered laminae strong second harmonic generation (SHG) from the granal regions was emitted. Upon illumination the chloroplasts changed their orientation affecting the SHG signal. Chloroplast is reoriented upon illumination.ConclusionsSHG signals were successfully obtained from the grana without any possible confusion from SHG starch grains due to their absence.     

Preparative isolation and purification of alkannin/shikonin derivatives from natural products by high-speed counter-current chromatography

Alkannin and shikonin (A/S) and their derivatives have been found in the roots of several Boraginaceous species and are also produced through plant tissue cultures. The chiral compounds A/S are potent pharmaceutical substances with a wide spectrum of biological and pharmacological activities like wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant activity. High-speed counter-current chromatography (HSCCC) was applied for the first time to the separation, preparative isolation and purification of A/S and their esters from extracts of Alkanna tinctoria roots, as well as commercial samples. The constituents of HSCCC fractions and their purity were determined by high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS), since DAD cannot detect oligomeric A/S derivatives that are present in most of the samples containing the respective monomeric derivatives. The purity of HSCCC fractions was compared with the one of fractions isolated by column chromatography (CC) using as stationary phases silica gel and Sephadex LH-20. As shown, the purity of monomeric alkannin/shikonin was greater by HSCCC than CC separation of commercial A/S samples.