Diagnostic of the unstable envelopes of Wolf-Rayet stars

The envelopes of stars near the Eddington limit are prone to various instabilities. A high Eddington factor in connection with the Fe opacity peak leads to convective instability, and a corresponding envelope inflation may induce pulsational instability. Here, we investigate the occurrence and consequences of both instabilities in models of Wolf-Rayet stars. We determine the convective velocities in the sub-surface convective zones to estimate the amplitude of the turbulent velocity at the base of the wind that potentially leads to the formation of small-scale wind structures, as observed in several WR stars. We also investigate the effect of mass loss on the pulsations of our models. We approximated solar metallicity WR stars by models of mass-losing helium stars, and we characterized the properties of convection in the envelope adopting the standard MLT. Our results show the occurrence of sub-surface convective regions in all studied models. Small surface velocity amplitudes are predicted for models with masses below 10Msun. For models with M>10Msun, the surface velocity amplitudes are of the order of 10km/s. Moreover we find the occurrence of pulsations for stars in the mass range 9-14Msun, while mass loss appears to stabilize the more massive WR stars. We confront our results with observationally derived line variabilities of 17 WN stars. The data suggest variability to occur for stars above 10Msun, which is increasing linearly with mass above this value, in agreement with our results. We further find some of our models to be unstable to radial pulsations, and predict local magnetic fields of the order of hundreds of Gauss in WR stars more massive than 10Msun. Our study relates the surface velocity fluctuations induced by sub-surface convection to the formation of clumping in the inner part of the wind. From this mechanism, we expect a stronger variability in more massive WR stars.Comment: A&A, accepte

Water-stable plasma-polymerized N,N-dimethylacrylamide coatings to control cellular adhesion

The plasma polymerization of amide-based precursors is a nearly unexplored research area, which is in contrast with the abundance of reports focusing on amide based surface modification using wet chemistry. Therefore, this study aims to profoundly investigate the near-atmospheric pressure plasma polymerization of N,N-dimethylacrylamide (DMAM) to obtain stable coatings. In contrast to the unstable coatings obtained at lower discharge powers, the stable coatings that were obtained at higher powers showed a lower hydrophilicity as assessed by water contact angle (WCA). This decrease in hydrophilicity with increasing plasma power was found to be related to a reduced preservation of the monomer structure, as observed by Fourier transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and XPS C-60 depth profiling, a rarely used but effective combination of techniques. Furthermore, the chemical composition of the coating was found to be in good agreement with the plasma active species observed by optical emission spectroscopy. Additionally, XPS C-60 depth profiling indicated a difference between the top layer and bulk of the plasma polymer due to spontaneous oxidation and/or postplasma coating deposition. Finally, the stable coatings were also found to have cell-interactive behavior toward MC3T3 as studied by in vitro live/dead fluorescence imaging and (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) assays. With the latter technique, a cell viability of up to 89% as compared with tissue culture plates after 1 day of cell culture was observed, indicating the potential of these coatings for tissue engineering purposes

Prognostic significance of endogenous adhesion/growth-regulatory lectins in lung cancer

Objective: To determine the expression of endogenous adhesion/growth-regulatory lectins and their binding sites using labeled tissue lectins as well as the binding profile of hyaluronic acid as an approach to define new prognostic markers. Methods: Sections of paraffin-embedded histological material of 481 lungs from lung tumor patients following radical lung excision processed by a routine immunohistochemical method (avidin-biotin labeling, DAB chromogen). Specific antibodies against galectins-1 and - 3 and the heparin-binding lectin were tested. Staining by labeled galectins and hyaluronic acid was similarly visualized by a routine protocol. After semiquantitative assessment of staining, the results were compared with the pT and pN stages and the histological type. Survival was calculated by univariate and multivariate methods. Results: Binding of galectin-1 and its expression tended to increase, whereas the parameters for galectin-3 decreased in advanced pT and pN stages at a statistically significant level. The number of positive cases was considerably smaller among the cases with small cell lung cancer than in the group with non-small-cell lung cancer, among which adenocarcinomas figured prominently with the exception of galectin-1 expression. Kaplan-Meier computations revealed that the survival rate of patients with galectin-3-binding or galectin-1-expressing tumors was significantly poorer than that of the negative cases. In the multivariate calculations of survival lymph node metastases ( p < 0.0001), histological type ( p = 0.003), galectin-3-binding capacity ( p = 0.01), galectin-3 expression ( p = 0.03) and pT status ( p = 0.003) proved to be independent prognostic factors, not correlated with the pN stage. Conclusion: The expression and the capacity to bind the adhesion/growth regulatory galectin-3 is defined as an unfavorable prognostic factor not correlated with the pTN stage. Copyright (C) 2005 S. Karger AG, Basel

Identification of a Potent Allosteric Inhibitor of Human Protein Kinase CK2 by Bacterial Surface Display Library Screening

Human protein kinase CK2 has emerged as promising target for the treatment of neoplastic diseases. The vast majority of kinase inhibitors known today target the ATP binding site, which is highly conserved among kinases and hence leads to limited selectivity. In order to identify non-ATP competitive inhibitors, a 12-mer peptide library of 6 × 105 variants was displayed on the surface of E. coli by autodisplay. Screening of this peptide library on variants with affinity to CK2 was performed by fluorophore-conjugated CK2 and subsequent flow cytometry. Single cell sorting of CK2-bound E. coli yielded new peptide variants, which were tested on inhibition of CK2 by a CE-based assay. Peptide B2 (DCRGLIVMIKLH) was the most potent inhibitor of both, CK2 holoenzyme and the catalytic CK2α subunit (IC50 = 0.8 µM). Using different ATP concentrations and different substrate concentrations for IC50 determination, B2 was shown to be neither ATP- nor substrate competitive. By microscale thermophoresis (MST) the KD value of B2 with CK2α was determined to be 2.16 µM, whereas no binding of B2 to CK2β-subunit was detectable. To our surprise, besides inhibition of enzymatic activity, B2 also disturbed the interaction of CK2α with CK2β at higher concentrations (≥25 µM)

Electrostatically confined monolayer graphene quantum dots with orbital and valley splittings

The electrostatic confinement of massless charge carriers is hampered by Klein tunneling. Circumventing this problem in graphene mainly relies on carving out nanostructures or applying electric displacement fields to open a band gap in bilayer graphene. So far, these approaches suffer from edge disorder or insufficiently controlled localization of electrons. Here we realize an alternative strategy in monolayer graphene, by combining a homogeneous magnetic field and electrostatic confinement. Using the tip of a scanning tunneling microscope, we induce a confining potential in the Landau gaps of bulk graphene without the need for physical edges. Gating the localized states towards the Fermi energy leads to regular charging sequences with more than 40 Coulomb peaks exhibiting typical addition energies of 7-20 meV. Orbital splittings of 4-10 meV and a valley splitting of about 3 meV for the first orbital state can be deduced. These experimental observations are quantitatively reproduced by tight binding calculations, which include the interactions of the graphene with the aligned hexagonal boron nitride substrate. The demonstrated confinement approach appears suitable to create quantum dots with well-defined wave function properties beyond the reach of traditional techniques

Varroakvalstrets effekt på virus i angripna honungsbisamhällen

Vilken effekt har varroakvalster på de virus som infekterar bisamhällen? Forskare vid INRA (Frankrikes nationella institution för jordbruksforskning) i Avignon, Frankrike, University of Otago i Nya Zeeland och Sveriges lantbruksuniversitet (SLU), nyttjade en unik situation i Nya Zeeland där landet, liksom Sverige, har varroaangripna respektive icke angripna regioner. Varroa är relativt nyetablerad i Nya Zeeland. Den påvisades först på Nordön år 2000, och har stadigt spridits söderut under de 14 åren som gått sedan introduktionen. Forskarna har undersökt virusprofilen hos bisamhällena sedan etablering av kvalstret i de olika regionerna. Studien, som publicerades 2014, visar en drastisk ändring av det virala landskapet i bisamhällena som sammanfaller med etablering av varroa, vilket ökar risken för synergier mellan olika virus som är skadliga för bina

Synthesis of Bivalent Lactosides Based on Terephthalamide, N,N0-Diglucosylterephthalamide, and Glycophane Scaffolds and Assessment of Their Inhibitory Capacity on Medically Relevant Lectins

Glycan recognition by lectins initiates clinically relevant processes such as toxin binding or tumor spread. Thus, the development of potent inhibitors has a medical perspective. Toward this goal, we report the synthesis of both rigid and flexible bivalent lactosides on scaffolds that include secondary and tertiary terephthalamides and N,N0-diglucosylterephthalamides. Construction of these compounds involved Schmidt-Michel glycosidation, and amide coupling or Ugi reactions of relevant glycosyl amines in key steps. A glycocluster based on a rigid glycophane was also prepared from coupling of a glucuronic acid derivative and p-xylylenediamine with subsequent ring-closing metathesis. Finally, a more flexible bivalent lactoside was produced from lactosyl azide with use of the copper-catalyzed azide-alkyne cycloaddition. Distances between lactose residues were analyzed computationally as were their orientations for the relatively rigid subset of compounds. Distinct spacing properties were revealed by varying the structure of the scaffold or by varying the location of the lactose residue on the scaffold. To relate these features to bioactivity a plant toxin and human adhesion/growth-regulatory galectins were used as sensors in three types of assay, i.e. measuring agglutination of erythrocytes, binding to glycans of a surface-immobilized glycoprotein, or binding to human cells.Methodologically, the common hemeagglutination assaywas found to be considerably less sensitive than both solid-phase and cell assays. The bivalent compounds were less effective at interfering with glycoprotein binding to the plant toxin than to human lectins. Significantly, a constrained compound was identified that displayed selectivity in its inhibitory potency between galectin-3 and its proteolytically processed form. Conversely, compounds with a high degree of flexibility showed notable ability to protect human cells fromplant toxin binding. The applied conjugation chemistry thus is compatiblewith the long-termaim to produce potent and selective lectin inhibitors

Fulgeo - towards an intuitive user interface for a semantics-enabled multimedia search engine

Multimedia documents like PowerPoint presentations or Flash documents are widely adopted in the Internet and exist in context of lots of different topics. However, so far there is no user friendly way to explore and search for this content. The aim of this work is to address this issue by developing a new, easy-to-use user interface approach and prototype search engine. Our system is called fulgeo and specifically focuses on a suitable multimedia interface for visualizing the query results of semantically-enriched Flash documents

Phenylenediamine-based bivalent glycocyclophanes: synthesis and analysis of the influence of scaffold rigidity and ligand spacing on lectin binding in cell systems with different glycomic profiles

The conjugation of carbohydrates to synthetic scaffolds has the goal of preparing potent inhibitors of lectin binding. We herein report the synthesis of a panel of bivalent compounds (cyclophane and terephthalamide-derivatives) then used to establish the influence of scaffold flexibility on respective inhibitory potency in a medically relevant test system. Synthetic routes to two phenylenediamine-based glycocyclophanes involving Ugi reactions of glucuronic acid derivatives and subsequent ring closing metathesis are described, as are improvements for producing terephthalamide-based carbohydrate carriers. Assays were performed with human tumour cells measuring quantitatively the influence of the test compounds on fluorescent surface staining by labelled lectins. Biological evaluation using two different lines of cancer cells as well as cells with known alterations in the glycomic profile (cells treated with an inhibitor of glycan processing and a glycosylation mutant) reduced the risk of generating premature generalizations regarding inhibitor potency. Bioactivity relative to free mannose was invariably determined for the synthetic compounds. A clear trend for enhanced inhibitory properties for macrocyclic compounds compared to non-macrocyclic derivatives was discerned for one type of glycocyclophane. Herein we also document the impact of altering the spacing between the mannose residues, altering cell surface ligand density and cell-type reactivity. The applied strategy for the cell assays is proposed to be of general importance in the quest to identify medically relevant lectin inhibitors