Cleaving-temperature dependence of layered-oxide surfaces

The surfaces generated by cleaving non-polar, two-dimensional oxides are often considered to be perfect or ideal. However, single particle spectroscopies on Sr2RuO4, an archetypal non-polar two dimensional oxide, show significant cleavage temperature dependence. We demonstrate that this is not a consequence of the intrinsic characteristics of the surface: lattice parameters and symmetries, step heights, atom positions, or density of states. Instead, we find a marked increase in the density of defects at the mesoscopic scale with increased cleave temperature. The potential generality of these defects to oxide surfaces may have broad consequences to interfacial control and the interpretation of surface sensitive measurements

Epitaxial influence on the ferromagnetic semiconducotor EuO

From first principles calculations we investigate the electronic structure and the magnetic properties of EuO under hydrostatic and epitaxial forces. There is a complex interdependence of the O 2p and Eu 4f and 5d bands on the magnetism in EuO, and decreasing lattice parameters is an ideal method to increase the Curie temperature, T_c. Compared to hydrostatic pressure, the out-of-plane compensation that is available to epitaxial films influences this increase in T_c, although it is minimized by the small value of poisson's ratio for EuO. We find the semiconducting gap closes at a 6% in-plane lattice compression for epitaxy, at which point a significant conceptual change must occur in the active exchange mechanisms

Screening of different Fusarium species to select potential species for the synthesis of silver nanoparticles

Eleven different Fusarium species were isolated from various infected plant materials and screened to select a potential species for the synthesis of silver nanoparticles. All the isolates were identified on the basis of cultural and microscopic characteristics using Fusarium identification keys. For the confirmation of preliminary identified isolates of Fusarium species, online BLAST analysis was carried out. All the eleven species demonstrated the ability for synthesis of silver nanoparticles. This was confirmed by UV-Vis spectroscopy, which gave characteristic peak around 420 nm. Further confirmation of silver nanoparticles was carried out using nanoparticles tracking analysis (NTA), zeta potential, photon correlation spectroscopy (PCS), powder X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The smallest size of silver nanoparticles was synthesized by F. oxysporum (3-25 nm) and largest size silver nanoparticles were synthesized by F. solani (3-50 nm).Onze diferentes espécies de Fusarium foram isoladas a partir de vários materiais vegetais infectados e selecionados para escolher uma espécie potencialmente importante para a síntese de nanopartículas de prata. Todos os isolados foram identificados com base nas características de cultivo e microscópicas usando as chaves de identificação de Fusarium. Para a confirmação e identificação preliminar dos isolados de espécies de Fusarium, a análise BLAST on-line foi utilizada. Das espécies isoladas onze mostraram a capacidade para a síntese de nanopartículas de prata. A síntese de nanopartículas de prata foi confirmada por espectroscopia de UV-Vis que monstrou um pico característico em torno de 420 nm. Além disso, a confirmação da síntese de nanopartículas de prata foi realizada utilizando a análise de rastreamento de nanoparticulas (nanoparticle tracking analysis-NTA), medidas de potencial zeta, espectroscopia de correlação de fótons (PCS), difratometria de raios X de pó (XRD), e microscopia eletrônica de transmissão (TEM). As menores nanopartículas de prata foram sintetizadas por F. oxysporum (3-25 nm), enquanto as maiores foram obtidas com F. solani (3-50 nm).19741982Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Doping dependence of the coupling of electrons to bosonic modes in the single-layer high-temperature Bi2Sr2CuO6 superconductor

A recent highlight in the study of high-Tc superconductors is the observation of band renormalization / self-energy effects on the quasiparticles. This is seen in the form of kinks in the quasiparticle dispersions as measured by photoemission and interpreted as signatures of collective bosonic modes coupling to the electrons. Here we compare for the first time the self-energies in an optimally doped and strongly overdoped, non-superconducting single-layer Bi-cuprate (Bi2Sr2CuO6). Besides the appearance of a strong overall weakening, we also find that weight of the self-energy in the overdoped system shifts to higher energies. We present evidence that this is related to a change in the coupling to c-axis phonons due to the rapid change of the c-axis screening in this doping range.Comment: 4 pages, 3 figure

Processing of Nonconjugative Resistance Plasmids by Conjugation Nicking Enzyme of Staphylococci

ABSTRACT Antimicrobial resistance in Staphylococcus aureus presents an increasing threat to human health. This resistance is often encoded on mobile plasmids, such as pSK41; however, the mechanism of transfer of these plasmids is not well understood. In this study, we first examine key protein-DNA interactions formed by the relaxase enzyme, NES, which initiates and terminates the transfer of the multidrug resistance plasmid pSK41. Two loops on the NES protein, hairpin loops 1 and 2, form extensive contacts with the DNA hairpin formed at the oriT region of pSK41, and here we establish that these contacts are essential for proper DNA cleavage and religation by the full 665-residue NES protein in vitro . Second, pSK156 and pCA347 are nonconjugative Staphylococcus aureus plasmids that contain sequences similar to the oriT region of pSK41 but differ in the sequence predicted to form a DNA hairpin. We show that pSK41-encoded NES is able to bind, cleave, and religate the oriT sequences of these nonconjugative plasmids in vitro . Although pSK41 could mobilize a coresident plasmid harboring its cognate oriT , it was unable to mobilize plasmids containing the pSK156 and pCA347 variant oriT mimics, suggesting that an accessory protein like that previously shown to confer specificity in the pWBG749 system may also be involved in transmission of plasmids containing a pSK41-like oriT . These data indicate that the conjugative relaxase in trans mechanism recently described for the pWBG749 family of plasmids also applies to the pSK41 family of plasmids, further heightening the potential significance of this mechanism in the horizontal transfer of staphylococcal plasmids. IMPORTANCE Understanding the mechanism of antimicrobial resistance transfer in bacteria such as Staphylococcus aureus is an important step toward potentially slowing the spread of antimicrobial-resistant infections. This work establishes protein-DNA interactions essential for the transfer of the Staphylococcus aureus multiresistance plasmid pSK41 by its relaxase, NES. This enzyme also processed variant oriT -like sequences found on numerous plasmids previously considered nontransmissible, suggesting that in conjunction with an uncharacterized accessory protein, these plasmids may be transferred horizontally via a relaxase in trans mechanism. These findings have important implications for our understanding of staphylococcal resistance plasmid evolution

Positive adjacency effects mediated by seed disperser birds in pine plantations

This study examines the consequences of adjacent elements for a given patch, through their effects on zoochorous dispersion by frugivorous birds. The case study consists of pine plantations (the focal patch) adjacent to other patches of native vegetation (mixed patches of native forest and shrublands), and/or pine plantations. Our hypothesis is that input of native woody species propagules generated by frugivorous birds within plantations strongly depends on the nature of the surrounding vegetation. To test this hypothesis, we studied frugivorous-bird abundance, seed dispersion, and seedling establishment in nine pine plantation plots in contact with patches of native vegetation. To quantify adjacency arrangement effects, we used the percentage of common border between a patch and each of its adjacent elements. Frugivorous bird occurrence in pine plantations is influenced by the adjacent vegetation: the greater the contact with native vegetation patches, the more abundant were the frugivorous birds within pine plantations. Furthermore, frugivorous birds introduce into plantations the seeds of a large sample of native fleshy-fruited species. The results confirm the hypothesis that zoochorous seed rain is strongly determined by the kind of vegetation surrounding a given plantation. This finding underlines the importance of the composition of the mosaic surrounding plantations and the availability of mobile link species as key landscape features conditioning passive restoration processes

Smoking and life expectancy among HIV-infected individuals on antiretroviral therapy in Europe and North America.

BACKGROUND: Cardiovascular disease and non-AIDS malignancies have become major causes of death among HIV-infected individuals. The relative impact of lifestyle and HIV-related factors are debated. METHODS: We estimated associations of smoking with mortality more than 1 year after antiretroviral therapy (ART) initiation among HIV-infected individuals enrolled in European and North American cohorts. IDUs were excluded. Causes of death were assigned using standardized procedures. We used abridged life tables to estimate life expectancies. Life-years lost to HIV were estimated by comparison with the French background population. RESULTS: Among 17 995 HIV-infected individuals followed for 79 760 person-years, the proportion of smokers was 60%. The mortality rate ratio (MRR) comparing smokers with nonsmokers was 1.94 [95% confidence interval (95% CI) 1.56-2.41]. The MRRs comparing current and previous smokers with never smokers were 1.70 (95% CI 1.23-2.34) and 0.92 (95% CI 0.64-1.34), respectively. Smokers had substantially higher mortality from cardiovascular disease, non-AIDS malignancies than nonsmokers [MRR 6.28 (95% CI 2.19-18.0) and 2.67 (95% CI 1.60-4.46), respectively]. Among 35-year-old HIV-infected men, the loss of life-years associated with smoking and HIV was 7.9 (95% CI 7.1-8.7) and 5.9 (95% CI 4.9-6.9), respectively. The life expectancy of virally suppressed, never-smokers was 43.5 years (95% CI 41.7-45.3), compared with 44.4 years among 35-year-old men in the background population. Excess MRRs/1000 person-years associated with smoking increased from 0.6 (95% CI -1.3 to 2.6) at age 35 to 43.6 (95% CI 37.9-49.3) at age at least 65 years. CONCLUSION: Well treated HIV-infected individuals may lose more life years through smoking than through HIV. Excess mortality associated with smoking increases markedly with age. Therefore, increases in smoking-related mortality can be expected as the treated HIV-infected population ages. Interventions for smoking cessation should be prioritized

Multigenerational pedigree analysis of wild individually marked black sparrowhawks suggests that dark plumage coloration is a dominant autosomal trait

The black sparrowhawk (Accipiter melanoleucus) is a color-polymorphic sub-Saharan raptor, with adults occurring in two discrete color morphs: dark and light. It has previously been suggested that plumage coloration is determined by a one-locus two-allele system, with the light allele being dominant over the dark allele. Here, we revisit that assumption with an extended dataset of 130 individuals and pedigree information from 75 individuals spanning five generations. We test the observed offspring phenotypic ratio against the expected ratio under the Hardy–Weinberg equilibrium and find significant deviations from the expected values. Contrary to the previous assumption, our data indicate that the dark allele is in fact dominant over the light allele. Similarly, the multigenerational pedigrees obtained are incompatible with a one-locus two-allele system, where the light allele is dominant but are consistent with a scenario where the dark allele is dominant instead. However, without knowledge of the underlying molecular basis of plumage polymorphism, uncertainty remains, and the intra-morph variation observed suggests that modifier genes or environmental factors may also be involved. Our study not only provides a foundation for future research on the adaptive function of color polymorphism in the species but also highlights the need for caution when drawing conclusions about the mode of inheritance in wild animal populations in the absence of genetic data, especially when one color variant is numerically much rarer than the other