Influence of the crosstalk on the intensity of HAADF-STEM images of quaternary semiconductor materials.

The influence of the neighbouring atomic-columns in determining the composition at atomic column scale of quaternary semiconductor compounds, using simulated HAADF-STEM images is evaluated. The InAlAsSb alloy, a promising material in the photovoltaic field, is considered. We find that the so called 'crosstalk' effect plays an important role for the aimed compositional determination. The intensity transfer is larger from neighbouring atomic columns with higher average Z, and towards atomic columns with smaller Z. Our results show that in order to obtain precise information on the column composition, the HAADF-STEM intensities of both columns need to be taken into account simultaneously.

Antimicrobial activity and chemical composition of fixed oil extracted from the body fat of the snake Spilotes pullatus.

CONTEXT: Ethnozoological studies have shown that Spilotes pullatus Linn. (Colubridae: Ophidia), is associated with medicinal and magic-religious uses in Brazil. OBJECTIVES: This study was designed to determine the chemical composition of the oil extracted from the body fat of S. pullatus and to test its antimicrobial properties, alone and in association with aminoglycosides, against fungi and bacterial strains in concentrations ranging between 1024 and 0.5 µg/mL. MATERIAL AND METHODS: The snakes were collected in the Chapada do Araripe, county of Crato, Ceará State, Brazil. The oil was extracted in a Soxhlet apparatus using hexane. The methyl esters of the fatty acids present in the samples were identified using GC-MS. The antimicrobial and drug modulatory activities of oil were tested by microdilution against fungal and bacterial strains. RESULTS: The chemical composition of the fixed oils of S. pullatus identified 10 constituents representing 94.97% of the total sample. The percentages of saturated and unsaturated fatty acids were 33.59 and 61.38%, respectively, with the most abundant components being elaidic (37.26%). The oil did not demonstrate any antimicrobial or antifungal activity when tested alone, presenting MIC values ≥ 1024 µg/mL. However, when associated with antibiotics, it demonstrated synergistic effects with gentamicin against all the bacterial lineages assayed, and antagonistic effects with amikacin and neomycin against strains of Escherichia coli. CONCLUSIONS: Oil extracted from the body fat of S. pullatus did not demonstrate any inhibitory effects on bacterial or fungal activities, but was effective in modulating the effects of certain antibiotics.

Investigation of the cytocidal potential of Rhinella jimi skin methanol extracts.

CONTEXT: Amphibian skins have wide variety of biologically active compounds associated with the natural defenses of these animals. OBJECTIVES: To study the in vitro anticancer activity of methanol extracts of the skin of Rhinella jimi Stevaux (Anura: Bufonidae). MATERIAL AND METHODS: The extract was obtained by cold methanol extraction for 96 h using dried skins (295 mg). The methanol skin extract was dried under reduced pressure, giving a 5.5% yield. In order to test for growth-inhibitory activity, in vitro tests were performed with the following cancer cell lines using concentrations ranging between 0.25-250 µg/mL of the extract by 48 h: K562 (leukemia), MCF-7 (breast), NCI-ADR (breast with MDR phenotype), UACC-62 (melanoma), NCI460 (lung), PCO3 (prostate), HT-29 (colon), OVCAR (ovary), and 786-0 (kidney). RESULTS: The methanol extract of R. jimi produced a growth inhibition in a dose-dependent manner against the most of the assayed cell lines. In addition to the growth inhibition, the extract induced the cell death in the ovary and colon lines (EC50 0.125 and 0.2 µg/mL, respectively), demonstrating 100% of inhibition with 2.5 µg/mL. However, prostate and leukemia cell lines demonstrated less sensitivity, with EC50 of 24 and 235 µg/mL, respectively. This is the first report about the anticancer activity by natural products from the skin of R. jimi. CONCLUSIONS: The methanol extracts of R. jimi significantly affected the growth of several cell lines, demonstrating that these compounds are a potential source of substances that could be utilized in cancer treatments.

Morphological evolution of InAs/InP quantum wires through aberration-corrected scanning transmission electron microscopy.

Evolution of the size, shape and composition of self-assembled InAs/InP quantum wires through the Stranski-Krastanov transition has been determined by aberration-corrected Z-contrast imaging. High resolution compositional maps of the wires in the initial, intermediate and final formation stages are presented. (001) is the main facet at their very initial stage of formation, which is gradually reduced in favour of [114] or [118], ending with the formation of mature quantum wires with {114} facets. Significant changes in wire dimensions are measured when varying slightly the amount of InAs deposited. These results are used as input parameters to build three-dimensional models that allow calculation of the strain energy during the quantum wire formation process. The observed morphological evolution is explained in terms of the calculated elastic energy changes at the growth front. Regions of the wetting layer close to the nanostructure perimeters have higher strain energy, causing migration of As atoms towards the quantum wire terraces, where the structure is partially relaxed; the thickness of the wetting layer is reduced in these zones and the island height increases until the (001) facet is removed.

Column-by-column compositional mapping by Z-contrast imaging.

A phenomenological method is developed to determine the composition of materials, with atomic column resolution, by analysis of integrated intensities of aberration-corrected Z-contrast scanning transmission electron microscopy images. The method is exemplified for InAs(x)P(1-x) alloys using epitaxial thin films with calibrated compositions as standards. Using this approach we have determined the composition of the two-dimensional wetting layer formed between self-assembled InAs quantum wires on InP(001) substrates.

Analysis of Bi Distribution in Epitaxial GaAsBi by Aberration-Corrected HAADF-STEM.

The Bi content in GaAs/GaAs1 - xBi x /GaAs heterostructures grown by molecular beam epitaxy at a substrate temperature close to 340 °C is investigated by aberration-corrected high-angle annular dark-field techniques. The analysis at low magnification of high-angle annular dark-field scanning transmission electron microscopy images, corroborated by EDX analysis, revealed planar defect-free layers and a non-homogeneous Bi distribution at the interfaces and within the GaAsBi layer. At high magnification, the qHAADF analysis confirmed the inhomogeneous distribution and Bi segregation at the GaAsBi/GaAs interface at low Bi flux and distorted dumbbell shape in areas with higher Bi content. At higher Bi flux, the size of the Bi gathering increases leading to roughly equiaxial Bi-rich particles faceted along zinc blende {111} and uniformly dispersed around the matrix and interfaces. FFT analysis checks the coexistence of two phases in some clusters: a rhombohedral pure Bi (rh-Bi) one surrounded by a zinc blende GaAs1 - xBi x matrix. Clusters may be affecting to the local lattice relaxation and leading to a partially relaxed GaAsBi/GaAs system, in good agreement with XRD analysis.

Growth of Low-Density Vertical Quantum Dot Molecules with Control in Energy Emission.

In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum dots (QD) in which a deliberate control of energy emission is achieved. The emission energy of the first layer of QD forming the molecule can be tuned by the deposition of controlled amounts of InAs at a nanohole template formed by GaAs droplet epitaxy. The QD of the second layer are formed directly on top of the buried ones by a strain-driven process. In this way, either symmetric or asymmetric vertically coupled structures can be obtained. As a characteristic when using a droplet epitaxy patterning process, the density of quantum dot molecules finally obtained is low enough (2 × 10(8) cm(-2)) to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure level are required.

Lung infection rates in two sympatric Tropiduridae lizard species by pentastomids and nematodes in northeastern Brazil.

We present data on pulmonary infection rates by parasites in the lizards Tropidurus hispidus Spix, 1825 and T. semitaeniatus (Spix, 1825) living sympatrically in the Chapada do Araripe mountain Range, northeastern Brazil. We found no parasite pulmonary infection in T. semitaeniatus. However, two pulmonary parasite species were found in the T. hispidus hosts, the pentastomid Raillietiella mottae Almeida, Freire and Lopes, 2008 and the nematode Rhabdias sp. Overall prevalence was 5%. Prevalence of R. mottae was 2.5% and corresponded to only one parasite on each infected host. Prevalence of Rhabdias sp. was 2.5% and the range of infection was 1-2 parasites per host. This represents the first record of Rhabdias infecting lizards of the family Tropiduridae in the Neotropical region. Furthermore, we present a comparison of parameters of infection by pulmonary parasites including some recent studies in Brazil.

Prevalence and intensity of infection by Raillietiella gigliolii Hett, 1924 (Pentastomida) in Amphisbaena alba Linnaeus, 1758 and A. vermicularis Wagler, 1824 (Amphisbaenidae) from Northeastern Brazil.

Raillietiella gigliolii is a Neotropical pentastomid parasite found in Amphisbaena alba. Collections were made in northeastern Brazil in a remnant area of Atlantic Forest (07 masculine 10' S and 35 masculine 05' W) in the municipality of Cruz do Espírito Santo, Paraíba State, and in a Humid Forest area (07 masculine 16' S and 39 masculine 26' W) on the slopes of the Chapada do Araripe Mountains, municipality of Crato, Ceará state, Brazil. Nine specimens of A. alba and 12 of A. vermicularis were collected to gather basic ecological data (prevalence and mean intensity of infection) concerning these parasites. Raillietiella gigliolii was found infecting the lungs of both species. The prevalence for A. alba was 55.5% (5/9), with a mean intensity of infection of 5.0 +/- 2.53 and amplitudes of 1-13. A. vermicularis demonstrated prevalence of 50%, with a mean intensity of infection of 5.3 +/- 2.1 and amplitudes of 1-14. This represents the first record of R. gigliolii as a parasite of A. vermicularis. Our results suggest that R. gigliolii is a generalist parasite species and that an overlapping diet is the determinant factor in the sharing of its final hosts.

Aberration-corrected scanning transmission electron microscopy: from atomic imaging and analysis to solving energy problems.

The new possibilities of aberration-corrected scanning transmission electron microscopy (STEM) extend far beyond the factor of 2 or more in lateral resolution that was the original motivation. The smaller probe also gives enhanced single atom sensitivity, both for imaging and for spectroscopy, enabling light elements to be detected in a Z-contrast image and giving much improved phase contrast imaging using the bright field detector with pixel-by-pixel correlation with the Z-contrast image. Furthermore, the increased probe-forming aperture brings significant depth sensitivity and the possibility of optical sectioning to extract information in three dimensions. This paper reviews these recent advances with reference to several applications of relevance to energy, the origin of the low-temperature catalytic activity of nanophase Au, the nucleation and growth of semiconducting nanowires, and the origin of the eight orders of magnitude increased ionic conductivity in oxide superlattices. Possible future directions of aberration-corrected STEM for solving energy problems are outlined.

Determination of the strain generated in InAs/InP quantum wires: prediction of nucleation sites.

The compositional distribution in a self-assembled InAs(P) quantum wire grown by molecular beam epitaxy on an InP(001) substrate has been determined by electron energy loss spectrum imaging. We have determined the strain and stress fields generated in and around this wire capped with a 5 nm InP layer by finite element calculations using as input the compositional map experimentally obtained. Preferential sites for nucleation of wires grown on the surface of this InP capping layer are predicted, based on chemical potential minimization, from the determined strain and stress fields on this surface. The determined preferential sites for wire nucleation agree with their experimentally measured locations. The method used in this paper, which combines electron energy loss spectroscopy, high-resolution Z contrast imaging, and elastic theory finite element calculations, is believed to be a valuable technique of wide applicability for predicting the preferential nucleation sites of epitaxial self-assembled nano-objects.

Lung infection rates in two sympatric Tropiduridae lizard species by pentastomids and nematodes in northeastern Brazil / Taxas de infecção pulmonar em duas espécies simpátricas de lagartos Tropiduridae por pentastomídeos e nematódeos na região Nordeste do Brasil

We present data on pulmonary infection rates by parasites in the lizards Tropidurus hispidus Spix, 1825 and T. semitaeniatus (Spix, 1825) living sympatrically in the Chapada do Araripe mountain Range, northeastern Brazil. We found no parasite pulmonary infection in T. semitaeniatus. However, two pulmonary parasite species were found in the T. hispidus hosts, the pentastomid Raillietiella mottae Almeida, Freire and Lopes, 2008 and the nematode Rhabdias sp. Overall prevalence was 5 percent. Prevalence of R. mottae was 2.5 percent and corresponded to only one parasite on each infected host. Prevalence of Rhabdias sp. was 2.5 percent and the range of infection was 1-2 parasites per host. This represents the first record of Rhabdias infecting lizards of the family Tropiduridae in the Neotropical region. Furthermore, we present a comparison of parameters of infection by pulmonary parasites including some recent studies in Brazil.

Apresentamos dados sobre taxas de infecção pulmonar por parasitas nos lagartos Tropidurus hispidus e T. semitaeniatus que vivem simpatricamente na encosta da Chapada do Araripe, situada na região Nordeste do Brasil. Não encontramos infecção parasitária nos pulmões dos espécimes de T. semitaeniatus. Entretanto, foram encontradas duas espécies de parasitas nos hospedeiros T. hispidus, os pentastomídeos Raillietiella mottae e os nematódeos Rhabdias sp. A prevalência geral de infecção foi de 5 por cento. A prevalência de infecção de R. mottae foi de 2,5 por cento correspondendo a apenas um parasita por hospedeiro. A prevalência de infecção de Rhabdias sp. foi de 2,5 por cento e a amplitude de infecção de 1-2 parasitas por hospedeiros. Esses resultados compreendem o primeiro registro de Rhabdias infectando lagartos da família Tropiduridae em toda a região Neotropical. Apresentamos também uma comparação com os parâmetros de infecção pulmonar por parasitas incluindo os estudos mais recentes no Brasil.