Long-term stability of transparent n/p ZnO homojunctions grown by rf-sputtering at room-temperature

ZnO-based n/p homojunctions were fabricated by sputtering from a single zinc nitride target at room temperature on metal or ITO-coated glass and Si substrates. A multi-target rf-sputtering system was used for the growth of all oxide films as multilayers in a single growth run without breaking the vacuum in the growth chamber. The nitrogen-containing films (less than 1.5 at.% of nitrogen) were n-type ZnO when deposited in oxygen-deficient Ar plasma (10% O2) and p-type ZnO when deposited in oxygen-rich Ar plasma (50% O2). The all-oxide homojunction ITO/n-ZnO/p-ZnO/ITO/glass was fabricated in a single deposition run and exhibited visible transparency in the range of 75–85%. The n/p ZnO homojunctions, having metallic contacts, formed on conventionally processed substrates showed a fairly unstable behavior concerning the current-voltage characteristics. However, the same homojunctions formed on Si3N4-patterned substrates and stored in atmosphere for a period of five months were stable exhibiting a turn-on voltage of around 1.5 V. The realization of a room temperature sputtered transparent and stable ZnO homojunction paves the way to the realization of all-oxide transparent optoelectronic devices

Timp1 interacts with beta-1 integrin and CD63 along melanoma genesis and confers anoikis resistance by activating PI3-K signaling pathway independently of Akt phosphorylation

Background: Anoikis resistance is one of the abilities acquired along tumor progression. This characteristic is associated with metastasis development, since tumorigenic cells must survive independently of cell-matrix interactions in this process. in our laboratory, it was developed a murine melanocyte malignant transformation model associated with a sustained stressful condition. After subjecting melan-a melanocytes to 1, 2, 3 and 4 cycles of anchorage impediment, anoikis resistant cells were established and named 1C, 2C, 3C and 4C, respectively. These cells showed altered morphology and PMA independent cell growth, but were not tumorigenic, corresponding to pre-malignant cells. After limiting dilution of 4C pre-malignant cells, melanoma cell lines with different characteristics were obtained. Previous data from our group showed that increased Timp1 expression correlated with anoikis-resistant phenotype. Timp1 was shown to confer anchorage-independent growth capability to melan-a melanocytes and render melanoma cells more aggressive when injected into mice. However, the mechanisms involved in anoikis regulation by Timp1 in tumorigenic cells are not clear yet.Methods: the beta 1-integrin and Timp1 expression were evaluated by Western blotting and CD63 protein expression by flow cytometry using specific antibodies. To analyze the interaction among Timp1, CD63 and beta 1-integrin, immunoprecipitation assays were performed, anoikis resistance capability was evaluated in the presence or not of the PI3-K inhibitors, Wortmannin and LY294002. Relative expression of TIMP1 and CD63 in human metastatic melanoma cells was analyzed by real time PCR.Results: Differential association among Timp1, CD63 and beta 1-integrins was observed in melan-a melanocytes, 4C pre-malignant melanocytes and 4C11- and 4C11+ melanoma cells. Timp1 present in conditioned medium of melanoma cells rendered melan-a melanocytes anoikis-resistant through PI3-K signaling pathway independently of Akt activation. in human melanoma cell lines, in which TIMP1 and beta-1 integrin were also found to be interacting, TIMP1 and CD63 levels together was shown to correlate significantly with colony formation capacity.Conclusions: Our results show that Timp1 is assembled in a supramolecular complex containing CD63 and beta 1-integrins along melanoma genesis and confers anoikis resistance by activating PI3-K signaling pathway, independently of Akt phosphorylation. in addition, our data point TIMP1, mainly together with CD63, as a potential biomarker of melanoma.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade Federal de São Paulo, Dept Pharmacol, São Paulo, BrazilUniversidade Federal de São Paulo, Microbiol Immunol & Parasitol Dept, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biochem, São Paulo, BrazilLudwig Inst Canc Res, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Pharmacol, São Paulo, BrazilUniversidade Federal de São Paulo, Microbiol Immunol & Parasitol Dept, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biochem, São Paulo, BrazilFAPESP: 2011/12306-1FAPESP: 2010/18715-8CAPES: 2867/10Web of Scienc

Non-polar GaN/AlGaN quantum-well polariton laser at room temperature

International audienceWe demonstrate room temperature (RT) polariton lasing in an all-dielectric microcavity containing non-polar III-nitride quantum wells (QWs) as active media. The microcavity is fabricated using the photo-electrochemical etching method, by which an optimally grown m-plane III-nitride active region is detached from the substrate in the form of a membrane, which is subsequently inserted between two SiO2/Ta2O5 distributed Bragg reflectors, with 4 and 10 pairs for the top and bottom mirrors, respectively. The active region consists of 25 GaN/Al0.1Ga0.9N (5 nm/3 nm) QWs. The produced microcavities exhibit two closely spaced polarization-resolved lower polariton branches at RT, in line with the selection rules of the non-polar orientation, having a Rabi splitting of 62 and 72 meV in the E∥a and E∥c polarizations, respectively. In a positively detuned 3λ/2-thick microcavity, polariton lasing is observed at ambient conditions in the E∥a polarization, with a threshold ∼ 3 times lower than previous state of the art, despite the use of a relatively weak top reflector

Ultra-smooth GaN membranes by photo-electrochemical etching for photonic applications

International audiencePhoto-electrochemical, bandgap selective, lateral etching is used to create 200 nm-thick, ultra-smooth GaN membranes, containing 10 pairs of GaN/AlGaN quantum wells. The use of electrolyte concentrations as low as 0.0004 M, along with appropriate excitation power and bias conditions, are shown to enhance the quality of freestanding membranes immensely, with an AFM roughness of 0.65 nm; the best ever reported value for GaN membranes fabricated using a similar technique. Transmission and photoluminescence experiments on these membranes were made possible at cryogenic temperatures by membrane transferring onto a double-side polished sapphire substrate, revealing pronounced excitonic features; the analysis of which strongly suggest that the absorption coefficients of GaN are at least 30 % higher than the values previously reported in the literature

A Rare Case of a Male with 45, XO, SRY+, ZFY+ with Short Stature and Mild Turner Stigmata

Background: Turner syndrome is hypothesized to result from haploinsufficiency of certain genes expressed from both sex chromosomes that escape X inactivation. Case Report: We present the rare case of a 4-year-old boy who was referred to the pediatric endocrinology unit for evaluation of slight growth delay. Results: Standard cytogenetic analysis showed a 45,XO karyotype. Molecular studies disclosed the presence of an intact SRY homeobox region and the ZFY region sited on the Y short arm. Other Y chromosome sequences which are normally found on the short arm of chromosome Y (p) were absent and their exact location on a different chromosome remained unclear. Subsequently, FISH (fluorescent in situ hybridization) analysis failed to detect any Y sequences, while haplotype analysis indicated that the present X chromosome was of paternal origin. Conclusion: Phenotype-genotype correlation studies were consistent with a male patient presenting with short stature and some of the Turner's syndrome stigmata. The consequences for the patients with this chromosomal abnormality and treatment with recombinant growth hormone are also discussed. Copyright © 2012 S. Karger AG, Basel

Ultra-low threshold polariton lasing at room temperature in a GaN membrane microcavity with a zero-dimensional trap

International audienc

Whole blood interferon-γ release assay is a useful tool for the diagnosis of tuberculosis infection particularly among bacille calmette guèrin-vaccinated children

The performance of QuantiFERON-tuberculosis (TB) Gold-In-Tube assay was compared with the tuberculin skin test for the diagnosis of TB among children. It was shown that among non-Bacille Calmette Guèrin immunized children, agreement between tests was excellent both in those with TB disease and in TB contacts. Among Bacille Calmette Guèrin-immunized children, agreement was fair in those with active disease and poor among TB contacts. It is concluded that QuantiFERON-TB Gold-In-Tube compares with the tuberculin skin test in the diagnosis of TB disease and latent tuberculosis infection in TB contacts among children and has enhanced specificity. © 2010 Lippincott Williams & Wilkins