Pulsed laser deposition of KNbO₃ thin films

The laser ablation of stationary KNbO3 single crystal targets induces a Nb enrichment of the target surface. In rotated targets this effect is observed only in those areas irradiated with low laser fluence. The composition of the plasma formed close to the target surface is congruent with the target composition; however, at further distances K-deficient films are formed due to the preferential backscattering of K in the plasma. This loss may be compensated for by using K-rich ceramic targets. Best results so far have been obtained with [K]/[Nb] = 2.85 target composition, and crystalline KNbO3 films are formed when heating the substrates to 650 °C. Films formed on (100)MgO single crystals are usually single phase and oriented with the (110) film plane parallel to the (100) substrate surface. (100)NbO may coexist with KNbO3 on (100)MgO. At substrate temperatures higher than 650 °C, niobium diffuses into MgO forming Mg4Nb2O9 and NbO, leading to K evaporation from the film. Films formed on (001) alpha-Al2O3 (sapphire) show the coexistence of (111), (110), and (001) orientations of KNbO3, and the presence of NbO2 is also observed. KNbO3 films deposited on (001)LiNbO3 crystallize with the (111) plane of the film parallel to the substrate surface. For the latter two substrates the Nb diffusion into the substrate is lower than in MgO and consequently the K concentration retained in the film is comparatively larger

Wear and corrosion resistance of niobium–chromium carbide coatings on AISI D2 produced through TRD

AbstractNiobium carbide, chromium carbide and niobium–chromium carbide coatings were deposited using the thermo-reactive diffusion (TRD) deposition technique on AISI D2 steel substrates, and their wear and corrosion resistance was studied. The morphology of the coatings was characterized through optical and scanning electron microscopy (SEM), and the crystalline structure was studied through X-ray diffraction (XRD). Chemical composition was evaluated via energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The hardness of the coatings was measured through nanoindentation, and their wear was studied using the ball on disk test. The electrochemical behavior was assessed with potentiodynamic polarization and electrochemical impedance (EIS) tests. The XRD results show the formation of the NbC for the niobium carbide coating, Cr23C6 and Cr7C3 for the chromium carbide coating, and NbC, Cr23C6 and Cr7C3 for the niobium–chromium coating. Hardness value for the niobium–chromium carbide coating was 27.62±2.56GPa, which was higher in comparison to 21.66±0.5GPa for niobium carbide, 14.7±1.1GPa for chromium carbide and 6.70±0.28GPa for the uncoated steel. The wear resistance obtained was higher for the niobium–chromium carbide coating. However, its corrosion resistance was lower than the corrosion resistance for binary coatings

Influence of the substrate bias voltage on the crystallographic structure and surface composition of Ti6A14V thin films deposited by rf magnetron sputtering

In this work, the influence of the substrate bias on the crystalline structure and surface composition of Ti6Al4V thin films prepared by rf magnetron sputtering were studied. Samples were grown onto two different types of substrates: AISI 420 steel and common glass using a Ti6Al4V (99.9 %) target. Substrate bias was varied from -100V to -200 V. Samples were characterized by X-ray diffraction (XRD), Energy Dispersive X-ray Analysis (EDX), Scanning Electron Microscopy (SEM), and X-Ray Photoelectron Spectroscopy (XPS). It was observed that the increase of the substrate voltage improved the crystallinity of the deposited films. The stoichiometry of the deposited thin films was studied by EDX and found to be slightly different from that of the target material. Finally, the passive film spontaneously formed on the deposited films upon exposure to the laboratory atmosphere was studied by XPS. The composition of the passive film is rather complex since it contains several forms of oxidized titanium and vanadium as well as Al2O3.Peer reviewe

A new version of the ERICA tool to facilitate impact assessments of radioactivity on wild plants and animals

A new version of the ERICA Tool (version 1.2) was released in November 2014; this constitutes the first major update of the Tool since release in 2007. The key features of the update are presented in this article. Of particular note are new transfer databases extracted from an international compilation of concentration ratios (CRwo-media) and the modification of ‘extrapolation’ approaches used to select transfer data in cases where information is not available. Bayesian updating approaches have been used in some cases to draw on relevant information that would otherwise have been excluded in the process of deriving CRwo-media statistics. All of these efforts have in turn led to the requirement to update Environmental Media Concentration Limits (EMCLs) used in Tier 1 assessments. Some of the significant changes with regard to EMCLs are highlighte

First-Principles Studies of Hydrogenated Si(111)--7×\times7

The relaxed geometries and electronic properties of the hydrogenated phases of the Si(111)-7$\times$7 surface are studied using first-principles molecular dynamics. A monohydride phase, with one H per dangling bond adsorbed on the bare surface is found to be energetically favorable. Another phase where 43 hydrogens saturate the dangling bonds created by the removal of the adatoms from the clean surface is found to be nearly equivalent energetically. Experimental STM and differential reflectance characteristics of the hydrogenated surfaces agree well with the calculated features.Comment: REVTEX manuscript with 3 postscript figures, all included in uu file. Also available at http://www.phy.ohiou.edu/~ulloa/ulloa.htm

Anisotropic optical response of the diamond (111)-2x1 surface

The optical properties of the 2$\times$1 reconstruction of the diamond (111) surface are investigated. The electronic structure and optical properties of the surface are studied using a microscopic tight-binding approach. We calculate the dielectric response describing the surface region and investigate the origin of the electronic transitions involving surface and bulk states. A large anisotropy in the surface dielectric response appears as a consequence of the asymmetric reconstruction on the surface plane, which gives rise to the zigzag Pandey chains. The results are presented in terms of the reflectance anisotropy and electron energy loss spectra. While our results are in good agreement with available experimental data, additional experiments are proposed in order to unambiguously determine the surface electronic structure of this interesting surface.Comment: REVTEX manuscript with 6 postscript figures, all included in uu file. Also available at http://www.phy.ohiou.edu/~ulloa/ulloa.html Submitted to Phys. Rev.

Gene expression profiling identifies IL-13 receptor alpha 2 chain as a therapeutic target in prostate tumor cells overexpressing adrenomedullin

Human adrenomedullin (AM) is a 52 amino acid peptide, which shares homology with the calcitonin gene-related peptide. Overexpression of AM in the prostate carcinoma cell line PC-3 results in growth inhibition with a 20% (for human AM) and 35% (for rat AM) increase in doubling time compared to parental or mock-transfected cells. We demonstrate by gene expression profiling that AM overexpression results in the dysregulation of approximately 100 genes. Examples of such genes include many involved in the formation of the cytoskeleton, cell adhesion and the extracellular matrix, as well as regulators of the cell cycle and apoptosis, cytokines and transcription factors. Several genes related to cell growth arrest, such as GADD45, IGF-BP6 and RUNX-3, are upregulated by AM. Interestingly, interleukin-13 receptor alpha 2 (IL-13R alpha 2) transcripts were significantly increased in clones overexpressing AM, which was confirmed by semiquantitative RT-PCR analysis. In addition, PC-3 cells treated with AM showed an overexpression of IL-13R alpha 2, which was abolished when cells were preincubated with an anti-AM blocking antibody. When PC-3 cells overexpressing AM and the IL-13R alpha 2 were treated with the highly specific IL13-PE38 cytotoxin, which binds to this receptor, a concentration-dependent inhibition of protein synthesis was observed. The IC(50) (concentration of cytotoxin inhibiting protein synthesis by 50%) ranged from 1 to 4 ng/ml. This cytotoxicity was specific as it was neutralized by the excess of IL-13 and confirmed by clonogenic assays. This study describes a novel AM-induced mechanism of tumor sensitization through the upregulation of functional IL-13R alpha 2 chain, an ideal target for the highly specific recombinant chimeric cytotoxin IL13-PE38

Regeneración de oreomunnea mexicana (Juglandaceae), una especie relicto, amenazada del bosque de niebla de sierra juárez, oaxaca, México

Oreomunnea mexicana (Stand.) J.F. Leroy is a relict species, threatened and a key species for cloud ecosystem functionof the Sierra Juárez, Oaxaca, the most extensive and best conserved in Mexico. This study includes a diagnostic on two critical stages of the process of population regeneration of O. mexicana. To this end, it analyzed the: 1) production, dispersion, viability and germination of seeds, 2) effect of predation on the growth and survival of the seedlings, and 3) effect of environmental variables (soil, canopy structure and solar radiation) on the regeneration of the species. The study was made from 2014 to 2015 in the cloud forest of Santiago Comaltepec, Oaxaca, Mexico, in two locations (San Bernardo and El Orquidiario). Differences in seed production were found between years and between locations, as well as low seed viability and a high percentage of seed parasitism. The establishment and growth of the seedlings are subject to find suitable microhabitats, since seedlings have specific illumination and soil requirements. The high edaphic specificity faced by the species could be a key factor for its fragmented and discontinuous distribution in Sierra Juárez. Further population regeneration studies are recommended to increase knowledge of the species and thereby achieve its conservation. © 2019, Instituto de Ecologia, A.C. All rights reserved

Correction to: A Phase II Study Evaluating Combined Neoadjuvant Cetuximab and Chemotherapy Followed by Chemoradiotherapy and Concomitant Cetuximab in Locoregional Oesophageal Cancer Patients

Errors were subsequently identified in the article and the following corrections should be note