This paper discusses the effect of order and disorder on the electrical and optical performance of ionic oxide semiconductors based on zinc oxide. These materials are used as active thin films in electronic devices such as pn heterojunction solar cells and thin-film transistors. Considering the expected conduction mechanism in ordered and disordered semiconductors the role of the spherical symmetry of the s electron conduction bands will be analyzed and compared to covalent semiconductors. The obtained results show p-type c-Si/a-IZO/poly-ZGO solar cells exhibiting efficiencies above 14% in device areas of about 2.34 cm2. Amorphous oxide TFTs based on the Ga-Zn-Sn-0 system demonstrate superior performance than the polycrystalline TFTs based on ZnO, translated by ION/IOFF ratio exceeding 107, turn-on voltage below 1-2 V and saturation mobility above 25 cm2/Vs. Apart from that, preliminary data on p-type oxide TFT based on the Zn-Cu-O system will also be presented. © 2009 SPIE.

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Nitric Oxide Reductase (NOR) is an integral membrane protein performing the reduction of NO to N2O. NOR is composed of two subunits: the large one (NorB) is a bundle of 12 transmembrane helices (TMH). It contains a b type heme and a binuclear iron site, which is believed to be the catalytic site, comprising a heme b and a non-hemic iron. The small subunit (NorC) harbors a cytochrome c and is attached to the membrane through a unique TMH. With the aim to perform structural and functional studies of NOR, we have immunized dromedaries with NOR and produced several antibody fragments of the heavy chain (VHHs, also known as nanobodies (TM)). These fragments have been used to develop a faster NOR purification procedure, to proceed to crystallization assays and to analyze the electron transfer of electron donors. BIAcore experiments have revealed that up to three VHHs can bind concomitantly to NOR with affinities in the nanomolar range. This is the first example of the use of VHHs with an integral membrane protein. Our results indicate that VHHs are able to recognize with high affinity distinct epitopes on this class of proteins, and can be used as versatile and valuable tool for purification, functional study and crystallization of integral membrane proteins.

The aim of this study was to evaluate the possibility of preparing dexamethasone-loaded starch-based porous matrices in a one-step process. Supercritical phase inversion technique was used to prepare composite scaffolds of dexamethasone and a polymeric blend of starch and poly(l-lactic acid) (SPLA) for tissue engineering purposes. Dexamethasone is used in osteogenic media to direct the differentiation of stem cells towards the osteogenic lineage. Samples with different drug concentrations (5-15 wt.{%} polymer) were prepared at 200 bar and 55 °C. The presence of dexamethasone did not affect the porosity or interconnectivity of the polymeric matrices. Water uptake and degradation studies were also performed on SPLA scaffolds. We conclude that SPLA matrices prepared by supercritical phase inversion have a swelling degree of nearly 90{%} and the material presents a weight loss of ∼25{%} after 21 days in solution. Furthermore, in vitro drug release studies were carried out and the results show that a sustained release of dexamethasone was achieved over 21 days. The fitting of the power law to the experimental data demonstrated that drug release is governed by an anomalous transport, i.e., both the drug diffusion and the swelling of the matrix influence the release of dexamethasone out of the scaffold. The kinetic constant was also determined. This study reports the feasibility of using supercritical fluid technology to process in one step a porous matrix loaded with a pharmaceutical agent for tissue engineering purposes. © 2009 Acta Materialia Inc.

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The isolation and characterization of a new metalloprotein containing Cu and Fe atoms is reported. The as-isolated Cu-Fe protein shows an UV-visible spectrum with absorption bands at 320 nm, 409 nm and 615 nm. Molecular mass of the native protein along with denaturating electrophoresis and mass spectrometry data show that this protein is a multimer consisting of 14+/-1 subunits of 15254.3+/-7.6 Da. Mössbauer spectroscopy data of the as-isolated Cu-Fe protein is consistent with the presence of [2Fe-2S](2+) centers. Data interpretation of the dithionite reduced protein suggest that the metallic cluster could be constituted by two ferromagnetically coupled [2Fe-2S](+) spin delocalized pairs. The biochemical properties of the Cu-Fe protein are similar to the recently reported molybdenum resistance associated protein from Desulfovibrio, D. alaskensis. Furthermore, a BLAST search from the DNA deduced amino acid sequence shows that the Cu-Fe protein has homology with proteins annotated as zinc resistance associated proteins from Desulfovibrio, D. alaskensis, D. vulgaris Hildenborough, D. piger ATCC 29098. These facts suggest a possible role of the Cu-Fe protein in metal tolerance.

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Supercritical fluid technology has proven to be useful for many pharmaceutical applications and is now emerging as an alternative to conventional processes for the preparation of 3D structures and injectable particles suitable to be used in regenerative medicine. A current overview of the basic principles underlying supercritical fluid technology, the state of the art and future potential of this technology are presented.

We have studied the properties of ZnO thin films grown by laser ablation of ZnO targets on (0 0 0 1) sapphire (Al2O3), under substrate temperatures around 400 8C. The films were characterized by different methods including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). XPS analysis revealed that the films are oxygen deficient, and XRD analysis with u–2u scans and rocking curves indicate that the ZnO thin films are highly c-axis oriented. All the films are ultraviolet (UV) sensitive. Sensitivity is maximum for the films deposited at lower temperature. The films deposited at higher temperatures show crystallite sizes of typically 500 nm, a high dark current and minimum photoresponse. In all films we observe persistent photoconductivity decay. More densely packed crystallites and a faster decay in photocurrent is observed for films deposited at lower temperature.

In order to enhance infrared light absorption in sub-bandgap transitions in an intermediate band solar cell, the scattered near-field potential from uncoated and coated metallic nanoparticles with a spheroidal shape is calculated with the electrostatic model. The absorption enhancement produced at the surface plasmon frequency of the nanoparticles can be of several orders of magnitude in some cases.

Supercritical fluid impregnation was tested to prepare a new scaffold loaded with a bioactive compound. Dexamethasone is used in osteogenic media to direct the differentiation of stem cells towards the osteogenic lineage. Dexamethasone was impregnated in chitosan scaffolds at different operating conditions, in order to optimize the impregnation process. Pressure and temperature affect the carbon dioxide density and influence the swelling of the polymer and the drug solubility in the fluid phase, therefore these are two important parameters that were studied in this work. Chitosan sponges prepared by freeze drying were impregnated with the active compound at pressures from 8.0 up to 14.0 MPa and temperatures from 35 up to 55 °C. The effect of the impregnation contact time (3 h and 6 h) was also evaluated. From the experiments performed we can conclude that the yield of impregnation is lower when increasing pressure and temperature. The contact time will mainly influence the amount of drug impregnated in the scaffold and for higher contact times the impregnation yield is also higher. Scanning electron microscopy shows particles of dexamethasone in the bulk of the scaffold, which confirms the feasibility of the supercritical fluid impregnation technology for the preparation of delivery devices. The loading capacity of the scaffolds was determined by spectroscopic analysis and the highest loading was achieved for the experiments performed at 8.0 MPa and 35 °C. Furthermore, in vitro drug release studies were carried out and the results show that dexamethasone was sustainably released. Supercritical fluid impregnation proved to be feasible for the preparation of a drug delivery system for bone tissue engineering purposes. © 2008 Elsevier Ltd. All rights reserved.

The aim of this study was to evaluate the possibility of preparing starch-based porous matrixes using supercritical fluid technology. Supercritical immersion precipitation technique was used to prepare scaffolds of a polymeric blend of starch and poly(l-lactic acid) for tissue engineering purposes.Immersion precipitation experiments were carried out at different operational conditions and highly porous and interconnected scaffolds were obtained. Two organic solvents, dichloromethane and chloroform were tested, and from the results obtained chloroform was the more favourable for the process. The effect of polymer solution concentration (5 up to 20 wt{%}), temperature (35 up to 55 °C) and pressure (100 up to 200 bar) in the SPLA (50:50 wt{%}) membrane morphology, porosity and interconnectivity was evaluated. All the conditions tested were in the region of total miscibility between the organic solvent and carbon dioxide. Additionally, a blend with a different starch-poly(l-lactic acid) ratio (30:70 wt{%}) was tested. Bicontinuous structures were formed indicating that the L-L demixing process that governs the phase inversion is the spinodal decomposition. © 2008 Elsevier B.V. All rights reserved.

The aim of this study was to develop a new process for the production of bioactive 3D scaffolds using a clean and environmentally friendly technology. The possibility of preparing composite scaffolds of Bioglass?? and a polymeric blend of starch and poly(l-lactic acid) (SPLA50) was evaluated. Supercritical phase-inversion technique was used to prepare inorganic particles loaded starch-based porous composite matrixes in a one-step process for bone tissue engineering purposes. Due to their osteoconductive properties some glasses and ceramics are interesting materials to be used for bone tissue engineering purposes; however their poor mechanical properties create the need of a polymeric support where the inorganic fraction can be dispersed. Samples impregnated with different concentrations of Bioglass?? (10 and 15{%} wt/wt polymer) were prepared at 200??bar and 55????C. The presence of Bioglass?? did not affect the porosity or interconnectivity of the polymeric matrixes. Dynamic mechanical analysis has proven that the modulus of the SPLA50 scaffolds increases when glass particles are impregnated within the matrix. In vitro bioactivity studies were carried out using simulated body fluid and the results show that a calcium-phosphate layer started to be formed after only 1??day of immersion. Chemical analysis of the apatite layer formed on the surface of the scaffold was performed by different techniques, namely EDS and FTIR spectroscopy and X-ray diffraction (XRD). The ion concentration in the simulated body fluid was also carried out by ICP analysis. Results suggest that a bone-like apatite layer was formed. This study reports the feasibility of using supercritical fluid technology to process, in one step, a porous matrix loaded with a bioactive material for tissue engineering purposes. ?? 2009 Elsevier B.V. All rights reserved.

Very high fluence implantation of 7Li+ ions was used to promote the formation of a thin and high density 7Li target in the surface region of Al samples. The implanted volume was characterized by particle induced gamma-ray emission, Rutherford backscattering spectrometry, X-ray photoelectron spectros- copy and nuclear reaction analysis, revealing that the implanted surface is a combination of Li2CO3, metallic lithium, LiOH and C, with almost no Al present. Radiation damage effects by proton beams were studied by observing the evolution of the 7Li(p,a)4He nuclear reaction yield with the accumulated charge, at different proton energies, revealing high stability of the produced Li target.

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Over the past several years, the definition of a scaffold for tissue engineering has changed dramatically, from a material that acts only as an inert structural support for cell attachment to serving as a more complex and dynamic environment for tissue development. This paper is a review on the existing and on the new emerging techniques based on supercritical fluid technology for the preparation of scaffolds and particles for tissue engineering applications. Supercritical fluid technology has already proven to be feasible for many pharmaceutical applications and is now emerging as an alternative to conventional materials' processing methods for the preparation of three-dimensional structures and injectable particles suitable to be used in regenerative medicine. The basic principles underlying each technique are here presented as well as the advantages and disadvantages of each process. The state of the art is reviewed and the major conclusions of the studies reported in the literature are discussed.

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In surface science, rutile TiO2 continues to be one of the most studied surfaces and in the catalysis field numerous groups study how adsorbates interact with this surface. All groups face the difficult problem of reproducibility due to surface preparation unknowns like defect concentration and the continuous aging of the crystals. Recent studies, using STM imaging, showed that hydroxyl adsorption takes place even in very good vacuum conditions. Upon adsorption, the surface electric field is reduced and the work function decreases. We found that this change may be readily detected in the onset energy of the secondary electrons. By following the onset region of secondary electron emission it is possible to track hydroxyl adsorption in quantities well below the detection level of XPS and LEIS. With this knowledge, we show that the time elapsed after surface preparation and water partial pressure should be accounted in the study of TiO2 surfaces.

{A stochastic representation for the solutions of the Poisson-Vlasov equation is obtained. The representation involves both an exponential and a branching process. The stochastic representation, besides providing an alternative existence proof and an intuitive characterization of the solutions, may also be used to obtain an intrinsic definition of the fluctuations. (c) 2007 Elsevier B.V. All rights reserved.}

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