Anodized Nanoporous Titania Thin Films for Dental Application: Structure’ Effect on Corrosion Behavior

Nanostructured Titania layers formed on the surface of titanium and titanium alloys by anodic oxidation play an important role in the enhancement of their biocompatibility and osseointegration in the human body. For this purpose, we aimed to study in the current work the structural and electrochemical properties of amorphous and crystallized nanostructured TiO2 thin films elaborated on Ti6Al4V substrate by electrochemical anodization in fluoride ions (F–) containing electrolyte at 10 V during 15 min and heat treated in air at 550 °C for 2 h. The morphology, chemical composition and phase composition of synthesized layers were investigated using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The corrosion resistance improvement of both as-anodized and annealed titania layers was evaluated in 0.9 wt. % NaCl solution with pH = 6.4 at room temperature by means of open circuit potential (Eoc),potentiodynamic polarization (PDYN) and electrochemical impedance spectroscopy (EIS)

Characterization of Thermally Oxidized Ti6Al4V Alloys for Dental Application

In this work, thermal oxidation processes in the temperature range of 500-800 °C in air for 4 hours were performed on Ti6Al4V medical grade alloys to modify their surface structure and morphology for better wear and corrosion resistance, osseointegration and biocompatibility. Different type and amount of nanostructured phases were obtained as revealed by the X-ray diffration (XRD) technique such as: alumina, anatase and rutile. X’pert high score plus software was used for the calculation of the percentage and crystallite sizes of these phases. Alumina phase exhibits the greater amount of the oxide layers when Ti6Al4V alloys annealed at 500 °C, while rutile was found to be the predominant phase at 800 °C

Mitochondrial targeting of recombinant RNAs modulates the level of a heteroplasmic mutation in human mitochondrial DNA associated with Kearns Sayre Syndrome

Mitochondrial mutations, an important cause of incurable human neuromuscular diseases, are mostly heteroplasmic: mutated mitochondrial DNA is present in cells simultaneously with wild-type genomes, the pathogenic threshold being generally >70% of mutant mtDNA. We studied whether heteroplasmy level could be decreased by specifically designed oligoribonucleotides, targeted into mitochondria by the pathway delivering RNA molecules in vivo. Using mitochondrially imported RNAs as vectors, we demonstrated that oligoribonucleotides complementary to mutant mtDNA region can specifically reduce the proportion of mtDNA bearing a large deletion associated with the Kearns Sayre Syndrome in cultured transmitochondrial cybrid cells. These findings may be relevant to developing of a new tool for therapy of mtDNA associated diseases

Correction of the consequences of mitochondrial 3243A>G mutation in the MT-TL1 gene causing the MELAS syndrome by tRNA import into mitochondria

Mutations in human mitochondrial DNA are often associated with incurable human neuromuscular diseases. Among these mutations, an important number have been identified in tRNA genes, including 29 in the gene MT-TL1 coding for the tRNALeu(UUR). The m.3243A>G mutation was described as the major cause of the MELAS syndrome (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes). This mutation was reported to reduce tRNALeu(UUR) aminoacylation and modification of its anti-codon wobble position, which results in a defective mitochondrial protein synthesis and reduced activities of respiratory chain complexes. In the present study, we have tested whether the mitochondrial targeting of recombinant tRNAs bearing the identity elements for human mitochondrial leucyl-tRNA synthetase can rescue the phenotype caused by MELAS mutation in human transmitochondrial cybrid cells. We demonstrate that nuclear expression and mitochondrial targeting of specifically designed transgenic tRNAs results in an improvement of mitochondrial translation, increased levels of mitochondrial DNA-encoded respiratory complexes subunits, and significant rescue of respiration. These findings prove the possibility to direct tRNAs with changed aminoacylation specificities into mitochondria, thus extending the potential therapeutic strategy of allotopic expression to address mitochondrial disorders

Design of Solar Cells p⁺/n Emitter by Spin-On Technique

In this paper spin-on dopant diffusion has been investigated as a technique for fabrication of p⁺/n monocrystalline silicon solar cell emitters. A homogeneous spreading onto the front wafer surface has been achieved by using 2 ml of boron-dopant solution and three-step spin-profile. Study of the wafers stacking arrangement has revealed that the highest doping level and the best emitter sheet resistance uniformity were obtained using the back-to-back wafers arrangement. The N₂/O₂ gas ratio variation during the diffusion process has shown that a higher percentage of nitrogen yields a slightly lower emitter sheet resistance. Study on temperature dependence of as-processed emitter resistivity revealed that 910°C results in targeted sheet resistance of around 48 Ω/sq. Using these preliminary experimental results, a batch of 6 silicon wafers was processed. After BSG and BRL chemical removal, the batch average sheet resistance of the emitter was 49.50 Ω/sq. The uniformity of a wafer and of the batch was below 7% and 13%, respectively. The ECV and SIMS depth profiling have shown the electrically active and the total boron surface concentration of 1.5× 10²⁰ atoms/cm³ and 2.5× 10²⁰ atoms/cm³, respectively. The junction depth was around 0.3 μm. Finally, by increasing the oxygen flow rate we reached an average sheet resistance of 51 Ω/sq. and a junction depth of 0.35 μm

Вплив товщини пластини та кількості сіток трафаретного друку на Al-BSF у кристалічних кремнієвих сонячних елементах

У роботі були проведені експериментальні дослідження процесу легування алюмінієвих (Al) паст, надрукованих трафаретним друком на кремнієвих поверхнях для сонячних елементів. Досліджений вплив товщини пластини та кількості сіток трафаретного друку на властивості поля задньої поверхні Al (Al-BSF) кремнієвих сонячних елементів Чохральського (Cz-Si). Використовувалися екрани з різною кількістю сіток (150, 200 і 400 меш) для друку різної кількості пасти Al (7, 9,4 та 12 мг/см2). Швидкий термічний відпал (RTP) при 750 °C і 800 °C протягом 60 с був застосований для формування ALBSF. SEM показав утворення шорсткої поверхні з шаром легуючого шару товщиною 4,31 мкм на об’ємній кремнієвій пластині. Аналіз ECV та SIMS показав, що пікова температура відпалу 750 °C і кількість пасти Al 12 мг/см2 підходять для створення оптимального Al-BSF. Ця робота виявила, що на властивості Al-BSF сильно впливає кількість меш, яка використовується для трафаретного друку пасти Al. Однак не було помічено монотонного зв’язку з товщиною пластини. Маска з 150 меш дозволила отримати високі концентрації Al на поверхні, максимальну глибину дифузії та більший середній час життя носіїв заряду.In this study, experiments on the alloying process from screen-printed aluminum (Al) pastes on silicon surfaces for solar cell applications were conducted. We investigated the effect of wafer thickness and screen-printing mesh counts on the Al back surface field (Al-BSF) properties of Czochralski silicon (Cz-Si) solar cells Screens with different mesh counts (150, 200 and 400 mesh) were used to print variable amounts of Al paste (7, 9.4 and 12 mg/cm2). Rapid thermal annealing (RTP) annealing processes of 750 °C and 800 °C for 60 s were applied to form AL-BSF. SEM micrographs showed the formation of a rough surface with 4.31 µm alloying layer over bulk Si wafer. ECV and SIMS analysis showed that an annealing peak temperature of 750 °C and an amount of Al paste of 12 mg/cm2 are suitable for the creation of an optimal Al-BSF. This work revealed that Al-BSF properties are strongly affected by the mesh counts used in screen-printing of Al paste. However, no monotonic relationship was noticed with the wafer thickness. The mask with 150 meshes allowed to obtain high Al concentrations at the surface, maximum diffusion depth and longer average lifetimes of charge carriers