Hydrogenated polymorphous silicon: establishing the link between hydrogen microstructure and irreversible solar cell kinetics during light soaking

This thesis is dedicated to hydrogenated polymorphous silicon (pm-Si:H) and solar cells based on this material. pm-Si:H is a nanostructured thin film deposited by conventional PECVD method. The effects of various deposition parameters (gas flow ratio, pressure, RF power, Ts) on material properties were investigated in order to optimize its quality. The strategy was to combine a wide range of diagnostics (spectroscopic ellipsometry, hydrogen exodiffusion, SIMS, FTIR, AFM, etc.). Due to the contribution of plasma synthesized silicon nanoparticles, the process condition of pm-Si:H shows the difference in contrary to a-Si:H deposition through ionized radicals. Studies on pm-Si:H deposition process allows to fabricate pm-Si:H PIN solar cells with a high initial efficiency of 9.22 % and fill factor of 74.1, but also demonstrate unusual light-induced effects, namely i) a rapid initial degradation, ii) an irreversible degradation, and iii) large macroscopic structural changes. Comprehensive investigation on the light-induced degradation kinetics of pm-Si:H PIN layer stacks reveals a pronounced hydrogen accumulation and delamination at the substrate/p-type layer interface under light-soaking, leading to macroscopic structural changes, e.g., peel-off and solar cell area loss. We have found that a PIN structure leads to facilitated delamination during lightsoaking, which we attribute to hydrogen accumulation at the substrate/p-layer interface, while use of a NIP structure prevents the hydrogen accumulation and delamination. This lead us to fabricate pm-Si:H NIP solar cells showing a high stabilized efficiency of 8.43 %, that shows a small (10 %) light-induced degradation after light-soaking for 500 hours.Cette thèse est consacrée au silicium polymorphe hydrogéné (pm-Si:H). Elle porte tout d'abord sur une étude du pm-Si :H puis sur une étude des cellules photovoltaïques fabriquées à partir de ce matériau. Le pm-Si:H est formé de couches minces nanostructurées et peut être déposé par PECVD conventionnelle. Les effets des différents paramètres de dépôt (mélanges gazeux, pression, puissance RF, température du substrat) sur les propriétés du matériau ont été étudiés pour optimiser sa qualité. La caractérisation des couches a été un enjeu primordial. Pour cela, nous avons choisi de combiner une palette très large de méthodes de caractérisation (ellipsomètrie spectroscopique, exodiffusion d'hydrogène, SIMS, FTIR, AFM, etc...). A cause de la contribution des nanoparticules de silicium dans le plasma, la nature du dépôt du pm-Si:H montre la différence contrairement au a-Si:H pour lequel le dépôt se fait par le biais de radicaux ionisés. L'étude des conditions du procédé nous a conduit à fabriquer des cellules solaires d'un rendement initial de 9.22 % avec un facteur de forme élevé (74.1), mais aussi de démontrer des effets de vieillissement inhabituels, tels que i) une dégradation initiale rapide, ii) une dégradation irréversible, et iii) de grands changements structuraux macroscopiques. Nous avons découvert que le principal problème se situe entre le substrat et la couche mince de silicium. L'hydrogène moléculaire diffuse et s'accumule à l'interface entre le substrat et la couche mince, ce qui introduit un délaminage local qui a pour conséquence une dégradation initiale rapide des performances des cellules. Nous avons trouvé que sous éclairement une structure PIN facilite l'accumulation d'hydrogène et le délaminage à l'interface entre le substrat et la couche dopée p. Cependant, l'utilisation d'une structure NIP empêche l'accumulation d'hydrogène et le délaminage. Cela nous a permis de fabriquer des cellules solaires pm-Si:H de structure NIP d'un rendement stable de 8.43 %, mais aussi de démontrer une degradation minimale (10 %) après un vieillissement de 500 heures

Bis(μ-trimethyl­silanolato-κ2 O:O)bis­{[2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentyl­phenolato-κ2 N,O]zinc}

The binuclear title complex, [Zn2(C22H28N3O)2(C3H9OSi)2], has a crystallographic imposed centre of symmetry. The ZnII atom is coordinated by three O and one N atom from one 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentyl­phenolate ligand and two bridging trimethyl­silanolate anions in a distorted tetra­hedral geometry. The dihedral angle between the benzotriazole ring system and the benzene ring is 19.83 (5)°. The tert-pentyl groups are disordered over two orientations with refined site-occupancy ratios of 0.858 (4):0.142 (4) and 0.665 (6):0.335 (6)

Aging Logarithmic Conformal Field Theory : a holographic view

We consider logarithmic extensions of the correlation and response functions of scalar operators for the systems with aging as well as Schr\"odinger symmetry. Aging is known to be the simplest nonequilibrium phenomena, and its physical significances can be understood by the two-time correlation and response functions. Their logarithmic part is completely fixed by the bulk geometry in terms of the conformal weight of the dual operator and the dual particle number. Motivated by recent experimental realizations of Kardar-Parisi-Zhang universality class in growth phenomena and its subsequent theoretical extension to aging, we investigate our two-time correlation functions out of equilibrium, which show several qualitatively different behaviors depending on the parameters in our theory. They exhibit either growing or aging, i.e. power-law decaying, behaviors for the entire range of our scaling time. Surprisingly, for some parameter ranges, they exhibit growing at early times as well as aging at later times.Comment: 1+26 pages, 15 figure

eIF2A, an initiator tRNA carrier refractory to eIF2 kinases, functions synergistically with eIF5B

The initiator tRNA (Met-tRNA(i)(Met)) at the P site of the small ribosomal subunit plays an important role in the recognition of an mRNA start codon. In bacteria, the initiator tRNA carrier, IF2, facilitates the positioning of Met-tRNAiMet on the small ribosomal subunit. Eukarya contain the Met-tRNAiMet carrier, eIF2 (unrelated to IF2), whose carrier activity is inhibited under stress conditions by the phosphorylation of its -subunit by stress-activated eIF2 kinases. The stress-resistant initiator tRNA carrier, eIF2A, was recently uncovered and shown to load Met-tRNAiMet on the 40S ribosomal subunit associated with a stress-resistant mRNA under stress conditions. Here, we report that eIF2A interacts and functionally cooperates with eIF5B (a homolog of IF2), and we describe the functional domains of eIF2A that are required for its binding of Met-tRNAiMet, eIF5B, and a stress-resistant mRNA. The results indicate that the eukaryotic eIF5B-eIF2A complex functionally mimics the bacterial IF2 containing ribosome-, GTP-, and initiator tRNA-binding domains in a single polypeptide.112Ysciescopu

Low Temperature Plasma Synthesis of Nanocrystals and their Application to the Growth of Crystalline Silicon and Germanium Thin Films

International audienceWe summarize our research studies on the synthesis of silicon and germanium nanocrystals and their application to the growth of a variety of thin films, spanning the range from fully disordered amorphous up to fully ordered crystalline. All these films are deposited in a standard radio-frequency glow discharge system at low temperature (~200 °C). We show how the plasma synthesis of silicon nanocrystals, initially a side effect of powder formation, has become over the years an exciting field of research which has opened the way to new opportunities in the field of materials deposition and their application to optoelectronic devices. Our results suggest that epitaxy requires the melting/amorphization of the nanocrystals upon impact on the substrate, the subsequent epitaxial growth being favored on (100) c-Si substrates. As a consequence, the control of the impact energy is a critical aspect of the growth which will require new strategies such as the use of tailored voltage waveforms

Measurement of Blood Pressure Using an Arterial Pulsimeter Equipped with a Hall Device

To measure precise blood pressure (BP) and pulse rate without using a cuff, we have developed an arterial pulsimeter consisting of a small, portable apparatus incorporating a Hall device. Regression analysis of the pulse wave measured during testing of the arterial pulsimeter was conducted using two equations of the BP algorithm. The estimated values of BP obtained by the cuffless arterial pulsimeter over 5 s were compared with values obtained using electronic or liquid mercury BP meters. The standard deviation between the estimated values and the measured values for systolic and diastolic BP were 8.3 and 4.9, respectively, which are close to the range of values of the BP International Standard. Detailed analysis of the pulse wave measured by the cuffless radial artery pulsimeter by detecting changes in the magnetic field can be used to develop a new diagnostic algorithm for BP, which can be applied to new medical apparatus such as the radial artery pulsimeter

High performance dye sensitized solar cells by adding titanate co-adsorbant

The open circuit voltage and the short circuit current density of dye sensitized solar cells were increased by adding a titanate co-adsorbant as a blocking agent. This blocking agent effectively prevents back electron transfer. As a result, DSSCs with titanate co-adsorbant showed significantly increased energy conversion efficiency.close0

The effect of the DLTIDDSYWYRI motif of the human laminin α2 chain on implant osseointegration

Considerable effort has been directed towards replacing lost teeth using tissue-engineering methods such as titanium implants. A number of studies have tried to modify bioinert titanium surfaces by coating them with functionally bioactive molecules for faster and stronger osseointegration than pure titanium surfaces. Recently, peptides have been recognized as valuable scientific tools in the field of tissue-engineering. The DLTIDDSYWYRI motif of the human laminin-2 α2 chain has been previously reported to promote the attachment of various cell types; however, the in vivo effects of the DLTIDDSYWYRI motif on new bone formation have not yet been studied. To examine whether a laminin-2-derived peptide can promote osseointegration by accelerating new bone formation in vivo, we applied titanium implants coated with the DLTIDDSYWYRI motif in a rabbit tibia model. The application of the DLTIDDSYWYRI motif-treated implant to tibia wounds enhanced collagen deposition and alkaline phosphatase expression. It significantly promoted implant osseointegration compared with treatment with scrambled peptide-treated implants by increasing the bone-to-implant contact ratio and bone area. These findings support the hypothesis that the DLTIDDSYWYRI motif acts as an effective osseointegration accelerator by enhancing new bone formation.Considerable effort has been directed towards replacing lost teeth using tissue-engineering methods such as titanium implants. A number of studies have tried to modify bioinert titanium surfaces by coating them with functionally bioactive molecules for faster and stronger osseointegration than pure titanium surfaces. Recently, peptides have been recognized as valuable scientific tools in the field of tissue-engineering. The DLTIDDSYWYRI motif of the human laminin-2 α2 chain has been previously reported to promote the attachment of various cell types; however, the in vivo effects of the DLTIDDSYWYRI motif on new bone formation have not yet been studied. To examine whether a laminin-2-derived peptide can promote osseointegration by accelerating new bone formation in vivo, we applied titanium implants coated with the DLTIDDSYWYRI motif in a rabbit tibia model. The application of the DLTIDDSYWYRI motif-treated implant to tibia wounds enhanced collagen deposition and alkaline phosphatase expression. It significantly promoted implant osseointegration compared with treatment with scrambled peptide-treated implants by increasing the bone-to-implant contact ratio and bone area. These findings support the hypothesis that the DLTIDDSYWYRI motif acts as an effective osseointegration accelerator by enhancing new bone formation.Tissue-engineeringThis work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by MEST (Grant No. 2011-0007662) and the Mid-career Researcher Program through NRF, funded by MEST (Grant No. 2010-0014662).OAIID:oai:osos.snu.ac.kr:snu2013-01/102/2008003883/1SEQ:1PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:2008003883ADJUST_YN:NEMP_ID:A078517DEPT_CD:861CITE_RATE:7.404FILENAME:Biomaterials 201305 34(16) 4027-37.pdfDEPT_NM:치의학과EMAIL:[email protected]_YN:YCONFIRM:

Comparative fracture strength analysis of Lava and Digident CAD/CAM zirconia ceramic crowns

PURPOSE: All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident.MATERIALS AND METHODS: Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns.RESULTS: THE MEAN FRACTURE STRENGTHS WERE AS FOLLOWS: 54.9 ± 15.6 N for the Lava CAD/CAM zirconia crowns and 87.0 ± 16.0 N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (P<.001). Lava CAD/CAM zirconia crowns showed a complete fracture of both the veneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain.CONCLUSION: The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain.OAIID:oai:osos.snu.ac.kr:snu2013-01/102/2008003883/8SEQ:8PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:2008003883ADJUST_YN:NEMP_ID:A078517DEPT_CD:861FILENAME:j adv prosthodont 201305 5(2) 92-7.pdfDEPT_NM:치의학과EMAIL:[email protected]_YN:NCONFIRM:

Comprehensive identification of sexually dimorphic genes in diverse cattle tissues using RNA-seq

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.Abstract Background Molecular mechanisms associated with sexual dimorphism in cattle have not been well elucidated. Furthermore, as recent studies have implied that gene expression patterns are highly tissue specific, it is essential to investigate gene expression in a variety of tissues using RNA-seq. Here, we employed and compared two statistical methods, a simple two group test and Analysis of deviance (ANODEV), in order to investigate bovine sexually dimorphic genes in 40 RNA-seq samples distributed across two factors: sex and tissue. Results As a result, we detected 752 sexually dimorphic genes across tissues from two statistical approaches and identified strong tissue-specific patterns of gene expression. Additionally, significantly detected sex-related genes shared between two mammal species (cattle and rat) were identified using qRT-PCR. Conclusions Results of our analyses reveal that sexual dimorphism of metabolic tissues and pituitary gland in cattle involves various biological processes. Several differentially expressed genes between sexes in cattle and rat species are shared, but show tissue-specific patterns. Finally, we concluded that two distinct statistical approaches have their advantages and disadvantages in RNA-seq studies investigating multiple tissues