Data Reduction and Error Analysis for the Physical Sciences

ABSTRACT Polycrystalline thin films (PTF) of p-WSe2, p-WS2, and p-MoSe2 have been prepared and characterized with respect to their photoelectrochemical properties, p-WS2 showed the highest open-circuit photovoltages and the highest conversion efficiencies in various redox couples. In addition, the band structure of all the films has been determined experimentally and compared to those reported for single crystals. Over the last two decades a great deal of interest has developed in the area of photoelectrochemistry, particularly in the application of photoelectrochemical systems to the problem of solar energy conversion and storage. The interest is to develop new energy sources to supplement and eventually replace fossil fuels. The first photoelectrochemical experiment was performed in 1839 by Becquerel (1), who demonstrated that a voltage and current are generated when a silver chloride electrode, immersed in an electrolytic solution and connected to a counterelectrode, is illuminated. Although the concept of a semiconductor did not exist at that time, it is now clear that the electrode which Becquerel used had semiconducting properties. In 1955, Brattain and Garett (2) used germanium as the first semiconductor electrode in photoelectrochemistry. Since then, the knowledge of semiconductors has grown steadily. Fujishima and Honda (3) were the first to point out the potential application of photoelectrochemical systems for solar energy conversion and storage. They demonstrated that the photo-oxidation of water to 02 was possible by utilizing an n-type semiconducting titanium dioxide photoanode. Since then, there has been a large and rapidly growing international interest in the study of photoelectrochemistry of semiconductors (4). The effective use of solar energy in photovoltaic or photoelectrochemical applications depends in part on the development of materials that can show high conversion efficiencies and long-term stability under operation. In ad-*Electrochemical Society Active Member. **Electrochemical Society Student Member. dition, the desirable materials should have a bandgap that closely matches the solar spectrum and be made of readily available and inexpensive materials. We have focused our attention on the transition metal dichalcogenides (e.g., WSe2, WS2, MoSe2, and others), also known as layered or d-d semiconductors. Tributsch's (5, 6) pioneering work on the use of these materials has stimulated intensive research in this area, and single Crystals of a number of materials have been studied extensively in both aqueous and nonaqueous solvents and in photovoltaic and photoelectrosynthetic cells. The advantages of using these materials are that they have bandgaps (1.1-1.6 eV) that closely match the solar spectrum and exhibit high conversion efficiencies as single crystals. In addition, they can achieve long-term stability due to the fact that the transitions are localized in the nonbonding d orbitals of the metal. These materials consist of metal dichalcogenide sandwiches (e.g., Se-W-Se) held together by van der Waals forces. The fact that there is strong covalent bonding within the layers, but only weak interactions between layers, makes these materials highly anisotropic in their properties. For example, the surface parallel to the C axis (IIC) is more conducting than the surface perpendicular to the C axis (• Therefore, edges and surface imperfections on the surface parallel to the C axis act as efficient recombination centers for photogenerated carriers or products (7

Kramers-Kronig Transforms as Validation of Electrochemical Immittance Data Near Discontinuity

International audienceImmittance data was recorded for copper rotating disk in concentrated copper sulphate/sulphuric acid electrolyte, and its evolution under potential control (PC) was analyzed starting from the active state at rest potential, through active/passive transition up to the stable passivity. In the potential range corresponding to the passivity under PC, the transition was observed from the nonminimum phase (nmp)-type of immittance to the minimum phase (mp) one which corresponded to Hopf bifurcation under current control. This transition was manifested by a resonance-like peak on the amplitude characteristic and the phase change from apparently discontinuous as displayed in [–180°, +180°] range (nonminimum) to the continuous (minimum) one. In complex coordinates this was featured by scattered impedance points. Validation by Kramers-Kronig (KK) transformation of nmp-type immittance data failed for impedance representation used in transformation but was successful for admittance representation as the latter was the form actually recorded under PC. This finding validates both nmp and mp immittance data in agreement with earlier suggestions of other authors. [See, Gabrielli et al., in Electrochemical Impedance: Analysis and Interpretation, p. 140, ASTM, Philadelphia, PA (1993).] Transition from mnp to mp type of electrode dynamics can be attributed to appearance of conduction channels representing local depassivation of the electrode

Transcriptional pattern of TGF-beta1 inhibitory effect on mouse C2C12 myoblasts differentiation

The aim of the present study was to define the effect of TGF-β1 on C2C12 myoblasts myogenesis. TGF-β1 together with its receptor is a negative auto-paracrine regulator of myogenesis, which influences the proliferation, differentiation, and functions of muscle cells. TGF-β1 exerts highly significant inhibitory effect on differentiation of C2C12 mouse myoblasts manifested by the impairment of cell fusion and very low expression of myosin heavy chain. The study of differentiating C2C12 mouse myoblasts treated with TGF-β1 revealed 502 genes (436 down-regulated and 66 up-regulated) with statistically different expression. TGF-β1-regulated genes were identified to be involved in 29 biological processes, 29 molecular functions groups and 59 pathways. The strongest inhibiting effect of TGF-β1 was observed in the cadherin and Wnt pathways. The key-genes that could play the role of TGF-β1 targets during myoblasts differentiation was identified such as: Max, Creb1, Ccna2, Bax, MdfI, Tef, Tubg1, Cxcl5, Rho, Calca and Lgals4

Nutraceutical functions of beta-glucans in human nutrition

Recent studies have shown that naturally occurring substances found in the food of the daily human diet are important for preventing chronic non-communicable diseases. One of them is beta-glucan, which is a natural polysaccharide, occurring in plant cell walls, mainly oats, barley and wheat. It is also present in baker’s yeast cells, fungal cell walls, and some microorganisms. Beta-glucan belongs to one of the dietary fiber fractions, which are attributed a number of beneficial health properties, including the prevention and treatment of certain digestive diseases and supporting the immune system. This compound has biological activity that depends on the size, molecular weight, conformation, frequency of bonds, solubility and changes in structure. Beta-glucan reduces cholesterol and glucose concentrations in the blood, which reduces the risk of cardiovascular disease and diabetes. In addition to its effects on lipid levels and glucose metabolism, beta-glucan also exhibits antioxidant properties by scavenging reactive oxygen species, thereby reducing the risk of diseases, including atherosclerosis, cardiovascular diseases, neurodegenerative diseases, diabetes, and cancer. Immunostimulatory and antitumor effects have also been reported. The immunostimulatory activity of beta-glucan occurs as a result of its attachment to specific receptors present on the immune cell surface. Beta-glucan belongs to the group of prebiotics which stimulate the growth and activity of the desired natural intestinal microbiota, while inhibiting the growth of pathogens. It plays an important role in the proper functioning of the gastrointestinal tract and preventing inflammation as well as colon cancer. Such a number of health benefits resulting from the properties of beta-glucan may play a key role in improving health and preventing chronic non-communicable diseases, such as diabetes, hypercholesterolemia, obesity, cardiovascular diseases, and cancer.Badania ostatnich lat dowiodły, iż w codziennej diecie człowieka znajdują się naturalnie występujące składniki żywności o istotnym znaczeniu w zapobieganiu niezakaźnym chorobom przewlekłym. Między innymi jest to beta-glukan, który jest naturalnym polisacharydem, występującym w ścianach komórkowych roślin, głównie owsa, jęczmienia i pszenicy. Obecny jest także w komórkach drożdży piekarniczych, ścianach komórkowych grzybów i w niektórych mikroorganizmach. Beta-glukan należy do jednej z frakcji błonnika pokarmowego, któremu przypisuje się szereg korzystnych właściwości zdrowotnych, między innymi w prewencji i leczeniu niektórych schorzeń układu pokarmowego oraz wspomaganiu układu odpornościowego. Związek ten wykazuje aktywność biologiczną, która zależy od wielkości masy cząsteczkowej. Beta-glukan obniża poziom cholesterolu oraz pozwala utrzymać prawidłowy poziom cukru we krwi, co wiąże się ze zmniejszonym ryzykiem zachorowalności na choroby sercowo-naczyniowe oraz cukrzycę. Oprócz wpływu na poziom lipidów i metabolizm glukozy beta-glukan wykazuje także właściwości przeciwutleniające poprzez wychwytywanie reaktywnych form tlenu, zmniejszając tym samym ryzyko wystąpienia, m.in.: chorób układu krążenia, chorób neurodegeneracyjnych, cukrzycy oraz nowotworów. Substancja ta wywiera również efekt immunostymulujący oraz antykancerogenny. Immunostymulujące działanie beta-glukanu polega na jego przyłączeniu się do specyficznych receptorów obecnych na powierzchni komórek układu odpornościowego. Beta-glukan należy do grupy prebiotyków, stymulujących wzrost i aktywność pożądanej, naturalnej mikrobioty jelitowej, hamując jednocześnie rozwój patogenów. Odgrywa to istotną rolę w prawidłowym funkcjonowaniu przewodu pokarmowego oraz zapobieganiu wystąpienia stanów zapalnych, jak również nowotworów jelita grubego. Wykazane korzyści zdrowotne wynikające z właściwości beta-glukanu mogą odgrywać kluczową rolę w poprawie stanu zdrowia oraz przeciwdziałaniu niezakaźnym chorobom przewlekłym, tj. Cukrzycy, hipercholesterolemii, otyłości, chorobom sercowo-naczyniowym oraz nowotworom

The transcriptomic signature of myostatin inhibitory influence on the differentiation of mouse C2C12 myoblasts

GDF8 (myostatin) is a unique cytokine strongly affecting the skeletal muscle phenotype in human and animals. The aim of the present study was to elucidate the molecular mechanism of myostatin influence on the differentiation of mouse C2C12 myoblasts, using the global-transcriptome analysis with the DNA microarray technique. Treatment with exogenous GDF8 strongly affected the growth and development of C2C12 mouse myoblasts. This was manifested by the inhibition of proliferation and differentiation as well as the impairment of cell fusion. DNA microarray analysis revealed 778 genes regulated by GDF8 in differentiating myoblasts (436 down-regulated and 235 up-regulated). Ontological analysis revealed their involvement in 17 types of biological processes, 10 types of molecular functions and 68 different signalling pathways. The effect of GDF8 was mainly mediated by the disruption of the cell cycle, calcium and insulin signalling pathways and expression of cytoskeletal and muscle specific proteins. The identified key-genes that could play a role as GDF8 targets in differentiating myoblasts are: Mef2, Hgf, Ilb1, Itgb1, Edn1, Ppargc1a