Synthesis of nanocomposite glass-like films containing semiconductor nanocrystals and noble bimetallic colloids by sol-gel route and their characterisation

Zwei Arten von Gläsern liegen im Schwerpunkt des aktuellen Interesses und werden zur Zeit intensiv untersucht. Dies sind zum einen dotierte Gläser mit halbleitenden Nanopartikeln und solche mit Edelmetallkolloiden. Zusätzlich zu ihren Anwendungen in der nichtlinearen Optik kann man die mit Halbleiterkolloiden dotierten Gläser dabei als zukünftige optische Filter ansehen. Edelmetallkolloidhaltige Gläser können als farbige Beschichtungen verwendet werden. Gegenstand dieser Arbeit war daher die auf dem Sol-Gel-Prozeß basierende Herstellung von nanokomposithaltigen glasartigen Beschichtungen, welche halbleitende Nanopartikel sowie gemischte und legierte Kolloide zweier Edelmetalle enthalten.Two type of glasses are currently of interest and being studied extensively. One is a glass doped with semiconducting nancrystals while the other type is doped with noble metal colloids. In addition to their applications in non-linear optics, the first type glasses can also be seen as future optical filters and the second type of glasses can be used as coloured glasses. Therefore the present work was carried out with an objective of synthesizing nano-composite glass like thin films containing semiconductor nanocrystals and mixed- and alloy- noble bimetallic colloids using the sol-gel process

CFD Analysis of Fuel Sloshing in a Cylindrical Tank with and Without Baffles Under Linear Acceleration

The phenomenon of sloshing can be understood as any motion of liquid surface. When any partially filled container is disturbed by any external forces, sloshing occurs for example a tank containing fluid put on a moving vehicle. But for occurrence of sloshing the container must have a free surface of liquid. The sloshing causes additional sloshing forces and moments which finally changes the system dynamics and stability. For a moving vehicle this may affect the steering and braking performance as the liquid interacts with the walls of the container. The sloshing phenomenon includes various fields such as propellant slosh in rockets and space crafts, cargo ships and also the trucks which carry different type of fluids. To suppress the sloshing and to limit the effects generated baffles are used. They change the fluid’s natural frequency and thus omits the chances of occurrence of resonance. The present study aims towards the design of different types of transverse baffles and their effects in reducing the magnitudes and variation of forces and moments generated in a cylindrical tank partially filled with gasoline subjected to linear acceleration and deceleration. A 3-D transient analysis of the tank was carried out for 20 seconds using ANSYS-FLUENT software at two different fill levels. Volume of Fluid (VOF) method was used to track the surface. The study shows that baffles with more no of holes on their surface reduces the longitudinal forces most effectively but vertical force are reduced with baffles having a single central cavity. For controlling the moments also baffles with single cavity proved to be more effective

Begomovirus DNA replication and pathogenicity

Begomoviridae is the largest genus of the family of single stranded DNA plant viruses, Geminiviridae and is responsible for significant agro-economic losses worldwide. Its small single-stranded DNA genome primarily replicates by rolling circle replication (RCR) mode with the help of certain viral and host factors. The role of virus encoded Rep protein in initiation and immediate post-initiation phases of RCR has been the subject of various studies. We have identified many host proteins which interact with Rep protein of a member of Begomovirus, namely, Mungbean yellow mosaic India virus, thereby playing a role in viral DNA replication. Of these, the role of host RAD54 protein is significant as the rad54 mutant of Arabidopsis does not permit mini viral DNA replication. The plant hosts protect themselves from begomoviruses by activating RNA interference (RNAi) pathways targeted against the viruses. However, the virus can also sometime overcome this form of host defence by encoding RNA silencing suppressors, which attenuate host RNAi and are regarded as major pathogenicity determinants. The viral suppressors do not share any signature sequences and are structurally and mechanistically dissimilar. These can be detected effectively, only through specialized functional assays. In this review, we also point out the potential biotechnological applications of the suppressors and discuss about various possible containment strategies for begomoviruses, including an exciting new approach involving artificial micro- RNAs

Effect of glass substrates on the formation of gold-silver colloids in nanocomposite thin films

A sol-gel route to synthesize nanocomposite thin films containing phase separated metal colloids of gold (Au) and silver (Ag) was developed. Ag - Au colloids were prepared in silica films using dip coating technique. The annealing of the samples in air results in the formation of phase separated Ag and Au colloids in SiO2 thin films, showing the surface plasmon peaks at 410 nm and 528 nm. For the synthesis of phase separated Ag and Au colloids on float glass substrates, formation of the silver colloids was found strongly dependent on the surface of the float glass. On the tin rich surface formation of both gold and silver colloids took place, whereas, on the tin poor surface the formation of only gold colloids was observed. The surface dependence of the formation of silver colloids was attributed to the presence of tin as Sn2+ state on the glass surface, which oxidizes into Sn4+ during heat treatment, reducing Ag+ into silver colloids

Hysteresis in a Solar Activity Cycle

We analyze in situ measurements of solar wind velocity obtained by the Advanced Composition Explorer (ACE) spacecraft during the solar activity cycle 23. We calculated a robust complexity measure, the permutation entropy (S) of solar wind time series at different phases of a solar activity cycle. The permutation entropy measure is first tested on the known dynamical data before its application to solar wind time series. It is observed that complexity of solar wind velocity fluctuations at 1 AU shows hysteresis phenomenon while following the ascending and descending phases of the activity cycle. This indicates the presence of multistability in the dynamics governing the solar wind velocity over a solar activity cycle.Comment: 10 pages, 5 figures; Solar Physics, 201

Synthesis of nanocomposite glass-like films containing semiconductor nanocrystals and noble bimetallic colloids by sol-gel route and their characterisation

Zwei Arten von Gläsern liegen im Schwerpunkt des aktuellen Interesses und werden zur Zeit intensiv untersucht. Dies sind zum einen dotierte Gläser mit halbleitenden Nanopartikeln und solche mit Edelmetallkolloiden. Zusätzlich zu ihren Anwendungen in der nichtlinearen Optik kann man die mit Halbleiterkolloiden dotierten Gläser dabei als zukünftige optische Filter ansehen. Edelmetallkolloidhaltige Gläser können als farbige Beschichtungen verwendet werden. Gegenstand dieser Arbeit war daher die auf dem Sol-Gel-Prozeß basierende Herstellung von nanokomposithaltigen glasartigen Beschichtungen, welche halbleitende Nanopartikel sowie gemischte und legierte Kolloide zweier Edelmetalle enthalten.Two type of glasses are currently of interest and being studied extensively. One is a glass doped with semiconducting nancrystals while the other type is doped with noble metal colloids. In addition to their applications in non-linear optics, the first type glasses can also be seen as future optical filters and the second type of glasses can be used as coloured glasses. Therefore the present work was carried out with an objective of synthesizing nano-composite glass like thin films containing semiconductor nanocrystals and mixed- and alloy- noble bimetallic colloids using the sol-gel process

A solid state 29Si and 13C NMR study on the synthesis of thin silicon-oxycarbide glass sheets by a sol-gel route

29Si and 13C MAS NMR spectroscopy, DTA-TG and elemental analysis were used to study the evolution of metastable oxycarbide phases starting from thin gel sheets derived from methyltriethoxysilane (MTEOS), tetraethoxysilane (TEOS) and a colloidal silica containing sol, up to 1450°C under a nitrogen atmosphere. The stoichiometric formulae of the glasses obtained by the semi-quantitative analysis of 29Si MAS NMR spectra were found to be in good agreement with those obtained by chemical analysis. It was found that the addition of colloidal silica sol delays the decomposition of methyl groups in MTEOS containing condensates. This delayed decomposition of the methyl groups was attributed to facilitate the strengthening of the matrix, thus leading to crack free sintering of sheets up to 400°C in air and for T>900°C under nitrogen. A significant portion (>40%) of the total carbon present in the glasses was found to exist as free carbon. 13C NMR showed that unsaturated C=C bonds exist in gels heat treated at 1000 °C, but they disappear in heat treated gels at 1200 and 1450°C. Both 29Si and 13C NMR spectra indicate the formation of a ca. 15 atom% SiC phase in the glass sheets sintered at 1450°C, which were found to be amorphous up to 1200°C

PHARMACOGNOSTICAL STUDIES AND PRELIMINARY PHYTOCHEMICAL INVESTIGATION ON THE BARK OF BAUHINIA VARIEGATA (CAESALPINIACEAEA)

Bauhinia variegata (Family - Caesalpiniaceaea) is a medium-sized, deciduous tree, found throughout India, ascending to an altitude up to 1800m in Himalayas. The objective of the study was to develop various standardization parameters for the evaluation of Bark of this plant. Microscopy, powder characteristics of bark were observed and results were recorded. Physicochemical analysis such as extractive value includes petroleum ether, ethanol, ethyl acetate and aqueous soluble extractive values of 2.88, 6.86, 2.96, and 8.88% w/w respectively; extracts were analysed by chemical test and showed presence of flavonoids, tannins, steroids and triterpenoids etc. The preliminary phytochemical investigation indicated presence of tannins, carbohydrates, flavenoieds and steroids. The results obtained from standardization of bark established the macro and microscopical parameters, physicochemical parameters, TLC profiles that characterize the genuine plant drug (B.variegata) so these parameters are useful for quick identification of drug and are particularly useful in the case of powdered materials