Thermal diffusivity of green river oil shale by the laser-flash technique

The thermal diffusivity of Green River oil shale has been measured by the laser-flash technique. Measurements were carried out in the temperature range 25–350°C and for various grades of shales ranging from 6 to 100 gal./ton. The thermal diffusivity (α) is seen to decrease with increasing temperature, especially for shales with low organic content. Richer shales, on the other hand, show very little sensitivity in their α values to temperature and grade. The α values measured for Green River oil shales fall in the range 0.1–0.9×10^?2 cm²/sec. Anisotropic effects were also observed for these α values; shales cored parallel to their bedding planes the diffusivities about 20–30% higher than those for the samples cored perpendicular to the stratigraphic planes. The presence of pore water in the shale is also shown to have a significant effect on α.     

Antimicrobial and Antimalarial Activity of Novel Synthetic Mononuclear Ruthenium(II) Compounds

The present work was aimed that the two Ruthenium compounds namely, [Ru(A)₂(B)]Cl₂, where A = 1,10‐phenanthroline; B = 2‐NO₂‐phenyl thiosemicarbazone (Compound R₁)/2‐OH‐phenyl thiosemicarbazone (Compound R₂) have been tested for antibacterial activity at the concentrations of 1 mg/mL against various Gram‐Positive organisms (Lactobacillus, Staphylococcus pyrogenes, Bacillus subtilis, Staphylococcus aureus & Bacillus megatarium) and Gram‐Negative organisms (Pseudomonas aeruginosa, Escherichia coli, Proteus vulgaris, Enterobacter aerogenes, Salmonella paratyphi, Klebsiella pneumonia & Proteus mirabilis). The compounds were also tested for antifungal activity against Aspergillus clavatus, Aspergillus niger, Colletotrichum & Penicillium notatum by using agar diffusion assay and antimalarial activity against Plasmodium falciparum (Strain 3D7) using MTT assay. The results concluded that the compound R₁ exhibited significant antibacterial activity than R₂ against Gram‐Negative bacteria with zones of inhibition ranging from 15‐20 mm. and mild antibacterial activity against Gram‐Positive bacteria in comparison to tetracycline, streptomycin and rifampicin. These complexes were found to have moderate antifungal activity with no activity was however observed against Aspergillus niger. The compound, R₁ exhibited antimalarial activity at 10 μg/mL, whereas R₂ did not show antimalarial activity upto 50 μg/mL. Sensitivity to the compounds was greatest in the gram‐negative bacteria, followed by the gram‐positive bacteria and fungi.     

Pd-mediated new synthesis of pyrroles: their evaluation as potential inhibitors of phosphodiesterase 4

A sequential Pd-mediated multi-component reaction followed by Suzuki or Heck or Sonogashira coupling in a single pot has been developed for the synthesis of functionalized pyrroles as potential inhibitors of PDE4.     

Comparative QSAR studies on PAMPA/modified PAMPA for high throughput profiling of drug absorption potential with respect to Caco-2 cells and human intestinal absorption

Despite the dramatic increase in speed of synthesis and biological evaluation of new chemical entities, the number of compounds that survive the rigorous processes associated with drug development is low. Thus, an increased emphasis on thorough ADMET (absorption, distribution, metabolism, excretion and toxicity) studies based on in vitro and in silico approaches allows for early evaluation of new drugs in the development phase. Artificial membrane permeability measurements afford a high throughput, relatively low cost but labor intensive alternative for in vitro determination of drug absorption potential; parallel artificial membrane permeability assays have been extensively utilized to determine drug absorption potentials. The present study provides comparative QSAR analysis on PAMPA/modified PAMPA for high throughput profiling of drugs with respect to Caco-2 cells and human intestinal absorption.     

UV-B-induced synthesis of mycosporine-like amino acids in three strains of Nodularia (cyanobacteria)

Three filamentous and heterocystous cyanobacterial strains of Nodularia, Nodularia baltica, Nodularia harveyana and Nodularia spumigena, have been tested for the presence and induction of ultraviolet-absorbing/screening mycosporine-like amino acids (MAAs) by simulated solar radiation in combination with 395 (receiving photosynthetically active radiation (PAR) only), 320 (receiving PAR + UV-A) and 295 (receiving PAR + UV-A + UV-B) nm cut-off filters. Absorption spectroscopic analyses of the methanolic extracts of samples revealed a typical MAA peak at 334 nm in all three cyanobacteria. Specific contents of MAAs had a pronounced induction in the samples covered with 295 nm cut-off filters after 72 h of irradiation. In comparison, there was little induction of MAAs in the samples covered by 395 and 320 nm cut-off filters. High performance liquid chromatographic (HPLC) studies revealed the presence of two types of MAAs in all three cyanobacteria, which were identified as shinorine and porphyra-334, both absorbing maximally at 334 nm. The occurrence of porphyra-334 is rare in cyanobacteria. Specific content of both shinorine and porphyra-334 were induced remarkably only in the samples covered with 295 nm cut-off filters. The results indicate that in comparison to UV-A and PAR, UV-B is more effective in eliciting MAAs induction in the studied cyanobacteria.     

Sulfur Deficiency Changes Mycosporine-like Amino Acid (MAA) Composition of Anabaena variabilis PCC 7937: A Possible Role of Sulfur in MAA Bioconversion

In the present investigation we show for the first time that bioconversion of a primary mycosporine-like amino acid (MAA) into a secondary MAA is regulated by sulfur deficiency in the cyanobacterium Anabaena variabilis PCC 7937. This cyanobacterium synthesizes the primary MAA shinorine (RT = 2.2 min, λ_max = 334 nm) under normal conditions (PAR + UV-A + UV-B); however, under sulfur deficiency, a secondary MAA palythine-serine (RT = 3.9 min, λ_max = 320 nm) appears. Addition of methionine to sulfur-deficient cultures resulted in the disappearance of palythine-serine, suggesting the role of primary MAAs under sulfur deficiency in recycling of methionine by donating the methyl group from the glycine subunit of shinorine to tetrahydrofolate to regenerate the methionine from homocysteine. This is also the first report for the synthesis of palythine-serine by cyanobacteria which has so far been reported only from corals. Addition of methionine also affected the conversion of mycosporine-glycine into shinorine, consequently, resulted in the appearance of mycosporine-glycine (RT = 3.6 min, λ_max = 310 nm). Our results also suggest that palythine-serine is synthesized from shinorine. Based on these results we propose that glycine decarboxylase is the potential enzyme that catalyzes the bioconversion of shinorine to palythine-serine by decarboxylation and demethylation of the glycine unit of shinorine.     

Investigation of secondary flow instability on an infinite yawed cylinder with 15 per cent. Thick joukowski profile as section

This paper contains a theoretical investigation of the secondary flow instability in the incompressible boundary layer on an infinite yawed cylinder with chordwise section as Joukowski profile of 15 per cent. thickness at zero incidence and with homogeneous suction, the suction mass flow coefficient being equal to 0·2085. Values of the instability criterion are obtained at different points of the wing section and for various angles of sweepback. It is found that the values of the criterion increase with the increasing sweepback whether the pressure gradient is favourable or adverse. The effect of adverse pressure gradient on the variation of the criterion is more pronounced than that of a favourable pressure gradient. At some points in adverse pressure gradients, there are two values of the criterion for a given sweepback. It is also found that the flow is intermittently laminar and turbulent for low values of the chordwise free stream Reynolds number and consists of an irregular sequence of laminar and turbulent regions.     

Selenium-modified titanium dioxide photochemical diode/electrolyte junctions: photocatalytic and electrochemical preparation, characterization, and model simulations

The photoelectrochemical behavior of TiO2 thin film electrodes, photocatalytically modified with Se islands, is described. The TiO2 thin films were electrodeposited on transparent conducting oxide glass substrates. The resultant electrode forms a n-TiO2/p-Se "photochemical diode" which, in turn, contacts an electrolyte phase. Both transient photocurrent profiles (in response to excitation light that is switched on or off) and steady-state current-potential curves in response to chopped irradiation are considered. We show that the relative dominance of the contributions from the TiO2 and Se components to the overall response of the photochemical diode/electrolyte junction crucially depends on the wavelength distribution of the excitation light source. A simple equivalent circuit representation of this junction is presented, comprised of a photodiode in parallel with two photodiodes connected in series back-to-back. Simulations of the transient and steady-state photoelectrochemical response of this system are presented, and are shown to be in good agreement with the corresponding experimental profiles.