Influence of pH on nanosized Mn–Zn ferrite synthesized by sol–gel auto combustion process

Sol–gel auto combustion process was employed to synthesize nanosized Mn–Zn ferrite at different pH values (<1, 5, 6, 7, 8 and 10). Although self propagating combustion behavior of gel was noted at pH 5 but more effective combustion was observed at pH 6. The smoldering effect was observed in gel prepared at pH 7, 8 and 10, whereas pH < 1 showed localized burning. Thermogravimetric (TG) and X-ray diffraction (XRD) analyses were done to investigate the effect of pH on the combustion behavior, particle size and the formation of desired magnetic (spinel) phase. From TG curves of burnt powders, activation energy of ignition reaction at each pH value was calculated. The results showed that fuel to oxidant ratio and the amount of gel residuals decided the value of activation energy required to further purify the burnt powders. Calcination parameters (time and temperature in air) of powders P1 and P6 synthesized at pH < 1 and pH 6 were also determined. B–H loop results showed that calcined powder C6 was more ferromagnetic than C1 due to fully developed spinel phase and larger particle size.     

The influence of slip on the peristaltic motion of a third order fluid in an asymmetric channel

In this investigation, the peristaltic flow of a third order fluid in an asymmetric channel is considered in the presence of a slip condition. The series solution of the stream function and longitudinal pressure gradient is given under long wave length and low Reynolds number approximations. Pressure rise and frictional forces per wave length are analyzed through numerical integration. Pumping and trapping phenomena are examined and the obtained results are compared with those of no-slip condition. Comparison is made with the results of no-slip and viscous fluid cases.     

Determination of free amino acids in biological samples: problems of quantitation

An automatic on-line high-performance liquid chromatographic method was developed to study the effects of various precipitating agents and delayed deproteinization procedures on the estimation of plasma levels of amino acids. The optimized method for analysis is based on pre-column derivatization with o-phthalaldehyde in the presence of 2-mercaptoethanol. The separation of 25 amino acids is accomplished within 45 min on a 5-microns C18 column, using a multi-step gradient with two solvents. The method is sensitive and reproducible, and the relationship between the fluorescence intensity and concentration is linear for each amino acid over a wide concentration range.     

Unroofing history of the Sillai Patti granite gneiss, Pakistan: constraints from zircon fission-track dating

A group of alkaline igneous rocks is exposed in the north of the Peshawar Plain, extending from Tarbela in the east up to Loe–Shilman near the Pakistan–Afghanistan border in the west. The alkaline rocks consist mainly of granites, syenites, gabbros, ijolites and carbonatites. Granitic gneisses of Paleozoic age are exposed at the Malakand and further westward at Sillai Patti. However, the fission-track dating studies on zircon, based on the present work, indicate that the age of the Sillai Patti granite gneiss is less than the absolute age of granite gneisses. Therefore, the zircon fission-track age of 24.28±2.97 Ma of the Sillai Patti granite gneiss, represents a time of post-metamorphic denudation history of the area, when these rocks passed through the 210°C isotherm, corresponding to a depth of about 6.7 km inside the earth's crust from their present position if a paleogeothermal gradient of 30°C/km is assumed to have prevailed. Our average fission-track zircon age of 24.28±2.97 Ma is very similar to the average fission-track zircon age of 25.4±0.7 Ma of Mansehra granites. Average cooling rates of the Mansehra and Sillai Patti granite gneisses have been computed to be (8.00±0.22)°C/Ma and (8.00±0.98)°C/Ma, while the average denudation rates of the Mansehra and Sillai Patti granite gneisses have been computed to be (0.262±0.007) and (0.274±0.034) mm/yr, respectively, on the basis of zircon fission-track ages for the period between 25 Ma and the present time. This indicates that the two complexes have experienced similar average cooling/uplift-induced denudation histories during the last 25 Ma or so.     

Cloning of the Orange Light‐Producing Luciferase from Photinus scintillans—A New Proposal on how Bioluminescence Color is Determined

Unlike the enchanting yellow‐green flashes of light produced on warm summer evenings by Photinus pyralis, the most common firefly species in North America, the orange lights of Photinus scintillans are infrequently observed. These Photinus species, and likely all bioluminescent beetles, use the same substrates beetle luciferin, ATP and oxygen to produce light. It is the structure of the particular luciferase enzyme that is the key to determining the color of the emitted light. We report here the molecular cloning of the P. scintillans luc gene and the expression and characterization of the corresponding novel recombinant luciferase enzyme. A comparison of the amino acid sequence with that of the highly similar P. pyralis enzyme and subsequent mutagenesis studies revealed that the single conservative amino acid change tyrosine to phenylalanine at position 255 accounted for the entire emission color difference. Additional mutagenesis and crystallographic studies were performed on a H‐bond network, which includes the position 255 residue and five other stringently conserved beetle luciferase residues, that is proximal to the substrate/emitter binding site. The results are interpreted in the context of a speculative proposal that this network is key to the understanding of bioluminescence color determination.     

Synthesis,characterization, electrochemistry and evaluation of biological activities of some ferrocenyl Schiff bases

Synthesis of ferrocenyl Schiff bases ( 1–6 ) was carried out by the condensation reaction of 4‐ferrocenyl aniline with different substituted aromatic aldehydes and acetyl acetone. Compounds were characterized by physical measurements, elemental analysis, FT‐IR, ¹H‐NMR and ¹³C‐NMR spectroscopy. Single crystal X‐ray analysis of compound 2 showed the co‐planarity of both aromatic rings connected by a C–N double bond. Compounds demonstrated reversible one‐electron redox behavior and their peak currents were found to increase linearly with the square root of the sweep rate ν^1/2. The overall electrode processes were found to be diffusion controlled. Compounds 1 and 4 showed low cytotoxicity and appreciable antifungal, antioxidant and DNA protection activities. Copyright © 2010 John Wiley & Sons, Ltd.