வேதியியல் அறிவியல் இதழ்

Reaction of 2-guanidinobenzimidazole and 2-guanidinebenzoxazole with several active methylene compounds revealed the formation of dihydropyrimidine and dihydropyrimidinone (DHPMs) derivatives via cyclo-condensation reaction. The products were obtained in a good yield, short time and a simple experimental procedure. The synthesized compounds were evaluated for their anti-bacterial activity against Gram-positive and Gram-negative bacteria. The compounds exhibited excellent zone of inhibition against tested bacteria. The investigation of antifungal screening data revealed that all the tested compounds showed moderate to good fungal inhibition. All compounds have been characterized based on IR, 1H-NMR, 13C-NMR and Mass spectrum data, in some cases the structure was established by X-Ray crystallography.

The dissolution of Barium hydroxide (Ba(OH)2) in pure water was used for finding out its thermodynamic parameters by conductivity method. The effect of ionic salts as well as the influence of some mixed solvent (1,2-propanediol and ethanol) were also studied. It was found that the added ionic salts produced fewer changes in the thermodynamic parameters compared to mixed solvents. Moreover, the combined salts and mixed solvent system collectively changed the thermodynamic parameters more differently as compared to the separate systems. These results were compared with the dielectric constant and ionic strength of the media.

The new symmetrically tetra substituted metallophthalocyanines (MPc) [MPc1-3, M = Co(II), Ni(II) and Cu(II)] bearing pyridyl moieties on peripheral positions have been synthesized via 1,3,4-oxadiazole bridge. The newly prepared compounds have been characterized by elemental analysis, FTIR, Solid State 13C NMR, Solid State UV–Vis, Thermogravimetric Analysis (TGA) and XRD analysis, the complexes are in good consistency with the experimental results. All the newly synthesized compounds exhibited good optical property showing the red shift of Q-band position and TGA results show admirable thermal stability (>400 °C). The MPc2 and 3 show high dielectric constant (ɛ′), 9800 and 11150 respectively, at 50 Hz. The ensuing MPc1-3 show low dielectric loss (tanδ) in the frequency range of 50 Hz to 5 MHz at room temperature. The shoulder nature is observed in the variation of tanδ with frequency for MPc2 and MPc3, which is understood on the basis of resonance between hopping frequencies of charge carriers and applied frequency. The variation of AC conductivity with frequency was explained by electron hopping model and values are in the range of 4.0x10-5–1.6x10-4 (S/m) at 5 MHz measured at 20 °C.

This work was done to study microwave assisted transesterification of Pongamia pinnata seed oil carried out for the production of Fatty Acid Methyl Esters (FAME, biodiesel). The experiments were carried out using methyl alcohol and two different alkali catalysts i.e., potassium hydroxide (KOH) and sodium hydroxide (NaOH). The experiments were carried out at 1:6 oil/alcohol molar ratio and 60 ˚C reaction temperature. The effect of catalyst concentration and reaction time on the yield and quality of biodiesel (FAME) was studied. The result of the study suggested that 0.5% sodium hydroxide and 1.0% potassium hydroxide catalyst concentration were optimum for biodiesel production from P. pinnata oil under microwave heating. There was a significant reduction in reaction time for microwave assisted transesterification as compared to conventional heating.

A method of estimating the solubility of water in hydrocarbons as a function of temperature is given here. Hydrocarbons, lacking strong permanent dipoles or traditional hydrogen bonding, do not strongly attract water molecules. The extreme case of a medium bereft of attractive forces is a vacuum, into which water, nonetheless, evaporates. The solubility of water in hydrocarbons at various temperatures can be correlated to the vapor pressure of water at those temperatures. A simple thermodynamic explanation of the dependence on vapor pressure is offered.

New series of potential biologically active agents have been synthesized by functionalization of ibuprofen core structure involving hydrazidic, heterocyclic, quinone and indole containing motifs. The targeted products have been achieved in a very good yield (average 75%) under conventional heat and irradiation conditions. All compounds have been characterized by IR, 1H-NMR, 13C-NMR and Mass spectra.

Caffeine is known to form c omplexes by self - association and with other organic compounds. Its biological activity in changing the effects of neurotoxins has been attributed to its f ormation of stacked complexes. Charge - transfer complexes of c affeine have also been reported. However, complexes reported are stoichiometric and exhib it color only in solution.

Maize fibres were pre-treated and chemically modified with 0.05 M citric acid. The adsorption of Cd21 and Pb21 ions onto the citric acid modified maize fibres was studied in batch experiment at ambient conditions. The study showed that the adsorption of Cd21 and Pb21 ions depends on metal ion concentration, adsorbent dosage and contact time. Langmuir and Freundlich adsorption models were used to model the equilibrium data. Based on linear regression value r2, the adsorption fits Langmuir adsorption model well compared that of Freundlich. The maximum binding capacity of the metal ions as obtained from the Langmuir fit were 4.93 and 4.88 mg g21 for Cd21 and Pb21 ions, respectively. The value of Freundlich constants, n and kF, obtained from Freundlich fit were 2.63 mg g21 and 0.60 for Cd21 and 2.79 mg g21 and 0.68 for Pb21. The rate constant and r2 values as obtained from pseudo first-order, pseudo second-order and intra-particle diffusion plots were 2.6 3 1022 min21, 0.997; 9.7 3 1022 g mg21 min21, 0.985 and 2.6 3 1022 min21, 0.997, respectively, for Cd21, while those for Pb21 were 2.6 3 1022 min21, 0.993; 7.1 3 1022 g mg21 min21, 0.990 and 2.6 3 1022 min21, 0.993, respectively. The r2 values showed that the metal ion adsorption onto citric acid modified maize fibres follows pseudo first-order kinetics and is controlled by intra-particle diffusion. This study suggests that citric acid modified maize fibres can be used in simple water treatment units to remove Cd21 and Pb21 ions.

The photosensitized reaction of 5–Methylthiazole (5MT) with benzophenone (BP) in aqueous alkaline medium using visible light has been studied to mineralize 5MT to less toxic ions. 5MT shows the λmax at 240 nm in the pH range of 2-12. The triplet–triplet energy transfer from the triplet excited state of the aromatic ketone BP to the substrate molecule takes place during the photosensitized reaction. The triplet excited 5MT breaks down on further exposure and photoproduct formation takes place. The reaction shows the participation of singlet oxygen during the photoreaction. The sulfate has been observed as photoproduct. The apparent rate of the reaction has been calculated and the effect of pH, concentration of the sensitizer, the light intensity on the apparent rate of the reaction has been studied. The quantum efficiency of the photochemical reaction is calculated using potassium ferri oxalate actinometer and the effect of the concentration of the substrate on the quantum efficiency is calculated. The reaction mechanism and the excited states involved have been suggested.

This review purports to fill the gap in knowledge that exists about the role of nanoparticles in Tissue Engineering. In this review, the use of the term nanoparticles will be exclusively confined to those materials or composites with grain sizes ranging from 100-500 nm. First, a brief description of the field will be provided. Next, research findings on the use of cells on ceramics, peptides, carbon, silicon, and diamond, will be scrutinized. Then, future applications and directions will be outlined. Finally, a succinct account will summarize some of the developments in the field of Tissue Engineering involving nanoparticles.