Synthesis and antitubercular activity evaluation of 4-furano-coumarins and 3-furano-chromones

The synthesis of novel 4-furano-coumarins and 3-furano-chromones has been achieved using silver-mediated oxidative C–H/C–H functionalization of 4-ethynylcoumarin/3-ethynylchromone with ethyl acetoacetate in 80%–90% and 82%–90% yields, respectively. The structure of the synthesized compounds was established on the basis of their spectral data analysis and the structure of one of the 4-furano-coumarins has been further confirmed on the basis of its X-ray crystallographic study. All eight synthesized 4-furano-coumarins and 3-furano-chromones exhibited moderate antitubercular activity against sensitive reference strain H37Rv of Mycobacterium tuberculosis.     

Effect of degradation on electronic properties of polymer solar cells

We present here the effect of degradation on electronic properties of polymer solar cells. Investigations were performed on two types of solar cells based on the bulk‐heterojunction network of poly(3‐hexylthiophene) and phenyl [6,6] C₆₁ butyric acid methyl ester, one with slow degradation whereas other with faster degradation. Samples were prepared in identical conditions with controlled atmosphere, but for faster degradation, one of the samples was exposed to ambient air (rich in O₂ and H₂O molecules) before deposition of top metal electrode. The sample with slow degradation showed linear degradation in short circuit current density (J_sc), whereas the sample with faster degradation exhibited exponential degradation in J_sc. Linear degradation happens due to degradation in the active layer only whereas the exponential degradation is because of through degradation of the solar cell. The effect of degradation is investigated on different diode parameters. Because of different degradation processes in the two samples, the variations in diode parameters with time are different. Copyright © 2013 John Wiley & Sons, Ltd.     

Radiation from relativistic positrons channeled in single crystals

The characteristic of the radiation emitted from relativistic positrons channelled between the major planes in single crystal have been calculated. The sharp peaks of the emission spectrum in the keV region is predicted correctly and is compared with previous calculations.     

Heating liquid dielectrics by time dependent fields

Steady state and time-resolved dielectric relaxation experiments are performed at high fields on viscous glycerol and the effects of energy absorption from the electric field are studied. Time resolution is obtained by a sinusoidal field whose amplitude is switched from a low to a high level and by recording voltage and current traces with an oscilloscope during this transition. Based on their distinct time and frequency dependences, three sources of modifying the dynamics and dielectric loss via an increase in the effective temperature can be distinguished: electrode temperature, real sample temperature, and configurational temperatures of the modes that absorbed the energy. Isothermal conditions that are desired for focusing on the configurational temperature changes (as in dielectric hole burning and related techniques) are maintained only for very thin samples and for moderate power levels. For high frequencies, say ν > 1 MHz, changes of the real temperature will exceed the effects of configurational temperatures in the case of macroscopic samples. Regarding microwave chemistry, heating via cell phone use, and related situations in which materials are subject to fields involving frequencies beyond the MHz regime, we conclude that changes in the configurational (or fictive) temperatures remain negligible compared with the increase of the real temperature. This simplifies the assessment of how time dependent electric fields modify the properties of materials.     

SYNTHESIS,SPECTRAL STUDIES,AND ANTIMICROBIAL ACTIVITIES OF [N-(UN)ALKYLATED-2-ARYLINDOL-3-YL]THIOCARBOXAMIDES

A series of [N-(un)alkylated-2-arylindol-3-yl]thiocarboxamides(6) have been synthesized by the condensation of alkyl [N-(un)alkylated-2-arylindol-3-yl]dithiocarboxylates (5) with appropriate secondary amines in absolute alcohol. Compound 5 was prepared by the reaction of N-(un)alkylated-2-arylindoles with carbon disulphide in the presence of potassium-t-butoxide followed by alkyl iodide under nitrogen atmosphere. All of the compounds have been characterized on the basis of their elemental and spectral data and have been screened for their antibacterial and antifungal activities. Some of the synthesized compounds have shown promising activity.     

Comparative extraction efficiencies of tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate and <Emphasis Type="Italic">N,N</Emphasis>-dihexyloctanamide for uranium recovery using supercritical CO<Subscript>2</Subscript>

Extraction of uranium from tissue paper, synthetic soil, and from its oxides (UO₂, UO₃ and U₃O₈) was carried out using supercritical carbon dioxide modified with methanol solutions of extractants such as tri-n-butyl phosphate (TBP) or N,N-dihexyl octanamide (DHOA). The effects of temperature, pressure, extractant/nitric acid (nitrate) concentration, and of hydrogen peroxide on uranium extraction were investigated. The dissolution and extraction of uranium in supercritical CO₂ modified with TBP, from oxide samples followed the order: UO₃ ≫ UO₂ > U₃O₈. Addition of hydrogen peroxide in the modifier solution enhanced the dissolution/extraction of uranium in dynamic mode. DHOA appeared better than TBP for recovery of uranium from different oxide samples. Similar enhancement in uranium extraction was observed in static mode experiments in the presence of hydrogen peroxide. Uranium estimation in the extracted fraction was carried out by spectrophotometry employing 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) as the chromophore.     

Neptunium estimation in the spent fuel dissolver solution by inductively coupled plasma-atomic emission spectroscopy

This paper deals with the optimization of experimental conditions for the estimation of Np in spent fuel dissolver solution using 2-thenoyltrifluoroacetone (HTTA) as extractant. The quantitative extraction of Np from the dissolver solution employing 0.5 M HTTA/xylene was followed by its estimation by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) after stripping it from the organic phase with 8 M HNO₃. The reliability of the method was checked by standard addition technique. The method is precise and accurate yielding Np analytical recovery of 99 ± 1%.     

Is high electric field capable of selectively inducing a covalent-like bond between polar and non-polar molecular species?

It is demonstrated through the present ab initio theoretical investigation that an external electric field can bring about a phenomenal enhancement in the strength of the bond between water and carbon-dioxide molecules from a van der Waals type (binding energy ~0.085 eV), to strong covalent type (binding energy ~7.45 eV), resulting in an exotic molecular complex. The onset of this effect is characterized by an abrupt change in the dipole moment of the composite system at a particular field-value, concomitant with the O–C=O ? O=C–O resonance in the CO₂ moiety of the complex. This field-induced bond formation is further confirmed by the emergence of a characteristic intermolecular stretching mode (~317 cm^?1) in the vibrational response of the system. This exotic bond that exhibits a covalent-like character, which accompanied by a charge-transfer, renders the carbon atom a substantial negative charge.     

Syntheses and antibacterial studies of some 2-[5-(Aryl)-[1,3,4]oxadiazole-2-ylsulfanyl] alkanoic Acids

Some new 2-[5-(aryl)-[1,3,4]oxadiazole-2-ylsulfanyl]alkanoic acids were synthesized and studied for their antibacterial activity. These compounds were prepared from aromatic carboxylic acid hydrazides. Aromatic carboxylic acid hydrazides 1 on refluxing with carbon disulfide and methanolic potassium hydroxide and then on subsequent acidification with hydrochloric acid furnish 5-aryl-1,3,4-oxadiazole-2-thiones 2. 2-Chloro alkanoic acids react with 2 in alkaline media and on acidification yield the title compounds 3. These compounds were characterised by CHN analyses, IR, mass and ¹H NMR spectral data. All the compounds were evaluated for their in vitro antibacterial activity against two Gram negative strains (Escherichia coli and Pseudomonas aeruginosa) and two Gram positive strains (Bacillus subtilis and Staphylococcus aureus) and their minimum inhibitory concentration (MIC) were determined.