Fate of an accretion disc around a black hole when both the viscosity and dark energy is in effect

This paper deals with the viscous accretion flow of a modified Chaplygin gas towards a black hole as the central gravitating object. A modified Chaplygin gas is a particular type of dark energy model which mimics of radiation era to phantom era depending on the different values of its parameters. We compare the dark energy accretion with the flow of adiabatic gas. An accretion disc flowing around a black hole is an example of a transonic flow. To construct the model, we consider three components of the Navier–Stokes equation, the equation of continuity and the modified Chaplygin gas equation of state. As a transonic flow passes through the sonic point, the velocity gradient being apparently singular there, it gives rise to two flow branches: one in-falling, the accretion and the other outgoing, the wind. We show that the wind curve is stronger and the wind speed reaches that of light at a finite distance from the black hole when dark energy is considered. Besides, if we increase the viscosity, the accretion disc is shortened in radius. These two processes acting together make the system deviate much from the adiabatic accretion case. It shows a weakening process for the accretion procedure by the work of the viscous system influencing both the angular momentum transport and the repulsive force of the modified Chaplygin gas.     

A Convenient Synthesis of Naturally Occuring Xanthones

Six naturally occuring xanthones are synthesized by the thermal condensation of methyl 2,6-dihydroxybenzoate, methyl 2,4-dihydroxybenzoate and methyl 2,4,6-trihydroxybenzoate with hydroquinone, catechol and pyrogallol.     

A review of bioanalytical methods for chronic lymphocytic leukemia drugs and metabolites in biological matrices

Quantitation of drugs used for the treatment of chronic lymphocytic leukemia in various biological matrices during both pre-clinical and clinical developments is very important, often in routine therapeutic drug monitoring. The first developed methods for quantitation were traditionally done on LC in combination with either UV or fluorescence detection. However, the emergence of LC with mass spectrometry in tandem in early 1990s has revolutionized the quantitation as it has provided better sensitivity and selectivity within a shorter run time; therefore it has become the choice of method for the analysis of various drugs. In this article, an overview of various bioanalytical methods (HPLC or LC–MS/MS) for the quantification of drugs for the treatment of chronic lymphocytic leukemia, along with applicability of these methods, is given.     

Preliminary Study of Cationic Copolymerization of α-Methylstyrene and Isobutyl Vinyl Ether. II

α-Methylstyrene (α-MS) and isobutyl vinyl ether (IBVE) were copolymerized by using the H₂O/EtAlCl₂ initiator system and CH₂Cl₂ and CH₃Cl solvent in the temperature range from -30 to -90°C. As compared to homopolymerization of α-MS, both yields and molecular weights are reduced upon addition of small amounts of IBVE to the feed. The reactivity ratios were calculated by the method of Kelen and Tödös as well as the Fineman and Ross method, and the combined effect of change of solvent and temperature on reactivity ratios was determined. Effects of feed composition and temperature on the copolymer yield, composition, and number-average molecular weight M _n were studied in detail. M _n showed a novel exponential dependence on the IBVE concentration in the feed. The overall activation energies of molecular weight were determined from the Arrhenius plots for both homo-and copolymerization systems. Based on these and the yield data, a speculation is made regarding reaction mechanism for molecular weight control. NMR and DTA data are reported, which establish the random nature of the copolymers.     

Molecular Modeling and 3D-QSAR Studies in 2-Aziridinyl-and 2,3-Bis(Aziridinyl)-1,4-Naphthoquinonyl Sulfonate and Acylate Derivatives as Potential Antimalarial Agents

Abstract

Malaria is still continuing to be one of the most dreadful diseases of the tropical countries particularly due to the development of resistance to the existing antimalarials. From observed, antimalarial activity of 2-aziridinyl- and 2,3-bis(aziridinyl)-1,4-naphthoquinonyl sulfonate and acylate derivatives acting through redox cycling mechanism, molecular modeling and three dimensional-quantitative structure activity relationship (3D-QSAR) studies have been carried out on a set of 63 compounds to identify important pharmacophors. Among several 3D-QSAR models generated, three models with correlation coefficient r > 0.82, match > 0.60 and chance = 0.00 have shown two common biophoric sites: one being the oxygen atom at position 1 of the naphthoquinone ring in terms of π-population, charge and electron donating ability while the second being the center of the phenyl ring in terms of its 6π-electrons. In addition to these sites, the models also share two common secondary sites: one positively contributing H-acceptor site while the second site contributing negatively in terms of steric refractivity. All these models showed good agreement between the experimental, calculated and predicted antimalarial activities.     

Intramolecular Ketone-Olefin Radical Cyclization with Low-Valent Titanium Reagent: Synthesis of Benzopyrans

A novel protocol for intramolecular ketyl-olefin radical cyclization with low-valent titanium reagent is outlined. It allows the formation of the benzopyran nucleus from ortho-allyloxy propiophenones as the sole product in moderate yields via intramolecular radical cyclization.     

Synthesis of 2, 2-Dimethyl-2H-chromenes via a Palladium (II) Catalysed Reaction

The antijuvenile hormones Precocene-I, Precocene-II and other bioactive 2, 2-dimethyl-2H-chromenes have been synthesised by intramolecular oxidative cyclisation of 2-isoprenyl phenols catalysed by a palla-dium(II) salt.     

Isolation and biological evaluation of chromone alkaloid dysoline,a new regioisomer of rohitukine from Dysoxylum binectariferum

The chromone alkaloid dysoline (1), a new regioisomer of rohitukine (2) along with rohitukine and rohitukine-N-oxide (3) were isolated from the stem barks of Dysoxylum binectariferum. The structure of dysoline (1) was determined by extensive 2D-NMR studies and the absolute configuration was established by NOESY and CD spectra. Dysoline (1) consisted of a 5,7-dihydroxy-2-methylchromone nucleus substituted with a 2′-hydroxylated N-Me piperidine ring at the C-6 position. Dysoline differs from rohitukine by the position of the piperidine ring on the chromone nucleus. Dysoline displayed promising cytotoxicity in HT1080 fibrosarcoma cells with an IC₅₀ of 0.21 μM, and also displayed significant inhibition of proinflammatory cytokines TNF-α and IL-6.