CHx hydrogenation on Co(0001): a density functional theory study

Hydrogenation is an important process in the Fischer-Tropsch synthesis. In this work, all the elementary steps of the hydrogenation from C to CH4 are studied on both flat and stepped Co(0001) using density functional theory (DFT). We found that (i) CH3 hydrogenation (CH3+H-->CH4) is the most difficult one among all the elementary reactions on both surfaces, possessing barriers of around 1.0 eV; (ii) the other elementary reactions have the barriers below 0.9 eV on the flat and stepped surfaces; (iii) CH2 is the least stable species among all the CHx(x=1-3) species on both surfaces; and (iv) surface restructuring may have little effect on the CHx(x=0-3) hydrogenation. The barriers of each elementary step on both flat and stepped surfaces are similar and energy profiles are also similar. The reason as to why CHx hydrogenation is not structure-sensitive is also discussed.     

An efficient approach for the synthesis of spirooxindole derivatives catalyzed by novel sulfated choline based heteropolyanion at room temperature

A new zwitterionic salt, sulfated choline based heteropolyanion, which was reported earlier by our group, has been found to be very effective for the synthesis of spirooxindole derivatives at room temperature. The heteropolyanion based on sulfated ionic liquid (HIL) showed promising features for the reaction, such as shorter reaction time, high product yields (about 90–95%), simple work up, easy removal, and reusability of the catalyst for several times without significant loss in its efficiency. This has made the protocol sustainable and economic.     

Molecular clock on a neutral network

The number of fixed mutations accumulated in an evolving population often displays a variance that is significantly larger than the mean (the overdispersed molecular clock). By examining a generic evolutionary process on a neutral network of high-fitness genotypes, we establish a formalism for computing all cumulants of the full probability distribution of accumulated mutations in terms of graph properties of the neutral network, and use the formalism to prove overdispersion of the molecular clock. We further show that significant overdispersion arises naturally in evolution when the neutral network is highly sparse, exhibits large global fluctuations in neutrality, and small local fluctuations in neutrality. The results are also relevant for elucidating aspects of neutral network topology from empirical measurements of the substitution process.     

Design,synthesis,in vitro evaluation of tetrahydropyrimidine-isatin hybrids as potential antibacterial,antifungal and anti-tubercular agents

A series of 5-substitued-3-(5-(4-(furan-2-yl)-6-methyl-2-oxo/thioxo-1,2,3,4-tetrahydropyrimidin-5-yl)-1,3,4-thiadiazol-2- ylimino)indolin-2-one derivatives were synthesized,characterized and were screened for anti-bacterial,anti-fungal and antitubercular activity.     

Design,synthesis and in vitro evaluation of tetrahydropyrimidine-isatin hybrids as potential antitubercular and antimalarial agents

A series of 5-substituted-3-[{5-(6-methyl-2-oxo/thioxo-4-phenyl-1,2,3,4-tetrahydropyrimidin-5-yl)-1,3,4-oxadiazol-2-yl}-imino] -1,3-dihydro-2H-indol-2-one were synthesized,characterized and screened for their anti-tubercular and antimalarial activity.     

Magnetic resonance imaging features in melanoma

T1 and T2 relaxation time shortening secondary to paramagnetic compounds has been described in melanoma. The purpose of this paper is to evaluate the signal behavior of melanoma involved in various body areas using short TR, TE and long TR, TE sequences. Twenty-seven sites of melanoma were evaluated with MR using T1 weighted and T2-weighted techniques. Using fat and muscle signal intensities as references tissues, lesions were graded into high, low or intermediate intensity categories for each of the sequences. Four signal patterns emerged. The typical pattern characterized by high signal on T1-weighted images and low signal on T2-weighted images reflected T1 and T2 shortening. The other pattern categories comprised of lesions demonstrating low signal T1-weighted images and high signal on T2-weighted images, high signal on both T1- and T2-weighted images and lesions showing intermediate signal on either T1- or T2-weighted images. We observed a tendency away from the typical signal pattern in extraocular melanoma cases with only one of 14 demonstrating this pattern. Moreover, only seven of thirteen ocular melanomas exhibited such behavior. Possible explanations for this findings as well as the existence of a variety of MR appearances to melanoma are offered. We conclude that while signal patterns showing T1 and T2 shortening are typical of melanoma, the absence of these does not exclude the diagnosis.     

A systematic study of CO oxidation on metals and metal oxides: density functional theory calculations

CO oxidation on Ru(0001), Rh(111), Pd(111), Os(0001), Ir(111), Pt(111), and their corresponding metal oxides is studied using density functional theory. It is found that (i) the reactivity of metal oxide is generally higher than that of the corresponding metal, and (ii) on both metals and metal oxides, the higher the chemisorption energy is in the initial state, the larger the reaction barrier. The barriers are further analyzed by decomposing them into electronic and geometric effects, and the higher reactivity of metal oxides is attributed mainly to the surface geometric effect. Moreover, the electronic effect on both metals and metal oxides follows the same pattern: the shorter the OC-O bond distance in the TS, the higher the barrier.     

Alteration in photosystem II photochemistry of thylakoids isolated from senescing leaves of wheat seedlings

Wheat seedlings, grown for 7 days in the light, were allowed to senesce in the light or dark, and the change in the photosystem II (PS II) photochemistry of chloroplasts isolated from the primary leaves of these seedlings was investigated. The decrease in oxygen evolution and the fast fluorescence results indicated that the impairment of PS II in the leaves of seedlings senescing in the light was different from that in the leaves of seedlings senescing in the dark. Thermoluminescence studies showed a structural modification in the Q_B protein of chloroplasts isolated from leaves senescing in the light and an alteration in the S state transition of chloroplasts isolated from leaves senescing in the dark.