Identification of destabilized metal hydrides for hydrogen storage using first principles calculations

Hydrides of period 2 and 3 elements are promising candidates for hydrogen storage but typically have heats of reaction that are too high to be of use for fuel cell vehicles. Recent experimental work has focused on destabilizing metal hydrides through alloying with other elements. A very large number of possible destabilized metal hydride reaction schemes exist. The thermodynamic data required to assess the enthalpies of these reactions, however, are not available in many cases. We have used first principles density functional theory calculations to predict the reaction enthalpies for more than 100 destabilization reactions that have not previously been reported. Many of these reactions are predicted not be useful for reversible hydrogen storage, having calculated reaction enthalpies that are either too high or too low. More importantly, our calculations identify five promising reaction schemes that merit experimental study: 3LiNH(2) + 2LiH + Si --> Li(5)N(3)Si + 4H(2), 4LiBH(4) + MgH(2) --> 4LiH + MgB(4) + 7H(2), 7LiBH(4) + MgH(2) --> 7LiH + MgB(7) + 11.5H(2), CaH(2) + 6LiBH(4) --> CaB(6) + 6LiH + 10H(2), and LiNH(2) + MgH(2) --> LiMgN + 2H(2).     

Synthesis of certain alkenyl purines and purine analogs

Synthesis of alkenyl derivatives of certain purines and purine analogs is described. Direct alkylation of the sodium salt of 6-chloropurine (1) either with 1-bromo-2-pentene or 4-bromo-2-methyl-2-butene in N,N-dimethylformamide furnished N-7, 4a and N-9, 3a , 3b alkenyl derivatives. Similar alkylation of 2-amino-6-chloropurine (2) provided the corresponding N-7, 4c-4e and N-9, 3c-3e alkenyl derivatives. Acid hydrolysis of these chloro derivatives 3a-3e, 4a,c-e furnished the corresponding alkenyl hypoxan-thines 6a, 6b and 7a or alkenyl guanines 6c-6e and 7c-7e. Treatment of 3a-3d with thiourea in absolute ethanol provided the corresponding 6-thio derivatives 5a-5d. Alkylation of the sodium salt of either purine-6-carboxamide (8) or 1,2,4-triazole-3-carboxamide (10) gave mainly one isomer 9a, 9b and 11a, 11b. The direct alkylation of pyrrolo[2,3-d]pyrimidin-4(3H)-one (12) gave N-3 alkenyl derivatives 13a, 13b , and the N-7 alkenyl derivatives 16a, 16b have been prepared starting from the 4-chloro derivative 14 . Synthesis of 2-amino-7-(2-penten-1-yl)pyrrolo[2,3-d]pyrimidin-4(3H)-one (19a) has been accomplished starting from 2-amino-4-methoxypyrrolo[2,3-d]pyrimidine (17) . These alkenyl derivatives were found to be devoid of anti-HCMV activity in vitro.     

Volumetric and viscometric study of aqueous binary mixtures of some glycol ethers at T = (275.15 and 283.15) K

The experimental data for the density (ρ) and viscosity (η) are reported for aqueous binary mixtures of different glycol ethers, namely ethylene glycol monomethyl ether (EGMME), ethylene glycol monoethyl ether (EGMEE), diethylene glycol monomethyl ether (DEGMME), and diethylene glycol monoethyl ether (DEGMEE), at different temperatures (T = 275.15 K and 283.15 K) within the concentration range 0 mol · kg⁻¹ to 0.1 mol · kg⁻¹. The values of density (ρ) and viscosity (η) of the solutions were used to compute different derived parameters, such as apparent molar volume (?_V) of the solute, excess molar volume (V^E) of the solution, viscosity B and D coefficients of solution and temperature coefficient of viscosity B-coefficient (dB/dT) of solution. The limiting apparent molar volume of the solutes () have been obtained for aqueous binary mixtures of these glycol ethers by smooth extrapolation of ?_V–m curves to zero concentration. By using the values of , the limiting excess partial molar volumes () have also been calculated. The results are interpreted in term of various interactions such as solute–solvent interactions and hydrogen bonding.     

Carboxylic acid–pyridine supramolecular heterocatemer in a co-crystal

Robustness of carboxylic acid–pyridine supramolecular heterosynthon was examined in three 1:2 binary co-crystals of 4,4′-bipyridine with monocarboxylic acids, (4,4′-bipyridine)·(dl-hydroxyphenylacetic acid)₂, 1; (4,4′-bipyridine)_0.5·(4-bromonaphthalene-1-carboxylic acid), 2 and (4,4′-bipyridine)_0.5·(4-methylbenzoic acid), 3. All the three co-crystals form “two-component supermolecules” (consisting of one molecule of 4,4′-bipyridine and two molecules of the relevant carboxylic acid) stabilized through carboxylic acid–pyridine heterosynthons. Co-crystals 1 and 2 exhibits the expected carboxylic acid–pyridine dimer (heterodimer I) whereas co-crystal 3 forms a novel carboxylic acid–pyridine catemer (heterocatemer II).     

Synthesis and bioactivities of some new 1H-pyrazole derivatives containing an aryl sulfonate moiety

A new series of 1H-pyrazole derivatives 5a-j bearing an aryl sulfonate moiety have been synthesized by a one-pot cyclo-condensation reaction of 2-(3-(dimethylamino)acryloyl)phenyl-4-methyl benzene sulfonates 4a-e and hydrazine hydrate or phenyl hydrazine in ethanol under reflux conditions.Some of the newly synthesized compounds were screened for their anti-inflammatory activity.All synthesized compounds were screened against Gram positive and Gram negative bacterial and fungal strains.The compound 5b was found to be a potent anti-inflammatory agent while the majority of the compounds were found to be active against microbial strains.     

Fluorescent uranyl ion lidded cucurbit[5]uril capsule

A novel fluorescent complex {(UO(2))(2)(CB5)}(NO(3))(4)·4HNO(3).3H(2)O (U2CB5) is obtained from cucurbit[5]uril (CB5) and uranyl nitrate under ambient temperature conditions. The crystal structure revealed that two uranyl ions are coordinated to the two open portals of CB5 giving a closed molecular capsule, which further connected through CB5 molecules to give two-dimensional frameworks. The U2CB5 complex was further investigated by NMR, FTIR and TGA techniques. The Fluorescence of uranyl ion was found to be enhanced due to complexation with cucurbituril.     

Instabilities in viscoelastic flow past a square cavity

Elastic flow transitions in viscoelastic flow past a square cavity adjacent to a channel are reported. The critical conditions for the onset of flow transitions and the qualitative and quantitative characterization of the secondary flows generated by the instability have been examined using streakline photography and instantaneous pressure measurements. Cellular type of instabilities inside the cavity is observed for flow rates beyond a critical value. Small and large scale eddies are observed at high flow rates. The flow inside the cavity and in the channel upstream and downstream of the cavity becomes weakly time-dependent for high flow rates.     

Identification of unbalance in a rotor bearing system

Model based methods for fault identification in rotating systems are gaining importance for the last three decades due to their ability to identify both location and severity of the fault. Model based methods are of different types. Among them, equivalent loads minimization method is one method. In this method, fault is identified in a rotor bearing system by minimizing difference between equivalent loads estimated in the system due to the fault and theoretical fault model loads. This method has a limitation that the error in identified fault parameters increases with decrease in number of measured vibrations. Thus a comprehensive methodology for fault identification with minimum error even in case of fewer measured vibrations is attempted in the present work. Two different approaches: equivalent loads minimization and vibration minimization method are applied for the identification of unbalance fault in a rotor system. Unbalance fault is identified using proposed methods by measuring transverse vibrations at only one location.