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121.
Conductivity spectra of ionic materials with disordered structures are usually thought to consist of several parts, i.e., the DC conductivity, a power-law component, a nearly-constant-loss feature (if identified) and the (far-)infrared conductivity caused by vibrational motion. Such a decomposition may, however, easily lead to a misinterpretation of the underlying dynamics. Here, we discuss broad-band conductivity data of the supercooled glass-forming melt calcium potassium nitrate, of composition 0.4 Ca(NO(3))(2).0.6 KNO(3), often abbreviated as CKN. Data have been taken at frequencies up to the far infrared. We show that the frequency-dependent conductivity is very well reproduced by a superposition of only two components. One of them is due to vibrations, the other is caused by displacements of the mobile ions. The latter component, which does not follow a power law, is described in terms of a physical model called the MIGRATION concept. This model treatment has been found to apply in many solid electrolytes as well and is, therefore, considered to provide a "standard" formulation of the ion dynamics. The gradual transition from a correlated forward-backward ("caged") ionic motion to a stepwise translational motion may be regarded as the main feature of the MIGRATION concept. 相似文献
122.
The Thermal Instability of 2,4 and 2,6‐N‐Alkylamino‐disubstituted and 2‐N‐Alkylamino‐substituted Nitrobenzenes in Weakly Alkaline Solution: sec‐Amino Effect
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Christopher Walczak Thomas J. Payne Colin B. Wade Matthew Yonkey Melissa Scheid Alec Badour Dilip K. Mohanty 《Journal of heterocyclic chemistry》2015,52(3):681-687
We report herein the preparation of two families of secondary amines by the reactions of two equivalents of monoamines with either 2,4 or 2,6‐difluoronitrobenzenes in N,N‐dimethylacetamide in the presence of anhydrous potassium carbonate, as precursors of biologically important nitric oxide donating N‐nitrosamines. In both instances, these compounds could be prepared in quantitative yield when the reaction temperature was held below 130°C. Above this reaction temperature, an unexpected cyclization reaction between the nitro and newly formed adjacent secondary amine group leads to the formation of benzimidazole or quinoxaline rings in low yields. Reasonable reaction mechanisms for the cyclization reaction are proposed. 相似文献
123.
Susanta K. Borthakur Lakhya J. Konwar Gayatri Nath Pabitra K. Kalita Sukanya Borthakur 《Journal of heterocyclic chemistry》2020,57(12):4210-4214
Synthesis of a new series of novel [1,3,4]thiadiazolo[3,2-c][1,3,5]thiadiazine-6,6-dioxide by [4 + 2] cycloaddition reaction of 3-benzylidineamino[1,3,4]thiadiazole with sulfene generated in situ from methanesulfonyl chloride in the presence of triethylamine is described. The novel compounds thus synthesized were screened for their antifungal activity against two fungal species, namely Rhizoctonia solani and Dreschslera oryzae. Carbendazim was the standard used for the evaluation of antifungal activity. 相似文献
124.
Pseudomonas aeruginosa strain OBP1, isolated from petroleum sludge, was used to produce biosurfactant from a modified mineral salt medium with 2%
n-hexadecane as sole source of carbon. The crude biosurfactant was fractionated using TLC and HPLC. Using FTIR spectroscopy,
1H NMR, and LC-MS analyses, the chemical structure of the purified fraction of crude biosurfactant was identified as rhamnolipid
species. The LC-MS spectra show that monorhamnolipid (l-rhamnopyranosyl-β-hydroxydecanoyl-β- hydroxydecanoate, Rha-C10-C10) was produced in abundance with the predominant congener [M–H]− ions for l-rhamnopyranosyl-l-rhamnopyranosyl-3-hydroxydecanoyl-3-hydroxydecanoate (Rha-Rha-C10-C10). Seven different carbon substrates and five nitrogen sources were examined for their effect on rhamnolipid production. Using
n-hexadecane (20 g/l) as carbon substrate and urea along with (NH4)2SO4 (2 g/l each) as nitrogen source was found to be the best, with a maximum yield of 4.8 g/l. The biosurfactant reduced the
surface tension of water to 31.1 mNm−1 with a critical micelle concentration of 45 mg/l. The biosurfactant showed a better emulsifying activity against a variety
of hydrocarbon and achieved a maximum emulsion index of 82% for diesel. The purified biosurfactant showed a significant antibacterial
activity against Staphylococcus aureus at a minimum inhibitory concentration of 8 μg/ml. 相似文献
125.
126.
We report conformationally averaged VDEs (VDE(w)(n)) for different sizes of NO(3)(-)·nH(2)O clusters calculated by using uncorrelated HF, correlated hybrid density functional (B3LYP, BHHLYP) and correlated ab intio (MP2 and CCSD(T)) theory. It is observed that the VDE(w)(n) at the B3LYP/6-311++G(d,p), B3LYP/Aug-cc-Pvtz and CCSD(T)/6-311++G(d,p) levels is very close to the experimentally measured VDE. It is shown that the use of calculated results of the conformationally averaged VDE for small-sized solvated negatively-charged clusters and a microscopic theory-based general expression for the same provides a route to obtain the VDE for a wide range of cluster sizes, including bulk. 相似文献
127.
The enantioselective synthesis of passifloricin A has been achieved in high diastereomeric excess. The 1,3-polyol moiety was constructed by iterative proline-catalyzed sequential α-aminoxylation and Horner-Wadsworth-Emmons (HWE) olefination of aldehydes while the synthesis of lactone moiety was achieved by ring-closing metathesis (RCM). 相似文献
128.
New bifunctional pyrazole based ligands of the type [C(3)HR(2)N(2)CONR'] (where R = H or CH(3); R' = CH(3), C(2)H(5), or (i)C(3)H(7)) were prepared and characterized. The coordination chemistry of these ligands with uranyl nitrate and uranyl bis(dibenzoyl methanate) was studied with infrared (IR), (1)H NMR, electrospray-mass spectrometry (ES-MS), elemental analysis, and single crystal X-ray diffraction methods. The structure of compound [UO(2)(NO(3))(2)(C(3)H(3)N(2)CON{C(2)H(5)}(2))] (2) shows that the uranium(VI) ion is surrounded by one nitrogen atom and seven oxygen atoms in a hexagonal bipyramidal geometry with the ligand acting as a bidentate chelating ligand and bonds through both the carbamoyl oxygen and pyrazolyl nitrogen atoms. In the structure of [UO(2)(NO(3))(2)(H(2)O)(2)(C(5)H(7)N(2)CON {C(2)H(5)}(2))(2)], (5) the pyrazole ligand acts as a second sphere ligand and hydrogen bonds to the water molecules through carbamoyl oxygen and pyrazolyl nitrogen atoms. The structure of [UO(2)(DBM)(2)C(3)H(3)N(2)CON{C(2)H(5)}(2)] (8) (where DBM = C(6)H(5)COCHCOC(6)H(5)) shows that the pyrazole ligand acts as a monodentate ligand and bonds through the carbamoyl oxygen to the uranyl group. The ES-MS spectra of 2 and 8 show that the ligand is similarly bonded to the metal ion in solution. Ab initio quantum chemical studies show that the steric effect plays the key role in complexation behavior. 相似文献
129.
Rai DK Landin B Griffiths WJ Alvelius G Green BN 《Journal of the American Society for Mass Spectrometry》2002,13(2):187-191
An electrospray mass spectrometric approach to the identification of a human hemoglobin (Hb) variant involving a Cys residue incorporation is presented. In Hb Ta-Li (beta83Gly --> Cys), Cys83 forms inter-molecular disulfide bridges. Routine analysis of the denatured Hb showed the presence of a minor beta chain variant whose mass apparently was 1 Da less than the expected mass difference of 46 Da for a Gly --> Cys substitution. Reduction of the globin chains with dithiothreitol gave an intense monomer with the expected mass difference for the Gly --> Cys substitution. After reprocessing the original raw data from the denatured Hb and taking into account the possibility of dimer formation, a component was revealed whose mass was consistent with a disulfide linked dimer of Ta-Li beta globins. The mutation was localized to peptide betaT10 by analysis of a tryptic digest. Tandem mass spectrometry and DNA sequencing confirmed the Gly --> Cys substitution occurred at residue 83 of the beta chain. Problems encountered in identifying the components in mixtures of monomers and dimers are discussed. 相似文献
130.
Anurag Jayswal Rajnish Kumar Dilip Kumar 《Journal of Applied Mathematics and Computing》2012,39(1-2):35-51
In this paper we move forward in the study of multiobjective fractional programming problem and established sufficient optimality conditions under the assumption of (p,r)????(??,??)-invexity. Weak, strong and strict converse duality theorems are also derived for three type of dual models related to multiobjective fractional programming problem involving aforesaid invex function. 相似文献