An unusual and unexpected synthesis of 3-(2-(arylamino)thiazol-4-yl)-2H-chromen-2-ones has been observed by the reaction of ethyl 2-(chloromethyl)-2-hydroxy-2H-chromene-3-carboxylate with various arylthioureas in ethanol under mild reaction conditions with excellent yields. The ambiguity in the structure of the obtained products has been solved by recording its single-crystal X-ray analysis. This protocol has been found to be a novel approach for the preparation of title compounds via benzopyran ring opening. A systematic plausible mechanism has been proposed for the formation of the product. Also, an efficient one-pot three-component method has been demonstrated for the formation of title compounds starting from salicylaldehyde.
The average and local thermal conductivity measurements of water-based Ag-nanofluid held in polypropylene and metallic containers using transient hot-wire method revealed a new phenomenon. The local thermal conductivity of water-based Ag nanofluid measured at different locations of containers was found to depend strongly upon the metallic container, but not on the polypropylene container. Similar observations have been found in water-based NiAl nanofluid, but not in water-based Al2O3 nanofluid. In contrast, this phenomenon was not observed for ethylene glycol-based Ag nanofluid, possibly due to the insignificant charge on the container wall, which partly explains the diversity in thermal conductivity by different researchers. 相似文献
Rhodamine-6G (Rh-6G) is embedded in sol-gel glass samples which have been prepared by three different methods namely: 1) using
HCl as catalyst and glycerol as Drying Control Chemical Additive (DCCA), 2) using HCl as catalyst at 60 °C and drying at room
temperature and 3) using HCl as catalyst at 60 °C and heated at 600 °C for 3 h. Comparative studies of spectroscopic and lasing
properties of the three types of Rh-6G containing samples were carried out with the lapse of time upto 8 months. Photostability
of Rh-6G containing sol-gel samples is measured in terms of half life under Nitrogen laser pumping as number of pulses of
N2 laser necessary to reduce the dye laser intensity to 50% of the original value and value is 7500 pulses at 1.67 Hz rate.
The best performance of Rh-6G, as far as its spectroscopic and lasing properties are concerned was found in third type of
host matrices using HCl as catalyst at 60 °C and heated at 600 °C for 3 h. 相似文献
We investigate the possibility of obtaining a low scale of supersymmetry breaking within the ISS framework using a metastable vacuum. This is achieved by introducing an R symmetry preserving gravitational coupling of the ISS sector to a relatively low scale inflationary sector. We find the allowed range for the supersymmetry breaking scale, 104 GeV?μ?108 GeV, which is low enough to be amenable to gauge supersymmetry breaking mediation. This scenario is based upon a so-called hilltop inflation phase whose initial condition problem is also addressed. 相似文献
The standard molar Gibbs free energy of formation of ZnRh2O4(s) has been determined using an oxide solid-state electrochemical cell wherein calcia-stabilized zirconia (CSZ) was used
as an electrolyte. The oxide cell can be represented by: . The electromotive force was measured in the temperature range from 943.9 to 1,114.2 K. The standard molar Gibbs energy of
formation of ZnRh2O4(s) from elements in their standard state using the oxide electrochemical cell has been calculated and can be represented
by: . Standard molar heat capacity Cop,m(T) of ZnRh2O4(s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges, from 127 to
299 and 307 to 845 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can be
represented by: . The heat capacity of ZnRh2O4(s), was used along with the data obtained from the oxide electrochemical cell to calculate the standard enthalpy and entropy
of formation of the compound at 298.15 K. 相似文献
Thiosemicarbazides and their derivatives are well known for their use in biological activity and many applications in pharmaceutical
and industrial fields. The cyclization of 1-benzoyl-4-(2-nitrophenyl)-3-thiosemicarbazide (BNPTSC) in dimethylformamide (DMF)
medium furnished N-(2-nitrophenyl)-5-phenyl-1,3,4-oxadiazole-2-amine (NPPOA). The chemical structure of the above substituted 1,3,4-oxadiazole
has been assigned by IR, mass and X-ray diffraction studies. The XRD studies reveal the presence of four types of hydrogen
bonds (N–H···O, N–H···N, C–H···O, C–H···N) in the crystal packing. The crystal system was found to be orthorhombic with a
space group Pca2(1) and the unit cell dimensions are: a = 26.873(3) ?, b = 6.0827(7) ?, c = 7.8502(10) ?, α = 90°, β = 90°, γ = 90° and Z = 4. 相似文献
The effects of different operational variables on the mechanistic function of laterite in removal of fluoride have been investigated. Thermodynamic parameters such as free energy change, enthalpy, and entropy of the process, as well as the sorption isotherm, were evaluated. The extent of solute removal is determined by initial solute concentration, operational conditions, laterite dose, and solution pH. For a fixed set of experimental conditions, a model equation is developed from which the percent removal corresponding to each load of fluoride is determined. The mechanism of fluoride adsorption is governed by the zero point charge of laterite and follows a first-order rate equation. pH has a vital role influencing the surface characteristics of laterite. To simulate the flow dynamics, fluoride solution was run through a fixed bed column. The pattern of breakthrough curves for different influent fluoride concentration, pH, and column bed height was characterized. The column efficiency was tested from the bed depth-service time model. The elution of the retained fluoride was studied and the effectiveness of column operation was determined by the retention-elution cycles. 相似文献
The structure, lattice imperfection, and properties of ceramic samples La0.6 ? xNdxSr0.3Mn1.1O3-δ (x = 0–0.4) have been investigated using the X-ray diffraction, resistive, magnetic (χac, 55Mn NMR), magnetoresistive and microscopic methods. It has been shown that there is a satisfactory agreement between the concentration decrease in the lattice parameters a of the rhombohedral (x = 0, 0.1, 0.2) and cubic (x = 0.3, 0.4) perovskite structures and the average ionic radii $\bar R$ for the lattice containing anion vacancies, cation vacancies, and nanostructured clusters with Mn2+ ions in A-positions. With an increase in the neodymium concentration x, the vacancy-type imperfection increases, the cluster-type imperfection decreases, the temperatures of metal-semiconductor phase transition Tms and ferromagnetic-paramagnetic phase transition TC decrease, and the content of the ferromagnetic phase decreases. The anomalous hysteresis is associated with the appearance of unidirectional exchange anisotropy induced in a clustered perovskite structure consisting of a ferromagnetic matrix and a planar antiferromagnetic cluster coherently coupled with it. An analysis of the asymmetrically broadened 55Mn NMR spectra has revealed a high-frequency electronic double exchange (Mn3+-O2?-Mn4+) ? (Mn4+-O2?-Mn3+) and an inhomogeneity of the magnetic and charge states of manganese due to the heterogeneous environment of the manganese ions by other ions and defects. The observed changes in the resonant frequency and width of the resonance curve are caused by changes in the ratio Mn3+/Mn4+ and magnetic inhomogeneity. An increase in the neodymium concentration x leads to a decrease in the ferromagnetic phase content determined from the dependences 4πNχac(T) and the 55Mn NMR curves. The phase diagram characterizes an interrelation between the composition, the imperfection of the structure, and the transport, magnetic, and magnetoresistive properties of lanthanum neodymium manganite perovskites. It has been found that there is a correlation between the imperfection, magnetic inhomogeneity, coercive force, and magnetoresistance effect exhibited by the perovskite structure. 相似文献
Ceramic samples of lanthanum strontium manganite perovskites La0.6Sr0.2Mn1.2 ? xNixO3 ± ?? (0 ?? x ?? 0.3) have been investigated using the X-ray diffraction, magnetic (??ac), 55Mn NMR, resistive, and magnetoresistive methods. The specific features of the influence of the composition on the structure and properties of nonstoichiometric manganite perovskites have been established. It has been found that the rhombohedrally (R$\bar 3$c) distorted perovskite structure contains cation and anion vacancies, as well as nanostructured clusters with Mn2+ ions in the A-positions. The substitution of Ni3+ ions (r = 0.74 ?) for Mn3+ ions (r = 0.785 ?) leads to a decrease in the lattice parameter a, the ferromagnetic-paramagnetic phase transition temperature TC, and the metal-semiconductor phase transition temperature Tms due to the disturbance of the superexchange interactions between heterovalent manganese ions Mn3+ and Mn4+. The observed anomalous magnetic hysteresis at 77 K has been explained by the antiferromagnetic effect of the unidirectional exchange anisotropy of the ferromagnetic matrix structure on the magnetic moments of the superstoichiometric manganese Mn2+ ions located in nanostructured planar clusters. An analysis of the asymmetrically broadened 55Mn NMR spectra of the compounds has revealed a high-frequency electronic superexchange of the ions Mn3+ ? O2? ? Mn4+; a local heterogeneity of their surrounding by other ions, vacancies, and clusters; and a partial localization of Mn4+ ions. The local hyperfine interaction fields on 55Mn nuclei have been determined. The concentration dependences of the activation energy and charge hopping frequency have confirmed that the Ni ions decrease the electrical conductivity due to the weakening of the electronic superexchange Mn3+ ? O2? ? Mn4+. Two types of magnetoresistive effects have been found: one effect, which is observed near the phase transition temperatures TC and Tms, is caused by scattering at intracrystalline nanostructured heterogeneities, and the other effect, which is observed in the low-temperature range, is induced by tunneling through intercrystalline mesostructured boundaries. The phase diagram has demonstrated that there is a strong correlation between magnetic and electrical properties in rare-earth manganites. 相似文献