This study investigated thermodynamic properties of uranium–titanium alloy to determine its suitability for storage of hydrogen isotopes. The enthalpy increments of U2Ti were measured using a high temperature inverse drop calorimeter in the temperature range of 299–1,169 K. Temperature dependence of the molar enthalpy increment and molar heat capacity is expressed in the form $ H^\circ_{\text{m}} (T) - H^\circ_{\text{m}} (298.15\,{\text{K}})({\text{J }}\,{\text{mol}}^{ - 1} ) = 23.236(T/{\text{K}}) + 53.292 \times 10^{ - 3} (T/{\text{K}})^{2} - 21.294 \times 10^{5} ({\text{K}}/T) - 4523 $ and $ C^\circ_{\text{p,m}} ({\text{J}}\,{\text{K}}^{ - 1} \,{\text{g}}^{ - 1} ) = 23.236 + 10.6584 \times 10^{ - 2} (T/{\text{K}}) + 21.294 \times 10^{5} ({\text{K}}/T)^{2} (300 \le T/{\text{K}} \le 900) $, respectively. A set of self consistent thermodynamic functions such as entropy, Gibbs energy function, heat capacity, and Gibbs energy and enthalpy values for U2Ti have been computed using data obtained in this study and required data from the literature. 相似文献
Reaction of diborane1 and disiamylborane2 with cyclic allenes, resulted in the formation of a mixture of products resulting from the addition of boron at the central carbon as well as terminal carbon. Fish has reported that addition of 4, 4, 6-trimethyl-1, 3, 2-dioxaborinane to 1, 3-disubstituted allenes takes place at the central carbon atom preferentially when the hydroboration was done at 130° for 35–50 h in a sealed tube.3 The reactivity and stability of catecholborane at high temperatures which is known to provide greater stearic 相似文献
A convenient, fast, efficient, and ecofriendly synthesis of metal‐free phthalocyanines from various substituted phthalonitriles in different hydroxyalkylammonium ionic liquids in the presence of 1,8‐diazabicyclo‐[5,4,0]‐undec‐7‐ene (DBU) is reported in moderate yields. The effect of concentration of DBU and temperature on the synthesis of phthalocyanine in N‐(2‐hydroxyethyl)‐N,N‐dimethylbutylammonium bromide ionic liquid has been examined, and the ionic liquid has been recovered and reused conveniently. 相似文献
Two silylated cyclohexenes products have been prepared by using a Tsuji–Trost palladium-catalyzed cyclization. It involves the generation of a cationic π-allylic palladium complex bearing a triethylsilyl group on C-3, which cyclizes via a 6-endo-trig process to afford the cyclohexene derivatives. It is also demonstrated that the position of the silyl group on the starting allylic substrate strongly influenced the reaction. It could favor either the production of the expected cyclohexenyl ring or a diene by an elimination that occurs on the silyl-substituted C-2 π-allylic palladium complex. 相似文献
We have carried out diffusion coefficient measurements in both aqueous micelles and microemulsions using the techniques of palaeography and quasielastic light scattering (QLS) The former method involves the determination of the diffusion coefficient of an electroactive oil soluble probe at a polarizable microelectrode. For high water content microemulsions, both methods yield the same diffusion coefficients, which can be identified as the self diffusion coefficient For cetyltrimethylammonium bromide (CTAB) micelles, both methods yield the same result at the salt (NaBr) concentration at which the QLS measurements are independent of CTAB concentration. In more concentrated microemulsions, QLS data gave diffusion coefficients in agreement with polarography only for a sodium cetyl sulfate (SCS) system at 65-75 wt % water. For the SCS microemulsions at 60% water, and CTAB microemulsion at 60-75% water, the QLS data yielded rapid, nonexponential decays. However, consistent polarographic diffusion coefficients could still be obtained, By using probes of varying chain length (oil solubility), it has been demonstrated that these CTAB and SCS microemulsions containing butanol and pentanol cosurfactants respectively, are not cosolubilized systems but do contain distinct hydrophilic and hydropobic regions. 相似文献
Abstract A new spectrophotometric method is described for the determination of thallium in soil by extraction of Tl(III) with a toluene solution of N,N′-diphenylbenzamidine after acidification with 0.2–4.0 M HCl, and reaction of the extract with Crystal violet in the presence of 0.01–0.8 M HCl. The value of molar absorptivity of Tl(III)-X-CV complex (where X = Cl or Br; CV = Crystal violet) in toluene is 7.00 × 104 1 mole?1 cm?1 at the absorption maximum of 610 nm. The detection limit of the method is 20 ng ml?1. The present method is free from interference of almost metal ions commonly associated with Tl. The method has been applied for analysis of the metal to soils. 相似文献
This paper offers conditions ensuring the existence of solutions of linear boundary value problems for systems of dynamic equations on time scales. Utilizing a method of Moore–Penrose pseudo‐inverse matrices leads to an analytical form of a criterion for the existence of solutions in a relevant space and, moreover, to the construction of a family of linearly independent solutions of such problems in a general case with the number of boundary conditions (defined by a linear vector functional) not coinciding with the number of unknowns of a system of dynamic equations. As an example of an application of the presented results, the problem of bifurcation of solutions of boundary value problems for systems of dynamic equations on time scales with a small parameter is considered. 相似文献
A number of 5′-O-dicarboxylic fatty acyl monoester derivatives of 3′-azido-3′-deoxythymidine (zidovudine, AZT), 2′,3′-didehydro-2′,3′-dideoxythymidine (stavudine, d4T), and 3′-fluoro-3′-deoxythymidine (alovudine, FLT) were synthesized to improve the lipophilicity and potentially the cellular delivery of parent polar 2′,3′-dideoxynucleoside (ddN) analogs. The compounds were evaluated for their anti-HIV activity. Three different fatty acids with varying chain length of suberic acid (octanedioic acid), sebacic acid (decanedioic acid), and dodecanedioic acid were used for the conjugation with the nucleosides. The compounds were evaluated for anti-HIV activity and cytotoxicity. All dicarboxylic ester conjugates of nucleosides exhibited significantly higher anti-HIV activity than that of the corresponding parent nucleoside analogs. Among all the tested conjugates, 5′-O-suberate derivative of AZT (EC50 = 0.10 nM) was found to be the most potent compound and showed 80-fold higher anti-HIV activity than AZT without any significant toxicity (TC50 >500 nM). 相似文献
Giloy Tulsi tablet is an Ayurvedic preparation containing Tinospora cordifolia (Giloy) and Ocimum sanctum (Tulsi) and it is recommended for boosting the body’s immune response. This research work is about the marker-based standardization of this Ayurvedic preparation using high-performance thin-layer chromatography method. Standardization is based on the determination and quantification of the phytoconstituents berberine and ursolic acid present in Giloy Tulsi tablets. Separation was performed on pre-coated silica gel 60 F254 plate as the stationary phase, with chloroform‒acetone‒formic acid (6:3.5:0.5, V/V) as the mobile phase. Identification and quantification were conducted densitometrically at 330 nm. The developed method resulted in good quality peak shape and enabled high-quality resolution of biomarkers. The RF value for berberine (0.46 ± 0.02) and for ursolic acid (0.68 ± 0.02) in both reference standard and formulation were found to be comparable. The method was validated for specificity, linearity, limit of detection, limit of quantification, intra-day and inter-day precisions, accuracy, and robustness. The limit of detection values were 91 and 153 ng/band for berberine and ursolic acid, respectively. The limit of quantification values were 175 and 465 ng/band for berberine and ursolic acid, respectively. Regression analysis of the calibration data revealed a good linear relationship between peak area response and concentration in the range 200‒1000 ng/band for berberine (r2 = 0.995) and 500‒2500 ng/band for ursolic acid (r2 = 0.9968). The accuracy of the method, determined by measurement of recovery at three different levels, was in the range 98‒102% for both markers. These results are indication of reliability, reproducibility, accuracy, and precision of the method.