Thermodynamics of vaporization of gallium trichloride

The unsaturated and saturated pressures of gallium trichloride vapor were measured by the static method with membrane-gauge manometers in wide pressure (0.2–760 Torr) and temperature (313–1071 K) intervals. Scanning calorimetry was used to determine the thermodynamic characteristics of GaCl₃ fusion. The thermodynamic characteristics were obtained for sublimation, fusion, vaporization, and association in the vapor of GaCl₃ molecules. The enthalpies of formation and the absolute entropies of GaCl₃ in the liquid and gaseous phases and Ga₂Cl₆ in the gaseous phase were calculated using literature data. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1266–1269, July, 2007.     

Exploration of the potential application of plutonium isotopes in source identification of sandstorm in the atmosphere of Beijing

Plutonium (Pu) is an anthropogenic radionuclide which mainly derived from atmospheric nuclear tests in the environment. In this study, the Pu isotopes (²³⁹Pu and ²⁴⁰Pu) in aerosol samples collected during the sandstorm and non-sandstorm period were measured by accelerator mass spectrometry (AMS) and the behavior of Pu was studied. The activity concentrations of ²³⁹Pu and ²⁴⁰Pu in the aerosol samples of Beijing were ranged from 0.62 nBq/m³ to 99.6 nBq/m³ for ²³⁹Pu and 3.51 nBq/m³ to 60.23 nBq/m³ for ²⁴⁰Pu, respectively. ²³⁹Pu and ²⁴⁰Pu concentrations exhibited a remarkable seasonal variation trend, with the higher results showed in spring, and the relatively lower concentrations in winter. The observed higher concentration of ²³⁹Pu and ²⁴⁰Pu detected in sandstorm samples further indicated Pu was closely related to the occurrence of sandstorms. The global fallout characteristics of ²⁴⁰Pu/²³⁹Pu atom ratios (average 0.20, ranging from 0.16 to 0.27) in aerosol samples indicating that global fallout was the major source of Pu in the atmosphere. Using aluminum (Al) as an indicator of soil resuspension, significant positive correlation between ²³⁹Pu and Al (r² = 0.934), ²⁴⁰Pu and Al (r² = 0.525) revealed that soil resuspension was a primary source of atmospheric Pu in Beijing. These results implied that the combination of ²³⁹Pu, ²⁴⁰Pu and Al could be used as the potential tracer of sandstorm.     

Kinetics of the thermal decomposition of dinitramide

The kinetic regularities of the thermal decomposition of dinitramide in aqueous solutions of HNO₃, in anhydrous acetic acid, and in several other organic solvents were studied. The rate of the decomposition of dinitramide in aqueous HNO₃ is determined by the decomposition of mixed anhydride of dinitramide and nitric acid (N₄O₆) formed in the solution in the reversible reaction. The decomposition of the anhydride is a reason for an increase in the decomposition rates of dinitramide in solutions of HNO₃ as compared to those in solutions in H₂SO₄ and the self-acceleration of the process in concentrated aqueous solutions of dinitramide. The increase in the decomposition rate of nondissociated dinitramide compared to the decomposition rate of the N(NO₂)₂ ⁻ anion is explained by a decrease in the order of the N−NO₂ bond. The increase in the rate constant of the decomposition of the protonated form of dinitramide compared to the corresponding value for neutral molecules is due to the dehydration mechanism of the reaction. For Part 1, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 41–47, January, 1998.     

Effect of the solvent on the properties of solutions of polysulfone-polyethersulfone blends

The effect of the solvent on the properties of concentrated solutions of polysulfone-polyethersulfone blends, which can be used to produce film and fibrous materials, is studied. It is found that equiconcentrated solutions of polysulfone-polyethersulfone blends, at the same ratio of polymers in N,N-dimethylacetamide and N-methyl-2-pyrrolidone, significantly differ in structure and rheological and optical properties. Solutions in N,N-dimethylacetamide are polydisperse emulsions, while solutions in N-methyl-2-pyrrolidone are systems composed of closely sized interpenetrating fields of polysulfone and polyethersulfone solutions, in which the dispersed phase and the dispersion medium cannot be detected. The turbidity-spectrum method is used to show that, after the introduction of the second (incompatible) polymer, the average size of supramolecular particles significantly increases in N,N-dimethylacetamide and hardly changes in N-methyl-2-pyrrolidone relative to the particle sizes in solutions of the individual polymers. It is determined that these differences results from the different thermodynamic qualities of N,N-dimethylacetamide and N-methyl-2-pyrrolidone with respect to polysulfone.     

Influence of the Degree of Dehydroxylation of Kaolinite on the Properties of Aluminosilicate Glasses

The degree of dehydroxylation of kaolinite, D_TG and D_IR, respectively, is characterized by thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FTIR). The relation between DTG and DIR based on the infrared absorptions at 3600–3700, 915, 810, and 540 cm⁻¹ is established. Three regions can clearly be distinguished: the dehydroxylation region (D_TG<0.9), the metakaolinite region (0.9<D_TG<1) and the ‘spinel’ region(D_TG=1). The effect of the degree of dehydroxylation of kaolinite on the amount of reactive material is measured by the reaction enthalpy, ΔH, of the low-temperature reaction of the dehydroxylated kaolinite with a potassium silicate solution using differential scanning calorimetry (DSC). |ΔH| increases almost linearly with DTG in the dehydroxylation region. In the metakaolinite region, ΔH and thus the amount of reactive material, becomes constant. |ΔH| is sharply decreasing when metakaolinite transforms into other phases in the ‘spinel’ region. No significant differences in the reactivity of the dehydroxylates is detected with DSC. According to FTIR, the use of partially dehydroxylated kaolinite is not influencing the molecular structure of the low-temperature synthesized aluminosilicates, but residual kaolinite is retrieved as an additive. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanism of acid hydrolysis of N-acetyl-D-glucosamine

The hydrolysis kinetics of the chitin monomer, N-acetyl-D-glucosamine, in HCl, HClO₄, and H₃PO₄ was studied in relation to the acid concentration. The rate constants of N-acetyl-D-glucosamine deacetylation and D(+)-glucosamine formation in HClO₄ and H₃PO₄ were determined for the first time. The rate of the acetamide bond hydrolysis in N-acetyl-D-glucosamine depends on the concentrations of hydrogen ions and water. The nucleophilicity of the acid residues does not affect the rate of N-acetyl-D-glucosamine hydrolysis.     

Determination of traces of sulfur in titanium

Summary The sample is dissolved in hydrochloric acid, and the evolved hydrogen sulfide and sulfur dioxide are absorbed in hydrogen peroxide and sodium hydroxide solutions. After complete dissolution, the sulfur in the absorbents and that remaining in the sample solution are converted with a hydriodic acid-formic acid-red phosphorus reducing mixture to hydrogen sulfide, which is absorbed in a zinc acetate solution and determined by the photometric methylene blue method. A few ppm of sulfur in titanium is determined with an error of ± 10% within 4 to 5 hours.

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Zusammenfassung Die Probe wird in Salzsäure gelöst; Schwefelwasserstoff und Schwefeldioxid, die dabei entstehen, werden in Wasserstoffperoxid und Natronlauge absorbiert. Nach vollständiger Auflösung der Probe wird der Schwefel in den Absorptionslösungen und der in der Probelösung enthaltene Schwefel mit Hilfe eines reduzierenden Gemisches aus Jodwasserstoffsäure, Ameisensäure und rotem Phosphor zu Schwefelwasserstoff umgesetzt, der in Zinkacetat absorbiert und als Methylenblau photometrisch gemessen wird. Wenige ppm Schwefel in Titan können in 4 bis 5 Stunden auf ± 10% genau bestimmt werden.

     

A study of the process of lignification of one-year willow wood

Conclusions 1. The content of lignin in the wood ofSalix viminalis andSalix acutifolia increases with the growth of the shoots during shortened days and also in drier climatic periods.2. The monosaccharides, glucose, fructose, and arabinose take part in the synthesis of the lignin of young wood ofSalix viminalis andSalix acutifolia. The formation of lignin of one-year willow wood takes place from May to January (with a maximum in June–July). The content of methoxyl groups in it gradually rises.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 6, pp. 546–550, 1969     

Loss of Acot12 contributes to NAFLD independent of lipolysis of adipose tissue

In this study, we hypothesized that deregulation in the maintenance of the pool of coenzyme A (CoA) may play a crucial role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Specific deletion of Acot12 (Acot12^−/−), the major acyl-CoA thioesterase, induced the accumulation of acetyl-CoA and resulted in the stimulation of de novo lipogenesis (DNL) and cholesterol biosynthesis in the liver. KEGG pathway analysis suggested PPARα signaling as the most significantly enriched pathway in Acot12^−/− livers. Surprisingly, the exposure of Acot12^−/− hepatocytes to fenofibrate significantly increased the accumulation of acetyl-CoA and resulted in the stimulation of cholesterol biosynthesis and DNL. Interaction analysis, including proximity-dependent biotin identification (BioID) analysis, suggested that ACOT12 may directly interact with vacuolar protein sorting-associated protein 33A (VPS33A) and play a role in vesicle-mediated cholesterol trafficking and the process of lysosomal degradation of cholesterol in hepatocytes. In summary, in this study, we found that ACOT12 deficiency is responsible for the pathogenesis of NAFLD through the accumulation of acetyl-CoA and the stimulation of DNL and cholesterol via activation of PPARα and inhibition of cholesterol trafficking.Subject terms: Gene expression, Disease model     

Evaluation of toxicity level of the polluted eco-system for an industrial city of Pakistan

The indiscriminate discharge of untreated industrial effluents and solid wastes into the open environment poses a serious threat to the ecosystem. Gujranwala is an industrial city of Pakistan wherein a large number of different industries are situated and majority of them are not equipped with proper recycling or effluent treatment plants. Unfortunately, untreated industrial effluents are locally used for the irrigation purposes which may result in higher concentrations of toxic metals in the crops and vegetables. Therefore, prime objective of the present study was to determine concentrations of toxic metals in the polluted soils, vegetables and crops grown in the vicinity of industrial areas using neutron activation analysis technique. The results obtained showed higher values of toxic metals in the studied samples. The observed highest concentration of As (0.94 ± 0.06) in spinach, Br (69 ± 9) in turnip, Co (0.83 ± 0.01) in millet, Cr (51.7 ± 4.2) in wheat, Mn (76.2 ± 7.3) in tomato, Sb (0.5 ± 0.06) in rice, Cl (31698 ± 3921) and Se (3.4 ± 0.4) in carrot. These values are higher than those reported in the literature.     

Kinetics of the Formation of Goethite in the Presence of Sulfates and Chlorides of Monovalent Cations

The synthesis of goethite by oxidation of Fe²⁺in presence of metallic iron was undertaken in an aqueous medium containing indifferent salts such as Na₂SO₄, (NH₄)₂SO₄, NaCl, and NH₄Cl. Temperature and bubbling air rate were maintained, respectively, at 70°C and 1 L/min. The influence of anions and cations on the kinetics of each step of the process has been followed distinctly, the iron dissolution rate has been determined by the variation of the medium acidity, and the precipitation of goethite has been determined by gravimetric measurements. With respect to Cl⁻, the SO₄²⁻anion decreases the rate of the two reactions. NH₄⁺acts as an inhibitor when it is present at low concentrations and as an accelerator for higher concentrations; the limit corresponding to the change of NH₄⁺behavior depends on the nature of the counter ion. The reaction product is composed of pure goethite in the presence of sulfate salts, whereas a mixture of goethite and lepidocrocite, respectively, 60–70 and 40–30%, was observed in the presence of chloride salts.     

LC Evaluation of Intestinal Transport of Praziquantel

Praziquantel (PZQ) is a highly lipophilic drug with low aqueous solubility. Despite this, it is well absorbed from the gastrointestinal tract. In this study, a simple LC method was developed and validated, in order to monitor the concentration of PZQ in TC-199 buffer in vitro, in the rat everted gut sac absorption model. PZQ was analyzed by a reversed-phase LC method with an isocratic mobile phase containing acetonitrile and water in the proportions 45:55. The flow-rate was 1 mL min⁻¹ and PZQ was determined by measuring absorbance at 215 nm, at 25 °C. The method was found to be specific, as none of the components of TC-199 or intestinal sac artefacts interfered with the drug peak. Recovery was within acceptable statistical limits. The limit of detection was 0.54 μg mL⁻¹ and the limit of quantitation was 1.63 μg mL⁻¹. The calibration curve was found to be linear in the concentration range of 10–90 μg mL⁻¹ PZQ. The proposed method was found to be rapid and selective and hence can be applied in the monitoring of the absorption of PZQ in in vitro everted gut sac absorption studies.     

Study of hydration of two cements of different strengths

Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, M_o, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700^oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date.     

Hydrolysis of esters of certain substitutes of 1,3,5-triazine

The mechanism of hydrolysis of esters of triazine substitutes was studied. It was shown that hydrolysis of l-menthyl esters in both alkaline and acid media at 80–120° C takes place with cleavage of the bond between the oxygen and carbon of triazine. The bond between the oxygen and carbon of alcohol is broken at 180–200° C in acid medium. The kinetics of alkaline hydrolysis of triazine esters was studied, and it was established that the stability of the latter increases in relation to the influence of the substitute in triazine in the order: C₆H₅ < NHC₆H₅ < NHC₂H₅ < N(C₂H₅)₂. A number of new C-substitutes of triazine was synthesized.We thank Prof. A. I. Korolev for the proposal, and the attention he gave to this work.     

Study of radical copolymerization of aminomethylated derivatives of alkenylphenols with styrene

Aminomethylated derivatives 2-propenyl-, 2-allyl-, and 4-isopropenylphenols are studied as comonomers in free-radical copolymerization with styrene in bulk. As evidenced by NMR studies, in o-aminomethyl derivatives of alkenylphenols, stable intramolecular hydrogen bonds form between nitrogen atom of the aminomethyl fragment and hydrogen atom of the hydroxyl group; these bonds are not destroyed up to 80°C Therefore, these compounds may be involved in free-radical copolymerization with styrene in which the inhibiting effect of OH groups is avoided at a temperature of 60°C. The values of r ₁ and r ₂ are determined for two pairs of comonomers: 6-morpholinomethyl-2-propenylphenol and styrene (r ₁ = 0.20 ± 0.01 and r ₂ = 2.40 ± 0.04) and 2-allyl-6-morpholinomethylphenol and styrene (r ₁ = 0.090 ± 0.009 and r ₂ = 2.40 ± 0.04).     

Effect of the self-assembly of collagen on crystallisation of calcium carbonate in aqueous solution

In order to investigate how the self-assembly of organic matrix influences crystallisation and growth of inorganic minerals, we selected collagen as the matrix and conducted three experiments of crystallisation of CaCO₃ in different reaction systems: H₂O system, as-assembled collagen fibrils system and self-assembling of collagen system. It is found that (i) the self-assembly process of organic matrix had a remarkable effect on the morphology of inorganic minerals: CaCO₃ crystals formed in the as-assembled collagen fibrils system were global clusters and those formed in the self-assembling of collagen system appeared as interlaced networks and (ii) the organic matrix decided the polymorph of crystals: CaCO₃ crystals were calcite in the H₂O system and appeared vaterite in the collagen system. From this study, we can conclude that the self-assembly of collagen fibrils greatly affect the crystallisation and growth of CaCO₃. Such results are significant in understanding the mechanism of biomineralisation in calcified tissues in general, and useful in the synthesis of biominerals.

(a)?CaCO₃ formed in the as-assembled collagen fibrils system. (b)?CaCO₃ formed in the self-assembling of collagen monomer system.The TEM images of samples obtained in the as-assembled collagen fibrils and self-assembling of collagen monomer system, were observed, respectively. The result shows that crystals CaCO₃ formed in the as-assembled collagen fibrils system were global clusters; crystals CaCO₃ formed in the self-assembling of collagen monomer system appeared interlaced networks.     

Dependence of the thermodynamic characteristics of the complexation of alanine-18-crown-6 on the composition of water-ethanol solvent

Standard thermodynamic parameters (Δ_r G○, Δ_r H○, TΔ_r S○) for the complexation reaction of 18-crown-6 ether (18C6) with D,L-alanine (Ala) in mixed water-ethanol (H₂O-EtOH) solvents are calculated from the data of calorimetric titrations performed at T = 298.15 K. It is established that an increase in the concentration of EtOH in mixed solvent leads to a rise in stability and an increase in the exothermicity of [Ala18C6] molecular complex formation; changes in the energetics of reaction upon a change in the solvent composition are determined by changes in the solvation state of 18C6, which is typical of the reactions of molecular complex formation of 18C6 with D,L-alanine and glycine in water-organic solvents.     

Specificity of the redox photoreaction of dimers of thiadicarbocyanine dyes

The primary steps of the redox reaction of dimers of the thiadicarbocyanine dye and its 5,5′-dichloro derivative in aqueous solutions were studied in the presence of 4-nitroacetophenone, ascorbic acid, or hydroquinone. In water the dye molecules (anion, M^?) mainly exist as dimers M₂ ^2?. The laser pulse irradiation (10 ns, 532 nm) results in the population of the lowest triplet level M₂ ^2?, whose depletion occurs due to both intersystem crossing to the ground state and photoinduced transition to the highest triplet state of the dimer followed by photoionization. Photoionization at low intensities of a laser pulse proceeds via the one-quantum mechanism going to the two-quantum mechanism with an increase in the laser pulse intensity. The photooxidation of the dimer in the lowest triplet state with 4-nitroacetophenone results in the formation of unstable radical anion M₂ ^?· that spontaneously dissociates to monomer M^? and radical M^· of the dye. In the presence of electron donors (ascorbic acid, hydroquinone), the dimers in the triplet state are not photoreduced, but the electron donors reduce M₂ ^?· and M^· to the dye dimer and monomer, respectively.