Mol Center Dot Research Articles

Structural, microstructural, and thermal characterizations of a chalcopyrite concentrate from the Singhbhum shear zone, India

The structural and morphological characterizations of a chalcopyrite concentrate, collected from the Indian Copper Complex, Ghatshila, India, were carried out by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The concentrate powder was composed mainly of free chalcopyrite and low quartz in about 3:1 weight ratio. The particle size was about 100 mu m. Spectroscopic studies (FTIR, Raman, UV-visible) of the concentrate supported the XRD findings, and also revealed a marginal oxidation of the sulfide phase. The energy band gap of the sulfide was found to be 3.4 eV. Differential thermal analysis and thermogravimetry of the concentrate showed a decomposition of chalcopyrite at 658 K with an activation energy of 208 kJ center dot mol(-1), and two successive structural changes of silica at 848 K and 1145 K. (Less)

Antimicrobial Effect of Chlorine Dioxide on Vase Life of Cut Rose ‘Beast’

This study was conducted to investigate the antimicrobial effect of chlorine dioxide (ClO2) on the vase life of cut rose 'Beast' (Rosa hybrida L.). Postharvest treatments to extend the vase life of cut roses were divided into two: holding solution treatment and pulsing solution treatment. In holding solution treatment, the cut roses were treated with preservative solutions containing tap water (TW, control), distilled water (DW), ClO2 2, 4, 6, and 8 mu L center dot L-1, and compared with a commercialized antimicrobial compound of 8-HQS 200 In pulsing solution treatment, cut roses were dipped into the ClO2 solutions of 50, 100, 150, 200, and 250 mu L center dot L-1 for 60 seconds and were placed in DW. The air temperature was 18.4 degrees C, RH 51.5%, and light (photosynthetically active radiation, PAR) 3.6 mu mol center dot m(-2)center dot s(-1) with 12 hour day length. The longest vase life of cut roses was observed in the holding solution with ClO2 4 mu L center dot L-1 as 13.8 days and pulsing with 200-250 mu L center dot L-1 as 13.5-13:7 days, where vase life were extended four days longer than TW. Whereas, the inclusion of 8-HQS 200 mu L center dot L-1 in vase solution resulted in phytotoxicity. The relative fresh weight and water uptake have similar tendencies. Bacteria inhibition by ClO2 and 8-HQS were very effective. But bacteria at TW and DW treatments on cut flower with stem were detected in 3.7 x 10(5) CFU center dot L-1 and 6.3 x 10(5) CFU center dot L-1, respectively (without stem in DW 1.4 x 10(4) CFU center dot L-1). The ClO2 contents in holding solution of all treatments were scavenged in two-four days after treatment. This study indicated that ClO2 4 mu L center dot L-1 holding solution treatment and 200-250 mu L center dot L-1 pulsing solution treatment can be applied to extend the postharvest life of cut roses.

Modeling of Temperature-Programmed Desorption (TPD) Flow Experiments from Cu/ZnO/Al2O3 Catalysts

Different procedures to extract the kinetics of hydrogen desorption from a Cu/ZnO/Al2O3 catalyst for methanol synthesis were studied by performing temperature-programmed desorption experiments under atmospheric pressure. The four methods include (i) heating rate variation, (ii) analysis using a fixed pre-exponential factor, (iii) lineshape analysis and (iv) full analysis. Before extracting the parameters, transport limitations could be excluded for all experiments and a criterion for inner particle mass transfer limitations could be extended in the case of activated re-adsorption. All methods could be valid in the whole range of experiments, with only one exception for the lineshape analysis at full coverage of hydrogen. However, each method requires different input to extract physically meaningful parameters. The best modeling results were obtained when repulsive interactions of adsorbed species were accounted for. This led to a k (des) = 3.75 center dot 10(10) s(-1)center dot exp (-(75 kJ center dot mol(-1)-5.5 kJ center dot mol(-1)center dot I similar to (H) (2.6) )/RT) in good agreement with the literature. Moreover, it was found that there is no difference, when extracting the kinetic parameters from a fresh or deactivated catalyst at full coverage.

Differential and Integral Isoconversional Non‐linear Methods and Their Application to Energetic Materials. III. Non‐isothermal Decomposition Reaction Kinetics of Benzotrifuroxan

The thermal behaviour and decomposition reaction kinetics of benzotrifuroxan (BTF) were determined by TG and DSC techniques. The kinetic parameters of the exothermic decomposition reaction in a temperature programmed mode (the apparent activation energy E(a) and pre-exponential factor A) were calculated by a single non-isothermal DSC curve. The E values calculated using the Kissinger and Flynn-Wall-Ozawa equations and integral isoconversional non-linear equations were used to check the validity of activation energy by a single non-isothermal DSC curve. The results show that the kinetic model function in integral form and the values of E(a) and A of the decomposition reaction of BTF are [-1n(1-alpha)](2/3), 109.95 kJ center dot mol(-1) and 10(8.16) s(-1), respectively. The values of Delta S(not equal), Delta H(not equal) and Delta G(not equal) of this reaction are -93.15.J center dot mol(-1)center dot K(-1), 150.72 kJ center dot mol(-1) and 153.15 kJ center dot mol(-1), respectively. The critical temperature of thermal explosion of BTF is 257.33 degrees C.

Synthesis, Characterization and Thermochemistry of the Hydrated Barium Nicotinate

A new compound. barium nicotinate trihydrate, wits synthesized by the method of room temperature solid phase synthesis and ball grinder. FTIR, chemical and elemental analyses, and X-ray powder diffraction techniques were applied to characterize the structure and composition of the complex. Low-temperature heat capacities of the solid coordination compound were measured by it precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A phase transition process occurred in the temperature range of 312-332 K in the heat capacity curve, and the peak temperature, molar enthalpy and entropy of the solid-to-solid phase transition of the complex were determined to be its follows: T-trs=(327.097+/-1.082) K, Delta H-trs(m)=(16.793+/-0.084) kJ center dot mol(-1) and Delta S-trs(m) =(51.340+/- 0.164) J center dot K-1 center dot mol(-1). The experimental values of the molar heat capacities in the temperature regions of 7 8-311 K and 333-400 K were respectively fitted to two polynomial equations. The polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature of 298.15 K were calculated and tabulated at an interval of 5 K. In accordance with Hess law, it thermochemical cycle was designed, the reaction enthalpy of the solid phase reaction was determined its Delta H-t(m)0 =-(84.12+/-0.38) kJ center dot mol(-1), and the standard molar enthalpy of formation of the complex was calculated as Delta H-f(m)0 [Ba(Nic)(2) center dot 3H(2)O(s)]=-(2115.13+/-1.90) kJ center dot mol(-1) by using an isoperibol solution-reaction calorimeter.

Thermodynamic Properties of 1-Docosanol

Heat capacity c-p.m of 1-docosanol was precisely measured in the temperature range from 78 to 400 k by means of an automated adiabatic calorimeter. the dependence of heat capacity on the temperature was fitted to polynomial equations with least square method. the melting temperature, molar enthalpy, and molar entropy of fusion were determined to be 340.844 k, 85.07 kj center dot mol(-1), and 249.6 j center dot k-1 center dot mol(-1), respectively. the thermodynamic functions, [h-1-h-298.15 and [s-t-s-298.15], were derived from the thermodynamic equations in the temperature range from 80 to 400 k with an interval of 5 k. the thermostability of the compound was further investigated by dsc and tg techniques from 400 to 900 k.

Low-temperature Heat Capacities and Thermodynamic Properties of Hydrated Sodium Cupric Arsenate [NaCuAsO4· 1.5H2O(s)

Low-temperature heat capacities of the solid compound NaCuAsO4 center dot 1.5 H2O (s) were measured using a precision automated adiabatic calorimeter over a temperature range of T = 78 K to T = 390 K. A dehydration process occurred in the temperature range of T = 368-374 K. The peak temperature of the dehydration was observed to be T-D = ( 371.828 +/- 0.146) K by means of the heat-capacity measurement. The molar enthalpy and entropy of the dehydration were Delta H-D(m) = (18.571 +/- 0.142) kJ/mol and Delta S-D(m) = (49.946 +/- 0.415) J/( K center dot mol), respectively. The experimental values of heat capacities for the solid( I) and the solid-liquid mixture( 11) were respectively fitted to two polynomial equations by the least square method. The smoothed values of the molar heat capacities and the fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated at an interval of 5 K.

Synthesis and Properties of Novel Fluorinated Poly(phenylene-co-imide)s

A new class of high-performance materials, fluorinated poly(phenylene-co-imide)s, were prepared by Ni(0)-catalytic coupling of 2,5-dichlorobenzophenone with fluorinated dichlorophthalimide. The synthesized copolymers have high molecular weights ((M) over bar (W)= 5.74 x 10(4)-17.3 x 10(4) g center dot mol(-1)), and a combination of desirable properties such as high solubility in common organic solvent, film-forming ability, and excellent mechanical properties. The glass transition temperature (T(g)s) of the copolymers was readily tuned to be between 219 and 354 degrees C via systematic variation of the ratio of the two comonomers. The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 66.7-266 MPa, 2.7-13.5%, and 3.13-4.09 GPa, respectively. The oxygen permeability coefficients (P-O2) and permeability selectivity of oxygen to nitrogen (P-O2/P-N2) of these copolymer membranes were in the range of 0.78-3.01 barrer [1 barrer = 10(-10) cm(3) (STP) cm/(cm(2) center dot s center dot cmHg)] and 5.09-6.2 5, respectively. Consequently, these materials have shown promise as engineering plastics and gas-separation membrane materials.

Thermal Stability and Kinetics of Thermal Decomposition for Protionamide

The thermal stability and the kinetics of thermal decomposition of protionamide were studied by thermogravimetry. activation energy e-a of thermal decomposition of this substance was obtained to be 54.65 kj center dot mol(-1) by kissinger method and ozawa-flynn-wall method. kinetics model function and frequency factor a of protionamide were predicted with the malek method, which were f(alpha)=alpha(0.391)(1-alpha)(0.145) and ina=13.12, respectively. moreover, melting point, molar enthalpy and entropy of fusion of this compound were determined to be 414.09 k, 23.21 kj center dot mol(-1), and 56.06 j center dot mol(-1) center dot k-1, respectively.

The Cooperative Inhibition Effects of Alkaline Earth Metal Ions and EDTA on the Corrosion of Pure Aluminum in an Alkaline Solution

The cooperative effects of alkaline earth metal ions and EDTA (ethylenediamine tetraacetic acid) on the corrosion inhibition of pure aluminum in 4 mol center dot L-1 KOH solution were investigated by hydrogen collection, polarization curve and electrochemical impedance spectroscopy (EIS). It was found that aluminum exhibits minimum corrosion rate in 4 mol center dot L-1 KOH solution containing 0.02 mol center dot L-1 EDTA, saturated Ca(OH)(2) and saturated Sr(OH)(2). EDAX analysis showed that alkaline earth metal ions and EDTA have no contribution to the formation of the surface film on aluminum. Therefore the inhibition effect may be caused by the adsorption of the inhibitor on aluminum surface. This fact indicates that these two ions act as interface inhibitors rather than inter-phase ones.

Low-Temperature Heat Capacities and Standard Molar Enthalpy of Formation of the Coordination Compound Zn(Leu)SO4·1/2H2O(s) (Leu = l-α-Leucine)

Low-temperature heat capacities of the solid coordination compound Zn(Leu)SO(4)center dot 1/2H(2)O(s) were measured by a precision automated adiabatic calorimeter over the temperature range between T = 78 K and T = 371 K. The initial dehydration temperature of the coordination compound was determined to be T-D = 326.50 K by analysis of the heat-capacity curve. The experimental values of molar heat capacities were fitted to a polynomial equation of heat capacities (C-p,C-m) with the reduced temperatures (x), [x = f (T)] by least-squares method. Enthalpies of dissolution of the [ZnSO(4)center dot 7H(2)O(s) + Leu(s)] ( Delta(sol)H degrees(m,1)) and the Zn(Leu)SO(4)center dot 1/2H(2)O(s) (Delta(sol)H degrees(m,2)) in 100.00 mL of 2 mol center dot dm(-3) HCl(aq) at T = 298.15 K were determined to be Delta solH degrees(m,1) = -(85.80 +/- 0.09) kJ center dot mol(-1) and Delta solH(m,2) = (55.97 +/- 0.06) kJ center dot mol(-1) by means of a homemade isoperibol solution-reaction calorimeter. The standard molar enthalpy of formation of the compound was determined as Delta H degrees(m)(Zn(Leu)SO(4)center dot 1/2H(2)O, s, 298.15 K) = -(1999.0 +/- 0.9) kJ center dot mol(-1) from the enthalpies of dissolution and other auxiliary thermodynamic data through a Hess thermochemical cycle. Furthermore, the reliability of the Hess thermochemical cycle was verified by comparing UV/Vis spectra and the refractive indexes of solution A (from dissolution of the [ZnSO(4)center dot 7H(2)O(s) + Leu(s)] mixture in 2 mol center dot dm(-3) hydrochloric acid) and solution A' (from dissolution of the complex Zn(Leu)SO(4)center dot 1/2H(2)O(S) in 2 mol center dot dm(-3) hydrochloric acid).

Carbon Dioxide Exchange Between the Atmosphere and an Alpine Shrubland Meadow During the Growing Season on the Qinghai‐Tibetan Plateau

Abstract: In the present study, we used the eddy covariance method to measure CO2 exchange between the atmosphere and an alpine shrubland meadow ecosystem (37°36’N, 101°18’E; 3 250 m a.s.l.) on the Qinghai‐Tibetan Plateau, China, during the growing season in 2003, from 20 April to 30 September. This meadow is dominated by formations of Potentilla fruticosa L. The soil is Mol‐Cryic Cambisols. During the study period, the meadow was not grazed. The maximum rates of CO2 uptake and release derived from the diurnal course of CO2 flux were ‐9.38 and 5.02 μmol·m‐2·s‐1, respectively. The largest daily CO2 uptake was 1.7 g C·m‐2·d‐1 on 14 July, which is less than half that of an alpine Kobresia meadow ecosystem at similar latitudes. Daily CO2 uptake during the measurement period indicated that the alpine shrubland meadow ecosystem may behave as a sink of atmospheric CO2 during the growing season. The daytime CO2 uptake was correlated exponentially or linearly with the daily photo synthetic photon flux density each month. The daytime average water use efficiency of the ecosystem was 6.47 mg CO2/g H2O. The efficiency of the ecosystem increased with a decrease in vapor pressure deficit.(Managing editor: Ya‐Qin HAN)

Vitamin E attenuates myocardial oxidative stress induced by DHEA in rested and exercised rats.

Sixty-four male Sprague-Dawley rats were randomly assigned to one of eight treatment groups to determine whether vitamin E (VitE) could help protect the heart from oxidative stress induced by either dehydroepiandrosterone (DHEA) or exercise. Oxidative stress was indicated by lipid peroxidation [i.e., thiobarbituric acid-reactive substances (TBARS)] and two scavenger enzymes. VitE supplementation (250 IU VitE/kg of diet) was given to one-half of the rats. DHEA acetate (0.35 mol/kg body wt) was injected intraperitoneally to one-half of the animals while the others were injected with corn oil vehicle. All treatments lasted for 5 wk. Next, 32 rats were randomly assigned to run for 1 h on a motorized rodent treadmill at 21 m/min up a 12% grade and then were killed. The remaining rats were killed at rest. Exercise increased TBARS in heart independent of treatment (1.94 +/- 0.12 vs. 2.43 +/- 0.11 nmol/mg protein). VitE attenuated the amount of TBARS in heart when DHEA was given. DHEA significantly increased TBARS in heart. Total and selenium-dependent glutathione peroxidase activities in heart were unaffected by any treatment. DHEA increased catalase activity at rest. Exercise increased catalase activity (71.5 +/- 7.9 vs. 97.4 +/- 9.5 mu mol x min-1 x mg protein-1); however, when VitE was given, the response to exercise was attenuated (74.1 +/- 8.4 vs. 80.9 +/- 9.9 mu mol center dot min-1 x mg protein-1). These results suggest that aerobic exercise and DHEA are mild oxidative stressors on the heart and that VitE supplementation can be beneficial in attenuating these combined stressors on the heart.

A limited sampling method to estimate methotrexate pharmacokinetics in patients with rheumatoid arthritis using a Bayesian approach and the population data modeling program P-PHARM.

This paper describes a methodology to calculate methotrexate (MTX) pharmacokinetic parameters after intramuscular administration using two samples and the population parameters. Total and free MTX were measured over a 36-h period in 56 rheumatoid arthritis patients; 14 patients were studied after a two-dose scheme at 15-day intervals. The Hill equation was used to relate the free MTX to the total MTX changes in plasma concentrations, and a two-compartment open model was used to fit the total MTX plasma concentrations. A non-linear mixed effect procedure was used to estimate the population parameters and to explore the interindividual variability in relation to the following covariables: age, weight, height, haemoglobin, erythrocyte sedimentation rate, platelet count, creatinine clearance, rheumatoid factor, C-reactive protein, swelling joint count, and Ritchie's articular index. Population parameters were evaluated for 40 patients using a three-step approach. The population average parameters and the interindividual variabilities expressed as coefficients of variation (CV%) were: CL, 6.94 l center dot h-1 (20.5%); V, 34.8 l (32.2%); k12, 0.0838 h-1 (47.7%); k21, 0.0769 h-1 (61.6%); ka, 4.31 h-1 (58%); Emax, 1.12 mu mol center dot l-1 (19.7%); gamma, 0.932 (12.3%); and EC50, 2.14 mu mol center dot l-1 (27.3%). Thirty additional data sets (16 new patients and 14 patients of the previous population but treated on a separate occasion) were used to evaluate the predictive performance of the population parameters. Twelve blood samples were collected from each individual in order to calculate individual parameters using standard fitting procedures. These values were compared to the ones estimated using a Bayesian approach with population parameters as a priori information together with two samples, selected from the individual observations. The results show that the bias was not statistically different from zero and the precision of these parameters was excellent.

Role of human liver microsomal CYP2C9 in the biotransformation of lornoxicam.

The nature of the enzyme(s) catalysing the biotransformation of lornoxicam to one of its major metabolites, 5'-hydroxy-lornoxicam, has been investigated in human liver microsomes. The reaction kinetics were characterised, the affinity of lornoxicam for three major human drug metabolising cytochrome P-450 isozymes (CYP2C9, CYP2D6 and CYP3A4) was determined, and inhibition of the reaction by known substrates (diclofenac, ibuprofen, mefenamic acid, phenytoin, tolbutamide and warfarin) and the prototype inhibitor (sulphaphenazole) of CYP2C9 was investigated. Lornoxicam 5'-hydroxylation displayed single enzyme Michaelis-Menten kinetics, with a KM of 3.6 mu mol center dot l-1 and a Vmax of 2.6 nmol center dot h-1 center dot mg-1 microsomal protein. The apparent affinity of lornoxicam was high for CYP2C9, but negligible for CYP3A4 and CYP2D6. Inhibition of lornoxicam 5'-hydroxylation by CYP2C9 substrates and sulphaphenazole competitively and completely inhibited lornoxicam 5'-hydroxylation (Ki = 0.31 mu mol center dot l-1 as well as lornoxicam clearance (Ki = 0.33 mu mol center dot l-1), partial metabolic clearance (fm) = 0.95). 5'-Hydroxylation appears to be the only cytochrome P-450 catalysed metabolic reaction of lornoxicam by human liver microsomes and this major in vivo biotransformation pathway is catalysed virtually exclusively by CYP2C9.

Purification and characterization of bleomycin hydrolase, which represents a new family of cysteine proteases, from rat skin.

Bleomycin (BLM) hydrolase, which hydrolyzes the carboxyamide bond in the beta-amino-alanine moiety, was purified from newborn rat skin. The enzyme was purified 2,500-fold over the crude extract to apparent homogeneity in five steps in the presence of 2-mercaptoethanol: 45-55% ammonium sulfate fractionation, followed by chromatographies on Sephacryl S-200, DEAE-cellulofine, Phe-Superose, and Mono Q ion-exchange. The native enzyme had a molecular mass of 280 kDa according to gel filtration. The subunit molecular mass was estimated as 48 kDa by SDS-PAGE, indicating that the enzyme was comprised of six identical subunits. The amino acid sequence of its NH2-terminus was determined to be acetyl-Met-Asn-Asn-Ala-Gly-Leu-Asn-Ser-Glu-Lys-, which was not found in the amino acid sequence database. The optimum pH of the enzyme was 7.5 with pepleomycin (PLM). The Km and Vmax values were 2.1 mM and 6.8 mu mol center dot mg-1 center dot h-1 for PLM, and 1.8 mM and 7.2 mu mol center dot mg-1 center dot h-1 for BLM-A2, respectively. The enzyme activity was inhibited by iodoacetic acid, N-ethylmaleinimide (NEM), and p-chloromercuribenzoic acid (pCMB) as well as divalent cations such as Cu2+, Cd2+, Hg2+, and Zn2+. It was effectively inhibited by a cysteine protease inhibitor E-64. However, cystatins A and C did not inhibit the activity. BLM hydrolase exhibited broad aminopeptidase substrate specificity towards aminoacyl-beta-naphthylamides such as basic, neutral, and hydrophobic amino acid residues, as well as acidic residues. These results indicated that BLM hydrolase represents a new family of cysteine proteases. Western blotting and immunohistochemical analyses showed that BLM hydrolase is ubiquitous in various rat tissues but at low levels in lung and adult skin tissues, suggesting that this enzyme plays an important role in the metabolism of antibiotics.