Determination of mass fractions of 12 elements in more common apple varieties in Iran by instrumental neutron activation analysis

In this study, the amount of 12 elements in five widespread varieties of apples (Malus pumila) used in the Arak markets in Iran (Uromieh golden apple—Maragheh golden apple—Semirom golden apple, Semirom green apple, Semirom red apple) were determined using the instrumental neutron activation analysis method. In this work, the Tehran research reactor was used as a source of thermal neutron flux. The highest concentrations of Cl, K, Mg, Na and Zn were detected in Maragheh golden apple which indicates that from the point of view of nutrition, the best cultivar of studied apples is Maragheh golden apple.

     

Nanocomposites and high-modulus fibers based on ultrahigh-molecular-weight polyethylene and silicates: Synthesis, structure, and properties

Nanocomposites based on ultrahigh-molecular-weight polyethylene and inorganic fillers—such as organomodified layered aluminosilicates, aerosil, and diatomite—are prepared via polymerization filling. The polymerization of ethylene was conducted in the suspension mode with the use of a conventional Ziegler-Natta catalyst, TiCl₄ + Al(i-Bu)₃, under mild conditions (a temperature of 30°C and a pressure of 0.1MPa). The structure and properties of the composites are studied via X-ray diffraction analysis and DSC. The polyethylene matrix features a high enthalpy, a high melting temperature (up to 143°C), a crystallinity of 70–80%, a content of the monoclinic phase of 12–15%, and a bulk density of 0.05–0.15 g/cm³; the molecular mass is (1.5–1.6) × 10⁶. High-modulus, high-strength fibers with an elastic modulus of 25–28 GPa and a strength of 0.65–0.70 GPa are prepared via direct solvent-free molding of nascent reactor powders based on ultrahigh-molecular-weight polyethylene filled (7 wt %) with aerosol or montmorillonite modified with vinyltrimethoxysilane.     

A biological process for the reclamation of flue gas desulfurization gypsum using mixed sulfate-reducing bacteria with inexpensive carbon sources

A combined chemical and biological process for the recycling of flue gas desulfurization (FGD) gypsum into calcium carbonate and elemental sulfur is demonstrated. In this process, a mixed culture of sulfate-reducing bacteria (SRB) utilizes inexpensive carbon sources, such as sewage digest or synthesis gas, to reduce FGD gypsum to hydrogen sulfide. The sulfide is then oxidized to elemental sulfur via reaction with ferric sulfate, and accumulating calcium ions are precipitated as calcium carbonate using carbon dioxide. Employing anaerobically digested municipal sewage sludge (AD-MSS) medium as a carbon source, SRBs in serum bottles demonstrated an FGD gypsum reduction rate of 8 mg/L/h (10⁹ cells)^-1. A chemostat with continuous addition of both AD-MSS media and gypsum exhibited sulfate reduction rates as high as 1.3 kg FGD gypsum/m³d. The increased biocatalyst density afforded by cell immobilization in a columnar reactor allowed a productivity of 152 mg SO₄ ^-2/Lh or 6.6 kg FGD gypsum/m³d. Both reactors demonstrated 100% conversion of sulfate, with 75–100% recovery of elemental sulfur and chemical oxygen demand utilization as high as 70%. Calcium carbonate was recovered from the reactor effluent on precipitation using carbon dioxide. It was demonstrated that SRBs may also use synthesis gas (CO, H₂, and CO₂ in the reduction of gypsum, further decreasing process costs. The formation of two marketable products—elemental sulfur and calcium carbonate—from FGD gypsum sludge, combined with the use of a low-cost carbon source and further improvements in reactor design, promises to offer an attractive alternative to the landfilling of FGD gypsum.

     

Effect of Technological Parameters of Interaction between SiF4 and CaH2 on the Nature of Filtration Combustion

Interaction of silicon tetrafluoride and calcium hydride in a metallic vertical flow-through reactor in the filtration combustion mode was studied. It was shown that the stationary course of the process requires that the reactor should be heated to 100°C, and the ignition furnace, to 150°C. If the reactor is heated to more than 110°C, and the ignition furnace, to more than 170°C, the stationary mode of the process is disrupted and the reaction front is doubled. If a porous phase of varied dispersity is charged, a standing combustion wave is formed.

     

Covering of nanometric calcite with α-cyclodextrin

In the present experiments, the monodisperse calcium carbonate nanoparticles obtained in the reactor (three-phase reaction) with rotating discs have been covered with α-cyclodextrin. Both pure CaCO₃ nanoparticle and α-cyclodextrin-coated CaCO₃ powders were deeply analysed by the use of the scanning electron microscope, the dynamic light scattering and the thermogravimetric method. The experimental data have allowed for determination of effective diameter of the obtained particles (aggregates of ca. 30 nm single crystals) and their size distribution (almost monodisperse—ca. 390 nm) as well as for distinction between α-cyclodextrin molecules present on calcite surface or free α-cyclodextrin molecules if presented in the sample. It was found that the nanometric CaCO₃ obtained in the reactor with rotating discs can be covered with a maximum of 1.15% α-cyclodextrin monolayer. The maximal coverage of the CaCO₃ calcite particles with α-cyclodextrin can be done by 24-h shaking of 50 mg nanometric calcium carbonate with 25 mg of 36.79 mM α-cyclodextrin aqueous solution.

     

A multipotential hydrolytic reactor using the yeast strainKluyveromyces marxianus

In previous publications, we described the continuous production of D-fructose from enzymatic hydrolysis of inulin with immobilized permeabiliized cells ofKluyveromyces marxianus and the increase of productivity obtained by using a mutant selected by NTG action on the wild-type strain. By improving reactor performance, it has been possible to reach 2000 g/L/d of liberated sugar from an inulin solution with the mutant strain.

In addition, it has been shown that the KF 28 mutant was an invertase and pectinase hyperproducer. These enzymatic activities are also secreted by the speciesKluyveromyces marxianus. Therefore, we investigated the possibility of using immobilized cells of this yeast as a multipotential hydrolysis reactor. A sucrose hydrolysis reactor and a pectin hydrolysis reactor were set up. It is shown here that the majority of the optimized parameters from the inulin hydrolysis reactor can be transported directly to the other reactors. However, some parameters have to be adapted, especially for pectin hydrolysis.

     

Boron-containing small rings: synthesis,properties, and application prospects

The studies published over the last 15 years on the synthesis, physicochemical properties, and application prospects of saturated and unsaturated three- and four-membered boron-containing carbocycles with one boron atom — boriranes, borirenes, boretanes, and 1,2-dihydroboretanes — are summarized and systematized. Original methods for the synthesis of boriran(en)es based on photochemical isomerization of organoboranes, double hydroboration of acetylenes with imidazol-2-ylideneboranes, and [2+1]-cycloaddition of borylenes (:B–R) to unsaturated compounds are considered. A new method for the synthesis of substituted boriranes by Cp₂TiCl₂-catalyzed cycloboration of olefins with boron halides in the presence of metallic Mg is presented. The not numerous data on the synthesis of four-membered boracyclanes (boretanes and 1,2-dihydroboretes) based on thermal isomerization of cyclopropylboranes, [2+2]-cycloaddition of methyleneboranes to nitriles, 1,1-diethoxyethylene, or alkynes, as well as transmetallation of 1,8-dilithium naphthalene and titanacyclobutenes with boron halides, are summarized.

     

Aluminum oxide-induced gas-phase ring-opening in methyl substituted <Emphasis Type="Italic">gem</Emphasis>-difluorocyclopropanes,leading to 2-fluorobuta-1,3-dienes and vinylacetylenes

A gas-phase pyrolysis of methyl-substituted gem-difluorocyclopropanes in a flow-tube reactor in the presence of Al₂O₃ at 185—250 °C gives 2-fluorobuta-1,3-dienes and vinylacetylenes.     

The Destruction of Carbon Tetrachloride Dissolved in Water in a Dielectric Barrier Discharge in Oxygen

The kinetics of decomposition of tetrachloromethane (TCM) in its aqueous solutions and the kinetics of decomposition products formation was investigated under the action of DBD at atmospheric pressure in oxygen in a falling-flow reactor. The range of initial concentrations of TCM was 25–325 μmol/l, the discharge power—2–11 W and O₂ flow rates—1–3 cm³/s. It is shown that the kinetics of the TCM decomposition can be described by the equation of pseudo-first kinetic order. The rate constant depended weakly on the discharge parameters and was?~?5 s^?1. The energy efficiency of the decomposition, depending on the parameters, was 0.1–1.3 molecules per 100 eV. When the residence time of the solution with the discharge zone is more than 1 s, it is possible to achieve almost 100% degree of TCM decomposition. It is shown that the main products of the TCM decomposition in the liquid phase are aldehydes and Cl^? ions, and in the gas phase—the molecules CO and CO₂. The results for energy efficiency are compared with the results obtained in other AOP’s processes (Fenton process, photocatalytic process, the radiation process by the action of high-energy electron flux). It is shown that the action of the DBD is more effective than the action of the above processes.

     

Dimephosphon,a new Phosphorus-Containing Medical Drug for Treatment of Acidosis: Chemistry and Technology

Abstract

Medical drug dimephosphon-dimethyl 1,l-dimethyl-3-oxobutnylphosphonate was created as a result of chemical and biological investigations of low-toxic organophosphorus compounds. This drug was selected from a number of acyclic transformation products of 1,2-oxyphospholene derivatives. A technology was worked out which is based on the Pudovik reaction and transformed into the continuous process. For this process an original continuous flow reactor has been created.     

Book Reviews

Abstract

HANDBOOK FOR ESTIMATING PHYSICOCHEMICAL PROPERTIES OF ORGANIC COMPOUNDS, by M. Reinhard and A. Drefal, 228 pages, J. Wiley, New York (1999). ISBN 0—471—172634. UK £ 210.00

THE CHEMISTRY OF POLLUTION, by G. Fellenberg, 192 pp. J. Wiley & Sons, Chichester, U.K. (1999). ISBN 0—471—980889. UK£ 24,95.

NATURAL ATTENUATION OF FUELS AND CHLORINATED SOLVENTS IN THE SUBSURFACE, by T.H. Wiedemeier, H.S. Rifai, C.J. Newell and J.T. Wilson, 617 pages, J. Wiley, New York (1999). ISBN 0—471—19749—1. UK £ 58.50

UNDERSTANDING OUR ENVIRONMENT, 3^rd, edition, edited by R.M. Harrison, 445 pages, The Royal Society of Chemistry, Cambridge (UK) (1999). ISBN 0—85404—584—8. UK£ 19.95

ENDOCRINE DISRUPTING CHEMICALS, Vol. 12 of Issues in Environmental Science and Technology, edited by R.E. Hester and R.H. Harrison, 152 pages, Royal Society of Chemistry, Cambridge (U.K.) (1999). ISBN 0—85404—255—5. UK£ 25,00

METHOD PERFORMANCE STUDIES FOR SPECIATION ANALYSIS. by P. Quevauviller, 271 pages, The Royal Society of Chemistry, Cambridge (U.K.) (1998). ISBN 0—85404—467—1. UK£ 59.50

GLOBAL AQUATIC AND ATMOSPHERIC ENVIRONMENT, by H.D. Kumar and D.P. Häder, 393 pages, Springer, Berlin (1999). ISBN 3—540—65369—4. USD 229.00

BIOACCUMULATION. New Aspects and Developments, edited by B. Beek, 284 pages, Springer, Heidelberg, 2000. ISBN 3—540—62575. USD 143.00

INTERLABORATORY STUDIES AND CERTIFIED REFERENCE MATERIALS FOR ENVIRONMENTAL ANALYSIS. The BCR approach, by Ph. Quevauviller and E.A. Maier, 558 pages, Elsevier Science, Amsterdam NL, (1999). ISBN 0—444—82389—1. USD 251.50 (Euro 224.62).     

Economic evaluation of the hydrolysis of lactose using immobilized β-galactosidase

A computer program for preliminary cost estimates of free and immobilized enzyme systems has been developed. The cost for the hydrolysis of lactose by β-galactosidase fromAspergillus oryzae has been calculated for a batch tank reactor, with free (BTRF) and immobilized (BTRI) enzymes, a continuously stirred tank reactor (CSTR) and a plug-flow tubular reactor (PFTR), considering the mass transfer behavior and deactivation of the enzyme.

Enzyme immobilization is economically feasible, compared with a system with free enzymes, despite a very high cost for the enzyme attachment. At a half-life time of 80 d, the PFTR gives the lowest cost (0.48 SEK/kg lactose), but the cost for the BTRI is just slightly higher (0.66 SEK/kg lactose) and still much lower than the BTRF (2.10 SEK/kg lactose).

     

The pyrolysis of octafluorocyclobutane—Revisited

A high-pressure, high-temperature reactor unit was developed to test batch-wise inter-conversions of hydrocarbons. A major ambiguity characterizes this reactor, as it does all similar units that have been described, determination of the time-temperature profile for the reacting mixture. Here we report on a solution to this problem—use of a “chemical thermometer,” based on the kinetics of dissociation of C₄F₈. We propose a revised set of rate constants that permit calibration of the reactor operation. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 171–177, 1998.     

Radioactive contamination of the environment as a result of uranium production: a case study at the abandoned Lincang uranium mine,Yunnan Province,China

The distribution of radioactive pollutants, such as²²²Rn, U, Th and²²⁶Ra in the air, surface waters, soils and crops around the Lincang uranium mine, Yunnan Province, China, is studied. The mechanical, geochemical and biogeochemical processes responsible for the transport and fate of the radioactive elements are discussed based on the monitoring data. The pollutants concentrations of effluents from the mine tunnels were dependent on pH and which were controlled by biochemical oxidation of sulfide in the ore/host rocks. Radon anomalies in air reached 4 km from the tailings pile depending on radon release from the site, topography and climate.²³⁸U and²²⁶Ra abnormities in stream sediments and soil were 40—90 cm deep and 790—800 m away downstream. Anomalies of radioactive contaminants of surface watercourses extended 7.5—13 km from the discharge of effluents of the site mainly depending on mechanical and chemical processes. There were about 2.86 ha rice fields and 1.59 km stream sediments contaminated. Erosion of tailings and mining debris with little or no containment or control accelerated the contamination processes.

     

Magmatism and deformation times of the Xidatan rock series,East Kunlun Mountains

The Xidatan rock series consist of mylonite, gneiss and granite. The U-Pb age shows that the granite was formed at 206 Ma, and the⁴⁰Ar/³⁹Ar ages of the biotite display that the mylonite was formed at 145 Ma when the Xidatan ductile shearzone occurred. At about 110—100 Ma, the Xidatan Fault reactivated again. As a result, the biotite and muscovite of Xidatan rock series opened their argon isotope system.

     

An effective synthesis of polynuclear tetraamines,monomers for polyheteroarylenes

An effective synthesis of polynuclear tetraamines via nucleophilic substitution of chlorine in 2-chloro-5-nitroaniline under ultrasonic irradiation followed by catalytic hydrogenation of dinitrodiaminoarenes in a flow reactor was proposed. A number of monomers, including those not described in the literature, were thus obtained. Two classes of polyheteroarylenes, namely, polynaphthoylenebenzimidazoles and polyphenylquinoxalines were synthesized by the polycyclocondensation in a supercritical carbon dioxide. Incorporation of trifluoromethyl substituents and flexible oxygen bridges into the structure of monomers allowed one to improve the solubility of the polymers. Some properties of synthesized polyheteroarylenes were investigated.

     

Thia- and Sulfonyl-Calix[4]Arene Methylphosphonous Acids: Synthesis,Structure, and Amino Acids Binding

Abstract

Thia- and sulfonyl-calix[4]arene methylphosphonous acids have been synthesized by hydrolysis of corresponding alkyl esters. Host-Guest complexation of the thiacalix[4]arene tetrakis-methylphosphonous acid with a series of 12 amino acids has been investigated by HPLC and molecular modeling methods. Stability constants of the complexes are within 530—10,140 M^?1 in water contained solution.     

Chiral Separation of Ketoprofen on a Chirobiotic T Column and Its Chiral Recognition Mechanisms

Purpose

In this study, direct separation of ketoprofen enantiomers was performed on a Chirobiotic T column.

Methods

The effects of the type and amount of the organic modifier, buffer concentration, pH value, temperature and flow rate on retention and selectivity were investigated. Experiments were carried out in the temperature range of 20–40 °C to study the effects of temperature. Thermodynamic parameters were calculated from plots of ln k or ln α versus 1/T. Molecular dynamics simulation was done to investigate interactions between ketoprofen enantiomers and the chiral selector—teicoplanin.

Results

It was observed that pH and flow rate had a large influence on resolution. Baseline separation of ketoprofen enantiomers could be achieved with low amounts of methanol, high temperature and high buffer concentrations.

Conclusions

Results from a thermodynamic study and molecular dynamics simulation show that steric hindrance effect, π–π complexation, hydrogen bonding and electrostatic forces are the main driving forces which cause chiral recognition of ketoprofen enantiomers.

     

Pair Potentials for Alumina from AB Initio Results on the Al2O3 Molecule

Abstract

We use results from an ab initio investigation by Chang et al., on energetically low-lying stationary points of the Al₂O₃ molecule to determine interionic potentials for the Al—O, O—O and Al—Al pairs. Our results are discussed in the perspective of previous studies of the condensed phases of alumina, with special regard to the structure of its molten state.