Application of TLSER method in predicting the aqueous solubility and n-octanol/water partition coefficient of PCBs,PCDDs and PCDFs

The theoretical linear solvation energy relationship(TLSER) approach was adopted to predict the aqueous solubility and n -octanol/water partition coefficient of three groups of environmentally important chemicals-polychlorinated biphenyls(PCBs), polychlorinated dibenzodioxins and dibenzofurans(PCDDs and PCDFs). For each compound, five quantum parameters were calculated using AM1 semiempirical molecular orbital methods and used as structure descriptors: average molecular polarizability(α), energy of the lowest unoccupied molecular orbit( E _ LUMO ), energy of the highest occupied molecular orbit( E _ HOMO ), the most positive charge on a hydrogen atom( q _+), and the most negative atomic partial charge( q _-) in the solute molecule. Then standard independent variables in TLSER equation was extracted and two series of quantitative equations between these quantum parameters and aqueous solubility and n -octanol/water partition coefficient were obtained by stepwise multiple linear regression(MLR) method. The developed equations have both quite high accuracy and explicit meanings. And the cross-validation test illustrated the good predictive power and stability of the established models. The results showed that TLSER could be used as a promising approach in the estimation of partition and solubility properties of macromolecular chemicals, such as persistent organic pollutants.

Characteristics of NO reduction with non-thermal plasma

As a new type of NO removal system, NO reduction in N_2-NO plasma was applied to solve the difficulties in the traditional methods, such as higher energy-consumption, larger equipment size and high cost, and so on. Using the experimental NO reduction system with single-pair electrode tip discharge structure, the NO reduction characteristics of N_2-NO system were revealed to guide the engineering practice; the results of NO reduction with single-pair electrode tip discharge plasma also have the same instructive meaning to the NO reduction with multi-pair electrode tip discharge plasma. The amount of both active N atom and NO removal rate increased with the distance l_g increasing between the two electrode tips and then dropped when the distance exceeded a certain value. The NO removal rate increased while the voltage between two electrode tips or the resident time of gas flow increased. The distance is a key geometrical variable factor that can determine the intensity of electric field between two electrode tips and the resident time of gas. In this paper, the effects of the dielectric features on NO reduction using dielectric-barrier discharge plasma system were also studied. The results of NO removal rate with different dielectrics such as Al_2O_3, CaO, MgO and glass showed that the electric field intensity is different with different dielectric, because it brings different energy to particles in discharge room and thus it causes different NO removal rate.

Influence of nonionic surfactant on the solubilization and biodegradation of phenanthrene

Phenanthrene was solubilized in two different nonionic surfactants, Tween80 and Triton X-100. The bioavailability of phenanthrene to the bacteria isolated from the petroleum contaminated soils was studied based on the rotary flasks experiments. The results showed that the concentration of nonionic surfactants above the critical micelle concentration(CMC) can increase the solubility of phenanthrene in water and were innoxious to the phenanthrene-degrading bacteria; phenanthrene solubilized in the micelles of Tween80 was bioavailable and biodegradable. The research demonstrated the potential of surfactant-enhanced bioremediation of soils contaminated by hydrophobic organic compounds(HOCs).

Mechanism of NO reduction with non-thermal plasma

Non-thermal plasma has been proved to be an effective and competitive technology for removing NO in flue gas since 1970. In this paper, the NO reduction mechanism of the non-thermal plasma reaction in NO/N_2/O_2 system was investigated using the method of spectral analysis and quantum chemistry. By the establishment of NO reduction and gas discharge plasma emission spectrum measuring system, the NO reduction results, gas discharge emission spectra of NO/N_2/O_2 and pure N_2 were obtained, and then the model of molecular orbit of N_2 either in ground state or its excited state was worked out using the method of molecular orbit Ab initio in Self-Consistent Field(SCF). It was found that NO reduction in NO/N_2 gas discharge plasma was achieved mainly through a series of fast elementary reactions and the N(E6) at excited state was the base for NO reduction.

Re-Os dating of Mo-bearing black shale of the Laoyaling deposit, Tongling, Anhui Province, China

Laoyaling is a typical stratiform deposit in the Tongling district and the molybdenum orebody is hosted by black shale of the Dalong Formation of the Upper Permian system. Eight black shale samples from the Laoyaling Mo orebody were dated by Re-Os technique using ICP-MS,which give an isochron age of 234.2±7.3 Ma with an initial ^187Os/^188 Os ratio of 1.37±0.39. The apparent Re-Os age is a few million years younger than the depositional age of the Late Permian. The young isochron age may be caused by the later hydrothermal disturbance or mass fractionation during ICP-MS measurement. However, the obtained isochron age is close to the depositional age and far earlier than those of the Late Yanshanian intrusions. It suggests that the Mo ore of the Laoyaling deposit is sedimentary in origin and not related to the Late Yanshanian magmatism. Black shales of the Upper Permian are distributed widely in the Mid-Lower Yangtze region, our result is important for understanding the ore-forming processes in the region and broadens the exploration target.

ON A PROBLEM OF SUMS OF MIXED POWERS(II)

Let R b,c (n) denote the number of representations of n as the sum of one square, four cubes, one b-th power and one c-th power of natural numbers. It is shown that if b=4, 4 c 35, or b=5, 5 c 13, or b=6, 6 c 9, or b=c=7, then R b,c (n)》n 5/6+1/b+1/c for all sufficiently large n.