Parameter Determination for Reductive Dechlorination of Chlorinated Solvents

The contamination of subsurface due to the chlorinated solvents such as tetrachlorethylene (PCE) and trichlorethylene (TCE) is one of the most difficult environmental problems to treat. Bioremediation has been shown by many researchers to be a remedial alternative for this type of contamination. Chlorinated solvents are not directly mineralized but rather are transformed by microorganisms into one or more intermediate compounds before converting into a final compound. These sequential reactions, termed “reductive dehalogenation”, consist of replacing a chlorine atom by a hydrogen atom. The pathway of degradation of PCE can be expressed by the following scheme PCE → TCE → DCE → VC → ETH, where dichloroethene (DCE), vinyl chloride (VC) and finally ETH is ethylene. Since the biotransformation rate coefficients of each intermediate compound are different, they have to be determined very precisely to establish an effective treatment operation. The sequential decay can be described by Michaelis–Menten’s kinetics, which constitutes a highly nonlinear system of ordinary differential equations (ODEs). This is very sensitive to the changes of biotransformation rate coefficients. In this study we introduce a methodology how to numerically estimate the rate coefficients for Michaelis–Menten’s equations from the knowledge of the concentrations of PCE, TCE, DCE, VC and ETH. The efficiency of the proposed method is demonstrated on some examples. Estimated biotransformation coefficients are employed to predict the concentrations of chlorinated solvents. Computations and measurements show a very good agreement.     

Novel synthesis of a unique helical quinone derivative by coupling reaction of 2-hydroxybenzo[c]phenanthrene

Oxidative coupling reaction of both 3-hydroxychrysene and 2-hydroxybenzo[c]phenanthrene by using Cu(NO₃)₂-3H₂O under atmospheric air is described. The former gave the aimed coupled biaryl derivative. However, the latter gave a further oxidized helical quinone derivative. The unique helical structure was characterized by X-ray and NMR analysis.     

An ab initio analysis of the electronic structure and harmonic frequencies of nickel porphyrin

Ab initio calculations are performed to understand the geometry, electronic structure, and vibrational frequencies of nickel porphyrin (NiP). Hartree-Fock (HF) and second-order perturbation (MP2) theories are applied with polarized basis sets. The calculated geometrical parameters are in very good agreement with the crystal structure determination. The electronic structure and bonding are analyzed in terms of complexation and correlation effects. Not unexpectedly, the HF depiction of the metal-porphyrin interaction is rather ionic while ligand σ donation is dominant at the MP2 level. Scaled HF frequencies of NiP and its isotopomers are in very good agreement with observed infrared and resonance Raman data. Received: 7 January 1997 / Accepted: 6 May 1997     

Compatible statistical interpretation of a wave packet

A compatible statistical interpretation of a wave packet is proposed. De Broglian probabilities which unite wave and particle features of quantons are evaluated for free wave packets and Jor a superposition of wave packets. The obtained expressions provide a very plausible and physically appealing explanation of coherence in apparently incoherent beams and of the characteristic modulation of the momentum distribution, found recently in neutron interferometry combined with spectral filtering. Certain conclusions about dualism and objectivity in quantum domain are also derived.     

Reinforcing effect of bi- and tri-cyclopolyprenols on ‘primitive’ membranes made of polyprenyl phosphates

Cholesterol plays the role of membrane reinforcer in eukaryotes, whereas hopanoids play the same role in bacteria. Which components could have reinforced ‘primitive’ membranes? We describe here an efficient biomimetic synthesis of bi- and tri-cyclopolyprenols and demonstrate that these compounds reinforce the membranes of polyprenyl phosphate, which we speculated as ‘primitive’ membranes.     

The lattice of subfields of a radical extension

Let x^m ? a be irreducible over F with char $\text{F?m}$ and let α be a root of x^m ? a. The purpose of this paper is to study the lattice of subfields of $\text{F(α)}\text{F}$ and to this end $\text{C(}\text{F(α)}\text{F}\text{, k)}$ is defined to be the number of subfields of F(α) of degree k over $\text{F. C(}\text{F(α)}\text{F}\text{, p}{}^{\mathrm{n}}\text{)}$ is explicitly determined for p a prime and the following structure theorem for the lattice of subfields is proved. Let N be the maximal normal subfield of F(α) over F and set n = |N : F|, then $\text{C(}\text{F(α)}\text{F}\text{, k) = C(}\text{F(α)}\text{F}\text{, (k, n)) = C(}\text{N}\text{F}\text{, (k, n))}$. The irreducible binomials x^s ? b, x^s ? c are said to be equivalent if there exist roots β^s = b, γ^s = a such that F(β) = F(γ). All the mutually inequivalent binomials which have roots in F(α) are determined. Finally these results are applied to the study of normal binomials and those irreducible binomials x^2e ? a which are normal over F (char F ≠ 2) together with their Galois groups are characterized.     

Conformational behavior of styrene–p-chlorostyrene triblock copolymers in dilute solutions. I. Composition dependence of conformational behavior

Dilute solution properties of (styrene-p-chlorostyrene) triblock copolymers in various solvents were studied over a wide range of molecular weight and composition. Viscosity and osmotic pressure results indicate that the conformational behavior of the B_mA_nB_m and A_mB_nA_m copolymers (A = styrene; B = p-chlorostyrene; m and n denote the number of units) are similar in nonselective solvents such as toluene and 2-butanone, but different in selective solvents such as carbon tetrachloride and cumene. Short-range and long-range interaction parameters of the block copolymers were determined by applying the Stockmayer–Fixman method to viscosity data and also by application of the equation relating the osmotic virial coefficient and the excluded volume. The results show that the unperturbed dimensions of the block copolymers vary linearly with composition, and long-range interaction parameters in nonselective solvents can be expressed by those of the parent homopolymers, the chemical composition, and values of the interaction parameter β_AB between styrene and p-chlorostyrene monomeric units.