Concentrations and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans in soils from Korea

Soil samples were collected from Changwon and Masan Cities, Korea, and analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/DFs). Nearly all tetra- through octachlorinated PCDDs/DFs including the 17 2,3,7,8-substituted PCDDs/DFs were detected in all samples. Total concentrations of PCDDs/DFs and of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TeCDD) equivalents (TEGs) in soils ranged from 35 to 121,400 pg/g, dry weight, and from 0.2 to 3720 pg of I-TEQ/g, respectively. On the basis of guidelines for TEQ concentrations established in Germany and the United States, 9 of 23 soil samples (39% of the total samples analyzed) could not be expected to pose human health hazards. The rest of 61% of soils need measures such as investigations of source identification, soil decontamination, and/or soil removal. Total concentrations of PCDDs/DFs were greater at or near four industrial sites, which are concerned with the steel industry, petrochemical-related industry, and industrial waste incineration, than other areas. This indicates the presence of potential source areas. Soil collected from a site 50 m from an open-burning industrial waste incinerator in an industrial complex was heavily contaminated, containing a total concentration of PCDDs/DFs of 121,400 pg/g, dry weight. PCDDs/DFs were also detected in soils from the top of a 200 m mountain indicating a wide dispersal of PCDDs/DFs by atmospheric transport from point source areas. The congener pattern and relative proportions of PCDFs in soils suggest that commercial PCB preparations such as Kanechlors may be one of the sources. The wide range of PCDD/DF isomers detected in soils from many locations also suggests a multitude of sources, in addition to commercial PCBs, such as incineration of industrial wastes such as car tires, scrap wires, plastics, papers, and emission of automobile exhaust.     

Spatial and temporal distribution of polycyclic aromatic hydrocarbons in sediments from Michigan inland lakes

Concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured in sediment cores collected from 11 inland lakes in Michigan for examination of spatial and temporal trends in accumulation and sources. Concentrations of PAHs varied widely among these lakes; the highest concentrations were found in sediment collected from Cass Lake, located in an urbanized watershed. Concentrations of PAHs were correlated with watershed population density on a spatial scale. PAH concentrations have decreased over time since the 1980s in nine of the 11 lakes studied, most of which are located in suburban and rural areas. The rate of decline in PAH concentration was faster in Gratiot Lake, a remote lake with no known local sources of pollution in recent years. Concentrations of PAHs in surface sediments from Cass and Cadillac Lakes were greater than the threshold for adverse effects. Despite the wide variations in total PAH concentrations, fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, and benzo[k]fluoranthene were the major PAHs in all of the lakes studied. The proportions of individual PAHs within the total PAH concentrations have changed both temporally and spatially, suggesting a shift in the sources of PAHs in the environment. A general increase in the proportion of high-molecular-weight PAHs suggests an increase in combustion-related sources recently.     

The Marcus Gunn phenomenon: discussion and report of three cases

The Marcus Gunn phenomenon and Marin Amat syndrome (inverted Marcus Gunn phenomenon) are discussed, along with their associated features. Two patients exhibiting the Marcus Gunn phenomenon only and one patient exhibiting both the Marcus Gunn phenomenon and Marin Amat syndrome are described.     

Point and interval estimation for Gaussian distribution, based on progressively Type-II censored samples

The likelihood equations based on a progressively Type-II censored sample from a Gaussian distribution do not provide explicit solutions in any situation except the complete sample case. This paper examines numerically the bias and mean square error of the MLE, and demonstrates that the probability coverages of the pivotal quantities (for location and scale parameters) based on asymptotic s-normality are unsatisfactory, and particularly so when the effective sample size is small. Therefore, this paper suggests using unconditional simulated percentage points of these pivotal quantities for constructing s-confidence intervals. An approximation of the Gaussian hazard function is used to develop approximate estimators which are explicit and are almost as efficient as the MLE in terms of bias and mean square error; however, the probability coverages of the corresponding pivotal quantities based on asymptotic s-normality are also unsatisfactory. A wide range of sample sizes and progressive censoring schemes are used in this study.     

Optimisation of immunoaffinity purification of Wuchereria bancrofti specific antibodies from human sera

Immunoaffinity column using Setaria digitata antigens coupled to cyanogen bromide activated Sepharose 4B beads were developed to purify antibodies from sera of filarial patients. Chaotropic (KSCN) ion elution was more efficient for purifying specific antibodies from the column in comparison to ]c elution. Dot blot analysis indicated that purified antibodies showed a high degree of reactivity with cattle filarial antigen and recombinant filarial protein but not with bacterial proteins of E. coli suggesting that the antibodies are specific.     

Technical note

The primary aim of this paper is to develop models for replacement strategies using genetic algorithms. Two models have been developed, one for implementing the strategy using a discrete function to replace the items whose efficiency deteriorates with time and the other for implementing the strategy using a continuous function. The main aim is to show how genetic algorithms can be applied to these models. For the quick convergence to the optimal solution for the replacement problems, Queen Bee strategy has been adopted.     

Hydrogen-bond induced side-chain liquid crystalline polymers based on nicotinic acid derivatives

Supramolecular side-chain liquid crystalline poly(acrylate)s have been prepared by self-assembly of H-bond donor and acceptor complexes through intermolecular complementary hydrogen bond formation. Poly[4-(m-acryloyloxyalkyloxy)benzoic acid]s [m = 6 (P1) and 8 (P2)] were employed as polymer components. Liquid crystalline nicotinic acid derivatives (C1, C2, C3, and C4) were used as complementary H-bond donor/acceptor counterparts. The liquid crystalline properties of the nicotinic acid derivatives, the polymers and their complexes were investigated by DSC and POM. Methylene spacers present at the terminal position of the nicotinic acid derivatives played a key role in mesophase arrangements. The columnar phase exhibited by the nicotinic acid derivatives completely disappeared in the H-bonded complexes to afford a nematic phase, thereby substantiating the complex formation.     

Growth of PbSe Quantum Dots Within High‐Index Lead‐Phosphate Glass for Infrared Saturable Absorbers

PbSe quantum dots (QDs) were grown in high‐refractive‐index low‐melting‐temperature lead‐phosphate glass. The lowest energy exciton transition of the QDs was tuned over a wide range within the infrared spectral region (0.93–2.75 μm) by a controlled heat treatment. The measured QD radius ranged between 2 and 5.3 nm, with a time (t) dependence of t^0.29 for long dwelling times during the heat treatment, indicating that the QD growth mechanism tends to follow Lifshitz‐Slyozov‐Wagner theory. The QD saturable absorber behavior at 1.2 μm had a measured saturation fluence of ~2.1 μJ/cm².