A comparison of polycyclic aromatic hydrocarbon and petroleum hydrocarbon uptake by mussels (Perna viridis) and semi-permeable membrane devices (SPMDs) in Hong Kong coastal waters

The ability of mussels (Perna viridis) and semi-permeable membrane devices (SPMDs) to accumulate polycyclic aromatic hydrocarbons (PAHs) and petroleum hydrocarbons (PHCs) from five sites in Hong Kong's coastal waters was compared. Mussels consistently had higher levels of contaminants, but their utility was limited at one highly polluted site due to mortality. Mussels and SPMDs ranked sites differently in terms of individual contaminant levels. Although SPMDs overcome many of the disadvantages of using living organisms to measure contaminants in marine waters, they cannot be used as "mimics" due to different PAH and PHC accumulation patterns.     

Effects of reactive hydrocarbons and hydrogen peroxide on antioxidant activity in cherry leaves

One-year-old cherry trees were fumigated with propene and gas-phase hydrogen peroxide, singly and in combination, in controlled-environment chambers for an 8-week period during the summer season. A UV light source was included with the combined propene and hydrogen peroxide regime to provide a source of hydroxyl radicals and ozone, and thus all the constituents of a photochemical smog. Measurements were made of soluble protein concentration and of glutathione reductase activity in leaf extracts from two or three leaf classes in plants from each treatment regime at the end of each fumigation period. Significant increases in soluble protein concentration with respect to the controls were found in plants fumigated with propene and hydrogen peroxide. The occurrence and extent of these differences depended on the leaf class and on the timing of the fumigation period over the summer with respect to bud break. The activity of glutathione reductase was found to be significantly increased in mature lower leaves of plants which had been fumigated with hydrogen peroxide. This effect was independent of the timing of fumigation with respect to bud break. Enzyme activity was also increased in propene and in propene plus hydrogen peroxide treatments, but only when plants were fumigated early in the growth season.     

Some biologically important low molecular weight organic acids in the sediments of Loch Eil

The isolation of biologically important low molecular weight organic acids from organically enriched sediments in Loch Eil, Scotland, was carried out by extraction of pore water with acidified ethyl acetate. High concentrations of acetic acid, up to 1.8 mg g^-1 dry weight of sediment were found at Station E-24. Propionate, butyrate, valerate, lactate and traces of succinate were also found. Succinate was present in significant amounts, 42.2 g g^-1 dry weight of sediment at Station E-70, which received a higher input of organic matter than E-24. Both propionate and succinate were absent from a control station in the Lynn of Lorne where the sediment was low in carbon compared with Loch Eil. In experimental tanks, acetate levels increased as the input of organic carbon (as cellulose) was increased up to a load level of 1.5 g m^-2 day^-1. Above this, acetate decreased and succinate appeared. Succinate was not detected in low-loaded tanks. Experiments with sieved mud showed a vertical distribution of the different acids with depth. Lactate and succinate reached highest concentration in the 0 to 3 cm layer, acetate at 3 to 6 cm and propionate at 6 to 9 cm. The results are discussed in relation to the role of these acids as food sources and as indicators of biochemical pathways taking place in sediments with different carbon input levels.     

Achondrogenesis type II (Langer–Saldino) in association with jugular lymphatic obstruction sequence

The prenatal diagnosis of achondrogenesis in association with cystic hygroma is described. Ultrasound findings of severe short-limbed dwarfism, decreased vertebral ossification, and normal ossification of the calvarium were all consistent with achondrogenesis type II. Although the unusual finding of associated cystic hygroma raised the suspicion of a concurrent chromosome abnormality, the karyotype of both fetal lymphocytes and fetal fibroblasts was normal. Autopsy confirmed dilated lymphatic channels in the basal endothelial layer of the skin, cystic hygroma, and coarctation of the aorta. Although previously unreported, we suggest that the features of this case of achondrogenesis indicate an association with lymphatic stasis and jugular lymphatic obstruction sequence in this syndrome.     

Estimation of the CDF of a finite population in the presence of acalibration sample

We compare the performance of a number of estimators of the cumulative distribution function (CDF) for the following scenario: imperfect measurements are taken on an initial sample from afinite population and perfect measurements are obtained on a small calibration subset of the initial sample. The estimators we considered include two naive estimators using perfect and imperfect measurements; the ratio, difference and regression estimators for a two-phasesample; a minimum MSE estimator; Stefanski and Bay's SIMEX estimator (1996); and two proposed estimators. The proposed estimators take the form of a weighted average of perfect and imperfect measurements. They are constructed by minimizing variance among the class of weighted averages subject to an unbiasedness constraint. They differ in the manner of estimating the weight parameters. The first one uses direct sample estimates. The second one tunes the unknown parameters to an underlying normal distribution. We compare the root mean square error (RMSE) of the proposed estimator against other potential competitors through computer simulations. Our simulations show that our second estimator has the smallest RMSE among thenine compared and that the reduction in RMSE is substantial when the calibration sample is small and the error is medium or large.