Relationships between tissue concentrations of chlorinated hydrocarbons (polychlorinated biphenyls and chlorinated pesticides) and antioxidative responses of marine mussels, Perna viridis

Marine mussels, Perna viridis, were transplanted from a reference site to various polluted sites around Hong Kong. After 30 d of exposure, antioxidative responses in the gills and hepatopancreas and tissue concentrations of chlorinated hydrocarbons [polychlorinated biphenyls (PCBs) and chlorinated pesticides (CPs)] were determined for individual mussels. Glutathione S transferase (GST) and glutathione (GSH) were positively correlated with tissue PCB concentrations. Only one of the enzymatic antioxidants, glutathione peroxidase (GPx), showed significant response to tissue PCB. No significant correlation was found between tissue concentrations of chlorinated hydrocarbons and other enzymatic antioxidants (superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and NADPH DT-diaphorase (DT-d). Oxidative stress, measured as thiobarbituric acid reactive substances, was correlated with chlorinated pesticide concentrations in tissues. This study demonstrated a correlation between GST/GSH and chlorinated hydrocarbons. The apparent lack of correlation between trace organic pollutants and some of the enzymatic antioxidants may be due to the inhibitory effects caused by these chemicals. The above results suggest that more investigations are needed before these enzymes can be used as biomarkers.     

Development of passive sampling devices for bioavailable contaminants of current and emerging concern: Waitemata Harbour case study

Bioavailable contaminant concentrations are an important component in assessing environmental effects as they directly affect ecosystem health. Shellfish contaminant monitoring programmes have traditionally filled this requirement but are being phased out in some jurisdictions. Passive sampling devices (PSDs) have the potential to replace shellfish monitoring; however, there are still knowledge gaps to address before this can occur. This study assessed the suitability of three different PSDs in providing the required information to replace shellfish monitoring. PSDs were deployed at three historic mussel monitoring sites with different levels of urban influence in the Waitemata Harbour, Auckland, New Zealand. Contaminants of interest were urban heavy metals, plus current and emerging organic contaminants. PSDs provided extremely low detection limits and, for some contaminants, very strong correlations to shellfish. PSDs can currently complement shellfish in monitoring, but it is premature to make conclusions as to the suitability of PSDs in replacing shellfish monitoring until more information is available.     

Skills in Professional Geography: An Assessment of Workforce Needs and Expectations

This study compares the skills of professional geographers and the needs of employer organizations across major sectors of the U.S. workforce. Following a series of focus groups, two surveys were developed to explore: (1) the extent to which specific skills were performed by geographers in different professional positions, and (2) the value of and anticipated demand for those skills from the perspective of employers. Overall, respondents in the focus groups and both surveys emphasized the need for general skills ranging from time management and writing ability to information management and computer literacy. Employers also cited many geographic skills as being vital for enhancing the work of professionals in all types of organizations. Competency in field methods, the ability to work across disciplinary boundaries, and spatial thinking were three skill areas that characterized the work of geographic professionals irrespective of specialty.     

Magnetic activity of the spotted dwarf AP149 in the α Persei open cluster

The simultaneous photometric and spectroscopic observations of the spotted G dwarf AP149 in the young open cluster α Persei are analyzed here.We reconstruct the observed light curves with a two-starspot model by means of a light curve modeling technique,and find that the active regions shift oppositely along longitude on a time scale of one day.Combining with the observational data obtained by other groups,we discuss the evolution of spotted regions in the photosphere,and find that its starspots evolve not ...     

Boundary element method with exterior collocation in two-dimensional elastodynamic problems

In the present paper, the boundary element method with exterior collocation was applied to two-dimensional elastodynamic problems. The stability of the numerical solution was discussed and the collocation rule of source points outside the region being studied was investigated in the frequency domain by means of the computed error in the boundary displacement and the condition number of the coefficient matrix for two typical wave propagation problems. The achieved results are helpful to the practical application of this method to earthquake ground motion analysis.     

Incremental time—space finite strip method for non-linear structural vibrations

Based on an incremental Hamilton's principle a versatile and systematic computer method for analysing non-linear structural vibrations is developed in this paper. The essence of the proposed method can be regarded as an incremental harmonic balance method associated with a finite strip procedure in the time-space domain. Only linearized equations in terms of frequency increment, amplitude increments, etc. have to be formulated and solved in each incremental step. This method is applicable to highly non-linear problems and may be generalized to related non-linear periodic structural motions such as dynamic stability, flutter and some motions of a rotating body, etc. To show the effectiveness and versatility of this method, a typical time-space finite strip for beam problems is worked out and examples for a wide variety of vibration problems including free and forced vibrations, super- and sub-harmonic resonances, and complicated phenomena such as internal resonance are computed. Comparisons with previous results are also made.     

Trace metals in Hong Kong waters

Hong Kong has a population of between four and five million and is becoming increasingly industrialized. Already there are some 19,000 factories concentrated in a few densely populated areas and most of the effluent and sewage is discharged untreated into the sea. Elevated heavy metal concentrations have been recorded in the receiving waters. Lead has 160 times and cadmium 180 times the concentration found in the open ocean.     

A transient model to predict the weekly temperatures of the ventilation air in a partially wetted airway

Summary Most theoretical methods for the prediction of strata heat flow in an underground airway assume that the air temperature remains constant or that only small changes take place over the ventilated age of the airway. This assumption is clearly not correct; air temperature (especially those measured in British coal mines) display variation of up to 5° C during any one week at any one point. These variations are periodic in nature and relate to both the daily and weekly production cycle. In order to predict the transient heat flow from strata the Duhamel Theorem is used. Details of the theorem incorporating the air temperature history to calculate the surface temperature of a partially wetted airway are derived. An algorithm is presented for the calculation of surface temperatures and hence the heat flux from the rock. The algorithm is used in the computation of heat and moisture transfer rates from the rock to the ventilating air in the airway. Finally, the air temperatures at the end of the airway are predicted due to the heat flows from the strata and they are compared to the measured data supplied by British Coal, United Kingdom.