Characteristics of arsenic adsorption to sorghum biomass.

The development of efficient and economic new adsorbent materials for the removal of arsenic from groundwater is a priority in regions where human health is directly affected by elevated arsenic concentrations. Adsorption of arsenic on sorghum biomass (SB) was investigated for the removal of arsenic from aqueous solutions. Potentiometric titrations and FTIR analysis evidenced two potential binding sites associated with carboxyl and hydroxyl groups. Batch experiments were carried out to determine the equilibrium time for arsenic adsorption to SB. The effect of pH on arsenic adsorption to SB was investigated for a pH range of 2.0-10.0. A strong influence of pH was demonstrated with a maximum removal of arsenic at pH 5.0. Freundlich and Langmuir isotherms were applied to equilibrium data. The Freundlich model fitted the equilibrium data and provided evidence for site heterogeneity at the binding surface. Column experiments were performed to obtain the breakthrough curves for both non-immobilized sorghum biomass and immobilized sorghum biomass.

Rapid sequence divergence in mammalian beta-defensins by adaptive evolution.

beta-Defensin genes encode broad spectrum antimicrobial cationic peptides. We have analysed the largest murine and human clusters of these genes, which localise to mouse and human chromosome 8. Using hidden Markov models, we identified novel mouse and human beta-defensin genes. We subsequently found full-length expressed transcripts for these novel genes. Expression in the mouse was high in brain and reproductive tissues. Fourteen murine beta-defensins could be grouped into two clear sub-groups by virtue of their position and high signal sequence (exon 1 encoded) identity. In contrast, there was a very low level of sequence conservation in the exon 2 region encoding the mature antimicrobial peptide. Evolutionary analysis revealed strong evidence that following gene duplication, exon 1 and surrounding non-coding DNA show little divergence within subfamilies. The focus for rapid sequence divergence is localised in the DNA encoding the mature peptide and this is driven by accelerated positive selection. In the human we also conclude that the locus has evolved by successive rounds of duplication followed by substantial divergence involving positive selection, to produce a diverse cluster of paralogous genes prior to human-baboon divergence. This mechanism of adaptive evolution is consistent with the role of this gene family as defence against bacterial pathogens. In order to look at function of these rapidly evolving genes, we characterised one of the novel mouse beta-defensin genes. This gene deviates from the canonical six cysteine motif present in the mature functional peptide of all other beta defensins. This defensin related gene (Defr1) is most highly expressed in testis and heart and the genomic organisation is highly similar to Defb3-6. A synthetic Defr1 peptide was shown to exist as a dimer and yet displayed both antimicrobial and chemotactic activity. The antimicrobial activity of Defr1 against S. aureus, E. coli and B. cepacia was found to be reduced in raised concentration of NaCl, but its action against P. aeruginosa was independent of NaCl concentration. These data have major implications on the structure and functions of these important host defence molecules.

A novel mouse beta defensin, Defb2, which is upregulated in the airways by lipopolysaccharide.

Studies have shown that beta defensins are present in the human airways and may be relevant to the pathogenesis of cystic fibrosis lung disease. Here we report the identification of a novel mouse gene, Defb2, which shows sequence similarity to previously described mouse and human airway beta defensins. Defb2 does not appear to be expressed in the airways of untreated mice but it is upregulated in response to lipopolysaccharide. The induced expression of this gene by an inflammatory stimulus strongly suggests that this defensin contributes to host defence at the mucosal surface of the airways.

Bioaccumulation of palladium, platinum and rhodium from urban particulates and sediments by the freshwater isopod Asellus aquaticus.

The three-way catalytic converters introduced to oxidize and reduce gaseous automobile emissions represent a source of platinum group elements (PGEs), in particular platinum, palladium and rhodium, to the urban environment. Abrasion of automobile exhausts leads to an increase of the concentration of PGEs in environmental matrices such as vegetation, soil and water bodies. The bioaccumulation of Pd, Pt and Rh by the freshwater isopod Asellus aquaticus was studied in natural ecosystems and under laboratory conditions. Owing to the low concentration level (ng g(-1)) of PGEs in the animals studied. analyses were performed with a quadrupole inductively coupled plasma mass spectrometry (ICP-MS) and hafnium, copper, yttrium, rubidium, strontium and lead were monitored for spectral interference correction. Asellus aquaticus collected in an urban river showed a content (mean +/- s) of 155.4 +/- 73.4, 38.0 +/- 34.6, and 17.9 +/- 12.2 ng g(-1) (dry weight) for Pd, Pt and Rh, respectively. The exposure of Asellus aquaticus to PGE standard solutions for a period of 24h give bioaccumulation factors of Bf: 150, 85, and 7 for Pd, Pt and Rh, respectively. Exposure of Asellus aquaticus to environmental samples for different exposure periods demonstrated that PGE bioaccumulation is time dependent. and shows a higher accumulation for the materials with a higher PGE content. While all three elements have the same uptake rate for exposure to catalyst materials, for exposure to environmental materials they havc a different uptake rate which can be attributed to transformations of the PGE species in the environment.

Perceptions of communication, cohesion, and adaptability in families of adolescents with and without learning handicaps.

Adaptability, cohesion, and communication patterns were studied in 30 families of learning-handicapped adolescents and 30 families of nonhandicapped adolescents. Parent and adolescent perspectives on each of these variables were solicited. The results indicated that adolescents in each of these groups had similar perspectives on adaptability, cohesion, and communication. The parents of the learning-handicapped adolescents, however, felt that their families were less cohesive and had lower levels of communication about problems than did their offspring. When levels of communication were related to adaptability and cohesion, it was evident for both groups that the families with high reported cohesiveness had the most positive communication patterns. Additionally, adolescents rated their families higher on communication if they also perceived a greater amount of flexibility in adaptation.

Inhibition of bacterial enzyme activity and luminescence by urban river sediments.

The toxicological and ecological effects of pollutants in urban river sediments were studied. The sediments were chemically or physically fractionated, using selective extractants to separate the effects of metal and organic contaminants, and subsequently tested for the inhibition of bacterial enzyme activity and luminescence. In many cases the enzyme activity of the sediment-dwelling bacteria was inhibited by metals. The variations in inhibition were attributed to differences in sediment complexation of, rather than bacterial community tolerance to, metals. Non-polar organic compounds significantly increased the toxicity of urban river sediments, and it is proposed that polyaromatic hydrocarbons from storm-water are an important source of sediment toxicity.

Platinum uptake by the freshwater isopod Asellus aquaticus in urban rivers.

Platinum has been increasing in the environment as a result of emissions from catalytic converters. The platinum emitted is principally located in the vicinity of roads but might be transported to urban rivers through highway and urban run-off water. Platinum concentrations in the freshwater isopod Asellus aquaticus were measured for two urban rivers and a stormwater detention pond. Concentrations ranged from 0.04 to 12.4 micrograms g-1 for direct analysis and from 0.16 to 4.5 micrograms g-1 after depuration. Analyses of water, pore water and sediments indicate that platinum in urban rivers is mostly found in the sediments and these provide the major contribution of platinum to Asellus aquaticus. Exposure experiments showed the importance of platinum speciation for uptake.

Influence of complexing agents and surfactants on metal speciation analysis in road runoff.

A combination of medium exchange and sample acidification techniques is used to enable the calculation of the individual effects of complexing agents and surfactants on the deposition and stripping steps in anodic stripping voltammetry for copper, lead and cadmium in road and urban runoff. A simple acidification procedure is presented for determination of the toxic fraction.

Determination of trace element speciation and the role of speciation in aquatic toxicity.

Knowledge of trace element speciation in waters is essential to an understanding of aquatic toxicity and bioaccumulation, as well as to the partitioning of elements between water and colloidal and particulate phases. In natural waters, only very small percentages of the dissolved heavy metals, such as copper, lead cadmium or zinc, are present as free (aquo) metal ion; most of the metal is adsorbed to colloidal particles or combined in complexes. For aquatic toxicity studies, the aim of the speciation measurement is to determine the fraction of total dissolved metal (the 'toxic fraction') that will react with, and be transported across, a biological membrane such as a fish gill. In this review, a range of trace element speciation techniques is discussed and compared. A simple anodic stripping voltammetric method is recommended for the measurement of the fraction of electroactive metal in a sample, i.e. the fraction of total dissolved metal that can be deposited into a mercury electrode at the natural pH of the sample. The electroactive fraction is believed to approximate the toxic fraction. A rapid ion exchange method, suitable for field use, is proposed for the determination of the toxic fraction of copper in waters.

Sources and storm loading variations of metal species in a gullypot catchment.

The temporal variations of metal species in the outflow from a single gullypot catchment are discussed for two storms with differing hydrological characteristics, and the major contributing sources within the system are identified from an analysis of six discrete storm events. Under low flow conditions the dissolved metals are complexed by organics present in the gullypot liquor and interstitial sediment waters, and the strongly bound fraction predominates in the gullypot outflow. As the flow increases the Chelex removable fraction becomes important due to acid washing initially of road-surface sediments and subsequently of the mobilized gullypot sediments. The particulate-associated metals exhibit distinct temporal similarities to the storm hydrograph and chemograph for suspended solids with the exchangeable fraction being dominant. Hydrodynamic sorting mechanisms on the road surface produce the earlier contributions for this fraction, with later inputs, particularly for Cd and Pb, from chemical exchange processes within overturned gullypot sediment. This basal sediment also provides important inputs of the carbonate and hydrous oxide fraction for Cu and Zn as the gullypot contents become oxygenated later in the storm. The consequences of these findings are discussed in terms of gullypot maintenance and the water quality of stormwater outfalls.

Phosphorus removal in a vertical upflow constructed wetland system.

Mechanisms for P removal in a vertical upflow macrophyte system were studied in controlled laboratory columns filled with sand and planted with Phragmites australis. Substrate P removal was shown to increase with flow rate, a parameter which can be enhanced through effluent recirculation. An alternative substrate (leca, light expanded clay aggregate) provided improved equilibrium adsorption characteristics, but uncrushed and within the kinetic constraints of a macrophyte system gave no improvement for P adsorption over sand. Intermittent loading of the sand based macrophyte system permitted control of the P concentration, with lower effluent peak concentrations for increased resting interval (no P inflow). Where P loading was targeted, continuous flow provided the optimum mass removal conditions.

Perspectives of social status of learning handicapped and nonhandicapped students.

The social status of mildly learning handicapped and nonhandicapped students and their own perceptions of and their ideal preference for social status were investigated. In study 1 the social-status perspectives of handicapped vs. nonhandicapped students in a regular-class environment into which the mildly learning handicapped students had been mainstreamed was compared. Results indicated that the mildly handicapped children overestimated their social status in the direction of their ideal. In Study 2 the social-status perspectives of the same mildly learning handicapped students in two classroom settings were compared. Although these children overestimated their social status in the regular-class setting, their estimates and ideals were accurate in their special-class settings. Implications for intervention were discussed.

The social status-socioempathy relationship among mildly handicapped and nonhandicapped children: analysis of the person X environment fit.

The notion of person X environment fit was explored as a framework for understanding the relationship between the social status and socioempathy abilities of 234 nonhandicapped and 85 mildly handicapped children in special- and regular-education settings. The results revealed that the amount of discrepancy between actual and estimated social status varied according to child characteristics and the classroom placement settings in which those measurements were taken. Additionally, the person X environment fit model was found to be appropriate for describing the relationship between social status and socioempathy. That is, accurate estimators of social status were significantly more popular than underestimators or overestimators. In turn, underestimators were more popular than overestimators. The same relationships were found for estimates of rejection. The above relationships were examined for integrated and segregated classroom settings.

Family profiles of adaptability, cohesion, and communication for learning handicapped and nonhandicapped adolescents.

The family functioning of 30 nonhandicapped and 30 learning handicapped adolescents and their parents was examined. Measures of adaptability, cohesion, and communication were taken from the parent and the adolescent perspectives. Parent and adolescent perspectives on these areas of functioning were analyzed with a cluster analytic technique, which resulted in five distinct profiles of family functioning. These statistical groupings were confirmed by information gathered through participant observation from an accompanying investigation. The nature of the five clusters confirmed the existence of similar family functioning across the nonhandicapped and learning handicapped groups. Additionally, variations in reaction and adjustment to the amount of structure in the family environment by different families was documented. The importance of considering adolescent and parent perspectives separately was highlighted.

Convergent and discriminant validity of project PRIME's Guess Who?

Two forms of the Guess Who?, a peer-assessment instrument, were administered to 1,095 mildly handicapped learners and 143 teachers. Factor analysis of the student and teacher ratings yielded three factors--disruptive, bright, and dull--for both sets of data. Factor scores for the student and teacher forms were then intercorrelated in a multitrait-multimethod matrix, and the results established the convergent and discriminant validity of the instrument. The finding that teachers could provide valid estimates of student perceptions of the three traits was interpreted as promising for future research.

System-identification of mildly mentally retarded children: implications for interpreting and conducting research.

The position was taken that the system identification of EMR children is designed to find children for service delivery and is not intended to identify a population with known parameters. Variability in the system derives from several sources: teacher judgment of academic failure, teacher referral, screening of referrals, and factors related to the assessment process. Moreover, recent litigation and sociopolitical forces have compounded this variability to the point of obscuring the population parameters of EMR or mildly mentally retarded children. The implications of such variability in characteristics of mildly retarded children were discussed in terms of interpreting past research and conducting future research.

Heterogeneity of platinum group metals in airborne particles.

The emission of three of the platinum group metals (PGMs), Pd, Pt, and Rh, from automobile catalysts and into the urban environment is a potential concern for human health. The analysis of low concentrations of PGMs in air particles is an analytical challenge, and it is demonstrated that interferences in inductively coupled plasma-mass spectrometry (ICP-MS) can be corrected mathematically for Pt and Rh and, at higher concentrations, for Pd. The PM10 concentrations of PGMs in urban air collected in Göteborg are 0.1-10 pg m-3 (Pd), 0.9-19 pg m-3 (Pt), and 0.3-4 pg m-3 (Rh), with higher values for greater traffic intensity. These concentrations provide a general background for the urban atmospheric environment, and the Pt:Rh ratio (4.2:1) agrees with known automobile catalyst composition. The analysis of filters from 10 parallel samplers indicated the significant heterogeneity of PGMs in samples of urban air particles. Scanning laser ablation ICP-MS provided the micron spatial resolution required to identify individual particles. Ablation across the filter surface demonstrated the presence of relatively few particles with a high concentration of PGMs. These occasional high concentration particles, which might be overlooked in conventional air sampling with total analysis, have a high Pt:Rh ratio (12.3:1), which can be attributed to catalyst aging during vehicle operation.