Greater Concentration (greater + concentration)

Distribution by Scientific Domains


Selected Abstracts


Presence of natural and anthropogenic organic contaminants and potential fish health impacts along two river gradients in Alberta, Canada

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2010
Ken M. Jeffries
Abstract In the current study, 28 organic contaminants were measured, many with estrogen-like activity, in water collected from 16 sites on two rivers in the South Saskatchewan River Basin, Alberta, Canada. The compounds detected included synthetic estrogens (birth control pill compounds and hormone therapy drugs) downstream of municipal wastewater effluents and natural hormones downstream of municipal wastewater effluents and in agricultural areas. Greater concentrations of cholesterol and derivatives, phytosterols, and fecal sterols were measured at the most downstream sites, which indicates cumulative inputs of such compounds in these rivers. A native minnow (longnose dace, Rhinichthys cataractae) was sampled to assess pathophysiological responses to exposure to compounds with estrogen-like activity. Hepatic vitellogenin protein was detected in at least one adult male longnose dace from 14 of 15 sites sampled for fish. Vitellogenin was negatively correlated with hepatosomatic (r,=,,0.47, p,<,0.001) and gonadosomatic (r,=,,0.44, p,<,0.003) indices, which suggests potential health impacts in male longnose dace in the South Saskatchewan River Basin. The current study demonstrates that organic contaminants, many with estrogen-like activity, are distributed over hundreds of kilometers throughout the South Saskatchewan River Basin and not just downstream of major point-sources. Therefore, many activities within these basins impact water quality in the South Saskatchewan River Basin and affect endemic longnose dace populations. Environ. Toxicol. Chem. 2010;29:2379,2387. © 2010 SETAC [source]


Spatial analysis of dental trauma in 12-year-old schoolchildren in Curitiba, Brazil

DENTAL TRAUMATOLOGY, Issue 4 2008
Simone Tetu Moysés
A geographic information system (GIS) was used, built by means of ArcView GIS 3.2 software and geographical databases of streets and districts defined within the boundaries of the city of Curitiba, provided by Curitiba's Institute of Research and Public Planning (IPPUC). The database used in the study was compiled based on an epidemiological survey undertaken in 1998 on a sample of 2126 schoolchildren 12 years old, residing in outlying urban suburbs distributed over 29 micro-areas in the city of Curitiba. The cases selected for this study were those with a history of dental trauma, thereby comprising a subsample of 327 schoolchildren. The spatial location of the schoolchildren's homes enabled the events to be visualized on a cartographic basis. The variables of gender, aetiology of the trauma and areas of substandard living conditions were included in the analysis and construction of thematic maps, thus making possible a descriptive analysis of the spatial distribution of dental trauma in the city. Intra-urban differentials were identified in the prevalence of dental trauma in 12-year-old schoolchildren in Curitiba. A greater concentration of occurrences was observed in the eastern region of the city, especially in areas of substandard living conditions. It was possible to conclude that socio-environmental and geophysical factors are associated with the determination of dental trauma in the city of Curitiba, pointing to the need for the development of public policies especially aimed at areas and populations at greater risk. [source]


CLINICAL STUDY: A comparison of exposure to carcinogens among roll-your-own and factory-made cigarette smokers

ADDICTION BIOLOGY, Issue 3 2009
Lion Shahab
ABSTRACT Consumption of roll-your-own (RYO) tobacco is rising, but little is known about its in vivo delivery of toxins relative to factory-made (FM) cigarettes. To start to address this issue, this study compared the concentrations of metabolites of recognized human carcinogens in smokers of RYO tobacco and FM cigarettes. We opportunistically recruited 127 FM and 28 RYO cigarette smokers in central London and collected saliva and urine samples. Saliva samples were assayed for cotinine while urinary samples were assayed for 1-hydroxypyrene (1-HOP) and total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), metabolic markers of polycyclic aromatic hydrocarbons and tobacco-specific N -nitrosamines, respectively. Data on socio-demographic, anthropometric and puffing characteristics were also obtained. Both unadjusted and adjusted analyses (controlling for age, sex, body mass index, puff flow, puff duration and cotinine) showed no difference in metabolic markers between RYO and FM cigarette smokers. However, significant main effects for cotinine levels and sex were observed in adjusted analyses. Greater levels of cotinine were associated with a greater concentration of both 1-HOP (B = 0.002, P = 0.037) and NNAL (B = 0.002, P < 0.001). In addition, women had significantly greater concentrations of urinary 1-HOP (B = 0.679, P = 0.004) and total NNAL metabolites (B = 0.117, P = 0.024) than men, irrespective of the type of cigarettes smoked. More research is now needed to confirm these findings and gender-specific effects in a larger, representative sample. However, results do not support the common belief that RYO cigarettes are less harmful than manufactured cigarettes. [source]


Liquid-liquid phase separation in acetone solutions of palm olein: Implications for solvent fractionation

EUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 4 2007
Kevin W. Smith
Abstract The quality of palm mid fractions (PMF) obtained by dry fractionation has increased, but the best-quality PMF for application in many confectionery fats are still produced by solvent fractionation. In the present study, liquid-liquid phase separation has been observed in acetone solutions both for pure triacylglycerols and for palm olein. The temperature at which phase separation occurs increases as the oil concentration is increased and linearly as the water content of the system is increased. The triacylglycerol compositions of the two liquid phases that form do not differ. However, the oil-rich phase is depleted with respect to the polar components. The temperature at which liquid-liquid phase separation occurs is reduced by about 0.2 and 0.4,°C per percent of free fatty acids and diacylglycerols, respectively. When oil-rich droplets appear, crystallisation occurs within them rather than in the oil-depleted phase, due to the higher oil concentration. Thus, liquid-liquid phase separation prior to crystallisation raises the nucleation temperature but may lead to a greater concentration of entrained olein in the filter cake, leading to a poorer-quality PMF. [source]


Size and phenotypic structure of microbial communities within soil profiles in relation to different playing areas on a UK golf course

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2008
M. D. Bartlett
Summary Amenity turf accounts for up to 4% of land-use in urban areas, providing key refuges for both above- and below-ground biodiversity. Golf courses occupy the largest surface area of all sports facilities; however, only a limited amount of microbial ecology has been carried out to investigate differences in the size and structure of microbial communities of the soil. The soil microbial community is a key agent in nutrient cycling and delivery of other ecosystem goods and services; however, there has been little work focused on amenity turf ecosystems in the UK. A study of soil microbial community size and structure, on the range of playing areas maintained for the game of golf at a single golf course in relation to depth through the soil profile, was carried out. Soil from different playing areas showed significant differences in the size (measured using chloroform fumigation extraction) of the microbial community (P < 0.01), with a greater concentration of microbial biomass at 0,75 mm from the surface, compared with deeper zones (P < 0.01). Principal component analysis of phospholipid fatty acid (PLFA) biomarkers indicated that the community structure was significantly different at 0,75 mm from the surface on all areas of the golf course investigated (P < 0.05, in all cases). The PLFA biomarkers consistently associated with such discrimination were 16:0 and 18:1,9 c. These findings suggest that there is a consistently larger and similarly structured microbial community associated with the surface thatch layer, commonly found in amenity turf. [source]


Formation of 2,4,D complexes on montmorillonites , an ab initio molecular dynamics study

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2007
D. Tunega
Summary Sorption of the anionic form of the pesticide 2,4,D (2,4,dichlorophenoxyacetic acid) on the surface of the clay mineral montmorillonite was investigated using a short-time ab initio molecular dynamics (MD) simulation at room temperature. Three different situations were modelled: sorption on a dry surface, on a hydrated surface and an intercalation between montmorillonite layers. In all three cases, the calcium cation compensates the excess negative charge of the montmorillonite layer and the negative charge of the 2,4,D anion. It was found that in all models with direct contact of the Ca2+ cation with the montmorillonite layer, the most stable position of Ca2+ is above the ditrigonal hole of the mineral layer. While in the case of a dry surface very stable bidentate binding is created between the 2,4,D anion and the Ca2+ cation, the formation of the monodentate complexes is preferred in all models that include water molecules. Hydrogen bonds formed between water molecules and the 2,4,D anion make a considerable contribution to the formation of the monodentate complexes. Tetrahedral substitutions in the montmorillonite layer have a significant effect on the formation of the complexes of any type. However, the MD simulations did not support the role of Ca2+ as a cation bridge in the adsorption mechanism. Calculations showed that hydrated 2,4,D···Ca2+ complexes are thermodynamically more stable than complexes in which the Ca2+ cation acts as a bridge to the surface. On the other hand, it is possible that phyllosilicates with a greater concentration of isomorphic substitutions (e.g. mica) will be able to form stable surface complexes with a cation bridge mechanism. [source]


Clubs, Spades, Diamonds and Disadvantage: the Geography of Electronic Gaming Machines in Melbourne

GEOGRAPHICAL RESEARCH, Issue 1 2001
D.C. Marshall
Opportunities to gamble, particularly on electronic gaming machines (EGMs) have been rapidly increasing in Australia during the 1990s. The increase in expenditure on gambling and the related problems have subsequently become a growing concern, particularly in relation to disadvantaged sectors of the population. Given this, the development of a geography of gambling is an important step in understanding the implications of this rapidly expanding industry. This paper addresses this issue at two distinct geographical scales in metropolitan Melbourne and considers the distribution of EGMs in relation to levels of economic well-being. Findings suggest that patterns evident at the wider Melbourne scale of greater concentration of EGMs in less advantaged regions are also reflected at a local level. These findings are related to the wider issues of accessibility to gambling facilities and problem gambling. [source]


Towards the Spatial Patterns of Sectoral Adjustments to Trade Liberalisation: The Case of NAFTA in Mexico

GROWTH AND CHANGE, Issue 4 2007
BENJAMIN FABER
ABSTRACT A recent string of "new economic geography" (NEG) models has set focus on the impacts of trade liberalisation on the intra-national distribution of economic activity. What the existing contributions have in common is a basic two-sector assumption (agriculture/manufacturing) and a resulting focus on the question of whether liberalisation leads to a greater concentration of aggregate manufacturing activity. Reconsidering these models from a multi-sectoral perspective, the aim is to allow for sectoral differences in the spatial adjustments to liberalisation. This introduces a conceptual nexus between comparative advantage (CA)-type sectoral recomposition effects of trade and NEG-type spatial adjustments. In the analysis of Mexican manufacturing location 1993,2003, incipient empirical evidence is found in favour of the hypothesis that sectors characterised by a revealed comparative advantage and/or cross-border intermediate supplies grow faster in regions with good foreign market access, whereas import competing ones gain in relative terms in regions with higher "natural protection" from poor market access. The relevancy of the proposed NEG/CA framework concerns both efficiency and equity objectives of trade adjustment policies, and opens a new perspective on the long-run effects of trade on spatial inequality. [source]


Effect of time of year on the development of immature stages of the Large Pine Weevil (Hylobius abietis L.) in stumps of Sitka spruce (Picea sitchensis Carr.) and influence of felling date on their growth, density and distribution

JOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2004
R. Moore
Abstract:, The time of year and time of felling of a commercial stand of Sitka spruce (Picea sitchensis Carr.) were both shown to influence the spatial distribution and development of the large pine weevil, Hylobius abietis (L). Stump and root systems were excavated over a 5-month period in 1997, between 18 and 27 months after felling, and all immature H. abietis removed. On a site with a 6-month spread of felling dates in 1995, mean larval weights in 1997 were higher in stumps from earlier fellings, but H. abietis numbers were higher in stumps from later fellings. This appeared to be due to the continued presence of older, heavier larvae, laid as eggs in 1995, in stumps from earlier fellings, combined with a greater concentration of oviposition having occurred in 1996 in the fresher stumps of later fellings. Pupae were first found in excavated stumps on 12 June 1997 and adults on 29 July 1997. Emergence of the ,new generation' of adult weevils commenced on 7 August 1997. On average, 25% of H. abietis adults emerged in autumn 1997, 41% in 1998 and 34% in 1999. First emergence (1997) was proportionally higher in the areas felled earlier in 1995 than those felled later that year. However, the opposite was found for third emergence (1999) where emergence was greater for stumps created later in 1995. Larger stumps contained greater densities of H. abietis. Total ,potential' emergence was estimated to be between 46400 and 170825 H. abietis/ha. However, emergence traps indicated that only 40,80% managed to complete their development and emerge successfully. It is suggested that within-season felling date may be one of the most important factors affecting larval development, distribution and abundance; as well as subsequent damage levels associated with adult feeding. Consequently, knowledge of felling date could be crucial to developing methods of integrated forest management for this major forest pest. [source]


The training needs of health care support workers: results of a study of workers and their managers

JOURNAL OF CLINICAL NURSING, Issue 12 2007
Laurence G Moseley MA
Aims and objectives., This study was designed to assess the training needs of health care support workers. In the past, opinions on the topic have been varied, but were rarely based on empirical evidence. Design and methods., The study was designed as a self-report questionnaire survey of health care support workers and their managers in six units in health and social care, using as its basis 32 descriptors from the NHS Knowledge and Skills Framework, levels 1 and 2. The achieved sample was 117, giving a 77% response rate. Results., Thirty-five per cent of respondents thought that health care support workers were ,unable' to perform six or more of the 32 descriptors used, whilst on the criterion of being ,less than able', the figure was 64%. Support workers and their managers agreed closely (rho = 0·8) on where the difficulties lay in achieving Knowledge and Skills Framework competencies. Those difficulties lay particularly in two areas: (1) biomedical/physiological knowledge and (2) data-handling. Conclusions., We concluded that the numbers in need of training were substantial and the areas of need were the two identified above. Relevance to clinical practice., The main implications for clinical practice are that (a) for those who supervise or mentor health care support workers, there should be a greater concentration on the more scientific areas of expertise and (b) a similar emphasis is needed for those who train mentors or supervisors. These implications will become more important over time as scientific knowledge about medicine and health care increases. [source]


Modeling and simulation of the formation and utilization of microbial products in aerobic granular sludge

AICHE JOURNAL, Issue 2 2010
Bing-Jie Ni
Abstract A mathematical model is established to simulate the formation of extracellular polymeric substances (EPS), soluble microbial products (SMP), and internal storage products (XSTO) in aerobic granular sludge. The sensitivity of these microbial products concentrations toward the key model parameters is analyzed. Independent experiments are conducted to find required parameter values and to test its predictive ability. The model is evaluated by using one-cycle operating experimental results of a lab-scale aerobic granule-based sequencing batch reactor (SBR) and batch experimental results. Results show that the model is able to describe the microbial product dynamics in aerobic granules and provide further insights into a granule-based SBR. The effect of the initial substrate and biomass concentrations on the formation of microbial products in aerobic granular sludge can therefore be analyzed by model simulation. A higher substrate concentration results in a greater concentration of EPS, SMP, and XSTO. An accumulation of biomass in the bioreactor leads to an increased production rate of EPS, SMP, and XSTO. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]


Osmium isotope constraints on the proportion of bolide component in Chicxulub impact melt rocks

METEORITICS & PLANETARY SCIENCE, Issue 6 2004
A. Gelinas
In this study, Re-Os isotopic analyses of impact melt breccias and lithic clasts from the Yaxcopoil-1 (Yax-1) borehole were used to determine the distribution and proportion of the bolide component in the target rocks. Because of the much greater concentration of Os in chondritic meteorites compared to the target rocks, little addition of the bolide component would be necessary to greatly perturb the Os concentration and isotopic composition of target rocks. Hence, this is a very sensitive means of examining bolide contributions to the target rocks. For the examined suite of samples, the initial 187Os/188Os ratios vary from 0.19 to 2.3. Conservative mixing calculations suggest that the bolide component comprised as much as approximately 0.1%, by mass, of some samples. Most samples, however, have negligible contributions from the bolide. No samples have Os that is dominated by the bolide component, so for this suite of samples, it is impossible to fingerprint the chemical nature of the bolide using relative abundances of siderophile elements. These results suggest that the bolide did not contribute a significant amount of material to the target rocks. This may, in turn, indicate that most of the bolide was vaporized upon impact or otherwise ejected without mixing with the melt from the target. [source]


Seasonal Homes and the Local Property Tax: Evidence from New York State

AMERICAN JOURNAL OF ECONOMICS AND SOCIOLOGY, Issue 2 2009
Lester Hadsell
This study examines the growth of seasonal (i.e., second or vacation) homes and their impact on local property tax rates using evidence from towns and villages in New York State between 1990 and 2000. We find that a greater concentration of seasonal homes in a municipality is associated with a lower effective property tax rate in towns, and a higher rate in small and rural villages. An alternative measure of tax burden, property taxes as a percentage of median household income, is not related to the presence of seasonal homes in towns but is positively related in small and rural villages. Our findings for towns contradict the findings of an earlier study by Fritz (1982) that found that an increase in town property allocated to vacation homes was significantly associated with an increasing property tax rate, although our findings for villages supports his findings. [source]


The American People in Crisis: A Content Analysis

POLITICAL PSYCHOLOGY, Issue 3 2002
Roderick P. Hart
This study examines how images of the American electorate were deployed after the 11 September 2001 terrorism incident and during the Clinton impeachment. Transcripts of congressional proceedings, news coverage, and presidential campaign addresses were analyzed to determine how the phrase the American people was used during these two crises and in unrelated presidential campaign speeches. The analysis considered the roles, actions, qualities, and circumstances ascribed to the people, as well as the time orientation and the forces aligned against the people. The results show that (1) relative to presidential campaign rhetoric, both crises resulted in greater concentration on the electorate; (2) the crises differed from one another as well, with the impeachment texts featuring a contentious electorate and the 11 September texts identifying the people's psychological strengths and anxieties; and (3) both crises were also affected by exogenous factors,partisanship in the case of impeachment, and the passage of time for the terrorism incident. [source]


Affiliation, integration, and information: ownership incentives and industry structure

THE JOURNAL OF INDUSTRIAL ECONOMICS, Issue 2 2004
Thomas N. Hubbard
This paper presents theory and evidence on horizontal industry structure. At issue is the question: what makes industries necessarily fragmented? The theoretical model examines trade-offs associated with affiliation and integration, and how they are affected by the contracting environment. I show how contractual incompleteness can lead industries to be necessarily fragmented. I also show that contractual improvements will tend to lead to a greater concentration of brands, but whether they lead industries to be more or less concentrated depends on what becomes contractible. I then discuss the propositions generated by the model through a series of case study examples. [source]


Discriminatory Dealing with Downstream Competitors: Evidence from the Cellular Industry

THE JOURNAL OF INDUSTRIAL ECONOMICS, Issue 3 2000
David Reiffen
One concern about regulated monopolies entering unregulated vertically-related markets is that they will discriminate against competitors of their unregulated affiliates. However, prohibiting regulated monopolies from offering related goods may preclude production by the most efficient provider. We take advantage of variation across geographic cellular phone markets in the US to examine the effect of integration on output, quality and prices. We find some evidence consistent with efficiencies (greater concentration of lines to users is associated with greater output and higher quality) and some consistent with discrimination (greater interconnection facility ownership concentration is associated with lower output and quality). [source]


Concentration Gradient Along the Scala Tympani After Local Application of Gentamicin to the Round Window Membrane,

THE LARYNGOSCOPE, Issue 7 2007
Stefan K. Plontke MD
Abstract Objectives: The distribution of gentamicin along the fluid spaces of the cochlea after local applications has never previously been demonstrated. Computer simulations have predicted that significant basal-apical concentration gradients might be expected, and histologic studies indicate that hair cell damage is greater at the base than at the apex after local gentamicin application. In the present study, gradients of gentamicin along the cochlea were measured. Methods: A recently developed method of sampling perilymph from the cochlear apex of guinea pigs was used in which the samples represent fluid originating from different regions along the scala tympani. Gentamicin concentration was determined in sequential apical samples that were taken after up to 3 hours of local application to the round window niche. Results: Substantial gradients of gentamicin along the length of the scala tympani were demonstrated and quantified, averaging more than 4,000 times greater concentration at the base compared with the apex at the time of sampling. Peak concentrations and gradients for gentamicin varied considerably between animals, likely resulting from variations in round window membrane permeability and rates of perilymph flow. Conclusions: The large gradients for gentamicin demonstrated here in guinea pigs account for how it is possible to suppress vestibular function in some patients with a local application of gentamicin without damaging auditory function. Variations in round window membrane permeability and in perilymph flow could account for why hearing losses are observed in some patients. [source]


Constitutional Change: A Note by the Bedside

THE POLITICAL QUARTERLY, Issue 2 2005
RICHARD WILSON
The British constitution is undergoing major change although it tends to be carried out piecemeal and is often ignored. There are contradictory trends in what is happening. Some changes are deliberate major reforms which tend to disperse power and strengthen the rights of the individual against the State. Other changes are incidental by-products of other government policies, and tend in the other direction, towards the greater concentration of power in, and within, central government, for instance by the weakening of local government and the treatment of individual rights in legislation against terrorism. This second trend makes it all the more important that the checks and balances on the exercise of power by central government are effective. The main responsibility for ensuring this must rest with Parliament, backed up by the courts. A Civil Service Bill and perhaps a code of governance for central government would in their different ways be useful. [source]


The influence of body weight on response to ovulation induction with gonadotrophins in 335 women with World Health Organization group II anovulatory infertility

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 10 2006
AH Balen
Objective, To assess the influence of body weight on the outcome of ovulation induction in women with World Health Organization (WHO) group II anovulatory infertility. Design, The combined results of two studies in which either a highly purified urinary follicle-stimulating hormone or highly purified urinary menotrophin were compared with recombinant follicle-stimulating hormone. Setting, Thirty-six fertility clinics. Population, A total of 335 women with WHO group II anovulatory infertility failing to ovulate or conceive on clomifene citrate. Methods, Ovarian stimulation using a low-dose step-up protocol. Main outcome measures, The effects of body weight on ovarian response, ovulation rate and pregnancy rate after one treatment cycle. Results, With increasing body mass index (BMI), a higher threshold dose of gonadotrophins was required and there were more days of stimulation; yet, despite a greater concentration of antral follicles, there were fewer intermediate and large follicles. There was no difference in the rates of ovulation and clinical pregnancy in relation to body weight. Conclusions, Body weight affects gonadotrophin requirements but not overall outcome of ovulation induction in women with anovulatory polycystic ovary syndrome and a BMI of less than 35 kg/m2. [source]


Uncoupling of oxidative phosphorylation enables Candida albicans to resist killing by phagocytes and persist in tissue

CELLULAR MICROBIOLOGY, Issue 2 2007
Shaoji Cheng
Summary After five serial passages of Candida albicans SC5314 through murine spleens by intravenous inoculation, we recovered a respiratory mutant (strain P5) that exhibited reduced colony size, stunted growth in glucose-deficient media, increased oxygen consumption and defective carbohydrate assimilation. Strain P5 was indistinguishable from SC5314 by DNA typing methods, but had a greater concentration of mitochondria by SYTO18 staining. Treatment with various inhibitors demonstrated that strain P5's electron transport chain was intact and oxidative phosphorylation was uncoupled. During disseminated candidiasis, the mutant did not kill mice or cause extensive damage to kidneys. The burden of strain P5 within kidneys on the first 3 days of disseminated candidiasis was significantly reduced. By days 28 and 60, it was similar to that at the time of death among mice infected with SC5314, suggesting that the mutant persisted and proliferated without killing mice. Strain P5 was resistant to phagocytosis by neutrophils and macrophages. It was also significantly more resistant to paraquat, suggesting that it is able to neutralize reactive oxygen species. Our findings indicate that regulation of respiration influences the interaction between C. albicans and the host. Uncoupling of oxidative phosphorylation might be a mechanism by which the organism adapts to stressful host environments. [source]


Reproductive health of bass in the Potomac, USA, drainage: Part 1.

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2009
Exploring the effects of proximity to wastewater treatment plant discharge
Abstract Intersex (specifically, testicular oocytes) has been observed in male smallmouth bass (SMB; Micropterus dolomieu) and other centrarchids in the South Branch of the Potomac River, USA, and forks of the Shenandoah River, USA, during the past five years. This condition often is associated with exposure to estrogenic endocrine-disrupting chemicals in some fish species, but such chemicals and their sources have yet to be identified in the Potomac. In an attempt to better understand the plausible causes of this condition, we investigated the reproductive health of bass sampled up- and downstream of wastewater treatment plant (WWTP) effluent point sources on the Potomac River in Maryland, USA. Smallmouth bass were sampled from the Conococheague Creek and the Monocacy River, and largemouth bass (LMB; Micropterus salmoides) were collected near the Blue Plains WWTP on the mainstem of the Potomac River. Chemical analyses of compounds captured in passive samplers at these locations also were conducted. A high prevalence of intersex (82,100%) was identified in male SMB at all sites regardless of collection area. A lower prevalence of intersex (23%) was identified in male LMB collected at the Blue Plains site. When up- and downstream fish were compared, significant differences were noted only in fish from the Conococheague. Differences included condition factor, gonadosomatic index, plasma vitellogenin concentration, and estrogen to testosterone ratio. In general, chemicals associated with waste-water effluent, storm-water runoff, and agriculture were more prevalent at the downstream sampling sites. An exception was atrazine and its associated metabolites, which were present in greater concentrations at the upstream sites. It appears that proximity to effluent from WWTPs may influence the reproductive health of bass in the Potomac watershed, but inputs from other sources likely contribute to the widespread, high incidence of testicular oocytes. [source]


Evaluation of the methoxytriazine herbicide prometon using a short-term fathead minnow reproduction test and a suite of in vitro bioassays

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2006
Daniel L. Villeneuve
Abstract Prometon is one of the most consistently detected herbicides in the U.S. environment. However, no previous assessment of the potential for prometon or related methoxytriazine herbicides to act as endocrine-disrupting chemicals has been conducted. This study used an array of in vitro bioassays to assess whether prometon, atraton, terbumeton, or secbumeton might act as potent (ant)agonists of the aryl hydrocarbon, estrogen, androgen, or glucocorticoid receptors or as aromatase inhibitors or inducers in vitro. Potential effects of prometon were also evaluated using a 21-d fathead minnow reproduction assay. Concentrations of methoxytriazines, as great as 1 mg/L (4.4 ,M), did not induce significant dioxin-like responses in H4IIE-luc cells, estrogenic responses in MVLN cells, or androgen or glucocorticoid receptor,mediated responses in MDA-kb2 cells, nor did the methoxytriazines significantly affect aromatase activity in vitro. In the fathead minnow assay, exposure to 20, 200, or 1,000 ,g prometon/L significantly reduced the weight of the male fat pad (an androgen-responsive tissue) relative to body weight. Exposure to 20 ,g prometon/L significantly increased female plasma testosterone concentrations, but the effect was not observed at greater concentrations. Overall, prometon did not significantly reduce fecundity over the 21-d exposure, nor were other endpoints, including plasma vitellogenin and estradiol concentrations, brain and ovary aromatase activity, and male tubercle index, significantly affected. Evidence from our work suggests that prometon may cause subtle endocrine and/or reproductive effects in fathead minnows, but no clear mechanism of action was observed. The relevance of these effects to hazard assessment for the pesticide is uncertain. [source]


Persistent organochlorine residues and their bioaccumulation profiles in resident and migratory birds from North Vietnam

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2002
Tu Binh Minh
Abstract Concentrations of persistent organochlorines (OCs), such as polychlorinated biphenyls (PCBs), 1 1,1-trichloro-2,2-bis(p -chlorophenyl)ethane (DDT) and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB), and chlordane compounds (CHLs), were determined in whole-body homogenates of resident and migratory birds collected from the Red River estuary, North Vietnam, during March and October 1997. Contamination pattern was in the order of DDTs > PCBs > HCHs > CHLs > HCB in both resident and migratory birds. Residue concentrations, according to the feeding habit, showed little variability, which may reflect relatively similar trophic levels of the bird species analyzed. Resident birds accumulated greater concentrations of DDTs as compared to migrants. In contrast, HCH residues were greater in migratory species. Higher proportions of p,p,-DDT to total DDT concentrations were found in many species of residents and migrants, indicating recent exposure to technical DDT in northern Vietnam. Congener-specific PCB analysis showed the predominance of penta- and hexachlorobiphenyls in all the species analyzed. Estimation of hepatic microsomal enzyme activities suggested higher metabolic capacity for PCB congeners in shore birds from Vietnam as compared to higher-trophic predator birds and marine mammals. Comparison of OC residues in avian species in Asia-Pacific revealed that DDT residues in resident birds in North Vietnam are among the highest values reported for the countries surveyed, suggesting recent usage of DDT in Vietnam. Available data for birds, fish, and bivalves from the recent Asia-Pacific Mussel Watch Program suggested that Vietnam might be a potential source of DDT contamination in Asian developing countries. To our knowledge, this is the first study of the OC accumulation in avian species from Vietnam. [source]


CLINICAL STUDY: A comparison of exposure to carcinogens among roll-your-own and factory-made cigarette smokers

ADDICTION BIOLOGY, Issue 3 2009
Lion Shahab
ABSTRACT Consumption of roll-your-own (RYO) tobacco is rising, but little is known about its in vivo delivery of toxins relative to factory-made (FM) cigarettes. To start to address this issue, this study compared the concentrations of metabolites of recognized human carcinogens in smokers of RYO tobacco and FM cigarettes. We opportunistically recruited 127 FM and 28 RYO cigarette smokers in central London and collected saliva and urine samples. Saliva samples were assayed for cotinine while urinary samples were assayed for 1-hydroxypyrene (1-HOP) and total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), metabolic markers of polycyclic aromatic hydrocarbons and tobacco-specific N -nitrosamines, respectively. Data on socio-demographic, anthropometric and puffing characteristics were also obtained. Both unadjusted and adjusted analyses (controlling for age, sex, body mass index, puff flow, puff duration and cotinine) showed no difference in metabolic markers between RYO and FM cigarette smokers. However, significant main effects for cotinine levels and sex were observed in adjusted analyses. Greater levels of cotinine were associated with a greater concentration of both 1-HOP (B = 0.002, P = 0.037) and NNAL (B = 0.002, P < 0.001). In addition, women had significantly greater concentrations of urinary 1-HOP (B = 0.679, P = 0.004) and total NNAL metabolites (B = 0.117, P = 0.024) than men, irrespective of the type of cigarettes smoked. More research is now needed to confirm these findings and gender-specific effects in a larger, representative sample. However, results do not support the common belief that RYO cigarettes are less harmful than manufactured cigarettes. [source]


Increases in pH and soluble salts influence the effect that additions of organic residues have on concentrations of exchangeable and soil solution aluminium

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2002
M. S. Mokolobate
Summary It has been suggested that additions of organic residues to acid soils can ameliorate Al toxicity. For this reason the effects of additions of four organic residues to an acid soil on pH and exchangeable and soil solution Al were investigated. The residues were grass, household compost, filter cake (a waste product from sugar mills) and poultry manure, and they were added at rates equivalent to 10 and 20 t ha,1. Additions of residues increased soil pH measured in KCl (pH(KCl)) and decreased exchangeable Al3+ in the order poultry manure > filter cake > household compost > grass. The mechanism responsible for the increase in pH differed for the different residues. Poultry manure treatment resulted in lower soil pH measured in water (pH(water)) and larger concentrations of total (AlT) and monomeric (Almono) Al in soil solution than did filter cake. This was attributed to a soluble salt effect, originating from the large cation content of poultry manure, displacing exchangeable Al3+ and H+ back into soil solution. The considerably larger concentrations of soluble C in soil solution originating from the poultry manure may also have maintained greater concentrations of Al in soluble complexed form. There was a significant negative correlation (r = ,0.94) between pH(KCl) and exchangeable Al. Concentrations of AlT and Almono in soil solution were not closely related with pH or exchangeable Al. The results suggest that although additions of organic residues can increase soil pH and decrease Al solubility, increases in soluble salt and soluble C concentrations in soil solution can substantially modify these effects. [source]


A comparison of the urea-induced unfolding of apoflavodoxin and flavodoxin from Desulfovibrio vulgaris

FEBS JOURNAL, Issue 1 2002
Brian Ó Nuallain
The kinetics and thermodynamics of the urea-induced unfolding of flavodoxin and apoflavodoxin from Desulfovibrio vulgaris were investigated by measuring changes in flavin and protein fluorescence. The reaction of urea with flavodoxin is up to 5000 times slower than the reaction with the apoprotein (0.67 s,1 in 3 m urea in 25 mm sodium phosphate at 25 °C), and it results in the dissociation of FMN. The rate of unfolding of apoflavodoxin depends on the urea concentration, while the reaction with the holoprotein is independent of urea. The rates decrease in high salt with the greater effect occurring with apoprotein. The fluorescence changes fit two-state models for unfolding, but they do not exclude the possibility of intermediates. Calculation suggests that 21% and 30% of the amino-acid side chains become exposed to solvent during unfolding of flavodoxin and apoflavodoxin, respectively. The equilibrium unfolding curves move to greater concentrations of urea with increase of ionic strength. This effect is larger with phosphate than with chloride, and with apoflavodoxin than with flavodoxin. In low salt the conformational stability of the holoprotein is greater than that of apoflavodoxin, but in high salt the relative stabilities are reversed. It is calculated that two ions are released during unfolding of the apoprotein. It is concluded that the urea-dependent unfolding of flavodoxin from D. vulgaris occurs because apoprotein in equilibrium with FMN and holoprotein unfolds and shifts the equilibrium so that flavodoxin dissociates. Small changes in flavin fluorescence occur at low concentrations of urea and these may reflect binding of urea to the holoprotein. [source]


Lability of organic carbon in lakes of different trophic status

FRESHWATER BIOLOGY, Issue 6 2009
A. P. OSTAPENIA
Summary 1. We used first-order kinetic parameters of biological oxygen demand (BOD), the constant of aerobic decomposition (k) and the asymptotic value of BOD (BODult), to characterise the lability of organic carbon pools in six lakes of different trophic state: L. Naroch, L. Miastro and L. Batorino (Belarus), L. Kinneret (Israel), L. Ladoga (Russia) and L. Mendota (U.S.A.). The relative contributions of labile and refractory organic carbon fractions to the pool of total organic carbon (TOC) in these lakes were quantified. We also determined the amounts of labile organic carbon within the dissolved and particulate TOC pools in the three Belarus lakes. 2. Mean annual chlorophyll concentrations (used as a proxy for lake trophic state) ranged from 2.3 to 50.6 ,g L,1, labile organic carbon (OCL = 0.3BODult) from 0.75 to 2.95 mg C L,1 and k from 0.044 to 0.14 day,1. 3. Our data showed that there were greater concentrations of OCL but lower k values in more productive lakes. 4. In all cases, the DOC fraction dominated the TOC pool. OCL was a minor component of the TOC pool averaging about 20%, irrespective of lake trophic state. 5. In all the lakes, most (c. 85%) of the DOC pool was refractory, corresponding with published data based on measurements of bacterial production and DOC depletion. In contrast, a larger fraction (27,55%) of the particulate organic carbon (POC) pool was labile. The relative amount of POC in the TOC pool tended to increase with increasing lake productivity. 6. Long-term BOD incubations can be valuable in quantifying the rates of breakdown of the combined particulate and dissolved organic carbon pools and in characterising the relative proportions of the labile and recalcitrant fractions of these pools. If verified from a larger number of lakes our results could have important general implications. [source]


Differences in temperature, organic carbon and oxygen consumption among lowland streams

FRESHWATER BIOLOGY, Issue 12 2005
KAJ SAND-JENSEN
Summary 1. Temperature, organic carbon and oxygen consumption were measured over a year at 13 sites in four lowlands streams within the same region in North Zealand, Denmark with the objectives of determining: (i) spatial and seasonal differences between open streams, forest streams and streams with or without lakes, (ii) factors influencing the temperature dependence of oxygen consumption rate, (iii) consequences of higher temperature and organic content in lake outlets on oxygen consumption rate, and (iv) possible consequences of forecasted global warming on degradation of organic matter. 2. High concentrations of easily degradable dissolved (DOC) and particulate organic carbon (POC) were found in open streams downstream of plankton-rich lakes, while high concentrations of recalcitrant DOC were found in a forest brook draining a forest swamp. Concentrations of predominantly recalcitrant POC and DOC were low in a groundwater-fed forest spring. Overall, DOC concentration was two to 18 times higher than POC concentrations. 3. Oxygen consumption rate at 20 °C was higher during summer than winter, higher in open than shaded streams and higher in lake outlets than inlets. Rate was closely related to concentrations of chlorophyll and POC but not to DOC. The ratio of oxygen consumption rate to total organic concentrations (DOC + POC), serving as a measure of organic degradability, was highest downstream of lakes, intermediate in open streams and lowest in forest streams. 4. Temperature coefficients describing the exponential increase of oxygen consumption rate between 4 and 20 °C averaged 0.121 °C,1 (Q10 of 3.35) in 70 measurements and showed no significant variations between seasons and stream sites or correlations with ambient temperature and organic content. 5. Oxygen consumption rate was enhanced downstream of lakes during summer because of higher temperature and, more significantly, greater concentrations of degradable organic carbon. Oxygen consumption rates were up to seven times higher in the stream with three impoundments than in a neighbouring unshaded stream and 21 times higher than in the groundwater-fed forest spring. 6. A regional climate model has calculated a dramatic 4,5 °C rise in air temperature over Denmark by 2070,2100. If this is realised, unshaded streams are estimated to become 2,3 °C warmer in summer and winter and 5,7 °C warmer in spring and, thereby, increase oxygen consumption rates at ambient temperature by 30,40% and 80,130%, respectively. Faster consumption of organic matter and dissolved oxygen downstream of point sources should increase the likelihood of oxygen stress of the stream biota and lead to the export of less organic matter but more mineralised nutrients to the coastal waters. [source]


Numerical modeling of hydrothermal zinc silicate and sulfide mineralization in the Vazante deposit, Brazil

GEOFLUIDS (ELECTRONIC), Issue 2 2009
M. S. APPOLD
Abstract The Vazante zinc deposit in central Brazil is currently the world's largest known example of a hypogene nonsulfide (i.e. willemite-dominant) zinc deposit. The mineralization is hypothesized to have formed as a result of mixing between a hot, acidic, reducing, metal-rich brine and a cool, more basic and dilute, metal-poor meteoric fluid. The present study sought to investigate this scenario by quantifying the individual effects of temperature, pH, salinity, and oxidation state on willemite and sphalerite solubility, and modeling their combined effects during mixing through reaction path and reactive transport modeling. Solubility calculations showed that in an initially hot, moderately acidic, reducing, metal-rich ore fluid saturated with respect to silica, willemite solubility is relatively insensitive to changes in temperature and log , but highly sensitive to changes in pH and salinity. In contrast, sphalerite solubility was highly sensitive to changes in temperature and log , as well as salinity, and was less sensitive than willemite to changes in pH. Reaction path models sought to extend these observations by modeling the geochemistry of mixing. The results show that mixing is able to produce most of the major zinc ore and gangue minerals observed in the field, though not necessarily at the same paragenetic stages, and that both compositional and temperature changes from mixing are needed. Reactive transport models were formulated to investigate spatial patterns of mineralization. The results showed that sphalerite deposition was strongly controlled by temperature and concentrated in the regions of greatest temperature change. Willemite deposition was concentrated along the interface between the metal-rich ore fluid and the surrounding meteoric fluid. The more rapid transport of solute than heat, in conjunction with the higher concentration of silica than sulfide in both fluids meant that willemite mineralization developed over a broader region and in greater concentrations compared with sphalerite. [source]


Macro- and Micro-Purge Soil-Gas Sampling Methods for the Collection of Contaminant Vapors

GROUND WATER MONITORING & REMEDIATION, Issue 1 2009
Brian A. Schumacher
Purging influence on soil-gas concentrations for volatile organic compounds (VOCs), as affected by sampling tube inner diameter and sampling depth (i.e., system volume) for temporary probes in fine-grained soils, was evaluated at three different field sites. A macro-purge sampling system consisted of a standard, hollow, 3.2-cm outer diameter (OD) drive probe with a retractable sampling point attached to an appropriate length of 0.48-cm inner diameter (ID) Teflon® tubing. The macro-purge sampling system had a purge system volume of 24.5 mL at a 1-m depth. In contrast, the micro-purge sampling systems were slightly different between the field sites and consisted of a 1.27-cm OD drive rod with a 0.10-cm ID stainless steel tube or a 3.2-cm OD drive rod with a 0.0254-cm inner diameter stainless steel tubing resulting in purge system volumes of 1.2 and 7.05 mL at 1-m depths, respectively. At each site and location within the site, with a few exceptions, the same contaminants were identified in the same relative order of abundances indicating the sampling of the same general soil atmosphere. However, marked differences in VOC concentrations were identified between the sampling systems, with micro-purge samples having up to 27 times greater concentrations than their corresponding macro-purge samples. The higher concentrations are the result of a minimal disturbance of the ambient soil atmosphere during purging. The minimal soil-gas atmospheric disturbance of the micro-purge sampling system allowed for the collection of a sample that is more representative of the soil atmosphere surrounding the sampling point. That is, a sample that does not contain an atmosphere that has migrated from distance through the geologic material or from the surface in response to the vacuum induced during purging soil-gas concentrations. It is thus recommended that when soil-gas sampling is conducted using temporary probes in fine-grained soils, the sampling system use the smallest practical ID soil-gas tubing and minimize purge volume to obtain the soil-gas sample with minimal risk of leakage so that proper decisions, based on more representative soil-gas concentrations, about the site can be made. [source]