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Biomedical subjects

D S Kosson

Publications and source records attributed to D S Kosson.

At least 19 recordsLinked to original sources
PubMed2006

The role of the amygdala and rostral anterior cingulate in encoding expected outcomes during learning.

Successful passive avoidance learning is thought to require the use of learned stimulus-reinforcement associations to guide decision making [Baxter, M.G., Murray, E.A., 2002. The amygdala and reward. Nature Reviews. Neuroscience 3, 563-573]. The current experiment investigated the neural correlates of successful passive avoidance learning in 19 healthy adults. Behaviorally, subjects showed a distinct pattern of performance: early indiscriminate responding to stimuli (pre-criterion performance), followed by relatively rapid learning before a plateau of successful performance (post-criterion performance). Neural responses to post-criterion correct responses were compared with neural responses to both incorrect responses and pre-criterion correct responses. Post-criterion correct responding was associated with increased activation in regions including rostral anterior cingulate, insula, caudate, hippocampal regions, and the amygdala.

Adult↗
PubMed2005

Probabilistic approach for estimating the release of contaminants under field management scenarios.

A probabilistic approach is presented for estimating the release of contaminants by leaching, when wastes are being considered for disposal in a class of landfills but the specific landfill disposal site is uncertain. A simple percolation and equilibrium-based release model is used in conjunction with laboratory testing results and observations of field leachate characteristics for municipal solid waste landfills, hazardous waste landfills and industrial co-disposal landfills. The approach is applied for assessing the efficacy of potential treatment processes for mercury contaminated soils. For each landfill scenario, historical values of leachate pH and annual leachate generation quantities were used to derive the probability distribution functions of the field pH and LS ratio that may be expected to contact the disposed material over an estimated time period of 100 years. For each potential treatment process, laboratory testing was used to establish the treated material's leaching characteristics as a function of pH LS ratio. This approach allowed determination of distribution frequencies and limit values for release estimates instead of single point estimates. The probability of the mass of a constituent of interest released exceeding a hypothetical threshold was examined for each treatment process and landfill system. Results of the probabilistic analysis allowed for integration of a range of data and provided a good basis for assessing the efficacy of the examined treatment processes over the three assumed disposal scenarios.

Hazardous Waste↗
PubMed2004

Changes in constituent equilibrium leaching and pore water characteristics of a Portland cement mortar as a result of carbonation.

Two equilibrium-based characterization protocols were applied to ground samples of a cement-based material containing metal oxide powders in both noncarbonated and carbonated states. The effects of carbonation were shown through comparison of (i) material buffering capacity, (ii) constituent equilibrium as a function of leachate pH, and (iii) constituent solubility and release as a function of liquid-to-solid (LS) ratio. As expected, the material alkalinity was significantly neutralized during carbonation. In addition, carbonation of the cement material led to the formation of calcium carbonate and a corresponding increase in arsenic release across the entire pH range. The solubility as a function of pH for lead and copper was lower in the alkaline pH range (pH>9) for carbonated samples compared with the parent material. When solubility and release as a function of LS ratio was compared, carbonation was observed to decrease calcium solubility, sodium and potassium release, and ionic strength. In response to carbonate solid formation, chloride and sulfate release as a function of LS ratio was observed to increase. Trends in constituent concentration as a function of LS ratio were extrapolated to estimate pore water composition at a 0.06 mL/g LS ratio. Significant differences were observed upon comparison of estimated pore water composition to leachate concentrations extracted at LS ratio of 5 mL/g. These differences show that practical laboratory extractions cannot be assumed directly representative of pore water concentrations.

Carbon↗
PubMed2004

The effects of auditory and visual linguistic distractors on target localization.

In this experiment, a Stroop-like paradigm was used to investigate the ability to attend to visuospatial cues while ignoring distracting stimuli in the auditory or visual modality. In Part 1, the authors investigated whether linguistic cue words (i.e., RIGHT, LEFT, DOWN, and UP) would induce endogenous shifts of attention to visual targets. In Part 2, a relevant distractor stimulus was introduced in a different modality from the endogenous cues to investigate effects of interference. Twenty-five right-handed students served as participants. Auditory and visual linguistic cues were effective in inducing shifts of visual attention when cues were presented alone. Furthermore, introducing a distractor stimulus decreased the efficacy of these cues differently depending on modality, suggesting that language processing and visuospatial attention may share neuronal resources. Implications for unimodal and supramodal mechanisms of selective attention and relevant neuronal networks are discussed.

Adult↗
PubMed2003

Environmental assessment of waste matrices contaminated with arsenic.

The use of equilibrium-based and mass transfer-based leaching tests has been proposed to provide an integrated assessment of leaching processes from solid wastes. The objectives of the research presented here are to (i) validate this assessment approach for contaminated soils and cement-based matrices, (ii) evaluate the use of diffusion and coupled dissolution-diffusion models for estimating constituent release, and (iii) evaluate model parameterization using results from batch equilibrium leaching tests and physical characterization. The test matrices consisted of (i) a soil contaminated with arsenic from a pesticide production facility, (ii) the same soil subsequently treated by a Portland cement stabilization/solidification (S/S) process, and (iii) a synthetic cement-based matrix spiked with arsenic(III) oxide. Results indicated that a good assessment of contaminant release from contaminated soils and cement-based S/S treated wastes can be obtained by the integrated use of equilibrium-based and mass transfer-based leaching tests in conjunction with the appropriate release model. During the time scale of laboratory testing, the release of arsenic from the contaminated soil matrix was governed by diffusion and the solubility of arsenic in the pore solution while the release of arsenic from the cement-based matrices was mainly controlled by solubilization at the interface between the matrix and the bulk leaching solution. In addition, results indicated that (i) estimation of the activity coefficient within the matrix pore water is necessary for accurate prediction of constituent release rates and (ii) inaccurate representation of the factors controlling release during laboratory testing can result in significant errors in release estimates.

Arsenic↗
PubMed2003

Multi-regime transport model for leaching behavior of heterogeneous porous materials.

Utilization of secondary materials in civil engineering applications (e.g. as substitutes for natural aggregates or binder constituents) requires assessment of the physical and environment properties of the product. Environmental assessment often necessitates evaluation of the potential for constituent release through leaching. Currently most leaching models used to estimate long-term field performance assume that the species of concern is uniformly dispersed in a homogeneous porous material. However, waste materials are often comprised of distinct components such as coarse or fine aggregates in a cement concrete or waste encapsulated in a stabilized matrix. The specific objectives of the research presented here were to (1) develop a one-dimensional, multi-regime transport model (i.e. MRT model) to describe the release of species from heterogeneous porous materials and, (2) evaluate simple limit cases using the model for species when release is not dependent on pH. Two different idealized model systems were considered: (1) a porous material contaminated with the species of interest and containing inert aggregates and, (2) a porous material containing the contaminant of interest only in the aggregates. The effect of three factors on constituent release were examined: (1) volume fraction of material occupied by the aggregates compared to a homogeneous porous material, (2) aggregate size and, (3) differences in mass transfer rates between the binder and the aggregates. Simulation results confirmed that assuming homogeneous materials to evaluate the release of contaminants from porous waste materials may result in erroneous long-term field performance assessment.

Humans↗
PubMed2002

The effect of storage in an inert atmosphere on the release of inorganic constituents during intermittent wetting of a cement-based material.

Monolithic waste materials (e.g. Portland cement treated wastes) in many field scenarios do not remain continuously saturated, but experience intermittent wetting interspersed with periods of storage in an unsaturated environment. During storage, the matrix may loss moisture to the environment, promoting precipitation or redistribution of species. In addition, the matrix may react with the surrounding atmosphere through carbonation or oxidation. Upon subsequent leaching, changes in the chemical and physical composition incurred over the storage interval can influence the release of inorganic species. Current assessment approaches, which use continuous leaching data to project release over some assessment interval, do not allow for changes in leachability resulting from intermittent wetting and storage. Thus, this study evaluates the effect of storage intervals in an inert atmosphere on subsequent release of inorganic species from a synthetic Portland cement matrix. Tank leaching in deionized water was interspersed with storage at three relative humidity (RH) levels (nominally 0, 50 and 100% RH) in a 100% nitrogen atmosphere. Leaching data from the three intermittent wetting cases were compared to continuous leaching for the release of structural species (Ca, OH), highly soluble species (Na, K, Cl) and pH-dependent species (As, Cd, Pb). The RH of storage environment, which acted as a boundary condition for the drying process, influenced the precipitation of species within dried pores and relaxation of pH and concentration gradients within water-filled regions. Gradient relaxation resulted from continued mass transport within saturated pores over the storage interval and was most evident when storage was conducted at 98% RH. However, when storage RH promoted drying of the matrix, the effect of gradient relaxation was balanced by precipitation. When release was normalized to total leaching time, relaxation of concentration gradients of highly soluble species resulted in greater cumulative release for the intermittently wetted cases than in the case of continuous leaching. The release of pH-dependent constituents was controlled by relaxation of the pH gradient and species solubility as a function of local pore water pH. Application of a current assessment protocol to estimate intermittent wetting release resulted in either over or underestimation of actual cumulative release, depending on the nature of the constituent of interest. These results imply that long-term constituent release from Portland cement-based waste forms should not be made by simple correction of saturated release assessments because alterations to the matrix leachability induced by the storage environment need to be considered.

Chemical Phenomena↗
PubMed2002

Leaching of inorganic contaminants from cement-based waste materials as a result of carbonation during intermittent wetting.

Characterization of the leaching behavior of wastes is a crucial step in the environmental assessment for reuse or disposal scenarios. The release of inorganic contaminants from waste materials is typically evaluated by tank leaching of continuously water-saturated material. However, materials, in many field or management scenarios, experience cyclic wetting and drying under varied environmental conditions (i.e. variable relative humidity, atmospheric CO2 or CO2 from biologic activities). During periods of storage in an unsaturated environment, many processes may occur that can influence the release potential and release rate of inorganic constituents. The research presented here was carried out to examine how the phenomena of carbonation during drying influence the release of inorganic contaminants from Portland cement-based materials during cyclic wetting and storage. Batch equilibrium leaching tests were used to determine constituent solubility as a function of pH. Dynamic leaching tests on monolithic material were carried out to determine the rate of constituent release as a function of leaching time and intermittent storage conditions. This paper presents the results observed for three typical waste constituents, arsenic, cadmium and lead.

Carbon Dioxide↗
PubMed2001

Measurement of iron(III) bioavailability in pure iron oxide minerals and soils using anthraquinone-2,6-disulfonate oxidation.

The quinol form (AHDS) of 9,10-anthraquinone-2,6-disulfonate (AQDS) was used as a titrant to determine bioavailability of Fe(III) in pure iron minerals and several soils. AHDS oxidation to AQDS was coupled to Fe(III) reduction to Fe(ll) in biological media consisting of trace salts and vitamins, providing estimates of bioavailability consistentwith the biogeochemical mechanisms and conditions that control Fe(III) availability to iron-reducing bacteria. Iron(III) oxide sources were synthetic oxides (amorphous and crystalline) and three soils separated into two size fractions each (0-500 and 500-1000 microm). This titration gave a measurement of the amount of Fe(III) available to dissimilatory iron-reducing bacteria and was compared to hydroxylamine reduction, oxalate extraction, and biological reduction by Shewanella alga BrY. The advantage of AHDS titration over existing chemical techniques is that it can be performed at normal soil pH and ionic strength, and it allows for distinction of iron(III) oxides rendered unavailable by sorption of Fe(II) or by other pH-dependent geochemical processes. This approach also allows distinction of Fe(III) present in micropores that is not directly available to bacteria but bioavailable in the presence of an electron shuttle capable of transporting electrons into the micropores.

Anthraquinones↗
PubMed2001

Characteristics, treatment and utilization of residues from municipal waste incineration.

Beneficial utilization of residues from municipal solid waste incineration is an important objective for integrated waste management in many jurisdictions. When residues are to be used as an aggregate substitute in construction applications, the release of constituents of concern to soils and water through leaching is an important environmental consideration. In this paper, residue characteristics that control constituent leaching and testing approaches for evaluating leaching are discussed. Quality control and potential improvement in case of beneficial application are addressed.

Conservation of Natural Resources↗
PubMed2001

Psychopathy and ethnicity: structural, item, and test generalizability of the Psychopathy Checklist--Revised (PCL-R) in Caucasian and African American Participants.

The Psychopathy Checklist--Revised (PCL-R) is an important measure in both applied and research settings. Evidence for its validity is mostly derived from male Caucasian participants. PCL-R ratings of 359 Caucasian and 356 African American participants were compared using confirmatory factor analysis (CFA) and item response theory (IRT) analyses. Previous research has indicated that 13 items of the PCL-R can be described by a 3-factor hierarchical model. This model was replicated in this sample. No cross-group difference in factor structure could be found using CFA; the structure of psychopathy is the same in both groups. IRT methods indicated significant but small differences in the performance of 5 of the 20 PCL-R items. No significant differential test functioning was found, indicating that the item differences canceled each other out. It is concluded that the PCL-R can be used, in an unbiased way, with African American participants.

Adult↗
PubMed2000

Pore structure of soot deposits from several combustion sources.

Soot was harvested from five combustion sources: a dodecane flame, marine and bus diesel engines, a wood stove, and an oil furnace. The soots ranged from 20% to 90% carbon by weight and molar C/H ratios from 1 to 7, the latter suggesting a highly condensed aromatic structure. Total surface areas (by nitrogen adsorption using the Brunauer Emmett Teller, BET method) ranged from 1 to 85 m2 g(-1). Comparison of the surface area and meso-pore (pores 2-50 nm) surface area predicted by density functional theory (DFT) suggested that the soot was highly porous. Total meso-pore volume and surface area ranged from 0.004-0.08 cm3 g(-1) and from 0.33-6.9 m2 g(-1) respectively, accounting for up 33% of the BET surface area. The micro-pore volume (pores <2 nm) calculated from CO2 adsorption data (by DFT) ranged from 0.0009 to 0.013 cm3 g(-1) and micro-pore surface area was 3.1-41 m2 g(-1), accounting for 10-20% of the total intra-particle (meso-plus micro-pores) pore volume and 70-90% of the total intra-particle surface area. Higher pore volume and surface area values were computed using the Dubinin Radushkevich plot technique; ranging from 0.004-0.04 cm3 g(-1) to 11-102 m2 g(-1) for micro-pore volume and surface area, respectively. Comparison of the C/H ratio and the micro-pore structure showed a strong correlation, suggesting a relationship between the condensation of the skeletal structure and micro-porosity of the soot. These data contradict literature reports that soot particles are non-porous and are consistent with recent literature reports that soil organic matter has large micro-pore surface areas.

Air Pollutants↗
PubMed2000

Handedness and psychopathy.

OBJECTIVES: The current study investigated whether psychopathic persons exhibit a pattern of motor dominance that differs from the left-hemisphere dominance that characterizes the majority of the population. BACKGROUND: Research with cognitive tasks suggests that psychopathy may be associated with an atypical pattern of cerebral organization characterized by either left-hemisphere dysfunction or decreased hemispheric asymmetry. However, studies that evaluate motor dominance in psychopathy have provided mixed results. METHOD: The handedness of 420 adult male inmates at a county jail was assessed using a scale developed by Chapman and Chapman as part of their participation in ongoing research. RESULTS: Psychopaths reported reduced right-hand dominance, which cannot be accounted for by differences in age, intelligence, or race. CONCLUSIONS: Psychopathy is associated with an increased proportion of mixed-handedness relative to that seen in nonpsychopathic persons. This finding is consistent with theory and research suggesting anomalous cerebral asymmetry in psychopathic offenders.

Adolescent↗
PubMed1996

Psychopathy and dual-task performance under focusing conditions.

Thirty psychopathic and 30 nonpsychopathic right-handed White male inmates (selected through R.D. Hare's, 1985b, Psychopathy Checklist) completed concurrent visual and auditory tasks under conditions focusing attention on the visual (i.e., primary) task. Performance indices tested 3 related hypotheses for cognitive deficits in psychopathic individuals: reduced attention to secondary tasks because of excess attention to immediate goals (interference), deficient shifts of attention, and reduced breadth of attention. The absence of differences in primary and secondary task accuracy contradicts the interference hypothesis. However, a trend toward deficits for psychopathic individuals responding with the right hand to primary task targets appearing after other targets, suggests poorer shifting of attention when left-hemisphere resources are engaged. Psychopathic individuals also overresponded to distractors following targets suggesting reduced attention to a peripheral dimension of two-dimensional stimuli.

Adult↗
PubMed1995

Interactions of aniline with soil and groundwater at an industrial spill site.

The interactions of aniline with soil at an industrial spill site were investigated. Sorption of aniline to the soil was observed to occur through a two-step mechanism. The first step was an ion exchange process with the protonated amine serving as an organic cation. This step was influenced by solution pH and ionic composition. The second step was covalent bonding most likely with quinone moieties and oxidation with polymerization of aniline. The extent of covalent bonding was influenced by the presence of oxygen and redox potential. The majority of aniline that was bound to the soil did not readily desorb under a variety of abiotic conditions. However, aniline was released to a significant extent in the presence of denitrifying and methanogenic microbial activity. Aniline in aqueous solution was readily biodegradable under aerobic and denitrifying conditions. Soil-bound aniline was observed not to be biodegradable. This paper provides an overview of results.

Accidents, Occupational↗
PubMed1994

The relation between socialization and antisocial behavior, substance use, and family conflict in college students.

Gough's (1960) Socialization (So) scale has been widely used as a measure of the extent to which societal values are internalized. It is well documented that antisocial individuals evidence low So scores but less clear that low So scores predict antisocial behavior in nonclinical samples. Two studies conducted at different universities in different geographical regions and different decades provided evidence consistent with this hypothesis. Results from Study 1 revealed that self-reports of several types of antisocial behavior and substance use were significantly more common among Low-So than High-So undergraduate men and women. Study 2 replicated principal findings for both men and women using correlational analyses. In addition, Study 2 yielded a significant relation between low So scores and greater family conflict as well as several gender differences reflecting stronger correlations in men than in women. These findings indicate substantial generality for the relations between socialization and antisocial behavior, especially in men, and are consistent with the use of the So scale to identify subjects who share important characteristics with criminal or psychopathic groups.

Adult↗
PubMed1993

Altering a dominant response: performance of psychopaths and low-socialization college students on a cued reaction time task.

The passive avoidance learning deficits of disinhibited Ss have been attributed to their difficulty inhibiting dominant responses. To date, evidence for this hypothesis has been derived from complex tasks. In two experiments, a cued reaction time task requiring no learning or memory was used to evaluate the degree to which groups of disinhibited Ss inhibit simple dominant responses. Disinhibited groups were incarcerated psychopaths identified with Hare's (1985) Psychopathy Checklist and undergraduate males who scored low on the Socialization Scale. Both disinhibited groups committed more errors than controls on trials containing misleading cues, but in both samples, findings were limited to trials in which Ss expected to make right-hand responses. Although alternative interpretations are possible, these data are consistent with the proposal that disinhibited individuals are less likely to inhibit well-established dominant responses.

Adult↗