Effect Of Exposure Duration Research Articles

0368 Disentangling the effect of exposure duration, intensity, and time since exposure in studies of chronic health effects

ObjectivesDue to their interrelatedness, modelling independent effects of intensity, duration, and time since exposure on disease risk is complex. The indiscriminate use of the cumulative exposure metric (product of intensity...

Spatial and seasonal population dynamics of sympatric Jassa species (Crustacea, Amphipoda)

Marine fouling communities are often characterised by dense aggregations of tube-building amphipod species of the genus Jassa. Although some species of this genus coexist in high densities, the development and relationships of sympatric populations are largely unknown. The current field study tested for the effects of exposure duration, seasonality and spatial heterogeneity on community composition, population structure and recruitment of three coexisting Jassa species. The establishment and succession of Jassa-dominated fouling communities on artificial substratum (PVC panels) were studied over two one-year periods off the island of Helgoland (German Bight, North Sea). At different seasonal times, and for different periods of time, panels were exposed at three stations: an exposed station (near water surface), a benthic station in 10m water depth, and a sheltered station (near water surface). Jassa falcata was the dominant species at the benthic station in 10m water depth, whereas Jassa marmorata and Jassa herdmani were more abundant on panels which were positioned near the water surface (exposed and sheltered station). The two latter species showed higher abundances at the exposed than at the sheltered station, although J. marmorata was always clearly the dominant species. The differences in the spatial distribution patterns of the three species may partly result from direct interspecific competition for space. Populations of all three Jassa species exhibited strong temporal changes in both abundances and population structure (sex ratio, proportions of reproductively active individuals, male morphs), most likely caused by seasonal factors. Rapid colonisation of free artificial surfaces was observed nearly throughout the year. Intensity of colonisation, however, followed a distinct seasonal pattern with a maximum in the summer months. Recruitment probably occurred via drifting juveniles which originated from amphipod communities in the surroundings. The observed differences among the species may mainly reflect adaptations to different environmental conditions. These differences, however, may also contribute to a stable long-term coexistence via some degree of resource partitioning along with ‘intermediate disturbance’ events.

The effect of gold nanoparticle on renal function in rats

Objective(s): This study aimed to address the gold nanoparticle(GNP)-dose and exposure duration effect on the kidney function of rats: in vivo. Materials and Methods: A total of 32 healthy male Wistar rats were used in this study. Animals were randomly divided into groups, three GNP-treated groups and control group. Group 1, 2 and 3 received. /5 cc of solution containing 5, 10,100 ppm Au via IP injection for 7 successive days, respectively. The control group was treated with 0.5% normal saline. Several biochemical parameters such as BUN (blood urea nitrogen), creatine and uric acid were evaluated at various time points (7 and 14 days). After 14 days, the tissue of kidney was collected and investigated. Results: There was no significant difference between the control and the intervention group regarding the amount of creatine-BUN and uric acid. The amount of creatine-BUN and uric acid showed increase in all the groups [except group1 (creatine) and group 2 (uric acid)] in the 7 and 14 days after intervention compared to the control group, but this difference was not significant. Results of histopatological tissue kidney showed: in group 1 and 3, complete destruction of the proximal tubules and distal cortical, in group 2, almost complete destruction of proximal tubules and distal. Conclusions: The induced histological alterations might be an indication of injured renal tubules due to GNPs toxicity that become unable to deal with the accumulated residues resulting from metabolic and structural disturbances caused by these NPs

Single and Combined Effects of Exposure Concentration and Duration on Biological Responses of Ceratophyllum demersum L. Exposed to Cr Species

This study aimed to demonstrate the ways in which two chromium species, Cr (III) and Cr (VI), can affect various physiological and biochemical parameters in the plant Ceratophyllum demersum L., and to evaluate the single and combined impact of exposure concentration and duration. C. demersum was exposed to Cr (III) and Cr (VI) at a variety of concentrations (1, 2, 5, and 10 mM) and for differing durations (1, 2, 4, and 7 days), after which Cr accumulation, relative growth rate (RGR), malondialdehyde (MDA) content, electrical conductivity (EC), photosynthetic pigmentation, proline content and antioxidant enzyme activities were examined. The single and combined effects of exposure duration and Cr concentration on each parameter were determined using a two-way analysis of variance. For both the Cr (III) and Cr (VI) applications, it was observed that concentration had a significant effect on all parameters assessed. However, duration had no statistically significant effect on proline content in the Cr (III) application, or on MDA and protein content in the Cr (VI) application. It was determined that concentration exerted greater effects than duration for both Cr species studied. In addition, the results indicated that duration and concentration had a synergistic effect on variations of RGR, EC, protein content, and antioxidant enzyme activities in both the Cr (III) and Cr (VI) applications. These results may be useful when planning further phytoremediation and plant biotechnology studies.

Growth and differentiation of osteoblasts regulated by low-intensity pulsed ultrasound of various exposure durations

Several studies have investigated the effect of low-intensity pulsed ultrasound (LIPUS) on fractured bone and bone cells. In general, positive results were reported, but they may vary depending on the LIPUS operational mode. In the present study, the effect of exposure duration associated with LIPUS insonification on osteoblasts was extensively investigated. In experiments, osteoblasts were insonified with LIPUS of 3, 5, 10, and 20 minutes, respectively. The employed LIPUS used a 1 MHz frequency, a 100 mW/cm 2 spatial-average-temporal-average intensity (ISATA), and a 20% duty cycle at a 1 kHz pulse repetition frequency. The effect of LIPUS on osteoblasts was assessed in terms of the growth and differentiation of cells corresponding to cell viability, alkaline phosphatase (ALP) activity, mRNA expression of ALP and osteocalcin (OCN), and Alizarin red-S staining. Results demonstrate that the growth and differentiation of insonified osteoblasts increased with increasing exposure duration for durations of up to 10 minutes. Specifically, with 10 minutes of LIPUS insonification, the proliferation and ALP activity of osteoblasts increased to 1.07- and 1.31-fold than those of the control groups, respectively; OCN mRNA expression and the mineralization of osteoblasts increased respectively to 2.23- and 2.5-fold than those of the control groups. When the exposure duration of LIPUS was further increased to 20 minutes, the growth and differentiation of insonified osteoblasts did not increase. This indicates that the effect of LIPUS insonification on osteoblasts is exposure-duration-dependent. Furthermore, the temperature of the medium corresponding to LIPUS insonfication varied within 0.5 °C , verifying that the LIPUS insonification provides a non-thermal effect on the regulation of cellular growth and differentiation. Consequently, with appropriate LIPUS exposure duration, the proliferation, differentiation, and mineralization of insonified osteoblasts can be regulated, which could be beneficial for the treatment of bone-related diseases.

Occupational exposure to noise and hearing thresholds among civilian aircraft maintenance workers

High noise exposure is anticipated to be present in the aircraft maintenance operations in civil aviation sector. The objective of the present study is the assessment of noise exposure and hearing threshold of the aircraft maintenance workers in this sector. Noise levels were measured in the aircraft hangers and in the workshops at a main international airport in Saudi Arabia. Two hundred aircraft maintenance workers were subjected to pure tone audiometry. The average Leq,8h at most of the aircraft maintenance operations was considerably high and most of the workers (89.5%) were exposed to noise levels ≥85 dBA. Frequency analysis of sound pressure levels revealed that the contribution of the octave bands 1, 2 and 4 kHz to the overall noise level was high. The audiograms of the examined workers showed significant hearing impairment as compared to non-noise-exposed Saudi employees. Although the observed excessive noise levels can cause hearing loss, the effect among the studied aircraft maintenance workers was mild. This might be attributed to the usage of hearing protection devices, the intermittent nature of the workers' exposure to noise and job rotation. Statistical analysis revealed significant association of both age and usage of hearing protectors with hearing loss. The effect of exposure duration on hearing loss was also detected. Relevance to industryUnlike military aircraft maintenance workers, exposure of civilian workers to noise is not sufficiently addressed. The data presented in this study may be used to set appropriate measures for hearing protection among those workers.

Emotion self-regulation and empathy depend upon longer stimulus exposure

Observation of others in pain induces positive elevation (pain effect) in late event-related potentials (ERP). This effect is associated with top-down attention regulating processes. It has previously been shown that stimulus exposure duration can affect top-down attentional modulation of response to threat-related stimuli. We investigated the effect of exposure duration on ERP response to others in pain. Two late ERP components, P3 and late positive potentials (LPP), from 18 healthy people were measured while they viewed pictures of hands in painful or neutral situations for either 200 or 500 ms, during two task conditions (pain judgment and counting hands). P3 and LPP pain effects during the pain judgment condition were significantly greater with 500 ms than 200 ms stimulus presentation. Ours is the first study to suggest that engagement of empathy-related self-regulatory processes reflected in late potentials requires longer exposure to the pain-related stimulus. Although this is important information about the relationship between early sensory and subsequent brain processing, and about engagement of self-regulatory processes, the neural basis of this time-dependence remains unclear. It might be important to investigate the relationship between stimulus duration and empathic response in clinical populations where issues of self-regulation, empathic response and speed of information processing exist.

The gold nanoparticle size and exposure duration effect on the liver and kidney function of rats: In vivo

Nanoparticles (NPs) offer a great possibility for biomedical application, not only to deliver pharmaceutics, but also to be used as novel diagnostic and therapeutic approaches. Currently, there are no data available regarding to what extent the degree of the toxicity and the accumulation of gold nanoparticles (GNPs) are present in in vivo administration. This study aimed to address the GNP size and exposure duration effect on the liver and kidney function of rats: in vivo. MethodsA total of 30 healthy male Wistar-Kyoto rats of the same age (12weeks old) and weighing 220–240g of King Saud University colony were used. Animals were randomly divided into groups, two GNP-treated rat groups and one control group (CG). The 50μl of 10 and 50nm GNPs was intraperitoneally administered in rats for exposure duration of 3days. Then, several biochemical parameters such as aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), alanine transaminase (ALT), alkaline phosphatase (ALP), urea (UREA) and creatinine (CREA) were evaluated. ResultsIn this study, the AST values increased with the administration of 10 and 50nm GNPs compared with the control. The AST values significantly increased with 10nm GNPs compared with 50nm GNPs and control. The GGT and ALT values decreased with the administration of 10 and 50nm GNPs compared with the control. The GGT and ALT values significantly decreased with 50nm GNPs compared with 10nm GNPs and control. The ALP values significantly decreased with the administration of 10 and 50nm GNPs compared with the control. The decrease in ALP values with 10nm GNPs was higher than those compared with 50nm GNPs. In this study, the levels of UREA and CREA values increased in a non significant manner after the administration of 10 and 50nm GNPs compared with the control. ConclusionsThis study demonstrates that the increase in the enzymes AST and the decrease in ALP are smaller GNPs (10nm) size-dependent for exposure duration of 3days; while the decrease in the enzymes GGT and ALT are bigger GNPs (50nm) size-dependent. The levels of UREA and CREA values indicated no significant changes with the administration of 10 and 50nm GNPs for exposure duration of 3days compared with the control. The administration of 10 and 50nm GNPs for short exposure duration of 3days induced only significant variations with some liver enzymes while kidney showed no significant variations. This study suggests that synthesis and metabolism of GNPs as well as the protection of the liver will be more important issues for medical applications of gold-based nanomaterials in future.

The confidence-accuracy relationship for eyewitness identification decisions: Effects of exposure duration, retention interval, and divided attention.

Prior research points to a meaningful confidence-accuracy (CA) relationship for positive identification decisions. However, there are theoretical grounds for expecting that different aspects of the CA relationship (calibration, resolution, and over/underconfidence) might be undermined in some circumstances. This research investigated whether the CA relationship for eyewitness identification decisions is affected by three, forensically relevant variables: exposure duration, retention interval, and divided attention at encoding. In Study 1 (N = 986), a field experiment, we examined the effects of exposure duration (5 s vs. 90 s) and retention interval (immediate testing vs. a 1-week delay) on the CA relationship. In Study 2 (N = 502), we examined the effects of attention during encoding on the CA relationship by reanalyzing data from a laboratory experiment in which participants viewed a stimulus video under full or divided attention conditions and then attempted to identify two targets from separate lineups. Across both studies, all three manipulations affected identification accuracy. The central analyses concerned the CA relation for positive identification decisions. For the manipulations of exposure duration and retention interval, overconfidence was greater in the more difficult conditions (shorter exposure; delayed testing) than the easier conditions. Only the exposure duration manipulation influenced resolution (which was better for 5 s than 90 s), and only the retention interval manipulation affected calibration (which was better for immediate testing than delayed testing). In all experimental conditions, accuracy and diagnosticity increased with confidence, particularly at the upper end of the confidence scale. Implications for theory and forensic settings are discussed.

Supplemental Material for The Confidence-Accuracy Relationship for Eyewitness Identification Decisions: Effects of Exposure Duration, Retention Interval, and Divided Attention

Supplemental Material for The Confidence-Accuracy Relationship for Eyewitness Identification Decisions: Effects of Exposure Duration, Retention Interval, and Divided Attention

S70 Mesenchymal Stem Cell Conditioned Media (MSC-CM) Suppress Wnt-3A and TGF-β1-Induced Myofibroblastic Differentiation

HypothesisIdiopathic pulmonary fibrosis (IPF) remains an incurable fibrotic lung disease. A mesenchymal stem cell (MSC)-mediated regenerative approach has been proposed; MSC-mediated anti-fibrotic effects have been demonstrated in animal lung-fibrosis models....

Effects of exposure duration on the response of Pocillopora damicornis larvae to elevated temperature and high pCO2

Efforts to evaluate the response of coral larvae to global climate change (GCC) and ocean acidification (OA) typically employ short experiments of fixed length, yet it is unknown how the response is affected by exposure duration. In this study, we exposed larvae from the brooding coral Pocillopora damicornis to contrasts of temperature (24.00°C [ambient] versus 30.49°C) and pCO2 (49.4Pa versus 86.2Pa) for varying periods (1–5days) to test the hypothesis that exposure duration had no effect on larval response as assessed by protein content, respiration, Symbiodinium density, and survivorship; exposure times were ecologically relevant compared to representative pelagic larval durations (PLD) for corals. Larvae differed among days for all response variables, and the effects of the treatment were relatively consistent regardless of exposure duration for three of the four response variables. Protein content and Symbiodinium density were unaffected by temperature and pCO2, but respiration increased with temperature (but not pCO2) with the effect intensifying as incubations lengthened. Survival, however, differed significantly among treatments at the end of the study, and by the 5th day, 78% of the larvae were alive and swimming under ambient temperature and ambient pCO2, but only 55–59% were alive in the other treatments. These results demonstrate that the physiological effects of temperature and pCO2 on coral larvae can reliably be detected within days, but effects on survival require ≥5days to detect. The detection of time-dependent effects on larval survivorship suggests that the influence of GCC and OA will be stronger for corals having long PLDs.

Impairment of green-lipped mussel (Perna canaliculus) physiology by waterborne cadmium: Relationship to tissue bioaccumulation and effect of exposure duration

Laboratory studies were performed to assess the impact of acute and subchronic cadmium (Cd) exposure on the green-lipped mussel, Perna canaliculus. A 96h median lethal concentration (LC50) value of 8160μgL−1 was determined, characterising this species as relatively tolerant to Cd exposure. Acute (96h; at 2000 and 4000μgCdL−1) and subchronic (28d; at 200 and 2000μgCdL−1) waterborne exposures were then conducted to investigate the impact of Cd exposure on physiological responses (e.g. clearance (feeding) rate, absorption efficiency, oxygen uptake, ammonia production, oxygen to nitrogen ratio, scope for growth) and tissue Cd accumulation. Cd accumulation in digestive gland showed saturation with respect to increasing exposure concentration, while the gill tissue Cd accumulation followed a positive linear relationship with Cd exposure level. Clearance rates declined during both acute and subchronic exposures at levels of 2000μgCdL−1 or higher. Impairments of clearance rates were strongly correlated with tissue Cd accumulation. Coupled with their importance as a food source, and their wide coastal distribution, these data suggests that P. canaliculus may be a species useful as an indicator species for trace metal pollution in coastal environments.

Effects of exposure time and cognitive operations on facial identification accuracy: a meta-analysis of two variables associated with initial memory strength

In the present study, we conducted two separate meta-analyses in order to quantify the influence on facial identification accuracy of two variables related to initial memory strength for an unfamiliar face, specifically, length of exposure at the time of encounter and encoding operations as manipulated via stimulus processing instructions. Proportion correct was significantly higher for longer (M = 0.66) as compared to shorter exposure durations (M = 0.53) and when participants made social judgments of faces (M = 0.75) than when they attended to individual facial features (M = 0.71). The effect of increased exposure time was non-linear, with comparable increases exerting a greater effect for relatively short versus relatively long exposures. Neither substantive nor methodological variables were found to moderate the effect of exposure duration, and only date of publication appeared to moderate the effect of encoding operations. Theoretical and practical implications of the findings are discussed.

The role of eye movements in decision making and the prospect of exposure effects

The aim of the current study was to follow on from previous findings that eye movements can have a causal influence on preference formation. Shimojo et al. (2003) previously found that faces that were presented for a longer duration in a two alternative forced choice task were more likely to be judged as more attractive. This effect only occurred when an eye movement was made towards the faces (with no effect when faces were centrally presented). The current study replicated Shimojo et al.’s (2003) design, whilst controlling for potential inter-stimuli interference in central presentations. As per previous findings, when eye movements were made towards the stimuli, faces that were presented for longer durations were preferred. However, faces that were centrally presented (thus not requiring an eye movement) were also preferred in the current study. The presence of an exposure duration effect for centrally presented faces casts doubt on the necessity of the eye movement in this decision making process and has implications for decision theories that place an emphasis on the role of eye movements in decision making.

Mixed emotions: Holistic and analytic perception of facial expressions

In the face literature, it is debated whether the identification of facial expressions requires holistic (i.e., whole face) or analytic (i.e., parts-based) information. In this study, happy and angry composite expressions were created in which the top and bottom face halves formed either an incongruent (e.g., angry top + happy bottom) or congruent composite expression (e.g., happy top + happy bottom). Participants reported the expression in the target top or bottom half of the face. In Experiment 1, the target half in the incongruent condition was identified less accurately and more slowly relative to the baseline isolated expression or neutral face conditions. In contrast, no differences were found between congruent and the baseline conditions. In Experiment 2, the effects of exposure duration were tested by presenting faces for 20, 60, 100 and 120 ms. Interference effects for the incongruent faces appeared at the earliest 20 ms interval and persisted for the 60, 100 and 120 ms intervals. In contrast, no differences were found between the congruent and baseline face conditions at any exposure interval. In Experiment 3, it was found that spatial alignment impaired the recognition of incongruent expressions, but had no effect on congruent expressions. These results are discussed in terms of holistic and analytic processing of facial expressions.

The effect of exposure duration on visual character identification in single, whole, and partial report.

The psychometric function of single-letter identification is typically described as a function of stimulus intensity. However, the effect of stimulus exposure duration on letter identification remains poorly described. This is surprising because the effect of exposure duration has played a central role in modeling performance in whole and partial report (Shibuya & Bundesen, 1988). Therefore, we experimentally investigated visual letter identification as a function of exposure duration. We compared the exponential, the gamma, and the Weibull psychometric functions, all with a temporal offset included, as well as the ex-Gaussian, the log-logistic, and finally the squared-logistic, which is a psychometric function that to our knowledge has not been described before. The log-logistic and the squared-logistic psychometric function fit well to experimental data. Also, we conducted an experiment to test the ability of the psychometric functions to fit single-letter identification data, at different stimulus contrast levels; also here the same psychometric functions prevailed. Finally, after insertion into Bundesen's Theory of Visual Attention (Bundesen, 1990), the same psychometric functions enable closer fits to data from a previous whole and partial report experiment.

Study on the Effect of Exposure Duration on Recommended Target of Cd-Contaminated Soil Remediation

Based on the process of health risk assessment for Cd contaminated sites, study the relationship between exposure duration and recommended target of soil remediation. This paper discusses the changes (from 7.7 mg/kg to 5.0 mg/kg, from 9.1 mg/kg to 3.8 mg/kg) of recommended target for soil remediation when the exposure duration has large changes (EDa ranges from 6a to 36a, EDc ranges from 1a to 12a). The results point out that both EDa and EDc have effects on recommended target of soil remediation, and in general, exposure duration and recommended target of soil remediation vary inversely.

Implications of full-scale building motion experience for serviceability design

While there are a number of guidelines used throughout the world in the assessment of acceptability of tall building accelerations, none are based on systematically conducted surveys of occupant reaction to wind-induced motion. In this study, occupant response data were gathered by both a self-reporting mechanism and by interviewer-conducted surveys in control tower structures over a period of four years. These two approaches were designed in conjunction with experimental psychologists to ensure unbiased reporting. The data allowed analysis of perception thresholds and tolerability at different building frequencies and in different wind climates. The long-term nature of the studies also allowed an investigation of the causes and effects of adaptation to building motion. As the surveys were designed to allow multiple use during single storms, the effects of exposure duration were investigated. A final exit survey was conducted at the primary survey location to investigate views of the acceptability of wind-induced motion and the factors underlying these views. The findings of the field studies indicate that none of the currently used acceleration guidelines address all of the factors that contribute to occupant dissatisfaction. An alternative framework for assessing acceleration acceptability is proposed.

Lung uptake of gold nanoparticles after intraperitoneal administration in vivo: Fluorescence study

Gold nanoparticles (GNPs) have potential applications in cancer diagnosis and therapy, drug delivery and food industry. Some studies indicate that certain nanoparticles (NPs) may cause adverse effects because of their small size and unique properties. However, little is known about the particle-size and exposure duration of intraperitoneal administration of GNPs in the rat lung tissue in vivo. The aim of the present study was to elucidate the particle size and exposure duration effects of intraperitoneal administration of GNPs on the rat lung tissue in vivo using fluorescence spectroscopy. Key words: Gold nanoparticles, sizes, exposure duration, lung tissue, fluorescence spectroscopy.