Feature distribution learning by passive exposure

Humans can rapidly estimate the statistical properties of groups of stimuli, including their average and variability. But recent studies of so-called Feature Distribution Learning (FDL) have shown that observers can quickly learn even more complex aspects of feature distributions. In FDL, observers learn the full shape of a distribution of features in a set of distractor stimuli and use this information to improve visual search: response times (RT) are slowed if the target feature lies inside the previous distractor distribution, and the RT patterns closely reflect the distribution shape. FDL requires only a few trials and is markedly sensitive to different distribution types. It is unknown, however, whether our perceptual system encodes feature distributions automatically and by passive exposure, or whether this learning requires active engagement with the stimuli. In two experiments, we sought to answer this question. During an initial exposure stage, participants passively viewed a display of 36 lines that included one orientation singleton or no singletons. In the following search display, they had to find an oddly oriented target. The orientations of the lines were determined either by a Gaussian or a uniform distribution. We found evidence for FDL only when the passive trials contained an orientation singleton. Under these conditions, RT decreased as a function of the orientation distance between the target and the exposed distractor distribution. These results suggest that FDL can occur by passive exposure, but only if an orientation singleton appears during exposure to the distribution.

Use of Theory-Driven Report Back to Promote Lung Cancer Risk Reduction

Report back is active sharing of research findings with participants to prompt behavior change. Research on theory-driven report back for environmental risk reduction is limited. The study aim is to evaluate the impact of a stage-tailored report back process with participants who had high home radon and/or air nicotine levels. An observational one-group pre-post design was used, with data collection at 3, 9, and 15 months post intervention. Participants from the parent study (N = 515) were randomized to the treatment or control group and this sample included all 87 treatment participants who: (1) had elevated radon and/or air nicotine at baseline; and (2) received stage-tailored report back of their values. Short-term test kits measured radon; passive airborne nicotine samplers assessed secondhand smoke (SHS) exposure. Stage of action was categorized as: (1) ‘Unaware,’ (2) ‘Unengaged,’ (3) ‘Deciding,’ (4) ‘Action,’ and (5) ‘Maintenance.’ Interventions were provided for free, such as in-person radon and SHS test kits and a brief telephonic problem-solving consultation. Stage of action for radon mitigation and smoke-free policy increased from baseline to 3 months and remained stable between 3 and 9 months. Stage of action for radon was higher at 15 months than baseline. Among those with high baseline radon, observed radon decreased by 15 months (p < 0.001). Tailored report back of contaminant values reduced radon exposure and changed the health behavior necessary to remediate radon and SHS exposure.

Determination of leachate toxicity through acute toxicity using Daphnia pulex and Anaerobic Toxicity Assays

The municipal solid waste (MSW) of large cities, in particular in developing countries, is mainly disposed of in landfills (LFs), whose inadequate management generates the emission of greenhouse gases and the production of leachates with high concentrations of organic and inorganic matter and occasionally heavy metals. In this study, the toxicity of the leachates from an intermediate-age municipal landfill was evaluated by ecotoxicity and anaerobic digestion tests. The acute toxicity assays with Daphnia pulex presented a toxic unit (TU) value of 49.5%, which indicates that these leachates should not be directly discharged into water sources or percolate into the soil because they would affect the ecosystems served by these waters. According to statistical analyses, the leachate toxicity is mainly associated with the inorganic fraction, with chlorides, calcium hardness and calcium having the greatest influence on the toxicity. The anaerobic toxicity assays showed that in the exposure stage, the methanogenic activity exceeded that of the control, which suggests that the anaerobic bacteria easily adapted to the leachate. Therefore, this treatment could be an alternative to mitigate the toxicity of the studied leachates. The inhibition presented in the recovery stage, represented by a reduction of the methanogenic activity, could arise because the amount of supplied substrate was not enough to fulfill the carbon and nutrient requirements of the bacterial population present.

Utilization of Sonography Compared With Magnetic Resonance Imaging in Determining the Cross-Sectional Area of the Median Nerve in a Sample of Working Macaca fascicularis

A preclinical study of 15 Macaca fascicularis monkeys was conducted to determine (1) the ability of detecting median mononeuropathy (MMN) within the median nerve after a work intervention and (2) the relationship between the layers of the median nerve during an acute inflammatory process by using sonography in conjunction with magnetic resonance imaging (MRI). Cross-sectional areas (CSAs) were imaged using MRI and sonography proximal to the carpal tunnel inlet (defined by the most distal portion of the radius) and further distal into the carpal tunnel (defined by the most proximal portion of the pisiform) at the prework exposure stage. CSAs measured on the outer edge of the median nerve were obtained from both modalities, at both anatomical locations. An intermodality t test demonstrated no statistical differences between the two sets of measurements (radius, P ≤ .15; pisiform, P ≤ .46). At the postwork exposure stage, sonographic measurements were obtained on the outer and inner borders of the median nerve at both anatomical levels. A two-tailed t test showed statistically significant differences within the carpal tunnel comparing pre- and postwork CSA measurements (radius, P ≤ .01; pisiform, P ≤ .297). The epineurial layer area was then determined as the difference between outer-border and inner-border CSAs. Pearson correlations between the epineurial layer and overall median nerve CSA within the carpal tunnel demonstrated a strong positive correlation that was statistically significant ( r = 0.97; P ≤ .01) after postwork exposure. Possible factors contributing to this acute phase of MMN could be hyperemia within the layers of the nerve and the development of Renault bodies. This work would need to be translated to human studies for further confirmation of the anatomic and clinical significance of this effect.

The Role of Injection Cues in the Associative Control of the US Pre-Exposure Effect in Flavour Aversion Learning

Two experiments, using rats as subjects, examined the role of contextual cues in producing the unconditioned stimulus (US) pre-exposure effect in conditioned taste aversion. Experiment 1 showed a significant US pre-exposure effect, when the pre-exposure was conducted in a familiar context, and that a change of context between the pre-exposure and conditioning phases did not attenuate this effect. Experiment 2 demonstrated that extinction of injection-related cues after the pre-exposure stage attenuated the US pre-exposure effect, when the pre-exposure was conducted in either a familiar or a novel context. Taken together, these results support the associative explanation of the US pre-exposure effect in terms of blocking, incorporating a role for injection-related cues in the context blocking analysis of the US pre-exposure effect.

Recognition and Interpretation of Polygenic Discontinuity Surfaces in the Middle Cretaceous Shu’aiba, Nahr Umr, and Natih Formations of Northern Oman

ABSTRACT Discontinuity surfaces that recorded superposition of marine hardground and subaerial exposure stages are common in the Middle Cretaceous of northern Oman. These surfaces formed during periods of rapid sea-level drop. The marine hardground stages are dominant in the field, whereas the subaerial exposure stage is documented in circumstantial petrographic, geochemical, and biological evidence. The record of a shoaling phase prior to exposure is commonly subtle and incomplete; supratidal deposits are conspicuously absent. Porosity in the limestones underlying the discontinuities is rearranged during subaerial exposure and subsequent burial and hence the permeability of large volumes of limestone is affected at a variety of scales. During marine hardground stages, carbonate cements, iron oxides, and manganese occludes some of the existing pore space. During burial, these intervals may thus have acted as either seals or efficient conduits of fluid flow. The surfaces under study in the Shu’aiba, Nahr Umr, and Natih formations are spaced ten to few tens of meters apart and many of them were traced laterally over distances of 100 kilometers and more between sections at Jebel Akhdar and in the Foothills. This implies that they play an important, but poorly understood role in compartmentalization of carbonate reservoir rocks.

Influence of Flow Regime on the Concentration of Cyanide Producing Anaerobic Process Inhibition

A study was conducted to analyze the effects of cyanide on methanogenic bacterial populations in both continuous and batch reactors. The appropriate toxicity assays were divided into two parts, i.e. 1) batch assays, and 2) continuous flow assays, using a 6.5-litre up-stream anaerobic sludge blanket reactor (UASB). A synthetic substrate was used as feed for both assays using 99% sucrose as a carbon source, and potassium cyanide (KCN) as a free cyanide source. In the first part, the treatments with the lowest and highest percentages of Specific Methanogenic Activity (SMA %) were 3 and 10 mg CN−/l. A 0.96 mg/l concentration of cyanide caused methanogenic activity inhibition by 50% during the exposure stage. During the recovery stage, Methanogenic Activity of treatments had a considerable increase compared to the results from direct cyanide exposure, except for treatments of 7 and 10 mg CN−/l. The concentration of cyanide that inhibits Specific Methanogenic Activity by 50% was 6.1 mg CN−/l during this stage. In the second part, the reactor was continuously fed with a synthetic substrate (COD≈ 1500 mg/l). After the anaerobic sludge became acclimated, cyanide concentrations from 0.5 and 130 mg CN−/l were progressively added. The hydraulic retention time remained constant at 12 hours throughout the entire experiment. Results indicated that while partial inhibition occurred for concentrations of 3, 20 and 100 mg CN−/l, severe inhibition occurred for 130 mg CN−/l.