Distributional versus singular approaches to probability and errors in probabilistic reasoning.

Four experiments examined differences in probabilistic reasoning as a function of whether problems were presented in a frequentist or case-specific form. The experiments demonstrated that these different forms influence the likelihood of Ss committing the conjunction and disjunction fallacies. The authors contend that these 2 forms elicit different approaches to probability. Frequency problems, it is argued, elicit a distributional approach in which probabilities are equated with relative frequencies, whereas case-specific problems elicit a singular approach in which probabilities are equated with the propensities or causal forces operating in an individual case. According to this account, distributional and singular approaches evoke different kinds of inferential rules and heuristic procedures, some of which are more closely aligned with extensional principles than others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of rate and level of lowered finger surface temperature on manual performance.

Tested 32 Army enlisted men on 6 manual tasks when the right forefinger surface temperature was either not lowered (control condition) or lowered to temperatures of 65., 55., and 48. Fahrenheit (18.3., 12.8., and 8.9. Centigrade) after 5 or 50 min of cooling. Performance on all tasks decreased with lowered surface temperature. The level of finger surface temperature associated with impaired performance and the extent of the performance decrements associated with additional cooling varied across tasks and cooling rate. The differential effects of local cooling on manual performance across tasks and cooling rates were analyzed in terms of the differential susceptibility of hand function to parameters of cold exposure and the selective requirements across aspects of manual performance for unimpaired functioning of the hands and arms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ELECTRO-OSMOTIC DEWATERING OF FINE SUSPENSIONS: THE EFFICACY OF CURRENT INTERRUPTIONS

An important factor in the dewatering of fine suspensions by electro-osmosis is efficient mechanical collection and removal of water that is electrically generated. The mechanical collection can be the rate-determining step,controlling the overall dewatering. When the water is not efficiently removed, on-off power regimes appear to give as good results as continuous power application. This is not the case when water removal is highly efficient. A true test of the effect of different power regimes is possible with a thin bed of the suspension in a vacuum-assisted electrofilter, which provides a strong driving force to collect the water. Under these conditions, the rate of dewatering for full-wave or continuous power is always about double that for half-wave or on-off power regimes. These results suggest that recurring claims in the literature of the advantages of current interruptions or reversals in electro-osmotic dewatering may be erroneous or only partially correct.     

Mundane remembering.

Reviews the book, Remembering Reconsidered: Ecological and Traditional Approaches to the Study of Memory by Ulric Neisser and Eugene Winograd (see record 1988-98127-000). This volume is the second in a series known as The Emory Symposia in Cognition. The first volume addressed the question of "ecological and intellectual factors in categorization" and this second collection of papers pursues the ecological theme into the challenging realm of memory. As often happens with published symposia, the collection of chapters is greatly enlivened by the integrative commentary of thoughtful critics. In this volume this function is particularly well served with separate contributions by Neisser, Winograd, McCauley, Fivush, and by Rubin. My only regret is that none of them managed to bring order into the chaotic use of the term functional as it appears in various parts of the symposium. These commentaries add to the primary contributions in a way that results in a volume that is thematically more integrated than many such symposium collections. None of the contributions digs deeply into the real issues underlying the relationship between naturalistic and laboratory studies, but most of them demonstrate by way of example that the two approaches can serve complementary roles and a common goal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tests of the fidelity of lake sediment core records of mercury deposition to known histories of mercury contamination

There has been recent controversy over the discrimination between natural and anthropogenic loadings of mercury to lakes. Sediment core profiles have been interpreted as evidence that inputs to lakes have increased. Some investigators have argued, however, that mercury may be sufficiently mobile in sediments to generate profiles that are misinterpreted as historical records. This argument can be tested where the histories of inputs of mercury are known independently from other kinds of information. We have such cases in Canadian lakes and we have been able to assemble sediment core records for comparison with known source histories. Three cases are represented by Clay Lake in Ontario where the source was a chlor-alkali plant with a known history of mercury discharges, Giauque Lake in the Northwest Territories where mercury was used at a gold mine to extract gold from ore, and Stuart Lake in British Columbia where a mercury mine operated for a known period at Pinchi Lake, the lake immediately upstream from Stuart Lake. In these cases lake sediment cores were dated using lead-210 and cesium-137 and then slices were analysed for mercury. The histories of mercury deposition derived from the cores agreed well with the known histories of inputs.     

Historical contamination of Yukon Lake sediments by PCBs and organochlorine pesticides: influence of local sources and watershed characteristics

PCBs and other persistent organochlorine (OC) pesticides were analyzed in sediment cores collected from six lakes in Yukon Territory and one in northern British Columbia, Canada, with the objective of establishing sources and historical trends of these contaminants. DDT was found to be the most prominent OC in the sediment profiles of most of the lakes. Maximum sigmaDDT levels (3.47-2680 ng g(-1) dw) were observed in sediment slices dated to the 1950s from lakes near populated areas. In contrast, in more remote lakes (Hanson, Kusawa and Lindeman), the maximum sigmaDDT concentrations were observed in the sediments dated to the 1970s. Highest sigmaPCB and sigmaDDT concentrations were measured in sediments from Watson Lake, near a suspected PCB waste disposal site and in a region where DDT was heavily applied in the 1950s and 1960s. Elevated sigmaPCB concentrations [16.1-93.6 ng g(-1) dry weight (dw)] were also observed in sediments from lakes situated near populated areas, relative to Kusawa and Lindeman (11.1 and 12.7 ng g(-1) dw, respectively). Recent sigmaPCB fluxes ranged from 621 ng m(-2) y(-1) in Kusawa Lake to 16400 ng m(-2) y(-1) in Little Atlin Lake. The extremely high sedimentation rate (2050 g m(-2) y(-1)) in glacial fed Lindeman Lake gave rise to elevated fluxes of sigmaPCB (2410 ng m(-2) y(-1)) and other OCs, despite much lower concentrations in the sediment. Levels of hexachlorocyclohexanes (sigmaHCH), chlordane-related compounds (sigmaCHL), and chlorobenzenes (sigmaCBz) were in the low ng g(-1) (dw) range in all lake sediments, similar to concentrations previously reported for Arctic lakes in Canada, indicating that their major source was long range atmospheric transport. Contamination of the lakes with PCBs and DDT near populated areas of the Yukon Territory appears to be a result of regional activities rather than long range transport and deposition. The results also point to glacial runoff as a significant source of OCs to small, high elevation lakes (Lindeman), but not to larger lakes within the Yukon River drainage basin that are also affected by glacial sources (Kusawa, Laberge).