The role of biodegradation in limiting the accumulation of petroleum hydrocarbons in raingarden soils

Previous studies have indicated that raingardens are effective at removing petroleum hydrocarbons from stormwater. There are concerns, however, that petroleum hydrocarbons could accumulate in raingarden soil, potentially resulting in liability for the site owner. In this work, 75 soil samples were collected from 58 raingardens and 4 upland (i.e., control) sites in the Minneapolis, Minnesota area, representing a range of raingarden ages and catchment land uses. Total petroleum hydrocarbon (TPH) concentrations in the samples were quantified, as were 16S rRNA genes for Bacteria and two functional genes that encode for enzymes used in the degradation of petroleum hydrocarbons. TPH levels in all of the raingarden soil samples were low (<3 μg/kg) and not significantly different from one another. The TPH concentration in raingarden soil samples was, however, significantly greater (p ≤ 0.002) than TPH levels in upland sites. In addition, the number of copies of Bacteria 16S rRNA genes and functional genes were greater in the raingardens planted with deeply-rooted natives and cultivars than in raingardens containing simply turf grass or mulch (p < 0.036), suggesting that planted raingardens may be better able to assimilate TPH inputs. The ability of microorganisms present in the soil samples to degrade a representative petroleum hydrocarbon (naphthalene) was also investigated in batch experiments. A sub-set of the field sites was selected for re-sampling, and all soil samples tested (n = 8) were able to mineralize naphthalene. In these experiments the initial mineralization rate correlated with the number of copies of Bacteria 16S rRNA genes present.     

Cultural differences in complex addition: Efficient Chinese versus adaptive Belgians and Canadians.

In the present study, the authors tested the effects of working-memory load on math problem solving in 3 different cultures: Flemish-speaking Belgians, English-speaking Canadians, and Chinese-speaking Chinese currently living in Canada. Participants solved complex addition problems (e.g., 58 + 76) in no-load and working-memory load conditions, in which either the central executive or the phonological loop was loaded. The authors used the choice/no-choice method to obtain unbiased measures of strategy selection and strategy efficiency. The Chinese participants were faster than the Belgians, who were faster and more accurate than the Canadians. The Chinese also required fewer working-memory resources than did the Belgians and Canadians. However, the Chinese chose less adaptively from the available strategies than did the Belgians and Canadians. These cultural differences in math problem solving are likely the result of different instructional approaches during elementary school (practice and training in Asian countries vs. exploration and flexibility in non-Asian countries), differences in the number language, and informal cultural norms and standards. The relevance of being adaptive is discussed as well as the implications of the results in regards to the strategy choice and discovery simulation model of strategy selection (J. Shrager & R. S. Siegler, 1998). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple routes to solution of single-digit multiplication problems.

Researchers have assumed that adults solve simple arithmetic problems by retrieving answers from a network of stored facts. In 2 studies, undergraduates described their solutions of single-digit multiplication problems. They reported direct retrieval on approximately 80% of trials but also reported rules (e.g., anything times 0 is 0), repeated addition (e.g., 2?×?4?=?4?+?4), number series (e.g., 3?×?5?=?5, 10, 15), and derived facts (e.g., 6?×?7?=?[6?×?6]?+?6). Participants were slower to retrieve problems that were most likely to be solved by nonretrieval procedures and faster to retrieve problems that were usually solved by retrieval. These results indicate that direct-retrieval models are incomplete accounts of adults' performance and support a continuing influence of learning and experience on the mental representation of simple multiplication problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiplication by eye and by ear for Chinese-speaking and English-speaking adults.

Under two conditions, 32 English-speaking and 32 Chinese-speaking adults solved single-digit multiplication problems. In one condition, problems were presented as visual digits (e.g., 8×9). In the other condition, problems were presented as auditory number words in the participant's first language (e.g., /eit/ /taimz/ /nain/). Chinese-speaking adults made proportionately more operand-intrusion errors (e.g., 4×8=24) than English-speaking adults. Both groups made more operand-intrusion errors with auditory than with visual presentation. These findings are similar to those found when participants solve problems presented as visual number words (e.g., eight×nine), suggesting that in both cases the activation of phonological codes interferes with processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Subgrain strengthening of aluminum conductor wires

The influence of wire processing variables on the formation of subgrain structures and strengthening in three aluminum conductor materials is described. Electrical conductor grade aluminum, an Al-Fe-Mg alloy and an Al-Fe-Co alloy each develop subgrain structures with mean linear intercepts (•L) in the range of 0.4 to 1.5 μm with several sequences of wiredrawing and partial annealing. The yield strengths of these wires were found to obey a a = σ₀ +k(•L) ^m relationship, with an exponentm = -1 independent of the processing sequence used to arrive at the structure. The role of precipitate particles in the alloys is to raisek above that for EC-A1 while Mg in solid solution increases σ₀. The precipitates also affect the development of the substructure during the wiredrawing and annealing.     

Effects of peptide hormone structure on H+ secretion by Necturus gastric mucosa

The actions of human synthetic gastrin I(G), the C-terminal tetrapeptide of gastrin (T), and the C-terminal octapeptide of cholecystokinin (OP) on acid secretion and transepithelial potential difference (PD) of the isolated Necturus gastric mucosa were determined. All three peptides induced H+ secretion, but the maximum H+ output was less with OP than with G or T. G and OP produced their maximum H+ output at lower molar concentrations than T. G- and OP-stimulated secretion was long sustained, but T-stimulated secretion rapidly returned to basal levels. T- and G-stimulated secretion was partially inhibited by the addition of OP. Evidence is presented that T rapidly disappears from solutions exposed to gastric mucosa, whereas G does not. Washing sensitized the mucosa to subsequent addition of T. The results suggest that the action of the common C-terminal tetrapeptide of G, T, and OP is modified by the preceding amino acid sequences, and that T, the smallest of the three peptides, is rapidly degraded by gastric tissue in vitro. The implications of the work for the study of gastrointestinal hormone structure-function relationships in isolated tissue preparations are discussed.     

Subgrain strengthening of aluminum conductor wires

The influence of wire processing variables on the formation of subgrain structures and strengthening in three aluminum conductor materials is described. Electrical conductor grade aluminum, an Al-Fe-Mg alloy and an Al-Fe-Co alloy each develop subgrain structures with mean linear intercepts (?L) in the range of 0.4 to 1.5 μm with several sequences of wiredrawing and partial annealing. The yield strengths of these wires were found to obey a a = σ₀ +k(?L)^m relationship, with an exponentm = -1 independent of the processing sequence used to arrive at the structure. The role of precipitate particles in the alloys is to raisek above that for EC-A1 while Mg in solid solution increases σ₀. The precipitates also affect the development of the substructure during the wiredrawing and annealing.

     

Reading skill as a source of individual differences in the processing of instructional texts.

Evidence was found in support of the hypothesis that skilled readers are more likely than less skilled readers to successfully retrieve an appropriate procedure by reading an instructional text. Subjects completed a standardized reading comprehension test and a test designed to reflect their processing of an instructional text and an example. The instructional text and the example either described the same procedure for answering test items (no conflict) or described different and mutually exclusive procedures (conflict). Subjects who had higher scores on the reading test were more likely to notice the conflict between the instructional text and the example, and those who noticed the conflict were more likely to use the instructional text. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Large wire drawing plastic deformation in aluminum and its dilute alloys

The microstructures and hardening characteristics of Al and Al with dilute additions of soluble and insoluble impurities were compared during wire drawing at room temperature to true strains (ε _w ) of 4.95. Three stages of microstructure change are observed: formation of a dislocation cell structure; cell boundary sharpening and cell size refinement; dynamic recrystallization. A minimum effective cell size is reached at an intermediate strain level corresponding approximately to the onset of dynamic recrystallization. The amounts and types of impurities at levels less than 1 pct have a great effect on the details of the microstructural changes as well as the hardening characteristics. 99.98 pct pure Al alternately saturates and hardens fromε _w = 0 to 4.95. Al-0.6 Fe (insoluble) work softens nearε _w = 3.5. Al-0.2 Mg (soluble) and EC Al (with 0.15 pct soluble and insoluble impurities) both work harden at a diminishing rate toε _w ≃1.25 then enter a linear hardening stage which persists toε _w ≃5. A linear relation between yield strength and inverse cell size is established for EC Al and Al-0.2 Mg in the cell refinement strain range; however, the Petch slope is much less than that of similar Al alloys subjected to elevated temperature dynamic or static recovery. Al-0.6 Fe does not exhibit a consistent linear relation between yield strength and inverse cell size. These differences can be attributed to the degree of recovery and the interrelation between cell size, cell boundary character and total dislocation density.     

Word knowledge and working memory as predictors of reading skill.

Three measures of working memory capacity and three measures of word knowledge were used as predictors of three different measures of reading skill. The results demonstrated that the size of a reader's vocabulary and the speed of accessing it are independent of a "depth" measure of word knowledge and that reading comprehension, reading speed, and text inferencing ability are all independent measures of reading skill. A series of regression analyses were conducted to derive a causal model of the three reading performance measures. The results indicated that working memory efficiency during reading was related to comprehension, whereas a more passive working memory capacity measure was related to reading speed. Moreover, text inferencing ability was related only to word knowledge. We conclude that concepts such as "reading skill," "working memory," and "word knowledge" are multidimensional constructs that cannot be captured by a single variable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)