Rational cubic spirals

We consider the problem of finding parametric rational Bézier cubic spirals (planar curves of monotonic curvature) that interpolate end conditions consisting of positions, tangents and curvatures. Rational cubics give more design flexibility than polynomial cubics for creating spirals, making them suitable for many applications. The problem is formulated to enable the numerical robustness and efficiency of the solution-algorithm which is presented and analyzed.     

Intermetallic and void formation in gold wirebonds to aluminum films

Gold ball bonds attached to either pure Al films or Al films with Cu and Si additions were annealed at temperatures in the range 77–277°C for periods of up to 3,000 h and then shear tested. The resulting fracture surfaces were observed to change progressively with time and temperature of annealing. The intermetallic phases and voids present after each annealing treatment were characterized by microscopic examination of the bond cross sections. Shear test results are discussed in terms of the observed microstructures.     

Role of epistemological beliefs and learned helplessness in secondary school students' learning science concepts from text.

This study examined the relationship between two variable sets: (a) epistemological beliefs (quick learning, simple knowledge, certain knowledge, and innate ability) and learned helplessness and (b) conceptual understanding and application reasoning in conceptual change learning (CCL). Hypothetical dimensions underlying the Epistemological Belief Questionnaire and effects of different kinds of prior knowledge on CCL were explored with 212 students in Grades 9–12 in 13 science classes at a rural public high school in Georgia. Exploratory factor analyses revealed 3 factors underlying epistemological beliefs: Quick Learning, Simple-Certain Knowledge, and Innate Ability. Canonical correlation analyses show that beliefs about Simple-Certain Knowledge contribute the most to CCL, whereas beliefs about Innate Ability contribute the least. Beliefs about Simple-Certain Knowledge and Quick Learning are important factors in CCL. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The individual response of saline lakes to a severe drought

A severe protracted drought between 1997 and 2009 has altered the physical and chemical hydrology of a series of lakes in the Corangamite Basin of southeast Australia. Leading up to the drying out of most lakes (many for the first time on record), we document the changes in lakes' water quantity (water levels and inundation), salinity (Cl concentrations), salinity processes (Cl/Br ratios), nutrient concentrations and ratios (ammonia, phosphate and NOx (nitrate and nitrite)) and algae (as chlorophyll-a) for six lakes. All lakes show record declines in inundated areas and increases in salinity from pre-drought (< 1997) to drought conditions. However, the magnitude of change in salinity varies for different lakes, and there is no systematic change in the controls on lake salinity processes. Four lakes show no change in salinity processes, one lake shows the beginnings of change; where halite dissolution reactions increased closer to the time of the lake drying up, and another lake shows a marked shift from predominantly evaporation to the cyclic dissolution and precipitation of halite. Changes in filterable reactive phosphorus (FRP) values and lake N and P limitation predictions also showed little systematic correlation with changes in lake salinity, and nutrient values varied between lakes and over time. The decline in NO_x concentrations in lakes where electrical conductivity (EC) values were above 100 mS/cm indicates some correlation with changes in salinity. Largely, these lakes exhibit individual changes in water quality parameters and salinity processes in response to the drought, indicating that while the stress of drought is regional, the hydrochemical response is local. In future changing climates, these results suggest that the catchment adaption strategies will require comprehensive plans for individual lake systems.     

Assignment methods in experimentation: When do nonrandomized experiments approximate answers from randomized experiments?

This meta-analysis compares effect size estimates from 51 randomized experiments to those from 47 nonrandomized experiments. These experiments were drawn from published and unpublished studies of Scholastic Aptitude Test coaching, ability grouping of students within classrooms, presurgical education of patients to improve postsurgical outcome, and drug abuse prevention with juveniles. The raw results suggest that the two kinds of experiments yield very different answers. But when studies are equated for crucial features (which is not always possible), nonrandomized experiments can yield a reasonably accurate effect size in comparison with randomized designs. Crucial design features include the activity level of the intervention given the control group, pretest effect size, selection and attrition levels, and the accuracy of the effect-size estimation method. Implications of these results for the conduct of meta-analysis and for the design of good nonrandomized experiments are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An investigation of six- to eleven-year-old children with allergic disorders.

Compared 6-11 yr. old children with and without allergic reactions on their intellectual ability, academic performance, social interaction patterns, medical history, TAT responses, and scores on a number of other psychological tests. Placement in the allergic sample was determined by a medical history provided by the parents of each child. The allergic sample included 199 boys and 172 girls, while the nonallergic sample consisted of 419 boys and 400 girls. Results indicate that Ss who did not exhibit allergic reactions were otherwise healthier and were rated as superior on a number of academic, social, and emotional adjustment dimensions. Results are related to studies of psychosomatic children. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rat strain differences in copulatory behavior after para-chlorophenylalanine and hormone treatment.

The potentiation of masculine copulatory behavior in castrated male rats following systemic parachlorophenylalanine (PCPA) treatment was found to be dependent upon the strain of rat and the recency of castration. Wistar (W) and Sprague-Dawley (SD) males displayed a decline in behavioral responsiveness to PCPA treatment following castration, the Ws retaining their behavioral responsiveness longer than SDs. Castrated Ws were also behaviorally more responsive to androgen replacement than were SDs. Ovariectomized W and SD females receiving estrogen replacement displayed a strain difference in hormonal sensitivity. In tests for feminine copulatory behavior, ovariectomized Ws were behaviorally more sensitive to estrogen treatment than SDs. Ovariectomized and estrogen-primed females of both strains displayed potentiated lordotic behavior following chronic PCPA treatment. Concomitant treatment with dexamethasone to reduce adrenal steroid output abolished the potentiation of lordotic behavior found with PCPA treatment. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)