The value of cognitive foundations for dynamic social theory

It is possible to develop models of social behavior that are predicated on detailed mechanical models of cognition. Cognitively based social models are potentially unified theoretical frameworks that can be used to explain a wide variety of social phenomena. Moreover, if a knowledge representation scheme and a knowledge acquisition scheme are specified in the underlying cognitive model then it is possible to produce a dynamic social model. The resulting social model can thus be used to predict and explain not only conditions for specific behaviors but changes in those behaviors over time.

Constructuralism is a theory of social behavior that rests on a cognitive model. The cognitive model specified has a knowledge representation scheme, knowledge acquisition procedures, and control procedures for shifting cognitive attention. The resulting social model is a dynamic model that can be used to explain both conditions for the occurrence of a behavior and social and individual changes that accrue do to a series of behaviors. The explanatory breadth of the model is illustrated by looking at predictions about a variety of social phenomena including: development of shared knowledge, identical behavior by members of the society, foreign language acquisition, clique formation, civil disobedience, and diffusion of innovative information.     

Efficacy of Different Concrete Models for Teaching the Part-Whole Construct for Fractions

The effectiveness of different concrete and pictorial models on students' understanding of the part-whole construct for fractions was investigated. Using interview data from fourth and fifth grade students from three different districts that adopted the Mathematics Trailblazers series, authors identified strengths and limitations of models used. Pattern blocks had limited value in aiding students' construction of mental images for the part-whole model as well as limited value in building meaning for adding and subtracting fractions. A paper fraction chart based on a paper folding model supported students' ability to order fractions with same numerators but was less useful in helping students on estimation tasks. The dot paper model and chips did not support fifth grade students' initial understanding of the algorithm.     

“We definitely wouldn't be able to solve it all by ourselves,but together…”: group synergy in tertiary students' problem-solving practices

The ability to address and solve problems in minimally familiar contexts is the core business of research mathematicians. Recent studies have identified key traits and techniques that individuals exhibit while problem solving, and revealed strategies and behaviours that are frequently invoked in the process. We studied advanced calculus students working in groups to identify what strategies they employed and how, including what encouraged the opportunities to invoke them. The study revealed behaviours not included in the original taxonomy, including one that we termed ‘group synergy’. We propose extensions to Carlson and Bloom's original taxonomy to encompass group behaviour and identify the importance of these behaviours in developing problem-solving skills. Finally, we suggest improvements for future problem-solving session iterations, with the goal of promoting opportunity for more expert performance.     

Persistence in systems of asymptotically autonomous difference equations

Asymptotically autonomous dynamical systems, both continuous and discrete, arise in the study of physical and biological systems that are modeled with explicit time-dependence.Convergence properties of such dynamical systems can be used to simplify analysis. In this paper, results are derived concerning the limiting behavior of a general asymptotically autonomous system of difference equations and its relationship to the dynamics of its limiting system. Examples from the biological literature are given.     

Solid‐state nuclear magnetic resonance investigation of neurosteroid compounds and magnesium interactions

The neurosteroid trans‐dehydroandrosterone (DHEA) and its analogs with slightly different modifications in the side chain attached to C17, that is, (3S)‐acetoxypregn‐5‐en‐20‐one ( 1 ) and (3S,20R)‐acetoxypregn‐5‐en‐20‐ol ( 2 ), have been synthesized to investigate DHEA–cation interactions. In this study, we applied solid‐state ¹H/¹³C cross‐polarization/magic‐angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy to a series of DHEA analog/Mg²⁺ mixtures at different Mg²⁺ concentrations. The high‐resolution ¹³C NMR spectra of 1 /Mg²⁺ mixtures exhibit two distinct ¹³C spectral patterns, one attributable to 1 free from Mg²⁺, and the other attributable to 1 with bound Mg²⁺. For 2 , the ¹³C NMR spectra exhibit three distinct spectral patterns; besides that of the free form, the other two can be assigned to Mg²⁺‐bound forms. Based on the analysis of the chemical shift deviations (CSDs), we conclude that both 1 and 2 might be subject to a cation–π interaction via the C5–C6 double bond, in contrast to that observed previously for DHEA. As demonstrated, DHEA possesses two Mg²⁺ binding sites, that is, C17–O and C5–C6 double bond, in which the binding affinity of the former is at least three times stronger than that of the latter. The solid‐state ¹³C NMR investigation allows better understanding of the underlying cation binding effects of neurosteroid molecules in vitro.     

Endoscopic and stroboscopic description of adults with paradoxical vocal fold dysfunction

The purpose of this study was to determine if endoscopic and stroboscopic parameters of voice were normal between attacks of paradoxical vocal fold dysfunction (PVFD). Fifty adults (38 females, 12 males) and 54 adult controls (40 females, 14 males) were examined via endoscopy with and without stroboscopy. Endoscopy indicated paradoxical adduction of the folds during the respiratory cycle of all 50 participants with PVFD, although they were asymptomatic. Atypical laryngeal configurations were observed including abnormality of the anterior-posterior dimension and ventricular fold medialization in both groups of subjects. Stroboscopy demonstrated abnormalities including unstable zero phase, decreased amplitude of vibration, decreased mucosal waves, and phase asymmetry primarily for the PVFD subjects alone. Results indicate that persons with PVFD demonstrate subtle laryngeal abnormality endoscopically and stroboscopically when dyspnea is not reported. This supports the hypothesis that PVFD is not episodic but exists as a continuum of laryngeal instability that may, due to various precipitating factors, be exacerbated to breathing attacks.     

Priming and sentence context support listening to noise-vocoded speech by younger and older adults

Older adults are known to benefit from supportive context in order to compensate for age-related reductions in perceptual and cognitive processing, including when comprehending spoken language in adverse listening conditions. In the present study, we examine how younger and older adults benefit from two types of contextual support, predictability from sentence context and priming, when identifying target words in noise-vocoded sentences. In the first part of the experiment, benefit from context based on primarily semantic knowledge was evaluated by comparing the accuracy of identification of sentence-final target words that were either highly predictable or not predictable from the sentence context. In the second part of the experiment, benefit from priming was evaluated by comparing the accuracy of identification of target words when noise-vocoded sentences were either primed or not by the presentation of the sentence context without noise vocoding and with the target word replaced with white noise. Younger and older adults benefited from each type of supportive context, with the most benefit realized when both types were combined. Supportive context reduced the number of noise-vocoded bands needed for 50% word identification more for older adults than their younger counterparts.     

Angle of incidence effects in a molecular solid

We investigate the influence of the angle of incidence on the sputter yield when bombarding molecular solid, benzene, with C₆₀. Our simulations show that at normal incidence, essentially all of the projectile energy is deposited into the substrate within ∼2.5 nm of the surface. However, at 75° incident angle, only 35% of the projectile energy is deposited within a depth of less than 1.5 nm of the surface while 65% of the projectile energy is reflected. Therefore, important aspects of the collision process which are dependent upon energy deposition, such as sputter yield, ejection depth, and molecule dissociation, may change as the incident angle changes.     

Paradigms and Paradoxes: Fractional and Other Non-integer Charges in Chemistry—an Understanding of Aromaticity

Structural Chemistry - In the current study, the energetics of fractionally (and indeed arbitrary non-integer) charged species is explicitly discussed for the enhanced understanding of aromaticity...