Solutions to certain classes of linearized reaction–diffusion equations

A systematic study is presented for the linear manifold of solutions to a generic system of reaction–diffusion equations in the neighborhood of a constant uniform (equilibrium) solution. The theory pertains directly to an arbitrary number of reacting and diffusing molecular or biological species in an arbitrary bounded spatial (1-, 2- or 3-dimensional) region with an impermeable boundary, so that the normal gradient of any species concentration function is zero at all boundary points. The stability analysis developed by previous authors is streamlined here for the case of two reacting and diffusing species, worked out completely for the case of three species, and made more amenable to specialized treatment for cases with four or more species. With the use of modern algebraic computational methods, explicit analytical general solutions to the linearized reaction–diffusion equations are derived for certain classes of model theories. These results either apply directly or admit extension to a wide range of practical reaction–diffusion problems in physical chemistry and biology.     

School threat assessment versus suicide assessment: Statewide prevalence and case characteristics

Threat assessment is a violence prevention strategy used to investigate and respond to threats to harm others. In 2013, Virginia mandated the use of threat assessment teams for threats to self and to others, effectively subsuming suicide assessment with threat assessment and raising questions about the distinction between the two practices. In a statewide sample of 2,861 cases from 926 schools, there were more threats to self (60%) than others (35%), with only 5% involving threats to both self and others. Threats to self were more likely to be made by females (odds ratio [OR] = 3.38) and students with fewer prior disciplinary actions (OR = 0.48). Threats to self were much less likely to involve a weapon (OR = 0.07), but more likely to be attempted (OR = 1.50) and result in mental health services (OR = 2.96). They were much less likely to result in out‐of‐school suspensions (OR = 0.07), legal action (OR = 0.17), and/or changes in placement (OR = 0.53). Overall, these findings support a clear distinction between suicide and threat assessment.     

Dynamics of the frame in visual composition

The position of an object within a visual composition produces an effect on the observer. Does an observer see the object as strong and active if it is in the center of the picture, in one corner, “floating” off-center? Does the framing of the object or the field surrounding it give an object more meaning? Forty-four college students rated six framed, black-andwhite, single-object pictures. The 264 observations were subjected to principal axis factoring, resulting in four dimensions: activity, potency, evaluative, and verticality.     

The flow of instructors through the segmented labor markets of academe

This paper focuses on two categories of teaching personnel, those inside and outside of the tenure stream, who together provide instruction in North American post-secondary institutions. Segmented labor market thinking is used to examine the extent to which entry to the tenure stream is achieved by those who begin on appointments outside of these internal labor markets. Tabulations provided by Statistics Canada on the fate of seven entering cohorts of full-time instructors at Canadian universites (excluding Quebec) seven years after their initial appointment are analyzed. We find that a consistent and meaningful proportion of each cohort achieves entrance to the tenure stream from an initial external labor market appointment and that such an employment history accounts for almost half of all entrants who actually remain. Thus, despite the hardships of many who have no opportunity to be considered for continuing employment, external labor market appointees are, nonetheless, an important pool for recruitment of permanent faculty. This study adds to the growing body of knowledge that identifies their major role in the provision of post-secondary instruction. Disadvantages accruing to women and young academics and their relationships to external labor markets are discussed, as are the implications of these patterns for the changing career trajectories of those currently entering academe.     

Writing performance assessments: how important is extended time?

Students in Grades 5 and 8 completed a 30-minute writing performance assessment and a writing performance assessment completed over 3 days. Assessments were evaluated on four traits (ideas, organization, conventions, and sentence fluency). A significant interaction was found at Grade 5 between length of time allotted for the assessment and students' educational classification (general or special education). Grade 5 students performed significantly better on the 3-day writing assessment, with students in special education benefiting the most. At Grade 8, there were no differences between scores on the 30-minute and the 3-day assessments. No significant differences were found in students' writing performance across various types of discourse (narrative, imaginative, persuasive, and expository); significant differences were reported across certain writing traits. We shared three hypotheses for reported differences: (a) students' proficiency with the writing process, (b) scoring scale bias, and (c) differences in the revision behaviors of developing and mature writers. Educational implications related to statewide test programs are discussed.     

Preference for signaled shock phenomenon: Direct and indirect evidence for modifiability factors in the shuttlebox

The experiments reported here investigated whether unauthorized shock modification is a factor which mediates the preference for signaled shock phenomenon (PSS) in the shuttlebox. This factor appearednot to have a critical role in PSS on the basis of earlier experiments which reported that PSS occurred in the shuttle-box even when shock was made unmodifiable by scrambling. However, the scrambling used in these experiments was not complete. In Experiments I and II reported here, no PSS occurred with completely scrambled grids; the phenomenon emerged only with unscrambled shock. Experiment III reports evidence indicating a connection between directly assessed modification and PSS with unscrambled shock, with PSS emerging only when modification had begun to occur. The pattern of results from these shuttlebox experiments parallels that found in an earlier study of PSS using a symmetrical-choice, barpress preparation.     

Equity among assistant professors in instructional work load

In recent years salary equity has been the focus of studies dealing with equity. This paper extends the concept of equity to include faculty instructional activities or work load. In an effort to determine to what extent instructional efforts differed between men and women at a large land-grant university, the following variables were investigated: number of weighted student credit hours, number of sections taught, number of different courses taught, and didactic hours by level of course. Because the faculty members varied in their full-time-equivalent instructional effort, it was necessary to normalize the data. When men and women were compared for equity of instructional activity (MANOVA) taking their college into consideration, there was no significant difference by sex or from the interaction of college with sex. When a balancing technique was used to review men and women by departments, again no significant differences were found in the pattern of instructional activity within the group of departments being compared.