A comparison of the supervisory services rendered by state departments of education to secondary schools in the New England area.

Thesis (Ed.M.)--Boston Universit

Minimizing Bias in Biomass Allometry: Model Selection and Log‐Transformation of Data

Nonlinear regression is increasingly used to develop allometric equations for forest biomass estimation (i.e., as opposed to the traditional approach of log‐transformation followed by linear regression). Most statistical software packages, however, assume additive errors by default, violating a key assumption of allometric theory and possibly producing spurious models. Here, we show that such models may bias stand‐level biomass estimates by up to 100 percent in young forests, and we present an alternative nonlinear fitting approach that conforms with allometric theory

Matching Kasteleyn Cities for Spin Glass Ground States

As spin glass materials have extremely slow dynamics, devious numerical methods are needed to study low-temperature states. A simple and fast optimization version of the classical Kasteleyn treatment of the Ising model is described and applied to two-dimensional Ising spin glasses. The algorithm combines the Pfaffian and matching approaches to directly strip droplet excitations from an excited state. Extended ground states in Ising spin glasses on a torus, which are optimized over all boundary conditions, are used to compute precise values for ground state energy densities.Comment: 4 pages, 2 figures; minor clarification

A two-dimensional representation of four-dimensional gravitational waves

The Einstein equation in D dimensions, if restricted to the class of space-times possessing n = D - 2 commuting hypersurface-orthogonal Killing vectors, can be equivalently written as metric-dilaton gravity in 2 dimensions with n scalar fields. For n = 2, this results reduces to the known reduction of certain 4-dimensional metrics which include gravitational waves. Here, we give such a representation which leads to a new proof of the Birkhoff theorem for plane-symmetric space--times, and which leads to an explanation, in which sense two (spin zero-) scalar fields in 2 dimensions may incorporate the (spin two-) gravitational waves in 4 dimensions. (This result should not be mixed up with well--known analogous statements where, however, the 4-dimensional space-time is supposed to be spherically symmetric, and then, of course, the equivalent 2-dimensional picture cannot mimic any gravitational waves.) Finally, remarks on hidden symmetries in 2 dimensions are made.Comment: 12 pages, LaTeX, no figures, Int. J. Mod. Phys. D in prin

Exploring the Differences in Stress Mindset between Former and Current College Student-Athletes

Stress is a universal experience, often believed to be negative, that has been linked with negative consequences. However, recent studies have shown that stress can lead to positive outcomes as well, including an increase in health and performance in a variety of domains. Research has also found one’s beliefs about the nature of stress (e.g., stress mindset) play a large role in the extent to which one experiences these beneficial outcomes of stress. Although two athletes may encounter the same stressor, their beliefs on stress impact whether they experience detrimental or enhancing outcomes resulting from the stressor. Given some athletes view pressures associated with sport participation as negative or harmful, sometimes resulting in the athlete terminating their sport participation, research is needed examining the stress mindset in current athletes and former athletes who retired or terminated their sport participation early. PURPOSE: To explore the differences, if any, in stress mindset and perceived amount of stress between current and former student-athletes. METHODS: A total of 113 students (n = 87 current athletes; n = 26 former athletes) participated in this study. Participants completed a demographic questionnaire and the Stress Mindset Measure (SMM) administered via an online survey tool. The SMM is a self-report assessment of participants’ beliefs about stress. Mann-Whitney U tests were conducted to assess differences in stress mindset and perceived amount of stress between former and current college athletes. RESULTS: There was no significant difference observed between former and current student-athletes stress mindset scores (U = 1231.5, p = .494, η2 = .004). Likewise, there was no significant difference observed between current and former athletes on perceived amount of current stress (U = 884, p = .171, η2 = .025). CONCLUSION: No statistically significant differences between groups in stress mindset scores or perceived stress were observed, but both current and former athletes were found to have a stress-is-debilitating mindset (i.e., they held negative beliefs about the nature of stress). Current student-athletes did report a slightly lower SMM score (M = 1.65) than former athletes (M = 1.8) and given that stress mindset reflects one’s view of the process of stress itself and not simply an appraisal of any given stressor, there may be a difference in the way student-athletes appraise their sport or stress stemming from their sport participation. As burnout was not measured in the present study, it is possible the current student-athletes in this study may be experiencing burnout but have not terminated their sport participation yet. Future studies should examine burnout in athletes alongside the stress mindset and should continue to explore this construct with a larger sample of former athletes

Persistence and Memory in Patchwork Dynamics for Glassy Models

Slow dynamics in disordered materials prohibits direct simulation of their rich nonequilibrium behavior at large scales. "Patchwork dynamics" is introduced to mimic relaxation over a very broad range of time scales by equilibrating or optimizing directly on successive length scales. This dynamics is used to study coarsening and to replicate memory effects for spin glasses and random ferromagnets. It is also used to find, with high confidence, exact ground states in large or toroidal samples.Comment: 4 pages, 4 figures; reference correctio

A quadtree driven image fusion quality assessment

In this paper a new method to compute saliency of source images is presented. This work is an extension to universal quality index founded by Wang and Bovik and improved by Piella. It defines the saliency according to the change of topology of quadratic tree decomposition between source images and the fused image. The saliency function provides higher weight for the tree nodes that differs more in the fused image in terms topology. Quadratic tree decomposition provides an easy and systematic way to add a saliency factor based on the segmented regions in the images. <br /