The Relationship Between School Board Governance Behaviors and Student Achievement

This non-experimental quantitative study examined the relationship between school board governance behavior (i.e. boardsmanship) and student achievement scores. Pearson\u27s r correlation was utilized to examine the relationship. Boardsmanship was defined by scores on the Board Self-Assessment Survey (BSAS) © designed by, and used with permission from, the Washington State School Directors Association (WSSDA). The BSAS consisted of a 69 item survey organized around 5 board Standards, 22 Benchmarks, and 69 Key Indicators (i.e. survey items). Board members from all 121 high school districts in Montana were invited to participate in the online survey. Seventy-four board members from 27 school districts returned complete and useable surveys for a response rate of 22.3% (27/121). Student achievement was defined by scores in reading, math, and science assessed by Montana\u27s Criterion Reference Test (CRT) given to all 10th graders. CRT scores were obtained from the Office of Public Instruction in Helena, MT. Data from both the BSAS and CRT were collected during the spring of AY 2011-2012. Statistically significant relationships were found between several aspects of student achievement and numerous elements of boardsmanship. Student achievement significantly correlated with some aspect of all five board Standards such as (a) providing responsible school district governance, (b) setting and communicating high expectations for student learning with clear goals and plans for meeting those expectations, (c) creating the conditions district wide for student and staff success, (d) holding the school district accountable for meeting student learning expectations, and (e) engaging the community. School boards that accomplish the items identified in the BSAS govern districts with the highest achievement scores. Each of these board Standards were further explicated through the Benchmarks and statistically significant Key Indicators which describe specific actions the board could take in order to participate in district efforts to raise student achievement. Boards do play a role in student achievement and their actions matter

Qualitative investigation of theoretical models: the value of process tracing

Political scientists frequently use qualitative evidence to support or evaluate the empirical applicability of formal models. Despite this widespread practice, neither the qualitative methods literature nor research on empirically evaluating formal models systematically address the topic. This article makes three contributions to bridge this gap. First, it demonstrates that formal models and qualitative evidence are indeed frequently combined in current research. Second, it shows how process tracing can be as important a tool for empirically assessing models as statistical testing, because models and process tracing share a common focus on understanding causal mechanisms. Last, it provides new guidelines for using process tracing that focus on issues specific to the modeling enterprise, illustrated with examples from recent research

Continued Fractions with Multiple Limits

For integers $m \geq 2$, we study divergent continued fractions whose numerators and denominators in each of the $m$ arithmetic progressions modulo $m$ converge. Special cases give, among other things, an infinite sequence of divergence theorems, the first of which is the classical Stern-Stolz theorem. We give a theorem on a general class of Poincar{\'e} type recurrences which shows that they tend to limits when the limits are taken in residue classes and the roots of their characteristic polynomials are distinct roots of unity. We also generalize a curious $q$-continued fraction of Ramanujan's with three limits to a continued fraction with $k$ distinct limit points, $k\geq 2$. The $k$ limits are evaluated in terms of ratios of certain unusual $q$ series. Finally, we show how to use Daniel Bernoulli's continued fraction in an elementary way to create analytic continued fractions with $m$ limit points, for any positive integer $m \geq 2$.Comment: 29 pages. Updated/new conten

The two-level atom laser: analytical results and the laser transition

The problem of the two-level atom laser is studied analytically. The steady-state solution is expressed as a continued fraction, and allows for accurate approximation by rational functions. Moreover, we show that the abrupt change observed in the pump dependence of the steady-state population is directly connected with the transition to the lasing regime. The condition for a sharp transition to Poissonian statistics is expressed as a scaling limit of vanishing cavity loss and light-matter coupling, $\kappa \to 0$, $g \to 0$, such that $g^2/\kappa$ stays finite and $g^2/\kappa > 2 \gamma$, where $\gamma$ is the rate of atomic losses. The same scaling procedure is also shown to describe a similar change to Poisson distribution in the Scully-Lamb laser model too, suggesting that the low-$\kappa$, low-$g$ asymptotics is of a more general significance for the laser transition.Comment: 23 pages, 3 figures. Extended discussion of the paper aim (in the Introduction) and of the results (Conclusions and Discussion). Results unchange

A Computational Comparison of Optimization Methods for the Golomb Ruler Problem

The Golomb ruler problem is defined as follows: Given a positive integer n, locate n marks on a ruler such that the distance between any two distinct pair of marks are different from each other and the total length of the ruler is minimized. The Golomb ruler problem has applications in information theory, astronomy and communications, and it can be seen as a challenge for combinatorial optimization algorithms. Although constructing high quality rulers is well-studied, proving optimality is a far more challenging task. In this paper, we provide a computational comparison of different optimization paradigms, each using a different model (linear integer, constraint programming and quadratic integer) to certify that a given Golomb ruler is optimal. We propose several enhancements to improve the computational performance of each method by exploring bound tightening, valid inequalities, cutting planes and branching strategies. We conclude that a certain quadratic integer programming model solved through a Benders decomposition and strengthened by two types of valid inequalities performs the best in terms of solution time for small-sized Golomb ruler problem instances. On the other hand, a constraint programming model improved by range reduction and a particular branching strategy could have more potential to solve larger size instances due to its promising parallelization features

On the possible role of cusp/cleft precipitation in the formation of polar-cap patches

International audienceThe work describes experimental observations of enhancements in the electron density of the ionospheric F-region created by cusp/cleft particle precipitation at the dayside entry to the polar-cap convection flow. Measurements by meridian scanning photometer and all-sky camera of optical red-line emissions from aurora are used to identify latitudinally narrow bands of soft-particle precipitation responsible for structured enhancements in electron density determined from images obtained by radio tomography. Two examples are discussed in which the electron density features with size scales and magnitudes commensurate with those of patches are shown to be formed by precipitation at the entry region to the anti-sunward flow. In one case the spectrum of the incoming particles results in ionisation being created, for the most part below 250 km, so that the patch will persist only for minutes after convecting away from the auroral source region. However in a second example, at a time when the plasma density of the solar wind was particularly high, a substantial part of the particle-induced enhancement formed above 250 km. It is suggested that, with the reduced recombination loss in the upper F-region, this structure will retain form as a patch during passage in the anti-sunward flow across the polar cap

MicroRNA-200 Family Members Differentially Regulate Morphological Plasticity and Mode of Melanoma Cell Invasion

A functional role of microRNAs (miRNAs or miRs) in neoplasia and metastasis is becoming clear, and the miR-200 family has received much attention for potentially regulating tumor progression. The miRNAs of this family have been shown to suppress epithelial-mesenchymal transition, and their down-regulation in some tumors promotes invasion and metastasis. Interestingly, while miR-200 is down-regulated in some cancers, it is up-regulated in others.We show that levels of miR-200 are increased in melanoma cell lines compared to normal melanocytes and that miR-200 family members play a role in determining modes of tumor cell migration. Individual tumor cells can invade in either elongated, "mesenchymal-type" or rounded, "amoeboid-like" modes and these two modes of invasion are inter-convertible [1]. In melanoma cell lines, expression of miR-200 members does not suppress invasion but rather leads to a switch between modes of invasion. MicroRNA-200c results in a higher proportion of cells adopting the rounded, amoeboid-like mode of invasion, while miR-200a results in a protrusion-associated elongated mode of invasion. Functional target identification studies suggest that the morphological effects of miR-200c may be mediated by reduced expression of MARCKS, which has been linked to formation of cell protrusions. In contrast miR-200a reduces actomyosin contractility, a feature of rounded morphology.Overall our findings call into question the general role of miR-200 in suppressing invasion and metastasis, and highlight novel distinguishing characteristics of individual miR-200 family members