The Relationship between Components of Effective Organizations and Teachers\u27 Instructional Practice

This purpose of this study is to determine whether the components of effective organizations are significantly related to teachers’ instructional practice as perceived by the teacher using data from the Program Capacity Survey (PCS) gathered during Year Two and Three of the STEM Career Awareness Program reform initiative. The PCS utilized Leithwood, Aitken and Jantzi’s (2001) monitoring tool and is based upon both Organizational Learning Theory and the Theory of Sustainability (Coburn, 2003). This study utilized selected questions from the PCS which were categorized into components of effective organizations. A factor analysis was used to establish the validity of the categorization. Using an ordinal logistic regression, data was analyzed to determine whether the components of effective organizations are significantly related to teachers’ instructional practice. In addition, the relationship and strength of association between the level of involvement in the decision making process and teachers’ perception of their instructional practice was analyzed. While the results of the ordinal regression were statistically nonsignificant, there was a statistically significant relationship based upon Cramer’s V for all five of the components of effective organizations at various collection periods throughout the reform implementation. There also was a statistically significant association between the level of involvement in the decision making process to adopt a new reform initiative and teachers’ instructional practice as perceived by the teacher. The findings support attending to and addressing components of effective organizations to create the conditions necessary to ensure a more successful reform implementation and increase the likelihood of sustainability

Nonequilibrium and Nonlinear Dynamics in Geomaterials I : The Low Strain Regime

Members of a wide class of geomaterials are known to display complex and fascinating nonlinear and nonequilibrium dynamical behaviors over a wide range of bulk strains, down to surprisingly low values, e.g., 10^{-7}. In this paper we investigate two sandstones, Berea and Fontainebleau, and characterize their behavior under the influence of very small external forces via carefully controlled resonant bar experiments. By reducing environmental effects due to temperature and humidity variations, we are able to systematically and reproducibly study dynamical behavior at strains as low as 10^{-9}. Our study establishes the existence of two strain thresholds, the first, epsilon_L, below which the material is essentially linear, and the second, epsilon_M, below which the material is nonlinear but where quasiequilibrium thermodynamics still applies as evidenced by the success of Landau theory and a simple macroscopic description based on the Duffing oscillator. At strains above epsilon_M the behavior becomes truly nonequilibrium -- as demonstrated by the existence of material conditioning -- and Landau theory no longer applies. The main focus of this paper is the study of the region below the second threshold, but we also comment on how our work clarifies and resolves previous experimental conflicts, as well as suggest new directions of research.Comment: 14 pages, 15 figure

The effect of crack orientation on the nonlinear interaction of a P wave with an S wave

Cracks, joints, fluids, and other pore-scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore-scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presence and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low-amplitude P wave probe by a high-amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal

Quasistatic loading of Berea sandstone

Запропонована феноменологiчна модель для опису властивостей напруження-деформацiя пiсковика пiд дiєю повiльного навантаження. Розглянута комбiнацiя трьох механiзмiв, якi пов’язуються з внутрiшнiми обмiнними процесами: механiзм стандартного релаксуючого твердого тiла, пружний механiзм з прилипанням, механiзм залишкової пластичної деформацiї. З малою кiлькiстю параметрiв модель вiдтворює як якiсно, так i кiлькiсно головнi експериментальнi данi по напруженню-деформацiї для пiсковика Береа. Модель правильно вiдтворює великi та малi петлi на траєкторiї напруження-деформацiя (пам’ять про кiнцеву точку). Власне запропонована залежнiсть деформацiї вiд напруження є не чим iншим, як рiвнянням стану пiсковика

Dobutamine-induced hypoperfusion without transient wall motion abnormalities: Less severe ischemia or less severe stress?

AbstractObjectives. This study sought to compare the clinical characteristics, hemodynamic response and severity of ischemia in patients with coronary artery disease and reversible perfusion defects on dobutamine 2-methoxy isobutyl isonitrile (MIBI) single-photon emission computed tomography (SPECT) with or without transient wall motion abnormalities.Background. The occurrence of reversible perfusion defects without concomitant wall motion abnormalities in patients with coronary artery disease was attributed to less severe ischemia. However, little data are available to support this observation.Methods. Fifty-four consecutive patients with significant coronary artery disease and reversible perfusion defects on dobutamine (up to 40 μg/kg body weight per min) MIBI SPECT were studied (mean [±SD] age 59 ± 11 years; 38 men, 16 women). All patients underwent simultaneous echocardiography. The myocardium was divided into six matched segments, and ischemic perfusion score was quantitatively derived in myocardial segments with reversible defects.Results. New or worsening wall motion abnormalities occurred in 40 patients (74%) (group A) and were absent in 14 (26%) (group B). There was no significant difference between the two groups with respect to age, previous myocardial infarction, number of abnormal coronary arteries (1.8 ± 0.8 vs. 1.6 ± 0.9), number of reversible perfusion defects (1.6 ± 0.9 vs. 1.8 ± 0.7) or ischemic perfusion score (412 ± 750 vs. 526 ± 553). Patients in group A had a higher prevalence of male gender (80% vs. 43%, p < 0.01), higher risk systolic blood pressure (147 ± 30 vs. 127 ± 31 mm Hu: < 0.05), higher peak rate-pressure product (19,632 ± 4,081 vs. 16,939 ± 4,344, p < 0.01) and a higher prevalence of angina (53% vs. 14%) and ST segment depression (55% vs. 14%) than group B (p < 0.05 for both).Conclusions. In patients with coronary artery disease and ischemia on dobutamine MIBI SPECT, the absence of transient wall motion abnormalities is associated with a similar extent and severity of reversible perfusion defects, a lower stress rate-pressure product and a higher prevalence of female gender than patients with transient wall motion abnormalities. Mechanically silent with transient wall motion abnormalities. Mechanically silent ischemia should not be regarded as a marker of less severe ischemia on myocardial perfusion scintigraphy