6,313 research outputs found
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Navigating the Turbulent Waters of School Reform Guided by Complexity Theory
The goal of this research study has been to develop, implement, and evaluate a school reform design experiment at a continuation high school with low-income, low-performing underrepresented minority students. The complexity sciences served as a theoretical framework for this design experiment. Treating an innovative college preparatory program as a nested complex adaptive system within a larger complex adaptive system, the school, we used features of complex adaptive systems (equilibrium, emergence, self-organization, and feedback loops) as a framework to design a strategy for school reform. The goal was to create an environment for change by pulling the school far from equilibrium using a strategy we call “purposeful perturbations” to disrupt the stable state of the school in a purposeful way. Over the four years of the study, several tipping points were reached, and we developed agent-based simulation models that capture important dynamic properties of the reform at these points. The study draws upon complexity theory in multiple ways that have supported improved education for low-achieving students
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Education as a Complex System: Conceptual and Methodological Implications
Education is a complex system, which has conceptual and methodological implications for education research and policy. In this article, an overview is first provided of the Complex Systems Conceptual Framework for Learning (CSCFL), which consists of a set of conceptual perspectives that are generally shared by educational complex systems, organized into two focus areas: collective behaviors of a system, and behaviors of individual agents in a system. Complexity and research methodologies for education are then considered, and it is observed that commonly used quantitative and qualitative techniques are generally appropriate for studying linear dynamics of educational systems. However, it is proposed that computational modeling approaches, being extensively used for studying nonlinear characteristics of complex systems in other fields, can provide a methodological complement to quantitative and qualitative education research approaches. Two research case studies of this approach are discussed. We conclude with a consideration of how viewing education as a complex system using complex systems’ conceptual and methodological tools can help advance education research and also inform policy
Relationship between volume status and blood pressure during chronic hemodialysis
Relationship between volume status and blood pressure during chronic hemodialysis.BackgroundThe relationship between volume status and blood pressure (BP) in chronic hemodialysis (HD) patients remains incompletely understood. Specifically, the effect of interdialytic fluid accumulation (or intradialytic fluid removal) on BP is controversial.MethodsWe determined the association of the intradialytic decrease in body weight (as an indicator of interdialytic fluid gain) and the intradialytic decrease in plasma volume (as an indicator of postdialysis volume status) with predialysis and postdialysis BP in a cross-sectional analysis of a subset of patients (N = 468) from the Hemodialysis (HEMO) Study. Fifty-five percent of patients were female, 62% were black, 43% were diabetic and 72% were prescribed antihypertensive medications. Dry weight was defined as the postdialysis body weight below which the patient developed symptomatic hypotension or muscle cramps in the absence of edema. The intradialytic decrease in plasma volume was calculated from predialysis and postdialysis total plasma protein concentrations and was expressed as a percentage of the plasma volume at the beginning of HD.ResultsPredialysis systolic and diastolic BP values were 153.1 ± 24.7 (mean ± SD) and 81.7 ± 14.8mm Hg, respectively; postdialysis systolic and diastolic BP values were 136.6 ± 22.7 and 73.9 ± 13.6mm Hg, respectively. As a result of HD, body weight was reduced by 3.1 ± 1.3kg and plasma volume was contracted by 10.1 ± 9.5%. Multiple linear regression analyses showed that eachkg reduction in body weight during HD was associated with a 2.95mm Hg (P = 0.004) and a 1.65mm Hg (P = NS) higher predialysis and postdialysis systolic BP, respectively. In contrast, each 5% greater contraction of plasma volume during HD was associated with a 1.50mm Hg (P = 0.026) and a 2.56mm Hg (P < 0.001) lower predialysis and postdialysis systolic BP, respectively. The effects of intradialytic decreases in body weight and plasma volume were greater on systolic BP than on diastolic BP.ConclusionsHD treatment generally reduces BP, and these reductions in BP are associated with intradialytic decreases in both body weight and plasma volume. The absolute predialysis and postdialysis BP levels are influenced differently by acute intradialytic decreases in body weight and acute intradialytic decreases in plasma volume; these parameters provide different information regarding volume status and may be dissociated from each other. Therefore, evaluation of volume status in chronic HD patients requires, at minimum, assessments of both interdialytic fluid accumulation (or the intradialytic decrease in body weight) and postdialysis volume overload
Education as a Complex System: Conceptual and Methodological Implications
Education is a complex system, which has conceptual and methodological implications for education research and policy. In this article, an overview is first provided of the Complex Systems Conceptual Framework for Learning (CSCFL), which consists of a set of conceptual perspectives that are generally shared by educational complex systems, organized into two focus areas: collective behaviors of a system, and behaviors of individual agents in a system. Complexity and research methodologies for education are then considered, and it is observed that commonly used quantitative and qualitative techniques are generally appropriate for studying linear dynamics of educational systems. However, it is proposed that computational modeling approaches, being extensively used for studying nonlinear characteristics of complex systems in other fields, can provide a methodological complement to quantitative and qualitative education research approaches. Two research case studies of this approach are discussed. We conclude with a consideration of how viewing education as a complex system using complex systems’ conceptual and methodological tools can help advance education research and also inform policy
Inflation from Extra Dimensions
The radial mode of n extra compact dimensions (the radion, b) can cause
inflation in theories where the fundamental gravity scale, M, is smaller than
the Planck scale M_P. For radion potentials V(b) with a simple polynomial form,
to get the observed density perturbations, the energy scale of V(b) must
greatly exceed M ~ 1 TeV: V(b)^{1/4} = M_v ~ 10^{-4} M_P. This gives a large
radion mass and reheat temperature ~ 10^9 GeV, thus avoiding the moduli
problem. Such a value of M_v can be consistent with the classical treatment if
the new dimensions started sufficiently small. A new possibility is that b
approaches its stable value from above during inflation. The same conclusions
about M_v may hold even if inflation is driven by matter fields rather than by
the radion.Comment: 4 pages, 4 figures, uses epsf.te
Quality of life measurement clarifies the cost-effectiveness of Helicobacter pylori eradication in peptic ulcer disease and uninvestigated dyspepsia 1
Previous economic studies of Helicobacter pylori eradication in dyspepsia and peptic ulcer disease have not measured quality of life using utilities (preference probabilities), which are needed to compare the cost-effectiveness of such treatment to other health care interventions. The goals of this study were to measure quality of life in patients with dyspepsia or peptic ulcer and apply these measurements to published models of disease management to determine cost-effectiveness in dollars per quality-adjusted life year (QALY) gained. Methods : Utilities for dyspepsia and peptic ulcer disease were measured in adult patients (n = 73) on chronic acid suppression for peptic ulcer or ulcer-like dyspepsia. Median utility values were applied to the results of published cost-effectiveness analyses and a previously validated dyspepsia model. Cost-utility ratios for early H. pylori eradication in uninvestigated dyspepsia and peptic ulcer disease were then computed. Results : The total disutility, or lost quality of life, for an ulcer was 0.11 QALY, of which 0.09 QALY was attributed to dyspeptic symptoms. After these results were incorporated into published studies, cost-utility ratios for ulcer treatment varied from 12,500 per QALY gained, whereas estimates for uninvestigated dyspepsia management ranged from 59,400 per QALY. Sensitivity analyses indicated a range of 27,300 per QALY for management of duodenal ulcer and 129,700 per QALY for dyspepsia. Conclusions: Strategies that emphasize early H. pylori eradication were cost-effective for patients with peptic ulcer and possibly cost-effective for patients with uninvestigated dyspepsia, relative to other medical interventions. Dyspeptic symptoms cause significant disutility that should be incorporated in future cost-effectiveness analyses of treatment strategies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73031/1/j.1572-0241.2001.03516.x.pd
Ultraviolet recall reaction after total body irradiation, etoposide, and methotrexate therapy.
Ultraviolet (UV) reactivation reactions are rare and can occur in areas of prior sunburn or UV light therapy after the administration of chemotherapy, antibiotics, and other medications. Reactions may occur within days, as described after methotrexate therapy, or may appear months later, as described with ampicillin. Such reactions have been variably termed UV recall, sunburn recall, photo recall, and photodermatitis reactivation, making classification difficult. We report a UV reactivation reaction in a patient with acute lymphocytic leukemia treated with total body irradiation, etoposide, and methotrexate. We propose the terms UV recall and UV enhancement be used in future reports to classify UV reactivation reactions in a scheme analogous to the terminology for cutaneous reactions after radiotherapy
Inflationary and Deflationary Branches in Extended Pre--Big Bang Cosmology
The pre--big bang cosmological scenario is studied within the context of the
Brans--Dicke theory of gravity. An epoch of superinflationary expansion may
occur in the pre--big bang phase of the Universe's history in a certain region
of parameter space. Two models are considered that contain a cosmological
constant in the gravitational and matter sectors of the theory, respectively.
Classical pre-- and post--big bang solutions are found for both models. The
existence of a curvature singularity forbids a classical transition between the
two branches. On the other hand, a quantum cosmological approach based on the
tunneling boundary condition results in a non--zero transition probability. The
transition may be interpreted as a spatial reflection of the wavefunction in
minisuperspace.Comment: 20 pages, latex, 3 figures available on reques
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