Service Learning: Driving School Reform in the 1990s

Introduction: New initiatives in education reform are sprouting up everywhere. Spurred on by A Nation At Risk, educators have been trying to find the magic formula for preventing dropouts while at the same time producing students who surpass the Germans, Japanese, and everyone else in test scores. Although exciting educational innovations have become institutionalized during the past decade, a cohesive strategy to meet the overwhelming need of our society to successfully educate all of our children is lacking

Laboratory oxide coatings: Physical form and surface chemistry

The impact of dissolved trace metals on aquatic ecosystems and human health is controlled by sorption, i.e., binding to the surfaces of environmental particles. Since many environmental particles are coated with highly reactive substances, and since discrepancies in trace metal sorption behavior persist between oxides developed in the laboratory and environmental oxide phases, it was hypothesized that the physical form of oxide coatings may influence the chemical properties of the coated particle. Therefore, relationships between the physical forms of several different Fe(III) oxide coatings and the Cu(II) sorption behavior of the coated solids were investigated in comparison with the component phases and natural sedimentary materials. Goethite (alpha-FeOOH) was coated onto quartz and kaolinite grains. Coating method and thickness were varied. Physical properties of the coated solids were probed using multipoint N2 (g) adsorption and desorption analysis (BET), The morphology of the particles was studied by scanning electron microscopy (SEM), and the uniformity of oxide distribution on the grain surfaces was assessed by energy-dispersive X-ray (EDS) analysis. Chemical properties were investigated via batch Cu(II) adsorption/desorption experiments. Goethite physical form was found to vary with coating method and substrate mineralogy. Cu(II) sorption (uptake and release of dissolved Cu from goethite-coated particles) depended on the coating method, substrate, and thickness of the coating. Analysis of these variations indicated physical changes in the form of the coating, interactions between goethite and substrate, and changes in the surface chemical properties of one or both solid phases (goethite and substrate). The combined physical and chemical alterations in the properties of the solids produced distinct behavior in each of the laboratory-prepared solids studied. A parallel set of experiments was conducted on three geologically related sedimentary materials. Several physical and chemical differences were observed between crude kaolin and a cleaned reference kaolinite. One laboratory-prepared goethite coating matched a surface soil at precipitation-dominated Cu loadings, and another coated solid matched a subsurface material at all Cu loading ranges sampled. These results suggest that more complex laboratory-prepared sorbent phases may better reflect trace metal sorption properties of environmental particles

Multi-modal MHD oscillations in the solar corona, and their use in coronal seismology

The solar atmosphere is a dynamic, inhomogeneous environment which acts as a natural plasma laboratory for a keen community of observers and researchers at the forefront of modern physics. Colossal plasma non-uniformities on the Sun are seen to host a wide variety of magnetoacoustic oscillatory motions, which may be used as probes into the local plasma conditions using the theory of long wavelength, large scale magnetohydrodynamics (MHD): this process is known as coronal seismology. The focus of this thesis is to contribute to the detailed observation of these waves and their use in coronal seismology, particularly the usefulness of observing multiple harmonics and understanding of dispersion. Fast kink-mode oscillations of coronal loops, observed as rapidly decaying transverse displacements, are a well-understood wave mode used for seismology. The simultaneous detection of multiple harmonics can provide more information, allowing one to match the observed dispersion with that predicted by theory. Extreme ultraviolet observations of a coronal loop hosting a standing kink oscillation are analysed using image processing and time series techniques. The presence of two simultaneous harmonics is revealed, a fundamental mode at a period of ∼ 8 minutes and its third harmonic at ∼ 2.6 minutes. The ratio of periods P1/3P3 was found to be ∼ 0.87, whose departure from unity indicates a non-uniform distribution of kink speed through the loop. For all locations, the ratio of damping time to period for the two harmonics were found to agree within error, validating the widely assumed 1d resonant absorption theory used to explain a kink oscillation’s rapid damping. This is the first time a measurement of the signal quality for a higher harmonic of a kink oscillation has been reported with spatially resolved data. One exciting development in coronal seismology is the recent detection of decay-less oscillations, which are a different regime of fast-kink oscillations omnipresent in coronal loops. The first detection of a coronal loop exhibiting multi-modal decay-less oscillations is presented, in which both the loop’s fundamental mode (P1 = 10.3 +1.5 −1.7 minutes) and its second harmonic (P2 = 7.4 +1.1 −1.3 minutes) are detected. To make this detection possible, the observational data was passed through a novel motion magnification algorithm to accentuate transverse oscillations. An illustration of seismology using the ratio P1/2P2 ∼ 0.7 to estimate the density scale height is presented. The existence of multiple harmonics has implications for understanding the driving and damping mechanisms for decay-less oscillations, and adds credence to their interpretation as standing kink mode oscillations. There is a myriad of MHD oscillation modes, and whilst fast-kink modes are observed as transverse displacements of the plasma non-uniformity, slow modes may be observed as intensity enhancements. Analysis of such propagating slow modes observed in a fan of coronal loops above a sunspot is performed. The instantaneous velocities and periods of these intensity enhancements are measured and compared in different temperature passbands and azimuthal angles. The waves seen in the 171˚A channel (∼ 0.6 MK) appeared slower than when observed co-spatially in the 193˚A (∼ 1.58 MK). This contradicts the expectation that the phase speed is approximately the local sound speed, which varies as the square root of the temperature. This discrepancy is resolved by attributing the difference in apparent velocity to different inclination angles, which are estimated to be 9° ± 3° from the vertical for the waves seen in 193 A, and 19° ± 4° when seen in 171 A. This provides some evidence supporting the theory that coronal loops are formed of several distinct, unresolved strands of different temperature. From the theoretical point of view, the dispersion relation governing slow MHD modes in the presence of a wave-induced misbalance between the plasma heating and cooling mechanisms is developed. The thin flux tube approximation is used to account for finite-β effects, and thermal conduction is also included. The dispersion relation in the limits of weak non-adiabaticity and strong non-adiabaticity with finite-β is identified. It is found that the characteristic timescales of this imbalance (e.g. damping time) may be expressed in terms of the partial derivatives of the combined heating/cooling function with respect to constant gas pressure and constant magnetic pressure. Moreover, these characteristic timescales for the thermal misbalance coincide with typical MHD wave periods for a large range of densities and temperatures typical of the corona. Thus in the general case the dispersion on slow waves by the wave-induced thermal misbalance should not be neglected, and its inclusion may resolve some contradictions that have arisen when attributing the rapid damping of slow modes to thermal conduction or compressive viscosity alone. Instability criteria for the slow mode and entropy (thermal) mode are expressed in terms of a parameterisation of the unknown coronal heating function, under this thin flux tube approximation. Finally, noting that observations of slow modes in the corona do not show over-stability, and that the thermal mode does not appear to be unstable in general (with the exception of coronal rain), a new way of constraining the coronal heating function is presented

The College News, 1929-11-20, Vol. 16, No. 07

Bryn Mawr College student newspaper. Merged with The Haverford News in 1968 to form the Bi-college News (with various titles from 1968 on). Published weekly (except holidays) during the academic year

Seismological constraints on the solar coronal heating function

Aims. The hot solar corona exists because of the balance between radiative and conductive cooling and some counteracting heating mechanism that remains one of the major puzzles in solar physics. Methods. The coronal thermal equilibrium is perturbed by magnetoacoustic waves, which are abundantly present in the corona, causing a misbalance between the heating and cooling rates. As a consequence of this misbalance, the wave experiences a back-reaction, either losing or gaining energy from the energy supply that heats the plasma, at timescales comparable to the wave period. Results. In particular, the plasma can be subject to wave-induced instability or over-stability, depending on the specific choice of the coronal heating function. In the unstable case, the coronal thermal equilibrium would be violently destroyed, which does not allow for the existence of long-lived plasma structures typical for the corona. Based on this, we constrained the coronal heating function using observations of slow magnetoacoustic waves in various coronal plasma structures

Cut-off of transverse waves through the solar transition region

Context. Transverse oscillations are ubiquitously observed in the solar corona, both in coronal loops and open magnetic flux tubes. Numerical simulations suggest that their dissipation could heat coronal loops, counterbalancing radiative losses. These models rely on a continuous driver at the footpoint of the loops. However, analytical works predict that transverse waves are subject to a cut-off in the transition region. It is thus unclear whether they can reach the corona, and indeed heat coronal loops. Aims. Our aims are to determine how the cut-off of kink waves affects their propagation into the corona, and to characterize the variation of the cut-off frequency with altitude. Methods. Using 3D magnetohydrodynamic simulations, we modelled the propagation of kink waves in a magnetic flux tube, embedded in a realistic atmosphere with thermal conduction, that starts in the chromosphere and extends into the corona. We drove kink waves at four different frequencies, and determined whether they experienced a cut-off. We then calculated the altitude at which the waves were cut-off, and compared it to the prediction of several analytical models. Results. We show that kink waves indeed experience a cut-off in the transition region, and we identified the analytical model that gives the best predictions. In addition, we show that waves with periods shorter than approximately 500 s can still reach the corona by tunnelling through the transition region, with little to no attenuation of their amplitude. This means that such waves can still propagate from the footpoints of loop, and result in heating in the corona.Comment: Accepted for publication in A&A. 8 pages, 7 figure

Evaluating patient and public involvement in health research: from theoretical model to practical workshop

© 2017 The Authors Health Expectations published by John Wiley & Sons Ltd Background: There is a growing literature on evaluating aspects of patient and public involvement (PPI). We have suggested that at the core of successful PPI is the dynamic interaction of different forms of knowledge, notably lay and professional. We have developed a four-dimensional theoretical framework for understanding these interactions. Aim: We explore the practical utility of the theoretical framework as a tool for mapping and evaluating the experience of PPI in health services research. Methods: We conducted three workshops with different PPI groups in which participants were invited to map their PPI experiences on wall charts representing the four dimensions of our framework. The language used to describe the four dimensions was modified to make it more accessible to lay audiences. Participants were given sticky notes to indicate their own positions on the different dimensions and to write explanatory comments if they wished. Participants’ responses were then discussed and analysed as a group. Results: The three groups were distinctive in their mapped responses suggesting different experiences in relation to having a strong or weak voice in their organization, having few or many ways of getting involved, addressing organizational or public concerns and believing that the organization was willing to change or not. Discussion: The framework has practical utility for mapping and evaluating PPI interactions and is sensitive to differences in PPI experiences within and between different organizations. The workshops enabled participants to reflect collaboratively on their experiences with a view to improving PPI experiences and planning for the future

China, Europe, and the Pandemic Recession: Beijing’s Investments and Transatlantic Security

Given the depth and breadth of the pandemic-induced recession in Europe, private companies in need of capital and governments looking to shed state-owned enterprises may be tempted to sell shares, assets, or outright ownership to investors with liquidity to spare. Of greatest concern is the role that China might play in Europe, building Beijing’s soft power, weakening allied geopolitical solidarity, and potentially reprising the role it played in the 2010s, when its investments in Europe expanded dramatically. More specifically, there is concern over China’s investments in infrastructure and sensitive technologies relevant to American and allied military operations and capabilities. Whether Europe is prepared and able to parry Beijing’s economic statecraft is somewhat unclear, given varied attitudes toward China and the patchwork of investment screening mechanisms across the continent. Regardless, the outcomes will have significant implications for US security and for the Defense Department specifically. In support of US European Command (EUCOM) and the Department of Homeland Security (DHS), the U.S. Army War College’s Strategic Studies Institute (SSI) assembled an interdisciplinary team to examine these issues and offer actionable policy recommendations for military leaders and decisionmakers on both sides of the Atlantic. Study sponsors (nonfunding): United States European Command, United States Department of Homeland Securityhttps://press.armywarcollege.edu/monographs/1945/thumbnail.jp

The dynamics and observability of circularly polarized kink waves

Context. Kink waves are routinely observed in coronal loops. Resonant absorption is a well-accepted mechanism that extracts energy from kink waves. Nonlinear kink waves are know to be affected by the Kelvin-Helmholtz instability. However, all previous numerical studies consider linearly polarized kink waves. Aims. We study the properties of circularly polarized kink waves on straight plasma cylinders, for both standing and propagating waves, and we compare them to the properties of linearly polarized kink waves. Methods. We used the code MPI-AMRVAC to solve the full 3D magnetohydrodynamic equations for a straight magnetic cylinder, excited by both standing and propagating circularly polarized kink (m = 1) modes. Results. The damping due to resonant absorption is independent of the polarization state. The morphology or appearance of the induced resonant flow is different for the two polarizations; however, there are essentially no differences in the forward-modeled Doppler signals. For nonlinear oscillations, the growth rate of small scales is determined by the total energy of the oscillation rather than the perturbation amplitude. We discuss possible implications and seismological relevance