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Saturn's quasi-periodic planet-encircling storms are the largest convecting outbursts in the Solar System. The last eruption was in 1990. A new eruption started in December 2010 and presented the first-ever opportunity to observe such episodic storms from a spacecraft in orbit around Saturn. Here, we analyze images acquired with the Cassini Imaging Science Subsystem (ISS), which captured the storm's birth, evolution and demise. In studying the end of the convective activity, we also analyze the Saturn Electrostatic Discharge (SED) signals detected by the Radio and Plasma Wave Science (RPWS) instrument. [...], Comment: 17 figures

This study addresses the question: Do the kinds and amounts of pre-service education and preparation that beginning teachers receive before they start teaching have any impact on whether they leave teaching? We examine a wide range of measures of teachers' subject-matter education and pedagogical preparation. We also compare different fields of teaching, with a particular focus on mathematics and science. Our data source is the National Center for Education Statistics' nationally representative 2003-04 Schools and Staffing Survey and its supplement, the 2004-05 Teacher Follow-up Survey. Our analyses show that beginning teachers widely varied in the pre-service education and preparation they received. In general, mathematics teachers and, especially, science teachers tended to have more subject-matter content education and more graduate-level education, and to have less pedagogical and methodological preparation than other teachers. Our analyses also show that, after controlling for the background characteristics of teachers and their schools, some aspects of the education and preparation that beginning teachers received were significantly associated with their attrition, while others were not. Specifically, the type of college, degree, entry route or certificate mattered little. What did matter was the substance and content of new teachers' pedagogical preparation. Those with more training in teaching methods and pedagogy--especially practice teaching, observation of other classroom teaching and feedback on their own teaching--were far less likely to leave teaching after their first year on the job.

Has the elementary and secondary teaching force changed in recent years? If so, how? Have the types and kinds of individuals going into teaching changed? Have the demographic characteristics of those working in classrooms altered? To answer these questions, the authors embarked on an exploratory research project to try to discover what trends and changes have, or have not, occurred in the teaching force over the past few decades. To explore these questions, the authors used the largest and most comprehensive source of data on teachers available--the Schools and Staffing Survey (SASS) and its supplement, the Teacher Follow-Up Survey (TFS). The data was used to explore what changes have taken place in the teaching force and teaching occupation over the two and a half decades from 1987 to 2012. The seven most popular trends and changes show the teaching force to be: (1) larger; (2) grayer; (3) greener; (4) more female; (5) more diverse, by race-ethnicity; (6) consistent in academic ability; and (7) less stable. For each of the trends, two large questions arise: (1) Why? What are the reasons for and sources of the trend?; and (2) So what? What difference does it make? What are the implications and consequences of the trend? In the initial edition of this report, released in November 2012, the analyses went up to 2008--the most current data then available. With the recent release of the 2011-12 SASS data, almost all of the findings for this new edition of the report have been updated. This report draws from a preliminary article published in "Educational Leadership" in May 2010 (Ingersoll & Merrill 2010). Support for some of the preliminary work on this project done in 2009-10 came from a grant from the National Commission on Teaching and America's Future, funded by the Gates Foundation. [For the preliminary article, "Who's Teaching Our Children?" (2010), see EJ896444.]

Reflected light curves observed for exoplanets indicate bright clouds at some of them. We estimate how the light curve and total stellar heating of a planet depend on forward and backward scattering in the clouds based on Pioneer and Cassini spacecraft images of Jupiter and Saturn. We fit analytical functions to the local reflected brightnesses of Jupiter and Saturn depending on the planet's phase. These observations cover broad bands at 0.59-0.72 and 0.39-0.5 {\mu}m, and narrow bands at 0.938 (atmospheric window), 0.889 (CH4 absorption band), and 0.24-0.28 {\mu}m. We simulate the images of the planets with a ray-tracing model, and disk-integrate them to produce the full-orbit light curves. For Jupiter, we also fit the modeled light curves to the observed full-disk brightness. We derive spherical albedos for Jupiter, Saturn, and for planets with Lambertian and Rayleigh-scattering atmospheres. Jupiter-like atmospheres can produce light curves that are a factor of two fainter at half-phase than the Lambertian planet, given the same geometric albedo at transit. The spherical albedo is typically lower than for a Lambertian planet by up to a factor of 1.5. The Lambertian assumption will underestimate the absorption of the stellar light and the equilibrium temperature of the planetary atmosphere. We also compare our light curves with the light curves of solid bodies: the moons Enceladus and Callisto. Their strong backscattering peak within a few degrees of opposition (secondary eclipse) can lead to an even stronger underestimate of the stellar heating., Comment: 21 pages, 4 figures

Estimates of the total particulate mass of the plumes of Enceladus are important to constrain theories of particle formation and transport at the surface and interior of the satellite. We revisit the calculations of Ingersoll & Ewald (2011), who estimated the particulate mass of the Enceladus plumes from strongly forward scattered light in Cassini ISS images. We model the plume as a combination of spherical particles and irregular aggregates resulting from the coagulation of spherical monomers, the latter of which allows for plumes of lower particulate mass. Though a continuum of solutions are permitted by the model, the best fits to the ISS data consist either of low mass plumes composed entirely of small aggregates or high mass plumes composed of mostly spheres. The high particulate mass plumes have total particulate masses of (166 $\pm$ 42) $\times$ 10$^3$ kg, consistent with the results of Ingersoll & Ewald (2011). The low particulate mass plumes have masses of (25 $\pm$ 4) $\times$ 10$^3$ kg, leading to a solid to vapor mass ratio of 0.07 $\pm$ 0.01 for the plume. If indeed the plumes are made of such aggregates, then a vapor-based origin for the plume particles cannot be ruled out. Finally, we show that the residence time of the monomers inside the plume vents is sufficiently long for Brownian coagulation to form the aggregates before they are ejected to space., Comment: 44 pages, 8 figures, 2 tables, Published in Icarus

The first observations of Saturn's visible-wavelength aurora were made by the Cassini camera. The aurora was observed between 2006 and 2013 in the northern and southern hemispheres. The color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000-1500 km above the horizon. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with laboratory simulated auroras. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs between 70 and 80 degree latitude north and between 65 and 80 degree latitude south, which sometimes spiral around the pole, and sometimes form double arcs. A large 10,000-km-scale longitudinal brightness structure persists for more than 100 hours. This structure rotates approximately together with Saturn. On top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. These brightenings repeat with a period of about 1 hour. Smaller, 1000-km-scale structures may move faster or lag behind Saturn's rotation on timescales of tens of minutes. The persistence of nearly-corotating large bright longitudinal structure in the auroral oval seen in two movies spanning 8 and 11 rotations gives an estimate on the period of 10.65 $\pm$0.15 h for 2009 in the northern oval and 10.8$\pm$ 0.1 h for 2012 in the southern oval. The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation (SKR) detected at that time., Comment: 39 pages, 8 figures, 1 table, 6 supplementary movies, accepted to Icarus

Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on tethered experiments with robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here we demonstrate a new aerodynamic force platform (AFP) for nonintrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo, which demonstrates that its upstroke is inactive., Comment: 7 pages, 2 figures, and 2 tables

This study examines and compares the recruitment and retention of minority and White elementary and secondary teachers and attempts to empirically ground the debate over minority teacher shortages. The data we analyze are from the National Center for Education Statistics' nationally representative Schools and Staffing Survey and its longitudinal supplement, the Teacher Follow-up Survey. Our data analyses show that a gap continues to persist between the percentage of minority students and the percentage of minority teachers in the U.S. school system. But this gap is not due to a failure to recruit new minority teachers. Over the past two decades, the number of minority teachers has almost doubled, outpacing growth in both the number of White teachers and the number of minority students. Minority teachers are also overwhelmingly employed in public schools serving high-poverty, high-minority and urban communities. Hence, the data suggest that widespread efforts over the past several decades to recruit more minority teachers and employ them in hard-to-staff and disadvantaged schools have been very successful. This increase in the proportion of teachers who are minority is remarkable because the data also show that over the past two decades, turnover rates among minority teachers have been significantly higher than among White teachers. Moreover, though schools' demographic characteristics appear to be highly important to minority teachers' initial employment decisions, this does not appear to be the case for their later decisions to stay or depart. Neither a school's poverty-level student enrollment, a school's minority student enrollment, a school's proportion of minority teachers, nor whether the school was in an urban or suburban community was consistently or significantly related to the likelihood that minority teachers would stay or depart, after controlling for other background factors. In contrast, organizational conditions in schools were strongly related to minority teacher departures. Indeed, once organizational conditions are held constant, there was no significant difference in the rates of minority and White teacher turnover. The schools in which minority teachers have disproportionately been employed have had, on average, less positive organizational conditions than the schools where White teachers are more likely to work, resulting in disproportionate losses of minority teachers. The organizational conditions most strongly related to minority teacher turnover were the level of collective faculty decision-making influence and the degree of individual classroom autonomy held by teachers; these factors were more significant than were salary, professional development or classroom resources. Schools allowing more autonomy for teachers in regard to classroom issues and schools with higher levels of faculty input into school-wide decisions had far lower levels of turnover. (Contains 6 figures, 10 tables and 7 endnotes.) [Funding for this paper was provided by the Center for Educational Research in the Interest of Underserved Students, University of California, Santa Cruz and the Sally Hewlett and the Flora Family Foundation.]

This study examines the magnitude, destinations, and determinants of the departures of mathematics and science teachers from public schools. The data are from the National Center for Education Statistics' nationally representative Schools and Staffing Survey and its longitudinal supplement, the Teacher Follow-up Survey. Our analyses show that rates of mathematics and science teacher turnover, both those moving between schools and those leaving teaching altogether, have increased over the past two decades, but have not been consistently different than those of non-mathematics/science teachers. Mathematics and science teachers who left teaching were also no more likely than other teachers to take non-education jobs, such as in technological fields, or to be working for private business or industry. The data also show that, like other teachers, there are large school-to-school differences in mathematics and science turnover. High poverty, high minority, and urban public schools have among the highest mathematics and science turnover levels. In the case of cross-school migration, the data show there is an annual asymmetric reshuffling of a significant portion of the mathematics and science teaching force from poor to not poor schools, from high-minority to low-minority schools, and from urban to suburban schools. However, our multivariate analyses showed that a number of key organizational characteristics and conditions of schools accounted for these school differences in turnover. The strongest factors for mathematics teachers were the degree of individual classroom autonomy held by teachers, the provision of useful professional development, and the degree of student discipline problems. For science teachers, the strongest factors were the maximum potential salary offered by school districts, the degree of student discipline problems in schools, and useful professional development. (Contains 3 figures, 8 tables and 8 endnotes.)

This recent brief from the National Council on Teacher Quality is concerned with the question of what factors should be considered when school districts must decide which teachers to lay off during periods of tight budgets. Most districts, according to the brief, base these decisions primarily on long-standing "Last Hired, First Fired" teacher seniority policies. The main point of this brief is to argue that seniority is not a fair, useful, or cost effective criterion; instead, teachers' quality and performance could and should be the main criteria used to make these employment decisions. The brief's arguments and recommendations are straightforward, reasonable and commonsense. However, proposals to measure, recognize and reward differences in teacher quality and utilize these in employment and promotion decisions are neither new nor unique. As the history of education reform has shown, implementing such proposals is challenging and often reform attempts have met little or no success. To its credit, this brief recognizes some of the many hurdles and difficulties that need to be overcome or addressed. A useful contribution of the brief is to document wide variations among districts in their layoff criteria and mechanisms and to summarize specific options and concrete alternatives used in particular districts. (Contains 11 notes.) [This paper reviews the following document: "Teacher Layoffs: Rethinking "Last-Hired, First-Fired" Policies" (ED512675).]

The objective of this study is to use nationally representative data to examine the rates, destinations and sources of math and science teacher turnover. There are four sets of research questions the authors address concerning the departure of mathematics and science teachers from their schools: (1) At what rates do mathematics/science teachers move from or leave their teaching jobs? How do their turnover rates compare to those of other teachers? Have their turnover rates changed over time? What is the magnitude of both math science teacher mobility and attrition?; (2) Which types of schools have higher levels of mathematics/science teacher turnover?; (3) What are the destinations of mathematics/science teachers who move from or leave their teaching jobs? What proportions of those departing move to other schools, quit to raise families, go to graduate school, go into non-teaching occupations within education (e.g., school administration, higher education, etc) or go into non-educational occupations?; and (4) Which particular factors, aspects, and conditions of schools and of teachers' jobs are most tied to the turnover of mathematics and science teachers? This study utilizes nationally representative data on teachers, and therefore the setting is the whole United States. Findings suggest that schools are not simply victims of inexorable demographic trends and that there is a significant role for the management of schools in both the genesis of, and solution to, school staffing problems. The data suggest that improvements in these conditions of the teaching job, such as increased teacher salaries, and enhanced faculty input into school decision making, would all contribute to lower rates of turnover, in turn, diminish school staffing problems, undermine the so-called teacher shortage and, hence, ultimately, aid the performance of schools.

Across the educational systems of the world, few issues receive more attention than the problem of ensuring that elementary- and secondary-school classrooms are staffed with adequately qualified teachers. Even in nations where students routinely score high on international exams, the issue of teacher quality is the subject of concern. It is widely believed that the quality of teachers and teaching are among the most important factors shaping the learning and growth of students, an impact that goes beyond student academic achievement. Across the world, observers routinely tie the performance of teachers to numerous, larger societal goals and problems, including economic competitiveness and productivity, juvenile delinquency, and moral and civic culture. Along with a general consensus among many nations that the quality of teachers and teaching is a vital resource, there is accordingly concern surrounding how equitably this resource is distributed within educational systems. Some nations suffer from an apparent paradox: despite an overall overproduction and oversupply of new teachers, there appear to be substantial numbers of students without access to qualified teachers. This brief summarizes the results from a collaborative, comparative study of the qualifications of elementary and secondary teachers undertaken by a group of scholars, policy makers and senior education officials from six nations and one region: United States, Korea, China, Hong Kong, Singapore, Thailand, and Japan. This study revealed both commonalities and differences in the preparation and qualifications of teachers among the seven systems examined. Comparative educational research can provide a useful function by placing educational systems in context. The study suggests at least three possible sources of the problem of under-qualified teachers: (1) Pre-employment requirements and standards; (2) Failure of the teaching force to meet existing requirements and standards; and (3) How teachers are utilized once on the job due to mis-assignment or out-of-field teaching. Focusing on upgrading the training requirements of teachers and teacher recruitment may overlook the impact of the organizational and occupational contexts within which teachers work. The data indicate that solutions to the problem of under-qualified teachers also must look to how schools are managed and how teachers are utilized once they are on the job. Recruiting thousands of new candidates and providing them with rigorous preparation will not solve the problem if large numbers of teachers receive assignments for which they are not prepared. (Contains 1 footnote and 3 tables.) [For full report, see ED498347.]

Across the educational systems of the world, few issues receive more attention than the problem of ensuring that elementary- and secondary-school classrooms are staffed with adequately qualified teachers. Even in nations where students routinely score high on international exams, the issue of teacher quality is the subject of concern. It is widely believed that the quality of teachers and teaching are among the most important factors shaping the learning and growth of students, an impact that goes beyond student academic achievement. Across the world, observers routinely tie the performance of teachers to numerous, larger societal goals and problems, including economic competitiveness and productivity, juvenile delinquency, and moral and civic culture. Along with a general consensus among many nations that the quality of teachers and teaching is a vital resource, there is accordingly concern surrounding how equitably this resource is distributed within educational systems. Some nations suffer from an apparent paradox: despite an overall overproduction and oversupply of new teachers, there appear to be substantial numbers of students without access to qualified teachers. This report presents the results from a collaborative, comparative study of the qualifications of elementary and secondary teachers undertaken by a group of scholars, policy makers and senior education officials from six nations and one region: United States, Korea, China, Hong Kong, Singapore, Thailand, and Japan. This study revealed both commonalities and differences in the preparation and qualifications of teachers among the seven systems examined. Comparative educational research can provide a useful function by placing educational systems in context. Results from each nation or region are individually presented. The study suggests at least three possible sources of the problem of under-qualified teachers: (1) Pre-employment requirements and standards; (2) Failure of the teaching force to meet existing requirements and standards; and (3) How teachers are utilized once on the job due to mis-assignment or out-of-field teaching. Focusing on upgrading the training requirements of teachers and teacher recruitment may overlook the impact of the organizational and occupational contexts within which teachers work. The data indicate that solutions to the problem of under-qualified teachers also must look to how schools are managed and how teachers are utilized once they are on the job. Recruiting thousands of new candidates and providing them with rigorous preparation will not solve the problem if large numbers of teachers receive assignments for which they are not prepared. (Individual chapters contain tables, figures, and references.) [This report by Richard M. Ingersoll was written with Ding Gang, Sun Meilu, Kwok Chan Lai, Hidenori Fujita, Ee-gyeong Kim, Steven K. S. Tan, Angela F. L. Wong, Pruet Siribanpitak, and Siriporn Boonyananta. For related policy brief, see ED498346.]

The MaddenJulian oscillation (MJO) is the dominant mode of intraseasonal variability in the tropics. Despite its primary importance, a generally accepted theory that accounts for fundamental features of the MJO, including its propagation speed, planetary horizontal scale, multi-scale features, and quadrupole structures, remains elusive. In this study, we use a shallow water model to simulate the MJO. In our model, convection is parameterized as a short-duration localized mass source, and is triggered when the layer thickness falls below a critical value. Radiation is parameterized as a steady uniform mass sink. Slowly eastward propagating (MJO-like) signals and red noise spectra are observed in our simulations. In the time-longitude domain, MJO-like signals with multi-scale structures are observed. In the Fourier domain, spectral peaks associated with the MJO-like signals are observed. In the longitude-latitude map view, quadrupole vortex structures associated with the MJO-like signals are observed. We propose that the simulated MJO signal is an interference pattern of westward and eastward inertia-gravity(WIG and EIG) waves. Its propagation speed is one half of the speed difference between the WIG and EIG waves. The horizontal scale of its large-scale envelope is determined by the bandwidth of the excited waves, and the bandwidth is controlled by number density of convection events. Our results suggest that the MJO perhaps is not a large-scale low-frequency wave, in which convection acts as quasi-equilibrium adjustment. Small-scale high-frequency waves might be important.

Aptly named, ice giants such as Uranus and Neptune contain significant amounts of water. While this water cannot be present near the cloud tops, it must be abundant in the deep interior. We investigate the likelihood of a liquid water ocean existing in the hydrogen-rich region between the cloud tops and deep interior. Starting from an assumed temperature at a given upper tropospheric pressure (the photosphere), we follow a moist adiabat downward. The mixing ratio of water to hydrogen in the gas phase is small in the photosphere and increases with depth. The mixing ratio in the condensed phase is near unity in the photosphere and decreases with depth; this gives two possible outcomes. If at some pressure level the mixing ratio of water in the gas phase is equal to that in the deep interior, then that level is the cloud base. Alternately, if the mixing ratio of water in the condensed phase reaches that in the deep interior, then the surface of a liquid ocean will occur. We find that Neptune is both too warm (photospheric temperature too high) and too dry (mixing ratio of water in the deep interior too low) for liquid oceans to exist at present. To have a liquid ocean, Neptune's deep interior water to gas ratio would have to be higher than current models allow, and the density at 19 kbar would have to be ~ 0.8 g/cm^3. Such a high density is inconsistent with gravitational data obtained during the Voyager flyby. As Neptune cools, the probability of a liquid ocean increases. Extrasolar "hot Neptunes," which presumably migrate inward toward their parent stars, cannot harbor liquid water oceans unless they have lost almost all of the hydrogen and helium from their deep interiors., Comment: 31 pages, 11 figures, accepted for publication in Icarus

This analysis examines the effects of school and organizational characteristics on teacher turnover and, in turn, school staffing problems. The analyses are based on data from the Schools and Staffing Survey and its supplement, the Teacher Followup Survey, a large, comprehensive, nationally representative survey of teachers and schools conducted by the National Center for Education Statistics. Teacher characteristics, such as specialty field, age, and retirement, account for a significant amount of turnover. There are also significant effects of school and organizational characteristics on turnover that have largely been overlooked by previous theory and research. The data show that while high-poverty public schools have moderately higher rates, neither larger schools, nor public schools in large school districts, nor urban schools have high rates of teacher turnover. In contrast, small private schools stand out for their high rates of turnover. The analysis also shows that math and science teachers are not more likely to depart than other teachers, once other factors are controlled. Moreover, the amount of turnover accounted for by retirement is relatively minor when compared to that resulting from two related causes teacher job dissatisfaction and teachers pursuing better jobs or other careers. Organizational characteristics such as inadequate support from the administration, low salaries, student discipline problems, and limited faculty input into school decision-making all contribute to higher rates of turnover, controlling for the characteristics of teachers and schools. The results suggest that school staffing problems are not solely a result of shortfalls driven by increasing retirement levels, but also a result of low retention due to organizational conditions. (Contains 99 references, 16 endnotes, 4 tables, and 2 figures.) (Author/MLF)