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At the poles of Jupiter, cyclonic vortices are clustered together in patterns made up of equilateral triangles called vortex crystals. Such patterns are seen in laboratory flows but never before in a planetary atmosphere, where the planet's rotation and gravity add new physics. Here we use the shallow water (SW) equations at the pole of a rotating planet to study the emergence and evolution of vortices starting from an initial random pattern of small-scale turbulence. The flow is in a single layer with a free surface whose slope produces the horizontal pressure gradient force. We explored three parameters in the problem: the mean kinetic energy of the initial turbulence, the horizontal scale of the initial turbulence, and the radius of deformation of the undisturbed fluid layer. We find that some regions of this parameter space lead to vortex crystals and others lead to chaotic behavior and mergers. Our results identified that the relative change of the layer thickness is the key quantity that determines whether the vortex crystal or chaotic patterns emerge.

Water and ammonia vapors are known to be the major sources of spectral absorption at pressure levels observed by the microwave radiometer (MWR) on Juno. However, the brightness temperatures and limb darkening observed by the MWR at its longest wavelength channel of 50 cm (600 MHz) in the first 9 perijove passes indicate the existence of an additional source of opacity in the deep atmosphere of Jupiter (pressures beyond 100 bar). The absorption properties of ammonia and water vapor, and their relative abundances in Jupiter's atmosphere do not provide sufficient opacity in deep atmosphere to explain the 600 MHz channel observation. Here we show that free electrons due to the ionization of alkali metals, i.e. sodium, and potassium, with sub-solar metallicity [M/H] (log based 10 relative concentration to solar) in the range of [M/H] = -2 to [M/H] = -5 can provide the missing source of opacity in the deep atmosphere. If the alkali metals are not the source of additional opacity in the MWR data, then their metallicity at 1000 bars can only be even lower. The upper bound of -2 on the metallicity of the alkali metals contrasts with the other heavy elements -- C, N, S, Ar, Kr, and Xe -- which are all enriched relative to their solar abundances having a metallicity of approximately +0.5., Comment: This manuscript has been accepted for publication in The Astrophysical Journal Letters. The final version of the paper will be available in the published journal. This arXiv version is provided for informational purposes

Juno Microwave Radiometer (MWR) observations of Jupiter's mid-latitudes reveal a strong correlation between brightness temperature contrasts and zonal winds, confirming that the banded structure extends throughout the troposphere. However, the microwave brightness gradient is observed to change sign with depth: the belts are microwave-bright in the $p<5$ bar range and microwave-dark in the $p>10$ bar range. The transition level (which we call the jovicline) is evident in the MWR 11.5 cm channel, which samples the 5-14 bar range when using the limb-darkening at all emission angles. The transition is located between 4 and 10 bars, and implies that belts change with depth from being NH$_3$-depleted to NH$_3$-enriched, or from physically-warm to physically-cool, or more likely a combination of both. The change in character occurs near the statically stable layer associated with water condensation. The implications of the transition are discussed in terms of ammonia redistribution via meridional circulation cells with opposing flows above and below the water condensation layer, and in terms of the `mushball' precipitation model, which predicts steeper vertical ammonia gradients in the belts versus the zones. We show via the moist thermal wind equation that both the temperature and ammonia interpretations can lead to vertical shear on the zonal winds, but the shear is $\sim50\times$ weaker if only NH$_3$ gradients are considered. Conversely, if MWR observations are associated with kinetic temperature gradients then it would produce zonal winds that increase in strength down to the jovicline, consistent with Galileo probe measurements; then decay slowly at higher pressures., Comment: Published in JGR: Planets

Jupiter's atmosphere is dominated by multiple jet streams which are strongly tied to its 3D atmospheric circulation. Lacking a rigid bottom boundary, several models exist for how the meridional circulation extends into the planetary interior. Here we show, collecting evidence from multiple instruments of the Juno mission, the existence of mid-latitudinal meridional circulation cells which are driven by turbulence, similar to the Ferrel cells on Earth. Different than Earth, which contains only one such cell in each hemisphere, the larger, faster rotating Jupiter can incorporate multiple cells. The cells form regions of upwelling and downwelling, which we show are clearly evident in Juno's microwave data between latitude 60S and 60N. The existence of these cells is confirmed by reproducing the ammonia observations using a simplistic model. This study solves a long-standing puzzle regarding the nature of Jupiter's sub-cloud dynamics and provides evidence for 8 cells in each Jovian hemisphere., Comment: 13 pages, 5 figures, Supporting information. Accepted to Geophysical Research Letters

The observed zonal winds at Jupiter's cloud tops have been shown to be closely linked to the asymmetric part of the planet's measured gravity field. However, other measurements suggest that in some latitudinal regions the flow below the clouds might be somewhat different from the observed cloud-level winds. Here we show, using both the symmetric and asymmetric parts of the measured gravity field, that the observed cloud-level wind profile between 25$^{\circ}$S and 25$^{\circ}$N must extend unaltered to depths of thousands of kilometers. Poleward, the midlatitude deep jets also contribute to the gravity signal, but might differ somewhat from the cloud-level winds. We analyze the likelihood of this difference and give bounds to its strength. We also find that to match the gravity measurements, the winds must project inward in the direction parallel to Jupiter's spin axis, and that their decay inward should be in the radial direction.

Observations of Jupiter's deep atmosphere by the Juno spacecraft have revealed several puzzling facts: The concentration of ammonia is variable down to pressures of tens of bars, and is strongly dependent on latitude. While most latitudes exhibit a low abundance, the Equatorial Zone of Jupiter has an abundance of ammonia that is high and nearly uniform with depth. In parallel, the Equatorial Zone is peculiar for its absence of lightning, which is otherwise prevalent most everywhere else on the planet. We show that a model accounting for the presence of small-scale convection and water storms originating in Jupiter's deep atmosphere accounts for the observations. Where strong thunderstorms are observed on the planet, we estimate that the formation of ammonia-rich hail ('mushballs') and subsequent downdrafts can deplete efficiency the upper atmosphere of its ammonia and transport it efficiently to the deeper levels. In the Equatorial Zone, the absence of thunderstorms shows that this process is not occurring, implying that small-scale convection can maintain a near-homogeneity of this region. A simple model satisfying mass and energy balance accounts for the main features of Juno's MWR observations and successfully reproduces the inverse correlation seen between ammonia abundance and the lightning rate as function of latitude. We predict that in regions where ammonia is depleted, water should also be depleted to great depths. The fact that condensates are not well mixed by convection until far deeper than their condensation level has consequences for our understanding of Jupiter's deep interior and of giant-planet atmospheres in general.

Oxygen is the most common element after hydrogen and helium in Jupiter's atmosphere, and may have been the primary condensable (as water ice) in the protoplanetary disk. Prior to the Juno mission, in situ measurements of Jupiter's water abundance were obtained from the Galileo Probe, which dropped into a meteorologically anomalous site. The findings of the Galileo Probe were inconclusive because the concentration of water was still increasing when the probe died. Here, we initially report on the water abundance in the equatorial region, from 0 to 4 degrees north latitude, based on 1.25 to 22 GHz data from Juno Microwave radiometer probing approximately 0.7 to 30 bars pressure. Because Juno discovered the deep atmosphere to be surprisingly variable as a function of latitude, it remains to confirm whether the equatorial abundance represents Jupiter's global water abundance. The water abundance at the equatorial region is inferred to be $2.5_{-1.6}^{+2.2}\times10^3$ ppm, or $2.7_{-1.7}^{+2.4}$ times the protosolar oxygen elemental ratio to H (1$\sigma$ uncertainties). If reflective of the global water abundance, the result suggests that the planetesimals formed Jupiter are unlikely to be water-rich clathrate hydrates., Comment: 27 pages, 7 figures

The source of the hummingbirds distinctive hum is not well understood, but there are clues to its origin in the acoustic nearfield and farfield. To unravel this mystery, we recorded the acoustic nearfield generated by six freely hovering Annas hummingbirds using a 2176 microphone array. We also directly measured the 3D aerodynamic forces generated by the hummingbird in vivo using a new aerodynamic force platform. To determine the degree to which the aerodynamic forces cause the hum, we developed a simple first-principles model to predict the acoustic field radiated by the 3D oscillating forces. The correspondence between the predicted and measured acoustic field shows the primary acoustic sources of the hum are the lift and drag forces that oscillate as the flapping wings move back and forth. The model also shows how the aerodynamic force profile of the flapping wing determines the hums timbre and sound pressure level: profiles that support bodyweight with higher harmonics radiate more acoustic power. Further, extending this model across birds and flying insects, we show how the radiated acoustic power scales with body mass to the second power - with allometric deviation making larger birds quieter and elongated flies louder. The model's ability to predict the acoustic signature of flapping wings suggests it can be applied for such diverse uses as differentiating wing and feather sounds in bird display behaviors to interpreting how insects generate courtship songs with their wings to making flapping robot wings more silent., Comment: 44 pages

The innovative Saturn Ring Skimmer mission concept enables a wide range of investigations that address fundamental questions about Saturn and its rings, as well as giant planets and astrophysical disk systems in general. This mission would provide new insights into the dynamical processes that operate in astrophysical disk systems by observing individual particles in Saturn's rings for the first time. The Ring Skimmer would also constrain the origin, history, and fate of Saturn's rings by determining their compositional evolution and material transport rates. In addition, the Ring Skimmer would reveal how the rings, magnetosphere, and planet operate as an inter-connected system by making direct measurements of the ring's atmosphere, Saturn's inner magnetosphere and the material owing from the rings into the planet. At the same time, this mission would clarify the dynamical processes operating in the planet's visible atmosphere and deep interior by making extensive high-resolution observations of cloud features and repeated measurements of the planet's extremely dynamic gravitational field. Given the scientific potential of this basic mission concept, we advocate that it be studied in depth as a potential option for the New Frontiers program., Comment: White paper submitted to the Planetary Science and Astrobiology Decadal Survey (submission #420)

This working paper summarizes the results of a study of leadership in elementary and secondary schools. The study focused in particular on instructional leadership -- the extent to which school leaders focus on the core activities of teaching and learning -- and teacher leadership -- the extent to which teachers have input into school decision-making. This paper is drawn from the full report of the study, entitled "School Leadership Counts" (Ingersoll, Dougherty and Sirinides 2017), available at www.newteachercenter.org. [This research was supported by a grant to the New Teacher Center from the Carnegie Corporation.]

This study examines and compares the recruitment, employment, and retention of minority and nonminority school teachers over the past quarter century. The objective of the study is to empirically ground the debate over minority teacher shortages. The data analyzed are from the National Center for Education Statistics' nationally representative Schools and Staffing Survey (SASS) and its longitudinal supplement, the Teacher Follow-Up Survey (TFS). Data analyses show that a gap persists between the percentage of minority students and the percentage of minority teachers in the U.S. school system. 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. However, the data also show that over the past two and a half decades, turnover rates among minority teachers have been significantly higher than among nonminority teachers. Organizational and working conditions in schools were strongly related to minority teacher departures. Once organizational conditions were held constant, there was no significant difference in the rates of minority and nonminority teacher turnover. While the number of minority teachers has increased, the schools in which they have disproportionately been employed have had, on average, less positive organizational conditions than the schools where nonminority teachers are more likely to work, resulting in disproportionate losses of minority teachers. [For the research brief, see ED606771.]

This report utilizes the nationally representative Schools and Staffing Survey (SASS) to examine changes in the elementary and secondary teaching force in the United States over the quarter century from 1987-88 to 2011-12. The report focuses on three key demographic characteristics: the size of the teaching force, the level of teaching experience of the teaching force, and the racial/ethnic composition of the teaching force. SASS is a large-scale sample survey of elementary and secondary teachers and schools in the United States. SASS has been conducted seven times--in school years 1987-88, 1990-91, 1993-94, 1999-2000, 2003-04, 2007-08, and 2011-12. SASS was developed to obtain comprehensive data on teachers, including a wide range of information on teachers' backgrounds, characteristics, qualifications, and workplaces (Haggstrom, Darling-Hammond, and Grissmer 1988; Ingersoll 1995). As a result, SASS is an excellent source of data for examining changes in the demographic characteristics of the teaching force in the United States. SASS is administered by the Institute of Education Sciences' National Center for Education Statistics (NCES), which is the statistical agency of the U.S. Department of Education. This report builds on and expands an earlier study by Ingersoll, Merrill, and Stuckey (2014) that analyzed SASS data to explore what demographic trends and changes have, or have not, occurred in the elementary and secondary teaching force since the late 1980s. This earlier study found considerable changes in the teacher force, with significant, but under-recognized implications. Among the key findings were that the teaching force has become: (1) larger--The teaching force dramatically increased in size, growing at over twice the rate of student enrollment; (2) less experienced--With increases in hiring there has also been a correspondingly large increase in the number of teachers who are beginners in their first several years of teaching. In 1987-88, the modal, or most common, teacher had 15 years of teaching experience. By 2007-08, the modal teacher was in his or her first year of teaching; and (3) more diverse--The teaching force has rapidly become more racially/ethnically diverse. Growth in the number of minority teachers has outpaced growth in minority students and has been more than twice the growth rate of White teachers. The objective of the Ingersoll, Merrill, and Stuckey (2014) study was to provide a broad overview of national changes in the demographic characteristics of the teaching force and to explore some of the possible reasons for, and implications of, the changes discovered. It did not disaggregate the data, nor did it investigate how the changes differ by type of teacher and by type of school. These variations are the subject of this report. This analysis investigates how changes in these characteristics of the teaching force--the number of teachers, the level of teaching experience, and the racial/ethnic diversity of the teaching force--varied across different types of teachers and across types of schools in the 25 years between 1987-88 and 2011-12. The data analysis shows that these changes have not been distributed evenly across teacher and school types. The following are appended: (1) Standard Error Tables; (2) Methodology and Technical Notes: Overview of the 2011-12 Schools and Staffing Survey and Overview of the 1987-88 Schools and Staffing Survey; (3) Description of Variables Used in This Report; and (4) Glossary of Terms. [For the previous report, "Seven Trends: The Transformation of the Teaching Force. Updated April 2014. CPRE Report. #RR-80," see ED566879.]

We present a virtual reality (VR) experience that creates a research-grade benchmark in assessing patients with active upper-limb tremor, while simultaneously offering the opportunity for patients to engage with VR experiences without their pathologic tremor. Accurate and precise use of handheld motion controllers in VR gaming applications may be limited for patients with upper limb tremor. In parallel, objective tools measuring tremor are not in widespread, routine clinical use. We used a commercially available VR system and designed a challenging virtual-balloon-popping test mimicking a common nose-to-target pointing task used by medical practitioners to subjectively evaluate tremor in the exam room. Within our VR experience, we offer a software mode which uses a low-pass filter to adjust hand position and pointing orientation over a series of past data points. This digital filter creates a smoothing function for hand movement which effectively removes the patient's tremor in the VR representation. While the patient completes trials of the reaching task, quantitative data on the pathologic tremor is digitally recorded. With speed, accuracy, and the tremor components computed across three axes of movement, patients can be evaluated for their tremor amplitudes in a quantitative, replicable, and enjoyable manner. Removal of tremor in digital space may allow patients having significant upper limb tremor to have both an objective clinical measurement of symptoms while providing patients positive feedback and interaction., Comment: 3 pages; 3 figures

We derived a new formula for calculating the moist adiabatic temperature profile of an atmosphere consisting of ideal gases with multiple condensing species. This expression unifies various formulas published in the literature and can be generalized to account for chemical reactions. Unlike previous methods, it converges to machine precision independent of mesh size. It accounts for any ratio of condensable vapors to dry gas, from zero to infinity, and for variable heat capacities as a function of temperature. Because the derivation is generic, the new formula is not only applicable to planetary atmosphere in the solar system, but also to hot Jupiters and brown dwarfs in which a variety of alkali metals, silicates and exotic materials condense. We demonstrate that even though the vapors are ideal gases, they interact in their effects on the moist adiabatic lapse rate. Finally, we apply the new thermodynamic model to study the effects of downdrafts on the distribution of minor constituents and thermal profile in the Galileo probe hotspot. We find that the Galileo Probe measurements can be interpreted as a strong downdraft that displaces an air parcel from 1 bar to the 4 bar level., Comment: 30 pages, 3 figures, accepted for publication in Journal of the Atmospheric Science

This brief summarizes the results from a study of the recruitment, employment, and retention of minority k-12 teachers. The study examines the extent and sources of the minority teacher shortage--the low proportion of minority teachers in comparison to the increasing numbers of minority students in the school system. Using the National Center for Education Statistics' Schools and Staffing Survey/Teacher Follow-Up Survey, we found that efforts over recent decades to recruit more minority teachers and place them in disadvantaged schools have been very successful. But these efforts have been undermined by the high turnover rates of minority teachers--largely because of poor working conditions in their schools. The conditions most strongly related to minority teacher turnover were the degree of teachers' classroom autonomy and input into school decisions--both increasingly important when coupled with accountability pressures. [For the full report, see ED606772.]

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.