Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation

Kepler-78b is a transiting planet that is 1.2 times the radius of Earth and orbits a young, active K dwarf every 8 hours. The mass of Kepler-78b has been independently reported by two teams based on radial velocity measurements using the HIRES and HARPS-N spectrographs. Due to the active nature of the host star, a stellar activity model is required to distinguish and isolate the planetary signal in radial velocity data. Whereas previous studies tested parametric stellar activity models, we modeled this system using nonparametric Gaussian process (GP) regression. We produced a GP regression of relevant Kepler photometry. We then use the posterior parameter distribution for our photometric fit as a prior for our simultaneous GP + Keplerian orbit models of the radial velocity datasets. We tested three simple kernel functions for our GP regressions. Based on a Bayesian likelihood analysis, we selected a quasi-periodic kernel model with GP hyperparameters coupled between the two RV datasets, giving a Doppler amplitude of 1.86 $\pm$ 0.25 m s$^{-1}$ and supporting our belief that the correlated noise we are modeling is astrophysical. The corresponding mass of 1.87 $^{+0.27}_{-0.26}$ M$_{\oplus}$ is consistent with that measured in previous studies, and more robust due to our nonparametric signal estimation. Based on our mass and the radius measurement from transit photometry, Kepler-78b has a bulk density of 6.0$^{+1.9}_{-1.4}$ g cm$^{-3}$. We estimate that Kepler-78b is 32$\pm$26% iron using a two-component rock-iron model. This is consistent with an Earth-like composition, with uncertainty spanning Moon-like to Mercury-like compositions.Comment: 10 pages, 5 figures, accepted to ApJ 6/16/201

Long-term radial-velocity variations of the Sun as a star: The HARPS view

Stellar radial velocities play a fundamental role in the discovery of extrasolar planets and the measurement of their physical parameters as well as in the study of stellar physical properties. We investigate the impact of the solar activity on the radial velocity of the Sun using the HARPS spectrograph to obtain measurements that can be directly compared with those acquired in the extrasolar planet search programs. We use the Moon, the Galilean satellites, and several asteroids as reflectors to measure the radial velocity of the Sun as a star and correlate it with disc-integrated chromospheric and magnetic indexes of solar activity that are similar to stellar activity indexes. We discuss in detail the systematic effects that affect our measurements and the methods to account for them. We find that the radial velocity of the Sun as a star is positively correlated with the level of its chromospheric activity at about 95 percent significance level. The amplitude of the long-term variation measured in the 2006-2014 period is 4.98 \pm 1.44 m/s, in good agreement with model predictions. The standard deviation of the residuals obtained by subtracting a linear best fit is 2.82 m/s and is due to the rotation of the reflecting bodies and the intrinsic variability of the Sun on timescales shorter than the activity cycle. A correlation with a lower significance is detected between the radial velocity and the mean absolute value of the line-of-sight photospheric magnetic field flux density. Our results confirm similar correlations found in other late-type main-sequence stars and provide support to the predictions of radial velocity variations induced by stellar activity based on current models.Comment: 11 pages, 7 figures, 2 tables, 1 Appendix; accepted by Astronomy and Astrophysic

The Impact of Site-based Management on Perceived Roles of Superintendents, Board Chairpersons, Principals and Selected Central Office Personnel in Tennessee School Systems

The introduction of site-based management has had an impact on the operation of school systems in Tennessee; however no one seems to know for certain what that impact was. Findings from this study revealed that there is a basic understanding of the impact of site-based management as perceived by superintendents, board chairpersons, principals, personnel, budget, curriculum, and staff development administrators. Findings also revealed that central office staff and principals, for the most part, perceive that the superintendents and board chairpersons were supportive of site-based management programs. One hundred and eighty-one educators, including board chairpersons, responded to a fifty-four item questionnaire. This questionnaire focused on the following areas: impact, roles, system-wide policies, personnel, relationships, staff development, morale, position authority, curriculum, policy making, budget and support. Using the F-test for analysis of variance, it was determined that significant differences in perceptions existed in the area of understanding the impact, sharing decisions at the school site, boards of education relinquishing policy making authority to the school site, and principals and faculties having control of the curriculum. The remaining eight (roles, system-wide policies, personnel, staff development, morale, position authority, budget, support) had no significant differences in the perceptions of the respondents. Conclusions of the study emphasize that in order for site-based management programs to be successful there must be a dramatic change in the traditional administrative role. Recommendations were extensive training, retraining, and education be provided so that all school and central office personnel and community members understand and have a sense of ownership of site-based management

The Impact of Site-based Management on Perceived Roles of Superintendents, Board Chairpersons, Principals and Selected Central Office Personnel in Tennessee School Systems

The introduction of site-based management has had an impact on the operation of school systems in Tennessee; however no one seems to know for certain what that impact was. Findings from this study revealed that there is a basic understanding of the impact of site-based management as perceived by superintendents, board chairpersons, principals, personnel, budget, curriculum, and staff development administrators. Findings also revealed that central office staff and principals, for the most part, perceive that the superintendents and board chairpersons were supportive of site-based management programs. One hundred and eighty-one educators, including board chairpersons, responded to a fifty-four item questionnaire. This questionnaire focused on the following areas: impact, roles, system-wide policies, personnel, relationships, staff development, morale, position authority, curriculum, policy making, budget and support. Using the F-test for analysis of variance, it was determined that significant differences in perceptions existed in the area of understanding the impact, sharing decisions at the school site, boards of education relinquishing policy making authority to the school site, and principals and faculties having control of the curriculum. The remaining eight (roles, system-wide policies, personnel, staff development, morale, position authority, budget, support) had no significant differences in the perceptions of the respondents. Conclusions of the study emphasize that in order for site-based management programs to be successful there must be a dramatic change in the traditional administrative role. Recommendations were extensive training, retraining, and education be provided so that all school and central office personnel and community members understand and have a sense of ownership of site-based management

The age structure of stellar populations in the solar vicinity. Clues of a two-phase formation history of the Milky Way disk

We analyze high quality abundances data of solar neighborhood stars and show that there are two distinct regimes of [alpha/Fe] versus age which we identify as the epochs of the thick and thin disk formation. A tight correlation between metallicity and [alpha/Fe] versus age is clearly identifiable on thick disk stars, implying that this population formed from a well mixed ISM, over a time scale of 4-5 Gyr. Thick disk stars vertical velocity dispersion correlate with age, with the youngest objects having as small scale heights as those of thin disk stars. A natural consequence of these two results is that a vertical metallicity gradient is expected in this population. We suggest that the thick disk set the initial conditions for the formation of the inner thin disk. This provides also an explanation of the apparent coincidence between the step in metallicity at 7-10 kpc in the thin disk and the confinment of the thick disk at about R<10 kpc. We suggest that the outer thin disk developped outside the influence of the thick disk, but also that the high alpha-enrichment of the outer regions may originate from a primordial pollution by the gas expelled from the thick disk. Local metal-poor thin disk stars, whose properties are best explained by an origin in the outer disk, are shown to be as old as the youngest thick disk (9-10 Gyr), implying that the outer thin disk started to form while the thick disk formation was still on-going in the inner Galaxy. We point out that, given the tight age-abundance relations in the thick disk, an inside-out process would give rise to a radial gradient in abundances in this population which is not observed. Finally, we argue that the data discussed here leave little room for radial migration, either to have contaminated the solar vicinity, or, to have redistributed stars in significant proportion across the solar annulus.Comment: Accepted in A&A, Revised version with new figures and extended discussio

The Milky Way as a High Redshift Galaxy: The Importance of Thick Disk Formation in Galaxies

We compare the star-formation history and dynamics of the Milky Way (MW) with the properties of distant disk galaxies. During the first ~4 Gyr of its evolution, the MW formed stars with a high star-formation intensity (SFI), Sigma_SFR~0.6 Msun/yr/kpc2 and as a result, generated outflows and high turbulence in its interstellar medium. This intense phase of star formation corresponds to the formation of the thick disk. The formation of the thick disk is a crucial phase which enables the MW to have formed approximately half of its total stellar mass by z~1 which is similar to "MW progenitor galaxies" selected by abundance matching. This agreement suggests that the formation of the thick disk may be a generic evolutionary phase in disk galaxies. Using a simple energy injection-kinetic energy relationship between the 1-D velocity dispersion and SFI, we can reproduce the average perpendicular dispersion in stellar velocities of the MW with age. This relationship, its inferred evolution, and required efficiency are consistent with observations of galaxies from z~0-3. The high turbulence generated by intense star formation naturally resulted in a thick disk, a chemically well-mixed ISM, and is the mechanism that links the evolution of MW to the observed characteristics of distant disk galaxies.Comment: 5 pages, 4 figures; accepted to ApJ Letter

Synthetic Design Of Coumarin And 2H-Chromene-2-Thione Derivatives To Inhibit Carcinogenesis

The goal of this project was the synthesis of 4-substitued coumarins and 2H-chromene-2-thione derivatives that can be used to inhibit or retard the growth of cancer cells. According to the American Cancer Society’s 2012 death statistics for prostate cancer, 28,170 men died from prostate cancer and there was 241,740 (29%) new cases of prostate cancer as well (Society, 2012). Few studies have been conducted on 2H-chromene-2-thiones and their ability to act as cancer chemopreventive or anticancer agents, therefore, we seek to synthesize a sequence of coumarins and 2H-chromene-2-thiones via the Von Pechmann reaction. We believe that the 2H chromene-2-thiones will exhibit better chemopreventive activity then the analogous coumarins because of the presence of the softer sulfur atom. The syntheses of the coumarin derivatives in this study were accomplished using green chemistry. The indium chloride catalyzed Von Pechmann condensation required no solvent and formed coumarins efficiently. Upon synthesizing coumarins, they were converted into their 2H-chromene-2-thione analogs using Lawesson’s reagent. Percent yields of the coumarin derivatives range from 40% to 80%. The 2H chromene-2-thione percent yields range from 11% to 61%

Nutrition in Rehabilitation

Diet has been implicated as a risk factor in atherosclerotic cardiovascular diseases, cancer, diabetes, osteoporosis, obesity, high blood pressure and chronic liver and kidney diseases. These diseases include almost all of the most common non-traumatic causes of death in the United States. It has been suggested that many physicians do not have the opportunity for specific training in nutrition while in medical school. Many studies have shown that patients admitted to a hospital are at risk of malnutrition and that this risk will increase as length of hospital stay increases. Other studies suggested nutritional deficiencies may result in delayed wound healing, major and minor complications, and increased mortality. These complications increase length of stay and hospital costs. A physical therapist, as part of a team, has the chance to impart basic nutritional information to patients. This information may be in addition to information provided to the patient by a physician, nurse, dietician or other health care worker. Patients with improved nutrition benefit from disease prevention through elimination of this risk factor. Patients with improved nutrition also benefit directly from increased energy to participate in physical therapy. This paper will be a review of the literature on the topics of prevalence of malnutrition in hospitals, physician education in nutrition, and nutrition in wound healing to summarize recent findings. From these findings, conclusions concerning nutrition in rehabilitation and recommendations for physical therapists will be provided

When the Milky Way turned off the lights: APOGEE provides evidence of star formation quenching in our Galaxy

Quenching, the cessation of star formation, is one of the most significant events in the life cycle of galaxies. We show here the first evidence that the Milky Way experienced a generalised quenching of its star formation at the end of its thick disk formation $\sim$9 Gyr ago. Elemental abundances of stars studied as part of the APOGEE survey reveal indeed that in less than $\sim$2 Gyr the star formation rate in our Galaxy dropped by an order-of-magnitude. Because of the tight correlation between age and alpha abundance, this event reflects in the dearth of stars along the inner disk sequence in the [Fe/H]-[$\alpha$/Fe] plane. Before this phase, which lasted about 1.5 Gyr, the Milky Way was actively forming stars. Afterwards, the star formation resumed at a much lower level to form the thin disk. These events are very well matched by the latest observation of MW-type progenitors at high redshifts. In late type galaxies, quenching is believed to be related to a long and secular exhaustion of gas. In our Galaxy, it occurred on a much shorter time scale, while the chemical continuity before and after the quenching indicates that it was not due to the exhaustion of the gas. While quenching is generally associated with spheroids, our results show that it also occurs in galaxies like the Milky Way, possibly when they are undergoing a morphological transition from thick to thin disks. Given the demographics of late type galaxies in the local universe, in which classical bulges are rare, we suggest further that this may hold true generally in galaxies with mass lower than or approximately $M^*$, where quenching could be directly a consequence of thick disk formation. We emphasize that the quenching phase in the Milky Way could be contemporaneous with, and related to, the formation of the bar. We sketch a scenario on how a strong bar may inhibit star formation.Comment: 17 pages, 8 figures. Published versio

A new look at the kinematics of the bulge from an N-body model

(Abridged) By using an N-body simulation of a bulge that was formed via a bar instability mechanism, we analyse the imprints of the initial (i.e. before bar formation) location of stars on the bulge kinematics, in particular on the heliocentric radial velocity distribution of bulge stars. Four different latitudes were considered: $b=-4^\circ$, $-6^\circ$, $-8^\circ$, and $-10^\circ$, along the bulge minor axis as well as outside it, at $l=\pm5^\circ$ and $l=\pm10^\circ$. The bulge X-shaped structure comprises stars that formed in the disk at different locations. Stars formed in the outer disk, beyond the end of the bar, which are part of the boxy peanut-bulge structure may show peaks in the velocity distributions at positive and negative heliocentric radial velocities with high absolute values that can be larger than 100 $\rm km$ $\rm s^{-1}$, depending on the observed direction. In some cases the structure of the velocity field is more complex and several peaks are observed. Stars formed in the inner disk, the most numerous, contribute predominantly to the X-shaped structure and present different kinematic characteristics. Our results may enable us to interpret the cold high-velocity peak observed in the APOGEE commissioning data, as well as the excess of high-velocity stars in the near and far arms of the X-shaped structure at $l$=$0^\circ$ and $b$=$-6^\circ$. When compared with real data, the kinematic picture becomes more complex due to the possible presence in the observed samples of classical bulge and/or thick disk stars. Overall, our results point to the existence of complex patterns and structures in the bulge velocity fields, which are generated by the bar. This suggests that caution should be used when interpreting the bulge kinematics: the presence of substructures, peaks and clumps in the velocity fields is not necessarily a sign of past accretion events.Comment: 21 pages, 18 figures. Accepted for publication in A&