Hubble Space Telescope Near-IR Transmission Spectroscopy of the Super-Earth HD 97658b

Recent results from the Kepler mission indicate that super-Earths (planets with masses between 1-10 times that of the Earth) are the most common kind of planet around nearby Sun-like stars. These planets have no direct solar system analogue, and are currently one of the least well-understood classes of extrasolar planets. Many super-Earths have average densities that are consistent with a broad range of bulk compositions, including both water-dominated worlds and rocky planets covered by a thick hydrogen and helium atmosphere. Measurements of the transmission spectra of these planets offer the opportunity to resolve this degeneracy by directly constraining the scale heights and corresponding mean molecular weights of their atmospheres. We present Hubble Space Telescope near-infrared spectroscopy of two transits of the newly discovered transiting super-Earth HD 97658b. We use the Wide Field Camera 3's scanning mode to measure the wavelength-dependent transit depth in thirty individual bandpasses. Our averaged differential transmission spectrum has a median 1 sigma uncertainty of 23 ppm in individual bins, making this the most precise observation of an exoplanetary transmission spectrum obtained with WFC3 to date. Our data are inconsistent with a cloud-free solar metallicity atmosphere at the 10 sigma level. They are consistent at the 0.4 sigma level with a flat line model, as well as effectively flat models corresponding to a metal-rich atmosphere or a solar metallicity atmosphere with a cloud or haze layer located at pressures of 10 mbar or higher.Comment: ApJ in press; revised version includes an updated orbital ephemeris for the plane

An HST/STIS Optical Transmission Spectrum of Warm Neptune GJ 436b

GJ 436b is a prime target for understanding warm Neptune exoplanet atmospheres and a target for multiple JWST GTO programs. Here, we report the first space-based optical transmission spectrum of the planet using two HST/STIS transit observations from 0.53-1.03 microns. We find no evidence for alkali absorption features, nor evidence of a scattering slope longward of 0.53 microns. The spectrum is indicative of moderate to high metallicity (~100-1000x solar) while moderate metallicity scenarios (~100x solar) require aerosol opacity. The optical spectrum also rules out some highly scattering haze models. We find an increase in transit depth around 0.8 microns in the transmission spectra of 3 different sub-Jovian exoplanets (GJ 436b, HAT-P-26b, and GJ 1214b). While most of the data come from STIS, data from three other instruments may indicate this is not an instrumental effect. Only the transit spectrum of GJ 1214b is well fit by a model with stellar plages on the photosphere of the host star. Our photometric monitoring of the host star reveals a stellar rotation rate of 44.1 days and an activity cycle of 7.4 years. Intriguingly, GJ 436 does not become redder as it gets dimmer, which is expected if star spots were dominating the variability. These insights into the nature of the GJ 436 system help refine our expectations for future observations in the era of JWST, whose higher precision and broader wavelength coverage will shed light on the composition and structure of GJ 436b's atmosphere.Comment: 20 pages, 11 figures, 5 tables, Accepted to AJ. A full version of table 1 is included as table1_mrt.tx

Dynamics of Quasi-ordered Structure in a Regio-regulated pi-Conjugated Polymer:Poly(4-methylthiazole-2,5-diyl)

Dynamics of regio-regulated Poly(4-methylthiazole-2,5-diyl) [HH-P4MeTz] was inves tigated by solid-state 1H, 2D, 13C NMR spectroscopies, and differential scanning calorimetry(DSC) measurements. DSC, 2D quadrupolar echo NMR, 13C cross-polarization and magic-angle spinning(CPMAS) NMR, and 2D spin-echo(2DSE) CPMAS NMR spectroscopy suggest existence of a quasi-ordered phase in which backbone twists take place with weakened pi-stackings. Two-dimensional exchange 2D NMR(2DEX) detected slow dynamics with a rate of an order of 10^2Hz for the CD_3 group in d_3-HH-P4MeTz at 288K. The frequency dependence of proton longitudinal relaxation rate at 288K shows a omega^-1/2 dependence, which is due to the one-dimensional diffusion-like motion of backbone conformational modulation waves. The diffusion rate was estimated as 3+/-2 GHz, which was approximately 10^7 times larger than that estimated by 2DEX NMR measurements. These results suggest that there exists anomalous dispersion of modulation waves in HH-P4MeTz. The one-dimensional group velocity of the wave packet is responsible for the behavior of proton longitudinal relaxation time. On the other hand, the 2DEX NMR is sensitive to phase velocity of the nutation of methyl groups that is associated with backbone twists. From proton T_1 and T_2 measurements, the activation energy was estimated as 2.9 and 3.4 kcal/mol, respectively. These were in agreement with 3.0 kcal/mol determined by Moller-Plesset(MP2) molecular orbital(MO) calculation. We also performed chemical shielding calculation of the methyl-carbon in order to understand chemical shift tensor behavior, leading to the fact that a quasi-ordered phase coexist with the crystalline phase.Comment: 14 pages, 11 figures, to appear in Phys.Rev.

Developing autonomous learning in first year university students using perspectives from positive psychology

Autonomous learning is a commonly occurring learning outcome from university study, and it is argued that students require confidence in their own abilities to achieve this. Using approaches from positive psychology, this study aimed to develop confidence in first‐year university students to facilitate autonomous learning. Psychological character strengths were assessed in 214 students on day one at university. Two weeks later their top three strengths were given to them in study skills modules as part of a psycho‐educational intervention designed to increase their self‐efficacy and self‐esteem. The impact of the intervention was assessed against a control group of 40 students who had not received the intervention. The results suggested that students were more confident after the intervention, and that levels of autonomous learning increased significantly compared to the controls. Character strengths were found to be associated with self‐efficacy, self‐esteem and autonomous learning in ways that were theoretically meaningful

AAPM Medical Physics Practice Guideline 2.a: Commissioning and quality assurance of X-ray–based image-guided radiotherapy systems

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. 1

Updated Parameters and a New Transmission Spectrum of HD 97658b

Recent years have seen increasing interest in the characterization of sub-Neptune-sized planets because of their prevalence in the Galaxy, contrasted with their absence in our solar system. HD 97658 is one of the brightest stars hosting a planet of this kind, and we present the transmission spectrum of this planet by combining four Hubble Space Telescope transits, 12 Spitzer/IRAC transits, and eight MOST transits of this system. Our transmission spectrum has a higher signal-to-noise ratio than those from previous works, and the result suggests that the slight increase in transit depth from wavelength 1.1–1.7 μm reported in previous works on the transmission spectrum of this planet is likely systematic. Nonetheless, our atmospheric modeling results are inconclusive, as no model provides an excellent match to our data. Nonetheless, we find that atmospheres with high C/O ratios (C/O ≳ 0.8) and metallicities of ≳100× solar metallicity are favored. We combine the mid-transit times from all of the new Spitzer and MOST observations and obtain an updated orbital period of P = 9.489295 ± 0.000005, with a best-fit transit time center at T₀ = 2456361.80690 ± 0.00038 (BJD). No transit timing variations are found in this system. We also present new measurements of the stellar rotation period (34 ± 2 days) and stellar activity cycle (9.6 yr) of the host star HD 97658. Finally, we calculate and rank the Transmission Spectroscopy Metric of all confirmed planets cooler than 1000 K and with sizes between 1 R⊕ and 4 R⊕. We find that at least a third of small planets cooler than 1000 K can be well characterized using James Webb Space Telescope, and of those, HD 97658b is ranked fifth, meaning that it remains a high-priority target for atmospheric characterization

Data and programming code from the studies on the learning curve for radical prostatectomy

Our group analyzed a multi-institutional data set to address the question of how the outcomes of surgery for prostate cancer are affected by surgeon-specific factors. The cohort consists of 9076 patients treated by open radical prostatectomy at one of four US academic institutions 1987 - 2003. The primary analyses focused on 7765 patients without neoadjuvant therapy. The most well-known finding is that of a surgical "learning curve", with rates of prostate cancer cure strongly dependent on surgeon experience. In this "data note", we provide the raw data set, as well as well-annotated programming code for the main analyses. Data include markers of cancer severity (stage, grade and prostate-specific antigen level), cancer outcome, and surgeon variables such as training and experience

Economic Impacts of Non-Native Forest Insects in the Continental United States

Reliable estimates of the impacts and costs of biological invasions are critical to developing credible management, trade and regulatory policies. Worldwide, forests and urban trees provide important ecosystem services as well as economic and social benefits, but are threatened by non-native insects. More than 450 non-native forest insects are established in the United States but estimates of broad-scale economic impacts associated with these species are largely unavailable. We developed a novel modeling approach that maximizes the use of available data, accounts for multiple sources of uncertainty, and provides cost estimates for three major feeding guilds of non-native forest insects. For each guild, we calculated the economic damages for five cost categories and we estimated the probability of future introductions of damaging pests. We found that costs are largely borne by homeowners and municipal governments. Wood- and phloem-boring insects are anticipated to cause the largest economic impacts by annually inducing nearly $1.7 billion in local government expenditures and approximately$830 million in lost residential property values. Given observations of new species, there is a 32% chance that another highly destructive borer species will invade the U.S. in the next 10 years. Our damage estimates provide a crucial but previously missing component of cost-benefit analyses to evaluate policies and management options intended to reduce species introductions. The modeling approach we developed is highly flexible and could be similarly employed to estimate damages in other countries or natural resource sectors

Water Vapor and Clouds on the Habitable-zone Sub-Neptune Exoplanet K2-18b

Results from the Kepler mission indicate that the occurrence rate of small planets (<3 R⊕) in the habitable zone of nearby low-mass stars may be as high as 80%. Despite this abundance, probing the conditions and atmospheric properties on any habitable-zone planet is extremely difficult and has remained elusive to date. Here, we report the detection of water vapor and the likely presence of liquid and icy water clouds in the atmosphere of the 2.6 R ⊕ habitable-zone planet K2-18b. The simultaneous detection of water vapor and clouds in the mid-atmosphere of K2-18b is particularly intriguing because K2-18b receives virtually the same amount of total insolation from its host star (1368^(+114)_(-107) W m⁻²) as the Earth receives from the Sun (1361 W m⁻²), resulting in the right conditions for water vapor to condense and explain the detected clouds. In this study we observed nine transits of K2-18b using Hubble Space Telescope/WFC3 in order to achieve the necessary sensitivity to detect the water vapor, and we supplement this data set with Spitzer and K2 observations to obtain a broader wavelength coverage. While the thick hydrogen-dominated envelope we detect on K2-18b means that the planet is not a true Earth analog, our observations demonstrate that low-mass habitable-zone planets with the right conditions for liquid water are accessible with state-of-the-art telescopes