Chromatic transit light curves of disintegrating rocky planets

Context. Kepler observations have revealed a class of short period exoplanets, of which Kepler-1520 b is the prototype, which have comet-like dust tails thought to be the result of small, rocky planets losing mass. The shape and chromaticity of the transits constrain the properties of the dust particles originating from the planet's surface, offering a unique opportunity to probe the composition and geophysics of rocky exoplanets. Aims. We aim to approximate the average Kepler long-cadence light curve of Kepler-1520 b and investigate how the optical thickness and transit cross-section of a general dust tail can affect the observed wavelength dependence and depth of transit light curves. Methods. We developed a new 3D model that ejects sublimating particles from the planet surface to build up a dust tail, assuming it to be optically thin, and used 3D radiative transfer computations that fully treat scattering using the distribution of hollow spheres (DHS) method, to generate transit light curves between 0.45 and 2.5 $\mu$m. Results. We show that the transit depth is wavelength independent for optically thick tails, potentially explaining why only some observations indicate a wavelength dependence. From the 3D nature of our simulated tails, we show that their transit cross-sections are related to the component of particle ejection velocity perpendicular to the planet's orbital plane and use this to derive a minimum ejection velocity of 1.2 kms$^{-1}$. To fit the average transit depth of Kepler-1520 b of 0.87%, we require a high dust mas-loss rate of 7 $-$ 80 M$_\oplus$ Gyr$^{-1}$ which implies planet lifetimes that may be inconsistent with the observed sample. Therefore, these mass-loss rates should be considered to be upper limits.Comment: 22 pages, 22 figures, accepted for publication in A&

Biodynamic lighting effects on the sleep pattern of people with dementia

Dementia can disturb the circadian rhythm more than in normal ageing people. And their biological clock is often not enough stimulated by light. Sleep disturbances form a high burden for informal caregivers and is the main reason for institutionalization. The effect of biodynamic lighting with varying intensity and colour resembling a daylight curve has hardly been objectively researched. In this study, we evaluate the exposure to biodynamic lighting on circadian functioning of 13 patients with dementia admitted to a psychiatric hospital. Three biodynamic lighting armatures designed for home use were placed in the common area for a period of three weeks and then removed for the same period. These periods were intermittent in an AB-phase design. Objective data of the sleeping pattern were collected using a bed sensor. During exposure the average frequency of night-time bed wandering significantly decreased from 11 to 5 times (P = 0.002). The average frequency of daytime napping significantly decreased from 16 to 7 times (P = 0.004). The average total night-time sleep significantly increased from 408 to 495 min (P = 0.007). The average total time out of bed at night significantly decreased from 180 to 104 min (P = 0.006). This pilot study found promising evidence (effect sizes >0.5) that biodynamic lighting, tailored to stimulate circadian entrainment, could be helpful in decreasing sleeping disturbances in patients with dementia. This biodynamic lighting setup could easily be used as a non-pharmacological intervention in a home situation

Dusty tails of evaporating exoplanets. II. Physical modelling of the KIC 12557548b light curve

Evaporating rocky exoplanets, such as KIC 12557548b, eject large amounts of dust grains, which can trail the planet in a comet-like tail. When such objects occult their host star, the resulting transit signal contains information about the dust in the tail. We aim to use the detailed shape of the Kepler light curve of KIC 12557548b to constrain the size and composition of the dust grains that make up the tail, as well as the mass loss rate of the planet. Using a self-consistent numerical model of the dust dynamics and sublimation, we calculate the shape of the tail by following dust grains from their ejection from the planet to their destruction due to sublimation. From this dust cloud shape, we generate synthetic light curves (incorporating the effects of extinction and angle-dependent scattering), which are then compared with the phase-folded Kepler light curve. We explore the free-parameter space thoroughly using a Markov chain Monte Carlo method. Our physics-based model is capable of reproducing the observed light curve in detail. Good fits are found for initial grain sizes between 0.2 and 5.6 micron and dust mass loss rates of 0.6 to 15.6 M_earth/Gyr (2-sigma ranges). We find that only certain combinations of material parameters yield the correct tail length. These constraints are consistent with dust made of corundum (Al2O3), but do not agree with a range of carbonaceous, silicate, or iron compositions. Using a detailed, physically motivated model, it is possible to constrain the composition of the dust in the tails of evaporating rocky exoplanets. This provides a unique opportunity to probe to interior composition of the smallest known exoplanets.Comment: 18 pages, 11 figures, A&A accepte

Process evaluation of a tailored intervention programme of cardiovascular risk management in general practices

Background: A tailored implementation programme to improve cardiovascular risk management (CVRM) in general practice had little impact on outcomes. The questions in this process evaluation concerned (1) impact on counselling skills and CVRM knowledge of practice nurses, (2) their use of the various components of the intervention programme and adoption of recommended practices and (3) patients’ perceptions of counselling for CVRM. Methods: A mixed-methods process evaluation was conducted. We assessed practice nurses’ motivational interviewing skills on audio-taped consultations using Motivational Interviewing Treatment Integrity (MITI). They also completed a clinical knowledge test. Both practice nurses and patients reported on their experiences in a written questionnaire and interviews. A multilevel regression analysis and an independent sample t test were used to examine motivational interviewing skills and CVRM knowledge. Framework analysis was applied to analyse qualitative data. Results: Data from 34 general practices were available, 19 intervention practices and 14 control practices. No improvements were measured on motivational interviewing skills in both groups. There appeared to be better knowledge of CVRM in the control group. On average half of the practice nurses indicated that they adopted the recommended interventions, but stated that they did not necessarily record this in patients’ medical files. The tailored programme was perceived as too large. Time, follow-up support and reminders were felt to be lacking. About 20% of patients in the intervention group visited the general practice during the intervention period, yet only a small number of these patients were referred to recommended options. Conclusions: The tailored programme was only partly used by practice nurses and had little impact on either their clinical knowledge and communication skills or on patient reported healthcare. If the assumed logical model of change is valid, a more intensive programme is needed to have an impact on CVRM in general practice at all

Diagnostic performance of <i>Schistosoma</i> real-time PCR in urine samples from Kenyan children infected with <i>Schistosoma haematobium</i>:day-to-day variation and follow-up after praziquantel treatment

BACKGROUND: In an effort to enhance accuracy of diagnosis of Schistosoma haematobium, this study explores day-to-day variability and diagnostic performance of real-time PCR for detection and quantification of Schistosoma DNA compared to other diagnostic tools in an endemic area before and after treatment. METHODOLOGY: Previously collected urine samples (N = 390) from 114 preselected proven parasitological and/or clinical S. haematobium positive Kenyan schoolchildren were analyzed by a Schistosoma internal transcribed spacer-based real-time PCR after 14 years of storage. Pre-treatment day-to-day fluctuations of PCR and microscopy over three consecutive days were measured for 24 children using intra-class correlation coefficient. A combined 'gold standard' (PCR and/or microscopy positive) was used to measure sensitivity and negative predictive value (NPV) of several diagnostic tools at baseline, two and 18 months post-treatment with praziquantel. PRINCIPAL FINDINGS: All 24 repeatedly tested children were PCR-positive over three days with little daily variation in median Ct-values, while 83.3% were found to be egg-positive for S. haematobium at day 1 and 75.0% at day 2 and 3 pre-treatment, signifying daily fluctuations in microscopy diagnosis. Of all 114 preselected schoolchildren, repeated microscopic measurements were required to detect 96.5% versus 100% of positive pre-treatment cases by single PCR. At two months post-treatment, microscopy and PCR detected 22.8% versus 69.3% positive children, respectively. Based on the 'gold standard', PCR showed high sensitivity (>92%) as compared to >31% sensitivity for microscopy, both pre- and post-treatment. CONCLUSIONS/SIGNIFICANCE: Detection and quantification of Schistosoma DNA in urine by real-time PCR was shown to be a powerful and specific diagnostic tool for detection of S. haematobium infections, with less day-to-day variation and higher sensitivity compared to microscopy. The superior performance of PCR before, and two and 18 months post-treatment provides a compelling argument for PCR as an accurate and reproducible tool for monitoring treatment efficacy

Mark correlations: relating physical properties to spatial distributions

Mark correlations provide a systematic approach to look at objects both distributed in space and bearing intrinsic information, for instance on physical properties. The interplay of the objects' properties (marks) with the spatial clustering is of vivid interest for many applications; are, e.g., galaxies with high luminosities more strongly clustered than dim ones? Do neighbored pores in a sandstone have similar sizes? How does the shape of impact craters on a planet depend on the geological surface properties? In this article, we give an introduction into the appropriate mathematical framework to deal with such questions, i.e. the theory of marked point processes. After having clarified the notion of segregation effects, we define universal test quantities applicable to realizations of a marked point processes. We show their power using concrete data sets in analyzing the luminosity-dependence of the galaxy clustering, the alignment of dark matter halos in gravitational $N$-body simulations, the morphology- and diameter-dependence of the Martian crater distribution and the size correlations of pores in sandstone. In order to understand our data in more detail, we discuss the Boolean depletion model, the random field model and the Cox random field model. The first model describes depletion effects in the distribution of Martian craters and pores in sandstone, whereas the last one accounts at least qualitatively for the observed luminosity-dependence of the galaxy clustering.Comment: 35 pages, 12 figures. to be published in Lecture Notes of Physics, second Wuppertal conference "Spatial statistics and statistical physics