Transit Light Curves with Finite Integration Time: Fisher Information Analysis

Kepler has revolutionized the study of transiting planets with its unprecedented photometric precision on more than 150,000 target stars. Most of the transiting planet candidates detected by Kepler have been observed as long-cadence targets with 30 minute integration times, and the upcoming Transiting Exoplanet Survey Satellite (TESS) will record full frame images with a similar integration time. Integrations of 30 minutes affect the transit shape, particularly for small planets and in cases of low signal-to-noise. Using the Fisher information matrix technique, we derive analytic approximations for the variances and covariances on the transit parameters obtained from fitting light curve photometry collected with a finite integration time. We find that binning the light curve can significantly increase the uncertainties and covariances on the inferred parameters when comparing scenarios with constant total signal-to-noise (constant total integration time in the absence of read noise). Uncertainties on the transit ingress/egress time increase by a factor of 34 for Earth-size planets and 3.4 for Jupiter-size planets around Sun-like stars for integration times of 30 minutes compared to instantaneously-sampled light curves. Similarly, uncertainties on the mid-transit time for Earth and Jupiter-size planets increase by factors of 3.9 and 1.4. Uncertainties on the transit depth are largely unaffected by finite integration times. While correlations among the transit depth, ingress duration, and transit duration all increase in magnitude with longer integration times, the mid-transit time remains uncorrelated with the other parameters. We provide code in Python and Mathematica for predicting the variances and covariances at www.its.caltech.edu/~eprice

How Low Can You Go? The Photoeccentric Effect for Planets of Various Sizes

It is well-known that the light curve of a transiting planet contains information about the planet's orbital period and size relative to the host star. More recently, it has been demonstrated that a tight constraint on an individual planet's eccentricity can sometimes be derived from the light curve via the "photoeccentric effect," the effect of a planet's eccentricity on the shape and duration of its light curve. This has only been studied for large planets and high signal-to-noise scenarios, raising the question of how well it can be measured for smaller planets or low signal-to-noise cases. We explore the limits of the photoeccentric effect over a wide range of planet parameters. The method hinges upon measuring $g$ directly from the light curve, where $g$ is the ratio of the planet's speed (projected on the plane of the sky) during transit to the speed expected for a circular orbit. We find that when the signal-to-noise in the measurement of $g$ is $< 10$, the ability to measure eccentricity with the photoeccentric effect decreases. We develop a "rule of thumb" that for per-point relative photometric uncertainties $\sigma = \{ 10^{-3}, 10^{-4}, 10^{-5} \}$, the critical values of planet-star radius ratio are $R_p / R_\star \approx \{ 0.1, 0.05, 0.03 \}$ for Kepler-like 30-minute integration times. We demonstrate how to predict the best-case uncertainty in eccentricity that can be found with the photoeccentric effect for any light curve. This clears the path to study eccentricities of individual planets of various sizes in the Kepler sample and future transit surveys

Predictors of hazardous alcohol consumption among young adult amphetamine-type stimulant users: a population-based prospective study

Background: Very high levels of alcohol consumption have been observed in young adult amphetamine-type stimulant (i.e., ecstasy and methamphetamine) users. The reasons for this association are poorly understood. Objective: To examine predictors of hazardous alcohol consumption in a sample of young adult amphetamine-type stimulant users after 30 months of follow-up, controlling for potential confounders. Method: Analysis of longitudinal data from a population-derived sample of Australian young adult amphetamine-type stimulant users (n = 292). A prediction model of alcohol use at 30 months was developed using generalized linear latent and mixed modeling (GLLAMM). Results: Concurrently using ecstasy (Adjusted Odds Ratio [AOR] = 2.67, 95% Confidence Interval [CI] = [1.41, 5.07]), frequently attending nightclubs (AOR = 2.53, 95% CI = [1.04, 6.16]), high baseline alcohol use patterns (AOR = 2.06, 95% CI = [1.32, 3.20]), and being male (AOR = 3.60, 95% CI = [1.48, 8.78]) were associated with an increased likelihood of hazardous alcohol use at 30 months. Conclusion: Concurrent, but not baseline, ecstasy use was associated with hazardous alcohol use, suggesting that combined use of these substances may have an instrumental role in terms of the social functions of drug use (e.g., increasing capacity to drink). Integration of educational interventions concerning alcohol and stimulants is warranted

Exploring the micro-scale controls on fracturing in a Carboniferous limestone, and their implications for carbon capture and storage

Characterising subsurface fracture properties is important for understanding their structure, distribution, and effect on fluid flow. Fractures often act to compartmentalise fluids in the crust, which has implications across a number of subsurface applications, including carbon-dioxide (CO2) storage. Within the U.K., limestone-rich Carboniferous strata are becoming increasingly economically important and as such it is vital to gain a better understanding of their mechanical properties in the subsurface. To help achieve this, core plugs (Ø 38mm) from one naturally fractured sample and one protolith (undisturbed) sample of the Namurian McDonald Limestone, exposed in the Spireslack Surface Coal Mine in East Ayrshire, were taken. To understand controls on newly formed fractures, i.e. those that may form as a result of CO2 injection, the protolith sample was deformed in axi-symmetric compression at 25 MPa confining pressures. The sample was deformed and then unloaded in order to replicate early stage deformation features. Early results indicate that fossil fragments in part control fracture propagation pathways. Carbonation (i.e. CO2-brine-limestone) experiments on the samples were conducted for 7.2 weeks in a batch high temperature/high pressure experimental system, in order to investigate their reactivity when in contact with supercritical CO2 under conditions representative of a CO2 storage reservoir in the North Sea region. XRT was performed on original and reacted samples to characterise fractures and deformation features occurring within the plugs. Early results indicate that, due to rock-fluid interactions, fracture surfaces have been partially dissolved and as a result are smoother and wider. Debris recovered in the batch cylinder after the experiment suggests that the induced fracture network (in the protolith sample) allowed for a higher interaction rate compared to the naturally fractured and un-fractured samples

Mutant Huntingtin Fragments Form Oligomers in a Polyglutamine Length-Dependent Manner \u3cem\u3ein Vitro\u3c/em\u3e and \u3cem\u3ein Vivo\u3c/em\u3e

Huntington disease (HD) is caused by an expansion of more than 35–40 polyglutamine (polyQ) repeats in the huntingtin (htt) protein, resulting in accumulation of inclusion bodies containing fibrillar deposits of mutant htt fragments. Intriguingly, polyQ length is directly proportional to the propensity for htt to form fibrils and the severity of HD and is inversely correlated with age of onset. Although the structural basis for htt toxicity is unclear, the formation, abundance, and/or persistence of toxic conformers mediating neuronal dysfunction and degeneration in HD must also depend on polyQ length. Here we used atomic force microscopy to demonstrate mutant htt fragments and synthetic polyQ peptides form oligomers in a polyQ length-dependent manner. By time-lapse atomic force microscopy, oligomers form before fibrils, are transient in nature, and are occasionally direct precursors to fibrils. However, the vast majority of fibrils appear to form by monomer addition coinciding with the disappearance of oligomers. Thus, oligomers must undergo a major structural transition preceding fibril formation. In an immortalized striatal cell line and in brain homogenates from a mouse model of HD, a mutant htt fragment formed oligomers in a polyQ length-dependent manner that were similar in size to those formed in vitro, although these structures accumulated over time in vivo. Finally, using immunoelectron microscopy, we detected oligomeric-like structures in human HD brains. These results demonstrate that oligomer formation by a mutant htt fragment is strongly polyQ length-dependent in vitro and in vivo, consistent with a causative role for these structures, or subsets of these structures, in HD pathogenesis

The sedimentology, architecture and depositional setting of the fluvial Spireslack 1 Sandstone of the Midland Valley, Scotland: insights from Spireslack surface coal mine.

Spireslack surface coal mine exposes a section in the Carboniferous Lawmuir Formation (Brigantian) into the Upper Limestone Formation (Arnsbergian). This paper describes the stratigraphy exposed at Spireslack for the first time and, in so doing, names the Spireslack Sandstone, a distinctive erosively based, sandstone-dominated unit in the Upper Limestone Formation. The Spireslack Sandstone comprises two fluvial sandstone channel sets and an upper possibly fluvio-estuarine succession. From an analysis of their internal architectural elements, the channel sets are interpreted as a low sinuosity, sand-dominated, mixed load fluvial system in which avulsion and variations in sediment load played a significant role. The lower channel set appears confined to erosional palaeovalleys of limited lateral extent and significant relief. The upper channel set is much more laterally extensive and displays evidence of a generally lower sediment load with a greater degree of lateral accretion and flooding. Consequently, the Spireslack Sandstone may represent a system responding to base level changes of higher magnitude and longer duration than the glacioeustatic scale commonly attributed to Carboniferous fluvio-deltaic cycles. Spireslack Sandstone may represent an important correlative marker in the Carboniferous of the Midland Valley, and may provide an alternative analogue for some Carboniferous fluvial sandstone stratigraphical traps

Novel verbal fluency scores and structural brain imaging for prediction of cognitive outcome in mild cognitive impairment

AbstractIntroductionThe objective of this study was to assess the utility of novel verbal fluency scores for predicting conversion from mild cognitive impairment (MCI) to clinical Alzheimer's disease (AD).MethodVerbal fluency lists (animals, vegetables, F, A, and S) from 107 MCI patients and 51 cognitively normal controls were transcribed into electronic text files and automatically scored with traditional raw scores and five types of novel scores computed using methods from machine learning and natural language processing. Additional scores were derived from structural MRI scans: region of interest measures of hippocampal and ventricular volumes and gray matter scores derived from performing ICA on measures of cortical thickness. Over 4 years of follow-up, 24 MCI patients converted to AD. Using conversion as the outcome variable, ensemble classifiers were constructed by training classifiers on the individual groups of scores and then entering predictions from the primary classifiers into regularized logistic regression models. Receiver operating characteristic curves were plotted, and the area under the curve (AUC) was measured for classifiers trained with five groups of available variables.ResultsClassifiers trained with novel scores outperformed those trained with raw scores (AUC 0.872 vs 0.735; P < .05 by DeLong test). Addition of structural brain measurements did not improve performance based on novel scores alone.ConclusionThe brevity and cost profile of verbal fluency tasks recommends their use for clinical decision making. The word lists generated are a rich source of information for predicting outcomes in MCI. Further work is needed to assess the utility of verbal fluency for early AD

Assessing Cyberbiosecurity Vulnerabilities and Infrastructure Resilience

The convergence of advances in biotechnology with laboratory automation, access to data, and computational biology has democratized biotechnology and accelerated the development of new therapeutics. However, increased access to biotechnology in the digital age has also introduced additional security concerns and ultimately, spawned the new discipline of cyberbiosecurity, which encompasses cybersecurity, cyber-physical security, and biosecurity considerations. With the emergence of this new discipline comes the need for a logical, repeatable, and shared approach for evaluating facility and system vulnerabilities to cyberbiosecurity threats. In this paper, we outline the foundation of an assessment framework for cyberbiosecurity, accounting for both security and resilience factors in the physical and cyber domains. This is a unique problem set, but despite the complexity of the cyberbiosecurity field in terms of operations and governance, previous experience developing and implementing physical and cyber assessments applicable to a wide spectrum of critical infrastructure sectors provides a validated point of departure for a cyberbiosecurity assessment framework. This approach proposes to integrate existing capabilities and proven methodologies from the infrastructure assessment realm (e.g., decision science, physical security, infrastructure resilience, cybersecurity) with new expertise and requirements in the cyberbiosecurity space (e.g., biotechnology, biomanufacturing, genomics) in order to forge a flexible and defensible approach to identifying and mitigating vulnerabilities. Determining where vulnerabilities reside within cyberbiosecurity business processes can help public and private sector partners create an assessment framework to identify mitigation options for consideration that are both economically and practically viable and ultimately, allow them to manage risk more effectively