Detectability of Surface Biosignatures for Directly Imaged Rocky Exoplanets.

Modeling the detection of life has never been more opportune. With next-generation space telescopes, such as the currently developing Habitable Worlds Observatory (HWO) concept, we will begin to characterize rocky exoplanets potentially similar to Earth. However, few realistic planetary spectra containing surface biosignatures have been paired with direct imaging telescope instrument models. Therefore, we use a HWO instrument noise model to assess the detection of surface biosignatures affiliated with oxygenic, anoxygenic, and nonphotosynthetic extremophiles. We pair the HWO telescope model to a one-dimensional radiative transfer model to estimate the required exposure times necessary for detecting each biosignature on planets with global microbial coverage and varying atmospheric water vapor concentrations. For modeled planets with 0-50% cloud coverage, we determine pigments and the red edge could be detected within 1000 hr (100 hr) at distances within 15 pc (11 pc). However, tighter telescope inner working angles (2.5 λ/D) would allow surface biosignature detection at further distances. Anoxygenic photosynthetic biosignatures could also be more easily detectable than nonphotosynthetic pigments and the photosynthetic red edge when compared against a false positive iron oxide slope. Future life detection missions should evaluate the influence of false positives on the detection of multiple surface biosignatures.

Developmental order, fibre caliber, and vascularization predict tract-wise declines: Testing retrogenesis and physiological predictions in white matter aging.

To understand the consistently observed spatial distribution of white-matter (WM) aging, developmentally driven theories of retrogenesis have gained traction, positing that the order WM development predicts declines. Regions that develop first are often expected to deteriorate the last, i.e. "last-in-first-out". Alternatively, regions which develop most rapidly may also decline most rapidly in aging, or the "gains-predict-loss" model. The validity of such theories remains uncertain, in part due to lack of clarity on the definition of developmental order. Our recent findings also suggest that WM degeneration may vary by physiological parameters such as perfusion. Furthermore, it is informative to link perfusion to fibre metabolic need, which varies with fibre size. Here we address the question of whether WM degeneration is determined by development trajectory or physiological state across both microstructural and perfusion measures using data drawn from the Human Connectome Project in Aging (HCP-A). Our results indicate that developmental order of tract myelination provides the strongest support for the retrogenesis hypothesis, with the last to complete myelination the first to decline. Moreover, higher mean axon diameter and lower macrovascular density are associated with lower degrees of WM degeneration across measures. Tract perfusion, in turn also tends to be higher and the arterial transit time longer for tracts that appear first. These findings suggest that WM degeneration in different tracts may be governed by their developmental trajectories and physiology, and ultimately influenced by each tract's metabolic demand.

Conscious expectancy rather than associative strength elicits brain activity during single-cue fear conditioning.

The neurocognitive processes underlying Pavlovian conditioning in humans are still largely debated. The conventional view is that conditioned responses (CRs) emerge automatically as a function of the contingencies between a conditioned stimulus (CS) and an unconditioned stimulus (US). As such, the associative strength model asserts that the frequency or amplitude of CRs reflects the strength of the CS-US associations. Alternatively, the expectation model asserts that the presentation of the CS triggers conscious expectancy of the US, which is responsible for the production of CRs. The present study tested the hypothesis that there are dissociable brain networks related to the expectancy and associative strength theories using a single-cue fear conditioning paradigm with a pseudo-random intermittent reinforcement schedule during functional magnetic resonance imaging. Participants' (n = 21) trial-by-trial expectations of receiving shock displayed a significant linear effect consistent with the expectation model. We also found a positive linear relationship between the expectancy model and activity in frontoparietal brain areas including the dorsolateral prefrontal cortex (PFC) and dorsomedial PFC. While an exploratory analysis found a linear relationship consistent with the associated strength model in the insula and early visual cortex, our primary results are consistent with the view that conscious expectancy contributes to CRs.

Emergent robotic versus laparoscopic surgery for perforated gastrojejunal ulcers: a retrospective cohort study of 44 patients.

BACKGROUND: Perforated gastrojejunal ulcers are a known complication following Roux-en-Y gastric bypass (RYGB) surgery requiring emergent surgical repair. The robotic approach has not been evaluated for emergency general surgery. METHODS: A retrospective cohort study from 2015 to 2019 was performed identifying all patients who underwent repair of perforated gastrojejunal ulcers after RYGB at a single institution. Patient characteristics and outcomes were compared by robotic or laparoscopic approach. RESULTS: Of the 44 patients analyzed, there were 24 robotic and 20 laparoscopic repairs of perforated gastrojejunal ulcers. No patients were initially approached with open surgery. In-room-to-surgery-start time was significantly faster in the robotic group than the laparoscopic group (25 versus 31 min, p = 0.01). Complication rate, complication severity, operating time, hospital length of stay, postoperative vasopressor requirement, discharge to home, hospital length of stay and 30-day readmission were all improved in the robotic group, although these were not statistically significant. Both total inpatient and procedural costs were more in the robotic group than the laparoscopic group. CONCLUSION: Perforated hollow viscus is not a contraindication for the use of the surgical robot, which may improve outcomes.

Intrapericardial diaphragmatic hernia in a 6-month-old girl: A case report and review of the literature.

INTRODUCTION: Intrapericardial congenital diaphragmatic hernia (IPCDH) is extremely rare: only 18 cases in children have been reported in the literature since 1981. We report the 19th case of infantile IPCDH in a 6-month-old girl and compare with previous reports. PRESENTATION OF CASE: Our patient initially presented with four days of dyspnea and was diagnosed with CDH by preoperative radiography. She was taken to the operating room, where an IPCDH was discovered, and successfully reduced. DISCUSSION: CDH may present with cardiopulmonary compromise, but IPCDH directly compress the heart, leading to acute or subacute heart failure. CONCLUSION: Pediatric surgeons should be aware of and prepared for the possibility of IPCDH when making surgical plans to correct CDH.

Exoplanet Biosignatures: A Framework for Their Assessment.

Finding life on exoplanets from telescopic observations is an ultimate goal of exoplanet science. Life produces gases and other substances, such as pigments, which can have distinct spectral or photometric signatures. Whether or not life is found with future data must be expressed with probabilities, requiring a framework of biosignature assessment. We present a framework in which we advocate using biogeochemical "Exo-Earth System" models to simulate potential biosignatures in spectra or photometry. Given actual observations, simulations are used to find the Bayesian likelihoods of those data occurring for scenarios with and without life. The latter includes "false positives" wherein abiotic sources mimic biosignatures. Prior knowledge of factors influencing planetary inhabitation, including previous observations, is combined with the likelihoods to give the Bayesian posterior probability of life existing on a given exoplanet. Four components of observation and analysis are necessary. (1) Characterization of stellar (e.g., age and spectrum) and exoplanetary system properties, including "external" exoplanet parameters (e.g., mass and radius), to determine an exoplanet's suitability for life. (2) Characterization of "internal" exoplanet parameters (e.g., climate) to evaluate habitability. (3) Assessment of potential biosignatures within the environmental context (components 1-2), including corroborating evidence. (4) Exclusion of false positives. We propose that resulting posterior Bayesian probabilities of life's existence map to five confidence levels, ranging from "very likely" (90-100%) to "very unlikely" (<10%) inhabited. Key Words: Bayesian statistics-Biosignatures-Drake equation-Exoplanets-Habitability-Planetary science. Astrobiology 18, 709-738.

Socially Responsible Surgery: Building Recognition and Coalition.

IMPORTANCE: Socially responsible surgery (SRS) integrates surgery and public health, providing a framework for research, advocacy, education, and clinical practice to address the social barriers of health that decrease surgical access and worsen surgical outcomes in underserved patient populations. These patients face disparities in both health and in health care, which can be effectively addressed by surgeons in collaboration with allied health professionals. OBJECTIVE: We reviewed the current state of surgical access and outcomes of underserved populations in American rural communities, American urban communities, and in low- and middle-income countries. EVIDENCE REVIEW: We searched PubMed using standardized search terms and reviewed the reference lists of highly relevant articles. We reviewed the reports of two recent global surgery commissions. CONCLUSION: There is an opportunity for scholarship in rural surgery, urban surgery, and global surgery to be unified under the concept of SRS. The burden of surgical disease and the challenges to management demonstrate that achieving optimal health outcomes requires more than excellent perioperative care. Surgeons can and should regularly address the social determinants of health experienced by their patients. Formalized research and training opportunities are needed to meet the growing enthusiasm among surgeons and trainees to develop their practice as socially responsible surgeons.

Factors affecting the United Nations' response to natural disasters: what determines the allocation of the Central Emergency Response Fund?

Natural disasters can overwhelm the domestic response of a country, leaving it dependent on external humanitarian relief. The Central Emergency Response Fund (CERF) of the United Nations centralises humanitarian funding and thus allows for a rapid response. This study combined data to analyse the factors that affected the allocation of CERF funding to countries that suffered a natural disaster between 2007 and 2013. It generated descriptive statistics and information on relative risks, and performed regressions of CERF funding across countries. There were 4,346 disasters in total in 188 countries between 2007 and 2013. CERF provided USD 2.98 billion to 87 countries, comprising 3.3 per cent of their total humanitarian funding. CERF more frequently supplied aid to countries in North Africa and the Middle East, and to those that had suffered geophysical disasters. Appropriately, it funds vulnerable countries experiencing severe natural disasters, yet its funding may be affected by variables beyond severity and vulnerability. Further investigation is warranted, therefore.

Titan solar occultation observations reveal transit spectra of a hazy world.

High-altitude clouds and hazes are integral to understanding exoplanet observations, and are proposed to explain observed featureless transit spectra. However, it is difficult to make inferences from these data because of the need to disentangle effects of gas absorption from haze extinction. Here, we turn to the quintessential hazy world, Titan, to clarify how high-altitude hazes influence transit spectra. We use solar occultation observations of Titan's atmosphere from the Visual and Infrared Mapping Spectrometer aboard National Aeronautics and Space Administration's (NASA) Cassini spacecraft to generate transit spectra. Data span 0.88-5 µm at a resolution of 12-18 nm, with uncertainties typically smaller than 1%. Our approach exploits symmetry between occultations and transits, producing transit radius spectra that inherently include the effects of haze multiple scattering, refraction, and gas absorption. We use a simple model of haze extinction to explore how Titan's haze affects its transit spectrum. Our spectra show strong methane-absorption features, and weaker features due to other gases. Most importantly, the data demonstrate that high-altitude hazes can severely limit the atmospheric depths probed by transit spectra, bounding observations to pressures smaller than 0.1-10 mbar, depending on wavelength. Unlike the usual assumption made when modeling and interpreting transit observations of potentially hazy worlds, the slope set by haze in our spectra is not flat, and creates a variation in transit height whose magnitude is comparable to those from the strongest gaseous-absorption features. These findings have important consequences for interpreting future exoplanet observations, including those from NASA's James Webb Space Telescope.

The effect of host star spectral energy distribution and ice-albedo feedback on the climate of extrasolar planets.

Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. In this study, we explored this effect with a one-dimensional (1-D), line-by-line, radiative transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy balance climate model. A three-dimensional (3-D) general circulation model was also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models, we simulated planets covered by ocean, land, and water-ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibited a stronger ice-albedo feedback. We found that ice extent was much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and that ice-covered conditions occurred on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO(2) (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets in addition to stronger absorption by water vapor and CO(2) in their atmospheres, which provides increased downwelling longwave radiation. Lowering the IR and visible-band surface ice and snow albedos for an M-dwarf planet increased the planet's climate stability against changes in instellation and slowed the descent into global ice coverage. The surface ice-albedo feedback effect becomes less important at the outer edge of the habitable zone, where atmospheric CO(2) could be expected to be high such that it maintains clement conditions for surface liquid water. We showed that ∼3-10 bar of CO(2) will entirely mask the climatic effect of ice and snow, leaving the outer limits of the habitable zone unaffected by the spectral dependence of water ice and snow albedo. However, less CO(2) is needed to maintain open water for a planet orbiting an M-dwarf star than would be the case for hotter main-sequence stars.

Properties of an Earth-like planet orbiting a Sun-like star: Earth observed by the EPOXI mission.

NASA's EPOXI mission observed the disc-integrated Earth and Moon to test techniques for reconnoitering extrasolar terrestrial planets, using the Deep Impact flyby spacecraft to observe Earth at the beginning and end of Northern Hemisphere spring, 2008, from a range of ∼1/6 to 1/3 AU. These observations furnish high-precision and high-cadence empirical photometry and spectroscopy of Earth, suitable as "ground truth" for numerically simulating realistic observational scenarios for an Earth-like exoplanet with finite signal-to-noise ratio. Earth was observed at near-equatorial sub-spacecraft latitude on 18-19 March, 28-29 May, and 4-5 June (UT), in the range of 372-4540 nm wavelength with low visible resolving power (λ/Δλ=5-13) and moderate IR resolving power (λ/Δλ=215-730). Spectrophotometry in seven filters yields light curves at ∼372-948 nm filter-averaged wavelength, modulated by Earth's rotation with peak-to-peak amplitude of ≤20%. The spatially resolved Sun glint is a minor contributor to disc-integrated reflectance. Spectroscopy at 1100-4540 nm reveals gaseous water and carbon dioxide, with minor features of molecular oxygen, methane, and nitrous oxide. One-day changes in global cloud cover resulted in differences between the light curve beginning and end of ≤5%. The light curve of a lunar transit of Earth on 29 May is color-dependent due to the Moon's red spectrum partially occulting Earth's relatively blue spectrum. The "vegetation red edge" spectral contrast observed between two long-wavelength visible/near-IR bands is ambiguous, not clearly distinguishing between the verdant Earth diluted by cloud cover versus the desolate mineral regolith of the Moon. Spectrophotometry in at least one other comparison band at short wavelength is required to distinguish between Earth-like and Moon-like surfaces in reconnaissance observations. However, measurements at 850 nm alone, the high-reflectance side of the red edge, could be sufficient to establish periodicity in the light curve and deduce Earth's diurnal period and the existence of fixed surface units.

Earth as an extrasolar planet: Earth model validation using EPOXI earth observations.

The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulations used to better understand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model. This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of ∼100 pixels on the visible disk, and four categories of water clouds, which were defined by using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to Earth's lightcurve, absolute brightness, and spectral data, with a root-mean-square (RMS) error of typically less than 3% for the multiwavelength lightcurves and residuals of ∼10% for the absolute brightness throughout the visible and NIR spectral range. We have extended our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of ∼7% and brightness temperature errors of less than 1 K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be used to simulate Earth's time-dependent brightness and spectral properties for wavelengths from the far ultraviolet to the far infrared. Key Words: Astrobiology-Extrasolar terrestrial planets-Habitability-Planetary science-Radiative transfer. Astrobiology 11, 393-408.