The atmospheres of rocky exoplanets : II. Influence of surface composition on the diversity of cloud condensates

O.H. acknowledges the PhD stipend form the University of St Andrews’ Centre for Exoplanet Science. P.W. and Ch.H. acknowledge funding from the European Union H2020-MSCA-ITN-2019 under Grant Agreement no. 860470 (CHAMELEON).Clouds are an integral part of planetary atmospheres, with most planets hosting clouds. Understanding not only the formation, but also the composition of clouds, is crucial to understand future observations. As observations of the planet's surface will remain very difficult, it is essential to link the observable high atmosphere gas and cloud composition to the surface conditions. We present a fast and simple chemical equilibrium model for the troposphere of rocky exoplanets, which is in chemical and phase equilibrium with the crust. The hydrostatic equilibrium atmosphere is built from bottom to top. In each atmospheric layer, chemical equilibrium is solved and all thermally stable condensates are removed, depleting the atmosphere above in the effected elements. These removed condensates build an upper limit for cloud formation and can be separated into high and low temperature condensates. The most important cloud condensates for 1000K >∼ Tgas >∼ 400K are KCl[s], NaCl[s], FeS[s], FeS2[s], FeO[s], Fe2O3[s], and Fe3O4[s]. For Tgas ∼< 400K H2O[l,s], C[s], NH3[s], NH4Cl[s], and NH4SH[s] are thermally stable, while for even lower temperatures of Tgas ≤ 150K CO2[s], CH4[s], NH3[s], and H2S[s] become stable. The inclusion of clouds with trace abundances results in the thermal stability of a total of 72 condensates for atmospheres with different surface conditions (300K ≤ Tsurf ≤ 1000K and psurf = 1 bar; 100 bar). The different cloud condensates are not independent of each other, but follow sequences of condensation, which are robust against changes in crust composition, surface pressure, and surface temperature. Independent of the existence of water as a crust condensate, H2O[l,s] is a thermally stable cloud condensate for all investigated elemental abundances. However, the water cloud base depends on the hydration level of the crust. Therefore, the detection of water condensates alone does not necessarily imply stable water on the surface, even if the temperature could allow for water condensation.Publisher PDFPeer reviewe

Modeling the Temporal Dynamics of Visual Working Memory

Abstract Visual working memory (VWM) is one of the most crucial parts of the human cognitive system. Research focuses on the apparent limits in the capacity of this system and the reasons for them. So far only a few formal models exist that can account for the temporal dynamics of the amount of information stored in VWM. We propose a combination of the well established theory of visual attention (TVA) with a dynamic memory model, resulting in an iterative, probabilistic framework for VWM. The model includes a consolidation as well as a decay mechanism and employs the strength concept to quantify the availability of a certain memory trace. We evaluate the model on available change detection data

Brillouin light scattering study of Co2_{2}Cr0.6_{0.6}Fe0.4_{0.4}Al and Co2_{2}FeAl Heusler compounds

The thermal magnonic spectra of Co$_{2}$Cr$_{0.6}$Fe$_{0.4}$Al (CCFA) and Co$_2$FeAl were investigated using Brillouin light scattering spectroscopy (BLS). For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 $\mu$erg/cm (203 meV A$^2$), while for Co$_2$FeAl the corresponding values of 1.55 $\mu$erg/cm (370 meV A$^2$) were found. The observed asymmetry in the BLS spectra between the Stokes and anti-Stokes frequencies was assigned to an interplay between the asymmetrical profiles of hybridized Damon-Esbach and perpendicular standing spin-wave modes, combined with the optical sensitivity of the BLS signal to the upper side of the CCFA or Co$_2$FeAl film

The effect of a preoperative subconjuntival injection of dexamethasone on blood–retinal barrier breakdown following scleral buckling retinal detachment surgery: a prospective randomized placebo-controlled double blind clinical trial

textabstractBackground: Blood-retinal barrier breakdown secondary to retinal detachment and retinal detachment repair is a factor in the pathogenesis of proliferative vitreoretinopathy (PVR). We wished to investigate whether an estimated 700 to 1000 ng/ml subretinal dexamethasone concentration at the time of surgery would decrease the blood-retinal barrier breakdown postoperatively. Methods: Prospective, placebo-controlled, double blind clinical trial. In 34 patients with rhegmatogenous retinal detachment scheduled for conventional scleral buckling retinal detachment surgery, a subconjunctival injection of 0.5 ml dexamethasone diphosphate (10 mg) or 0.5 ml placebo was given 5-6 hours before surgery. Differences in laser flare photometry (KOWA) measurements taken 1, 3 and 6 weeks after randomisation between dexamethasone and placebo were analysed using mixed model ANOVA, while correcting for the preoperative flare measurement. Results: Six patients did not complete the study, one because of recurrent detachment within 1 week, and five because they missed their postoperative laser flare visits. The use of dexamethasone resulted in a statistically significant decrease in laser flare measurements at the 1-week postoperative visit. Conclusion: The use of a preoperative subconjunctival injection of dexamethasone decreased 1-week postoperative blood-retina barrier breakdown in patients undergoing conventional scleral buckling retinal detachment surgery. This steroid priming could be useful as a part of a peri-operative regime that would aim at decreasing the incidence of PVR

Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b : I. Cloud and chemistry mapping

Context . Of the presently known ≈3900 exoplanets, sparse spectral observations are available for ≈100. Ultra-hot Jupiters have recently attracted interest from observers and theoreticians alike, as they provide observationally accessible test cases. Confronting detailed theoretical models with observations is of preeminent importance in preparation for upcoming space-based telescopes. Aims . We aim to study cloud formation on the ultra-hot Jupiter HAT-P-7b, the resulting composition of the local gas phase, and how their global changes affect wavelength-dependent observations utilised to derive fundamental properties of the planet. Methods . We apply a hierarchical modelling approach as a virtual laboratory to study cloud formation and gas-phase chemistry. We utilise 97 vertical 1D profiles of a 3D GCM for HAT-P-7b to evaluate our kinetic cloud formation model consistently with the local equilibrium gas-phase composition. We use maps and slice views to provide a global understanding of the cloud and gas chemistry. Results . The day/night temperature difference on HAT-P-7b (ΔT ≈ 2500 K) causes clouds to form on the nightside (dominated by H2/He) while the dayside (dominated by H/He) retains cloud-free equatorial regions. The cloud particles vary in composition and size throughout the vertical extension of the cloud, but also globally. TiO2[s]/Al2O3[s]/CaTiO3[s]-particles of cm-sized radii occur in the higher dayside-latitudes, resulting in a dayside dominated by gas-phase opacity. The opacity on the nightside, however, is dominated by 0.01…0.1μm particles made of a material mix dominated by silicates. The gas pressure at which the atmosphere becomes optically thick is ~10−4 bar in cloudy regions, and ~0.1 bar in cloud-free regions. Conclusions . HAT-P-7b features strong morning/evening terminator asymmetries, providing an example of patchy clouds and azimuthally-inhomogeneous chemistry. Variable terminator properties may be accessible by ingress/egress transmission photometry (e.g., CHEOPS and PLATO) or spectroscopy. The large temperature differences of ≈2500 K result in an increasing geometrical extension from the night- to the dayside. The H2O abundance at the terminator changes by <1 dex with altitude and ≲0.3 dex (a factor of 2) across the terminator for a given pressure, indicating that H2O abundances derived from transmission spectra can be representative of the well-mixed metallicity at P ≳ 10 bar. We suggest the atmospheric C/O as an important tool to trace the presence and location of clouds in exoplanet atmospheres. The atmospheric C/O can be sub- and supersolar due to cloud formation. Phase curve variability of HAT-P-7b is unlikely to be caused by dayside clouds.Publisher PDFPeer reviewe

Rhegmatogenous retinal detachment in uveitis

Abstract Background Retinal detachment is more common among uveitis patients than in the general population. Here, we aimed to assess the prevalence of rhegmatogenous retinal detachment (RRD) in a uveitis population. Methods We retrospectively studied 851 uveitis patients, recording characteristics such as uveitis duration, anatomical location, and cause; RRD occurrence; proliferative vitreoretinopathy (PVR) at presentation; surgical approach; reattachment rate; and initial and final visual acuity (VA). Results RRD occurred in 26 patients (3.1%; 29 affected eyes) and was significantly associated with posterior uveitis (p < 0.001), infectious uveitis (p < 0.001), and male gender (p = 0.012). Among cases of infectious uveitis, cytomegalovirus and varicella zoster virus were most commonly associated with RRD development. RRD in non-infectious uveitis was not found to be associated with any specific uveitis entity. The rate of single-operation reattachment was 48%, and the rate of final reattachment was 83%. Mean final VA was 20/125, with 41% of eyes ultimately having a VA of less than 20/200. Conclusion Uveitis is a risk factor for RRD development, which carries a poor prognosis

Clinical features and outcomes of patients with tubercular uveitis treated with antitubercular therapy in the collaborative ocular tuberculosis study (COTS)-1

IMPORTANCE Eradication of systemic tuberculosis (TB) has been limited by neglected populations and the HIV pandemic. Whereas ocular TB often presents as uveitis without any prior evidence of systemic TB, the existing uncertainty in the diagnosis of TB uveitis may perpetuate missed opportunities to address systemic TB. OBJECTIVE To examine the clinical features of TB uveitis and the associations with response to antitubercular therapy (ATT). DESIGN, SETTING, AND PARTICIPANTS This retrospective multinational cohort study included patients from 25 ophthalmology referral centers diagnosed with TB uveitis and treated with ATT from January 1, 2004, through December 31, 2014, with a minimum follow-up of 1 year. MAIN OUTCOMES AND MEASURES Treatment failure, defined as a persistence or recurrence of inflammation within 6 months of completing ATT, inability to taper oral corticosteroids to less than 10mg/d or topical corticosteroid drops to less than 2 drops daily, and/or recalcitrant inflammation necessitating corticosteroid-sparing immunosuppressive therapy. RESULTS A total of 801 patients (1272 eyes) were studied (mean [SD] age, 40.5 [14.8] years; 413 [51.6%] male and 388 [48.4%] female; 577 [73.6%] Asian). Most patients had no known history (498 of 661 [75.3%]) of systemic TB. Most patients had bilateral involvement (471 of 801 [58.8%]). Common clinical signs reported include vitreous haze (523 of 1153 [45.4%]), retinal vasculitis (374 of 874 [42.8%]), and choroidal involvement (419 of 651 [64.4%]). Treatment failure developed in 102 of the 801 patients (12.7%). On univariate regression analysis, the hazard ratios (HRs) associated with intermediate uveitis (HR, 2.21; 95%CI, 1.07-4.55; P = .03), anterior uveitis (HR, 2.68; 95%CI, 1.32-2.35; P = .006), and panuveitis (HR, 3.28; 95%CI, 1.89-5.67; P &lt; .001) were significantly higher compared with posterior distribution. The presence of vitreous haze had a statistically significant association (HR, 1.95; 95%CI, 1.26-3.02; P = .003) compared with absence of vitreous haze. Bilaterality had an associated HR of 1.50 (95%CI, 0.96-2.35) compared with unilaterality (HR, 1 [reference]), although this finding was not statistically significant (P = .07). On multivariate Cox proportional hazards regression analysis, the presence of vitreous haze had an adjusted HR of 2.98 (95%CI, 1.50-5.94; P = .002), presence of snow banking had an adjusted HR of 3.71 (95%CI, 1.18-11.62; P = .02), and presence of choroidal involvement had an adjusted HR of 2.88 (95%CI, 1.22-6.78; P = .02). CONCLUSIONS AND RELEVANCE A low treatment failure rate occurred in patients with TB uveitis treated with ATT. Phenotypes and test results are studied whereby patients with panuveitis having vitreous and choroidal involvement had a higher risk of treatment failure. These findings are limited by retrospectivemethods. A prospectively derived composite clinical risk score might address this diagnostic uncertainty through holistic and standardized assessment of the combinations of clinical features and investigation results that may warrant diagnosis of TB uveitis and treatment with ATT

A definition of habit for socio-economics

The paper argues that it is a mistake to define habit as behaviour or action; as a regular conjunction of actions; as a stock; as a form of automaticity (although habit is acquired and activated automatically); as a tendency, propensity or disposition (even though habit acts tendentially); as a mechanism; and as a process (even though habit is acquired and activated via several processes). A taxonomic definition is provided wherein habit is a cognitive representation of a cue-action response

CARMENES: high-resolution spectra and precise radial velocities in the red and infrared

SPIE Astronomical Telescopes + Instrumentation (2018, Austin, Texas, United States