The surface of Mars has preserved the record of early environments in which its basaltic crust was altered by liquid water. These aqueous environments have survived in the form of hydrological ...morphologies and alteration minerals, including clays and hydrated salts. Because these minerals probe on Earth aqueous environments compatible with biotic activity, understanding their formation processes on Mars is of great exobiological relevance and also offers insight into Earth's now erased ancient water environments. Using remote sensing, we conducted a large‐scale investigation of the distribution, composition, age, and geomorphic settings of hydrous minerals on Mars, providing a sharpened global view of the early aqueous environments and their evolution with time. Aqueous alteration seems to have produced clays on a planetary scale but these are found to be restricted to the oldest observable terrains on Mars (∼4 Gyr). However, very diverse aqueous environments have also been found which suggest widespread, complex aqueous settings from the surface to kilometric depths, and spanning over 1 Gyr. By building a robust statistical sample of detections, the global trends inferred here attempt to provide a broad view of our current understanding of hydrous minerals on Mars and provide context for more localized, in‐depth analyses. Collectively, these trends suggest that at least transient conditions have existed on Mars which may have been favorable for pre‐biotic to biotic activity.
Key Points
Mars experienced aqueous alteration on a planetary scale
Hydrous mineral diversity reveals diversity of formation environments
Most of the alteration took place ~4 Gyr ago but still occurred 1 Gyr later
We present the photometric calibration of the Swift Ultraviolet/Optical Telescope (UVOT) which includes: optimum photometric and background apertures, effective area curves, colour transformations, ...conversion factors for count rates to flux and the photometric zero-points (which are accurate to better than 4 per cent) for each of the seven UVOT broad-band filters. The calibration was performed with observations of standard stars and standard star fields that represent a wide range of spectral star types. The calibration results include the position-dependent uniformity, and instrument response over the 1600–8000 Å operational range. Because the UVOT is a photon-counting instrument, we also discuss the effect of coincidence loss on the calibration results. We provide practical guidelines for using the calibration in UVOT data analysis. The results presented here supersede previous calibration results.
The Ultraviolet/Optical Telescope (UVOT) is one of three instruments onboard the Swift observatory. The photometric calibration has been published, and this paper follows up with details on other ...aspects of the calibration including a measurement of the point spread function with an assessment of the orbital variation and the effect on photometry. A correction for large-scale variations in sensitivity over the field of view is described, as well as a model of the coincidence loss which is used to assess the coincidence correction in extended regions. We have provided a correction for the detector distortion and measured the resulting internal astrometric accuracy of the UVOT, also giving the absolute accuracy with respect to the International Celestial Reference System. We have compiled statistics on the background count rates, and discuss the sources of the background, including instrumental scattered light. In each case, we describe any impact on UVOT measurements, whether any correction is applied in the standard pipeline data processing or whether further steps are recommended.
We present the calibration of the Swift Ultraviolet and Optical Telescope (UVOT ) grisms, of which there are two, providing low-resolution field spectroscopy in the ultraviolet and optical bands, ...respectively. The UV grism covers the range λ1700–5000 Å with a spectral resolution (λ/Δλ) of 75 at λ2600 Å for source magnitudes of u=10–16 mag, while the visible grism covers the range λ2850–6600 Å with a spectral resolution of 100 at λ4000 Å for source magnitudes of b=12–17 mag. This calibration extends over all detector positions, for all modes used during operations. The wavelength accuracy (1σ) is 9 Å in the UV grism clocked mode, 17 Å in the UV grism nominal mode and 22 Å in the visible grism. The range below λ2740 Å in the UV grism and λ5200 Å in the visible grism never suffers from overlapping by higher spectral orders. The flux calibration of the grisms includes a correction we developed for coincidence loss in the detector. The error in the coincidence loss correction is less than 20 per cent. The position of the spectrum on the detector only affects the effective area (sensitivity) by a few per cent in the nominal modes, but varies substantially in the clocked modes. The error in the effective area is from 9 per cent in the UV grism clocked mode to 15 per cent in the visible grism clocked mode.
PCR-based immunoglobulin (Ig)/T-cell receptor (TCR) clonality testing in suspected lymphoproliferations has largely been standardized and has consequently become technically feasible in a routine ...diagnostic setting. Standardization of the pre-analytical and post-analytical phases is now essential to prevent misinterpretation and incorrect conclusions derived from clonality data. As clonality testing is not a quantitative assay, but rather concerns recognition of molecular patterns, guidelines for reliable interpretation and reporting are mandatory. Here, the EuroClonality (BIOMED-2) consortium summarizes important pre- and post-analytical aspects of clonality testing, provides guidelines for interpretation of clonality testing results, and presents a uniform way to report the results of the Ig/TCR assays. Starting from an immunobiological concept, two levels to report Ig/TCR profiles are discerned: the technical description of individual (multiplex) PCR reactions and the overall molecular conclusion for B and T cells. Collectively, the EuroClonality (BIOMED-2) guidelines and consensus reporting system should help to improve the general performance level of clonality assessment and interpretation, which will directly impact on routine clinical management (standardized best-practice) in patients with suspected lymphoproliferations.
Background
Despite the availability of effective drug therapies that reduce low‐density lipoprotein (LDL)‐cholesterol (LDL‐C), cardiovascular disease (CVD) remains an important cause of mortality and ...morbidity. Therefore, additional LDL‐C reduction may be warranted, especially for people who are unresponsive to, or unable to take, existing LDL‐C‐reducing therapies. By inhibiting the proprotein convertase subtilisin/kexin type 9 (PCSK9) enzyme, monoclonal antibodies (PCSK9 inhibitors) reduce LDL‐C and CVD risk.
Objectives
Primary
To quantify the effects of PCSK9 inhibitors on CVD, all‐cause mortality, myocardial infarction, and stroke, compared to placebo or active treatment(s) for primary and secondary prevention.
Secondary
To quantify the safety of PCSK9 inhibitors, with specific focus on the incidence of influenza, hypertension, type 2 diabetes, and cancer, compared to placebo or active treatment(s) for primary and secondary prevention.
Search methods
We identified studies by systematically searching CENTRAL, MEDLINE, Embase, and Web of Science in December 2019. We also searched ClinicalTrials.gov and the International Clinical Trials Registry Platform in August 2020 and screened the reference lists of included studies. This is an update of the review first published in 2017.
Selection criteria
All parallel‐group and factorial randomised controlled trials (RCTs) with a follow‐up of at least 24 weeks and adult participants with or without a history of CVD were eligible if they compared PCSK9 inhibitors alirocumab or evolocumab to placebo or active treatments such as statins, ezetimibe, or a combination of these.
Data collection and analysis
Two review authors independently reviewed and extracted data. Where data were available, we calculated pooled effect estimates. We used GRADE to assess certainty of evidence and in 'Summary of findings' tables.
Main results
We included 24 studies with data on 60,997 participants. Eighteen trials randomised participants to alirocumab and six to evolocumab. All participants received background lipid‐lowering treatment or lifestyle counselling. Six alirocumab studies used an active treatment comparison group (the remaining used placebo), compared to three evolocumab active comparison trials. Follow‐up ranged from 6 to 36 months for the comparisons with placebo and from 6 to 12 months for comparisons with active treatment. Most of the available studies preferentially enrolled people with either established CVD or at a high risk already, and evidence in low‐ to medium‐risk settings is minimal.
Alirocumab compared with placebo decreased the risk of CVD events, with an absolute risk difference (RD) of –2% (odds ratio (OR) 0.87, 95% confidence interval (CI) 0.80 to 0.94; 10 studies, 23,868 participants; high‐certainty evidence), decreased the risk of mortality (RD –1%; OR 0.83, 95% CI 0.72 to 0.96; 12 studies, 24,797 participants; high‐certainty evidence), and MI (RD –2%; OR 0.86, 95% CI 0.79 to 0.94; 9 studies, 23,352 participants; high‐certainty evidence) and for any stroke (RD 0%; OR 0.73, 95% CI 0.58 to 0.91; 8 studies, 22,835 participants; high‐certainty evidence).
Alirocumab compared with ezetimibe and statins: for CVD, the RD was 1% (OR 1.37, 95% CI 0.65 to 2.87; 3 studies, 1379 participants; low‐certainty evidence); for mortality, RD was –1% (OR 0.51, 95% CI 0.18 to 1.40; 5 studies, 1333 participants; low‐certainty evidence); for MI, RD was 1% (OR 1.45, 95% CI 0.64 to 3.28, 5 studies, 1734 participants; low‐certainty evidence); and for any stroke, RD was less than 1% (OR 0.85, 95% CI 0.13 to 5.61; 5 studies, 1734 participants; low‐certainty evidence).
Evolocumab compared with placebo: for CVD, the RD was –2% (OR 0.84, 95% CI 0.78 to 0.91; 3 studies, 29,432 participants; high‐certainty evidence); for mortality, RD was less than 1% (OR 1.04, 95% CI 0.91 to 1.19; 3 studies, 29,432 participants; high‐certainty evidence); for MI, RD was –1% (OR 0.72, 95% CI 0.64 to 0.82; 3 studies, 29,432 participants; high‐certainty evidence); and for any stroke RD was less than –1% (OR 0.79, 95% CI 0.65 to 0.94; 2 studies, 28,531 participants; high‐certainty evidence).
Evolocumab compared with ezetimibe and statins: for any CVD event RD was less than –1% (OR 0.66, 95% CI 0.14 to 3.04; 1 study, 218 participants; very low‐certainty evidence); for all‐cause mortality, the RD was less than 1% (OR 0.43, 95% CI 0.14 to 1.30; 3 studies, 5223 participants; very low‐certainty evidence); and for MI, RD was less than 1% (OR 0.66, 95% CI 0.23 to 1.85; 3 studies, 5003 participants; very low‐certainty evidence). There were insufficient data on any stroke.
Authors' conclusions
The evidence for the clinical endpoint effects of evolocumab and alirocumab versus placebo were graded as high. There is a strong evidence base for the benefits of PCSK9 monoclonal antibodies to people who might not be eligible for other lipid‐lowering drugs, or to people who cannot meet their lipid goals on more traditional therapies, which was the main patient population of the available trials.
The evidence base of PCSK9 inhibitors compared with ezetimibe and statins is much weaker (low very‐ to low‐certainty evidence) and it is unclear whether evolocumab or alirocumab might be effectively used as replacement therapies.
Finally, there is very limited evidence on any potential safety issues of both evolocumab and alirocumab. While the current evidence synthesis does not reveal any adverse signals, neither does it provide evidence against such signals. This suggests careful consideration of alternative lipid lowering treatments before prescribing PCSK9 inhibitors.
Summary
The COVID‐19 pandemic has led to the production of novel devices intended to protect airway managers during the aerosol‐generating procedure of tracheal intubation. Using an in‐situ ...simulation model, we evaluated laryngoscopist exposure of airborne particles sized 0.3 ‐ 5.0 microns using five aerosol containment devices (aerosol box; sealed box with and without suction; vertical drape; and horizontal drape) compared with no aerosol containment device. Nebulised saline was used as the aerosol‐generating model for 300 s, at which point, the devices were removed to assess particle spread. Primary outcome was the quantity and size of airborne particles measured at the level of the laryngoscopist’s head at 30, 60, 120 and 300 s, as well as 360 s (60 s after device removal). Airborne particles sizes of 0.3, 0.5, 1.0, 2.5 and 5.0 microns were quantified using an electronic airborne particle counter. Compared with no device use, the sealed intubation box with suction resulted in a decrease in 0.3, 0.5, 1.0 and 2.5 micron, but not 5.0 micron, particle exposure over all time‐periods (p = 0.003 for all time periods). Compared with no device use, the aerosol box showed an increase in 1.0, 2.5 and 5.0 micron airborne particle exposure at 300 s (p = 0.002, 0.008, 0.002, respectively). Compared with no device use, neither horizontal nor vertical drapes showed any difference in any particle size exposure at any time. Finally, when the patient coughed, use of the aerosol box resulted in a marked increase in airborne particle exposure compared with other devices or no device use. In conclusion, novel devices intended to protect the laryngoscopist require objective testing to ensure they are fit for purpose and do not result in increased airborne particle exposure.
The composition of the ancient martian crust is a key ingredient in deciphering the environment and evolution of early Mars. We present an analysis of the composition of large craters in the martian ...northern plains based on data from spaceborne imaging spectrometers. Nine of the craters have excavated assemblages of phyllosilicates from ancient, Noachian crust buried beneath the plains' cover. The phyllosilicates are indistinguishable from those exposed in widespread locations in the southern highlands, demonstrating that liquid water once altered both hemispheres of Mars.
Identifying efficient electrocatalysts with low overpotential and high selectivity for producing ammonia from nitrogen gas is essential for any future electrocatalytic nitrogen reduction reaction ...(NRR)-based ammonia synthesis. Via density functional theory calculations and the computational hydrogen electrode model, we systematically examine the prospect of using a single-transition-metal (TM)-atom-doped graphene-like GaN (g-GaN) monolayer as an electrocatalyst for artificial nitrogen reduction. Among 15 TMs investigated, the Mo-doped g-GaN (Mo@g-GaN) monolayer is the only electrocatalyst predicted to be feasible for the NRR. The Mo@g-GaN monolayer satisfies all screening criteria considered for activating the inert NN triple bond effectively, including stabilization of the adsorbed (*) NRR intermediate *NNH and destabilization of the *NH2 species. This monolayer also possesses sufficient overall stability. A complete analysis of the likely mechanisms involved in the NRR on this catalyst suggests that the Mo@g-GaN monolayer could exhibit promising NRR catalytic activity. It achieves this via one specific (distal) pathway, which has a very low onset potential of −0.33 V vs the reversible hydrogen electrode (RHE), corresponding to a low overpotential of 0.42 V vs the RHE, defined using the measured equilibrium potential for NRR of 0.09 V vs the RHE. The potential-determining step, conversion of *NH2 to *NH3, also exhibits a surmountable barrier of 0.42 eV, suggesting kinetics will be facile. Finally, the Mo@g-GaN monolayer is predicted to exhibit substantial selectivity (∼31%) toward ammonia synthesis over the competing hydrogen evolution reaction. These findings may open a potential route for artificial ammonia synthesis using a single-atom catalyst under ambient conditions.
Solar System Physics for Exoplanet Research Horner, J.; Kane, S. R.; Marshall, J. P. ...
Publications of the Astronomical Society of the Pacific,
10/2020, Letnik:
132, Številka:
1016
Journal Article
Recenzirano
Odprti dostop
Over the past three decades, we have witnessed one of the great revolutions in our understanding of the cosmos-the dawn of the Exoplanet Era. Where once we knew of just one planetary system (the ...solar system), we now know of thousands, with new systems being announced on a weekly basis. Of the thousands of planetary systems we have found to date, however, there is only one that we can study up-close and personal-the solar system. In this review, we describe our current understanding of the solar system for the exoplanetary science community-with a focus on the processes thought to have shaped the system we see today. In section one, we introduce the solar system as a single well studied example of the many planetary systems now observed. In section two, we describe the solar system's small body populations as we know them today-from the two hundred and five known planetary satellites to the various populations of small bodies that serve as a reminder of the system's formation and early evolution. In section three, we consider our current knowledge of the solar system's planets, as physical bodies. In section four we discuss the research that has been carried out into the solar system's formation and evolution, with a focus on the information gleaned as a result of detailed studies of the system's small body populations. In section five, we discuss our current knowledge of planetary systems beyond our own-both in terms of the planets they host, and in terms of the debris that we observe orbiting their host stars. As we learn ever more about the diversity and ubiquity of other planetary systems, our solar system will remain the key touchstone that facilitates our understanding and modeling of those newly found systems, and we finish section five with a discussion of the future surveys that will further expand that knowledge.
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