Validation of the surface downwelling solar irradiance estimates of the HelioClim-3 database in Egypt

International audienceHelioClim-3 (HC3) is a database providing time series of the surface downwelling solar irradiance that are computed from images of the Meteosat satellites. This paper presents the validation results of the hourly global horizontal irradiance (GHI) and direct normal irradiance (DNI), i.e., beam irradiance at normal incidence, of versions four and five of HC3 at seven Egyptian sites. The validation is performed for all-sky conditions, as well as cloud-free conditions. Both versions of HC3 provide similar OPEN ACCESS Remote Sens. 2015, 7 9270 performances whatever the conditions. Another comparison is made with the estimates provided by the McClear database that is restricted to cloud-free conditions. All databases capture well the temporal variability of the GHI in all conditions, McClear being superior for cloud-free cases. In cloud-free conditions for the GHI, the relative root mean square error (RMSE) are fairly similar, ranging from 6% to 15%; both HC3 databases exhibit a smaller bias than McClear. McClear offers an overall better performance for the cloud-free DNI estimates. For all-sky conditions, the relative RMSE for GHI ranges from 10% to 22%, except one station, while, for the DNI, the results are not so good for the two stations with DNI measurements

Synthesizing Systems with Optimal Average-Case Behavior for Ratio Objectives

We show how to automatically construct a system that satisfies a given logical specification and has an optimal average behavior with respect to a specification with ratio costs. When synthesizing a system from a logical specification, it is often the case that several different systems satisfy the specification. In this case, it is usually not easy for the user to state formally which system she prefers. Prior work proposed to rank the correct systems by adding a quantitative aspect to the specification. A desired preference relation can be expressed with (i) a quantitative language, which is a function assigning a value to every possible behavior of a system, and (ii) an environment model defining the desired optimization criteria of the system, e.g., worst-case or average-case optimal. In this paper, we show how to synthesize a system that is optimal for (i) a quantitative language given by an automaton with a ratio cost function, and (ii) an environment model given by a labeled Markov decision process. The objective of the system is to minimize the expected (ratio) costs. The solution is based on a reduction to Markov Decision Processes with ratio cost functions which do not require that the costs in the denominator are strictly positive. We find an optimal strategy for these using a fractional linear program.Comment: In Proceedings iWIGP 2011, arXiv:1102.374

Effect of Hydrocortisone on Mortality and Organ Support in Patients With Severe COVID-19: The REMAP-CAP COVID-19 Corticosteroid Domain Randomized Clinical Trial.

Importance: Evidence regarding corticosteroid use for severe coronavirus disease 2019 (COVID-19) is limited. Objective: To determine whether hydrocortisone improves outcome for patients with severe COVID-19. Design, Setting, and Participants: An ongoing adaptive platform trial testing multiple interventions within multiple therapeutic domains, for example, antiviral agents, corticosteroids, or immunoglobulin. Between March 9 and June 17, 2020, 614 adult patients with suspected or confirmed COVID-19 were enrolled and randomized within at least 1 domain following admission to an intensive care unit (ICU) for respiratory or cardiovascular organ support at 121 sites in 8 countries. Of these, 403 were randomized to open-label interventions within the corticosteroid domain. The domain was halted after results from another trial were released. Follow-up ended August 12, 2020. Interventions: The corticosteroid domain randomized participants to a fixed 7-day course of intravenous hydrocortisone (50 mg or 100 mg every 6 hours) (n = 143), a shock-dependent course (50 mg every 6 hours when shock was clinically evident) (n = 152), or no hydrocortisone (n = 108). Main Outcomes and Measures: The primary end point was organ support-free days (days alive and free of ICU-based respiratory or cardiovascular support) within 21 days, where patients who died were assigned -1 day. The primary analysis was a bayesian cumulative logistic model that included all patients enrolled with severe COVID-19, adjusting for age, sex, site, region, time, assignment to interventions within other domains, and domain and intervention eligibility. Superiority was defined as the posterior probability of an odds ratio greater than 1 (threshold for trial conclusion of superiority >99%). Results: After excluding 19 participants who withdrew consent, there were 384 patients (mean age, 60 years; 29% female) randomized to the fixed-dose (n = 137), shock-dependent (n = 146), and no (n = 101) hydrocortisone groups; 379 (99%) completed the study and were included in the analysis. The mean age for the 3 groups ranged between 59.5 and 60.4 years; most patients were male (range, 70.6%-71.5%); mean body mass index ranged between 29.7 and 30.9; and patients receiving mechanical ventilation ranged between 50.0% and 63.5%. For the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively, the median organ support-free days were 0 (IQR, -1 to 15), 0 (IQR, -1 to 13), and 0 (-1 to 11) days (composed of 30%, 26%, and 33% mortality rates and 11.5, 9.5, and 6 median organ support-free days among survivors). The median adjusted odds ratio and bayesian probability of superiority were 1.43 (95% credible interval, 0.91-2.27) and 93% for fixed-dose hydrocortisone, respectively, and were 1.22 (95% credible interval, 0.76-1.94) and 80% for shock-dependent hydrocortisone compared with no hydrocortisone. Serious adverse events were reported in 4 (3%), 5 (3%), and 1 (1%) patients in the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively. Conclusions and Relevance: Among patients with severe COVID-19, treatment with a 7-day fixed-dose course of hydrocortisone or shock-dependent dosing of hydrocortisone, compared with no hydrocortisone, resulted in 93% and 80% probabilities of superiority with regard to the odds of improvement in organ support-free days within 21 days. However, the trial was stopped early and no treatment strategy met prespecified criteria for statistical superiority, precluding definitive conclusions. Trial Registration: ClinicalTrials.gov Identifier: NCT02735707

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

A new generator for mineral dust aerosol production from soil samples in the laboratory : GAMEL

International audienceA generator has been developed for producing mineral dust from small samples of desert soils. The objective is to perform a thorough characterization of this new tool and show that it is adapted to the future laboratory studies of the relationship between aerosols and their parent soils. This work describes the principles and operating protocol of the so-called GAMEL generator. A first series of detailed measurements was performed with a Niger soil. During these tests the aerosol size-distribution was monitored in real time with an optical counter and the particles collected on filters submitted to XRF analysis. This allowed characterizing the emission in terms of time evolution of the aerosol production, repeatability of the experiment, and assessing the influence of such generation parameters as the mass of soil and the frequency and duration of the shaking. For this sandy Niger soil, the optimal generation parameters were found to be 1 g of soil agitated 9 min at the frequency of 500 cycles/min, but the effect of modifications of these recommended values have also been quantified. In terms of size-distribution as well as of elemental composition, the generated aerosol is found to compare well to the one collected in natural conditions during local events. For testing the capability of the GAMEL to produce aerosols from different soils, tests were also performed with 3 other soils from arid and semi-arid areas. Results showed that the GAMEL is able to produce aerosols whose characteristics encompass the regional variability of naturally produced mineral aerosols

Size-resolved deposition fluxes and deposition velocities over a sandy surface: In-situ experimental determination and comparison with existing parameterizations

International audienceKey words dust dry deposition, measurements, test of parameterizations An intense dust deposition event occurred in June 2006 in Niger. It was the consequence of the turn-back of a dust cloud resulting from a large wind erosion event that occurred the day before due to the passage of a mesoscale convective system. Bulk and size resolved particle concentrations were measured at 2.1 and 6.5 m over an agricultural field. At the date of the experiment (mid-June), almost all the vegetative residues from the previous year were decomposed or grazed and the sandy surface was almost bare, with only few percents of residues remaining. In the wind direction, the fetch was greater than 500 m. Bulk concentrations measurements were performed using two TEOM instruments and size resolved particle concentrations in 15 channels (from 0.3 µm to 20 µm) using two Optical Particle Counters (OPC, GRIMM instruments). These instruments have been carefully cross-calibrated before the campaign. At each level, the particle concentrations from TEOM and the particle volume from OPC were highly correlated with a slope 2.265 (+/-0.02) which is the apparent mass density of the particles. In complement wind and temperature profiles were measured at 5 and 4 different heights, respectively. The stability conditions remained near-neutral (-0.05<1/L<0.01) for the 10h duration of the deposition period. The dust deposition event was so huge that the difference in particles concentrations over a H = 4.4 m reached 100 µg m-3. All these observations allowed to compute size-resolved dust deposition fluxes and dry deposition velocities with a good confidence level. The deposition fluxes and velocities were computed using a 20-min sliding average and a 5-min time step. Size-resolved dry deposition velocities were computed only if the difference in concentrations for the considered channel between the two levels was greater than 5%. Deposition fluxes derived from bulk particle concentrations measured by TEOM instruments and those derived from size-resolved concentration measurements performed by OPC are in very good agreement. The evolution of the dust deposition fluxes during the day follows the dust concentration: higher deposition fluxes being recorded when the concentrations were maximal. This is not the case of the dry deposition velocities that are mainly controlled by the sensible heat flux in the early morning and by the wind friction velocity the rest of the day. Dry deposition velocities exhibit a maximum around noon as frequently reported in the literature. Size-resolved dry deposition velocities were compared with the rare existing data of dust deposition over bare sandy soils. A very good agreement was found with the data obtained by Lamaud et al. (1994) in Niger for submicron particles and with those obtained in wind tunnel for deposition of dust particles (1 to 40 µm) over sand and sandy loam by Zhang et al. (2014). Then, our in situ measurements were confronted to exiting parameterizations of deposition velocity (Slinn, 1982; Zhang et al., 2001; Zhang and Shao, 2014). The parameterization of Zhang and Shao (2014) is the only one that reproduces with a good confidence level the dry deposition velocities on sandy soils for particles in the size range 1-10 µm. This good agreement is mainly because, unlike the others, this model considers the bare sandy surfaces as rough surfaces allowing the interception of dust particles by the sand grains and small roughness elements present at the surface

Inter-annual variability of southerly winds in a coastal area of the Atacama Desert: implications for the export of aeolian sediments to the adjacent marine environment

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A simple model accounting for the uptake, transport, and deposition of wind-eroded mineral particles in the hyperarid coastal Atacama Desert of northern Chile

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Tackling the mortality from long-term exposure to outdoor air pollution in megacities: Lessons from the Greater Cairo case study

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SIZE RESOLVED DUST EMISSION FLUXES MEASURED BY THE GRADIENT METHOD DURING 6 DUST STORMS OF THE WIND-O-V's 2017 EXPERIMENT IN SOUTHERN TUNISIA

International audienceDust size distribution is a critical parameter to understand the interactions of mineral dust with its environment throughoutits life cycle [1]. This is why it is important to document this characteristic of mineral dust from emission to deposition,included the atmospheric transport phase. Until recently, because of the limitation of the available instrumentation, onlythe total dust mass flux could be measured at emission, and this with a limited (half hourly at best) temporal resolution.The development of optical particle counters has allowed overcoming this limitation and the dust size distributions cannow be measured at high frequency.Using a dedicated experimental setup, size resolved dust emission fluxes were documented on a bare plot in southernTunisia in the framework of the first intensive observing period of the WIND-O-V (WIND erOsion in presence ofVegetation) program (grant ANR-15-CE02-0013). The experiment was conducted from 1 March to 15 May 2017 in theDar Dhaoui Experimental Range of the Institut des Régions Arides of Médenine. Size resolved dust emission fluxes werecomputed using the gradient method [2] and using for the first time WELAS optical particle counters.During the field campaign, 6 dust storms were sampled. In the present work, the size resolved dust emission fluxesmeasured during the dust storms are presented and discussed in relation with the meteorological characteristics of thestorms and the characteristics of the soil surface