10 research outputs found
Linear polarization signatures of atmospheric dust with the SolPol direct-sun polarimeter
Dust particles in lofted atmospheric layers may present a preferential orientation, which could be detected from the resulting dichroic extinction of the transmitted sunlight. The first indications were provided relatively recently on atmospheric dust layers using passive polarimetry, when astronomical starlight observations of known polarization were found to exhibit an excess in linear polarization, during desert dust events that reached the observational site. We revisit the previous observational methodology by targeting dichroic extinction of transmitted sunlight through extensive atmospheric dust layers utilizing a direct-sun polarimeter, which is capable to continuously monitor the polarization of elevated aerosol layers. In this study, we present the unique observations from the Solar Polarimeter (SolPol) for different periods within 2 years, when the instrument was installed in the remote monitoring station of PANGEA – the PANhellenic GEophysical observatory of Antikythera – in Greece. SolPol records polarization, providing all four Stokes parameters, at a default wavelength band centred at 550 nm with a detection limit of 10−7.
We, overall, report on detected increasing trends of linear polarization, reaching up to 700 parts per million, when the instrument is targeting away from its zenith and direct sunlight propagates through dust concentrations over the observatory. This distinct behaviour is absent on measurements we acquire on days with lack of dust particle concentrations and in general of low aerosol content. Moreover, we investigate the dependence of the degree of linear polarization on the layers' optical depth under various dust loads and solar zenith angles and attempt to interpret these observations as an indication of dust particles being preferentially aligned in the Earth's atmosphere
Aerosol absorption profiling from the synergy of lidar and sun-photometry : The ACTRIS-2 campaigns in Germany, Greece and Cyprus
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).Aerosol absorption profiling is crucial for radiative transfer calculations and climate modelling. Here, we utilize the synergy of lidar with sun-photometer measurements to derive the absorption coefficient and single scattering albedo profiles during the ACTRIS-2 campaigns held in Germany, Greece and Cyprus. The remote sensing techniques are compared with in situ measurements in order to harmonize and validate the different methodologies and reduce the absorption profiling uncertainties.Peer reviewe
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Abstract
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries
Clinically Silent Small Vessel Disease of the Brain in Patients with Obstructive Sleep Apnea Hypopnea Syndrome
Obstructive sleep apnea hypopnea syndrome (OSAHS) is associated with increased risk of cerebrovascular disease. The aim of the present study was to investigate the association between the presence of the small vessel disease (SVD) of the brain in patients with OSAHS. The study included 24 patients with moderate to severe OSAHS and 34 healthy volunteers. All the subjects underwent magnetic resonance imaging (MRI) of the brain, in order to sought periventricular white matter (PVWM), deep white matter (DWM) and brainstem SVD. Among patients with OSAHS, 79.1% had SVD (grade 1–3, Fazekas score) in DWM and 91.7% in PVWM while 22.4% had brainstem—white matter hyperintensities (B-WMH). Patients with OSAHS had a much higher degree of SVD in the DWM and PVWM compared to the control group (p < 0.001). The multivariate analysis showed an independent significant association of OSAHS with SVD (DWM and PVWM) (p = 0.033, OR 95% CI: 8.66 (1.19–63.08) and: p = 0.002, OR 95% CI: 104.98 (5.15–2141)). The same analysis showed a moderate association of OSAHS with B-WMH (p = 0.050, OR 15.07 (0.97–234.65)). Our study demonstrated an independent significant association of OSAHS with SVD and a moderate association of OSAHS with B-WMH
Real-time UV index retrieval in Europe using Earth observation-based techniques: system description and quality assessment
This study introduces an Earth observation (EO)-based system which is
capable of operationally estimating and continuously monitoring the
ultraviolet index (UVI) in Europe. UVIOS (i.e., UV-Index Operating
System) exploits a synergy of radiative transfer models with
high-performance computing and EO data from satellites (Meteosat Second
Generation and Meteorological Operational Satellite-B) and retrieval
processes (Tropospheric Emission Monitoring Internet Service, Copernicus
Atmosphere Monitoring Service and the Global Land Service). It provides
a near-real-time nowcasting and short-term forecasting service for UV
radiation over Europe. The main atmospheric inputs for the UVI
simulations include ozone, clouds and aerosols, while the impacts of
ground elevation and surface albedo are also taken into account. The
UVIOS output is the UVI at high spatial and temporal resolution (5 km
and 15 min, respectively) for Europe (i.e., 1.5 million pixels) in real
time. The UVI is empirically related to biologically important UV dose
rates, and the reliability of this EO-based solution was verified
against ground-based measurements from 17 stations across Europe.
Stations are equipped with spectral, broadband or multi-filter
instruments and cover a range of topographic and atmospheric conditions.
A period of over 1 year of forecasted 15 min retrievals under all-sky
conditions was compared with the ground-based measurements. UVIOS
forecasts were within +/- 0.5 of the measured UVI for at least 70 % of
the data compared at all stations. For clear-sky conditions the
agreement was better than 0.5 UVI for 80 % of the data. A sensitivity
analysis of EO inputs and UVIOS outputs was performed in order to
quantify the level of uncertainty in the derived products and to
identify the covariance between the accuracy of the output and the
spatial and temporal resolution and the quality of the inputs. Overall,
UVIOS slightly overestimated the UVI due to observational uncertainties
in inputs of cloud and aerosol. This service will hopefully contribute
to EO capabilities and will assist the provision of operational early
warning systems that will help raise awareness among European Union
citizens of the health implications of high UVI doses