Efficient radiative transfer calculation and sensor performance requirements for the aerosol retrieval by airborne imaging spectroscopy

Detailed aerosol measurements in time and space are crucial to address open questions in climate research. Earth observation is a key instrument for that matter but it is biased by large uncertainties. Using airborne imaging spectroscopy, such as ESA's upcoming airborne Earth observing instrument APEX, allows determining the widely used aerosol optical depth (AOD) with unprecedented accuracy thanks to its high spatial and spectral resolution, optimal calibration and high signal-to-noise ratios (SNR). This study was carried out within the overall aim of developing such a tropospheric aerosol retrieval algorithm. Basic and efficient radiative transfer equations were applied to determine the sensor performance requirement and a sensitivity analysis in context of the aerosol retrieval. The AOD retrieval sensitivity requirement was chosen according to the demands of atmospheric correction processes. Therefore, a novel parameterization of the diffuse path-radiance was developed to simulate the atmospheric and surface effects on the signal at the sensor level. It was found for typical remote sensing conditions and a surface albedo of less than 30% that a SNR of circa 300 is sufficient to meet the AOD retrieval sensitivity requirement at 550nm. A surface albedo around 50% requires much more SNR, which makes the AOD retrieval very difficult. The retrieval performance is further analyzed throughout the visual spectral range for a changing solar geometry and different aerosol characteristics. As expected, the blue spectral region above dark surfaces and high aerosol loadings will provide the most accurate retrieval results. In general, the AOD retrieval feasibility could be proven for the analyzed cases for APEX under realistic simulated conditions

Sudden cardiac death in the young (5-39 years) in the canton of Vaud, Switzerland.

Sudden cardiac death (SCD) among the young is a rare and devastating event, but its exact incidence in many countries remains unknown. An autopsy is recommended in every case because some of the cardiac pathologies may have a genetic origin, which can have an impact on the living family members. The aims of this retrospective study completed in the canton of Vaud, Switzerland were to determine both the incidence of SCD and the autopsy rate for individuals from 5 to 39 years of age. The study was conducted from 2000 to 2007 on the basis of official statistics and analysis of the International Classification of Diseases codes for potential SCDs and other deaths that might have been due to cardiac disease. During the 8 year study period there was an average of 292'546 persons aged 5-39 and there were a total of 1122 deaths, certified as potential SCDs in 3.6% of cases. The calculated incidence is 1.71/100'000 person-years (2.73 for men and 0.69 for women). If all possible cases of SCD (unexplained deaths, drowning, traffic accidents, etc.) are included, the incidence increases to 13.67/100'000 person-years. However, the quality of the officially available data was insufficient to provide an accurate incidence of SCD as well as autopsy rates. The presumed autopsy rate of sudden deaths classified as diseases of the circulatory system is 47.5%. For deaths of unknown cause (11.1% of the deaths), the autopsy was conducted in 13.7% of the cases according to codified data. The incidence of presumed SCD in the canton of Vaud, Switzerland, is comparable to the data published in the literature for other geographic regions but may be underestimated as it does not take into account other potential SCDs, as unexplained deaths. Increasing the autopsy rate of SCD in the young, better management of information obtained from autopsies as well developing of structured registry could improve the reliability of the statistical data, optimize the diagnostic procedures, and the preventive measures for the family members

Magnitude of urban heat islands largely explained by climate and population

Urban heat islands (UHIs) exacerbate the risk of heat-related mortality associated with global climate change. The intensity of UHIs varies with population size and mean annual precipitation, but a unifying explanation for this variation is lacking, and there are no geographically targeted guidelines for heat mitigation. Here we analyse summertime differences between urban and rural surface temperatures (ΔTs) worldwide and find a nonlinear increase in ΔTs with precipitation that is controlled by water or energy limitations on evapotranspiration and that modulates the scaling of ΔTs with city size. We introduce a coarse-grained model that links population, background climate, and UHI intensity, and show that urban–rural differences in evapotranspiration and convection efficiency are the main determinants of warming. The direct implication of these nonlinearities is that mitigation strategies aimed at increasing green cover and albedo are more efficient in dry regions, whereas the challenge of cooling tropical cities will require innovative solutions

Seasonal study of directional reflectance properties of snow

We present an analysis of the hemispherical-directional reflectance factor (HDRF) of snow, using 16 seasonal datasets of the spectral range from 400 to 2,500 nm. The data was measured under clear sky conditions in Davos Dorf (Grisons, Switzerland, 1,560 m a. s. l.). Fieldwork was carried out on seven days between February 5 and March 30 2004 with the Swiss Field Goniometer System (FIGOS). In addition to the HDRF measurements, snow stratigraphy, temperature and density were measured, and chemical and photomicroscopical analyses of snow samples were performed. Concentration of organic and elemental carbon was determined by chemical analysis. The grain size analyses through image processing of micrographs revealed relatively small differences of 0.21 to 0.33 mm mean radius in the top layers of snow cover. Seven datasets present HDRF of wet snow surfaces with similar anisotropy at smaller sun zenith angles (qI = 3.3 to 64.5°) compared to the nine surfaces measured at larger sun zenith angles (qI = 6.5 to 75.3°). Spectral albedo is relatively constant throughout datasets of different sun zenith angles of the same day, but has large variability among measurements of different days. With increasing wavelength, it decreases significantly faster for wet surfaces than for dry surfaces. The forward scattering peak was found to strengthen with increasing sun zenith angle and with increasing wavelength for both wet and dry surfaces at wavelengths above 700 nm. Finally, a spectral wet snow determination method is performed and the cross-sensitivity to HDRF variation could be derived. The best differentiability was found for 1,380 nm. This basis work increases the understanding of snow signatures for potential imaging spectroscopy applications in alpine regions

APEX status pt.1: instrument development and performance

ESA APEX (Airborne Prism EXperiment) is a project for the realisation of an airborne dispersive pushbroom imaging spectrometer, a dedicated data Processing and Archiving Facility (PAF, hosted at VITO) and a Calibration Home Base (CHB, hosted at DLR) for instrument calibration operation. It has been developed by a joint Swiss-Belgian consortium. The APEX instrument is facing its finalisation phase undergoing intense experimental activities in view of its validation and performance assessment. Environmental tests were executed to simulate flight environment conditions. The first APEX airborne campaign has been held in June 2009 covering a variety of water targets over Switzerland and Belgium. Extensive pre- and postflight characterisation and calibration campaigns were accomplished. Instrument data evaluation, performance analysis and optimisation of the data processing schemes adopted have followed. This paper outlines the activities performed and presents the first products achieved

Inflammatory arthritis in HIV positive patients: A practical guide

Background: Musculoskeletal manifestations of the human immunodeficiency virus (HIV) have been described since the outset of the global HIV epidemic. Articular syndromes that have been described in association with HIV include HIV-associated arthropathy, seronegative spondyloarthropathies (SPA) (reactive arthritis, psoriatic arthritis (PsA) and undifferentiated SPA), rheumatoid arthritis (RA) and painful articular syndrome. Methods: We carried out a computer-assisted search of PubMed for the medical literature from January 1981 to January 2015 using the keywords HIV, acquired immune-deficiency syndrome, rheumatic manifestations, arthritis, spondyloarthropathy, anti-TNF and disease modifying antirheumatic drugs. Only English language literature was included and only studies involving adult human subjects were assessed. Results: There are challenges in the management of inflammatory arthritis in patients who are HIV-positive, including difficulties in the assessment of disease activity and limited information on the safety of immunosuppressive drugs in these individuals. Conclusions: This review focuses on the clinical characteristics of the inflammatory articular syndromes that have been described in association with HIV infection and discusses the therapeutic options for these patients

Open and hidden agendas of "asymptomatic" patients who request check-up exams

BACKGROUND: Current guidelines for a check-up recommend routine screening not triggered by specific symptoms for some known risk factors and diseases in the general population. Patients' perceptions and expectations regarding a check-up exam may differ from these principles. However, quantitative and qualitative data about the discrepancy between patient- and provider expectations for this type of clinic consultation is lacking. METHODS: For a year, we prospectively enrolled 66 patients who explicitly requested a "check-up" at our medical outpatient division. All patients actively denied upon prompting having any symptoms or specific health concerns at the time they made their appointment. All consultations were videotaped and analysed for information about spontaneously mentioned symptoms and reasons for the clinic consultation ("open agendas") and for cues to hidden patient agendas using the Roter interaction analysis system (RIAS). RESULTS: All patients initially declared to be asymptomatic but this was ultimately the case in only 7 out of 66 patients. The remaining 59 patients spontaneously mentioned a mean of 4.2 ± 3.3 symptoms during their first consultation. In 23 patients a total of 31 hidden agendas were revealed. The primary categories for hidden agendas were health concerns, psychosocial concerns and the patient's concept of disease. CONCLUSIONS: The majority of patients requesting a general check-up tend to be motivated by specific symptoms and health concerns and are not "asymptomatic" patients who primarily come for preventive issues. Furthermore, physicians must be alert for possible hidden agendas, as one in three patients have one or more hidden reasons for requesting a check-up