The characteristics of indoor light (intensity, spectral, spatial distribution) originating from outdoors have been studied using experimental and modeling tools. They are influenced by many ...parameters such as building location, meteorological conditions, and the type of window. They have a direct impact on indoor air quality through a change in chemical processes by varying the photolysis rates of indoor pollutants. Transmittances of different windows have been measured and exhibit different wavelength cutoffs, thus influencing the potential of different species to be photolysed. The spectral distribution of light entering indoors through the windows was measured under different conditions and was found to be weakly dependent on the time of day for indirect cloudy, direct sunshine, partly cloudy conditions contrary to the light intensity, in agreement with calculations of the transmittance as a function of the zenithal angle and the calculated outdoor spectral distribution. The same conclusion can be drawn concerning the position within the room. The impact of these light characteristics on the indoor chemistry has been studied using the INCA‐Indoor model by considering the variation in the photolysis rates of key indoor species. Depending on the conditions, photolysis processes can lead to a significant production of radicals and secondary species.
The heterogeneous reaction of Cl radicals with submicron palmitic acid (PA) particles was studied in an aerosol flow tube in the presence or in the absence of O2. Fine particles were generated by ...homogeneous condensation of PA vapours and introduced into the reactor, where chlorine atoms were produced by photolysis of Cl2 using UV lamps surrounding the reactor. The effective reactive uptake coefficient (γ) has been determined from the rate loss of PA measured by gas chromatography–mass spectrometer (GC/MS) analysis of reacted particles as a function of the chlorine exposure. In the absence of O2, γ = 14 ± 5 indicates efficient secondary chemistry involving Cl2. GC/MS analysis has shown the formation of monochlorinated and polychlorinated compounds in the oxidized particles. Although the PA particles are solid, the complete mass can be consumed. In the presence of oxygen, the reaction is still dominated by secondary chemistry but the propagation chain length is smaller than in the absence of O2, which leads to an uptake coefficient γ = 3 ± 1. In the particulate phase, oxocarboxylic acids and dicarboxylic acids were identified by GC/MS. The formation of alcohols and monocarboxylic acids is also suspected. A reaction pathway for the main products and more functionalized species is proposed. All these results show that solid organic particles could be efficiently oxidized by gas-phase radicals not only on their surface but also in bulk by mechanisms which are still unclear. They help to understand the aging of primary tropospheric aerosol containing fatty acids.
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In this paper, we describe in detail the BMV (
Biréfringence Magnétique du Vide
) experiment, a novel apparatus to study the propagation of light in a transverse magnetic field. It is based on a ...very high finesse Fabry-Perot cavity and on pulsed magnets specially designed for this purpose. We justify our technical choices and we present the current status and perspectives.
Combustion and other high-temperature processes frequently result
in the emission of aerosols in the form of polydisperse fractal-like
aggregates made of condensed-phase nanoparticles (soot for ...instance). If
certain conditions are met, the emitted aerosol particles are known to
evolve into important cloud condensation nuclei (CCN) in the atmosphere. In
this work, the hygroscopic parameter κ of complex morphology
aggregates is calculated from the supersaturation-dependent activated
fraction Fa=Fa(SS) in the frame of κ-Köhler theory. The particle size distribution is approximated with the
morphology-corrected volume equivalent diameter calculated from the
electrical mobility diameter by taking into account the diameter of the
primary particle and the fractal dimension of the aggregate experimentally
obtained from transmission electron microscopy measurements. Activation
experiments are performed in water supersaturation conditions using a
commercial CCN-100 condensation nuclei counter. The model is tested in
close-to-ideal conditions of size-selected, isolated spherical
particles (ammonium sulfate nanoparticles dispersed in nitrogen), then with
complex polydisperse fractal-like aggregates (soot particles activated by
exposure to ozone with κ as low as 5×10-5) that
represent realistic anthropogenic emissions in the atmosphere.
Field campaigns have been carried out with the FAGE (fluorescence assay by gas expansion) technique in remote biogenic environments in the last decade to quantify the in situ concentrations of OH, ...the main oxidant in the atmosphere. These data have revealed concentrations of OH radicals up to a factor of 10 higher than predicted by models, whereby the disagreement increases with decreasing NO concentration. This was interpreted as a major lack in our understanding of the chemistry of biogenic VOCs (volatile organic compounds), particularly isoprene, which are dominant in remote pristine conditions. But interferences in these measurements of unknown origin have also been discovered for some FAGE instruments: using a pre-injector, all ambient OH is removed by fast reaction before entering the FAGE cell, and any remaining OH signal can be attributed to an interference. This technique is now systematically used for FAGE measurements, allowing the reliable quantification of ambient OH concentrations along with the signal due to interference OH. However, the disagreement between modelled and measured high OH concentrations of earlier field campaigns as well as the origin of the now-quantifiable background OH is still not understood. We present in this paper the compelling idea that this interference, and thus the disagreement between model and measurement in earlier field campaigns, might be at least partially due to the unexpected decomposition of a new class of molecule, ROOOH, within the FAGE instruments. This idea is based on experiments, obtained with the FAGE set-up of the University of Lille, and supported by a modelling study. Even though the occurrence of this interference will be highly dependent on the design and measurement conditions of different FAGE instruments, including ROOOH in atmospheric chemistry models might reflect a missing piece of the puzzle in our understanding of OH in clean atmospheres.
Total hydroxyl radical (OH) reactivity measurements were conducted during the LANDEX intensive
field campaign in a coniferous temperate forest located in the Landes area,
southwestern France, during ...July 2017. In order to investigate inter-canopy and intra-canopy variability, measurements were performed inside (6 m) and above the canopy level (12 m), as well as at two different locations within the canopy, using a comparative reactivity method (CRM) and a laser photolysis–laser-induced fluorescence (LP-LIF) instrument. The two techniques were intercompared at the end of the campaign by performing measurements at the same location. Volatile organic compounds were also monitored at both levels with a proton transfer time-of-flight mass spectrometer and online gas chromatography instruments to evaluate their contribution to total OH reactivity, with monoterpenes being the main reactive species emitted in this forest dominated by Pinus pinaster Aiton. Total OH reactivity varied diurnally, following the trend of biogenic volatile organic compounds (BVOCs), the emissions and concentrations of which were dependent on meteorological parameters. Average OH reactivity was around 19.2 and 16.5 s−1 inside and above the canopy, respectively. The highest levels of total OH reactivity were observed during nights with a low turbulence (u*≤0.2 m s−1), leading to lower mixing of emitted species within the canopy and thus an important vertical stratification characterized by a strong concentration gradient. Comparing the measured and the calculated OH reactivity highlighted an average missing OH reactivity of 22 % and 33 % inside and above the canopy, respectively. A day–night variability was observed on missing OH reactivity at both heights. Investigations showed that during daytime, missing OH sinks could be due to primary emissions and secondary products linked to a temperature-enhanced photochemistry. Regarding nighttime missing OH reactivity, higher levels were seen for the stable and warm night of 4–5 July, showing that these conditions could have been favorable for the accumulation of long-lived species (primary and secondary species) during the transport of the air mass from nearby forests.
Introduction. –
La lithiase biliaire est fréquente chez l’enfant drépanocytaire. Ses complications sont difficiles à différencier des crises douloureuses abdominales vaso-occlusives et elles peuvent ...parfois menacer le pronostic vital du patient.
Matériel et méthode. –
Nous avons étudié les résultats de l’échographie abdominale de 185 enfants drépanocytaires âgés de zéro à 18 ans et leur suivi à l’hôpital d’enfants Armand-Trousseau (Paris) de 1982 à 1998.
Résultats. –
Une lithiase biliaire était présente chez 26 patients. La lithiase a été découverte chez 12 patients devant une manifestation clinique. Vingt-huit pour cent des patients asymptomatiques porteurs d’une lithiase ont développé secondairement des manifestations cliniques dans un délai maximum de deux ans et demi. Une cholécystectomie par cœlioscopie a été effectuée dans neuf cas et par laparotomie dans 17 cas. La durée d’hospitalisation postopératoire était en moyenne plus courte dans le groupe de patients opérés par cœlioscopie que dans le groupe de patients opérés par laparotomie. L’examen anatomopathologique montrait des lésions de cholécystite subaiguë ou chronique dans 85 % des cas.
Conclusion. –
Chez l’enfant drépanocytaire, nous conseillons de rechercher attentivement une lithiase biliaire devant toute manifestation abdominale. Nous préconisons d’effectuer une échographie abdominale annuellement dès l’âge de sept ans. Nous recommandons de faire une cholécystectomie dès la découverte d’une lithiase biliaire.
Background. –
Gallstones are frequently encountered in sickle cell disease. Their complications are difficult to distinguish from vaso-occlusive abdominal pain and they can sometimes threaten the patient’s life. The aim of this study was to describe our local experience with cholelithiasis in children with sickle cell disease.
Patients and methods. –
We analyzed the follow-up records and abdominal sonography results of 185 children with sickle cell anemia, aged zero to 18 years, followed up in Trousseau Children’s Hospital (Paris) from 1982 to 1998.
Results. –
Cholelithiasis was detected in 26 patients. The youngest patient was five years old. Cholelithiasis was discovered because of clinical manifestations in 12 patients. Asymptomatic cholelithiasis patients developed clinical manifestations in 28% cases in a maximum delay of two and a half years after its diagnosis. Laparoscopic cholecystectomy was performed in nine cases and open cholecystectomy in 17 cases. The mean postoperative length of stay was significantly shorter in the group of patients with laparoscopy in comparison with the group with open cholecystectomy. Histologic analysis of the gallbladders noted 85 % of acute or chronic cholecystis.
Conclusion. –
We suggest that cholelithiasis should be carefully sought in the presence of abdominal manifestations in sickle cell patients. We recommend that annual abdominal sonography be performed in sickle cell patients as early as seven years of age and elective cholecystectomy be performed on patients with cholelithiasis.
Due to life in extreme environments, cyanobacteria and algae from cave biofilms that form at the entrances or deep inside the cave around artificial lights are of increasing interest to many ...scientists. It is well-known that many phototrophic microorganisms are first to colonize exposed substrata and produce the organic matter on which other biofilm constituents relly. Many studies dealing with phototrophic microorganisms from biofilms focus on the diversity and community composition of cyanobacteria and algae, while quantitative assessments are rarely implemented. Biofilm sampling was conducted in Degurić and Vernjikica Cave located in Western and Eastern Serbia, respectively. Ecological parameters (temperature, relative humidity, light intensity) and distance from the entrance were measured. Additionally, chlorophyll content, as well as biofilm parameters (water content, organic and inorganic matter) were determined. The abundance of phototrophic microorganisms was assessed on microscope slides which contained 1 mg of biofilm that was dehydrated for a short period of time and homogenized prior to slide preparation, and then rehydratated. The biomass of recorded cyanobacterial and algal taxa was calculated by applying geometric approximations and standard mathematical formulas. In Degurić Cave, at the sampling site where the highest biomass was documented, the higher diversity, water content and chlorophyll values were also recorded, while in Vernjikica Cave a high content of organic matter was documented. According to the multivariate analyses performed, the biomass of simple trichal Cyanobacteria, Bacillariophyta, and Xanthophyta was positively correlated with the content of organic matter in biofilm and light intensity, while coccoid and heterocytous Cyanobacteria and Chlorophyta showed a positive correlation with water content in the biofilm, relative humidity and distance from the entrance. The total biomass was positively correlated with the chlorophyll content, organic matter and light intensity, and negatively with the distance from the entrance.
We report on the testing and application of a compact transportable pulsed magnet system providing an average transverse field of up to 11T over a length of 50 cm. Our magnet consists of two ...interlaced long coils forming a flat X so as to leave openings at both ends while producing a maximum field of 14 T near the central intersection. It can be produced on conventional coil winding machines and exists in several versions adapted to different applications.
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