Simulation numérique de la condensation / évaporation et de la coagulation des nanoparticules

National audienceAware of the risks related to nanoparticles (particles which present at least one dimension less than 100 nanometers), INERIS decided in 2009 to create a research program in order to develop a model that would be able to simulate the dynamic of nanoparticles in both confined and free atmospheres. The distinction with usual models is that we need to follow the evolution of the number of particles together with their the mass : in order to simulate the evolution of nanoparticles, the number is much more relevant. A comparative review of algorithms currently used in air quality models and new algorithms adapted to nanoparticles is presented. This first study addresses condensational growth, evaporation and coagulation. The model is to be integrated in chemistry-transport models (CHIMERE) and in CFD models (code_Saturne EdF).Conscient des risques liés aux nanoparticules (particules dont au moins une des dimensions est inférieure à 100 nanomètres), l'INERIS(1) a engagé en 2009 un programme de recherche en collaboration avec le CEREA(2) afin de développer un modèle capable de simuler les transformations des nanoparticules dans les ambiances intérieures (espaces confinés) comme dans l'atmosphère. En effet, les nanoparticules sont notamment susceptibles de coaguler, de grossir par condensation, et de se déposer sur les parois; ce qui modifie leur granulométrie. Une des problématiques liée à la modélisation des nanoparticules est que leur nombre est déterminant devant leur masse, tout au contraire des particules étudiées jusqu'à présent (particules fines ou grossières dont une des dimensions est supérieure à 100 nanomètre). Différents schémas numériques ont été développés pour simuler la condensation/évaporation d'une population de particules, et un noyau de coagulation issu d'algorithmes usuels a été intégré. L'inter-comparaison de ces schémas met en évidence que certains sont plus adaptés que d'autres pour les nanoparticules. Les algorithmes qui sont appropriés pour toutes les tailles de particules sont présentés. A terme, ce modèle de dynamique des nanoparticules a vocation à être intégré dans des modèles de dispersion atmosphérique (CHIMERE) et des modèles CFD (code_Saturne EdF

Monitoring SO2 emission at the Soufriere Hills Volcano: implications for changes in erruptive conditions

FLWINinfo:eu-repo/semantics/publishe

MANUAL JET VENTILATION V. HIGH FREQUENCY JET VENTILATION DURING LASER RESECTION OF TRACHEO-BRONCHIAL STENOSIS

SUMMARY Manual jet ventilation (20 b.p.m.) and high frequency jet ventilation (300 b.p.m.) were compared during laser resection of tracheo-bronchial stenosis under general anaesthesia. Both methods provided similar blood-gas tension* at the 10th min of surgery in patients with tracheal stenosis. In patients with bronchial stenosis high frequency jet ventilation resulted in modest hypercarbia and manual jet ventilation appeared to be the pretexted method in these particular patients. Although high frequency jet ventilation has been used experimentally PATIENTS AND METHODS Patients Forty patients with severe airway stenosis were studied during laser photoresection. The method of ventilation was HFJV (300 b.p.m.) in the first group of 20 patients and manual JV (20 b.p.m.) in the second group. Twenty-three patients presented with tracheal stenosis (13 in the HFJV group, 10 in the JV group) and 17 with stenosis of a main bronchus (seven in the HFJV group, 10 in the JV group). Methods Anaesthesia and bronchoscopic technique were as described previously (Vourc'h et al., 1983). The tip of the bronchoscope was kept just above the stenosis, either in the trachea or in a main bronchus. In this latter instance, ventilation of the contralateral lung was provided through side vents (Jardine, Harrisson and Healy, 1975). Statistical analysis Results were expressed as the mean ± standard deviation. Statistical analysis used Student's ftest for comparison between the two groups of patients; A probability of P< 0.05 was regarded as statistically significant. RESULTS The results are summarized in table I. Blood-gas tensions were similar in the two groups before anaesthesia; 10 min following the beginning of surgery Pao? did not differ but PacOj was greater in the HFJV group (5.43 ± 1.76 kPa) than in the JV group (4.34 ± 0.9 kPa)(P< 0.02). Comparison between the two types of ventilation in patients with tracheal stenosis showed no differenc

Data assimilation in atmospheric chemistry models: current status and future prospects for coupled chemistry meteorology models

Abstract. Data assimilation is used in atmospheric chemistry models to improve air quality forecasts, construct re-analyses of three-dimensional chemical (including aerosol) concentrations and perform inverse modeling of input variables or model parameters (e.g., emissions). Coupled chemistry meteorology models (CCMM) are atmospheric chemistry models that simulate meteorological processes and chemical transformations jointly. They offer the possibility to assimilate both meteorological and chemical data; however, because CCMM are fairly recent, data assimilation in CCMM has been limited to date. We review here the current status of data assimilation in atmospheric chemistry models with a particular focus on future prospects for data assimilation in CCMM. We first review the methods available for data assimilation in atmospheric models, including variational methods, ensemble Kalman filters, and hybrid methods. Next, we review past applications that have included chemical data assimilation in chemical transport models (CTM) and in CCMM. Observational data sets available for chemical data assimilation are described, including surface data, surface-based remote sensing, airborne data, and satellite data. Several case studies of chemical data assimilation in CCMM are presented to highlight the benefits obtained by assimilating chemical data in CCMM. A case study of data assimilation to constrain emissions is also presented. There are few examples to date of joint meteorological and chemical data assimilation in CCMM and potential difficulties associated with data assimilation in CCMM are discussed. As the number of variables being assimilated increases, it is essential to characterize correctly the errors; in particular, the specification of error cross-correlations may be problematic. In some cases, offline diagnostics are necessary to ensure that data assimilation can truly improve model performance. However, the main challenge is likely to be the paucity of chemical data available for assimilation in CCMM

CPT spectroscopy on low-temperature sealed MEMS rubidium vapour cells

In recent years there has been a strong effort to reduce the size and power consumption of vapour cell atomic clocks [1,2]. The progress in this direction is driven by several factors such as the use low power laser diodes (VCSEL), Coherent Population Trapping resonances (CPT), and micro-fabricated (MEMS) alkali-vapour cells. Here the micro-fabrication of vapour cells has proven a challenging task. All results reported on this task use anodic bonding at high-temperatures (>300°C) to seal the cell [3]. However, the low melting point and high vapour pressure of the alkali-metal combined with long bonding-times (>1hour) complicate this process. We have recently developed a low temperature (~150°C) sealing technique with fast process time (<1min) based on soldering [4]. We report here on the measurement of 85Rb σ+ CPT resonance in low temperature sealed MEMS-fabricated vapour cells containing natural rubidium and buffer gas. The resonance is recorded on the rubidium D1-line (795nm) using a circular polarized and current-modulated VCSEL. We record the resonance shift, linewidth and amplitude as function of several experimental parameters such as light intensity, cell-temperature, and buffer gas pressure- and mixture. In addition we perform noise measurements on the resonance signal to characterize the cell for clock-applications. Preliminary results show a contrast of 1.7% and linewidth of 900Hz for a 4mm long cell with 70mbar of nitrogen buffer gas. Finally we present and characterize two problems related to the application of 85Rb resonance in clock-applications. First, the low modulation frequency of the VCSEL (1.5GHz) leads to a strong asymmetry in the first order sideband spectrum due to the combined effect of AM- and FM modulation. Second, the buffer gas broadening of the absorption spectrum combined with the small separation between VCSEL carrier and sideband reduces the CPT contrast due to off-resonant absorption. We demonstrate that the impact of both these effects can be reduced by modulating the VCSEL at 3GHz and probing the CPT resonance with the carrier and first order sideband. We acknowledge support from the European Space Agency ESA (ESTEC contract number 20794/07/NL/GLC), the Conference Universitaire Suisse CUS (project CIMENT), the Swiss Space Office SSO, and SpectraTime SA (Neuchâtel, Switzerland)

ruvA Mutants that resolve Holliday junctions but do not reverse replication forks

RuvAB and RuvABC complexes catalyze branch migration and resolution of Holliday junctions (HJs) respectively. In addition to their action in the last steps of homologous recombination, they process HJs made by replication fork reversal, a reaction which occurs at inactivated replication forks by the annealing of blocked leading and lagging strand ends. RuvAB was recently proposed to bind replication forks and directly catalyze their conversion into HJs. We report here the isolation and characterization of two separation-of-function ruvA mutants that resolve HJs, based on their capacity to promote conjugational recombination and recombinational repair of UV and mitomycin C lesions, but have lost the capacity to reverse forks. In vivo and in vitro evidence indicate that the ruvA mutations affect DNA binding and the stimulation of RuvB helicase activity. This work shows that RuvA's actions at forks and at HJs can be genetically separated, and that RuvA mutants compromised for fork reversal remain fully capable of homologous recombination

Approach to Dyslipidemia, Lipodystrophy, and Cardiovascular Risk in Patients with HIV Infection

There is a significant prevalence (20%–80% depending on the population and the study) of lipid disorders and other cardiovascular risk factors in people living with HIV infection. This review focuses on HIV and HIV treatment–associated metabolic and cardiovascular concerns, including dyslipidemias, lipodystrophy syndromes, endothelial dysfunctions, and associated metabolic events such as insulin resistance. Emerging hypotheses of the underlying pathophysiology of these issues, with impact on selection of specific antiretroviral treatment (ART) strategies, therapy, and preventive approaches to decreasing cardiovascular risk and other problems associated with these syndromes are discussed. Screening for cardiovascular risk as part of the decision of starting antiretroviral therapy, and during care of patients with HIV regardless of ART therapy status, is suggested with particular areas of focus. Statins, other hyperlipidemic therapies, treatment for specific problems arising due to lipodystrophy, and implications on ART selection to avoid drug interactions and adverse effects are also discussed

Mercury sources to Lake Ozette and Lake Dickey : highly contaminated remote coastal lakes, Washington State, USA

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Water, Air, & Soil Pollution 208 (2009): 275-286, doi:10.1007/s11270-009-0165-y.Mercury concentrations in largemouth bass and mercury accumulation rates in age-dated sediment cores were examined at Lake Ozette and Lake Dickey in Washington State. Goals of the study were to compare concentrations in fish tissues at the two lakes with lakes in a larger statewide dataset and evaluate factors influencing lake loading at Ozette and Dickey, which may include: catchment disturbances, coastal mercury cycling, and the role of trans-Pacific Asian mercury. Mercury fish tissue concentrations at the lakes were among the highest recorded in Washington State. Wet deposition and historical atmospheric monitoring from the area show no indication of enhanced deposition from Asian sources or coastal atmospheric processes. Sediment core records from the lakes displayed rapidly increasing sedimentation rates coinciding with commercial logging. The unusually high mercury flux rates and mercury tissue concentrations recorded at Lake Ozette and Lake Dickey appear to be associated with logging within the catchments

Sphingomyelin is associated with kidney disease in type 1 diabetes (The FinnDiane Study)

Diabetic kidney disease, diagnosed by urinary albumin excretion rate (AER), is a critical symptom of chronic vascular injury in diabetes, and is associated with dyslipidemia and increased mortality. We investigated serum lipids in 326 subjects with type 1 diabetes: 56% of patients had normal AER, 17% had microalbuminuria (20 ≤ AER < 200 μg/min or 30 ≤ AER < 300 mg/24 h) and 26% had overt kidney disease (macroalbuminuria AER ≥ 200 μg/min or AER ≥ 300 mg/24 h). Lipoprotein subclass lipids and low-molecular-weight metabolites were quantified from native serum, and individual lipid species from the lipid extract of the native sample, using a proton NMR metabonomics platform. Sphingomyelin (odds ratio 2.53, P < 10−7), large VLDL cholesterol (odds ratio 2.36, P < 10−10), total triglycerides (odds ratio 1.88, P < 10−6), omega-9 and saturated fatty acids (odds ratio 1.82, P < 10−5), glucose disposal rate (odds ratio 0.44, P < 10−9), large HDL cholesterol (odds ratio 0.39, P < 10−9) and glomerular filtration rate (odds ratio 0.19, P < 10−10) were associated with kidney disease. No associations were found for polyunsaturated fatty acids or phospholipids. Sphingomyelin was a significant regressor of urinary albumin (P < 0.0001) in multivariate analysis with kidney function, glycemic control, body mass, blood pressure, triglycerides and HDL cholesterol. Kidney injury, sphingolipids and excess fatty acids have been linked in animal models—our exploratory approach provides independent support for this relationship in human patients with diabetes

Resolution of Joint Molecules by RuvABC and RecG Following Cleavage of the Escherichia coli Chromosome by EcoKI

DNA double-strand breaks can be repaired by homologous recombination involving the formation and resolution of Holliday junctions. In Escherichia coli, the RuvABC resolvasome and the RecG branch-migration enzyme have been proposed to act in alternative pathways for the resolution of Holliday junctions. Here, we have studied the requirements for RuvABC and RecG in DNA double-strand break repair after cleavage of the E. coli chromosome by the EcoKI restriction enzyme. We show an asymmetry in the ability of RuvABC and RecG to deal with joint molecules in vivo. We detect linear DNA products compatible with the cleavage-ligation of Holliday junctions by the RuvABC pathway but not by the RecG pathway. Nevertheless we show that the XerCD-mediated pathway of chromosome dimer resolution is required for survival regardless of whether the RuvABC or the RecG pathway is active, suggesting that crossing-over is a common outcome irrespective of the pathway utilised. This poses a problem. How can cells resolve joint molecules, such as Holliday junctions, to generate crossover products without cleavage-ligation? We suggest that the mechanism of bacterial DNA replication provides an answer to this question and that RecG can facilitate replication through Holliday junctions