Aerosol Size Distribution Estimation And Associated Uncertainty For Measurement With a SMPS

International audienceScanning Mobility Particle Sizer (SMPS) is a high resolution nanoparticle sizing system that has long been hailed as the researcher's choice for airborne nanoparticle size characterization for nano applications including nanotechnology research and development. SMPS is widely used as the standard method to measure airborne particle size distributions below 1 m. It is composed of two devices: a Di erential Mobility Analyzer (DMA) selects particle sizes thanks to their electrical mobility and a Condensation Particle Counter (CPC) enlarges particles to make them detectable by common optical counters. System raw data represent the number of particles counted over several classes of mobility diameters. Then, common inversion procedures lead to the estimation of the aerosol size distribution. In this paper, we develop a methodology to compute the uncertainties associated with the estimation of the size distribution when several experiences have been carried out. The requirement to repeat the measure ensures a realistic variability on the simulated data to be generated. The work we present consists in considering both the uncertainties coming from the experimental dispersion and the uncertainties induced by the lack of knowledge on physical phenomena. Experimental dispersion is quanti ed with the experimental data while the lack of knowledge is modelled via the existing physical theories and the judgements of experts in the eld of aerosol science. Thus, running Monte-Carlo simulations give an estimation of the size distribution and its corresponding con dence region

Scanning Mobility Particle Sizer: Fast data Inversion and uncertainty analysis

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Evaluation des incertitudes associées à la mesure granulométrique d'un aérosol par technique SMPS

National audienceLa détermination de la granulométrie en nombre d'un aérosol (concentration en nombre de particules en fonction du diamètre) à partir de mesures effectuées par un SMPS (Scanning Mobility Particle Sizer) est un problème mathématiquement mal posé. Une procédure d'inversion pour l'estimation de ce mesurande fonctionnel est proposée ainsi qu'une méthodologie pour propager l'incertitude résultant à la fois des erreurs de mesure et du manque de connaissances sur la physique sous-jacente au processus de mesure. L'inversion consiste en la décomposition du signal sur une base d'ondelettes discrètes couplée à des techniques de régularisation. Une comparaison entre la méthode développée et une technique de régularisation standard avec contraintes de lissage lorsque l'on considère une distribution de taille simulée avec des pics larges et étroits est proposée. Les résultats montrent un meilleur accord entre la reconstruction moyenne calculée par simulations de Monte-Carlo et la granulométrie originale pour la nouvelle procédure d'inversion

Gene expression profiling of brains from bovine spongiform encephalopathy (BSE)-infected cynomolgus macaques

BACKGROUND: Prion diseases are fatal neurodegenerative disorders whose pathogenesis mechanisms are not fully understood. In this context, the analysis of gene expression alterations occurring in prion-infected animals represents a powerful tool that may contribute to unravel the molecular basis of prion diseases and therefore discover novel potential targets for diagnosis and therapeutics. Here we present the first large-scale transcriptional profiling of brains from BSE-infected cynomolgus macaques, which are an excellent model for human prion disorders. RESULTS: The study was conducted using the GeneChip\uae Rhesus Macaque Genome Array and revealed 300 transcripts with expression changes greater than twofold. Among these, the bioinformatics analysis identified 86 genes with known functions, most of which are involved in cellular development, cell death and survival, lipid homeostasis, and acute phase response signaling. RT-qPCR was performed on selected gene transcripts in order to validate the differential expression in infected animals versus controls. The results obtained with the microarray technology were confirmed and a gene signature was identified. In brief, HBB and HBA2 were down-regulated in infected macaques, whereas TTR, APOC1 and SERPINA3 were up-regulated. CONCLUSIONS: Some genes involved in oxygen or lipid transport and in innate immunity were found to be dysregulated in prion infected macaques. These genes are known to be involved in other neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Our results may facilitate the identification of potential disease biomarkers for many neurodegenerative diseases

Non-adiabatic and time-resolved photoelectron spectroscopy for molecular systems

We quantify the non-adiabatic contributions to the vibronic sidebands of equilibrium and explicitly time-resolved non-equilibrium photoelectron spectra for a vibronic model system of Trans-Polyacetylene. Using exact diagonalization, we directly evaluate the sum-over-states expressions for the linear-response photocurrent. We show that spurious peaks appear in the Born-Oppenheimer approximation for the vibronic spectral function, which are not present in the exact spectral function of the system. The effect can be traced back to the factorized nature of the Born-Oppenheimer initial and final photoemission states and also persists when either only initial, or final states are replaced by correlated vibronic states. Only when correlated initial and final vibronic states are taken into account, the spurious spectral weights of the Born-Oppenheimer approximation are suppressed. In the non-equilibrium case, we illustrate for an initial Franck-Condon excitation and an explicit pump-pulse excitation how the vibronic wavepacket motion of the system can be traced in the time-resolved photoelectron spectra as function of the pump-probe delay

Generation of phase-controlled ultraviolet pulses and characterization by a simple autocorrelator setup

A versatile femtosecond ultraviolet (UV) pulse generation, a phase modulation, and a characterization setup for coherent control applications are demonstrated. For high-performance phase control of ultrashort pulses direct in the UV a microelectromechanical-system-based 2D mirror array is applied. Multiple examples for successful phase control of ultrashort UV pulses are given, such as arbitrarily phase tailoring and pulse recompression in open and closed loop schemes. For simple and effective characterization of the generated pulses, a UV autocorrelator based on two-photon absorption in a solar blind photomultiplier is constructed. The effects of space-time coupling on split mirror autocorrelation measurements are addressed and minimized. © 2009 Optical Society of America

Genetically enhanced asynapsis of autosomal chromatin promotes transcriptional dysregulation and meiotic failure

During meiosis, pairing of homologous chromosomes and their synapsis are essential prerequisites for normal male gametogenesis. Even limited autosomal asynapsis often leads to spermatogenic impairment, the mechanism of which is not fully understood. The present study was aimed at deliberately increasing the size of partial autosomal asynapsis and analysis of its impact on male meiosis. For this purpose, we studied the effect of t12 haplotype encompassing four inversions on chromosome 17 on mouse autosomal translocation T(16;17)43H (abbreviated T43H). The T43H/T43H homozygotes were fully fertile in both sexes, while +/T43H heterozygous males, but not females, were sterile with meiotic arrest at late pachynema. Inclusion of the t12 haplotype in trans to the T43H translocation resulted in enhanced asynapsis of the translocated autosome, ectopic phosphorylation of histone H2AX, persistence of RAD51 foci, and increased gene silencing around the translocation break. Increase was also on colocalization of unsynapsed chromatin with sex body. Remarkably, we found that transcriptional silencing of the unsynapsed autosomal chromatin precedes silencing of sex chromosomes. Based on the present knowledge, we conclude that interference of meiotic silencing of unsynapsed autosomes with meiotic sex chromosome inactivation is the most likely cause of asynapsis-related male sterility

Parameter study of microdroplet formation by impact of millimetre-size droplets onto a liquid film

The objective of this work is to carry out an experimental investigation on the influence of different parameters such as liquid properties (viscosity and liquid-gas surface tension), impacting droplet properties (velocity vi and diameter di) and the thickness of liquid film on the emission of airborne particles produced by the impact of millimetre-size droplets onto a liquid film. Our results show that in the variation range studied, the increase of vi and di or the decrease in liquid film thickness produces an increase in the mean number of microdroplets emitted by impact in the size range 2-50 μm. Furthermore, it was also observed that an increase in viscosity involves a steep decrease in the mean number of microdroplets emitted. These microdroplets may be produced by the fingers pinching of the crown formed during impact. In the case of low surface tension liquid, the formation of bubbles involves high production of droplets smaller than 15 μm. The results presented here constitute a database of the micro-droplets produced to validate models of droplet impact outcomes. © 2009 Elsevier Ltd. All rights reserved

Study of the coalescence/splash threshold of droplet impact on liquid films and its relevance in assessing airborne particle release

International audienceImpingement of droplets on surfaces occurs in many industrial and natural processes. The study of droplet break-up is fundamental in order to determine the potential sources of airborne contamination for scenarios of hazardous liquid falls such as dripping. There are very few data in the literature describing the case of impact of millimetre-size droplets. The purposes of this work were to study experimentally particle emission during the impact of droplets on a liquid film and to assess the use of coalescence/splash relations to predict airborne particle release. The results are described using dimensionless numbers taking into account the inertial, viscosity and surface tension forces. Experiments were carried out for Weber numbers between 62 and 1754 and for Ohnesorge numbers between 2.0×10 -3 and 1.5×10 -2. New results on coalescence/splash thresholds are obtained using highly sensitive aerosol measurement and allow a prediction concerning the presence or absence of airborne particles according to a threshold relation. Moreover, we propose a modification of the Cossali et al.'s [1] relation in order to describe the coalescence/prompt splash threshold. © 2011 Elsevier Inc