Possible Overestimation of Nitrogen Dioxide Outgassing during the Beirut 2020 Explosion

On 4 August 2020, a strong explosion occurred near the Beirut seaport, Lebanon and killed more than 200 people and damaged numerous buildings in the vicinity. As Amonium Nitrate (AN) caused the explosion, many studies claimed the release of large amounts of NO2 in the atmosphere may have resulted in a health hazard in Beirut and the vicinity. In order to reasonably evaluate the significance of NO2 amounts released in the atmosphere, it is important to investigate the spatio-temporal distribution of NO2 during and after the blast and compare it to the average day-to-day background emissions from vehicle and ship traffic in Beirut. In the present study, we use Sentinel-5 TROPOMI data to study NO2 emissions in the atmosphere close to the affected area prior, during, and after the Beirut explosion (28 July–8 August 2020). Analysis shows an increase in NO2 concentrations over Beirut up to about 1.8 mol/m2 one day after the explosion that was gradually dissipated in about 4 days. Seven days before the blast (on 28 July 2020) NO2 concentration was, however, observed to be up to about 4.3 mol/m2 over Beirut, which is mostly attributed to vehicle emissions in Lebanon, ships passing by the Beirut seaport and possibly the militant activities in Syria during 20–26 July. It is found that the Beirut blast caused a temporarily and spatially limited increase in NO2. The blast mostly affected the coastal areas in Lebanon, while it did not have much effect on inland regions. TROPOMI data are also analyzed for the Greater Cairo Area (GCA), Suez Canal, Egypt, and in Nicosia, Cyprus to confirm the effect of human activities, vehicles, and ship traffic on NO2 emissions in relatively high and relatively low populated zones

Spectroscopie à champ proche optique de nanoparticules hybrides pour application en capteurs biologique et microscopie confocale de nanocristaux de sillicium uniques.

The domain of nanomatrials plays an important role in many biological, medical and electronic applications. In this work, we present results concerning two types of nanoparticles : the first kind treats with hybrid nanoparitcls chemically synthesized for biological means, the second concerns silicon nanocrystals fabricated by laser pyrolisis for optoelectronic applications. The studies are done by using two different optical techniques, one in the far field, the other in the near field. In the nanohybrids case, we are interested by spectroscopic, and imaging near field characterization, by particularly using a waveguide configuration. We will first shed light about the emission properties of such nanoparticles, and then discuss artefact problems, in addition to the resolution of the images we can attain in our setup. We will prove the essential importance of the role of nanohybrids as biological markers with two different types of biosensors. The small sized silicon nanoparticles (< 3 nm) are essentially studied by confocal microscopy. More precisely, we will be interested by the different luminescence processes taking place during the excitation of a unique nanoparticle, by taking into consideration the surface effects. We will search to study the influence of the nanoparticles environment on their spectral properties by placing them in thin films having different dielectric properties. We will conclude with a small description of the stark effects which take place in such a systemLe domaine des nanomatériaux joue un rôle de plus en plus important dans de nombreuses applications, qu’elles soient de natures biologique, médicales électroniques etc… Dans ce travail, nous présenterons des résultats concernant deux types de nanoparticules, le premier genre traite de nanoparticules hybrides confectionnées chimiquement pour des fins biologiques, le deuxième concerne des nanocristaux de silicium fabriqués par pyrolise laser pour des applications potentielles en optoélectronique. Les études sont menées en mettant en œuvre deux différentes techniques optiques, l’une en champ lointain, l’autre en champ proche. Dans le cas des nanohybrides, nous nous intéresserons à une caractérisation par microscopie en champ proche, qu’elle soit de nature spectroscopique ou d’imagerie simple, en utilisant en particulier une configuration optique guidante. Nous ferons un premier point à propos de l’émission de ses nanoparticules, puis discuterons des problèmes d’artefacts et de la résolution des images que nous pouvons atteindre avec notre montage. Nous prouverons l’importance essentielle du rôle des nanohybrides en tant que marqueur biologiques, et ceci dans deux différentes types de configuration de capteurs biologiques. Les nanoparticules de silicium de petites tailles (< 3 nm) seront étudiées essentiellement par microscopie confocale. Plus précisément, nous nous intéressons aux différents procédés de luminescence qui ont lieu lors de l’excitation d’une nanoparticule unique, en tenant compte des effets de taille et de surface. Nous chercherons à étudier l’influence de l’environnement des nanoparticules sur leurs propriétés spectrales en les plaçant dans des couches minces de natures diélectriques différentes. Nous conclurons enfin sur une brève description des différents effets Sark qui prennent lieu dans un tel système

Electronic structure with dipole moment and ionicity calculations of the low-lying electronic states of ZnF molecule

Adiabatic potential energy curves of the 28 low-lying doublet and quartet electronic states in the representation 2s+1Λ(±) of the zinc monofluoride molecule are investigated using the complete active space self consistent field (CASSCF) with multi-reference configuration interaction MRCI method including single and double excitations with Davidson correction (+Q). The internuclear distance Re, the harmonic frequency e, the static and transition dipole moment µ, the rotational constant Be and the electronic transition energy with respect to the ground state Te are calculated for the bound states. The transition dipole moment between some doublet states are used to determine the Einstein spontaneous and induced emission coefficients as well as the spontaneous radiative lifetime, emission wavelength and oscillator strength. The ionicity and the equilibrium dissociation energy DE,e of the ground state are also computed. The comparison between the values of the present work and those available in the literature for several electronic states shows very good agreement. Twenty-three new electronic states have been studied in the present work for the first time.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Possible Overestimation of Nitrogen Dioxide Outgassing during the Beirut 2020 Explosion

On 4 August 2020, a strong explosion occurred near the Beirut seaport, Lebanon and killed more than 200 people and damaged numerous buildings in the vicinity. As Amonium Nitrate (AN) caused the explosion, many studies claimed the release of large amounts of NO2 in the atmosphere may have resulted in a health hazard in Beirut and the vicinity. In order to reasonably evaluate the significance of NO2 amounts released in the atmosphere, it is important to investigate the spatio-temporal distribution of NO2 during and after the blast and compare it to the average day-to-day background emissions from vehicle and ship traffic in Beirut. In the present study, we use Sentinel-5 TROPOMI data to study NO2 emissions in the atmosphere close to the affected area prior, during, and after the Beirut explosion (28 July&ndash;8 August 2020). Analysis shows an increase in NO2 concentrations over Beirut up to about 1.8 mol/m2 one day after the explosion that was gradually dissipated in about 4 days. Seven days before the blast (on 28 July 2020) NO2 concentration was, however, observed to be up to about 4.3 mol/m2 over Beirut, which is mostly attributed to vehicle emissions in Lebanon, ships passing by the Beirut seaport and possibly the militant activities in Syria during 20&ndash;26 July. It is found that the Beirut blast caused a temporarily and spatially limited increase in NO2. The blast mostly affected the coastal areas in Lebanon, while it did not have much effect on inland regions. TROPOMI data are also analyzed for the Greater Cairo Area (GCA), Suez Canal, Egypt, and in Nicosia, Cyprus to confirm the effect of human activities, vehicles, and ship traffic on NO2 emissions in relatively high and relatively low populated zones

Nanohybrids Near-Field Optical Microscopy: From Image Shift to Biosensor Application

Near-Field Optical Microscopy is a valuable tool for the optical and topographic study of objects at a nanometric scale. Nanoparticles constitute important candidates for such type of investigations, as they bear an important weight for medical, biomedical, and biosensing applications. One, however, has to be careful as artifacts can be easily reproduced. In this study, we examined hybrid nanoparticles (or nanohybrids) in the near-field, while in solution and attached to gold nanoplots. We found out that they can be used for wavelength modulable near-field biosensors within conditions of artifact free imaging. In detail, we refer to the use of topographic/optical image shift and the imaging of Local Surface Plasmon hot spots to validate the genuineness of the obtained images. In summary, this study demonstrates a new way of using simple easily achievable comparative methods to prove the authenticity of near-field images and presents nanohybrid biosensors as an application

Détection de molécules biologiques par luminescence dans le domaine du champ proche optique

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How nanoparticles encapsulating fluorophores allow a double detection of biomolecules by localized surface plasmon resonance and luminescence

International audienceThe paper shows how polysiloxane particles encapsulating fluorophores can be successfully used to detect biotin-streptavidin binding by two types of technique. After functionalization of the particles by streptavidin, the fixation of the biomolecule can indeed be detected by a shift of the localized surface plasmon resonance of the biotinylated gold dots used as substrate and by the luminescence of the fluorophores evidenced by scanning near-field optical microscopy. The development of particles allowing such a double detection opens a route for increasing the reliability of biological detection and for multi-labelling strategies crossing both detection principles

Double détection de molécules biologiques utilisant la résonance de plasmons de surface localisés et la luminescence de nanohybrides sur des nanoparticules d'or

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