Face-masks save us from SARS-CoV-2 transmission

We present results on the infection risk from SARS-CoV-2 under different scenarios based on measured particle size-dependent mask penetration, measured total inward leakage, measured human aerosol emission for sizes from 10nm to 1mm, and re-hydration on inhalation. Well-mixed room models significantly underestimate the risk of infection for short and direct exposure. To this end, we estimate the upper bound for infection risk with the susceptible in the infectious exhalation cloud or wearing masks by having the masked susceptible inhale the entire exhalation of a masked infectious. Social distances without a mask, even at 3m between speaking individuals results in an upper bound of 90\% for risk of infection after a few minutes. If both wear a surgical mask, the risk of infection for the person speaking remains below 26\% even after 60 minutes. When both the infectious and susceptible wear a well-fitting FFP2 mask, the upper bound for risk is reduced by a factor of 60 compared to surgical masks. In both cases, face leakage is very important. For FFP2 masks, leakage is low in the nasal region and directed upward, which can be further reduced significantly by applying double-sided medical tape there. Considering that the calculated upper bound greatly overestimates the risk of infection, and the fact that with a poorly worn mask even the upper bound we calculated is very low, we conclude that wearing a mask, even with some leakage, provides excellent third party and self-protection

Numerical Modeling Of Collision And Agglomeration Of Adhesive Particles In Turbulent Flows

Particle motion, clustering and agglomeration play an important role in natural phenomena and industrial processes. In classical computational fluid dynamics (CFD), there are three major methods which can be used to predict the flow field and consequently the behavior of particles in flow-fields: 1) direct numerical simulation (DNS) which is very expensive and time consuming, 2) large eddy simulation (LES) which resolves the large scale but not the small scale fluctuations, and 3) Reynolds-Averaged Navier-Stokes (RANS) which can only predict the mean flow. In order to make LES and RANS usable for studying the behavior of small suspended particles, we need to introduce small scale fluctuations to these models, since these small scales have a huge impact on the particle behavior. The first part of this dissertation both extends and critically examines a new method for the generation of small scale fluctuations for use with RANS simulations. This method, called the stochastic vortex structure (SVS) method, uses a series of randomly positioned and oriented vortex tubes to induce the small-scale fluctuating flow. We first use SVS in isotropic homogenous turbulence and validate the predicted flow characteristics and collision and agglomeration of particles from the SVS model with full DNS computations. The calculation speed for the induced velocity from the vortex structures is improved by about two orders of magnitude using a combination of the fast multiple method and a local Taylor series expansion. Next we turn to the problem of extension of the SVS method to more general turbulent flows. We propose an inverse method by which the initial vortex orientation can be specified to generate a specific anisotropic Reynolds stress field. The proposed method is validated for turbulence measures and colliding particle transport in comparison to DNS for turbulent jet flow. The second part of the dissertation uses DNS to examine in more detail two issues raised during developing the SVS model. The first issue concerns the effect of two-way coupling on the agglomeration of adhesive particles. The SVS model as developed to date does not account for the effect of particles on the flow-field (one-way coupling). We focused on examination of the local flow around agglomerates and the effect of agglomeration on modulation of the turbulence. The second issue examines the microphysics of turbulent agglomeration by examining breakup and collision of agglomerates in a shear flow. DNS results are reported both for one agglomerate in shear and for collision of two agglomerates, with a focus on the physics and role of the particle-induced flow field on the particle dynamics

Fundamental principles of cloud and aerosol physics

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Report of the 2005 Workshop on Ocean Ecodynamics Comparison in the Subarctic Pacific

I. Scientific Issues Posed by OECOS II. Participant Contributions to the OECOS Workshop A. ASPECTS OF PHYTOPLANKTON ECOLOGY IN THE SUBARCTIC PACIFIC Microbial community compositions by Karen E. Selph Subarctic Pacific lower trophic interactions: Production-based grazing rates and grazing-corrected production rates by Nicholas Welschmeyer Phytoplankton bloom dynamics and their physiological status in the western subarctic Pacific by Ken Furuya Temporal and spatial variability of phytoplankton biomass and productivity in the northwestern Pacific by Sei-ichi Saitoh, Suguru Okamoto, Hiroki Takemura and Kosei Sasaoka The use of molecular indicators of phytoplankton iron limitation by Deana Erdner B. IRON CONCENTRATION AND CHEMICAL SPECIATION Iron measurements during OECOS by Zanna Chase and Jay Cullen 25 The measurement of iron, nutrients and other chemical components in the northwestern North Pacific Ocean by Kenshi Kuma The measurement of iron, nutrients and other chemical components in the northwestern North Pacific Ocean by Kenshi Kuma C. PHYSICAL OCEANOGRAPHY, FINE-SCALE DISTRIBUTION PATTERNS AND AUTONOMOUS DRIFTERS The use of drifters in Lagrangian experiments: Positives, negatives and what can really be measured by Peter Strutton The interaction between plankton distribution patterns and vertical and horizontal physical processes in the eastern subarctic North Pacific by Timothy J. Cowles D. MICROZOOPLANKTON Microzooplankton processes in oceanic waters of the eastern subarctic Pacific: Project OECOS by Suzanne Strom Functional role of microzooplankton in the pelagic marine ecosystem during phytoplankton blooms in the western subarctic Pacific by Takashi Ota and Akiyoshi Shinada E. MESOZOOPLANKTON Vertical zonation of mesozooplankton, and its variability in response to food availability, density stratification, and turbulence by David L. Mackas and Moira Galbraith Marine ecosystem characteristics and seasonal abundance of dominant calanoid copepods in the Oyashio region by Atsushi Yamaguchi, Tsutomu Ikeda and Naonobu Shiga OECOS: Proposed mesozooplankton research in the Oyashio region, western subarctic Pacific by Tsutomu Ikeda Some background on Neocalanus feeding by Michael Dagg Size and growth of interzonally migrating copepods by Charles B. Miller Growth of large interzonal migrating copepods by Toru Kobari F. MODELING Ecosystem and population dynamics modeling by Harold P. Batchelder III. Reports from Workshop Breakout Groups A. PHYSICAL AND CHEMICAL ASPECTS WITH EMPHASIS ON IRON AND IRON SPECIATION B. PHYTOPLANKTON/MICROZOOPLANKTON STUDIES C. MESOZOOPLANKTON STUDIES IV. Issues arising during the workshop A. PHYTOPLANKTON STOCK VARIATIONS IN HNLC SYSTEMS AND TROPHIC CASCADES IN THE NANO AND MICRO REGIMES B. DIFFERENCES BETWEEN EAST AND WEST IN SITE SELECTION FOR OECOS TIME SERIES C. TIMING OF OECOS EXPEDITIONS D. CHARACTERIZATION OF PHYSICAL OCEANOGRAPHY V. Concluding Remarks VI. References (109 page document

The Pierre Auger Observatory: Contributions to the 34th International Cosmic Ray Conference (ICRC 2015)

Contributions of the Pierre Auger Collaboration to the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The NetherlandsComment: 24 proceedings, the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands; will appear in PoS(ICRC2015

Research and Technology

Langley Research Center is engaged in the basic an applied research necessary for the advancement of aeronautics and space flight, generating advanced concepts for the accomplishment of related national goals, and provding research advice, technological support, and assistance to other NASA installations, other government agencies, and industry. Highlights of major accomplishments and applications are presented

Analysis of External Radioactive Releases for an In-Vessel Break in the Power Plant Conceptual Study Using the ECART Code

This work is related to the application of the CESI and EdF ECART code on the analysis of the tritium and dusts external releases for an in-vessel break in the helium cooling loop of the first wall / blanket for the Power Plant Conceptual Study (PPCS). In particular the influence on the releases of a Detritiation System (DS) and of a dust scrubber with constant decontamination factor, not implemented in the original PPCS design, are analysed. Furthermore, some parametrical analysis on the influence, on the external releases, of the mass fraction of dust resuspended inside the VV at the beginning of the sequence have been also performed. These analyses are the follow-up of a previous DIMNP study about the phenomenological behaviour of the PPCS containment (vacuum vessel walls and expansion volume walls), giving the first indications on the amount of the external radioactive releases. The activities have been also carried out in the general framework of the validation phase of the ECART code, initially developed for integrated analysis of severe accidents in LWRs, for its application on incidental sequences related to fusion plants. ECART was originally designed and validated for safety analyses of fission NPPs and is internationally recognized as a relevant nuclear source term code for these fission plants. It permits the simulation of chemical reactions and transport of radioactive gases and aerosols under two-phase flow transients in generic flow systems, using a built-in thermal-hydraulic model

A comparison of scavenging and deposition processes in global models: results from the WCRP Cambridge Workshop of 1995

We report on results from a World Climate Research Program workshop on representations of scavenging and deposition processes in global transport models of the atmosphere. 15 models were evaluated by comparing simulations of radon, lead, sulfur dioxide, and sulfate against each other, and against observations of these constituents. This paper provides a survey on the simulation differences between models. It identifies circumstances where models are consistent with observations or with each other, and where they differ from observations or with each other. The comparison shows that most models are able to simulate seasonal species concentrations near the surface over continental sites to within a factor of 2 over many regions of the globe. Models tend to agree more closely over source (continental) regions than for remote (polar and oceanic) regions. Model simulations differ most strongly in the upper troposphere for species undergoing wet scavenging processes. There are not a sufficient number of observations to characterize the climatology (long-term average) of species undergoing wet scavenging in the upper troposphere. This highlights the need for either a different strategy for model evaluation (e.g., comparisons on an event by event basis) or many more observations of a few carefully chosen constituents