Gas-phase filters breakthrough models at low concentration – Effect of relative humidity

We report a study on the reactions of pure metal clusters Nbn− with dioxygen in the gas phase. It is found that the presence of low-concentration dioxygen reactants results in...

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SENSIBILIDAD DE LA GARRAPATA COMÚN DEL BOVINO Rhipicephalus (Boophilus) microplus A IVERMECTINA ESTIMADA CON EL MODELO SIGMOIDEO DE RESPUESTA MÁXIMA O DE HILL

FAVE Sección Ciencias Veterinarias ◽

10.14409/favecv.v19isuplemento.10943 ◽

2021 ◽

Vol 19 (suplemento) ◽

Author(s):

J Torrents

Keyword(s):

Statistical Analysis ◽

Boophilus Microplus ◽

Susceptible Strain ◽

Maximum Response ◽

Hill Coefficient ◽

Concentration Effect ◽

Hill Model ◽

Low Concentration ◽

Immersion Technique ◽

The Hill

The aim of this study was to obtain pharmacodynamics parameters to detect resistance or susceptibility of R. microplus strains to ivermectin (IVM). Two larvae samples; a susceptible strain (S) and field isolation (T) were treated with increasing concentrations of IVM using the larvae immersion technique the efficacy values measured at 24 hours were analysed with the sigmoidal maximum response so called Hill model as statistical analysis. The results obtained showed that the IVM have an all or nothing response represented by the Hill coefficient value >1 in both samples. Additionally, a low concentration effect was observed as E0 de 12.83% (S) and 9.91% (T). The field isolation larvae were susceptible to IVM in comparison with the susceptible strain by the resistance ratio (RR) which in one case was not significantly greater that one (RR50= 0.756 and RR90=1.009).

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Volatile organic compound (VOC) adsorption on material: influence of gas phase concentration, relative humidity and VOC type

Indoor Air ◽

10.1111/j.1600-0668.2005.00421.x ◽

2006 ◽

Vol 16 (3) ◽

pp. 236-247 ◽

Cited By ~ 60

Author(s):

H. Huang ◽

F. Haghighat ◽

P. Blondeau

Keyword(s):

Organic Compound ◽

Relative Humidity ◽

Gas Phase ◽

Volatile Organic Compound ◽

Phase Concentration ◽

Voc Adsorption ◽

Volatile Organic

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Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-11069-2011 ◽

2011 ◽

Vol 11 (21) ◽

pp. 11069-11102 ◽

Cited By ~ 730

Author(s):

B. Ervens ◽

B. J. Turpin ◽

R. J. Weber

Keyword(s):

Relative Humidity ◽

Gas Phase ◽

Atmospheric Chemistry ◽

Secondary Organic Aerosol ◽

Current Knowledge ◽

Laboratory Data ◽

Organic Aerosol ◽

Current Data ◽

Aerosol Formation ◽

Model Studies

Abstract. Progress has been made over the past decade in predicting secondary organic aerosol (SOA) mass in the atmosphere using vapor pressure-driven partitioning, which implies that SOA compounds are formed in the gas phase and then partition to an organic phase (gasSOA). However, discrepancies in predicting organic aerosol oxidation state, size and product (molecular mass) distribution, relative humidity (RH) dependence, color, and vertical profile suggest that additional SOA sources and aging processes may be important. The formation of SOA in cloud and aerosol water (aqSOA) is not considered in these models even though water is an abundant medium for atmospheric chemistry and such chemistry can form dicarboxylic acids and "humic-like substances" (oligomers, high-molecular-weight compounds), i.e. compounds that do not have any gas phase sources but comprise a significant fraction of the total SOA mass. There is direct evidence from field observations and laboratory studies that organic aerosol is formed in cloud and aerosol water, contributing substantial mass to the droplet mode. This review summarizes the current knowledge on aqueous phase organic reactions and combines evidence that points to a significant role of aqSOA formation in the atmosphere. Model studies are discussed that explore the importance of aqSOA formation and suggestions for model improvements are made based on the comprehensive set of laboratory data presented here. A first comparison is made between aqSOA and gasSOA yields and mass predictions for selected conditions. These simulations suggest that aqSOA might contribute almost as much mass as gasSOA to the SOA budget, with highest contributions from biogenic emissions of volatile organic compounds (VOC) in the presence of anthropogenic pollutants (i.e. NOx) at high relative humidity and cloudiness. Gaps in the current understanding of aqSOA processes are discussed and further studies (laboratory, field, model) are outlined to complement current data sets.

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Glyoxal's impact on dry ammonium salts: fast and reversible surface aerosol browning

10.5194/acp-2020-203 ◽

2020 ◽

Author(s):

David O. De Haan ◽

Lelia N. Hawkins ◽

Kevin Jansen ◽

Hannah G. Welsh ◽

Raunak Pednekar ◽

...

Keyword(s):

Relative Humidity ◽

Gas Phase ◽

Ammonium Sulfate ◽

Aerosol Particles ◽

Ammonium Salts ◽

Carbon Formation ◽

Cloud Droplets ◽

Brown Carbon ◽

Dicarbonyl Compounds ◽

Dry Conditions

Abstract. Alpha-dicarbonyl compounds are believed to form brown carbon in the atmosphere via reactions with ammonium sulfate (AS) in cloud droplets and aqueous aerosol particles. In this work, brown carbon formation in AS and other aerosol particles was quantified as a function of relative humidity (RH) during exposure to gas-phase glyoxal (GX) in chamber experiments. Under dry conditions (RH

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Measurements of the timescales for the mass transfer of water in glassy aerosol at low relative humidity and ambient temperature

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-4739-2011 ◽

2011 ◽

Vol 11 (10) ◽

pp. 4739-4754 ◽

Cited By ~ 132

Author(s):

H.-J. Tong ◽

J. P. Reid ◽

D. L. Bones ◽

B. P. Luo ◽

U. K. Krieger

Keyword(s):

Mass Transfer ◽

Glass Transition ◽

Relative Humidity ◽

Gas Phase ◽

Mass Transfer Rate ◽

Solution Viscosity ◽

Bulk Solution ◽

Size Change ◽

Return To Equilibrium ◽

Kinetics Of

Abstract. The influence of glassy states and highly viscous solution phases on the timescale of aerosol particle equilibration with water vapour is examined. In particular, the kinetics of mass transfer of water between the condensed and gas phases has been studied for sucrose solution droplets under conditions above and below the glass transition relative humidity (RH). Above the glass transition, sucrose droplets are shown to equilibrate on a timescale comparable to the change in RH. Below the glass transition, the timescale for mass transfer is shown to be extremely slow, with particles remaining in a state of disequilibrium even after timescales of more than 10 000 s. A phenomenological approach for quantifying the time response of particle size is used to illustrate the influence of the glassy aerosol state on the kinetics of mass transfer of water: the time is estimated for the droplet to reach the halfway point from an initial state towards a disequilibrium state at which the rate of size change decreases below 1 nm every 10 000 s. This half-time increases above 1000 s once the particle can be assumed to have formed a glass. The measurements are shown to be consistent with kinetic simulations of the slow diffusion of water within the particle bulk. When increasing the RH from below to above the glass transition, a particle can return to equilibrium with the gas phase on a timescale of 10's to 100's of seconds, once again forming a solution droplet. This is considerably shorter than the timescale for the size change of the particle when glassy and suggests that the dissolution of the glassy core can proceed rapidly, at least at room temperature. Similar behaviour in the slowing of the mass transfer rate below the glass transition RH is observed for binary aqueous raffinose solution droplets. Mixed component droplets of sucrose/sodium chloride/water also show slow equilibration at low RH, illustrating the importance of understanding the role of the bulk solution viscosity on the rate of mass transfer with the gas phase, even under conditions that may not lead to the formation of a glass.

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Droplet phase (Heterogeneous) and gas phase (homogeneous) contributions to secondary ambient aerosol formation as functions of relative humidity

Journal of Geophysical Research Atmospheres ◽

10.1029/jc088ic09p05101 ◽

1983 ◽

Vol 88 (C9) ◽

pp. 5101-5108 ◽

Cited By ~ 76

Author(s):

P. H. McMurry ◽

J. C. Wilson

Keyword(s):

Relative Humidity ◽

Gas Phase ◽

Aerosol Formation ◽

Ambient Aerosol ◽

Droplet Phase

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Changing shapes and implied viscosities of suspended submicron particles

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-7819-2015 ◽

2015 ◽

Vol 15 (14) ◽

pp. 7819-7829 ◽

Cited By ~ 68

Author(s):

Y. Zhang ◽

M. S. Sanchez ◽

C. Douet ◽

Y. Wang ◽

A. P. Bateman ◽

...

Keyword(s):

Relative Humidity ◽

Gas Phase ◽

Shape Change ◽

Particle Diameter ◽

Submicron Particles ◽

Flow Tube ◽

Shape Factors ◽

Tube Reactor ◽

Organic Particles ◽

Dynamic Shape

Abstract. The change in shape of atmospherically relevant organic particles is used to estimate the viscosity of the particle material without the need for removal from aerosol suspension. The dynamic shape factors χ of particles produced by α-pinene ozonolysis in a flow tube reactor, under conditions of particle coagulation, were measured while altering the relative humidity (RH) downstream of the flow tube. As relative humidity was increased, the results showed that χ could change from 1.27 to 1.02, corresponding to a transition from aspherical to nearly spherical shapes. The shape change could occur at elevated RH because the organic material had decreased viscosity and was therefore able to flow to form spherical shapes, as favored by the minimization of surface area. Numerical modeling was used to estimate the particle viscosity associated with this flow. Based on particle diameter and RH exposure time, the viscosity dropped from 10(8.7±2.0) to 10(7.0±2.0) Pa s (two sigma) for an increase in RH from < 5 to 58 % at 293 K. These results imply that the equilibration of the chemical composition of the particle phase with the gas phase can shift from hours at mid-range RH to days at low RH.

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