Influence of medium range transport of particles from nucleation burst on particle number concentration within the urban airshed

An elevated particle number concentration (PNC) observed during nucleation events could play a significant contribution to the total particle load and therefore to the air pollution in the urban environments. Therefore, a field measurement study of PNC was commenced to investigate the temporal and spatial variations of PNC within the urban airshed of Brisbane, Australia. PNC was monitored at urban (QUT), roadside (WOO) and semi-urban (ROC) areas around the Brisbane region during 2009. During the morning traffic peak period, the highest relative fraction of PNC reached about 5% at QUT and WOO on weekdays. PNC peaks were observed around noon, which correlated with the highest solar radiation levels at all three stations, thus suggesting that high PNC levels were likely to be associated with new particle formation caused by photochemical reactions. Wind rose plots showed relatively higher PNC for the NE direction, which was associated with industrial pollution, accounting for 12%, 9% and 14% of overall PNC at QUT, WOO and ROC, respectively. Although there was no significant correlation between PNC at each station, the variation of PNC was well correlated among three stations during regional nucleation events. In addition, PNC at ROC was significantly influenced by upwind urban pollution during the nucleation burst events, with the average enrichment factor of 15.4. This study provides an insight into the influence of regional nucleation events on PNC in the Brisbane region and it the first study to quantify the effect of urban pollution on semi-urban PNC through the nucleation events. © 2012 Author(s).

Lagrangian transport of particles in Ria de Aveiro lagoon, Portugal

A two-dimensional vertically integrated hydrodynamic model coupled to a particle tracking model is applied to study the dispersion processes and residence time in Ria de Aveiro lagoon (Portugal). The only dispersion process that is considered in this study is the advection, according to the main characteristics of the local hydrodynamic. The particle tracking model computes the particles position at each time step, using a fourth-order Runge-Kutta integration method. The dispersion of passive particles released along the lagoon and in critical areas are studied in this work. The residence time is also determined for the entire lagoon. The results show that the mixture between particles coming from different channels of the lagoon is negligible in a time scale higher than 2 tidal cycles. The residence time for the lagoon central area is about 2 days, revealing a strong marine influence in this area. At the upper reaches of the channels were found values higher than 2 weeks.

Generalized compound transport of charged particles in turbulent magnetized plasmas

The transport of charged particles in partially turbulent magnetic systems is investigated from first principles. A generalized compound transport model is proposed, providing an explicit relation between the mean-square deviation of the particle parallel and perpendicular to a magnetic mean field, and the mean-square deviation which characterizes the stochastic field-line topology. The model is applied in various cases of study, and the relation to previous models is discussed.

Transport of nanoparticles into polymersomes : a minimal model system of particles passage through biological membranes

This thesis focuses on the design and characterization of a novel, artificial minimal model membrane system with chosen physical parameters to mimic a nanoparticle uptake process driven exclusively by adhesion and softness of the bilayer. The realization is based on polymersomes composed of poly(dimethylsiloxane)-b-poly(2-methyloxazoline) (PMDS-b-PMOXA) and nanoscopic colloidal particles (polystyrene, silica), and the utilization of powerful characterization techniques. rnPDMS-b-PMOXA polymersomes with a radius, Rh ~100 nm, a size polydispersity, PD = 1.1 and a membrane thickness, h = 16 nm, were prepared using the film rehydratation method. Due to the suitable mechanical properties (Young’s modulus of ~17 MPa and a bending modulus of ~7⋅10-8 J) along with the long-term stability and the modifiability, these kind of polymersomes can be used as model membranes to study physical and physicochemical aspects of transmembrane transport of nanoparticles. A combination of photon (PCS) and fluorescence (FCS) correlation spectroscopies optimizes species selectivity, necessary for a unique internalization study encompassing two main efforts. rnFor the proof of concepts, the first effort focused on the interaction of nanoparticles (Rh NP SiO2 = 14 nm, Rh NP PS = 16 nm; cNP = 0.1 gL-1) and polymersomes (Rh P = 112 nm; cP = 0.045 gL-1) with fixed size and concentration. Identification of a modified form factor of the polymersome entities, selectively seen in the PCS experiment, enabled a precise monitor and quantitative description of the incorporation process. Combining PCS and FCS led to the estimation of the incorporated particles per polymersome (about 8 in the examined system) and the development of an appropriate methodology for the kinetics and dynamics of the internalization process. rnThe second effort aimed at the establishment of the necessary phenomenology to facilitate comparison with theories. The size and concentration of the nanoparticles were chosen as the most important system variables (Rh NP = 14 - 57 nm; cNP = 0.05 - 0.2 gL-1). It was revealed that the incorporation process could be controlled to a significant extent by changing the nanoparticles size and concentration. Average number of 7 up to 11 NPs with Rh NP = 14 nm and 3 up to 6 NPs with Rh NP = 25 nm can be internalized into the present polymersomes by changing initial nanoparticles concentration in the range 0.1- 0.2 gL-1. Rapid internalization of the particles by polymersomes is observed only above a critical threshold particles concentration, dependent on the nanoparticle size. rnWith regard possible pathways for the particle uptake, cryogenic transmission electron microscopy (cryo-TEM) has revealed two different incorporation mechanisms depending on the size of the involved nanoparticles: cooperative incorporation of nanoparticles groups or single nanoparticles incorporation. Conditions for nanoparticle uptake and controlled filling of polymersomes were presented. rnIn the framework of this thesis, the experimental observation of transmembrane transport of spherical PS and SiO2 NPs into polymersomes via an internalization process was reported and examined quantitatively for the first time. rnIn a summary the work performed in frames of this thesis might have significant impact on cell model systems’ development and thus improved understanding of transmembrane transport processes. The present experimental findings help create the missing phenomenology necessary for a detailed understanding of a phenomenon with great relevance in transmembrane transport. The fact that transmembrane transport of nanoparticles can be performed by artificial model system without any additional stimuli has a fundamental impact on the understanding, not only of the nanoparticle invagination process but also of the interaction of nanoparticles with biological as well as polymeric membranes. rn

Selective transport of attached particles across the pulp-froth interface

A technique for determining the recovery of attached particles across the froth phase in flotation that relies on measuring the rate at which bubble-particle aggregates enter the froth is used to investigate the selectivity of attached particles across the froth phase. Combining these measurements with those of other techniques for determining the froth recovery of attached particles provides an insight into the different sub-processes of particle rejection in the froth phase. The results of experiments conducted in a 3 m(3) Outokumpu tank cell show that the detachment of particles from aggregates in the froth phase occurs largely at the pulp-froth interface. In particular it is shown that the pulp-froth interface selectively detaches particles from aggregates according to their physical attributes. (C) 2005 Elsevier Ltd. All rights reserved.

Selective transport of attached particles across the pulp-froth interface

A technique for determining the recovery of attached particles across the froth phase in flotation that relies on measuring the rate at which bubble-particle aggregates enter the froth is used to investigate the selectivity of attached particles across the froth phase. Combining these measurements with those of other techniques for determining the froth recovery of attached particles provides an insight into the different subprocesses of particle rejection in the froth phase. The results of experiments conducted in a 3 m3 Outokumpu tank cell show that the detachment of particles from aggregates in the froth phase occurs largely at the pulp-froth interface. In particular it is shown that the pulp-froth interface selectively detaches particles from aggregates according to their physical attributes.

Revival resonant scattering, perfect caustics and isotropic transport of pseudospin-1 particles

This work was supported by ONR under Grant No. N00014-16-1-2828.

Observations of production and transport of NOx formed by energetic particle precipitation in the polar night atmosphere

This work is focused on the effects of energetic particle precipitation of solar or magnetospheric origin on the polar middle atmosphere. The energetic charged particles have access to the atmosphere in the polar areas, where they are guided by the Earth's magnetic field. The particles penetrate down to 20-100 km altitudes (stratosphere and mesosphere) ionising the ambient air. This ionisation leads to production of odd nitrogen (NOx) and odd hydrogen species, which take part in catalytic ozone destruction. NOx has a very long chemical lifetime during polar night conditions. Therefore NOx produced at high altitudes during polar night can be transported to lower stratospheric altitudes. Particular emphasis in this work is in the use of both space and ground based observations: ozone and NO2 measurements from the GOMOS instrument on board the European Space Agency's Envisat-satellite are used together with subionospheric VLF radio wave observations from ground stations. Combining the two observation techniques enabled detection of NOx enhancements throughout the middle atmosphere, including tracking the descent of NOx enhancements of high altitude origin down to the stratosphere. GOMOS observations of the large Solar Proton Events of October-November 2003 showed the progression of the SPE initiated NOx enhancements through the polar winter. In the upper stratosphere, nighttime NO2 increased by an order of magnitude, and the effect was observed to last for several weeks after the SPEs. Ozone decreases up to 60 % from the pre-SPE values were observed in the upper stratosphere nearly a month after the events. Over several weeks the GOMOS observations showed the gradual descent of the NOx enhancements to lower altitudes. Measurements from years 2002-2006 were used to study polar winter NOx increases and their connection to energetic particle precipitation. NOx enhancements were found to occur in a good correlation with both increased high-energy particle precipitation and increased geomagnetic activity. The average wintertime polar NOx was found to have a nearly linear relationship with the average wintertime geomagnetic activity. The results from this thesis work show how important energetic particle precipitation from outside the atmosphere is as a source of NOx in the middle atmosphere, and thus its importance to the chemical balance of the atmosphere.

Factors influencing the downstream transport of sediment in the Lough Feeagh catchment, Burrishoole, Co. Mayo, Ireland

Research laboratories in the Burrishoole catchment have been the focus of salmonid research since 1955. One aspect of the research has been to monitor the number of salmon and sea trout migrating to sea as smolts and returning to the catchment as adults. In the early 1990s it became clear that the smolt output from the catchment had declined over the previous two decades. At about the same time the presence of fine particles of peat silt in the hatchery became increasingly apparent and led to a higher incidence of mortality of young fry. These observations and management difficulties led to a study of silt transport in the surface waters of the catchment, which is described in this article. The authors describe geology, soils, climate and hydrology of Burrishoole before examining the sediment deposition in Lough Feeagh.

Sand storms: CFD analysis of Reynolds stress and collision stress of particles near sand bed

Sand storm is a serious environmental threat to humans. Sand particles are transported by saltation and suspension, causing soil erosion in one place and deposition in another. In order to prevent and predict sand storms, the causes and the manners of particle motions must be studied in detail. In this paper a standard k-epsilon model is used for the gas phase simulation and the discrete element method (DEM) is used to predict the movements of particles using an in-house procedure. The data are summarized in an Eulerian-Eulerian regime after simulation to get the statistical particle Reynolds stress and particle collision stress. The results show that for the current case the Reynolds stress and the air shear stress predominate in the region 20-250 mm above the initial sand bed surface. However, in the region below 3 mm, the collision stress must be taken into account in predicting particle movement. (C) 2010 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Effects of soil type on leaching and runoff transport of rare earth elements and phosphorous in laboratory experiments

Through leaching experiments and simulated rainfall experiments, characteristics of vertical leaching of exogenous rare earth elements (REEs) and phosphorus (P) and their losses with surface runoff during simulated rainfall in different types of soils (terra nera soil, cinnamon soil, red soil, loess soil, and purple soil) were investigated. Results of the leaching experiments showed that vertical transports of REEs and P were relatively low, with transport depths less than 6 cm. The vertical leaching rates of REEs and P in the different soils followed the order of purple soil > terra nera soil > red soil > cinnamon soil > loess soil. Results of the simulated rainfall experiments (83 mm h(-1)) revealed that more than 92% of REEs and P transported with soil particles in runoff. The loss rates of REEs and P in surface runoff in the different soil types were in the order of loess soil > terra nera soil > cinnamon soil > red soil > purple soil. The total amounts of losses of REEs and P in runoff were significantly correlated.

A New Theory for Perpendicular Transport of Cosmic Rays

We present an improved nonlinear theory for the perpendicular transport of charged particles. This approach is based on an improved nonlinear treatment of field-line random walk in combination with a generalized compound diffusion model. The generalized compound diffusion model employed is more systematic and reliable, in comparison with previous theories. Furthermore, the theory shows remarkably good agreement with test-particle simulations and solar wind observations.

The transport of cosmic rays in self-excited magnetic turbulence

The process of diffusive shock acceleration relies on the efficacy with which hydromagnetic waves can scatter charged particles in the precursor of a shock. The growth of self-generated waves is driven by both resonant and non-resonant processes. We perform high-resolution magnetohydrodynamic simulations of the non-resonant cosmic ray driven instability, in which the unstable waves are excited beyond the linear regime. In a snapshot of the resultant field, particle transport simulations are carried out. The use of a static snapshot of the field is reasonable given that the Larmor period for particles is typically very short relative to the instability growth time. The diffusion rate is found to be close to, or below, the Bohm limit for a range of energies. This provides the first explicit demonstration that self-excited turbulence reduces the diffusion coefficient and has important implications for cosmic-ray transport and acceleration in supernova remnants.