Electroviscous Forces on a Charged Cylinder Moving Near a Charged Wall

The refined theory of the electroviscous lift forces is presented for the case when the separation distance between the particle and the wall is larger than the double-layer thickness. The theory is based on the lubrication approximation for motion of a long cylinder near a solid wall in creeping flow. The approximate analytical formula for the lift force valid for Pe相似文献   

MCTTFA applied to differential biomonitoring in Sado estuary region

Transplants of the epiphytic lichen Parmelia sulcata were suspended in nylon bags within a rectangle of 15 km wide and 25 km long on a grid 2.5 km'2.5 km in the Sado estuary region. The transplants were oriented towards the wind (F) and opposing the wind (T) and were collected after 3, 6 and 9 months of exposure. Samples were analyzed by INAA and PIXE. Source identification was made by Monte Carlo Target Transformation Factor Analysis (MCTTFA) using three different combinations of data (all data, F data and T data). Five factors were identified for all the combinations performed. For two factors, F and T differentiation was observed.     

Burn wood influence on outdoor air quality in a small village: Foros de Arr?o, Portugal

One Plus Sequential Air Sampler??Partisol was placed in a small village (Foros de Arr?o) in central Portugal to collect PM₁₀ (particles with an aerodynamic diameter below 10???m), during the winter period for 3?months (December 2009?CMarch 2010). Particles masses were gravimetrically determined and the filters were analyzed by instrumental neutron activation analysis to assess their chemical composition. The water-soluble ion compositions of the collected particles were determined by Ion-exchange Chromatography. Principal component analysis was applied to the data set of chemical elements and soluble ions to assess the main sources of the air pollutants. The use of both analytical techniques provided information about elemental solubility, such as for potassium, which was important to differentiate sources.     

Off-line chromatographic assessment of Fe(II) in seawater

The speciation of iron in seawater is receiving much attention worldwide, and several methods have been developed to measure its various chemical species. Although probably the most important in algal iron accumulation, Fe(II) is very unstable in seawater, is rapidly oxidised to Fe(III), thus the time between collection of the samples and the actual Fe(II) assessment may have significant impact on the obtained results. Especially for kinetic analysis, where radiotracer methods ask for off-line counting, waiting times should be taken into account.The present paper presents a model to account for waiting time in off-line Fe(II) assessment. The model comprises Fe(II) oxidation in a reducing environment (∼1 × 10⁻⁵ M Na₂SO₃ in filtered seawater) and binding to column-associated ferrozine, for use with ferrozine preloaded SepPak^® C₁₈ cartridges. The model is essentially based on mathematical treatment of transport in micro-vessels and uses known rate factors for the oxidation and reduction of Fe. In off-line chromatographic Fe(II) assessment, the model was shown to account for variances in Fe(II) recoveries ranging from 10 to 54%, and for waiting times ranging from 2 to 80 min. The presented data shows that waiting time resulted in underestimation up to a factor 10 as measured by direct recovery counting of loaded Fe(II). As excess amounts of ferrozine were used for these experiments, this underestimation will be mainly caused by the oxidation of ferrous iron during this waiting time. The data also suggests that time-modelling may account for all effects, thus permitting off-line counting of Fe(II) without loss of data quality.     

<Emphasis Type="Italic">Parmelia sulcata</Emphasis> lichen transplants positioning towards wind direction (Part I): precipitation volumes,total element deposition and lichen element content

Parmelia sulcata transplants were used in three different exposure systems, focused on three different influxes: free influx, horizontal influx and vertical influx. The total element deposition and the precipitation volumes were found to be positively correlated for Fe and Ni only. The element contents in lichen transplants and in total element deposition showed significant correlations for Ca, Fe and Mn in the free influx system and for Na, Ni and V in the horizontal influx system. No significant positive correlations were found for the vertical influx. The results indicate that, apart from response rates, the transplant positioning systems may have effects on element-specific net accumulation.     

Local and regional sources as given by aerosol measurements and biomonitoring at Sado estuary area, Portugal

Gent air samplers were used for air particulate matter sampling in Sado estuary area, separating fine and coarse fractions. Three sampling sites were chosen (Palmela, Faralh?o and Tróia), inside a 15 km × 25 km area at Setúba region, 50 km south of Lisbon, Portugal. Transplants of Parmelia sulcata Taylor were suspended in nylon bags within the same area following a 2.5 km × 2.5 km grid, during the same period as the aerosol collection. Both lichen transplants and filters were analysed by k ₀-INAA. This work compares MCTTFA results given by the two air pollution monitoring procedures. The main differences concern a physiological factor in biomonitors and a better definition of traffic and re-suspension by aerosols.     

Influence of meteorological conditions on PM<Subscript>2.5</Subscript> and PM<Subscript>2.5–10</Subscript> elemental concentrations on Sado estuary area,Portugal

Aerosol chemical composition data for PM_2.5 and PM_2.5–10 was acquired, in two sampling stations, at an industrialized area located in Sado Estuary. Two methods were used to have an insight on the origin of the particles: the comparison between the measurements obtained in the two sampling stations and the association between the wind direction and the element concentrations. Results showed that Ce, Fe, La, Sc, Sm, Na, Co and Se were associated with non-local sources whereas As, K, Sb, Zn, Hg, Br, Cr, Hf and U had a local origin.     

Two-temperature model for pulsed-laser-induced subsurface modifications in Si

We investigated the laser–material interaction during the production of laser-induced subsurface modifications in silicon with a numerical model. Such modifications are of interest for subsurface wafer dicing. To predict the shape of these modifications, a two-temperature model and an optical model were combined. We compared the model results with experimental data obtained by focusing laser pulses in the bulk of silicon wafers using a microscope objective. This comparison revealed a good agreement between the simulations and the experimental results. A parameter study was performed to investigate the effect of the laser wavelength, pulse duration and pulse energy on the formation of subsurface modifications. We found that both single- and multi-photon absorption may be used to produce subsurface modifications in silicon.     

Is there a future for biomonitoring of elemental air pollution? A review focused on a larger-scaled health-related (epidemiological) context

The present paper focuses on biomonitoring of elemental atmospheric pollution, which is reviewed in terms of larger-scaled biomonitoring surveys in an epidemiological context. Based on the literature information, today’s availability of solar-powered small air filter samplers and fibrous ion exchange materials is regarded as adequate or an even better alternative for biomonitor transplant materials used in small-scaled set-ups, but biomonitors remain valuable in larger-scaled set-ups and in unforeseen releases and accidental situations. In the latter case, in-situ biomonitoring is seen as the only option for a retrospective study: biomoniors are there before one even knows that they are needed. For biomonitoring, nuclear analytical techniques are discussed as key techniques, especially because of the necessary multi-element assessments in both source recognition and single-element interpretation. To live up to the demands in an epidemiological context, larger-scaled in-situ biomonitoring asks for large numbers of samples, and consequently, for large total sample masses, this all to ensure representation of both local situations and survey area characteristics. Possibly, this point should direct studies into new “easy-to-sample” biomonitor organisms, of which high masses and numbers may be obtained in field work, rather than continue with biomonitors such as lichens. This also means that both sample handling and processing are of key importance in these studies. To avoid problems in comparability of analytical general procedures in milling, homogenization and digestion of samples of large masses, the paper proposes to involve only few but high-quality laboratories in the total element assessment routines. In this respect, facilities that can handle large sample masses in the assessment of element concentrations are to be preferred. This all highlights the involvement of large-sample-volume nuclear facilities, which, however, should be upgraded and automated in their operation to ensure the necessary sample throughput in larger-scaled biomonitoring.