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‣ Curva de retenção na avaliação da qualidade física do solo; Soil water retention curve on evaluation of soil physical quality

Gimenes, Fernando Henrique Setti
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/01/2013 Português
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O solo é um importante recurso natural e a sua conservação é essencial para uma produção sustentável. A qualidade de um solo, por sua vez, pode ser definida como a capacidade deste em exercer sua função em um ecossistema e pode ser descrita por meio de parâmetros físicos, químicos e biológicos. Os atributos físicos do solo descrevem a organização de sua estrutura, de modo que esta é responsável pela movimentação e disponibilidade da solução do solo para as plantas e depende da dimensão, forma e arranjo de suas partículas sólidas e de seus poros. Portanto, a discussão dos mecanismos de movimento e retenção da água no solo é relevante na inferência da sua qualidade física. A curva de retenção da água no solo é o gráfico da umidade do solo em função do potencial mátrico da água no solo, a qual é uma ferramenta importante na avaliação da qualidade física do solo. No Brasil, os Latossolos são de grande importância, devido a sua extensão e potencial produtivo. Estes solos são muito intemperizados, com elevada estabilidade de agregados e podem ser originados a partir de materiais distintos, o que interfere na resposta física. Portanto, o objetivo geral deste trabalho foi avaliar a qualidade físico-hídrica do solo por meio da análise da curva de retenção da água em três Latossolos...

‣ Determination of pore size distribution in soybean seed coats by mercury porosimetry

La Scala, N.; Florentino, A. O.; Carvalho, N. M.
Fonte: Ista Publicador: Ista
Tipo: Artigo de Revista Científica Formato: 371-375
Português
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In this work we applied mercury porosimetry for the investigation of soybean seed coats. By using this method it was possible to determine the pore size distribution and also the pore size dispersion that is present in seed coats. The results showed that for the studied soybean genotype the seed coats had a characteristic pore diameter, but deviation of this size was not negligible. Finally, the results were confirmed by electron microscopy.

‣ Differences and similarities in the pore size distribution of soybean seed coats

La Scala, N.; Florentino, A. O.; Carvalho, N. M.
Fonte: Ista Publicador: Ista
Tipo: Artigo de Revista Científica Formato: 365-369
Português
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In this work we apply the mercury porosimetry technique to determine the pore size distribution in soybean seed coats of different varieties. The analyses show that the porosity of soybean seed coats is different when seeds of different genotypes are compared. This result points the possibility of using pore size distribution to varietal discrimination.

‣ Pore size evolution during sintering of ceramic oxides

Varela, José Arana; Whittemore, O. J.; Longo, Elson
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 177-189
Português
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This paper reviews the influence of particle size distribution, agglomerates, rearrangement, sintering atmospheres and impurities on the pore evolution of some commonly studied oxides. These factors largely affect sintering mechanisms due to modifications of diffusion coefficients or evaporation-condensation. Very broad particle size distribution leads to grain growth and agglomerates densify first. Rearrangement of particles due to neck asymmetry mainly in the early stage of sintering is responsible for a high rate of densification in the first minutes of sintering by collapse of large pores. Sintering atmospheres play an important role in both densification and pore evolution. The chemical interaction of water molecules with several oxides like MgO, ZnO and SnO2 largely affects surface diffusion. As a consequence, there is an increase in the rates of pore growth and densification for MgO and ZnO and in the rate of pore growth for SnO2. Carbon dioxide does not affect the rate of sintering of MgO but greatly affects both rates of pore growth and densification of ZnO. Oxygen concentration in the atmosphere can especially affect semiconductor oxides but significantly affects the rate of pore growth of SnO2. Impurities like chlorine ions increase the rate of pore growth in MgO due to evaporation of HCl and Mg(OH)Cl...

‣ Pore size distribution of unsupported SnO2 membranes prepared by sol-gel process - Code: EP21

de Souza Brito, Giancarlo Espósito; Pulcinelli, Sandra Helena; Santilli, Celso Valentim
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 575-579
Português
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Unsupported SnO2 membranes were prepared by sol-gel process and characterized by N2 adsorption-desorption isotherms and X-ray diffraction. Results show that the texture of dried samples does not change appreciably with the concentration of electrolyte. All of the pore size range used in ultrafiltration process was screened using sintering temperature between 300 and 700°C. © 1994 Kluwer Academic Publishers.

‣ Anisotropy of crystallite growth during sintering of SnO2 xerogels

Brito, G. E S; Pulcinelli, S. H.; Santilli, C. V.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 4087-4092
Português
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The crytallite and pore-size evolution during isothermal sintering (400 ≤ T ≤ 700°C) of SnO2 xerogels was studied by X-ray line broadening and nitrogen adsorption-desorption isotherms. The experimental results show a strong anisotropy of crystallite growth between [110] and [101] directions. The preferential growth at [101] is followed by an increase in the mean pore size, reduction of the specific surface area and invariance of total pore volume. This behaviour is typical of grain coalescence sintering. The kinetic analysis of experimental results suggests that the crystallite coalescence at [101] is governed by lattice diffusion. The strong anisotropy of the growth causes pore-size distribution broadening, hindering the macroscopic shrinkage of the compact during sintering. © 1996 Chapman & Hall.

‣ Dynamic mechanical behavior of starch-based scaffolds in dry and physiologically simulated conditions : effect of porosity and pore size

Ghosh, Satyabrata; Gutierrez, Victor; Fernández, Carolina; Rodriguez-Perez, M. A.; Viana, J. C.; Reis, R. L.; Mano, J. F.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
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The three-dimensional scaffolds of a blend of starch and poly(L-lactic) acid, SPLA70, were produced using compression molding of polymer/salt mixture followed by leaching of salt. One series of scaffolds were prepared with varying polymer-to-salt ratio while keeping the salt size constant, and the other series of scaffolds were prepared with varying salt sizes while keeping the polymer-to-salt ratio constant. The X-ray microcomputed tomography and scanning electron microscopy assay were used to analyze the porous morphologies, porosity and distribution of porosity of the porous scaffolds. Salt-free and integrated SPLA70 scaffolds with porosities ranging from 74% to 82% and pore sizes of 125–250 to 500–1000 lm can be fabricated using the present fabrication technique. The water uptake of the SPLA70 scaffolds increases with increasing porosities and also with increasing pore size. In dry state, the storage modulus decreases with increasing porosity and also with increasing pore size. The normalized modulus values are related to normalized density of the scaffolds by a power-law function with an exponent between 2 and 3. For the immersed scaffolds under physiological conditions, the storage modulus was less dependent on porosity and pore size. However...

‣ Analysis of Filter Performance as function of Particle Diameter, Filter Internal Surface and Filter Pore Size Distribution

Reis, A.; Miguel, A. F.; Aydin, M.
Fonte: CGE-UEvora Publicador: CGE-UEvora
Tipo: Artigo de Revista Científica
Português
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It is well known that filter performance drops to a minimum corresponding to a particle diameter that is a characteristic of each filter. We analyse this behaviour in light of two competing trends: adhesion of particles onto the internal surface and particle trapping at the interstices. The calculations show that particle adhesion to the internal surface decreases with particle diameter while particle trapping becomes less effective as particle diameter decreases. Therefore, the filter efficiency is found to have a minimum corresponding to a specific particle diameter that depends on the filter internal surface area and on the filter pore size distribution. Filter efficiency is found to drop significantly at a time corresponding to filter half lifetime.

‣ Size exclusion during particle suspension transport in porous media: stochastic and averaged equations

Santos,A.; Bedrikovetsky,P.
Fonte: Sociedade Brasileira de Matemática Aplicada e Computacional Publicador: Sociedade Brasileira de Matemática Aplicada e Computacional
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2004 Português
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A pore scale population balance model is formulated for deep bed filtration of stable particulate suspensions in porous media. The particle capture from the suspension by the rock occurs by the size exclusion mechanism. The equations for particle and pore size distributions have been derived from the stochastic Master equation. The model proposed is a generalization of stochastic Sharma-Yortsos equations – it accounts for particle flux reduction due to restriction for large particles to move via small pores. Analytical solution for low particle concentration is obtained for any particle and pore size distributions. The averaged macro scale equations, derived from the stochastic pore scale model, significantly differ from the traditional deep bed filtration model.

‣ FRACTAL SCALING OF PARTICLE AND PORE SIZE DISTRIBUTIONS AND ITS RELATION TO SOIL HYDRAULIC CONDUCTIVITY

BACCHI,O.O.S.; REICHARDT,K.; VILLA NOVA,N.A.
Fonte: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" Publicador: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/1996 Português
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Fractal scaling has been applied to soils, both for void and solid phases, as an approach to characterize the porous arrangement, attempting to relate particle-size distribution to soil water retention and soil water dynamic properties. One important point of such an analysis is the assumption that the void space geometry of soils reflects its solid phase geometry, taking into account that soil pores are lined by the full range of particles, and that their fractal dimension, which expresses their tortuosity, could be evaluated by the fractal scaling of particle-size distribution. Other authors already concluded that although fractal scaling plays an important role in soil water retention and porosity, particle-size distribution alone is not sufficient to evaluate the fractal structure of porosity. It is also recommended to examine the relationship between fractal properties of solids and of voids, and in some special cases, look for an equivalence of both fractal dimensions. In the present paper data of 42 soil samples were analyzed in order to compare fractal dimensions of pore-size distribution, evaluated by soil water retention curves (SWRC) of soils, with fractal dimensions of soil particle-size distributions (PSD), taking the hydraulic conductivity as a standard variable for the comparison...

‣ Software Image J to study soil pore distribution

Passoni,Sabrina; Borges,Fernando da Silva; Pires,Luiz Fernando; Saab,Sérgio da Costa; Cooper,Miguel
Fonte: Editora da Universidade Federal de Lavras Publicador: Editora da Universidade Federal de Lavras
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2014 Português
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In the soil science, a direct method that allows the study of soil pore distribution is the bi-dimensional (2D) digital image analysis. Such technique provides quantitative results of soil pore shape, number and size. The use of specific softwares for the treatment and processing of images allows a fast and efficient method to quantify the soil porous system. However, due to the high cost of commercial softwares, public ones can be an interesting alternative for soil structure analysis. The objective of this work was to evaluate the quality of data provided by the Image J software (public domain) used to characterize the voids of two soils, characterized as Geric Ferralsol and Rhodic Ferralsol, from the southeast region of Brazil. The pore distribution analysis technique from impregnated soil blocks was utilized for this purpose. The 2D image acquisition was carried out by using a CCD camera coupled to a conventional optical microscope. After acquisition and treatment of images, they were processed and analyzed by the software Noesis Visilog 5.4® (chosen as the reference program) and ImageJ. The parameters chosen to characterize the soil voids were: shape, number and pore size distribution. For both soils, the results obtained for the image total porosity (%)...

‣ A solid with a hierarchical tetramodal micro-meso-macro pore size distribution

Ren, Yu; Ma, Zhen; Morris, Russell E.; Liu, Zheng; Jiao, Feng; Dai, Sheng; Bruce, Peter G.
Fonte: Nature Pub. Group Publicador: Nature Pub. Group
Tipo: Artigo de Revista Científica
Publicado em 14/06/2013 Português
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Porous solids have an important role in addressing some of the major energy-related problems facing society. Here we describe a porous solid, α-MnO2, with a hierarchical tetramodal pore size distribution spanning the micro-, meso- and macro pore range, centred at 0.48, 4.0, 18 and 70 nm. The hierarchical tetramodal structure is generated by the presence of potassium ions in the precursor solution within the channels of the porous silica template; the size of the potassium ion templates the microporosity of α-MnO2, whereas their reactivity with silica leads to larger mesopores and macroporosity, without destroying the mesostructure of the template. The hierarchical tetramodal pore size distribution influences the properties of α-MnO2 as a cathode in lithium batteries and as a catalyst, changing the behaviour, compared with its counterparts with only micropores or bimodal micro/mesopores. The approach has been extended to the preparation of LiMn2O4 with a hierarchical pore structure.

‣ Impact of Matric Potential and Pore Size Distribution on Growth Dynamics of Filamentous and Non-Filamentous Soil Bacteria

Wolf, Alexandra B.; Vos, Michiel; de Boer, Wietse; Kowalchuk, George A.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 31/12/2013 Português
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The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to what extent, filamentous bacteria may also display similar advantages over non-filamentous bacteria in soils with low hydraulic connectivity. In addition to allowing for microbial interactions and competition across connected micro-sites, water films also facilitate the motility of non-filamentous bacteria. To examine these issues, we constructed and characterized a series of quartz sand microcosms differing in matric potential and pore size distribution and, consequently, in connection of micro-habitats via water films. Our sand microcosms were used to examine the individual and competitive responses of a filamentous bacterium (Streptomyces atratus) and a motile rod-shaped bacterium (Bacillus weihenstephanensis) to differences in pore sizes and matric potential. The Bacillus strain had an initial advantage in all sand microcosms, which could be attributed to its faster growth rate. At later stages of the incubation, Streptomyces became dominant in microcosms with low connectivity (coarse pores and dry conditions). These data...

‣ Evaluation of methods for determining the pore size distribution and pore-network connectivity of porous carbons

Cai, Q.; Buts, A.; Biggs, M.; Seaton, N.
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: Artigo de Revista Científica
Publicado em //2007 Português
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The pore size distribution (PSD) and the pore-network connectivity of a porous material determine its properties in applications such as gas storage, adsorptive separations, and catalysis. Methods for the characterization of the pore structure of porous carbons are widely used, but the relationship between the structural parameters measured and the real structure of the material is not yet clear. We have evaluated two widely used and powerful characterization methods based on adsorption measurements by applying the methods to a model carbon which captures the essential characteristics of real carbons but (unlike a real material) has a structure that is completely known. We used three species (CH4, CF4, and SF6) as adsorptives and analyzed the results using an intersecting capillaries model (ICM) which was modeled using a combination of Monte Carlo simulation and percolation theory to obtain the PSD and the pore-network connectivity. There was broad agreement between the PSDs measured using the ICM and the geometric PSD of the model carbon, as well as some systematic differences which are interpreted in terms of the pore structure of the carbon. The measured PSD and connectivity are shown to be able to predict adsorption in the model carbon...

‣ Erratum: Size exclusion during particle suspension transport in porous media: stochastic and averaged equations

Santos, A.; Bedrikovetski, P.
Fonte: Birkhauser Boston Inc Publicador: Birkhauser Boston Inc
Tipo: Artigo de Revista Científica
Publicado em //2005 Português
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A pore scale population balance model is formulated for deep bed filtration of stable particulate suspensions in porous media. The particle capture from the suspension by the rock occurs by the size exclusion mechanism. The equations for particle and pore size distributions have been derived from the stochastic Master equation. The model proposed is a generalization of stochastic Sharma-Yortsos equations – it accounts for particle flux reduction due to restriction for large particles to move via small pores. Analytical solution for low particle concentration is obtained for any particle and pore size distributions. The averaged macro scale equations, derived from the stochastic pore scale model, significantly differ from the traditional deep bed filtration model.; A. Santos and P. Bedrikovetsky

‣ A novel and consistent method (TriPOD) to characterize an arbitrary porous solid for its accessible volume, accessible geometrical surface area and accessible pore size

Herrera, L.F.; Fan, C.; Do, D.D.; Nicholson, D.
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
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88.51284%
We present an improved Monte Carlo integration method to calculate the accessible pore size distribution of a porous solid having known configuration of solid atoms. The pore size distribution obtained with the present method is consistent with the accessible volume and the accessible geometric surface area presented in previous publications (Do and Do, in J. Colloid Interface Sci. 316(2):317–330, 2007; Do et al. in Adsorpt. J., 2010). The accessible volume, accessible geometrical surface area and the pore size distribution method construct an unambiguous and robust single framework to characterize porous solids. This framework is based on the derivation of the space accessible to the center of mass of a probe molecule. The accessible pore size presented is an absolute quantity in the sense that a zero value is possible. We present the entire framework of this characterization method and compare the improved method with the one presented previously for a set of porous solids such as graphitic slit pores, defective slit pores, bundle of carbon nanotubes, zeolite and some metal organic frameworks.; L. F. Herrera, Chunyan Fan, D. D. Do, D. Nicholson

‣ Yield stress fluids method to determine the pore size distribution of a porous medium

OUKHLEF, Aimad; CHAMPMARTIN, Stéphane; AMBARI, Abdelhak
Fonte: ELSEVIER Publicador: ELSEVIER
Português
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In this paper a new method is presented in order to determine the pore size distribution in a porous medium. This original technique uses the rheological properties of some non-Newtonian yield stress fluids flowing through the porous sample. This technique is based on the capillary bundle model (like the other classical methods) which, despite its apparent simplicity, is capable of properly characterizing the percolating pore size distribution. Then this distribution can be simply obtained from the measurement of the total flow rate as a function of the imposed pressure gradient. The present technique is successfully tested analytically and numerically for usual pore size distributions such as the Gaussian mono and multimodal distributions, using Bingham and Casson fluids. The technique can also be extended to any yield stress fluid and any kind of distribution.

‣ Pore size distribution in soils irrigated with sodic water and wastewater; Distribuição de poros em solos irrigados com água salina e com água residuária

GONÇALVES, Roberta Alessandra Bruschi; GLOAGUEN, Thomas Vincent; FOLEGATTI, Marcos Vinicius; LIBARDI, Paulo Leonel; LUCAS, Yves; MONTES, Célia Regina
Fonte: Sociedade Brasileira de Ciência do Solo Publicador: Sociedade Brasileira de Ciência do Solo
Tipo: Artigo de Revista Científica
Português
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Soil porosity, especially pore size distribution, is an important controlling factor for soil infiltration, hydraulic conductivity, and water retention. This study aimed to verify the effect of secondary-treated domestic wastewater (STW) on the porosity of a sandy loam Oxisol in the city of Lins, state of São Paulo, Brazil. The two-year experiment was divided into three plots: soil cultivated with corn and sunflower and irrigated with STW, soil cultivated and irrigated with sodic groundwater, and non-irrigated and non-cultivated soil (control). At the end of the experiment, undisturbed core samples were sampled from 0 to 2.0 m (8 depths). The water retention curves were obtained by tension plates and Richard's pressure plate apparatus, and the pore size distribution inferred from the retention curves. It was found that irrigation with treated wastewater and treated groundwater led to a decrease in microporosity (V MI), defined as the pore class ranging from 0.2 to 50 μm diameter. On the other hand, a significant increase in cryptoporosity (V CRI) (< 0.2 μm) was identified throughout the soil profile. The presence of Na+ in both waters confirmed the role of this ion on pore size distribution and soil moisture (higher water retention).; A porosidade do solo...

‣ Pore size distribution in soils irrigated with sodic water and wastewater

Gonçalves,Roberta Alessandra Bruschi; Gloaguen,Thomas Vincent; Folegatti,Marcos Vinicius; Libardi,Paulo Leonel; Lucas,Yves; Montes,Célia Regina
Fonte: Sociedade Brasileira de Ciência do Solo Publicador: Sociedade Brasileira de Ciência do Solo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 Português
Relevância na Pesquisa
68.382793%
Soil porosity, especially pore size distribution, is an important controlling factor for soil infiltration, hydraulic conductivity, and water retention. This study aimed to verify the effect of secondary-treated domestic wastewater (STW) on the porosity of a sandy loam Oxisol in the city of Lins, state of São Paulo, Brazil. The two-year experiment was divided into three plots: soil cultivated with corn and sunflower and irrigated with STW, soil cultivated and irrigated with sodic groundwater, and non-irrigated and non-cultivated soil (control). At the end of the experiment, undisturbed core samples were sampled from 0 to 2.0 m (8 depths). The water retention curves were obtained by tension plates and Richard's pressure plate apparatus, and the pore size distribution inferred from the retention curves. It was found that irrigation with treated wastewater and treated groundwater led to a decrease in microporosity (V MI), defined as the pore class ranging from 0.2 to 50 μm diameter. On the other hand, a significant increase in cryptoporosity (V CRI) (< 0.2 μm) was identified throughout the soil profile. The presence of Na+ in both waters confirmed the role of this ion on pore size distribution and soil moisture (higher water retention).

‣ The use of gel chromatography for the determination of sizes and relative molecular masses of proteins. Interpretation of calibration curves in terms of gel-pore-size distribution.

le Maire, M; Ghazi, A; Møller, J V; Aggerbeck, L P
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/04/1987 Português
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The separation of proteins by gel-exclusion chromatography has been explained in terms of partitioning of the macromolecules within the gel by a distribution of pores of various radii. The assumption that the distribution of pore sizes is Gaussian has led to the prediction of a linear relationship between the molecular Stokes radius (RS) of the protein and the function erf-1 (1-KD), where KD is the partition coefficient [Ackers (1967) J. Biol. Chem. 242, 3237-3238]. Since careful calibrations of classical (agarose and dextran) gels and h.p.l.c. gels have shown that such a linear relationship is not verified experimentally over a wide range of native protein sizes, we have reinvestigated the model of Ackers (above reference). We show that Ackers' (above reference) derivation is not valid except for a particular Gaussian distribution of pore sizes centred at the origin. Relaxation of this restriction to allow for other types of Gaussian distributions cannot account for the non-linear calibration curves that we have obtained. Instead we show that the pore-size distribution can be calculated from the experimentally determined function KD = f(RS) and that this distribution is bimodal (non-Gaussian). One distribution is centred below 2 nm...