Search

The purpose of this study was to compare swing time and golf club angle parameters during golf swings using three, two dimensional (2D) low cost, Augmented-Video-based-Portable-Systems (AVPS) (Kinovea, SiliconCoach Pro, SiliconCoach Live). Twelve right-handed golfers performed three golf swings whilst being recorded by a high-speed 2D video camera. Footage was then analysed using AVPS-software and the results compared using both descriptive and inferential statistics. There were no significant differences for swing time and the golf phase measurements between the 2D and 3D software comparisons. In general, the results showed a high Intra class Correlation Coefficient (ICC > 0.929) and Cronbach’s Coefficient Alpha (CCA > 0.924) reliability for both the kinematic and temporal parameters. The inter-rater reliability test for the swing time and kinematic golf phase measurements on average were strong. Irrespective of the AVPS software investigated, the cost effective AVPS can produce reliable output measures that benefit golf analyses.

BACKGROUND: Electromyographic systems are widely used in scientific and clinical practice. The reproducibility and reliability of these measures are crucial when conducting scientific research and collecting experimental data. OBJECTIVE: To test the reliability of surface electromyography signals from both the Flexor Digitorum Superficialis (FDS) and Extensor Carpi Radialis Brevis (ECRB) muscles of both the left and right arms during an individual, static multi-planar maximum voluntary contraction handgrip task using the Myon 320 system (Myon AG, Switzerland). METHODS: Eight right-handed male participants performed two maximal handgrip tests in five separate wrist positions using both hands. Muscle activity was recorded from both forearms. Reliability was measured using the Standard Error of Measurement (SEM), Coefficient of Variation (CV) and Intra-class correlation coefficients. Wrist joint position correlations within and between the FDS and ECRB muscle activities were also analysed. RESULTS: Absolute reliability was shown across all positions for both hands with CV and SEM recorded at below 10%. The output measures indicate that the Myon 320 system (Myon AG, Switzerland) produces good to fair reliability when assessing forearm muscle activity. Correlations in the left FDS muscles were negative. Correlations between the left ECRB and left FDS muscles were variable but positive between the right ECRB and right FDS muscles. CONCLUSIONS: The data sets retrieved from all participants were reliably evaluated. Wrist position correlations within and between the FDS and ECRB muscles may have been influenced by hand dominance. The findings demonstrate that the methods and systems outlined in this study can be used reliably in future research.

Animal communication has long been thought to be subject to pressures and constraints associated with social relationships. However, our understanding of how the nature and quality of social relationships relates to the use and evolution of communication is limited by a lack of directly comparable methods across multiple levels of analysis. Here, we analysed observational data from 111 wild groups belonging to 26 non-human primate species, to test how vocal communication relates to dominance style (the strictness with which a dominance hierarchy is enforced, ranging from 'despotic' to 'tolerant'). At the individual-level, we found that dominant individuals who were more tolerant vocalized at a higher rate than their despotic counterparts. This indicates that tolerance within a relationship may place pressure on the dominant partner to communicate more during social interactions. At the species-level, however, despotic species exhibited a larger repertoire of hierarchy-related vocalizations than their tolerant counterparts. Findings suggest primate signals are used and evolve in tandem with the nature of interactions that characterize individuals' social relationships. Publisher PDF

For over a half a century, researchers have been aware of the fact that the physical and chemical characteristics of microenvironments in soils strongly influence the activity, growth and metabolism of microorganisms. However, many aspects of the effect of soil physical characteristics, such as the pore geometry, remain poorly understood. Therefore, the objective of the present research was to determine the influence of soil pore characteristics on the spread of bacteria, observed at the scale relevant to microbes. Pseudomonas fluorescens was introduced in columns filled with 1–2 mm soil aggregates, packed at different bulk densities. Soil microcosms were scanned at 10.87 μm voxel resolution using X‐ray computed tomography (CT) to characterize the geometry of pores. Thin sections were prepared to determine the spread and colonization of bacteria. The results showed that average bacterial cell density was 174 cells mm⁻² in soil with bulk density of 1.3 g cm⁻³ and 99 cells mm⁻² in soil with bulk density of 1.5 g cm⁻³. Soil porosity and solid‐pore interfaces influence the spread of bacteria and their colonization of the pore space at lower bulk density, resulting in relatively higher bacterial densities in larger pore spaces. The study also demonstrates that thin sectioning of resin‐impregnated soil samples can be combined with X‐ray CT to visualize bacterial colonization of a 3D pore volume. This research therefore represents a significant step towards understanding how environmental change and soil management impact bacterial diversity in soils. HIGHLIGHTS: We used a quantitative approach to study bacterial spread in soil at scales relevant to microbes. The rate of pseudomonas spread decreased with increased bulk density of soil. Soil porosity and soil‐pore interface influence Pseudomonas in lower bulk density soil. Soil structure with different pore characteristics effects spread and activity of bacteria in soil.

Part 2: Cybersecurity Knowledge Within the Organisation; International audience; Organizations can struggle to cope with the rapidly advancing threat landscape. A cyber threat intelligence (CTI) function broadly aims to understand how threats operate to better protect the organization from future attacks. This seems like a natural step to take in hardening security. However, CTI is understood and experienced differently across organizations. To explore the value of this function this study used a qualitative method, guided by the Socio-Technical Framework, to understand how the CTI function is interpreted by organizations in South Africa. Thematic analysis was used to provide an in-depth view of how each organization implemented its CTI function and what benefits and challenges they’ve experienced. Findings show that CTI tasks tend to be more manual and resource-intensive, but these challenges can be resolved through automation. It was noted that only larger organizations seem to have the budget and resources available to implement the CTI function, whereas smaller organizations put more reliance on tools. It was observed that skills for the CTI function can be learned on the job, but that formal education provides a good foundation. The findings illustrate the value the CTI function can provide an organization but also the challenges, thereby enabling other organizations to improve preparation before such a function is adopted.

n/a – Critical survey essay retheorising the concept of 'affordance' in digital media context. Lead article in a special issue on the topic, co-edited by the authors for the journal Media Theory.

Part 3: Southern-Driven Human-Computer Interaction; International audience; Human-Computer Interaction for Development (HCI4D) research aims to maximise the usability of interfaces for interacting with technologies designed specifically for under-served, under-resourced, and under-represented populations. In this paper, we provide a snapshot of Southern African HCI4D research against the background of the global HCI4D research landscape. We commenced with a systematic literature review of HCI4D (2010–2017) then surveyed Southern African researchers working in the area. The contribution is to highlight the context-specific themes and challenges that emerged from our investigation.

International audience; Computer networks are ubiquitous and growing exponentially, with a predicted 50 billion devices connected by 2050. This tremendous growth dramatically increases the attack surface of both private and public networks. These attacks often influence the behaviour of the system, leading to the detection of the attack. In this manuscript we model the path of an attack through the network by graphs. The model developed aims to better integer attackers intentions. Using the data produced by 5 honeypots, we apply our model. The preliminary results show that the approach is useful to rapidly detect anomalies in the experiment dataset.

Soils deliver the regulating ecosystem services of water infiltration and distribution, which can be controlled bymacropores. Parameterizing macropore hydraulic properties is challenging due to the lack of direct measurementmethods. With tension-disc infiltrometry hydraulic properties near saturation can be measured.Differentiating between hydrologically active and non-active pores, at a given water potential, indirectly assessesmacropore continuity. Water flow through macropores is controlled by macropore size distribution, tortuosity,and connectivity, which can be directly derived by X-ray computed tomography (CT). Our objective was toparameterize macropore hydraulic properties based on the imaged macropore network of three horizons of anAndosol and a Gleysol. Hydraulic conductivity Kunsat was derived from infiltration measurements. Soil cores fromthe infiltration areas were scanned with X-ray CT. Kunsat was significantly higher in the Andosol than in theGleysol at all water potentials, and decreased significantly with depth in both soils. The in situ measurementsguided the definition of new macroporosity parameters from the X-ray CT reconstructions. For the Andosol,Kunsat was best predicted using the imaged-limited macroporosity. A low total macroporosity, coupled with ahigh macropore density, indicated the abundance of smaller macropores, leading to homogeneous matrix flux.Imaged macropores were not well connected. In contrast, the Gleysol had a bi-modal macropore system with fewvery large, but well-connected macropores. Kunsat was best predicted using the imaged macroporosity consistingonly of macropores with diameters between 0.75 and 3 mm. Our research demonstrates that linking traditionalsoil physical measurements with soil-visualization techniques has a huge potential to improve parameterizingmacropore hydraulic properties. The relevance of the relationships found in this study for larger scales and othersoil types still needs to be tested, for example by a multi-scale investigation including a much wider range ofdifferent soils.

Soil structure provides a home to large numbers of microorganisms offering them a food base, support, accessto water, air and nutrients and protection from predators. To be able to function, soils need to deliver theseessential requirements for life, at micro-habitat scales. Soil structure is the soil characteristic that makes thispossible. Therefore, soil structure holds the key to life in soil, regulates many ecosystem services and ultimatelyunderpins sustainable life on Earth. Despite this, the exact way in which soil structure exerts its control is notfully understood and considered to be too complex to be explicitly included in modelling of key processes suchas SOM dynamics.In this study we ask: can we develop a predictive framework for fungal ecology in heterogeneous soil thatbridges scales, and what benefits would it bring?To address this question we developed a model that considers fungal interactions at scales directly relevant tothe organisms (micro-meters) in order to predict ecosystem services, such as the evolution of CO2, as anemergent property of these interactions. The model is based on fungal traits, and explores through scenariomodelling how these impact upon exploration of pore networks as determined by X-ray CT, and how this isaffected by the location of particulate organic matter and the distribution of water within the pore space. Themodel predicted two important behaviours that are not captured by other models: (i) the evolution of CO2increases in a non-linear way with increasing organic matter content. This response suggests a criticalbehaviour could be expected in microbial processes involved in the decomposition of SOM; (ii) the sameamount of SOM in a soil sample (e.g. represented as a bulk property) can lead to substantial different CO2evolutions, predicted to differing by a factor 200, depending on the spatial distribution and accessibility withinthe soil structure. This is the first modelling framework that is capable of combining fungal dynamics instructured soil with SOM dynamics and evolution of CO2. The advantage of the modelling approach is thatscenarios can be rapidly explored beyond what is experimentally tractable, and as such can explore parameterspaces where soil functioning and biodiversity may be resilient to change, and can guide further experimentaltesting.

Simplified experimental systems, often referred to as microcosms, have played a central role in the development of modern ecological thinking on issues ranging from competitive exclusion to examination of spatial resources and competition mechanisms, with important model-driven insights to the field. It is widely recognized that soil architecture is the key driver of biological and physical processes underpinning ecosystem services, and the role of soil architecture and soil physical conditions is receiving growing interest. The difficulty to capture the architectural heterogeneity in microcosms means that we typically disrupt physical architecture when collecting soils. We then use surrogate measures of soil architecture such as aggregate size distribution and bulk-density, in an attempt to recreate conditions encountered in the field. These bulk-measures are too crude and do not describe the heterogeneity at microscopic scales where microorganisms operate. In the current paper we therefore ask the following questions: (i) To what extent can we control the pore geometry at microscopic scales in microcosm studies through manipulation of common variables such as density and aggregate size?; (ii) What is the effect of pore geometry on the growth and spread dynamics of bacteria following introduction into soil? To answer these questions, we focus on Pseudomonas sp. and Bacillus sp. We study the growth of populations introduced in replicated microcosms packed at densities ranging from 1.2 to 1.6 g cm−3, as well as packed with different aggregate sizes at identical bulk-density. We use X-ray CT and show how pore geometrical properties at microbial scales such as connectivity and solid-pore interface area, are affected by the way we prepare microcosms. At a bulk-density of 1.6 g cm−3 the average number of Pseudomonas was 63% lower than at a bulk-density of 1.3 g cm−3. For Bacillus this reduction was 66%. Depending on the physical conditions, bacteria in half the samples took between 1.62 and 9.22 days to spread 1.5 cm. Bacillus did spread faster than Pseudomonas and both did spread faster at a lower bulk-density. Our results highlight the importance that soil physical properties be considered in greater detail in soil microbiological studies than is currently the case.

The pore size distribution (PSD) of the void space is widely used to predict a range of processes in soils. Recent advances in X-ray computed tomography (CT) now afford novel ways to obtain exact data on pore geometry, which has stimulated the development of algorithms to estimate the pore size distribution from 3D data sets. To date there is however no clear consensus on how PSDs should be estimated, and in what form PSDs are best presented. In this article, we first review the theoretical principles shared by the various methods for PSD estimation. Then we select methods that are widely adopted in soil science and geoscience, and we use a robust statistical method to compare their application to synthetic image samples, for which analytical solutions of PSDs are available, and X-ray CT images of soil samples selected from different treatments to obtain wide ranging PSDs. Results indicate that, when applied to the synthetic images, all methods presenting PSDs as pore volume per class size (i.e., Avizo, CTAnalyser, BoneJ, Quantim4, and DTM), perform well. Among them, the methods based on Maximum Inscribed Balls (Bone J, CTAnalyser, Quantim4) also produce similar PSDs for the soil samples, whereas the Delaunay Triangulation Method (DTM) produces larger estimates of the pore volume occupied by small pores, and Avizo yields larger estimates of the pore volume occupied by large pores. By contrast, the methods that calculate PSDs as object population fraction per volume class (Avizo, 3DMA, DFS-FIJI) perform inconsistently on the synthetic images and do not appear well suited to handle the more complex geometries of soils. It is anticipated that the extensive evaluation of method performance carried out in this study, together with the recommendations reached, will be useful to the porous media community to make more informed choices relative to suitable PSD estimation methods, and will help improve current practice, which is often ad hoc and heuristic.

Accounting for microbial habitats in modeling soil organic matter dynamics. EGU 2017, European Geophysical Union General Assembly 2017

The extreme heterogeneity of soils constituents, architecture and inhabitants at the microscopic scale is increasingly recognized. Microbial communities exist and are active in a complex 3-D physical frame-work of mineral and organic particles defining pores of various sizes, more or less inter-connected. This results in a frequent spatial disconnection between soil carbon, energy sources and the decomposer organisms and a variety of microhabitats that are more or less suitable for microbial growth and activity. However, current biogeochemical models account for C dynamics at the macroscale (cm, m) and consider time and spatially averaged relationships between microbial activity and soil characteristics. Different modelling approaches have intended to account for this microscale heterogeneity, based either on considering aggregates as surrogates for microbial habitats, or pores. Innovative modelling approaches are based on an explicit representation of soil structure at the fine scale, i.e. at μm to mm scales: pore architecture and their saturation with water, localization of organic resources and of microorganisms. Three recent models are presented here, that describe the hetero-trophic activity of either bacteria or fungi and are based upon different strategies to represent the complex soil pore system (Mosaic, LBios and μFun). These models allow to hierarchize factors of mi-crobial activity in soil’s heterogeneous architecture. Present limits of these approaches and challenges are presented, regarding the extensive information required on soils at the microscale and to up-scale microbial functioning from the pore to the core scale. Accounting for microbial habitats in modelling soil organic matter dynamics can be based on an explicit representation for the microorganisms’environment.

Aims This study discusses the effect of phenolic compounds extracted from brown seaweed (phlorotannins) on mixed microbial cultures found in anaerobic systems. Methods and Results Assays were conducted with phloroglucinol as the nonpolymerized form of phlorotannin and with phlorotannins extracted from the brown seaweed Laminaria digitata. Electron micrographs revealed that phlorotannins induce significant extra- and intracellular effects upon cells, with the disruption of cell membranes observed with most micro-organisms. Microscopy results were further confirmed by cell membrane leakage assays demonstrating that phloroglucinol strongly affects cell membrane permeability. However, cell membrane leakage could not be observed with phlorotannins as the cell suspension immediately started to coagulate and impaired spectrophotometric measurements. Conclusions Results suggest that the bactericidal activity of phlorotannins is a function of the level of polymerization of the compounds. By monitoring intermediary compounds during the anaerobic digestion of phlorotannins, it was also found that higher energy consumption is required by micro-organisms for survival under stress induced by phlorotannins. Significance and Impact of the Study The successful anaerobic degradation of brown seaweed is thus likely to be dependant on the concentration of phenolic compounds present and their bactericidal effect on micro-organisms. This is the first article to posit a probable mode of action for the antimicrobial effect of phlorotannins.

conference abstractconference abstract; Recently, innovative modeling tools have been developed to describe the physico-chemical processes occurring in soil pores at scales directly relevant to microorganisms. Modelling efforts have attempted to understand how microbial processes such as decomposition or competition among species are affected by diffusion in 2-D or 3-D environments. Most of these models use a virtual representative pore network that can have the same features as soil pores with regular lattice grid. The most recent and innovative of these models use real images of soil structure from binarized 3D images. These models are able to simulate microbial degradation although microorganisms and organic matter are placed at different locations in the pore space. Then, the encounter of nutrients and microorganisms is achieved through the implementation of the diffusion process of the soluble substrates in the connected water-filled space. The high computational demand of this type of approach restricts its applicability to small-scale systems, typically in the order of micrometers or millimeters. The numerical techniques used to solve the equations include the lattice Boltzmann method, algorithmic methods and finite element methods. Most of these models have not yet been tested with experimental data because of the difficulties of investigating such small scales. On the other hand, many experimental results developed at the core scale have showed the importance of soil microbial habitat and especially how physical characteristics (pore sizes, connectivity) control the decomposition of organic substrates via their accessibility by microorganisms. The general question we have now to answer is whether information on the spatial heterogeneity of soils at the microscale can be used to predict the processes observed at the macroscale in soils.

absent

There is currently a significant need to improve our understanding of the factors that control a number of critical soil processes by integrating physical, chemical and biological measurements on soils at microscopic scales to help produce 3D maps of the related properties. Because of technological limitations, most chemical and biological measurements can be carried out only on exposed soil surfaces or 2-dimensional cuts through soil samples. Methods need to be developed to produce 3D maps of soil properties based on spatial sequences of 2D maps. In this general context, the objective of the research described here was to develop a method to generate 3D maps of soil chemical properties at the microscale by combining 2D SEM-EDX data with 3D X-ray computed tomography images. A statistical approach using the regression tree method and ordinary kriging applied to the residuals was developed and applied to predict the 3D spatial distribution of carbon, silicon, iron, and oxygen at the microscale. The spatial correlation between the X-ray grayscale intensities and the chemical maps made it possible to use a regression-tree model as an initial step to predict the 3D chemical composition. For chemical elements, e.g., iron, that are sparsely distributed in a soil sample, the regression-tree model provides a good prediction, explaining as much as 90% of the variability in some of the data. However, for chemical elements that are more homogenously distributed, such as carbon, silicon, or oxygen, the additional kriging of the regression tree residuals improved significantly the prediction with an increase in the R2 value from 0.221 to 0.324 for carbon, 0.312 to 0.423 for silicon, and 0.218 to 0.374 for oxygen, respectively. The present research develops for the first time an integrated experimental and theoretical framework, which combines geostatistical methods with imaging techniques to unveil the 3-D chemical structure of soil at very fine scales. The methodology presented in this study can be easily adapted and applied to other types of data such as bacterial or fungal population densities for the 3D characterization of microbial distribution.

Sequestration of C in soils has a major influence on climate change. Fungi play an important role in carbon de- composition and sequestration but the effect of soil structure and input of fresh organic matter (particulate organic matter POM) is still unclear. Fungi is predominant involved in cellulose decomposition and the priming effect (PE) where old SOM is decomposed by using fresh carbon as a source of energy. Information on how soil structure affects colonisation and decomposition of POM and SOM by fungi could help to get explain processes involved in carbon sequestration and CO2respiration. The objective of this study was to get a better understanding on the involvement of fungi in CO2 emissions arising from soils and to gain information on what factors in the soil are driving organic matter (OM) decomposition. Experimental data on fungal growth and carbon decomposition as affected by POM abundance and soil structure were obtained. Sterilised maize straw (1-2 mm2) and soil (

Predicting the response of soil organic matter microbial decomposition to moisture. EGU General Assembly 2014

Fungiplayanimportantroleincarbondecompositionandsequestrationbuthowsoilstructurecontrolstheiractivityisstillunclear.Soilstructureseemstobethekeyfactoronfungalspreadinsoil,inparticularthesize,continuityandairfilledfractionofsoilpores.PhysicalaccessoffungitoSOMwillalsodependontheabundanceofdecomposableSOM.Fungiarepredominantinvolvedinresiduescellwalldecompositionandintheprimingeffect(PE)whereoldsoilor‐ganicmatter(SOM)isdecomposedbyusingfreshcarbonasasourceofenergy.InformationonhowsoilstructureaffectscolonisationanddecompositionoffreshorganicmatterandSOMbyfungicouldhelptogetabetterunderstandingoftheprocessesinvolvedincarbonsequestrationandCO2respiration.TheobjectiveofthisstudywastotesthowfungalexplorationofthesoilandprobabilityofcontactbetweenOMandhyphaedeterminesCmineralization.Forthiswema‐nipulatedthesoilporesystembycompactionandtheabundanceofOMbyaddingfreshorganicmatterindifferentamounts.Maizestrawandsoilweresterilisedandmixedtodifferentratiosandpackedtotwodifferentbulkdensities(1.3and1.5Mgm‐3).Theinitialwatercontentineachsamplewasadjustedtoanairfilledporosityof17%.EachsamplewasinoculatedwithRhizocto‐niasolaniandstoredat20⁰C.CO2concentrationandtheisotopicratioofcarbonweremeasuredondayoveraperiodof42daystodistinguishtheC‐CO2originatingfromthefreshorganicmate‐rial(δ13C=12‰)andtheC‐CO2originatingfromthesoilorganicmatter(SOMδ13C=27‰).Fasterdecompositionrateswerefoundinthelesscompactedsoilsthaninverydensesoilasthefungalspreadisprobablyhinderedduetofewerporesthemyceliumcangrowthrough.GreateramountsofCCO2releasedfromSOMweremeasuredwhenlargeramountsoffreshorganicmat‐terwereaddedwithgreaterdifferencesinsoilsamplespackedto1.3Mgg‐3thaninsoilsamplespackedto1.5Mgg‐3,showingthattheabilityoffungitocolonizesoillimiteddecomposition.TheamountofC‐CO2producedpermgofC‐freshorganicmatterdecreasedastheirconcentrationincreased.TheadditionoffreshorganicmatterinducedapositiveprimingofSOM.Thesedatawillhelpustocalibrateanexistingmodelsoffungalgrowthinsoilinresponsetonativeandaddedsoilorganicmattertobetterunderstandtheroleoffungiincarbondecompositionandsequestration.

This paper deals with the simulation of microbial degradation of organic matter in soil within the pore space at a microscopic scale. Pore space was analysed with micro-computed tomography and described using a sphere network coming from a geometrical modelling algorithm. The biological model was improved regarding previous work in order to include the transformation of dissolved organic compounds and diffusion processes. We tested our model using experimental results of a simple substrate decomposition experiment (fructose) within a simple medium (sand) in the presence of different bacterial strains. Separate incubations were carried out in microcosms using five different bacterial communities at two different water potentials of −10 and −100 cm of water. We calibrated the biological parameters by means of experimental data obtained at high water content, and we tested the model without changing any parameters at low water content. Same as for the experimental data, our simulation results showed that the decrease in water content caused a decrease of mineralization rate. The model was able to simulate the decrease of connectivity between substrate and microorganism due the decrease of water content.

Living in soil pores: physical and nutritional constraints for microbial decomposers of soil organic matter. Goldschmidt 2013

Colloque avec actes et comité de lecture. Internationale.; International audience

Propagation systems for seedling growth play a major role in agriculture, and in notable cases (such as organic systems), are under constant threat from soil and seedborne fungal plant pathogens such as Rhizoctonia solani or Pythium spp. Yet, to date little is known that links the risk of disease invasion to the host density, which is an agronomic characteristic that can be readily controlled. We introduce here, for the first time in an agronomic system, a percolation framework to analyze the link. We set up an experiment to study the spread of the ubiquitous fungus R. solani in replicated propagation systems with different planting densities, and fit a percolation-based epidemiological model to the data using Bayesian inference methods. The estimated probability of pathogen transmission between infected and susceptible plants is used to calculate the risk of invasion. By comparing the transmission probability and the risk values obtained for different planting densities, we are able to give evidence of a nonlinear relationship between disease invasion and the inter-plant spacing, hence to demonstrate the existence of a spatial threshold for epidemic invasion. The implications and potential use of our methods for the evaluation of disease control strategies are discussed. © 2013 The American Phytopathological Society.

International audience; Metal ions appear to play an important role in several neurodegenerative (ND) diseases. Evidence suggests that metal ions bind directly to causative amyloidogenic proteins and modulate their aggregation into amyloids, considered to be a key event in the etiology of ND diseases. Apart from this well-documented binding of essential metals to amyloidogenic proteins, other, non-essential metal ions have been considered to be environmental hazards for neuronal disorders, but tight causative relations have yet to be established. The present article provides a review of the potential role of manganese, lead, and mercury as environmental risk factors in ND diseases, and covers in detail environmental availability of these metals, their uptake and distribution in the body and cells, and their role in Alzheimer's, Parkinson's and Prion diseases.

Effet de la structure du sol sur la biodégradation de la matière organique native du sol et sur la matière organique apportée. 11. Journées d'Etude des Sols (JES)

Heterogeneity in host populations is an important factor affecting the ability of a pathogen to invade, yet the quantitative investigation of its effects on epidemic spread is still an open problem. In this paper, we test recent theoretical results, which extend the established “percolation paradigm” to the spread of a pathogen in discrete heterogeneous host populations. In particular, we test the hypothesis that the probability of epidemic invasion decreases when host heterogeneity is increased. We use replicated experimental microcosms, in which the ubiquitous pathogenic fungus Rhizoctonia solani grows through a population of discrete nutrient sites on a lattice, with nutrient sites representing hosts. The degree of host heterogeneity within different populations is adjusted by changing the proportion and the nutrient concentration of nutrient sites. The experimental data are analysed via Bayesian inference methods, estimating pathogen transmission parameters for each individual population. We find a significant, negative correlation between heterogeneity and the probability of pathogen invasion, thereby validating the theory. The value of the correlation is also in remarkably good agreement with the theoretical predictions. We briefly discuss how our results can be exploited in the design and implementation of disease control strategies., Author Summary Pathogen spread and epidemic invasion in plant, animal and human populations depend on host properties (infectivity, susceptibility) that can vary amongst hosts within the same population. However, such host variability (or heterogeneity) is typically difficult to control experimentally, and little explicit research has been done on its effects on pathogen invasion. We present the first systematic investigation on the spread of a pathogen (the fungal plant pathogen Rhizoctonia solani) in repeatable microcosm populations (nutrient sites, representing hosts, on a lattice) with varying heterogeneity. Recent theoretical models for heterogeneity make the following prediction, that we set as our hypothesis: increasing heterogeneity (keeping all other properties fixed) results in a decrease of the probability of pathogen invasion. We validate the hypothesis using a combination of statistical methods. Moreover, we find that the decrease in probability of invasion is also in good quantitative agreement with the theoretical predictions. We discuss how our results can be exploited for disease control strategies that increase the heterogeneity of a system in order to limit pathogen spread.

International audience; The extreme heterogeneity and interconnectivity of the 3-dimensional pore space within soil makes it a unique habitat for the diverse microbial population and has a pivotal role in microbial interactions. Manipulation and quantification of the 3-dimensional pore space and the spatial distribution of micro-organisms is therefore essential if we are to fully understand microbial interactions. Here we pack soil microcosms at different bulk-densities to manipulate soil structure and use x-ray micro tomography and soil thin sections to analyse the effect on the connectivity of the pore volume and on fungal exploration.

International audience

6 pages; International audience; The fate of organic herbicides applied to agricultural fields may be affected by other soil amendments, such as copper applied as a fungicide. The effect of copper on the leaching of diuron and glyphosate through a granitic and a calcareous soil was studied in the laboratory using sieved-soil columns. Each soil was enriched with copper sulfate to obtain soil copper concentrations of 125, 250, 500, and 1000 mg kg(-1). Glyphosate leaching was influenced by soil pH and copper concentration, whereas diuron leaching was not. In the calcareous soil, glyphosate leaching decreased as copper levels increased from 17 mg kg(-1) (background) to 500 mg kg(-1). In the granitic soil, glyphosate leaching increased as copper levels increased from 34 mg kg(-1) (background) to 500 mg kg(-1). The shapes of the copper elution curves in presence of glyphosate were similar to shapes of the glyphosate curves, suggesting the formation of Cu-glyphosate complexes that leach through the soil. Soil copper concentration does not influence diuron leaching. In contrast, increasing copper concentrations reduces glyphosate leaching through calcareous soils, and conversely, increases glyphosate leaching through granitic soils. Our findings suggest that the risk of groundwater contamination by glyphosate increases in granitic soils with elevated copper concentrations.

7 pages; International audience; The response of microorganisms to metal contamination of soils varies significantly from one investigation to another. One explanation is that metals are heterogeneously distributed at spatial scales relevant to microbes and that microoorganisms are able to avoid zones of intense contamination. This article aims to assess the microscale distribution of Cu in a vineyard soil. The spatial distribution of Cu was measured at two resolutions (0.3 mm and 20 microm) in thin sections of the surface 4 cm of undisturbed soil by electron microprobe and synchrotron X-ray microfluo-rescence spectroscopy. Bulk physicochemical analyses of Cu, pH, organic matter, texture, and mineralogy were performed. The results indicate that the Cu distribution is strongly heterogeneous at both scales of observation. Entire regions of the thin sections are virtually devoid of Cu, whereas highly localized "hotspots" have Cu signal intensities thousands of times higher than background. The distribution of Rb, or Al and Si, indicators of clay minerals, or Fe (iron (hydr)oxides), show that Cu is not preferentially associated with these mineral phases. Instead, Cu hotspots are associated with particulate organic matter. These observations suggest modification of current sampling protocols, and design of ecotoxicological experiments involving microorganisms, for contaminated soils.

International audience

International audience; ME (Myalgic Encephalomyelitis) or CFS (chronic fatigue syndrome) is a debilitating illness for which no cause or medical tests have been identified. Debates over its nature have generated interest from qualitative researchers. However, participants are difficult to recruit because of the nature of their condition. Therefore, this study explores the utility of the internet as a means of eliciting accounts. We analyse data from focus groups and the internet in order to ascertain the extent to which previous research findings apply to the internet domain. Interviews were conducted among 49 members of internet groups (38 chatline, 11 personal) and 7 members of two face-to-face support groups. Discourse analysis of descriptions and accounts of ME or CFS revealed similar devices and interactional concerns in both internet and face-to-face communication. Participants constructed their condition as serious, enigmatic and not psychological. These functioned to deflect problematic assumptions about ME or CFS and to manage their accountability for the illness and its effects.

There is a growing body of evidence that the spatial distribution of bacteria and their relationships with other soil features play a significant role in the macroscopic function of soil. In the past this has not been widely appreciated, possibly due to the difficulty of studying soils at scales that are relevant to bacterial communities. This paper reviews the evidence for the influence of microscale interactions on function at larger scales and describes recent methodological advances that allow the microscale spatial distribution of bacterial cells and bacterial activities to be quantified. Approaches for integrating the microscale into models of soil function are briefly discussed as are new techniques that have the potential to improve our understanding of microbial – habitat interactions and of how these are linked to soil function.

International audience

International audience; We investigated the utility of combining micro-scale computed tomography (micro-CT), image analysis and geostatistics to quantify pore geometry at spatial scales ranging from 4.4 [mu m to 2 mm. To facilitate this, we investigated soil taken from an old permanent upland pasture known to support very high levels of microbial diversity and that had not been cultivated for many centuries. Aggregates (< 3 mm in diameter) from three treatments (control, sewage sludge amended and biocide treated) derived from the site were imaged using synchrotron-based computed microtomography. Image analysis was used to determine aggregate porosity and pore shape parameters, and semivariance analysis was used to measure the spatial correlation of pore space within the three land treatments. For all plots high porosities were observed (c. 30%) at scales below 3 mm. High variations of porosity were also observed, ranging from 22% to 47%, but no significant differences among treatments were found. No significant differences among treatments were found in the distribution of pores within aggregates, as revealed by semivariance analysis, or in pore shape parameters. No treatment effects were observed. However, the work presented here shows that the combination of approaches adopted has great potential for quantifying the soil microbial physical habitat. Future work, should investigate the use of these novel techniques in more controlled soil ecosystems to provide an exciting new way of understanding the soil-microbe interactions at appropriate scales. (c) 2005 Elsevier B.V. All rights reserved