Mechanisms of root reinforcement in soils: an experimental methodology using four-dimensional X-ray computed tomography and digital volume correlation.

Vegetation on railway or highway slopes can improve slope stability through the generation of soil pore water suctions by plant transpiration and mechanical soil reinforcement by the roots. To incorporate the enhanced shearing resistance and stiffness of root-reinforced soils in stability calculations, it is necessary to understand and quantify its effectiveness. This requires integrated and sophisticated experimental and multi-scale modelling approaches to develop an understanding of the processes at different length scales, from individual root-soil interaction through to full soil-profile or slope scale. One of the challenges with multi-scale models is ensuring that they sufficiently closely represent real behaviour. This requires calibration against detailed high-quality and data-rich experiments. This study presents a novel experimental methodology, which combines in situ direct shear loading of a willow root-reinforced soil with X-ray computed tomography to capture the three-dimensional chronology of soil and root deformation within the shear zone. Digital volume correlation (DVC) analysis was applied to the computed tomography dataset to obtain full-field three-dimensional displacement and strain information. This paper demonstrates the feasibility and discusses the challenges associated with DVC experiments on root-reinforced soils.

Transcriptome-wide analysis of wild Asari (=Manila) clams affected by the Brown Muscle Disease: Etiology and impacts of the disease.

Recently, we reported an emerging pathology named Brown Muscle Disease (BMD) affecting Asari clams inhabiting the most productive area for this species in France, the Arcachon Bay. The main macroscopic feature of the pathology relies on the atrophy of the posterior adductor muscle, affecting the ability of clams to burry. The research of the etiological agent of BMD privileged a viral infection. Contrary to healthy clams, infected animals are always found at the surface of the sediment and exhibit 30 nm virus-like particles in muscle, granulocytic and rectal cells. In order to get more insights on the etiology and impacts of the BMD on clams, we took advantage in the present study of next generation sequencing technologies. An RNA-Seq approach was used (i) to test whether viral RNA sequences can be specifically found in the transcriptome of diseased animals and (ii) to identify the genes that are differentially regulated between diseased and healthy clams. Contrary to healthy buried animals, in diseased clams one sequence showing extensive homologies with retroviridae-related genes was detected. Among the biological processes that were affected in diseased clams, the synaptic transmission process was the most represented. To deepen this result, a new sampling was carried out and the transcription level of genes involved in synaptic transmission was determined in healthy and diseased clams but also in clams with no visible sign of pathology but located at the surface of the sediment. Our findings suggest that muscle atrophy is a latter sign of the pathology and that nervous system could be instead a primary target of the BMD agent.

To boldly climb: behavioural and cognitive differences in migrating European glass eels.

European eel (Anguilla anguilla) is a catadromous fish species that received substantial attention as its population has markedly declined in the last three decades. The possible causes of this decline include habitat fragmentation factors such as dams and weirs. In some cases, these obstacles are equipped with fish friendly passage devices that may select young eels according to their climbing behaviour. We tested how individual climbing tendency was related to the event of fishway passage experienced in the field and classified fish climbing profiles as climbing 'leaders', 'followers', 'finishers' and 'no climbers'. Moreover, we analysed the brain transcription level of genes related to neurogenesis and synaptic plasticity and compared it to climbing profiles. We found that fish from the upstream segments of an impounded river had a higher climbing propensity. Their behaviour was also more repeatable throughout the whole test than the obstacle-naive fish from the downstream segment. Moreover, we found that boldly climbing 'leaders' had lower levels of transcription of synapse-related genes than the climbing 'followers'. These differences could be related to coping styles of fish, where proactive 'leaders' express a routine and risky behaviour, whereas reactive fish need an environmental assessment before exploratory behaviour. Our study showed that differences in climbing propensity exist in glass eels separated by water obstacles. Moreover, eels could adopt climbing different strategies according to the way they deal with environmental stress and to the cognitive abilities they possess.

RAD sequencing reveals within-generation polygenic selection in response to anthropogenic organic and metal contamination in North Atlantic Eels.

Measuring the effects of selection on the genome imposed by human-altered environment is currently a major goal in ecological genomics. Given the polygenic basis of most phenotypic traits, quantitative genetic theory predicts that selection is expected to cause subtle allelic changes among covarying loci rather than pronounced changes at few loci of large effects. The goal of this study was to test for the occurrence of polygenic selection in both North Atlantic eels (European Eel, Anguilla anguilla and American Eel, A. rostrata), using a method that searches for covariation among loci that would discriminate eels from 'control' vs. 'polluted' environments and be associated with specific contaminants acting as putative selective agents. RAD-seq libraries resulted in 23 659 and 14 755 filtered loci for the European and American Eels, respectively. A total of 142 and 141 covarying markers discriminating European and American Eels from 'control' vs. 'polluted' sampling localities were obtained using the Random Forest algorithm. Distance-based redundancy analyses (db-RDAs) were used to assess the relationships between these covarying markers and concentration of 34 contaminants measured for each individual eel. PCB153, 4'4'DDE and selenium were associated with covarying markers for both species, thus pointing to these contaminants as major selective agents in contaminated sites. Gene enrichment analyses suggested that sterol regulation plays an important role in the differential survival of eels in 'polluted' environment. This study illustrates the power of combining methods for detecting signals of polygenic selection and for associating variation of markers with putative selective agents in studies aiming at documenting the dynamics of selection at the genomic level and particularly so in human-altered environments.

Climbing experience in glass eels: A cognitive task or a matter of physical capacities?

The European eel is a panmictic species, whose decline has been recorded since the last 30 years. Among human-induced environmental factors of decline, the impact of water dams during species migration is questioned. Indeed, water impoundments can be a severe obstacle for young eels trying to reach the upstream freshwater zones, even if they are equipped with fish-friendly passes. The passage by such devices could be an important event shaping the outcome of the future life and life history traits of eels. We studied what phenotypic traits were associated with the event of experience of passage by water obstacles. We analyzed specific enzyme activities and/or gene transcription levels in the muscle and brain to test whether the obstacle passage is rather a physical or cognitive task. We found that after a long period of maintenance under homogenous conditions, transcription levels of several genes linked to synaptic plasticity, neurogenesis and thyroid activity differed among the field-experience groups. In contrast, muscle gene transcription levels or enzymatic activities did not show any differences among fish groups. We suggest that cognitive processes such as learning and memory acquisition rather than swimming-related metabolic capacities are involved in passage of water obstacles by young eels.

Extension of the Optimized Virtual Fields Method to estimate viscoelastic material parameters from 3D dynamic displacement fields.

In-vivo measurement of the mechanical properties of soft tissues is essential to provide necessary data in biomechanics and medicine (early cancer diagnosis, study of traumatic brain injuries, etc.). Imaging techniques such as Magnetic Resonance Elastography (MRE) can provide 3D displacement maps in the bulk and in vivo, from which, using inverse methods, it is then possible to identify some mechanical parameters of the tissues (stiffness, damping etc.). The main difficulties in these inverse identification procedures consist in dealing with the pressure waves contained in the data and with the experimental noise perturbing the spatial derivatives required during the processing. The Optimized Virtual Fields Method (OVFM) [1], designed to be robust to noise, present natural and rigorous solution to deal with these problems. The OVFM has been adapted to identify material parameter maps from Magnetic Resonance Elastography (MRE) data consisting of 3-dimensional displacement fields in harmonically loaded soft materials. In this work, the method has been developed to identify elastic and viscoelastic models. The OVFM sensitivity to spatial resolution and to noise has been studied by analyzing 3D analytically simulated displacement data. This study evaluates and describes the OVFM identification performances: different biases on the identified parameters are induced by the spatial resolution and experimental noise. The well-known identification problems in the case of quasi-incompressible materials also find a natural solution in the OVFM. Moreover, an a posteriori criterion to estimate the local identification quality is proposed. The identification results obtained on actual experiments are briefly presented.

Beyond Hopkinson's bar.

In order to perform experimental identification of high strain rate material models, engineers have only a very limited toolbox based on test procedures developed decades ago. The best example is the so-called split Hopkinson pressure bar based on the bar concept introduced 100 years ago by Bertram Hopkinson to measure blast pulses. The recent advent of full-field deformation measurements using imaging techniques has allowed novel approaches to be developed and exciting new testing procedures to be imagined for the first time. One can use this full-field information in conjunction with efficient numerical inverse identification tools such as the virtual fields method (VFM) to identify material parameters at high rates. The underpinning novelty is to exploit the inertial effects developed in high strain rate loading. This paper presents results from a new inertial impact test to obtain stress-strain curves at high strain rates (here, up to 3000 s(-1)). A quasi-isotropic composite specimen is equipped with a grid and images are recorded with the new HPV-X camera from Shimadzu at 5 Mfps and the SIMX16 camera from Specialised Imaging at 1 Mfps. Deformation, strain and acceleration fields are then input into the VFM to identify the stiffness parameters with unprecedented quality.

The application of digital volume correlation (DVC) to study the microstructural behaviour of trabecular bone during compression.

Digital Volume Correlation (DVC) has been emerged recently as an innovative approach to full volume (i.e. internal) displacement and strain field measurement in materials and structures, particularly in conjunction with high resolution X-ray computed tomography (CT). As a relatively novel technique certain aspects of precision, accuracy and the breadth of application are yet to be fully established. This study has applied DVC to volume images of porcine trabecular bone assessing the effect of noise and sub-volume size on strain measurement. Strain resolutions ranging between 70 and 800µÎµ were obtained for the optimum sub-volume size of 64 voxels with a 50% overlap for metrological studies conducted. These values allowed the mechanical behaviour of porcine trabecular bone during compression to be investigated. During compression a crushed layer formed adjacent to the boundary plate which increased in thickness as the specimen was further deformed. The structure of the crushed layer was altered to such an extent that it confounded the correlation method. While investigating this factor, it was found that for reliable strain calculations a correlation coefficient of 0.90 or above was required between the sub-volumes in the reference and the deformed volumes. Good agreements between the results and published bone strain failures were obtained. Using the full field strain measurements, Poisson's ratio was identified for each compression step using a dedicated inverse method called the virtual fields method (VFM). It was found that for a given region outside of the crushed zone the Poisson ratio decreased from 0.32 to 0.21 between the first and the final compression steps, which was hypothesised to be due to the bone geometry and its resulting deformation behaviour. This study demonstrates that volumetric strain measurement can be obtained successfully using DVC, making it a useful tool for quantitatively investigating the micro-mechanical behaviour of macroscale bone specimens.

The use of Eugenol and electro-narcosis as anaesthetics: transcriptional impacts on the European eel (Anguilla anguilla L.).

Ecotoxicological studies aim to assess the potential environmental risks of various products. This implies the use of various biological models and tests on live animals. In case of handling fish and mammals, ethical rules have to be respected. The use of anaesthesia is considered to be the best way to ensure animal welfare. Eugenol and electro-narcosis are among the most popular chemical and physical anaesthetics used in fisheries and by field biologists. In this study, the genetic and endocrine impacts of these anaesthetics were assessed in order to establish whether the use of such methods could skew the results of ecotoxicological studies. Twenty yellow European eels (Anguilla anguilla) were submitted to Eugenol (50mg/L) and electro-narcosis until they reached a level of deep anaesthesia, while 20 other eels were kept aware. Five anaesthetized and five unanaesthetized eels were sacrificed and analysed directly after treatment and after 1, 7 and 21 days of recovery. At the brain level, Eugenol triggered an increase in the transcription level of genes encoding proteins involved in oxidative stress responses (catalase expression 2.5-fold, mitochondrial superoxide dismutase expression 3-fold), probably due to a hypoxic event during anaesthesia. Later impacts were detected in muscles 21 days after anaesthesia (ATP synthase subunit 6 3-fold, NADH deshydrogenase subunit 5 4-fold and mitochondrial superoxide dismutase 3-fold increased) revealing oxidative stress from an accrued mitochondrial respiratory metabolism. Hormone dosages showed that the use of Eugenol reduced the release of plasma cortisol during anaesthesia. However, this impact seemed to be reversible within one day. In case of electro-narcosis, no significant variation in transcriptional levels could be detected between anaesthetized and unanaesthetized eels. Our results suggest that the use of Eugenol as an aesthetic in ecotoxicological studies measuring gene expression or plasma cortisol concentration is not appropriate, while electro-narcosis does not seem to have any impact, at least on the parameters taken into consideration in this study.

French transportable laser ranging station: scientific objectives, technical features, and performance.

The French Transportable Laser Ranging Station (FTLRS) is a highly mobile satellite laser ranging (SLR) system unit that weighs 300 kg and is housed in eight containers. This telemetry laser station is dedicated to the tracking of geodetic satellites equipped with retroreflectors. There are fascinating uses in the geosciences for such a system: in tectonics, oceanography, terrestrial reference frames, and precise positioning. The idea is to use a very small 13-cm-diameter telescope installed on a motorized mount and derived from a geodetic motorized theodolite of high precision. The laser is also compact, and the use of an avalanche photodiode makes detection possible at a single photoelectron level. On-site installation of this new SLR system is fast, and the system's routine operation is quite automated. It started its operational phase in late 1996. At present, it can track satellites at altitudes of as much as 3000 km and is designed to range to the Laser Geodynamic Earth Orientation Satellite (LAGEOS) at 6000 km in a further step. The standard error of individual measurements during the first observation campaign in Corsica is estimated to be of the order of 2-3 cm. Since then, significant improvements have been implemented. A technical description of the FTLRS is given, and the main results of the Corsica campaign are summarized.

[Detection and surveillance of left atrial thrombosis by transesophageal echocardiography]. / Détection et surveillance des caillots de l'oreillette gauche par échographie transoesophagienne.

Out of 1,141 successive transoesophageal echocardiographic studies performed prospectively between 01/05/1993 and 31/12/1995, 26 cases of left atrial thrombosis were observed (2.2%); 5 were in the left atrium (20%), 19 in the left atrial appendage (73%) and the thrombi were in both atrium and left atrial appendage in 2 cases (7%). The 26 patients included 15 women and 11 men, with an average age of 69 +/- 16 years (range 25-89 years); 22 patients (84%) had permanent atrial fibrillation and 4 were in sinus rhythm. Only 5 of the patients were on oral anticoagulant therapy. All had underlying cardiac disease: 11 mitral valve diseases; 10 dilated cardiomyopathies; 2 hypertrophic cardiomyopathies; 3 other cardiac diseases. The indication for transoesophageal echocardiography was systemic embolism in 13 cases (50%); before D.C. cardioversion in 10 cases (38%) and before percutaneous mitral valvuloplasty in 3 cases. The thrombus was adherent in 18 cases (69%) and mobile in 8 cases (31%). Spontaneous contrast was observed in 23 cases (88%). Intravenous heparin was given as soon as the diagnosis was made. In 4 patients, thrombectomy was indicated in view of the threatening nature of the thrombus and/or the necessity for associated valve replacement. In 22 patients, heparin was relayed by oral anticoagulants on the 10th day of treatment. Control transoesophageal echocardiography was not performed because of the patient's refusal or poor general condition. The other 15 patients were reexamined 1 to 5 times between the 4th day and 12th month: a regression was observed in 13 cases (86%) which was complete in 11 and partial in 2 cases. No cases of embolism occurred during follow-up but six patients died: 1 of the operated cases and 5 of the patients treated medically (3 cardiac failures and 2 cerebral haemorrhages). The authors conclude that left atrial thrombosis is rare in the absence of classical embolic cardiac disease. With the exception of the surgical indication of a life-threatening thrombus and/or associated surgical mitral valve disease, anticoagulant therapy results in complete or partial regression of the thrombus visualised by transoesophageal echocardiography which is essential for follow-up. The prognosis depends on the severity of the underlying heart disease.

Coronary artery spasm in patients with normal or near normal coronary arteries. Long-term follow-up of 277 patients.

Most studies on the natural course of coronary artery spasm in patients with normal or nearly normal coronary arteries are based on medium-term follow-up in small populations. The present series includes 277 successive patients with a median follow-up of 89 months (range: 1 to 198 months). There were 206 men and 71 women whose mean age was 53.6 +/- 9.3 years. They were all assessed with coronary arteriography which revealed no stenoses greater than 50%. Spasm was confirmed during the coronary arteriography in 157 patients (56.7%), by a positive provocation test following the arteriography in 113 patients (40.8%), and by an electrocardiogram which showed Prinzmetal's variant angina in seven patients (2.5%). The majority of patients, 264 (95.3%) were treated with calcium channel blockers. At the end of this study: 35 patients (12.6%) were lost to follow-up; 20 patients (7.2% died) including 10 (3.6%) from cardiac causes; 18 patients (6.5%) experienced myocardial infarction in 11 of whom repeat coronary arteriography consistently demonstrated one or more significant stenoses (greater than 70%); 109 patients (39%) had persistent angina, in 52 of whom the severity (more than one episode per month) warranted repeat coronary arteriography which detected significant stenosis in 19 cases; 95 patients (34.3%) were asymptomatic. Multivariate statistical analyses showed that only predictors of major coronary events (death, myocardial infarction or angina requiring repeat coronary arteriography) were systemic hypertension or the finding of minor parietal irregularities on the initial coronary arteriogram. Conclusion. Despite treatment with calcium channel blockers, persistent or recurrent episodes of angina are frequently observed whereas complications such as myocardial infarction or death are rare.

[Spasm of normal or irregular coronary arteries. Long-term outcome of 277 patients]. / Spasme sur artères coronaires normales ou irrégulières. Devenir à long terme de 277 patients.

The outcome of patients presenting with spasm of normal or subnormal coronary arteries is only known in small series of patients at medium-term. The authors reviewed the outcome of 277 successive patients over an average period of 86 +/- 43 months (12 to 174 months). There were 206 men and 71 women with a mean age of 54 +/- 9 years. Coronary angiography was performed in all cases and did not show any stenosis greater than 50%. Spasm was documented during coronary angiography in 157 cases (57%) by a positive Methergin test after coronary angiography in 113 cases (41%) and by an ECG recording of Prinzmetal angina in 7 cases (2.5%). Nearly all patients (264: 95%) were treated by calcium antagonists. At the end of follow-up, there were: 35 lost to follow-up (12.6%), 20 deaths (7.2%) of which 10 were cardiac (3.6%), 18 myocardial infarctions (6.5%): 11 had repeat coronary angiography which showed one or more new significant (> 70%) coronary lesions in all cases; 109 patients had persistence of chest pain (39%). The severity of symptoms in 52 cases (over one attack of chest pain per month) led to repeat coronary angiography which showed significant coronary disease in 19 cases; 95 patients (34%) were asymptomatic. A multivariate statistical analysis showed hypertension or subnormal appearances on the initial coronary angiography to be significant predictive factors for new coronary events (death, myocardial infarction or angina requiring repeat coronary angiography). The authors conclude that coronary spasm of angiographically normal or subnormal arteries is only well controlled at long-term in 39% of patients not lost to follow-up and is responsible for death or myocardial infarction in 11.6% of cases (nearly 1.5% per year).