Treatment of displaced intra-articular calcaneal fractures using a sinus tarsi approach. Surgical technique. / Técnica quirúrgica del manejo de las fracturas de calcáneo a través de un abordaje del seno del tarso.

Calcaneal articular fractures are fractures classically associated with a high rate of complications and poor outcomes. Osteosynthesis of the calcaneus through a sinus tarsi approach has shown results equal to or superior to those of the extended approach, having become the new gold standard. The objective of this article is to detail step by step the surgical technique of osteosynthesis of intra-articular fractures of the calcaneus through a sinus tarsi approach, from the selection of the fracture, positioning of the patient, layout of the operating room and the fluoroscope, the entire surgical process until postoperative treatment. The surgical technique described below is described in 6 steps. Anatomical reduction of complex calcaneal fractures through an Sinus Tarsi Approach requires an understanding of the fracture and its associated deformities. Following the described sequence step by step will help to achieve a better reduction in order to achieve better functional results.

Continuing invariant solutions towards the turbulent flow.

A new mathematical framework is proposed for characterizing the coherent motion of fluctuations around a mean turbulent channel flow. We search for statistically invariant coherent solutions of the unsteady Reynolds-averaged Navier-Stokes equations written in a perturbative form with respect to the turbulent mean flow, using a suitable approximation of the Reynolds stress tensor. This is achieved by setting up a continuation procedure of known solutions of the perturbative Navier-Stokes equations, based on the continuous increase of the turbulent eddy viscosity towards its turbulent value. The recovered solutions, being sustained only in the presence of the Reynolds stress tensor, are representative of the statistically coherent motion of turbulent flows. For small friction Reynolds number and/or domain size, the statistically invariant motion is almost identical to the corresponding invariant solution of the Navier-Stokes equations. Whereas, for sufficiently large friction number and/or domain size, it considerably departs from the starting invariant solution of the Navier-Stokes equations, presenting spatial structures, main wavelengths and scaling very close to those characterizing both large- and small-scale motion of turbulent channel flows. This article is part of the theme issue 'Mathematical problems in physical fluid dynamics (part 2)'.

Water and ion diffusion in partially-water saturated compacted kaolinite: Role played by vapor-phase diffusion in water mobility.

Diffusion is the main transport process of water and solutes in clay-rich porous media owing to their very low permeability, so they are widely used as barriers against contaminant spreading. However, the prediction of contaminant mobility can be very complicated when these media are partially water-saturated. We conducted diffusion experiments for water (HTO and HDO) and ions (22Na+ and 125I-) through partially water saturated compacted kaolinite, a weakly charged clay material, to quantify the distinct diffusive behavior of these species. The osmosis method was used to set kaolinite samples at 67, 86 and 100% saturation. The results showed that desaturation led to a sharp decrease in diffusive rates by factors of 6.5, 18 and 35 for HTO, 125I- and 22Na+, respectively, from 100 to 67% of the degree of saturation. Thus, to interpret water diffusivities, we proposed a model taking into account the diffusion of water in both gas and liquid phases, using diffusion data obtained for ions, considered as inert species. This model was capable of properly predicting water diffusive flux, especially at a low degree of saturation (67% saturation), for which the assumption made for the occurrence of air phase continuity throughout the sample appears to be more relevant than at 86% saturation.

Uranium retention in a Callovo-Oxfordian clay rock formation: From laboratory-based models to in natura conditions.

For the performance assessment of radioactive waste disposal, it is critical to predict the mobility of radionuclides in the geological barrier that hosts it. A key challenge consists of assessing the transferability of current knowledge on the retention properties deduced from model systems to in natura situations. The case of the redox-sensitive element uranium in the Callovo-Oxfordian clay formation (COx) is presented herein. Extensive experimental work was carried out with respect to parameters affecting uranium speciation (pH, PCO2, [Ca] and redox potential) with illite, COx clay fraction and raw COx claystone. The "bottom-up" approach implemented, with illite and montmorillonite as reactive phases, quantitatively explains the adsorption results of U(VI) and U(IV) on COx. While retention is high for U(IV) (Rd∼104 L kg-1), it remains very low for U(VI) (Rd∼4 L kg-1) due to the formation of soluble ternary Ca(Mg)-U(VI)-carbonate complexes. The applicability of the sorption model was then assessed by comparing predictive analyses with data characterizing the behavior of naturally-occurring U (<3 mg kg-1). The COx clay phase is the largest reservoir of naturally-occurring U (∼65%) but only a small fraction appears to be adsorbed (∼1%). Under representative site conditions (especially with respect to reducing conditions), we have concluded that ternary U(VI) complexes control U speciation in solution while U(IV) surface species dominate U adsorption, with Rd values > 70 L kg-1.

Diffusion of organic anions in clay-rich media: Retardation and effect of anion exclusion.

The transport of emerging organic contaminants through the geosphere is often an environmental issue. The sorption of organic compounds slows their transport in soils and porous rocks and retardation is often assessed by extrapolation of batch experiments. However, transport experiments are preferable to strengthen migration data and modelling. In this context, we evaluated the adsorption of various organic acids by means of through-diffusion experiments in a sedimentary clay-rich rock (Callovo-Oxfordian, East of Paris Basin, France). A low diffusivity of organic anions was quantified with effective diffusion coefficients, De, ranged between 0.5 and 7 10-12 m2 s-1. These values indicated an organic anion exclusion. As for chloride, the porosity accessible to organic anions was lower than that of water: εa(organic anions) < ε(water). The partial exclusion of organic anions from rock porosity was linked to both charge and size effects. A significant retardation was observed for organic anions such as oxalate, citrate or α-isosaccharinate. Yet, retardation measured by diffusion experiments was significantly lower than expected from batch experiments on crushed samples. An empirical correction factor is proposed to account for a possible decrease of retardation with accessible porosity of diffusing solute. This feature has significant implications for the estimation of migration parameters of organic compounds in the environment.

How mobile is tritiated water through unsaturated cement-based materials? New insights from two complementary approaches.

This work presents two complementary approaches (for low and high desaturation) to study tritiated water (HTO) diffusion through unsaturated cement-based materials. The first approach was based on through-diffusion experiments where suction was controlled by osmosis. In the second approach, diffusion experiments were performed in humidity chambers controlled by under-saturated saline solutions. Results revealed a decrease of effective diffusion coefficient by a factor of 10 from 100% to 23% of saturation degree. Comparison with gaseous H2 suggests that HTO diffuses through unsaturated cement-based materials at rates 4 orders of magnitude lower.

Technical aspects and complications in the surgical treatment of poliomyelitis-affected lower limb fractures. / Aspectos técnicos y complicaciones en el tratamiento de las fracturas de los miembros inferiores con secuelas de poliomielitis.

OBJECTIVE: Post-polio patients present problems such as small and deformed bones, with narrow intramedullary canal and osteoporosis, affecting surgical treatment. The aim of this article is to describe the main preoperative and intraoperative complications of the surgical treatment of fractures in this population. MATERIAL AND METHODS: A retrospective analysis was conducted between 1995 and 2014. Data obtained from the medical records included patient age, fracture pattern (AO/OTA), device used, technical aspects of the surgery that changed compared to a standard procedure, and the presence of intraoperative skeletal complications. RESULTS: Sixty-four patients with 78 fractures were included in the study. Forty-seven percent of the fractures were at the proximal femur. The main complications of hip arthroplasty (14 patients) were absent hip abductors and intraoperative instability (3), bad cup fixation (3) and intraoperative periprosthetic fracture (2). The main problems of intramedullary nailing were due to a narrow canal and previous bone deformity. Main problems reported when plating included difficulty to fit a precontoured plate, and oversized hardware. CONCLUSION: Given the large number of intraoperative complications, in preoperative planning we must include nails of small diameter and length, locking plates and external fixators, and, in the case of hip arthroplasty, long and thin stems and restrictive or dual mobility acetabular systems.

Open synovectomy of the ankle joint in young haemophiliacs: mid-term to long- term results of a single-centre series of 32 procedures.

INTRODUCTION: In haemophiliacs, recurrent hemarthrosis and chronic synovitis lead to chronic arthropathy. Synovectomy is indicated when medical treatment fails. Few studies report the results of open synovectomy of the ankle in haemophiliacs with a small number of procedures and also a limited follow-up. AIM: The aim of this paper is to report the long-term results of open surgical synovectomy of the tibio-talar joint. METHODS: Thirty-two open synovectomies were performed in 21 young haemophiliacs in the same haemophilia center using an antero-lateral and postero-medial approaches. The median follow-up was 15.4 years. Clinical (Petrini scores) and radiological evaluations (Pettersson scores) were made preoperatively and at each multidisciplinary follow-up visit. Wilcoxon and Spearman's tests were used for the statistical analysis. RESULTS: Preoperative median Petrini score was 6 (range 3-12), and improved at 2 and 5 years follow-up (P = 0.0003 and P = 0.0001 respectively). At 10 and 15 years follow-ups, median score remained below preoperative score (median 3.5, range 0-11). Ten ankles had a follow-up of more than 20 years. Preoperative median Petterson score presented a slight but continuous worsening in the first 2 and 5 years of follow-ups (P = 0.02, P = 0.003), but not correlation between clinical and radiological results was observed. CONCLUSION: Our long-term results support that clinical scores are improved even if radiological scores progress. Open synovectomy retards the progression of the arthropathy, but not stops it. Bleeding and pain are controlled and even if recurrence of bleedings is frequent, it is less severe, less painful and requiring less factors replacement.

The influence of a pressure wavepacket's characteristics on its acoustic radiation.

Noise generation by flows is modeled using a pressure wavepacket to excite the acoustic medium via a boundary condition of the homogeneous wave equation. The pressure wavepacket is a generic representation of the flow unsteadiness, and is characterized by a space envelope of pseudo-Gaussian shape and by a subsonic phase velocity. The space modulation yields energy in the supersonic range of the wavenumber spectrum, which is directly responsible for sound radiation and directivity. The influence of the envelope's shape on the noise emission is studied analytically and numerically, using an acoustic efficiency defined as the ratio of the acoustic power generated by the wavepacket to that involved in the modeled flow. The methodology is also extended to the case of acoustic propagation in a uniformly moving medium, broadening possibilities toward practical flows where organized structures play a major role, such as co-flow around cruising jet, cavity, and turbulent boundary layer flows. The results of the acoustic efficiency show significant sound pressure levels, especially for asymmetric wavepackets radiating in a moving medium.

Radioprotección en quirófanos de traumatología: ¿en qué situación estamos? / Radiation safety in orthopaedic operating theatres. what is the current situation?

Objetivo. Analizar la exposición a radiaciones ionizantes por parte de dos cirujanos ortopédicos en su práctica diaria y revisar las principales recomendaciones nacionales e internacionales al respecto. Material y método. Se efectúo un estudio retrospectivo de la actividad quirúrgica con uso de fluoroscopia realizado por dos cirujanos ortopédicos en un año. Se calculó la radiación recibida basándose en mediciones por procesos publicados en la bilbliografía. Revisión bibliográfica de recomendaciones y normativas internacionales. Resultado. La radiación recibida en un año por los dos cirujanos ortopédicos no sobrepasó el límite de la legislación actual ni el de las nuevas recomendaciones europeas e internacionales. La exposición fue asimétrica, siendo las manos la zona más radiada. Las nuevas recomendaciones rebajan los niveles permitidos de radiación en ojos. Discusión. La estimación de radiación recibida hace necesario proteger y vigilar especialmente las manos y los ojos. Son necesarios conocimientos del funcionamiento del fluoroscopio y de las medidas de radioprotección (AU)

Objective. To analyse the exposure of two Orthopaedic Surgeons to ionizing radiations in their daily work, and to review the main national and international recommendations on this subject. Material and methods. A retrospective study was conducted on the surgical treatments that use fluoroscopy performed by two Orthopaedic Surgeons during a one year period. An evaluation was made of the radiation received, based on measurements of the processes published in the bibliography section. A literature review of international recommendations and regulations is also presented. Results. The radiation received by the two Orthopaedic Surgeons during one year did not exceed the limits of present-day legislation or the new European and international recommendations. The exposure was asymmetrical, with the hands being the most radiated part. The new recommendations reduce the permitted level of radiation on eyes. Discussion. The evaluation of the radiation received demonstrates the need for radiation protection, paying particular attention to the hands and eyes. Good knowledge of operating a fluoroscope and radiation safety measures are also essential (AU)

[Radiation safety in orthopaedic operating theatres. What is the current situation?]. / Radioprotección en quirófanos de traumatología: ¿en qué situación estamos?

OBJECTIVE: To analyse the exposure of two Orthopaedic Surgeons to ionizing radiations in their daily work, and to review the main national and international recommendations on this subject. MATERIAL AND METHODS: A retrospective study was conducted on the surgical treatments that use fluoroscopy performed by two Orthopaedic Surgeons during a one year period. An evaluation was made of the radiation received, based on measurements of the processes published in the bibliography section. A literature review of international recommendations and regulations is also presented. RESULTS: The radiation received by the two Orthopaedic Surgeons during one year did not exceed the limits of present-day legislation or the new European and international recommendations. The exposure was asymmetrical, with the hands being the most radiated part. The new recommendations reduce the permitted level of radiation on eyes. DISCUSSION: The evaluation of the radiation received demonstrates the need for radiation protection, paying particular attention to the hands and eyes. Good knowledge of operating a fluoroscope and radiation safety measures are also essential.

Efecto del fresado y enclavado endomedular sobre la producción de factores de crecimiento en el callo de fractura de fémur en ratas / Effect of intramedullary reaming and nailing on the production of growth factors in the femur fracture callus in rats

Introducción. Existen muchos estudios referentes a los diferentes efectos producidos por el fresado intramedular en el callo de fractura, pero no existe evidencia en la literatura del efecto de dicho fresado en la osteogénesis. Realizamos un estudio prospectivo para analizar el efecto del fresado endomedular y enclavado en la producción de factores de crecimiento durante el proceso de consolidación de la fractura en el fémur producida en ratas. Material y métodos. Producimos una fractura diafisaria, transversa, no conminuta de fémur en 64 ratas: 34 ratas no recibieron ningún tratamiento y las otras 30 se trataron mediante un procedimiento quirúrgico estandarizado, consistente en fresado del canal medular de distal a proximal y fijación de la fractura con una aguja de Kirschner. Las ratas fueron sacrificadas a las 24 h, 4.°, 7.° y 15.° días después de la fractura. Medimos la cantidad de factores de crecimiento (PDGFA, TGF2 y TGFBeta-R2) en el callo de fractura mediante estudio anatomopatológico en los diferentes momentos del sacrificio. Resultados. Los resultados de las variables primarias del estudio, estratificadas por tiempo hasta el sacrificio, no mostraron diferencias estadísticas significativas. Discusión. Aunque la presencia de una aguja intramedular facilita la estabilización de la fractura y la formación del callo de fractura, no hemos encontrado ninguna evidencia significativa de que el fresado endomedular produzca cambios en la expresión de los factores de crecimiento estudiados (TGFBEta-R2, PDGFA y TGFBeta2) durante la formación del callo de fractura de fémur en ratas (AU)

Introduction: Many studies have been conducted to determine the different effects that reaming or intramedullary nailing have on fracture healing, but there is no evidence in the literature of the effect of intramedullary reaming on osteogenesis. We performed a prospective study to analyse the effect of intramedullary reaming and nailing on the production of growth factors during the process of fracture healing in the femur of rats. Material and methods: A transverse mid-shaft non-comminuted femur fracture was produced in 64 rats; 34 rats did not receive any treatment, and a standardized surgical procedure was performed on 30 rats, by exposing the left knee, reaming the medullary canal from distal to proximal, and then fixing the fracture with a steel pin. The rats were sacrificed at the 24th hour, 4th, 7th and 15th days after the fracture. The amount of growth factors that appeared in the callus fracture was measured using histopathology studies. The primary categorical variables analysed were PDGFA, TGF2 and TGFBeta-R2. These variables were analysed in each group at the different sacrifice times. Results: The results of the primary variables of the study, stratified by the time until sacrifice, showed no statistically significant differences. Discussion: Even if the presence of an intramedullary wire facilitates the fracture repair and the stabilising the bridge of bone between both edges of the fracture site, no evidence was found that reaming changes the expression of the growth factors studied (PDGFA, TGFBeta-R2 and TGFBeta) during the callus formation in rats (AU)

[Effect of intramedullary reaming and nailing on the production of growth factors in the femur fracture callus in rats]. / Efecto del fresado y enclavado endomedular sobre la producción de factores de crecimiento en el callo de fractura de fémur en ratas.

INTRODUCTION: Many studies have been conducted to determine the different effects that reaming or intramedullary nailing have on fracture healing, but there is no evidence in the literature of the effect of intramedullary reaming on osteogenesis. We performed a prospective study to analyse the effect of intramedullary reaming and nailing on the production of growth factors during the process of fracture healing in the femur of rats. MATERIAL AND METHODS: A transverse mid-shaft non-comminuted femur fracture was produced in 64 rats; 34 rats did not receive any treatment, and a standardized surgical procedure was performed on 30 rats, by exposing the left knee, reaming the medullary canal from distal to proximal, and then fixing the fracture with a steel pin. The rats were sacrificed at the 24th hour, 4th, 7th and 15th days after the fracture. The amount of growth factors that appeared in the callus fracture was measured using histopathology studies. The primary categorical variables analysed were PDGFA, TGF2 and TGFß-R2. These variables were analysed in each group at the different sacrifice times. RESULTS: The results of the primary variables of the study, stratified by the time until sacrifice, showed no statistically significant differences. DISCUSSION: Even if the presence of an intramedullary wire facilitates the fracture repair and the stabilising the bridge of bone between both edges of the fracture site, no evidence was found that reaming changes the expression of the growth factors studied (PDGFA, TGFß-R2 and TGFß2) during the callus formation in rats.

El abordaje posterolateral en las fracturas trimaleolares de tobillo. Técnica quirúrgica / Posterolateral approach in trimalleolar ankle fractures: surgical technique

Introducción. Las fracturas de tobillo que incluyen un fragmento posterior se asocian a un peor resultado clínico. Es comúnmente aceptada la indicación de reducción y síntesis del maléolo posterior cuando incluye más de un 25% de la línea articular en proyección lateral. El método de fijación de estas fracturas tiene poca repercusión en la literatura. El objetivo de este trabajo, es describir la técnica quirúrgica y los resultados clínicos obtenidos. Material y métodos. Durante un período de 6 años, 10 pacientes han sido intervenidos por el primer autor. Todos ellos presentaban fracturas que incluían un fragmento posterior mayor de un 25%. Se tomaron datos de la clasificación de la fractura, del manejo postoperatorio, calidad de la reducción postoperatoria en la radiología postoperatoria, así como de cualquier complicación postoperatoria. Todos los pacientes completaron 2 cuestionarios de valoración clínica: American Orthopaedic Foot and Ankle Society (AOFAS) y Weber modificado. Se describe en detalle el abordaje posterolateral del maleolo posterior. Resultados. Diez pacientes con edades comprendidas entre 19 y 82 años fueron tratados con esta técnica. Todas las fracturas se redujeron anatómicamente. Los resultados son buenos, 9 pacientes obtuvieron un resultado excelente o bueno en las escalas de AOFAS y Weber modificada. No hubo pérdidas de reducción, infección, síndrome de distrofia simpático refleja o lesión iatrogénica del nervio sural. Una paciente precisó de la retirada del material de osteosíntesis por molestias de este. Todas las fracturas consolidaron. Discusión. Dado que la fractura del maléolo posterior es casi siempre posterolateral, el abordaje descrito permite una excelente visualización de la fractura, lo que permite su reducción anatómica y síntesis con tornillos posteroanteriores. Los resultados obtenidos son al menos equivalentes a otras series clínicas (AU)

Introduction. Ankle fractures involving a posterior malleolar fragment are associated with worse clinical outcomes. The standard indication for its fixation is a displaced fragment that involves more than 25% of the distal articular tibia. The method of reduction and fixation of these fractures has not received much attention. The purpose of this paper is to describe the surgical technique and clinical results. Material and methods. Over a 6 year period 10 patients with an ankle fracture involving more than 25% posterior malleolus were admitted for surgery, which was performed by the first author. Postoperative management and complications were recorded, reduction accuracy evaluated in the first postoperative radiograph, and functional outcomes were measured using the American Orthopaedic Foot and Ankle Society (AOFAS) hind foot-ankle score and the modified Weber protocol. The surgical technique is described. Results. A total of 10 patients were included in the study; and the overall mean age was 53.8 (range: 19-82) years. With regard to complications, none of the 10 patients had any postoperative complication. No cases of reflex sympathetic dystrophy syndrome, superficial infection, iatrogenic lesion of the sural nerve or failure of internal fixation were recorded. One of them had screw and plate removal surgery. Clinical results were good; 9 patients regained their pre-injury activity level, with excellent or good results in both AOFAS and modified Weber protocol. Discussion. Given that posterior malleolus fractures are usually posterolateral, this approach allows perfect visualization of the fracture, articular anatomical reduction, and strong fixation. Clinical results obtained were at least equal to other case series published (AU)

[Posterolateral approach in trimalleolar ankle fractures: surgical technique]. / El abordaje posterolateral en las fracturas trimaleolares de tobillo. Técnica quirúrgica.

INTRODUCTION: Ankle fractures involving a posterior malleolar fragment are associated with worse clinical outcomes. The standard indication for its fixation is a displaced fragment that involves more than 25% of the distal articular tibia. The method of reduction and fixation of these fractures has not received much attention. The purpose of this paper is to describe the surgical technique and clinical results. MATERIAL AND METHODS: Over a 6 year period 10 patients with an ankle fracture involving more than 25% posterior malleolus were admitted for surgery, which was performed by the first author. Postoperative management and complications were recorded, reduction accuracy evaluated in the first postoperative radiograph, and functional outcomes were measured using the American Orthopaedic Foot and Ankle Society (AOFAS) hind foot-ankle score and the modified Weber protocol. The surgical technique is described. RESULTS: A total of 10 patients were included in the study; and the overall mean age was 53.8 (range: 19-82) years. With regard to complications, none of the 10 patients had any postoperative complication. No cases of reflex sympathetic dystrophy syndrome, superficial infection, iatrogenic lesion of the sural nerve or failure of internal fixation were recorded. One of them had screw and plate removal surgery. Clinical results were good; 9 patients regained their pre-injury activity level, with excellent or good results in both AOFAS and modified Weber protocol. DISCUSSION: Given that posterior malleolus fractures are usually posterolateral, this approach allows perfect visualization of the fracture, articular anatomical reduction, and strong fixation. Clinical results obtained were at least equal to other case series published.

Rapid path to transition via nonlinear localized optimal perturbations in a boundary-layer flow.

Recent studies have suggested that in some cases transition can be triggered by some purely nonlinear mechanisms. Here we aim at verifying such an hypothesis, looking for a localized perturbation able to lead a boundary-layer flow to a chaotic state, following a nonlinear route. Nonlinear optimal localized perturbations have been computed by means of an energy optimization which includes the nonlinear terms of the Navier-Stokes equations. Such perturbations lie on the turbulent side of the laminar-turbulent boundary, whereas, for the same value of the initial energy, their linear counterparts do not. The evolution of these perturbations toward a turbulent flow involves the presence of streamwise-inclined vortices at short times and of hairpin structures prior to breakdown.

[Use of Rapid Antigen Detection Test (RADT) among general practitioner teachers at the Paris Descartes University: 2005-2007]. / Evolution de la pratique du test diagnostic rapide (TDR) de l'angine streptococcique parmi les médecins généralistes, maîtres de stage de la faculté de médecine Paris Descartes : 2005-2007.

UNLABELLED: The distribution of the Rapid Antigen Detection Test (RADT) and the National Health Insurance's information campaign should efficiently reduce the unjustified use antibiotic. However, a preliminary survey among GP trainers at the Paris Descartes University indicated that the RADT was seldom used. OBJECTIVES: This study had for aim to describe the RADT use trend among trainers since 2005 and the main obstacles to its widespread use, and to assess the Mac Isaac score use and antibiotic prescriptions. METHODS: Between February and May 2007, a survey was carried out among 66 GPs who were required to report their first ten patients over three years of age presenting with pharyngitis. RADT use and antibiotic prescriptions were compared with those of the 2005 survey. RESULTS: RADT use had decreased (52.5% [48.2-56.8] versus 57.5% [52.1-68.8], p<0.05). GPs did not use the RADT because they considered it "useless in decision making". Clinical findings were sufficient in most cases. The Mac Isaac score was not widely used by GPs (28.3%) and antibiotic prescription had increased except for macrolides which had decreased (10% vs 15%). Among patients with a negative RADT, 11.9% (vs 10.5% en 2005, p<0.001) were prescribed antibiotics. CONCLUSIONS: The RADT use decreased in two years among GP trainers. GPs still prescribe treatment according to clinical findings, most without using diagnostic tools.

Direct simulation of heterogeneous diffusion and inversion procedure applied to an out-diffusion experiment. Test case of Palmottu granite.

An out-diffusion laboratory experiment using a non-reactive tracer was fitted using the Time Domain Diffusion (TDD) method. This rapid particle tracking method allows simulation of the heterogeneous diffusion based on pore-scale images and local values of diffusivities. The superimposed porosity and mineral 2D maps act as computation grids to condition diffusion pathways. We focused on a Palmottu granite sample, in which the connected pore space has a composite microstructure with cracks linking microporous minerals and is above the percolation threshold. Three main results were achieved: (i) When compared to the fitting obtained with one coefficient (best mean square residual R = 1.6 x 10(-2)), diffusion is shown to be suitably characterised with two coefficients related to cracks and microporous minerals (best R = 6.5 x 10(-4)), (ii) rather than imposing a local apparent diffusion coefficient D(a) independent of the local porosity Phi, a best fit is obtained by applying Archie's relationship D(a) = D(0) x G with G = Phi(m) to each pixel of the calculation grids (G is the geometry factor, D(0) is the diffusion coefficient in free fluid, and m is Archie's exponent), and (iii) the order of magnitude of the fitted diffusion coefficient or Archie's exponents (m=0 for microcracks and m=1.82 for microporous minerals) is physically realistic.