Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Mobile-immobile mass transfer is widely used to model non-Fickian dispersion in porous media. Nevertheless, the memory function, implemented in the sink/source term of the transport equation to characterize diffusion in the matrix (i.e., the immobile domain), is rarely measured directly. Therefore, the question can be posed as to whether the memory function is just a practical way of increasing the degrees of freedom for fitting tracer test breakthrough curves or whether it actually models the physics of tracer transport. In this paper we first present a technique to measure the memory function of aquifer samples and then compare the results with the memory function fitted from a set of field-scale tracer tests performed in the same aquifer. The memory function is computed by solving the matrix diffusion equation using a random walk approach. The properties that control diffusion (i.e., mobile-immobile interface and immobile domain cluster shapes, porosity, and tortuosity) are investigated by X-ray microtomography. Once the geometry of the matrix clusters is measured, the shape of the memory function is controlled by the value of the porosity at the percolation threshold and of the tortuosity of the diffusion path. These parameters can be evaluated from microtomographic images. The computed memory function compares well with the memory function deduced from the field-scale tracer tests. We conclude that for the reservoir rock studied here, the atypical non-Fickian dispersion measured from the tracer test is well explained by microscale diffusion processes in the immobile domain. A diffusion-controlled mobileimmobile mass transfer model therefore appears to be valid for this specific case.
ISSN: 0043-1397

insu-00373705
https://hal-insu.archives-ouvertes.fr/insu-00373705
https://hal-insu.archives-ouvertes.fr/insu-00373705/document
https://hal-insu.archives-ouvertes.fr/insu-00373705/file/Gouze_et_al-2008-Water_Resources_Research.pdf
DOI : 10.1029/2007WR006690

Éditeur(s) : HAL CCSD Oxford University Press
Résumé : International audience
ISSN: 1369-3786

hal-01118199
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118199
DOI : 10.3109/13693786.2010.511287
PUBMED : 21067335

Éditeur(s) : HAL CCSD
Résumé : oral presentation, 22nd European Meeting on Hypertension and Cardiovascular protection, London, 26-29 april 2012
To assess the relationship between socioeconomic factors and the expression of multiple cardiovascular risk factors in an adult Caribbean population.
https://hal.univ-antilles.fr/hal-00739783

Droits : info:eu-repo/semantics/OpenAccess
hal-00739783
https://hal.univ-antilles.fr/hal-00739783
https://hal.univ-antilles.fr/hal-00739783/document
https://hal.univ-antilles.fr/hal-00739783/file/High_cardiovascular_risk_cor.pdf

Éditeur(s) : HAL CCSD
Résumé : poster presentation, 22nd European Meeting on Hypertension and Cardiovascular protection, London,26-29 April 2012
OBJECTIVE: Several studies demonstrate that the perception of overweight is associated with attempts at weight control in overweight subjects. Our objective is to describe the factors associated with the perception of overweight in an adult Caribbean population, and in particular, to assess the relationship between the perception of overweight and previous medical diagnosis of overweight. METHOD AND DESIGN: Consant was a cross-sectional study carried out in 2007 on a representative sample of the adult Guadeloupean population. Included were 1,005 subjects aged 25-74 years, drawn from stratified random sampling, and interviewed at home. The perception of overweight was evaluated by the question: "Do you consider yourself to be overweight?" with a binary response. RESULTS: Among overweight subjects (Body Mass Index ≥ 25 kg/m2, n = 576), 38.6% provided an incorrect assessment of their weight status. This proportion falls to 17.4% in those who stated to have previously received a medical diagnosis of overweight. However, only 48.8% of overweight subjects stated to have received such a diagnosis. A logistic regression shows that the underestimation of weight status is associated with the absence of previous diagnosis for overweight (OR: 5.35 - p < 10-3), as well as an age greater than or equal to 55 years (OR: 2.91 - p < 10-3), a BMI of less than 30 kg/m² (OR: 2.26 - p: 0.001), the male sex (OR: 1.86 - p: 0.004), and a low income level (OR: 1.62 - p: 0.030), but not a lack of awareness regarding the role of weight control in the prevention of cardiovascular diseases. Similar results are observed if waist circumference is taken as a factor instead of BMI. CONCLUSION: In this population, the lack of medical diagnosis of overweight was the leading factor associated with misperception of overweight. Screening for overweight therefore appears to be one of the preconditions to weight management, and remains a fundamental but often unused element in the fight against obesity.
https://hal.univ-antilles.fr/hal-00739785

Droits : info:eu-repo/semantics/OpenAccess
hal-00739785
https://hal.univ-antilles.fr/hal-00739785
https://hal.univ-antilles.fr/hal-00739785/document
https://hal.univ-antilles.fr/hal-00739785/file/The_lacksur screening_is_the_leading_factor_associated_with_the_misperceptionsur overweight_cor.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : The correct characterization of the effective reactive transport dynamics is an important issue for modeling reactive transport on the Darcy scale, specifically in situations in which reactions are localized, that is when different reactions occur in different portions of the porous medium. Under such conditions the conventional approach of homogenizing only the porous medium chemistry is not appropriate. We consider here reactive transport in a porous medium that is characterized by mass transfer between a mobile and a distribution of immobile regions. Chemical and physical heterogeneities are reflected by distributions of kinetic reaction rate constants and residence times in the immobile zones. We derive an effective reactive transport equation for the mobile solute that is characterized by non-local physical mass transfer and reaction terms. Specifically, chemical heterogeneity is upscaled in terms of a reactive memory function that integrates both chemical and physical heterogeneity. Mass transfer limitations due to physical heterogeneity yield effective kinetic rate coefficients that can be much smaller than the volumetric average of the local scale coefficients. These results help to explain and quantify the often reported discrepancy between observed field reaction rate constants and the ones obtained under well mixed laboratory conditions. Furthermore, these results indicate that transport under physical and chemical heterogeneity cannot be upscaled separately.
ISSN: 0169-7722

hal-00617674
https://hal.archives-ouvertes.fr/hal-00617674
DOI : 10.1016/j.jconhyd.2010.06.002

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Heletz sandstone (Israel) reactivity is studied by means of CO2-rich brine percolation experiments and modeling. Experiments are performed at in situ temperature and pressure conditions with two distinctly different injection flow rates and for two different brine compositions: the genuine Heletz brine and a similar brine but in equilibrium with gypsum. The Heletz sandstone is composed of quartz, dolomite, ankerite, K-feldspar, clay minerals and minor amounts of gypsum and pyrite. The main reaction is the dissolution of the carbonates which is fastest for the highest flow rate injection and for the genuine Heletz brine. Permeability increases during the five percolation experiments, regardless of flow rate and brine type. This increase in permeability is associated to a decrease in porosity during the gypsum-equilibrated brine experiments due to gypsum precipitation. The precipitation of secondary minerals (kaolinite, muscovite and smectite) is mainly controlled by the dissolution of K-feldspar and largest at low flow rate injection, indicating that these precipitation processes are diffusion-controlled and localized in immobile zones where favorable chemical micro-environments exist. These processes are quantified by means of a reactive transport model. These results indicated that the CO2 injection at the Heletz site should trigger both permeability increase in interface between brine and CO2, which may extend over a large extension and where mixing processes are very active, especially near the well under intermittent injection conditions.
ISSN: 1750-5836

hal-01356329
https://hal.archives-ouvertes.fr/hal-01356329
DOI : 10.1016/j.ijggc.2015.10.023

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
OBJECTIVE: To assess the relationship between hypertension and perceived material insecurity in a disadvantaged Caribbean population. PATIENTS AND METHODS: We used data from a cross-sectional study involving 2420 disadvantaged subjects aged 18-69 years, included consecutively at three Guadeloupian health centers. Hypertension was diagnosed over two consultations with a total of six blood pressure measurements. Perceived material insecurity was assessed using a closed-ended question. RESULTS: The prevalence of hypertension was estimated at 17.7% among subjects who believed their material situation would improve in the future, at 28.2% among those who believed it would remain the same, and at 43.3% among those who believed it would deteriorate. A multivariate logistic regression analysis showed that hypertension risk more than doubled (OR: 2.35 - P: 0.002) among subjects who believed that their material situation would deteriorate in the future compared to those who believed that their situation would improve, with no significant sex-related differences. This relationship was especially strong among subjects aged 40 years or more (OR: 3.30 - P<10(-3)), and among subjects with low education level (OR: 3.81 - P: 0.003), but was independent of the other tested variables. CONCLUSION: In this disadvantaged population, perceived material insecurity is a psychosocial factor strongly associated with hypertension, independently of subjects' risk behaviors. Subjects aged 40 years or more and subjects with a low education level seem the most vulnerable.
ISSN: 0003-3928

hal-00739792
https://hal.univ-antilles.fr/hal-00739792
https://hal.univ-antilles.fr/hal-00739792/document
https://hal.univ-antilles.fr/hal-00739792/file/HTA_et_precarite_percue_en_guadeloupe_-_Copie.pdf
DOI : 10.1016/j.ancard.2012.04.023

Éditeur(s) : HAL CCSD
Résumé : poster presentation, 22nd European Meeting on Hypertension and Cardiovascular protection, London, 26-29 April 2012
To asssess and specify the relationship between hypertension and general obesity and/or abdominal obesity in an adult Caribbean population.
https://hal.univ-antilles.fr/hal-00739787

Droits : info:eu-repo/semantics/OpenAccess
hal-00739787
https://hal.univ-antilles.fr/hal-00739787
https://hal.univ-antilles.fr/hal-00739787/document
https://hal.univ-antilles.fr/hal-00739787/file/Hypertension_is_more_strongly_associated_with_waist_circumference_than_BMI_cor.pdf