Monitoring living tissues by electrical impedance spectroscopy

Solving the experimental difficulties associated with measurement of the electrical impedance of living tissues gives access to valuable tissue compartment parameters which are sensed within seconds using minimally invasive, simple metallic electrodes. Extracellular conductivity and cell membrane capacitance can be followed over time under conditions of metabolic toxicity, perfusion loss and thermal stress in liver, brain cortex, and muscle, respectively. Application of this technique in burns therapy allows an accurate estimation of the severity of thermal injury to skeletal muscle, supporting predictions on tissue survival.     

Effects of rilmenidine on rats made insulin resistant and hypertensive by a high fructose diet

This study was aimed to determine the effects of rilmenidine, an hypertensive drug, in an animal model of hypertension associated with insulin resistance, i.e. rats fed on a high fructose diet. Wistar rats were fed during four weeks either on a standard diet (S) or on a high fructose diet (F, 34.5% de fructose). In half of the F groups, rilmenidine (1 mg/kg/day) was added to the drinking water during the two last weeks of the diet (FR). Arterial blood pressure as well as insulin efficiency were determined at the end of the four weeks. Body weight gain was higher in F than in S rats (66 +/- 8 g versus 45 +/- 8 g; p < 0.05), this was prevented by rilmenidine treatment (32 +/- 2 g). Arterial systolic blood pressure was increased in F rats (162 +/- 2 vs 155 +/- 2 mmHg; p < 0.05), rilmenidine brought this value back to normal (149 +/- 3 mmHg). During the euglycemic hyperinsulinemic clamp, glucose utilization was lower (10 +/- 1 vs 14 +/- 1.5 mg/min/kg; p < 0.05) and hepatic glucose production higher (1 +/- 0.01 vs 0 mg/min/kg; p < 0.01) in F than in S rats. These changes in insulin action were totally abolished by rilmenidine. These data demonstrate that rilmenidine can ameliorate the deleterious effects of a high fructose diet, i.e. weight gain, hypertension and resistance to the effects of insulin Rilmenidine could represent a potential therapeutic agent for the treatment of hypertension associated with metabolic disorders such as syndrom X and obesity.     

The geometric nature of plasticity laws

This paper concerns the plasticity constitutive laws in small strain. In the thermodynamic approach developed here, the key concept is that of internal variables. The differential nature of plasticity law has been pointed out for a long time. If we unite the invariance condition of these laws in a state variable transformation, this involves, ultimately, that the natural mathematic frame of plasticity theory is Differential Geometry. The system state is defined as a point of a differentiable manifold. The state variable are the local coordinates of this point in a chart. The internal stresses are the components of a covariant vector of the cotangent bundle to internal state manifold and the elastic domain is a convex part of cotangent vector space. The plastic yield criteria such as von Mises condition define a Riemannian structure over the manifold. The metric element is identified with the internal dissipation element. Constitutive laws link the covariant derivatives of the thermodynamic stress with the state variable. Hardening modulus splits up in two parts, kinematic hardening and metric hardening. This last is defined by Christoffel connection coefficients. Applied to von Mises isotropic yield condition, the metric hardening is identified with isotropic hardening. The Baltov-Sawczuk model is also analysed. The use of appropriate polar coordinates simplifies significantly the computations. Generalization to a significant category of non-differentiable yield criteria, such as Tresca condition, is considered by introducting a metric tensor family. The adaptation of Drucker's postulate to the proposed model requires the introduction of parallel transport of the internal stress covector. Generally, this transport is different over distinctive paths joining two points. This fact expresses internal state manifold curvature. The Riemann-Christoffel tensor is computed for von Mises, Baltov-Sawczuk and Tresca models.     

Kinetic Monte Carlo simulations of radiation induced segregation and precipitation

Kinetics of radiation induced segregation and precipitation in binary alloys are studied by Monte Carlo simulations. The simulations are based on a simple atomic model of diffusion under electron irradiation, which takes into account the creation of point defects, the recombination of close vacancy-interstitial pairs and the point defect annihilation at sinks. They can reproduce the coupling between point defect fluxes towards sinks and atomic fluxes, which controls the segregation tendency. In pure metals and ideal solid solutions, the Monte Carlo results are found to be in very good agreement with classical models based on rate equations. In alloys with an unmixing tendency, we show how the interaction between the point defect distribution, the solute segregation and the precipitation driving force can generate complex microstructural evolutions, which depend on the very details of atomic-scale diffusion properties.     

Recovering spectral data from natural scenes with an RGB digital camera and colored filters

Many spectral‐recovery methods using RGB digital cameras assume the underlying smoothness of illuminant and reflectance spectra, and apply low‐dimensional linear models. The aim of the present work was to test whether a direct‐mapping method could be used instead of a linear‐models approach to recover spectral radiances and reflectances from natural scenes with an RGB digital camera and colored filters. In computer simulations, a conventional RGB digital camera with up to three colored filters was used to image scenes drawn from a hyperspectral image database. Three measures were used to evaluate recovery with the direct‐mapping method: goodness‐of‐fit, root‐mean‐square error, and a color‐difference metric. It was found that with two and three filters both spectral radiances and reflectances could be recovered sufficiently accurately for many practical applications. With little increase in computational complexity, an RGB camera and a few colored filters can provide significantly better recovery of natural scenes than an RGB camera alone. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 352–360, 2007     

Preferential Oxidation of CO in H2-Rich Gas at Low Temperatures over Au Nanoparticles Supported on Metal Oxides

We investigated Au catalysts supported on TiO₂, Fe₂O₃, and ZnO for their preferential oxidation of CO in a H₂-rich atmosphere. Both full conversion and selectivity were achieved over Au/Fe₂O₃ and Au/ZnO around room temperature, but at higher temperatures the CO conversion was suppressed due to competition between CO and H₂.     

AgNO<Subscript>3</Subscript> spray tests: advantages,weaknesses, and various applications to quantify chloride ingress into concrete. Part 1: Non-steady-state diffusion tests and exposure to natural conditions

Within the framework of the evaluation and the prediction of chloride-induced corrosion risks, simple and rapid AgNO₃ spray tests can be proposed for various issues. This paper forms the first part of a series. In this first part, the Maultzsch procedure (spraying of 0.1-N AgNO₃ solution + K₂CrO₄) as well as the procedure based on the use of a sole AgNO₃ solution have been investigated on a broad range of concretes. These procedures have also been compared to the Collepardi procedure (spraying of 0.1-N AgNO₃ + fluoresceine). The feasibility of these colorimetric techniques on saturated specimens cast in laboratory, after non-steady-state diffusion tests carried out in various conditions, is discussed. In addition, the results obtained from applying such spray tests in field conditions on cores drilled out from various RC test specimens exposed to a marine environment (tidal zone) and to a road and cold environment (freezing-thawing cycles and spraying of deicing salts) are presented. Colorimetric methods have in particular been applied here to the assessment of the average chloride penetration depth and of its evolution versus time (kinetics). Moreover, the detection threshold of these techniques has been investigated in various environments. The possible sources of discrepancy on the results have been analysed.     

Glyconanoparticle-DNA interactions: an atomic force microscopy study.

Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents.     

Standardizing formats of corporate source data

This paper describe an approach for improving the data quality of corporate sources when databases are used for bibliometric purposes. Research management relies on bibliographic databases and citation index systems as analytical tools, yet the raw resources for bibliometric studies are plagued by a lack of consistency in fied formatting for institution data. The present contribution puts forth a Natural Language Processing (NLP)-oriented method for the identification of the structures guiding corporate data and their mapping into a standardized format. The proposed unification process is based on the definition of address patterns and the ensuing application of Enhanced Finite-State Transducers (E-FST). Our procedure was tested on address formats downloaded from the INSPEC, MEDLINE and CAB Abstracts. The results demonstrate the helpfulness of the method as long as close control of errors is exercised as far as the formats to be unified. The computational efficacy of the model is noteworthy, due to the fact that it is firmly guided by the definition of data in the application domain.