The present study examines combined conduction-radiation heat transfer in non-gray gases within a two-dimensional rectangular domain, representing a section of a combustion chamber. The participating gases considered are 10%CO2/N2, 20%H2O/N2 and their corresponding mixture, whereas N2 is treated as non-participating. A correlated SLW model is developed to evaluate the Planck-mean absorption coefficients by summing the products of discrete gray absorption coefficients and their associated weights. The radiative properties of the non-gray gases are obtained over their absorption spectral bands using data from HITEMP2010, while thermal conductivities are computed using the Sutherland relation. An exact semi-analytical formulation based on ray tracing, Bickley-Naylor functions, and Gauss quadrature is employed to solve the radiative transfer equation (RTE) using Planck-mean absorption coefficients. The energy equation is discretised using a finite-difference approach with a Crank-Nicolson scheme. The effects of gas thermal properties, gas temperature, the number of discrete gray gases, gas species, and mixture ratios on thermal quantities are analysed in detail. Numerical simulations of dimensionless conduction-radiation temperature and total heat flux are presented.

The ray-tracing method and the SLW correlated model have been implemented to address the problem of radiative heat transfer in a two-dimensional geometry filled with non-gray gases. Mixtures with 10%CO2 and 20%H2O were treated as the participating non-gray gases, while N2 was regarded as non-participating in the radiative transfer process. The SLW correlated method has been used to compute discrete absorption coefficients, their associated weights, and the Planck-mean absorption coefficient. An exact semi-analytical method using Bickley-Naylor functions, Gauss quadrature, and the ray tracing method has been developed to solve the radiative transfer equation (RTE). Radiative properties of the non-gray gases have been calculated for different temperatures to describe the thermal behavior of the medium. The effect of the reference temperature and non-gray gas radiative properties on the RTE integral solutions, was also examined. Dimensionless temperature and radiative heat flux distributions were simulated and tabulated under radiative equilibrium, then presented and discussed. The computed radiative quantities showed good agreement with established reference models.

Selenium is an essential trace element co-translationally incorporated into selenoproteins with important biological functions. Health benefits have long been associated with selenium supplementation. However, cytotoxicity is observed upon excessive selenium intake. The aim of this study is to investigate the metabolic pathways underlying the response to the selenium-containing amino acids selenomethionine and selenocysteine in a normal human breast epithelial cell model. We show that both selenomethionine and selenocystine inhibit the proliferation of non-cancerous MCF-10A cells in the same concentration range as cancerous MCF-7 and Hela cells, which results in apoptotic cell death. Selenocystine exposure in MCF-10A cells caused a severe depletion of free low molecular weight thiols, which might explain the observed upregulation of the expression of the oxidative stress pathway transcription factor NRF2. Both selenomethionine and selenocystine induced the expression of target genes of the unfolded protein response (GRP78, ATF4, CHOP). Using a redox-sensitive fluorescent probe targeted to the endoplasmic reticulum (ER), we show that both selenoamino acids shifted the ER redox balance towards an even more oxidizing environment. These results suggest that alteration of the redox state of the ER may disrupt protein folding and cause ER stress-induced apoptosis in MCF-10A cells exposed to selenoamino acids.

The radiative transfer in atmosphere-ocean systems with different atmosphere models is evaluated by the discrete spherical harmonics method. Four standard atmosphere models, namely, Tropical, Mid-Latitude Summer, Mid-Latitude Winter, and U.S. Standard (1976) limited to a height of 16 km are considered above an ocean. Two monochromatic radiations are considered according to the preponderance of the interaction they present with the participating medium, namely, lambda = 0:55 lm for scattering by particles and lambda = 16:8 lm for absorption and emission by water vapor and carbon dioxide. The absorption by the atmospheric gases considered is analyzed by the statistical narrow-band correlated-k method. The optical properties of aerosols and water clouds considered are calculated by Lorenz-Mie theory. The results obtained by the proposed discrete spherical harmonics method are in agreement with those of the literature and demonstrate the efficiency and accuracy of the developed radiative transfer code. The effects of the governing parameters of the system are investigated and show that the presence of the ocean contributes to increasing the upward radiation fluxes in the atmosphere. The presence of aerosols in the atmosphere leads to downward radiance curves at ground level that show significant peaks around the zenith angle of observation theta = 0 deg. Additionally, the presence of the cloud in the atmosphere creates a discontinuity in the radiation flux curves at the height of the cloud.

An exact semi-analytical determination of the incident radiation and radiative flux inside a nonisothermal grey absorbing-emitting semi-transparent medium enclosed in a square cavity with reflecting surfaces, which contains a centered square opaque and reflecting obstacle is proposed.

The mobility of solute in unsaturated soil column from the surface to the groundwater induced with moisture and heat transfer processes is investigated using the spectral element method. The problem is mathematically described using partial differential equations. The heat and moisture are assumed to be one-dimensional processes and the unsaturated soil has variable thermal, hydraulic and convective properties. The goal is to provide analysis concerning the solute transport in unsaturated soil. The investigation quantifies the solute spatial–temporal variations and studies the effects of the related characteristic parameters. The established highly nonlinear equations describing the heat and mass transfer processes are solved using a developed MATLAB program. The numerical prediction of solute movement is compared with the analytical benchmark solution from the literature and good performance is exhibited. The fully coupled solute transport with heat and water flow is conducted and the corresponding transient flowing of temperature and moisture distributions are estimated. The results show that the thermal model developed has a little influence on soil solute prediction at low upper surface boundary with temperature valued of 20 °C when compared to the isothermal model. Affected with the soil gravity, isothermal and thermal solute predictions are equivalent for small time variations, non-large soil depth as well as for high solute diffusivity. However, a great discrepancy is observed between isothermal and thermal predictions when increasing the input variation of the soil surface temperature to 30 °C. At this relatively high soil temperature changes, the output solute breakthrough magnitude decreases which generally leads to its fast transportation in soil.

An exact semi-analytical determination of the incident radiation and radiative flux inside a non-isothermal grey absorbing-emitting semi-transparent medium enclosed in a square cavity with reflecting surfaces, which contains a centered square opaque and reflecting obstacle is proposed. Due to the reflection at all the surfaces, the radiosity technique is used to determine the radiosity temperatures on the surfaces, taking into account the non-isothermal medium, before including them in the calculation of the incident radiation. The surfaces integrals are fully developed by using the Altaç angular integrated Bickley-Naylor functions of order 2, while the double angular and space integrals are partially discretized with the help of a Gauss quadrature on an adequate meshing grid, following an iterative scheme to calculate the temperature field at radiative equilibrium. Once the temperature distribution is obtained, the radiative flux vector inside the participating medium is calculated by using the Altaç functions and of order 3 associated to the surfaces integrals. An accuracy criterion based on the surface radiative normal flux integrated on internal centred virtual squares has been proposed, and the effects of different parameters such as the size of the square inner obstacle, the surface emissivities and the medium’s absorption coefficient, on the cavity’s temperature field and the radiative flux field behavior at radiative equilibrium have also been investigated.

Methylselenol (MeSeH) has been suggested to be a critical metabolite for anticancer activity of selenium, although the mechanisms underlying its activity remain to be fully established. The aim of this study was to identify metabolic pathways of MeSeH in Saccharomyces cerevisiae to decipher the mechanism of its toxicity. We first investigated in vitro the formation of MeSeH from methylseleninic acid (MSeA) or dimethyldiselenide. Determination of the equilibrium and rate constants of the reactions between glutathione (GSH) and these MeSeH precursors indicates that in the conditions that prevail in vivo, GSH can reduce the major part of MSeA or dimethyldiselenide into MeSeH. MeSeH can also be enzymatically produced by glutathione reductase or thioredoxin/thioredoxin reductase. Studies on the toxicity of MeSeH precursors (MSeA, dimethyldiselenide or a mixture of MSeA and GSH) in S.cerevisiae revealed that cytotoxicity and selenomethionine content were severely reduced in a met17 mutant devoid of O-acetylhomoserine sulfhydrylase. This suggests conversion of MeSeH into selenomethionine by this enzyme. Protein aggregation was observed in wild-type but not in met17 cells. Altogether, our findings support the view that MeSeH is toxic in S. cerevisiae because it is metabolized into selenomethionine which, in turn, induces toxic protein aggregation.

Selenium (Se) is an essential trace element of considerable interest in humans from both a nutritional and a toxicological perspective because of the narrow margin between intakes that result in efficacy and toxicity. It is used as selenocysteine in a few selenoproteins with important physiological functions. Moreover, at supranutritional doses, Se-containing compounds have attracted interest as potential anticancer agents with high efficacy and selectivity against cancer cells. Thus, Se is becoming a widely used dietary supplement. However, accumulating evidence indicate that adverse health effects are associated with excess dietary supplementation. Therefore, characterizing the toxicity of Se metabolic intermediates are important steps to better understand both the beneficial and toxic mechanisms of Se. This review focuses on the metabolism of Se and the biological mechanisms explaining the toxicity of important Se-metabolites in the yeast Saccharomyces cerevisiae, which can be used as a model system to understand the mode of action and the biological effects of supranutritional Se in higher eukaryotes.

In this work, a physical model based on the radiative transfer equation is presented to estimate the global solar irradiance on top of the Earth's atmosphere surface. A link is established among the radiative transfer through the atmosphere, the geographic coordinates of a city (longitude, latitude), time of day, and date of the year. The discrete spherical harmonics method is applied to solve the radiative transfer equation. The city of Dschang in Cameroon is taken as an example of application of the model. This city is located at latitude 5°44'N and longitude 10°04'E. It is assumed that the atmosphere of the city is inhomogeneous and composed of non-polarizing Haze L aerosol particles in gamma distribution, while the ground surface diffuses radiation isotropically. The predictions are compared under clear sky conditions to some existing models of irradiance such as the Bird model and Davies and Hay model for a homogeneous atmosphere. Results demonstrate that the present investigation matches well with the Bird and the Davies and Hay models and is valuable for ground solar irradiance estimation. The effects of the inhomogeneity of the atmosphere on total insolation are also studied, and our results indicate that the inhomogeneity of the atmosphere reduces local insolation. The present study shows that the radiative transfer model is an efficient technique for estimating global solar radiation at any level of the stratified atmosphere and under different atmospheric conditions.

An exact semi-analytical determination of the radiosity temperatures on the diffusely reflecting surfaces of a square cavity filled with a non-isothermal absorbing and emitting semi-transparent medium containing a centred reflecting opaque obstacle is proposed. One develops first the obstacle's surfaces radiosity temperatures formulation before detailing all the different possible configurations existing for the cavity's surfaces radiosity temperatures determination. Thanks to the radiosity technique, the integrals solutions of the radiative transfer equation are calculated for all listed cases. Then, the numerical results of the radiosity temperatures are obtained from a Gauss quadrature and an adequate meshing grid, following an iterative scheme. The effects of different parameters such as the size of the internal obstacle, the emissivities and the absorption coefficient on the cavity's radiosity temperatures behaviour have also been investigated.

Methylselenol (MeSeH) is a major cytotoxic metabolite of selenium, causing apoptosis in cancer cells through mechanisms that remain to be fully established. Previously, we demonstrated that, in Saccharomyces cerevisiae, MeSeH toxicity was mediated by its metabolization into selenomethionine by O-acetylhomoserine (OAH)-sulfhydrylase, an enzyme that is absent in higher eukaryotes. In this report, we used a mutant met17 yeast strain, devoid of OAH- sulfhydrylase activity, to identify alternative targets of MeSeH. Exposure to dimethyldiselenide (DMDSe), a direct precursor of MeSeH, caused an endoplasmic reticulum (ER) stress, as evidenced by increased expression of the ER chaperone Kar2p. Mutant strains (∆ire1 and ∆hac1) unable to activate the unfolded protein response were hypersensitive to MeSeH precursors but not to selenomethionine. In contrast, deletion of YAP1 or SKN7, required to activate the oxidative stress response, did not affect cell growth in the presence of DMDSe. ER maturation of newly synthesized carboxypeptidase Y was impaired, indicating that MeSeH/DMDSe caused protein misfolding in the ER. Exposure to DMDSe resulted in induction of the expression of the ER oxidoreductase Ero1p with concomitant reduction of its regulatory disulfide bonds. These results suggest that MeSeH disturbs protein folding in the ER by generating a reductive stress in this compartment.

This article presents a summary of the characteristics and advantages of thermoelectric modules to be applied in residences.These modules are able to convert thermal energy into electrical energy without to use steam and have no moving parts such as turbines.They can also be used for air conditioning for heating or cooling a room or office.In this article, numerical simulations through TRNSYS are suggested to perform the calculations of power, voltage and heat transfer.Optimization of the modules is also suggested in order to obtain more power generated and cooling power from thermoelectric modules.

The present paper deals with an exact semi-analytical formulation of a combined conductive-radiative heat transfer, applied to a two-dimensional semi-transparent medium carrying a square centered obstacle. The gray participating medium with black boundaries absorbs, emits but does not scatter radiation. One intends to evaluate the temperature and radiative heat flux distributions within the semi-transparent medium. The radiative transfer equation has been solved using an exact analytical expansion of Bickley-Naylor and Altaç angular integrated Bickley-Naylor functions, then solved numerically with Gauss quadrature. Energy equation has been directly discretized and approximated numerically using the centered finite differences method and consequently the dimensionless temperature has been obtained after an iterative scheme. The results of radiative quantities obtained have been verified with benchmark with an excellent agreement, both for simple and complex geometries. Simulations have been performed to obtain results for different sizes of the centered obstacle and the optical thickness. The effects of the conduction-radiation parameters, discrete directions and the size of the obstacle have also been investigated.

Radiation-vegetation canopy interaction is analyzed using a semi-analytic discrete ordinates characteristics solution. The plant canopy is considered as a single layer containing a set of leave ensembles of bi-Lambertian surfaces and the radiation-plant canopy interaction is described by a radiative transfer equation in which the plant canopy radiative properties depend on the incident radiation direction. An analytical expression for anisotropic plant canopy radiance is derived. Radiance and hemispherical reflectance/transmittance for different boundary conditions and the plant canopy in the visible and near infrared are predicted. Results show that the discrete ordinates characteristics solution using the moderate number of double-Gauss ordinates direction compete well with the FN or “facile” and analytical discrete ordinates methods, which are two other literature quasi-analytical methods for phonon transport in the anisotropic plant canopy. Results also reveal that the proposed method matches exact Chandrasekhar benchmark, except for view cosine direction µ≥0.9, where the accuracy on transmitted radiance is less than 0.3% for low angular discretization. Comparisons between numerical predictions and soybean reflectance experiments indicate that the leaf area index and soil reflectance effects are significant in the near infrared plateau.

The subject dealt with is an accurate semi-analytical modeling of two-dimensional radiative heat transfer.The semi-transparent medium is gray and has an absorbing-emitting rectangular shape hollowed by internal square fluid cavity, bounded by black surfaces.The aim is to establish some benchmark results either for radiative intensity, or flux and temperature field, from which forwards analysis will be compared.Hence, analytical incoming radiative intensity, flux and temperature fields inside the gray medium are established, in function of the center coordinates of the fluid cavity.Only radiative transfer mode is considered at equilibrium state.Therefore, radiative quantities are spatially and angularly integrated using special functions in order to avoid ray effects on results.Thanks to double Gauss quadrature, which will allow to obtain numerically the radiative equations.Finally, results validation is done when the size of internal hollowed cavity becomes very small and expected results remain with good agreement with literature.

Exact semi-analytical expressions of the incident radiation and radiative flux fields are developped, inside a two-dimensional semi-transparent medium and followed by numerical simulations. A rectangular cavity is filled-in with a gray absorbing-emitting, but non-scattering semi-transparent medium at radiative equilibrium. An opaque inner centered cavity with black and imposed temperatures surfaces is set as a non-participating medium, nevertheless its external boudary surfaces participate to radiative transfer. An exact method based on ray tracing and specific functions is performed to evaluate the incident radiation and radiative flux fields. Spatial and angular discretization are ensured with a Gauss quadrature by Numerical issue. Temperature field is computed with an iterative process until convergence. Verification of results is done both for simple and complex geometries, and remains in good agreement with literature. Hence, the other one results of radiative quantities are tabulated as benchmark solutions and simulated for several sizes of the inner square cavity for different ranges of optical thickness. (C) 2019 Elsevier Ltd. All rights reserved.

Nonlinear hyperbolic heat conduction problems are analyzed thanks to the Cattaneo-Vernotte model, which takes what happens at very short times into account.First, the case of the coupled conductive-radiative heat transfer in planar and spherical media is considered.The accuracy of the Lattice Boltzmann heat conduction model coupled with an analytical layered spherical harmonics solution of the radiative transport equation is investigated.The effects of different parameters such as scattering albedo on both temperature and conductive heat flux distributions within the medium are studied for steady and transient states.The present predictions agree well with literature benchmarks.It is also shown that the parameters have a significant effect on both temperature profile and hyperbolic sharp wave front.Second, the non-Fourier heat conduction in a thermoelectric thin layer is investigated under several boundary conditions by performing a specific quadrupole method.The expressions of the temperature and the heat flux of the small-scale thermoelectric materials are obtained and the whole matrix formulation is given explicitly.Good agreement is observed between quadrupole temperature predictions and analytical results for the Fourier heat conduction problems.

The analytical layered solution for radiative transfer through participating optically complex media is developed. The angular processing of radiation is based on double spherical harmonics method (DPN) which split up the radiative intensity into two stream components before expanding in Legendre polynomial basis. The proposed layered radiative solution assumes that the optically complex media is a set of thin layers dealing with homogeneous properties. Therefore, the analytical solution for radiative transfer is performed and then coupled to the finite volume method (FVM), to solve the non - linear hyperbolic thermal conduction problems, formulated thanks to Cattaneo-Vernotte flux. In developing the FVM, the Roe's corrections of interface fluxes is adopted in order to enhance the performances of the method. The accuracy of the proposed model for dealing with inhomogeneous radiation/conduction problems is investigated by considering participating media such as slab, solid or hollow spheres, with temperature dependent thermal conductivity. The effects of different parameters, known as scattering albedo, graded index function, thermal conductivity, boundary emissivity and the conduction-radiation parameter on both temperature and heat flux distributions for purely radiation, steady and transient states are studied. Results of the present work compare well with those available in the literature with maximum relative error less than 1%. These results show that the listed parameters have a significant effect on both temperature profiles and hyperbolic sharp wave front. It also comes from this study that the proposed layered approach is an efficient, robust, and accurate method for radiative flow analysis in inhomogeneous media while the Roe's correction of interface fluxes in FVM is suitable to accommodate thermal wave front in non - Fourier analysis. (C) 2019 Elsevier Ltd. All rights reserved.

The propagation of radiation in an absorbing-scattering soil with constant or spatial variation of the refractive index is investigated. The soil consists of a plane parallel with Fresnel reflection at the boundaries and is exposed at one boundary to a diffuse or collimated incident radiation. The discrete spherical harmonics method using Marshak boundary conditions is introduced to approximate the directional hemispherical reflectance and transmittance as well as the bidirectional reflectance. The effect in spatial variation of the refractive index on the reflectance and transmittance predictions is examined. A comparison of the directional transmittance and reflectance with the literature results demonstrates that the present method gives accurate results for optically thin and thick soil with a maximum relative error in all cases less than 1%. The bidirectional radiance for variable refractive index soils also shows excellent agreement as compared to the literature results. The results demonstrated that the anisotropic soil interfaces cause a significant decrease of energy reflected and transmitted as well as the bidirectional reflectance.