Lead, cadmium, iron, zinc, copper, manganese, calcium and magnesium in SPF male rats exposed to a dilution of automotive exhaust gas throughout their lives

Male pathogen free CFE albino Sprague Dawley rats were exposed 8 h per day, 5 days per week, for three years to a 1/1000 dilution of automotive exhaust gas, containing 58 ppm carbon monoxide, 0.37% carbon dioxide, 23 ppm nitrogen oxides, 2 ppm aldehydes, less than 5 mg/l hydrocarbons and 8.5 micrograms/m3 lead. Lead, cadmium, iron, zinc, calcium and magnesium were measured by atomic absorption in the femurs and tibias of the rats which died during the experiment. A comparison with two control groups revealed that the only significant difference in the elements measured in the bones was a 500% increase in lead concentration. The calculations of the correlations between the percentages of the elements in bones, the ages and the body weights of the rats, as well as cluster analysis, did not show consistent variations of the water, calcium, magnesium concentrations nor of the other studied metals related to this increase in lead concentration. Moreover, longevity was the same in the 3 groups of rats, but the body weight was statistically smaller (4%) in the group exposed to the auto exhaust dilution.     

Numerical absorbing boundary conditions for the scalar and vectorwave equations

Electromagnetic field computation may be carried out conveniently by using the finite element method (FEM). When solving open region problems using this technique, it becomes necessary to enclose the scatterer with an outer boundary upon which an absorbing boundary condition (ABC) is applied; analytically-derived ABCs have been used extensively for this purpose. Numerical absorbing boundary conditions (NABCs) have been proposed as alternatives to analytical ABCs. For the two-dimensional (2-D) Helmholtz equation, it has been demonstrated analytically that these NABCs become equivalent to many of the existing analytical ABs in the limit as the cell size tends to zero. In addition, the numerical efficiency of these NABCs has been evaluated by using as an indicator the reflection coefficient for plane and cylindrical waves incident upon an arbitrary boundary. We have extended this procedure to the study of the NABCs derived, for the three-dimensional (3-D) scalar and vector wave equations from the point of view of their numerical implementation in node- and edge-based FEM formulations, respectively     

Genetic factors and acute carbon monoxide intoxication

LD_12:12 (L = 100 lux) synchronized, 5–10 grouped small laboratory vertebrates, were during part of the L period (0900–1130) exposed to an acute carbon monoxide intoxication, resulting in an overall 50 % mortality. Interspecific and interstrain differences were found in outbred and inbred mice (CBA, C57B1, OF₁), outbred rats (Sprague-Dawley, Wistar), guinea-pigs, chicks (R+, R-), and Japanese quails. In this last bird species, a genetic selection produced two genotypes, one sensitive and one resistant to a carbon monoxide acute intoxication.     

A theoretical study of numerical absorbing boundary conditions

Electromagnetic field computation involving inhomogeneous, arbitrarily-shaped objects may be carried out conveniently by using partial differential equation techniques, e.g., the finite element method (FEM). When solving open region problems using these techniques, it becomes necessary to enclose the scatterer with an outer boundary on which an absorbing boundary condition (ABC) is applied, and analytically-derived ABCs, e.g., the Bayliss-Gunzburger-Turkel and Engquist-Majda boundary conditions have been used extensively for this purpose. Numerical absorbing boundary conditions (NABCs) have been proposed as alternatives to analytical ABCs, and they are based upon a numerically-derived relationship that links the values of the field at the boundary nodes to those at the neighboring nodes. In the paper the authors demonstrate, analytically, that these NABCs become equivalent to many of the existing analytical ABCs in the limit as the cell size tends to zero. In addition, one can evaluate the numerical efficiency of these NABCs by using as an indicator the reflection coefficient for plane and cylindrical waves incident upon an arbitrary boundary     

Impedance boundary conditions for finite planar and curved frequency selective surfaces

We consider the time-harmonic electromagnetic scattering problem from a finite planar or curved, infinitesimally thin, frequency selective surface (FSS), the periodic unit cells of which are constituted, exclusively, by electric conductors and free-space. In order to avoid the meshing of these cells, the problem is solved by employing an integral equation formulation in conjunction with approximate impedance boundary conditions (IBC) prescribed on the sheet that models the FSS. The impedance in the IBC is derived from the exact reflection coefficient calculated, for the fundamental Floquet mode, on the infinite planar FSS illuminated by a plane-wave at a given incidence. When the FSS is curved, and/or the direction of the incident wave is unknown, higher order IBCs are proposed that are valid in a large angular range and can be implemented in a standard method of moments formulation. Also, a simple technique is presented that allows to reproduce the radiating Floquet modes in the scattered field even though those are not accounted for in these IBCs. Their numerical efficiencies are evaluated for a curved strip grating translationally invariant along one direction. Finally, we present an alternative approach where the impedance is approximated by its truncated Fourier series, that considerably enhances the accuracy of the results at the cost, however, of a denser mesh of the sheet.     

A fast-domain decomposition method for the solution ofelectromagnetic scattering by large objects

A nonoverlapping domain decomposition method is proposed for the finite element solution of the scattering problem by electrically large, inhomogeneous, infinite cylinders of arbitrary cross section. To minimize the size of the total computational domain, a second-order-absorbing boundary condition (ABC) is applied upon an outer boundary of arbitrary shape which may be conformal to the surface of the scatterer. This domain is then partitioned into concentric subdomains circumscribing the object. A second-order transmission condition, derived from the ABC, is prescribed upon the interfaces between two adjacent subdomains. This particular configuration is responsible for the fast convergence of the domain decomposition iterative algorithm, which is parallelizable. Numerical results obtained with a nonparallelized computer code are presented, which emphasize the superiority of this technique in terms of memory storage requirements and computing times over the standard finite element approach, as well as over the rigorous hybrid finite element-integral equation formulation     

Sex-related factors in acute carbon monoxide intoxication in one strain of mice

In the OF1 mouse strain, males are less resistant than females to acute carbon monoxide intoxication. Castration of males increases their resistance to carbon monoxide. For Neonates injected with four different doses of testosterone (20-500 mg per kg) or oestradiol (2-50 mg per kg), more effect on resistance to carbon monoxide in the (adult) mice was found for oestradiol than for testosterone. Pregnancy decreases resistance to carbon monoxide intoxication. Experiments performed with males and females of different ages, in various societal conditions, show the effects of sex-related dimorphism and aggressiveness. The sex-related difference in carbon monoxide resistance is not modified by a previous hypoxic stress (nitrogen hypoxia, carbon monoxide intoxication, sodium cyanide injection) but is suppressed when the CO intoxication is carried out at a low ambient temperature (13 degrees C).     

Numerical implementation of second- and third-order conformalabsorbing boundary conditions for the vector-wave equation

A rigorous implementation, in an edge-based finite-element formulation of second- and third-order conformal absorbing boundary conditions (ABCs) is presented for the solution of three-dimensional (3-D) scattering problems when the boundary S terminating the mesh is the surface of a parallelepiped. A special treatment is provided for the singularities (edges) of S. A systematic numerical study is carried out that compares the performances of these ABCs with those of the standard zero-order ABC, as well as of a more simple, though less rigorous, implementation of the second-order ABC. When S is separated from the scatterer by only one or two layers of elements, the numerical results that are presented demonstrate the good level of numerical accuracy achieved when the second- and third-order ABCs are employed and the singularities of S are appropriately dealt with     

Influence of recent modification of behavioral relationships of male and female OF1 mice on resistance to nitrogen or carbon monoxide hypoxia

A decrease of resistance to hypoxia is obtained in OF1 mice, 24 hours after an hyperactivity resulting from a grouping by 13 of male or female mice previously isolated. Besides, this decrease is statistically significant in an acute nitrogen hypoxia but not in an acute carbon monoxide poisoning. In both hypoxias, in mice of same age the males are less resistant than females.     

Absorbing boundary conditions on arbitrary boundaries for thescalar and vector wave equations

The solution of open region scattering problems involving inhomogeneous arbitrarily shaped objects may be performed through the use of partial differential equation techniques, which require enclosing the scatterer by an outer boundary on which an absorbing boundary condition (ABC) is applied. In order to minimize the size of the domain to be meshed and, consequently, the number of unknowns, if may be advisable to implement ABC's devised for outer boundaries of arbitrary shapes. Such ABC's are obtained for the 3D scalar and vector wave equations; they incorporate most of existing boundary conditions. When used in conjunction with a finite element technique, the numerical results derived by using a simplified form of these ABC's compare favourably to those obtained by using a rigorous hybrid finite element-integral equation formulation. These boundary conditions have been obtained in the frequency-domain framework; they may, however, be used in time-domain calculations