Stabilization of clayey soil using fibre reinforcement

The paper presents experimental and numerical investigations on crack evolution during desiccation, on unsaturated, compacted and reinforced clay using natural Alfa fibres. The effect of fibre content is investigated and a comparison between experimental and numerical simulations is made. A modified model for tensile strength is updated in the finite element program CODE_BRIGHT and used to predict tensile cracks induced by desiccation on reinforced soil. The results show that the soil desiccation cracking behaviour is significantly influenced by fibre inclusion and that experimental and numerical results are in good agreement.Postprint (published version

Capital Ownership And Its Impact On International Trade And Economic Growth: The Tunisian Experience

Despite the widespread belief that a privatized economy performs better than a centrally planned one, there is no empirical evidence on whether changing the structure of capital ownership affects trade and growth in developing countries. This paper addresses this issue by analyzing and comparing the distinctive effects of privately and publicly owned capital on international trade and economic growth. Based on a modified version of the neo-classical one-sector aggregate production technology, we investigate the intertemporal interactions among the growth rate of real output, private capital, public capital, international trade and labor. The results of applying our methodology to data from Tunisia suggest that private capital performs better than public capital in promoting economic growth and international trade.  Despite the widespread belief that a privatized economy performs better than a centrally planned one, there is no empirical evidence on whether changing the structure of capital ownership affects trade and growth in developing countries. This paper addresses this issue by analyzing and comparing the distinctive effects of privately and publicly owned capital on international trade and economic growth. Based on a modified version of the neo-classical one-sector aggregate production technology, we investigate the intertemporal interactions among the growth rate of real output, private capital, public capital, international trade and labor. The results of applying our methodology to data from Tunisia suggest that private capital performs better than public capital in promoting economic growth and international trade. &nbsp

In vitro screening of soil bacteria for inhibiting phytopathogenic fungi

At present, the greatest interest resides with the development and application of specific biocontrol agent for the control of diseases on plant and this form the focus of this work. Several soil bacteria were evaluated in vitro for their effectiveness on the basis of their ability to suppress fungi in plate inhibition assays. 51 strains of 12 bacterial species were performed against 12 strains of 10 phytopathogenic mould species. Almost all soil bacteria species; but about 50% of the bacteria strains, showed an antagonistic activity against at least one phytopathogenic fungus. Sphingomonans spp was the only specie that did not show any antagonistic effect to all fungi. Bradyrhizobium japonicum could highly inhibit the mycelial growth of five moulds (Botrytis cinerea, Phoma medicaginis, Fusarium verticilloides, Rhizoctonia solani and Phytophtora infestans) with a growth inhibition varying between 12.38 and 37.61%. 12 Bacillus strains and five Pseudomonas strains were antagonistic to the major phytopathogenic moulds used in this trial. Bacillus subtilis exhibited strong antagonism against fungi both from cultural medium and from sterile filtrate. Results show that bacterial suspension and bacterial supernatant did not operate in the same way. Supernatant from bacterial strains seemed to be efficient against phytopathogenic moulds. The mycelial growth of R. solani, P. medicaginis and F. verticilloides was inhibited by 12-fold dilution of the supernatant from B. japonicum. The latter draws a conclusion that bacteria isolated from soil are promising natural biocontrol agents and should be further studied and tested for the control of numerous plant diseases. Additional studies are required to definitively determine their mode of antifungal action, safety and biocompatibility.Keywords: Bacteria, phytopathogenic fungi, antagonis

Computational Laser Spectroscopy in a Biological Tissue

We present a numerical spectroscopic study of visible and infrared laser radiation in a biological tissue. We derive a solution of a general two-dimensional time dependent radiative transfer equation in a tissue-like medium. The used model is suitable for many situations especially when the external source is time-dependent or continuous. We use a control volume-discrete ordinate method associated with an implicit three-level second-order time differencing scheme. We consider a very thin rectangular biological-tissue-like medium submitted to a visible or a near infrared light sources. The RTE is solved for a set of different wavelength source. All sources are assumed to be monochromatic and collimated. The energetic fluence rate is computed at a set of detector points on the boundaries. According to the source type, we investigate either the steady-state or transient response of the medium. The used model is validated in the case of a heterogeneous tissue-like medium using referencing experimental results from the literature. Also, the developed model is used to study changes on transmitted light in a rat-liver tissue-like medium. Optical properties depend on the source wavelength and they are taken from the literature. In particular, light-transmission in the medium is studied for continuous wave and for short pulse

Decreased Sialidase Activity in Alveolar Macrophages of Guinea Pigs Exposed to Coal Mine Dust

International audienceThe origin of immune dysfunctions that are observed in pneumoconiotic miners still remains unknown. There is evidence that the carbohydrate moiety of membrane glycoconjugates is of primary importance in many functions of immunocompetent cells. The glycosylation, and especially the sialylation level of membrane components of various lymphocyte and macrophage subsets, vary depending on the state of cellular differentiation and activation. Sialidases, which may regulate the amount of sialic acids exposed on the cell membrane, can thus be considered as immunoregulatory enzymes. In this report, the sialidase activity has been measured in alveolar macrophages (AM) and in cell-free bronchoalveolar lavage fluid (BALF) from guinea pigs exposed for 4 months to coal mine dust at a concentration of 300 mg/m3. The samples were collected by bronchoalveolar lavage 2 months after cessation of exposure. The sialidase activity in the cell-free fluid and in the purified alveolar macrophages showed a 10-fold decrease (p < 0.001). Kinetic parameters of the enzyme such as K(m) and optimum pH did not change. This changed activity was specific for sialidase, as two other lysosomal glycosidases, beta-galactosidase and N-acetylglucosaminidase, showed unchanged activities. These results suggest the possibility that, by inducing a decreased sialidase activity, exposure to coal mine dust may lead to a modified expression of AM membrane-associated sialic acids giving rise to altered immune functions (i. e., phagocytosis, antigen processing response to cytokines, etc.)

Oxygen-vacancy-related giant permittivity and ethanol sensing response in SrTiO3-δ ceramics

The ethanol sensing properties of SrTiO3-δ (δ = 0.075 and 0.125) ceramics was analyzed by dielectric measurements. The ceramics were prepared by solid state reaction method followed by the creation of oxygen vacancies-δ, through a thermal activated process. The crystal symmetry, space group and unit cell dimensions were derived from the X-ray diffraction (XRD) data using FullProf software whereas grain's size distribution was assessed by scanning electron microscopy (SEM). The prepared samples have been analyzed by impedance spectroscopy over the frequency range from 100 Hz to 1 MHz and temperature range from 240 to 340 K. The dielectric properties of SrTiO3-δ ceramics showed a quite remarkable stability of giant permittivity (>104) as well as a low dielectric loss, which open ways for several applications such as over voltage protections of electronic devices. A low-frequency dielectric relaxation behavior was found, and the carriers for electrical conduction result from the first-ionization of oxygen vacancies. The conductivity and gas sensitivity of SrTiO3-δ-based sensors were investigated. Results demonstrated that the conductivity decreases after the introduction of the ethanol gas, and p-type semiconductor gas-sensing materials were obtained. Both characteristics present higher responses at lower optimal operating temperatures.publishe

Theoretical and experimental study of the orientational ordering in the field-induced intermediaite phase from the SmC*FI2 phase in chiral smectic liquid crystals

Under an electric field, chiral smectic liquid crystals transit usually to the unwound SmC* phase where the helical structure is completely unrolled. Sometimes the sample transits initially towards an intermediate polar state before the total destruction of the helix. Based on the extension of the H-T model, a theoretical study of these field-induced phase transitions was carried out. Two hypotheses of the dynamics that give rise to the appearance of the intermediate phase have been discussed. The results of a numerical analysis confirm the known experimental results; the intermediate phase has a three-layer periodicity structure

Block to granular-like transition in dense bubble flows

We have experimentally investigated 2-dimensional dense bubble flows underneath inclined planes. Velocity profiles and velocity fluctuations have been measured. A broad second-order phase transition between two dynamical regimes is observed as a function of the tilt angle $\theta$. For low $\theta$ values, a block motion is observed. For high $\theta$ values, the velocity profile becomes curved and a shear velocity gradient appears in the flow.Comment: Europhys. Lett. (2003) in pres