Ministry of Agriculture

About: Ministry of Agriculture is a government organization based out in Rio de Janeiro, Brazil. It is known for research contribution in the topics: Chemistry & Salmonella. The organization has 1153 authors who have published 1189 publications receiving 14442 citations.

New Contributions to the Optics of Intensely Light-Scattering Materials. Part II: Nonhomogeneous Layers*

Abstract: The derived laws apply to layers whose scattering coefficient S and absorption coefficient K vary vertically to the surface of the layer. In the general case the differential equations of the preceding paper [ P. Kubelka , J. Opt. Soc. Am.38, 448 ( 1948)] must be used; the coefficients, however, hitherto constant, now are functions of the distance x from the surface. In the practically important case in which K/S is constant, one may introduce the variable p, such that p≡∫0x(x)dx. One reduces thereby the nonhomogeneous to the previously treated homogeneous case.Transmittance T1,2 and reflectance R1,2 of two nonhomogeneous sheets can be calculated by the following equations: T1,2=T1T21-R1R2, R1,2=R1+T12R21-R1R2,where T1, T2, R1, R2 are the transmittances and reflectances of the single sheets, and R1 represents the reflectance of the first sheet when illuminated in the inverse direction. Analogous formulas for more sheets and formulas relating transmittance, reflectance for specimens upon black, gray or white backing surfaces, and contrast ratio, are derived.It is shown by theory and experiment that reflectance and absorption of a nonhomogeneous specimen depend on the direction of illumination, whereas transmittance does not.

Pathogenesis and pathobiology of brucellosis in livestock

Abstract: Summary Brucella species are facultative, intracellular, Gram-negative bacteria with marked tropism for the pregnant reproductive tract of domestic animals. All Brucella species establish persistent infection in the reticuloendothelial system of their natural hosts. The mechanisms of placenta localisation, trophoblast tropism and abortion are poorly understood. A complete picture of the molecular determinants and mechanisms of the cell internalisation process began to emerge only recently. Cyclic β-1,2-glucan is a molecule secreted into the periplasm of Brucella and is required for intracellular Brucella to avoid fusion of the phagosome with lysosomes. The type IV secretion system translocates Brucella effector proteins into host cells and is critical for both survival and replication of Brucella in infected host cells. Some aspects of the pathogenesis and pathobiology of brucellosis in productive domestic animals are discussed in this section.