Vanishing Loss Effect on the Effective ac Conductivity behavior for 2D Composite Metal-Dielectric Films At The Percolation Threshold

We study the imaginary part of the effective $ac$ conductivity as well as its distribution probability for vanishing losses in 2D composites. This investigation showed that the effective medium theory provides only informations about the average conductivity, while its fluctuations which correspond to the field energy in this limit are neglected by this theory.Comment: 6 pages, 2 figures, submitted to Phys.Rev.

Mapping potential soil vulnerability to water erosion in Tafna watershed (North-West of Algeria)

L’érosion hydrique est la principale forme de dégradation des sols en Algérie septentrionale. Ce phénomène naturel inévitable qui affecte notamment la partie nord-ouest du pays est exacerbé par les pratiques effarantes de l’homme et la fragilité des sols. La vulnérabilité des sols à l’érosion hydrique a été étudiée dans le bassin versant de la Tafna à travers une analyse spatiale basée sur l’utilisation de la télédétection et des systèmes d’information géographiques. Le bassin versant de Tafna, un des grands bassins versants de l’Algérie septentrionale, constitue la région la plus arrosée de l’Ouest et la plus productive de la Wilaya de Tlemcen. Sa superficie totale est de 724 500 ha, dont 27% en territoire marocain. L’approche cartographique suivie a été élaborée dans le cadre du programme d’actions prioritaires du plan d’actions pour la Méditerranée (PAP-PAM) avec la direction générale de la conservation de la nature de Madrid (DGCOM) et la FAO en 1998. Cinq classes de vulnérabilité à l’érosion hydrique ont été distinguées. Les zones à sensibilité très faible couvrent 7,32% de la surface du bassin, les zones à sensibilité faible à moyenne couvrent plus de la moitié (51,87%) et les zones à sensibilité élevée et très élevée couvrent 40,80%. La partie aval du bassin est la plus touchée par l’érosion hydrique, notamment linéaire, à cause de la dominance des terrains accidentés et la présence de substrats tendres. La partie amont, grâce à sa composition lithologique résistante à l’érosion, est plus stable. L’effet de la pente et la dégradation du couvert végétal occasionnent des inondations lors des pluies intenses. Toutes les formes de l’érosion hydrique ont été observées et les plus catastrophiques sont les badlands et les glissements de terrain, qui occasionnent des pertes considérables de terre agricole et mobilisent des sédiments importants menaçant les structures en aval (agglomérations, routes, barrages, etc.). Pour ralentir ce processus il faut freiner la dégradation du couvert végétal et favoriser l’utilisation des méthodes traditionnelles de conservation de l’eau et des sols. Mots clés: Vulnérable des sols, Erosion hydrique, SIG, Cartographie, Bassin versant de Tafna, Nord-Ouest AlgérienWater erosion is the main form of soil degradation in northern Algeria. This inevitable natural phenomenon which particularly affects the north-western part of the country is exacerbated by the human’s appalling practices and the fragility of the soils. The vulnerability of soils to water erosion was studied in the Tafna watershed through a spatial analysis based on the use of remote sensing and geographic information systems. The Tafna watershed, one of the major watersheds of northern Algeria, is the wettest region in the west and the most productive in the Wilaya of Tlemcen. Its total area is 724,500 ha, of which 27% is in Moroccan territory. The cartographic approach followed was developed within the framework of the Priority Action Program of the Mediterranean Action Plan (PAP-MAP) with the General Directorate of Nature Conservation of Madrid (GDCOM) and FAO in 1998. Five classes of vulnerability to water erosion have been distinguished. Very low sensitivity areas cover 7.32% of the pool area, low to medium sensitivity areas cover more than half (51.87%) and high and very high sensitivity areas cover 40.80%. The downstream part of the dock is the most affected by water erosion, especially linear erosion, due to the dominance of rugged terrain and the presence of soft substrates. The upstream part, is more stable thanks to its erosion-resistant lithological composition. The effect of the slope and the degradation of the vegetation cover cause flooding during heavy rains. All forms of water erosion have been observed and the most catastrophic are badlands and landslides, which cause considerable loss of agricultural land and mobilize significant sediments threatening downstream structures (towns, roads, dams, etc.). To slow down this process, the degradation of the plant cover must be slowed down and the use of traditional methods of water and soil conservation should be encouraged.  Keywords: Vulnerable soils, Water erosion, GIS, Cartography, Tafna watershed, North-West Algeri

Monte Carlo simulation of the transmission of measles: Beyond the mass action principle

We present a Monte Carlo simulation of the transmission of measles within a population sample during its growing and equilibrium states by introducing two different vaccination schedules of one and two doses. We study the effects of the contact rate per unit time $\xi$ as well as the initial conditions on the persistence of the disease. We found a weak effect of the initial conditions while the disease persists when $\xi$ lies in the range 1/L-10/L ($L$ being the latent period). Further comparison with existing data, prediction of future epidemics and other estimations of the vaccination efficiency are provided. Finally, we compare our approach to the models using the mass action principle in the first and another epidemic region and found the incidence independent of the number of susceptibles after the epidemic peak while it strongly fluctuates in its growing region. This method can be easily applied to other human, animals and vegetable diseases and includes more complicated parameters.Comment: 15 pages, 4 figures, 1 table, Submitted to Phys.Rev.

The Molecular Background Associated with the Progression of Hepatitis C to Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a major health problem worldwide. The DNA PM of cancer-related genes plays an important role in the development and progression of HCC. The data reported in our studies provide evidence that PM of p73, p14, and O6-MGMT is associated with HCC, whereas PM of the APC gene is more common in chronic hepatitis (CH) cases. Thus, it could be used as a maker for early detection of HCV-induced chronic active hepatitis. A panel of four genes APC, p73, p14, and O6-MGMT independently affected the classification of cases into HCC and CH with accuracy (89.9%), sensitivity (83.9%), and specificity (94.7%). Also, the detection of PM of APC, FHIT, p15, p16, and E-cadherin in peripheral blood of HCV-infected patients is a highly sensitive and specific. Therefore, blood could be used as efficiently as tissue biopsies to assess PM of different genes. This could help in the follow-up of CH patients and early detection of HCC. We did not observe a significant difference in the methylation status according to the virus type HBV versus HCV. So, plasma DNA is a reliable resource for methylation studies in the future, irrespective of the type of hepatitis infection

Localization and Absorption of Light in 2D Composite Metal-Dielectric Films at the Percolation Threshold

We study in this paper the localization of light and the dielectric properties of thin metal-dielectric composites at the percolation threshold and around a resonant frequency where the conductivities of the two components are of the same order. In particular, the effect of the loss in metallic components are examined. To this end, such systems are modelized as random $L-C$ networks, and the local field distribution as well as the effective conductivity are determined by using two different methods for comparison: an exact resolution of Kirchoff equations, and a real space renormalization group method. The latter method is found to give the general behavior of the effective conductivity but fails to determine the local field distribution. It is also found that the localization still persists for vanishing losses. This result seems to be in agreement with the anomalous absorption observed experimentally for such systems.Comment: 14 page latex, 3 ps figures. submitte

Genetic profile of Egyptian hepatocellular-carcinoma associated with hepatitis C virus Genotype 4 by 15 K cDNA microarray: Preliminary study

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