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This article presents a study of the formation of pseudo-periodic micro-structures on titanium surfaces upon irradiation of a single-mode pulsed nanosecond ytterbium fibre laser. It investigates the effect of short 100 ns pulsed laser beam properties including laser power, laser frequency, beam polarization, angle of incidence, and scanning speed on the formation of pseudo-periodic microstructures. The associated process parameters are grouped into two representing quantities: laser intensity and effective energy. The study demonstrates the effect of these two quantities on the surface topography (shape, periodicity, and roughness), heat affected zone (HAZ), chemical composition (oxidation and titanium phase transformation) and mechanical properties (hardness) of the modified surface. It is shown that the microstructures initiation is not possible until laser intensity reaches a certain value close to the damage threshold of the material. After the microstructures are initiated, the laser intensity may remain constant and the growth of structures is mainly controlled by the effective energy. [ABSTRACT FROM AUTHOR]

Children living in malaria-endemic regions have high incidence of Burkitt's lymphoma (BL), the aetiology of which involvesPlasmodium falciparummalaria and Epstein–Barr virus (EBV) infections. Acute malarial infection impairs the EBV-specific immune responses with the consequent increase in the number of EBV-carrying B cells in the circulation. To further understand the potential influence of malarial infection on the EBV persistence in children living in malaria-endemic areas, we studied the occurrence and quantified cell-free EBV-DNA in plasma from 73 Ghanaian children with and without acute malarial infection. Viral DNA was detected in 40% of the samples (47% in the malaria-infected and 34% in the nonmalaria group) but was absent in plasma from Ghanaian adults and healthy Italian children. These findings provide evidence that viral reactivation is common among children living in malaria-endemic areas, and may contribute to the increased risk for endemic BL. The data also suggest that the epidemiology of EBV infection and persistence varies in different areas of the world. [ABSTRACT FROM AUTHOR]