Majorana-Oppenheimer approach to Maxwell electrodynamics in Riemannian space-time

The Riemann -- Silberstein -- Majorana -- Oppengeimer approach to the Maxwell electrodynamics in presence of electrical sources and arbitrary media is investigated within the matrix formalism. The symmetry of the matrix Maxwell equation under transformations of the complex rotation group SO(3.C) is demonstrated explicitly. In vacuum case, the matrix form includes four real $4 \times 4$ matrices $\alpha^{b}$. In presence of media matrix form requires two sets of $4 \times 4$ matrices, $\alpha^{b}$ and $\beta^{b}$ -- simple and symmetrical realization of which is given. Relation of $\alpha^{b}$ and $\beta^{b}$ to the Dirac matrices in spinor basis is found. Minkowski constitutive relations in case of any linear media are given in a short algebraic form based on the use of complex 3-vector fields and complex orthogonal rotations from SO(3.C) group. The matrix complex formulation in the Esposito's form, based on the use of two electromagnetic 4-vector, is studied and discussed. Extension of the 3-vector complex matrix formalism to arbitrary Riemannian space-time in accordance with tetrad method by Tetrode-Weyl-Fock-Ivanenko is performed.Comment: 32pages. Proccedings of the 14th Conference-School "Foundation & Advances in Nonlinear Science", Minsk, September 22-25, 2008. P. 20-49; ed. V.I. Kuvshinov, G.G. Krylov, Minsk, 200

Childhood and adolescent cancer in Germany – an overview

Background: Childhood and adolescent cancer constitutes only a very small fraction of the cancer cases in Germany and throughout the world, but it is the most frequent cause of disease-related death in children. The diagnostic spectrum differs markedly from that of adults. More than 90% of all cases of childhood and adolescent cancer in Germany are treated according to centralised protocols or in therapy studies. Methods: The main epidemiological data for this group are collected by the German Childhood Cancer Registry (GCCR) since 1980. Based on this data, three typical diagnoses and their incidence and prognosis are described in exemplary manner: Lymphoid leukaemia (LL), astrocytoma and neuroblastoma. Results: Approximately 2,250 new cancers are diagnosed in children and adolescents under the age of 18 in Germany every year. In this age group, leukaemia and lymphoma account for almost 50% of all new cancer cases, predominately acute forms. Overall, the prognosis is considerably better than in adults. Conclusions: There is relatively little consistent evidence available on external factors as risk factors for childhood cancer, despite decades of research. For LL, the immune system and infections are assumed to play a role, as early training of the immune system appears to be protective. To an increasing degree, research is identifying genetic risk factors for many types of childhood and adolescent cancer. The therapy is sometimes very intensive and leads to a variety of late effects for at least 75% of the survivors, which may occur soon after the primary diagnosis, but also decades later