Geometric conditions for the existence of positive eigenvalues of matrices

Finite-dimensional theorems of Perron-Frobenius type are proved. For A∈$\text{C}$ⁿⁿ and a nonnegative integer k, we let w_k (A) be the cone generated by A^k, A^k+1,…in $\text{C}$ⁿⁿ. We show that A satisfies the Perron-Schaefer condition if and only if the closure $\text{W}$_k(A) of w_k(A) is a pointed cone. This theorem is closely related to several known results. If k?v₀(A), the index of the eigenvalue 0 in spec A, we prove that A has a positive eigenvalue if and only if w_k(A) is a pointed nonzero cone or, equivalently $\text{W}$_k(A) is not a real subspace of $\text{C}$ⁿⁿ. Our proofs are elementary and based on a method of Birkhoff's. We discuss the relation of this method to Pringsheim's theorem.     

Applications of photoconductivity measurements in n-InSb under crossed fields

The photocurrent in n-InSb at 85K was measured as function of the applied longitudinal voltage and an additionally applied transverse magnetic field. In the driftconfiguration the photoionized electron-hole plasma was driven into the sample volume, and negative photocurrents resulted from the negative feedback of this motion. With the magnetic field being reversed, in the Suhl configuration, only positive photocurrents were measured. All results are in agreement with the theory in [1]. They were used to determine recombination coefficients in n-InSb, and, principally, the transverse diffusion coefficientD _⊥. As first observed in [13],D _⊥ proved to be anomalously enhanced above classical values if plasma instabilities were generated in the samples.     

Fluorid

Ohne Zusammenfassung     

Radiation sensitivity of thick core all-glass fibers in reactor radiation fields

Radiation induced losses and the recovery behavior of several optical fibers have been determined by in situ steady state and by pulse measurements in a nuclear reactor. Agreement with the literature was found for Suprasil and Fibropsil core fibers in ionizing radiation, but our results on Suprasil-W core fibers show an appreciably higher radiation hardness of this material than reported elsewhere. Additionally, increased long term losses were observed, when the mixed radiation flux contained a noticeable content of neutrons.     

Lattice dynamics,electronic structure and electrical properties of simple metals

The Fourier transform of the effective electron-ion-potential of Pb has been determined from the measured phonon dispersion curves. For Rb and Cs, we used the elastic constants and the fact, that only the Coulomb interaction between the ions contributes significantly to the phonon frequencies of the lowest transverse [110]-branch. Using this model potential we calculated the distortions of the Fermi surface and the electrical resistivity.     

Kinetik der direkten Synthese der Methylchlorsilane unter Druck

Ohne Zusammenfassung     

Bestimmung von Antik?rpern gegen Cytomegalievirus (CMV), Varizella/Zoster-Virus (VZV) und Herpes simplex-Virus Typ 1 (HSV-1) im Enzyme-Linked-Immunosorbent-Assay (ELISA)

Ohne Zusammenfassung

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Determination of antibodies to Cytomegalovirus (CMV), Varicella/Zoster-Virus (VZV) and Herpes simplex-Virus Type 1 (HSV-1) by the Enzyme-Linked-Immunosorbent-Assay (ELISA)

     

On the crack formation of laser treated carbon steel

High power lasers are useful instrument in producing hard and wear resistant surfaces on steel. It is shown that the mechanical behaviour of such surfaces is controlled by their residual stress state and their ductility which both can be varied considerably by changing the laser treatment parameters.