Experimental evidence of differences in the absorption spectra of clustered and isolated ions in erbium doped fibers

The absorption spectra of clustered and isolated ions in erbium-doped germanosilicate fibers have been experimentally studied. The ground state absorption spectra broaden as the degree of erbium-ion clustering increases, indicating that the absorption spectra of clustered ions is significantly different from that of the homogeneous ions. This is confirmed by comparing the broadened absorption spectra with the fibre unbleachable loss spectrum; a direct measurement of the clustered ions. This is the first experimental evidence indicating different absorption cross-sections for the two species of ions in germanosilicate glass, an assumption used in the theoretical description of self-pulsing in erbium doped fiber lasers, but in direct contradiction to the pair-induced quenching model widely used to characterise EDFAs

Hepatitis C virus genotypes in liver transplant recipients: Impact on posttransplant recurrence, infections, response to interferon-α therapy and outcome

Background. End-stage liver disease due to hepatitis C virus (HCV) is the most common indication for liver transplantation in U.S. veterans. We investigated the influence of HCV genotypes on the incidence and timing of recurrent HCV hepatitis, survival, infectious morbidity, and response to interferon-α therapy in this unique patient population. Methods. HCV genotype was determined by direct sequencing of the NS5 region of HCV with type-specific primers. Results. Genotype 1a (66%, 32/47) was the predominant genotype. Type 1b was found in 25% (12/47) of patients and type 2b was found in 9% (4/47). His topathologically recurrent HCV hepatitis developed in 53% (25/47) of the patients after transplantation. This group included 45% (14/31) of the patients with type 1a, 67% (8/12) of the patients with type 1b, and 25% (1/4) of the patients with type 2b (P>0.5). The time to recurrence and the severity of HCV recurrence as defined by aminotransferase levels or Knodell scores were not different among the three genotypes. There was a trend toward a higher incidence of major infections in patients with type 1b (75%) versus type 1a (48%) and type 2b (50%) (P=0.11). The response to interferon-α therapy did not differ significantly among the genotypes. Mortality at 5 years was 16% (5/31) in patients with genotype 1a, 42% (5/12) in patients with genotype 1b, and 50% (2/4) in patients with genotype 2b (P=0.06). Conclusions. The incidence, time to recurrence, and response to interferon-α therapy did not differ be tween the various genotypes in our liver transplant recipients. However, there was a trend toward higher infectious morbidity and overall mortality in patients with genotype 1b after transplantation

Dzyaloshinsky-Moriya Spin Canting in the LTT Phase of La2-x-yEuySrxCuO4

The Cu spin magnetism in La2-x-yEuySrxCuO4 (x<=0.17; y<=0.2) has been studied by means of magnetization measurements up to 14 T. Our results clearly show that in the antiferromagnetic phase Dzyaloshinsky-Moriya (DM)superexchange causes Cu spin canting not only in the LTO phase but also in the LTLO and LTT phases. In La1.8Eu0.2CuO4 the canted DM-moment is about 50% larger than in pure La2CuO4 which we attribute to the larger octahedral tilt angle. We also find clear evidence that the size of the DM-moment does not change significantly at the structural transition at T_LT from LTO to LTLO and LTT. The most important change induced by the transition is a significant reduction of the magnetic coupling between the CuO2 planes. As a consequence, the spin-flip transition of the canted Cu spins which is observed in the LTO phase for magnetic field perpendicular to the CuO2 planes disappears in the LTT phase. The shape of the magnetization curves changes from the well known spin-flip type to a weak-ferromagnet type. However, no spontaneous weak ferromagnetism is observed even at very low temperatures, which seems to indicate that the interlayer decoupling in our samples is not perfect. Nonetheless, a small fraction (<15%) of the DM-moments can be remanently magnetized throughout the entire antiferromagnetically ordered LTT/LTLO phase, i.e. for T<T_LT and x<0.02. It appears that the remanent DM-moment is perpendicular to the CuO2 planes. For magnetic field parallel to the CuO2 planes we find that the critical field of the spin-flop transition decreases in the LTLO phase, which might indicate a competition between different in-plane anisotropies. To study the Cu spin magnetism in La2-x-yEuySrxCuO4, a careful analysis of the Van Vleck paramagnetism of the Eu3+ ions was performed.Comment: 22 pages, 27 figure

Inhomogeneous Low Frequency Spin Dynamics in La_{1.65}Eu_{0.2}Sr_{0.15}CuO_4

We report Cu and La nuclear magnetic resonance (NMR) measurements in the title compound that reveal an inhomogeneous glassy behavior of the spin dynamics. A low temperature peak in the La spin lattice relaxation rate and the ``wipeout'' of Cu intensity both arise from these slow electronic spin fluctuations that reveal a distribution of activation energies. Inhomogeneous slowing of spin fluctuations appears to be a general feature of doped lanthanum cuprate.Comment: 4 pages, 2 figures. Very slight modifications to figure

And the first shall be the last

This study analyzes the puzzle of Hungarian economic drifting in a long run perspective. The underlying puzzle for the investigation is why bad policies are invariably popular and good policies unpopular, thus why political and economic rationality never overlap. The first part of the article summarizes in eight points the basic features of the postwar period. Then six lessons are offered, which might be useful for other countries in transition or for students of comparative economics and politics, lessons that can be generalized on the basis of the individual country experience