B cell hyperresponsiveness and expansion of mature follicular B cells but not of marginal zone B cells in NFATc2/c3 double-deficient mice

Marginal zone (MZ) B cells and peritoneal B-I cells provide a first defense system of thymus-independent Ab responses against foreign pathogens and therefore share a number of functional properties. Recently, development of B-1a cells was shown to be controlled by the transcription factor NFATc1. We show here that mice deficient for NFATc2 and c3 display a distinct lower representation of MZ B cells, which is correlated with a reduced capturing of trinitrophenyl-Ficoll. In contrast, mature follicular B cells from NFATc2/c3(-/-) mice are strongly increased in number. NFATc2/c3-/- B cells exhibit a marked increase in BCR-induced intracellular Ca(2+) mobilization and proliferation. However, trinitrophenyl-Ficoll-specific IgM and IgG3 responses of NFATc2/c3-deficient mice are intact, and chimeric mice reconstituted with NFATc2/3-deficient B cells show a normal number of MZ B cells and normal BCR responses. These observations suggest that the strongly elevated Th2 cytokine milieu in NFATc2/c3-deficient mice leads to a hyperactivation of mature, follicular B cells, whereas MZ B cells are less responsive to these signals

Swift Heavy Ion Induced Modification Studies of C60 Thin Films

Modification induced by 110 MeV Ni ion irradiated thin film samples of C60 on Si and quartz substrates were studied at various fluences. The pristine and irradiated samples were investigated using Raman spectroscopy, electrical conductivity and optical absorption spectroscopy. The Raman data and band gap measurements indicate that swift ions at low fluences result in formations that involve multiple molecular units like dimer or polymer. High fluence irradiation resulted in sub-molecular formations and amorphous semiconducting carbon, indicating overall damage of the fullerene molecules. These sub-molecular units have been identified with nanocrystalline diamond and nanocrystalline graphite like formations.Comment: 7 pages, 29 references and 9 figures submitted to J. Appl. Phy

Defect Levels in Gallium Arsenide after Irradiation with Light Ions

Deep level centers in GaAs implanted with light ions (H$\text{}^{+}$, He$\text{}^{+}$) were studied by means of deep level transient spectroscopy, double correlation deep level transient spectroscopy and capacity voltage carrier profiling directly after the implantation process and after annealing at various temperatures. Five different electron traps with energy positions between 0.13-0.75 eV are detected. From the evaluated defect production and carrier trapping yields and their annealing behavior we conclude that each of these traps efficiently contributes to the trapping of free carriers. The EL2 defect is created in too low concentrations in order to significantly account for the removal of free carriers

Erbium Luminescence in Silicon

We report on high resolution photoluminescence investigations of Er-implanted Si and demonstrate the variety of Er centers or complexes with impurities and native Si-defects formed depending on the processing parameters. These centers are shown to differ in the efficiency of excitation transfer as well as high temperature photoluminescence yield. The mechanisms responsible for the photoluminescence quenching at different temperature regimes are discussed

Influence of Coimplantation on Activation of Er Emission in Si

The results of high resolution photoluminescence studies of erbium implanted silicon are presented. We show that the apparent enhancement of Er emission by coimplantation with light elements is not due to formation of Er-dopant complexes, but rather to Er forming complexes with defects induced by the implantation process alone