We present an X-ray timing analysis of the Crab pulsar, PSR B0531＋21, using archival RXTE data. We have investigated the stability of the Crab pulse profile, in soft （2-20keV） and hard （30-100 keV） X-ray energies...We present an X-ray timing analysis of the Crab pulsar, PSR B0531＋21, using archival RXTE data. We have investigated the stability of the Crab pulse profile, in soft （2-20keV） and hard （30-100 keV） X-ray energies, over the last decade of RXTE operation. The analysis includes measurement of the separation between the two pulse peaks and the intensity and widths of the two peaks. We did not find any significant time dependency in the pulse shape. The two peaks have been stable in phase, intensity and width for the last ten years. The first pulse is relatively stronger at soft X-rays. The first pulse peak is narrower than the second peak in both soft and hard X-ray energies. Both the peaks show a slow rise and a steeper fall. The ratio of the pulsed photons in the two peaks is also constant in time.展开更多
A correct antibody response requires the participation of both B and T lymphocytes and antigen presenting cells. In this review we address the role of follicular helper T lymphocytes(T FH) in this reaction. We shall f...A correct antibody response requires the participation of both B and T lymphocytes and antigen presenting cells. In this review we address the role of follicular helper T lymphocytes(T FH) in this reaction. We shall focus on the regulation of their development and function in health and disease. T FH can be characterized on the basis of their phenotype and the pattern of secretion of cytokines. This fact is useful to study their participation in the generation of antibody deficiency in primary immunodeficiency diseases such as common variable immunodeficiency, X-linked hyper Ig M syndrome orX-linked lymphoproliferative disease. Increased numbers of T FH have been demonstrated in several autoimmune diseases and are thought to play a role in the development of autoantibodies. In chronic viral infections caused by the human immunodeficiency virus, hepatitis B or C virus, increased circulating T FH have been observed, but their role in the protective immune response to these agents is under discussion. Likewise, an important role of T FH in the control of some experimental protozoan infections has been proposed, and it will be important to assess their relevance in order to design effective vaccination strategies.展开更多
文摘We present an X-ray timing analysis of the Crab pulsar, PSR B0531＋21, using archival RXTE data. We have investigated the stability of the Crab pulse profile, in soft （2-20keV） and hard （30-100 keV） X-ray energies, over the last decade of RXTE operation. The analysis includes measurement of the separation between the two pulse peaks and the intensity and widths of the two peaks. We did not find any significant time dependency in the pulse shape. The two peaks have been stable in phase, intensity and width for the last ten years. The first pulse is relatively stronger at soft X-rays. The first pulse peak is narrower than the second peak in both soft and hard X-ray energies. Both the peaks show a slow rise and a steeper fall. The ratio of the pulsed photons in the two peaks is also constant in time.
基金Supported by Consejo Nacional de Investigaciones Científicas y Técnicas,CONICET,PIP Nos.0032 and 11220120100619CO
文摘A correct antibody response requires the participation of both B and T lymphocytes and antigen presenting cells. In this review we address the role of follicular helper T lymphocytes(T FH) in this reaction. We shall focus on the regulation of their development and function in health and disease. T FH can be characterized on the basis of their phenotype and the pattern of secretion of cytokines. This fact is useful to study their participation in the generation of antibody deficiency in primary immunodeficiency diseases such as common variable immunodeficiency, X-linked hyper Ig M syndrome orX-linked lymphoproliferative disease. Increased numbers of T FH have been demonstrated in several autoimmune diseases and are thought to play a role in the development of autoantibodies. In chronic viral infections caused by the human immunodeficiency virus, hepatitis B or C virus, increased circulating T FH have been observed, but their role in the protective immune response to these agents is under discussion. Likewise, an important role of T FH in the control of some experimental protozoan infections has been proposed, and it will be important to assess their relevance in order to design effective vaccination strategies.
