Loss of cold atoms due to collisions with residual gases in free flight in a magneto-optical trap

The loss rate of cold atoms in a trap due to residual gas collisions differs from that in a free state after the cold atoms are released from the trap. In this paper, the loss rate in a cold rubidium-87 atom cloud was measured in a magneto-optical trap （MOT） and during its free flight. The residual gas pressure was analyzed by a residual gas analyzer, and the pressure distribution in a vacuum chamber was numerically calculated by the angular coefficient method. The decay factor, which describes the decay behavior of cold atoms due to residual gas collisions during a free flight, was calculated. It was found that the decay factor agrees well with theoretical predictions under various vacuum conditions.

Ginsenoside metabolite compound K alleviate collegen-induced arthritis through impairing dendritic cells function

OBJECTIVE Ginsenoside metabolite compound K(CK)is a degradation product of ginsenoside in the intestine by bacteria.The anti-inflammatory and immunomodulatory activities of CK have been reported.This study investigated whether CK exerted its immunoregulatory effect through modulation of dendritic cells(DCs)function.METHODS In vivo,severity of collegen-induced arthritis(CIA),T cells and DCs subsets,phenotype of DC were assayed by flow cytometry,CCL19 and CCL21 level in lymph nodes assayed by ELISA.In vitro,bone marrow-derived DCs from normal mice were matured with lipopolysaccharide and treated with CK for 48 h.In vivo,bone marrow-derived DCs were generated from CIA mice before and 2 weeks into CK treatment.DCs were analyzed for migration,phenotype and T-cell stimulatory capacity.RESULTS CK alleviated the severity of CIA,decreased pD Cs and mo-DCs,increased na?ve T cells in CIA mice lymph nodes,and suppressed CCL21 expression in lymph nodes.CK suppressed DCs migration induced by CCL21 and T cells-stimulatory capability of DC,down-regulated LPS-induced expression of CD80,CD86,MHCII and CCR7 on DCs.CONCLUSION This study elucidated the novel immunomodulatory property of CK via impairing function of DCs in priming T cells activation.These results provide an interesting novel insight into the potential mechanism by which CK contribute to the restoration of immunoregulation in autoimmune conditions.