expressions for some specific liquids in a certain range of atomising conditions.5 As the atomising mode depends This paper investigates the effects of atomiser design critically upon the liquid flow conditions on the atomiser, and processing parameters on the morphology and it is critical to understand the behaviour of the liquid flow size distribution of centrifugally atomised tin powder.on the disc in order to obtain powders with the desired Premature solidification of the melt on the atomiser properties. The flow behaviour of the melt in centrifugal and poor wetting of the atomiser by the melt were atomisation is usually complicated. Mathematical modelfound to be the main causes of unsuccessful atomisling can be used to calculate the thickness and velocity ation. The particle size distributions of the powders profiles of the liquid metal film and thus to predict or follow a lognormal distribution. The median particle explain the experimental results, such as particle shape and size increased with decreasing atomiser rotation speed size distribution.6-8 However, these models need to be and with increasing melt flowrate. Cups with a high experimentally validated before they can be used with included angle made significantly finer powders than confidence. flat discs under the same operating conditions.Sufficient wetting of the atomiser by the molten metal is PM/1053 essential for rapid acceleration and consequently effective disintegration of the melt. In the centrifugal atomisation of Dr Xie
To understand why vaccine-activated tumor-specific T cells often fail to generate antitumor effects, we studied two α-fetoprotein–specific CD8+ T cells (Tet499 and Tet212) that had different antitumor effects. We found that Tet499 required high antigen doses for re-activation, but could survive persistent antigen stimulation and maintain their effector functions. In contrast, Tet212 had a low threshold of re-activation, but underwent exhaustion and apoptosis in the presence of persistent antigen. In vivo, Tet499 cells expanded more than Tet212 upon re-encountering antigen and generated stronger antitumor effects. The different antigen responsiveness and antitumor effects of Tet212 and Tet499 cells correlated with their activation and differentiation states. Compared to Tet212, the population of Tet499 cells was less activated and contained more stem-like memory T cells (Tscm) that could undergo expansion in vivo. The TCR signaling strength on Tet499 was weaker than Tet212, correlating with more severe Tet499 TCR downregulation. Weak TCR signaling may halt T-cell differentiation at the Tscm stage during immune priming and also explains why Tet499 re-activation requires a high antigen dose. Weak TCR signaling of Tet499 cells in the effector stage will also protect them from exhaustion and apoptosis when they re-encounter persistent antigen in tumor lesion, which generates antitumor effects. Further investigation of TCR downregulation and manipulation of TCR signaling strength may help design cancer vaccines to elicit a mix of tumor-specific CD8+ T cells, including Tscm, capable of surviving antigen re-stimulation to generate antitumor effects.
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