Effect of Nano-SiO2 Content on the Setting Time and Mechanical Properties of Tricalcium Silicate

Using analytically pure calcium carbonate and silica as raw materials, high purity tricalcium silicate (C3S) is prepared by solid-state reaction. The tricalcium silicate was sintered at a temperature of 1550°C with the heat preservation time of 6 h. The final sample needs three times of calcination circles. Ultrasonic cleaning machine was used to disperse the water and different amount of nano-SiO2 (0, 1, 2, and 3 wt%) for 5 min, then mixed with C3S, and formed into standard blocks. The setting time and compressive strength of each age (1, 3, 7, and 28 days) was measured to investigate the effect of nano-SiO2 on the setting time and mechanical properties of C3S. The results show that the content of free calcium oxide (f-CaO) in C3S sample is lower than 0.8% tested by glycol ethanol method sensitive, C3S crystal type is triclinic system T1 by X ray diffraction (XRD). The nano-SiO2 cut down the setting time of C3S and the setting time of C3S is decreasing with the increasing content of nano-SiO2. The initial setting time of C3S with different content of nano-SiO2 (0, 1, 2, and 3 wt%) are 187, 129, 105, and 85 min, respectively, the final setting time are 219, 194, 158, and 130 min. The addition of nano-SiO2 can significantly improve the early compressive strength of C3S, but the effect of nano-SiO2 on improving compressive strength of C3S is gradually weakened with the hydration of C3S

Phagraphene: A Low-energy Graphene Allotrope composed of 5-6-7 Carbon Rings with Distorted Dirac Cones

Using systematic evolutionary structure searching we propose a new carbon allotrope, phagraphene, standing for penta-hexa-hepta-graphene, because the structure is composed of 5-6-7 carbon rings. This two-dimensional (2D) carbon structure is lower in energy than most of the predicted 2D carbon allotropes due to its sp2-hybridization and density of atomic packing comparable to graphene. More interestingly, the electronic structure of phagraphene has distorted Dirac cones. The direction-dependent cones are further proved to be robust against external strain with tunable Fermi velocities.Comment: 5 pages, 3 figure

Autoreactive marginal zone B cells enter the follicles and interact with CD4+ T cells in lupus-prone mice

<p>Abstract</p> <p>Backgound</p> <p>Marginal zone B cells have been implicated in the production of autoantibodies in murine models of lupus. It has been suggested that they contribute to lupus immunopathogenesis through their enhanced effector functions and their repertoire that is biased toward autoreactive specificities. In the B6.NZM2410.<it>Sle.Sle2.Sle3 </it>(B6.TC) model of lupus, the majority of marginal zone B cells are located outside the marginal zone and inside the follicles. Genetic alterations of this strain have shown a correlation between autoimmune pathogenesis and the presence of intrafollicular marginal zone B cells. This study was designed first to strengthen our original observations and to determine how the marginal zone B cells from the lupus-prone mice respond to stimulations and interact with T cells.</p> <p>Results</p> <p>The intrafollicular location of B6.TC MZB cells starts before disease manifestations and puts MZB cells in direct contact with CD4⁺T cells. Two different autoreactive B cell receptor (BCR) transgenic models showed that the expression of the <it>Sle </it>susceptibility loci enhances the presence of MZB cells inside the follicles. <it>In vitro</it>, B6.TC MZB cells were better effectors than B6 MZB cells with enhanced proliferation and antibody (Ab) production, including anti-DNA Ab, in response to stimulation with TLR ligands, immune complexes or anti-CD40. Furthermore, B6.TC MZB and CD4⁺T cells showed a reciprocally enhanced activation, which indicated that their contacts inside B6.TC follicles have functional consequences that suggest an amplification loop between these two cell types.</p> <p>Conclusions</p> <p>These results showed that the NZM2410 susceptibility loci induce MZB cells to locate into the follicles, and that this breach of follicular exclusion occurs early in the development of the autoimmune pathogenesis. The enhanced responses to stimulation and increased effector functions of MZB cells from lupus-prone mice as compare to non-autoimmune MZB cells provide a mechanism by which the failure of MZB cell follicular exclusion contributes to the autoimmune process.</p