Positive effects of PVP in MIC:Preparation and characterization of Al-Core heterojunction fibers

The core-shell metastable intermolecular composites(MIC)have attracted much attention in the past few years due to their unique properties.Here,the preparation of Al-Core heterojunction fibers using PVP as a template is proposed.The nano-Al was directly added to the precursor solution of cupric acetate monohydrate(CAM)/Polyvinylpyrrolidone(PVP),and the initial Al@CAM/PVP fibers were obtained via electrospinning.The core-shell MIC fibers are then obtained by calcining the initial fibers.The morphology,structure,and composition of Al-core MIC fibers were characterized,that the energetic fibers calcined at 300℃,350℃,and 400℃have a core-shell structure with shell compositions CuxO and PVP,CuxO and Cu O,respectively.The energy release characteristics of Al-core MIC were investigated,and preliminary ignition tests were performed using an ignition temperature measuring instrument and a pulsed laser.The energetic fibers calcined at 300℃exhibited unique properties.The decomposition of PVP in the shell layer promoted exotherm,and a low-temperature exothermic peak was shown at 372-458℃.Lower ignition temperatures and higher flame heights were observed in the combustion tests than calcination at 350℃and 400℃.An unexpected result was that PVP can play a positive role in Al/CuO nanothermites.Simultaneously,this preparation method provided an idea for the integrated preparation of core-shell Al-Core MIC fibers and tuning the properties of MIC.

Thermodynamics and performance of Al/CuO nanothermite with different storage time

The storage stability of energetic materials is important for its application. Here, the storage stability of Al/CuO nanothermite, which was prepared by electrospray method and stored with different storage time, was systematically researched. The activation energy of Al/CuO nanothermite was calculated by differential scanning calorimetry(DSC). The ignition temperature and the curve pressure history of Al/Cu O nanothermite was measured using ignition temperature measuring device and constant-volume pressurization tests, respectively. Further, the thermites were characterized by X-ray Diffractometer(XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM) and Transmission electron microscopy(TEM). The results show that the morphology of the thermites did not change significantly. The activation energy was decreased from 254.1 k J/mol to 181.8 k J/mol after storage for 13 months. When stored for 0, 7 and 13 months, the peak pressures of Al/CuO nanothermite were 685.8 k Pa,626.3 k Pa and 625.5 k Pa, respectively. In addition to the ignition temperature, it was 775 ℃, 739 ℃ and754 ℃, respectively. This result indicated that the ignition and combustion properties of Al/CuO nanothermite are obviously reduced when stored for a long time, at room temperature.

Fabrication and characterization of AleCuO nanocomposites prepared by sol-gel method

In this study,AleCuO nanocomposites were fabricated by sol-gel method.As a contrast,the thermite was prepared by physical mixing at the equivalence ratio of 0.5,1,2,respectively.The intermediates and samples as prepared were characterized by SEM and XRD.The exothermic properties of the two samples prepared at different equivalence ratios were tested and the reaction products were characterized by XRD.The SEM results show that the sample prepared by the sol-gel method demonstrates a micron-sized agglomerated sphere formed by a mutual wrapping of Al NPs and CuO NPs,and the particles are evenly distributed in the agglomerate.In addition,when the content of Al powder is seriously insufficient,the heat release of the sample prepared by physical mixing is 1.6 times that of by sol-gel method.With the increase of Al powder content,the exothermic properties of Al/CuO NPs prepared by sol-gel method began to increase significantly compared with physical mixing and the difference is 1.5 times when the equivalence ratio increases to 2.It can be concluded that the reason for this result may be attributed to the different mass transfer modes of components due to the different morphologies of samples.

Effect of vitamin D3 on maturation and antigen-presenting function of dendritic cells treated with Mycobacterium tuberculosis

Objective:To investigate the phenotypic characteristics and functional capability differences of mouse bone marrow-derived dendritic cells after stimulation with Mycobacterium tuberculosis in the presence or absence of vitamin 03.Methods:Mouse bone marrow-derived cells were cultured with GM-CSF(20 ng/mL).Then,one was added with 100 nmol/L of 25(OH)D3,while the other did not.On day 6.5 μg/mL of BCG was added to stimulate the cells for 24 h.On day 7,suspension cells were harvested for phenotypic and functional analyses.Results:The percentages of CD86 dendritic cells(DCs) in the control group and 25(OH)D3 group were 66.97%± 8.29%and 52.18%± 8.52%.respectively;the mean fluorescence intensities of MHC- Ⅱ in the control group and 25(OH)D3 group were 1 102.16 ± 371.02 and 681.62± 292.71.The expression levels of MHC- Ⅱ and CD86 on the surface of the DCs in 25(OH)D3 group were significantly lower than those of the control group.The ability of the DCs to stimulate proliferation of T-lymphocytes was also significantly lower than that of the control group.Conclusions:These findings suggest that 25(OH)D3 modulates the immune response by affecting the maturation and function of DCs in Mycobacterium tuberculosis period.

A Suspected Person-to-person Transmission of Avian Influenza A （H7N9） Case in Ward

Since throat swab specimens obtained from three adult Chinese patients were confirmed as an avian-origin influenza A （H7N9） virus by local Centers for Disease Control and Prevention （CDC） in 2013,many confirmed cases have been reported in Mainland of China.