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1.
Although curcumin is considered to have various therapeutic effects, its use as a functional food or supplement is restricted owing to its low water solubility and bioavailability. To increase the solubility of curcumin in water, the use of polyvinylpyrrolidone (PVP) and vinylpyrrolidone-vinyl acetate copolymers with a pyrrolidone skeleton was noted to be promising. In particular, the bi-component formulations of curcumin/PVP prepared through spray drying exhibited an amorphous state in powder X-ray diffraction observations and temporally increased the apparent solubility of curcumin to over 5000 times that of untreated curcumin; nevertheless, after 24 h, the solubility decreased owing to the unstable supersaturated state of curcumin. The addition of α-cyclodextrin (α-CyD) in the bi-component curcumin/PVP formulation helped maintain the supersaturated state of curcumin, whereas the addition of β- and γ-CyD led to the collapse of the supersaturated state. The addition of α-CyD can likely help inhibit the nucleation and crystal growth of curcumin, through the interaction among the solubilized units of curcumin/PVP and α-CyD.  相似文献   
2.
文章在对造成二总线火灾报警系统带载能力差的原因分析的基础上,指出了探测器的工人流是影响其带载能力的重要因素,并提出了解决办法。  相似文献   
3.
阐述探测器基本工作原理,并给出探测器使用过程中的易受扰部位和主要的外界电磁干扰源.在此基础上从前置放大器、电源滤波器、PCB设计、结构屏蔽四个方面给出设计方案,以提高探测器的电磁抗扰度能力.经实际测试和现场使用,采用了EMC设计的探测器能够满足GB 15631-2008《特种火灾探测器》的要求.  相似文献   
4.
朱飞  刘国正  彭红明 《山西建筑》2014,(33):156-157
通过了解国内外隧道工程超前地质预报的发展现状及对目前几种常用的超前预报方法的分析,总结出几种常用的隧道超前预报的优缺点及适用范围,并对未来的发展趋势进行了展望,探索了计算机技术在隧道超前预报发展中的应用。  相似文献   
5.
1,1?-Diamino-4,4?,5,5?-tetranitro-2,2?-biimidazole (DATNBI) was synthesized, by employing one-pot facile method, from 4,4?,5,5?-tetranitro-2,2?-biimidazole. The crystal structure was determined by X-ray diffraction for the first time. DATNBI crystallized in monoclinic system P21/c, with a crystal density of 1.934 g cm?3 at 293(2) K and 2.019 g cm?3 at 130(2) K, respectively. Its crystal parameters at 293 K are = 4.8833(15) Å, = 6.960(2) Å, = 6.928(4) Å, α γ = 90°, β = 93.418(6)°, = 591.1(3) ?3, = 2, μ = 0.178 mm?1, and F(000) = 348. The thermal stability and non-isothermal kinetics of DATNBI were studied by differential scanning calorimeter (DSC) with heating rates of 5, 10, 15, and 20 K min?1. The apparent activation energy (Ea) at the first decomposition peak calculated by Kissinger, Ozawa, and Starink equations were 85.50, 89.67, and 86.10 kJ mol?1, respectively. For the second peak, these were 116.49, 119.82, and 117.45 kJ mol?1, respectively, with individual pre-exponential factors ln= 18.40 s?1 and ln= 25.11 s?1. The thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) analysis of thermal decomposition products reveals that the main decomposition gas products are H2O, N2O, CO2, and NO2. Based on the new crystalline densities, the detonation velocity and pressure predicted by EXPLO5 are 9062 m s?1 and 36.4 GPa, respectively.  相似文献   
6.
《食品工业科技》2013,(01):317-318
建立液相色谱柱后补偿与电雾式检测器(CAD)结合的方法测定了茶叶粗提物中的茶氨酸。结果表明:茶氨酸线性回归方程为Y=0.1412X-0.0614,相关系数r=0.9998,线性范围为1.50~50.00μg/mL,方法最低检出限为0.50μg/mL(以S/N=3计),定量限为1.50μg/mL(以S/N=10计);空白样品加标回收率为97.62%~112.13%;重现性实验表明(n=5),茶氨酸的保留时间差值小于0.2min,峰面积的相对标准偏差(RSD值)为0.62%,重现性较好。该方法重现性好、灵敏度高,操作简单,适用于茶叶提取物中茶氨酸的检测。   相似文献   
7.
Plasmid DNA is useful for investigating the DNA damaging effects of ionizing radiation. In this study, we have explored the feasibility of plasmid DNA-based detectors to assess the DNA damaging effectiveness of two radiotherapy X-ray beam qualities after undergoing return shipment of ~8000 km between two institutions. The detectors consisted of 18 μL of pBR322 DNA enclosed with an aluminum seal in nine cylindrical cavities drilled into polycarbonate blocks. We shipped them to Toronto, Canada for irradiation with either 100 kVp or 6 MV  X-ray beams to doses of 10, 20, and 30 Gy in triplicate before being shipped back to San Diego, USA. The Toronto return shipment also included non-irradiated controls and we kept a separate set of controls in San Diego. In San Diego, we quantified DNA single strand breaks (SSBs), double strand breaks (DSBs), and applied Nth and Fpg enzymes to quantify oxidized base damage. The rate of DSBs/Gy/plasmid was 2.8±0.7 greater for the 100 kVp than the 6 MV irradiation. The 100 kVp irradiation also resulted in 5±2 times more DSBs/SSB than the 6 MV beam, demonstrating that the detector is sensitive enough to quantify relative DNA damage effectiveness, even after shipment over thousands of kilometers.  相似文献   
8.
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the current COVID-19 pandemic. In SARS-CoV-2, the channel-forming envelope (E) protein is almost identical to the E protein in SARS-CoV, and both share an identical α-helical channel-forming domain. Structures for the latter are available in both detergent and lipid membranes. However, models of the extramembrane domains have only been obtained from solution NMR in detergents, and show no β-strands, in contrast to secondary-structure predictions. Herein, we have studied the conformation of purified SARS-CoV-2 E protein in lipid bilayers that mimic the composition of ER–Golgi intermediate compartment (ERGIC) membranes. The full-length E protein at high protein-to-lipid ratios produced a clear shoulder at 1635 cm−1, consistent with the β-structure, but this was absent when the E protein was diluted, which instead showed a band at around 1688 cm−1, usually assigned to β-turns. The results were similar with a mixture of POPC:POPG (2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine/3-glycerol) and also when using an E-truncated form (residues 8–65). However, the latter only showed β-structure formation at the highest concentration tested, while having a weaker oligomerization tendency in detergents than in full-length E protein. Therefore, we conclude that E monomer–monomer interaction triggers formation of the β-structure from an undefined structure (possibly β-turns) in at least about 15 residues located at the C-terminal extramembrane domain. Due to its proximity to the channel, this β-structure domain could modulate channel activity or modify membrane structure at the time of virion formation inside the cell.  相似文献   
9.
提出以溶胶凝胶法制备含银Na2O-B2O3-SiO2玻璃的工艺及制备过程,用X射线衍射及红外吸收光谱分析制备过程中结构变化,用光学吸收谱、透射电镜及能谱分析确定银胶体粒子的存在及其分布.结果表明,溶胶凝胶法制备与传统熔融法制备的玻璃有相同的结构,且通过适当的热处理工艺可以获得尺寸有一定分布的银粒子.该方法既可以用于颜色玻璃的制备,其产品也可作为制备其他材料的原料.  相似文献   
10.
湖南省四地区室内氡调查   总被引:1,自引:0,他引:1  
采用CR-39固体径迹探测器,在湖南省4地区进行了居室内氡浓度调查,统计学分析表明,4地区室内氡浓度呈对数正态分布。在地形分布上,有西北高、东南低的特点,反映了地质构造和建筑材料等对室内氡浓度的影响。  相似文献   
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