Effect of bases with different solubility on the release behavior of risperidone loaded PLGA microspheres

Poly (D, L-lactide-co-glycolide) (PLGA) microspheres are attractive delivery vehicles due to their excellent sustained release capabilities. One major problem with PLGA microspheres is that the hydrophobic properties of PLGA generally cause a lag period in the process of drug release, leading to fluctuation of drug concentration in the blood and various resulting adverse reactions. Herein, Mg(OH)?, an inorganic base, and arginine, an organic base, were separately co-encapsulated into risperidone-loaded PLGA microspheres at varying concentration using the solvent evaporation method to improve release profiles from the microspheres. High encapsulation efficiencies were obtained in all formulations. The surface of base-free microspheres was smooth, whereas a few pores formed in base co-encapsulated microspheres. After 7-days degradation, many inter-connecting pores were formed in the interior of the microspheres containing 10 mg Mg(OH)?. The final pH in the microspheres with Mg(OH)? was higher than in those with arginine after 28-days degradation. The initial release of risperidone from microspheres containing Mg(OH)? was higher than from those containing arginine, and the latter release exhibited a more uniform pattern. Microspheres with 5mg and 10mg arginine exhibited zero-order release kinetics. However, both bases eliminated the lag phase of release. These results indicate that the incorporation of bases has potential in addressing the problem of the lag period in drug release from PLGA microspheres, and improving release behavior toward an ideal model.     

Rattle-type microspheres as a support of tiny gold nanoparticles for highly efficient catalysis

SiO(2)/poly(ethyleneglycol dimethacrylate) (PEGDMA) rattle-type microspheres loaded with tiny sized gold nanoparticles (~2 nm) were prepared through a facile and novel method. Catalyzed reduction of 4-nitrophenol with NaBH(4) demonstrated that this rattle-type microsphere possessed high catalytic efficiency.     

A novel method for quantitative determination of tea polysaccharide by resonance light scattering

A new method for the determination of tea polysaccharide (TPS) in green tea (Camellia sinensis) leaves has been developed. The method was based on the enhancement of resonance light scattering (RLS) of TPS in the presence of cetylpyridinium chloride (CPC)-NaOH system. Under the optimum conditions, the RLS intensity of CPC was greatly enhanced by adding TPS. The maximum peak of the enhanced RLS spectra was located at 484.02 nm. The enhanced RLS intensity was proportional to the concentration of TPS in the range of 2.0-20 μg/ml. It showed that the new method and phenol-sulfuric acid method give some equivalent results by measuring the standard compounds. The recoveries of the two methods were 96.39-103.7% (novel method) and 100.15-103.65% (phenol-sulfuric acid method), respectively. However, it showed that the two methods were different to some extent. The new method offered a limit of detection (LOD) of 0.047 μg/ml, whereas the phenol-sulfuric acid method gives a LOD of 1.54 μg/ml. Interfered experiment demonstrated that the new method had highly selectivity, and was more suitable for the determination of TPS than phenol-sulfuric method. Stability test showed that new method had good stability. Moreover, the proposed method owns the advantages of easy operation, rapidity and practicability, which suggested that the proposed method could be satisfactorily applied to the determination of TPS in green tea.     

次近邻跃迁对石墨烯纳米带输运性质的影响

根据紧束缚模型,利用格林函数的方法,将次近邻跃迁考虑在内,研究了扶手椅型石墨烯纳米带的输运性质.通过数值计算,给出了不同尺寸和不同次近邻跃迁能下系统的能量-电导和电流-电压特征曲线.结果表明,次近邻跃迁对扶手椅型石墨烯纳米带的输运性质有显著的影响.它破坏了电导共振峰关于能量的对称分布,增强了系统的导电性,减小了电子导电偏压阈值,加速了系统输运性能由半导体向导体转变. 次近邻跃迁能和石墨烯纳米带的尺寸越大,这种影响越明显     

An elementary evaluation of an intriguing integral via Fourier series

We use Fourier series to obtain an elementary real variable proof of the result $\int_0^\pi {\left( {\ln \left( {2\cos \tfrac{t} {2}} \right)} \right)^2 dt = \tfrac{{11\pi ^5 }} {{180}}} $ .     

色散和非线性效应对高斯脉冲综合影响的理论分析

从光孤子传输所满足的非线性薛定谔方程出发,采用单独分析和综合分析对比,分析了影响高斯脉冲传输的色散、非线性等因素,结果表明：二阶色散参量只会影响脉冲的幅值,对脉冲形状影响不大,而输入脉冲的啁啾则是使脉冲发生形变的主要原因|在啁啾、三阶色散和五阶非线性的共同作用下,它们对脉冲都会产生较大的影响,且存在相互影响和制约作用,在某一临界值,对脉冲存在着较高的压缩增益效应和“整形”作用.从理论上提出了改善高斯光脉冲在光纤中传输特性的解决方案,这对光纤孤子通信的实践过程具有一定的理论借鉴意义.     

涂硼GEM中子束流监测器物理过程的蒙特卡罗模拟

基于硼转换的GEM(Gas Electron Multiplier)探测器性能突出,计数率高达10 MHz以上,耐辐射,信号读出方式简单、灵活,位置与时间分辨率高,是下一代中子束流监测器极具优势的候选者。这种新型中子束流监测器主要由硼中子转换层、气体电离粒子放大的GEM以及二维读出电极组成。通过Geant4程序包对探测器物理过程进行蒙特卡罗(Monte Carlo)模拟,主要研究了硼中子转换层转换效率与厚度及中子波长的关系、出射粒子的能谱、不同气体比分不同气体厚度中的能量沉积、以及γ的能量沉积,计算比较了不同厚度GEM膜对快中子产生的影响。模拟结果表明,出射粒子在漂移区的能量沉积几乎与气体比分无关,硼层厚度取0.1μm以下,漂移区厚度6 mm时,可以确保出射粒子在漂移区能量完全沉积,同时具有最佳n/γ区分能力。     

溶菌酶活性测定方法的改进及其在重组人溶菌酶质量标准建立中的应用

获得一种趋于均相反应体系的比浊法,用于重组人溶菌酶活性的研究,并建立相关操作规程和质量标准。通过显微计数法进行底物菌液质控,改进酶与菌液的混合方式和最佳酶用量,采用"双直线法"优化反应计时区间,并精确测定重组人溶菌酶含量。显微镜菌体计数法确定0.3 mg/mL底物菌液中菌体数保持在1.1×108个/mL左右;酶与菌液在样品池内经吸排法快速混合可趋近均相体系;酶的最佳用量为3μg;确定反应计时区间为0~60 s;依据所制定的酶活性操作规程,确定重组人溶菌酶活性质量标准为45 000~65 000U/mg,日内、日间相对标准偏差均小于5%;优选Lowry法并精确测定蛋白含量为(1.0±0.1)mg/mL。改进后的方法稳定性得到明显提高,且操作简便、结果可靠,已被3家研究单位、企业验证并接受。建立的重组人溶菌酶活性和含量测定质量标准及操作规程具有实际参考价值。     

Regio- and Chemoselective Formal (4+1) Carbocyclization of Chalcones with Internal Alkynes via Rhodium(III) Catalysis

A rhodium(III)-catalyzed oxidative cyclization of chalcones with internal alkynes is reported, generating biologically important 3,3-disubstituted 1-indanones along with reusable aromatic aldehydes. This transformation features unique (4+1) reaction mode, excellent regioselectivity in alkyne insertion, broad substrate scope, allows for the construction of quaternary carbon centers, and is scalable. Steric hindrance from substrate and ligand probably controls the chemoselectivity of this carbocyclization. Importantly, this discovery enables a practical two-step protocol switching the overall reaction of acetophenones with internal alkynes from a (3+2) to a (4+1) annulation.