Preparation of bamboo-derived magnetic biochar for solid-phase microextraction of fentanyls from urine

In this study, a biochar-based magnetic solid-phase microextraction method, coupled with liquid chromatography–mass spectrometry, was developed for analyzing fentanyl analogs from urine sample. Magnetic biochar was fabricated through a one-step pyrolysis carbonization and magnetization process, followed by an alkali treatment. In order to achieve desired extraction efficiency, feed stocks (wood and bamboo) and different pyrolysis temperatures (300–700°C) were optimized. The magnetic bamboo biochar pyrolyzed at 400°C was found to have the greatest potential for extraction of fentanyls, with enrichment factors ranging from 58.9 to 93.7, presumably due to H-bonding and π–π interactions between biochar and fentanyls. Various extraction parameters, such as type and volume of desorption solvent, pH, and extraction time, were optimized, respectively, to achieve the highest extraction efficiency for the target fentanyls. Under optimized conditions, the developed method was found to have detection limits of 3.0–9.4 ng/L, a linear range of 0.05–10 μg/L, good precisions (1.9–9.4% for intrabatch, 2.9–9.9% for interbatch), and satisfactory recoveries (82.0–111.3%). The developed method by using magnetic bamboo biochar as adsorbent exhibited to be an efficient and promising pretreatment procedure and could potentially be applied for drug analysis in biological samples.     

近紫外LED激发荧光粉Ba0.11Sr2.89-2xCexNaxAlO4F发光特性

采用高温固相法反应制备Ba0.11Sr2.89-2x Ce x Na x AlO4F(x=0.01,0.02,0.05,0.07,0.10,0.15)荧光粉。Ba0.11Sr2.89AlO4F体系中存在Sr(1)2+和Sr2+(2)两个格位。Sr2+(1)离子位于Wyck.4a格位,为十配位多面体构型。Sr2+(2)离子位于Wyck.8h格位,为八配位的多面体构型。研究了Ba0.11Sr2.89-2x Ce x Na x AlO4F荧光粉的紫外-可见激发、发射光谱、荧光寿命及能量传递过程,讨论并指认了Ce3+在上述两个格位中的激发带位置及能级重心,发射光谱曲线分别由两个~463,~505和~550 nm宽带发射构成。随着Ce3+浓度增加,长波发射~550 nm逐渐增强,而色品坐标(x=0.199,y=0.351)蓝绿区逐渐变化到黄绿区域(x=0.389,y=0.489)。     

Phosphoric acid purification by suspension melt crystallization: Parametric study of the crystallization and sweating steps

In order to purify phosphoric acid, the suspension melt crystallization process was studied. The suspension crystallization experiments were carried out with 80, 84 and 88 wt% phosphoric acid melt at the cooling rates of 0.05, 0.1 and 0.2 K/min, respectively. Sweating experiments were executed for various crystals obtained in suspension crystallization step. The purification effects of the sweating parameters including sweating time, initial inclusion amount and initial impurity content were studied. The inclusion fraction increases with the increase in cooling rate. The inclusion fraction of the crystals which were formed with feed concentration of 84 wt% phosphoric acid melt is lowest among the three feed concentrations. Different impurities have different purification performances during sweating. High inclusion amount and low impurity concentration favor the purification of H₃PO₄·0.5H₂O crystals during sweating.     

柱前荧光衍生-高效液相色谱法测定尿和血清中的环境雌激素

建立了同时测定人尿和血清中环境雌激素双酚A、4-壬基酚、17α-乙炔基雌二醇及内源性雌激素雌三醇、17α-雌二醇和17β-雌二醇的对硝基苯甲酰氯柱前荧光衍生-高效液相色谱测定方法。尿样经酸水解、固相萃取柱浓缩、净化分离;血清样品经乙腈沉淀蛋白后,用乙醚萃取游离态雌激素,N2气流挥干、在无水条件下,雌激素与对硝基苯甲酰氯反应生成荧光产物,用高效液相色谱法定量。检出限为2．7—8．3μg／L;加标回收率尿样为78．0％-102．5％,血清样为72．6％-98．6％;方法精密度为1．29％-4．52％。应用本法对20份尿样和10份血清样进行了测定,结果满意。     

分块半相依线性回归模型的参数估计

考虑一般的分块半相依线性回归（SUR）模型及其相应的简约模型，给出简约模型下未知回归系数及其可估函数的协方差改进估计仍是分块SUR模型下相应参数的协方差改进估计的一个充要条件．     

Immuno-laser capture microdissection of frozen prolactioma sections to prepare proteomic samples

Laser capture microdissection (LCM) technology combined with immunohistochemistry (immuno-LCM) is a valuable tool to obtain specific target cell populations and therefore this technique enables more accurate proteomic profile. In this study, we optimized the regular immuno-LCM technique to isolate and stain pure prolactin cells from either normal human pituitary (n = 6) or prolactioma (n = 11). Compared with the routine procedure, more intense and specific staining could be obtained when sections were pretreated with 0.2% Triton X-100 for 4 min. Interestingly, longer pretreatment (0.2% Triton X-100 for 10 min) or higher concentration (2% Triton X-100 for 4 and 10 min) greatly impaired labeling intensity and cell shape. Further scanning electron microscope study revealed that the component extracted from the cell surface by Triton X-100 was lipid. Using the optimized immuno-LCM technique, more pure prolactin cells could be isolated and prepared for further proteomic analysis. Taken together, we reported an optimized immuno-LCM technique that could effectively dissect pure target cells in different type pituitary adenomas for further proteomics analysis.     

Three-dimensional ghost imaging based on periodic diffraction correlation imaging

We experimentally demonstrate a three-dimensional （3D） ghost imaging method based on period diffraction correlation imaging. Compared with conventional ghost imaging, our method can easily retrieve the images of different focal planes. Due to the correlation between the disturbed object beam and the reference beams which do not pass through any scattering, the clear images can be periodically obtained in the uncovered zones even through a scattering medium. The analysis of the 3D imaging resolution reveals that the proper resolution for actual demand can be achieved by designing our devices. The implementation of this experiment is quite simple and low-cost. It facilitates the practical applications of ghost imaging.     

基于DSP实现的数字化闭环光纤陀螺

提出一种基于高速数字信号处理专用DSP芯片使用的数字化闭环光纤陀螺系统方案,并着重讨论其数字快速算法的实现。这种快速算法采用多抽样率数字信号系统中抽取的高效结构实现,能够在保证系统的实时性和精度的条件下,极大地减少了DSP系统的运算量和存储量。     

Preparation, characterization, and application of electrodes modified with electropolymerized one-dimensional Magnus' green salts: Pt(NH3)4 · PtCl4 and Pt(NH3)4 · PtCl6

We report the modification of various electrode surfaces with electropolymerized Magnus' green salts, [Pt(NH₃)₄ · PtCl₄] _n and [Pt(NH₃)₄ · PtCl₆] _n . The modified electrodes were prepared by cyclic scanning of the electrode potential in an aqueous solution containing Pt(NH₃)₄ ²⁺ and PtCl₄ ²⁻ or PtCl₆ ²⁻ and the supporting electrolyte. The conditions for the film deposition were studied in detail. Several surface analytical techniques, including micro-Raman scattering and X-ray diffraction, were employed to characterize the modifier film. The electrochemical behavior of the modified electrode was studied in detail and the modified electrodes display very good electrocatalytic activity in the oxidation of ascorbic acid, hydrogen peroxide, thiosulfate, and especially nitric oxide. Received: 22 April 1999 / Accepted: 30 June 1999     

A delay-dependent model with HIV drug resistance during therapy

The use of combination antiretroviral therapy has proven remarkably effective in controlling HIV disease progression and prolonging survival. However, the emergence of drug resistance can occur. It is necessary that we gain a greater understanding of the evolution of drug resistance. Here, we consider an HIV viral dynamical model with general form of target cell density, drug resistance and intracellular delay incorporating antiretroviral therapy. The model includes two strains: wild-type and drug-resistant. The basic reproductive ratio for each strain is obtained for the existence of steady states. Qualitative analysis of the model such as the well-posedness of the solutions and the equilibrium stability is provided. Global asymptotic stability of the disease-free and drug-resistant steady states is shown by constructing Lyapunov functions. Furthermore, sufficient conditions related to the properties of the target cell density are obtained for the local asymptotic stability of the positive steady state. Numerical simulations are conducted to study the impact of target cell density and intracellular delay focusing on the stability of the positive steady state. The occurrence of Hopf bifurcation of periodic solutions is shown to depend on the target cell density.