Switching Between Giant Positive and Negative Thermal Expansions of a YFe(CN)6-based Prussian Blue Analogue Induced by Guest Species

The control of thermal expansion of solid compounds is intriguing but remains challenging. The effect of guests on the thermal expansion of open-framework structures was investigated. Notably, the presence of guest ions (K⁺) and molecules (H₂O) can substantially switch thermal expansion of YFe(CN)₆ from negative (α_v=−33.67×10⁻⁶ K⁻¹) to positive (α_v=+42.72×10⁻⁶ K⁻¹)—a range that covers the thermal expansion of most inorganic compounds. The mechanism of such substantial thermal expansion switching is revealed by joint studies with synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting negative thermal expansion. An effective method is demonstrated to control the thermal expansion in open-framework materials by adjusting the presence of guests.     

Quantitative Analysis of Fudosteine in Human Plasma Using a Simple Precipitation Step Followed by LC–MS–MS

Fudosteine [(-)-(R)-2-amino-3-(3-hydroxypropylthio) propionic acid] is a synthetic derivative of l-cysteine as a novel expectorant. To facilitate pharmacokinetics studies of fudosteine in man, a sensitive and specific LC–MS–MS method for the quantitative detection of fudosteine in human plasma was developed and validated. The method involved the addition of fosfomycin as internal standards, protein-precipitation, HPLC separation, and quantification by MS/MS system using negative electrospray ionization in the multiple reaction monitoring mode. The precursor → product ion transitions were monitored at 177.6 → 90.9 and 136.8 → 78.9 for fudosteine and the IS, respectively. The lower limit of quantitation (LLOQ) was 5 ng mL⁻¹. The calibration curves for fudosteine was linear over a concentration range of 0.005–10 µg mL⁻¹. The intra- and inter-day analyses of QC samples at 0.01, 1, 10 µg mL⁻¹ indicated good precision %RSD between 92.00 and 101.02%. The fudosteine was stable in human plasma stored at room temperature for at least 12 h, 4 °C for at least 12 h, −20 °C for at least 20 days, and at least three freeze–thaw cycles procedures. This accurate and highly specific assay provides a useful method for evaluating the pharmacokinetics of fudosteine in human.

     

微小型球形飞行器飞行控制系统设计

根据微小型球形飞行器的结构特点和工作原理,设计了一套基于ARM Cortex-M3 STM32F103RBT6微控制器的飞行控制系统,进行了主要模块的功能设计与性能分析,给出了研究结论与选型依据,还设计并完成了姿态传感器两轴转台实验和飞行器室内飞行试验。测试结果表明,该控制系统的姿态传感器姿态测量精度高,能够为飞行控制提供姿态参考信息;飞行器能够圆满实现空中悬停、低空机动等飞行动作,且空中飞行姿态稳定、实时、可靠。该飞行控制系统功能可靠、性能稳定,能够较好地满足微小型球形飞行器的飞行控制要求,具有一定的实用性与扩展性。     

Lipase-catalyzed synthesis of biodegradable copolymer containing malic acid units in solvent-free system

This work is to explore a new route to synthesize functional polyesters bearing pendant hydroxyl groups. The approach is via biocatalyzed direct polycondensation. l-Malic acid, adipic acid and 1,8-octanediol were used as comonomers and lipase Novozym 435 as a biocatalyst. ¹H NMR studies on the structure of the products indicated that Novozym 435 was strictly selective for esterification of l-malic acid carboxyl groups while leaving the hydroxyl groups unchanged. The influences of the monomer feeding ratio, reaction temperature, and reaction time on the molecular weight of the products were investigated. By varying l-malic acid feed ratio in the total monomers from 0 to 20 mol%, the molecular weight (M_W) of the product changed from 9.5 kilo Dalton (kD) to 4.7 kD while reaction was held at 70 °C for 48 h. The maximum M_W could reach 7.4 kD at 80 °C when varying temperature between 70 and 90 °C if l-malic acid is 20 mol% and reaction time is 48 h. At 75 °C the M_W increased from 5.2 kD to 6.6 kD when reaction time was elongated from 48 h to 72 h. However, little change in M_W was observed at 80 and 85 °C when the reaction time was above 48 h. Thermal property of the copolyesters was studied by differential scanning calorimetry (DSC). Increasing the l-malic acid content in copolyesters resulted in melting temperature depression.