Freeze-drying of mononuclear cells and whole blood of human cord blood

The research on haematopoietic stem cells of human cord blood has become more important recently. People have concentrated on the preservation of cord blood stem cells. At present, cord blood can be preserved at ultra-low temperatures. In this study, we try to preserve cord blood and its constituents by freeze-drying. The experiments on both the mononuclear cell content and the whole blood of human cord blood were carried out respectively. The samples were frozen firstly by different cooling protocols in the presence of PVP, sucrose, and mannitol. Afterwards, they were vacuum-dried at a selected shelf temperature of -30 degree C for the main drying stage, and then vacuum-dried at 15 degree C for the second drying stage. The entire time of the freeze drying was 52 hours. Samples were stored at room temperature for 2 days prior to evaluation. Subsequently, the dried samples were suspended in an isotonic phosphate-buffered saline solution. The recovery of the cells were tested by a haemacytometer, and the highest cell numerical count recovery of MNC was 75.0 percent (SD = 4.1 percent) (P = 0.01), obtained in the protocol of 40 percent PVP + 20 percent sucrose + 10 percent Mannitol. The viability of the nucleated cells measured by PI staining and the ratio of the number of CD34+ to the number of lymphocytes (by the FITC anti-human CD34+ conjugated antibody method) were measured using a flow cytometer (FCM). The protocol of 40 percent PVP + 20 percent sucrose + 10 percent fetal bovine serum had the highest viability of 98.6 percent (SD = 0.7 percent) (P = 0.01). The highest ratio of CD34+ to lymphocytes was 1.2%, and the highest recovery of CD34+ was 68.4 percent (SD = 39.5 percent) (P = 0.05). Comparing the results of the lyophilized MNC subfraction with that of the whole blood, the lyophilization of the isolated MNC was more successful than that of whole blood.     

A QM/MM study of a nucleophilic aromatic substitution reaction catalyzed by 4-chlorobenzoyl-CoA dehalogenase

Calculated using a QM/MM method, the free energy profile for the conversion of 4-chlorobenzoate to 4-hydroxybenzoate catalyzed by 4-chlorobenzoyl-CoA dehalogenase indicates the existence of a stable Meisenheimer complex.     

Genetic differentiation and subspecies development of the giant panda as revealed by DNA fingerprinting

Over the last 100 years giant pandas (Ailuropoda melanoleuca) have been separated into six completely isolated mountain ranges. DNA fingerprinting revealed different differentiation patterns in giant pandas, including early-stage, late-stage, recent divergence and recent genetic depression. A separation around 10 000 years ago resulted in highly significant differences in DNA fingerprints and morphological characteristics between Qinling and Sichuan populations. Supported by morphological differences, the genetic data were used to classify the Qinling population as a new subspecies, A. m. qinlingensis, while the Sichuan populations were classified into the original subspecies, A. m. melanoleuca. Thus, the Qinling population deserves management as a separate unit. In the Sichuan populations, two management units were defined, including Qionglai-Minshan and Daxiangling-Xiaoxiangling-Liangshan. Our data suggest urgent measures are needed to establish green corridors between subpopulations in each mountain range to increase gene flow and genetic variation to ensure long-term survival.     

Highly proton conductive polyimide electrolytes containing fluorenyl groups

Novel sulfonated polyimides containing fluorenyl groups show good thermal and oxidative stability as well as a high proton conductivity of 1.67 S cm(-1) at 120 degrees C and 100% RH.     

A Novel Gelatin–Carbon Nanotubes Hybrid Hydrogel

This letter focuses on the first result of the preparation and the swelling behavior of a novel hybrid gelatin hydrogel with carbon nanotubes. A novel hybrid gelatin hydrogel with carbon nanotubes was synthesized by a physical mixing method. The structure of the novel hydrogel obtained was characterized by SEM. Besides, the swelling behavior of the synthesized hydrogel was measured at two different temperatures. The results indicate that carbon nanotubes added could maintain the stability of the hybrid hydrogel without cross‐linking at 37 °C. This suggests that the hybrid gelatin hydrogel with carbon nanotubes could be used in biomedical field. Besides, its application in protein separation is discussed.

SEM image of the gelatin‐MWNTs hybrid gel at 10 000 × magnification.     

Novel Broadband Reflectarray Antenna with Windmill-Shaped Elements for Millimeter-Wave Application

A novel broadband millimeter-wave reflectarray antenna composed of windmill-shaped elements of variable lengths is proposed. Compared to the conventional single-layer reflectarray elements, the windmill-shaped elements can realize much larger phase variation range (over 600°), leading to broader bandwidth. Using this technique, a 15°-beam-steering reflectarray operating at 30 GHz is designed. The computed results demonstrate the agreement of the main beam steering with the design requirement, and a 1-dB gain bandwidth close to 20% is obtained. The validity of the obtained results is verified by comparing the ones generated by Ansoft High Frequency Structure Simulator (HFSS) with those produced by Ansoft Designer. The antenna is useful for millimeter-wave applications. This work was supported by the National Natural Science Foundation of China (No. 90505001), the High-Tech Research and Development Program of China (No. 2006AA01Z275), and the Creative Research Group Program of UESTC.     

空间CCD相机的定标方法研究

介绍了相机定标的测试方法。通过对空间CCD相机成像时的地物辐射能量进行分析,提出了以成像方式进行相机定标测试的方法,并对数据处理方式进行了分析。     

杂质对多电子方形量子点系统基态能的影响

根据密度泛函理论,用自洽迭代的方法求解二维方形量子点中有杂质时电子(N=1~12)的薛定谔方程,对绝对零度情况下处于基态电子的总能量进行了数值计算,并讨论了杂质对量子点中电子基态能量的影响,得出了方形量子点中多电子系统基态的一些性质.     

掺铥PLZT透明光电陶瓷的光辐射特性

根据J-O理论研究掺Tm3+的光电陶瓷PLZT的激光潜能，利用Tm3+的420?2000 nm的吸收光谱拟合出了其强度参量，即?2=9.133￡10-21 cm2, ?4=1.529￡10-21 cm2和?6=1.712￡10-21 cm2，进而由强度参量计算了辐射跃迁几率、辐射寿命、荧光分支比和1865 nm荧光峰的受激发射截面等光学参数．     

Effects of composition and sintering temperature on properties of NiZn and NiCuZn ferrites

Effects of composition and sintering temperature on grain size, porosity and magnetic properties of the NiZn and NiCuZn ferrites were investigated. It was found that the lowest power loss could be obtained with the equimolar composition for both NiZn and NiCuZn ferrites, which could be attributed to the lowest porosity. A slight deficiency or excess of Fe₂O₃ content had no pronounced influence on saturation magnetic flux density (B_s) in our testing range. However, a slight excess of Fe₂O₃ was effective to improve the initial permeability, which could be attributed to decrease of the magnetocrystalline anisotropy. With the increase of sintering temperature, the initial permeability and power loss of the NiZn and NiCuZn ferrites had different development trend, which could be explained by the different variation trend of the grain size and porosity. Power losses of the NiCuZn ferrite samples were lower than that of the NiZn ferrite samples at any sintering temperature. Synthetically, the NiCuZn ferrites had a better performance than the NiZn ferrites in power field use.