Characterization of the antibacterial activity and the chemical components of the volatile oil of the leaves of Rubus parvifolius L

Rubus parvifolius L. (Rp) is a medicinal herb that possesses antibacterial activity. In this study, we extracted the volatile oil from the leaves of Rp to assess its antibacterial activity and analyze its chemical composition. A uniform distribution design was used to optimize the extraction procedure, which yielded 0.36% (w/w) of light yellowish oil from the water extract of Rp leaves. We found that the extracted oil effectively inhibited the growth of a wide range of Gram positive and negative bacteria, including Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumanii, Bacillus cloacae, and Klebsiella pneumoniae. We further analyzed the components contained in the hydro-distillated Rp volatile oil by gas chromatography-mass spectroscopy. Twenty nine compounds were identified, including 4-hydroxy-3-methoxystyrene (66%), 3,7,11,15-tetramethyl-2-hexadecen-1-ol (10%) and 4-tert-butylbenzoic acid (2%). Our results suggest that one or multiple constituents contained in Rp volatile oil may account for its antibacterial activity.     

聚氯乙烯树脂的不饱和度和热稳定性的关系

用紫外 可见光谱法表征了不同来源的聚氯乙烯树脂（ＰＶＣ）的热稳定性，用一氯化碘加成法测量了ＰＶＣ的总的双键含量，用红外光谱法测量了ＰＶＣ的孤立双键和共轭双键的相对含量．结果表明，ＰＶＣ在加工期间的初期着色行为和长期热稳定性并不直接相关，前者取决于ＰＶＣ分子链中共轭双键的含量，而后者则和孤立双键的含量有关     

Computer simulation of intravascular ultrasound plaque images

A method is proposed to simulate intravascular ultrasound （IVUS） images of athero-sclerotic plaques. To accomplish the simulation of static IVUS plaque images, the ringdown and guidewire artifacts are introduced into the polar image-formation model （PIFM）, and the fibrous, lipid and calcific contents are synthesized in plaques respectively. The simulation of sequential IVUS images can be achieved by utilizing characteristics of the pulsatile artery. The results on static images demonstrate that it outperforms the PIFM method by 56.9% in terms of the correlation coefficient （CC）, and 24.3% in terms of the mutual information （MI）. The results on sequential images demonstrate that it outperforms the PIFM method by 51.0% in terms of CC, and 10.3% in terms of MI.     

Copper-catalyzed cross-coupling of chloramine salts and arylboronic acids in water: A green and practical route to N-arylsulfonamides

A green and practical method for the synthesis of N-arylsulfonamides from chloramine salts and arylboronic acids is herein developed. The reaction proceeds readily in the presence of 5?mol% of CuI and 2.5?equiv. K₂CO₃ in water at room temperature, generating a variety of N-arylsulfonamides in moderate to good yields with good functional group tolerance.     

Carbon-dot-encapsulated molecularly imprinted mesoporous organosilica for fluorescent sensing of rhodamine 6G

A highly sensitive molecularly imprinted fluorescent sensor for rhodamine 6G (R6G) was fabricated using carbon dot (CD)-embedded mesoporous organosilica as scaffold through a one-pot self-assembly process. The embedded CDs and R6G exhibit efficient fluorescence resonance energy transfer (FRET) due to the overlap between the emission band of energy donor CDs and the excitation band of energy acceptor R6G, as well as their nanometer-sized distance. After acid treatment, molecularly imprinted silica for recognition of R6G with excellent performance in terms of sensitivity and selectivity was obtained, being attributed to the FRET effect between CDs and R6G and the spatial recognition ability for R6G.     

γ-Fe2O3磁粉的表面特性

要提高磁带、磁盘等磁记录材料的记录密度,"分散"问题是关键之一,而分散过程中的润湿、磁粉团的解体和粒子的凝聚都直接与磁粉的表面特性有关。本文通过各种极性或非极性液体对密堆积磁粉的渗透速度以及磁粉在这些液体中沉降体积测定,研究了液体对磁粉的润湿特性,估测了它们的接触角;文内还尝试按Fowkes理论假定进行了计算,求得γ-Fe₂O₃磁粉表面张力为:γ_s^d=24dyn/cm,γ_s^p=17dyn/cm,γ_s=γ_s^d+γ_s^p=41dyn/cm。