冻融作用对石油污染土壤酶活性和水溶性碳的影响

通过现场采样调查及室内分析测试,研究了石油污染土壤经过10个冻融循环和恒温处理后,土壤中过氧化氢酶和脲酶的活性、土壤呼吸速率、水溶性有机碳及微生物量碳的变化特征.结果表明,冻融作用对中重度污染土壤中过氧化氢酶和脲酶的活性有促进作用,过氧化氢酶活性提高6.64%,脲酶活性增加41.11%,但对土壤微生物量碳影响不大;水溶性有机碳受冻融作用影响较大,其比恒温处理提高67.04 mg·kg-1,且土壤中总石油烃含量越高,水溶性有机碳变化越大;中重度石油污染土壤经过冻融处理后,其石油烃含量较之恒温处理减少明显,两种不同处理的差值达290.268 mg·kg-1,而对于高度石油污染土壤来说,冻融作用则可能不利于石油烃的降解.     

ULTRASONOGRAPHIC EVALUATION OF CRANIAL CRUCIATE LIGAMENT RUPTURE VIA DYNAMIC INTRA-ARTICULAR SALINE INJECTION

Ultrasonographic examination of both stifle joints of five clinically and radiographically normal adult dogs was performed before and after surgical transection of the cranial cruciate ligament (CrCL). At pre- and postsurgery, the hyperechoic patellar ligament and the infrapatellar fat interfered with sonographic visualization of the CrCL. When the stifle joint, however, was imaged via dynamic intra-articular saline injection, the hyperechoic ligament was visualized because of the separation of the infrapatellar fat and the CrCL and the contrasting effect of anechoic saline. When the stifle joint was imaged by real-time scanning after the transection of the CrCL, flutter of the ligament and an anechoic area between the bone and the CrCL were identified. The increased diameter of the ligament and the increased thickness of the joint space were identified as well. Ultrasonographic examination via dynamic saline injection into the joint space has potential as a diagnostic tool for assessing CrCL rupture.     

Synthesis of fluorescently labeled pyrazole derivative induceing a triple response in Arabidopsis seedlings

A fluorescent labeled pyrazole derivative with a dansyl moiety (EH-DF) was synthesized. Design of EH-DF was carried out by using a dansyl moiety to substitute the naphthalene moiety of the parent compound (EH-1). At a concentration of 30 µM, EH-DF displayed biological activity on inducing a triple response in Arabidopsis seedlings. Compared with the non-chemical treated control, the hypocotyl length of EH-DF-treated Arabidopsis seedlings was reduced from approximately 9.2±0.7 mm to 2.4±0.2 mm. The length of the roots was reduced from 1.7±0.1 mm to 1.0±0.1 mm, and the curvature of the hook of Arabidopsis seedlings increased from 60±16 degrees to 245±35 degrees. The maxim excitation wavelength and emission wavelength of EH-DF were 350 and 535 nm, respectively. Data obtained via fluorescent microscope analysis indicated that intensive fluorescent signals of EH-DF were observed in the shoot of Arabidopsis seedlings.     

Taeanamides A and B,Nonribosomal Lipo-Decapeptides Isolated from an Intertidal-Mudflat-Derived Streptomyces sp.

Two new lipo-decapeptides, namely taeanamides A and B (1 and 2), were discovered from the Gram-positive bacterium Streptomyces sp. AMD43, which was isolated from a mudflat sample from Anmyeondo, Korea. The exact molecular masses of 1 and 2 were revealed by high-resolution mass spectrometry, and the planar structures of 1 and 2 were elucidated using NMR spectroscopy. The absolute configurations of 1 and 2 were determined using a combined analysis of ¹H-¹H coupling constants and ROESY correlations, the advanced Marfey’s method, and bioinformatics. The putative nonribosomal peptide synthetase pathway for the taeanamides was identified by analyzing the full genome sequence data of Streptomyces sp. AMD43. We also found that taeanamide A exhibited mild anti-tuberculosis bioactivity, whereas taeanamide B showed significant bioactivity against several cancer cell lines.     

Antibacterial Meroterpenoids,Merochlorins G–J from the Marine Bacterium Streptomyces sp.

Four new chlorinated meroterpenoids, merochlorins G−J (1−4), and 10, a dihydronaphthalenedione precursor, along with known merochlorins A (5) and C−F (6−9), were obtained from cultivation of the bacterium strain Streptomyces sp. CNH-189, which was isolated from marine sediment. The planar structures of compounds 1−4 and 10 were elucidated by interpretation of MS, UV, and NMR spectroscopic data. The relative configurations of compounds 1−4 were determined via analysis of nuclear Overhauser effect (NOE) spectroscopic data, after which their absolute configurations were established by comparing the experimental electronic circular dichroism (ECD) spectra of compounds 1−4 to those of previously reported possible enantiomer models and DP4 calculations. Compound 3 displayed strong antibacterial activities against Bacillus subtilis, Kocuria rhizophila, and Staphylococcus aureus, with MIC values of 1, 2, and 2 μg/mL, respectively, whereas compound 1 exhibited weak antibacterial effects on these three strains, with a 16−32 μg/mL MIC value range.     

The mechanical properties of polyurethane foam wound dressing hybridized with alginate hydrogel and jute fiber

The purpose of this study is to fabricate a smart wound dressing by hybridizing hydrophilic polyurethane foam (PUF) and alginate hydrogel. Hydrophilic PUF is used to maintain damaged tissue in a moist environment. Despite its many strong points as a wound dressing, hydrophilic PUF cannot be loaded with ingredients such as growth factors and cytokines that would enhance wound healing. Therefore, we introduce a pH-sensitive alginate hydrogel with the ability to selectively release drugs within the pH range of wounded skin. Due to the small pore size of PUF and the high viscosity of the alginate solution, the two are not easily penetrable. As such, a vacuum method is used to insert alginate hydrogel into the PUF. The optimum conditions for the vacuum method chosen are to be proposed. However, the mechanical strength of PUF decreased after containing alginate hydrogel. Therefore, Na-alginate powder for PUF, various types of crosslinking agents and jute fiber for alginate hydrogel were introduced to improve the mechanical properties of hydrogel/PUF hybrid wound dressing. Three different types of crosslinking agents are used for the gel formation. The most suitable crosslinking agent and its concentration for alginate hydrogel is also determined by the experiments. The experimental results are discussed with proper schemes and reasonable explanations.     

Oscillatory mass transport in vapor-liquid-solid growth of sapphire nanowires

In vapor-liquid-solid (VLS) growth, the liquid phase plays a pivotal role in mediating mass transport from the vapor source to the growth front of a nanowire. Such transport often takes place through the liquid phase. However, we observed by in situ transmission electron microscopy a different behavior for self-catalytic VLS growth of sapphire nanowires. The growth occurs in a layer-by-layer fashion and is accomplished by interfacial diffusion of oxygen through the ordered liquid aluminum atoms. Oscillatory growth and dissolution reactions at the top rim of the nanowires occur and supply the oxygen required to grow a new (0006) sapphire layer. A periodic modulation of the VLS triple-junction configuration accompanies these oscillatory reactions.