Search

为了提高麻疯树种子的开发利用价值，采用体外抗氧化实验对麻疯树籽仁/壳乙醇提取物抗氧化活性进行了研究。分别以麻疯树种子中的籽仁和籽壳为原料，经75%乙醇提取，在对提取物主要成分进行分析的基础上，以VE为阳性对照，测定两种提取物对自由基（DPPH自由基、ABTS+自由基、羟自由基和超氧自由基）的清除能力、还原能力以及抑制亚油酸自氧化能力。结果表明：麻疯树籽仁/壳乙醇提取物中多糖类物质总含量分别为47.67%和52.21%，酮类物质总含量分别为0.774%和 4.22%，麻疯树籽壳乙醇提取物中还含有0.30%的多酚类物质；麻疯树籽仁/壳乙醇提取物均具有一定的抗氧化活性，其中籽壳乙醇提取物对DPPH自由基、ABTS+自由基、羟自由基、超氧自由基的清除效果较好；麻疯树籽仁/壳乙醇提取物的还原能力和对亚油酸自氧化的抑制能力相对较弱。麻疯树籽壳乙醇提取物的抗氧化活性优于籽仁乙醇提取物，可能与籽壳乙醇提取物中含有较多的黄酮类和多酚类物质有关。 In order to improve the exploitation value of Jatropha curcas seed, the antioxidant activities of ethanol extracts of Jatropha curcas seed kernel and shell were investigated using in vitro antioxidant assays.The kernel and shell of Jatropha curcas seed were extracted by 75% ethanol respectively, and based on the analysis of the main components of the extracts, vitamin E was used as positive control, the scavenging ability on free radical (DPPH radical, ABTS+ radical, hydroxyl radical and superoxide radical ), reducing power and inhibition ability for linoleic acid autoxidation of the two extracts were determined.The results showed that the total content of polysaccharides in the ethanol extract of Jatropha curcas seed kernel/shell was 47.67% and 52.21%, and the total content of ketones was 0.774% and 4.22%, respectively. The ethanol extract of Jatropha curcas seed shell also contained 0.30% polyphenols. The two extracts had certain antioxidant activity, and the extract of seed shell was more effective in scavenging DPPH radical, ABTS+ radical, hydroxyl radical and superoxide radical than that of the extract of seed kernel. The reducing ability and inhibitory ability of linoleic acid autoxidation of the two extracts were relatively weak. The antioxidant activity of the ethanol extract of Jatropha curcas seed shell was better than that of the ethanol extract of Jatropha curcas seed kernel, which may be related to the rich content of flavonoids and polyphenols in the ethanol extract of shell.

Sandwich structures are widely used in various fields. Curved sandwich structures have attracted the attention of researchers owing to their superior stiffness and strength. With the application of the structures in engineering, it is required that the structures can not only meet the needs of mechanical loads but also can cope with thermal, acoustic, optical, and electrical loads. Sound insulation is one of the most common problems in the fields of aerospace, transportation, and architecture, so it is imperative to research new structures with good mechanical and acoustic properties. In this paper, a composite structure which is coupled with curve shell sandwich structure and acoustic metamaterials is proposed to obtain good mechanical and acoustic properties. Based on the harmonic expansion method and principle of virtual work, the theoretical model is established and the sound transmission loss (STL) performance is studied. Then, the effects of the geometry of the structure and material parameters on the STL of the structure are discussed. [ABSTRACT FROM AUTHOR]

Cylindrical structures are used in various fields owing to their good mechanical properties. At the same time, the requirements for their acoustic performances continue to increase in the application of cylindrical shell structures. Thus, the acoustic performance and application in sound insulation attract increasing attention. Sandwich cores have been inserted into cylindrical structures to improve the sound insulation performance of the structure. To improve both mechanical and acoustic properties of the cylindrical sandwich structure, a frame structure that strengthens the internal nodes of the pyramidal truss core was added. A theoretical model corresponding to the structure was established to study the sound insulation performance of the structure. The influences of the overall thickness of the structure, number of lattice unit cells, material density, and angle of incident sound waves on the sound insulation performance were analyzed. [ABSTRACT FROM AUTHOR]

Honeycomb sandwich structures have been widely used in the field of engineering owing to their outstanding mechanical properties. However, for a honeycomb sandwich structure with large spatial periodicity, there is a low-frequency sound insulation valley. Here, the sound transmission across locally resonant honeycomb sandwich meta-structures was investigated to overcome this sound-insulation valley. An analytical model was developed based on the space-harmonic approach and the low-frequency sound insulation valley was determined analytically and numerically. The results indicate that the resonator distributed at the center of the face panel has a significant impact on the sound transmission performance of the honeycomb sandwich structure, whereas the resonator distributed on the wall of the honeycomb core does not contribute to overcoming this sound-insulation valley. Based on the research results, a design strategy for overcoming this sound-insulation valley was determined by tuning the damping parameter and constructing graded resonators. Moreover, sound transmission under the excitation of oblique incidence sound waves was also investigated. Compared with the method of filling porous materials, the proposed design method is more effective, and more importantly, the mass of the resonator is only 1.23% of that of the porous materials. [ABSTRACT FROM AUTHOR]

Abstract: A new fluorescent molecule clip derived from diethoxycarbonyl glycoluril with two 2,5-diphenyl-furan sidewalls was designed and synthesized. Its structure and conformation was confirmed by single-crystal X-ray diffraction. Its binding [...]

Recently, sandwich structures have been widely used in different fields because of their good mechanical properties, but these structures are weak in acoustic performance. In this paper, by combining pyramidal truss core sandwich structure with frame, a new structure is proposed with both good mechanical properties and excellent acoustic performance at low frequency. An analytical model of the pyramidal truss core sandwich structure with frame is developed to investigate the sound transmission loss (STL) performance. Finite element method (FEM) is also used to investigate the STL performance at low frequency. The effects of the incident wave angle and the geometrical parameters on the STL of the structure are discussed. [ABSTRACT FROM AUTHOR]

Objective To investigate the clinical characteristics of meningeal carcinomatosis with nervous system syndrome as initial symptom. Methods Clinical data, laboratory and imageing examinations were retrospectively analyzed in 23 patients of meningeal carcinomatosis from June 2009 to December 2017. Results Twenty patients (86.96%) had headache as initial symptom and 12 (52.17%) had headache with vomiting. Head enhanced MRI showed obvious enhancement in meningeal lesions, and 13 cases (59.09% ) had meningeal enhancement with enlargement of ventricular system; CT showed enlargement of supratentorial ventricular system (1 case). About 65.22% (15/23) primary lesions were originated from lung cancer, and others were originated from colon cancer, hematological lymphoma, gastric cancer, spinal astrocytoma (4.35%, 1/23 respectively), and some unknown origin (17.39%, 4/23). About 82.61% (19/23) patients cerebrospinal fluid pressure increased obviously, Tumor markers especially carcinoembryonic antigen (CEA) were mostly increased in serum (11/17) and cerebrospinal fluid (7/10). Conclusions Headache and vomiting are the most common clinical symptoms of meningeal carcinomatosis. Enhanced MRI shows meningeal enhancement or communicating hydrocephalus. Cerebrospinal fluid pressure tends to increase significantly. Carcinoembryonic antigen is significantly increased in serum and cerebrospinal fluid. Primary lesions of meningeal carcinomatosis mostly originate from lung cancer. Finding tumor cells in cerebrospinal fluid is the "golden standard" of diagnosis. [ABSTRACT FROM AUTHOR]