分类: 物理学 >> 核物理学 提交时间: 2023-08-11
摘要: A new scintillating fiber detector inside magnetic shielding tube was designed and assembled for use in the next round of fusion experiments in the experimental advanced superconducting tokamak to provide DT neutron yield with time resolution. In this study, Geant4 simulations were used to obtain the pulse-height spectra for ideal signals produced when detecting neutrons and gamma rays of multiple energies. One of the main sources of interference was found to be low-energy neutrons below 10-5 MeV, which can generate numerous secondary particles in the detector components, such as the magnetic shielding tube, leading to high-amplitude output signals. To address this issue, a compact thermal neutron shield containing a 1 mm Cd layer outside the magnetic shielding tube and a 5 mm inner Pb layer was specifically designed. Adverse effects on the measurement of fast neutrons and the shielding effect on gamma rays were considered. This can suppress the height of the signals caused by thermal neutrons to a level below the height corresponding to neutrons above 4 MeV because the yield of the latter is used for detector calibration. In addition, the detector has relatively flat sensitivity curves in the fast neutron region, with the intrinsic detection efficiencies (IDEs) of approximately 40 %. For gamma rays with energies that are not too high (
分类: 生物学 >> 植物学 提交时间: 2017-07-14
摘要: Three new cycloheximide congeners, 2,3-dehydro--epi-isocycloheximide (1), (E)- and (Z)-2,3-dehydro-anhydrocycloheximides (2 and 3), together with three known compounds, anhydroisoheximide (4), cycloheximide (5), and isocycloheximide (6), were obtained from the cultures of Streptomyces sp. SC0581. Their structures were elucidated by extensive spectroscopic analysis in combination with theoretical conformational analysis and ECD computations. The photoinduced interconversion between 2 and 3 was observed and verified and the possible reaction path and mechanism were proposed by theoretical computations. The antifungal and cytotoxic activities of 1–6 were evaluated and suggested that 2,3-dehydrogenation results in the loss of the activities and supported the OH- is important to the activities of cycloheximide congeners.
分类: 生物学 >> 生物物理学 >> 肿瘤学 提交时间: 2016-05-11
摘要: Malignant pleural effusion (MPE) is a common complication caused by malignant diseases. However, subjectivity, poor sensitivity, and substantial false-negative rates of cytology assay hamper accurate MPE diagnosis. The aim of this study was to assess whether CD163+CD14+ tumor-associated macrophages (TAMs) could be used as a biomarker for enabling sensitive and specific MPE diagnosis. Pleural effusion samples and peripheral blood samples were collected from 50 MPE patients and 50 non-malignant pleural effusion (NMPE) patients, respectively. Flow cytometry was performed to analyze cell phenotypes, and RT-qPCR was used to detect cytokine expression in these monocytes and macrophages. A blinded validation study (n = 40) was subsequently performed to confirm the significance of CD163+CD14+ TAMs in MPE diagnosis. Student's t test, rank sum test, and receiver operating characteristic curve analysis were used for statistical analysis. Notably, CD163+CD14+ cell frequency in MPE was remarkably higher than that in NMPE (P < 0.001). In a blinded validation study, a sensitivity of 78.9 % and a specificity of 100 % were obtained with CD163+CD14+ TAMs as a MPE biomarker. In total (n = 140), by using a cutoff level of 3.65 %, CD163+CD14+ cells had a sensitivity of 81.2 % and a specificity of 100 % for MPE diagnosis. Notably, MPE diagnosis by estimating CD163+CD14+ cells in pleural effusion could be obtained one week earlier than that obtained by cytological examination. CD163+CD14+ macrophages could be potentially used as an immune diagnostic marker for MPE and has better assay sensitivity than that of cytological analysis.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-11
摘要: Lipid droplets (LDs) are ubiquitous organelles that serve as a neutral lipid reservoir and a hub for lipid metabolism. Manipulating LD formation, evolution, and mobilization in oleaginous species may lead to the production of fatty acid-derived biofuels and chemicals. However, key factors regulating LD dynamics remain poorly characterized. Here we purified the LDs and identified LD-associated proteins from cells of the lipid-producing yeast Rhodosporidium toruloides cultured under nutrient-rich, nitrogen-limited, and phosphorus-limited conditions. The LD proteome consisted of 226 proteins, many of which are involved in lipid metabolism and LD formation and evolution. Further analysis of our previous comparative transcriptome and proteome data sets indicated that the transcription level of 85 genes and protein abundance of 77 proteins changed under nutrient-limited conditions. Such changes were highly relevant to lipid accumulation and partially confirmed by reverse transcription-quantitative PCR. We demonstrated that the major LD structure protein Ldp1 is an LD marker protein being upregulated in lipid-rich cells. When overexpressed in Saccharomyces cerevisiae, Ldp1 localized on the LD surface and facilitated giant LD formation, suggesting that Ldp1 plays an important role in controlling LD dynamics. Our results significantly advance the understanding of the molecular basis of lipid overproduction and storage in oleaginous yeasts and will be valuable for the development of superior lipid producers.