分类: 核科学技术 >> 核科学与技术 提交时间: 2023-06-16
摘要: In certain exceptional cases, capillary samples must be used to measure X-ray absorption spectra (XAS). However, the inhomogeneous thickness of capillary samples causes XAS distortion. This study discusses the distortion and correction of the XAS curve caused by the inhomogeneous thickness of capillary samples. The relationship between the distorted XAS curve mdeq (measured values) and the real absorption coefficient msdeq (true values) of the sample was established. The distortion was slight and negligible when the vertical size (2h) of the X-ray beam spot was smaller than 60% of the capillary tubes inner diameter (2Rin). When h/Rin >1, X-ray leakage is inevitable and should be avoided during measurement. Partial X-ray leakage caused by an X-ray beam spot size larger than the inner diameter of the capillary tube leads to serious compressed distortion of the XAS curve. When h/Rin <1, the distorted XAS data were well corrected. Possible errors and their influence on the corrected XAS are also discussed. Simulations and corrections for distortions verify the feasibility and effectiveness of the corrected method.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-15
摘要: Background: Aldosterone synthase (CYP11B2) is one of the most studied candidate genes related to essential hypertension (EH) and left ventricular hypertrophy (LVH). Some studies have focused on the relationship between -344C/T polymorphism (rs1799998) in the CYP11B2 gene and LVH, but the results are controversial. This meta-analysis is purposed to reveal the relationship between the -344C/T and the left ventricular structure and function, including left ventricular end diastolic dimension (LVEDD), left ventricular end systolic diameter (LVESD), left ventricular mass/left ventricular mass index (LVM/LVMI), left ventricular posterior wall thickness (LVPWT), and interventricular septal wall thickness (IVS). Methods: A literature search of PubMed and Embase databases was conducted on articles published before January 27, 2014. The odds ratios with 95% confidence intervals were calculated. Heterogeneity analyses were performed using meta-regression. Tests for publication bias were also performed and biased studies should be removed from subsequent analyses. Results: There were 20 studies with a total of 6780 subjects meeting the inclusion criteria. The main finding was that concentration levels of LVEDD and LVESD were higher in CC homozygous individuals than in TT homozygous individuals in the whole group. In the Asian subgroup, TT homozygous individuals had larger IVS than CC homozygous individuals. In the Caucasian normotension subgroup, CC homozygous individuals had larger LVM/LVMI than TT homozygous individuals. In the Asian essential hypertension subgroup, TT homozygous individuals had larger LVPWT values than CC homozygous individuals. Conclusions: The present findings support the hypothesis that CC homozygous individuals may have greater left ventricular diameters (LVEDD and LVESD) regardless of their ethnicities or physical conditions.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-11
摘要: Body size is one of the features that distinguish one species from another in the biological world. Animals have developed mechanisms to control their body size during normal development. However, how animals cope with genetic alterations and/or environmental stresses to develop into normal-sized adults remain poorly understood. The ability of the animals to develop into a normal-sized adult after the challenges of genetic alterations and/or environmental stresses reveals a robustness of body size control. Here we show that the mutation of dGPAT4, a de novo synthase of lysophosphatidic acid, is a genetic alteration that triggers such a robust response of the animals to body size challenges in Drosophila. Loss of dGPAT4 leads to a severe delay of development, slow growth and resultant small-sized animals during the larval stages, but results in normal-sized adult flies. The robust body size adjustment of the dGPAT4 mutant is likely achieved by corresponding changes in ecdysone and insulin signaling, which is also manifested by compromised food intake. Thus, we propose that a strategy has been evolved by the animals to reach final body size when challenged by genetic alterations, which requires the coordinated ecdysone and insulin signaling.