分类： 物理学 >> 核物理学 提交时间： 2023-05-31
Guan Yongjing
Chen Wu
Wang Shenzhen
Hua Yuxin
Jing Qiaoyan
Liu Zhiyong
Huang Chunping
Wang Deyu
Wang Huijuan
He Xianwen
Mario De Cesare
Cui Liangjia
He Hua
Fan Kaidi
Guo Zichen
摘要：The spatial distributions of 239+240Pu and 137Cs in soils from Longji Rice Terraces were investigated to evaluate soil erosion. The activity concentrations of 239+240Pu and 137Cs in the surface soils of the paddy fields were in the range of 0.089-0.734 and 1.80-7.88 mBq/g, respectively. The activities of 239+240Pu and 137Cs showed very similar distribution trends, first increasing and then decreasing with increasing elevation. The 240Pu/239Pu atom ratios in the surface soils ranged from 0.162–0.232. The activities of 239+240Pu and 137Cs in the soil cores tended to be uniformly distributed within the plowed layer and declined exponentially below this depth. The mean soil erosion rates of Longji Rice Terraces estimated by 239+240Pu and 137Cs tracer methods were 5.44 t/(ha·a) and 5.16 t/(ha·a), respectively, which demonstrated that plutonium can replace 137Cs as an ideal tracer for soil erosion research in the future. Landform features are the main factors affecting the distribution of plutonium and 137Cs as well as soil erosion in the Longji Rice Terraces.
分类： 生物学 >> 生物物理学 >> 细胞生物学 提交时间： 2016-05-12
摘要：Super-resolution microscopy techniques have overcome the limit of optical diffraction. Recently, the Bayesian analysis of Bleaching and Blinking data (3B) method has emerged as an important tool to obtain super-resolution fluorescence images. 3B uses the change in information caused by adding or removing fluorophores in the cell to fit the data. When adding a new fluorophore, 3B selects a random initial position, optimizes this position and then determines its reliability. However, the fluorophores are not evenly distributed in the entire image region, and the fluorescence intensity at a given position positively correlates with the probability of observing a fluorophore at this position. In this paper, we present a Bayesian analysis of Bleaching and Blinking microscopy method based on fluorescence intensity distribution (FID3B). We utilize the intensity distribution to select more reliable positions as the initial positions of fluorophores. This approach can improve the reconstruction results and significantly reduce the computational time. We validate the performance of our method using both simulated data and experimental data from cellular structures. The results confirm the effectiveness of our method.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-11
Han, Renmin
Xu, Fan
Ren, Fei
Zhang, Fa
Han, Renmin
Xu, Fan
Ren, Fei
Zhang, Fa
Han, Renmin
Xu, Fan
Wang, Liansan
Zhang, Yongdeng
Zhang, Mingshu
Liu, Zhiyong
摘要：Background: The recent developments of far-field optical microscopy (single molecule imaging techniques) have overcome the diffraction barrier of light and improve image resolution by a factor of ten compared with conventional light microscopy. These techniques utilize the stochastic switching of probe molecules to overcome the diffraction limit and determine the precise localizations of molecules, which often requires a long image acquisition time. However, long acquisition times increase the risk of sample drift. In the case of high resolution microscopy, sample drift would decrease the image resolution. Results: In this paper, we propose a novel metric based on the distance between molecules to solve the drift correction. The proposed metric directly uses the position information of molecules to estimate the frame drift. We also designed an algorithm to implement the metric for the general application of drift correction. There are two advantages of our method: First, because our method does not require space binning of positions of molecules but directly operates on the positions, it is more natural for single molecule imaging techniques. Second, our method can estimate drift with a small number of positions in each temporal bin, which may extend its potential application. Conclusions: The effectiveness of our method has been demonstrated by both simulated data and experiments on single molecular images.
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：Although the topic of fiducial marker-based alignment in electron tomography (ET) has been widely discussed for decades, alignment without human intervention remains a difficult problem. Specifically, the emergence of subtomogram averaging has increased the demand for batch processing during tomographic reconstruction; fully automatic fiducial marker-based alignment is the main technique in this process. However, the lack of an accurate method for detecting and tracking fiducial markers precludes fully automatic alignment. In this paper, we present a novel, fully automatic alignment scheme for ET. Our scheme has two main contributions: First, we present a series of algorithms to ensure a high recognition rate and precise localization during the detection of fiducial markers. Our proposed solution reduces fiducial marker detection to a sampling and classification problem and further introduces an algorithm to solve the parameter dependence of marker diameter and marker number. Second, we propose a novel algorithm to solve the tracking of fiducial markers by reducing the tracking problem to an incomplete point set registration problem. Because a global optimization of a point set registration occurs, the result of our tracking is independent of the initial image position in the tilt series, allowing for the robust tracking of fiducial markers without pre-alignment. The experimental results indicate that our method can achieve an accurate tracking, almost identical to the current best one in IMOD with half automatic scheme. Furthermore, our scheme is fully automatic, depends on fewer parameters (only requires a gross value of the marker diameter) and does not require any manual interaction, providing the possibility of automatic batch processing of electron tomographic reconstruction. (C) 2015 Elsevier Inc. All rights reserved.
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