Subjects: Nuclear Science and Technology >> Nuclear Detection Technology and Nuclear Electronics submitted time 2024-04-07
Abstract： Background Rapid and accurate measurements of radionuclide activities in the field play an important role in radiological medical diagnosis. Purpose This study aims to develop a capacitance-integrated activity meter. Methods A circuit structure of the capacitive-integral type was adopted, and a low-noise preamplifier circuit was designed. The designed structure was matched with high-precision signal acquisition and processing circuit to successfully develop a weak current measurement circuit, achieving weak current measurements ranging from 20 fA to 10 μA. Results The test results show that the repeatability of the proposed radioactivity meter is consistent with the performance of the commercial RM-905A, with a background lower than 0.065 MBq, a repeatability not exceeding 0.84%, and an instability of 1.94%. Conclusions We designed a capacitive integral weak-current preamplifier and built a prototype radioactivity meter device.
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Other Disciplines of Agriculture, Forestry,Livestock & Aquatic Products Science submitted time 2024-06-17 Cooperative journals: 《智慧农业（中英文）》
Abstract： Objective The widespread prevalence of sclerotinia disease poses a significant challenge to the cultivation and supply of oilseed rape, not only results in substantial yield losses and decreased oil content in infected plant seeds but also severely impacts crop productivity and quality, leading to significant economic losses. To solve the problems of complex operation, environmental pollution, sample destruction and low detection efficiency of traditional chemical detection methods, a Bi-directional Gate Recurrent Unit (Bi-GRU) model based on space-spectrum feature fusion was constructed to achieve hyperspectral images (HSIs) segmentation of oilseed rape sclerotinia infected area. Methods The spectral characteristics of sclerotinia disease from a spectral perspective was initially explored. Significantly varying spectral reflectance was notably observed around 550 nm and within the wavelength range of 750−1 000 nm at different locations on rapeseed leaves. As the severity of sclerotinia infection increased, the differences in reflectance at these wavelengths became more pronounced. Subsequently, a rapeseed leaf sclerotinia disease dataset comprising 400 HSIs was curated using an intelligent data annotation tool. This dataset was divided into three subsets: a training set with 280 HSIs, a validation set with 40 HSIs, and a test set with 80 HSIs. Expanding on this, a 7×7 pixel neighborhood was extracted as the spatial feature of the target pixel, incorporating both spatial and spectral features effectively. Leveraging the Bi-GRU model enabled simultaneous feature extraction at any point within the sequence data, eliminating the impact of the order of spatial-spectral data fusion on the model’s performance. The model comprises four key components: an input layer, hidden layers, fully connected layers, and an output layer. The Bi-GRU model in this study consisted of two hidden layers, each housing 512 GRU neurons. The forward hidden layer computed sequence information at the current time step, while the backward hidden layer retrieves the sequence in reverse, incorporating reversed-order information. These two hidden layers were linked to a fully connected layer, providing both forward and reversed-order information to all neurons during training. The Bi-GRU model included two fully connected layers, each with 1 000 neurons, and an output layer with two neurons representing the healthy and diseased classes, respectively. Results and Discussions To thoroughly validate the comprehensive performance of the proposed Bi-GRU model and assess the effectiveness of the spatial-spectral information fusion mechanism, relevant comparative analysis experiments were conducted. These experiments primarily focused on five key parameters—ClassAP(1), ClassAP(2), mean average precision (mAP), mean intersection over union (mIoU), and Kappa coefficient—to provide a comprehensive evaluation of the Bi-GRU model’s performance. The comprehensive performance analysis revealed that the Bi-GRU model, when compared to mainstream convolutional neural network (CNN) and long short-term memory (LSTM) models, demonstrated superior overall performance in detecting rapeseed sclerotinia disease. Notably, the proposed Bi-GRU model achieved an mAP of 93.7%, showcasing a 7.1% precision improvement over the CNN model. The bidirectional architecture, coupled with spatial-spectral fusion data, effectively enhanced detection accuracy. Furthermore, the study visually presented the segmentation results of sclerotinia disease-infected areas using CNN, Bi-LSTM, and Bi-GRU models. A comparison with the Ground-Truth data revealed that the Bi-GRU model outperformed the CNN and Bi-LSTM models in detecting sclerotinia disease at various infection stages. Additionally, the Dice coefficient was employed to comprehensively assess the actual detection performance of different models at early, middle, and late infection stages. The dice coefficients for the Bi-GRU model at these stages were 83.8%, 89.4% and 89.2%, respectively. While early infection detection accuracy was relatively lower, the spatial-spectral data fusion mechanism significantly enhanced the effectiveness of detecting early sclerotinia infections in oilseed rape. Conclusions This study introduces a Bi-GRU model that integrates spatial and spectral information to accurately and efficiently identify the infected areas of oilseed rape sclerotinia disease. This approach not only addresses the challenge of detecting early stages of sclerotinia infection but also establishes a basis for high-throughput non-destructive detection of the disease.
Subjects: Biology >> Zoology submitted time 2017-10-11 Cooperative journals: 《动物营养学报》
Abstract：本试验旨在探究不同生殖阶段、胎次繁殖母羊的氧化应激及氧化损伤状态。试验1选取体重、体况相近的2~3胎空怀期、妊娠期（30、60、120 d）、分娩及哺乳期（21 d）的崇明白山羊各5只；试验2选取后备、1胎、2~3胎、4~5胎、6胎及以上的崇明白山羊母羊各5只。分别采集血样，测定血清自由基代谢指标[皮质醇、过氧化氢(H2O2)含量]、抗氧化指标[总抗氧化能力（T-AOC）、谷胱甘肽过氧化物酶(GSH-Px)和超氧化物歧化酶(SOD)活性]、氧化损伤指标[丙二醛(MDA)、8-异前列腺素-F2α（8-ISO-PGF2α）、8-羟基脱氧鸟苷（8-OHDG）、蛋白质羰基化（PC）含量]。结果表明：试验1，从空怀期至哺乳期，血清皮质醇、H2O2含量呈先上升后降低的趋势，在分娩时达最高值，较空怀期显著提高（P0.05)，4~5胎、6胎及以上血清H2O2含量显著高于其他胎次(P0.05)，血清SOD及GSH-Px活力逐级递减，6胎及以上较后备母羊下降显著(P<0.05)；血清MDA、8-ISO-PGF2α、8-OHDG和PC含量逐渐增加，6胎及以上显著高于其他胎次(P<0.05)。综上所述，伴随着妊娠的进行，母羊体内的自由基代谢逐渐增强，与此同时，体内的抗氧化水平也相应提高以维持氧化-抗氧化体系平衡，但在妊娠后期至哺乳期激增的活性氧自由基破坏了自由基稳衡体系，导致氧化应激和氧化损伤；随着母羊胎次的增加，抗氧化能力逐渐减弱，高胎次母羊氧化损伤严重。
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