分类: 心理学 >> 发展心理学 提交时间: 2023-03-28 合作期刊: 《心理科学进展》
摘要: 人类对感觉阈限附近的视觉刺激的知觉不总是一致的。为探究这种视知觉不一致的现象及其神经机制, 一些研究者关注刺激前脑内自发alpha神经振荡(8~13 Hz)对视知觉的影响。近年来的研究发现, 刺激前alpha振荡能量的降低能提高被试的探测击中率, 但不能提高知觉精确度; 而刺激前alpha振荡的相位能预测被试能否成功探测刺激。刺激前alpha能量被认为调控了视皮层的基础活动强度; alpha能量的降低反映了皮层基础活动的增强, 进而提高了对较弱刺激的探测率。刺激前alpha相位则被认为调控了皮层兴奋和抑制的时间; 大脑在刺激呈现时的不同状态(兴奋/抑制)决定了最终的知觉结果。
分类: 心理学 >> 认知心理学 提交时间: 2020-01-14
摘要: 人类对感觉阈限附近的视觉刺激的知觉不总是一致的。为探究这种视知觉不一致的现象及其神经机制,一些研究者关注刺激前脑内自发alpha神经振荡(8~13 Hz)对视知觉的影响。近年来的研究发现,刺激前alpha振荡能量的降低能提高被试的探测击中率,但不能提高知觉精确度;而刺激前alpha振荡的相位能预测被试能否成功探测刺激。刺激前alpha能量被认为调控了视皮层的基础活动强度;alpha能量的降低反映了皮层基础活动的增强,进而提高了对较弱刺激的探测率。刺激前alpha相位则被认为调控了皮层兴奋和抑制的时间;大脑在刺激呈现时的不同状态(兴奋/抑制)决定了最终的知觉结果。
分类: 生物学 >> 生物物理学 提交时间: 2016-05-15
摘要: Background Cilostazol, an anti-platelet drug for treating coronary heart disease, has been reported to modulate immune cell functions. Plasmacytoid dendritic cells (pDCs) have been found to participate in the progression of atherosclerosis mainly through interferon a (IFN-alpha) production. Whether cilostazol influences pDCs activation is still not clear. In this study, we aimed to investigate the effects of cilostazol on cell activation and antigen presentation of pDCs in vitro in this study. Methods Peripheral blood mononuclear cells isolated by Ficoll centrifugation and pDCs sorted by flow cytometry were used in this study. After pretreated with cilostazol for 2 h, cells were stimulated with CpG-A, R848 or virus for 6 h or 20 h, or stimulated with CpG-B for 48 h and then co-cultured with naive T cell for five days. Cytokines in supernatant and intracellular cytokines were analyzed by ELISA or flow cytometry respectively. Results Our data indicated that cilostazol could inhibit IFN-alpha and tumor necrosis factor a (TNF-alpha) production from pDCs in a dose-dependent manner. In addition, the ability of priming naive T cells of pDCs was also impaired by cilostazol. The inhibitory effect was not due to cell killing since the viability of pDCs did not change upon cilostazol treatment. Conclusion Cilostazol inhibits pDCs cell activation and antigen presentation in vitro, which may explain how cilostazol protects against atherosclerosis.
分类: 物理学 >> 核物理学 提交时间: 2017-08-22
摘要: Starting from the WKB approximation, a new barrier penetration formula is proposed for poten- tial barriers containing a long-range Coulomb interaction. This formula is especially proper for the barrier penetration with penetration energy much lower than the Coulomb barrier. The penetra- bilities calculated from the new formula agree well with the results from the WKB method. As a first attempt, this new formula is used to evaluate α decay half-lives of atomic nuclei and a good agreement with the experiment is obtained.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: In this paper, a genetic-algorithm-based artificial neural network (GAANN) model radioactivity prediction is proposed, which is verified by measuring results from Long Range Alpha Detector (LRAD). GAANN can integrate capabilities of approximation of Artificial Neural Networks (ANN) and of global optimization of Genetic Algorithms (GA) so that the hybrid model can enhance capability of generalization and prediction accuracy, theoretically. With this model, both the number of hidden nodes and connection weights matrix in ANN are optimized using genetic operation. The real data sets are applied to the introduced method and the results are discussed and compared with the traditional Back Propagation (BP) neural network, showing the feasibility and validity of the proposed approach.
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: Macrophage phagocytosis of tumor cells mediated by CD47-specific blocking antibodies has been proposed to be the major effector mechanism in xenograft models. Here, using syngeneic immunocompetent mouse tumor models, we reveal that the therapeutic effects of CD47 blockade depend on dendritic cell but not macrophage cross-priming of T cell responses. The therapeutic effects of anti-CD47 antibody therapy were abrogated in T cell-deficient mice. In addition, the antitumor effects of CD47 blockade required expression of the cytosolic DNA sensor STING, but neither MyD88 nor TRIF, in CD11c(+) cells, suggesting that cytosolic sensing of DNA from tumor cells is enhanced by anti-CD47 treatment, further bridging the innate and adaptive responses. Notably, the timing of administration of standard chemotherapy markedly impacted the induction of antitumor T cell responses by CD47 blockade. Together, our findings indicate that CD47 blockade drives T cell-mediated elimination of immunogenic tumors.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-09-02
摘要: The accumulation of 222Rn and 220Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public. A previous study indicated that satisfactory results in determining the 222Rn and 220Rn progeny concentrations by measuring the total alpha counts at five time intervals within 560 min should be expected only in the case of high progeny concentrations in air. To complete the measurement within a relatively short period and adapt it for simultaneous measurements at comparatively lower 222Rn and 220Rn progeny concentrations, a novel mathematical model was proposed based on the radioactive decay law. This model employs a nonlinear fitting method to distinguish nuclides with overlapping spectra by utilizing the alpha particle counts of nonoverlapping spectra within consecutive measurement cycles to obtain the concentrations of 222Rn and 220Rn progeny in air. Several verification experiments were conducted using an alpha spectrometer. The experimental results demonstrate that the concentrations of 222Rn and 220Rn progeny calculated by the new method align more closely with the actual circumstances than those calculated by the total count method, and their relative uncertainties are all within ± 16%. Furthermore, the measurement time was reduced to 90 min, representing an acceleration of 84%. The improved capability of the new method in distinguishing alpha particles with similar energies emitted from 218Po and 212Bi, both approximately 6 MeV, contributed to realizing more accurate results. The proposed method has the potential advantage of measuring relatively low concentrations of 222Rn and 220Rn progeny in air more quickly via air filtration.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-09-01
摘要: Active Target Time Projection Chambers (AT-TPCs) are state-of-the-art tools in the field of low-energy nuclear physics, particularly suitable for experiments using low-intensity radioactive ion beams or gamma rays. The Fudan Multi-purpose Active Target Time Projection Chamber (fMeta-TPC) with 2048 channels has been developed to study \alpha-clustering nuclei. In this work, the focus is on the study of the photonuclear reaction with the Laser Compton Scattering (LCS) gamma source, especially for the decay of the highly excited \alpha-cluster state. The design of fMeta-TPC is described and a comprehensive evaluation of its offline performance is performed by ultraviolet (UV) laser and ^{241}Am \alpha source. The result shows that the intrinsic angular resolution of the detector is within \ang{0.30} and has an energy resolution of 6.85\% for \SI{3.0}{MeV} \alpha particles. The gain uniformity of the detector is about 10\% (RMS/Mean), tested by the ^{55}Fe X-ray source.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2025-02-25
摘要: Cadmium telluride (CdTe), which has a high average atomic number and a unique band structure, is a leadingmaterial for room-temperature X/γ-ray detectors. Resistivity and mobility are the two most importantproperties of detector-grade CdTe single crystals. However, despite decades of research, the fabrication ofhigh-resistivity and high-mobility CdTe single crystals faces persistent challenges, primarily because the stoichiometriccomposition cannot be well controlled owing to the high volatility of Cd under high-temperatureconditions. This volatility introduces Te inclusions and cadmium vacancies (VCd) into the as-grown CdTe ingot,which significantly degrades the device performance. In this study, we successfully obtained detector-gradeCdTe single crystals by simultaneously employing a Cd reservoir and chlorine (Cl) dopants via a vertical gradientfreeze (VGF) method. By installing a Cd reservoir, we can maintain the Cd pressure under the crystalgrowth conditions, thereby preventing the accumulation of Te in the CdTe ingot. Additionally, the existenceof the Cl dopant helps improve the CdTe resistivity by minimizing VCd density through the formation of anacceptor complex (ClTe-VCd)−1. The crystalline quality of the obtained CdTe(Cl) was evidenced by a reductionin large Te inclusions, high optical transmission (60%), and a sharp absorption edge (1.456 eV). Thepresence of substitutional Cl dopants, known as Cl+ Te, simultaneously supports the record high resistivity of1.5 × 1010 Ω · c meter and remarkable electron mobility of 1075±88 cm2 V−1 s−1 simultaneously, has beenconfirmed by photoluminescence spectroscopy. Moreover, using our crystals, we fabricated a planar detectorwith μτe of (1.11 ± 0.04) × 10−4 cm2/V, which performed with a decent radiation-detection feature. Thisstudy demonstrates that the vapor-pressure-controlled VGF method is a viable technical route for fabricatingdetector-grade CdTe crystals.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Shanghai Synchrotron Radiation Facility (SSRF) will implement its Phase II beamline project in the near future. Two long straight sections of the SSRF storage ring will be installed with dual-canted insertion devices in this project. Double-mini-y optics in the long straight sections is designed and optimized in order to obtain high brightness and good machine performance. In this paper, the results are summarized. The Phase II project proposes a lattice upgrade of super-bend, and the double-mini-y optics with this upgraded lattice is presented, too.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Considering the mixture after muon-catalyzed fusion (CF) reaction as overdense plasma, we analyze muon motion in the plasma induced by a linearly polarized two-colour laser, particularly, the effect of laser parameters on the muon momentum and trajectory. The results show that muon drift along the propagation of laser and oscillation perpendicular to the propagation remain after the end of the laser pulse. Under appropriate parameters, muon can go from the skin layer into field-free matter in a time period of much less than the pulse duration. The electric-field strength ratio or frequency ratio of the fundamental to the harmonic has more influence on muon oscillation. The laser affects little on other particles in the plasma. Hence, in theory, this work can avoid muon sticking to effectively and reduce muon-loss probability in CF.
分类: 数学 >> 数学(综合) 提交时间: 2016-07-05
摘要: In this paper, the Pazy's Fixed Point Theorems of monotone \alpha-nonexpansive mapping T are proved in a uniformly convex Banach space E with the partial order ``\leq". That is, we obtain that the fixed point set of T with respect to the partial order ``\leq" is nonempty whenever the Picard iteration \{T^nx_0\} is bounded for some comparable initial point x_0 and its image Tx_0. When restricting the demain of T to the cone P, a monotone \alpha-nonexpansive mapping T has at least a fixed point if and only if the Picard iteration \{T^n0\} is bounbed. Furthermore, with the help of the properties of the normal cone P, the weakly and strongly convergent theorems of the Picard iteration \{T^nx_0\} are showed for finding a fixed point of T with respect to the partial order ``\leq" in uniformly convex ordered Banach space.
分类: 物理学 >> 核物理学 提交时间: 2024-12-27
摘要: Targeted alpha therapy, as a shining new star in the field of nuclear medicine, is showing great potential in the treatment of metastatic diseases with its unique advantages. 225Ac, as an important α-emitting medical radionuclide, its current production of less than 1.7 Ci/year restricts its development and widespread application. Therefore, exploring and optimizing the production method of 225Ac to increase its yield is crucial. Using a 35 MeV @ 2 mA electron accelerator to bombard a converter target produces a large number of photons. Through the photonuclear reaction 226Ra(γ, n)225Ra, 225Ra is generated, which can then undergo beta decay to produce 225Ac. Two kinds of isotope target, namely the solid plate radium target (“solid target” for short) and the solution radium target (“solution target” for short), were designed according to the special structure of the neutron source target station in this study. Under each kind of target, three target schemes, namely the internal target, the backend target and the U-shaped target were proposed. The FLUKA program was used to investigate the influence of both geometric and irradiation parameters of isotope and converter targets on the yield of 225Ac. The study shows that, the production capability of 225Ac is stronger with a solid target than with a solution target, and the 225Ac production capability of both solid and liquid targets is directly proportional to the irradiation time. In the internal target scheme, with a radium target containing 1.0 g of 226Ra and an irradiation time of 10 days, it is estimated that a 35 MeV @ 2 mA electron accelerator has an annual production capacity of 117.3 Ci of 225Ac when using a solid target and 12.32Ci when using a solution target. The results indicate that bombarding radium targets with an electron accelerator enables large-scale production of 225Ac, ensuring a stable isotope supply for medical, research, and other applications.
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: 2016-05-12
摘要: Tristetraprolin (TTP) regulates the expression of AU-rich element-containing mRNAs through promoting the degradation and repressing the translation of target mRNA. While the mechanism for promoting target mRNA degradation has been extensively studied, the mechanism underlying translational repression is not well established. Here, we show that TTP recruits eukaryotic initiation factor 4E2 (eIF4E2) to repress target mRNA translation. TTP interacted with eIF4E2 but not with eIF4E. Overexpression of eIF4E2 enhanced TTP-mediated translational repression, and downregulation of endogenous eIF4E2 or overexpression of a truncation mutant of eIF4E2 impaired TTP-mediated translational repression. Overexpression of an eIF4E2 mutant that lost the cap-binding activity also impaired TTP's activity, suggesting that the cap-binding activity of eIF4E2 is important in TTP-mediated translational repression. We further show that TTP promoted eIF4E2 binding to target mRNA. These results imply that TTP recruits eIF4E2 to compete with eIF4E to repress the translation of target mRNA. This notion is supported by the finding that downregulation of endogenous eIF4E2 increased the production of tumor necrosis factor alpha (TNF-alpha) protein without affecting the mRNA levels in THP-1 cells. Collectively, these results uncover a novel mechanism by which TTP represses target mRNA translation.
分类: 物理学 >> 核物理学 提交时间: 2025-06-09
摘要: To mitigate the dark pulse and attain low background level measurements, the liquid scintillation counter (LSC) is generally equipped with two or three photomultiplier tubes (PMT) for coincidence measurements. However, traditional identification method in the LSC only utilize the anode pulse from a single PMT to identify alpha/beta particles, which limits their ability to identify particles. We developed a three-channel Convolutional Neural Network (TCNN) model, which integrates pulses from three PMT anodes to identify particle categories. Anode pulses are organized into a shape (3,512) and subsequently fed into the TCNN for alpha/beta pulse discrimination. To train and validate TCNN, we prepared two samples: 241Am sample as alpha emitter and 90Sr/90Y sample as beta emitter. In the validation set, TCNN performed significantly better than traditional convolutional neural networks (CNN) in identifying alpha/beta pulses, achieving accuracy, recall, and F1 score of 99.44%, 99.23%, and 99.34%, respectively. We also prepared a mixed-emitter sample exhibiting a β activity of approximately 172Bq and an α activity of 98Bq to evaluate the impact of the TCNN on the spectral performance in practical applications. Firstly, the category of the pulse from the sample is identified by the TCNN, and then it’s height is recorded in an α-MCA spectrum or β-MCA spectrum according to the identified category. The alpha particle peak in the α-MCA spectrum is used to evaluate spectral performance. The optimal detection limit for the alpha particle peak is 0.3337 cps, which shows a sensitivity increase of 31.16% compared to the CNN method. This indicates that the TCNN can effectively utilize the three-channel pulses to enhance the ability to distinguish between alpha and beta particles when analyzing both simultaneously, thereby significantly improving the sensitivity of the detector.
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-09-09
摘要: By combining experimental \alpha-decay energies and half-lives, the \alpha-particle preformation factor for nuclei around neutron magic numbers N of 126,152 , and 162 were extracted using the two-potential approach. The nuclei around the shell closure were more tightly bound than adjacent nuclei. Additionally, based on the WS4 mass model [Phys. Lett. B 734, 215 (2014)], we extended the two-potential approach to predict the \alpha-decay half-lives of nuclei around N values of 178 and 184 with Z of 119 and 120 . We believe that our findings will serve as guidelines for future experimental studies.
分类: 物理学 >> 核物理学 提交时间: 2024-12-27
摘要: In recent years, terbium radioisotopes have been investigated for their potential therapeutic and diagnostic applications in nuclear medicine. This study aimed to investigate the production of 152Tb and 155Tb by alpha induced reaction in detail, with a specific focus on determining the optimum production parameters and testing existing nuclear models. Given the limited number of experiments conducted on reactions related to terbium isotope production, it is necessary to perform theoretical calculations of cross sections over a wide energy range in order to gain a detailed understanding of terbium isotope production. In order to achieve this objective, the cross sections of the 151Eu(α,n)154Tb reactions were calculated up to 60 MeV using the TALYS computer code with 432 different combinations of optical model parameters, level density, and strength function models. The theoretical reaction cross section results were compared with the experimental results in the literature. The best input parameters were determined using the Threshold Logic Unit method and these parameters were used in all isotope production calculations. Once the optimal model combination had been determined, the total activity production and isotopic fraction of 152Tb and 155Tb isotopes were calculated in detail for beam energies of 17-50 MeV, different irradiation times, and varying 151Eu and 153Eu target thicknesses.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway has been identified as an important pathway in renal cell carcinoma (RCC). We have reported a nonsense mutation in PIK3R1, which encodes the regulatory subunit of PI3K, in a metastatic RCC (mRCC), while the mutation was absent in the corresponding primary RCC (pRCC). To identify the function of PIK3R1 in RCC, we examined its expression in normal kidney, pRCC and mRCC by immunohistochemistry and real-time polymerase chain reaction. The expression of PIK3R1 significantly decreased in pRCC and was further reduced in mRCC compared with normal tissue. Besides, its expression levels were negatively correlated with T-category of tumor stage. Additionally, 786-O and A-704 cells with PIK3R1 depletion introduced by CRISPR/Cas9 system displayed enhanced proliferation, migration and epithelial-mesenchymal transition (EMT), and acquired a stem-like phenotype. Moreover, the PIK3R1 depletion promoted the phosphorylation of AKT in the cells. The knockdown of AKT by shRNA reduced p-GSK3 beta and CTNNB1 expression in the cells, while the depletion of CTNNB1 impaired stem-like phenotype of the cells. Overall, PIK3R1 down-regulation in RCC promotes propagation, migration, EMT and stem-like phenotype in renal cancer cells through the AKT/GSK3 beta/CTNNB1 pathway, and may contribute to progression and metastasis of RCC.
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: 2016-05-05
摘要: Oxidative stress is a major cause of sporadic Parkinson's disease (PD). Here, we demonstrated that c-Abl plays an important role in oxidative stress-induced neuronal cell death. C-Abl, a nonreceptor tyrosine kinase, was activated in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP)-induced acute PD model. Conditional knockout of c-Abl in neurons or treatment of mice with STI571, a c-Abl family kinase inhibitor, reduced the loss of dopaminergic neurons and ameliorated the locomotive defects induced by short-term MPTP treatment. By combining the SILAC (stable isotope labeling with amino acids in cell culture) technique with other biochemical methods, we identified p38 alpha as a major substrate of c-Abl both in vitro and in vivo and c-Abl-mediated phosphorylation is critical for the dimerization of p38 alpha. Furthermore, p38 alpha inhibition mitigated the MPTP-induced loss of dopaminergic neurons. Taken together, these data suggested that c-Abl-p38 alpha signaling may represent a therapeutic target for PD.
分类: 心理学 >> 社会心理学 提交时间: 2023-03-27 合作期刊: 《心理学报》
摘要: 本研究通过两个实验探讨了长时记忆联结表征如何影响当下工作记忆任务的加工。长时记忆联结表征采用无语义联系、无视觉相似性的Emoji图片对, 提前一天让被试完成联结表征的建立, 正式工作记忆任务采用独立探测的变化觉察范式。实验1控制呈现时间(500 ms / 1000 ms)与呈现方式(联结/独立), 发现两种呈现时间均显示出联结条件的正确率与记忆容量显著低于独立条件, 说明长时记忆联结表征抑制了当前工作记忆的加工。实验2设置了记忆项目数(2/4/6项)与呈现方式(联结/独立), 采用alpha震荡作为脑电指标, 考察长时联结表征在工作记忆维持阶段的作用。结果发现在维持阶段, 独立条件的alpha震荡随着记忆项目数量的增加而增大(2项 < 4项 < 6项), 而联结条件在4项已经到达顶点(2项 < 4项 = 6项)。实验2进一步说明长时联结表征在维持阶段降低了当前工作记忆容量。本研究的两个实验结果表明, 长时记忆联结表征对当前的工作记忆任务有一定的抑制作用, 这种抑制作用产生的机制可能来自于联结表征干扰了维持阶段的注意分配。