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排序方式: 共有3649条查询结果,搜索用时 46 毫秒
991.
赵玉兰 《常州信息职业技术学院学报》2014,13(4):60-62
"中国梦"就是要实现国家富强、民族振兴、人民幸福,"中国梦"就是人民的梦。"中国梦"内涵丰富,对高职学生进行"中国梦"宣传教育意义重大。应以"中国梦"为引领,通过思想政治理论课、校园文化建设、加强自我教育、发挥党员学生先锋作用等途径,探索建立一套长效的教育、学习机制,为实现"中国梦"而努力。 相似文献
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995.
Joana Poejo Jairo Salazar Ana M. Mata Carlos Gutierrez-Merino 《International journal of molecular sciences》2021,22(4)
Lipid rafts are a primary target in studies of amyloid β (Aβ) cytotoxicity in neurons. Exogenous Aβ peptides bind to lipid rafts, which in turn play a key role in Aβ uptake, leading to the formation of neurotoxic intracellular Aβ aggregates. On the other hand, dysregulation of intracellular calcium homeostasis in neurons has been observed in Alzheimer’s disease (AD). In a previous work, we showed that Aβ(1–42), the prevalent Aβ peptide found in the amyloid plaques of AD patients, binds with high affinity to purified calmodulin (CaM), with a dissociation constant ≈1 nM. In this work, to experimentally assess the Aβ(1–42) binding capacity to intracellular CaM, we used primary cultures of mature cerebellar granule neurons (CGN) as a neuronal model. Our results showed a large complexation of submicromolar concentrations of Aβ(1–42) dimers by CaM in CGN, up to 120 ± 13 picomoles of Aβ(1–42) /2.5 × 106 cells. Using fluorescence microscopy imaging, we showed an extensive co-localization of CaM and Aβ(1–42) in lipid rafts in CGN stained with up to 100 picomoles of Aβ(1–42)-HiLyteTM-Fluor555 monomers. Intracellular Aβ(1–42) concentration in this range was achieved by 2 h incubation of CGN with 2 μM Aβ(1–42), and this treatment lowered the resting cytosolic calcium of mature CGN in partially depolarizing 25 mM potassium medium. We conclude that the primary cause of the resting cytosolic calcium decrease is the inhibition of L-type calcium channels of CGN by Aβ(1–42) dimers, whose activity is inhibited by CaM:Aβ(1–42) complexes bound to lipid rafts. 相似文献
996.
This paper investigates the fundamental behavior of long water waves propagating through branching channels of uniform depth and width. Numerical simulations based on the Boussinesq long wave model were carried out to investigate the effects of channel width b, effective wavelength λe, wave amplitude α, and angle θ between channel branches on wave transmission and reflection. Our results showed that the transmission and reflection of long waves through branching channels are dominantly governed by a single dimensionless parameter b/λe, whereas other parameters such as the angle between channel branches are less important. Detailed quantitative results for predicting long wave transmission and reflection in different branching channels based on the similarity parameter b/λe were determined. From these results, we have discovered some very interesting and distinct long wave behaviors in narrow and wide branching channels. To verify the numerical results, experiments were conducted in a right-angled branching channel, and the experimental results showed good agreement with the numerical predictions. 相似文献
997.
A simplified model for the computation of boundary shear stress distributions acting on the flow perimeter of closed ducts is presented. The model assumes that the surplus energy within any control volume in a three-dimensional flow will be transferred towards the nearest boundary to be dissipated. Based on this model, the flow cross sectional area in the closed duct is divided into subflow regions corresponding to the side walls and bed, and the shear distributions over the wetted perimeter within each subflow area are assessed. Analytical equations, valid for all channel aspect ratios, for the prediction of local and mean shear stresses along the bed and side walls in smooth rectangular duct flow are derived. The formulae give good predictions of the shear stress distributions when compared with existing experimental data in the literature. The possible applications of the model to nonrectangular duct flows are also discussed. 相似文献
998.
Vidhyacharan Bhaskar Author Vitae Laurie L. Joiner Author Vitae 《Computers & Electrical Engineering》2005,31(3):217-240
This paper presents a method of code rate adaptation using punctured convolutional codes for direct sequence spread spectrum communication systems over slowly fading channels. A blind channel estimation technique is used to estimate the nature of the multi-user channel at the detector (before the decoder). The path gains obtained from the channel estimation technique are used to adapt the code rates. Punctured codes derived from a specific rate 1/2 (M = 4) mother code are used to provide error protection corresponding to the actual channel state. The upper and lower bounds on the bit error probability and the upper bound on the error event probability are derived for hard-decision and soft-decision decoding over Rayleigh and Rician fading channels. The throughput gains obtained using the adaptive scheme and the performances of the punctured codes are studied. 相似文献
999.
Ruhallah AliHemmati Author Vitae Author Vitae 《Computers & Electrical Engineering》2005,31(7):431-443
Saeedi et al. have recently proposed a DFT-based method (DBM) for Orthogonal Frequency Division Multiplexing (OFDM) systems to compensate for the performance degradation caused by clipping distortion. They have analyzed the performance of the DBM only in an additive white Gaussian noise channel. But, it is known that the main advantage of an OFDM system is its robustness in fading channels where this system turns a frequency selective channel into a set of parallel flat non-selective fading sub-channels. In this paper, we analyze the performance of the DBM over a frequency selective fading channel with flat fading Rician sub-channels. Our results show that similar to additive white Gaussian noise channel case, the DBM can properly mitigate the clipping distortion in OFDM signals over fading channels. Furthermore, the performance of a Hybrid method that consists of a channel coding method and the DBM is also examined over fading channels. 相似文献
1000.
Since wireless networks which can carry high bit rates have become ubiquitous, mobile computing is no longer just spoken about. Mobile computing always implies access through a wireless network to an IP network such as the Internet. In order to understand the performance of such links, we propose an analytic model for the down link delay of IP traffic between the Mobile Gateway Server and the End User in a UMTS mobile network. Traffic arriving at the Gateway Server is considered to be bursty in nature and we use a Batch Markovian Arrival Process (BMAP) to model this arrival process. We model the wireless link itself as a modified multi-state Gilbert–Elliot Markov model which takes into account the number of interfering users and whether the channel experiences Ricean fading or not for what we consider a typical indoor, IP-centric environment. We also account in both the analytical model and the simulation for the Forward Error Correction provided by Turbo coding in UMTS to establish realistic packet retransmission rates. Finally we calibrate and verify the correctness of the model with a discrete event simulator. 相似文献