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81.
While dedicated spectrum occupancy monitoring provides vital information for frequency planning and management, it usually
cannot tell the common properties in spectrum occupancy. As a complement, the models approach can be used to describe and
compare the occupancy situations under similar conditions. Time series analysis has been applied to modeling the radio spectrum
occupancy. This paper categorizes different time series models to different occupancy patterns. Occupancy analysis of the
Global System for Mobile communications (GSM) band is given as an example. 相似文献
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Mohammad Asaduddin Laskar Syed Kashif Ali Sana Siddiqui 《The International journal of environmental studies》2017,74(1):105-118
Widespread pollution by heavy metals requires an efficient, cheap and eco-friendly removal technique. This paper reports the use of discarded leaves of Mangifera indica L. modified to enhance their adsorption efficiency in the removal of heavy metal pollutant. The adsorbent was then characterized through X-ray diffraction study, Fourier transform infrared spectroscopy and application to mathematical models. The adsorption process was found to fit the Langmuir’s isotherm model and pseudo-first-order kinetic model. The intra-particle diffusion model was found to be the rate limiting step for the adsorption process. Its rapid kinetics, high hydrophilicity, and easy regenerability with mild mineral acid (like 0.005 M HCl) make this adsorbent suitable for the fixed bed column technique. 相似文献
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E. Deniz Eren Wouter H. Nijhuis Freek van der Weel Aysegul Dede Eren Sana Ansari Paul H.H. Bomans Heiner Friedrich Ralph J. Sakkers Harrie Weinans Gijsbertus de With 《Microscopy research and technique》2022,85(2):469-486
Bone is a complex natural material with a complex hierarchical multiscale organization, crucial to perform its functions. Ultrastructural analysis of bone is crucial for our understanding of cell to cell communication, the healthy or pathological composition of bone tissue, and its three-dimensional (3D) organization. A variety of techniques has been used to analyze bone tissue. This article describes a combined approach of optical, scanning electron, and transmission electron microscopy for the ultrastructural analysis of bone from the nanoscale to the macroscale, as illustrated by two pathological bone tissues. By following a top-down approach to investigate the multiscale organization of pathological bones, quantitative estimates were made in terms of calcium content, nearest neighbor distances of osteocytes, canaliculi diameter, ordering, and D-spacing of the collagen fibrils, and the orientation of intrafibrillar minerals which enable us to observe the fine structural details. We identify and discuss a series of two-dimensional (2D) and 3D imaging techniques that can be used to characterize bone tissue. By doing so we demonstrate that, while 2D imaging techniques provide comparable information from pathological bone tissues, significantly different structural details are observed upon analyzing the pathological bone tissues in 3D. Finally, particular attention is paid to sample preparation for and quantitative processing of data from electron microscopic analysis. 相似文献
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Min Seong Kwon Seung Kyoon Woo David B. Kurland Sung Hwan Yoon Andre F. Palmer Uddyalok Banerjee Sana Iqbal Svetlana Ivanova Volodymyr Gerzanich J. Marc Simard 《International journal of molecular sciences》2015,16(3):5028-5046
Neuroinflammation is a well-recognized consequence of subarachnoid hemorrhage (SAH), and may be responsible for important complications of SAH. Signaling by Toll-like receptor 4 (TLR4)-mediated nuclear factor κB (NFκB) in microglia plays a critical role in neuronal damage after SAH. Three molecules derived from erythrocyte breakdown have been postulated to be endogenous TLR4 ligands: methemoglobin (metHgb), heme and hemin. However, poor water solubility of heme and hemin, and lipopolysaccharide (LPS) contamination have confounded our understanding of these molecules as endogenous TLR4 ligands. We used a 5-step process to obtain highly purified LPS-free metHgb, as confirmed by Fourier Transform Ion Cyclotron Resonance mass spectrometry and by the Limulus amebocyte lysate assay. Using this preparation, we show that metHgb is a TLR4 ligand at physiologically relevant concentrations. metHgb caused time- and dose-dependent secretion of the proinflammatory cytokine, tumor necrosis factor α (TNFα), from microglial and macrophage cell lines, with secretion inhibited by siRNA directed against TLR4, by the TLR4-specific inhibitors, Rs-LPS and TAK-242, and by anti-CD14 antibodies. Injection of purified LPS-free metHgb into the rat subarachnoid space induced microglial activation and TNFα upregulation. Together, our findings support the hypothesis that, following SAH, metHgb in the subarachnoid space can promote widespread TLR4-mediated neuroinflammation. 相似文献
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It is shown that sequential plasma-enhanced chemical vapor deposition (PECVD) of SiN and SiO2 can produce a very effective double-layer antireflection (AR) coating. This AR coating is compared with the frequently used and highly efficient MgF2/ZnS double layer coating. The SiO2/SiN coating improves the short-circuit current (J SC) by 47%, open-circuit voltage (V OC) by 3.7%, and efficiency (Eff) by 55% for silicon cells with oxide surface passivation. The counterpart MgF2/ZnS coating gives similar but slightly smaller improvement in V OC and Eff. However, if silicon cells do not have the oxide passivation, the PECVD SiO2/SiN gives much greater improvement in the cell parameters, 57% in J SC, 8% in V OC, and 66% in efficiency, compared to the MgF2/ZnS coating which improves J SC by 50%, V OC by 2%, and cell efficiency by 54%. This significant additional improvement results from the PECVD deposition-induced surface/defect passivation. The internal quantum efficiency (IQE) measurements showed that the PECVD SiO2/SiN coating a absorbs fair amount of photons in the short-wavelength range (<500 nm); however, the improved surface/defect passivation more than compensates for the loss in J SC and gives higher improvement in the cell efficiency compared to the MgF2/ZnS coating 相似文献
90.
Changle Li Beibei Zhang Xiaoming Yuan Sana Ullah Athanasios V. Vasilakos 《Wireless Networks》2018,24(3):719-733
Wireless body area networks (WBANs) support the inter-operability of biomedical sensors and medical institutions with convenience and high-efficiency, which makes it an appropriate solution for the pervasive healthcare. Typically, WBANs comprise in-body or around-body sensor nodes for collecting data of physiological feature. Therefore, the efficient medium access control (MAC) protocol is a crucial paramount to coordinate these devices and forward data to the medical center in an efficient and reliable way. However, the extensive use of wireless channel and coexistence of WBANs may result in inevitable interference which will cause performance degradation. Besides, contention-based access in single channel in WBANs is less efficient for dense medical traffic on account of large packet delay, energy consumption and low priority starvation. To address these issues above, we propose a multi-channel MAC (MC-MAC) scheme to obtain better network performance. Considering the characteristic and emergency degree of medical traffic, we introduce a novel channel mapping and selection mechanism, cooperating with conflict avoidance strategy, to organize nodes to access available channels without collisions. In addition, we have evaluated the performance of MC-MAC and the standard IEEE 802.15.6 via simulation and hardware test. The test is conducted by hardware platform based on prototype system of WBANs. Both of the analysis and simulation results show that MC-MAC outperforms the IEEE 802.15.6 in terms of packet delay, throughput, packet error rate and frame error rate. 相似文献