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201.
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研究了一类具有周期性潜伏期的常微分SEIR传染病模型.首先借助于染病年龄分布函数导出了模型.紧接着定义了模型的基本再生数R_0并利用耗散动力系统的相关理论证明R_0是决定疾病是否继续流行的阈值.最后,利用数值方法进一步验证了结论,并分析了忽略潜伏期的周期性对估计疾病传播能力的影响. 相似文献
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可变荧光量与藻类活体细胞数有良好的相关性,然而在浮游藻类种类、尺寸及生长周期等条件不同的情况下,藻类单细胞的可变荧光量存在明显差异,直接利用可变荧光强度计算藻类活体细胞数将存在很大误差。因此,提出了一种基于可变荧光统计学分布的水体藻类活体细胞数分析方法。根据子样本细胞数的分布形状与可变荧光量一致的特点,利用可变荧光量的分布形状直接计算样品中藻类活体细胞数。研究结果表明,在浮游藻类单细胞的可变荧光量变化44倍的条件下,基于可变荧光统计学分析方法计算的活体藻细胞密度与显微镜的镜检结果基本一致,两者线性拟合的相关系数在0.93以上,相对误差绝对值的平均值在5.98%~16.94%之间,说明所提方法基本解决了藻类单细胞的可变荧光量对活体藻细胞计数结果的影响。 相似文献
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James M. Ludlow III Mary Jane Saunders Mingjun Huang Zaihong Guo Charles N. Moorefield Stephen Z. D. Cheng 《Supramolecular chemistry》2017,29(1):69-79
Long chain (C16) alkylated metallocycles are synthesised and characterised. Their ordered aggregation was studied via TEM to gauge to the effects of molecular topology, solvent, counterion and metal centre(s) on morphology and nanoscale structure. The results indicate that their amphiphilicity significantly enhanced their self-ordering characteristics relative to controls and enabled the formation of nanoscale structures. Similar ordering was observed for both labile and non-labile analogues with SAXD showing comparable d-spacing values, suggesting the presence of intramolecular π–π stacking. Effect of counterion and solvent was studied with the non-labile system. Nanotubular, ribbon, or sheet-like structures were afforded depending upon conditions. 相似文献
207.
Xue‐Hui Dong Kan Yue Zhiwei Lin Xueyan Feng Mingjun Huang Wen‐Bin Zhang Stephen Z. D. Cheng 《Journal of Polymer Science.Polymer Physics》2014,52(20):1309-1325
Giant surfactants are polymer‐tethered molecular nanoparticles (MNPs) and can be considered as a subclass of giant molecules. The MNPs serve as functionalized heads with persistent shape and volume, which may vary in size, symmetry, and surface chemistry. The covalent conjugation of MNPs and polymer tails affords giant surfactants with diverse composition and architecture. Synthetic strategies such as “grafting‐from” and “grafting‐onto” have been successfully applied to the precise synthesis of giant surfactants, which is further facilitated by the emergence of “click” chemistry reactions. In many aspects, giant surfactants capture the essential features of small‐molecule surfactants, yet they have much larger sizes. They bridge the gap between small‐molecule surfactants and traditional amphiphilic macromolecules. Their self‐assembly behaviors in solution are summarized in this Review. Micelle formation is affected not only by their primary chemical structures, but also by the experimental conditions. This new class of materials is expected to deliver general implications on the design of novel functional materials based on MNP building blocks in the bottom‐up fabrication of well‐defined nanostructures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1309–1325 相似文献
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Asymptotic Behavior of Solutions to a Class of Semilinear Parabolic Equations with Boundary Degeneracy 下载免费PDF全文
This paper concerns the asymptotic behavior of solutions to one-dimensional semilinear parabolic equations with boundary degeneracy both
in bounded and unbounded intervals. For the problem in a bounded interval, it is shown that there exist both nontrivial global solutions for small initial
data and blowing-up solutions for large one if the degeneracy is not strong.
Whereas in the case that the degeneracy is strong enough, the nontrivial solution must blow up in a finite time. For the problem in an unbounded interval,
blowing-up theorems of Fujita type are established. It is shown that the critical
Fujita exponent depends on the degeneracy of the equation and the asymptotic
behavior of the diffusion coefficient at infinity, and it may be equal to one or
infinity. Furthermore, the critical case is proved to belong to the blowing-up
case. 相似文献
210.
Towards Molecular Construction Platforms: Synthesis of a Metallotricyclic Spirane Based on Bis(2,2′:6′,2“‐Terpyridine)RuII Connectivity 下载免费PDF全文
Dr. Ting‐Zheng Xie Kai Guo Mingjun Huang Dr. Xiaocun Lu Sheng‐Yun Liao Rajarshi Sarkar Dr. Charles N. Moorefield Prof. Stephen Z. D. Cheng Prof. Chrys Wesdemiotis Prof. George R. Newkome 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11291-11294
The design and construction of the first multicomponent stepwise assembly of a <tpy‐RuII‐tpy>‐based (tpy=terpyridine), three‐dimensional, propeller‐shaped trismacrocycle, 8 , are reported. Key steps in the synthesis involve the preparation of a hexaterpyridinyl triptycene and its reaction with dimeric, 60°‐directional, bisterpyridine‐RuII building blocks. Characterization includes ESI‐ and ESI‐TWIM‐MS and TEM, along with 1D and 2D 1H NMR spectroscopy. 相似文献