摘要：
In this paper, we consider a mathematical model for HIV-1 infection with intracellular delay and cell-mediated immune response. A novel feature is that both cytotoxic T lymphocytes (CTLs) and the intracellular delay are incorporated into the model. We obtain a necessary and sufficient condition for the global stability of the infection-free equilibrium and give sufficient conditions for the local stability of the two infection equilibria: one without CTLs being activated and the other with. We also perform some numerical simulations which support the obtained theoretical results. These results show that larger intracellular delay may help eradicate the virus, while the activation of CTLs can only help reduce the virus load and increase the healthy CD(4)(+) cells population in the long term sense.
期刊：
Journal of Fluids and Structures,2010年26(5):793-803 ISSN：0889-9746
通讯作者：
Guo, C. Q.
作者机构：
[Guo, C. Q.; Zhang, C. H.] Tsinghua Univ, Dept Hydraul Engn, Beijing 100084, Peoples R China.;[Guo, C. Q.] Univ S China, Sch Math & Phys, Hengyang 421001, Hunan, Peoples R China.;[Paidoussis, M. P.] McGill Univ, Dept Mech Engn, Montreal, PQ H3A 2K6, Canada.
通讯机构：
[Guo, C. Q.] Tsinghua Univ, Dept Hydraul Engn, Beijing 100084, Peoples R China.
关键词：
Fluid-conveying pipe;Equation of motion;Critical flow velocity;Laminar flow;Turbulent flow
摘要：
Considering the non-uniformity of the flow velocity distribution in fluid-conveying pipes caused by the viscosity of real fluids, the centrifugal force term in the equation of motion of the pipe is modified for laminar and turbulent flow profiles. The flow-profile-modification factors are found to be 1.333, 1.015-1.040 and 1.035-1.055 for laminar flow in circular pipes, turbulent flow in smooth-wall circular pipes and turbulent flow in rough-wall circular pipes, respectively. The critical flow velocities for divergence in the above-mentioned three cases are found to be 13.4%, 0.74-1.9% and 1.7-2.6%, respectively, lower than that with plug flow, while those for flutter are even lower, which could reach 36% for the laminar flow profile. By introducing two new concepts of equivalent flow velocity and equivalent mass, fluid-conveying pipe problems with different flow profiles can be solved with the equation of motion for plug flow. (C) 2010 Elsevier Ltd. All rights reserved.
关键词：
Fractional differential equation;Optimal control;Relaxation property;Nonconvex constraint;Feedback control
摘要：
We consider the minimization problem of an integral functional with integrand that is not convex in the control on solutions of a control system described by fractional differential equation with mixed nonconvex constraints on the control. A relaxation problem is treated along with the original problem. It is proved that, under general assumptions, the relaxation problem has an optimal solution, and that for each optimal solution there is a minimizing sequence of the original problem that converges to the optimal solution with respect to the trajectory, the control, and the functional in appropriate topologies simultaneously. (C) 2013 Elsevier Inc. All rights reserved.
摘要：
In this paper, a six-neuron BAM neural network model with discrete delays is considered. By analyzing the associated characteristic transcendental equation, the linear stability of the model is investigated and Hopf bifurcation is demonstrated. Some explicit formulae determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by using the normal form method and center manifold theory. Finally, numerical simulations supporting the theoretical analysis are given. (C) 2010 Elsevier B.V. All rights reserved.
作者机构：
[Du, Dan; Peng, Zhi-Hua; Chen, Xue-Kun] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.;[Liu, Jun] Cent S Univ, Coll Chem & Chem Engn, Changsha 410083, Hunan, Peoples R China.;[Chen, Ke-Qiu] Hunan Univ, Sch Phys & Elect, Dept Appl Phys, Changsha 410082, Hunan, Peoples R China.;[Chen, Ke-Qiu] Synerget Innovat Ctr Quantum Effects & Applicat H, Changsha 410081, Hunan, Peoples R China.
通讯机构：
[Chen, Xue-Kun] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.;[Chen, Ke-Qiu] Hunan Univ, Sch Phys & Elect, Dept Appl Phys, Changsha 410082, Hunan, Peoples R China.;[Chen, Ke-Qiu] Synerget Innovat Ctr Quantum Effects & Applicat H, Changsha 410081, Hunan, Peoples R China.
摘要：
Nonlinear thermal transport in graphene/hexagonal boron nitride (h-BN) heterostructure is investigated by the nonequilibrium molecular dynamics method. It is found that negative differential thermal resistance (NDTR) will appear as the applied temperature difference increases. Detailed phonon spectra analysis reveals that the excited out-of-plane acoustic wave plays an important role in the heat transport across such interface. That is, the mechanical wave results in a significant mismatch between the lattice vibrations of graphene and h-BN domains and hinders interfacial thermal transport. In addition, NDTR can be tuned through the temperature parameter. Interestingly, the regime of NDTR becomes smaller and eventually vanishes with increasing the heterostructure length. However, NDTR is insensitive to the variation of system width. The work may be useful for nanoscale thermal managements utilizing the graphene/h-BN heterostructure. Published by AIP Publishing.
摘要：
In this paper, a class of delayed predator-prey model of prey dispersal in two-patch environments is considered. By analyzing the associated characteristic transcendental equation, its linear stability is investigated and Hopf bifurcation is demonstrated. Some explicit formulae determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by using the normal form theory and center manifold theory. Some numerical simulation for justifying the theoretical analysis are also provided. Finally, biological explanations and main conclusions are given. (C) 2010 Elsevier Inc. All rights reserved.
摘要：
In this paper, a three-species predator-prey system with two delays is investigated. By choosing the sum tau of two delays as a bifurcation parameter, we first show that Hopf bifurcation at the positive equilibrium of the system can occur as tau crosses some critical values. Second, we obtain the formulae determining the direction of the Hopf bifurcations and the stability of the bifurcating periodic solutions by using the normal form theory and center manifold theorem. Finally, numerical simulations supporting our theoretical results are also included. (C) 2011 Elsevier B.V. All rights reserved.
摘要：
Essential proteins are vitally important for cellular survival and development, and identifying essential proteins is very meaningful research work in the post-genome era. Rapid increase of available protein-protein interaction (PPI) data has made it possible to detect protein essentiality at the network level. A series of centrality measures have been proposed to discover essential proteins based on the PPI networks. However, the PPI data obtained from large scale, high-throughput experiments generally contain false positives. It is insufficient to use original PPI data to identify essential proteins. How to improve the accuracy, has become the focus of identifying essential proteins. In this paper, we proposed a framework for identifying essential proteins from active PPI networks constructed with dynamic gene expression. Firstly, we process the dynamic gene expression profiles by using time-dependent model and time-independent model. Secondly, we construct an active PPI network based on co-expressed genes. Lastly, we apply six classical centrality measures in the active PPI network. For the purpose of comparison, other prediction methods are also performed to identify essential proteins based on the active PPI network. The experimental results on yeast network show that identifying essential proteins based on the active PPI network can improve the performance of centrality measures considerably in terms of the number of identified essential proteins and identification accuracy. At the same time, the results also indicate that most of essential proteins are active.
摘要：
In this paper, a two-species Lotka-Volterra predator-prey model with two delays is considered. By analyzing the associated characteristic transcendental equation, the linear stability of the positive equilibrium is investigated and Hopf bifurcation is demonstrated. Some explicit formulae for determining the stability and direction of Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by using normal form theory and center manifold theory. Some numerical simulations for supporting the theoretical results are also included.
作者机构：
[Gao, Yangyang; Yuan, Yali; Hu, Jianbang; Tang, Qiong; Xiao, Xilin; Ma, Dandan] Univ South China, Sch Chem & Chem Engn, Hengyang 421001, Hunan, Peoples R China.;[Guo, Ping] Univ South China, Sch Math & Phys, Hengyang 421001, Hunan, Peoples R China.
通讯机构：
[Yuan, Yali] Univ South China, Sch Chem & Chem Engn, Hengyang 421001, Hunan, Peoples R China.
关键词：
DNAzyme;Electrochemical;Ferrocene;UO 2 2+
摘要：
We have developed a uranyl-specific DNAzyme that was immobilized on the surface of a gold electrode to give a highly sensitive and selective biosensor for uranyl ion. The typical DNAzyme system consisted of the RNA (rA) as the substrate (ADNA), and the other strand is the enzyme (TDNA) with a ferrocene (Fc). The presence of uranyl ion induces the cleavage of the DNA substrate strand at the rA position to form two fragments. The Fc unit thereby is released from the surface of the electrode, and this results in a decreased peak current. This electrochemical biosensor has a dynamic range from 2 nM to 14 nM of uranyl ion, with a detection limit at 1 nM. It exhibits high sensitivity and excellent selectivity over other metal ions, and thus represents a promising technique for simple, fast, on-site, and real-time electrochemical sensing of UO2(II) ion. It also serves as a guide in choosing different methods for designing electrochemical sensors for other metal ions. Figure We have developed a uranyl-specific DNAzyme that was immobilized on the surface of a gold electrode to give a highly sensitive and selective biosensor for uranyl ion. The typical DNAzyme system consisted of the RNA as the substrate and the other strand is the enzyme with a ferrocene (Fc). This electrochemical biosensor exhibits high sensitivity and excellent selectivity, and represents a promising technique for simple, fast, on-site, and real-time electrochemical sensing of UO2(II) ion.
作者：
Li, Jing-Chun;Gong, Xue-Yu*;Dong, Jia-Qi;Wang, Jun;Yin, Lan
期刊：
Chinese Physics B,2016年25(4):45201-1-45201-8 ISSN：1674-1056
通讯作者：
Gong, Xue-Yu
作者机构：
[Gong, Xue-Yu; Li, Jing-Chun] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Wang, Jun; Dong, Jia-Qi] Southwestern Inst Phys, POB 432, Chengdu 610041, Peoples R China.;[Yin, Lan] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.
通讯机构：
[Gong, Xue-Yu] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.
关键词：
HL-2M;electron–cyclotron current drive;neoclassical tearing modes;sawtooth
摘要：
The capabilities of current drive, neoclassical tearing mode (NTM) stabilization, and sawtooth control are analyzed for the electron–cyclotron wave (ECW) system in a HL-2M tokamak. Better performance of the upper launcher is demonstrated in comparison with that of a dropped upper launcher, in terms of J_(EC)/J_(bs) for NTM stabilization and I_(ECCD)/(?_ρ(tor))~2 for sawtooth control. 1-MW ECW power is enough for the 3/2 NTM stabilization, and 1.8-MW ECW power is required to suppress 2/1 NTM in a single null divertor equilibrium with 1.2-MA toroidal current with the upper launcher. Optimization simulation of electron–cyclotron current drive (ECCD) is carried out for three mirrors in an equatorial port, indicating that the middle mirror has a good performance compared with the top and bottom mirrors. The results for balanced co-and counter-ECCD in an equatorial port are also presented.
摘要：
Based on the ideal solution approximation, the model for size-dependent melting temperature of pure metal nanoparticles is extended to binary alloy systems. The developed model, free of any adjustable parameter, demonstrates that the melting temperature is related to the size and composition of alloy nanoparticles. The melting temperature of CuNi, PbBi and SnIn binary alloy nanocrystals is found to be consistent with the experiments and molecular dynamics simulations. The research reveals that alloy nanocrystals have similar melting nature as pure metal.
摘要：
In this paper, we study the multiplicity and concentration of solutions for the following critical fractional Schrödinger–Poisson system: \begin{eqnarray*} \left\{ \begin{array}{ll} \epsilon^{2s}(-\triangle)^{s} {u}+ V(x)u+\phi u =f(u)+|u|^{2^*_{s}-2}u &\mbox{in}\,\,\R^3, \\[2.5mm] \epsilon^{2t}(-\triangle)^{t}{\phi}=u^2 &\mbox{in}\,\, \R^3, \end{array} \right. \end{eqnarray*} where <i>ϵ<i/>> 0 is a small parameter, (− △ )<sup><i>α<i/><sup/> denotes the fractional Laplacian of order <i>α<i/> = <i>s,t<i/> ∈ (0,1), where 2<sub><i>α<i/><sub/><sup>∗<sup/>6/3−2α is the fractional critical exponent in Dimension 3; <i>V<i/> ∈ <i>C<i/><sup>1<sup/>(ℝ<sup>3<sup/>,ℝ<sup>+<sup/>) and <i>f<i/> is subcritical. We first prove that for <i>ϵ<i/>> 0 sufficiently small, the system has a positive ground state solution. With minimax theorems and Ljusternik–Schnirelmann theory, we investigate the relation between the number of positive solutions and the topology of the set where <i>V<i/> attains its minimum for small <i>ϵ<i/>. Moreover, each positive solution <i>u<i/><sub><i>ϵ<i/><sub/> converges to the least energy solution of the associated limit problem and concentrates around a global minimum point of <i>V<i/>.