FORCED OSCILLATIONS OF A CLASS OF NONLINEAR DISPERSIVE WAVE EQUATIONS AND THEIR STABILITY

It has been observed in laboratory experiments that when nonlinear dispersive waves are forced periodically from one end of undisturbed stretch of the medium of propagation, the signal eventually becomes temporally periodic at each spatial point. The observation has been confirmed mathematically in the context of the damped Korteweg-de Vries （KdV） equation and the damped Benjamin-Bona-Mahony （BBM） equation. In this paper we intend to show the same results hold for the pure KdV equation （without the damping terms） posed on a finite domain. Consideration is given to the initial-boundary-value problem {ut＋ux＋uux＋uxxx=0, u（x,0）=φ（x）, 0〈x〈1, t〉0,u（0,t）=h（t）, u（1,t） = 0, ux（1,t） = 0, t〉0.It is shown that if the boundary forcing h is periodic with small ampitude, then the small amplitude solution u of （＊） becomes eventually time-periodic. Viewing （＊） （without the initial condition） as an infinite-dimensional dynamical system in the Hilbert space L^2（0, 1）, we also demonstrate that for a given periodic boundary forcing with small amplitude, the system （＊） admits a （locally） unique limit cycle, or forced oscillation, which is locally exponentially stable. A list of open problems are included for the interested readers to conduct further investigations.     

Molecular evolution of rice S 5 n and functional comparison among different sequences

The wide compatibility gene, S ₅ ⁿ , can overcome embryo sac sterility between indica and japonica subspecies of rice. Therefore, it is very important to characterize the features of the S ₅ ⁿ sequence to reveal the origin and evolution of S ₅ ⁿ . In this paper, 26 cultivated rice haplotypes and 22 wild rice accessions harboring S ₅ ⁿ were used to sequence S ₅ ⁿ . The results showed that 15 genotypes among the 48 materials were fully consistent with control cultivar 02428 (CK). The other 33 accessions had different degrees of variation in the S ₅ ⁿ sequence. Variations in the coding region mainly occurred in the second exon and eight materials showed a 10-bp deletion at 1710?C1719 bp, including wild (O. nivara) and cultivated rice, such as IRW501 and Yuetai B. S ₅ ⁿ sequences were not biased and evolved neutrally. The 48 materials could be divided into 4 categories using a phylogenetic tree of the amino acid sequences. Most of the wild rice clustered together, and the cultivated rice clustered into another group. Eight cultivated rice and O. nivara (wild rice) clustered in another group, which were found to lack 10 consecutive bases in exon 2. Eight rice varieties with high numbers of differences in their S ₅ ⁿ coding regions were crossed with testers (typically indica and japonica) to produced test cross F₁ populations. The F₁s were examined for their ability to overcome indica-japonica hybrid sterility. The result showed that the embryo sac fertility of S ₅ ⁿ -containing hybrids increased significantly compared with control hybrids, but there were no differences among the materials with divergent sequences, indirectly proving that S ₅ ⁿ is a non-functional gene.     

Chaotification in the stretch-twist-fold (STF) flow

Chaotic behavior and detailed parameter analysis of stretch-twist-fold (STF) flow are investigated. STF flow is associated with fluid particle motion which naturally arises in the dynamo theory. It proposes a mechanism, by which a celestial bodies, such as earth and sun, can maintain and amplify the magnetic field continuously. Parameter analysis is performed using linearization theory for different choices of parameters. The existence of Heteroclinic trajectory of Sil’nikov type is proved using an undetermined coefficient method. It connects two non trivial equilibrium points. As a consequence, the Sil’nikov criterion guarantees that STF flow has Smale horseshoes chaos.     

微塑料和全氟辛烷磺酸类物质共暴露对翡翠贻贝滤食率和抗氧化系统的影响

为了探索微塑料和全氟辛烷磺酸类物质(PFOS)在海洋生物体内的复合污染毒性机制, 以翡翠贻贝为研究对象, 在聚苯乙烯微塑料(0.2 μm) 4.55×10⁸个/L以及PFOS浓度为10, 100和1000 μg/L的条件下, 研究PFOS或微塑料单独暴露以及二者复合暴露对翡翠贻贝滤食率、活性氧水平(ROS)、丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性、谷胱甘肽巯基转移酶(GST)活性和谷胱甘肽还原酶(GR)活性的影响。结果表明, 与溶剂对照组相比, 暴露于微塑料和PFOS后翡翠贻贝的滤食率均没有显著变化。在翡翠贻贝的鳃、内脏团和性腺中, 微塑料或PFOS的胁迫都会引起酶响应的显著变化。与PFOS单独暴露组相比, 微塑料和 1000 μg/L PFOS共同暴露时, ROS水平在鳃和性腺中显著提升, 在内脏团中显著下降; MDA含量在鳃和内脏团中显著提升, 在性腺中显著下降; GST和GR活性在鳃中显著下降, 在性腺中显著提高。研究结果说明微塑料会改变翡翠贻贝对PFOS的氧化应激响应。     

Meta-analysis of genome-wide association studies of asthma in ethnically diverse North American populations

Asthma is a common disease with a complex risk architecture including both genetic and environmental factors. We performed a meta-analysis of North American genome-wide association studies of asthma in 5,416 individuals with asthma (cases) including individuals of European American, African American or African Caribbean, and Latino ancestry, with replication in an additional 12,649 individuals from the same ethnic groups. We identified five susceptibility loci. Four were at previously reported loci on 17q21, near IL1RL1, TSLP and IL33, but we report for the first time, to our knowledge, that these loci are associated with asthma risk in three ethnic groups. In addition, we identified a new asthma susceptibility locus at PYHIN1, with the association being specific to individuals of African descent (P = 3.9 × 10(-9)). These results suggest that some asthma susceptibility loci are robust to differences in ancestry when sufficiently large samples sizes are investigated, and that ancestry-specific associations also contribute to the complex genetic architecture of asthma.     

Transmit Power Optimization for Relay-Aided Multi-Carrier D2D Communication

In this paper,we consider the power optimization problem in Orthogonal Frequency Division Multiplexing(OFDM)-based relay-enhanced device-to-device(D2D) communication.In a single cell transmission scenario,dualhop communication is assumed in which each D2D user re-uses the spectrum of just one Cellular User(CU).In this work,we formulate a joint optimization scheme under a Decode-and-Forward(DF) relaying protocol to maximize the sum throughput of D2D and cellular networks via power allocation over different sub-carriers.The problem is thus transformed into a standard convex optimization,subject to individual power constraints at different transmitting nodes.We exploit the duality theory to decompose the problem into several sub-problems and use Karush–Kuhn–Tucker(KKT) conditions to solve each sub-problem.We provide simulation results to validate the performance of our proposed scheme.     

一种引入互斥关系的功能单元分配算法

为使条件分支数据通道中功能单元的分配结果得到进一步优化,在数据流图操作相容性分析中引入操作间互斥关系,并构建基于图论的分配模型.使用团划分算法在该模型上进行功能单元分配,同时提出一种针对功能单元分配问题的团划分启发式方法.不仅提高了团划分算法求解功能单元分配问题的计算结果一致性,而且使算法的收敛速度得以提高.根据实验结果,该算法得到的数据通道中所需功能单元平均减少了41%,同时执行速度加快了50%.     

Regulation of the bacterial cell cycle by an integrated genetic circuit

How bacteria regulate cell cycle progression at a molecular level is a fundamental but poorly understood problem. In Caulobacter crescentus, two-component signal transduction proteins are crucial for cell cycle regulation, but the connectivity of regulators involved has remained elusive and key factors are unidentified. Here we identify ChpT, an essential histidine phosphotransferase that controls the activity of CtrA, the master cell cycle regulator. We show that the essential histidine kinase CckA initiates two phosphorelays, each requiring ChpT, which lead to the phosphorylation and stabilization of CtrA. Downregulation of CckA activity therefore results in the dephosphorylation and degradation of CtrA, which in turn allow the initiation of DNA replication. Furthermore, we show that CtrA triggers its own destruction by promoting cell division and inducing synthesis of the essential regulator DivK, which feeds back to downregulate CckA immediately before S phase. Our results define a single integrated circuit whose components and connectivity can account for the cell cycle oscillations of CtrA in Caulobacter.