Edge mode based graphene nanomechanical resonators for high-sensitivity mass sensor

We perform both molecular dynamics simulations and theoretical analysis to study the sensitivity of the graphene nanomechanical resonator based mass sensors, which are actuated following the global extended mode or the localized edge mode. We find that the mass detection sensitivity corresponding to the edge mode is about three times higher than that corresponding to the extended mode. Our analytic derivations reveal that the enhancement of the sensitivity originates in the reduction of the effective mass for the edge mode due to its localizing feature

External Shocks, Structural Breaks and Unemployment Hysteresis in China

This paper aims to investigate the unemployment hysteresis hypothesis, in which the endogenously determined break points are incorporated, by using annual data of actual urban unemployment rates during 1978-2009 in China. We treat the break date as unknown and utilize recursive, rolling and sequential tests to determine the endogenous structural breaks which are caused by external shocks. Our empirical findings show that three structural breaks existed in the time series of China’s actual urban unemployment rates and we can not reject the unit-root hypothesis, which is consistent with the hysteresis hypothesis of unemployment. Key words: Structural breaks; Unemployment hysteresis; External shock

Nucleon sea in the effective chiral quark model

The asymmetries of both light-flavor antiquark $\bar{d}(x)-\bar{u}(x)$ and strange-antistrange $s(x)-\bar{s}(x)$ distributions of the nucleon sea are considered with more details in the effective chiral quark model. We find that the asymmetric distribution of light-flavor antiquarks $\bar{d}(x)-\bar{u}(x)$ matches the experiment data well and that the asymmetry of strange and antistrange distributions can bring about 60-100% correction to the NuTeV anomaly of $\sin^{2}\theta_{w}$, which are three standard deviations from the world average value measured in other electroweak processes. The results on the correction to the NuTeV anomaly are insensitive to the inputs of the constituent quark distributions and the cut-off parameters. The ratios of $\bar{d}(x)/\bar{u}(x)$ and $s(x)/\bar{s}(x)$ are also discussed, and it is found that the ratio $s(x)/\bar{s}(x)$ is compatible with the available experiments with an additional symmetric sea contribution being considered effectively.Comment: 24 Latex pages, 8 figure

The domination number and the least QQ-eigenvalue

A vertex set $D$ of a graph $G$ is said to be a dominating set if every vertex of $V(G)\setminus D$ is adjacent to at least a vertex in $D$, and the domination number $\gamma(G)$ ($\gamma$, for short) is the minimum cardinality of all dominating sets of $G$. For a graph, the least $Q$-eigenvalue is the least eigenvalue of its signless Laplacian matrix. In this paper, for a nonbipartite graph with both order $n$ and domination number $\gamma$, we show that $n\geq 3\gamma-1$, and show that it contains a unicyclic spanning subgraph with the same domination number $\gamma$. By investigating the relation between the domination number and the least $Q$-eigenvalue of a graph, we minimize the least $Q$-eigenvalue among all the nonbipartite graphs with given domination number.Comment: 13 pages, 3 figure

Codon usage analysis of prokaryotic mechanosensation genes

[Abstract]: In the present study, we examined GC nucleotide composition, relative synonymous codon usage (RSCU), effective number of codons (ENC), codon adaptation index (CAI) and gene length for 308 prokaryotic mechanosensitive ion channel (MSC) genes from six evolutionary groups: Euryarchaeota, Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Firmicutes, and Gammaproteobacteria. Results showed that 1). a wide variation of overrepresentation of nucleotides exists in the MSC genes; 2). codon usage bias varies considerably among the MSC genes; 3). both nucleotide constraint and gene length play an important role in shaping codon usage of the bacterial MSC genes and 4). synonymous codon usage of prokaryotic MSC genes is phylogenetically conserved. Knowledge of codon usage in prokaryotic MSC genes may benefit for the study of the MSC genes in eukaryotes in which few MSC genes have been identified and functionally analysed