VANET网络中一种支持优先级区分的新机制

提出一种支持优先级区分的MAC机制,并引入了两种新的操作机制,即接力传输和接力中断。受IEEE 802.11协议段突发机制启发,对于高优先级业务,MAC帧由源端被接力传输至目的端;对于不同优先级的业务,产生不同次数的接力中断。每次接力中断增加一次信道竞争,由此达到不同优先级业务的区分。NS-2仿真证明了该机制的有效性。

一种增强MANET网络QoS性能的MAC机制

采用一种增强MANET网络QoS性能的MAC机制,引用“接力传输”和“接力中断”两种新的操作方法。对高优先级业务,MAC帧由源端被“接力”传输至目的端;对不同优先级的业务,产生不同次数的“接力中断”。每次接力中断增加一次信道竞争,由此达到不同优先级业务的区分。NS-2仿真表明此机制的有效性。

A novel chloroplast-localized protein EMB1303 is required for chloroplast development in Arabidopsis

To understand the molecular mechanisms underlying chloroplast development, we isolated and characterized the albino mutant emb1303-1 in Arabidopsis. The mutant displayed a severe dwarf phenotype with small albino rosette leaves and short roots on a synthetic medium containing sucrose. It is pigment-deficient and seedling lethal when grown in soil. Embryo development was delayed in the mutant, although seed germination was not significantly impaired. The plastids of embl303-1 were arrested in early developmental stages without the classical stack of thylakoid membrane. Genetic and molecular analyses uncovered that the EMB1303 gene encodes a novel chloroplast-localized protein. Microarray and RT-PCR analyses revealed that a number of nuclear- and plastid-encoded genes involved in photosynthesis and chloroplast biogenesis were substantially downregulated in the mutant. Moreover, the accumulation of several major chloroplast proteins was severely compromised in emb1303-1. These results suggest that EMB1303 is essential for chloroplast development.

The effect of acupuncture at “Jǐng Jiājǐ”(颈夹脊) on auditory brainstem response threshold of guinea pigs with sensorineural hearing loss

Objective To explore the effect of acupuncture at ＂Jing Jiaji＂ （颈夹背） on sudden hearing loss by observing the changes of the threshold of auditory brainstem response （ABR） of deaf guinea pigs. Methods Sixty healthy guinea pigs were selected, with computer randomization, 20 were randomly divided into a normal control group （group A）, while the rest were randomly and equally divided into a model group （group B） and an acupuncture group （group C） when turned deaf after gentamycin sulfate and furosemide were administered. No treatment was administered for either the group A or the group B, while acupuncture at ＂Jing Jiaji＂ was given for the group C for 30 days. The ABR thresholds of each group were observed and recorded separately after the treatment for 15 days and 30 days. Results The ABR threshold in the group C was lower than that in the group B after the treatment of 15 days （P〈O.05）. After the treatment of 30 days, the ABR threshold in the group C was obviously lower than that in the group B （P〈0.01）, and was obviously lower than that before acupuncture （P〈0.01）. Conclusion Acupuncture at ＂Jing Jiaji＂ has definite effect on improving the hearing of deaf guinea pigs.

Emergent symmetry at superradiance transition of a Bose condensate in two crossed beam cavities

Recently an experiment on superradiant transition of a Bose condensate in two crossed beam cavities has been reported by Leonard et al. in Nature 543, 87 （2017）. The surprise is they find that across the superradiant transition, the cavity light can be emitted in any superposition of these two cavity modes. This indicates an additional U（1） symmetry that does not exist in the full Hamiltonian. In this paper we show that this symmetry is an emergent symmetry in the vicinity of the phase transition. We identify all the necessary conditions that are required for this emergent U（I ） symmetry and show that this experiment is a special case that satisfies these conditions. We further show that the superradiant transition in this system can also be driven to a first order one when the system is tuned away from the point having the emergent svmmetrv.