Percolation transition in networks with degree-degree correlation

We introduce an exponential random graph model for networks with a fixed degree distribution and with a tunable degree-degree correlation. We then investigate the nature of a percolation transition in the correlated network with the Poisson degree distribution. It is found that negative correlation is irrelevant in that the percolation transition in the disassortative network belongs to the same universality class of the uncorrelated network. Positive correlation turns out to be relevant. The percolation transition in the assortative network is characterized by the non-diverging mean size of finite clusters and power-law scalings of the density of the largest cluster and the cluster size distribution in the non-percolating phase as well as at the critical point. Our results suggest that the unusual type percolation transition in the growing network models reported recently may be inherited from the assortative degree-degree correlation.Comment: 7 pages, 11 figur

Reproductive isolation between two sympatric simultaneous hermaphroditic shrimp, Lysmata wurdemanni and L. boggessi

To investigate pre- and post-zygotic isolation between two sympatric and phylogenetically related species of Lysmata shrimp, two assays were conducted in the laboratory: (1) no specific mate choice where mating between the two species was ‘forced’; (2) specific mate choice or preference where a female had a choice between conspecific and heterospecifc males. Behavioural studies reveal that female L. wurdemanni accepted only conspecific male shrimp, whereas L. boggessi females would mate with an interspecific male if there was no conspecific male present. When males of both species were present, L. boggessi females always mated with the conspecific male. Male L. boggessi in general did not respond to the sex pheromones secreted by female L. wurdemanni and did not display any pre-copulatory behaviour to newly moulted female L. wurdemanni. On the other hand, some male L. wurdemanni responded to female L. boggessi. Although mating was successful between male L. wurdemanni and female L. boggessi, the resulting embryos lived at most for 10 days and failed to hatch. The results indicate that the two species are both pre-zygotically and post-zygotically isolated. Behavioural observation suggests that chemical cues are most likely responsible for pre-zygotic isolation

158µJ pulses from a single transverse mode, large mode-area EDFA

We report the amplification of 10pJ-100pJ, semiconductor diode pulses up to an energy of 158µJ and peak powers >100kW in a multi-stage fibre amplifier chain based on a single-mode, large mode-area erbium doped amplifier design. These results represent the highest single-mode pulse energy ever extracted from any doped fibre system

Effect of the Kondo correlation on thermopower in a Quantum Dot

In this paper we study the thermopower of a quantum dot connected to two leads in the presence of Kondo correlation by employing a modified second-order perturbation scheme at nonequilibrium. A simple scheme, Ng's ansatz [Phys. Rev. Lett. {\bf 76}, 487 (1996)], is adopted to calculate nonequilibrium distribution Green's function and its validity is further checked with regard to the Onsager relation. Numerical results demonstrate that the sign of the thermopower can be changed by tuning the energy level of the quantum dot, leading to a oscillatory behavior with a suppressed magnitude due to the Kondo effect. We also calculate the thermal conductance of the system, and find that the Wiedemann-Franz law is obeyed at low temperature but violated with increasing temperature, corresponding to emerging and quenching of the Kondo effect.Comment: 6 pages, 4 figures; accepted for publication in J Phys.: Condensed Matte