Positive current noise cross-correlations in capacitively coupled double quantum dots with ferromagnetic leads

We examine cross-correlations (CCs) in the tunneling currents through two parallel interacting quantum dots coupled to four independent ferromagnetic electrodes. We find that when either one of the two circuits is in the parallel configuration with sufficiently strong polarization strength, a new mechanism of dynamical spin blockade, i.e., a spin-dependent bunching of tunneling events, governs transport through the system together with the inter-dot Coulomb interaction, leading to a sign-reversal of the zero-frequency current CC in the dynamical channel blockade regime, and to enhancement of positive current CC in the dynamical channel anti-blockade regimes, in contrast to the corresponding results for the case of paramagnetic leads.Comment: 9 pages, 3 figure

Black hole mass and accretion rate of active galactic nuclei with double-peaked broad emission lines

(Abridged) Using an empirical relation between the broad line region size and optical continuum luminosity, we estimated the black hole mass and accretion rate for 135 AGNs with double-peaked broad emission lines in two samples. With black hole masses from $3\times 10^7M_\odot$ to $5\times 10^9M_\odot$, these AGNs have the dimensionless accretion rates (Eddington ratios) between 0.001 and 0.1, and the bolometric luminosity between $10^{43}erg/s$ and $10^{46}erg/s$, both being significantly larger than those of several previously known low-luminosity double-peaked AGNs. The optical-X-ray spectra indices, $\alpha_{OX}$, of these high-luminosity double-peaked AGNs is between 1 and 1.9. Modest correlations of the $\alpha_{OX}$ value with the Eddington ratio and bolometric luminosity indicate that double-peaked AGNs with higher Eddington ratio or higher luminosity tend to have larger $\alpha_{OX}$ value. Therefore we suggested that the accretion process in some high-luminosity double-peaked AGNs is probably different from that of low-luminosity objects where an ADAF-like accretion flow was thought to exist. This is also supported by the presence of possible big blue bumps in the spectra of some double-peaked AGNs with higher Eddington ratios. We noticed that the prototype double-peaked emission line AGN, Arp 102B, may be an ``intermediate'' object between the high and low luminosity double-peaked AGNs. In addition, we found an apparent strong anti-correlation between the peak separation of double-peaked profile and Eddington ratio. If it is real, it may provide us a clue to understand why double-peaked broad emission lines were hardly found in luminous AGNs with Eddington ratio larger than 0.1.Comment: 24 pages, 6 figures, accepted by Ap

Heavy-tailed statistics in short-message communication

Short-message (SM) is one of the most frequently used communication channels in the modern society. In this Brief Report, based on the SM communication records provided by some volunteers, we investigate the statistics of SM communication pattern, including the interevent time distributions between two consecutive short messages and two conversations, and the distribution of message number contained by a complete conversation. In the individual level, the current empirical data raises a strong evidence that the human activity pattern, exhibiting a heavy-tailed interevent time distribution, is driven by a non-Poisson nature.Comment: 4 pages, 4 figures and 1 tabl

Photosystem 2 photochemistry and pigment composition of Dicranopteris dichotoma Bernh under different irradiances

The distribution of rare earth elements (REEs) in the lamina and chloroplast of fern Dicranopteris dichotoma Bernh from a light rare earth elements mine (LRM) and a non-mining (NM) area in Longnan county of Jiangxi province, China, were investigated by means of inductively coupled plasma-mass spectrometry (ICP-MS). The photosynthetic characteristics and pigment composition in immature and mature leaves of D. dichotoma were studied by chlorophyll (Chl) a fluorescence kinetics and high performance liquid chromatography (HPLC). Results show that contents of REEs in the lamina and chloroplast of D. dichotoma in LRM were higher than those ferns in NM. By comparing with D. dichotoma from NM area, the efficiency of photosystem 2 photochemistry and electron transport rate were significantly enhanced in mature lamina of the plant from LRM because D. dichotoma could change its xanthophyll cycle content to avoid the damaging effect of high REEs content. However, high irradiance decreased the photosystem 2 photochemistry efficiency in lamina from ferns in LRM suggested that large amount of REEs reduce the capacities to avoid photo damage in D. dichotoma.Key words: Dicranopteris dichotoma, photoinhibition, rare earth element, xanthophylls

Prediction of open-hole tensile strength of unidirectional flax yarn reinforced polypropylene composite by analytical and numerical models

Open-hole tensile strength of unidirectional flax yarn reinforced polypropylene composites has been predicted fordifferent laminates with varying lay-up through analytical and numerical models. Point stress criterion (PSC), modified PSCand finite element modeling (FEM) have been applied to examine the effect of different open-hole sizes on the stressbearing capacity. The characteristic length (d0) of the composites has been confirmed by PSC which depends on thespecimen geometry. The modified PSC has been used with stress concentration factor, notch sensitivity factor, andexponential parameter for evaluating the open-hole tensile strength. The stress distribution and the open-hole tensile strengthhave also been obtained by finite element simulation. The best correlations between the experimental and predicted resultshave been achieved from modified PSC model than with traditional PSC and FEM models

Astrophysics: Most distant cosmic blast seen

The most distant -ray burst yet sighted is the earliest astronomical object ever observed in cosmic history. This ancient beacon offers a glimpse of the little-known cosmic dark ages.Comment: Published in Nature News & View

Raman and Infra-red properties and layer dependence of the phonon dispersions in multi-layered graphene

The symmetry group analysis is applied to classify the phonon modes of $N$-stacked graphene layers (NSGL's) with AB- and AA-stacking, particularly their infra-red and Raman properties. The dispersions of various phonon modes are calculated in a multi-layer vibrational model, which is generalized from the lattice vibrational potentials of graphene to including the inter-layer interactions in NSGL's. The experimentally reported red shift phenomena in the layer number dependence of the intra-layer optical C-C stretching mode frequencies are interpreted. An interesting low frequency inter-layer optical mode is revealed to be Raman or Infra-red active in even or odd NSGL's respectively. Its frequency shift is sensitive to the layer number and saturated at about 10 layers.Comment: enlarged versio

Comment on ``Scientific collaboration networks. II. Shortest paths, weighted networks, and centrality"

In this comment, we investigate a common used algorithm proposed by Newman [M. E. J. Newman, Phys. Rev. E {\bf 64}, 016132(2001)] to calculate the betweenness centrality for all vertices. The inaccurateness of Newman's algorithm is pointed out and a corrected algorithm, also with O($MN$) time complexity, is given. In addition, the comparison of calculating results for these two algorithm aiming the protein interaction network of Yeast is shown.Comment: 3 pages, 2 tables, and 2 figure

Topological regluing of rational functions

Regluing is a topological operation that helps to construct topological models for rational functions on the boundaries of certain hyperbolic components. It also has a holomorphic interpretation, with the flavor of infinite dimensional Thurston--Teichm\"uller theory. We will discuss a topological theory of regluing, and trace a direction in which a holomorphic theory can develop.Comment: 38 page