Responsive multipath TCP in SDN-based datacenters

Conference Theme: Smart City & Smart WorldA basic need in datacenter networks is to provide high throughput for large flows such as the massive shuffle traffic flows in a MapReduce application. Multipath TCP (MPTCP) has been investigated as an effective approach toward this goal, by spreading one TCP flow onto multiple paths. However, the current MPTCP implementation has two major limitations: (1) a fixed number of subflows are used without reacting to the actual traffic condition; (2) the routing of subflows of a multipath TCP connection relies heavily on the ECMP-based random hashing. The former may lead to a waste of both the server and network resources, while the latter can cause throughput degradation when multiple subflows collide on the same path. This paper proposes a responsive MPTCP system to resolve the two limitations simultaneously. Our system employs a centralized controller for intelligent subflow route calculation and a monitor running on each server for actively adjusting the number of subflows. Working in synergy, the two modules enable MPTCP flows to respond to the traffic conditions and pursue high throughput on the fly, at very low computation and messaging overhead. NS3-based experiments show that our system achieves satisfactory throughput with less resource overhead, or better throughput at similar amounts of overhead, as compared to common alternatives.published_or_final_versio

Influence of uniaxial tensile stress on the mechanical and piezoelectric properties of short-period ferroelectric superlattice

Tetragonal ferroelectric/ferroelectric BaTiO3/PbTiO3 superlattice under uniaxial tensile stress along the c axis is investigated from first principles. We show that the calculated ideal tensile strength is 6.85 GPa and that the superlattice under the loading of uniaxial tensile stress becomes soft along the nonpolar axes. We also find that the appropriately applied uniaxial tensile stress can significantly enhance the piezoelectricity for the superlattice, with piezoelectric coefficient d33 increasing from the ground state value by a factor of about 8, reaching 678.42 pC/N. The underlying mechanism for the enhancement of piezoelectricity is discussed

Chaotic Properties of Subshifts Generated by a Non-Periodic Recurrent Orbit

The chaotic properties of some subshift maps are investigated. These subshifts are the orbit closures of certain non-periodic recurrent points of a shift map. We first provide a review of basic concepts for dynamics of continuous maps in metric spaces. These concepts include nonwandering point, recurrent point, eventually periodic point, scrambled set, sensitive dependence on initial conditions, Robinson chaos, and topological entropy. Next we review the notion of shift maps and subshifts. Then we show that the one-sided subshifts generated by a non-periodic recurrent point are chaotic in the sense of Robinson. Moreover, we show that such a subshift has an infinite scrambled set if it has a periodic point. Finally, we give some examples and discuss the topological entropy of these subshifts, and present two open problems on the dynamics of subshifts

The extraction of nuclear sea quark distribution and energy loss effect in Drell-Yan experiment

The next-to-leading order and leading order analysis are performed on the differential cross section ratio from Drell-Yan process. It is found that the effect of next-to-leading order corrections can be negligible on the differential cross section ratios as a function of the quark momentum fraction in the beam proton and the target nuclei for the current Fermilab and future lower beam proton energy. The nuclear Drell-Yan reaction is an ideal tool to study the energy loss of the fast quark moving through cold nuclei. In the leading order analysis, the theoretical results with quark energy loss are in good agreement with the Fermilab E866 experimental data on the Drell-Yan differential cross section ratios as a function of the momentum fraction of the target parton. It is shown that the quark energy loss effect has significant impact on the Drell-Yan differential cross section ratios. The nuclear Drell-Yan experiment at current Fermilab and future lower energy proton beam can not provide us with more information on the nuclear sea quark distribution.Comment: 17 pages, 4 figure

Energy-momentum for Randall-Sundrum models

We investigate the conservation law of energy-momentum for Randall-Sundrum models by the general displacement transform. The energy-momentum current has a superpotential and are therefore identically conserved. It is shown that for Randall-Sundrum solution, the momentum vanishes and most of the bulk energy is localized near the Planck brane. The energy density is $\epsilon = \epsilon_0 e^{-3k \mid y \mid}$.Comment: 13 pages, no figures, v4: introduction and new conclusion added, v5: 11 pages, title changed and references added, accepted by Mod. Phys. Lett.

Cloning and expression of a tomato glutathione S- transferase (GST) in Escherichia coli

Glutathione S- transferases (GSTs) fulfill a diverse range of functions in an organism. In a previous study, a putative glutathione S-transferase gene (ShGSTU1) from a wild-type tomato, Solanum habrochaites G1.1560, was identified to be a key gene in pathogen resistant response against powdery mildew in tomato. In this study, ShGSTU1 was cloned into plasmid pET-28a, efficiently expressed in Escherichia coli upon isopropyl-β-D-1-thiogalactopyronoside (IPTG) induction, purified with Ni2+ affinity chromatography and biochemically characterized. The results show that the optimal conditions for the expression of recombinant ShGSTU1 in E. coli were growth under 37°C, and 4-h IPTG induction with 1 mM concentration. About 18.93 mg ShGSTU1 was recovered from 1 g wet bacteria. The recombinant ShGSTU1 exhibited enzymatic activity with specific activity 0.625 U/mg. These results might provide a significant foundation for the later research on the mechanism of ShGSTU1 in tomato resistance to powdery mildew.Key words: Tomato, glutathione S-transferase, expression, purification, enzyme activity

The influence of collective neutrino oscillations on a supernova r-process

Recently, it has been demonstrated that neutrinos in a supernova oscillate collectively. This process occurs much deeper than the conventional matter-induced MSW effect and hence may have an impact on nucleosynthesis. In this paper we explore the effects of collective neutrino oscillations on the r-process, using representative late-time neutrino spectra and outflow models. We find that accurate modeling of the collective oscillations is essential for this analysis. As an illustration, the often-used "single-angle" approximation makes grossly inaccurate predictions for the yields in our setup. With the proper multiangle treatment, the effect of the oscillations is found to be less dramatic, but still significant. Since the oscillation patterns are sensitive to the details of the emitted fluxes and the sign of the neutrino mass hierarchy, so are the r-process yields. The magnitude of the effect also depends sensitively on the astrophysical conditions - in particular on the interplay between the time when nuclei begin to exist in significant numbers and the time when the collective oscillation begins. A more definitive understanding of the astrophysical conditions, and accurate modeling of the collective oscillations for those conditions, is necessary.Comment: 27 pages, 10 figure

Disentangling effects of abiotic factors and biotic interactions on cross-taxon congruence in species turnover patterns of plants, moths and beetles

High cross-taxon congruence in species diversity patterns is essential for the use of surrogate taxa in biodiversity conservation, but presence and strength of congruence in species turnover patterns, and the relative contributions of abiotic environmental factors and biotic interaction towards this congruence, remain poorly understood. In our study, we used variation partitioning in multiple regressions to quantify cross-taxon congruence in community dissimilarities of vascular plants, geometrid and arciinid moths and carabid beetles, subsequently investigating their respective underpinning by abiotic factors and biotic interactions. Significant cross-taxon congruence observed across all taxon pairs was linked to their similar responses towards elevation change. Changes in the vegetation composition were closely linked to carabid turnover, with vegetation structure and associated microclimatic conditions proposed causes of this link. In contrast, moth assemblages appeared to be dominated by generalist species whose turnover was weakly associated with vegetation changes. Overall, abiotic factors exerted a stronger influence on cross-taxon congruence across our study sites than biotic interactions. The weak congruence in turnover observed particularly between plants and moths highlights the importance of multi-taxon approaches based on groupings of taxa with similar turnovers, rather than the use of single surrogate taxa or environmental proxies, in biodiversity assessments