Coopetition spectrum trading in cognitive radio networks

Spectrum trading is a promising method to improve spectrum usage efficiency. Several issues must be addressed, however, to enable spectrum trading that goes beyond conservative trading idle bands and achieve cooperation between primary and secondary users. In this paper, we argue that spectrum holes should be explicitly endogenous and negotiated by spectrum trading participants. To this end, we proposed an a Vickery auction based, coopetive framework to foster cooperation, while allowing competition for spectrum sharing. Incentive schemes and penalty for revocable spectrum are proposed to increase the spectrum access opportunities for SUs while protecting PUs spectrum value. A simultation study shows that the proposed framework outperforms conservative trading approaches, in a variety of scenarios with different levels of cooperation and bidding strategies. © 2013 IEEE

Enhanced large-scale production of laccases from Coriolopsis polyzona for use in dye bioremediation

Pollution from synthetic dyes, released by textile and paper pulping plants, draws major concern. Textile effluents have negative impact both on the environment and human health because they are toxic and some are carcinogenic. Apart from the textile industry, dyes are also widely used in manufacturing industries for leather products, cosmetics, pharmaceuticals, foods and beverages. It is known that white rot fungi can decolourise and detoxify various industrial effluents through the production of extracellular lignin modifying enzymes, a major class of which are laccases (EC 1.10.3.2). Considering the above, three strains of white rot fungi, Coriolopsis polyzona (MUCL 38443), Pleurotus ostreatus (ATCC no. MYA-2306) and Pycnoporus sanguineus (MUCL 41582) were studied for their ability to produce laccases in liquid media. The effects of mannan oligosaccharides (MO) as elicitor and ferulic acid as inducer were studied using central composite experimental design in liquid cultures of the three strains. The results showed that MO, either added alone or combined with ferulic acid, enhanced laccase activity in the three different cultures and the enhancement was species specific. The highest increase was in liquid cultures of P. sanguineus (88-fold) followed by P. ostreatus (3-fold) and C. polyzona (2-fold), among which C. polyzona resulted in the highest laccase activity. The combined addition of 150 mg/l of MO and 1 mM ferulic acid resulted in the optimal laccase activity by C. polyzona, whereas additions of 75 mg/l MO to the cultures of P. sanguineus and P. ostreatus led to the optimal activity. Extracellular laccase activity was considerably increased when C. polyzona was grown in glucose-bactopetone based culture medium induced by ferulic acid. The effect of inoculum conditions on laccase production was studied at reactor scales. Laccase activity achieved with conidia inoculation was higher compared with mycelium inoculation at the early stage of fermentation. However, the laccase levels were similar after 23 days of fermentation (110 U/ml and 100 U/ml for the conidia and mycelia pre-culture respectively). The conidia inoculation is preferred in scale-up when time-cost is considered. The maximal laccase activity with conidia inoculation in a 2 litre stirred tank reactor was 27% higher compared to that in shaken flasks. This showed that C. polyzona cultures have the potential to be scaled-up for increased laccase activity by applying conidia inoculum. The fermentation of C. polyzona was scaled-up to 20 litre and 150 litre stirred tank reactors applying fed-bath strategy. This resulted in 100 % enhancement of laccase activity. Addition of oak wood powder in the culture medium increased total laccase activity indicating the potential of lignocellulosic wastes as alternative substrates for enhanced laccase production with reducing cost. In order to investigate the application of laccases in dye decolourisation, two major laccase isozymes (Lac I & II) from C. polyzona were purified to apparent eletrophoretic homogenetity using hydrophobic interaction chromatography and ionexchange chromatography. Both enzymes were found to be monomeric proteins with the same molecular mass of 63 kDa, and isoelectronic point of 4.3. Their catalytic activities were studied under various substrates, pHs and temperatures. The highest enzyme affinity and efficiency were obtained with 2,2′-azino-bis- (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Compared with other fungal laccases, the laccases from C. polyzona have very low Km values with ABTS as a susbtrate. The optimum pHs were 2.8, 3.0 and 5.0 on ABTS, 2, 6-dimethoxyphenol (DMP) and syringaldazine, respectively. Both isozymes had acidic optimal pH values. However, they were more stable in netural pH rather than at acidic pH. Moreover, mass spectrometry (MS) analysis of tryptic digestion products of the two isozymes was performed, which showed further similarity of these two isozymes. As common physical or chemical methods for dye removal are expensive, have low efficiency and sometimes generate other pollutants, the decolourisation of industrial effluents containing single and mixed dyes was investigated using purified laccase (Lac I) from C. polyzona as well as whole cell culture. The method appeared to be an attractive alternative for dye removal. Anthraquinone dyes were found to be more easily decolourised by Lac I compared to azo dyes. The addition of redox mediator ABTS and violuric acid (VA) improved considerably the catalytic efficiencies of azo dyes. Decolourisation, 40-50 %, was achieved for the reactive and the direct dye baths. Response surface technology (RSM) was applied to optimise the decolourisation of the diazo dye reactive black 5 (RB 5) by Lac I. Box-Behnken experimental design with three variables including laccase activity (100, 200, 300 U/l), pH (5, 7, 9) and VA concentration (0, 1.25, 2.5 mM) was studied to identify a significant correlation between the effect of these variables on decolourisation of RB5. The experimental values were in good agreement with the predicted values with the correlation coefficient of 97.4%

Dynamical stability of entanglement between spin ensembles

We study the dynamical stability of the entanglement between the two spin ensembles in the presence of an environment. For a comparative study, we consider the two cases: a single spin ensemble, and two ensembles linearly coupled to a bath, respectively. In both circumstances, we assume the validity of the Markovian approximation for the bath. We examine the robustness of the state by means of the growth of the linear entropy which gives a measure of the purity of the system. We find out macroscopic entangled states of two spin ensembles can stably exist in a common bath. This result may be very useful to generate and detect macroscopic entanglement in a common noisy environment and even a stable macroscopic memory.Comment: 4 pages, 1 figur

Bose Condensation and Temperature

A quantitative analysis of the process of condensation of bosons both in harmonic traps and in gases is made resorting to two ingredients only: Bose classical distribution and spectral discretness. It is shown that in order to take properly into account statistical correlations, temperature must be defined from first principles, based on Shannon entropy, and turns out to be equal to $\beta^{-1}$ only for $T > T_c$ where the usual results are recovered. Below $T_c$ a new critical temperature $T_d$ is found, where the specific heat exhibits a sharp spike, similar to the $\lambda$-peak of superfluidity.Comment: 4 pages, 5 figure

Neutron-Capture Elements in the Double-Enhanced Star HE 1305-0007: a New s- and r-Process Paradigm

The star HE 1305-0007 is a metal-poor double-enhanced star with metallicity [Fe/H] $=-2.0$, which is just at the upper limit of the metallicity for the observed double-enhanced stars. Using a parametric model, we find that almost all s-elements were made in a single neutron exposure. This star should be a member of a post-common-envelope binary. After the s-process material has experienced only one neutron exposure in the nucleosynthesis region and is dredged-up to its envelope, the AGB evolution is terminated by the onset of common-envelope evolution. Based on the high radial-velocity of HE 1305-0007, we speculate that the star could be a runaway star from a binary system, in which the AIC event has occurred and produced the r-process elements.Comment: 4 pages, 3 figures, paper accepted for publication in Chinese Physics letter

Multiparticle Entanglement in the Lipkin-Meshkov-Glick Model

The multiparticle entanglement in the Lipkin-Meshkov-Glick model has been discussed extensively in this paper. Measured by the global entanglement and its generalization, our calculation shows that the multiparticle entanglement can faithfully detect quantum phase transitions. For an antiferromagnetic case the multiparticle entanglement reaches the maximum at the transition point, whereas for ferromagnetic coupling, two different behaviors of multiparticle entanglement can be identified, dependent on the anisotropic parameter in the coupling.Comment: 7 pages and 5 figure

Spectroscopic signatures of the Larkin-Ovchinnikov state in the conductance characteristics of a normal-metal/superconductor junction

Using a discrete-lattice approach, we calculate the conductance spectra between a normal metal and an s-wave Larkin-Ovchinnikov (LO) superconductor, with the junction interface oriented {\em along} the direction of the order-parameter (OP) modulation. The OP sign reversal across one single nodal line can induce a sizable number of zero-energy Andreev bound states around the nodal line, and a hybridized midgap-states band is formed amid a momentum-dependent gap as a result of the periodic array of nodal lines in the LO state. This band-in-gap structure and its anisotropic properties give rise to distinctive features in both the point-contact and tunneling spectra as compared with the BCS and Fulde-Ferrell cases. These spectroscopic features can serve as distinguishing signatures of the LO state.Comment: 8 pages, 5 figures; version as publishe