Intermittent behavior of cosmic mass field revealed by QSO's Ly_alpha forests

The intermittent behavior of the space-scale distribution of Ly$\alpha$ transmitted flux of QSO HS1700+64 has been analyzed via a discrete wavelet transform. We found that there are strong indications of intermittency on scales down to about 10 $h^{-1}$ kpc. These are: 1.) the probability distribution function of the local fluctuations of the flux is significantly long-tailed on small scales, and 2.) the local power spectrum of the flux shows prominent spiky structures on small scales. Moreover, the local power spectrum averaged on regions with different sizes shows similar spiky structures. Therefore, the random mass density field traced by the Ly$\alpha$ forests is rougher on smaller scales, consistent with singular clustering.Comment: Accepted for publication in ApJ Letters, 12 pages, 3 figure

The large-scale rms bulk velocity estimated from QSOs' Lyα\alpha forests

We propose a method for estimating the large-scale rms bulk velocity of the cosmic mass field from the transmitted fluxes of Ly$\alpha$ forests. It is based on two linear relationships on large scales: 1) the relation between the fluctuations of the transmission and the underlying density field, and 2) the relation between the density fluctuations and the peculiar velocity field. We show that, with a multiscale decomposition, the two relations can be effectively employed for predicting the rms bulk velocity. Since QSO's Ly$\alpha$ forest is due to the absorptions of diffusely distributed and photoionized IGM, this method provides an independent estimate of the rms bulk velocity at high redshifts, on large scales, and free from the bias of galaxies. Using the transmitted flux of 60 moderate-resolution QSO spectra, the rms bulk velocity is found to be 230$\pm$50 km s$^{-1}$ around redshift $z=2.25$ on scale 23 h$^{-1}$Mpc, and down to 110$\pm$45 km s$^{-1}$ around $z=3.25$ on scale 92 h$^{-1}$Mpc for an LCDM universe ($\Omega=0.3$ and $\Lambda=0.7$). The results are basically consistent with the linear evolution theory.Comment: 14 pages, 1 figure, ApJ accepte

The Multiphase Intracluster Medium in Galaxy Groups Probed by the Lyman Alpha Forest

The case is made that the intracluster medium (ICM) in spiral-rich galaxy groups today probably has undergone much slower evolution than that in elliptical-rich groups and clusters. The environments of proto-clusters and proto-groups at z > 2 are likely similar to spiral-rich group environments at lower redshift. Therefore, like the ICM in spiral-rich groups today, the ICM in proto-groups and proto-clusters at z > 2 is predicted to be significantly multiphased. The QSO Lyman alpha forest in the vicinity of galaxies is an effective probe of the ICM at a wide range of redshift. Two recent observations of Lyman alpha absorption around galaxies by Adelberger et al. and by Pascarelle et al are reconciled, and it is shown that observations support the multiphase ICM scenario. Galaxy redshifts must be very accurate for such studies to succeed. This scenario can also explain the lower metallicity and lower hot gas fraction in groups.Comment: 4 pages, 1 figure, replaced with the version after proo

Cloud computing resource scheduling and a survey of its evolutionary approaches

A disruptive technology fundamentally transforming the way that computing services are delivered, cloud computing offers information and communication technology users a new dimension of convenience of resources, as services via the Internet. Because cloud provides a finite pool of virtualized on-demand resources, optimally scheduling them has become an essential and rewarding topic, where a trend of using Evolutionary Computation (EC) algorithms is emerging rapidly. Through analyzing the cloud computing architecture, this survey first presents taxonomy at two levels of scheduling cloud resources. It then paints a landscape of the scheduling problem and solutions. According to the taxonomy, a comprehensive survey of state-of-the-art approaches is presented systematically. Looking forward, challenges and potential future research directions are investigated and invited, including real-time scheduling, adaptive dynamic scheduling, large-scale scheduling, multiobjective scheduling, and distributed and parallel scheduling. At the dawn of Industry 4.0, cloud computing scheduling for cyber-physical integration with the presence of big data is also discussed. Research in this area is only in its infancy, but with the rapid fusion of information and data technology, more exciting and agenda-setting topics are likely to emerge on the horizon

One-point Statistics of the Cosmic Density Field in Real and Redshift Spaces with A Multiresolutional Decomposition

In this paper, we develop a method of performing the one-point statistics of a perturbed density field with a multiresolutional decomposition based on the discrete wavelet transform (DWT). We establish the algorithm of the one-point variable and its moments in considering the effects of Poisson sampling and selection function. We also establish the mapping between the DWT one-point statistics in redshift space and real space, i.e. the algorithm for recovering the DWT one-point statistics from the redshift distortion of bulk velocity, velocity dispersion, and selection function. Numerical tests on N-body simulation samples show that this algorithm works well on scales from a few hundreds to a few Mpc/h for four popular cold dark matter models. Taking the advantage that the DWT one-point variable is dependent on both the scale and the shape (configuration) of decomposition modes, one can design estimators of the redshift distortion parameter (beta) from combinations of DWT modes. When the non-linear redshift distortion is not negligible, the beta estimator from quadrupole-to-monopole ratio is a function of scale. This estimator would not work without adding information about the scale-dependence, such as the power-spectrum index or the real-space correlation function of the random field. The DWT beta estimators, however, do not need such extra information. Numerical tests show that the proposed DWT estimators are able to determine beta robustly with less than 15% uncertainty in the redshift range 0 < z < 3.Comment: 39 pages, 12 figures, ApJ accepte

Resource-aware distributed differential evolution for training expensive neural-network-based controller in power electronic circuit

The neural-network (NN)-based control method is a new emerging promising technique for controller design in a power electronic circuit (PEC). However, the optimization of NN-based controllers (NNCs) has significant challenges in two aspects. The first challenge is that the search space of the NNC optimization problem is such complex that the global optimization ability of the existing algorithms still needs to be improved. The second challenge is that the training process of the NNC parameters is very computationally expensive and requires a long execution time. Thus, in this article, we develop a powerful evolutionary computation-based algorithm to find a high-quality solution and reduce computational time. First, the differential evolution (DE) algorithm is adopted because it is a powerful global optimizer in solving a complex optimization problem. This can help to overcome the premature convergence in local optima to train the NNC parameters well. Second, to reduce the computational time, the DE is extended to distribute DE (DDE) by dispatching all the individuals to different distributed computing resources for parallel computing. Moreover, a resource-aware strategy (RAS) is designed to further efficiently utilize the resources by adaptively dispatching individuals to resources according to the real-time performance of the resources, which can simultaneously concern the computing ability and load state of each resource. Experimental results show that, compared with some other typical evolutionary algorithms, the proposed algorithm can get significantly better solutions within a shorter computational time

Electrochemical-driven water reduction catalyzed by a water soluble cobalt(III) complex with Schiff base ligand

A B S T R A C T A new molecular catalyst based on cobalt complex [LCoCl] (1) is formed by the reaction of N, N-dimethylethylenediamino-N,N-bis(2,4-dimethyl) phenol (H 2 L) with CoCl 2 Á6H 2 O for electrolytic water reduction. To our knowledge 1 is by far the most active electrocatalyst for hydrogen generation from water with a turnover frequency (TOF) of 2744 mol of hydrogen per mole of catalyst per hour at an overpotential of À638 mV (pH 7.0). This is attributed to the ionic ligand, L 2À , that coordinates strongly through two nitrogen atoms and two oxygen atoms to the cobalt center, leaving one Cl À ion in axial position and making the Cl À ion ionize in water

Two-tiered mutualism improves survival and competitiveness of cross-feeding soil bacteria.

Metabolic cross-feeding is a pervasive microbial interaction type that affects community stability and functioning and directs carbon and energy flows. The mechanisms that underlie these interactions and their association with metal/metalloid biogeochemistry, however, remain poorly understood. Here, we identified two soil bacteria, Bacillus sp. BP-3 and Delftia sp. DT-2, that engage in a two-tiered mutualism. Strain BP-3 has low utilization ability of pyruvic acid while strain DT-2 lacks hexokinase, lacks a phosphotransferase system, and is defective in glucose utilization. When strain BP-3 is grown in isolation with glucose, it releases pyruvic acid to the environment resulting in acidification and eventual self-killing. However, when strain BP-3 is grown together with strain DT-2, strain DT-2 utilizes the released pyruvic acid to meet its energy requirements, consequently rescuing strain BP-3 from pyruvic acid-induced growth inhibition. The two bacteria further enhance their collective competitiveness against other microbes by using arsenic as a weapon. Strain DT-2 reduces relatively non-toxic methylarsenate [MAs(V)] to highly toxic methylarsenite [MAs(III)], which kills or suppresses competitors, while strain BP-3 detoxifies MAs(III) by methylation to non-toxic dimethylarsenate [DMAs(V)]. These two arsenic transformations are enhanced when strains DT-2 and BP-3 are grown together. The two strains, along with their close relatives, widely co-occur in soils and their abundances increase with the soil arsenic concentration. Our results reveal that these bacterial types employ a two-tiered mutualism to ensure their collective metabolic activity and maintain their ecological competitive against other soil microbes. These findings shed light on the intricateness of bacterial interactions and their roles in ecosystem functioning

A new approach to the study of the ground-state properties of 2D Ising spin glass

A new approach known as flat histogram method is used to study the +/-J Ising spin glass in two dimensions. Temperature dependence of the energy, the entropy, and other physical quantities can be easily calculated and we give the results for the zero-temperature limit. For the ground-state energy and entropy of an infinite system size, we estimate e0 = -1.4007 +/- 0.0085 and s0 = 0.0709 +/- 0.006, respectively. Both of them agree well with previous calculations. The time to find the ground-states as well as the tunneling times of the algorithm are also reported and compared with other methods.Comment: 11 pages, 4 figure