A hybrid algorithm for k-medoid clustering of large data sets

In this paper, we propose a novel local search heuristic and then hybridize it with a genetic algorithm for k-medoid clustering of large data sets, which is an NP-hard optimization problem. The local search heuristic selects k-medoids from the data set and tries to efficiently minimize the total dissimilarity within each cluster. In order to deal with the local optimality, the local search heuristic is hybridized with a genetic algorithm and then the Hybrid K-medoid Algorithm (HKA) is proposed. Our experiments show that, compared with previous genetic algorithm based k-medoid clustering approaches - GCA and RAR/sub w/GA, HKA can provide better clustering solutions and do so more efficiently. Experiments use two gene expression data sets, which may involve large noise components

A niching memetic algorithm for simultaneous clustering and feature selection

Clustering is inherently a difficult task, and is made even more difficult when the selection of relevant features is also an issue. In this paper we propose an approach for simultaneous clustering and feature selection using a niching memetic algorithm. Our approach (which we call NMA_CFS) makes feature selection an integral part of the global clustering search procedure and attempts to overcome the problem of identifying less promising locally optimal solutions in both clustering and feature selection, without making any a priori assumption about the number of clusters. Within the NMA_CFS procedure, a variable composite representation is devised to encode both feature selection and cluster centers with different numbers of clusters. Further, local search operations are introduced to refine feature selection and cluster centers encoded in the chromosomes. Finally, a niching method is integrated to preserve the population diversity and prevent premature convergence. In an experimental evaluation we demonstrate the effectiveness of the proposed approach and compare it with other related approaches, using both synthetic and real data

Magnetic control of the pair creation in spatially localized supercritical fields

We examine the impact of a perpendicular magnetic field on the creation mechanism of electron-positron pairs in a supercritical static electric field, where both fields are localized along the direction of the electric field. In the case where the spatial extent of the magnetic field exceeds that of the electric field, quantum field theoretical simulations based on the Dirac equation predict a suppression of pair creation even if the electric field is supercritical. Furthermore, an arbitrarily small magnetic field outside the interaction zone can bring the creation process even to a complete halt, if it is sufficiently extended. The mechanism for this magnetically induced complete shutoff can be associated with a reopening of the mass gap and the emergence of electrically dressed Landau levels

Bs0→η(′)η(′)B_s^0 \to \eta^{(\prime)} \eta^{(\prime)} decays in the pQCD approach

We calculate the CP averaged branching ratios and CP-violating asymmetries for $B_s^0 \to \eta \eta, \eta \eta^\prime$ and $\eta^\prime \eta^\prime$ decays in the perturbative QCD (pQCD) approach here. The pQCD predictions for the CP-averaged branching ratios are Br(B_s^0 \to \eta \eta) = \left (14.2^{+18.0}_{-7.5}) \times 10^{-6}, Br(B_s^0 \to \eta \eta^\prime)= \left (12.4 ^{+18.2}_{-7.0}) \times 10^{-6}, and Br(B_s^0 \to \eta^{\prime} \eta^{\prime}) = \left (9.2^{+15.3}_{-4.9}) \times 10^{-6}, which agree well with those obtained by employing the QCD factorization approach and also be consistent with available experimental upper limits. The gluonic contributions are small in size: less than 7% for $B_s \to \eta \eta$ and $\eta \eta^\prime$ decays, and around 18% for $B_s \to \eta' \eta'$ decay. The CP-violating asymmetries for three decays are very small: less than 3% in magnitude.Comment: 11 pages, 1 ps figure, Revte

Characterizing Short Necklace States in Logarithmic Transmission Spectrum of Strongly Localized Systems

High transmission plateaus exist widely in the logarithmic transmission spectra of localized systems. Their physical origins are short chains of coupled-localized-states embedded inside the localized system, which are dubbed as "short necklace states". In this work, we define the essential quantities and then, based on these quantities, we investigate the short necklace states' properties statistically and quantitatively. Two different approaches are utilized and the results from them agree with each other very well. In the first approach, the typical plateau-width and the typical order of short necklace states are obtained from the correlation function of logarithmic transmission. In the second approach, we investigate statistical distributions of the peak/plateau-width measured in logarithmic transmission spectra. A novel distribution is found, which can be exactly fitted by the summation of two Gaussian distributions. These two distributions are the results of sharp peaks of localized states and the high plateaus of short necklace states. The center of the second distribution also tells us the typical plateau-width of short necklace states. With increasing the system length, the scaling property of typical plateau-width is very special since it almost does not decrease. The methods and the quantities defined in this work can be widely used on Anderson localization studies.Comment: 6 pages, 4 figure

Histological study of intestinal goblet cells, IgA, and CD3+ lymphocyte distribution in Huang-huai white goat

Background: Ten healthy adult Huang-huai white goats were selected and sacrificed by jugular vein bleeding after anaesthesia to observe the distribution characteristics of the histological structure of the intestinal mucosa, goblet cells, IgA, and CD3+ lymphocytes. Materials and methods: Three sections of the duodenum, the jejunum, and the ileum were immediately collected and fixed with 4% paraformaldehyde for 72 h to prepare tissue sections. After haematoxylin and eosin, periodic acid Schiff, and immunohistochemical staining was performed, the distribution characteristics of goblet cells, IgA-positive cells, and CD3+ lymphocytes were observed. Results showed high columnar epithelial cells in the duodenum and jejunum of Huang-huai white goat and low columnar epithelial cells in the ileum mucosa. Results: Mucopolysaccharides secreted by intestinal goblet cells were mainly neutral, and the number of ileum goblet cells was significantly higher than that of the duodenum and the jejunum (p < 0.05). IgA-positive cells were distributed in the lamina propria of the duodenum, and the number of cells was significantly higher than that in the jejunum and the ileum (p < 0.01). The significant difference was found between the jejunum and the ileum (p < 0.01). The CD3+ cells in the intestinal mucosa were distributed in the lamina propria mucosae, and some of the positive cells in the jejunum were distributed between epithelial cells. CD3+ cells had the largest number in the jejunal lamina propria but had the lowest number in the ileum. Conclusions: The jejunum was significantly higher than the duodenum (p < 0.05), and the ileum was much less than the jejunum (p < 0.01)

Efficient Phase-Encoding Quantum Key Generation with Narrow-Band Single Photons

We propose an efficient phase-encoding quantum secret key generation scheme with heralded narrow-band single photons. The key information is carried by the phase modulation directly on the single-photon temporal waveform without using any passive beam splitters or optical switches. We show that, when the technique is applied to the conventional fiber-based phase-encoding BB84 and differential phase shift (DPS) quantum key distribution schemes, the key generation efficiencies can be improved by a factor of 2 and 3, respectively. For N(>3)-period DPS systems, the key generation efficiency can be improved by a factor of N. The technique is suitable for quantum memory-based long-distance fiber communication system.Comment: 5 pages, 5 figure