Brightest Cluster Research Articles

Velocity Segregation and Systematic Biases in Velocity Dispersion Estimates with the SPT-GMOS Spectroscopic Survey

Abstract The velocity distribution of galaxies in clusters is not universal; rather, galaxies are segregated according to their spectral type and relative luminosity. We examine the velocity distributions of different populations of galaxies within 89 Sunyaev Zel’dovich (SZ) selected galaxy clusters spanning . Our sample is primarily draw from the SPT-GMOS spectroscopic survey, supplemented by additional published spectroscopy, resulting in a final spectroscopic sample of 4148 galaxy spectra—2868 cluster members. The velocity dispersion of star-forming cluster galaxies is 17 ± 4% greater than that of passive cluster galaxies, and the velocity dispersion of bright ( ) cluster galaxies is 11 ± 4% lower than the velocity dispersion of our total member population. We find good agreement with simulations regarding the shape of the relationship between the measured velocity dispersion and the fraction of passive versus star-forming galaxies used to measure it, but we find a small offset between this relationship as measured in data and simulations, which suggests that our dispersions are systematically low by as much as 3% relative to simulations. We argue that this offset could be interpreted as a measurement of the effective velocity bias that describes the ratio of our observed velocity dispersions and the intrinsic velocity dispersion of dark matter particles in a published simulation result. Measuring velocity bias in this way suggests that large spectroscopic surveys can improve dispersion-based mass-observable scaling relations for cosmology even in the face of velocity biases, by quantifying and ultimately calibrating them out.

Long-term homeostasis and wound healing in an in vitro epithelial stem cell niche model

Cultures of epithelial cells are limited by the proliferative capacity of primary cells and cell senescence. Herein we show that primary human epithelial cell sheets cultured without dermal equivalents maintained homeostasis in vitro for at least 1 year. Transparency of these sheets enabled live observation of pigmented melanocytes and Fluorescent Ubiquitination-based Cell Cycle Indicator (FUCCI) labeled epithelial cells during wound healing. Cell turn over and KRT15 expression pattern stabilized within 3 months, when KRT15 bright clusters often associated with niche-like melanocytes became apparent. EdU labels were retained in a subset of epithelial cells and melanocytes after 6 months chasing, suggesting their slow cell cycling property. FUCCI-labeling demonstrated robust cell migration and proliferation following wounding. Transparency and long-term (1 year) homeostasis of this model will be a powerful tool for the study of wound healing and cell linage tracing.

A novel “top‐down” strategy for preparing organosilica micelle encapsulating multiple hydrophobic quantum dots as efficient fluorescent label

Organosilica micelle incorporating multiple hydrophobic CdSe/ZnS quantum dots (QDs) was prepared by a surfactant free microemulsion approach assisted by ultrasonication. The size of emulsion droplets along with their QDs loading amount was controlled and determined by QDs concentration in alkylsilane. Sodium silicate deposition was important in transforming the amorphous micelles into spherical beads with well defined QDs/SiO2 structure. These QD micelles were subsequently modified with epoxy group by silane coupling and covalently conjugated to transferrin. After incubated with Hela cells, these fluorescent micelles were detected as bright clusters in cells, which demonstrated the efficient cell internalization of these functionalized particles.

DNA-protected silver emitters: charge dependent switching of fluorescence.

The relationship between the state of charge and spectroscopy of DNA-protected silver emitters is not yet well understood. This remains one of the major issues to unveil in order to fully disentangle the spectroscopic features of these novel systems. It is a well known fact that a fluorescence response arises upon chemical reduction of silver cations attached to DNA, leading to neutral (or partially oxidized) "bright" clusters. It is important to note that the absence of fluorescence in completely ionic complexes is universal in the sense that it does not depend on any experimental variable. This suggests that its origin may be founded on the nature of the interaction between DNA bases and silver cations. Nevertheless, to the best of our knowledge, no explanation exists for this charge dependent switching between dark completely ionic complexes and bright (neutral or partially oxidized) clusters. In this brief report we address this experimental fact on the basis of the electronic structure of the complex as a function of its charge and quantum dynamical simulations of the processes following photoexcitation. These data provide a dynamical picture of the correlation between charge and fluorescence.

Reinvestigation of the T-Cell Inactivation Achieved for the Prevention of TA GV HD By 2500 Gy of Gamma Irradiation, a Comparison with Pathogen Reduction

▪Background: Transfusion Associated Graft vs. Host Disease (TA GVHD) results in high morbidity and mortality, caused by contaminating T-cells present in transfused blood products. Gamma irradiation (GI) of platelet components (PC) with a dose of 2500 cGy is the approved methodology to prevent TA GVHD in high-risk patients. That methodology has been established based on in vitro Limiting Dilution Assays (LDA) that quantify the inactivation of T-cells. The limited natural abundance of T-cells in blood products and the number of T-cells that can be reproducibly cultured in single wells have defined LDA assay sensitivity. LDA assays usually have a dynamic range of 4-5 log10. Even though that methodology has been used for decades with presumable success, cases of GVHD recognized as transfusion associated, have to be connected temporally and phenotypically to the blood product in use, in order to be characterized as such. That leaves open the possibility that some atypical cases of GVHD in blood product recipients may be miss-assigned and go unrecognized.An alternative methodology to prevent TA GVHD is the photochemical treatment of PC with amotosalen/UVA (PCT; INTERCEPTTM Blood System). PCT has replaced GI in Europe for pathoen inactivated PC for more than 10 years. In this study, we evaluated both GI and PCT on inactivation of T-cells using a highly sensitive approach that includes the use of higher numbers of PBMCs isolated by leukapheresis, and an increased number of cells cultured in a single well (107/well) by using larger wells and optimizing culture conditions.Methods: PBMCs harvested by leukapheresis from individual donors (AllCells, Alameda, CA) were spiked (106/mL) into identical units of human plasma and inactivated using either GI with 2500 cGy, PCT, or were retained as untreated control. For the LDA assay, PCT- or GI-treated cells isolated post treatment, were incubated in individual wells for 14 days in the presence of pooled allostimulator cells from 10 unrelated donors (5X106 treated with 7500 cGy) and growth stimulating factors (PHA and IL-2) under standard culture conditions. Proliferation was assessed by tritiated thymidine ([3H]TdR6.7 Ci/mmol) incorporation into PBMC, as well as by the observation of bright large clusters that were clearly observed at 40x magnification.Results: Initial experiments showed that 107PBMCs/well or 106PBMCs/well resulted in proliferation after GI at 2500 cGy, while 105 PBMCs/well did not. On the other hand, 107 PCT treated-PBMCs/well were found neither to proliferate, nor to incorporate [3H]TdRabove background. T-cell precursor frequency was measured for each donor by incubation of serial dilutions of viable PBMCs (50 - 1 /well; 12 wells per dilution) in the presence of 107 inactivated PBMCs. The experiment was repeated 10 times with PBMCs from different donors.For GI, [3H]TdR incorporation above background indicative of T-cell growth, as well as T-cell proliferating colonies were observed in 4 of 10 experiments when 106PBMCs/ well were cultured. No T-cell growth was detected by [3H]TdR incorporation when 105 GI PBMCs/well were cultured, while proliferating colonies were observed in 1 of 10 experiments. No T-cell proliferation was detected by either criterion, when 107 PCT-treated PBMCs/well were cultured.Conclusions: The accepted dose of 2500 cGy gamma irradiation for prevention of TA GVHD results in more than 4.2log10 but less than 6.2 log10 T-cell inactivation. However, it still allows the proliferation of T-cell clones from some donors. Treatment of T-cells with amotosalen/UVA results in complete inactivation of T-cells (>6.2 log10) with no break though proliferation detected.The data in this study have not been reviewed by the FDA. DisclosuresMerkel:Cerus Corporation: Other: fee for service with Cerus Corporation. Giclas:Cerus Corporation: Other: fee for service with Cerus Corporation. Gibula:Cerus Corporation: Other: fee for service with Cerus Corporation. Andersen:Cerus Corporation: Other: fee for service with Cerus Corporation. Knight:Cerus Corporation: Other: fee for service with Cerus Corporation. Lin:Cerus corp: Employment. Castro:Cerus Corporation: Employment. Green:Cerus Corporation: Employment. Stassinopoulos:Cerus Corporation: Employment.

A YOUNG ECLIPSING BINARY AND ITS LUMINOUS NEIGHBORS IN THE EMBEDDED STAR CLUSTER Sh 2-252E

ABSTRACT We present a photometric and light curve analysis of an eccentric eclipsing binary in the K2 Campaign 0 field, which resides in Sh 2-252E, a young star cluster embedded in an H ii region. We describe a spectroscopic investigation of the three brightest stars in the crowded aperture to identify which is the binary system. We find that none of these stars are components of the eclipsing binary system, which must be one of the fainter nearby stars. These bright cluster members all have remarkable spectra: Sh 2-252a (EPIC 202062176) is a B0.5 V star with razor sharp absorption lines, Sh 2-252b is a Herbig A0 star with disk-like emission lines, and Sh 2-252c is a pre-main-sequence star with very red color.

Globular clusters in the far-ultraviolet: evidence for He-enriched second populations in extragalactic globular clusters?

We investigate the integrated far-ultraviolet (FUV) emission from globular clusters. We present new FUV photometry of M~87's clusters based on archival HST WFPC2 F170W observations. We use these data to test the reliability of published photometry based on HST STIS FUV-MAMA observations, which are now known to suffer from significant red-leak. We generally confirm these previous FUV detections, but suggest they may be somewhat fainter. We compare the FUV emission from bright ($M_{V} < -9.0$) clusters in the Milky Way, M~31, M~81 and M~87 to each other and to the predictions from stellar populations models. Metal-rich globular clusters show a large spread in FUV-V, with some clusters in M~31, M~81 and M~87 being much bluer than standard predictions. This requires that some metal-rich clusters host a significant population of blue/extreme horizontal branch (HB) stars. These hot HB stars are not traditionally expected in metal-rich environments, but are a natural consequence of multiple populations in clusters - since the enriched population is observed to be He-enhanced and will therefore produce bluer HB stars, even at high metallicity. We conclude that the observed FUV emission from metal-rich clusters in M~31, M~81 and M~87 provides evidence that He-enhanced second populations, similar to those observed directly in the Milky Way, may be a ubiquitous feature of globular clusters in the local universe. Future HST FUV photometry is required to both confirm our interpretation of these archival data and provide constraints on He-enriched second populations of stars in extra-galactic globular clusters.

Brain image segmentation using a combination of expectation‐maximization algorithm and watershed transform

ABSTRACTWatershed transformation is an effective segmentation algorithm that originates from the mathematical morphology field. This algorithm is widely used in medical image segmentation because it produces complete division even under poor contrast. However, over‐segmentation is its most significant limitation. Therefore, this article proposes a combination of watershed transformation and the expectation‐maximization (EM) algorithm to segment MR brain images efficiently. The EM algorithm is used to form clusters. Then, the brightest cluster is considered and converted into a binary image. A Sobel operator applied on the binary image generates the initial gradient image. Morphological reconstruction is applied to find the foreground and background markers. The final gradient image is obtained using the minima imposition technique on the initial gradient magnitude along with markers. In addition, watershed segmentation applied on the final gradient magnitude generates effective gray matter and cerebrospinal fluid segmentation. The results are compared with simple marker controlled watershed segmentation, watershed segmentation combined with Otsu multilevel thresholding, and local binary fitting energy model for validation. © 2016 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 26, 225–232, 2016

Simulation tests of galaxy cluster constraints on chameleon gravity

We use two new hydrodynamical simulations of $\Lambda$CDM and $f(R)$ gravity to test the methodology used by Wilcox et al. 2015 (W15) in constraining the effects of a fifth force on the profiles of clusters of galaxies. We construct realistic simulated stacked weak lensing and X-ray surface brightness cluster profiles from these cosmological simulations, and then use these data projected along various lines-of-sight to test the spherical symmetry of our stacking procedure. We also test the applicability of the NFW profile to model weak lensing profiles of clusters in $f(R)$ gravity. Finally, we test the validity of the analytical model developed in W15 against the simulated profiles. Overall, we find our methodology is robust and broadly agrees with these simulated data. We also apply our full Markov Chain Monte Carlo (MCMC) analysis from W15 to our simulated X-ray and lensing profiles, providing consistent constraints on the modified gravity parameters as obtained from the real cluster data, e.g. for our $\Lambda$CDM simulation we obtain $|f_{\rm{R}0}| < 8.3 \times 10^{-5}$ (95% CL), which is in good agreement with the W15 measurement of $|f_{\rm{R}0}| < 6 \times 10^{-5}$. Overall, these tests confirm the power of our methodology which can now be applied to larger cluster samples available with the next generation surveys.

Imaging and spectroscopic observations of a strange elliptical bubble in the northern arm of the spiral galaxy NGC 6946

NGC 6946, known as the Fireworks galaxy because of its high supernova rate and high star formation, is embedded in a very extended HI halo. Its northern spiral arm is well detached from the galactic main body. We found that this arm contains a large (~300 pc in size) Red Ellipse, named according to a strong contamination of the H-alpha emission line on its optical images. The ellipse is accompanied by a short parallel arc and a few others still smaller and less regular; a bright star cluster is seen inside these features. The complicated combination of arcs seems to be unique, it is only a bit similar to some SNRs. However, the long-slit spectral data obtained with the Russian 6-m telescope did not confirm the origin of the nebula as a result of a single SN outburst. The emission-line spectrum corresponds to the photoionization by young hot stars with a small contribution of shock ionization. The most likely explanation of the Red Ellipse is a superbbuble created by a collective feedback of massive stars in the star cluster located in the NE side of the Red Ellipse. However, the very regular elliptical shape of the nebulae seems strange.

The XXL Survey

Context. The XXL Survey is the largest survey carried out by the XMM-Newton satellite and covers a total area of 50 square degrees distributed over two fields. It primarily aims at investigating the large-scale structures of the Universe using the distribution of galaxy clusters and active galactic nuclei as tracers of the matter distribution. Aims. This article presents the XXL bright cluster sample, a subsample of 100 galaxy clusters selected from the full XXL catalogue by setting a lower limit of $3\times 10^{-14}\,\mathrm{erg \,s^{-1}cm^{-2}}$ on the source flux within a 1$^{\prime}$ aperture. Methods. The selection function was estimated using a mixture of Monte Carlo simulations and analytical recipes that closely reproduce the source selection process. An extensive spectroscopic follow-up provided redshifts for 97 of the 100 clusters. We derived accurate X-ray parameters for all the sources. Scaling relations were self-consistently derived from the same sample in other publications of the series. On this basis, we study the number density, luminosity function, and spatial distribution of the sample. Results. The bright cluster sample consists of systems with masses between $M_{500}=7\times 10^{13}$ and $3\times 10^{14} M_\odot$, mostly located between $z=0.1$ and 0.5. The observed sky density of clusters is slightly below the predictions from the WMAP9 model, and significantly below the predictions from the Planck 2015 cosmology. In general, within the current uncertainties of the cluster mass calibration, models with higher values of $\sigma_8$ and/or $\Omega_m$ appear more difficult to accommodate. We provide tight constraints on the cluster differential luminosity function and find no hint of evolution out to $z\sim1$. We also find strong evidence for the presence of large-scale structures in the XXL bright cluster sample and identify five new superclusters.

The XXL Survey

The XXL survey is the largest survey carried out by XMM-Newton. Covering an area of 50deg$^2$, the survey contains $\sim450$ galaxy clusters out to a redshift $\sim$2 and to an X-ray flux limit of $\sim5\times10^{-15}erg\,s^{-1}cm^{-2}$. This paper is part of the first release of XXL results focussed on the bright cluster sample. We investigate the scaling relation between weak-lensing mass and X-ray temperature for the brightest clusters in XXL. The scaling relation is used to estimate the mass of all 100 clusters in XXL-100-GC. Based on a subsample of 38 objects that lie within the intersection of the northern XXL field and the publicly available CFHTLenS catalog, we derive the $M_{WL}$ of each system with careful considerations of the systematics. The clusters lie at $0.1<z<0.6$ and span a range of $ T\simeq1-5keV$. We combine our sample with 58 clusters from the literature, increasing the range out to 10keV. To date, this is the largest sample of clusters with $M_{WL}$ measurements that has been used to study the mass-temperature relation. The fit ($M\propto T^b$) to the XXL clusters returns a slope $b=1.78^{+0.37}_{-0.32}$ and intrinsic scatter $\sigma_{\ln M|T}\simeq0.53$; the scatter is dominated by disturbed clusters. The fit to the combined sample of 96 clusters is in tension with self-similarity, $b=1.67\pm0.12$ and $\sigma_{\ln M|T}\simeq0.41$. Overall our results demonstrate the feasibility of ground-based weak-lensing scaling relation studies down to cool systems of $\sim1keV$ temperature and highlight that the current data and samples are a limit to our statistical precision. As such we are unable to determine whether the validity of hydrostatic equilibrium is a function of halo mass. An enlarged sample of cool systems, deeper weak-lensing data, and robust modelling of the selection function will help to explore these issues further.

The XXL Survey

The XXL Survey is the largest homogeneous survey carried out with XMM-Newton. Covering an area of 50 deg$^{2}$, the survey contains several hundred galaxy clusters out to a redshift of $\approx$2 above an X-ray flux limit of $\sim$5$\times10^{-15}$ erg cm$^{-2}$ s$^{-1}$. This paper belongs to the first series of XXL papers focusing on the bright cluster sample. We investigate the luminosity-temperature (LT) relation for the brightest clusters detected in the XXL Survey, taking fully into account the selection biases. We investigate the form of the LT relation, placing constraints on its evolution. We have classified the 100 brightest clusters in the XXL Survey based on their measured X-ray flux. These 100 clusters have been analysed to determine their luminosity and temperature to evaluate the LT relation. We used three methods to fit the LT relation, with two of these methods providing a prescription to fully take into account the selection effects of the survey. We measure the evolution of the LT relation internally using the broad redshift range of the sample. Taking into account selection effects, we find a slope of the bolometric LT relation of B$_{\rm LT}=3.08\pm$0.15, steeper than the self-similar expectation (B$_{\rm LT}$=2). Our best-fit result for the evolution factor is $E(z)^{1.64\pm0.77}$, consistent with "strong self-similar" evolution where clusters scale self-similarly with both mass and redshift. However, this result is marginally stronger than "weak self-similar" evolution, where clusters scale with redshift alone. We investigate the sensitivity of our results to the assumptions made in our model, finding that using an external LT relation as a low-z baseline can have a profound effect on the measured evolution. However, more clusters are needed to break the degeneracy between the choice of likelihood model and mass-temperature relation on the derived evolution.

THE FORNAX DEEP SURVEY WITH VST. I. THE EXTENDED AND DIFFUSE STELLAR HALO OF NGC 1399 OUT TO 192 kpc

ABSTRACT We have started a new, deep multi-imaging survey of the Fornax cluster, dubbed the Fornax Deep Survey (FDS), at the VLT Survey Telescope (VST). In this paper we present the deep photometry inside two square degrees around the bright galaxy NGC 1399 in the core of the cluster. We found that the core of the Fornax cluster is characterized by a very extended and diffuse envelope surrounding the luminous galaxy NGC 1399: we map the surface brightness out to 33 arcmin (∼192 kpc) from the galaxy center and down to μ g ∼ 31 mag arcsec−2 in the g band. The deep photometry allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC 1399 and toward NGC 1387. By analyzing the integrated colors of this feature, we argue that it could be due to the ongoing interaction between the two galaxies, where the outer envelope of NGC 1387 on its east side is stripped away. By fitting the light profile, we found that there exists a physical break radius in the total light distribution at R = 10 arcmin (∼58 kpc) that sets the transition region between the bright central galaxy and the outer exponential halo, and that the stellar halo contributes 60% of the total light of the galaxy (Section 3.5). We discuss the main implications of this work on the build-up of the stellar halo at the center of the Fornax cluster. By comparing with the numerical simulations of the stellar halo formation for the most massive bright cluster galaxies (i.e., 13 &lt; log M 200 / M &CircleDot; &lt; 14 ?> ), we find that the observed stellar halo mass fraction is consistent with a halo formed through the multiple accretion of progenitors with stellar mass in the range 108–1011 M ⊙. This might suggest that the halo of NGC 1399 has also gone through a major merging event. The absence of a significant number of luminous stellar streams and tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early formation epoch. Therefore, different from the Virgo cluster, the extended stellar halo around NGC 1399 is characterized by a more diffuse and well-mixed component, including the intracluster light.

GLOBULAR CLUSTERS AND SPUR CLUSTERS IN NGC 4921, THE BRIGHTEST SPIRAL GALAXY IN THE COMA CLUSTER

ABSTRACT We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in the Coma cluster. We also find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3 × 105 M ⊙. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions of the blue (metal-poor) GCs (0.70 &lt; (V − I) ≤ 1.05) in the halo are estimated V(max) = 27.11 ± 0.09 mag and I(max) = 26.21 ± 0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max) = 26.25 ± 0.03 mag. Adopting M I (max) = −8.56 ± 0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies to be 91 ± 4 Mpc. Combining this with the Coma radial velocity, we derive a value of the Hubble constant, H 0 = 77.9 ± 3.6 km s−1 Mpc−1. We estimate the GC specific frequency of NGC 4921 to be S N = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s.

Richness-based masses of rich and famous galaxy clusters

We present a catalog of galaxy cluster masses derived by exploiting the tight correlation between mass and richness, i.e., a properly computed number of bright cluster galaxies. The richness definition adopted in this work is properly calibrated, shows a small scatter with mass, and has a known evolution, which means that we can estimate accurate ($0.16$ dex) masses more precisely than by adopting any other richness estimates or X-ray or SZ-based proxies based on survey data. We measured a few hundred galaxy clusters at $0.05<z<0.22$ in the low-extinction part of the Sloan Digital Sky Survey footprint that are in the 2015 catalog of Planck-detected clusters, that have a known X-ray emission, that are in the Abell catalog, or that are among the most most cited in the literature. Diagnostic plots and direct images of clusters are individually inspected and we improved cluster centers and, when needed, we revised redshifts. Whenever possible, we also checked for indications of contamination from other clusters on the line of sight, and found ten such cases. All this information, with the derived cluster mass values, are included in the distributed value-added cluster catalog of the 275 clusters with a derived mass larger than $10^{14}$ M$_{\odot}$. A web front-end is available at http://www.brera.mi.astro.it/$\sim$andreon/famous.html . Finally, in a technical appendix we illustrate with Planck clusters how to minimize the sensitivity of comparisons between masses listed in different catalogs to the specific overlapping of the considered subsamples, a problem recognized

Suzaku observation of a high-entropy cluster Abell 548W

Abstract Abell 548W, one of the galaxy clusters located in the Abell 548 region, has about an order of magnitude lower X-ray luminosity compared to ordinal clusters in view of the well-known intracluster medium (ICM) temperature vs. X-ray luminosity (kT–LX) relation. The cluster hosts a pair of diffuse radio sources to the northwest and north, both about 10′ apart from the cluster center. They are candidate radio relics, frequently associated with merging clusters. A Suzaku deep observation with exposure of 84.4 ks was performed to search for signatures of merging in this cluster. The XIS detectors successfully detected the ICM emission out to 16′ from the cluster center. The temperature is ∼ 3.6 keV around its center, and ∼ 2 keV at the outermost regions. The hot region (∼ 6 keV) beside the relic candidates shifted to the cluster center reported by XMM-Newton was not seen in the Suzaku data, although its temperature of 3.6 keV itself is higher than the average temperature of 2.5 keV around the radio sources. In addition, the signature of a cool (kT ∼ 0.9 keV) component was found around the northwest source. A marginal temperature jump at its outer edge was also found, consistent with the canonical idea of the shock acceleration origin of the radio relics. The cluster has among the highest central entropy of ∼ 400 keV cm2 and is one of the so-called low surface brightness clusters. Taking into account the fact that its shape itself is relatively circular and smooth and also that its temperature structure is nearly flat, possible scenarios for merging are discussed.

Этапы жизненного цикла экономического кластера: состояние, движущие силы и процессы

The modern economy is viewed as a set of clusters. Experience of cluster stimulation has shown that cluster policy should be based on a systemic presentation of the clusters as object of governing. Purpose of the article is to describe the life cycles of cluster. Cluster has the following developmental stages: agglomeration, emerging cluster, developing cluster, mature cluster and downturn. Each stage has its own features of reached state, driving force and direction of changes. Mature cluster provides bright cluster effects, high competitiveness and innovation; it provides developed markets of the final product and factors of production, effective information exchange mechanisms. Driving forces of cluster are the strong competition and developed cooperation, and effects of social capital; the cluster is capable of playing the role of "growth pole" of the territory. As a whole understanding of inner structure (composition and connections) and dynamics of development is highly important for design of a cluster policy. Determining the stage of the developed cluster state must be one of the first steps of the development of cluster policy. These factors must be in mind at selection of the tools of cluster policy and measures of cluster support.

Face recognition based on the proximity measure clustering

In this paper problems of featureless face recognition are considered. The recognition is based on clustering the proximity measures between the distributions of brightness clusters cardinality for segmented images. As a proximity measure three types of distances are used in this work: the Euclidean, cosine and Kullback-Leibler distances. Image segmentation and proximity measure clustering are carried out by means of a software model of the recurrent neural network. Results of the experimental studies of the proposed approach are presented.

The abundance and colours of galaxies in high-redshift clusters in the cold dark matter cosmology

High-redshift galaxy clusters allow us to examine galaxy formation in extreme environments. Here we compile data for 15 $z>1$ galaxy clusters to test the predictions from a state-of-the-art semi-analytical model of galaxy formation. The model gives a good match to the slope and zero-point of the cluster red sequence. The model is able to match the cluster galaxy luminosity function at faint and bright magnitudes, but underestimates the number of galaxies around the break in the cluster luminosity function. We find that simply assuming a weaker dust attenuation improves the model predictions for the cluster galaxy luminosity function, but worsens the predictions for the red sequence at bright magnitudes. Examination of the properties of the bright cluster galaxies suggests that the default dust attenuation is large due to these galaxies having large reservoirs of cold gas as well as small radii. We find that matching the luminosity function and colours of high-redshift cluster galaxies, whilst remaining consistent with local observations, poses a challenge for galaxy formation models.