High-resolution observations of the globular cluster NGC 7099

NASA Astrophysics Data System (ADS)

Sams, Bruce Jones, III

The globular cluster NGC 7099 is a prototypical collapsed core cluster. Through a series of instrumental, observational, and theoretical observations, I have resolved its core structure using a ground based telescope. The core has a radius of 2.15 arcsec when imaged with a V band spatial resolution of 0.35 arcsec. Initial attempts at speckle imaging produced images of inadequate signal to noise and resolution. To explain these results, a new, fully general signal-to-noise model has been developed. It properly accounts for all sources of noise in a speckle observation, including aliasing of high spatial frequencies by inadequate sampling of the image plane. The model, called Full Speckle Noise (FSN), can be used to predict the outcome of any speckle imaging experiment. A new high resolution imaging technique called ACT (Atmospheric Correlation with a Template) was developed to create sharper astronomical images. ACT compensates for image motion due to atmospheric turbulence. ACT is similar to the Shift and Add algorithm, but uses apriori spatial knowledge about the image to further constrain the shifts. In this instance, the final images of NGC 7099 have resolutions of 0.35 arcsec from data taken in 1 arcsec seeing. The PAPA (Precision Analog Photon Address) camera was used to record data. It is subject to errors when imaging cluster cores in a large field of view. The origin of these errors is explained, and several ways to avoid them proposed. New software was created for the PAPA camera to properly take flat field images taken in a large field of view. Absolute photometry measurements of NGC 7099 made with the PAPA camera are accurate to 0.1 magnitude. Luminosity sampling errors dominate surface brightness profiles of the central few arcsec in a collapsed core cluster. These errors set limits on the ultimate spatial accuracy of surface brightness profiles.

Hierarchical Spatio-temporal Visual Analysis of Cluster Evolution in Electrocorticography Data

DOE PAGES

Murugesan, Sugeerth; Bouchard, Kristofer; Chang, Edward; ...

2016-10-02

Here, we present ECoG ClusterFlow, a novel interactive visual analysis tool for the exploration of high-resolution Electrocorticography (ECoG) data. Our system detects and visualizes dynamic high-level structures, such as communities, using the time-varying spatial connectivity network derived from the high-resolution ECoG data. ECoG ClusterFlow provides a multi-scale visualization of the spatio-temporal patterns underlying the time-varying communities using two views: 1) an overview summarizing the evolution of clusters over time and 2) a hierarchical glyph-based technique that uses data aggregation and small multiples techniques to visualize the propagation of clusters in their spatial domain. ECoG ClusterFlow makes it possible 1) tomore » compare the spatio-temporal evolution patterns across various time intervals, 2) to compare the temporal information at varying levels of granularity, and 3) to investigate the evolution of spatial patterns without occluding the spatial context information. Lastly, we present case studies done in collaboration with neuroscientists on our team for both simulated and real epileptic seizure data aimed at evaluating the effectiveness of our approach.« less

A theoretical and experimental benchmark study of core-excited states in nitrogen

NASA Astrophysics Data System (ADS)

Myhre, Rolf H.; Wolf, Thomas J. A.; Cheng, Lan; Nandi, Saikat; Coriani, Sonia; Gühr, Markus; Koch, Henrik

2018-02-01

The high resolution near edge X-ray absorption fine structure spectrum of nitrogen displays the vibrational structure of the core-excited states. This makes nitrogen well suited for assessing the accuracy of different electronic structure methods for core excitations. We report high resolution experimental measurements performed at the SOLEIL synchrotron facility. These are compared with theoretical spectra calculated using coupled cluster theory and algebraic diagrammatic construction theory. The coupled cluster singles and doubles with perturbative triples model known as CC3 is shown to accurately reproduce the experimental excitation energies as well as the spacing of the vibrational transitions. The computational results are also shown to be systematically improved within the coupled cluster hierarchy, with the coupled cluster singles, doubles, triples, and quadruples method faithfully reproducing the experimental vibrational structure.

H II REGIONS, EMBEDDED PROTOSTARS, AND STARLESS CORES IN SHARPLESS 2-157

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Chian-Chou; Williams, Jonathan P.; Pandian, Jagadheep D., E-mail: ccchen@ifa.hawaii.edu, E-mail: jpw@ifa.hawaii.edu, E-mail: jagadheep@iist.ac.in

2012-06-20

We present arcsecond resolution 1.4 mm observations of the high-mass star-forming region, Sharpless 2-157, that reveal the cool dust associated with the first stages of star formation. These data are compared with archival images at optical, infrared, and radio wavelengths, and complemented with new arcsecond resolution mid-infrared data. We identify a dusty young H II region, numerous infrared sources within the cluster envelope, and four starless condensations. Three of the cores lie in a line to the south of the cluster peak, but the most massive one is right at the center and associated with a jumble of bright radiomore » and infrared sources. This presents an interesting juxtaposition of high- and low-mass star formation within the same cluster which we compare with similar observations of other high-mass star-forming regions and discuss in the context of cluster formation theory.« less

GLOBULAR CLUSTER ABUNDANCES FROM HIGH-RESOLUTION, INTEGRATED-LIGHT SPECTROSCOPY. III. THE LARGE MAGELLANIC CLOUD: Fe AND AGES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colucci, Janet E.; Bernstein, Rebecca A.; Cameron, Scott A.

2011-07-01

In this paper, we refine our method for the abundance analysis of high-resolution spectroscopy of the integrated light of unresolved globular clusters (GCs). This method was previously demonstrated for the analysis of old (>10 Gyr) Milky Way (MW) GCs. Here, we extend the technique to young clusters using a training set of nine GCs in the Large Magellanic Cloud. Depending on the signal-to-noise ratio of the data, we use 20-100 Fe lines per cluster to successfully constrain the ages of old clusters to within a {approx}5 Gyr range, the ages of {approx}2 Gyr clusters to a 1-2 Gyr range, andmore » the ages of the youngest clusters (0.05-1 Gyr) to a {approx}200 Myr range. We also demonstrate that we can measure [Fe/H] in clusters with any age less than 12 Gyr with similar or only slightly larger uncertainties (0.1-0.25 dex) than those obtained for old MW GCs (0.1 dex); the slightly larger uncertainties are due to the rapid evolution in stellar populations at these ages. In this paper, we present only Fe abundances and ages. In the next paper in this series, we present our complete analysis of {approx}20 elements for which we are able to measure abundances. For several of the clusters in this sample, there are no high-resolution abundances in the literature from individual member stars; our results are the first detailed chemical abundances available. The spectra used in this paper were obtained at Las Campanas with the echelle on the du Pont Telescope and with the MIKE spectrograph on the Magellan Clay Telescope.« less

High-resolution clustered pinhole (131)Iodine SPECT imaging in mice.

PubMed

van der Have, Frans; Ivashchenko, Oleksandra; Goorden, Marlies C; Ramakers, Ruud M; Beekman, Freek J

2016-08-01

High-resolution pre-clinical (131)I SPECT can facilitate development of new radioiodine therapies for cancer. To this end, it is important to limit resolution-degrading effects of pinhole edge penetration by the high-energy γ-photons of iodine. Here we introduce, optimize and validate (131)I SPECT performed with a dedicated high-energy clustered multi-pinhole collimator. A SPECT-CT system (VECTor/CT) with stationary gamma-detectors was equipped with a tungsten collimator with clustered pinholes. Images were reconstructed with pixel-based OSEM, using a dedicated (131)I system matrix that models the distance- and energy-dependent resolution and sensitivity of each pinhole, as well as the intrinsic detector blurring and variable depth of interaction in the detector. The system performance was characterized with phantoms and in vivo static and dynamic (131)I-NaI scans of mice. Reconstructed image resolution reached 0.6mm, while quantitative accuracy measured with a (131)I filled syringe reaches an accuracy of +3.6±3.5% of the gold standard value. In vivo mice scans illustrated a clear shape of the thyroid and biodistribution of (131)I within the animal. Pharmacokinetics of (131)I was assessed with 15-s time frames from the sequence of dynamic images and time-activity curves of (131)I-NaI. High-resolution quantitative and fast dynamic (131)I SPECT in mice is possible by means of a high-energy collimator and optimized system modeling. This enables analysis of (131)I uptake even within small organs in mice, which can be highly valuable for development and optimization of targeted cancer therapies. Copyright © 2016 Elsevier Inc. All rights reserved.

Flying across Galaxy Clusters with Google Earth: additional imagery from SDSS co-added data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hao, Jiangang; Annis, James; /Fermilab

2010-10-01

Galaxy clusters are spectacular. We provide a Google Earth compatible imagery for the deep co-added images from the Sloan Digital Sky Survey and make it a tool for examing galaxy clusters. Google Earth (in sky mode) provides a highly interactive environment for visualizing the sky. By encoding the galaxy cluster information into a kml/kmz file, one can use Google Earth as a tool for examining galaxy clusters and fly across them freely. However, the resolution of the images provided by Google Earth is not very high. This is partially because the major imagery google earth used is from Sloan Digitalmore » Sky Survey (SDSS) (SDSS collaboration 2000) and the resolutions have been reduced to speed up the web transferring. To have higher resolution images, you need to add your own images in a way that Google Earth can understand. The SDSS co-added data are the co-addition of {approx}100 scans of images from SDSS stripe 82 (Annis et al. 2010). It provides the deepest images based on SDSS and reach as deep as about redshift 1.0. Based on the co-added images, we created color images in a way as described by Lupton et al. (2004) and convert the color images to Google Earth compatible images using wcs2kml (Brewer et al. 2007). The images are stored at a public server at Fermi National Accelerator Laboratory and can be accessed by the public. To view those images in Google Earth, you need to download a kmz file, which contains the links to the color images, and then open the kmz file with your Google Earth. To meet different needs for resolutions, we provide three kmz files corresponding to low, medium and high resolution images. We recommend the high resolution one as long as you have a broadband Internet connection, though you should choose to download any of them, depending on your own needs and Internet speed. After you open the downloaded kmz file with Google Earth (in sky mode), it takes about 5 minutes (depending on your Internet connection and the resolution of images you want) to get some initial images loaded. Then, additional images corresponding to the region you are browsing will be loaded automatically. So far, you have access to all the co-added images. But you still do not have the galaxy cluster position information to look at. In order to see the galaxy clusters, you need to download another kmz file that tell Google Earth where to find the galaxy clusters in the co-added data region. We provide a kmz file for a few galaxy clusters in the stripe 82 region and you can download and open it with Google Earth. In the SDSS co-added region (stripe 82 region), the imagery from Google Earth itself is from the Digitized Sky Survey (2007), which is in very poor quality. In Figure1 and Figure2, we show screenshots of a cluster with and without the new co-added imagery in Google Earth. Much more details have been revealed with the deep images.« less

Globular Cluster Contributions to the Galactic Halo

NASA Astrophysics Data System (ADS)

Martell, Sarah; Grebel, Eva; Lai, David

2010-08-01

The goal of this project is to confirm chemically that globular clusters are the source of as much as half the population of the Galactic halo. Using moderate-resolution spectroscopy from the SEGUE survey, we have identified a previously unknown population of halo field giants with distinctly strong CN features. CN variations are typically only observed in globular clusters, so these stars are interpreted as immigrants to the halo that originally formed in globular clusters. In one night of Keck/HIRES time, we will obtain high-quality, high- resolution spectra for five such stars, and determine abundances of O, Na, Mg, Al, alpha, iron-peak and neutron-capture elements. With this information we can state clearly whether these unusual CN-strong halo stars carry the full abundance pattern seen in CN-strong globular cluster stars, with depleted C, O, and Mg and enhanced N, Na, and Al. This type of coarse ``chemical tagging'' will allow a clearer division of the Galactic halo into contributions from globular clusters and from dwarf galaxies, and will place constraints on theoretical models of globular cluster formation and evolution.

Where Water Is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster

PubMed Central

Yano, Junko; Kern, Jan; Sauer, Kenneth; Latimer, Matthew J.; Pushkar, Yulia; Biesiadka, Jacek; Loll, Bernhard; Saenger, Wolfram; Messinger, Johannes; Zouni, Athina; Yachandra, Vittal K.

2014-01-01

The oxidation of water to dioxygen is catalyzed within photosystem II (PSII) by a Mn4Ca cluster, the structure of which remains elusive. Polarized extended x-ray absorption fine structure (EXAFS) measurements on PSII single crystals constrain the Mn4Ca cluster geometry to a set of three similar high-resolution structures. Combining polarized EXAFS and x-ray diffraction data, the cluster was placed within PSII, taking into account the overall trend of the electron density of the metal site and the putative ligands. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 angstrom–resolution x-ray structures or other previously proposed models. PMID:17082458

Re-solution of xenon clusters in plutonium dioxide under the collision cascade impact: A molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Seitov, D. D.; Nekrasov, K. A.; Kupryazhkin, A. Ya.; Gupta, S. K.; Akilbekov, A. T.

2017-09-01

The interaction of xenon clusters with the collision cascades in the PuO2 crystals is investigated using the molecular dynamics simulation and the approximation of the pair interaction potentials. The potentials of interaction of Xe atoms with the surrounding particles in the crystal lattice are suggested, that are valid in the range of high collision energies. The cascades created by the recoil 235U ions formed as the plutonium α-decay product are considered, and the influence of such cascades on the structure of the xenon clusters is analyzed. It is shown, that the cascade-cluster interaction leads to release of the xenon atoms from the clusters and their subsequent re-solution in the crystal bulk.

A theoretical and experimental benchmark study of core-excited states in nitrogen

DOE PAGES

Myhre, Rolf H.; Wolf, Thomas J. A.; Cheng, Lan; ...

2018-02-14

The high resolution near edge X-ray absorption fine structure spectrum of nitrogen displays the vibrational structure of the core-excited states. This makes nitrogen well suited for assessing the accuracy of different electronic structure methods for core excitations. We report high resolution experimental measurements performed at the SOLEIL synchrotron facility. These are compared with theoretical spectra calculated using coupled cluster theory and algebraic diagrammatic construction theory. The coupled cluster singles and doubles with perturbative triples model known as CC3 is shown to accurately reproduce the experimental excitation energies as well as the spacing of the vibrational transitions. In conclusion, the computationalmore » results are also shown to be systematically improved within the coupled cluster hierarchy, with the coupled cluster singles, doubles, triples, and quadruples method faithfully reproducing the experimental vibrational structure.« less

A theoretical and experimental benchmark study of core-excited states in nitrogen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myhre, Rolf H.; Wolf, Thomas J. A.; Cheng, Lan

The high resolution near edge X-ray absorption fine structure spectrum of nitrogen displays the vibrational structure of the core-excited states. This makes nitrogen well suited for assessing the accuracy of different electronic structure methods for core excitations. We report high resolution experimental measurements performed at the SOLEIL synchrotron facility. These are compared with theoretical spectra calculated using coupled cluster theory and algebraic diagrammatic construction theory. The coupled cluster singles and doubles with perturbative triples model known as CC3 is shown to accurately reproduce the experimental excitation energies as well as the spacing of the vibrational transitions. In conclusion, the computationalmore » results are also shown to be systematically improved within the coupled cluster hierarchy, with the coupled cluster singles, doubles, triples, and quadruples method faithfully reproducing the experimental vibrational structure.« less

Blue stragglers in the core of the globular cluster 47 Tucanae

NASA Technical Reports Server (NTRS)

Paresce, F.; Meylan, G.; Shara, M.; Baxter, D.; Greenfield, P.

1991-01-01

High-resolution observations of the core of the globular cluster 47 Tucanae with the Faint Object Camera on the Hubble Space Telescope reveal a high density of 'blue straggler' stars, occupying the upper end of the main sequence from which all stars in the cluster should have long since evolved. Their presence in the dense core supports the hypothesis that they formed by stellar collision and coalescence, and, as the heaviest objects in the cluster, have drifted to the core.

Determination of Cluster Distances from Chandra Imaging Spectroscopy and Sunyaev-Zeldovich Effect Measurements. I; Analysis Methods and Initial Results

NASA Technical Reports Server (NTRS)

Bonamente, Massimiliano; Joy, Marshall K.; Carlstrom, John E.; LaRoque, Samuel J.

2004-01-01

X-ray and Sunyaev-Zeldovich Effect data ca,n be combined to determine the distance to galaxy clusters. High-resolution X-ray data are now available from the Chandra Observatory, which provides both spatial and spectral information, and interferometric radio measurements of the Sunyam-Zeldovich Effect are available from the BIMA and 0VR.O arrays. We introduce a Monte Carlo Markov chain procedure for the joint analysis of X-ray and Sunyaev-Zeldovich Effect data. The advantages of this method are the high computational efficiency and the ability to measure the full probability distribution of all parameters of interest, such as the spatial and spectral properties of the cluster gas and the cluster distance. We apply this technique to the Chandra X-ray data and the OVRO radio data for the galaxy cluster Abell 611. Comparisons with traditional likelihood-ratio methods reveal the robustness of the method. This method will be used in a follow-up paper to determine the distance of a large sample of galaxy clusters for which high-resolution Chandra X-ray and BIMA/OVRO radio data are available.

Massively parallel unsupervised single-particle cryo-EM data clustering via statistical manifold learning

PubMed Central

Wu, Jiayi; Ma, Yong-Bei; Congdon, Charles; Brett, Bevin; Chen, Shuobing; Xu, Yaofang; Ouyang, Qi

2017-01-01

Structural heterogeneity in single-particle cryo-electron microscopy (cryo-EM) data represents a major challenge for high-resolution structure determination. Unsupervised classification may serve as the first step in the assessment of structural heterogeneity. However, traditional algorithms for unsupervised classification, such as K-means clustering and maximum likelihood optimization, may classify images into wrong classes with decreasing signal-to-noise-ratio (SNR) in the image data, yet demand increased computational costs. Overcoming these limitations requires further development of clustering algorithms for high-performance cryo-EM data processing. Here we introduce an unsupervised single-particle clustering algorithm derived from a statistical manifold learning framework called generative topographic mapping (GTM). We show that unsupervised GTM clustering improves classification accuracy by about 40% in the absence of input references for data with lower SNRs. Applications to several experimental datasets suggest that our algorithm can detect subtle structural differences among classes via a hierarchical clustering strategy. After code optimization over a high-performance computing (HPC) environment, our software implementation was able to generate thousands of reference-free class averages within hours in a massively parallel fashion, which allows a significant improvement on ab initio 3D reconstruction and assists in the computational purification of homogeneous datasets for high-resolution visualization. PMID:28786986

Massively parallel unsupervised single-particle cryo-EM data clustering via statistical manifold learning.

PubMed

Wu, Jiayi; Ma, Yong-Bei; Congdon, Charles; Brett, Bevin; Chen, Shuobing; Xu, Yaofang; Ouyang, Qi; Mao, Youdong

2017-01-01

Structural heterogeneity in single-particle cryo-electron microscopy (cryo-EM) data represents a major challenge for high-resolution structure determination. Unsupervised classification may serve as the first step in the assessment of structural heterogeneity. However, traditional algorithms for unsupervised classification, such as K-means clustering and maximum likelihood optimization, may classify images into wrong classes with decreasing signal-to-noise-ratio (SNR) in the image data, yet demand increased computational costs. Overcoming these limitations requires further development of clustering algorithms for high-performance cryo-EM data processing. Here we introduce an unsupervised single-particle clustering algorithm derived from a statistical manifold learning framework called generative topographic mapping (GTM). We show that unsupervised GTM clustering improves classification accuracy by about 40% in the absence of input references for data with lower SNRs. Applications to several experimental datasets suggest that our algorithm can detect subtle structural differences among classes via a hierarchical clustering strategy. After code optimization over a high-performance computing (HPC) environment, our software implementation was able to generate thousands of reference-free class averages within hours in a massively parallel fashion, which allows a significant improvement on ab initio 3D reconstruction and assists in the computational purification of homogeneous datasets for high-resolution visualization.

Probing high-redshift clusters with HST/ACS gravitational weak-lensing and Chandra x-ray observations

NASA Astrophysics Data System (ADS)

Jee, Myungkook James

2006-06-01

Clusters of galaxies, the largest gravitationally bound objects in the Universe, are useful tracers of cosmic evolution, and particularly detailed studies of still-forming clusters at high-redshifts can considerably enhance our understanding of the structure formation. We use two powerful methods that have become recently available for the study of these distant clusters: spaced- based gravitational weak-lensing and high-resolution X-ray observations. Detailed analyses of five high-redshift (0.8 < z < 1.3) clusters are presented based on the deep Advanced Camera for Surveys (ACS) and Chandra X-ray images. We show that, when the instrumental characteristics are properly understood, the newly installed ACS on the Hubble Space Telescope (HST) can detect subtle shape distortions of background galaxies down to the limiting magnitudes of the observations, which enables the mapping of the cluster dark matter in unprecedented high-resolution. The cluster masses derived from this HST /ACS weak-lensing study have been compared with those from the re-analyses of the archival Chandra X-ray data. We find that there are interesting offsets between the cluster galaxy, intracluster medium (ICM), and dark matter centroids, and possible scenarios are discussed. If the offset is confirmed to be uniquitous in other clusters, the explanation may necessitate major refinements in our current understanding of the nature of dark matter, as well as the cluster galaxy dynamics. CL0848+4452, the highest-redshift ( z = 1.27) cluster yet detected in weak-lensing, has a significant discrepancy between the weak- lensing and X-ray masses. If this trend is found to be severe and common also for other X-ray weak clusters at redshifts beyond the unity, the conventional X-ray determination of cluster mass functions, often inferred from their immediate X-ray properties such as the X-ray luminosity and temperature via the so-called mass-luminosity (M-L) and mass-temperature (M-T) relations, will become highly unstable in this redshift regime. Therefore, the relatively unbiased weak-lensing measurements of the cluster mass properties can be used to adequately calibrate the scaling relations in future high-redshift cluster investigations.

Cluster analysis of bone microarchitecture from high resolution peripheral quantitative computed tomography demonstrates two separate phenotypes associated with high fracture risk in men and women.

PubMed

Edwards, M H; Robinson, D E; Ward, K A; Javaid, M K; Walker-Bone, K; Cooper, C; Dennison, E M

2016-07-01

Osteoporosis is a major healthcare problem which is conventionally assessed by dual energy X-ray absorptiometry (DXA). New technologies such as high resolution peripheral quantitative computed tomography (HRpQCT) also predict fracture risk. HRpQCT measures a number of bone characteristics that may inform specific patterns of bone deficits. We used cluster analysis to define different bone phenotypes and their relationships to fracture prevalence and areal bone mineral density (BMD). 177 men and 159 women, in whom fracture history was determined by self-report and vertebral fracture assessment, underwent HRpQCT of the distal radius and femoral neck DXA. Five clusters were derived with two clusters associated with elevated fracture risk. "Cluster 1" contained 26 women (50.0% fractured) and 30 men (50.0% fractured) with a lower mean cortical thickness and cortical volumetric BMD, and in men only, a mean total and trabecular area more than the sex-specific cohort mean. "Cluster 2" contained 20 women (50.0% fractured) and 14 men (35.7% fractured) with a lower mean trabecular density and trabecular number than the sex-specific cohort mean. Logistic regression showed fracture rates in these clusters to be significantly higher than the lowest fracture risk cluster [5] (p<0.05). Mean femoral neck areal BMD was significantly lower than cluster 5 in women in cluster 1 and 2 (p<0.001 for both), and in men, in cluster 2 (p<0.001) but not 1 (p=0.220). In conclusion, this study demonstrates two distinct high risk clusters in both men and women which may differ in etiology and response to treatment. As cluster 1 in men does not have low areal BMD, these men may not be identified as high risk by conventional DXA alone. Copyright © 2016. Published by Elsevier Inc.

HIGH-RESOLUTION IMAGES OF ORBITAL MOTION IN THE ORION TRAPEZIUM CLUSTER WITH THE LBT AO SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Close, L. M.; Males, J. R.; Skemer, A.

2012-04-20

The new 8.4 m LBT adaptive secondary AO system, with its novel pyramid wavefront sensor, was used to produce very high Strehl ({approx}> 75% at 2.16 {mu}m) near-infrared narrowband (Br{gamma}: 2.16 {mu}m and [Fe II]: 1.64 {mu}m) images of 47 young ({approx}1 Myr) Orion Trapezium {theta}{sup 1} Ori cluster members. The inner {approx}41 Multiplication-Sign 53'' of the cluster was imaged at spatial resolutions of {approx}0.''050 (at 1.64 {mu}m). A combination of high spatial resolution and high S/N yielded relative binary positions to {approx}0.5 mas accuracies. Including previous speckle data, we analyze a 15 year baseline of high-resolution observations of thismore » cluster. We are now sensitive to relative proper motions of just {approx}0.3 mas yr{sup -1} (0.6 km s{sup -1} at 450 pc); this is a {approx}7 Multiplication-Sign improvement in orbital velocity accuracy compared to previous efforts. We now detect clear orbital motions in the {theta}{sup 1} Ori B{sub 2} B{sub 3} system of 4.9 {+-} 0.3 km s{sup -1} and 7.2 {+-} 0.8 km s{sup -1} in the {theta}{sup 1} Ori A{sub 1} A{sub 2} system (with correlations of P.A. versus time at >99% confidence). All five members of the {theta}{sup 1} Ori B system appear likely a gravitationally bound 'mini-cluster'. The very lowest mass member of the {theta}{sup 1} Ori B system (B{sub 4}; mass {approx}0.2 M{sub Sun }) has, for the first time, a clearly detected motion (at 4.3 {+-} 2.0 km s{sup -1}; correlation = 99.7%) w.r.t. B{sub 1}. However, B{sub 4} is most likely in a long-term unstable (non-hierarchical) orbit and may 'soon' be ejected from this 'mini-cluster'. This 'ejection' process could play a major role in the formation of low-mass stars and brown dwarfs.« less

Source Identification of PM2.5 in Steubenville, Ohio Using a Hybrid Method for Highly Time-resolved Data

EPA Science Inventory

A new source-type identification method, Reduction and Species Clustering Using Episodes (ReSCUE), was developed to exploit the temporal synchronicity between species to form clusters of species that vary together. High time-resolution (30 min) PM_2.5 sampling was condu...

The first high resolution image of coronal gas in a starbursting cool core cluster

NASA Astrophysics Data System (ADS)

Johnson, Sean

2017-08-01

Galaxy clusters represent a unique laboratory for directly observing gas cooling and feedback due to their high masses and correspondingly high gas densities and temperatures. Cooling of X-ray gas observed in 1/3 of clusters, known as cool-core clusters, should fuel star formation at prodigious rates, but such high levels of star formation are rarely observed. Feedback from active galactic nuclei (AGN) is a leading explanation for the lack of star formation in most cool clusters, and AGN power is sufficient to offset gas cooling on average. Nevertheless, some cool core clusters exhibit massive starbursts indicating that our understanding of cooling and feedback is incomplete. Observations of 10^5 K coronal gas in cool core clusters through OVI emission offers a sensitive means of testing our understanding of cooling and feedback because OVI emission is a dominant coolant and sensitive tracer of shocked gas. Recently, Hayes et al. 2016 demonstrated that synthetic narrow-band imaging of OVI emission is possible through subtraction of long-pass filters with the ACS+SBC for targets at z=0.23-0.29. Here, we propose to use this exciting new technique to directly image coronal OVI emitting gas at high resolution in Abell 1835, a prototypical starbursting cool-core cluster at z=0.252. Abell 1835 hosts a strong cooling core, massive starburst, radio AGN, and at z=0.252, it offers a unique opportunity to directly image OVI at hi-res in the UV with ACS+SBC. With just 15 orbits of ACS+SBC imaging, the proposed observations will complete the existing rich multi-wavelength dataset available for Abell 1835 to provide new insights into cooling and feedback in clusters.

High-resolution X-ray spectroscopy of M87 with the Einstein observatory - The detection of an O VIII emission line

NASA Technical Reports Server (NTRS)

Canizares, C. R.; Clark, G. W.; Markert, T. H.; Berg, C.; Smedira, M.; Bardas, D.; Schnopper, H.; Kalata, K.

1979-01-01

The paper deals with high-resolution X-ray spectroscopy performed to study the extended source surrounding the giant elliptical galaxy, M87, in the Virgo cluster. From observations carried out with a focal plane crystal spectrometer, L-alpha emission was detected from hydrogenic oxygen (O VIII). Upper limits could be set on lines from intermediate ionization states of iron. The presence of a quantity of cooler matter surrounding M87 was revealed, which has important implications for cluster models and favors a radiatively controlled accretion mechanism.

The X-ray structure of a galaxy cluster at z = 0.54 - Implications for cluster evolution and cosmology

NASA Technical Reports Server (NTRS)

White, S. D. M.; Silk, J.; Henry, J. P.

1981-01-01

High-resolution X-ray observations of the rich cluster 0016+16 at a redshift of 0.541 are presented. The emitting gas in this cluster is hot and extremely luminous, and its structure resembles that seen in the brightest nearby cluster sources. In most of its properties, 0016+16 resembles a richer version of the Coma cluster, and it offers little support to the hypothesis that clusters at z greater than 0.5 differ fundamentally from nearer objects.

High Resolution Diffusion Tensor Imaging of Cortical-Subcortical White Matter Tracts in TBI

DTIC Science & Technology

2010-10-01

by the individual (e.g., car full of lettuce ) or words that share phonemic qualities (e.g., chair/cat; sofa/soup). The observed bidirectional...subjective clustering score minus the expected subjective clustering score. An example is if the word pair car/ lettuce (subjective observed score of 1) is...adjusted subjective clustering formula of observed subjective clustering (car/ lettuce , subjective observed score of 1) minus expected subjective

Feedback in the Antennae Galaxies (NGC 4038/9): I. High-Resolution Infrared Spectroscopy of Winds from Super Star Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert, A; Graham, J

2007-06-05

We present high-resolution (R {approx} 24,600) near-IR spectroscopy of the youngest super star clusters (SSCs) in the prototypical starburst merger, the Antennae Galaxies. These SSCs are young (3-7 Myr old) and massive (10{sup 5}-10{sup 7} M{sub {circle_dot}} for a Kroupa IMF) and their spectra are characterized by broad, extended Brackett {gamma} emission, so we refer to them as emission-line clusters (ELCs) to distinguish them from older SSCs. The Br {gamma} lines of most ELCs have supersonic widths (60-110 km s{sup -1} FWHM) and non-Gaussian wings whose velocities exceed the clusters escape velocities. This high-velocity unbound gas is flowing out inmore » winds that are powered by the clusters massive O and W-R stars over the course of at least several crossing times. The large sizes of some ELCs relative to those of older SSCs may be due to expansion caused by these outflows; many of the ELCs may not survive as bound stellar systems, but rather dissipate rapidly into the field population. The observed tendency of older ELCs to be more compact than young ones is consistent with the preferential survival of the most concentrated clusters at a given age.« less

Inorganic material profiling using Arn+ cluster: Can we achieve high quality profiles?

NASA Astrophysics Data System (ADS)

Conard, T.; Fleischmann, C.; Havelund, R.; Franquet, A.; Poleunis, C.; Delcorte, A.; Vandervorst, W.

2018-06-01

Retrieving molecular information by sputtering of organic systems has been concretized in the last years due to the introduction of sputtering by large gas clusters which drastically eliminated the compound degradation during the analysis and has led to strong improvements in depth resolution. Rapidly however, a limitation was observed for heterogeneous systems where inorganic layers or structures needed to be profiled concurrently. As opposed to organic material, erosion of the inorganic layer appears very difficult and prone to many artefacts. To shed some light on these problems we investigated a simple system consisting of aluminum delta layer(s) buried in a silicon matrix in order to define the most favorable beam conditions for practical analysis. We show that counterintuitive to the small energy/atom used and unlike monoatomic ion sputtering, the information depth obtained with large cluster ions is typically very large (∼10 nm) and that this can be caused both by a large roughness development at early stages of the sputtering process and by a large mixing zone. As a consequence, a large deformation of the Al intensity profile is observed. Using sample rotation during profiling significantly improves the depth resolution while sample temperature has no significant effect. The determining parameter for high depth resolution still remains the total energy of the cluster instead of the energy per atom in the cluster.

High-resolution Spectroscopic Abundances of Red Giant Branch Stars in NGC 6584 and NGC 7099

NASA Astrophysics Data System (ADS)

O’Malley, Erin M.; Chaboyer, Brian

2018-04-01

We obtain high-resolution spectra of red giant branch stars in NGC 6584 and NGC 7099 to perform a detailed abundance analysis. We confirm cluster membership for these stars based on consistent radial velocities measured in this study and small pixel offsets between the observations of Sarajedini et al. and Piotto et al. We find mean metallicities of [Fe/H] = ‑1.53 ± 0.08 dex and [Fe/H] = ‑2.29 ± 0.07 dex for NGC 6584 and NGC 7099, respectively. We also find these clusters to be enhanced in their [α/Fe] ratios, consistent with what is expected for metal-poor globular clusters. Additionally, we find evidence of a statistically significant Na–O anti-correlation in both clusters. Finally, with the use of HST photometry, we compare the location of the enhanced and pristine populations in chromosome maps of the clusters to confirm previous photometric evidence of multiple stellar populations. Although we cannot confirm the nature of the polluter stars responsible for the abundance differences, our results can be used to constrain pollution models.

Modeling and analysis of the spectrum of the globular cluster NGC 2419

NASA Astrophysics Data System (ADS)

Sharina, M. E.; Shimansky, V. V.; Davoust, E.

2013-06-01

The properties of the stellar population of the unusual object NGC 2419 are studied; this is the most distant high-mass globular cluster of the Galaxy's outer halo, and a spectrum taken with the 1.93-m telescope of the Haute Provence Observatory displays elemental abundance anomalies. Since traditional high-resolution spectroscopicmethods are applicable to bright stars only, spectroscopic information for the cluster's stellar population as a whole, integrated along the spectrograph slit placed in various positions, is used. Population synthesis is carried out for the spectrum of NGC 2419 using synthetic spectra calculated from a grid of stellar model atmospheres, based on the theoretical isochrone from the literature that best fits the color-magnitude diagram of the cluster. The derived age (12.6 billion years), metallicity ([Fe/H] = -2.25 dex), and abundances of helium ( Y = 0.26) and other chemical elements (a total of 14) are in a good qualitative agreement with estimates from the literature made from high-resolution spectra of eight red giants in the cluster. The influence on the spectrum of deviations from local thermodynamic equilibrium is considered for several elements. The derived abundance of α-elements ([ α/Fe] = 0.13 dex, as the mean of [O/Fe], [Mg/Fe], and [Ca/Fe]) differs from the mean value in the literature ([ α/Fe] = 0.4 for the eight brightest red giants) and may be explained by recently discovered in NGC2419 large [a/Fe] dispersion. Further studies of the integrated properties of the stellar population in NGC 2419 using higher-resolution spectrographs in various wavelength ranges should help improve our understanding of the cluster's chemical anomalies.

Precipitation Cluster Distributions: Current Climate Storm Statistics and Projected Changes Under Global Warming

NASA Astrophysics Data System (ADS)

Quinn, Kevin Martin

The total amount of precipitation integrated across a precipitation cluster (contiguous precipitating grid cells exceeding a minimum rain rate) is a useful measure of the aggregate size of the disturbance, expressed as the rate of water mass lost or latent heat released, i.e. the power of the disturbance. Probability distributions of cluster power are examined during boreal summer (May-September) and winter (January-March) using satellite-retrieved rain rates from the Tropical Rainfall Measuring Mission (TRMM) 3B42 and Special Sensor Microwave Imager and Sounder (SSM/I and SSMIS) programs, model output from the High Resolution Atmospheric Model (HIRAM, roughly 0.25-0.5 0 resolution), seven 1-2° resolution members of the Coupled Model Intercomparison Project Phase 5 (CMIP5) experiment, and National Center for Atmospheric Research Large Ensemble (NCAR LENS). Spatial distributions of precipitation-weighted centroids are also investigated in observations (TRMM-3B42) and climate models during winter as a metric for changes in mid-latitude storm tracks. Observed probability distributions for both seasons are scale-free from the smallest clusters up to a cutoff scale at high cluster power, after which the probability density drops rapidly. When low rain rates are excluded by choosing a minimum rain rate threshold in defining clusters, the models accurately reproduce observed cluster power statistics and winter storm tracks. Changes in behavior in the tail of the distribution, above the cutoff, are important for impacts since these quantify the frequency of the most powerful storms. End-of-century cluster power distributions and storm track locations are investigated in these models under a "business as usual" global warming scenario. The probability of high cluster power events increases by end-of-century across all models, by up to an order of magnitude for the highest-power events for which statistics can be computed. For the three models in the suite with continuous time series of high resolution output, there is substantial variability on when these probability increases for the most powerful precipitation clusters become detectable, ranging from detectable within the observational period to statistically significant trends emerging only after 2050. A similar analysis of National Centers for Environmental Prediction (NCEP) Reanalysis 2 and SSM/I-SSMIS rain rate retrievals in the recent observational record does not yield reliable evidence of trends in high-power cluster probabilities at this time. Large impacts to mid-latitude storm tracks are projected over the West Coast and eastern North America, with no less than 8 of the 9 models examined showing large increases by end-of-century in the probability density of the most powerful storms, ranging up to a factor of 6.5 in the highest range bin for which historical statistics are computed. However, within these regional domains, there is considerable variation among models in pinpointing exactly where the largest increases will occur.

AMOEBA clustering revisited. [cluster analysis, classification, and image display program

NASA Technical Reports Server (NTRS)

Bryant, Jack

1990-01-01

A description of the clustering, classification, and image display program AMOEBA is presented. Using a difficult high resolution aircraft-acquired MSS image, the steps the program takes in forming clusters are traced. A number of new features are described here for the first time. Usage of the program is discussed. The theoretical foundation (the underlying mathematical model) is briefly presented. The program can handle images of any size and dimensionality.

Massive Binaries in the R 136 Cluster

NASA Astrophysics Data System (ADS)

Morrell, N. I.; Massey, P.; Degioia-Eastwood, K.; Penny, L. R.; Gies, D. R.; Tsitkin, Y.; Darnell, E.

2008-08-01

As part of a large project aimed to the discovery and follow up of massive eclipsing systems in young clusters and stellar associations, we have obtained V-band CCD imaging of the R136 cluster in 30 Doradus, and high resolution spectroscopy of several among the variable stars we found there. Here we summarize our preliminary analysis of light and radial velocity variations for 4 massive multiple systems in the R136 cluster.

Deformation band clusters on Mars and implications for subsurface fluid flow

USGS Publications Warehouse

Okubo, C.H.; Schultz, R.A.; Chan, M.A.; Komatsu, G.

2009-01-01

High-resolution imagery reveals unprecedented lines of evidence for the presence of deformation band clusters in layered sedimentary deposits in the equatorial region of Mars. Deformation bands are a class of geologic structural discontinuity that is a precursor to faults in clastic rocks and soils. Clusters of deformation bands, consisting of many hundreds of individual subparallel bands, can act as important structural controls on subsurface fluid flow in terrestrial reservoirs, and evidence of diagenetic processes is often preserved along them. Deformation band clusters are identified on Mars based on characteristic meter-scale architectures and geologic context as observed in data from the High-Resolution Imaging Science Experiment (HiRISE) camera. The identification of deformation band clusters on Mars is a key to investigating the migration of fluids between surface and subsurface reservoirs in the planet's vast sedimentary deposits. Similar to terrestrial examples, evidence of diagenesis in the form of light- and dark-toned discoloration and wall-rock induration is recorded along many of the deformation band clusters on Mars. Therefore, these structures are important sites for future exploration and investigations into the geologic history of water and water-related processes on Mars. ?? 2008 Geological Society of America.

Low cost, high performance processing of single particle cryo-electron microscopy data in the cloud.

PubMed

Cianfrocco, Michael A; Leschziner, Andres E

2015-05-08

The advent of a new generation of electron microscopes and direct electron detectors has realized the potential of single particle cryo-electron microscopy (cryo-EM) as a technique to generate high-resolution structures. Calculating these structures requires high performance computing clusters, a resource that may be limiting to many likely cryo-EM users. To address this limitation and facilitate the spread of cryo-EM, we developed a publicly available 'off-the-shelf' computing environment on Amazon's elastic cloud computing infrastructure. This environment provides users with single particle cryo-EM software packages and the ability to create computing clusters with 16-480+ CPUs. We tested our computing environment using a publicly available 80S yeast ribosome dataset and estimate that laboratories could determine high-resolution cryo-EM structures for $50 to $1500 per structure within a timeframe comparable to local clusters. Our analysis shows that Amazon's cloud computing environment may offer a viable computing environment for cryo-EM.

An Introverted Starburst: Gas and SSC Formation in NGC 5253

NASA Astrophysics Data System (ADS)

Turner, J. L.; Beck, S. C.

2004-06-01

High resolution Brackett line spectroscopy with the Keck Telescope reveals relatively narrow recombination lines toward the embedded young super star cluster nebula in NGC 5253. The gas within this nebula is almost certainly gravitationally bound by the massive and compact young star cluster.

SZ observations to study the physics of the intra-cluster medium

NASA Astrophysics Data System (ADS)

Pointecouteau, E.

2017-10-01

Recent Sunyaev-Zeldovich surveys have delivered new catalogues of galaxy clusters over the whole sky and out to distant redshifts. The new generation of SZ facilities (NIKA, MUSTANG, ALMA) now focuses on high angular resolution and high sensitivity. I will discuss the current status of SZ observations and the perspective with the future instruments for the measurement of physical properties of galaxy clusters, and their relevance to the study of the ICM physics. I will also discuss the natural synergy between the SZ signal and the X-ray emission from the hot intra-cluster medium.

Star Clusters within FIRE

NASA Astrophysics Data System (ADS)

Perez, Adrianna; Moreno, Jorge; Naiman, Jill; Ramirez-Ruiz, Enrico; Hopkins, Philip F.

2017-01-01

In this work, we analyze the environments surrounding star clusters of simulated merging galaxies. Our framework employs Feedback In Realistic Environments (FIRE) model (Hopkins et al., 2014). The FIRE project is a high resolution cosmological simulation that resolves star forming regions and incorporates stellar feedback in a physically realistic way. The project focuses on analyzing the properties of the star clusters formed in merging galaxies. The locations of these star clusters are identified with astrodendro.py, a publicly available dendrogram algorithm. Once star cluster properties are extracted, they will be used to create a sub-grid (smaller than the resolution scale of FIRE) of gas confinement in these clusters. Then, we can examine how the star clusters interact with these available gas reservoirs (either by accreting this mass or blowing it out via feedback), which will determine many properties of the cluster (star formation history, compact object accretion, etc). These simulations will further our understanding of star formation within stellar clusters during galaxy evolution. In the future, we aim to enhance sub-grid prescriptions for feedback specific to processes within star clusters; such as, interaction with stellar winds and gas accretion onto black holes and neutron stars.

Geomorphological analysis of boulders and polygons on Martian periglacial patterned ground terrains

NASA Astrophysics Data System (ADS)

Orloff, Travis C.

Images from the High Resolution Imaging Science Experiment Camera onboard the Mars Reconnaisance Orbiter show the surface in higher detail than previously capable. I look at a landscape on Mars called permafrost patterned ground which covers ˜10 million square kilometers of the surface at high latitudes (>50°). Using the new high resolution images available we objectively characterize permafrost patterned ground terrains as an alternative to observational surveys which while detailed suffer from subjective bias. I take two dimensional Fourier transforms of individual images of Martian permafrost patterned ground to find the scale most representative of the terrain. This scale acts as a proxy for the size of the polygons themselves. Then I look at the distribution of spectral scales in the northern hemisphere between 50-70° and find correlations to previous studies and with the extent of ground ice in the surface. The high resolution images also show boulders clustering with respect to the underlying pattern. I make the first detailed observations of these clustered boulders and use crater counting to place constraints on the time it takes for boulders to cluster. Finally, I present a potential mechanism for the process that clusters the boulders that takes the specifics of the Martian environment to account. Boulders lying on the surface get trapped in seasonal CO2 frost while ice in the near surface contracts in the winter. The CO2 frost sublimates in spring/summer allowing the boulders to move when the near surface ice expands in summer. Repeated iterations lead to boulders that cluster in the polygon edges. Using a thermal model of the subsurface with Mars conditions and an elastic model of a polygon I show boulders could move as much as ˜0.1mm per year in the present day.

Advanced Solar Observatory (ASO) accommodations requirements study

NASA Technical Reports Server (NTRS)

1989-01-01

Results of an accommodations analysis for the Advanced Solar Observatory on Space Station Freedom are reported. Concepts for the High Resolution Telescope Cluster, Pinhole/Occulter Facility, and High Energy Cluster were developed which can be accommodated on Space Station Freedom. It is shown that workable accommodations concepts are possible. Areas of emphasis for the next stage of engineering development are identified.

Ultra high resolution molecular beam cars spectroscopy with application to planetary atmospheric molecules

NASA Technical Reports Server (NTRS)

Byer, R. L.

1982-01-01

The measurement of high resolution pulsed and continuous wave (CW) coherent anti-Stokes Raman spectroscopy (CARS) measurements in pulsed and steady state supersonic expansions were demonstrated. Pulsed molecular beam sources were characterized, and saturation of a Raman transition and, for the first time, the Raman spectrum of a complex molecular cluster were observed. The observation of CW CARS spectra in a molecular expansion and the effects of transit time broadening is described. Supersonic expansion is established as a viable technique for high resolution Raman spectroscopy of cold molecules with resolutions of 100 MH2.

Graphics Processing Unit (GPU) Acceleration of the Goddard Earth Observing System Atmospheric Model

NASA Technical Reports Server (NTRS)

Putnam, Williama

2011-01-01

The Goddard Earth Observing System 5 (GEOS-5) is the atmospheric model used by the Global Modeling and Assimilation Office (GMAO) for a variety of applications, from long-term climate prediction at relatively coarse resolution, to data assimilation and numerical weather prediction, to very high-resolution cloud-resolving simulations. GEOS-5 is being ported to a graphics processing unit (GPU) cluster at the NASA Center for Climate Simulation (NCCS). By utilizing GPU co-processor technology, we expect to increase the throughput of GEOS-5 by at least an order of magnitude, and accelerate the process of scientific exploration across all scales of global modeling, including: The large-scale, high-end application of non-hydrostatic, global, cloud-resolving modeling at 10- to I-kilometer (km) global resolutions Intermediate-resolution seasonal climate and weather prediction at 50- to 25-km on small clusters of GPUs Long-range, coarse-resolution climate modeling, enabled on a small box of GPUs for the individual researcher After being ported to the GPU cluster, the primary physics components and the dynamical core of GEOS-5 have demonstrated a potential speedup of 15-40 times over conventional processor cores. Performance improvements of this magnitude reduce the required scalability of 1-km, global, cloud-resolving models from an unfathomable 6 million cores to an attainable 200,000 GPU-enabled cores.

Dust-enshrouded super star-clusters

NASA Astrophysics Data System (ADS)

Sauvage, Marc; Plante, Stéphanie

2003-04-01

With the advent of either sensitive space-born infrared cameras, or their high-resolution ground-based siblings, we are uncovering a new category of star clusters: the dust-enshrouded super-star clusters. These manifest themselves only beyond a few microns, as their shroud of dust is able to block all light emitted by the stars themselves. Here we present our results on the spectacular cluster in SBS 0335-052, a very metal-poor galaxy. We also point to the growing number of galaxy analogs to SBS 0335-052, revealing the possibility that these clusters signal a major mode of star formation in starbursts. We conclude by listing a number of open points these clusters raise, in particular with respect to high-redshift counterparts.

Emerging Massive Star Clusters Revealed: High-Resolution Imaging of NGC 4449 from the Radio to the Ultraviolet

NASA Astrophysics Data System (ADS)

Reines, Amy E.; Johnson, Kelsey E.; Goss, W. M.

2008-06-01

We present a multi-wavelength study of embedded massive clusters in the nearby (3.9 Mpc) starburst galaxy NGC 4449 in an effort to uncover the earliest phases of massive cluster evolution. By combining high-resolution imaging from the radio to the ultraviolet, we reveal these clusters to be in the process of emerging from their gaseous and dusty birth cocoons. We use Very Large Array (VLA) observations at centimeter wavelengths to identify young clusters surrounded by ultra-dense H II regions, detectable via their production of thermal free-free radio continuum. Ultraviolet, optical and infrared observations are obtained from the Hubble and Spitzer Space Telescope archives for comparison. We detect 39 compact radio sources toward NGC 4449 at 3.6 cm using the highest resolution (1farcs3) and sensitivity (~12 μJy) VLA image of the galaxy to date. We reliably identify 13 thermal radio sources and derive their physical properties using both nebular emission from the H II regions and spectral energy distribution fitting to the stellar continuum. These radio-detected clusters have ages lsim5 Myr and stellar masses of order 104 M sun. The measured extinctions are quite low: 12 of the 13 thermal radio sources have A V lsim 1.5, while the most obscured source has A V ≈ 4.3. By combining results from the nebular and stellar emission, we find an I-band excess that is anti-correlated with cluster age and an apparent mass-age correlation. Additionally, we find evidence that local processes such as supernovae and stellar winds likely play an important role in triggering the current bursts of star formation within NGC 4449.

Globular Cluster Abundances from High-Resolution Integrated-Light Spectra. I. 47 Tuc

NASA Astrophysics Data System (ADS)

McWilliam, Andrew; Bernstein, Rebecca A.

2008-09-01

We describe the detailed chemical abundance analysis of a high-resolution (R ~ 35,000), integrated-light (IL), spectrum of the core of the Galactic globular cluster 47 Tuc, obtained using the du Pont echelle at Las Campanas. We develop an abundance analysis strategy that can be applied to spatial unresolved extragalactic clusters. We have computed abundances for Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Ba, La, Nd, and Eu. For an analysis with the known color-magnitude diagram (CMD) for 47 Tuc we obtain a mean [Fe/H] value of -0.75 +/- 0.026 +/- 0.045 dex (random and systematic error), in good agreement with the mean of five recent high-resolution abundance studies, at -0.70 dex. Typical random errors on our mean [X/Fe] ratios are 0.07-0.10 dex, similar to studies of individual stars in 47 Tuc. Na and Al appear enhanced, perhaps due to proton burning in the most luminous cluster stars. Our IL abundance analysis with an unknown CMD employed theoretical Teramo isochrones; however, we apply zero-point abundance corrections to account for the factor of 3 underprediction of stars at the AGB bump luminosity. While line diagnostics alone provide only mild constraints on the cluster age (ruling out ages younger than ~2 Gyr), when theoretical IL B - V colors are combined with metallicity derived from the Fe I lines, the age is constrained to 10-15 Gyr and we obtain [ Fe/H ] = - 0.70 +/- 0.021 +/- 0.052 dex. We find that Fe I line diagnostics may also be used to constrain the horizontal-branch morphology of an unresolved cluster. Lastly, our spectrum synthesis of 5.4 million TiO lines indicates that the 7300-7600 Å TiO window should be useful for estimating the effect of M giants on the IL abundances, and important for clusters more metal-rich than 47 Tuc.

Spectrum syntheses of high-resolution integrated light spectra of Galactic globular clusters

NASA Astrophysics Data System (ADS)

Sakari, Charli M.; Shetrone, Matthew; Venn, Kim; McWilliam, Andrew; Dotter, Aaron

2013-09-01

Spectrum syntheses for three elements (Mg, Na and Eu) in high-resolution integrated light spectra of the Galactic globular clusters 47 Tuc, M3, M13, NGC 7006 and M15 are presented, along with calibration syntheses of the solar and Arcturus spectra. Iron abundances in the target clusters are also derived from integrated light equivalent width analyses. Line profiles in the spectra of these five globular clusters are well fitted after careful consideration of the atomic and molecular spectral features, providing levels of precision that are better than equivalent width analyses of the same integrated light spectra, and that are comparable to the precision in individual stellar analyses. The integrated light abundances from the 5528 and 5711 Å Mg I lines, the 6154 and 6160 Å Na I lines, and the 6645 Å Eu II line fall within the observed ranges from individual stars; however, these integrated light abundances do not always agree with the average literature abundances. Tests with the second parameter clusters M3, M13 and NGC 7006 show that assuming an incorrect horizontal branch morphology is likely to have only a small ( ≲ 0.06 dex) effect on these Mg, Na and Eu abundances. These tests therefore show that integrated light spectrum syntheses can be applied to unresolved globular clusters over a wide range of metallicities and horizontal branch morphologies. Such high precision in integrated light spectrum syntheses is valuable for interpreting the chemical abundances of globular cluster systems around other galaxies.

Cold Fronts in Clusters of Galaxies: Observations and Modeling

NASA Technical Reports Server (NTRS)

Markevitch, Maxim

2012-01-01

Mergers of galaxy clusters -- some of the most energetic events in the Universe -- produce disturbances in hot intracluster medium, such as shocks and cold fronts, that can be used as tools to study the physics of galaxy clusters. Cold fronts may constrain viscosity and the structure and strength of the cluster magnetic fields. Combined with radio data, these observations also shed light on the production of ultrarelativistic particles that are known to coexist with the cluster thermal plasma. This talk will summarize the current X-ray observations of cluster mergers, as well as some recent radio data and high resolution hydrodynamic simulations.

Scanning Probe Platform | Materials Science | NREL

Science.gov Websites

level; this image obtained using a scanning tunneling microscope shows gray and white clusters of produce high-resolution color images or maps like this one obtained using scanning tunneling luminescence gray clusters. Gold substrate: (Left) STM image reveals the terraces of the H2 flamed substrate. (Right

HRI observations of the Pleiades

NASA Technical Reports Server (NTRS)

Harnden, F. R., Jr.; Caillault, J.-P.; Damiani, F.; Kashyap, V.; Micela, G.; Prosser, C.; Rosner, R.; Sciortino, S.; Stauffer, J.

1996-01-01

The preliminary analysis of the data from the first four Rosat high resolution imager (HRI) pointings provided many new faint Pleiades detections. The completion of the high resolution survey of the most source-confused regions of this open cluster will lead to the construction of proper X-ray luminosity functions and will yield a definitive assessment of the coronal emission of the Pleiades members.

Experimental proof of the existence of water clusters in fullerene-like PrF3 nanoparticles

NASA Astrophysics Data System (ADS)

Alakshin, E. M.; Blokhin, D. S.; Sabitova, A. M.; Klochkov, A. V.; Klochkov, V. V.; Kono, K.; Korableva, S. L.; Tagirov, M. S.

2012-10-01

Synthesized fullerene-like nanoparticles of the Van Vleck paramagnet PrF3 have been studied by nuclear magnetic resonance cryoporometry. Water clusters have been discovered in the internal cavities of the nanoparticles. The analysis of the experimental data indicates that the cluster radius is 1-2.3 nm. The obtained data agree well with the high-resolution transmission electron microscopy data.

The dynamics of cyclone clustering in re-analysis and a high-resolution climate model

NASA Astrophysics Data System (ADS)

Priestley, Matthew; Pinto, Joaquim; Dacre, Helen; Shaffrey, Len

2017-04-01

Extratropical cyclones have a tendency to occur in groups (clusters) in the exit of the North Atlantic storm track during wintertime, potentially leading to widespread socioeconomic impacts. The Winter of 2013/14 was the stormiest on record for the UK and was characterised by the recurrent clustering of intense extratropical cyclones. This clustering was associated with a strong, straight and persistent North Atlantic 250 hPa jet with Rossby wave-breaking (RWB) on both flanks, pinning the jet in place. Here, we provide for the first time an analysis of all clustered events in 36 years of the ERA-Interim Re-analysis at three latitudes (45˚ N, 55˚ N, 65˚ N) encompassing various regions of Western Europe. The relationship between the occurrence of RWB and cyclone clustering is studied in detail. Clustering at 55˚ N is associated with an extended and anomalously strong jet flanked on both sides by RWB. However, clustering at 65(45)˚ N is associated with RWB to the south (north) of the jet, deflecting the jet northwards (southwards). A positive correlation was found between the intensity of the clustering and RWB occurrence to the north and south of the jet. However, there is considerable spread in these relationships. Finally, analysis has shown that the relationships identified in the re-analysis are also present in a high-resolution coupled global climate model (HiGEM). In particular, clustering is associated with the same dynamical conditions at each of our three latitudes in spite of the identified biases in frequency and intensity of RWB.

The Outer Limits of Galaxy Clusters: Observations to the Virial Radius with Suzaku, XMM,and Chandra

NASA Technical Reports Server (NTRS)

Miller, Eric D.; Bautz, Marshall; George, Jithin; Mushotzky, Richard; Davis, David; Henry, J. Patrick

2012-01-01

The outskirts of galaxy clusters, near the virial radius, remain relatively unexplored territory and yet are vital to our understanding of cluster growth, structure, and mass. In this presentation, we show the first results from a program to constrain the sate of the outer intra-cluster medium (ICM) in a large sample of galaxy clusters, exploiting the strengths of three complementary X-ray observatories: Suzaku (low, stable background), XMM-Newton (high sensitivity),and Chandra (good spatial resolution). By carefully combining observations from the cluster core to beyond r200, we are able to identify and reduce systematic uncertainties that would impede our spatial and spectral analysis using a single telescope. Our sample comprises nine clusters at z is approximately 0.1-0.2 fully covered in azimuth to beyond r200, and our analysis indicates that the ICM is not in hydrostatic equilibrium in the cluster outskirts, where we see clear azimuthal variations in temperature and surface brightness. In one of the clusters, we are able to measure the diffuse X-ray emission well beyond r200, and we find that the entropy profile and the gas fraction are consistent with expectations from theory and numerical simulations. These results stand in contrast to recent studies which point to gas clumping in the outskirts; the extent to which differences of cluster environment or instrumental effects factor in this difference remains unclear. From a broader perspective, this project will produce a sizeable fiducial data set for detailed comparison with high-resolution numerical simulations.

Investigation of Damage with Cluster Ion Beam Irradiation Using HR-RBS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seki, Toshio; Aoki, Takaaki; Matsuo, Jiro

2008-11-03

Cluster ion beam can process targets with shallow damage because of the very low irradiation energy per atom. However, it is needed to investigate the damage with cluster ion beam irradiation, because recent applications demand process targets with ultra low damage. The shallow damage can be investigated from depth profiles of specific species before and after ion irradiation. They can be measured with secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectroscopy (RBS). High resolution Rutherford backscattering spectroscopy (HR-RBS) is a non destructive measurement method and depth profiles can be measured with nano-resolution. The cluster ion beam mixing of thinmore » Ni layer in carbon targets can be investigated with HR-RBS. The mixing depth with cluster ion irradiation at 10 keV was about 10 nm. The mixing depth with cluster ion irradiation at 1 keV and 5 keV were less than 1 nm and 5 nm, respectively. The number of displaced Ni atoms with cluster ion irradiation was very larger than that with monomer ion irradiation of same energy. This result shows that violent mixing occurs with single cluster impact.« less

Slow Photoelectron Velocity-Map Imaging of Cryogenically Cooled Anions

NASA Astrophysics Data System (ADS)

Weichman, Marissa L.; Neumark, Daniel M.

2018-04-01

Slow photoelectron velocity-map imaging spectroscopy of cryogenically cooled anions (cryo-SEVI) is a powerful technique for elucidating the vibrational and electronic structure of neutral radicals, clusters, and reaction transition states. SEVI is a high-resolution variant of anion photoelectron spectroscopy based on photoelectron imaging that yields spectra with energy resolution as high as 1-2 cm‑1. The preparation of cryogenically cold anions largely eliminates hot bands and dramatically narrows the rotational envelopes of spectral features, enabling the acquisition of well-resolved photoelectron spectra for complex and spectroscopically challenging species. We review the basis and history of the SEVI method, including recent experimental developments that have improved its resolution and versatility. We then survey recent SEVI studies to demonstrate the utility of this technique in the spectroscopy of aromatic radicals, metal and metal oxide clusters, nonadiabatic interactions between excited states of small molecules, and transition states of benchmark bimolecular reactions.

VizieR Online Data Catalog: H-band spectroscopic analysis of 25 bright M31 GCs (Sakari+, 2016)

NASA Astrophysics Data System (ADS)

Sakari, C. M.; Shetrone, M. D.; Schiavon, R. P.; Bizyaev, D.; Prieto, C. A.; Beers, T. C.; Caldwell, N.; Garcia-Hernandez, D. A.; Lucatello, S.; Majewski, S.; O'Connell, R. W.; Pan, K.; Strader, J.

2016-11-01

H-band spectra (1.51-1.69um) of the target clusters were obtained with the moderately high resolution (R=22500) APOGEE spectrograph on the 2.5m Telescope at Apache Point Observatory in 2011 and 2013. The details of the observations can be found in Majewski+ (2015arXiv150905420M) and Zasowski+ (2013AJ....146...81Z), including descriptions of the plates and fibers that were utilized for the observations. The high-resolution optical abundances from Colucci et al. (2009, J/ApJ/704/385 and 2014ApJ...797..116C) are supplemented with new results for five globular clusters (GCs). The new optical spectra were obtained in 2009 and 2010 with the High Resolution Spectrograph on the Hobby-Eberly Telescope at McDonald Observatory in Fort Davis, TX (R=30000; spectral coverage over ~5320-6290 and ~6360-7340Å in the blue and the red, respectively). (5 data files).

Effect of dose and size on defect engineering in carbon cluster implanted silicon wafers

NASA Astrophysics Data System (ADS)

Okuyama, Ryosuke; Masada, Ayumi; Shigematsu, Satoshi; Kadono, Takeshi; Hirose, Ryo; Koga, Yoshihiro; Okuda, Hidehiko; Kurita, Kazunari

2018-01-01

Carbon-cluster-ion-implanted defects were investigated by high-resolution cross-sectional transmission electron microscopy toward achieving high-performance CMOS image sensors. We revealed that implantation damage formation in the silicon wafer bulk significantly differs between carbon-cluster and monomer ions after implantation. After epitaxial growth, small and large defects were observed in the implanted region of carbon clusters. The electron diffraction pattern of both small and large defects exhibits that from bulk crystalline silicon in the implanted region. On the one hand, we assumed that the silicon carbide structure was not formed in the implanted region, and small defects formed because of the complex of carbon and interstitial silicon. On the other hand, large defects were hypothesized to originate from the recrystallization of the amorphous layer formed by high-dose carbon-cluster implantation. These defects are considered to contribute to the powerful gettering capability required for high-performance CMOS image sensors.

Low cost, high performance processing of single particle cryo-electron microscopy data in the cloud

PubMed Central

Cianfrocco, Michael A; Leschziner, Andres E

2015-01-01

The advent of a new generation of electron microscopes and direct electron detectors has realized the potential of single particle cryo-electron microscopy (cryo-EM) as a technique to generate high-resolution structures. Calculating these structures requires high performance computing clusters, a resource that may be limiting to many likely cryo-EM users. To address this limitation and facilitate the spread of cryo-EM, we developed a publicly available ‘off-the-shelf’ computing environment on Amazon's elastic cloud computing infrastructure. This environment provides users with single particle cryo-EM software packages and the ability to create computing clusters with 16–480+ CPUs. We tested our computing environment using a publicly available 80S yeast ribosome dataset and estimate that laboratories could determine high-resolution cryo-EM structures for $50 to $1500 per structure within a timeframe comparable to local clusters. Our analysis shows that Amazon's cloud computing environment may offer a viable computing environment for cryo-EM. DOI: http://dx.doi.org/10.7554/eLife.06664.001 PMID:25955969

Gas loss in simulated galaxies as they fall into clusters

PubMed Central

Cen, Renyue; Pop, Ana Roxana; Bahcall, Neta A.

2014-01-01

We use high-resolution cosmological hydrodynamic galaxy formation simulations to gain insights into how galaxies lose their cold gas at low redshift as they migrate from the field to the high-density regions of clusters of galaxies. We find that beyond three cluster virial radii, the fraction of gas-rich galaxies is constant, representing the field. Within three cluster-centric radii, the fraction of gas-rich galaxies declines steadily with decreasing radius, reaching <10% near the cluster center. Our results suggest galaxies start to feel the effect of the cluster environment on their gas content well beyond the cluster virial radius. We show that almost all gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits. Furthermore, we find that almost no galaxy moving outward at the cluster virial radius is gas-rich (with a gas-to-baryon ratio greater than 1%). These results suggest that galaxies that fall into clusters lose their cold gas within a single radial round-trip. PMID:24843167

Gas loss in simulated galaxies as they fall into clusters.

PubMed

Cen, Renyue; Pop, Ana Roxana; Bahcall, Neta A

2014-06-03

We use high-resolution cosmological hydrodynamic galaxy formation simulations to gain insights into how galaxies lose their cold gas at low redshift as they migrate from the field to the high-density regions of clusters of galaxies. We find that beyond three cluster virial radii, the fraction of gas-rich galaxies is constant, representing the field. Within three cluster-centric radii, the fraction of gas-rich galaxies declines steadily with decreasing radius, reaching <10% near the cluster center. Our results suggest galaxies start to feel the effect of the cluster environment on their gas content well beyond the cluster virial radius. We show that almost all gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits. Furthermore, we find that almost no galaxy moving outward at the cluster virial radius is gas-rich (with a gas-to-baryon ratio greater than 1%). These results suggest that galaxies that fall into clusters lose their cold gas within a single radial round-trip.

Use of ion-mobility mass spectrometry (IMS-MS) to map polyoxometalate Keplerate clusters and their supramolecular assemblies.

PubMed

Robbins, Philip J; Surman, Andrew J; Thiel, Johannes; Long, De-Liang; Cronin, Leroy

2013-03-07

We present the high-resolution (HRES-MS) and ion-mobility (IMS-MS) mass spectrometry studies of icosahedral nanoscale polyoxometalate-based {L(30)}{(Mo)Mo(5)} Keplerate clusters, and demonstrate the use of IMS-MS to resolve and map intact nanoclusters, and its potential for the discovery of new structures, in this case the first gas phase observation of 'proto-clustering' of higher order Keplerate supramolecular aggregates.

Ultraviolet gas absorption and dust extinction toward M8

NASA Technical Reports Server (NTRS)

Boggs, Don; Bohm-Vitense, Erika

1990-01-01

Interstellar absorption lines are analyzed using high-resolution IUE spectra of 11 stars in the young cluster NGC 6530 located in the M8 region. High-velocity clouds at -35 km/s and -60 km/s are seen toward all cluster stars. The components arise in gases that are part of large interstellar bubbles centered on the cluster and driven by stellar winds of the most luminous members. Absorption lines of species of different ionization states are separated in velocity. The velocity stratification is best explained as a 'champagne' flow of ionized gas away from the cluster. The C IV/Si IV ratios toward the hotter cluster members are consistent with simple photoionization models if the gas-phase C/Si ratio is increased by preferential accretion onto dust grains. High ion column densities in the central cluster decline with distance from W93, suggesting that radiation from a hot source near W93 has photoionized gas in the central cluster.

The First Non-Dispersive High-Resolution Spectroscopy of an X-ray-bright Galaxy Cluster

NASA Astrophysics Data System (ADS)

Yamaguchi, Hiroya; Hitomi Collaboration

2018-06-01

The Hitomi X-ray Observatory was equipped with the Soft X-ray Spectrometer (SXS), an X-ray microcalorimeter that achieved an energy resolution of 5 eV (@0.5-10 keV) for extended objects. This offered an unprecedented benchmark of atomic modeling and database for hot collisional plasmas, revealing both successes and challenges in the current atomic codes that are widely used by the X-ray astronomy community. I will review the Hitomi observations of the brightest part of the Perseus Cluster, whose X-ray spectrum is dominated by thermal emission from the intra-cluster medium (ICM). The SXS successfully measured the turbulent velocities and metal abundances of the ICM, which radically altered our understanding of the dynamics and chemical enrichment in this object. At the same time, the high-resolution X-ray data led to significant improvement in the atomic models, such as AtomDB and SPEX -- I will briefly overview how this improvement was made. Nevertheless, there are still significant discrepancies among the public atomic models, causing systematic uncertainties in measurements of the temperature, abundance, and degree of the resonance scattering. Requirements for future improvements will be summarized in this context.

VizieR Online Data Catalog: Trumpler 5 photometric BV catalog (Donati+, 2015)

NASA Astrophysics Data System (ADS)

Donati, P.; Cocozza, G.; Bragaglia, A.; Pancino, E.; Cantat-Gaudin, T.; Carrera, R.; Tosi, M.

2014-11-01

We combined high-quality photometric observations obtained with WFI and high-resolution spectra obtained with FLAMES to determine accurate cluster parameters, namely age, distance, reddening, and metallicity. (2 data files).

Single-particle cryo-EM-Improved ab initio 3D reconstruction with SIMPLE/PRIME.

PubMed

Reboul, Cyril F; Eager, Michael; Elmlund, Dominika; Elmlund, Hans

2018-01-01

Cryogenic electron microscopy (cryo-EM) and single-particle analysis now enables the determination of high-resolution structures of macromolecular assemblies that have resisted X-ray crystallography and other approaches. We developed the SIMPLE open-source image-processing suite for analysing cryo-EM images of single-particles. A core component of SIMPLE is the probabilistic PRIME algorithm for identifying clusters of images in 2D and determine relative orientations of single-particle projections in 3D. Here, we extend our previous work on PRIME and introduce new stochastic optimization algorithms that improve the robustness of the approach. Our refined method for identification of homogeneous subsets of images in accurate register substantially improves the resolution of the cluster centers and of the ab initio 3D reconstructions derived from them. We now obtain maps with a resolution better than 10 Å by exclusively processing cluster centers. Excellent parallel code performance on over-the-counter laptops and CPU workstations is demonstrated. © 2017 The Protein Society.

Implications of a High Angular Resolution Image of the Sunyaev-Zel'Dovich Effect in RXJ1347-1145

NASA Technical Reports Server (NTRS)

Mason, B. S.; Dicker, S. R.; Korngut, P. M.; Devlin, M.; Cotton, W. D.; Koch, P. M.; Molnar, S. M.; Sievers, J.; Aguirre, J. E.; Benford, D.;

Rapid Disaster Damage Estimation

NASA Astrophysics Data System (ADS)

Vu, T. T.

2012-07-01

The experiences from recent disaster events showed that detailed information derived from high-resolution satellite images could accommodate the requirements from damage analysts and disaster management practitioners. Richer information contained in such high-resolution images, however, increases the complexity of image analysis. As a result, few image analysis solutions can be practically used under time pressure in the context of post-disaster and emergency responses. To fill the gap in employment of remote sensing in disaster response, this research develops a rapid high-resolution satellite mapping solution built upon a dual-scale contextual framework to support damage estimation after a catastrophe. The target objects are building (or building blocks) and their condition. On the coarse processing level, statistical region merging deployed to group pixels into a number of coarse clusters. Based on majority rule of vegetation index, water and shadow index, it is possible to eliminate the irrelevant clusters. The remaining clusters likely consist of building structures and others. On the fine processing level details, within each considering clusters, smaller objects are formed using morphological analysis. Numerous indicators including spectral, textural and shape indices are computed to be used in a rule-based object classification. Computation time of raster-based analysis highly depends on the image size or number of processed pixels in order words. Breaking into 2 level processing helps to reduce the processed number of pixels and the redundancy of processing irrelevant information. In addition, it allows a data- and tasks- based parallel implementation. The performance is demonstrated with QuickBird images captured a disaster-affected area of Phanga, Thailand by the 2004 Indian Ocean tsunami are used for demonstration of the performance. The developed solution will be implemented in different platforms as well as a web processing service for operational uses.

ATCA observations of the MACS-Planck Radio Halo Cluster Project. II. Radio observations of an intermediate redshift cluster sample

NASA Astrophysics Data System (ADS)

Martinez Aviles, G.; Johnston-Hollitt, M.; Ferrari, C.; Venturi, T.; Democles, J.; Dallacasa, D.; Cassano, R.; Brunetti, G.; Giacintucci, S.; Pratt, G. W.; Arnaud, M.; Aghanim, N.; Brown, S.; Douspis, M.; Hurier, J.; Intema, H. T.; Langer, M.; Macario, G.; Pointecouteau, E.

2018-04-01

Aim. A fraction of galaxy clusters host diffuse radio sources whose origins are investigated through multi-wavelength studies of cluster samples. We investigate the presence of diffuse radio emission in a sample of seven galaxy clusters in the largely unexplored intermediate redshift range (0.3 < z < 0.44). Methods: In search of diffuse emission, deep radio imaging of the clusters are presented from wide band (1.1-3.1 GHz), full resolution ( 5 arcsec) observations with the Australia Telescope Compact Array (ATCA). The visibilities were also imaged at lower resolution after point source modelling and subtraction and after a taper was applied to achieve better sensitivity to low surface brightness diffuse radio emission. In case of non-detection of diffuse sources, we set upper limits for the radio power of injected diffuse radio sources in the field of our observations. Furthermore, we discuss the dynamical state of the observed clusters based on an X-ray morphological analysis with XMM-Newton. Results: We detect a giant radio halo in PSZ2 G284.97-23.69 (z = 0.39) and a possible diffuse source in the nearly relaxed cluster PSZ2 G262.73-40.92 (z = 0.421). Our sample contains three highly disturbed massive clusters without clear traces of diffuse emission at the observed frequencies. We were able to inject modelled radio haloes with low values of total flux density to set upper detection limits; however, with our high-frequency observations we cannot exclude the presence of RH in these systems because of the sensitivity of our observations in combination with the high z of the observed clusters. The reduced images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A94

Properties of the Open Cluster Tombaugh 1 from High-resolution Spectroscopy and uvbyCaHβ Photometry

NASA Astrophysics Data System (ADS)

Sales Silva, João V.; Carraro, Giovanni; Anthony-Twarog, Barbara J.; Moni Bidin, Christian; Costa, Edgardo; Twarog, Bruce A.

2016-01-01

Open clusters can be the key to deepening our knowledge on various issues involving the structure and evolution of the Galactic disk and details of stellar evolution because a cluster’s properties are applicable to all its members. However, the number of open clusters with detailed analysis from high-resolution spectroscopy or precision photometry imposes severe limitations on studies of these objects. To expand the number of open clusters with well-defined chemical abundances and fundamental parameters, we investigate the poorly studied, anticenter open cluster Tombaugh 1. Using precision uvbyCaHβ photometry and high-resolution spectroscopy, we derive the cluster’s reddening, obtain photometric metallicity estimates, and, for the first time, present a detailed abundance analysis of 10 potential cluster stars (nine clump stars and one Cepheid). Using the radial position from the cluster center and multiple color indices, we have isolated a sample of unevolved, probable single-star members of Tombaugh 1. From 51 stars, the cluster reddening is found to be E(b-y) = 0.221 ± 0.006 or E(B-V) = 0.303 ± 0.008, where the errors refer to the internal standard errors of the mean. The weighted photometric metallicity from m1 and hk is [Fe/H] = -0.10 ± 0.02, while a match to the Victoria-Regina Strömgren isochrones leads to an age of 0.95 ± 0.10 Gyr and an apparent modulus of (m-M) = 13.10 ± 0.10. Radial velocities identify six giants as probable cluster members, and the elemental abundances of Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Y, Ba, Ce, and Nd have been derived for both the cluster and the field stars. Tombaugh 1 appears to be a typical inner thin disk, intermediate-age open cluster of slightly subsolar metallicity, located just beyond the solar circle, with solar elemental abundance ratios except for the heavy s-process elements, which are a factor of two above solar. Its metallicity is consistent with a steep metallicity gradient in the galactocentric region between 9.5 and 12 kpc. Our study also shows that Cepheid XZ CMa is not a member of Tombaugh 1 and reveals that this Cepheid presents signs of barium enrichment, making it a probable binary star. Based on observations carried out at Las Campanas Observatory (program ID: CN2009B-042) and Cerro Tololo Inter-American Observatory.

A super resolution framework for low resolution document image OCR

NASA Astrophysics Data System (ADS)

Ma, Di; Agam, Gady

2013-01-01

Optical character recognition is widely used for converting document images into digital media. Existing OCR algorithms and tools produce good results from high resolution, good quality, document images. In this paper, we propose a machine learning based super resolution framework for low resolution document image OCR. Two main techniques are used in our proposed approach: a document page segmentation algorithm and a modified K-means clustering algorithm. Using this approach, by exploiting coherence in the document, we reconstruct from a low resolution document image a better resolution image and improve OCR results. Experimental results show substantial gain in low resolution documents such as the ones captured from video.

a Snapshot Survey of X-Ray Selected Central Cluster Galaxies

NASA Astrophysics Data System (ADS)

Edge, Alastair

1999-07-01

Central cluster galaxies are the most massive stellar systems known and have been used as standard candles for many decades. Only recently have central cluster galaxies been recognised to exhibit a wide variety of small scale {<100 pc} features that can only be reliably detected with HST resolution. The most intriguing of these are dust lanes which have been detected in many central cluster galaxies. Dust is not expected to survive long in the hostile cluster environment unless shielded by the ISM of a disk galaxy or very dense clouds of cold gas. WFPC2 snapshot images of a representative subset of the central cluster galaxies from an X-ray selected cluster sample would provide important constraints on the formation and evolution of dust in cluster cores that cannot be obtained from ground-based observations. In addition, these images will allow the AGN component, the frequency of multiple nuclei, and the amount of massive-star formation in central cluster galaxies to be ass es sed. The proposed HST observatio ns would also provide high-resolution images of previously unresolved gravitational arcs in the most massive clusters in our sample resulting in constraints on the shape of the gravitational potential of these systems. This project will complement our extensive multi-frequency work on this sample that includes optical spectroscopy and photometry, VLA and X-ray images for the majority of the 210 targets.

X-ray Optics Development at MSFC

NASA Technical Reports Server (NTRS)

Sharma, Dharma P.

2017-01-01

Development of high resolution focusing telescopes has led to a tremendous leap in sensitivity, revolutionizing observational X-ray astronomy. High sensitivity and high spatial resolution X-ray observations have been possible due to use of grazing incidence optics (paraboloid/hyperboloid) coupled with high spatial resolution and high efficiency detectors/imagers. The best X-ray telescope flown so far is mounted onboard Chandra observatory launched on July 23,1999. The telescope has a spatial resolution of 0.5 arc seconds with compatible imaging instruments in the energy range of 0.1 to 10 keV. The Chandra observatory has been responsible for a large number of discoveries and has provided X-ray insights on a large number of celestial objects including stars, supernova remnants, pulsars, magnetars, black holes, active galactic nuclei, galaxies, clusters and our own solar system.

Quantitative spectroscopic J-band study of red supergiants in Perseus OB-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gazak, J. Zachary; Kudritzki, Rolf; Davies, Ben

2014-06-10

We demonstrate how the metallicities of red supergiant (RSG) stars can be measured from quantitative spectroscopy down to resolutions of ≈3000 in the J-band. We have obtained high resolution spectra on a sample of the RSG population of h and χ Persei, a double cluster in the solar neighborhood. We show that careful application of the MARCS model atmospheres returns measurements of Z consistent with solar metallicity. Using two grids of synthetic spectra–one in pure LTE and one with non-LTE (NLTE) calculations for the most important diagnostic lines–we measure Z = +0.04 ± 0.10 (LTE) and Z = –0.04 ±more » 0.08 (NLTE) for the sample of eleven RSGs in the cluster. We degrade the spectral resolution of our observations and find that those values remain consistent down to resolutions of less than λ/δλ of 3000. Using measurements of effective temperatures we compare our results with stellar evolution theory and find good agreement. We construct a synthetic cluster spectrum and find that analyzing this composite spectrum with single-star RSG models returns an accurate metallicity. We conclude that the RSGs make ideal targets in the near infrared for measuring the metallicities of star forming galaxies out to 7-10 Mpc and up to 10 times farther by observing the integrated light of unresolved super star clusters.« less

Control of Chemical Effects in the Separation Process of a Differential Mobility / Mass Spectrometer System

PubMed Central

Schneider, Bradley B.; Coy, Stephen L.; Krylov, Evgeny V.; Nazarov, Erkinjon G.

2013-01-01

Differential mobility spectrometry (DMS) separates ions on the basis of the difference in their migration rates under high versus low electric fields. Several models describing the physical nature of this field mobility dependence have been proposed but emerging as a dominant effect is the clusterization model sometimes referred to as the dynamic cluster-decluster model. DMS resolution and peak capacity is strongly influenced by the addition of modifiers which results in the formation and dissociation of clusters. This process increases selectivity due to the unique chemical interactions that occur between an ion and neutral gas phase molecules. It is thus imperative to bring the parameters influencing the chemical interactions under control and find ways to exploit them in order to improve the analytical utility of the device. In this paper we describe three important areas that need consideration in order to stabilize and capitalize on the chemical processes that dominate a DMS separation. The first involves means of controlling the dynamic equilibrium of the clustering reactions with high concentrations of specific reagents. The second area involves a means to deal with the unwanted heterogeneous cluster ion populations emitted from the electrospray ionization process that degrade resolution and sensitivity. The third involves fine control of parameters that affect the fundamental collision processes, temperature and pressure. PMID:20065515

Cross-Contextual Variability in Parents' and School Tutors' Conflict Resolution Styles and Positive Development

ERIC Educational Resources Information Center

Rodríguez-Ruiz, Beatriz; Rodrigo, María José; Martínez-González, Raquel-Amaya

2015-01-01

The authors examined how the variability in adult conflict resolution styles in family and school contexts was related to adolescents' positive development. Cluster analysis classified 440 fathers, 440 mothers, and 125 tutors into 4 clusters, based on self-reports of their conflict resolution styles. Adolescents exposed to Cluster 1 (inconsistency…

High-resolution Spectroscopic Abundances of Red Giant Branch Stars in NGC 6681

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Malley, Erin M.; Chaboyer, Brian; Knaizev, Alexei

We obtain high-resolution spectra of nine red giant branch stars in NGC 6681 and perform the first detailed abundance analysis of stars in this cluster. We confirm cluster membership for these stars based on consistent radial velocities of 214.5 ± 3.7 km s{sup −1} and find a mean [Fe/H] = −1.63 ± 0.07 dex and [ α /Fe] = 0.42 ± 0.11 dex. Additionally, we confirm the existence of a Na–O anti-correlation in NGC 6681 and identify two populations of stars with unique abundance trends. With the use of HST photometry from Sarajedini et al. and Piotto et al. wemore » are able to identify these two populations as discrete sequences in the cluster CMD. Although we cannot confirm the nature of the polluter stars responsible for the abundance differences in these populations, these results do help put constraints on possible polluter candidates.« less

Massive star clusters in a z=1 star-forming galaxy seen at a 100 pc scale thanks to strong gravitational lensing

NASA Astrophysics Data System (ADS)

Dessauges-Zavadsky, Miroslava; Cava, Antonio; Richard, Johan; Schaerer, Daniel; Egami, Eiichi

2015-08-01

Deep and high-resolution imaging has revealed clumpy, rest-frame UV morphologies among z=1-3 galaxies. The majority of these galaxies has been shown to be dominated by ordered disk rotation, which led to the conclusion that the observed giant clumps, resolved on kpc-scales, are generated from disk fragmentation due to gravitational instability. State-of-the-art numerical simulations show that they may occupy a relevant role in galaxy evolution, contributing to the galactic bulge formation. Despite the high resolution attained by the most advanced ground- and space-based facilities, as well as in numerical simulations, the intrinsic typical masses and scale sizes of these star-forming clumps remain unconstrained, since they are barely resolved at z=1-3.Thanks to the amplification and stretching power provided by strong gravitational lensing, we are likely to reach the spatial resolving power for unveiling the physics of these star-forming regions. We report on the study of clumpy star formation observed in the Cosmic Snake, a strongly lensed galaxy at z=1, representative of the typical star-forming population close to the peak of Universe activity. About 20 clumps are identified in the HST images. Benefiting from extreme amplification factors up to 100, they are resolved down to an intrinsic scale of 100 pc, never reached before at z=1.The HST multi-wavelength analysis of these individual star clusters allows us to determine their intrinsic physical properties, showing stellar masses (Ms) from 106 to 108.3 Msun, sizes from 100 to 400 pc, and ages from 106 to 108.5 yr. The masses we find are in line with the new, very high resolution numerical simulations, which also suggest that the massive giant clumps previously observed at high redshift with Ms as high as 109-10 Msun may suffer from low resolution effects, being unresolved conglomerates of less massive star clusters. We also compare our results with those of massive young clusters in nearby galaxies. Our approved ALMA observations will reach the same 100 pc scale, which is essential for the study of associated giant molecular clouds in this galaxy.

Swarm v2: highly-scalable and high-resolution amplicon clustering.

PubMed

Mahé, Frédéric; Rognes, Torbjørn; Quince, Christopher; de Vargas, Colomban; Dunthorn, Micah

2015-01-01

Previously we presented Swarm v1, a novel and open source amplicon clustering program that produced fine-scale molecular operational taxonomic units (OTUs), free of arbitrary global clustering thresholds and input-order dependency. Swarm v1 worked with an initial phase that used iterative single-linkage with a local clustering threshold (d), followed by a phase that used the internal abundance structures of clusters to break chained OTUs. Here we present Swarm v2, which has two important novel features: (1) a new algorithm for d = 1 that allows the computation time of the program to scale linearly with increasing amounts of data; and (2) the new fastidious option that reduces under-grouping by grafting low abundant OTUs (e.g., singletons and doubletons) onto larger ones. Swarm v2 also directly integrates the clustering and breaking phases, dereplicates sequencing reads with d = 0, outputs OTU representatives in fasta format, and plots individual OTUs as two-dimensional networks.

Shocks and Cool Cores: An ALMA View of Massive Galaxy Cluster Formation at High Redshifts

NASA Astrophysics Data System (ADS)

Basu, Kaustuv

2017-07-01

These slides present some recent results on the Sunyaev-Zel'dovich (SZ) effect imaging of galaxy cluster substructures. The advantage of SZ imaging at high redshifts or in the low density cluster outskirts is already well-known. Now with ALMA a combination of superior angular resolution and high sensitivity is available. One example is the first ALMA measurement of a merger shock at z=0.9 in the famous El Gordo galaxy cluster. Here comparison between SZ, X-ray and radio data enabled us to put constraints on the shock Mach number and magnetic field strength for a high-z radio relic. Second example is the ALMA SZ imaging of the core region of z=1.4 galaxy cluster XMMU J2235.2-2557. Here ALMA data provide an accurate measurement of the thermal pressure near the cluster center, and from a joint SZ/X-ray analysis we find clear evidence for a reduced core temperature. This result indicate that a cool core establishes itself early enough in the cluster formation history while the gas accumulation is still continuing. The above two ALMA measurements are among several other recent SZ results that shed light on the formation process of massive clusters at high redshifts.

Optimal integrated abundances for chemical tagging of extragalactic globular clusters

NASA Astrophysics Data System (ADS)

Sakari, Charli M.; Venn, Kim; Shetrone, Matthew; Dotter, Aaron; Mackey, Dougal

2014-09-01

High-resolution integrated light (IL) spectroscopy provides detailed abundances of distant globular clusters whose stars cannot be resolved. Abundance comparisons with other systems (e.g. for chemical tagging) require understanding the systematic offsets that can occur between clusters, such as those due to uncertainties in the underlying stellar population. This paper analyses high-resolution IL spectra of the Galactic globular clusters 47 Tuc, M3, M13, NGC 7006, and M15 to (1) quantify potential systematic uncertainties in Fe, Ca, Ti, Ni, Ba, and Eu and (2) identify the most stable abundance ratios that will be useful in future analyses of unresolved targets. When stellar populations are well modelled, uncertainties are ˜0.1-0.2 dex based on sensitivities to the atmospheric parameters alone; in the worst-case scenarios, uncertainties can rise to 0.2-0.4 dex. The [Ca I/Fe I] ratio is identified as the optimal integrated [α/Fe] indicator (with offsets ≲ 0.1 dex), while [Ni I/Fe I] is also extremely stable to within ≲ 0.1 dex. The [Ba II/Eu II] ratios are also stable when the underlying populations are well modelled and may also be useful for chemical tagging.

High-Resolution Imaging of Colliding and Merging Galaxies

NASA Astrophysics Data System (ADS)

Whitmore, Brad

1991-07-01

We propose to obtain high-resolution images, using the WF/PC, of two colliding and merging galaxies (i.e., NGC 4038/4039 = "The Antennae" and NGC 7252 ="Atoms-for-Peace Galaxy". Our goal is to use HST to make critical observations of each object in order to gain a better understanding of the various phases of the merger process. Our primary objective is to determine whether globular clusters are formed during mergers\\?

Young massive star clusters in the era of HST and integral field spectroscopy

NASA Astrophysics Data System (ADS)

Zeidler, Peter; Nota, Antonella; Sabbi, Elena; Grebel, Eva K.; Pasquali, Anna

2018-01-01

With an age of 1 – 2 Myr at a distance of 4 kpc and a total stellar mass of 3.7×104 M⊙, Westerlund 2 (Wd2) is one of the most massive young star clusters in the Milky Way. We present a detailed analysis of its prominent pre-main-sequence population using the data of a high-resolution multi-band survey in the optical and near-infrared with the Hubble Space Telescope (HST), in combination with our spectroscopic survey, observed with the VLT/MUSE integral field unit. With our derived high-resolution extinction map of the region, which is absolutely essential giving the dominating presences of the gas and dust, we derived the spatial dependence of the mass function and quantify the degree of mass segregation down to 0.65 M⊙ with a completeness level better than 50%. Studying the radial dependence of the mass function of Wd2 and quantifying the degree of mass segregation in this young massive star cluster showed that it consists of two sub-clumps, namely the main cluster and the northern clump. From the MUSE data, we can extract individual stellar spectra and spectral energy distributions of the stars, based on the astrometry, provided by our high-resolution HST photometric catalog. This data will provide us with an almost complete spectral classification of a young massive star cluster down to 1.0 M⊙. The combination of the MUSE data, together with 3 more years of approved HST data will allow us to obtain, for the first time, the 3D motions of the stars with an accuracy of 1-2 km s-2 to determine the stellar velocity dispersion in order to study the fate of Wd2. This information is of great importance to adjust the initial conditions in cluster evolution models in order to connect these young massive star clusters and the old globular cluster population. Additionally, the combination of the photometric and spectroscopic datasets allows us to study the stars and their feedback onto the surrounding HII region simultaneously, as well as peculiar objects such as the massive, eclipsing Wolf-Rayet binary, WR20a or a possible Herbig-Haro object in the northern clump.

Detection of Galaxy Cluster Motions with the Kinematic Sunyaev-Zel'dovich Effect

NASA Technical Reports Server (NTRS)

Hand, Nick; Addison, Graeme E.; Aubourg, Eric; Battaglia, Nick; Battistelli, Elia S.; Bizyaev, Dmitry; Bond, J. Richard; Brewington, Howard; Brinkmann, Jon; Brown, Benjamin R.;

High-resolution electron microscopy and electron energy-loss spectroscopy of giant palladium clusters

NASA Astrophysics Data System (ADS)

Oleshko, V.; Volkov, V.; Gijbels, R.; Jacob, W.; Vargaftik, M.; Moiseev, I.; van Tendeloo, G.

1995-12-01

Combined structural and chemical characterization of cationic polynuclear palladium coordination compounds Pd561L60(OAc)180, where L=1,10-phenantroline or 2,2'-bipyridine has been carried out by high-resolution electron microscopy (HREM) and analytical electron microscopy methods including electron energy-loss spectroscopy (EELS), zero-loss electron spectroscopic imaging, and energy-dispersive X-ray spectroscopy (EDX). The cell structure of the cluster matter with almost completely uniform metal core size distributions centered around 2.3 ±0.5 nm was observed. Zero-loss energy filtering allowed to improve the image contrast and resolution. HREM images showed that most of the palladium clusters had a cubo-octahedral shape. Some of them had a distorted icosahedron structure exhibiting multiple twinning. The selected-area electron diffraction patterns confirmed the face centered cubic structure with lattice parameter close to that of metallic palladium. The energy-loss spectra of the populations of clusters contained several bands, which could be assigned to the delayed Pd M4, 5-edge at 362 eV, the Pd M3-edge at 533 eV and the Pd M2-edge at 561 eV, the NK-edge at about 400 eV, the O K-edge at 532 eV overlapping with the Pd M3-edge and the carbon C K-edge at 284 eV. Background subtraction was applied to reveal the exact positions and fine structure of low intensity elemental peaks. EELS evaluations have been confirmed by EDX. The recorded series of the Pd M-edges and the N K-edge in the spectra of the giant palladium clusters obviously were related to Pd-Pd- and Pd-ligand bonding.

High quality high spatial resolution functional classification in low dose dynamic CT perfusion using singular value decomposition (SVD) and k-means clustering

NASA Astrophysics Data System (ADS)

Pisana, Francesco; Henzler, Thomas; Schönberg, Stefan; Klotz, Ernst; Schmidt, Bernhard; Kachelrieß, Marc

2017-03-01

Dynamic CT perfusion acquisitions are intrinsically high-dose examinations, due to repeated scanning. To keep radiation dose under control, relatively noisy images are acquired. Noise is then further enhanced during the extraction of functional parameters from the post-processing of the time attenuation curves of the voxels (TACs) and normally some smoothing filter needs to be employed to better visualize any perfusion abnormality, but sacrificing spatial resolution. In this study we propose a new method to detect perfusion abnormalities keeping both high spatial resolution and high CNR. To do this we first perform the singular value decomposition (SVD) of the original noisy spatial temporal data matrix to extract basis functions of the TACs. Then we iteratively cluster the voxels based on a smoothed version of the three most significant singular vectors. Finally, we create high spatial resolution 3D volumes where to each voxel is assigned a distance from the centroid of each cluster, showing how functionally similar each voxel is compared to the others. The method was tested on three noisy clinical datasets: one brain perfusion case with an occlusion in the left internal carotid, one healthy brain perfusion case, and one liver case with an enhancing lesion. Our method successfully detected all perfusion abnormalities with higher spatial precision when compared to the functional maps obtained with a commercially available software. We conclude this method might be employed to have a rapid qualitative indication of functional abnormalities in low dose dynamic CT perfusion datasets. The method seems to be very robust with respect to both spatial and temporal noise and does not require any special a priori assumption. While being more robust respect to noise and with higher spatial resolution and CNR when compared to the functional maps, our method is not quantitative and a potential usage in clinical routine could be as a second reader to assist in the maps evaluation, or to guide a dataset smoothing before the modeling part.

High-resolution optical imaging of the core of the globular cluster M15 with FastCam

NASA Astrophysics Data System (ADS)

Díaz-Sánchez, Anastasio; Pérez-Garrido, Antonio; Villó, Isidro; Rebolo, Rafael; Pérez-Prieto, Jorge A.; Oscoz, Alejandro; Hildebrandt, Sergi R.; López, Roberto; Rodríguez, Luis F.

2012-07-01

We present high-resolution I -band imaging of the core of the globular cluster M15 obtained at the 2.5-m Nordic Optical Telescope with FastCam, a low readout noise L3CCD-based instrument. Short exposure times (30 ms) were used to record 200 000 images (512 × 512 pixels each) over a period of 2 h and 43 min. The lucky imaging technique was then applied to generate a final image of the cluster centre with full width at half-maximum ˜0.1 arcsec and 13 × 13 arcsec 2 field of view. We obtained a catalogue of objects in this region with a limiting magnitude of I = 19.5. I -band photometry and astrometry are reported for 1181 stars. This is the deepest I -band observation of the M15 core at this spatial resolution. Simulations show that crowding is limiting the completeness of the catalogue. At shorter wavelengths, a similar number of objects have been reported using Hubble Space Telescope (HST )/Wide Field Planetary Camera observations of the same field. The cross-match with the available HST catalogues allowed us to produce colour-magnitude diagrams where we identify new blue straggler star candidates and previously known stars of this class.

Genome-wide high-resolution aCGH analysis of gestational choriocarcinomas.

PubMed

Poaty, Henriette; Coullin, Philippe; Peko, Jean Félix; Dessen, Philippe; Diatta, Ange Lucien; Valent, Alexander; Leguern, Eric; Prévot, Sophie; Gombé-Mbalawa, Charles; Candelier, Jean-Jacques; Picard, Jean-Yves; Bernheim, Alain

2012-01-01

Eleven samples of DNA from choriocarcinomas were studied by high resolution CGH-array 244 K. They were studied after histopathological confirmation of the diagnosis, of the androgenic etiology and after a microsatellite marker analysis confirming the absence of contamination of tumor DNA from maternal DNA. Three cell lines, BeWo, JAR, JEG were also studied by this high resolution pangenomic technique. According to aCGH analysis, the de novo choriocarcinomas exhibited simple chromosomal rearrangements or normal profiles. The cell lines showed various and complex chromosomal aberrations. 23 Minimal Critical Regions were defined that allowed us to list the genes that were potentially implicated. Among them, unusually high numbers of microRNA clusters and imprinted genes were observed.

Some characteristics of matrix-assisted UV laser desorption/ionization mass spectrometric analysis of large proteins

NASA Astrophysics Data System (ADS)

Perera, I. K.; Kantartzoglou, S.; Dyer, P. E.

1996-12-01

We have performed experiments to explore the characteristics of the matrix-assisted laser desorption/ionization (MALDI) process and to ascertain optimal operational conditions for observing intact molecular ions of large proteins. In this study, several methods have been adopted for the preparation of analyte samples. Of these, the samples prepared with the simple dried-droplet method were found to be the most suitable for the generation of the large molecular clusters, while the near-uniform spin-coated samples were observed to produce highly reproducible molecular ion signals of relatively high mass resolutions. A resulting mass spectrum which illustrates the formation of cluster ions up to the 26-mer [26M+H]+ of bovine insulin corresponding to a mass of about 150,000 Da, is presented. The effect of fluence on the extent of clustering of protein molecules has been studied, the results revealing the existence of an optimum fluence for detecting the large cluster ions. Investigations have also indicated that the use of polyethylene-coated metallic substrates as sample supports can considerably reduce the fragmentation of the matrix/analyte molecular ions and the desorption of "neat" MALDI matrices deposited on these polyethylene-coated sample probes enhance their aggregation, forming up to the heptamer [7M+H]+ of the matrix, ferulic acid. The dependence of the mass resolution on the applied acceleration voltage and the desorption fluence has been examined and the results obtained are discussed in terms of a simple analysis of the linear time-of-flight mass spectrometer. A spectrum of chicken egg lysozyme (M~14,306) displaying the high mass resolutions (M/[Delta]M~690) that can be attained when the mass spectrometer is operated in the reflectron mode is also presented.

Hitomi Constraints on the 3.5 keV Line in the Perseus Galaxy Cluster

DOE PAGES

Aharonian, F. A.; Akamatsu, H.; Akimoto, F.; ...

2017-03-03

High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentifiedmore » $$E\\approx 3.5\\,\\mathrm{keV}$$ emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported high flux level. Taking into account the XMM measurement uncertainties for this region, the inconsistency with Hitomi is at a 99% significance for a broad dark matter line and at 99.7% for a narrow line from the gas. We do not find anomalously high fluxes of the nearby faint K line or the Ar satellite line that were proposed as explanations for the earlier 3.5 keV detections. We do find a hint of a broad excess near the energies of high-n transitions of S xvi ($$E\\simeq 3.44\\,\\mathrm{keV}$$ rest-frame)—a possible signature of charge exchange in the molecular nebula and another proposed explanation for the unidentified line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. In conclusion, a confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.« less

Application of a XMM-Newton EPIC Monte Carlo to Analysis And Interpretation of Data for Abell 1689, RXJ0658-55 And the Centaurus Clusters of Galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersson, Karl E.; /Stockholm U. /SLAC; Peterson, J.R.

2007-04-17

We propose a new Monte Carlo method to study extended X-ray sources with the European Photon Imaging Camera (EPIC) aboard XMM Newton. The Smoothed Particle Inference (SPI) technique, described in a companion paper, is applied here to the EPIC data for the clusters of galaxies Abell 1689, Centaurus and RXJ 0658-55 (the ''bullet cluster''). We aim to show the advantages of this method of simultaneous spectral-spatial modeling over traditional X-ray spectral analysis. In Abell 1689 we confirm our earlier findings about structure in temperature distribution and produce a high resolution temperature map. We also confirm our findings about velocity structuremore » within the gas. In the bullet cluster, RXJ 0658-55, we produce the highest resolution temperature map ever to be published of this cluster allowing us to trace what looks like the motion of the bullet in the cluster. We even detect a south to north temperature gradient within the bullet itself. In the Centaurus cluster we detect, by dividing up the luminosity of the cluster in bands of gas temperatures, a striking feature to the north-east of the cluster core. We hypothesize that this feature is caused by a subcluster left over from a substantial merger that slightly displaced the core. We conclude that our method is very powerful in determining the spatial distributions of plasma temperatures and very useful for systematic studies in cluster structure.« less

Reducing Earth Topography Resolution for SMAP Mission Ground Tracks Using K-Means Clustering

NASA Technical Reports Server (NTRS)

Rizvi, Farheen

2013-01-01

The K-means clustering algorithm is used to reduce Earth topography resolution for the SMAP mission ground tracks. As SMAP propagates in orbit, knowledge of the radar antenna footprints on Earth is required for the antenna misalignment calibration. Each antenna footprint contains a latitude and longitude location pair on the Earth surface. There are 400 pairs in one data set for the calibration model. It is computationally expensive to calculate corresponding Earth elevation for these data pairs. Thus, the antenna footprint resolution is reduced. Similar topographical data pairs are grouped together with the K-means clustering algorithm. The resolution is reduced to the mean of each topographical cluster called the cluster centroid. The corresponding Earth elevation for each cluster centroid is assigned to the entire group. Results show that 400 data points are reduced to 60 while still maintaining algorithm performance and computational efficiency. In this work, sensitivity analysis is also performed to show a trade-off between algorithm performance versus computational efficiency as the number of cluster centroids and algorithm iterations are increased.

Changes in tropical precipitation cluster size distributions under global warming

NASA Astrophysics Data System (ADS)

Neelin, J. D.; Quinn, K. M.

2016-12-01

The total amount of precipitation integrated across a tropical storm or other precipitation feature (contiguous clusters of precipitation exceeding a minimum rain rate) is a useful measure of the aggregate size of the disturbance. To establish baseline behavior in current climate, the probability distribution of cluster sizes from multiple satellite retrievals and National Center for Environmental Prediction (NCEP) reanalysis is compared to those from Coupled Model Intercomparison Project (CMIP5) models and the Geophysical Fluid Dynamics Laboratory high-resolution atmospheric model (HIRAM-360 and -180). With the caveat that a minimum rain rate threshold is important in the models (which tend to overproduce low rain rates), the models agree well with observations in leading properties. In particular, scale-free power law ranges in which the probability drops slowly with increasing cluster size are well modeled, followed by a rapid drop in probability of the largest clusters above a cutoff scale. Under the RCP 8.5 global warming scenario, the models indicate substantial increases in probability (up to an order of magnitude) of the largest clusters by the end of century. For models with continuous time series of high resolution output, there is substantial spread on when these probability increases for the largest precipitation clusters should be detectable, ranging from detectable within the observational period to statistically significant trends emerging only in the second half of the century. Examination of NCEP reanalysis and SSMI/SSMIS series of satellite retrievals from 1979 to present does not yield reliable evidence of trends at this time. The results suggest improvements in inter-satellite calibration of the SSMI/SSMIS retrievals could aid future detection.

Joint spatial-spectral hyperspectral image clustering using block-diagonal amplified affinity matrix

NASA Astrophysics Data System (ADS)

Fan, Lei; Messinger, David W.

2018-03-01

The large number of spectral channels in a hyperspectral image (HSI) produces a fine spectral resolution to differentiate between materials in a scene. However, difficult classes that have similar spectral signatures are often confused while merely exploiting information in the spectral domain. Therefore, in addition to spectral characteristics, the spatial relationships inherent in HSIs should also be considered for incorporation into classifiers. The growing availability of high spectral and spatial resolution of remote sensors provides rich information for image clustering. Besides the discriminating power in the rich spectrum, contextual information can be extracted from the spatial domain, such as the size and the shape of the structure to which one pixel belongs. In recent years, spectral clustering has gained popularity compared to other clustering methods due to the difficulty of accurate statistical modeling of data in high dimensional space. The joint spatial-spectral information could be effectively incorporated into the proximity graph for spectral clustering approach, which provides a better data representation by discovering the inherent lower dimensionality from the input space. We embedded both spectral and spatial information into our proposed local density adaptive affinity matrix, which is able to handle multiscale data by automatically selecting the scale of analysis for every pixel according to its neighborhood of the correlated pixels. Furthermore, we explored the "conductivity method," which aims at amplifying the block diagonal structure of the affinity matrix to further improve the performance of spectral clustering on HSI datasets.

Pressure distribution of the high-redshift cluster of galaxies CL J1226.9+3332 with NIKA

NASA Astrophysics Data System (ADS)

Adam, R.; Comis, B.; Macías-Pérez, J.-F.; Adane, A.; Ade, P.; André, P.; Beelen, A.; Belier, B.; Benoît, A.; Bideaud, A.; Billot, N.; Blanquer, G.; Bourrion, O.; Calvo, M.; Catalano, A.; Coiffard, G.; Cruciani, A.; D'Addabbo, A.; Désert, F.-X.; Doyle, S.; Goupy, J.; Kramer, C.; Leclercq, S.; Martino, J.; Mauskopf, P.; Mayet, F.; Monfardini, A.; Pajot, F.; Pascale, E.; Perotto, L.; Pointecouteau, E.; Ponthieu, N.; Revéret, V.; Ritacco, A.; Rodriguez, L.; Savini, G.; Schuster, K.; Sievers, A.; Tucker, C.; Zylka, R.

2015-04-01

The thermal Sunyaev-Zel'dovich (tSZ) effect is expected to provide a low scatter mass proxy for galaxy clusters since it is directly proportional to the cluster thermal energy. The tSZ observations have proven to be a powerful tool for detecting and studying them, but high angular resolution observations are now needed to push their investigation to a higher redshift. In this paper, we report high angular (<20 arcsec) resolution tSZ observations of the high-redshift cluster CL J1226.9+3332 (z = 0.89). It was imaged at 150 and 260 GHz using the NIKA camera at the IRAM 30-m telescope. The 150 GHz map shows that CL J1226.9+3332 is morphologically relaxed on large scales with evidence of a disturbed core, while the 260 GHz channel is used mostly to identify point source contamination. NIKA data are combined with those of Planck and X-ray from Chandra to infer the cluster's radial pressure, density, temperature, and entropy distributions. The total mass profile of the cluster is derived, and we find M500 = 5.96+1.02-0.79 × 1014M⊙ within the radius R500 = 930+50-43 kpc, at a 68% confidence level. (R500 is the radius within which the average density is 500 times the critical density at the cluster's redshift.) NIKA is the prototype camera of NIKA2, a KIDs (kinetic inductance detectors) based instrument to be installed at the end of 2015. This work is, therefore, part of a pilot study aiming at optimizing tSZ NIKA2 large programs. The FITS file of the published maps is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/576/A12

HIGH RESOLUTION SPECTROSCOPY IN THE GAS PHASE: Even Large Molecules Have Well-Defined Shapes

NASA Astrophysics Data System (ADS)

Pratt, David W.

1998-10-01

A review of recent high-resolution microwave, infrared, and optical spectroscopy experiments demonstrates that remarkable progress has been made in the past 20 years in determining the equilibrium geometries of large polyatomic molecules and their clusters in the gas phase, and how these geometries change when the photon is absorbed. A special focus is on the dynamical information that can be obtained from such studies, particularly of electronically excited states.

Chemical composition of stars in Ruprecht 106 .

NASA Astrophysics Data System (ADS)

François, P.

High resolution spectra of 9 stars belonging to the globular cluster Rup 106 have been used to determine their chemical composition. The results reveal that Ruprecht 106 exhibits abundance anomalies when compared to galactic globular cluster of similar metallicity. The chemical composition of these stars is similar to what is found in Dwarf spheroidal galaxies favoring the hypothesis that Rup 106 has not been formed in our Galaxy.

High Redshift Radio Galaxies: Laboratories for Massive Galaxy and Cluster Formation in the Early Universe

DTIC Science & Technology

2010-01-01

Lyα (blue, resolution ∼1”) obtained with ESO’s very Large Telescope (VLT), delineating the gaseous nebula and radio 8 GHz contours (red, resolution...0.3”) obtained with NRAO’s VLA, delineating the non-thermal radio emission. The gaseous nebula extends for >200 kpc and is comparable in size with the

A point mutation in the [2Fe–2S] cluster binding region of the NAF-1 protein (H114C) dramatically hinders the cluster donor properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamir, Sagi; Eisenberg-Domovich, Yael; Conlan, Andrea R.

2014-06-01

NAF-1 has been shown to be related with human health and disease, is upregulated in epithelial breast cancer and suppression of its expression significantly suppresses tumor growth. It is shown that replacement of the single His ligand with Cys resulted in dramatic changes to the properties of its 2Fe-2S clusters without any global crystal structural changes. NAF-1 is an important [2Fe–2S] NEET protein associated with human health and disease. A mis-splicing mutation in NAF-1 results in Wolfram Syndrome type 2, a lethal childhood disease. Upregulation of NAF-1 is found in epithelial breast cancer cells, and suppression of NAF-1 expression bymore » knockdown significantly suppresses tumor growth. Key to NAF-1 function is the NEET fold with its [2Fe–2S] cluster. In this work, the high-resolution structure of native NAF-1 was determined to 1.65 Å resolution (R factor = 13.5%) together with that of a mutant in which the single His ligand of its [2Fe–2S] cluster, His114, was replaced by Cys. The NAF-1 H114C mutant structure was determined to 1.58 Å resolution (R factor = 16.0%). All structural differences were localized to the cluster binding site. Compared with native NAF-1, the [2Fe–2S] clusters of the H114C mutant were found to (i) be 25-fold more stable, (ii) have a redox potential that is 300 mV more negative and (iii) have their cluster donation/transfer function abolished. Because no global structural differences were found between the mutant and the native (wild-type) NAF-1 proteins, yet significant functional differences exist between them, the NAF-1 H114C mutant is an excellent tool to decipher the underlying biological importance of the [2Fe–2S] cluster of NAF-1 in vivo.« less

THE YOUNG OPEN CLUSTER BERKELEY 55

DOE Office of Scientific and Technical Information (OSTI.GOV)

Negueruela, Ignacio; Marco, Amparo, E-mail: ignacio.negueruela@ua.es, E-mail: amparo.marco@ua.es

We present UBV photometry of the highly reddened and poorly studied open cluster Berkeley 55, revealing an important population of B-type stars and several evolved stars of high luminosity. Intermediate-resolution far-red spectra of several candidate members confirm the presence of one F-type supergiant and six late supergiants or bright giants. The brightest blue stars are mid-B giants. Spectroscopic and photometric analyses indicate an age 50 {+-} 10 Myr. The cluster is located at a distance d Almost-Equal-To 4 kpc, consistent with other tracers of the Perseus Arm in this direction. Berkeley 55 is thus a moderately young open cluster withmore » a sizable population of candidate red (super)giant members, which can provide valuable information about the evolution of intermediate-mass stars.« less

On the Chemical Abundances of Miras in Clusters: V1 in the Metal-rich Globular NGC 5927

NASA Astrophysics Data System (ADS)

D’Orazi, V.; Magurno, D.; Bono, G.; Matsunaga, N.; Braga, V. F.; Elgueta, S. S.; Fukue, K.; Hamano, S.; Inno, L.; Kobayashi, N.; Kondo, S.; Monelli, M.; Nonino, M.; Przybilla, N.; Sameshima, H.; Saviane, I.; Taniguchi, D.; Thevenin, F.; Urbaneja-Perez, M.; Watase, A.; Arai, A.; Bergemann, M.; Buonanno, R.; Dall’Ora, M.; Da Silva, R.; Fabrizio, M.; Ferraro, I.; Fiorentino, G.; Francois, P.; Gilmozzi, R.; Iannicola, G.; Ikeda, Y.; Jian, M.; Kawakita, H.; Kudritzki, R. P.; Lemasle, B.; Marengo, M.; Marinoni, S.; Martínez-Vázquez, C. E.; Minniti, D.; Neeley, J.; Otsubo, S.; Prieto, J. L.; Proxauf, B.; Romaniello, M.; Sanna, N.; Sneden, C.; Takenaka, K.; Tsujimoto, T.; Valenti, E.; Yasui, C.; Yoshikawa, T.; Zoccali, M.

2018-03-01

We present the first spectroscopic abundance determination of iron, α-elements (Si, Ca, and Ti), and sodium for the Mira variable V1 in the metal-rich globular cluster NGC 5927. We use high-resolution (R ∼ 28,000), high signal-to-noise ratio (∼200) spectra collected with WINERED, a near-infrared (NIR) spectrograph covering simultaneously the wavelength range 0.91–1.35 μm. The effective temperature and the surface gravity at the pulsation phase of the spectroscopic observation were estimated using both optical (V) and NIR time-series photometric data. We found that the Mira is metal-rich ([Fe/H] = ‑0.55 ± 0.15) and moderately α-enhanced ([α/Fe] = 0.15 ± 0.01, σ = 0.2). These values agree quite well with the mean cluster abundances based on high-resolution optical spectra of several cluster red giants available in the literature ([Fe/H] = ‑ 0.47 ± 0.06, [α/Fe] = + 0.24 ± 0.05). We also found a Na abundance of +0.35 ± 0.20 that is higher than the mean cluster abundance based on optical spectra (+0.18 ± 0.13). However, the lack of similar spectra for cluster red giants and that of corrections for departures from local thermodynamical equilibrium prevents us from establishing whether the difference is intrinsic or connected with multiple populations. These findings indicate a strong similarity between optical and NIR metallicity scales in spite of the difference in the experimental equipment, data analysis, and in the adopted spectroscopic diagnostics. Based on spectra collected with the WINERED spectrograph available as a visitor instrument at the ESO New Technology Telescope (NTT), La Silla, Chile (ESO Proposal: 098.D-0878(A), PI: G. Bono).

High Resolution X-ray Spectroscopy and Star Formation: HETG Observations of the Pre-Main Sequence Stellar Cluster IC 348

NASA Astrophysics Data System (ADS)

Principe, David; Huenemoerder, David P.; Schulz, Norbert; Kastner, Joel H.; Weintraub, David; Preibisch, Thomas

2018-01-01

We present Chandra High Energy Transmission Grating (HETG) observations of the ∼3 Myr old pre-main sequence (pre-MS) stellar cluster IC 348. With 400-500 cluster members at a distance of ∼300 pc, IC 348 is an ideal target to observe a large number of X-ray sources in a single pointing and is thus an extremely efficient use of Chandra-HETG. High resolution X-ray spectroscopy offers a means to investigate detailed spectral characteristic of X-ray emitting plasmas and their surrounding environments. We present preliminary results where we compare X-ray spectral signatures (e.g., luminosity, temperature, column density, abundance) of the X-ray brightest pre-MS stars in IC 348 with spectral type, multiwavelength signatures of accretion, and the presence of circumstellar disks at multiple stages of pre-MS stellar evolution. Assuming all IC 348 members formed from the same primordial molecular cloud, any disparity between coronal abundances of individual members, as constrained by the identification and strength of emission lines, will constrain the source(s) of coronal chemical evolution at a stage of pre-MS evolution vital to the formation of planets.

A high time and spatial resolution MRPC designed for muon tomography

NASA Astrophysics Data System (ADS)

Shi, L.; Wang, Y.; Huang, X.; Wang, X.; Zhu, W.; Li, Y.; Cheng, J.

2014-12-01

A prototype of cosmic muon scattering tomography system has been set up in Tsinghua University in Beijing. Multi-gap Resistive Plate Chamber (MRPC) is used in the system to get the muon tracks. Compared with other detectors, MRPC can not only provide the track but also the Time of Flight (ToF) between two detectors which can estimate the energy of particles. To get a more accurate track and higher efficiency of the tomography system, a new type of high time and two-dimensional spatial resolution MRPC has been developed. A series of experiments have been done to measure the efficiency, time resolution and spatial resolution. The results show that the efficiency can reach 95% and its time resolution is around 65 ps. The cluster size is around 4 and the spatial resolution can reach 200 μ m.

Proposal for grid computing for nuclear applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Idris, Faridah Mohamad; Ismail, Saaidi; Haris, Mohd Fauzi B.

2014-02-12

The use of computer clusters for computational sciences including computational physics is vital as it provides computing power to crunch big numbers at a faster rate. In compute intensive applications that requires high resolution such as Monte Carlo simulation, the use of computer clusters in a grid form that supplies computational power to any nodes within the grid that needs computing power, has now become a necessity. In this paper, we described how the clusters running on a specific application could use resources within the grid, to run the applications to speed up the computing process.

VizieR Online Data Catalog: IN-SYNC. III. Radial velocities of IC348 stars (Cottaar+, 2015)

NASA Astrophysics Data System (ADS)

Cottaar, M.; Covey, K. R.; Foster, J. B.; Meyer, M. R.; Tan, J. C.; Nidever, D. L.; Drew Chojnowski, S.; da Rio, N.; Flaherty, K. M.; Frinchaboy, P. M.; Majewski, S.; Skrutskie, M. F.; Wilson, J. C.; Zasowski, G.

2015-11-01

Cottaar et al. (Paper I, 2014, J/ApJ/794/125) describes the analysis of the high-resolution near-infrared spectra obtained by the APOGEE multi-object spectrograph from stars in IC 348, NGC 1333, NGC 2264, and Orion A as part of the INfrared Spectroscopy of Young Nebulous Clusters (IN-SYNC) ancillary program. Using radial velocities determined from APOGEE spectra of 380 likely cluster members, we have measured the radial velocity distribution of the young (2-6Myr) cluster IC 348. (2 data files).

Promoting Interests in Atmospheric Science at a Liberal Arts Institution

NASA Astrophysics Data System (ADS)

Roussev, S.; Sherengos, P. M.; Limpasuvan, V.; Xue, M.

2007-12-01

Coastal Carolina University (CCU) students in Computer Science participated in a project to set up an operational weather forecast for the local community. The project involved the construction of two computing clusters and the automation of daily forecasting. Funded by NSF-MRI, two high-performance clusters were successfully established to run the University of Oklahoma's Advance Regional Prediction System (ARPS). Daily weather predictions are made over South Carolina and North Carolina at 3-km horizontal resolution (roughly 1.9 miles) using initial and boundary condition data provided by UNIDATA. At this high resolution, the model is cloud- resolving, thus providing detailed picture of heavy thunderstorms and precipitation. Forecast results are displayed on CCU's website (https://marc.coastal.edu/HPC) to complement observations at the National Weather Service in Wilmington N.C. Present efforts include providing forecasts at 1-km resolution (or finer), comparisons with other models like Weather Research and Forecasting (WRF) model, and the examination of local phenomena (like water spouts and tornadoes). Through these activities the students learn about shell scripting, cluster operating systems, and web design. More importantly, students are introduced to Atmospheric Science, the processes involved in making weather forecasts, and the interpretation of their forecasts. Simulations generated by the forecasts will be integrated into the contents of CCU's course like Fluid Dynamics, Atmospheric Sciences, Atmospheric Physics, and Remote Sensing. Operated jointly between the departments of Applied Physics and Computer Science, the clusters are expected to be used by CCU faculty and students for future research and inquiry-based projects in Computer Science, Applied Physics, and Marine Science.

Individualized Functional Parcellation of the Human Amygdala Using a Semi-supervised Clustering Method: A 7T Resting State fMRI Study.

PubMed

Zhang, Xianchang; Cheng, Hewei; Zuo, Zhentao; Zhou, Ke; Cong, Fei; Wang, Bo; Zhuo, Yan; Chen, Lin; Xue, Rong; Fan, Yong

2018-01-01

The amygdala plays an important role in emotional functions and its dysfunction is considered to be associated with multiple psychiatric disorders in humans. Cytoarchitectonic mapping has demonstrated that the human amygdala complex comprises several subregions. However, it's difficult to delineate boundaries of these subregions in vivo even if using state of the art high resolution structural MRI. Previous attempts to parcellate this small structure using unsupervised clustering methods based on resting state fMRI data suffered from the low spatial resolution of typical fMRI data, and it remains challenging for the unsupervised methods to define subregions of the amygdala in vivo . In this study, we developed a novel brain parcellation method to segment the human amygdala into spatially contiguous subregions based on 7T high resolution fMRI data. The parcellation was implemented using a semi-supervised spectral clustering (SSC) algorithm at an individual subject level. Under guidance of prior information derived from the Julich cytoarchitectonic atlas, our method clustered voxels of the amygdala into subregions according to similarity measures of their functional signals. As a result, three distinct amygdala subregions can be obtained in each hemisphere for every individual subject. Compared with the cytoarchitectonic atlas, our method achieved better performance in terms of subregional functional homogeneity. Validation experiments have also demonstrated that the amygdala subregions obtained by our method have distinctive, lateralized functional connectivity (FC) patterns. Our study has demonstrated that the semi-supervised brain parcellation method is a powerful tool for exploring amygdala subregional functions.

High-resolution Spectroscopic Observations of Single Red Giants in Three Open Clusters: NGC 2360, NGC 3680, and NGC 5822

NASA Astrophysics Data System (ADS)

Peña Suárez, V. J.; Sales Silva, J. V.; Katime Santrich, O. J.; Drake, N. A.; Pereira, C. B.

2018-02-01

Single stars in open clusters with known distances are important targets in constraining the nucleosynthesis process since their ages and luminosities are also known. In this work, we analyze a sample of 29 single red giants of the open clusters NGC 2360, NGC 3680, and NGC 5822 using high-resolution spectroscopy. We obtained atmospheric parameters, abundances of the elements C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd, as well as radial and rotational velocities. We employed the local thermodynamic equilibrium atmospheric models of Kurucz and the spectral analysis code MOOG. Rotational velocities and light-element abundances were derived using spectral synthesis. Based on our analysis of the single red giants in these three open clusters, we could compare, for the first time, their abundance pattern with that of the binary stars of the same clusters previously studied. Our results show that the abundances of both single and binary stars of the open clusters NGC 2360, NGC 3680, and NGC 5822 do not have significant differences. For the elements created by the s-process, we observed that the open clusters NGC 2360, NGC 3680, and NGC 5822 also follow the trend already raised in the literature that young clusters have higher s-process element abundances than older clusters. Finally, we observed that the three clusters of our sample exhibit a trend in the [Y/Mg]-age relation, which may indicate the ability of the [Y/Mg] ratio to be used as a clock for the giants. Based on the observations made with the 2.2 m telescope at the European Southern Observatory (La Silla, Chile) under an agreement with Observatório Nacional and under an agreement between Observatório Nacional and Max-Planck Institute für Astronomie.

A Search for Ram-pressure Stripping in the Hydra I Cluster

NASA Technical Reports Server (NTRS)

Brown, B.

2005-01-01

Ram-pressure stripping is a method by which hot interstellar gas can be removed from a galaxy moving through a group or cluster of galaxies. Indirect evidence of ram-pressure stripping includes lowered X-ray brightness in a galaxy due to less X-ray emitting gas remaining in the galaxy. Here we present the initial results of our program to determine whether cluster elliptical galaxies have lower hot gas masses than their counterparts in less rich environments. This test requires the use of the high-resolution imaging of the Chandra Observatory and we present our analysis of the galaxies in the nearby cluster Hydra I.

A Search for Ram-pressure Stripping in the Hydra I Cluster

NASA Technical Reports Server (NTRS)

Brown, B. A.

2005-01-01

Ram-pressure stripping is a method by which hot interstellar gas can be removed from a galaxy moving through a group or cluster of galaxies. Indirect evidence of ram-pressure stripping includes lowered X- ray brightness in a galaxy due to less X-ray emitting gas remaining in the galaxy. Here we present the initial results of our program to determine whether cluster elliptical galaxies have lower hot gas masses than their counterparts in less rich environments. This test requires the use of the high-resolution imaging of the Chundru Observatory and we present our analysis of the galaxies in the nearby cluster Hydra I.

Correlating Fluorescence and High-Resolution Scanning Electron Microscopy (HRSEM) for the study of GABAA receptor clustering induced by inhibitory synaptic plasticity.

PubMed

Orlando, Marta; Ravasenga, Tiziana; Petrini, Enrica Maria; Falqui, Andrea; Marotta, Roberto; Barberis, Andrea

2017-10-23

Both excitatory and inhibitory synaptic contacts display activity dependent dynamic changes in their efficacy that are globally termed synaptic plasticity. Although the molecular mechanisms underlying glutamatergic synaptic plasticity have been extensively investigated and described, those responsible for inhibitory synaptic plasticity are only beginning to be unveiled. In this framework, the ultrastructural changes of the inhibitory synapses during plasticity have been poorly investigated. Here we combined confocal fluorescence microscopy (CFM) with high resolution scanning electron microscopy (HRSEM) to characterize the fine structural rearrangements of post-synaptic GABA A Receptors (GABA A Rs) at the nanometric scale during the induction of inhibitory long-term potentiation (iLTP). Additional electron tomography (ET) experiments on immunolabelled hippocampal neurons allowed the visualization of synaptic contacts and confirmed the reorganization of post-synaptic GABA A R clusters in response to chemical iLTP inducing protocol. Altogether, these approaches revealed that, following the induction of inhibitory synaptic potentiation, GABA A R clusters increase in size and number at the post-synaptic membrane with no other major structural changes of the pre- and post-synaptic elements.

Genome-Wide High-Resolution aCGH Analysis of Gestational Choriocarcinomas

PubMed Central

Poaty, Henriette; Coullin, Philippe; Peko, Jean Félix; Dessen, Philippe; Diatta, Ange Lucien; Valent, Alexander; Leguern, Eric; Prévot, Sophie; Gombé-Mbalawa, Charles; Candelier, Jean-Jacques; Picard, Jean-Yves; Bernheim, Alain

2012-01-01

Eleven samples of DNA from choriocarcinomas were studied by high resolution CGH-array 244 K. They were studied after histopathological confirmation of the diagnosis, of the androgenic etiology and after a microsatellite marker analysis confirming the absence of contamination of tumor DNA from maternal DNA. Three cell lines, BeWo, JAR, JEG were also studied by this high resolution pangenomic technique. According to aCGH analysis, the de novo choriocarcinomas exhibited simple chromosomal rearrangements or normal profiles. The cell lines showed various and complex chromosomal aberrations. 23 Minimal Critical Regions were defined that allowed us to list the genes that were potentially implicated. Among them, unusually high numbers of microRNA clusters and imprinted genes were observed. PMID:22253721

An improved experimental scheme for simultaneous measurement of high-resolution zero electron kinetic energy (ZEKE) photoelectron and threshold photoion (MATI) spectra

NASA Astrophysics Data System (ADS)

Michels, François; Mazzoni, Federico; Becucci, Maurizio; Müller-Dethlefs, Klaus

2017-10-01

An improved detection scheme is presented for threshold ionization spectroscopy with simultaneous recording of the Zero Electron Kinetic Energy (ZEKE) and Mass Analysed Threshold Ionisation (MATI) signals. The objective is to obtain accurate dissociation energies for larger molecular clusters by simultaneously detecting the fragment and parent ion MATI signals with identical transmission. The scheme preserves an optimal ZEKE spectral resolution together with excellent separation of the spontaneous ion and MATI signals in the time-of-flight mass spectrum. The resulting improvement in sensitivity will allow for the determination of dissociation energies in clusters with substantial mass difference between parent and daughter ions.

Medium-resolution Spectroscopy of Red Giant Branch Stars in ω Centauri

NASA Astrophysics Data System (ADS)

An, Deokkeun; Lee, Young Sun; In Jung, Jae; Rey, Soo-Chang; Rhee, Jaehyon; Lee, Jae-Woo; Lee, Young-Wook; Joe, Young Hoon

2017-10-01

We present [Fe/H] and [Ca/Fe] of ˜600 red giant branch (RGB) members of the globular cluster Omega Centauri (ω {Cen}). We collect medium-resolution (R˜ 2000) spectra using the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory equipped with Hydra, the fiber-fed multi-object spectrograph. We demonstrate that blending of stellar light in optical fibers severely limits the accuracy of spectroscopic parameters in the crowded central region of the cluster. When photometric temperatures are taken in the spectroscopic analysis, our kinematically selected cluster members, excluding those that are strongly affected by flux from neighboring stars, include relatively fewer stars at intermediate metallicity ([{Fe}/{{H}}]˜ -1.5) than seen in the previous high-resolution survey for brighter giants in Johnson & Pilachowski. As opposed to the trend of increasing [Ca/Fe] with [Fe/H] found by those authors, our [Ca/Fe] estimates, based on Ca II H & K measurements, show essentially the same mean [Ca/Fe] for most of the metal-poor and metal-intermediate populations in this cluster, suggesting that mass- or metallicity-dependent SN II yields may not be necessary in their proposed chemical evolution scenario. Metal-rich cluster members in our sample show a large spread in [Ca/Fe], and do not exhibit a clear bimodal distribution in [Ca/Fe]. We also do not find convincing evidence for a radial metallicity gradient among RGB stars in ω {Cen}.

Nanoparticle formation of deposited Agn-clusters on free-standing graphene

NASA Astrophysics Data System (ADS)

Al-Hada, M.; Peters, S.; Gregoratti, L.; Amati, M.; Sezen, H.; Parisse, P.; Selve, S.; Niermann, T.; Berger, D.; Neeb, M.; Eberhardt, W.

2017-11-01

Size-selected Agn-clusters on unsupported graphene of a commercial Quantifoil sample have been investigated by surface and element-specific techniques such as transmission electron microscopy (TEM), spatially-resolved inner-shell X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). An agglomeration of the highly mobile clusters into nm-sized Ag-nanodots of 2-3 nm is observed. Moreover, crystalline as well as non-periodic fivefold symmetric structures of the Ag-nanoparticles are evident by high-resolution TEM. Using a lognormal size-distribution as revealed by TEM, the measured positive binding energy shift of the air-exposed Ag-nanodots can be explained by the size-dependent dynamical liquid-drop model.

Swarm v2: highly-scalable and high-resolution amplicon clustering

PubMed Central

Quince, Christopher; de Vargas, Colomban; Dunthorn, Micah

2015-01-01

Previously we presented Swarm v1, a novel and open source amplicon clustering program that produced fine-scale molecular operational taxonomic units (OTUs), free of arbitrary global clustering thresholds and input-order dependency. Swarm v1 worked with an initial phase that used iterative single-linkage with a local clustering threshold (d), followed by a phase that used the internal abundance structures of clusters to break chained OTUs. Here we present Swarm v2, which has two important novel features: (1) a new algorithm for d = 1 that allows the computation time of the program to scale linearly with increasing amounts of data; and (2) the new fastidious option that reduces under-grouping by grafting low abundant OTUs (e.g., singletons and doubletons) onto larger ones. Swarm v2 also directly integrates the clustering and breaking phases, dereplicates sequencing reads with d = 0, outputs OTU representatives in fasta format, and plots individual OTUs as two-dimensional networks. PMID:26713226

SPECTROSCOPIC ABUNDANCES AND MEMBERSHIP IN THE WOLF 630 MOVING GROUP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bubar, Eric J.; King, Jeremy R., E-mail: ebubar@gmail.co, E-mail: jking2@ces.clemson.ed

The concept of kinematic assemblages evolving from dispersed stellar clusters has remained contentious since Eggen's initial formulation of moving groups in the 1960s. With high-quality parallaxes from the Hipparcos space astrometry mission, distance measurements for thousands of nearby, seemingly isolated stars are currently available. With these distances, a high-resolution spectroscopic abundance analysis can be brought to bear on the alleged members of these moving groups. If a structure is a relic of an open cluster, the members can be expected to be monolithic in age and abundance in as much as homogeneity is observed in young open clusters. In thismore » work, we have examined 34 putative members of the proposed Wolf 630 moving group using high-resolution stellar spectroscopy. The stars of the sample have been chemically tagged to determine abundance homogeneity and confirm the existence of a homogeneous subsample of 19 stars. Fitting the homogeneous subsample with Yale-Yonsei isochrones yields a single evolutionary sequence of {approx}2.7 {+-} 0.5 Gyr. It is concluded that this 19 star subsample of the Wolf 630 moving group sample of 34 stars could represent a dispersed cluster with an ([Fe/H]) = -0.01 {+-} 0.02 and an age of 2.7 {+-} 0.5 Gyr. In addition, chemical abundances of Na and Al in giants are examined for indications of enhancements as observed in field giants of old open clusters; overexcitation/ionization effects are explored in the cooler dwarfs of the sample; and oxygen is derived from the infrared triplet and the forbidden line at {lambda}6300.« less

The young SMC cluster NGC 330

NASA Technical Reports Server (NTRS)

Carney, B. W.; Janes, K. A.; Flower, P. J.

1985-01-01

A color-magnitude diagram has been obtained for the young SMC cluster NGC 330. The diagram shows a well-defined main sequence, a group of blue supergiants, a group of red supergiants between B-V = 1.2 m and 1.6 m about one magnitude fainter, and an empty Hertzsprung gap. The surrounding field is a composite of a very gold population resembling galactic globular clusters and a very young population. DDO and infrared photometry strongly suggest that the cluster is metal-poor, but a definitive measure could not be made because of calibration difficulties. The cluster's age is estimated at 12 million years, with the surrounding field about 50 percent older. The cluster will prove very useful in testing stellar evolution models for young, metal-poor stars if the cluster's metallicity can be established via high-resolution spectroscopy.

CO near the Pleiades: Encounter of a star cluster with a small molecular cloud

NASA Technical Reports Server (NTRS)

Bally, J.; White, R. E.

1986-01-01

Although there is a large amount of interstellar matter near the Pleiades star cluster, the observed dust and gas is not a remnant of the placental molecular cloud from which the star cluster was formed. Carbon monoxide (CO) associated with the visible reflection nebulae was discovered by Cohen (1975). Its radial velocity differs from that of the cluster by many times the cluster escape velocity, which implies that the cloud-cluster association is the result of a chance encounter. This circumstance and the proximity of the Pleiades to the sun creates an unique opportunity for study of interstellar processes at high spatial resolution. To study the molecular component of the gas, a 1.7 square degree field was mapped with the AT&T Bell Laboratories 7-meter antenna (1.7' beam) on a 1' grid in the J=1.0 C(12)O line, obtaining over 6,000 spectra with 50 kHz resolution. The cloud core was mapped in the J=1-0 line of C(13)O. Further observations include an unsuccessful search for CS (J=2-1) at AT&T BL, and some C(12)O J=2-1 spectra obtained at the Millimeter Wave Observatory of the University of Texas.

Testing cosmic ray acceleration with radio relics: a high-resolution study using MHD and tracers

NASA Astrophysics Data System (ADS)

Wittor, D.; Vazza, F.; Brüggen, M.

2017-02-01

Weak shocks in the intracluster medium may accelerate cosmic-ray protons and cosmic-ray electrons differently depending on the angle between the upstream magnetic field and the shock normal. In this work, we investigate how shock obliquity affects the production of cosmic rays in high-resolution simulations of galaxy clusters. For this purpose, we performed a magnetohydrodynamical simulation of a galaxy cluster using the mesh refinement code ENZO. We use Lagrangian tracers to follow the properties of the thermal gas, the cosmic rays and the magnetic fields over time. We tested a number of different acceleration scenarios by varying the obliquity-dependent acceleration efficiencies of protons and electrons, and by examining the resulting hadronic γ-ray and radio emission. We find that the radio emission does not change significantly if only quasi-perpendicular shocks are able to accelerate cosmic-ray electrons. Our analysis suggests that radio-emitting electrons found in relics have been typically shocked many times before z = 0. On the other hand, the hadronic γ-ray emission from clusters is found to decrease significantly if only quasi-parallel shocks are allowed to accelerate cosmic ray protons. This might reduce the tension with the low upper limits on γ-ray emission from clusters set by the Fermi satellite.

Obscuring and Feeding Supermassive Black Holes with Evolving Nuclear Star Clusters

NASA Astrophysics Data System (ADS)

Schartmann, M.; Burkert, A.; Krause, M.; Camenzind, M.; Meisenheimer, K.; Davies, R. I.

2010-05-01

Recently, high-resolution observations made with the help of the near-infrared adaptive optics integral field spectrograph SINFONI at the VLT proved the existence of massive and young nuclear star clusters in the centers of a sample of Seyfert galaxies. With the help of high-resolution hydrodynamical simulations with the pluto code, we follow the evolution of such clusters, especially focusing on mass and energy feedback from young stars. This leads to a filamentary inflow of gas on large scales (tens of parsecs), whereas a turbulent and very dense disk builds up on the parsec scale. Here we concentrate on the long-term evolution of the nuclear disk in NGC 1068 with the help of an effective viscous disk model, using the mass input from the large-scale simulations and accounting for star formation in the disk. This two-stage modeling enables us to connect the tens-of-parsecs scale region (observable with SINFONI) with the parsec-scale environment (MIDI observations). At the current age of the nuclear star cluster, our simulations predict disk sizes of the order 0.8 to 0.9 pc, gas masses of order 106 M⊙, and mass transfer rates through the inner boundary of order 0.025 M⊙ yr-1, in good agreement with values derived from observations.

Precise strong lensing mass profile of the CLASH galaxy cluster MACS 2129

NASA Astrophysics Data System (ADS)

Monna, A.; Seitz, S.; Balestra, I.; Rosati, P.; Grillo, C.; Halkola, A.; Suyu, S. H.; Coe, D.; Caminha, G. B.; Frye, B.; Koekemoer, A.; Mercurio, A.; Nonino, M.; Postman, M.; Zitrin, A.

2017-04-01

We present a detailed strong lensing (SL) mass reconstruction of the core of the galaxy cluster MACS J2129.4-0741 (zcl = 0.589) obtained by combining high-resolution Hubble Space Telescope photometry from the CLASH (Cluster Lensing And Supernovae survey with Hubble) survey with new spectroscopic observations from the CLASH-VLT (Very Large Telescope) survey. A background bright red passive galaxy at zsp = 1.36, sextuply lensed in the cluster core, has four radial lensed images located over the three central cluster members. Further 19 background lensed galaxies are spectroscopically confirmed by our VLT survey, including 3 additional multiple systems. A total of 31 multiple images are used in the lensing analysis. This allows us to trace with high precision the total mass profile of the cluster in its very inner region (R < 100 kpc). Our final lensing mass model reproduces the multiple images systems identified in the cluster core with high accuracy of 0.4 arcsec. This translates to a high-precision mass reconstruction of MACS 2129, which is constrained at a level of 2 per cent. The cluster has Einstein parameter ΘE = (29 ± 4) arcsec and a projected total mass of Mtot(<ΘE) = (1.35 ± 0.03) × 1014 M⊙ within such radius. Together with the cluster mass profile, we provide here also the complete spectroscopic data set for the cluster members and lensed images measured with VLT/Visible Multi-Object Spectrograph within the CLASH-VLT survey.

X-ray and optical emission-line filaments in the cooling flow cluster 2A 0335 + 096

NASA Technical Reports Server (NTRS)

Sarazin, Craig L.; O'Connell, Robert W.; Mcnamara, Brian R.

1992-01-01

We present a new high-resolution X-ray image of the 2A 0335 + 096 cluster of galaxies obtained with the High Resolution Imager (HRI) aboard the ROSAT satellite. The presence of dense gas having a very short cooling time in the central regions confirms its earlier identification as a cooling flow. The X-ray emission from the central regions of the cooling flow shows a great deal of filamentary structure. Using the crude spectral resolution of the HRI, we show that these filaments are the result of excess emission, rather than foreground X-ray absorption. Although there are uncertainties in the pointing, many of the X-ray features in the cooling flow region correspond to features in H-alpha optical line emission. This suggests that the optical emission line gas has resulted directly from the cooling of X-ray-emitting gas. The filament material cannot be in hydrostatic equilibrium, and it is likely that other forces such as rotation, turbulence, and magnetic fields influence the dynamical state of the gas.

From atoms to layers: in situ gold cluster growth kinetics during sputter deposition

NASA Astrophysics Data System (ADS)

Schwartzkopf, Matthias; Buffet, Adeline; Körstgens, Volker; Metwalli, Ezzeldin; Schlage, Kai; Benecke, Gunthard; Perlich, Jan; Rawolle, Monika; Rothkirch, André; Heidmann, Berit; Herzog, Gerd; Müller-Buschbaum, Peter; Röhlsberger, Ralf; Gehrke, Rainer; Stribeck, Norbert; Roth, Stephan V.

2013-05-01

The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources.The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources. Electronic supplementary information (ESI) available: The full GISAXS image sequence of the experiment, the model-based IsGISAXS-simulation sequence as movie files for comparison and detailed information about sample cleaning, XRR, FESEM, IsGISAXS, comparison μGIWAXS/μGISAXS, and sampling statistics. See DOI: 10.1039/c3nr34216f

Massive and refined: A sample of large galaxy clusters simulated at high resolution. I: Thermal gas and properties of shock waves

NASA Astrophysics Data System (ADS)

Vazza, F.; Brunetti, G.; Gheller, C.; Brunino, R.

2010-11-01

We present a sample of 20 massive galaxy clusters with total virial masses in the range of 6 × 10 14 M ⊙ ⩽ Mvir ⩽ 2 × 10 15 M ⊙, re-simulated with a customized version of the 1.5. ENZO code employing adaptive mesh refinement. This technique allowed us to obtain unprecedented high spatial resolution (≈25 kpc/h) up to the distance of ˜3 virial radii from the clusters center, and makes it possible to focus with the same level of detail on the physical properties of the innermost and of the outermost cluster regions, providing new clues on the role of shock waves and turbulent motions in the ICM, across a wide range of scales. In this paper, a first exploratory study of this data set is presented. We report on the thermal properties of galaxy clusters at z = 0. Integrated and morphological properties of gas density, gas temperature, gas entropy and baryon fraction distributions are discussed, and compared with existing outcomes both from the observational and from the numerical literature. Our cluster sample shows an overall good consistency with the results obtained adopting other numerical techniques (e.g. Smoothed Particles Hydrodynamics), yet it provides a more accurate representation of the accretion patterns far outside the cluster cores. We also reconstruct the properties of shock waves within the sample by means of a velocity-based approach, and we study Mach numbers and energy distributions for the various dynamical states in clusters, giving estimates for the injection of Cosmic Rays particles at shocks. The present sample is rather unique in the panorama of cosmological simulations of massive galaxy clusters, due to its dynamical range, statistics of objects and number of time outputs. For this reason, we deploy a public repository of the available data, accessible via web portal at http://data.cineca.it.

High-Resolution Remote Sensing Image Building Extraction Based on Markov Model

NASA Astrophysics Data System (ADS)

Zhao, W.; Yan, L.; Chang, Y.; Gong, L.

2018-04-01

With the increase of resolution, remote sensing images have the characteristics of increased information load, increased noise, more complex feature geometry and texture information, which makes the extraction of building information more difficult. To solve this problem, this paper designs a high resolution remote sensing image building extraction method based on Markov model. This method introduces Contourlet domain map clustering and Markov model, captures and enhances the contour and texture information of high-resolution remote sensing image features in multiple directions, and further designs the spectral feature index that can characterize "pseudo-buildings" in the building area. Through the multi-scale segmentation and extraction of image features, the fine extraction from the building area to the building is realized. Experiments show that this method can restrain the noise of high-resolution remote sensing images, reduce the interference of non-target ground texture information, and remove the shadow, vegetation and other pseudo-building information, compared with the traditional pixel-level image information extraction, better performance in building extraction precision, accuracy and completeness.

The micro-mechanics of strength, durability and damage tolerance in composites: new insights from high resolution computed tomography

NASA Astrophysics Data System (ADS)

Spearing, S. Mark; Sinclair, Ian

2016-07-01

Recent work, led by the authors, on impact damage resistance, particle toughening and tensile fibre failure is reviewed in order to illustrate the use of high-resolution X-ray tomography to observe and quantify damage mechanisms in carbon fibre composite laminates. Using synchrotron and micro-focus X-ray sources resolutions of less than 1 μm have been routinely achieved. This enables individual broken fibres and the micromechanisms of particle toughening to be observed and quantified. The data for fibre failure, cluster formation and overall tensile strength are compared with model predictions. This allows strategies for future model development to be identified. The overall implications for using such high-resolution 3-D measurements to inform a “data-rich mechanics” approach to materials evaluation and modeling is discussed.

The old open cluster NGC 2112: updated estimates of fundamental parameters based on a membership analysis†

NASA Astrophysics Data System (ADS)

Carraro, G.; Villanova, S.; Demarque, P.; Moni Bidin, C.; McSwain, M. V.

2008-05-01

We report on a new, wide-field (20 × 20 arcmin2), multicolour (UBVI), photometric campaign in the area of the nearby old open cluster NGC 2112. At the same time, we provide medium-resolution spectroscopy of 35 (and high-resolution of additional 5) red giant and turn-off stars. This material is analysed with the aim to update the fundamental parameters of this traditionally difficult cluster, which is very sparse and suffers from heavy field star contamination. Among the 40 stars with spectra, we identified 21 bona fide radial velocity members which allow us to put more solid constraints on the cluster's metal abundance, long suggested to be as low as the metallicity of globulars. As indicated earlier by us on a purely photometric basis, the cluster [Fe/H] abundance is slightly supersolar ([Fe/H] = 0.16 +/- 0.03) and close to the Hyades value, as inferred from a detailed abundance analysis of three of the five stars with higher resolution spectra. Abundance ratios are also marginally supersolar. Based on this result, we revise the properties of NGC 2112 using stellar models from the Padova and Yale-Yonsei groups. For this metal abundance, we find that the cluster's age, reddening and distance values are 1.8 Gyr, 0.60 mag and 940 pc, respectively. Both the Yale-Yonsei and Padova models predict the same values for the fundamental parameters within the errors. Overall, NGC 2112 is a typical solar neighbourhood, thin-disc star cluster, sharing the same chemical properties of F-G stars and open clusters close to the Sun. This investigation outlines the importance of a detailed membership analysis in the study of disc star clusters. This paper includes data gathered with the 6.5 Magellan Telescopes, located at Las Campanas Observatory, Chile. The data discussed in this paper will be made available at the WEBDA open cluster data base http://www.univie.ac.at/webda, which is maintained by E. Paunzen and J.-C. Mermilliod. ‡ E-mail: gcarraro@eso.org (GC); sandro.villanova@unipd.it (SV); demarque@astro.yale.edu (PD); mbidin@das.uchile.cl (CMB); mcswain@lehigh.edu(MVM)

High-Resolution Metabolomics for Nutrition and Health Assessment of Armed Forces Personnel.

PubMed

Accardi, Carolyn Jonas; Walker, Douglas I; Uppal, Karan; Quyyumi, Arshed A; Rohrbeck, Patricia; Pennell, Kurt D; Mallon, Col Timothy M; Jones, Dean P

2016-08-01

The aim of this study was to test the utility of high-resolution metabolomics (HRM) for analysis of nutritional status and health indicators in military personnel. Serum samples from 400 military personnel were obtained from the Department of Defense Serum Repository (DoDSR) and analyzed for metabolites related to nutrition and health status. Metabolic profile organization was studied using modulated modularity clustering (MMC). HRM provided quantitative measures of 61 metabolites across chemical classes for use as nutritional and clinical biomarkers. Levels were comparable to reported values except for arginine and glutamine, which were above and below reference ranges, respectively. MMC generated five clusters, three of which were associated and contained amino acids. The others contained lipids and mitochondria-related metabolites. HRM analysis of serum is suitable for real-time and/or retrospective evaluation of nutrition and health status of specific military cohorts.

Keck/LRIS Spectroscopy of the Distant Cluster Cl0016+16

NASA Astrophysics Data System (ADS)

Wirth, Gregory D.; Koo, David C.

1994-12-01

The rich galaxy cluster Cl0016+16 at z=0.55 initially achieved visibility (Koo 1981) for being the original ``anti Butcher-Oemler effect'' cluster: its galaxy population was found to be almost entirely red, indistinguishable in rest-frame color from local E/S0 galaxies, despite the expectation that higher redshift clusters should have a greater proportion of blue galaxies (Butcher & Oemler 1978, 1984). Interest in this cluster has heightened over the last decade as: X-ray observations found it to be among the most luminous clusters known (Henry et al. 1992); radio observations showed it to be among only a handful of clusters exhibiting a Sunyaev-Zel'dovich microwave decrement, useful for measuring the Hubble Constant (Lasenby 1992); optical spectroscopy revealed a significant population of ``E+A'' galaxies, enigmatic objects with spectra suggesting a recently-concluded episode of star formation (Dressler & Gunn 1992). Further observations by ROSAT, ASCA, and HST have established Cl0016+16 as among the best-studied clusters beyond Coma. The red nature of its galaxy population makes Cl0016+16 a prime candidate for the study of cluster galaxy evolution. As part of an ongoing effort to study the early-type galaxies in this cluster, we recently used the Keck Telescope and Low-Resolution Imaging Spectrograph to obtain high quality spectra of 19 cluster members at 6 Angstroms (FWHM) resolution. This poster describes the preliminary results from these data, which will allow us to investigate galaxy age and metallicity at lookback times nearly halfway to the Big Bang, probe the internal kinematics of galaxies at z=0.55, and thus perhaps trace the evolution of the ``fundamental plane'' for E/S0 galaxies.

A Lagrangian analysis of cold cloud clusters and their life cycles with satellite observations

PubMed Central

Esmaili, Rebekah Bradley; Tian, Yudong; Vila, Daniel Alejandro; Kim, Kyu-Myong

2018-01-01

Cloud movement and evolution signify the complex water and energy transport in the atmosphere-ocean-land system. Detecting, clustering, and tracking clouds as semi-coherent cluster objects enables study of their evolution which can complement climate model simulations and enhance satellite retrieval algorithms, where there are large gaps between overpasses. Using an area-overlap cluster tracking algorithm, in this study we examine the trajectories, horizontal extent, and brightness temperature variations of millions of individual cloud clusters over their lifespan, from infrared satellite observations at 30-minute, 4-km resolution, for a period of 11 years. We found that the majority of cold clouds were both small and short-lived and that their frequency and location are influenced by El Niño. More importantly, this large sample of individually tracked clouds shows their horizontal size and temperature evolution. Longer lived clusters tended to achieve their temperature and size maturity milestones at different times, while these stages often occurred simultaneously in shorter lived clusters. On average, clusters with this lag also exhibited a greater rainfall contribution than those where minimum temperature and maximum size stages occurred simultaneously. Furthermore, by examining the diurnal cycle of cluster development over Africa and the Indian subcontinent, we observed differences in the local timing of the maximum occurrence at different life cycle stages. Over land there was a strong diurnal peak in the afternoon while over the ocean there was a semi-diurnal peak composed of longer-lived clusters in the early morning hours and shorter-lived clusters in the afternoon. Building on regional specific work, this study provides a long-term, high-resolution, and global survey of object-based cloud characteristics. PMID:29744257

A Lagrangian analysis of cold cloud clusters and their life cycles with satellite observations.

PubMed

Esmaili, Rebekah Bradley; Tian, Yudong; Vila, Daniel Alejandro; Kim, Kyu-Myong

2016-10-16

Cloud movement and evolution signify the complex water and energy transport in the atmosphere-ocean-land system. Detecting, clustering, and tracking clouds as semi-coherent cluster objects enables study of their evolution which can complement climate model simulations and enhance satellite retrieval algorithms, where there are large gaps between overpasses. Using an area-overlap cluster tracking algorithm, in this study we examine the trajectories, horizontal extent, and brightness temperature variations of millions of individual cloud clusters over their lifespan, from infrared satellite observations at 30-minute, 4-km resolution, for a period of 11 years. We found that the majority of cold clouds were both small and short-lived and that their frequency and location are influenced by El Niño. More importantly, this large sample of individually tracked clouds shows their horizontal size and temperature evolution. Longer lived clusters tended to achieve their temperature and size maturity milestones at different times, while these stages often occurred simultaneously in shorter lived clusters. On average, clusters with this lag also exhibited a greater rainfall contribution than those where minimum temperature and maximum size stages occurred simultaneously. Furthermore, by examining the diurnal cycle of cluster development over Africa and the Indian subcontinent, we observed differences in the local timing of the maximum occurrence at different life cycle stages. Over land there was a strong diurnal peak in the afternoon while over the ocean there was a semi-diurnal peak composed of longer-lived clusters in the early morning hours and shorter-lived clusters in the afternoon. Building on regional specific work, this study provides a long-term, high-resolution, and global survey of object-based cloud characteristics.

A Lagrangian Analysis of Cold Cloud Clusters and Their Life Cycles With Satellite Observations

NASA Technical Reports Server (NTRS)

Esmaili, Rebekah Bradley; Tian, Yudong; Vila, Daniel Alejandro; Kim, Kyu-Myong

2016-01-01

Cloud movement and evolution signify the complex water and energy transport in the atmosphere-ocean-land system. Detecting, clustering, and tracking clouds as semi coherent cluster objects enables study of their evolution which can complement climate model simulations and enhance satellite retrieval algorithms, where there are large gaps between overpasses. Using an area-overlap cluster tracking algorithm, in this study we examine the trajectories, horizontal extent, and brightness temperature variations of millions of individual cloud clusters over their lifespan, from infrared satellite observations at 30-minute, 4-km resolution, for a period of 11 years. We found that the majority of cold clouds were both small and short-lived and that their frequency and location are influenced by El Nino. More importantly, this large sample of individually tracked clouds shows their horizontal size and temperature evolution. Longer lived clusters tended to achieve their temperature and size maturity milestones at different times, while these stages often occurred simultaneously in shorter lived clusters. On average, clusters with this lag also exhibited a greater rainfall contribution than those where minimum temperature and maximum size stages occurred simultaneously. Furthermore, by examining the diurnal cycle of cluster development over Africa and the Indian subcontinent, we observed differences in the local timing of the maximum occurrence at different life cycle stages. Over land there was a strong diurnal peak in the afternoon while over the ocean there was a semi-diurnal peak composed of longer-lived clusters in the early morning hours and shorter-lived clusters in the afternoon. Building on regional specific work, this study provides a long-term, high-resolution, and global survey of object-based cloud characteristics.

Potential impacts of robust surface roughness indexes on DTM-based segmentation

NASA Astrophysics Data System (ADS)

Trevisani, Sebastiano; Rocca, Michele

2017-04-01

In this study, we explore the impact of robust surface texture indexes based on MAD (median absolute differences), implemented by Trevisani and Rocca (2015), in the unsupervised morphological segmentation of an alpine basin. The area was already object of a geomorphometric analysis, consisting in the roughness-based segmentation of the landscape (Trevisani et al. 2012); the roughness indexes were calculated on a high resolution DTM derived by means of airborne Lidar using the variogram as estimator. The calculated roughness indexes have been then used for the fuzzy clustering (Odeh et al., 1992; Burrough et al., 2000) of the basin, revealing the high informative geomorphometric content of the roughness-based indexes. However, the fuzzy clustering revealed a high fuzziness and a high degree of mixing between textural classes; this was ascribed both to the morphological complexity of the basin and to the high sensitivity of variogram to non-stationarity and signal-noise. Accordingly, we explore how the new implemented roughness indexes based on MAD affect the morphological segmentation of the studied basin. References Burrough, P.A., Van Gaans, P.F.M., MacMillan, R.A., 2000. High-resolution landform classification using fuzzy k-means. Fuzzy Sets and Systems 113, 37-52. Odeh, I.O.A., McBratney, A.B., Chittleborough, D.J., 1992. Soil pattern recognition with fuzzy-c-means: application to classification and soil-landform interrelationships. Soil Sciences Society of America Journal 56, 505-516. Trevisani, S., Cavalli, M. & Marchi, L. 2012, "Surface texture analysis of a high-resolution DTM: Interpreting an alpine basin", Geomorphology, vol. 161-162, pp. 26-39. Trevisani, S. & Rocca, M. 2015, "MAD: Robust image texture analysis for applications in high resolution geomorphometry", Computers and Geosciences, vol. 81, pp. 78-92.

Globular Cluster Abundances from High-resolution, Integrated-light Spectroscopy. IV. The Large Magellanic Cloud: α, Fe-peak, Light, and Heavy Elements

NASA Astrophysics Data System (ADS)

Colucci, Janet E.; Bernstein, Rebecca A.; Cameron, Scott A.; McWilliam, Andrew

2012-02-01

We present detailed chemical abundances in eight clusters in the Large Magellanic Cloud (LMC). We measure abundances of 22 elements for clusters spanning a range in age of 0.05-12 Gyr, providing a comprehensive picture of the chemical enrichment and star formation history of the LMC. The abundances were obtained from individual absorption lines using a new method for analysis of high-resolution (R ~ 25,000), integrated-light (IL) spectra of star clusters. This method was developed and presented in Papers I, II, and III of this series. In this paper, we develop an additional IL χ2-minimization spectral synthesis technique to facilitate measurement of weak (~15 mÅ) spectral lines and abundances in low signal-to-noise ratio data (S/N ~ 30). Additionally, we supplement the IL abundance measurements with detailed abundances that we measure for individual stars in the youngest clusters (age < 2 Gyr) in our sample. In both the IL and stellar abundances we find evolution of [α/Fe] with [Fe/H] and age. Fe-peak abundance ratios are similar to those in the Milky Way (MW), with the exception of [Cu/Fe] and [Mn/Fe], which are sub-solar at high metallicities. The heavy elements Ba, La, Nd, Sm, and Eu are significantly enhanced in the youngest clusters. Also, the heavy to light s-process ratio is elevated relative to the MW ([Ba/Y] >+0.5) and increases with decreasing age, indicating a strong contribution of low-metallicity asymptotic giant branch star ejecta to the interstellar medium throughout the later history of the LMC. We also find a correlation of IL Na and Al abundances with cluster mass in the sense that more massive, older clusters are enriched in the light elements Na and Al with respect to Fe, which implies that these clusters harbor star-to-star abundance variations as is common in the MW. Lower mass, intermediate-age, and young clusters have Na and Al abundances that are lower and more consistent with LMC field stars. Our results can be used to constrain both future chemical evolution models for the LMC and theories of globular cluster formation. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

First results from the faint object camera - High-resolution observations of the central object R136 in the 30 Doradus nebula

NASA Technical Reports Server (NTRS)

Weigelt, G.; Albrecht, R.; Barbieri, C.; Blades, J. C.; Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen, P.; Kamperman, T. M.

1991-01-01

R136 is the luminous central object of the giant H II region 30 Doradus in the LMC. The first high-resolution observations of R136 with the Faint Object Camera on board the Hubble Space Telescope are reported. The physical nature of the brightest component R136a has been a matter of some controversy over the last few years. The UV images obtained show that R136a is a very compact star cluster consisting of more than eight stars within 0.7 arcsec diameter. From these high-resolution images a mass upper limit can be derived for the most luminous stars observed in R136.

High-resolution Self-Organizing Maps for advanced visualization and dimension reduction.

PubMed

Saraswati, Ayu; Nguyen, Van Tuc; Hagenbuchner, Markus; Tsoi, Ah Chung

2018-05-04

Kohonen's Self Organizing feature Map (SOM) provides an effective way to project high dimensional input features onto a low dimensional display space while preserving the topological relationships among the input features. Recent advances in algorithms that take advantages of modern computing hardware introduced the concept of high resolution SOMs (HRSOMs). This paper investigates the capabilities and applicability of the HRSOM as a visualization tool for cluster analysis and its suitabilities to serve as a pre-processor in ensemble learning models. The evaluation is conducted on a number of established benchmarks and real-world learning problems, namely, the policeman benchmark, two web spam detection problems, a network intrusion detection problem, and a malware detection problem. It is found that the visualization resulted from an HRSOM provides new insights concerning these learning problems. It is furthermore shown empirically that broad benefits from the use of HRSOMs in both clustering and classification problems can be expected. Copyright © 2018 Elsevier Ltd. All rights reserved.

Investigating Microphysics of Intracluster Medium with Advanced Hydrodynamic Simulations and X-Ray Observations

NASA Astrophysics Data System (ADS)

Markevitch, Maxim

Clusters of galaxies are the largest virialized mass concentrations in the Universe, and have long been recognized as sensitive cosmological probes. It is becoming increasingly clear that to realize their full potential for cosmology, we need to drastically reduce uncertainties in the cluster mass estimates and their relation to various cluster observables that arise from our lack of knowledge of the microphysics of the intracluster medium (ICM). Such ICM properties as thermal conductivity, viscosity, strength and structure of the magnetic fields, the energy in the cosmic ray components and electron-ion equilibration rates are very uncertain. Each of these can have a significant impact on the cluster thermal balance and the quantities that we observe in the X-ray, SZ, and radio bands. Theoretical estimates of thermal conductivity and viscosity are particularly uncertain -- by orders of magnitude. The heat can be conducted only along the magnetic field lines, but by some estimates, even along the lines it can be effectively suppressed by small- scale field fluctuations. Even less understood is the physical nature and the magnitude of viscosity, which bears directly on the ICM heating and mixing processes and the damping of turbulence. We have identified a method to constrain these quantities by contrasting high-quality X-ray observations of merging clusters with our high-resolution magnetohydrodynamic simulations that would follow the evolution of the magnetic field and include various levels of anisotropic conduction and viscosity. Thermal conduction can best be constrained by comparing X-ray temperature maps for several well-observed merging clusters with the maps for their simulated analogs. The conduction at interesting levels is expected to erase any small-scale temperature nonuniformities on timescales comparable to that of the merger. Currently, the most readily observable effect of viscosity is the suppression of instabilities in the cluster `cold fronts' -- sharp, arc-like contact discontinuities often observed in the cluster high- resolution X-ray images. Most of the observed cold fronts are very smooth, but some are visibly affected by instabilities. We will constrain the viscosity (largely independently of its exact physical nature) by including various levels of viscosity in the simulation of a strategically selected sample of cold front clusters. The forthcoming Astro-H mission opens another avenue to study the ICM viscosity and related phenomena -- by directly observing turbulence in merging and relaxed clusters. The turbulence in our merger simulations with varying viscosity could be directly compared to the levels eventually observed by Astro-H. Over the past several years, we have developed most of the machinery necessary for the above simulations by adding the appropriate code for diffusive physics into FLASH -- the high-resolution, grid-based magnetohydrodynamic code. As part of the proposed project, we will (a) add a few missing physical ingredients to the code and (b) simulate a sample of merging clusters, carefully selected from the XMM and Chandra archives to provide the strongest constraints on thermal conduction and viscosity in the ICM. The comparison with observations will result in strict limits on these microphysical quantities, adding an important element into the astrophysical foundation for the use of clusters as cosmological tools. The proposed research is directly relevant to the ROSES ATP solicitation, because it is a theoretical/numerical study of the physical processes in galaxy clusters, which will lead to predictions that can be tested with observations by the NASA space astrophysics missions XMM, Chandra and Astro-H.

Evolution of a double-front Rayleigh-Taylor system using a graphics-processing-unit-based high-resolution thermal lattice-Boltzmann model.

PubMed

Ripesi, P; Biferale, L; Schifano, S F; Tripiccione, R

2014-04-01

We study the turbulent evolution originated from a system subjected to a Rayleigh-Taylor instability with a double density at high resolution in a two-dimensional geometry using a highly optimized thermal lattice-Boltzmann code for GPUs. Our investigation's initial condition, given by the superposition of three layers with three different densities, leads to the development of two Rayleigh-Taylor fronts that expand upward and downward and collide in the middle of the cell. By using high-resolution numerical data we highlight the effects induced by the collision of the two turbulent fronts in the long-time asymptotic regime. We also provide details on the optimized lattice-Boltzmann code that we have run on a cluster of GPUs.

The impact of clustering and angular resolution on far-infrared and millimeter continuum observations

NASA Astrophysics Data System (ADS)

Béthermin, Matthieu; Wu, Hao-Yi; Lagache, Guilaine; Davidzon, Iary; Ponthieu, Nicolas; Cousin, Morgane; Wang, Lingyu; Doré, Olivier; Daddi, Emanuele; Lapi, Andrea

2017-11-01

Follow-up observations at high-angular resolution of bright submillimeter galaxies selected from deep extragalactic surveys have shown that the single-dish sources are comprised of a blend of several galaxies. Consequently, number counts derived from low- and high-angular-resolution observations are in tension. This demonstrates the importance of resolution effects at these wavelengths and the need for realistic simulations to explore them. We built a new 2 deg2 simulation of the extragalactic sky from the far-infrared to the submillimeter. It is based on an updated version of the 2SFM (two star-formation modes) galaxy evolution model. Using global galaxy properties generated by this model, we used an abundance-matching technique to populate a dark-matter lightcone and thus simulate the clustering. We produced maps from this simulation and extracted the sources, and we show that the limited angular resolution of single-dish instruments has a strong impact on (sub)millimeter continuum observations. Taking into account these resolution effects, we are reproducing a large set of observables, as number counts and their evolution with redshift and cosmic infrared background power spectra. Our simulation consistently describes the number counts from single-dish telescopes and interferometers. In particular, at 350 and 500 μm, we find that the number counts measured by Herschel between 5 and 50 mJy are biased towards high values by a factor 2, and that the redshift distributions are biased towards low redshifts. We also show that the clustering has an important impact on the Herschel pixel histogram used to derive number counts from P(D) analysis. We find that the brightest galaxy in the beam of a 500 μm Herschel source contributes on average to only 60% of the Herschel flux density, but that this number will rise to 95% for future millimeter surveys on 30 m-class telescopes (e.g., NIKA2 at IRAM). Finally, we show that the large number density of red Herschel sources found in observations but not in models might be an observational artifact caused by the combination of noise, resolution effects, and the steepness of color- and flux density distributions. Our simulation, called Simulated Infrared Dusty Extragalactic Sky (SIDES), is publicly available. Our simulation Simulated Infrared Dusty Extragalactic Sky (SIDES) is available at http://cesam.lam.fr/sides.

Clustering analysis of proteins from microbial genomes at multiple levels of resolution.

PubMed

Zaslavsky, Leonid; Ciufo, Stacy; Fedorov, Boris; Tatusova, Tatiana

2016-08-31

Microbial genomes at the National Center for Biotechnology Information (NCBI) represent a large collection of more than 35,000 assemblies. There are several complexities associated with the data: a great variation in sampling density since human pathogens are densely sampled while other bacteria are less represented; different protein families occur in annotations with different frequencies; and the quality of genome annotation varies greatly. In order to extract useful information from these sophisticated data, the analysis needs to be performed at multiple levels of phylogenomic resolution and protein similarity, with an adequate sampling strategy. Protein clustering is used to construct meaningful and stable groups of similar proteins to be used for analysis and functional annotation. Our approach is to create protein clusters at three levels. First, tight clusters in groups of closely-related genomes (species-level clades) are constructed using a combined approach that takes into account both sequence similarity and genome context. Second, clustroids of conservative in-clade clusters are organized into seed global clusters. Finally, global protein clusters are built around the the seed clusters. We propose filtering strategies that allow limiting the protein set included in global clustering. The in-clade clustering procedure, subsequent selection of clustroids and organization into seed global clusters provides a robust representation and high rate of compression. Seed protein clusters are further extended by adding related proteins. Extended seed clusters include a significant part of the data and represent all major known cell machinery. The remaining part, coming from either non-conservative (unique) or rapidly evolving proteins, from rare genomes, or resulting from low-quality annotation, does not group together well. Processing these proteins requires significant computational resources and results in a large number of questionable clusters. The developed filtering strategies allow to identify and exclude such peripheral proteins limiting the protein dataset in global clustering. Overall, the proposed methodology allows the relevant data at different levels of details to be obtained and data redundancy eliminated while keeping biologically interesting variations.

ROSAT HRI images of Abell 85 and Abell 496: Evidence for inhomogeneities in cooling flows

NASA Technical Reports Server (NTRS)

Prestwich, Andrea H.; Guimond, Stephen J.; Luginbuhl, Christian B.; Joy, Marshall

1995-01-01

We present ROSAT high-resolution images of two clusters of galaxies with cooling flows, Abell 496 and Abell 85. In these clusters, X-ray emission on small scales above the general cluster emission is significant at the 3 sigma level. There is no evidence for optical counterparts. If real, the enhancements may be associated with clumps of gas at a lower temperature and higher density than the ambient medium, or hotter, denser gas perhaps compressed by magnetic fields. These observations can be used to test models of how thermal instabilities form and evolve in cooling flows.

Update on ONC's Substellar IMF: A Second Peak in the Brown Dwarf Regime

NASA Astrophysics Data System (ADS)

Drass, Holger; Bayo, A.; Chini, R.; Haas, M.

2017-06-01

The Orion Nebular Cluster (ONC) has become the prototype cluster for studying the Initial Mass Function (IMF). In a deep JHK survey of the ONC with HAWK-I we detected a large population of 900 Brown Dwarfs and Planetary Mass Object candidates presenting a pronounced second peak in the substellar IMF. One of the most obvious issues of this result is the verification of cluster membership. The analysis so far was mainly based on statistical consideration. In this presentation I will show the results from using different high-resolution extinction map to determine the ONC membership.

The implementation of sea ice model on a regional high-resolution scale

NASA Astrophysics Data System (ADS)

Prasad, Siva; Zakharov, Igor; Bobby, Pradeep; McGuire, Peter

2015-09-01

The availability of high-resolution atmospheric/ocean forecast models, satellite data and access to high-performance computing clusters have provided capability to build high-resolution models for regional ice condition simulation. The paper describes the implementation of the Los Alamos sea ice model (CICE) on a regional scale at high resolution. The advantage of the model is its ability to include oceanographic parameters (e.g., currents) to provide accurate results. The sea ice simulation was performed over Baffin Bay and the Labrador Sea to retrieve important parameters such as ice concentration, thickness, ridging, and drift. Two different forcing models, one with low resolution and another with a high resolution, were used for the estimation of sensitivity of model results. Sea ice behavior over 7 years was simulated to analyze ice formation, melting, and conditions in the region. Validation was based on comparing model results with remote sensing data. The simulated ice concentration correlated well with Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and Ocean and Sea Ice Satellite Application Facility (OSI-SAF) data. Visual comparison of ice thickness trends estimated from the Soil Moisture and Ocean Salinity satellite (SMOS) agreed with the simulation for year 2010-2011.

Structure of the Ebola VP35 interferon inhibitory domain.

PubMed

Leung, Daisy W; Ginder, Nathaniel D; Fulton, D Bruce; Nix, Jay; Basler, Christopher F; Honzatko, Richard B; Amarasinghe, Gaya K

2009-01-13

Ebola viruses (EBOVs) cause rare but highly fatal outbreaks of viral hemorrhagic fever in humans, and approved treatments for these infections are currently lacking. The Ebola VP35 protein is multifunctional, acting as a component of the viral RNA polymerase complex, a viral assembly factor, and an inhibitor of host interferon (IFN) production. Mutation of select basic residues within the C-terminal half of VP35 abrogates its dsRNA-binding activity, impairs VP35-mediated IFN antagonism, and attenuates EBOV growth in vitro and in vivo. Because VP35 contributes to viral escape from host innate immunity and is required for EBOV virulence, understanding the structural basis for VP35 dsRNA binding, which correlates with suppression of IFN activity, is of high importance. Here, we report the structure of the C-terminal VP35 IFN inhibitory domain (IID) solved to a resolution of 1.4 A and show that VP35 IID forms a unique fold. In the structure, we identify 2 basic residue clusters, one of which is important for dsRNA binding. The dsRNA binding cluster is centered on Arg-312, a highly conserved residue required for IFN inhibition. Mutation of residues within this cluster significantly changes the surface electrostatic potential and diminishes dsRNA binding activity. The high-resolution structure and the identification of the conserved dsRNA binding residue cluster provide opportunities for antiviral therapeutic design. Our results suggest a structure-based model for dsRNA-mediated innate immune antagonism by Ebola VP35 and other similarly constructed viral antagonists.

Chandra/HETG Observations of NGC1275

NASA Astrophysics Data System (ADS)

Reynolds, Christopher

2017-09-01

NGC1275 is the active galactic nucleus (AGN) at the heart of the Perseus cluster of galaxies responsible for the mechanical heating of the intracluster medium (ICM) cool core. We propose a deep (500ks) HETG observation of NGC1275, allowing the first high-S/N, high resolution spectrum of this AGN free from contamination by the bright ICM. We will seek the signatures of powerful winds, answering the central question of whether galactic-scale quasar-mode feedback is occuring simultaneously with cluster-scale radio-mode feedback. We also probe circumnuclear gas (i.e. the fuel supply) through the 6.4keV line previously seen by XMM and Hitomi. These issues are crucial unknowns in our models for the evolution of the most massive galaxies and cluster cores.

High-resolution neutron and X-ray diffraction room-temperature studies of an H-FABP-oleic acid complex: study of the internal water cluster and ligand binding by a transferred multipolar electron-density distribution.

PubMed

Howard, E I; Guillot, B; Blakeley, M P; Haertlein, M; Moulin, M; Mitschler, A; Cousido-Siah, A; Fadel, F; Valsecchi, W M; Tomizaki, Takashi; Petrova, T; Claudot, J; Podjarny, A

2016-03-01

Crystal diffraction data of heart fatty acid binding protein (H-FABP) in complex with oleic acid were measured at room temperature with high-resolution X-ray and neutron protein crystallography (0.98 and 1.90 Å resolution, respectively). These data provided very detailed information about the cluster of water molecules and the bound oleic acid in the H-FABP large internal cavity. The jointly refined X-ray/neutron structure of H-FABP was complemented by a transferred multipolar electron-density distribution using the parameters of the ELMAMII library. The resulting electron density allowed a precise determination of the electrostatic potential in the fatty acid (FA) binding pocket. Bader's quantum theory of atoms in molecules was then used to study interactions involving the internal water molecules, the FA and the protein. This approach showed H⋯H contacts of the FA with highly conserved hydrophobic residues known to play a role in the stabilization of long-chain FAs in the binding cavity. The determination of water hydrogen (deuterium) positions allowed the analysis of the orientation and electrostatic properties of the water molecules in the very ordered cluster. As a result, a significant alignment of the permanent dipoles of the water molecules with the protein electrostatic field was observed. This can be related to the dielectric properties of hydration layers around proteins, where the shielding of electrostatic interactions depends directly on the rotational degrees of freedom of the water molecules in the interface.

STED super-resolution microscopy reveals an array of MINOS clusters along human mitochondria

PubMed Central

Jans, Daniel C.; Wurm, Christian A.; Riedel, Dietmar; Wenzel, Dirk; Stagge, Franziska; Deckers, Markus; Rehling, Peter; Jakobs, Stefan

2013-01-01

The mitochondrial inner membrane organizing system (MINOS) is a conserved large hetero-oligomeric protein complex in the mitochondrial inner membrane, crucial for the maintenance of cristae morphology. MINOS has been suggested to represent the core of an extended protein network that controls mitochondrial function and structure, and has been linked to several human diseases. The spatial arrangement of MINOS within mitochondria is ill-defined, however. Using super-resolution stimulated emission depletion (STED) microscopy and immunogold electron microscopy, we determined the distribution of three known human MINOS subunits (mitofilin, MINOS1, and CHCHD3) in mammalian cells. Super-resolution microscopy revealed that all three subunits form similar clusters within mitochondria, and that MINOS is more abundant in mitochondria around the nucleus than in peripheral mitochondria. At the submitochondrial level, mitofilin, a core MINOS subunit, is preferentially localized at cristae junctions. In primary human fibroblasts, mitofilin labeling uncovered a regularly spaced pattern of clusters arranged in parallel to the cell growth surfaces. We suggest that this array of MINOS complexes might explain the observed phenomenon of largely horizontally arranged cristae junctions that connect the inner boundary membrane to lamellar cristae. The super-resolution images demonstrate an unexpectedly high level of regularity in the nanoscale distribution of the MINOS complex in human mitochondria, supporting an integrating role of MINOS in the structural organization of the organelle. PMID:23676277

Climbing the Ladder of Star Formation Feedback

NASA Astrophysics Data System (ADS)

Frank, Adam

2012-10-01

While much is understood about isolated star formation, the opposite is true for star formation in clusters of both low and high mass. In particular the mechanisms by which many coevally formed stars affect their parent cloud environment remains poorly characterized. Fundamental questions such as interplay between multiple outflows, ionization fronts and turbulence are just beginning to be fully articulated. Distinguishing between the nature of feedback in clusters of different mass is also critical. In high mass clusters O stars are expected to dominate energetics while in low mass clusters multiple collimated outflows may represent the dominant feedback mechanism. Thus the issue of feedback modalities in clusters of different masses represents one of the major challenges to the next generation of star formation studies. In this proposal we seek to carry forward a focused theoretical study of feedback in both low and high-mass cluster environments with direct connections to observations. Using a state-of-the-art Adaptive Mesh Refinement MHD multi-physics code {developed by our group} we propose two computational studies: {1} multiple, interacting outflows and their role in altering the properties of a parent low mass cluster {2} Poorly collimated outburst/outflows from massive star{s} and their effect on high mass cluster star forming environments. In both cases we will use initial conditions derived from high-resolution AMR MHD simulations of cloud/cluster formation. Synthetic observations derived from the simulations {in a variety of emission lines from ions to atoms to molecules} will allow for direct contact with HST and other star formation databases.

The X-Ray Surveyor Mission: A Concept Study

NASA Technical Reports Server (NTRS)

Gaskin, Jessica A.; Weisskopf, Martin C.; Vikhlinin, Alexey; Tananbaum, Harvey D.; Bandler, Simon R.; Bautz, Marshall W.; Burrows, David N.; Falcone, Abraham D.; Harrison, Fiona A.; Heilmann, Ralf K.;

Peering into the heart of galactic star formation: A detailed characterization of infrared-dark clouds

NASA Astrophysics Data System (ADS)

Ragan, Sarah E.

2009-09-01

Everything we know about other galaxies is based on light from massive stars, yet, in our own Galaxy, it's the formation of massive stars that is the least understood. Star formation studies to date have focused on nearby, low-mass regions, but the bulk of star formation takes place in massive clusters, which takes place primarily in the inner-Galaxy, where the bulk of the molecular gas resides. To learn about the conditions under which massive clusters form, we seek out their precursors, called infrared-dark clouds (IRDCs). We present the results of a high-resolution multi-wavelength observational study of IRDCs, which vastly improves our knowledge of the initial conditions of cluster formation. Beginning with IRDC candidates identified with Midcourse Science Experiment (MSX) survey data, we map 41 IRDCs in the N 2 H + 1 [arrow right] 0, CS 2 [arrow right] 1 and C 18 O 1 [arrow right] 0 molecular transitions using the Five College Radio Astronomy Observatory. We examine the stellar content and absorption structure with Spitzer Space Telescope observations of eleven IRDCs, and we use Very Large Array NH 3 observations to probe the kinematics and chemistry of six IRDCs. Our comprehensive high-resolution study of IRDCs confirms that these objects are cold and dense precursors to massive stars and clusters. For the first time. we quantify IRDC sub-structure on sub-parsec scales and show the kinematic structure of IRDCs is diverse and depends on associated local star- formation activity. Overall, IRDCs exhibit non-thermal dynamics, suggesting that turbulence and systematic motions dominate. IRDC temperatures are between 8 and 16 K and are mostly flat with hints of a rise near the edges due to external heating. This study shows that IRDCs are a unique star-forming environment, one that dominates the star formation in the Milky Way. Using high-resolution observations, we have quantified the structure, star formation, kinematics, and chemistry of infrared-dark clouds. Our study of sub- structure in particular shows that IRDCs are undergoing fragmentation and are the precursors to star clusters, and thus we have placed IRDCs in context with Galactic star formation. The characterization presented here offers new constraints on theories of molecular cloud fragmentation and clustered star formation.

Dynamical Mass Segregation Versus Disruption of Binary Stars in Dense Stellar Systems

NASA Astrophysics Data System (ADS)

de Grijs, Richard; Li, C.; Deng, L.

2013-01-01

Upon their formation, dynamically cool (collapsing) star clusters will, within only a few million years, achieve stellar mass segregation for stars down to a few solar masses due to gravitational two-body encounters. Since binary systems are, on average, more massive than single stars, one would expect them to also rapidly mass segregate dynamically. Contrary to these expectations and based on high-resolution Hubble Space Telescope observations, we show that the compact, 15-30 Myr-old Large Magellanic Cloud cluster NGC 1818 is characterized by an increasing fraction of F-star binary systems (with combined masses of 1.3-1.6 solar masses) with increasing distance from the cluster center. This offers unprecedented support of the theoretically predicted but thus far unobserved dynamical disruption processes of the significant population of "soft" binary systems (with relatively low binding energies compared to the kinetic energy of their stellar members) in star clusters, which we could unravel by virtue of the cluster's unique combination of youth and high stellar density.

Fast Plasma Instrument for MMS: Simulation Results

NASA Technical Reports Server (NTRS)

Figueroa-Vinas, Adolfo; Adrian, Mark L.; Lobell, James V.; Simpson, David G.; Barrie, Alex; Winkert, George E.; Yeh, Pen-Shu; Moore, Thomas E.

2008-01-01

Magnetospheric Multiscale (MMS) mission will study small-scale reconnection structures and their rapid motions from closely spaced platforms using instruments capable of high angular, energy, and time resolution measurements. The Dual Electron Spectrometer (DES) of the Fast Plasma Instrument (FPI) for MMS meets these demanding requirements by acquiring the electron velocity distribution functions (VDFs) for the full sky with high-resolution angular measurements every 30 ms. This will provide unprecedented access to electron scale dynamics within the reconnection diffusion region. The DES consists of eight half-top-hat energy analyzers. Each analyzer has a 6 deg. x 11.25 deg. Full-sky coverage is achieved by electrostatically stepping the FOV of each of the eight sensors through four discrete deflection look directions. Data compression and burst memory management will provide approximately 30 minutes of high time resolution data during each orbit of the four MMS spacecraft. Each spacecraft will intelligently downlink the data sequences that contain the greatest amount of temporal structure. Here we present the results of a simulation of the DES analyzer measurements, data compression and decompression, as well as ground-based analysis using as a seed re-processed Cluster/PEACE electron measurements. The Cluster/PEACE electron measurements have been reprocessed through virtual DES analyzers with their proper geometrical, energy, and timing scale factors and re-mapped via interpolation to the DES angular and energy phase-space sampling measurements. The results of the simulated DES measurements are analyzed and the full moments of the simulated VDFs are compared with those obtained from the Cluster/PEACE spectrometer using a standard quadrature moment, a newly implemented spectral spherical harmonic method, and a singular value decomposition method. Our preliminary moment calculations show a remarkable agreement within the uncertainties of the measurements, with the results obtained by the Cluster/PEACE electron spectrometers. The data analyzed was selected because it represented a potential reconnection event as currently published.

[Styles of interpersonal conflict in patients with panic disorder, alcoholism, rheumatoid arthritis and healthy controls: a cluster analysis study].

PubMed

Eher, R; Windhaber, J; Rau, H; Schmitt, M; Kellner, E

2000-05-01

Conflict and conflict resolution in intimate relationships are not only among the most important factors influencing relationship satisfaction but are also seen in association with clinical symptoms. Styles of conflict will be assessed in patients suffering from panic disorder with and without agoraphobia, in alcoholics and in patients suffering from rheumatoid arthritis. 176 patients and healthy controls filled out the Styles of Conflict Inventory and questionnaires concerning severity of clinical symptoms. A cluster analysis revealed 5 types of conflict management. Healthy controls showed predominantely assertive and constructive styles, patients with panic disorder showed high levels of cognitive and/or behavioral aggression. Alcoholics showed high levels of repressed aggression, and patients with rheumatoid arthritis often did not exhibit any aggression during conflict. 5 Clusters of conflict pattern have been identified by cluster analysis. Each patient group showed considerable different patterns of conflict management.

Depth of focus extended microscope configuration for imaging of incorporated groups of molecules, DNA constructs and clusters inside bacterial cells

NASA Astrophysics Data System (ADS)

Fessl, Tomas; Ben-Yaish, Shai; Vacha, Frantisek; Adamec, Frantisek; Zalevsky, Zeev

2009-07-01

Imaging of small objects such as single molecules, DNA clusters and single bacterial cells is problematic not only due to the lateral resolution that is obtainable in currently existing microscopy but also, and as much fundamentally limiting, due to the lack of sufficient axial depth of focus to have the full object focused simultaneously. Extension in depth of focus is helpful also for single molecule steady state FRET measurements. In this technique it is crucial to obtain data from many well focused molecules, which are often located in different axial depths. In this paper we present the implementation of an all-optical and a real time technique of extension in the depth of focus that may be incorporated in any high NA microscope system and to be used for the above mentioned applications. We demonstrate experimentally how after the integration of special optical element in high NA 100× objective lens of a single molecule imaging microscope system, the depth of focus is significantly improved while maintaining the same lateral resolution in imaging applications of incorporated groups of molecules, DNA constructs and clusters inside bacterial cells.

Segmentation of High Angular Resolution Diffusion MRI using Sparse Riemannian Manifold Clustering

PubMed Central

Wright, Margaret J.; Thompson, Paul M.; Vidal, René

2015-01-01

We address the problem of segmenting high angular resolution diffusion imaging (HARDI) data into multiple regions (or fiber tracts) with distinct diffusion properties. We use the orientation distribution function (ODF) to represent HARDI data and cast the problem as a clustering problem in the space of ODFs. Our approach integrates tools from sparse representation theory and Riemannian geometry into a graph theoretic segmentation framework. By exploiting the Riemannian properties of the space of ODFs, we learn a sparse representation for each ODF and infer the segmentation by applying spectral clustering to a similarity matrix built from these representations. In cases where regions with similar (resp. distinct) diffusion properties belong to different (resp. same) fiber tracts, we obtain the segmentation by incorporating spatial and user-specified pairwise relationships into the formulation. Experiments on synthetic data evaluate the sensitivity of our method to image noise and the presence of complex fiber configurations, and show its superior performance compared to alternative segmentation methods. Experiments on phantom and real data demonstrate the accuracy of the proposed method in segmenting simulated fibers, as well as white matter fiber tracts of clinical importance in the human brain. PMID:24108748

Localization-based super-resolution imaging meets high-content screening.

PubMed

Beghin, Anne; Kechkar, Adel; Butler, Corey; Levet, Florian; Cabillic, Marine; Rossier, Olivier; Giannone, Gregory; Galland, Rémi; Choquet, Daniel; Sibarita, Jean-Baptiste

2017-12-01

Single-molecule localization microscopy techniques have proven to be essential tools for quantitatively monitoring biological processes at unprecedented spatial resolution. However, these techniques are very low throughput and are not yet compatible with fully automated, multiparametric cellular assays. This shortcoming is primarily due to the huge amount of data generated during imaging and the lack of software for automation and dedicated data mining. We describe an automated quantitative single-molecule-based super-resolution methodology that operates in standard multiwell plates and uses analysis based on high-content screening and data-mining software. The workflow is compatible with fixed- and live-cell imaging and allows extraction of quantitative data like fluorophore photophysics, protein clustering or dynamic behavior of biomolecules. We demonstrate that the method is compatible with high-content screening using 3D dSTORM and DNA-PAINT based super-resolution microscopy as well as single-particle tracking.

A High-Resolution Cluster of Oceanographic Instruments for Boundary Layer Measurements under Ice.

DTIC Science & Technology

1985-11-01

arrangement for use with laser velocimetry. The EO components are mounted on an aluminum chassis, which is in turn placed in an underwater housing made...temperature/conductivity probe pair used * on the HRC cluster. It consists of a thermistor probe (FASTIP, Model FP07, Thermometrics , Inc.) and a dual...component. The orientation of all three DLT)V pairs is shown in Figure 1. 3.2 Temperature and Conductivity Probes The FASTIP thermistor by Thermometrics

Analysis of plasmaspheric plumes: CLUSTER and IMAGE observations and numerical simulations

NASA Technical Reports Server (NTRS)

Darouzet, Fabien; DeKeyser, Johan; Decreau, Pierrette; Gallagher, Dennis; Pierrard, Viviane; Lemaire, Joseph; Dandouras, Iannis; Matsui, Hiroshi; Dunlop, Malcolm; Andre, Mats

2005-01-01

Plasmaspheric plumes have been routinely observed by CLUSTER and IMAGE. The CLUSTER mission provides high time resolution four-point measurements of the plasmasphere near perigee. Total electron density profiles can be derived from the plasma frequency and/or from the spacecraft potential (note that the electron spectrometer is usually not operating inside the plasmasphere); ion velocity is also measured onboard these satellites (but ion density is not reliable because of instrumental limitations). The EUV imager onboard the IMAGE spacecraft provides global images of the plasmasphere with a spatial resolution of 0.1 RE every 10 minutes; such images acquired near apogee from high above the pole show the geometry of plasmaspheric plumes, their evolution and motion. We present coordinated observations for 3 plume events and compare CLUSTER in-situ data (panel A) with global images of the plasmasphere obtained from IMAGE (panel B), and with numerical simulations for the formation of plumes based on a model that includes the interchange instability mechanism (panel C). In particular, we study the geometry and the orientation of plasmaspheric plumes by using a four-point analysis method, the spatial gradient. We also compare several aspects of their motion as determined by different methods: (i) inner and outer plume boundary velocity calculated from time delays of this boundary observed by the wave experiment WHISPER on the four spacecraft, (ii) ion velocity derived from the ion spectrometer CIS onboard CLUSTER, (iii) drift velocity measured by the electron drift instrument ED1 onboard CLUSTER and (iv) global velocity determined from successive EUV images. These different techniques consistently indicate that plasmaspheric plumes rotate around the Earth, with their foot fully co-rotating, but with their tip rotating slower and moving farther out.

The linkage between ribosomal crystallography, metal ions, heteropolytungstates and functional flexibility

PubMed Central

Bashan, Anat; Yonath, Ada

2009-01-01

Crystallography of ribosomes, the universal cell nucleoprotein assemblies facilitating the translation of the genetic-code into proteins, met with severe problems owing to their large size, complex structure, inherent flexibility and high conformational variability. For the case of the small ribosomal subunit, which caused extreme difficulties, post crystallization treatment by minute amounts of a heteropolytungstate cluster allowed structure determination at atomic resolution. This cluster played a dual role in ribosomal crystallography: providing anomalous phasing power and dramatically increased the resolution, by stabilization of a selected functional conformation. Thus, four out of the fourteen clusters that bind to each of the crystallized small subunits are attached to a specific ribosomal protein in a fashion that may control a significant component of the subunit internal flexibility, by “gluing” symmetrical related subunits. Here we highlight basic issues in the relationship between metal ions and macromolecules and present common traits controlling in the interactions between polymetalates and various macromolecules, which may be extended towards the exploitation of polymetalates for therapeutical treatment. PMID:19915655

Star Cluster Formation in Cosmological Simulations. I. Properties of Young Clusters

NASA Astrophysics Data System (ADS)

Li, Hui; Gnedin, Oleg Y.; Gnedin, Nickolay Y.; Meng, Xi; Semenov, Vadim A.; Kravtsov, Andrey V.

2017-01-01

We present a new implementation of star formation in cosmological simulations by considering star clusters as a unit of star formation. Cluster particles grow in mass over several million years at the rate determined by local gas properties, with high time resolution. The particle growth is terminated by its own energy and momentum feedback on the interstellar medium. We test this implementation for Milky Way-sized galaxies at high redshift by comparing the properties of model clusters with observations of young star clusters. We find that the cluster initial mass function is best described by a Schechter function rather than a single power law. In agreement with observations, at low masses the logarithmic slope is α ≈ 1.8{--}2, while the cutoff at high mass scales with the star formation rate (SFR). A related trend is a positive correlation between the surface density of the SFR and fraction of stars contained in massive clusters. Both trends indicate that the formation of massive star clusters is preferred during bursts of star formation. These bursts are often associated with major-merger events. We also find that the median timescale for cluster formation ranges from 0.5 to 4 Myr and decreases systematically with increasing star formation efficiency. Local variations in the gas density and cluster accretion rate naturally lead to the scatter of the overall formation efficiency by an order of magnitude, even when the instantaneous efficiency is kept constant. Comparison of the formation timescale with the observed age spread of young star clusters provides an additional important constraint on the modeling of star formation and feedback schemes.

Medium resolution spectroscopy and chemical composition of Galactic globular clusters

NASA Astrophysics Data System (ADS)

Khamidullina, D. A.; Sharina, M. E.; Shimansky, V. V.; Davoust, E.

We used integrated-light medium-resolution spectra of six Galactic globular clusters and model stellar atmospheres to carry out population synthesis and to derive chemical composition and age of the clusters. We used medium-resolution spectra of globular clusters published by Schiavon et al. (2005), as well as our long-slit observations with the 1.93 m telescope of the Haute Provence Observatory. The observed spectra were fitted to the theoretical ones interactively. As an initial approach, we used masses, radii and log g of stars in the clusters corresponding to the best fitting isochrones in the observed color-magnitude diagrams. The computed synthetic blanketed spectra of stars were summed according to the Chabrier mass function. To improve the determination of age and helium content, the shape and depth of the Balmer absorption lines was analysed. The abundances of Mg, Ca, C and several other elements were derived. A reasonable agreement with the literature data both in chemical composition and in age of the clusters is found. Our method might be useful for the development of stellar population models and for a better understanding of extragalactic star clusters.

Multiple Stellar Populations in Star Clusters

NASA Astrophysics Data System (ADS)

Piotto, G.

2013-09-01

For half a century it had been astronomical dogma that a globular cluster (GC) consists of stars born at the same time out of the same material, and this doctrine has borne rich fruits. In recent years, high resolution spectroscopy and high precision photometry (from space and ground-based observations) have shattered this paradigm, and the study of GC populations has acquired a new life that is now moving it in new directions. Evidence of multiple stellar populations have been identified in the color-magnitude diagrams of several Galactic and Magellanic Cloud GCs where they had never been imagined before.

Simulating the interaction of jets with the intracluster medium

NASA Astrophysics Data System (ADS)

Weinberger, Rainer; Ehlert, Kristian; Pfrommer, Christoph; Pakmor, Rüdiger; Springel, Volker

2017-10-01

Jets from supermassive black holes in the centres of galaxy clusters are a potential candidate for moderating gas cooling and subsequent star formation through depositing energy in the intracluster gas. In this work, we simulate the jet-intracluster medium interaction using the moving-mesh magnetohydrodynamics code arepo. Our model injects supersonic, low-density, collimated and magnetized outflows in cluster centres, which are then stopped by the surrounding gas, thermalize and inflate low-density cavities filled with cosmic rays. We perform high-resolution, non-radiative simulations of the lobe creation, expansion and disruption, and find that its dynamical evolution is in qualitative agreement with simulations of idealized low-density cavities that are dominated by a large-scale Rayleigh-Taylor instability. The buoyant rising of the lobe does not create energetically significant small-scale chaotic motion in a volume-filling fashion, but rather a systematic upward motion in the wake of the lobe and a corresponding back-flow antiparallel to it. We find that, overall, 50 per cent of the injected energy ends up in material that is not part of the lobe, and about 25 per cent remains in the inner 100 kpc. We conclude that jet-inflated, buoyantly rising cavities drive systematic gas motions that play an important role in heating the central regions, while mixing of lobe material is subdominant. Encouragingly, the main mechanisms responsible for this energy deposition can be modelled already at resolutions within reach in future, high-resolution cosmological simulations of galaxy clusters.

The MICE grand challenge lightcone simulation - I. Dark matter clustering

NASA Astrophysics Data System (ADS)

Fosalba, P.; Crocce, M.; Gaztañaga, E.; Castander, F. J.

2015-04-01

We present a new N-body simulation from the Marenostrum Institut de Ciències de l'Espai (MICE) collaboration, the MICE Grand Challenge (MICE-GC), containing about 70 billion dark matter particles in a (3 Gpc h-1)3 comoving volume. Given its large volume and fine spatial resolution, spanning over five orders of magnitude in dynamic range, it allows an accurate modelling of the growth of structure in the universe from the linear through the highly non-linear regime of gravitational clustering. We validate the dark matter simulation outputs using 3D and 2D clustering statistics, and discuss mass-resolution effects in the non-linear regime by comparing to previous simulations and the latest numerical fits. We show that the MICE-GC run allows for a measurement of the BAO feature with per cent level accuracy and compare it to state-of-the-art theoretical models. We also use sub-arcmin resolution pixelized 2D maps of the dark matter counts in the lightcone to make tomographic analyses in real and redshift space. Our analysis shows the simulation reproduces the Kaiser effect on large scales, whereas we find a significant suppression of power on non-linear scales relative to the real space clustering. We complete our validation by presenting an analysis of the three-point correlation function in this and previous MICE simulations, finding further evidence for mass-resolution effects. This is the first of a series of three papers in which we present the MICE-GC simulation, along with a wide and deep mock galaxy catalogue built from it. This mock is made publicly available through a dedicated web portal, http://cosmohub.pic.es.

Infrared spectra of seeded hydrogen clusters: (para-H2)N-N2O and (ortho-H2)N-N2O, N = 2-13.

PubMed

Tang, Jian; McKellar, A R W

2005-09-15

High-resolution infrared spectra of clusters containing para-H2 and/or ortho-H2 and a single nitrous oxide molecule are studied in the 2225-cm(-1) region of the upsilon1 fundamental band of N2O. The clusters are formed in pulsed supersonic jet expansions from a cooled nozzle and probed using a tunable infrared diode laser spectrometer. The simple symmetric rotor-type spectra generally show no resolved K structure, with prominent Q-branch features for ortho-H2 but not para-H2 clusters. The observed vibrational shifts and rotational constants are reported. There is no obvious indication of superfluid effects for para-H2 clusters up to N=13. Sharp transitions due to even larger clusters are observed, but no definite assignments are possible. Mixed (para-H2)N-(ortho-H2)M-N2O cluster line positions can be well predicted by linear interpolation between the corresponding transitions of the pure clusters.

MERGING GALAXY CLUSTERS: OFFSET BETWEEN THE SUNYAEV-ZEL'DOVICH EFFECT AND X-RAY PEAKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Molnar, Sandor M.; Hearn, Nathan C.; Stadel, Joachim G., E-mail: sandor@phys.ntu.edu.tw

2012-03-20

Galaxy clusters, the most massive collapsed structures, have been routinely used to determine cosmological parameters. When using clusters for cosmology, the crucial assumption is that they are relaxed. However, subarcminute resolution Sunyaev-Zel'dovich (SZ) effect images compared with high-resolution X-ray images of some clusters show significant offsets between the two peaks. We have carried out self-consistent N-body/hydrodynamical simulations of merging galaxy clusters using FLASH to study these offsets quantitatively. We have found that significant displacements result between the SZ and X-ray peaks for large relative velocities for all masses used in our simulations as long as the impact parameters were aboutmore » 100-250 kpc. Our results suggest that the SZ peak coincides with the peak in the pressure times the line-of-sight characteristic length and not the pressure maximum (as it would for clusters in equilibrium). The peak in the X-ray emission, as expected, coincides with the density maximum of the main cluster. As a consequence, the morphology of the SZ signal, and therefore the offset between the SZ and X-ray peaks, change with viewing angle. As an application, we compare the morphologies of our simulated images to observed SZ and X-ray images and mass surface densities derived from weak-lensing observations of the merging galaxy cluster CL0152-1357, we find that a large relative velocity of 4800 km s{sup -1} is necessary to explain the observations. We conclude that an analysis of the morphologies of multi-frequency observations of merging clusters can be used to put meaningful constraints on the initial parameters of the progenitors.« less

Dynamics and stellar population of the Galactic Center (French Title: Étude de la cinématique et de la population stellaire du Centre Galactique)

NASA Astrophysics Data System (ADS)

Paumard, Thibaut

2003-09-01

The central parsec of the Galaxy has been observed using BEAR spectroimagery at high spectral resolution (up to 21 km/s) and medium spatial resolution (0.5"), in Bracket gamma (2.16 microns) and He I (2.06 microns), and high resolution imaging. These data were used to study the young, massive stars of the central parsec, and the structure and dynamics of ionized gas in Sgr A West. The stellar population has been separated into two groups: the IRS 16 complex of 6 LBVs, and at least 20 Wolf-Rayets. The IRS 13E complex has been identified as a cluster of at least 6 massive stars. All this is consistent with the young stars being born in a massive cluster a few tens of parsecs from the Galactic Centre. Providing a deep insight into the morphology of Sgr A West, our data allowed us to derive a kinematic model for the Northern Arm. Our results are in agreement with the idea that the Minispiral is made of ionisation fronts of wider neutral clouds, gravitationally stretched, coming from the CND.

A Tale of Tidal Tales in the Milky Way

NASA Astrophysics Data System (ADS)

Casey, Andrew R.

2014-05-01

Hundreds of globular clusters and dwarf galaxies encircle the Milky Way. Many of these systems have undergone partial disruption due to tidal forces, littering the halo with stellar streams. These tidal tails are sensitive to the Galactic potential, facilitating an excellent laboratory to investigate galaxy formation and evolution. To better understand the emergence of the Milky Way, this thesis examines the dynamics and chemistry of a number of known stellar streams. In particular the Sagittarius, Orphan and Aquarius streams are investigated. Low-resolution spectra for hundreds of stars in the direction of the Virgo Over-Density and the Sagittarius northern leading arms have been obtained. Multiple significant kinematic groups are recovered in this accretion-dominated region, confirming detections by previous studies. A metal-poor population ([Fe/H] = -1.7) in the Sagittarius stream is discovered due to a photometric selection that was inadvertently biased towards more metal-poor stars. Positions and kinematics of Sagittarius stream members are compared with existing best-fitting dark matter models, and a triaxial dark matter halo distribution is favoured. The Orphan stream is appropriately named, as no parent system has yet been identified. The stream has an extremely low surface brightness, which makes distinguishing stream members from field stars particularly challenging. From low-resolution spectra obtained for hundreds of stars, we identify likely Orphan stream red giant branch stars on the basis of velocity, metallicity, surface gravity, and proper motions. A negligible intrinsic velocity dispersion is found, and a wide spread in metallicities is observed, which suggests the undiscovered parent is similar to the present-day dwarf galaxies in the Milky Way. High-resolution spectra were obtained for five Orphan stream candidates, and the intrinsic chemical dispersion found from low-resolution spectra is confirmed from these data. Detailed chemical abundances for high-probability Orphan stream candidates further indicates a dwarf galaxy host. Low [α/Fe] abundance ratios are observed, and lower limits for [Ba/Y] are found, which sit well above the observed chemical evolution in the Milky Way. This thesis provides the first detailed chemical evidence for a dwarf galaxy origin, allowing us to rule out any association between the Orphan stream and the globular cluster NGC 2419. High-resolution, high S/N spectra for one third of the Aquarius stream have also been obtained. Contrary to previous work, there is no evidence that the Aquarius stream has resulted from a disrupted globular cluster. Detailed chemistry suggests that the Aquarius stars are galactic in origin, and not disrupted members from either a globular cluster or a dwarf galaxy. In the absence of compelling dynamic and/or chemical evidence to suggest otherwise, we advocate the 'Aquarius Group' as a more appropriate description, and hypothesise that the moving group has resulted from a disk-satellite interaction. The high-resolution spectra presented in this thesis has been analysed using custom written software, ironically named 'Spectroscopy Made Hard'. A detailed description of the software, capabilities and algorithms are presented. Spectroscopy Made Hard includes an intuitive graphical user interface, allowing the spectroscopist to interactively modify any aspect of their analysis. The software is designed to facilitate the transition between small and massive sample sizes, while ensuring data provenance, tangibility, and reproducibility. Future applications for this software are outlined, with a particular focus on the large scale high-resolution spectroscopic surveys being planned or currently undertaken.

Resolution of the apparent discrepancy between the number of massive subhaloes in Abell 2744 and ΛCDM

NASA Astrophysics Data System (ADS)

Mao, Tian-Xiang; Wang, Jie; Frenk, Carlos S.; Gao, Liang; Li, Ran; Wang, Qiao; Cao, Xiaoyue; Li, Ming

2018-07-01

Schwinn et al. have recently compared the abundance and distribution of massive substructures identified in a gravitational lensing analysis of Abell 2744 by Jauzac et al. and N-body simulation, and found no cluster in Lambda cold dark matter (ΛCDM) simulation that is similar to Abell 2744. Schwinn et al. identified the measured projected aperture masses with the actual masses associated with subhaloes in the Millenium XXL N-body simulation. We have used the high-resolution Phoenix cluster simulations to show that such an identification is incorrect: the aperture mass is dominated by mass in the body of the cluster that happens to be projected along the line of sight to the subhalo. This enhancement varies from factors of a few to factors of more than 100, particularly for subhaloes projected near the centre of the cluster. We calculate aperture masses for subhaloes in our simulation and compare them to the measurements for Abell 2744. We find that the data for Abell 2744 are in excellent agreement with the matched predictions from ΛCDM. We provide further predictions for aperture mass functions of subhaloes in idealized surveys with varying mass detection thresholds.

Weighing galaxy clusters with gas. II. On the origin of hydrostatic mass bias in ΛCDM galaxy clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, Kaylea; Nagai, Daisuke; Yu, Liang

2014-02-20

The use of galaxy clusters as cosmological probes hinges on our ability to measure their masses accurately and with high precision. Hydrostatic mass is one of the most common methods for estimating the masses of individual galaxy clusters, which suffer from biases due to departures from hydrostatic equilibrium. Using a large, mass-limited sample of massive galaxy clusters from a high-resolution hydrodynamical cosmological simulation, in this work we show that in addition to turbulent and bulk gas velocities, acceleration of gas introduces biases in the hydrostatic mass estimate of galaxy clusters. In unrelaxed clusters, the acceleration bias is comparable to themore » bias due to non-thermal pressure associated with merger-induced turbulent and bulk gas motions. In relaxed clusters, the mean mass bias due to acceleration is small (≲ 3%), but the scatter in the mass bias can be reduced by accounting for gas acceleration. Additionally, this acceleration bias is greater in the outskirts of higher redshift clusters where mergers are more frequent and clusters are accreting more rapidly. Since gas acceleration cannot be observed directly, it introduces an irreducible bias for hydrostatic mass estimates. This acceleration bias places limits on how well we can recover cluster masses from future X-ray and microwave observations. We discuss implications for cluster mass estimates based on X-ray, Sunyaev-Zel'dovich effect, and gravitational lensing observations and their impact on cluster cosmology.« less

Weighing Galaxy Clusters with Gas. II. On the Origin of Hydrostatic Mass Bias in ΛCDM Galaxy Clusters

NASA Astrophysics Data System (ADS)

Nelson, Kaylea; Lau, Erwin T.; Nagai, Daisuke; Rudd, Douglas H.; Yu, Liang

2014-02-01

The use of galaxy clusters as cosmological probes hinges on our ability to measure their masses accurately and with high precision. Hydrostatic mass is one of the most common methods for estimating the masses of individual galaxy clusters, which suffer from biases due to departures from hydrostatic equilibrium. Using a large, mass-limited sample of massive galaxy clusters from a high-resolution hydrodynamical cosmological simulation, in this work we show that in addition to turbulent and bulk gas velocities, acceleration of gas introduces biases in the hydrostatic mass estimate of galaxy clusters. In unrelaxed clusters, the acceleration bias is comparable to the bias due to non-thermal pressure associated with merger-induced turbulent and bulk gas motions. In relaxed clusters, the mean mass bias due to acceleration is small (lsim 3%), but the scatter in the mass bias can be reduced by accounting for gas acceleration. Additionally, this acceleration bias is greater in the outskirts of higher redshift clusters where mergers are more frequent and clusters are accreting more rapidly. Since gas acceleration cannot be observed directly, it introduces an irreducible bias for hydrostatic mass estimates. This acceleration bias places limits on how well we can recover cluster masses from future X-ray and microwave observations. We discuss implications for cluster mass estimates based on X-ray, Sunyaev-Zel'dovich effect, and gravitational lensing observations and their impact on cluster cosmology.

Spatiotemporal source analysis in scalp EEG vs. intracerebral EEG and SPECT: a case study in a 2-year-old child.

PubMed

Aarabi, A; Grebe, R; Berquin, P; Bourel Ponchel, E; Jalin, C; Fohlen, M; Bulteau, C; Delalande, O; Gondry, C; Héberlé, C; Moullart, V; Wallois, F

2012-06-01

This case study aims to demonstrate that spatiotemporal spike discrimination and source analysis are effective to monitor the development of sources of epileptic activity in time and space. Therefore, they can provide clinically useful information allowing a better understanding of the pathophysiology of individual seizures with time- and space-resolved characteristics of successive epileptic states, including interictal, preictal, postictal, and ictal states. High spatial resolution scalp EEGs (HR-EEG) were acquired from a 2-year-old girl with refractory central epilepsy and single-focus seizures as confirmed by intracerebral EEG recordings and ictal single-photon emission computed tomography (SPECT). Evaluation of HR-EEG consists of the following three global steps: (1) creation of the initial head model, (2) automatic spike and seizure detection, and finally (3) source localization. During the source localization phase, epileptic states are determined to allow state-based spike detection and localization of underlying sources for each spike. In a final cluster analysis, localization results are integrated to determine the possible sources of epileptic activity. The results were compared with the cerebral locations identified by intracerebral EEG recordings and SPECT. The results obtained with this approach were concordant with those of MRI, SPECT and distribution of intracerebral potentials. Dipole cluster centres found for spikes in interictal, preictal, ictal and postictal states were situated an average of 6.3mm from the intracerebral contacts with the highest voltage. Both amplitude and shape of spikes change between states. Dispersion of the dipoles was higher in the preictal state than in the postictal state. Two clusters of spikes were identified. The centres of these clusters changed position periodically during the various epileptic states. High-resolution surface EEG evaluated by an advanced algorithmic approach can be used to investigate the spatiotemporal characteristics of sources located in the epileptic focus. The results were validated by standard methods, ensuring good spatial resolution by MRI and SPECT and optimal temporal resolution by intracerebral EEG. Surface EEG can be used to identify different spike clusters and sources of the successive epileptic states. The method that was used in this study will provide physicians with a better understanding of the pathophysiological characteristics of epileptic activities. In particular, this method may be useful for more effective positioning of implantable intracerebral electrodes. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Chandra and XMM observations of cluster mergers and what we can learn from them

NASA Astrophysics Data System (ADS)

Markevitch, M.

Chandra and XMM are now routinely producing high-resolution maps of the density and temperature of the intracluster gas. These maps tell us a lot about the hydrodynamical and other processes occurring during cluster mergers. While most mergers are complicated and their interpretation requires the help of simulations, there is a number of interesting things we can learn directly from the data. I will review such results, including cold fronts and shock fronts, limits on thermal conductivity of the intracluster plasma, limits on the dark matter self-interaction cross-section, and insights into the origin of the cluster synchrotron radio halos.

Architecture of Eph receptor clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Himanen, Juha P.; Yermekbayeva, Laila; Janes, Peter W.

2010-10-04

Eph receptor tyrosine kinases and their ephrin ligands regulate cell navigation during normal and oncogenic development. Signaling of Ephs is initiated in a multistep process leading to the assembly of higher-order signaling clusters that set off bidirectional signaling in interacting cells. However, the structural and mechanistic details of this assembly remained undefined. Here we present high-resolution structures of the complete EphA2 ectodomain and complexes with ephrin-A1 and A5 as the base unit of an Eph cluster. The structures reveal an elongated architecture with novel Eph/Eph interactions, both within and outside of the Eph ligand-binding domain, that suggest the molecular mechanismmore » underlying Eph/ephrin clustering. Structure-function analysis, by using site-directed mutagenesis and cell-based signaling assays, confirms the importance of the identified oligomerization interfaces for Eph clustering.« less

The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Optical Extension for Neutron Capture Elements

NASA Astrophysics Data System (ADS)

Melendez, Matthew; O'Connell, Julia; Frinchaboy, Peter M.; Donor, John; Cunha, Katia M. L.; Shetrone, Matthew D.; Majewski, Steven R.; Zasowski, Gail; Pinsonneault, Marc H.; Roman-Lopes, Alexandre; Stassun, Keivan G.; APOGEE Team

2017-01-01

The Open Cluster Chemical Abundance & Mapping (OCCAM) survey is a systematic survey of Galactic open clusters using data primarily from the SDSS-III/APOGEE-1 survey. However, neutron capture elements are very limited in the IR region covered by APOGEE. In an effort to fully study detailed Galactic chemical evolution, we are conducting a high resolution (R~60,000) spectroscopic abundance analysis of neutron capture elements for OCCAM clusters in the optical regime to complement the APOGEE results. As part of this effort, we present Ba II, La II, Ce II and Eu II results for a few open clusters without previous abundance measurements using data obtained at McDonald Observatory with the 2.1m Otto Struve telescope and Sandiford Echelle Spectrograph.This work is supported by an NSF AAG grant AST-1311835.

Exploratory visualization of astronomical data on ultra-high-resolution wall displays

NASA Astrophysics Data System (ADS)

Pietriga, Emmanuel; del Campo, Fernando; Ibsen, Amanda; Primet, Romain; Appert, Caroline; Chapuis, Olivier; Hempel, Maren; Muñoz, Roberto; Eyheramendy, Susana; Jordan, Andres; Dole, Hervé

2016-07-01

Ultra-high-resolution wall displays feature a very high pixel density over a large physical surface, which makes them well-suited to the collaborative, exploratory visualization of large datasets. We introduce FITS-OW, an application designed for such wall displays, that enables astronomers to navigate in large collections of FITS images, query astronomical databases, and display detailed, complementary data and documents about multiple sources simultaneously. We describe how astronomers interact with their data using both the wall's touchsensitive surface and handheld devices. We also report on the technical challenges we addressed in terms of distributed graphics rendering and data sharing over the computer clusters that drive wall displays.

Mapping Emission from Clusters of CdSe/ZnS Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryan, Duncan P.; Goodwin, Peter M.; Sheehan, Chris J.

In this paper, we have carried out correlated super-resolution and SEM imaging studies of clusters of CdSe/ZnS nanoparticles containing up to ten particles to explore how the fluorescence behavior of these clusters depends on the number of particles, the specific cluster geometry, the shell thickness, and the technique used to produce the clusters. The total emission yield was less than proportional to the number of particles in the clusters for both thick and thin shells. With super-resolution imaging, the emission center of the cluster could be spatially resolved at distance scales on the order of the cluster size. The intrinsicmore » fluorescence intermittency of the nanoparticles altered the emission distribution across the cluster, which enabled the identification of relative emission intensities of individual particles or small groups of particles within the cluster. Finally, for clusters undergoing interparticle energy transfer, donor/acceptor pairs and regions where energy was funneled could be identified.« less

Mapping Emission from Clusters of CdSe/ZnS Nanoparticles

DOE PAGES

Ryan, Duncan P.; Goodwin, Peter M.; Sheehan, Chris J.; ...

2018-01-24

In this paper, we have carried out correlated super-resolution and SEM imaging studies of clusters of CdSe/ZnS nanoparticles containing up to ten particles to explore how the fluorescence behavior of these clusters depends on the number of particles, the specific cluster geometry, the shell thickness, and the technique used to produce the clusters. The total emission yield was less than proportional to the number of particles in the clusters for both thick and thin shells. With super-resolution imaging, the emission center of the cluster could be spatially resolved at distance scales on the order of the cluster size. The intrinsicmore » fluorescence intermittency of the nanoparticles altered the emission distribution across the cluster, which enabled the identification of relative emission intensities of individual particles or small groups of particles within the cluster. Finally, for clusters undergoing interparticle energy transfer, donor/acceptor pairs and regions where energy was funneled could be identified.« less

Absorption line indices in the UV. I. Empirical and theoretical stellar population models

NASA Astrophysics Data System (ADS)

Maraston, C.; Nieves Colmenárez, L.; Bender, R.; Thomas, D.

2009-01-01

Aims: Stellar absorption lines in the optical (e.g. the Lick system) have been extensively studied and constitute an important stellar population diagnostic for galaxies in the local universe and up to moderate redshifts. Proceeding towards higher look-back times, galaxies are younger and the ultraviolet becomes the relevant spectral region where the dominant stellar populations shine. A comprehensive study of ultraviolet absorption lines of stellar population models is however still lacking. With this in mind, we study absorption line indices in the far and mid-ultraviolet in order to determine age and metallicity indicators for UV-bright stellar populations in the local universe as well as at high redshift. Methods: We explore empirical and theoretical spectral libraries and use evolutionary population synthesis to compute synthetic line indices of stellar population models. From the empirical side, we exploit the IUE-low resolution library of stellar spectra and system of absorption lines, from which we derive analytical functions (fitting functions) describing the strength of stellar line indices as a function of gravity, temperature and metallicity. The fitting functions are entered into an evolutionary population synthesis code in order to compute the integrated line indices of stellar populations models. The same line indices are also directly evaluated on theoretical spectral energy distributions of stellar population models based on Kurucz high-resolution synthetic spectra, In order to select indices that can be used as age and/or metallicity indicators for distant galaxies and globular clusters, we compare the models to data of template globular clusters from the Magellanic Clouds with independently known ages and metallicities. Results: We provide synthetic line indices in the wavelength range ~1200 Å to ~3000 Å for stellar populations of various ages and metallicities.This adds several new indices to the already well-studied CIV and SiIV absorptions. Based on the comparison with globular cluster data, we select a set of 11 indices blueward of the 2000 Å rest-frame that allows us to recover well the ages and the metallicities of the clusters. These indices are ideal to study ages and metallicities of young galaxies at high redshift. We also provide the synthetic high-resolution stellar population SEDs.

Elimination-Fusion Self-Assembly of a Nanometer-Scale 72-Nucleus Silver Cluster Caging a Pair of [EuW10 O36 ]9- Polyoxometalates.

PubMed

Zhang, Shan-Shan; Su, Hai-Feng; Wang, Zhi; Wang, Xing-Po; Chen, Wen-Xian; Zhao, Quan-Qin; Tung, Chen-Ho; Sun, Di; Zheng, Lan-Sun

2018-02-06

The largest known polyoxometalate (POM)-templated silver-alkynyl cluster, [(EuW 10 O 36 ) 2 @Ag 72 (tBuC≡C) 48 Cl 2 ⋅4 BF 4 ] (SD/Ag20), was isolated under solvothermal conditions and structurally characterized. It was confirmed by single-crystal X-ray diffraction (SCXRD) as a {EuW 10 } 2 -in-{Ag 72 } clusters-in-cluster rod-like compound. The high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) shows that such a double anion-templated cluster is assembled from a crucial single anion-templated Ag 42 intermediate in the solution. The crystallization of Ag 42 species (SD/Ag21), followed by SCXRD, gave an important clue about the assembly route of SD/Ag20 in solution: the Ag 42 cluster eliminates six silver atoms laterally, then fuses together at the vacant face to form the final Ag 72 cluster (elimination-fusion mechanism). The characteristic emission of [EuW 10 O 36 ] 9- is well maintained in SD/Ag20. This work not only provides a new method for the synthesis of larger silver clusters as well as the functional integration of the silver cluster and POMs, but also gives deep insights about the high-nuclear silver cluster assembly mechanism. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Effect of Resolution on Detecting Visually Salient Preattentive Features

DTIC Science & Technology

2015-06-01

resolutions in descending order (a–e). The plot compiles the areas of interest displayed in the images and each symbol represents 1 of the images. Data...to particular regions in a scene by highly salient 2 features, for example, the color of the flower discussed in the previous example. These...descending order (a–e). The plot compiles the areas of interest displayed in the images and each symbol represents 1 of the images. Data clusters

Identification of high-confidence RNA regulatory elements by combinatorial classification of RNA-protein binding sites.

PubMed

Li, Yang Eric; Xiao, Mu; Shi, Binbin; Yang, Yu-Cheng T; Wang, Dong; Wang, Fei; Marcia, Marco; Lu, Zhi John

2017-09-08

Crosslinking immunoprecipitation sequencing (CLIP-seq) technologies have enabled researchers to characterize transcriptome-wide binding sites of RNA-binding protein (RBP) with high resolution. We apply a soft-clustering method, RBPgroup, to various CLIP-seq datasets to group together RBPs that specifically bind the same RNA sites. Such combinatorial clustering of RBPs helps interpret CLIP-seq data and suggests functional RNA regulatory elements. Furthermore, we validate two RBP-RBP interactions in cell lines. Our approach links proteins and RNA motifs known to possess similar biochemical and cellular properties and can, when used in conjunction with additional experimental data, identify high-confidence RBP groups and their associated RNA regulatory elements.

Whistler Waves Driven by Anisotropic Strahl Velocity Distributions: Cluster Observations

NASA Technical Reports Server (NTRS)

Vinas, A.F.; Gurgiolo, C.; Nieves-Chinchilla, T.; Gary, S. P.; Goldstein, M. L.

2010-01-01

Observed properties of the strahl using high resolution 3D electron velocity distribution data obtained from the Cluster/PEACE experiment are used to investigate its linear stability. An automated method to isolate the strahl is used to allow its moments to be computed independent of the solar wind core+halo. Results show that the strahl can have a high temperature anisotropy (T(perpindicular)/T(parallell) approximately > 2). This anisotropy is shown to be an important free energy source for the excitation of high frequency whistler waves. The analysis suggests that the resultant whistler waves are strong enough to regulate the electron velocity distributions in the solar wind through pitch-angle scattering

Star cluster formation in cosmological simulations. I. Properties of young clusters

DOE PAGES

Li, Hui; Gnedin, Oleg Y.; Gnedin, Nickolay Y.; ...

2017-01-03

We present a new implementation of star formation in cosmological simulations by considering star clusters as a unit of star formation. Cluster particles grow in mass over several million years at the rate determined by local gas properties, with high time resolution. The particle growth is terminated by its own energy and momentum feedback on the interstellar medium. We test this implementation for Milky Way-sized galaxies at high redshift by comparing the properties of model clusters with observations of young star clusters. We find that the cluster initial mass function is best described by a Schechter function rather than a single power law. In agreement with observations, at low masses the logarithmic slope ismore » $$\\alpha \\approx 1.8\\mbox{–}2$$, while the cutoff at high mass scales with the star formation rate (SFR). A related trend is a positive correlation between the surface density of the SFR and fraction of stars contained in massive clusters. Both trends indicate that the formation of massive star clusters is preferred during bursts of star formation. These bursts are often associated with major-merger events. We also find that the median timescale for cluster formation ranges from 0.5 to 4 Myr and decreases systematically with increasing star formation efficiency. Local variations in the gas density and cluster accretion rate naturally lead to the scatter of the overall formation efficiency by an order of magnitude, even when the instantaneous efficiency is kept constant. As a result, comparison of the formation timescale with the observed age spread of young star clusters provides an additional important constraint on the modeling of star formation and feedback schemes.« less

Star cluster formation in cosmological simulations. I. Properties of young clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Hui; Gnedin, Oleg Y.; Gnedin, Nickolay Y.

We present a new implementation of star formation in cosmological simulations by considering star clusters as a unit of star formation. Cluster particles grow in mass over several million years at the rate determined by local gas properties, with high time resolution. The particle growth is terminated by its own energy and momentum feedback on the interstellar medium. We test this implementation for Milky Way-sized galaxies at high redshift by comparing the properties of model clusters with observations of young star clusters. We find that the cluster initial mass function is best described by a Schechter function rather than a single power law. In agreement with observations, at low masses the logarithmic slope ismore » $$\\alpha \\approx 1.8\\mbox{–}2$$, while the cutoff at high mass scales with the star formation rate (SFR). A related trend is a positive correlation between the surface density of the SFR and fraction of stars contained in massive clusters. Both trends indicate that the formation of massive star clusters is preferred during bursts of star formation. These bursts are often associated with major-merger events. We also find that the median timescale for cluster formation ranges from 0.5 to 4 Myr and decreases systematically with increasing star formation efficiency. Local variations in the gas density and cluster accretion rate naturally lead to the scatter of the overall formation efficiency by an order of magnitude, even when the instantaneous efficiency is kept constant. As a result, comparison of the formation timescale with the observed age spread of young star clusters provides an additional important constraint on the modeling of star formation and feedback schemes.« less

IDENTIFICATION OF UNANTICIPATED COMPOUNDS BY HIGH RESOLUTION MASS SPECTROMETRY

EPA Science Inventory

Localized outbreaks of acute illness could result from deliberate addition of unanticipated
compounds into water, air, or food. Cancer clusters resulting from long-term exposure to trace-
levels of compounds are more difficult to detect, but can be revealed by epidemiolog...

Three years of ULTRASPEC at the Thai 2.4-m telescope: Capabilities and scientific highlights

NASA Astrophysics Data System (ADS)

Yadav, Ram Kesh; Richichi, Andrea; Irawati, Puji; Dhillon, Vikram Singh; Marsh, Thomas R.; Soonthornthum, Boonrucksar

2018-04-01

High temporal resolution observations enable the study of rapid phenomena such as the flux variations in binary system objects, e.g. cataclysmic variables, compact binary systems, the flux variations in young star clusters, stellar occultations and more. The 2.4-m Thai National Telescope (TNT) is ideally suited for this niche research, being the largest facility in Southeast Asia and being equipped with ULTRASPEC, a high-speed imager based on a low-noise frame transfer electron-multiplying CCD. In the sub-window mode, ULTRASPEC can record uninterrupted sequences with frame rates as fast as few milliseconds. We present some of the key results obtained in the area of high time resolution with ULTRASPEC. We also present the results of a recent worldwide campaign to observe the current series of lunar occultations of Aldebaran (α Tauri) carried out in close collaboration with the Devasthal facilities, the out-of-eclipse variations on the post common-envelope system J1021+1744, and pre-main-sequence variables in young open cluster Stock 8.

GLASS: The Grism Lens-Amplified Survey From Space. HST Grism Spectroscopy of the Frontier Fields

NASA Astrophysics Data System (ADS)

Schmidt, Kasper B.; Schmidt

The Grism Lens-Amplified Survey From Space (GLASS) is a 140 orbit spectroscopic survey of 10 massive galaxy clusters, including the six Hubble Frontier Fields. GLASS has observed the cluster cores with the HST-WFC3 G102 and G141 grisms providing a wide wavelength coverage in the near-infrared from roughly 0.8-1.7μm. The parallel fields were observed through the optical ACS G800L grism. Taking advantage of the lensing magnification of the clusters, GLASS reaches intrinsic spectroscopic 1σ flux limits of roughly 10-18erg/s/cm2 and improved spatial resolution for lensed sources behind the clusters. These features are particularly useful for the three main science drivers of GLASS which are, I) exploring the universe at the epoch of reionization, II) describe how metals cycle in and out of galaxies, and III) asses the environmental dependence of galaxy evolution. The former two benefit highly from the improved depth and increased resolution provided by the cluster lensing. Apart from the main science drivers, a slew of ancillary science has been enabled by the survey, including improving cluster lens modeling and searches for supernovae. Here we present the survey and the GLASS data releases, which are continuously being made available to the community through https://archive.stsci.edu/prepds/glass/. For further information we refer to Schmidt et al. (2014), Treu et al. (2015), and http://glass.physics.ucsb.edu.

Rural cases of equine West Nile virus encephalomyelitis and the normalized difference vegetation index

USGS Publications Warehouse

Ward, M.P.; Ramsay, B.H.; Gallo, K.

2005-01-01

Data from an outbreak (August to October, 2002) of West Nile virus (WNV) encephalomyelitis in a population of horses located in northern Indiana was scanned for clusters in time and space. One significant (p = 0.04) cluster of case premises was detected, occurring between September 4 and 10 in the south-west part of the study area (85.70??N, 45.50??W). It included 10 case premises (3.67 case premises expected) within a radius of 2264 m. Image data were acquired by the Advanced Very High Resolution Radiometer (AVHRR) sensor onboard a National Oceanic and Atmospheric Administration polar-orbiting satellite. The Normalized Difference Vegetation Index (NDVI) was calculated from visible and near-infrared data of daily observations, which were composited to produce a weekly-1km2 resolution raster image product. During the epidemic, a significant (p<0.01) decrease (0.025 per week) in estimated NDVI was observed at all case and control premise sites. The median estimated NDVI (0.659) for case premises within the cluster identified was significantly (p<0.01) greater than the median estimated NDVI for other case (0.571) and control (0.596) premises during the same period. The difference in median estimated NDVI for case premises within this cluster, compared to cases not included in this cluster, was greatest (5.3% and 5.1%, respectively) at 1 and 5 weeks preceding occurrence of the cluster. The NDVI may be useful for identifying foci of WNV transmission. ?? Mary Ann Liebert, Inc.

Study of Small-Scale Anisotropy of Ultra-High-Energy Cosmic Rays Observed in Stereo by the High Resolution Fly's Eye Detector

NASA Astrophysics Data System (ADS)

Abbasi, R. U.; Abu-Zayyad, T.; Amann, J. F.; Archbold, G.; Atkins, R.; Bellido, J. A.; Belov, K.; Belz, J. W.; BenZvi, S.; Bergman, D. R.; Boyer, J. H.; Burt, G. W.; Cao, Z.; Clay, R. W.; Connolly, B. M.; Dawson, B. R.; Deng, W.; Fedorova, Y.; Findlay, J.; Finley, C. B.; Hanlon, W. F.; Hoffman, C. M.; Holzscheiter, M. H.; Hughes, G. A.; Hüntemeyer, P.; Jui, C. C. H.; Kim, K.; Kirn, M. A.; Knapp, B. C.; Loh, E. C.; Maestas, M. M.; Manago, N.; Mannel, E. J.; Marek, L. J.; Martens, K.; Matthews, J. A. J.; Matthews, J. N.; O'Neill, A.; Painter, C. A.; Perera, L.; Reil, K.; Riehle, R.; Roberts, M. D.; Sasaki, M.; Schnetzer, S. R.; Seman, M.; Simpson, K. M.; Sinnis, G.; Smith, J. D.; Snow, R.; Sokolsky, P.; Song, C.; Springer, R. W.; Stokes, B. T.; Thomas, J. R.; Thomas, S. B.; Thomson, G. B.; Tupa, D.; Westerhoff, S.; Wiencke, L. R.; Zech, A.; HIRES Collaboration

2004-08-01

The High Resolution Fly's Eye (HiRes) experiment is an air fluorescence detector which, operating in stereo mode, has a typical angular resolution of 0.6d and is sensitive to cosmic rays with energies above 1018 eV. The HiRes cosmic-ray detector is thus an excellent instrument for the study of the arrival directions of ultra-high-energy cosmic rays. We present the results of a search for anisotropies in the distribution of arrival directions on small scales (<5°) and at the highest energies (>1019 eV). The search is based on data recorded between 1999 December and 2004 January, with a total of 271 events above 1019 eV. No small-scale anisotropy is found, and the strongest clustering found in the HiRes stereo data is consistent at the 52% level with the null hypothesis of isotropically distributed arrival directions.

Nuclear Star Formation in the Hot-Spot Galaxy NGC 2903

NASA Technical Reports Server (NTRS)

Alonso-Herrero, A.; Ryder, S. D.; Knapen, J. H.

1994-01-01

We present high-resolution near-infrared imaging obtained using adaptive optics and HST/NICMOS and ground-based spectroscopy of the hot-spot galaxy NGC 2903. Our near-infrared resolution imaging enables us to resolve the infrared hot spots into individual young stellar clusters or groups of these. The spatial distribution of the stellar clusters is not coincident with that of the bright H II regions, as revealed by the HST/NICMOS Pace image. Overall, the circumnuclear star formation in NGC 2903 shows a ring-like morphology with an approximate diameter of 625 pc. The SF properties of the stellar clusters and H II regions have been studied using the photometric and spectroscopic information in conjunction with evolutionary synthesis models. The population of bright stellar clusters shows a very narrow range of ages, 4 to 7 x 10(exp 6) yr after the peak of star formation, or absolute ages 6.5 to 9.5 x 10(exp 6) yr (for the assumed short-duration Gaussian bursts), and luminosities similar to the clusters found in the Antennae interacting galaxy. This population of young stellar clusters accounts for some 7 - 12% of the total stellar mass in the central 625 pc of NGC 2903. The H II regions in the ring of star formation have luminosities close to that of the super-giant H II region 30 Doradus, they are younger than the stellar clusters, and will probably evolve into bright infrared stellar clusters similar to those observed today. We find that the star formation efficiency in the central regions of NGC 2903 is higher than in normal galaxies, approaching the lower end of infrared luminous galaxies.

Probing the atomic structure of metallic nanoclusters with the tip of a scanning tunneling microscope.

PubMed

Schouteden, Koen; Lauwaet, Koen; Janssens, Ewald; Barcaro, Giovanni; Fortunelli, Alessandro; Van Haesendonck, Chris; Lievens, Peter

2014-02-21

Preformed Co clusters with an average diameter of 2.5 nm are produced in the gas phase and are deposited under controlled ultra-high vacuum conditions onto a thin insulating NaCl film on Au(111). Relying on a combined experimental and theoretical investigation, we demonstrate visualization of the three-dimensional atomic structure of the Co clusters by high-resolution scanning tunneling microscopy (STM) using a Cl functionalized STM tip that can be obtained on the NaCl surface. More generally, use of a functionalized STM tip may allow for systematic atomic structure determination with STM of nanoparticles that are deposited on metal surfaces.

MicroED Structure of Au146(p-MBA)57 at Subatomic Resolution Reveals a Twinned FCC Cluster.

PubMed

Vergara, Sandra; Lukes, Dylan A; Martynowycz, Michael W; Santiago, Ulises; Plascencia-Villa, Germán; Weiss, Simon C; de la Cruz, M Jason; Black, David M; Alvarez, Marcos M; López-Lozano, Xochitl; Barnes, Christopher O; Lin, Guowu; Weissker, Hans-Christian; Whetten, Robert L; Gonen, Tamir; Yacaman, Miguel Jose; Calero, Guillermo

2017-11-16

Solving the atomic structure of metallic clusters is fundamental to understanding their optical, electronic, and chemical properties. Herein we present the structure of the largest aqueous gold cluster, Au 146 (p-MBA) 57 (p-MBA: para-mercaptobenzoic acid), solved by electron micro-diffraction (MicroED) to subatomic resolution (0.85 Å) and by X-ray diffraction at atomic resolution (1.3 Å). The 146 gold atoms may be decomposed into two constituent sets consisting of 119 core and 27 peripheral atoms. The core atoms are organized in a twinned FCC structure, whereas the surface gold atoms follow a C 2 rotational symmetry about an axis bisecting the twinning plane. The protective layer of 57 p-MBAs fully encloses the cluster and comprises bridging, monomeric, and dimeric staple motifs. Au 146 (p-MBA) 57 is the largest cluster observed exhibiting a bulk-like FCC structure as well as the smallest gold particle exhibiting a stacking fault.

MicroED structure of Au146(p-MBA)57 at subatomic resolution reveals a twinned FCC cluster

PubMed Central

Vergara, Sandra; Lukes, Dylan A.; Martynowycz, Michael W.; Santiago, Ulises; Plascencia-Villa, German; Weiss, Simon C.; de la Cruz, M. Jason; Black, David M.; Alvarez, Marcos M.; Lopez-Lozano, Xochitl; Barnes, Christopher O.; Lin, Guowu; Weissker, Hans-Christian; Whetten, Robert L.; Gonen, Tamir; Jose-Yacaman, Miguel; Calero, Guillermo

2018-01-01

Solving the atomic structure of metallic clusters is fundamental to understanding their optical, electronic, and chemical properties. Herein we present the structure of the largest aqueous gold cluster, Au146(p-MBA)57 (p-MBA: para-mercaptobenzoic acid), solved by electron diffraction (MicroED) to subatomic resolution (0.85 Å) and by X-ray diffraction at atomic resolution (1.3 Å). The 146 gold atoms may be decomposed into two constituent sets consisting of 119 core and 27 peripheral atoms. The core atoms are organized in a twinned FCC structure whereas the surface gold atoms follow a C2 rotational symmetry about an axis bisecting the twinning plane. The protective layer of 57 p-MBAs fully encloses the cluster and comprises bridging, monomeric, and dimeric staple motifs. Au146(p-MBA)57 is the largest cluster observed exhibiting a bulk-like FCC structure as well as the smallest gold particle exhibiting a stacking fault. PMID:29072840

Hemagglutinin Clusters in the Plasma Membrane Are Not Enriched with Cholesterol and Sphingolipids

DOE PAGES

Wilson, Robert L.; Frisz, Jessica F.; Klitzing, Haley A.; ...

2015-04-07

The clusters of the influenza envelope protein, hemagglutinin, within the plasma membrane are hypothesized to be enriched with cholesterol and sphingolipids. Here in this paper, we directly tested this hypothesis by using high-resolution secondary ion mass spectrometry to image the distributions of antibody-labeled hemagglutinin and isotope-labeled cholesterol and sphingolipids in the plasma membranes of fibroblast cells that stably express hemagglutinin. We found that the hemagglutinin clusters were neither enriched with cholesterol nor colocalized with sphingolipid domains. Thus, hemagglutinin clustering and localization in the plasma membrane is not controlled by cohesive interactions between hemagglutinin and liquid-ordered domains enriched with cholesterol andmore » sphingolipids, or from specific binding interactions between hemagglutinin, cholesterol, and/or the majority of sphingolipid species in the plasma membrane.« less

Observations on Si-based micro-clusters embedded in TaN thin film deposited by co-sputtering with oxygen contamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Young Mi; Jung, Min-Sang; Choi, Duck-Kyun, E-mail: duck@hanyang.ac.kr, E-mail: mcjung@oist.jp

2015-08-15

Using scanning electron microscopy (SEM) and high-resolution x-ray photoelectron spectroscopy with the synchrotron radiation we investigated Si-based micro-clusters embedded in TaSiN thin films having oxygen contamination. TaSiN thin films were deposited by co-sputtering on fixed or rotated substrates and with various power conditions of TaN and Si targets. Three types of embedded micro-clusters with the chemical states of pure Si, SiO{sub x}-capped Si, and SiO{sub 2}-capped Si were observed and analyzed using SEM and Si 2p and Ta 4f core-level spectra were derived. Their different resistivities are presumably due to the different chemical states and densities of Si-based micro-clusters.

Defect Clustering and Nano-phase Structure Characterization of Multicomponent Rare Earth-Oxide-Doped Zirconia-Yttria Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

2004-01-01

Advanced thermal barrier coatings (TBCs) have been developed by incorporating multicomponent rare earth oxide dopants into zirconia-based thermal barrier coatings to promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nanophases within the coating systems. In this paper, the defect clusters, induced by Nd, Gd, and Yb rare earth dopants in the zirconia-yttria thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The TEM lattice imaging, selected area diffraction (SAD), and electron energy-loss spectroscopy (EELS) analyses demonstrated that the extensive nanoscale rare earth dopant segregation exists in the plasma-sprayed and electron-physical-vapor-deposited (EB PVD) thermal barrier coatings. The nanoscale concentration heterogeneity and the resulting large lattice distortion promoted the formation of parallel and rotational defective lattice clusters in the coating systems. The presence of the 5-to 100-nm-sized defect clusters and nanophases is believed to be responsible for the significant reduction of thermal conductivity, improved sintering resistance, and long-term high temperature stability of the advanced thermal barrier coating systems.

Markov Chain Monte Carlo Joint Analysis of Chandra X-Ray Imaging Spectroscopy and Sunyaev-Zel'dovich Effect Data

NASA Technical Reports Server (NTRS)

Bonamente, Massimillano; Joy, Marshall K.; Carlstrom, John E.; Reese, Erik D.; LaRoque, Samuel J.

2004-01-01

X-ray and Sunyaev-Zel'dovich effect data can be combined to determine the distance to galaxy clusters. High-resolution X-ray data are now available from Chandra, which provides both spatial and spectral information, and Sunyaev-Zel'dovich effect data were obtained from the BIMA and Owens Valley Radio Observatory (OVRO) arrays. We introduce a Markov Chain Monte Carlo procedure for the joint analysis of X-ray and Sunyaev- Zel'dovich effect data. The advantages of this method are the high computational efficiency and the ability to measure simultaneously the probability distribution of all parameters of interest, such as the spatial and spectral properties of the cluster gas and also for derivative quantities such as the distance to the cluster. We demonstrate this technique by applying it to the Chandra X-ray data and the OVRO radio data for the galaxy cluster A611. Comparisons with traditional likelihood ratio methods reveal the robustness of the method. This method will be used in follow-up paper to determine the distances to a large sample of galaxy cluster.

The Atacama Cosmology Telescope: High-Resolution Sunyaev-Zel'dovich Array Observations of ACT SZE-Selected Clusters from the Equatorial Strip

NASA Technical Reports Server (NTRS)

Reese, Erik D.; Mroczkowski, Tony; Menanteau, Felipe; Hilton, Matt; Sievers, Jonathan; Aguirre, Paula; Appel, John William; Baker, Andrew J.; Bond, J. Richard; Das, Sudeep;

The Atacama Cosmology Telescope: High-Resolution Sunyaev-Zeldovich Array Observations of ACT SZE-Selected Clusters from the Equatorial Strip

NASA Technical Reports Server (NTRS)

Reese, Erik; Mroczkowski, Tony; Menateau, Felipe; Hilton, Matt; Sievers, Jonathan; Aguirre, Paula; Appel, John William; Baker, Andrew J.; Bond, J. Richard; Das, Sudeep;

Use of Patterned CNT Arrays for Display Purposes

NASA Technical Reports Server (NTRS)

Delzeit, Lance D. (Inventor); Schipper, John F. (Inventor)

2009-01-01

Method and system for providing a dynamically reconfigurable display having nanometer-scale resolution, using a patterned array of multi-wall carbon nanotube (MWCNT) clusters. A diode, phosphor or other light source on each MWCNT cluster is independently activated, and different color light sources (e.g., red, green, blue, grey scale, infrared) can be mixed if desired. Resolution is estimated to be 40-100 nm, and reconfiguration time for each MWCNT cluster is no greater than one microsecond.

Resonant scattering as a sensitive diagnostic of current collisional plasma models

NASA Astrophysics Data System (ADS)

Ogorzalek, Anna; Zhuravleva, Irina; Allen, Steven W.; Pinto, Ciro; Werner, Norbert; Mantz, Adam; Canning, Rebecca; Fabian, Andrew C.; Kaastra, Jelle S.; de Plaa, Jelle

2017-08-01

Resonant scattering is a subtle process that suppresses fluxes of some of the brightest optically thick X-ray emission lines produced by collisional plasmas in galaxy clusters and massive early-type galaxies. The amplitude of the effect depends on the turbulent structure of the hot gas, making it a sensitive velocity probe. It is therefore crucial to properly model this effect in order to correctly interpret high resolution X-ray spectra. Our measurements of resonant scattering with XMM-Newton Reflection Grating Spectrometer in giant elliptical galaxies and with Hitomi in the center of Perseus Cluster show that the potentially rich inference from this effect is limited by the uncertainties in the atomic data underlying plasma codes such as APEC and SPEX. Typically, the effect is of the order of 10-20%, while the discrepancy between the two codes is of similar order or even higher. Precise knowledge of the emissivity and oscillator strengths of lines emitted by Fe XVII and Fe XXV, as well as their respective uncertainties propagated through plasma codes are key to understanding gas dynamics and microphysics in giant galaxies and cluster ICM, respectively. This is especially crucial for massive ellipticals, where sub-eV resolution would be needed to measure line broadening precisely, making resonant scattering an important velocity diagnostic in these systems for the foreseeable future. In this poster, I will summarize current status of resonant scattering measurements and show how they depend on the assumed atomic data. I will also discuss which improvements are essential to maximize scientific inference from future high resolution X-ray spectra.

The Formation and Evolution of Star Clusters in Interacting Galaxies

NASA Astrophysics Data System (ADS)

Maji, Moupiya; Zhu, Qirong; Li, Yuexing; Charlton, Jane; Hernquist, Lars; Knebe, Alexander

2017-08-01

Observations of globular clusters show that they have universal lognormal mass functions with a characteristic peak at ˜ 2× {10}5 {M}⊙ , but the origin of this peaked distribution is highly debated. Here we investigate the formation and evolution of star clusters (SCs) in interacting galaxies using high-resolution hydrodynamical simulations performed with two different codes in order to mitigate numerical artifacts. We find that massive SCs in the range of ˜ {10}5.5{--}{10}7.5 {M}⊙ form preferentially in the highly shocked regions produced by galaxy interactions. The nascent cluster-forming clouds have high gas pressures in the range of P/k˜ {10}8{--}{10}12 {{K}} {{cm}}-3, which is ˜ {10}4{--}{10}8 times higher than the typical pressure of the interstellar medium but consistent with recent observations of a pre-super-SC cloud in the Antennae Galaxies. Furthermore, these massive SCs have quasi-lognormal initial mass functions with a peak around ˜ {10}6 {M}⊙ . The number of clusters declines with time due to destructive processes, but the shape and the peak of the mass functions do not change significantly during the course of galaxy collisions. Our results suggest that gas-rich galaxy mergers may provide a favorable environment for the formation of massive SCs such as globular clusters, and that the lognormal mass functions and the unique peak may originate from the extreme high-pressure conditions of the birth clouds and may survive the dynamical evolution.

Cloning and heterologous expression of the entire gene clusters for PD 116740 from Streptomyces strain WP 4669 and tetrangulol and tetrangomycin from Streptomyces rimosus NRRL 3016.

PubMed Central

Hong, S T; Carney, J R; Gould, S J

1997-01-01

The genes for the complete pathways for two polycyclic aromatic polyketides of the angucyclinone class have been cloned and heterologously expressed. Genomic DNAs of Streptomyces rimosus NRRL 3016 and Streptomyces strain WP 4669 were partially digested with MboI, and libraries (ca. 40-kb fragments) in Escherichia coli XL1-Blue MR were prepared with the cosmid vector pOJ446. Hybridization with the actI probe from the actinorhodin polyketide synthase genes identified two clusters of polyketide genes from each organism. After transfer of the four clusters to Streptomyces lividans TK24, expression of one cluster from each organism was established through the identification of pathway-specific products by high-performance liquid chromatography with photodiode array detection. Peaks were identified from the S. rimosus cluster (pksRIM-1) for tetrangulol, tetrangomycin, and fridamycin E. Peaks were identified from the WP 4669 cluster (pksWP-2) for tetrangulol, 19-hydroxytetrangulol, 8-O-methyltetrangulol, 19-hydroxy-8-O-methyltetrangulol, and PD 116740. Structures were confirmed by 1H nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. PMID:8990300

Cloning and heterologous expression of the entire gene clusters for PD 116740 from Streptomyces strain WP 4669 and tetrangulol and tetrangomycin from Streptomyces rimosus NRRL 3016.

PubMed

Hong, S T; Carney, J R; Gould, S J

1997-01-01

The genes for the complete pathways for two polycyclic aromatic polyketides of the angucyclinone class have been cloned and heterologously expressed. Genomic DNAs of Streptomyces rimosus NRRL 3016 and Streptomyces strain WP 4669 were partially digested with MboI, and libraries (ca. 40-kb fragments) in Escherichia coli XL1-Blue MR were prepared with the cosmid vector pOJ446. Hybridization with the actI probe from the actinorhodin polyketide synthase genes identified two clusters of polyketide genes from each organism. After transfer of the four clusters to Streptomyces lividans TK24, expression of one cluster from each organism was established through the identification of pathway-specific products by high-performance liquid chromatography with photodiode array detection. Peaks were identified from the S. rimosus cluster (pksRIM-1) for tetrangulol, tetrangomycin, and fridamycin E. Peaks were identified from the WP 4669 cluster (pksWP-2) for tetrangulol, 19-hydroxytetrangulol, 8-O-methyltetrangulol, 19-hydroxy-8-O-methyltetrangulol, and PD 116740. Structures were confirmed by 1H nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry.

Probing the X-ray Emission from the Massive Star Cluster Westerlund 2

NASA Astrophysics Data System (ADS)

Lopez, Laura

2017-09-01

We propose a 300 ks Chandra ACIS-I observation of the massive star cluster Westerlund 2 (Wd2). This region is teeming with high-energy emission from a variety of sources: colliding wind binaries, OB and Wolf-Rayet stars, two young pulsars, and an unidentified source of very high-energy (VHE) gamma-rays. Our Chandra program is designed to achieve several goals: 1) to take a complete census of Wd2 X-ray point sources and monitor variability; 2) to probe the conditions of the colliding winds in the binary WR 20a; 3) to search for an X-ray counterpart of the VHE gamma-rays; 4) to identify diffuse X-ray emission; 5) to compare results to other massive star clusters observed by Chandra. Only Chandra has the spatial resolution and sensitivity necessary for our proposed analyses.

Diversity of ecological communities of the United States

Treesearch

J.D. Wickham; T.G. Wade; K.B. Jones; Kurt H. Riitters; R.V. O' Neill

1995-01-01

Biodiversity, although recognized as encompassing several levels of biological organization, is often thought of as species diversity. Three diversity estimates were calculated for the conterminous United States using satellite data acquired from the Advanced Very High Resolution Radiometer (AVHRR): land cover richness, vegetation richness, and vegetation clustering....

Active Galactic Nucleus Feedback with the Square Kilometre Array and Implications for Cluster Physics and Cosmology

NASA Astrophysics Data System (ADS)

Iqbal, Asif; Kale, Ruta; Majumdar, Subhabrata; Nath, Biman B.; Pandge, Mahadev; Sharma, Prateek; Malik, Manzoor A.; Raychaudhury, Somak

2017-12-01

Active Galactic Nuclei (AGN) feedback is regarded as an important non-gravitational process in galaxy clusters, providing useful constraints on large-scale structure formation. It modifies the structure and energetics of the intra-cluster medium (ICM) and hence its understanding is crucially needed in order to use clusters as high precision cosmological probes. In this context, particularly keeping in mind the upcoming high quality radio data expected from radio surveys like Square Kilometre Array (SKA) with its higher sensitivity, high spatial and spectral resolutions, we review our current understanding of AGN feedback, its cosmological implications and the impact that SKA can have in revolutionizing our understanding of AGN feedback in large-scale structures. Recent developments regarding the AGN outbursts and its possible contribution to excess entropy in the hot atmospheres of groups and clusters, its correlation with the feedback energy in ICM, quenching of cooling flows and the possible connection between cool core clusters and radio mini-halos, are discussed. We describe current major issues regarding modeling of AGN feedback and its impact on the surrounding medium. With regard to the future of AGN feedback studies, we examine the possible breakthroughs that can be expected from SKA observations. In the context of cluster cosmology, for example, we point out the importance of SKA observations for cluster mass calibration by noting that most of z>1 clusters discovered by eROSITA X-ray mission can be expected to be followed up through a 1000 hour SKA1-mid programme. Moreover, approximately 1000 radio mini halos and ˜ 2500 radio halos at z<0.6 can be potentially detected by SKA1 and SKA2 and used as tracers of galaxy clusters and determination of cluster selection function.

Stellar abundances and ages for metal-rich Milky Way globular clusters. Stellar parameters and elemental abundances for 9 HB stars in NGC 6352

NASA Astrophysics Data System (ADS)

Feltzing, S.; Primas, F.; Johnson, R. A.

2009-01-01

Context: Metal-rich globular clusters provide important tracers of the formation of our Galaxy. Moreover, and not less important, they are very important calibrators for the derivation of properties of extra-galactic metal-rich stellar populations. Nonetheless, only a few of the metal-rich globular clusters in the Milky Way have been studied using high-resolution stellar spectra to derive elemental abundances. Additionally, Rosenberg et al. identified a small group of metal-rich globular clusters that appeared to be about 2 billion years younger than the bulk of the Milky Way globular clusters. However, it is unclear if like is compared with like in this dataset as we do not know the enhancement of α-elements in the clusters and the amount of α-elements is well known to influence the derivation of ages for globular clusters. Aims: We derive elemental abundances for the metal-rich globular cluster NGC 6352 and we present our methods to be used in up-coming studies of other metal-rich globular clusters. Methods: We present a study of elemental abundances for α- and iron-peak elements for nine HB stars in the metal-rich globular cluster NGC 6352. The elemental abundances are based on high-resolution, high signal-to-noise spectra obtained with the UVES spectrograph on VLT. The elemental abundances have been derived using standard LTE calculations and stellar parameters have been derived from the spectra themselves by requiring ionizational as well as excitational equilibrium. Results: We find that NGC 6352 has [Fe/H] = -0.55, is enhanced in the α-elements to about +0.2 dex for Ca, Si, and Ti relative to Fe. For the iron-peak elements we find solar values. Based on the spectroscopically derived stellar parameters we find that an E(B-V) = 0.24 and (m-M) ≃ 14.05 better fits the data than the nominal values. An investigation of log gf-values for suitable Fe i lines lead us to the conclusion that the commonly used correction to the May et al. (1974) data should not be employed. Full Table [see full text] are also only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/493/913 Based on observations collected at the European Southern Observatory, Chile, ESO No. 69.B-0467.

Exploring cosmic origins with CORE: Extragalactic sources in cosmic microwave background maps

NASA Astrophysics Data System (ADS)

De Zotti, G.; González-Nuevo, J.; Lopez-Caniego, M.; Negrello, M.; Greenslade, J.; Hernández-Monteagudo, C.; Delabrouille, J.; Cai, Z.-Y.; Bonato, M.; Achúcarro, A.; Ade, P.; Allison, R.; Ashdown, M.; Ballardini, M.; Banday, A. J.; Banerji, R.; Bartlett, J. G.; Bartolo, N.; Basak, S.; Bersanelli, M.; Biesiada, M.; Bilicki, M.; Bonaldi, A.; Bonavera, L.; Borrill, J.; Bouchet, F.; Boulanger, F.; Brinckmann, T.; Bucher, M.; Burigana, C.; Buzzelli, A.; Calvo, M.; Carvalho, C. S.; Castellano, M. G.; Challinor, A.; Chluba, J.; Clements, D. L.; Clesse, S.; Colafrancesco, S.; Colantoni, I.; Coppolecchia, A.; Crook, M.; D'Alessandro, G.; de Bernardis, P.; de Gasperis, G.; Diego, J. M.; Di Valentino, E.; Errard, J.; Feeney, S. M.; Fernández-Cobos, R.; Ferraro, S.; Finelli, F.; Forastieri, F.; Galli, S.; Génova-Santos, R. T.; Gerbino, M.; Grandis, S.; Hagstotz, S.; Hanany, S.; Handley, W.; Hervias-Caimapo, C.; Hills, M.; Hivon, E.; Kiiveri, K.; Kisner, T.; Kitching, T.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamagna, L.; Lasenby, A.; Lattanzi, M.; Le Brun, A.; Lesgourgues, J.; Lewis, A.; Liguori, M.; Lindholm, V.; Luzzi, G.; Maffei, B.; Mandolesi, N.; Martinez-Gonzalez, E.; Martins, C. J. A. P.; Masi, S.; Massardi, M.; Matarrese, S.; McCarthy, D.; Melchiorri, A.; Melin, J.-B.; Molinari, D.; Monfardini, A.; Natoli, P.; Notari, A.; Paiella, A.; Paoletti, D.; Partridge, R. B.; Patanchon, G.; Piat, M.; Pisano, G.; Polastri, L.; Polenta, G.; Pollo, A.; Poulin, V.; Quartin, M.; Remazeilles, M.; Roman, M.; Rossi, G.; Roukema, B. F.; Rubiño-Martín, J.-A.; Salvati, L.; Scott, D.; Serjeant, S.; Tartari, A.; Toffolatti, L.; Tomasi, M.; Trappe, N.; Triqueneaux, S.; Trombetti, T.; Tucci, M.; Tucker, C.; Väliviita, J.; van de Weygaert, R.; Van Tent, B.; Vennin, V.; Vielva, P.; Vittorio, N.; Young, K.; Zannoni, M.

2018-04-01

We discuss the potential of a next generation space-borne Cosmic Microwave Background (CMB) experiment for studies of extragalactic sources. Our analysis has particular bearing on the definition of the future space project, CORE, that has been submitted in response to ESA's call for a Medium-size mission opportunity as the successor of the Planck satellite. Even though the effective telescope size will be somewhat smaller than that of Planck, CORE will have a considerably better angular resolution at its highest frequencies, since, in contrast with Planck, it will be diffraction limited at all frequencies. The improved resolution implies a considerable decrease of the source confusion, i.e. substantially fainter detection limits. In particular, CORE will detect thousands of strongly lensed high-z galaxies distributed over the full sky. The extreme brightness of these galaxies will make it possible to study them, via follow-up observations, in extraordinary detail. Also, the CORE resolution matches the typical sizes of high-z galaxy proto-clusters much better than the Planck resolution, resulting in a much higher detection efficiency; these objects will be caught in an evolutionary phase beyond the reach of surveys in other wavebands. Furthermore, CORE will provide unique information on the evolution of the star formation in virialized groups and clusters of galaxies up to the highest possible redshifts. Finally, thanks to its very high sensitivity, CORE will detect the polarized emission of thousands of radio sources and, for the first time, of dusty galaxies, at mm and sub-mm wavelengths, respectively.

Detecting Blind Fault with Fractal and Roughness Factors from High Resolution LiDAR DEM at Taiwan

NASA Astrophysics Data System (ADS)

Cheng, Y. S.; Yu, T. T.

2014-12-01

There is no obvious fault scarp associated with blind fault. The traditional method of mapping this unrevealed geological structure is the cluster of seismicity. Neither the seismic event nor the completeness of cluster could be captured by network to chart the location of the entire possible active blind fault within short period of time. High resolution DEM gathered by LiDAR could denote actual terrain information despite the existence of plantation. 1-meter interval DEM of mountain region at Taiwan is utilized by fractal, entropy and roughness calculating with MATLAB code. By jointing these handing, the regions of non-sediment deposit are charted automatically. Possible blind fault associated with Chia-Sen earthquake at southern Taiwan is served as testing ground. GIS layer help in removing the difference from various geological formation, then multi-resolution fractal index is computed around the target region. The type of fault movement controls distribution of fractal index number. The scale of blind fault governs degree of change in fractal index. Landslide induced by rainfall and/or earthquake possesses larger degree of geomorphology alteration than blind fault; special treatment in removing these phenomena is required. Highly weathered condition at Taiwan should erase the possible trace remained upon DEM from the ruptured of blind fault while reoccurrence interval is higher than hundreds of years. This is one of the obstacle in finding possible blind fault at Taiwan.

Ionized Gas Kinematics at High Resolution. IV. Star Formation and a Rotating Core in the Medusa (NGC 4194)

NASA Technical Reports Server (NTRS)

Beck, Sara C.; Lacy, John; Neff, Susan Gale; Turner, Jean; Greathouse, Thomas; Neff, Susan

2014-01-01

NGC 4194 is a post-merger starburst known as The Medusa for its striking tidal features.We present here a detailed study of the structure and kinematics of ionized gas in the central 0.65 kpc of the Medusa. The data include radio continuum maps with resolution up to 0".18 (35 pc) and a 12.8 micron [Ne II] data cube with spectral resolution approx. 4 km/s: the first high-resolution, extinction-free observations of this remarkable object. The ionized gas has the kinematic signature of a core in solid-body rotation. The starburst has formed a complex of bright compact H II regions, probably excited by deeply embedded super star clusters, but none of these sources is a convincing candidate for a Galactic nucleus. The nuclei of the merger partners that created the Medusa have not yet been identified.

The split in the ancient cold front in the Perseus cluster

NASA Astrophysics Data System (ADS)

Walker, Stephen A.; ZuHone, John; Fabian, Andy; Sanders, Jeremy

2018-04-01

Sloshing cold fronts in clusters, produced as the dense cluster core moves around in the cluster potential in response to in-falling subgroups, provide a powerful probe of the physics of the intracluster medium and the magnetic fields permeating it1,2. These sharp discontinuities in density and temperature rise gradually outwards with age in a characteristic spiral pattern, embedding into the intracluster medium a record of the minor merging activity of clusters: the further from the cluster centre a cold front is, the older it is. Recently, it was discovered that these cold fronts can survive out to extremely large radii in the Perseus cluster3. Here, we report on high-spatial-resolution Chandra observations of the large-scale cold front in Perseus. We find that rather than broadening through diffusion, the cold front remains extremely sharp (consistent with abrupt jumps in density) and instead is split into two sharp edges. These results show that magnetic draping can suppress diffusion for vast periods of time—around 5 Gyr—even as the cold front expands out to nearly half the cluster virial radius.

Deconvoluting simulated metagenomes: the performance of hard- and soft- clustering algorithms applied to metagenomic chromosome conformation capture (3C)

PubMed Central

DeMaere, Matthew Z.

2016-01-01

Background Chromosome conformation capture, coupled with high throughput DNA sequencing in protocols like Hi-C and 3C-seq, has been proposed as a viable means of generating data to resolve the genomes of microorganisms living in naturally occuring environments. Metagenomic Hi-C and 3C-seq datasets have begun to emerge, but the feasibility of resolving genomes when closely related organisms (strain-level diversity) are present in the sample has not yet been systematically characterised. Methods We developed a computational simulation pipeline for metagenomic 3C and Hi-C sequencing to evaluate the accuracy of genomic reconstructions at, above, and below an operationally defined species boundary. We simulated datasets and measured accuracy over a wide range of parameters. Five clustering algorithms were evaluated (2 hard, 3 soft) using an adaptation of the extended B-cubed validation measure. Results When all genomes in a sample are below 95% sequence identity, all of the tested clustering algorithms performed well. When sequence data contains genomes above 95% identity (our operational definition of strain-level diversity), a naive soft-clustering extension of the Louvain method achieves the highest performance. Discussion Previously, only hard-clustering algorithms have been applied to metagenomic 3C and Hi-C data, yet none of these perform well when strain-level diversity exists in a metagenomic sample. Our simple extension of the Louvain method performed the best in these scenarios, however, accuracy remained well below the levels observed for samples without strain-level diversity. Strain resolution is also highly dependent on the amount of available 3C sequence data, suggesting that depth of sequencing must be carefully considered during experimental design. Finally, there appears to be great scope to improve the accuracy of strain resolution through further algorithm development. PMID:27843713

High-Resolution Analysis by Whole-Genome Sequencing of an International Lineage (Sequence Type 111) of Pseudomonas aeruginosa Associated with Metallo-Carbapenemases in the United Kingdom.

PubMed

Turton, Jane F; Wright, Laura; Underwood, Anthony; Witney, Adam A; Chan, Yuen-Ting; Al-Shahib, Ali; Arnold, Catherine; Doumith, Michel; Patel, Bharat; Planche, Timothy D; Green, Jonathan; Holliman, Richard; Woodford, Neil

2015-08-01

Whole-genome sequencing (WGS) was carried out on 87 isolates of sequence type 111 (ST-111) of Pseudomonas aeruginosa collected between 2005 and 2014 from 65 patients and 12 environmental isolates from 24 hospital laboratories across the United Kingdom on an Illumina HiSeq instrument. Most isolates (73) carried VIM-2, but others carried IMP-1 or IMP-13 (5) or NDM-1 (1); one isolate had VIM-2 and IMP-18, and 7 carried no metallo-beta-lactamase (MBL) gene. Single nucleotide polymorphism analysis divided the isolates into distinct clusters; the NDM-1 isolate was an outlier, and the IMP isolates and 6/7 MBL-negative isolates clustered separately from the main set of 73 VIM-2 isolates. Within the VIM-2 set, there were at least 3 distinct clusters, including a tightly clustered set of isolates from 3 hospital laboratories consistent with an outbreak from a single introduction that was quickly brought under control and a much broader set dominated by isolates from a long-running outbreak in a London hospital likely seeded from an environmental source, requiring different control measures; isolates from 7 other hospital laboratories in London and southeast England were also included. Bayesian evolutionary analysis indicated that all the isolates shared a common ancestor dating back ∼50 years (1960s), with the main VIM-2 set separating approximately 20 to 30 years ago. Accessory gene profiling revealed blocks of genes associated with particular clusters, with some having high similarity (≥95%) to bacteriophage genes. WGS of widely found international lineages such as ST-111 provides the necessary resolution to inform epidemiological investigations and intervention policies. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

The Discovery of Lensed Radio and X-ray Sources Behind the Frontier Fields Cluster MACS J0717.5+3745 with the JVLA and Chandra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weeren, R. J. van; Ogrean, G. A.; Jones, C.

We report on high-resolution JVLA and Chandra observations of the Hubble Space Telescope (HST) Frontier Cluster MACS J0717.5+3745. MACS J0717.5+3745 offers the largest contiguous magnified area of any known cluster, making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0–6.5 GHz JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the HST imaging. Within this sample, we find seven lensed sources with amplification factors larger than two. None of these sources are identified as multiply lensed. Based on the radio luminosities,more » the majority of these sources are likely star-forming galaxies with star-formation rates (SFRs) of 10–50 M ⊙ yr -1 located at 1≲ z ≲ 2. Two of the lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely active galactic nuclei, given their 2–10 keV X-ray luminosities of ~ 10 43-44 erg s -1. From the derived radio luminosity function, we find evidence for an increase in the number density of radio sources at 0.6 < z < 2.0, compared to a z < 0.3 sample. Lastly, our observations indicate that deep radio imaging of lensing clusters can be used to study star-forming galaxies, with SFRs as low as ~10M ⊙ yr -1, at the peak of cosmic star formation history.« less

The Discovery of Lensed Radio and X-ray Sources Behind the Frontier Fields Cluster MACS J0717.5+3745 with the JVLA and Chandra

DOE PAGES

Weeren, R. J. van; Ogrean, G. A.; Jones, C.; ...

2016-01-27

We report on high-resolution JVLA and Chandra observations of the Hubble Space Telescope (HST) Frontier Cluster MACS J0717.5+3745. MACS J0717.5+3745 offers the largest contiguous magnified area of any known cluster, making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0–6.5 GHz JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the HST imaging. Within this sample, we find seven lensed sources with amplification factors larger than two. None of these sources are identified as multiply lensed. Based on the radio luminosities,more » the majority of these sources are likely star-forming galaxies with star-formation rates (SFRs) of 10–50 M ⊙ yr -1 located at 1≲ z ≲ 2. Two of the lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely active galactic nuclei, given their 2–10 keV X-ray luminosities of ~ 10 43-44 erg s -1. From the derived radio luminosity function, we find evidence for an increase in the number density of radio sources at 0.6 < z < 2.0, compared to a z < 0.3 sample. Lastly, our observations indicate that deep radio imaging of lensing clusters can be used to study star-forming galaxies, with SFRs as low as ~10M ⊙ yr -1, at the peak of cosmic star formation history.« less

Low Altitude AVIRIS Data for Mapping Land Cover in Yellowstone National Park: Use of Isodata Clustering Techniques

NASA Technical Reports Server (NTRS)

Spruce, Joe

2001-01-01

Yellowstone National Park (YNP) contains a diversity of land cover. YNP managers need site-specific land cover maps, which may be produced more effectively using high-resolution hyperspectral imagery. ISODATA clustering techniques have aided operational multispectral image classification and may benefit certain hyperspectral data applications if optimally applied. In response, a study was performed for an area in northeast YNP using 11 select bands of low-altitude AVIRIS data calibrated to ground reflectance. These data were subjected to ISODATA clustering and Maximum Likelihood Classification techniques to produce a moderately detailed land cover map. The latter has good apparent overall agreement with field surveys and aerial photo interpretation.

Advances in Patch-Based Adaptive Mesh Refinement Scalability

DOE PAGES

Gunney, Brian T.N.; Anderson, Robert W.

2015-12-18

Patch-based structured adaptive mesh refinement (SAMR) is widely used for high-resolution simu- lations. Combined with modern supercomputers, it could provide simulations of unprecedented size and resolution. A persistent challenge for this com- bination has been managing dynamically adaptive meshes on more and more MPI tasks. The dis- tributed mesh management scheme in SAMRAI has made some progress SAMR scalability, but early al- gorithms still had trouble scaling past the regime of 105 MPI tasks. This work provides two critical SAMR regridding algorithms, which are integrated into that scheme to ensure efficiency of the whole. The clustering algorithm is an extensionmore » of the tile- clustering approach, making it more flexible and efficient in both clustering and parallelism. The partitioner is a new algorithm designed to prevent the network congestion experienced by its prede- cessor. We evaluated performance using weak- and strong-scaling benchmarks designed to be difficult for dynamic adaptivity. Results show good scaling on up to 1.5M cores and 2M MPI tasks. Detailed timing diagnostics suggest scaling would continue well past that.« less

Advances in Patch-Based Adaptive Mesh Refinement Scalability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gunney, Brian T.N.; Anderson, Robert W.

Patch-based structured adaptive mesh refinement (SAMR) is widely used for high-resolution simu- lations. Combined with modern supercomputers, it could provide simulations of unprecedented size and resolution. A persistent challenge for this com- bination has been managing dynamically adaptive meshes on more and more MPI tasks. The dis- tributed mesh management scheme in SAMRAI has made some progress SAMR scalability, but early al- gorithms still had trouble scaling past the regime of 105 MPI tasks. This work provides two critical SAMR regridding algorithms, which are integrated into that scheme to ensure efficiency of the whole. The clustering algorithm is an extensionmore » of the tile- clustering approach, making it more flexible and efficient in both clustering and parallelism. The partitioner is a new algorithm designed to prevent the network congestion experienced by its prede- cessor. We evaluated performance using weak- and strong-scaling benchmarks designed to be difficult for dynamic adaptivity. Results show good scaling on up to 1.5M cores and 2M MPI tasks. Detailed timing diagnostics suggest scaling would continue well past that.« less

High-resolution spectra of stars in globular clusters. VI - Oxygen-deficient red giant stars in M13

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, J.A.; Wallerstein, G.; Oke, J.B.

From high-resolution, high signal-to-noise spectra, abundances of carbon, nitrogen, and oxygen and the C-12/C-13 ratio for five red giants in M13, including star II-67, which has previously been reported to be deficient in oxygen have been determined. Three of the five stars exhibit substantial oxygen deficiencies; O/Fe values range from +0.5 to less than about 0.3. The sum of the CNO nuclides is the same for all stars, which is interpreted as evidence that mixing of CNO-cycled material into the envelope is the cause of the variations in oxygen abundance. 41 refs.

http://www.esa.int/esaSC/Pr_21_2004_s_en.html

NASA Astrophysics Data System (ADS)

2004-09-01

X-ray brightness map hi-res Size hi-res: 38 Kb Credits: ESA/ XMM-Newton/ Patrick Henry et al. X-ray brightness map This map shows "surface brightness" or how luminous the region is. The larger of the two galaxy clusters is brighter, shown here as a white and red spot. A second cluster resides about "2 o'clock" from this, shown by a batch of yellow surrounded by green. Luminosity is related to density, so the densest regions (cluster cores) are the brightest regions. The white color corresponds to regions of the highest surface brightness, followed by red, orange, yellow, green, blue and purple. High resolution version (JPG format) 38 Kb High resolution version (TIFF format) 525 Kb Temperature map Credits: NASA Artist’s impression of cosmic head on collision The event details what the scientists are calling the perfect cosmic storm: galaxy clusters that collided like two high-pressure weather fronts and created hurricane-like conditions, tossing galaxies far from their paths and churning shock waves of 100-million-degree gas through intergalactic space. The tiny dots in this artist's concept are galaxies containing thousand million of stars. Animated GIF version Temperature map hi-res Size hi-res: 57 Kb Credits: ESA/ XMM-Newton/ Patrick Henry et al. Temperature map This image shows the temperature of gas in and around the two merging galaxy clusters, based directly on X-ray data. The galaxies themselves are difficult to identify; the image highlights the hot ‘invisible’ gas between the clusters heated by shock waves. The white colour corresponds to regions of the highest temperature - million of degrees, hotter than the surface of the Sun - followed by red, orange, yellow and blue. High resolution version (JPG format) 57 Kb High resolution version (TIFF format) 819 Kb The event details what the scientists are calling the ‘perfect cosmic storm’: galaxy clusters that collided like two high-pressure weather fronts and created hurricane-like conditions, tossing galaxies far from their paths and churning shock waves of 100-million-degree gas through intergalactic space. This unprecedented view of a merger in action crystallises the theory that the Universe built its magnificent hierarchal structure from the ‘bottom up’ - essentially through mergers of smaller galaxies and galaxy clusters into bigger ones. "Here before our eyes we see the making of one of the biggest objects in the Universe," said Dr Patrick Henry of the University of Hawaii, who led the study. "What was once two distinct but smaller galaxy clusters 300 million years ago is now one massive cluster in turmoil.” Henry and his colleagues, Alexis Finoguenov and Ulrich Briel of the Max-Planck Institute for Extraterrestrial Physics in Germany, present these results in an upcoming issue of the Astrophysical Journal. The forecast for the new super-cluster, they said, is 'clear and calm' now that the worst of the storm has passed. Galaxy clusters are the largest gravitationally bound structures in Universe, containing hundreds to thousands of galaxies. Our Milky Way galaxy is part of a small group of galaxies but is not gravitationally bound to the closest cluster, the Virgo Cluster. We are destined for a collision in a few thousand million years, though. The cluster named Abell 754 in the constellation Hydra has been known for decades. However, to the scientists' surprise, the new observation reveals that the merger may have occurred from the opposite direction than what was thought. They found evidence for this by tracing the wreckage today left in the merger's wake, spanning a distance of millions of light years. While other large mergers are known, none has been measured in such detail as Abell 754. For the first time, the scientists could create a complete ‘weather map’ of Abell 754 and thus determine a forecast. This map contains information about the temperature, pressure and density of the new cluster. As in all clusters, most the ordinary matter is in the form of gas between the galaxies and not locked up in the galaxies or stars themselves. The massive forces of the merging clusters accelerated intergalactic gas to great speeds. This resulted in shock waves that heat the gas to very high temperatures, which then radiated X-ray light, far more energetic than the visible light our eyes can detect. XMM-Newton, in orbit, detects this type of high-energy light. The dynamics of the merger revealed by XMM-Newton point to a cluster in transition. "One cluster has apparently smashed into the other from the 'north-west' and has since made one pass through," said Finoguenov. "Now, gravity will pull the remnants of this first cluster back towards the core of the second. Over the next few thousand million of years, the remnants of the clusters will settle and the merger will be complete." The observation implies that the largest structures in the Universe are essentially still forming in the modern era. Abell 754 is relatively close, about 800 million light years away. The construction boom may soon be over in a few more thousand million years though. A mysterious substance dubbed 'dark energy' appears to be accelerating the Universe's expansion rate. This means that objects are flying apart from each other at an ever-increasing speed and that clusters may eventually never have the opportunity to collide with each other. X-ray observations of galaxy clusters such as Abell 754 will help to better define dark energy and also dark matter, an ‘invisible’ and mysterious substance that appears to comprise over 80 percent of a galaxy cluster's mass. Notes for editors: This observation was announced at a NASA Internet press conference today. A paper describing these results, by Patrick Henry and his collaborators, will be published in the Astrophysical Journal. Images and other visual material are available at: http://www.gsfc.nasa.gov/topstory/2004/0831galaxymerger_media.html More about XMM-Newton ESA's XMM-Newton can detect more X-ray sources than any previous satellite and is helping to solve many cosmic mysteries of the violent Universe, from black holes to the formation of galaxies. It was launched on 10 December 1999, using an Ariane-5 rocket, from French Guiana. It is expected to return data for a decade. XMM-Newton's high-tech design uses over 170 wafer-thin cylindrical mirrors spread over three telescopes. Its orbit takes it almost a third of the way to the Moon, so that astronomers can enjoy long, uninterrupted views of celestial objects.

Gamma-Ray Emission from Galaxy Clusters : DARK MATTER AND COSMIC-RAYS

NASA Astrophysics Data System (ADS)

Pinzke, Anders

The quest for the first detection of a galaxy cluster in the high energy gamma-ray regime is ongoing, and even though clusters are observed in several other wave-bands, there is still no firm detection in gamma-rays. To complement the observational efforts we estimate the gamma-ray contributions from both annihilating dark matter and cosmic-ray (CR) proton as well as CR electron induced emission. Using high-resolution simulations of galaxy clusters, we find a universal concave shaped CR proton spectrum independent of the simulated galaxy cluster. Specifically, the gamma-ray spectra from decaying neutral pions, which are produced by CR protons, dominate the cluster emission. Furthermore, based on our derived flux and luminosity functions, we identify the galaxy clusters with the brightest galaxy clusters in gamma-rays. While this emission is challenging to detect using the Fermi satellite, major observations with Cherenkov telescopes in the near future may put important constraints on the CR physics in clusters. To extend these predictions, we use a dark matter model that fits the recent electron and positron data from Fermi, PAMELA, and H.E.S.S. with remarkable precision, and make predictions about the expected gamma-ray flux from nearby clusters. In order to remain consistent with the EGRET upper limit on the gamma-ray emission from Virgo, we constrain the minimum mass of substructures for cold dark matter halos. In addition, we find comparable levels of gamma-ray emission from CR interactions and dark matter annihilations without Sommerfeld enhancement.

High-Resolution Spatial Distribution and Estimation of Access to Improved Sanitation in Kenya.

PubMed

Jia, Peng; Anderson, John D; Leitner, Michael; Rheingans, Richard

2016-01-01

Access to sanitation facilities is imperative in reducing the risk of multiple adverse health outcomes. A distinct disparity in sanitation exists among different wealth levels in many low-income countries, which may hinder the progress across each of the Millennium Development Goals. The surveyed households in 397 clusters from 2008-2009 Kenya Demographic and Health Surveys were divided into five wealth quintiles based on their national asset scores. A series of spatial analysis methods including excess risk, local spatial autocorrelation, and spatial interpolation were applied to observe disparities in coverage of improved sanitation among different wealth categories. The total number of the population with improved sanitation was estimated by interpolating, time-adjusting, and multiplying the surveyed coverage rates by high-resolution population grids. A comparison was then made with the annual estimates from United Nations Population Division and World Health Organization /United Nations Children's Fund Joint Monitoring Program for Water Supply and Sanitation. The Empirical Bayesian Kriging interpolation produced minimal root mean squared error for all clusters and five quintiles while predicting the raw and spatial coverage rates of improved sanitation. The coverage in southern regions was generally higher than in the north and east, and the coverage in the south decreased from Nairobi in all directions, while Nyanza and North Eastern Province had relatively poor coverage. The general clustering trend of high and low sanitation improvement among surveyed clusters was confirmed after spatial smoothing. There exists an apparent disparity in sanitation among different wealth categories across Kenya and spatially smoothed coverage rates resulted in a closer estimation of the available statistics than raw coverage rates. Future intervention activities need to be tailored for both different wealth categories and nationally where there are areas of greater needs when resources are limited.

Some Psychometric and Design Implications of Game-Based Learning Analytics

ERIC Educational Resources Information Center

Gibson, David; Clarke-Midura, Jody

2013-01-01

The rise of digital game and simulation-based learning applications has led to new approaches in educational measurement that take account of patterns in time, high resolution paths of action, and clusters of virtual performance artifacts. The new approaches, which depart from traditional statistical analyses, include data mining, machine…

Classification of Microcalcifications for the Diagnosis of Breast Cancer Using Artificial Neural Networks.

DTIC Science & Technology

1997-09-01

employed to classify benign and malignant microcalcifications in the radiographs of pathological specimen that were digitized at a high resolution of...21 microns x 21 microns. The CNN achieved an Az value of 0.90 in classifying clusters of microcalcifications associated with benign and malignant processes

The Relationship of Sodium and Oxygen in Galactic Field RR Lyrae Stars

NASA Astrophysics Data System (ADS)

Andrievsky, S.; Wallerstein, G.; Korotin, S.; Lyashko, D.; Kovtyukh, V.; Tsymbal, V.; Davis, C. E.; Gomez, T.; Huang, W.; Farrell, E. M.

2018-02-01

We analyzed 62 high-resolution spectra of 30 Galactic Field RR Lyrae-type stars with the aim of deriving their atmospheric parameters (T eff , {log}g, V t ), metallicity ([Fe/H]), radial velocities, and NLTE abundances of oxygen and sodium. We found that there is no clear anti-correlation between [O/Fe] and [Na/Fe] as is seen in globular clusters. On this basis, we conclude that the majority of field RR Lyrae-type stars should hardly be considered to be remnants of the dissolution of globular clusters.

Graphics Processing Units (GPU) and the Goddard Earth Observing System atmospheric model (GEOS-5): Implementation and Potential Applications

NASA Technical Reports Server (NTRS)

Putnam, William M.

2011-01-01

Earth system models like the Goddard Earth Observing System model (GEOS-5) have been pushing the limits of large clusters of multi-core microprocessors, producing breath-taking fidelity in resolving cloud systems at a global scale. GPU computing presents an opportunity for improving the efficiency of these leading edge models. A GPU implementation of GEOS-5 will facilitate the use of cloud-system resolving resolutions in data assimilation and weather prediction, at resolutions near 3.5 km, improving our ability to extract detailed information from high-resolution satellite observations and ultimately produce better weather and climate predictions

Resolved magnetic dynamo action in the simulated intracluster medium

NASA Astrophysics Data System (ADS)

Vazza, F.; Brunetti, G.; Brüggen, M.; Bonafede, A.

2018-02-01

Faraday rotation and synchrotron emission from extragalactic radio sources give evidence for the presence of magnetic fields extending over ˜ Mpc scales. However, the origin of these fields remains elusive. With new high-resolution grid simulations, we studied the growth of magnetic fields in a massive galaxy cluster that in several aspects is similar to the Coma cluster. We investigated models in which magnetic fields originate from primordial seed fields with comoving strengths of 0.1 nG at redshift z = 30. The simulations show evidence of significant magnetic field amplification. At the best spatial resolution (3.95 kpc), we are able to resolve the scale where magnetic tension balances the bending of magnetic lines by turbulence. This allows us to observe the final growth stage of the small-scale dynamo. To our knowledge, this is the first time that this is seen in cosmological simulations of the intracluster medium. Our mock observations of Faraday rotation provide a good match to observations of the Coma cluster. However, the distribution of magnetic fields shows strong departures from a simple Maxwellian distribution, suggesting that the three-dimensional structure of magnetic fields in real clusters may be significantly different than what is usually assumed when inferring magnetic field values from rotation measure observations.

Stable clustering and the resolution of dissipationless cosmological N-body simulations

NASA Astrophysics Data System (ADS)

Benhaiem, David; Joyce, Michael; Sylos Labini, Francesco

2017-10-01

The determination of the resolution of cosmological N-body simulations, I.e. the range of scales in which quantities measured in them represent accurately the continuum limit, is an important open question. We address it here using scale-free models, for which self-similarity provides a powerful tool to control resolution. Such models also provide a robust testing ground for the so-called stable clustering approximation, which gives simple predictions for them. Studying large N-body simulations of such models with different force smoothing, we find that these two issues are in fact very closely related: our conclusion is that the accuracy of two-point statistics in the non-linear regime starts to degrade strongly around the scale at which their behaviour deviates from that predicted by the stable clustering hypothesis. Physically the association of the two scales is in fact simple to understand: stable clustering fails to be a good approximation when there are strong interactions of structures (in particular merging) and it is precisely such non-linear processes which are sensitive to fluctuations at the smaller scales affected by discretization. Resolution may be further degraded if the short distance gravitational smoothing scale is larger than the scale to which stable clustering can propagate. We examine in detail the very different conclusions of studies by Smith et al. and Widrow et al. and find that the strong deviations from stable clustering reported by these works are the results of over-optimistic assumptions about scales resolved accurately by the measured power spectra, and the reliance on Fourier space analysis. We emphasize the much poorer resolution obtained with the power spectrum compared to the two-point correlation function.

Automatic Segmentation of Fluorescence Lifetime Microscopy Images of Cells Using Multi-Resolution Community Detection -A First Study

PubMed Central

Hu, Dandan; Sarder, Pinaki; Ronhovde, Peter; Orthaus, Sandra; Achilefu, Samuel; Nussinov, Zohar

2014-01-01

Inspired by a multi-resolution community detection (MCD) based network segmentation method, we suggest an automatic method for segmenting fluorescence lifetime (FLT) imaging microscopy (FLIM) images of cells in a first pilot investigation on two selected images. The image processing problem is framed as identifying segments with respective average FLTs against the background in FLIM images. The proposed method segments a FLIM image for a given resolution of the network defined using image pixels as the nodes and similarity between the FLTs of the pixels as the edges. In the resulting segmentation, low network resolution leads to larger segments, and high network resolution leads to smaller segments. Further, using the proposed method, the mean-square error (MSE) in estimating the FLT segments in a FLIM image was found to consistently decrease with increasing resolution of the corresponding network. The MCD method appeared to perform better than a popular spectral clustering based method in performing FLIM image segmentation. At high resolution, the spectral segmentation method introduced noisy segments in its output, and it was unable to achieve a consistent decrease in MSE with increasing resolution. PMID:24251410

Analyzing Protein Clusters on the Plasma Membrane: Application of Spatial Statistical Analysis Methods on Super-Resolution Microscopy Images.

PubMed

Paparelli, Laura; Corthout, Nikky; Pavie, Benjamin; Annaert, Wim; Munck, Sebastian

2016-01-01

The spatial distribution of proteins within the cell affects their capability to interact with other molecules and directly influences cellular processes and signaling. At the plasma membrane, multiple factors drive protein compartmentalization into specialized functional domains, leading to the formation of clusters in which intermolecule interactions are facilitated. Therefore, quantifying protein distributions is a necessity for understanding their regulation and function. The recent advent of super-resolution microscopy has opened up the possibility of imaging protein distributions at the nanometer scale. In parallel, new spatial analysis methods have been developed to quantify distribution patterns in super-resolution images. In this chapter, we provide an overview of super-resolution microscopy and summarize the factors influencing protein arrangements on the plasma membrane. Finally, we highlight methods for analyzing clusterization of plasma membrane proteins, including examples of their applications.

The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII): High Angular Resolution Astronomy at Far-Infrared Wavelengths

NASA Technical Reports Server (NTRS)

Rinehart, Stephen A.

2008-01-01

Astronomical studies at infrared wavelengths have dramatically improved our understanding of the universe, and observations with Spitzer, the upcoming Herschel mission. and SOFIA will continue to provide exciting new discoveries. The comparatively low spatial resolution of these missions, however. is insufficient to resolve the physical scales on which mid- to far-infrared emission arises, resulting in source and structure ambiguities that limit our ability to answer key science questions. Interferometry enables high angular resolution at these wavelengths. We have proposed a new high altitude balloon experiment, the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII). High altitude operation makes far-infrared (30- 300micron) observations possible, and BETTII's 8-meter baseline provides unprecedented angular resolution (-0.5 arcsec) in this band. BETTII will use a double- Fourier instrument to simultaneously obtain both spatial and spectral informatioT. he spatially resolved spectroscopy provided by BETTII will address key questions about the nature of disks in young cluster stars and active galactic nuclei and the envelopes of evolved stars. BETTII will also lay the groundwork for future space interferometers.

NGC 6535: the lowest mass Milky Way globular cluster with a Na-O anti-correlation? Cluster mass and age in the multiple population context

NASA Astrophysics Data System (ADS)

Bragaglia, A.; Carretta, E.; D'Orazi, V.; Sollima, A.; Donati, P.; Gratton, R. G.; Lucatello, S.

2017-11-01

To understand globular clusters (GCs) we need to comprehend how their formation process was able to produce their abundance distribution of light elements. In particular, we seek to figure out which stars imprinted the peculiar chemical signature of GCs. One of the best ways is to study the light-element anti-correlations in a large sample of GCs that are analysed homogeneously. As part of our spectroscopic survey of GCs with FLAMES, we present here the results of our study of about 30 red giant member stars in the low-mass, low-metallicity Milky Way cluster NGC 6535. We measured the metallicity (finding [Fe/H] =-1.95, rms = 0.04 dex in our homogeneous scale) and other elements of the cluster and, in particular, we concentrate here on O and Na abundances. These elements define the normal Na-O anti-correlation of classical GCs, making NGC 6535 perhaps the lowest mass cluster with a confirmed presence of multiple populations. We updated the census of Galactic and extragalactic GCs for which a statement on the presence or absence of multiple populations can be made on the basis of high-resolution spectroscopy preferentially, or photometry and low-resolution spectroscopy otherwise; we also discuss the importance of mass and age of the clusters as factors for multiple populations. Based on observations collected at ESO telescopes under programme 093.B-0583.Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A44

3D ToF-SIMS Analysis of Peptide Incorporation into MALDI Matrix Crystals with Sub-micrometer Resolution.

PubMed

Körsgen, Martin; Pelster, Andreas; Dreisewerd, Klaus; Arlinghaus, Heinrich F

2016-02-01

The analytical sensitivity in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is largely affected by the specific analyte-matrix interaction, in particular by the possible incorporation of the analytes into crystalline MALDI matrices. Here we used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to visualize the incorporation of three peptides with different hydrophobicities, bradykinin, Substance P, and vasopressin, into two classic MALDI matrices, 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (HCCA). For depth profiling, an Ar cluster ion beam was used to gradually sputter through the matrix crystals without causing significant degradation of matrix or biomolecules. A pulsed Bi3 ion cluster beam was used to image the lateral analyte distribution in the center of the sputter crater. Using this dual beam technique, the 3D distribution of the analytes and spatial segregation effects within the matrix crystals were imaged with sub-μm resolution. The technique could in the future enable matrix-enhanced (ME)-ToF-SIMS imaging of peptides in tissue slices at ultra-high resolution. Graphical Abstract ᅟ.

3D ToF-SIMS Analysis of Peptide Incorporation into MALDI Matrix Crystals with Sub-micrometer Resolution

NASA Astrophysics Data System (ADS)

Körsgen, Martin; Pelster, Andreas; Dreisewerd, Klaus; Arlinghaus, Heinrich F.

2016-02-01

The analytical sensitivity in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is largely affected by the specific analyte-matrix interaction, in particular by the possible incorporation of the analytes into crystalline MALDI matrices. Here we used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to visualize the incorporation of three peptides with different hydrophobicities, bradykinin, Substance P, and vasopressin, into two classic MALDI matrices, 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (HCCA). For depth profiling, an Ar cluster ion beam was used to gradually sputter through the matrix crystals without causing significant degradation of matrix or biomolecules. A pulsed Bi3 ion cluster beam was used to image the lateral analyte distribution in the center of the sputter crater. Using this dual beam technique, the 3D distribution of the analytes and spatial segregation effects within the matrix crystals were imaged with sub-μm resolution. The technique could in the future enable matrix-enhanced (ME)-ToF-SIMS imaging of peptides in tissue slices at ultra-high resolution.

VizieR Online Data Catalog: Line list for seven target PAndAS clusters (Sakari+, 2015)

NASA Astrophysics Data System (ADS)

Sakari, C. M.; Venn, K. A.; Mackey, D.; Shetrone, M. D.; Dotter, A.; Ferguson, A. M. N.; Huxor, A.

2017-11-01

The targets were observed with the Hobby-Eberly Telescope (HET; Ramsey et al. 1998, Proc. SPIE, 3352, 34; Shetrone et al. 2007PASP..119..556S) at McDonald Observatory in Fort Davis, TX in 2011 and early 2012. The High Resolution Spectrograph (HRS; Tull 1998, Proc. SPIE, 3355, 387) was utilized with the 3-arcsec fibre and a slit width of 1 arcsec, yielding an instrumental spectral resolution of R=30000. With the 600 g/mm cross-disperser set to a central wavelength of 6302.9Å, wavelength coverages of ~5320-6290 and ~6360-7340Å were achieved in the blue and the red, respectively. The 3-arcsec fibre provided coverage of the clusters past their half-light radii; the additional sky fibres (located 10 arcsec from the central object fibre) provided simultaneous observations for sky subtraction. Exposure times were calculated to obtain a total signal-to-noise ratio (S/N)=80 (per resolution element), although not all targets received sufficient time to meet this goal. (2 data files).

A New Look at the Molecular Gas in M42 and M43: Possible Evidence for Cloud–Cloud Collision that Triggered Formation of the OB Stars in the Orion Nebula Cluster

NASA Astrophysics Data System (ADS)

Fukui, Yasuo; Torii, Kazufumi; Hattori, Yusuke; Nishimura, Atsushi; Ohama, Akio; Shimajiri, Yoshito; Shima, Kazuhiro; Habe, Asao; Sano, Hidetoshi; Kohno, Mikito; Yamamoto, Hiroaki; Tachihara, Kengo; Onishi, Toshikazu

2018-06-01

The Orion Nebula Cluster toward the H II region M42 is the most outstanding young cluster at the smallest distance (410 pc) among the rich high-mass stellar clusters. By newly analyzing the archival molecular data of the 12CO(J = 1–0) emission at 21″ resolution, we identified at least three pairs of complementary distributions between two velocity components at 8 and 13 km s‑1. We present a hypothesis that the two clouds collided with each other and triggered formation of the high-mass stars, mainly toward two regions including the nearly 10 O stars in M42 and the B star, NU Ori, in M43. The timescale of the collision is estimated to be ∼0.1 Myr by a ratio of the cloud size and velocity corrected for projection, which is consistent with the age of the youngest cluster members less than 0.1 Myr. The majority of the low-mass cluster members were formed prior to the collision in the last Myr. We discuss the implications of the present hypothesis and the scenario of high-mass star formation by comparing with the other eight cases of triggered O-star formation via cloud–cloud collision.

Experimental and theoretical investigation of the magnetization dynamics of an artificial square spin ice cluster

NASA Astrophysics Data System (ADS)

Pohlit, Merlin; Stockem, Irina; Porrati, Fabrizio; Huth, Michael; Schröder, Christian; Müller, Jens

2016-10-01

We study the magnetization dynamics of a spin ice cluster which is a building block of an artificial square spin ice fabricated by focused electron-beam-induced deposition both experimentally and theoretically. The spin ice cluster is composed of twelve interacting Co nanoislands grown directly on top of a high-resolution micro-Hall sensor. By employing micromagnetic simulations and a macrospin model, we calculate the magnetization and the experimentally investigated stray field emanating from a single nanoisland. The parameters determined from a comparison with the experimental hysteresis loop are used to derive an effective single-dipole macrospin model that allows us to investigate the dynamics of the spin ice cluster. Our model reproduces the experimentally observed non-deterministic sequences in the magnetization curves as well as the distinct temperature dependence of the hysteresis loop.

Probing Massive Star Cluster Formation with ALMA

NASA Astrophysics Data System (ADS)

Johnson, Kelsey

2015-08-01

Observationally constraining the physical conditions that give rise to massive star clusters has been a long-standing challenge. Now with the ALMA Observatory coming on-line, we can finally begin to probe the birth environments of massive clusters in a variety of galaxies with sufficient angular resolution. In this talk I will give an overview of ALMA observations of galaxies in which candidate proto-super star cluster molecular clouds have been identified. These new data probe the physical conditions that give rise to super star clusters, providing information on their densities, pressures, and temperatures. In particular, the observations indicate that these clouds may be subject to external pressures of P/k > 108 K cm-3, which is consistent with the prevalence of optically observed adolescent super star clusters in interacting galaxy systems and other high pressure environments. ALMA observations also enable an assessement of the molecular cloud chemical abundances in the regions surrounding super star clusters. Molecular clouds associated with existing super star clusters are strongly correlated with HCO+ emission, but appear to have relatively low ratio of CO/HCO+ emission compared to other clouds, indicating that the super star clusters are impacting the molecular abundances in their vicinity.

Atomistic observation and simulation analysis of spatio-temporal fluctuations during radiation-induced amorphization.

PubMed

Watanabe, Seiichi; Hoshino, Misaki; Koike, Takuto; Suda, Takanori; Ohnuki, Soumei; Takahashi, Heishichirou; Lam, Nighi Q

2003-01-01

We performed a dynamical-atomistic study of radiation-induced amorphization in the NiTi intermetallic compound using in situ high-resolution high-voltage electron microscopy and molecular dynamics simulations in connection with image simulation. Spatio-temporal fluctuations as non-equilibrium fluctuations in an energy-dissipative system, due to transient atom-cluster formation during amorphization, were revealed by the present spatial autocorrelation analysis.

Analyzing gene expression time-courses based on multi-resolution shape mixture model.

PubMed

Li, Ying; He, Ye; Zhang, Yu

2016-11-01

Biological processes actually are a dynamic molecular process over time. Time course gene expression experiments provide opportunities to explore patterns of gene expression change over a time and understand the dynamic behavior of gene expression, which is crucial for study on development and progression of biology and disease. Analysis of the gene expression time-course profiles has not been fully exploited so far. It is still a challenge problem. We propose a novel shape-based mixture model clustering method for gene expression time-course profiles to explore the significant gene groups. Based on multi-resolution fractal features and mixture clustering model, we proposed a multi-resolution shape mixture model algorithm. Multi-resolution fractal features is computed by wavelet decomposition, which explore patterns of change over time of gene expression at different resolution. Our proposed multi-resolution shape mixture model algorithm is a probabilistic framework which offers a more natural and robust way of clustering time-course gene expression. We assessed the performance of our proposed algorithm using yeast time-course gene expression profiles compared with several popular clustering methods for gene expression profiles. The grouped genes identified by different methods are evaluated by enrichment analysis of biological pathways and known protein-protein interactions from experiment evidence. The grouped genes identified by our proposed algorithm have more strong biological significance. A novel multi-resolution shape mixture model algorithm based on multi-resolution fractal features is proposed. Our proposed model provides a novel horizons and an alternative tool for visualization and analysis of time-course gene expression profiles. The R and Matlab program is available upon the request. Copyright © 2016 Elsevier Inc. All rights reserved.

AMI-CL J0300+2613: a Galactic anomalous-microwave-emission ring masquerading as a galaxy cluster

NASA Astrophysics Data System (ADS)

Perrott, Yvette C.; Cantwell, Therese M.; Carey, Steve H.; Elwood, Patrick J.; Feroz, Farhan; Grainge, Keith J. B.; Green, David A.; Hobson, Michael P.; Javid, Kamran; Jin, Terry Z.; Pooley, Guy G.; Razavi-Ghods, Nima; Rumsey, Clare; Saunders, Richard D. E.; Scaife, Anna M. M.; Schammel, Michel P.; Scott, Paul F.; Shimwell, Timothy W.; Titterington, David J.; Waldram, Elizabeth M.

2018-01-01

The Arcminute Microkelvin Imager (AMI) carried out a blind survey for galaxy clusters via their Sunyaev-Zel'dovich effect decrements between 2008 and 2011. The first detection, known as AMI-CL J0300+2613, has been reobserved with AMI equipped with a new digital correlator with high dynamic range. The combination of the new AMI data and more recent high-resolution sub-mm and infrared maps now shows the feature in fact to be a ring of positive dust-correlated Galactic emission, which is likely to be anomalous microwave emission (AME). If so, this is the first completely blind detection of AME at arcminute scales.

Thermal Conduction in Simulated Galaxy Clusters

NASA Astrophysics Data System (ADS)

Dolag, K.; Jubelgas, M.; Springel, V.; Borgani, S.; Rasia, E.

2004-05-01

We study the formation of clusters of galaxies using high-resolution hydrodynamic cosmological simulations that include the effect of thermal conduction with an effective isotropic conductivity of 1/3 the classical Spitzer value. We find that, for both a hot (TLX~=12 keV) and several cold (TLX~=2 keV) galaxy clusters, the baryonic fraction converted into stars does not change significantly when thermal conduction is included. However, the temperature profiles are modified, particularly in our simulated hot system, where an extended isothermal core is readily formed. As a consequence of heat flowing from the inner regions of the cluster both to its outer parts and into its innermost resolved regions, the entropy profile is altered as well. This effect is almost negligible for the cold cluster, as expected based on the strong temperature dependence of the conductivity. Our results demonstrate that while thermal conduction can have a significant influence on the properties of the intracluster medium (ICM) of rich clusters, it appears unlikely to provide by itself a solution for the overcooling problem in clusters or to explain the current discrepancies between the observed and simulated properties of the ICM.

Population changes in residential clusters in Japan.

PubMed

Sekiguchi, Takuya; Tamura, Kohei; Masuda, Naoki

2018-01-01

Population dynamics in urban and rural areas are different. Understanding factors that contribute to local population changes has various socioeconomic and political implications. In the present study, we use population census data in Japan to examine contributors to the population growth of residential clusters between years 2005 and 2010. The data set covers the entirety of Japan and has a high spatial resolution of 500 × 500 m2, enabling us to examine population dynamics in various parts of the country (urban and rural) using statistical analysis. We found that, in addition to the area, population density, and age, the shape of the cluster and the spatial distribution of inhabitants within the cluster are significantly related to the population growth rate of a residential cluster. Specifically, the population tends to grow if the cluster is "round" shaped (given the area) and the population is concentrated near the center rather than periphery of the cluster. Combination of the present results and analysis framework with other factors that have been omitted in the present study, such as migration, terrain, and transportation infrastructure, will be fruitful.

Fullerene-like Polyoxotitanium Cage with High Solution Stability.

PubMed

Gao, Mei-Yan; Wang, Fei; Gu, Zhi-Gang; Zhang, De-Xiang; Zhang, Lei; Zhang, Jian

2016-03-02

We present the formation of the largest titanium-oxo cluster, [Ti42(μ3-O)60(OiPr)42(OH)12)](6-), with the first fullerene-like Ti-O shell structure. The {Ti42O60} core of this compound exemplifies the same icosahedral (Ih) symmetry as C60, the highest possible symmetry for molecules. According to the coordination environments, the Ti centers in this cluster can be arranged into a Platonic {Ti12} icosahedron and an Archimedean {Ti30} icosidodecahedron. The solution stability of this cluster was confirmed by electrospray ionization mass spectrometry. The spherical body of the {Ti42O60} core has an inside diameter of 1.05 nm and an outside diameter of 1.53 nm, which could be directly visualized by high-resolution transmission electron microscopy. Our results demonstrate that titanium oxide can also form fullerene-like shell structures.

Self-assembled mesoporous Co and Ni-ferrite spherical clusters consisting of spinel nanocrystals prepared using a template-free approach.

PubMed

Yu, Byong Yong; Kwak, Seung-Yeop

2011-10-21

Based on a self-assembly strategy, spherical mesoporous cobalt and nickel ferrite nanocrystal clusters with a large surface area and narrow size distribution were successfully synthesized for the first time via a template-free solvothermal process in ethylene glycol and subsequent heat treatment. In this work, the mesopores in the ferrite clusters were derived mainly from interior voids between aggregated primary nanoparticles (with crystallite size of less than 7 nm) and disordered particle packing domains. The concentration of sodium acetate is shown herein to play a crucial role in the formation of mesoporous ferrite spherical clusters. These ferrite clusters were characterized in detail using wide-angle X-ray diffraction, thermogravimetric-differential thermal analysis, (57)Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, standard and high-resolution transmission electron microscopy, and other techniques. The results confirmed the formation of both pure-phase ferrite clusters with highly crystalline spinel structure, uniform size (about 160 nm) and spherical morphology, and worm-like mesopore structures. The BET specific surface areas and mean pore sizes of the mesoporous Co and Ni-ferrite clusters were as high as 160 m(2) g(-1) and 182 m(2) g(-1), and 7.91 nm and 6.87 nm, respectively. A model for the formation of the spherical clusters in our system is proposed on the basis of the results. The magnetic properties of both samples were investigated at 300 K, and it was found that these materials are superparamagnetic. This journal is © The Royal Society of Chemistry 2011

Hubble Space Telescope Fine Guidance Sensor interferometric observations of the core of 30 doradus

NASA Technical Reports Server (NTRS)

Lattanzi, M. G.; Hershey, J. L.; Burg, R.; Taff, L. G.; Holfeltz, S. T.; Bucciarelli, B.; Evans, I. N.; Gilmozzi, R.; Pringle, J.; Walborn, N. R.

1994-01-01

We present the results of the first high angular resolution observations taken with a Fine Guidance Sensor (FGS) aboard the Hubble Space Telescope (HST) of a star cluster embedded in very bright background. The strong and complex background around the R136 cluster in the 30 Dor nebula does not prevent the FGS from achieving performance close to its angular resolution limit of approximately 0.015 sec per axis with reliable photometry. These FGS observations establish that the central object in R136a is a triple star with the third component delta V = 1.1 mag fainter than the primary star al approximately 0.08 sec way. We estimate from the grid of models of Maeder (1990) that the present mass of al is between 30 and 80 solar masses, with the main-sequence progenitor between 60 and 120 solar masses.

Geomorphology of Impact Features on Tethys Using High Resolution Mosaics

DTIC Science & Technology

2017-03-01

Space Exploration, Arizona State University, Tempe, AZ 85282 NIA 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM...8217 coorbital moons are very likely to impact Tethys. The distribution, impact velocities, and impact angles of the debris are spatially-variable. In...particular, high-velocity debris (>5 km/s) with low impact angles are highly clustered along the equator in Tethys’ leading hemisphere. Slower impacts

Spatial and temporal changes in household structure locations using high-resolution satellite imagery for population assessment: an analysis in southern Zambia, 2006-2011.

PubMed

Shields, Timothy; Pinchoff, Jessie; Lubinda, Jailos; Hamapumbu, Harry; Searle, Kelly; Kobayashi, Tamaki; Thuma, Philip E; Moss, William J; Curriero, Frank C

2016-05-31

Satellite imagery is increasingly available at high spatial resolution and can be used for various purposes in public health research and programme implementation. Comparing a census generated from two satellite images of the same region in rural southern Zambia obtained four and a half years apart identified patterns of household locations and change over time. The length of time that a satellite image-based census is accurate determines its utility. Households were enumerated manually from satellite images obtained in 2006 and 2011 of the same area. Spatial statistics were used to describe clustering, cluster detection, and spatial variation in the location of households. A total of 3821 household locations were enumerated in 2006 and 4256 in 2011, a net change of 435 houses (11.4% increase). Comparison of the images indicated that 971 (25.4%) structures were added and 536 (14.0%) removed. Further analysis suggested similar household clustering in the two images and no substantial difference in concentration of households across the study area. Cluster detection analysis identified a small area where significantly more household structures were removed than expected; however, the amount of change was of limited practical significance. These findings suggest that random sampling of households for study participation would not induce geographic bias if based on a 4.5-year-old image in this region. Application of spatial statistical methods provides insights into the population distribution changes between two time periods and can be helpful in assessing the accuracy of satellite imagery.

Spatiotemporal Analysis of Corn Phenoregions in the Continental United States

NASA Astrophysics Data System (ADS)

Konduri, V. S.; Kumar, J.; Hoffman, F. M.; Ganguly, A. R.; Hargrove, W. W.

2017-12-01

The delineation of regions exhibiting similar crop performance has potential benefits for agricultural planning and management, policymaking and natural resource conservation. Studies of natural ecosystems have used multivariate clustering algorithms based on environmental characteristics to identify ecoregions for species range prediction and habitat conservation. However, few studies have used clustering to delineate regions based on crop phenology. The aim of this study was to perform a spatiotemporal analysis of phenologically self-similar clusters, or phenoregions, for the major corn growing areas in the Continental United States (CONUS) for the period 2008-2016. Annual trajectories of remotely sensed normalized difference vegetation index (NDVI), a useful proxy for land surface phenology, derived from Moderate Resolution Spectroradiometer (MODIS) instruments at 8-day intervals and 250 m resolution was used as the phenological metric. Because of the large data volumes involved, the phenoregion delineation was performed using a highly scalable, unsupervised clustering technique with the help of high performance computing. These phenoregions capture the spatial variability in the timing of important crop phenological stages (like emergence and maturity dates) and thus could be used to develop more accurate parameterizations for crop models applied at regional to global scales. Moreover, historical crop performance from phenoregions, in combination with climate and soils data, could be used to improve production forecasts. The temporal variability in NDVI at each location could also be used to develop an early warning system to identify locations where the crop deviates from its expected phenological behavior. Such deviations may indicate a need for irrigation or fertilization or suggest where pest outbreaks or other disturbances have occurred.

Digital Signal Processing Based on a Clustering Algorithm for Ir/Au TES Microcalorimeter

NASA Astrophysics Data System (ADS)

Zen, N.; Kunieda, Y.; Takahashi, H.; Hiramoto, K.; Nakazawa, M.; Fukuda, D.; Ukibe, M.; Ohkubo, M.

2006-02-01

In recent years, cryogenic microcalorimeters using their superconducting transition edge have been under development for possible application to the research for astronomical X-ray observations. To improve the energy resolution of superconducting transition edge sensors (TES), several correction methods have been developed. Among them, a clustering method based on digital signal processing has recently been proposed. In this paper, we applied the clustering method to Ir/Au bilayer TES. This method resulted in almost a 10% improvement in the energy resolution. Conversely, from the point of view of imaging X-ray spectroscopy, we applied the clustering method to pixellated Ir/Au-TES devices. We will thus show how a clustering method which sorts signals by their shapes is also useful for position identification

A research of road centerline extraction algorithm from high resolution remote sensing images

NASA Astrophysics Data System (ADS)

Zhang, Yushan; Xu, Tingfa

2017-09-01

Satellite remote sensing technology has become one of the most effective methods for land surface monitoring in recent years, due to its advantages such as short period, large scale and rich information. Meanwhile, road extraction is an important field in the applications of high resolution remote sensing images. An intelligent and automatic road extraction algorithm with high precision has great significance for transportation, road network updating and urban planning. The fuzzy c-means (FCM) clustering segmentation algorithms have been used in road extraction, but the traditional algorithms did not consider spatial information. An improved fuzzy C-means clustering algorithm combined with spatial information (SFCM) is proposed in this paper, which is proved to be effective for noisy image segmentation. Firstly, the image is segmented using the SFCM. Secondly, the segmentation result is processed by mathematical morphology to remover the joint region. Thirdly, the road centerlines are extracted by morphology thinning and burr trimming. The average integrity of the centerline extraction algorithm is 97.98%, the average accuracy is 95.36% and the average quality is 93.59%. Experimental results show that the proposed method in this paper is effective for road centerline extraction.

High-resolution spectroscopic observations of binary stars and yellow stragglers in three open clusters: NGC 2360, NGC 3680, and NGC 5822

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sales Silva, J. V.; Peña Suárez, V. J.; Katime Santrich, O. J.

2014-11-01

Binary stars in open clusters are very useful targets in constraining the nucleosynthesis process. The luminosities of the stars are known because the distances of the clusters are also known, so chemical peculiarities can be linked directly to the evolutionary status of a star. In addition, binary stars offer the opportunity to verify a relationship between them and the straggler population in both globular and open clusters. We carried out a detailed spectroscopic analysis to derive the atmospheric parameters for 16 red giants in binary systems and the chemical composition of 11 of them in the open clusters NGC 2360,more » NGC 3680, and NGC 5822. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employ the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. We found that the stars NGC 2360-92 and 96, NGC 3680-34, and NGC 5822-4 and 312 are yellow straggler stars. We show that the spectra of NGC 5822-4 and 312 present evidence of contamination by an A-type star as a secondary star. For the other yellow stragglers, evidence of contamination is given by the broad wings of the Hα. Detection of yellow straggler stars is important because the observed number can be compared with the number predicted by simulations of binary stellar evolution in open clusters. We also found that the other binary stars are not s-process enriched, which may suggest that in these binaries the secondary star is probably a faint main-sequence object. The lack of any s-process enrichment is very useful in setting constraints for the number of white dwarfs in the open cluster, a subject that is related to the birthrate of these kinds of stars in open clusters and also to the age of a cluster. Finally, rotational velocities were also determined and their values were compared with those already determined for field giant stars.« less

The Impact of Non-Thermal Processes in the Intracluster Medium on Cosmological Cluster Observables

NASA Astrophysics Data System (ADS)

Battaglia, Nicholas Ambrose

In this thesis we describe the generation and analysis of hydrodynamical simulations of galaxy clusters and their intracluster medium (ICM), using large cosmological boxes to generate large samples, in conjunction with individual cluster computations. The main focus is the exploration of the non-thermal processes in the ICM and the effect they have on the interpretation of observations used for cosmological constraints. We provide an introduction to the cosmological structure formation framework for our computations and an overview of the numerical simulations and observations of galaxy clusters. We explore the cluster magnetic field observables through radio relics, extended entities in the ICM characterized by their of diffuse radio emission. We show that statistical quantities such as radio relic luminosity functions and rotation measure power spectra are sensitive to magnetic field models. The spectral index of the radio relic emission provides information on structure formation shocks, e.g., on their Mach number. We develop a coarse grained stochastic model of active galaxy nucleus (AGN) feed-back in clusters and show the impact of such inhomogeneous feedback on the thermal pressure profile. We explore variations in the pressure profile as a function of cluster mass, redshift, and radius and provide a constrained fitting function for this profile. We measure the degree of the non-thermal pressure in the gas from internal cluster bulk motions and show it has an impact on the slope and scatter of the Sunyaev-Zel'dovich (SZ) scaling relation. We also find that the gross shape of the ICM, as characterized by scaled moment of inertia tensors, affects the SZ scaling relation. We demonstrate that the shape and the amplitude of the SZ angular power spectrum is sensitive to AGN feedback, and this affects the cosmological parameters determined from high resolution ACT and SPT cosmic microwave background data. We compare analytic, semi-analytic, and simulation-based methods for calculating the SZ power spectrum, and characterize their differences. All the methods must rely, one way or another, on high resolution large-scale hydrodynamical simulations with varying assumptions for modelling the gas of the sort presented here. We show how our results can be used to interpret the latest ACT and SPT power spectrum results. We provide an outlook for the future, describing follow-up work we are undertaking to further advance the theory of cluster science.

(F)UV Spectroscopy of K648: Abundance Determination of Trace Elements

NASA Astrophysics Data System (ADS)

Mohamad-Yob, S. J.; Ziegler, M.; Rauch, T.; Werner, K.

2010-11-01

We present preliminary results of an ongoing spectral analysis of K 648, the central star of the planetary nebula Ps 1, based on high resolution FUV spectra. K 648, in M 15 is one of only four known PNe in globular clusters. The formation of this post-AGB object in a globular cluster is still unclear. Our aim is to determine Teff, log g, and the abundances of trace elements, in order to improve our understanding of post-AGB evolution of extremely metal-poor stars, especially PN formation in globular clusters. We analyzed FUSE, HST/STIS, and HST/FOS observations. A grid of stellar model atmospheres was calculated using the Tübingen NLTE Model Atmosphere Package (TMAP).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, Robert L.; Frisz, Jessica F.; Klitzing, Haley A.

The clusters of the influenza envelope protein, hemagglutinin, within the plasma membrane are hypothesized to be enriched with cholesterol and sphingolipids. Here in this paper, we directly tested this hypothesis by using high-resolution secondary ion mass spectrometry to image the distributions of antibody-labeled hemagglutinin and isotope-labeled cholesterol and sphingolipids in the plasma membranes of fibroblast cells that stably express hemagglutinin. We found that the hemagglutinin clusters were neither enriched with cholesterol nor colocalized with sphingolipid domains. Thus, hemagglutinin clustering and localization in the plasma membrane is not controlled by cohesive interactions between hemagglutinin and liquid-ordered domains enriched with cholesterol andmore » sphingolipids, or from specific binding interactions between hemagglutinin, cholesterol, and/or the majority of sphingolipid species in the plasma membrane.« less

12C/13C isotopic ratios in red-giant stars of the open cluster NGC 6791

NASA Astrophysics Data System (ADS)

Szigeti, László; Mészáros, Szabolcs; Smith, Verne V.; Cunha, Katia; Lagarde, Nadège; Charbonnel, Corinne; García-Hernández, D. A.; Shetrone, Matthew; Pinsonneault, Marc; Allende Prieto, Carlos; Fernández-Trincado, J. G.; Kovács, József; Villanova, Sandro

2018-03-01

Carbon isotope ratios, along with carbon and nitrogen abundances, are derived in a sample of 11 red-giant members of one of the most metal-rich clusters in the Milky Way, NGC 6791. The selected red-giants have a mean metallicity and standard deviation of [Fe/H] = +0.39 ± 0.06 (Cunha et al. 2015). We used high-resolution H-band spectra obtained by the SDSS-IV Apache Point Observatory Galactic Evolution Experiment. The advantage of using high-resolution spectra in the H band is that lines of CO are well represented and their line profiles are sensitive to the variation of 12C/13C. Values of the 12C/13C ratio were obtained from a spectrum synthesis analysis. The derived 12C/13C ratios varied between 6.3 and 10.6 in NGC 6791, in agreement with the final isotopic ratios from thermohaline-induced mixing models. The ratios derived here are combined with those obtained for more metal poor red-giants from the literature to examine the correlation between 12C/13C, mass, metallicity, and evolutionary status.

Gravitational Conundrum? Dynamical Mass Segregation versus Disruption of Binary Stars in Dense Stellar Systems

NASA Astrophysics Data System (ADS)

de Grijs, Richard; Li, Chengyuan; Zheng, Yong; Deng, Licai; Hu, Yi; Kouwenhoven, M. B. N.; Wicker, James E.

2013-03-01

Upon their formation, dynamically cool (collapsing) star clusters will, within only a few million years, achieve stellar mass segregation for stars down to a few solar masses, simply because of gravitational two-body encounters. Since binary systems are, on average, more massive than single stars, one would expect them to also rapidly mass segregate dynamically. Contrary to these expectations and based on high-resolution Hubble Space Telescope observations, we show that the compact, 15-30 Myr old Large Magellanic Cloud cluster NGC 1818 exhibits tantalizing hints at the >~ 2σ level of significance (>3σ if we assume a power-law secondary-to-primary mass-ratio distribution) of an increasing fraction of F-star binary systems (with combined masses of 1.3-1.6 M ⊙) with increasing distance from the cluster center, specifically between the inner 10''-20'' (approximately equivalent to the cluster's core and half-mass radii) and the outer 60''-80''. If confirmed, then this will offer support for the theoretically predicted but thus far unobserved dynamical disruption processes of the significant population of "soft" binary systems—with relatively low binding energies compared to the kinetic energy of their stellar members—in star clusters, which we have access to here by virtue of the cluster's unique combination of youth and high stellar density.

Pre-treatment functional MRI of breast cancer: T2* evaluation at 3 T and relationship to dynamic contrast-enhanced and diffusion-weighted imaging.

PubMed

Kousi, Evanthia; O'Flynn, Elizabeth A M; Borri, Marco; Morgan, Veronica A; deSouza, Nandita M; Schmidt, Maria A

2018-05-31

Baseline T2* relaxation time has been proposed as an imaging biomarker in cancer, in addition to Dynamic Contrast-Enhanced (DCE) MRI and diffusion-weighted imaging (DWI) parameters. The purpose of the current work is to investigate sources of error in T2* measurements and the relationship between T2* and DCE and DWI functional parameters in breast cancer. Five female volunteers and thirty-two women with biopsy proven breast cancer were scanned at 3 T, with Research Ethics Committee approval. T2* values of the normal breast were acquired from high-resolution, low-resolution and fat-suppressed gradient-echo sequences in volunteers, and compared. In breast cancer patients, pre-treatment T2*, DCE MRI and DWI were performed at baseline. Pathologically complete responders at surgery and non-responders were identified and compared. Principal component analysis (PCA) and cluster analysis (CA) were performed. There were no significant differences between T2* values from high-resolution, low-resolution and fat-suppressed datasets (p > 0.05). There were not significant differences between baseline functional parameters in responders and non-responders (p > 0.05). However, there were differences in the relationship between T2* and contrast-agent uptake in responders and non-responders. Voxels of similar characteristics were grouped in 5 clusters, and large intra-tumoural variations of all parameters were demonstrated. Breast T2* measurements at 3 T are robust, but spatial resolution should be carefully considered. T2* of breast tumours at baseline is unrelated to DCE and DWI parameters and contribute towards describing functional heterogeneity of breast tumours. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Analysis of earthquake clustering and source spectra in the Salton Sea Geothermal Field

NASA Astrophysics Data System (ADS)

Cheng, Y.; Chen, X.

2015-12-01

The Salton Sea Geothermal field is located within the tectonic step-over between San Andreas Fault and Imperial Fault. Since the 1980s, geothermal energy exploration has resulted with step-like increase of microearthquake activities, which mirror the expansion of geothermal field. Distinguishing naturally occurred and induced seismicity, and their corresponding characteristics (e.g., energy release) is important for hazard assessment. Between 2008 and 2014, seismic data recorded by a local borehole array were provided public access from CalEnergy through SCEC data center; and the high quality local recording of over 7000 microearthquakes provides unique opportunity to sort out characteristics of induced versus natural activities. We obtain high-resolution earthquake location using improved S-wave picks, waveform cross-correlation and a new 3D velocity model. We then develop method to identify spatial-temporally isolated earthquake clusters. These clusters are classified into aftershock-type, swarm-type, and mixed-type (aftershock-like, with low skew, low magnitude and shorter duration), based on the relative timing of largest earthquakes and moment-release. The mixed-type clusters are mostly located at 3 - 4 km depth near injection well; while aftershock-type clusters and swarm-type clusters also occur further from injection well. By counting number of aftershocks within 1day following mainshock in each cluster, we find that the mixed-type clusters have much higher aftershock productivity compared with other types and historic M4 earthquakes. We analyze detailed spatial variation of 'b-value'. We find that the mixed-type clusters are mostly located within high b-value patches, while large (M>3) earthquakes and other types of clusters are located within low b-value patches. We are currently processing P and S-wave spectra to analyze the spatial-temporal correlation of earthquake stress parameter and seismicity characteristics. Preliminary results suggest that the mixed-type clusters and high b-value patches are spatially correlated with low stress drop earthquakes, indicating high-productivity microearthquakes within low differential stress region, potentially due to deeper injection activities.

Observational Evidence for a Dark Side to NGC 5128's Globular Cluster System

NASA Astrophysics Data System (ADS)

Taylor, Matthew A.; Puzia, Thomas H.; Gomez, Matias; Woodley, Kristin A.

2015-05-01

We present a study of the dynamical properties of 125 compact stellar systems (CSSs) in the nearby giant elliptical galaxy NGC 5128, using high-resolution spectra (R ≈ 26, 000) obtained with Very Large Telescope/FLAMES. Our results provide evidence for a new type of star cluster, based on the CSS dynamical mass scaling relations. All radial velocity (vr) and line-of-sight velocity dispersion (σlos) measurements are performed with the penalized pixel fitting (ppxf ) technique, which provided σppxf estimates for 115 targets. The σppxf estimates are corrected to the 2D projected half-light radii, σ1/2, as well as the cluster cores, σ0, accounting for observational/aperture effects and are combined with structural parameters, from high spatial resolution imaging, in order to derive total dynamical masses ({{M}dyn}) for 112 members of NGC 5128’s star cluster system. In total, 89 CSSs have dynamical masses measured for the first time along with the corresponding dynamical mass-to-light ratios (\\Upsilon Vdyn). We find two distinct sequences in the \\Upsilon Vdyn-{{M}dyn} plane, which are well approximated by power laws of the forms \\Upsilon Vdyn\\propto Mdyn0.33+/- 0.04 and \\Upsilon Vdyn\\propto Mdyn0.79+/- 0.04. The shallower sequence corresponds to the very bright tail of the globular cluster luminosity function (GCLF), while the steeper relation appears to be populated by a distinct group of objects that require significant dark gravitating components such as central massive black holes and/or exotically concentrated dark matter distributions. This result would suggest that the formation and evolution of these CSSs are markedly different from the “classical” globular clusters in NGC 5128 and the Local Group, despite the fact that these clusters have luminosities similar to the GCLF turnover magnitude. We include a thorough discussion of myriad factors potentially influencing our measurements. Based on observations collected under program 081.D-0651 (PI: Matias Gomez) with FLAMES at the Very Large Telescope of the Paranal Observatory in Chile, operated by the ESO.

Spatial imaging of carbon reactivity centers in Pd/C catalytic systems† †Electronic supplementary information (ESI) available: Detailed experimental procedures and FE-SEM images. See DOI: 10.1039/c5sc00802f

PubMed Central

Pentsak, E. O.; Kashin, A. S.; Polynski, M. V.; Kvashnina, K. O.; Glatzel, P.

2015-01-01

Gaining insight into Pd/C catalytic systems aimed at locating reactive centers on carbon surfaces, revealing their properties and estimating the number of reactive centers presents a challenging problem. In the present study state-of-the-art experimental techniques involving ultra high resolution SEM/STEM microscopy (1 Å resolution), high brilliance X-ray absorption spectroscopy and theoretical calculations on truly nanoscale systems were utilized to reveal the role of carbon centers in the formation and nature of Pd/C catalytic materials. Generation of Pd clusters in solution from the easily available Pd2dba3 precursor and the unique reactivity of the Pd clusters opened an excellent opportunity to develop an efficient procedure for the imaging of a carbon surface. Defect sites and reactivity centers of a carbon surface were mapped in three-dimensional space with high resolution and excellent contrast using a user-friendly nanoscale imaging procedure. The proposed imaging approach takes advantage of the specific interactions of reactive carbon centers with Pd clusters, which allows spatial information about chemical reactivity across the Pd/C system to be obtained using a microscopy technique. Mapping the reactivity centers with Pd markers provided unique information about the reactivity of the graphene layers and showed that >2000 reactive centers can be located per 1 μm2 of the surface area of the carbon material. A computational study at a PBE-D3-GPW level differentiated the relative affinity of the Pd2 species to the reactive centers of graphene. These findings emphasized the spatial complexity of the carbon material at the nanoscale and indicated the importance of the surface defect nature, which exhibited substantial gradients and variations across the surface area. The findings show the crucial role of the structure of the carbon support, which governs the formation of Pd/C systems and their catalytic activity. PMID:29511504

Disrupted Cerebro-cerebellar Intrinsic Functional Connectivity in Young Adults with High-functioning Autism Spectrum Disorder: A Data-driven, Whole-brain, High Temporal Resolution fMRI Study.

PubMed

Arnold Anteraper, Sheeba; Guell, Xavier; D'Mello, Anila; Joshi, Neha; Whitfield-Gabrieli, Susan; Joshi, Gagan

2018-06-13

To examine the resting-state functional-connectivity (RsFc) in young adults with high-functioning autism spectrum disorder (HF-ASD) using state-of-the-art fMRI data acquisition and analysis techniques. Simultaneous multi-slice, high temporal resolution fMRI acquisition; unbiased whole-brain connectome-wide multivariate pattern analysis (MVPA) techniques for assessing RsFc; and post-hoc whole-brain seed-to-voxel analyses using MVPA results as seeds. MVPA revealed two clusters of abnormal connectivity in the cerebellum. Whole-brain seed-based functional connectivity analyses informed by MVPA-derived clusters showed significant under connectivity between the cerebellum and social, emotional, and language brain regions in the HF-ASD group compared to healthy controls. The results we report are coherent with existing structural, functional, and RsFc literature in autism, extend previous literature reporting cerebellar abnormalities in the neuropathology of autism, and highlight the cerebellum as a potential target for therapeutic, diagnostic, predictive, and prognostic developments in ASD. The description of functional connectivity abnormalities using whole-brain, data-driven analyses as reported in the present study may crucially advance the development of ASD biomarkers, targets for therapeutic interventions, and neural predictors for measuring treatment response.

Young star clusters in the circumnuclear region of NGC 2110

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durré, Mark; Mould, Jeremy, E-mail: mdurre@swin.edu.au

2014-03-20

High-resolution observations in the near infrared show star clusters around the active galactic nucleus (AGN) of the Seyfert 1 NGC 2110, along with a 90 × 35 pc bar of shocked gas material around its nucleus. These are seen for the first time in our imaging and gas kinematics of the central 100 pc with the Keck OSIRIS instrument with adaptive optics. Each of these clusters is two to three times brighter than the Arches cluster close to the center of the Milky Way. The core star formation rate is 0.3 M {sub ☉} yr{sup –1}. The photoionized gas (Hemore » I) dynamics imply an enclosed mass of 3-4 × 10{sup 8} M {sub ☉}. These observations demonstrate the physical linkage between AGN feedback, which triggers star formation in massive clusters, and the resulting stellar (and supernovae) winds, which cause the observed [Fe II] emission and feed the black hole.« less

THE TEMPERATURE OF HOT GAS IN GALAXIES AND CLUSTERS: BARYONS DANCING TO THE TUNE OF DARK MATTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, Steen H.; Maccio, Andrea V.; Romano-Diaz, Emilio

2011-06-10

The temperature profile of hot gas in galaxies and galaxy clusters is largely determined by the depth of the total gravitational potential and thereby by the dark matter (DM) distribution. We use high-resolution hydrodynamical simulations of galaxy formation to derive a surprisingly simple relation between the gas temperature and DM properties. We show that this relation holds not just for galaxy clusters but also for equilibrated and relaxed galaxies at radii beyond the central stellar-dominated region of typically a few kpc. It is then clarified how a measurement of the temperature and density of the hot gas component can leadmore » to an indirect measurement of the DM velocity anisotropy in galaxies. We also study the temperature relation for galaxy clusters in the presence of self-regulated, recurrent active galactic nuclei (AGNs), and demonstrate that this temperature relation even holds outside the inner region of {approx}30 kpc in clusters with an active AGN.« less

Local matrix learning in clustering and applications for manifold visualization.

PubMed

Arnonkijpanich, Banchar; Hasenfuss, Alexander; Hammer, Barbara

2010-05-01

Electronic data sets are increasing rapidly with respect to both, size of the data sets and data resolution, i.e. dimensionality, such that adequate data inspection and data visualization have become central issues of data mining. In this article, we present an extension of classical clustering schemes by local matrix adaptation, which allows a better representation of data by means of clusters with an arbitrary spherical shape. Unlike previous proposals, the method is derived from a global cost function. The focus of this article is to demonstrate the applicability of this matrix clustering scheme to low-dimensional data embedding for data inspection. The proposed method is based on matrix learning for neural gas and manifold charting. This provides an explicit mapping of a given high-dimensional data space to low dimensionality. We demonstrate the usefulness of this method for data inspection and manifold visualization. 2009 Elsevier Ltd. All rights reserved.

Anchoring the Distance Scale via X-Ray/Infrared Data for Cepheid Clusters: SU Cas

NASA Astrophysics Data System (ADS)

Majaess, D.; Turner, D. G.; Gallo, L.; Gieren, W.; Bonatto, C.; Lane, D. J.; Balam, D.; Berdnikov, L.

2012-07-01

New X-ray (XMM-Newton) and JHKs (Observatoire du Mont-Mégantic) observations for members of the star cluster Alessi 95, which Turner et al. discovered hosts the classical Cepheid SU Cas, were used in tandem with UCAC3 (proper motion) and Two Micron All Sky Survey observations to determine precise cluster parameters: E(J - H) = 0.08 ± 0.02 and d = 405 ± 15 pc. The ensuing consensus among cluster, pulsation, and trigonometric distances (d=414+/- 5(\\sigma _{\\bar{x}}) +/- 10 (\\sigma) pc) places SU Cas in a select group of nearby fundamental Cepheid calibrators (δ Cep, ζ Gem). High-resolution X-ray observations may be employed to expand that sample as the data proved pertinent for identifying numerous stars associated with SU Cas. Acquiring X-ray observations of additional fields may foster efforts to refine Cepheid calibrations used to constrain H 0.

Tracing the Chemical Evolution of Metal-rich Galactic Bulge Globular Clusters

NASA Astrophysics Data System (ADS)

Munoz Gonzalez, Cesar; Saviane, Ivo; Geisler, Doug; Villanova, Sandro

2018-01-01

We present in this poster the metallicity characterization of the four metal rich Bulge Galactic Gobular Clusters, which have controversial metallicities. We analyzed our high-resolution spectra (using UVES-580nm and GIRAFFE-HR13 setups) for a large sample of RGB/AGB targets in each cluster in order to measure their metallicity and prove or discard the iron spread hypothesis. We have also characterized chemically stars with potentially different iron content by measuring light (O, Na, Mg, Al), alpha (Si, Ca, Ti), iron–peak (V, Cr, Ni, Mn) and s and r process (Y, Zr, Ba, Eu) elements. We have identified possible channels responsible for the chemical heterogeneity of the cluster populations, like AGB or massive fast-rotating stars contamination, or SN explosion. Also, we have analyzed the origin and evolution of these bulge GCs and their connection with the bulge itself.

Implications for gravitational lensing and the dark matter content in clusters of galaxies from spatially resolved x-ray spectra

NASA Technical Reports Server (NTRS)

Loewenstein, M.

1994-01-01

A simple method for deriving well-behaved temperature solutions to the equation of hydrostatic equilibrium for intracluster media with X-ray imaging observations is presented and applied to a series of generalized models as well as to observations of the Perseus cluster and Abell 2256. In these applications the allowed range in the ratio of nonbaryons to baryons as a function of radius is derived, taking into account the uncertainties and crude spatial resolution of the X-ray spectra and considering a range of physically reasonable mass models with various scale heights. Particular attention is paid to the central regions of the cluster, and it is found that the dark matter can be sufficiently concentrated to be consistent with the high central mass surface densities for moderate-redshift clusters from their gravitational lensing properties.

Identifying Few-Molecule Water Clusters with High Precision on Au(111) Surface.

PubMed

Dong, Anning; Yan, Lei; Sun, Lihuan; Yan, Shichao; Shan, Xinyan; Guo, Yang; Meng, Sheng; Lu, Xinghua

2018-06-01

Revealing the nature of a hydrogen-bond network in water structures is one of the imperative objectives of science. With the use of a low-temperature scanning tunneling microscope, water clusters on a Au(111) surface were directly imaged with molecular resolution by a functionalized tip. The internal structures of the water clusters as well as the geometry variations with the increase of size were identified. In contrast to a buckled water hexamer predicted by previous theoretical calculations, our results present deterministic evidence for a flat configuration of water hexamers on Au(111), corroborated by density functional theory calculations with properly implemented van der Waals corrections. The consistency between the experimental observations and improved theoretical calculations not only renders the internal structures of absorbed water clusters unambiguously, but also directly manifests the crucial role of van der Waals interactions in constructing water-solid interfaces.

Experimental and theoretical investigation of the magnetization dynamics of an artificial square spin ice cluster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pohlit, Merlin, E-mail: pohlit@physik.uni-frankfurt.de; Porrati, Fabrizio; Huth, Michael

We study the magnetization dynamics of a spin ice cluster which is a building block of an artificial square spin ice fabricated by focused electron-beam-induced deposition both experimentally and theoretically. The spin ice cluster is composed of twelve interacting Co nanoislands grown directly on top of a high-resolution micro-Hall sensor. By employing micromagnetic simulations and a macrospin model, we calculate the magnetization and the experimentally investigated stray field emanating from a single nanoisland. The parameters determined from a comparison with the experimental hysteresis loop are used to derive an effective single-dipole macrospin model that allows us to investigate the dynamicsmore » of the spin ice cluster. Our model reproduces the experimentally observed non-deterministic sequences in the magnetization curves as well as the distinct temperature dependence of the hysteresis loop.« less

Metal-poor Type II Cepheids with Periods Less Than Three Days

NASA Astrophysics Data System (ADS)

Kovtyukh, V.; Wallerstein, G.; Yegorova, I.; Andrievsky, S.; Korotin, S.; Saviane, I.; Belik, S.; Davis, C. E.; Farrell, E. M.

2018-05-01

We have analyzed 10 high-resolution spectra of Type II Cepheids with periods less than 3 days. We find that they clearly separate into two groups: those with near or slightly below solar metallicities, and those with [Fe/H] between ‑1.5 and ‑2.0. While the former are usually called BL Her stars, we suggest that the latter be called UY Eri stars. The UY Eri subclass appears to be similar to the short period variables in globular clusters of the Galactic Halo. Globular clusters with [Fe/H] > ‑1.0 almost never have Type II Cepheids.

Highly-evolved stars

NASA Technical Reports Server (NTRS)

Heap, S. R.

1981-01-01

The ways in which the IUE has proved useful in studying highly evolved stars are reviewed. The importance of high dispersion spectra for abundance analyses of the sd0 stars and for studies of the wind from the central star of NGC 6543 and the wind from the 0 type component of Vela X-1 is shown. Low dispersion spectra are used for absolute spectrophotometry of the dwarf nova, Ex Hya. Angular resolution is important for detecting and locating UV sources in globular clusters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zemcov, M.; Cooray, A.; Bock, J.

We have observed four massive galaxy clusters with the SPIRE instrument on the Herschel Space Observatory and measure a deficit of surface brightness within their central region after removing detected sources. We simulate the effects of instrumental sensitivity and resolution, the source population, and the lensing effect of the clusters to estimate the shape and amplitude of the deficit. The amplitude of the central deficit is a strong function of the surface density and flux distribution of the background sources. We find that for the current best fitting faint end number counts, and excellent lensing models, the most likely amplitudemore » of the central deficit is the full intensity of the cosmic infrared background (CIB). Our measurement leads to a lower limit to the integrated total intensity of the CIB of I{sub 250{mu}m}>0.69{sub -0.03}{sup +0.03}(stat.){sub -0.06}{sup +0.11}(sys.) MJy sr{sup -1}, with more CIB possible from both low-redshift sources and from sources within the target clusters. It should be possible to observe this effect in existing high angular resolution data at other wavelengths where the CIB is bright, which would allow tests of models of the faint source component of the CIB.« less

The High Time Resolution Universe

NASA Astrophysics Data System (ADS)

Bailes, Matthew; Possenti, Andrea; Johnston, Simon; Kramer, Michael; Burgay, Marta; Bhat, Ramesh; Keith, Michael; Burke-Spolaor, Sarah; van Straten, Willem; Stappers, Benjamin; Bates, Samuel

2008-04-01

The Parkes multibeam surveys heralded a new era in pulsar surveys, more than doubling the number of pulsars known. However, at high time resolution, they were severely limited by the analogue backend system, which limited the volume of sky they could effectively survey to just the local 2-3 kpc. Here we propose to use a new digital backend coupled with Australia's most powerful (16 Tflop) supercomputing cluster to conduct three ambitious surveys for millisecond and relativistic pulsars with the Parkes telescope. We hope to discover over 200 new millisecond and relativistic pulsars that will define the recycled pulsar period distribution, supply pulsars for the timing array and aid in our understanding of binary evolution.

Classification of simulated and actual NOAA-6 AVHRR data for hydrologic land-surface feature definition. [Advanced Very High Resolution Radiometer

NASA Technical Reports Server (NTRS)

Ormsby, J. P.

1982-01-01

An examination of the possibilities of using Landsat data to simulate NOAA-6 Advanced Very High Resolution Radiometer (AVHRR) data on two channels, as well as using actual NOAA-6 imagery, for large-scale hydrological studies is presented. A running average was obtained of 18 consecutive pixels of 1 km resolution taken by the Landsat scanners were scaled up to 8-bit data and investigated for different gray levels. AVHRR data comprising five channels of 10-bit, band-interleaved information covering 10 deg latitude were analyzed and a suitable pixel grid was chosen for comparison with the Landsat data in a supervised classification format, an unsupervised mode, and with ground truth. Landcover delineation was explored by removing snow, water, and cloud features from the cluster analysis, and resulted in less than 10% difference. Low resolution large-scale data was determined useful for characterizing some landcover features if weekly and/or monthly updates are maintained.

The Lithium Depletion Boundary and the Age of the Hyades Cluster

NASA Astrophysics Data System (ADS)

Martín, Eduardo L.; Lodieu, Nicolas; Pavlenko, Yakiv; Béjar, Víctor J. S.

2018-03-01

Determination of the lithium depletion boundary (LDB), i.e., the observational limit below which the cores of very low-mass objects do not reach high enough temperatures for Li destruction, has been used to obtain ages for several open clusters and stellar associations younger than 200 Myr—which until now has been considered the practical upper limit on the range of applicability of this method. In this work, we show that the LDB method can be extended to significant older ages than previously thought. Intermediate resolution optical spectra of six L-type candidate members in the Hyades cluster obtained using Optical System for Imaging and Low Resolution Integrated Spectroscopy at the 10.4 m Gran Telescopio Canarias are presented. The {Li} {{I}} 670.8 nm resonance doublet is clearly detected only in the two faintest and coolest of these objects, which are classified as L3.5 to L4 brown dwarf (BD) cluster members with luminosities around 10‑4 solar. Lithium depletion factors are estimated for our targets with the aid of synthetic spectra and they are compared with predictions from evolutionary models. An LDB age of 650 ± 70 Myr for the Hyades provides a consistent description of our data using a set of state-of-the-art evolutionary models for BDs calculated by Baraffe et al. Based on data obtained at the Gran Telescopio Canarias.

Large-scale clustering as a probe of the origin and the host environment of fast radio bursts

NASA Astrophysics Data System (ADS)

Shirasaki, Masato; Kashiyama, Kazumi; Yoshida, Naoki

2017-04-01

We propose to use degree-scale angular clustering of fast radio bursts (FRBs) to identify their origin and the host galaxy population. We study the information content in autocorrelation of the angular positions and dispersion measures (DM) and in cross-correlation with galaxies. We show that the cross-correlation with Sloan Digital Sky Survey (SDSS) galaxies will place stringent constraints on the mean physical quantities associated with FRBs. If ˜10 ,000 FRBs are detected with ≲deg resolution in the SDSS field, the clustering analysis with the intrinsic DM scatter of 100 pc /cm3 can constrain the global abundance of free electrons at z ≲1 and the large-scale bias of FRB host galaxies (the statistical relation between the distribution of host galaxies and cosmic matter density field) with fractional errors (with a 68% confidence level) of ˜10 % and ˜20 %, respectively. The mean near-source dispersion measure and the delay-time distribution of FRB rates relative to the global star forming rate can be also determined by combining the clustering and the probability distribution function of DM. Our approach will be complementary to high-resolution (≪deg ) event localization using e.g., VLA and VLBI for identifying the origin of FRBs and the source environment. We strongly encourage future observational programs such as CHIME, UTMOST, and HIRAX to survey FRBs in the SDSS field.

Analysis of Spectral-type A/B Stars in Five Open Clusters

NASA Astrophysics Data System (ADS)

Wilhelm, Ronald J.; Rafuil Islam, M.

2014-01-01

We have obtained low resolution (R = 1000) spectroscopy of N=68, spectral-type A/B stars in five nearby open star clusters using the McDonald Observatory, 2.1m telescope. The sample of blue stars in various clusters were selected to test our new technique for determining interstellar reddening and distances in areas where interstellar reddening is high. We use a Bayesian approach to find the posterior distribution for Teff, Logg and [Fe/H] from a combination of reddened, photometric colors and spectroscopic line strengths. We will present calibration results for this technique using open cluster star data with known reddening and distances. Preliminary results suggest our technique can produce both reddening and distance determinations to within 10% of cluster values. Our technique opens the possibility of determining distances for blue stars at low Galactic latitudes where extinction can be large and differential. We will also compare our stellar parameter determinations to previously reported MK spectral classifications and discuss the probability that some of our stars are not members of their reported clusters.

Whole-Genome Sequencing of Recent Listeria monocytogenes Isolates from Germany Reveals Population Structure and Disease Clusters.

PubMed

Halbedel, Sven; Prager, Rita; Fuchs, Stephan; Trost, Eva; Werner, Guido; Flieger, Antje

2018-06-01

Listeria monocytogenes causes foodborne outbreaks with high mortality. For improvement of outbreak cluster detection, the German consiliary laboratory for listeriosis implemented whole-genome sequencing (WGS) in 2015. A total of 424 human L. monocytogenes isolates collected in 2007 to 2017 were subjected to WGS and core-genome multilocus sequence typing (cgMLST). cgMLST grouped the isolates into 38 complexes, reflecting 4 known and 34 unknown disease clusters. Most of these complexes were confirmed by single nucleotide polymorphism (SNP) calling, but some were further differentiated. Interestingly, several cgMLST cluster types were further subtyped by pulsed-field gel electrophoresis, partly due to phage insertions in the accessory genome. Our results highlight the usefulness of cgMLST for routine cluster detection but also show that cgMLST complexes require validation by methods providing higher typing resolution. Twelve cgMLST clusters included recent cases, suggesting activity of the source. Therefore, the cgMLST nomenclature data presented here may support future public health actions. Copyright © 2018 American Society for Microbiology.

Visual Field Map Clusters in Macaque Extrastriate Visual Cortex

PubMed Central

Kolster, Hauke; Mandeville, Joseph B.; Arsenault, John T.; Ekstrom, Leeland B.; Wald, Lawrence L.; Vanduffel, Wim

2009-01-01

The macaque visual cortex contains more than 30 different functional visual areas, yet surprisingly little is known about the underlying organizational principles that structure its components into a complete ‘visual’ unit. A recent model of visual cortical organization in humans suggests that visual field maps are organized as clusters. Clusters minimize axonal connections between individual field maps that represent common visual percepts, with different clusters thought to carry out different functions. Experimental support for this hypothesis, however, is lacking in macaques, leaving open the question of whether it is unique to humans or a more general model for primate vision. Here we show, using high-resolution BOLD fMRI data in the awake monkey at 7 Tesla, that area MT/V5 and its neighbors are organized as a cluster with a common foveal representation and a circular eccentricity map. This novel view on the functional topography of area MT/V5 and satellites indicates that field map clusters are evolutionarily preserved and may be a fundamental organizational principle of the old world primate visual cortex. PMID:19474330

Formation of Cool Cores in Galaxy Clusters via Hierarchical Mergers

NASA Astrophysics Data System (ADS)

Motl, Patrick M.; Burns, Jack O.; Loken, Chris; Norman, Michael L.; Bryan, Greg

2004-05-01

We present a new scenario for the formation of cool cores in rich galaxy clusters, based on results from recent high spatial dynamic range, adaptive mesh Eulerian hydrodynamic simulations of large-scale structure formation. We find that cores of cool gas, material that would be identified as a classical cooling flow on the basis of its X-ray luminosity excess and temperature profile, are built from the accretion of discrete stable subclusters. Any ``cooling flow'' present is overwhelmed by the velocity field within the cluster; the bulk flow of gas through the cluster typically has speeds up to about 2000 km s-1, and significant rotation is frequently present in the cluster core. The inclusion of consistent initial cosmological conditions for the cluster within its surrounding supercluster environment is crucial when the evolution of cool cores in rich galaxy clusters is simulated. This new model for the hierarchical assembly of cool gas naturally explains the high frequency of cool cores in rich galaxy clusters, despite the fact that a majority of these clusters show evidence of substructure that is believed to arise from recent merger activity. Furthermore, our simulations generate complex cluster cores in concordance with recent X-ray observations of cool fronts, cool ``bullets,'' and filaments in a number of galaxy clusters. Our simulations were computed with a coupled N-body, Eulerian, adaptive mesh refinement, hydrodynamics cosmology code that properly treats the effects of shocks and radiative cooling by the gas. We employ up to seven levels of refinement to attain a peak resolution of 15.6 kpc within a volume 256 Mpc on a side and assume a standard ΛCDM cosmology.

On the estimation of the current density in space plasmas: Multi- versus single-point techniques

NASA Astrophysics Data System (ADS)

Perri, Silvia; Valentini, Francesco; Sorriso-Valvo, Luca; Reda, Antonio; Malara, Francesco

2017-06-01

Thanks to multi-spacecraft mission, it has recently been possible to directly estimate the current density in space plasmas, by using magnetic field time series from four satellites flying in a quasi perfect tetrahedron configuration. The technique developed, commonly called ;curlometer; permits a good estimation of the current density when the magnetic field time series vary linearly in space. This approximation is generally valid for small spacecraft separation. The recent space missions Cluster and Magnetospheric Multiscale (MMS) have provided high resolution measurements with inter-spacecraft separation up to 100 km and 10 km, respectively. The former scale corresponds to the proton gyroradius/ion skin depth in ;typical; solar wind conditions, while the latter to sub-proton scale. However, some works have highlighted an underestimation of the current density via the curlometer technique with respect to the current computed directly from the velocity distribution functions, measured at sub-proton scales resolution with MMS. In this paper we explore the limit of the curlometer technique studying synthetic data sets associated to a cluster of four artificial satellites allowed to fly in a static turbulent field, spanning a wide range of relative separation. This study tries to address the relative importance of measuring plasma moments at very high resolution from a single spacecraft with respect to the multi-spacecraft missions in the current density evaluation.

Kinematics of the Optically Visible YSOs toward the Orion B Molecular Cloud

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kounkel, Marina; Hartmann, Lee; Mateo, Mario

2017-08-01

We present results from high-resolution optical spectra toward 66 young stars in the Orion B molecular cloud to study their kinematics and other properties. Observations of the H α and Li i 6707 Å lines are used to check membership and accretion properties. While the stellar radial velocities of NGC 2068 and L1622 are in good agreement with that of the molecular gas, many of the stars in NGC 2024 show a considerable offset. This could be a signature of either the expansion of the cluster, the high degree of the ejection of the stars from the cluster through dynamicalmore » interaction, or the acceleration of the gas due to stellar feedback.« less

Electron-induced chemistry in imidazole clusters embedded in helium nanodroplets

NASA Astrophysics Data System (ADS)

Kuhn, Martin; Raggl, Stefan; Martini, Paul; Gitzl, Norbert; Darian, Masoomeh Mahmoodi; Goulart, Marcelo; Postler, Johannes; Feketeová, Linda; Scheier, Paul

2018-02-01

Electron-induced chemistry in imidazole (IMI) clusters embedded in helium nanodroplets (with an average size of 2 × 105 He atoms) has been investigated with high-resolution time-of-flight mass spectrometry. The formation of both, negative and positive, ions was monitored as a function of the cluster size n. In both ion spectra a clear series of peaks with IMI cluster sizes up to at least 25 are observed. While the anions are formed by collisions of IMI n with He*-, the cations are formed through ionization of IMI n by He+ as the measured onset for the cation formation is observed at 24.6 eV (ionization energy of He). The most abundant series of anions are dehydrogenated anions IMI n-1(IMI-H)-, while other anion series are IMI clusters involving CN and C2H4 moieties. The formation of cations is dominated by the protonated cluster ions IMI n H+, while the intensity of parent cluster cations IMI n + is also observed preferentially for the small cluster size n. The observation of series of cluster cations [IMI n CH3]+ suggests either CH3+ cation to be solvated by n neutral IMI molecules, or the electron-induced chemistry has led to the formation of protonated methyl-imidazole solvated by ( n - 1) neutral IMI molecules.

Facile Syntheses of Monodisperse Ultra-Small Au Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bertino, Massimo F.; Sun, Zhong-Ming; Zhang, Rui

2006-11-02

During our effort to synthesize the tetrahedral Au20 cluster, we found a facile synthetic route to prepare monodisperse suspensions of ultra-small Au clusters AuN (N<12) using diphosphine ligands. In our monophasic and single-pot synthesis, a Au precursor ClAu(I)PPh3 and a bidentate phosphine ligand P(Ph)2(CH2)MP(Ph)2 (Ph = phenyl) are dissolved in an organic solvent. Au(I) is reduced slowly by a borane-tert-butylamine complex to form Au clusters coordinated by the diphosphine ligand. The Au clusters are characterized by both high resolution mass spectrometry and UV-Vis absorption spectroscopy. We found that the mean cluster size obtained depends on the chain length M ofmore » the ligand. In particular, a single monodispersed Au11 cluster is obtained with the P(Ph)2(CH2)3P(Ph)2 ligand, whereas P(Ph)2(CH2)MP(Ph)2 ligands with M = 5 and 6 yield Au10 and Au8 clusters. The simplicity of our synthetic method makes it suitable for large-scale production of nearly monodisperse ultrasmall Au clusters. It is suggested that diphosphines provide a set of flexible ligands to allow size-controlled synthesis of Au nanoparticles.« less

Helium cluster isolation spectroscopy

NASA Astrophysics Data System (ADS)

Higgins, John Paul

Clusters of helium, each containing ~103- 104 atoms, are produced in a molecular beam and are doped with alkali metal atoms (Li, Na, and K) and large organic molecules. Electronic spectroscopy in the visible and UV regions of the spectrum is carried out on the dopant species. Since large helium clusters are liquid and attain an equilibrium internal temperature of 0.4 K, they interact weakly with atoms or molecules absorbed on their surface or resident inside the cluster. The spectra that are obtained are characterized by small frequency shifts from the positions of the gas phase transitions, narrow lines, and cold vibrational temperatures. Alkali atoms aggregate on the helium cluster surface to form dimers and trimers. The spectra of singlet alkali dimers exhibit the presence of elementary excitations in the superfluid helium cluster matrix. It is found that preparation of the alkali molecules on the surface of helium clusters leads to the preferential formation of high-spin, van der Waals bound, triplet dimers and quartet trimers. Four bound-bound and two bound-free transitions are observed in the triplet manifold of the alkali dimers. The quartet trimers serve as an ideal system for the study of a simple unimolecular reaction in the cold helium cluster environment. Analysis of the lowest quartet state provides valuable insight into three-body forces in a van der Waals trimer. The wide range of atomic and molecular systems studied in this thesis constitutes a preliminary step in the development of helium cluster isolation spectroscopy, a hybrid technique combining the advantages of high resolution spectroscopy with the synthetic, low temperature environment of matrices.

Application of multi-scale wavelet entropy and multi-resolution Volterra models for climatic downscaling

NASA Astrophysics Data System (ADS)

Sehgal, V.; Lakhanpal, A.; Maheswaran, R.; Khosa, R.; Sridhar, Venkataramana

2018-01-01

This study proposes a wavelet-based multi-resolution modeling approach for statistical downscaling of GCM variables to mean monthly precipitation for five locations at Krishna Basin, India. Climatic dataset from NCEP is used for training the proposed models (Jan.'69 to Dec.'94) and are applied to corresponding CanCM4 GCM variables to simulate precipitation for the validation (Jan.'95-Dec.'05) and forecast (Jan.'06-Dec.'35) periods. The observed precipitation data is obtained from the India Meteorological Department (IMD) gridded precipitation product at 0.25 degree spatial resolution. This paper proposes a novel Multi-Scale Wavelet Entropy (MWE) based approach for clustering climatic variables into suitable clusters using k-means methodology. Principal Component Analysis (PCA) is used to obtain the representative Principal Components (PC) explaining 90-95% variance for each cluster. A multi-resolution non-linear approach combining Discrete Wavelet Transform (DWT) and Second Order Volterra (SoV) is used to model the representative PCs to obtain the downscaled precipitation for each downscaling location (W-P-SoV model). The results establish that wavelet-based multi-resolution SoV models perform significantly better compared to the traditional Multiple Linear Regression (MLR) and Artificial Neural Networks (ANN) based frameworks. It is observed that the proposed MWE-based clustering and subsequent PCA, helps reduce the dimensionality of the input climatic variables, while capturing more variability compared to stand-alone k-means (no MWE). The proposed models perform better in estimating the number of precipitation events during the non-monsoon periods whereas the models with clustering without MWE over-estimate the rainfall during the dry season.

Family Functioning, Identity Formation, and the Ability of Conflict Resolution among Adolescents

ERIC Educational Resources Information Center

Kiani, Behnaz; Hojatkhah, Seyed Mohsen; Torabi-Nami, Mohammad

2016-01-01

Family is perhaps the most influential system in individuals' life in which various behaviors are learnt. Family functioning refers to the ability of family to meet its responsibilities. The present correlation study used a multi-stage cluster sampling method to recruit 686 subjects including 338 males and 348 females from all high school students…

Occurrence and Distribution of Fe-0 Globules in Lunar Agglutinates

NASA Technical Reports Server (NTRS)

Basu, Abhijit; Wentworth, Susan J.; McKay, David S.

2001-01-01

High-resolution Backscattered Electron Imaging (BSE) of agglutinitic glass shows immiscible metallic Fe(o) globules (greater than 99% are less than 15 nm; greater than 50% are less than 50 nm) in agglutinitic melt defining flow-lines, occurring in clusters, and rimming clasts (approx. 5%). Additional information is contained in the original extended abstract.

Hurricane Forecasting with the High-resolution NASA Finite-volume General Circulation Model

NASA Technical Reports Server (NTRS)

Atlas, R.; Reale, O.; Shen, B.-W.; Lin, S.-J.; Chern, J.-D.; Putman, W.; Lee, T.; Yeh, K.-S.; Bosilovich, M.; Radakovich, J.

2004-01-01

A high-resolution finite-volume General Circulation Model (fvGCM), resulting from a development effort of more than ten years, is now being run operationally at the NASA Goddard Space Flight Center and Ames Research Center. The model is based on a finite-volume dynamical core with terrain-following Lagrangian control-volume discretization and performs efficiently on massive parallel architectures. The computational efficiency allows simulations at a resolution of a quarter of a degree, which is double the resolution currently adopted by most global models in operational weather centers. Such fine global resolution brings us closer to overcoming a fundamental barrier in global atmospheric modeling for both weather and climate, because tropical cyclones and even tropical convective clusters can be more realistically represented. In this work, preliminary results of the fvGCM are shown. Fifteen simulations of four Atlantic tropical cyclones in 2002 and 2004 are chosen because of strong and varied difficulties presented to numerical weather forecasting. It is shown that the fvGCM, run at the resolution of a quarter of a degree, can produce very good forecasts of these tropical systems, adequately resolving problems like erratic track, abrupt recurvature, intense extratropical transition, multiple landfall and reintensification, and interaction among vortices.

Automatic segmentation of fluorescence lifetime microscopy images of cells using multiresolution community detection--a first study.

PubMed

Hu, D; Sarder, P; Ronhovde, P; Orthaus, S; Achilefu, S; Nussinov, Z

2014-01-01

Inspired by a multiresolution community detection based network segmentation method, we suggest an automatic method for segmenting fluorescence lifetime (FLT) imaging microscopy (FLIM) images of cells in a first pilot investigation on two selected images. The image processing problem is framed as identifying segments with respective average FLTs against the background in FLIM images. The proposed method segments a FLIM image for a given resolution of the network defined using image pixels as the nodes and similarity between the FLTs of the pixels as the edges. In the resulting segmentation, low network resolution leads to larger segments, and high network resolution leads to smaller segments. Furthermore, using the proposed method, the mean-square error in estimating the FLT segments in a FLIM image was found to consistently decrease with increasing resolution of the corresponding network. The multiresolution community detection method appeared to perform better than a popular spectral clustering-based method in performing FLIM image segmentation. At high resolution, the spectral segmentation method introduced noisy segments in its output, and it was unable to achieve a consistent decrease in mean-square error with increasing resolution. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Automated Segmentation of High-Resolution Photospheric Images of Active Regions

NASA Astrophysics Data System (ADS)

Yang, Meng; Tian, Yu; Rao, Changhui

2018-02-01

Due to the development of ground-based, large-aperture solar telescopes with adaptive optics (AO) resulting in increasing resolving ability, more accurate sunspot identifications and characterizations are required. In this article, we have developed a set of automated segmentation methods for high-resolution solar photospheric images. Firstly, a local-intensity-clustering level-set method is applied to roughly separate solar granulation and sunspots. Then reinitialization-free level-set evolution is adopted to adjust the boundaries of the photospheric patch; an adaptive intensity threshold is used to discriminate between umbra and penumbra; light bridges are selected according to their regional properties from candidates produced by morphological operations. The proposed method is applied to the solar high-resolution TiO 705.7-nm images taken by the 151-element AO system and Ground-Layer Adaptive Optics prototype system at the 1-m New Vacuum Solar Telescope of the Yunnan Observatory. Experimental results show that the method achieves satisfactory robustness and efficiency with low computational cost on high-resolution images. The method could also be applied to full-disk images, and the calculated sunspot areas correlate well with the data given by the National Oceanic and Atmospheric Administration (NOAA).

Correlation Functions Quantify Super-Resolution Images and Estimate Apparent Clustering Due to Over-Counting

PubMed Central

Veatch, Sarah L.; Machta, Benjamin B.; Shelby, Sarah A.; Chiang, Ethan N.; Holowka, David A.; Baird, Barbara A.

2012-01-01

We present an analytical method using correlation functions to quantify clustering in super-resolution fluorescence localization images and electron microscopy images of static surfaces in two dimensions. We use this method to quantify how over-counting of labeled molecules contributes to apparent self-clustering and to calculate the effective lateral resolution of an image. This treatment applies to distributions of proteins and lipids in cell membranes, where there is significant interest in using electron microscopy and super-resolution fluorescence localization techniques to probe membrane heterogeneity. When images are quantified using pair auto-correlation functions, the magnitude of apparent clustering arising from over-counting varies inversely with the surface density of labeled molecules and does not depend on the number of times an average molecule is counted. In contrast, we demonstrate that over-counting does not give rise to apparent co-clustering in double label experiments when pair cross-correlation functions are measured. We apply our analytical method to quantify the distribution of the IgE receptor (FcεRI) on the plasma membranes of chemically fixed RBL-2H3 mast cells from images acquired using stochastic optical reconstruction microscopy (STORM/dSTORM) and scanning electron microscopy (SEM). We find that apparent clustering of FcεRI-bound IgE is dominated by over-counting labels on individual complexes when IgE is directly conjugated to organic fluorophores. We verify this observation by measuring pair cross-correlation functions between two distinguishably labeled pools of IgE-FcεRI on the cell surface using both imaging methods. After correcting for over-counting, we observe weak but significant self-clustering of IgE-FcεRI in fluorescence localization measurements, and no residual self-clustering as detected with SEM. We also apply this method to quantify IgE-FcεRI redistribution after deliberate clustering by crosslinking with two distinct trivalent ligands of defined architectures, and we evaluate contributions from both over-counting of labels and redistribution of proteins. PMID:22384026

Comparative study of icy patches on comet nuclei

NASA Astrophysics Data System (ADS)

Oklay, Nilda; Pommerol, Antoine; Barucci, Maria Antonietta; Sunshine, Jessica; Sierks, Holger; Pajola, Maurizio

2016-07-01

Cometary missions Deep Impact, EPOXI and Rosetta investigated the nuclei of comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko respectively. Bright patches were observed on the surfaces of each of these three comets [1-5]. Of these, the surface of 67P is mapped at the highest spatial resolution via narrow angle camera (NAC) of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS, [6]) on board the Rosetta spacecraft. OSIRIS NAC is equipped with twelve filters covering the wavelength range of 250 nm to 1000 nm. Various filters combinations are used during surface mapping. With high spatial resolution data of comet 67P, three types of bright features were detected on the comet surface: Clustered, isolated and bright boulders [2]. In the visible spectral range, clustered bright features on comet 67P display bluer spectral slopes than the average surface [2, 4] while isolated bright features on comet 67P have flat spectra [4]. Icy patches observed on the surface of comets 9P and 103P display bluer spectral slopes than the average surface [1, 5]. Clustered and isolated bright features are blue in the RGB composites generated by using the images taken in NIR, visible and NUV wavelengths [2, 4]. This is valid for the icy patches observed on comets 9P and 103P [1, 5]. Spectroscopic observations of bright patches on comets 9P and 103P confirmed the existence of water [1, 5]. There were more than a hundred of bright features detected on the northern hemisphere of comet 67P [2]. Analysis of those features from both multispectral data and spectroscopic data is an ongoing work. Water ice is detected in eight of the bright features so far [7]. Additionally, spectroscopic observations of two clustered bright features on the surface of comet 67P revealed the existence of water ice [3]. The spectral properties of one of the icy patches were studied by [4] using OSIRIS NAC images and compared with the spectral properties of the active regions observed on comet 67P. Additionally jets rising from the same clustered bright feature were detected visually [4]. We analyzed bright patches on the surface of comets 9P, 103P and 67P using multispectral data obtained by the high-resolution instrument (HRI), medium- resolution instrument (MRI) and OSIRIS NAC using various spectral analysis techniques. Clustered bright features on comet 67P have similar visible spectra to the bright patches on comets 9P and 103P. The comparison of the bright patches includes the published results of the IR spectra. References: [1] Sunshine et al., 2006, Science, 311, 1453 [2] Pommerol et al., 2015, A&A, 583, A25 [3] Filacchione et al., 2016, Nature, 529, 368-372 [4] Oklay et al., 2016, A&A, 586, A80 [5] Sunshine et al. 2012, ACM [6] Keller et al., 2007, Space Sci. Rev., 128, 433 [7] Barucci et al., 2016, COSPAR, B04

Microbial community development in a dynamic gut model is reproducible, colon region specific, and selective for Bacteroidetes and Clostridium cluster IX.

PubMed

Van den Abbeele, Pieter; Grootaert, Charlotte; Marzorati, Massimo; Possemiers, Sam; Verstraete, Willy; Gérard, Philippe; Rabot, Sylvie; Bruneau, Aurélia; El Aidy, Sahar; Derrien, Muriel; Zoetendal, Erwin; Kleerebezem, Michiel; Smidt, Hauke; Van de Wiele, Tom

2010-08-01

Dynamic, multicompartment in vitro gastrointestinal simulators are often used to monitor gut microbial dynamics and activity. These reactors need to harbor a microbial community that is stable upon inoculation, colon region specific, and relevant to in vivo conditions. Together with the reproducibility of the colonization process, these criteria are often overlooked when the modulatory properties from different treatments are compared. We therefore investigated the microbial colonization process in two identical simulators of the human intestinal microbial ecosystem (SHIME), simultaneously inoculated with the same human fecal microbiota with a high-resolution phylogenetic microarray: the human intestinal tract chip (HITChip). Following inoculation of the in vitro colon compartments, microbial community composition reached steady state after 2 weeks, whereas 3 weeks were required to reach functional stability. This dynamic colonization process was reproducible in both SHIME units and resulted in highly diverse microbial communities which were colon region specific, with the proximal regions harboring saccharolytic microbes (e.g., Bacteroides spp. and Eubacterium spp.) and the distal regions harboring mucin-degrading microbes (e.g., Akkermansia spp.). Importantly, the shift from an in vivo to an in vitro environment resulted in an increased Bacteroidetes/Firmicutes ratio, whereas Clostridium cluster IX (propionate producers) was enriched compared to clusters IV and XIVa (butyrate producers). This was supported by proportionally higher in vitro propionate concentrations. In conclusion, high-resolution analysis of in vitro-cultured gut microbiota offers new insight on the microbial colonization process and indicates the importance of digestive parameters that may be crucial in the development of new in vitro models.

Clusters of Monoisotopic Elements for Calibration in (TOF) Mass Spectrometry

NASA Astrophysics Data System (ADS)

Kolářová, Lenka; Prokeš, Lubomír; Kučera, Lukáš; Hampl, Aleš; Peňa-Méndez, Eladia; Vaňhara, Petr; Havel, Josef

2017-03-01

Precise calibration in TOF MS requires suitable and reliable standards, which are not always available for high masses. We evaluated inorganic clusters of the monoisotopic elements gold and phosphorus (Au n +/Au n - and P n +/P n -) as an alternative to peptides or proteins for the external and internal calibration of mass spectra in various experimental and instrumental scenarios. Monoisotopic gold or phosphorus clusters can be easily generated in situ from suitable precursors by laser desorption/ionization (LDI) or matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Their use offers numerous advantages, including simplicity of preparation, biological inertness, and exact mass determination even at lower mass resolution. We used citrate-stabilized gold nanoparticles to generate gold calibration clusters, and red phosphorus powder to generate phosphorus clusters. Both elements can be added to samples to perform internal calibration up to mass-to-charge ( m/z) 10-15,000 without significantly interfering with the analyte. We demonstrated the use of the gold and phosphorous clusters in the MS analysis of complex biological samples, including microbial standards and total extracts of mouse embryonic fibroblasts. We believe that clusters of monoisotopic elements could be used as generally applicable calibrants for complex biological samples.

Infrared spectra of CO2-doped hydrogen clusters, (H2)N-CO2.

PubMed

McKellar, A R W

2012-03-07

Clusters of para-H(2) and/or ortho-H(2) containing a single carbon dioxide molecule are studied by high resolution infrared spectroscopy in the 2300 cm(-1) region of the CO(2) ν(3) fundamental band. The (H(2))(N)-CO(2) clusters are formed in a pulsed supersonic jet expansion from a cooled nozzle and probed using a rapid scan tunable diode laser. Simple symmetric rotor type spectra are observed with little or no resolved K-structure, and prominent Q-branch features for ortho-H(2) but not para-H(2). Observed rotational constants and vibrational shifts are reported for ortho-H(2) up to N = 7 and para-H(2) up to N = 15, with the N > 7 assignments only made possible with the help of theoretical simulations. The para-H(2) cluster with N = 12 shows clear evidence for superfluid effects, in good agreement with theory. The presence of larger clusters with N > 15 is evident in the spectra, but specific assignments are not possible. Mixed para- + ortho-H(2) cluster transitions are well predicted by linear interpolation between corresponding pure cluster line positions. © 2012 American Institute of Physics

How supernovae launch galactic winds?

NASA Astrophysics Data System (ADS)

Fielding, Drummond; Quataert, Eliot; Martizzi, Davide; Faucher-Giguère, Claude-André

2017-09-01

We use idealized three-dimensional hydrodynamic simulations of global galactic discs to study the launching of galactic winds by supernovae (SNe). The simulations resolve the cooling radii of the majority of supernova remnants (SNRs) and thus self-consistently capture how SNe drive galactic winds. We find that SNe launch highly supersonic winds with properties that agree reasonably well with expectations from analytic models. The energy loading (η _E= \\dot{E}_wind/ \\dot{E}_SN) of the winds in our simulations are well converged with spatial resolution while the wind mass loading (η _M= \\dot{M}_wind/\\dot{M}_\\star) decreases with resolution at the resolutions we achieve. We present a simple analytic model based on the concept that SNRs with cooling radii greater than the local scaleheight break out of the disc and power the wind. This model successfully explains the dependence (or lack thereof) of ηE (and by extension ηM) on the gas surface density, star formation efficiency, disc radius and the clustering of SNe. The winds our simulations are weaker than expected in reality, likely due to the fact that we seed SNe preferentially at density peaks. Clustering SNe in time and space substantially increases the wind power.

Zodiacal Exoplanets in Time (ZEIT). IV. Seven Transiting Planets in the Praesepe Cluster

NASA Astrophysics Data System (ADS)

Mann, Andrew W.; Gaidos, Eric; Vanderburg, Andrew; Rizzuto, Aaron C.; Ansdell, Megan; Medina, Jennifer Vanessa; Mace, Gregory N.; Kraus, Adam L.; Sokal, Kimberly R.

2017-02-01

Open clusters and young stellar associations are attractive sites to search for planets and to test theories of planet formation, migration, and evolution. We present our search for, and characterization of, transiting planets in the 800 Myr old Praesepe (Beehive, M44) Cluster from K2 light curves. We identify seven planet candidates, six of which we statistically validate to be real planets, the last of which requires more data. For each host star, we obtain high-resolution NIR spectra to measure its projected rotational broadening and radial velocity, the latter of which we use to confirm cluster membership. We combine low-resolution spectra with the known cluster distance and metallicity to provide precise temperatures, masses, radii, and luminosities for the host stars. Combining our measurements of rotational broadening, rotation periods, and our derived stellar radii, we show that all planetary orbits are consistent with alignment to their host star’s rotation. We fit the K2 light curves, including priors on stellar density to put constraints on the planetary eccentricities, all of which are consistent with zero. The difference between the number of planets found in Praesepe and Hyades (8 planets, ≃ 800 Myr) and a similar data set for Pleiades (0 planets, ≃125 Myr) suggests a trend with age, but may be due to incompleteness of current search pipelines for younger, faster-rotating stars. We see increasing evidence that some planets continue to lose atmosphere past 800 Myr, as now two planets at this age have radii significantly larger than their older counterparts from Kepler.

Optimized multiple linear mappings for single image super-resolution

NASA Astrophysics Data System (ADS)

Zhang, Kaibing; Li, Jie; Xiong, Zenggang; Liu, Xiuping; Gao, Xinbo

2017-12-01

Learning piecewise linear regression has been recognized as an effective way for example learning-based single image super-resolution (SR) in literature. In this paper, we employ an expectation-maximization (EM) algorithm to further improve the SR performance of our previous multiple linear mappings (MLM) based SR method. In the training stage, the proposed method starts with a set of linear regressors obtained by the MLM-based method, and then jointly optimizes the clustering results and the low- and high-resolution subdictionary pairs for regression functions by using the metric of the reconstruction errors. In the test stage, we select the optimal regressor for SR reconstruction by accumulating the reconstruction errors of m-nearest neighbors in the training set. Thorough experimental results carried on six publicly available datasets demonstrate that the proposed SR method can yield high-quality images with finer details and sharper edges in terms of both quantitative and perceptual image quality assessments.

EPE The Extreme Physics Explorer

NASA Technical Reports Server (NTRS)

Garcia, Michael; Elvis, Martin; Bookbinder, Jay; Brenneman, Laura; Bulbul, Esra; Nulsen, Paul; Patnaude, Dan; Smith, Randall; Bandler, Simon; Okajima, Takashi;

Dynamic Cluster Analysis: An Unbiased Method for Identifying A + 2 Element Containing Compounds in Liquid Chromatographic High-Resolution Time-of-Flight Mass Spectrometric Data.

PubMed

Andersen, Aaron John Christian; Hansen, Per Juel; Jørgensen, Kevin; Nielsen, Kristian Fog

2016-12-20

Dynamic cluster analysis (DCA) is an automated, unbiased technique which can identify Cl, Br, S, and other A + 2 element containing metabolites in liquid chromatographic high-resolution mass spectrometric data. DCA is based on three features, primarily the previously unutilized A + 1 to A + 2 isotope cluster spacing which is a strong classifier in itself but improved with the addition of the monoisotopic mass, and the well-known A:A+2 intensity ratio. Utilizing only the A + 1 to A + 2 isotope cluster spacing and the monoisotopic mass it was possible to filter a chromatogram for metabolites which contain Cl, Br, and S. Screening simulated isotope patterns of the Antibase Natural Products Database it was determined that the A + 1 to A + 2 isotope cluster spacing can be used to correctly classify 97.4% of molecular formulas containing these elements, only misclassifying a few metabolites which were either over 2800 u or metabolites which contained other A + 2 elements, such as Cu, Ni, Mg, and Zn. It was determined that with an interisotopic mass accuracy of 1 ppm, in a fully automated process, using all three parameters, it is possible to specifically filter a chromatogram for S containing metabolites with monoisotopic masses less than 825 u. Furthermore, it was possible to specifically filter a chromatogram for Cl and Br containing metabolites with monoisotopic masses less than 1613 u. Here DCA is applied on (i) simulated isotope patterns of the Antibase natural products databases, (ii) LC-QTOF data of reference standards, and (iii) LC-QTOF data of crude extracts of 10 strains of laboratory grown cultures of the microalga Prymnesium parvum where it identified known metabolites of the prymnesin series as well as over 20 previously undescribed prymnesin-like molecular features.

The Wide Field X-ray Telescope Mission

NASA Astrophysics Data System (ADS)

Murray, Stephen S.; WFXT Team

2010-01-01

To explore the high-redshift Universe to the era of galaxy formation requires an X-ray survey that is both sensitive and extensive, which complements deep wide-field surveys at other wavelengths. The Wide-Field X-ray Telescope (WFXT) is designed to be two orders of magnitude more effective than previous and planned X-ray missions for surveys. WFXT consists of three co-aligned wide-field X-ray telescopes with a 1 sq. deg. field of view and <10 arc sec (goal of 5 arc sec) angular resolution over the full field. With nearly ten times Chandra's collecting area and more than ten times Chandra's field of view, WFXT will perform sensitive deep surveys that will discover and characterize extremely large populations of high redshift AGN and galaxy clusters. In five years, WFXT will perform three extragalactic surveys: 1) 20,000 sq. deg. of extragalactic sky at 100-1000 times the sensitivity, and twenty times better angular resolution than the ROSAT All Sky Survey; 2) 3000 sq.deg. to deep Chandra sensitivity; and 3) 100 sq.deg. to the deepest Chandra sensitivity. WFXT will generate a legacy dataset of >500,000 galaxy clusters to redshifts about 2, measuring redshift, gas abundance and temperature for a significant fraction of them, and a sample of more than 10 million AGN to redshifts > 6, many with X-ray spectra sufficient to distinguish obscured from unobscured quasars. These surveys will address fundamental questions of how supermassive black holes grow and influence the evolution of the host galaxy and how clusters form and evolve, as well as providing large samples of massive clusters that can be used in cosmological studies. WFXT surveys will map systems spanning many square degrees including Galactic star forming regions, the Magellanic Clouds and the Virgo Cluster. WFXT data will become public through annual Data Releases that will constitute a vast scientific legacy.

Pore-scale micro-computed-tomography imaging: Nonwetting-phase cluster-size distribution during drainage and imbibition

NASA Astrophysics Data System (ADS)

Georgiadis, A.; Berg, S.; Makurat, A.; Maitland, G.; Ott, H.

2013-09-01

We investigated the cluster-size distribution of the residual nonwetting phase in a sintered glass-bead porous medium at two-phase flow conditions, by means of micro-computed-tomography (μCT) imaging with pore-scale resolution. Cluster-size distribution functions and cluster volumes were obtained by image analysis for a range of injected pore volumes under both imbibition and drainage conditions; the field of view was larger than the porosity-based representative elementary volume (REV). We did not attempt to make a definition for a two-phase REV but used the nonwetting-phase cluster-size distribution as an indicator. Most of the nonwetting-phase total volume was found to be contained in clusters that were one to two orders of magnitude larger than the porosity-based REV. The largest observed clusters in fact ranged in volume from 65% to 99% of the entire nonwetting phase in the field of view. As a consequence, the largest clusters observed were statistically not represented and were found to be smaller than the estimated maximum cluster length. The results indicate that the two-phase REV is larger than the field of view attainable by μCT scanning, at a resolution which allows for the accurate determination of cluster connectivity.

Quasi-Likelihood Techniques in a Logistic Regression Equation for Identifying Simulium damnosum s.l. Larval Habitats Intra-cluster Covariates in Togo.

PubMed

Jacob, Benjamin G; Novak, Robert J; Toe, Laurent; Sanfo, Moussa S; Afriyie, Abena N; Ibrahim, Mohammed A; Griffith, Daniel A; Unnasch, Thomas R

2012-01-01

The standard methods for regression analyses of clustered riverine larval habitat data of Simulium damnosum s.l. a major black-fly vector of Onchoceriasis, postulate models relating observational ecological-sampled parameter estimators to prolific habitats without accounting for residual intra-cluster error correlation effects. Generally, this correlation comes from two sources: (1) the design of the random effects and their assumed covariance from the multiple levels within the regression model; and, (2) the correlation structure of the residuals. Unfortunately, inconspicuous errors in residual intra-cluster correlation estimates can overstate precision in forecasted S.damnosum s.l. riverine larval habitat explanatory attributes regardless how they are treated (e.g., independent, autoregressive, Toeplitz, etc). In this research, the geographical locations for multiple riverine-based S. damnosum s.l. larval ecosystem habitats sampled from 2 pre-established epidemiological sites in Togo were identified and recorded from July 2009 to June 2010. Initially the data was aggregated into proc genmod. An agglomerative hierarchical residual cluster-based analysis was then performed. The sampled clustered study site data was then analyzed for statistical correlations using Monthly Biting Rates (MBR). Euclidean distance measurements and terrain-related geomorphological statistics were then generated in ArcGIS. A digital overlay was then performed also in ArcGIS using the georeferenced ground coordinates of high and low density clusters stratified by Annual Biting Rates (ABR). This data was overlain onto multitemporal sub-meter pixel resolution satellite data (i.e., QuickBird 0.61m wavbands ). Orthogonal spatial filter eigenvectors were then generated in SAS/GIS. Univariate and non-linear regression-based models (i.e., Logistic, Poisson and Negative Binomial) were also employed to determine probability distributions and to identify statistically significant parameter estimators from the sampled data. Thereafter, Durbin-Watson test statistics were used to test the null hypothesis that the regression residuals were not autocorrelated against the alternative that the residuals followed an autoregressive process in AUTOREG. Bayesian uncertainty matrices were also constructed employing normal priors for each of the sampled estimators in PROC MCMC. The residuals revealed both spatially structured and unstructured error effects in the high and low ABR-stratified clusters. The analyses also revealed that the estimators, levels of turbidity and presence of rocks were statistically significant for the high-ABR-stratified clusters, while the estimators distance between habitats and floating vegetation were important for the low-ABR-stratified cluster. Varying and constant coefficient regression models, ABR- stratified GIS-generated clusters, sub-meter resolution satellite imagery, a robust residual intra-cluster diagnostic test, MBR-based histograms, eigendecomposition spatial filter algorithms and Bayesian matrices can enable accurate autoregressive estimation of latent uncertainity affects and other residual error probabilities (i.e., heteroskedasticity) for testing correlations between georeferenced S. damnosum s.l. riverine larval habitat estimators. The asymptotic distribution of the resulting residual adjusted intra-cluster predictor error autocovariate coefficients can thereafter be established while estimates of the asymptotic variance can lead to the construction of approximate confidence intervals for accurately targeting productive S. damnosum s.l habitats based on spatiotemporal field-sampled count data.

Modeling defect cluster evolution in irradiated structural materials: Focus on comparing to high-resolution experimental characterization studies

DOE PAGES

Wirth, Brian D.; Hu, Xunxiang; Kohnert, Aaron; ...

2015-03-02

Exposure of metallic structural materials to irradiation environments results in significant microstructural evolution, property changes, and performance degradation, which limits the extended operation of current generation light water reactors and restricts the design of advanced fission and fusion reactors. Further, it is well recognized that these irradiation effects are a classic example of inherently multiscale phenomena and that the mix of radiation-induced features formed and the corresponding property degradation depend on a wide range of material and irradiation variables. This inherently multiscale evolution emphasizes the importance of closely integrating models with high-resolution experimental characterization of the evolving radiation-damaged microstructure. Lastly,more » this article provides a review of recent models of the defect microstructure evolution in irradiated body-centered cubic materials, which provide good agreement with experimental measurements, and presents some outstanding challenges, which will require coordinated high-resolution characterization and modeling to resolve.« less

Direct evidence on Ta-Metal Phases Igniting Resistive Switching in TaOx Thin Film

PubMed Central

Kyu Yang, Min; Ju, Hyunsu; Hwan Kim, Gun; Lee, Jeon-Kook; Ryu, Han-Cheol

2015-01-01

A Ta/TaOx/Pt stacked capacitor-like device for resistive switching was fabricated and examined. The tested device demonstrated stable resistive switching characteristics including uniform distribution of resistive switching operational parameters, highly promising endurance, and retention properties. To reveal the resistive switching mechanism of the device, micro structure analysis using high-resolution transmission electron microscope (HR-TEM) was performed. From the observation results, two different phases of Ta-metal clusters of cubic α-Ta and tetragonal β-Ta were founded in the amorphous TaOx mother-matrix after the device was switched from high resistance state (HRS) to low resistance state (LRS) by externally applied voltage bias. The observed Ta metal clusters unveiled the origin of the electric conduction paths in the TaOx thin film at the LRS. PMID:26365532

Direct evidence on Ta-Metal Phases Igniting Resistive Switching in TaOx Thin Film

NASA Astrophysics Data System (ADS)

Kyu Yang, Min; Ju, Hyunsu; Hwan Kim, Gun; Lee, Jeon-Kook; Ryu, Han-Cheol

2015-09-01

A Ta/TaOx/Pt stacked capacitor-like device for resistive switching was fabricated and examined. The tested device demonstrated stable resistive switching characteristics including uniform distribution of resistive switching operational parameters, highly promising endurance, and retention properties. To reveal the resistive switching mechanism of the device, micro structure analysis using high-resolution transmission electron microscope (HR-TEM) was performed. From the observation results, two different phases of Ta-metal clusters of cubic α-Ta and tetragonal β-Ta were founded in the amorphous TaOx mother-matrix after the device was switched from high resistance state (HRS) to low resistance state (LRS) by externally applied voltage bias. The observed Ta metal clusters unveiled the origin of the electric conduction paths in the TaOx thin film at the LRS.

Organization and Dynamics of Receptor Proteins in a Plasma Membrane.

PubMed

Koldsø, Heidi; Sansom, Mark S P

2015-11-25

The interactions of membrane proteins are influenced by their lipid environment, with key lipid species able to regulate membrane protein function. Advances in high-resolution microscopy can reveal the organization and dynamics of proteins and lipids within living cells at resolutions <200 nm. Parallel advances in molecular simulations provide near-atomic-resolution models of the dynamics of the organization of membranes of in vivo-like complexity. We explore the dynamics of proteins and lipids in crowded and complex plasma membrane models, thereby closing the gap in length and complexity between computations and experiments. Our simulations provide insights into the mutual interplay between lipids and proteins in determining mesoscale (20-100 nm) fluctuations of the bilayer, and in enabling oligomerization and clustering of membrane proteins.

Probing dark matter physics with galaxy clusters

NASA Astrophysics Data System (ADS)

Dalal, Neal

2016-10-01

We propose a theoretical investigation of the effects of a class of dark matter (DM) self-interactions on the properties of galaxy clusters and their host dark matter halos. Recent work using HST has claimed the detection of a particular form of DM self-interaction, which can lead to observable displacements between satellite galaxies within clusters and the DM subhalos hosting them. This form of self-interaction is highly anisotropic, favoring forward scattering with low momentum transfer, unlike isotropically scattering self-interacting dark matter (SIDM) models. This class of models has not been simulated numerically, clouding the interpretation of the claimed offsets between galaxies and lensing peaks observed by HST. We propose to perform high resolution simulations of cosmological structure formation for this class of SIDM model, focusing on three observables accessible to existing HST observations of clusters. First, we will quantify the extent to which offsets between baryons and DM can arise in these models, as a function of the cross section. Secondly, we will also quantify the effects of this type of DM self-interaction on halo concentrations, to determine the range of cross-sections allowed by existing stringent constraints from HST. Finally we will compute the so-called splashback feature in clusters, specifically focusing on whether SIDM can resolve the current discrepancy between observed values of splashback radii in clusters compared to theoretical predictions for CDM. The proposed investigations will add value to all existing deep HST observations of galaxy clusters by allowing them to probe dark matter physics in three independent ways.

The Large-scale Structure of the Universe: Probes of Cosmology and Structure Formation

NASA Astrophysics Data System (ADS)

Noh, Yookyung

The usefulness of large-scale structure as a probe of cosmology and structure formation is increasing as large deep surveys in multi-wavelength bands are becoming possible. The observational analysis of large-scale structure guided by large volume numerical simulations are beginning to offer us complementary information and crosschecks of cosmological parameters estimated from the anisotropies in Cosmic Microwave Background (CMB) radiation. Understanding structure formation and evolution and even galaxy formation history is also being aided by observations of different redshift snapshots of the Universe, using various tracers of large-scale structure. This dissertation work covers aspects of large-scale structure from the baryon acoustic oscillation scale, to that of large scale filaments and galaxy clusters. First, I discuss a large- scale structure use for high precision cosmology. I investigate the reconstruction of Baryon Acoustic Oscillation (BAO) peak within the context of Lagrangian perturbation theory, testing its validity in a large suite of cosmological volume N-body simulations. Then I consider galaxy clusters and the large scale filaments surrounding them in a high resolution N-body simulation. I investigate the geometrical properties of galaxy cluster neighborhoods, focusing on the filaments connected to clusters. Using mock observations of galaxy clusters, I explore the correlations of scatter in galaxy cluster mass estimates from multi-wavelength observations and different measurement techniques. I also examine the sources of the correlated scatter by considering the intrinsic and environmental properties of clusters.

Density-based cluster algorithms for the identification of core sets

NASA Astrophysics Data System (ADS)

Lemke, Oliver; Keller, Bettina G.

2016-10-01

The core-set approach is a discretization method for Markov state models of complex molecular dynamics. Core sets are disjoint metastable regions in the conformational space, which need to be known prior to the construction of the core-set model. We propose to use density-based cluster algorithms to identify the cores. We compare three different density-based cluster algorithms: the CNN, the DBSCAN, and the Jarvis-Patrick algorithm. While the core-set models based on the CNN and DBSCAN clustering are well-converged, constructing core-set models based on the Jarvis-Patrick clustering cannot be recommended. In a well-converged core-set model, the number of core sets is up to an order of magnitude smaller than the number of states in a conventional Markov state model with comparable approximation error. Moreover, using the density-based clustering one can extend the core-set method to systems which are not strongly metastable. This is important for the practical application of the core-set method because most biologically interesting systems are only marginally metastable. The key point is to perform a hierarchical density-based clustering while monitoring the structure of the metric matrix which appears in the core-set method. We test this approach on a molecular-dynamics simulation of a highly flexible 14-residue peptide. The resulting core-set models have a high spatial resolution and can distinguish between conformationally similar yet chemically different structures, such as register-shifted hairpin structures.

Time-series Spectroscopy of Two Candidate Double Degenerates in the Open Cluster NGC 6633

NASA Astrophysics Data System (ADS)

Williams, Kurtis A.; Serna-Grey, Donald; Chakraborty, Subho; Gianninas, A.; Canton, Paul A.

2015-12-01

SNe Ia are heavily used tools in precision cosmology, yet we still are not certain what the progenitor systems are. General plausibility arguments suggest there is potential for identifying double degenerate SN Ia progenitors in intermediate-age open star clusters. We present time-resolved high-resolution spectroscopy of two white dwarfs (WDs) in the field of the open cluster NGC 6633 that had previously been identified as candidate double degenerates in the cluster. However, three hours of continuous observations of each candidate failed to detect any significant radial velocity variations at the ≳10 km s-1 level, making it highly unlikely that either WD is a double degenerate that will merge within a Hubble Time. The WD LAWDS NGC 6633 4 has a radial velocity inconsistent with cluster membership at the 2.5σ level, while the radial velocity of LAWDS NGC 6633 7 is consistent with cluster membership. We conservatively conclude that LAWDS 7 is a viable massive double degenerate candidate, though unlikely to be a Type Ia progenitor. Astrometric data from GAIA will likely be needed to determine if either WD is truly a cluster member. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

Cluster Physics with Merging Galaxy Clusters

NASA Astrophysics Data System (ADS)

Molnar, Sandor

Collisions between galaxy clusters provide a unique opportunity to study matter in a parameter space which cannot be explored in our laboratories on Earth. In the standard ΛCDM model, where the total density is dominated by the cosmological constant (Λ) and the matter density by cold dark matter (CDM), structure formation is hierarchical, and clusters grow mostly by merging. Mergers of two massive clusters are the most energetic events in the universe after the Big Bang, hence they provide a unique laboratory to study cluster physics. The two main mass components in clusters behave differently during collisions: the dark matter is nearly collisionless, responding only to gravity, while the gas is subject to pressure forces and dissipation, and shocks and turbulence are developed during collisions. In the present contribution we review the different methods used to derive the physical properties of merging clusters. Different physical processes leave their signatures on different wavelengths, thus our review is based on a multifrequency analysis. In principle, the best way to analyze multifrequency observations of merging clusters is to model them using N-body/HYDRO numerical simulations. We discuss the results of such detailed analyses. New high spatial and spectral resolution ground and space based telescopes will come online in the near future. Motivated by these new opportunities, we briefly discuss methods which will be feasible in the near future in studying merging clusters.

Response to "Comparison and Evaluation of Clustering Algorithms for Tandem Mass Spectra".

PubMed

Griss, Johannes; Perez-Riverol, Yasset; The, Matthew; Käll, Lukas; Vizcaíno, Juan Antonio

2018-05-04

In the recent benchmarking article entitled "Comparison and Evaluation of Clustering Algorithms for Tandem Mass Spectra", Rieder et al. compared several different approaches to cluster MS/MS spectra. While we certainly recognize the value of the manuscript, here, we report some shortcomings detected in the original analyses. For most analyses, the authors clustered only single MS/MS runs. In one of the reported analyses, three MS/MS runs were processed together, which already led to computational performance issues in many of the tested approaches. This fact highlights the difficulties of using many of the tested algorithms on the nowadays produced average proteomics data sets. Second, the authors only processed identified spectra when merging MS runs. Thereby, all unidentified spectra that are of lower quality were already removed from the data set and could not influence the clustering results. Next, we found that the authors did not analyze the effect of chimeric spectra on the clustering results. In our analysis, we found that 3% of the spectra in the used data sets were chimeric, and this had marked effects on the behavior of the different clustering algorithms tested. Finally, the authors' choice to evaluate the MS-Cluster and spectra-cluster algorithms using a precursor tolerance of 5 Da for high-resolution Orbitrap data only was, in our opinion, not adequate to assess the performance of MS/MS clustering approaches.

Dynamical Organization of Syntaxin-1A at the Presynaptic Active Zone

PubMed Central

Ullrich, Alexander; Böhme, Mathias A.; Schöneberg, Johannes; Depner, Harald; Sigrist, Stephan J.; Noé, Frank

2015-01-01

Synaptic vesicle fusion is mediated by SNARE proteins forming in between synaptic vesicle (v-SNARE) and plasma membrane (t-SNARE), one of which is Syntaxin-1A. Although exocytosis mainly occurs at active zones, Syntaxin-1A appears to cover the entire neuronal membrane. By using STED super-resolution light microscopy and image analysis of Drosophila neuro-muscular junctions, we show that Syntaxin-1A clusters are more abundant and have an increased size at active zones. A computational particle-based model of syntaxin cluster formation and dynamics is developed. The model is parametrized to reproduce Syntaxin cluster-size distributions found by STED analysis, and successfully reproduces existing FRAP results. The model shows that the neuronal membrane is adjusted in a way to strike a balance between having most syntaxins stored in large clusters, while still keeping a mobile fraction of syntaxins free or in small clusters that can efficiently search the membrane or be traded between clusters. This balance is subtle and can be shifted toward almost no clustering and almost complete clustering by modifying the syntaxin interaction energy on the order of only 1 kBT. This capability appears to be exploited at active zones. The larger active-zone syntaxin clusters are more stable and provide regions of high docking and fusion capability, whereas the smaller clusters outside may serve as flexible reserve pool or sites of spontaneous ectopic release. PMID:26367029

Real & Simulated IFU Observations of Low-Mass Early-Type Galaxies: Environmental Influence Probed for Cluster Galaxies

NASA Astrophysics Data System (ADS)

Sybilska, Agnieszka; Łokas, Ewa Luiza; Fouquet, Sylvain

2017-03-01

We combine high-quality IFU data with a new set of numerical simulations to study low-mass early type galaxies (dEs) in dense environments. Our earlier study of dEs in the Virgo cluster has produced the first large-scale maps of kinematic and stellar population properties of dEs in those environments (Ryś et al. 2013, 2014, 2015). A quantitative discrimination between various (trans)formation processes proposed for these objects is, however, a complex issue, requiring a priori assumptions about the progenitors of galaxies we observe and study today. To bridge this gap between observations and theoretical predictions, we use the expertise gained in the IFU data analysis to look ``through the eye of SAURON'' at our new suite of high-resolution N-body simulations of dEs in the Virgo cluster. Mimicking the observers perspective as closely as possible, we can also indicate the existing instrumental and viewer limitations regarding what we are/are not able to detect as observers.

ALMA-SZ Detection of a Galaxy Cluster Merger Shock at Half the Age of the Universe

NASA Astrophysics Data System (ADS)

Basu, K.; Sommer, M.; Erler, J.; Eckert, D.; Vazza, F.; Magnelli, B.; Bertoldi, F.; Tozzi, P.

2016-10-01

We present ALMA measurements of a merger shock using the thermal Sunyaev-Zel’dovich (SZ) effect signal, at the location of a radio relic in the famous El Gordo galaxy cluster at z≈ 0.9. Multi-wavelength analysis in combination with the archival Chandra data and a high-resolution radio image provides a consistent picture of the thermal and non-thermal signal variation across the shock front and helps to put robust constraints on the shock Mach number as well as the relic magnetic field. We employ a Bayesian analysis technique for modeling the SZ and X-ray data self-consistently, illustrating respective parameter degeneracies. Combined results indicate a shock with Mach number { M }={2.4}-0.6+1.3, which in turn suggests a high value of the magnetic field (of the order of 4-10 μ {{G}}) to account for the observed relic width at 2 GHz. At roughly half the current age of the universe, this is the highest-redshift direct detection of a cluster shock to date, and one of the first instances of an ALMA-SZ observation in a galaxy cluster. It shows the tremendous potential for future ALMA-SZ observations to detect merger shocks and other cluster substructures out to the highest redshifts.

Effect of Self-Assembly of Fullerene Nano-Particles on Lipid Membrane

PubMed Central

Zhang, Saiqun; Mu, Yuguang; Zhang, John Z. H.; Xu, Weixin

2013-01-01

Carbon nanoparticles can penetrate the cell membrane and cause cytotoxicity. The diffusion feature and translocation free energy of fullerene through lipid membranes is well reported. However, the knowledge on self-assembly of fullerenes and resulting effects on lipid membrane is poorly addressed. In this work, the self-assembly of fullerene nanoparticles and the resulting influence on the dioleoylphosphtidylcholine (DOPC) model membrane were studied by using all-atom molecular dynamics simulations with explicit solvents. Our simulation results confirm that gathered small fullerene cluster can invade lipid membrane. Simulations show two pathways: 1) assembly process is completely finished before penetration; 2) assembly process coincides with penetration. Simulation results also demonstrate that in the membrane interior, fullerene clusters tend to stay at the position which is 1.0 nm away from the membrane center. In addition, the diverse microscopic stacking mode (i.e., equilateral triangle, tetrahedral pentahedral, trigonal bipyramid and octahedron) of these small fullerene clusters are well characterized. Thus our simulations provide a detailed high-resolution characterization of the microscopic structures of the small fullerene clusters. Further, we found the gathered small fullerene clusters have significant adverse disturbances to the local structure of the membrane, but no great influence on the global integrity of the lipid membrane, which suggests the prerequisite of high-content fullerene for cytotoxicity. PMID:24204827

Molecular Typing of Mycobacterium Tuberculosis Complex by 24-Locus Based MIRU-VNTR Typing in Conjunction with Spoligotyping to Assess Genetic Diversity of Strains Circulating in Morocco

PubMed Central

Bouklata, Nada; Supply, Philip; Jaouhari, Sanae; Charof, Reda; Seghrouchni, Fouad; Sadki, Khalid; El Achhab, Youness; Nejjari, Chakib; Filali-Maltouf, Abdelkarim

2015-01-01

Background Standard 24-locus Mycobacterial Interspersed Repetitive Unit Variable Number Tandem Repeat (MIRU-VNTR) typing allows to get an improved resolution power for tracing TB transmission and predicting different strain (sub) lineages in a community. Methodology During 2010–2012, a total of 168 Mycobacterium tuberculosis Complex (MTBC) isolates were collected by cluster sampling from 10 different Moroccan cities, and centralized by the National Reference Laboratory of Tuberculosis over the study period. All isolates were genotyped using spoligotyping, and a subset of 75 was genotyped using 24-locus based MIRU-VNTR typing, followed by first line drug susceptibility testing. Corresponding strain lineages were predicted using MIRU-VNTRplus database. Principal Findings Spoligotyping resulted in 137 isolates in 18 clusters (2–50 isolates per cluster: clustering rate of 81.54%) corresponding to a SIT number in the SITVIT database, while 31(18.45%) patterns were unique of which 10 were labelled as “unknown” according to the same database. The most prevalent spoligotype family was LAM; (n = 81 or 48.24% of isolates, dominated by SIT42, n = 49), followed by Haarlem (23.80%), T superfamily (15.47%), >Beijing (2.97%), > U clade (2.38%) and S clade (1.19%). Subsequent 24-Locus MIRU-VNTR typing identified 64 unique types and 11 isolates in 5 clusters (2 to 3isolates per cluster), substantially reducing clusters defined by spoligotyping only. The single cluster of three isolates corresponded to two previously treated MDR-TB cases and one new MDR-TB case known to be contact a same index case and belonging to a same family, albeit residing in 3 different administrative regions. MIRU-VNTR loci 4052, 802, 2996, 2163b, 3690, 1955, 424, 2531, 2401 and 960 were highly discriminative in our setting (HGDI >0.6). Conclusions 24-locus MIRU-VNTR typing can substantially improve the resolution of large clusters initially defined by spoligotyping alone and predominating in Morocco, and could therefore be used to better study tuberculosis transmission in a population-based, multi-year sample context. PMID:26285026

Harmonium: An Ultrafast Vacuum Ultraviolet Facility.

PubMed

Arrell, Christopher A; Ojeda, José; Longetti, Luca; Crepaldi, Alberto; Roth, Silvan; Gatti, Gianmarco; Clark, Andrew; van Mourik, Frank; Drabbels, Marcel; Grioni, Marco; Chergui, Majed

2017-05-31

Harmonium is a vacuum ultraviolet (VUV) photon source built within the Lausanne Centre for Ultrafast Science (LACUS). Utilising high harmonic generation, photons from 20-110 eV are available to conduct steady-state or ultrafast photoelectron and photoion spectroscopies (PES and PIS). A pulse preserving monochromator provides either high energy resolution (70 meV) or high temporal resolution (40 fs). Three endstations have been commissioned for: a) PES of liquids; b) angular resolved PES (ARPES) of solids and; c) coincidence PES and PIS of gas phase molecules or clusters. The source has several key advantages: high repetition rate (up to 15 kHz) and high photon flux (1011 photons per second at 38 eV). The capabilities of the facility complement the Swiss ultrafast and X-ray community (SwissFEL, SLS, NCCR MUST, etc.) helping to maintain Switzerland's leading role in ultrafast science in the world.

Study on the coloration response of a radiochromic film to MeV cluster ion beams

NASA Astrophysics Data System (ADS)

Yuri, Yosuke; Narumi, Kazumasa; Chiba, Atsuya; Hirano, Yoshimi; Saitoh, Yuichi

2017-11-01

A radiochromic film, Gafchromic HD-V2, is applied to a possible method of measuring a two-dimensional (2D) spatial profile of MeV cluster ion beams. The coloration responses of the HD-V2 film to MeV carbon and gold cluster ion beams are experimentally investigated since some cluster effect may appear. The degree of the film coloration is quantified as a change in optical density (OD) by reading the films with an image scanner for high-resolution measurement of the 2D beam profile. The OD response of HD-V2 is characterized as a function of the ion and atom fluence for comparison. The dependences of the OD response on the cluster size, kinetic energy, and ion species are discussed. It is found that the sensitivity of the OD change is reduced when the cluster size is large. The beam profile of MeV cluster ion beams delivered from the tandem accelerator in TIARA is characterized from the measurement result using HD-V2 films. The present results show that the use of the Gafchromic HD-V2 film is suitable for the detail beam profile measurement of MeV cluster ions, especially C60 ions, whose available intensity is rather low in comparison with that of monatomic ion beams.

Exploring the atomic structure of 1.8nm monolayer-protected gold clusters with aberration-corrected STEM.

PubMed

Liu, Jian; Jian, Nan; Ornelas, Isabel; Pattison, Alexander J; Lahtinen, Tanja; Salorinne, Kirsi; Häkkinen, Hannu; Palmer, Richard E

2017-05-01

Monolayer-protected (MP) Au clusters present attractive quantum systems with a range of potential applications e.g. in catalysis. Knowledge of the atomic structure is needed to obtain a full understanding of their intriguing physical and chemical properties. Here we employed aberration-corrected scanning transmission electron microscopy (ac-STEM), combined with multislice simulations, to make a round-robin investigation of the atomic structure of chemically synthesised clusters with nominal composition Au 144 (SCH 2 CH 2 Ph) 60 provided by two different research groups. The MP Au clusters were "weighed" by the atom counting method, based on their integrated intensities in the high angle annular dark field (HAADF) regime and calibrated exponent of the Z dependence. For atomic structure analysis, we compared experimental images of hundreds of clusters, with atomic resolution, against a variety of structural models. Across the size range 123-151 atoms, only 3% of clusters matched the theoretically predicted Au 144 (SR) 60 structure, while a large proportion of the clusters were amorphous (i.e. did not match any model structure). However, a distinct ring-dot feature, characteristic of local icosahedral symmetry, was observed in about 20% of the clusters. Copyright © 2017. Published by Elsevier B.V.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Christian I.; Caldwell, Nelson; Rich, R. Michael

We present radial velocities and chemical abundances for red giant branch stars in the Galactic bulge globular clusters NGC 6342 and NGC 6366. The velocities and abundances are based on measurements of high-resolution ( R ≳ 20,000) spectra obtained with the MMT–Hectochelle and WIYN–Hydra spectrographs. We find that NGC 6342 has a heliocentric radial velocity of +112.5 km s{sup −1} ( σ = 8.6 km s{sup −1}), NGC 6366 has a heliocentric radial velocity of −122.3 km s{sup −1} ( σ = 1.5 km s{sup −1}), and both clusters have nearly identical metallicities ([Fe/H] ≈ −0.55). NGC 6366 shows evidencemore » of a moderately extended O–Na anti-correlation, but more data are needed for NGC 6342 to determine if this cluster also exhibits the typical O–Na relation likely found in all other Galactic globular clusters. The two clusters are distinguished from similar metallicity field stars as having larger [Na/Fe] spreads and enhanced [La/Fe] ratios, but we find that NGC 6342 and NGC 6366 display α and Fe-peak element abundance patterns that are typical of other metal-rich ([Fe/H] > −1) inner Galaxy clusters. However, the median [La/Fe] abundance may vary from cluster-to-cluster.« less

Simulations of the Formation and Evolution of X-ray Clusters

NASA Astrophysics Data System (ADS)

Bryan, G. L.; Klypin, A.; Norman, M. L.

1994-05-01

We describe results from a set of Omega = 1 Cold plus Hot Dark Matter (CHDM) and Cold Dark Matter (CDM) simulations. We examine the formation and evolution of X-ray clusters in a cosmological setting with sufficient numbers to perform statistical analysis. We find that CDM, normalized to COBE, seems to produce too many large clusters, both in terms of the luminosity (dn/dL) and temperature (dn/dT) functions. The CHDM simulation produces fewer clusters and the temperature distribution (our numerically most secure result) matches observations where they overlap. The computed cluster luminosity function drops below observations, but we are almost surely underestimating the X-ray luminosity. Because of the lower fluctuations in CHDM, there are only a small number of bright clusters in our simulation volume; however we can use the simulated clusters to fix the relation between temperature and velocity dispersion, allowing us to use collisionless N-body codes to probe larger length scales with correspondingly brighter clusters. The hydrodynamic simulations have been performed with a hybrid particle-mesh scheme for the dark matter and a high resolution grid-based piecewise parabolic method for the adiabatic gas dynamics. This combination has been implemented for massively parallel computers, allowing us to achive grids as large as 512(3) .

GLASS: The Grism Lens-Amplified Survey From Space. HST Grism Spectroscopy of the Frontier Fields.

NASA Astrophysics Data System (ADS)

Borello Schmidt, Kasper

2015-08-01

The Grism Lens-Amplified Survey From Space (GLASS) is a 140 orbit spectroscopic survey of 10 massive galaxy clusters, including the six Hubble Frontier Fields. GLASS has observed the cluster cores in the HST-WFC3 G102 and G141 grisms providing a wide wavelength coverage in the near-infrared from roughly 0.8 - 1.7 μm. The parallel fields were observed through the optical ACS G800L grism. Taking advantage of the lensing magnification of the clusters, GLASS reaches excellent spectroscopic limits of ˜10-18 erg/s/cm2 and improved spatial resolution for lensed sources behind the clusters. These features are particularly useful for the three main science drivers of GLASS, which are: I) Use the hundreds of spectra of galaxies at z>6 to shed light on the epoch of reionization, the role galaxies play in reionizing the universe, and the Lyα escape fraction at the cosmic dawn. II) Study gas accretion, star formation, and outflows by spatially mapping resolved star formation and determine metallicity gradients from emission lines at z˜2. III) Explore the environmental dependence of galaxy evolution using the first comprehensive census of spatially resolved star formation in dense environments, i.e., the cluster cores as well as the cluster infall regions. The former two benefit highly from the improved depth and increased resolution provided by the cluster lensing. Apart from the main science drivers, a slew of ancillary science has been enabled by the survey. One particularly interesting example is the search for supernovae in the more than 40 GLASS visits, which resulted in the detection of the first multiple imaged supernova, SN Refsdal. I will present the survey, give an update on the current science results, in particular on the GLASS galaxies at the epoch of reionization, and provide a status report on the GLASS data releases, which are continuously being made available to the community.

Cluster secondary ion mass spectrometry microscope mode mass spectrometry imaging.

PubMed

Kiss, András; Smith, Donald F; Jungmann, Julia H; Heeren, Ron M A

2013-12-30

Microscope mode imaging for secondary ion mass spectrometry is a technique with the promise of simultaneous high spatial resolution and high-speed imaging of biomolecules from complex surfaces. Technological developments such as new position-sensitive detectors, in combination with polyatomic primary ion sources, are required to exploit the full potential of microscope mode mass spectrometry imaging, i.e. to efficiently push the limits of ultra-high spatial resolution, sample throughput and sensitivity. In this work, a C60 primary source was combined with a commercial mass microscope for microscope mode secondary ion mass spectrometry imaging. The detector setup is a pixelated detector from the Medipix/Timepix family with high-voltage post-acceleration capabilities. The system's mass spectral and imaging performance is tested with various benchmark samples and thin tissue sections. The high secondary ion yield (with respect to 'traditional' monatomic primary ion sources) of the C60 primary ion source and the increased sensitivity of the high voltage detector setup improve microscope mode secondary ion mass spectrometry imaging. The analysis time and the signal-to-noise ratio are improved compared with other microscope mode imaging systems, all at high spatial resolution. We have demonstrated the unique capabilities of a C60 ion microscope with a Timepix detector for high spatial resolution microscope mode secondary ion mass spectrometry imaging. Copyright © 2013 John Wiley & Sons, Ltd.

High-resolution typing of Chlamydia trachomatis: epidemiological and clinical uses.

PubMed

de Vries, Henry J C; Schim van der Loeff, Maarten F; Bruisten, Sylvia M

2015-02-01

A state-of-the-art overview of molecular Chlamydia trachomatis typing methods that are used for routine diagnostics and scientific studies. Molecular epidemiology uses high-resolution typing techniques such as multilocus sequence typing, multilocus variable number of tandem repeats analysis, and whole-genome sequencing to identify strains based on their DNA sequence. These data can be used for cluster, network and phylogenetic analyses, and are used to unveil transmission networks, risk groups, and evolutionary pathways. High-resolution typing of C. trachomatis strains is applied to monitor treatment efficacy and re-infections, and to study the recent emergence of lymphogranuloma venereum (LGV) amongst men who have sex with men in high-income countries. Chlamydia strain typing has clinical relevance in disease management, as LGV needs longer treatment than non-LGV C. trachomatis. It has also led to the discovery of a new variant Chlamydia strain in Sweden, which was not detected by some commercial C. trachomatis diagnostic platforms. After a brief history and comparison of the various Chlamydia typing methods, the applications of the current techniques are described and future endeavors to extend scientific understanding are formulated. High-resolution typing will likely help to further unravel the pathophysiological mechanisms behind the wide clinical spectrum of chlamydial disease.

Magnesium Isotope Ratios in ω Centauri Red Giants

NASA Astrophysics Data System (ADS)

Da Costa, G. S.; Norris, John E.; Yong, David

2013-05-01

We have used the high-resolution observations obtained at the Anglo-Australian Telescope with Ultra-High Resolution Facility (R ~ 100,000) and at Gemini-S with b-HROS (R ~ 150,000) to determine magnesium isotope ratios for seven ω Cen red giants that cover a range in iron abundance from [Fe/H] = -1.78 to -0.78 dex, and for two red giants in M4 (NGC 6121). The ω Cen stars sample both the "primordial" (i.e., O-rich, Na- and Al-poor) and the "extreme" (O-depleted, Na- and Al-rich) populations in the cluster. The primordial population stars in both ω Cen and M4 show (25Mg, 26Mg)/24Mg isotopic ratios that are consistent with those found for the primordial population in other globular clusters with similar [Fe/H] values. The isotopic ratios for the ω Cen extreme stars are also consistent with those for extreme population stars in other clusters. The results for the extreme population stars studied indicate that the 26Mg/24Mg ratio is highest at intermediate metallicities ([Fe/H] < -1.4 dex), and for the highest [Al/Fe] values. Further, the relative abundance of 26Mg in the extreme population stars is notably higher than that of 25Mg, in contrast to model predictions. The 25Mg/24Mg isotopic ratio in fact does not show any obvious dependence on either [Fe/H] or [Al/Fe] nor, intriguingly, any obvious difference between the primordial and extreme population stars.

High-Resolution Melting-Curve Analysis of Ligation-Mediated Real-Time PCR for Rapid Evaluation of an Epidemiological Outbreak of Extended-Spectrum-Beta-Lactamase-Producing Escherichia coli ▿

PubMed Central

Woksepp, Hanna; Jernberg, Cecilia; Tärnberg, Maria; Ryberg, Anna; Brolund, Alma; Nordvall, Michaela; Olsson-Liljequist, Barbro; Wisell, Karin Tegmark; Monstein, Hans-Jürg; Nilsson, Lennart E.; Schön, Thomas

2011-01-01

Methods for the confirmation of nosocomial outbreaks of bacterial pathogens are complex, expensive, and time-consuming. Recently, a method based on ligation-mediated PCR (LM/PCR) using a low denaturation temperature which produces specific melting-profile patterns of DNA products has been described. Our objective was to further develop this method for real-time PCR and high-resolution melting analysis (HRM) in a single-tube system optimized in order to achieve results within 1 day. Following the optimization of LM/PCR for real-time PCR and HRM (LM/HRM), the method was applied for a nosocomial outbreak of extended-spectrum-beta-lactamase (ESBL)-producing and ST131-associated Escherichia coli isolates (n = 15) and control isolates (n = 29), including four previous clusters. The results from LM/HRM were compared to results from pulsed-field gel electrophoresis (PFGE), which served as the gold standard. All isolates from the nosocomial outbreak clustered by LM/HRM, which was confirmed by gel electrophoresis of the LM/PCR products and PFGE. Control isolates that clustered by LM/PCR (n = 4) but not by PFGE were resolved by confirmatory gel electrophoresis. We conclude that LM/HRM is a rapid method for the detection of nosocomial outbreaks of bacterial infections caused by ESBL-producing E. coli strains. It allows the analysis of isolates in a single-tube system within a day, and the discriminatory power is comparable to that of PFGE. PMID:21956981

High-resolution melting-curve analysis of ligation-mediated real-time PCR for rapid evaluation of an epidemiological outbreak of extended-spectrum-beta-lactamase-producing Escherichia coli.

PubMed

Woksepp, Hanna; Jernberg, Cecilia; Tärnberg, Maria; Ryberg, Anna; Brolund, Alma; Nordvall, Michaela; Olsson-Liljequist, Barbro; Wisell, Karin Tegmark; Monstein, Hans-Jürg; Nilsson, Lennart E; Schön, Thomas

2011-12-01

Methods for the confirmation of nosocomial outbreaks of bacterial pathogens are complex, expensive, and time-consuming. Recently, a method based on ligation-mediated PCR (LM/PCR) using a low denaturation temperature which produces specific melting-profile patterns of DNA products has been described. Our objective was to further develop this method for real-time PCR and high-resolution melting analysis (HRM) in a single-tube system optimized in order to achieve results within 1 day. Following the optimization of LM/PCR for real-time PCR and HRM (LM/HRM), the method was applied for a nosocomial outbreak of extended-spectrum-beta-lactamase (ESBL)-producing and ST131-associated Escherichia coli isolates (n = 15) and control isolates (n = 29), including four previous clusters. The results from LM/HRM were compared to results from pulsed-field gel electrophoresis (PFGE), which served as the gold standard. All isolates from the nosocomial outbreak clustered by LM/HRM, which was confirmed by gel electrophoresis of the LM/PCR products and PFGE. Control isolates that clustered by LM/PCR (n = 4) but not by PFGE were resolved by confirmatory gel electrophoresis. We conclude that LM/HRM is a rapid method for the detection of nosocomial outbreaks of bacterial infections caused by ESBL-producing E. coli strains. It allows the analysis of isolates in a single-tube system within a day, and the discriminatory power is comparable to that of PFGE.

Establishing a community-wide DNA barcode library as a new tool for arctic research.

PubMed

Wirta, H; Várkonyi, G; Rasmussen, C; Kaartinen, R; Schmidt, N M; Hebert, P D N; Barták, M; Blagoev, G; Disney, H; Ertl, S; Gjelstrup, P; Gwiazdowicz, D J; Huldén, L; Ilmonen, J; Jakovlev, J; Jaschhof, M; Kahanpää, J; Kankaanpää, T; Krogh, P H; Labbee, R; Lettner, C; Michelsen, V; Nielsen, S A; Nielsen, T R; Paasivirta, L; Pedersen, S; Pohjoismäki, J; Salmela, J; Vilkamaa, P; Väre, H; von Tschirnhaus, M; Roslin, T

2016-05-01

DNA sequences offer powerful tools for describing the members and interactions of natural communities. In this study, we establish the to-date most comprehensive library of DNA barcodes for a terrestrial site, including all known macroscopic animals and vascular plants of an intensively studied area of the High Arctic, the Zackenberg Valley in Northeast Greenland. To demonstrate its utility, we apply the library to identify nearly 20 000 arthropod individuals from two Malaise traps, each operated for two summers. Drawing on this material, we estimate the coverage of previous morphology-based species inventories, derive a snapshot of faunal turnover in space and time and describe the abundance and phenology of species in the rapidly changing arctic environment. Overall, 403 terrestrial animal and 160 vascular plant species were recorded by morphology-based techniques. DNA barcodes (CO1) offered high resolution in discriminating among the local animal taxa, with 92% of morphologically distinguishable taxa assigned to unique Barcode Index Numbers (BINs) and 93% to monophyletic clusters. For vascular plants, resolution was lower, with 54% of species forming monophyletic clusters based on barcode regions rbcLa and ITS2. Malaise catches revealed 122 BINs not detected by previous sampling and DNA barcoding. The insect community was dominated by a few highly abundant taxa. Even closely related taxa differed in phenology, emphasizing the need for species-level resolution when describing ongoing shifts in arctic communities and ecosystems. The DNA barcode library now established for Zackenberg offers new scope for such explorations, and for the detailed dissection of interspecific interactions throughout the community. © 2015 John Wiley & Sons Ltd.

ULTRA-COMPACT DWARFS IN THE COMA CLUSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiboucas, Kristin; Tully, R. Brent; Marzke, R. O.

2011-08-20

We have undertaken a spectroscopic search for ultra-compact dwarf galaxies (UCDs) in the dense core of the dynamically evolved, massive Coma cluster as part of the Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) Coma Cluster Treasury Survey. UCD candidates were initially chosen based on color, magnitude, degree of resolution within the ACS images, and the known properties of Fornax and Virgo UCDs. Follow-up spectroscopy with Keck/Low-Resolution Imaging Spectrometer confirmed 27 candidates as members of the Coma cluster, a success rate >60% for targeted objects brighter than M{sub R} = -12. Another 14 candidates may also prove to be Coma members,more » but low signal-to-noise spectra prevent definitive conclusions. An investigation of the properties and distribution of the Coma UCDs finds these objects to be very similar to UCDs discovered in other environments. The Coma UCDs tend to be clustered around giant galaxies in the cluster core and have colors/metallicity that correlate with the host galaxy. With properties and a distribution similar to that of the Coma cluster globular cluster population, we find strong support for a star cluster origin for the majority of the Coma UCDs. However, a few UCDs appear to have stellar population or structural properties which differentiate them from the old star cluster populations found in the Coma cluster, perhaps indicating that UCDs may form through multiple formation channels.« less

The structure of deposited metal clusters generated by laser evaporation

NASA Astrophysics Data System (ADS)

Faust, P.; Brandstättner, M.; Ding, A.

1991-09-01

Metal clusters have been produced using a laser evaporation source. A Nd-YAG laser beam focused onto a solid silver rod was used to evaporate the material, which was then cooled to form clusters with the help of a pulsed high pressure He beam. TOF mass spectra of these clusters reveal a strong occurrence of small and medium sized clusters ( n<100). Clusters were also deposited onto grid supported thin layers of carbon-films which were investigated by transmission electron microscopy. Very high resolution pictures of these grids were used to analyze the size distribution and the structure of the deposited clusters. The diffraction pattern caused by crystalline structure of the clusters reveals 3-and 5-fold symmetries as well as fcc bulk structure. This can be explained in terms of icosahedron and cuboctahedron type clusters deposited on the surface of the carbon layer. There is strong evidence that part of these cluster geometries had already been formed before the depostion process. The non-linear dependence of the cluster size and the cluster density on the generating conditions is discussed. Therefore the samples were observed in HREM in the stable DEEKO 100 microscope of the Fritz-Haber-Institut operating at 100 KV with the spherical aberration c S =0.5 mm. The quality of the pictures was improved by using the conditions of minimum phase contrast hollow cone illumination. This procedure led to a minimum of phase contrast artefacts. Among the well-crystallized particles were a great amount of five- and three-fold symmetries, icosahedra and cuboctahedra respectively. The largest clusters with five- and three-fold symmetries have been found with diameters of 7 nm; the smallest particles displaying the same undistorted symmetries were of about 2 mm. Even smaller ones with strong distortions could be observed although their classification is difficult. The quality of the images was improved by applying Fourier filtering techniques.

NGC 6273: Towards Defining A New Class of Galactic Globular Clusters?

NASA Astrophysics Data System (ADS)

Johnson, Christian I.; Rich, Robert Michael; Pilachowski, Catherine A.; Caldwell, Nelson; Mateo, Mario L.; Ira Bailey, John; Crane, Jeffrey D.

2016-01-01

A growing number of observations have found that several Galactic globular clusters exhibit abundance dispersions beyond the well-known light element (anti-)correlations. These clusters tend to be very massive, have >0.1 dex intrinsic metallicity dispersions, have complex sub-giant branch morphologies, and have correlated [Fe/H] and s-process element enhancements. Interestingly, nearly all of these clusters discovered so far have [Fe/H]~-1.7. In this context, we have examined the chemical composition of 18 red giant branch (RGB) stars in the massive, metal-poor Galactic bulge globular cluster NGC 6273 using high signal-to-noise, high resolution (R~27,000) spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph mounted on the Magellan-Clay 6.5m telescope at Las Campanas Observatory. We find that the cluster exhibits a metallicity range from [Fe/H]=-1.80 to -1.30 and is composed of two dominant populations separated in [Fe/H] and [La/Fe] abundance. The increase in [La/Eu] as a function of [La/H] suggests that the increase in [La/Fe] with [Fe/H] is due to almost pure s-process enrichment. The most metal-rich star in our sample is not strongly La-enhanced, but is α-poor and may belong to a third "anomalous" stellar population. The two dominant populations exhibit the same [Na/Fe]-[Al/Fe] correlation found in other "normal" globular clusters. Therefore, NGC 6273 joins ω Centauri, M 22, M 2, and NGC 5286 as a possible new class of Galactic globular clusters.

Numerical analysis of base flowfield at high altitude for a four-engine clustered nozzle configuration

NASA Technical Reports Server (NTRS)

Wang, Ten-See

1993-01-01

The objective of this study is to benchmark a four-engine clustered nozzle base flowfield with a computational fluid dynamics (CFD) model. The CFD model is a pressure based, viscous flow formulation. An adaptive upwind scheme is employed for the spatial discretization. The upwind scheme is based on second and fourth order central differencing with adaptive artificial dissipation. Qualitative base flow features such as the reverse jet, wall jet, recompression shock, and plume-plume impingement have been captured. The computed quantitative flow properties such as the radial base pressure distribution, model centerline Mach number and static pressure variation, and base pressure characteristic curve agreed reasonably well with those of the measurement. Parametric study on the effect of grid resolution, turbulence model, inlet boundary condition and difference scheme on convective terms has been performed. The results showed that grid resolution and turbulence model are two primary factors that influence the accuracy of the base flowfield prediction.

Clustering methods applied in the detection of Ki67 hot-spots in whole tumor slide images: an efficient way to characterize heterogeneous tissue-based biomarkers.

PubMed

Lopez, Xavier Moles; Debeir, Olivier; Maris, Calliope; Rorive, Sandrine; Roland, Isabelle; Saerens, Marco; Salmon, Isabelle; Decaestecker, Christine

2012-09-01

Whole-slide scanners allow the digitization of an entire histological slide at very high resolution. This new acquisition technique opens a wide range of possibilities for addressing challenging image analysis problems, including the identification of tissue-based biomarkers. In this study, we use whole-slide scanner technology for imaging the proliferating activity patterns in tumor slides based on Ki67 immunohistochemistry. Faced with large images, pathologists require tools that can help them identify tumor regions that exhibit high proliferating activity, called "hot-spots" (HSs). Pathologists need tools that can quantitatively characterize these HS patterns. To respond to this clinical need, the present study investigates various clustering methods with the aim of identifying Ki67 HSs in whole tumor slide images. This task requires a method capable of identifying an unknown number of clusters, which may be highly variable in terms of shape, size, and density. We developed a hybrid clustering method, referred to as Seedlink. Compared to manual HS selections by three pathologists, we show that Seedlink provides an efficient way of detecting Ki67 HSs and improves the agreement among pathologists when identifying HSs. Copyright © 2012 International Society for Advancement of Cytometry.

Methods in Computational Cosmology

NASA Astrophysics Data System (ADS)

Vakili, Mohammadjavad

State of the inhomogeneous universe and its geometry throughout cosmic history can be studied by measuring the clustering of galaxies and the gravitational lensing of distant faint galaxies. Lensing and clustering measurements from large datasets provided by modern galaxy surveys will forever shape our understanding of the how the universe expands and how the structures grow. Interpretation of these rich datasets requires careful characterization of uncertainties at different stages of data analysis: estimation of the signal, estimation of the signal uncertainties, model predictions, and connecting the model to the signal through probabilistic means. In this thesis, we attempt to address some aspects of these challenges. The first step in cosmological weak lensing analyses is accurate estimation of the distortion of the light profiles of galaxies by large scale structure. These small distortions, known as the cosmic shear signal, are dominated by extra distortions due to telescope optics and atmosphere (in the case of ground-based imaging). This effect is captured by a kernel known as the Point Spread Function (PSF) that needs to be fully estimated and corrected for. We address two challenges a head of accurate PSF modeling for weak lensing studies. The first challenge is finding the centers of point sources that are used for empirical estimation of the PSF. We show that the approximate methods for centroiding stars in wide surveys are able to optimally saturate the information content that is retrievable from astronomical images in the presence of noise. The fist step in weak lensing studies is estimating the shear signal by accurately measuring the shapes of galaxies. Galaxy shape measurement involves modeling the light profile of galaxies convolved with the light profile of the PSF. Detectors of many space-based telescopes such as the Hubble Space Telescope (HST) sample the PSF with low resolution. Reliable weak lensing analysis of galaxies observed by the HST camera requires knowledge of the PSF at a resolution higher than the pixel resolution of HST. This PSF is called the super-resolution PSF. In particular, we present a forward model of the point sources imaged through filters of the HST WFC3 IR channel. We show that this forward model can accurately estimate the super-resolution PSF. We also introduce a noise model that permits us to robustly analyze the HST WFC3 IR observations of the crowded fields. Then we try to address one of the theoretical uncertainties in modeling of galaxy clustering on small scales. Study of small scale clustering requires assuming a halo model. Clustering of halos has been shown to depend on halo properties beyond mass such as halo concentration, a phenomenon referred to as assembly bias. Standard large-scale structure studies with halo occupation distribution (HOD) assume that halo mass alone is sufficient to characterize the connection between galaxies and halos. However, assembly bias could cause the modeling of galaxy clustering to face systematic effects if the expected number of galaxies in halos is correlated with other halo properties. Using high resolution N-body simulations and the clustering measurements of Sloan Digital Sky Survey (SDSS) DR7 main galaxy sample, we show that modeling of galaxy clustering can slightly improve if we allow the HOD model to depend on halo properties beyond mass. One of the key ingredients in precise parameter inference using galaxy clustering is accurate estimation of the error covariance matrix of clustering measurements. This requires generation of many independent galaxy mock catalogs that accurately describe the statistical distribution of galaxies in a wide range of physical scales. We present a fast and accurate method based on low-resolution N-body simulations and an empirical bias model for generating mock catalogs. We use fast particle mesh gravity solvers for generation of dark matter density field and we use Markov Chain Monti Carlo (MCMC) to estimate the bias model that connects dark matter to galaxies. We show that this approach enables the fast generation of mock catalogs that recover clustering at a percent-level accuracy down to quasi-nonlinear scales. Cosmological datasets are interpreted by specifying likelihood functions that are often assumed to be multivariate Gaussian. Likelihood free approaches such as Approximate Bayesian Computation (ABC) can bypass this assumption by introducing a generative forward model of the data and a distance metric for quantifying the closeness of the data and the model. We present the first application of ABC in large scale structure for constraining the connections between galaxies and dark matter halos. We present an implementation of ABC equipped with Population Monte Carlo and a generative forward model of the data that incorporates sample variance and systematic uncertainties. (Abstract shortened by ProQuest.).

X-ray-emitting filaments in the cooling flow cluster A2029

NASA Technical Reports Server (NTRS)

Sarazin, Craig L.; O'Connell, Robert W.; Mcnamara, Brian R.

1992-01-01

High-resolution X-ray observations of the cluster A2029 are presented which confirm the presence of a cooling flow, despite the lack of optical line emission or evidence for recent star formation. The cooling rate and radius are about 370 solar mass/yr and 230 kpc, respectively. Emission from the inner cooling flow is dominated by a number of X-ray-emitting filaments. This may be the first case where such inhomogeneities are clearly resolved. The filaments are theorized to be supported in part by magnetic fields and may be connected with the filaments of very strong Faraday rotation seen in several nearly cooling flows.

National Laboratory for Advanced Scientific Visualization at UNAM - Mexico

NASA Astrophysics Data System (ADS)

Manea, Marina; Constantin Manea, Vlad; Varela, Alfredo

2016-04-01

In 2015, the National Autonomous University of Mexico (UNAM) joined the family of Universities and Research Centers where advanced visualization and computing plays a key role to promote and advance missions in research, education, community outreach, as well as business-oriented consulting. This initiative provides access to a great variety of advanced hardware and software resources and offers a range of consulting services that spans a variety of areas related to scientific visualization, among which are: neuroanatomy, embryonic development, genome related studies, geosciences, geography, physics and mathematics related disciplines. The National Laboratory for Advanced Scientific Visualization delivers services through three main infrastructure environments: the 3D fully immersive display system Cave, the high resolution parallel visualization system Powerwall, the high resolution spherical displays Earth Simulator. The entire visualization infrastructure is interconnected to a high-performance-computing-cluster (HPCC) called ADA in honor to Ada Lovelace, considered to be the first computer programmer. The Cave is an extra large 3.6m wide room with projected images on the front, left and right, as well as floor walls. Specialized crystal eyes LCD-shutter glasses provide a strong stereo depth perception, and a variety of tracking devices allow software to track the position of a user's hand, head and wand. The Powerwall is designed to bring large amounts of complex data together through parallel computing for team interaction and collaboration. This system is composed by 24 (6x4) high-resolution ultra-thin (2 mm) bezel monitors connected to a high-performance GPU cluster. The Earth Simulator is a large (60") high-resolution spherical display used for global-scale data visualization like geophysical, meteorological, climate and ecology data. The HPCC-ADA, is a 1000+ computing core system, which offers parallel computing resources to applications that requires large quantity of memory as well as large and fast parallel storage systems. The entire system temperature is controlled by an energy and space efficient cooling solution, based on large rear door liquid cooled heat exchangers. This state-of-the-art infrastructure will boost research activities in the region, offer a powerful scientific tool for teaching at undergraduate and graduate levels, and enhance association and cooperation with business-oriented organizations.

Resolutions of the Coulomb operator: VIII. Parallel implementation using the modern programming language X10.

PubMed

Limpanuparb, Taweetham; Milthorpe, Josh; Rendell, Alistair P

2014-10-30

Use of the modern parallel programming language X10 for computing long-range Coulomb and exchange interactions is presented. By using X10, a partitioned global address space language with support for task parallelism and the explicit representation of data locality, the resolution of the Ewald operator can be parallelized in a straightforward manner including use of both intranode and internode parallelism. We evaluate four different schemes for dynamic load balancing of integral calculation using X10's work stealing runtime, and report performance results for long-range HF energy calculation of large molecule/high quality basis running on up to 1024 cores of a high performance cluster machine. Copyright © 2014 Wiley Periodicals, Inc.

The Advanced Gamma-ray Imaging System (AGIS): Extragalactic Science

NASA Astrophysics Data System (ADS)

Coppi, Paolo S.; Extragalactic Science Working Group; AGIS Collaboration

2010-03-01

The Advanced Gamma-ray Imaging System (AGIS), a proposed next-generation array of Cherenkov telescopes, will provide an unprecedented view of the high energy universe. We discuss how AGIS, with its larger effective area, improved angular resolution, lower threshold, and an order of magnitude increase in sensitivity, impacts the extragalactic science possible in the very high energy domain. Likely source classes detectable by AGIS include AGN, GRBs, clusters, star-forming galaxies, and possibly the cascade radiation surrounding powerful cosmic accelerators. AGIS should see many of the sources discovered by Fermi. With its better sensitivity and angular resolution, AGIS then becomes a key instrument for identifying and characterizing Fermi survey sources, the majority of which will have limited Fermi photon statistics and localizations.

Matilda: A mass filtered nanocluster source

NASA Astrophysics Data System (ADS)

Kwon, Gihan

Cluster science provides a good model system for the study of the size dependence of electronic properties, chemical reactivity, as well as magnetic properties of materials. One of the main interests in cluster science is the nanoscale understanding of chemical reactions and selectivity in catalysis. Therefore, a new cluster system was constructed to study catalysts for applications in renewable energy. Matilda, a nanocluster source, consists of a cluster source and a Retarding Field Analyzer (RFA). A moveable AJA A310 Series 1"-diameter magnetron sputtering gun enclosed in a water cooled aggregation tube served as the cluster source. A silver coin was used for the sputtering target. The sputtering pressure in the aggregation tube was controlled, ranging from 0.07 to 1torr, using a mass flow controller. The mean cluster size was found to be a function of relative partial pressure (He/Ar), sputtering power, and aggregation length. The kinetic energy distribution of ionized clusters was measured with the RFA. The maximum ion energy distribution was 2.9 eV/atom at a zero pressure ratio. At high Ar flow rates, the mean cluster size was 20 ˜ 80nm, and at a 9.5 partial pressure ratio, the mean cluster size was reduced to 1.6nm. Our results showed that the He gas pressure can be optimized to reduce the cluster size variations. Results from SIMION, which is an electron optics simulation package, supported the basic function of an RFA, a three-element lens and the magnetic sector mass filter. These simulated results agreed with experimental data. For the size selection experiment, the channeltron electron multiplier collected ionized cluster signal at different positions during Ag deposition on a TEM grid for four and half hours. The cluster signal was high at the position for neutral clusters, which was not bent by a magnetic field, and the signal decreased rapidly far away from the neutral cluster region. For cluster separation according to mass to charge ratio in a magnetic sector mass filter, the ion energy of the cluster and its distribution must be precisely controlled by acceleration or deceleration. To verify the size separation, a high resolution microscope was required. Matilda provided narrow particle sized distribution from atomic scale to 4nm in size with different pressure ratio without additional mass filter. It is very economical way to produce relatively narrow particle size distribution.

High Resolution Imaging Testbed Utilizing Sodium Laser Guide Star Adaptive Optics: The Real Time Wavefront Reconstructor Computer

DTIC Science & Technology

2008-07-31

Unlike the Lyrtech, each DSP on a Bittware board offers 3 MB of on-chip memory and 3 GFLOPs of 32-bit peak processing power. Based on the performance...Each NVIDIA 8800 Ultra features 576 GFLOPS on 128 612-MHz single-precision floating-point SIMD processors, arranged in 16 clusters of eight. Each

Two Massive White Dwarfs from NGC 2323 and the Initial-Final Mass Relation for Progenitors of 4 to 6.5 M

NASA Astrophysics Data System (ADS)

Cummings, Jeffrey D.; Kalirai, Jason S.; Tremblay, P.-E.; Ramirez-Ruiz, Enrico

2016-02-01

We observed a sample of 10 white dwarf candidates in the rich open cluster NGC 2323 (M50) with the Keck Low-Resolution Imaging Spectrometer. The spectroscopy shows eight to be DA white dwarfs, with six of these having high signal-to-noise ratio appropriate for our analysis. Two of these white dwarfs are consistent with singly evolved cluster membership, and both are high mass ˜1.07 M⊙, and give equivalent progenitor masses of 4.69 M⊙. To supplement these new high-mass white dwarfs and analyze the initial-final mass relation (IFMR), we also looked at 30 white dwarfs from publicly available data that are mostly all high-mass (≳ 0.9 M⊙). These original published data exhibited significant scatter, and to test if this scatter is true or simply the result of systematics, we have uniformly analyzed the white dwarf spectra and have adopted thorough photometric techniques to derive uniform cluster parameters for their parent clusters. The resulting IFMR scatter is significantly reduced, arguing that mass-loss rates are not stochastic in nature and that within the ranges of metallicity and mass analyzed in this work mass loss is not highly sensitive to variations in metallicity. Lastly, when adopting cluster ages based on Y2 isochrones, the slope of the high-mass IFMR remains steep and consistent with that found from intermediate-mass white dwarfs, giving a linear IFMR from progenitor masses between 3 and 6.5 M⊙. In contrast, when adopting the slightly younger cluster ages based on PARSEC isochrones, the high-mass IFMR has a moderate turnover near an initial mass of 4 M⊙. Based on observations with the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, was made possible by the generous financial support of the W.M. Keck Foundation.

Automatic building detection based on Purposive FastICA (PFICA) algorithm using monocular high resolution Google Earth images

NASA Astrophysics Data System (ADS)

Ghaffarian, Saman; Ghaffarian, Salar

2014-11-01

This paper proposes an improved FastICA model named as Purposive FastICA (PFICA) with initializing by a simple color space transformation and a novel masking approach to automatically detect buildings from high resolution Google Earth imagery. ICA and FastICA algorithms are defined as Blind Source Separation (BSS) techniques for unmixing source signals using the reference data sets. In order to overcome the limitations of the ICA and FastICA algorithms and make them purposeful, we developed a novel method involving three main steps: 1-Improving the FastICA algorithm using Moore-Penrose pseudo inverse matrix model, 2-Automated seeding of the PFICA algorithm based on LUV color space and proposed simple rules to split image into three regions; shadow + vegetation, baresoil + roads and buildings, respectively, 3-Masking out the final building detection results from PFICA outputs utilizing the K-means clustering algorithm with two number of clusters and conducting simple morphological operations to remove noises. Evaluation of the results illustrates that buildings detected from dense and suburban districts with divers characteristics and color combinations using our proposed method have 88.6% and 85.5% overall pixel-based and object-based precision performances, respectively.

Whole Genome Sequence and Phylogenetic Analysis Show Helicobacter pylori Strains from Latin America Have Followed a Unique Evolution Pathway

PubMed Central

Muñoz-Ramírez, Zilia Y.; Mendez-Tenorio, Alfonso; Kato, Ikuko; Bravo, Maria M.; Rizzato, Cosmeri; Thorell, Kaisa; Torres, Roberto; Aviles-Jimenez, Francisco; Camorlinga, Margarita; Canzian, Federico; Torres, Javier

2017-01-01

Helicobacter pylori (HP) genetics may determine its clinical outcomes. Despite high prevalence of HP infection in Latin America (LA), there have been no phylogenetic studies in the region. We aimed to understand the structure of HP populations in LA mestizo individuals, where gastric cancer incidence remains high. The genome of 107 HP strains from Mexico, Nicaragua and Colombia were analyzed with 59 publicly available worldwide genomes. To study bacterial relationship on whole genome level we propose a virtual hybridization technique using thousands of high-entropy 13 bp DNA probes to generate fingerprints. Phylogenetic virtual genome fingerprint (VGF) was compared with Multi Locus Sequence Analysis (MLST) and with phylogenetic analyses of cagPAI virulence island sequences. With MLST some Nicaraguan and Mexican strains clustered close to Africa isolates, whereas European isolates were spread without clustering and intermingled with LA isolates. VGF analysis resulted in increased resolution of populations, separating European from LA strains. Furthermore, clusters with exclusively Colombian, Mexican, or Nicaraguan strains were observed, where the Colombian cluster separated from Europe, Asia, and Africa, while Nicaraguan and Mexican clades grouped close to Africa. In addition, a mixed large LA cluster including Mexican, Colombian, Nicaraguan, Peruvian, and Salvadorian strains was observed; all LA clusters separated from the Amerind clade. With cagPAI sequence analyses LA clades clearly separated from Europe, Asia and Amerind, and Colombian strains formed a single cluster. A NeighborNet analyses suggested frequent and recent recombination events particularly among LA strains. Results suggests that in the new world, H. pylori has evolved to fit mestizo LA populations, already 500 years after the Spanish colonization. This co-adaption may account for regional variability in gastric cancer risk. PMID:28293542

New z>2 clusters unveiled by Planck, Herschel & Spitzer - prospects for JWST & Euclid

NASA Astrophysics Data System (ADS)

Dole, Herve A.

2015-08-01

Searching for z>2 clusters/protoclusters is an active field in cosmology, and quite successfull using wide near-infrared surveys (e.g. Spitzer). We present a new approach by selecting highly star forming high-z cluster candidates over the whole sky using Planck, taking benefit of the redshifted far-infrared peak into the Planck submillimetre channels and a clean component separation (among which Galactic cirrus & CMB). Out of more than 1000 Planck high-z candidates, about 230 were confirmed by a Herschel/SPIRE follow-up as significant overdensities of red sources, confirming their high-z spectral energy distribution and high star formation rates (typically 700 Msun/yr per SPIRE source, and >5000 Msun/yr for each structure). These overdensities could be protoclusters in their intense star formation phase. Few targets have spectroscopic redshift (in the NIR and mm) confirmations, all in the range 1.7-2.3, while photometric analysis indicates z>2 for all the Planck counterparts.The key points here are the wavelength plus the angular and resolution coverage from Planck, Herschel and Spitzer. 40 fields were followed-up by Spitzer down to 1uJy 5sigma, and show unambiguous presence of galaxy overdensities compatible with z~2 based on color analysis on 4 band photometry (J, K, 3.6 and 4.5um). These targetted Spitzer observations can serve as pilot project for the more extended data coming in the next decade with JWST and Euclid.This new window on the high-z (z>2) protocluster may yield powerful constraints on structure formation (e.g., SFR vs environnement at high-z, z>2 mass assembly in clusters, bias). Furthermore, these objects will allow to better quantify the prediction for clusters to be detected by WFIRST and Euclid. Finally, these clusters will help us extending the current search for high-z clusters, in nice complementarity with current selections in the near-infrared (dominated by stellar mass) and the millimeter (dominated by hot gas and SZ effect), using the far-infrared and submillimetre (dominated by star formation). My talk will review all these aspects.

New z>2 clusters unveiled by Planck, Herschel & Spitzer - prospects for JWST, Euclid, WFIRST

NASA Astrophysics Data System (ADS)

Dole, Herve A.

2015-08-01

Searching for z>2 clusters/protoclusters is an active field in cosmology, and quite successfull using wide near-infrared surveys (e.g. Spitzer). We present a new approach by selecting highly star forming high-z cluster candidates over the whole sky using Planck, taking benefit of the redshifted far-infrared peak into the Planck submillimetre channels and a clean component separation (among which Galactic cirrus & CMB). Out of more than 1000 Planck high-z candidates, about 230 were confirmed by a Herschel/SPIRE follow-up as significant overdensities of red sources, confirming their high-z spectral energy distribution and high star formation rates (typically 700 Msun/yr per SPIRE source, and >5000 Msun/yr for each structure). These overdensities could be protoclusters in their intense star formation phase. Few targets have spectroscopic redshift (in the NIR and mm) confirmations, all in the range 1.7-2.3, while photometric analysis indicates z>2 for all the Planck counterparts.The key points here are the wavelength plus the angular and resolution coverage from Planck, Herschel and Spitzer. 40 fields were followed-up by Spitzer down to 1uJy 5sigma, and show unambiguous presence of galaxy overdensities compatible with z~2 based on color analysis on 4 band photometry (J, K, 3.6 and 4.5um). These targetted Spitzer observations can serve as pilot project for the more extended data coming in the next decade with JWST and Euclid.This new window on the high-z (z>2) protocluster may yield powerful constraints on structure formation (e.g., SFR vs environnement at high-z, z>2 mass assembly in clusters, bias). Furthermore, these objects will allow to better quantify the prediction for clusters to be detected by WFIRST and Euclid. Finally, these clusters will help us extending the current search for high-z clusters, in nice complementarity with current selections in the near-infrared (dominated by stellar mass) and the millimeter (dominated by hot gas and SZ effect), using the far-infrared and submillimetre (dominated by star formation). My talk will review all these aspects.

A versatile genome-scale PCR-based pipeline for high-definition DNA FISH.

PubMed

Bienko, Magda; Crosetto, Nicola; Teytelman, Leonid; Klemm, Sandy; Itzkovitz, Shalev; van Oudenaarden, Alexander

2013-02-01

We developed a cost-effective genome-scale PCR-based method for high-definition DNA FISH (HD-FISH). We visualized gene loci with diffraction-limited resolution, chromosomes as spot clusters and single genes together with transcripts by combining HD-FISH with single-molecule RNA FISH. We provide a database of over 4.3 million primer pairs targeting the human and mouse genomes that is readily usable for rapid and flexible generation of probes.

X-Ray Properties of AGN in Brightest Cluster Galaxies. I. A Systematic Study of the Chandra Archive in the 0.2 < z < 0.3 and 0.55 < z < 0.75 Redshift Range

NASA Astrophysics Data System (ADS)

Yang, Lilan; Tozzi, Paolo; Yu, Heng; Lusso, Elisabeta; Gaspari, Massimo; Gilli, Roberto; Nardini, Emanuele; Risaliti, Guido

2018-05-01

We present a search for nuclear X-ray emission in the brightest cluster galaxies (BCGs) of a sample of groups and clusters of galaxies extracted from the Chandra archive. The exquisite angular resolution of Chandra allows us to obtain robust photometry at the position of the BCG, and to firmly identify unresolved X-ray emission when present, thanks to an accurate characterization of the extended emission at the BCG position. We consider two redshift bins (0.2 < z < 0.3 and 0.55 < z < 0.75) and analyze all the clusters observed by Chandra with exposure time larger than 20 ks. Our samples have 81 BCGs in 73 clusters and 51 BCGs in 49 clusters in the low- and high-redshift bins, respectively. X-ray emission in the soft (0.5–2 keV) or hard (2–7 keV) band is detected only in 14 and 9 BCGs (∼18% of the total samples), respectively. The X-ray photometry shows that at least half of the BCGs have a high hardness ratio, compatible with significant intrinsic absorption. This is confirmed by the spectral analysis with a power-law model plus intrinsic absorption. We compute the fraction of X-ray bright BCGs above a given hard X-ray luminosity, considering only sources with positive photometry in the hard band (12/5 sources in the low/high-z sample).

Object Manifold Alignment for Multi-Temporal High Resolution Remote Sensing Images Classification

NASA Astrophysics Data System (ADS)

Gao, G.; Zhang, M.; Gu, Y.

2017-05-01

Multi-temporal remote sensing images classification is very useful for monitoring the land cover changes. Traditional approaches in this field mainly face to limited labelled samples and spectral drift of image information. With spatial resolution improvement, "pepper and salt" appears and classification results will be effected when the pixelwise classification algorithms are applied to high-resolution satellite images, in which the spatial relationship among the pixels is ignored. For classifying the multi-temporal high resolution images with limited labelled samples, spectral drift and "pepper and salt" problem, an object-based manifold alignment method is proposed. Firstly, multi-temporal multispectral images are cut to superpixels by simple linear iterative clustering (SLIC) respectively. Secondly, some features obtained from superpixels are formed as vector. Thirdly, a majority voting manifold alignment method aiming at solving high resolution problem is proposed and mapping the vector data to alignment space. At last, all the data in the alignment space are classified by using KNN method. Multi-temporal images from different areas or the same area are both considered in this paper. In the experiments, 2 groups of multi-temporal HR images collected by China GF1 and GF2 satellites are used for performance evaluation. Experimental results indicate that the proposed method not only has significantly outperforms than traditional domain adaptation methods in classification accuracy, but also effectively overcome the problem of "pepper and salt".

Canibalismo Extremo y Lente Gravitacional Intensa en el Cúmulo de Galaxias Abell 3827

NASA Astrophysics Data System (ADS)

Díaz, R. J.; West, M.; Bergmann, M.; Carrasco, E. R.; Gomez, P.; Lee, H.; Miller, B.; Turner, J.

Abell 3827 is one of the most massive known clusters and at its center we observe an extreme example of galactic canibalism: a super giant elliptical galaxy in its formation process, devoring five massive galaxies at the same time. Using high spatial resolution Gemini+GMOS imagery and multi-object spectroscopy, we derived the redshift (z=0.099) and the radial velocity dispersion of the 55 brightest galaxies in the cluster central region (1134 +- 125 km/s). The estimated virial mass is ~ 1E14 M(sun) inside a radius of 300 kpc of the cluster center. We have also found features corresponding to a strong gravitational lense, four anular features arranged in an Einstein Ring from a galaxy (z=0.2) at double redshift than the cluster, and a fifth arclet feature corresponding to the lensed light of a farther galaxy (z=0.4). The possible Einstein Ring is of small angular size and the gravitational lense morphology would confirm that the cluster is indeed very massive and dense. FULL TEXT IN SPANISH.

Uncovering the Protostars in Serpens South with ALMA: Continuum Sources and Their Outflow Activity

NASA Astrophysics Data System (ADS)

Plunkett, Adele; Arce, H.; Corder, S.; Dunham, M.

2017-06-01

Serpens South is an appealing protostellar cluster to study due the combination of several factors: (1) a high protostar fraction that shows evidence for very recent and ongoing star formation; (2) iconic clustered star formation along a filamentary structure; (3) its relative proximity within a few hundred parsecs. An effective study requires the sensitivity, angular and spectral resolution, and mapping capabilities recently provided with ALMA. Here we present a multi-faceted data set acquired from Cycles 1 through 3 with ALMA, including maps of continuum sources and molecular outflows throughout the region, as well as a more focused kinematical study of the protostar that is the strongest continuum source at the cluster center. Together these data span spatial scales over several orders of magnitude, allowing us to investigate the outflow-driving sources and the impact of the outflows on the cluster environment. Currently, we focus on the census of protostars in the cluster center, numbering about 20, including low-flux, low-mass sources never before detected in mm-wavelengths and evidence for multiplicity that was previously unresolved.

Deprotonated Water Dimers: The Building Blocks of Segmented Water Chains on Rutile RuO2(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mu, Rentao; Cantu Cantu, David; Glezakou, Vassiliki Alexandra

2015-10-15

Despite the importance of RuO2 in photocatalytic water splitting and catalysis in general, the interactions of water with even its most stable (110) surface are not well-understood. In this study we employ a combination of high-resolution scanning tunneling microscopy imaging with density functional theory based ab initio molecular dynamics, and we follow the formation and binding of linear water clusters on coordinatively unsaturated ruthenium rows. We find that clusters of all sizes (dimers, trimers, tetramers, extended chains) are stabilized by donating one proton per every two water molecules to the surface bridge bonded oxygen sites, in contrast with water monomersmore » that do not show a significant propensity for dissociation. The clusters with odd number of water molecules are less stable than the clusters with even number, and are generally not observed under thermal equilibrium. For all clusters with even numbers, the dissociated dimers represent the fundamental building blocks with strong intra-dimer hydrogen bonds and only very weak inter-dimer interactions resulting in segmented water chains.« less

A Deep Near-Infrared Survey of the N 49 Region around the Soft Gamma-Ray Repeater 0526-66

NASA Technical Reports Server (NTRS)

Klose, S.; Henden, A. A.; Geppert, U.; Greiner, J.; Guetter, H. H.; Hartmann, D. H.; Kouveliotou, C.; Luginbuhl, C. B.; Stecklurn, B.; Vrba, F. J.

2004-01-01

We report the results of a deep near-infrared survey of the vicinity of supernova remnant N49 in the Large Magellanic Cloud (LMC), which contains the soft gamma-ray repeater (SGR) 0526-66. Two of the four confirmed SGRs are potentially associated with compact stellar clusters. We thus searched for a similar association of SGR0526-66, and find the unexplored young stellar cluster SL 463 at a projected distance of approx. 30 pc from the SGR. This constitutes the third cluster-SGR link, and lends support to scenarios in which SGR progenitors originate in young, embedded clusters. If real, the cluster-SGR association constrains the age and thus the initial mass of these stars. In addition, our high-resolution images of the super- nova remnant N49 reveal an area of excess K-band flux in the southeastern part of the SNR. This feature coincides with the maximum flux area at 8.28 microns as detected by the Midcourse Space Experiment (MSX satellite), which we identify with IRAS 052594607.

NASA Space Science and a Search for Ram-Pressure Stripping in the Hydra I Cluster

NASA Technical Reports Server (NTRS)

Brown, Beth

2005-01-01

The NASA Goddard Space Flight Center's Sciences and Exploration Directorate seeks to expand scientific knowledge through observational and theoretical research in the study of the Earth-Sun system, the solar system and the origins of life, and the birth and evolution of the universe. This talk will discuss some of the cutting-edge space science research being conducted at Goddard. In addition, I will discuss my research on ram-pressure stripping in cluster elliptical galaxies. Ram-pressure stripping is a method by which hot interstellar gas can be removed from a galaxy moving through a group or cluster of galaxies. Indirect evidence of ram-pressure stripping includes lowered X-ray brightness in a galaxy due to less X-ray emitting gas remaining in the galaxy. Here we present the initial results of our program to determine whether cluster elliptical galaxies have lower hot gas masses than their counterparts in less rich environments. This test requires the use of the high-resolution imaging of the Chandra Observatory and we present our analysis of the galaxies in the nearby cluster Hydra I.

High-Resolution CCD Spectra of Stars in Globular Clusters. IX. The "Young" Clusters Ruprecht 106 and PAL 12

NASA Astrophysics Data System (ADS)

Brown, Jeffrey A.; Wallerstein, George; Zucker, Daniel

1997-07-01

We have performed a spectroscopic abundance analysis of two stars each in the anomalously young globular clusters Rup 106 and Pal 12. We find [Fe/H] =~ -1.45 for Rup 106 and -1.0 for Pal 12. The abundance ratios in both clusters are peculiar in comparison to other globulars: the alpha -elements are not enhanced over the solar ratio. We find that oxygen in Rup 106 is also relatively low, with [O/Fe] =~ 0.0 - +0.1. The similarity of the ratio of the alpha-elements to iron to the solar ratio shows that species contributed by supernovae of type Ia have ``caught up" with species produced by SN II's. The similar contributions of the alpha - and Fe-peak species to disk stars shows that age, not metallicity, is the determining factor in the ratio of SN II/SN Ia nucleosynthesis. Galactic enrichment models show that these abundance ratios can be understood as being the result of these two clusters coming from an environment with multiple discontinuous star formation events.

Measurements of resonant scattering in the Perseus cluster core with Hitomi SXS

NASA Astrophysics Data System (ADS)

Sato, K.; Zhuravleva, I.

2017-10-01

Hitomi (ASTRO-H) SXS allows us to investigate fine structures of emission lines in extended X-ray sources for the first time. Thanks to its high energy resolution of 5 eV at 6 keV in orbit, Hitomi SXS finds a quiescent atmosphere in the Intra cluster medium of the Perseus cluster core where the gas has a line-of-sight velocity dispersion below 200 km/sec from the line width in the spectral analysis (Hitomi collaboration, Nature, 2016). The resonant scattering is also important to measure the gas velocity as a complementary probe of the direct measurement from the line width. Particularly in the cluster core, resonant scattering should be taken into account when inferring physical properties from line intensities because the optical depth of the He-alpha resonant line is expected to be larger than 1. The observed line flux ratio of Fe XXV He-α resonant to forbidden lines is found to be lower in the cluster core when compared to the outer region, consistent with resonant scattering of the resonant line and also in support of the low turbulent velocity.

Blue straggler stars beyond the Milky Way: a non-segregated population in the Large Magellanic Cloud cluster NGC 2213

NASA Astrophysics Data System (ADS)

Li, Chengyuan; Hong, Jongsuk

2018-06-01

Using the high-resolution observations obtained by the Hubble Space Telescope, we analysed the blue straggler stars (BSSs) in the Large Magellanic Cloud cluster NGC 2213. We found that the radial distribution of BSSs is consistent with that of the normal giant stars in NGC 2213, showing no evidence of mass segregation. However, an analytic calculation carried out for these BSSs shows that they are already dynamically old, because the estimated half-mass relaxation time for these BSSs is significantly shorter than the isochronal age of the cluster. We also performed direct N-body simulations for an NGC 2213-like cluster to understand the dynamical processes that lead to this non-segregated radial distribution of BSSs. Our numerical simulation shows that the presence of black hole subsystems inside the cluster centre can significantly affect the dynamical evolution of BSSs. The combined effects of the delayed segregation, binary disruption, and exchange interactions of BSS progenitor binaries may result in this non-segregated radial distribution of BSSs in NGC 2213.

The Atacama Cosmology Telescope (ACT): Beam Profiles and First SZ Cluster Maps

NASA Technical Reports Server (NTRS)

Hincks, A. D.; Acquaviva, V.; Ade, P. A.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Battistelli, E. S.; Bond, J. R.; Brown, B.;

He-Ion Microscopy as a High-Resolution Probe for Complex Quantum Heterostructures in Core-Shell Nanowires.

PubMed

Pöpsel, Christian; Becker, Jonathan; Jeon, Nari; Döblinger, Markus; Stettner, Thomas; Gottschalk, Yeanitza Trujillo; Loitsch, Bernhard; Matich, Sonja; Altzschner, Marcus; Holleitner, Alexander W; Finley, Jonathan J; Lauhon, Lincoln J; Koblmüller, Gregor

2018-06-13

Core-shell semiconductor nanowires (NW) with internal quantum heterostructures are amongst the most complex nanostructured materials to be explored for assessing the ultimate capabilities of diverse ultrahigh-resolution imaging techniques. To probe the structure and composition of these materials in their native environment with minimal damage and sample preparation calls for high-resolution electron or ion microscopy methods, which have not yet been tested on such classes of ultrasmall quantum nanostructures. Here, we demonstrate that scanning helium ion microscopy (SHeIM) provides a powerful and straightforward method to map quantum heterostructures embedded in complex III-V semiconductor NWs with unique material contrast at ∼1 nm resolution. By probing the cross sections of GaAs-Al(Ga)As core-shell NWs with coaxial GaAs quantum wells as well as short-period GaAs/AlAs superlattice (SL) structures in the shell, the Al-rich and Ga-rich layers are accurately discriminated by their image contrast in excellent agreement with correlated, yet destructive, scanning transmission electron microscopy and atom probe tomography analysis. Most interestingly, quantitative He-ion dose-dependent SHeIM analysis of the ternary AlGaAs shell layers and of compositionally nonuniform GaAs/AlAs SLs reveals distinct alloy composition fluctuations in the form of Al-rich clusters with size distributions between ∼1-10 nm. In the GaAs/AlAs SLs the alloy clustering vanishes with increasing SL-period (>5 nm-GaAs/4 nm-AlAs), providing insights into critical size dimensions for atomic intermixing effects in short-period SLs within a NW geometry. The straightforward SHeIM technique therefore provides unique benefits in imaging the tiniest nanoscale features in topography, structure and composition of a multitude of diverse complex semiconductor nanostructures.

Integrated light chemical tagging analyses of seven M31 outer halo globular clusters from the Pan-Andromeda Archaeological Survey

NASA Astrophysics Data System (ADS)

Sakari, Charli M.; Venn, Kim A.; Mackey, Dougal; Shetrone, Matthew D.; Dotter, Aaron; Ferguson, Annette M. N.; Huxor, Avon

2015-04-01

Detailed chemical abundances are presented for seven M31 outer halo globular clusters (with projected distances from M31 greater than 30 kpc), as derived from high-resolution integrated light spectra taken with the Hobby-Eberly Telescope. Five of these clusters were recently discovered in the Pan-Andromeda Archaeological Survey (PAndAS) - this paper presents the first determinations of integrated Fe, Na, Mg, Ca, Ti, Ni, Ba, and Eu abundances for these clusters. Four of the target clusters (PA06, PA53, PA54, and PA56) are metal poor ([Fe/H] < -1.5), α-enhanced (though they are possibly less α-enhanced than Milky Way stars at the 1σ level), and show signs of star-to-star Na and Mg variations. The other three globular clusters (H10, H23, and PA17) are more metal rich, with metallicities ranging from [Fe/H] = -1.4 to -0.9. While H23 is chemically similar to Milky Way field stars, Milky Way globular clusters, and other M31 clusters, H10 and PA17, have moderately low [Ca/Fe], compared to Milky Way field stars and clusters. Additionally, PA17's high [Mg/Ca] and [Ba/Eu] ratios are distinct from Milky Way stars, and are in better agreement with the stars and clusters in the Large Magellanic Cloud. None of the clusters studied here can be conclusively linked to any of the identified streams from PAndAS; however, based on their locations, kinematics, metallicities, and detailed abundances, the most metal-rich PAndAS clusters H23 and PA17 may be associated with the progenitor of the Giant Stellar Stream, H10 may be associated with the SW cloud, and PA53 and PA56 may be associated with the eastern cloud.

Whole Genome Sequencing Demonstrates Limited Transmission within Identified Mycobacterium tuberculosis Clusters in New South Wales, Australia

PubMed Central

Gurjav, Ulziijargal; Outhred, Alexander C.; Jelfs, Peter; McCallum, Nadine; Wang, Qinning; Hill-Cawthorne, Grant A.; Marais, Ben J.; Sintchenko, Vitali

2016-01-01

Australia has a low tuberculosis incidence rate with most cases occurring among recent immigrants. Given suboptimal cluster resolution achieved with 24-locus mycobacterium interspersed repetitive unit (MIRU-24) genotyping, the added value of whole genome sequencing was explored. MIRU-24 profiles of all Mycobacterium tuberculosis culture-confirmed tuberculosis cases diagnosed between 2009 and 2013 in New South Wales (NSW), Australia, were examined and clusters identified. The relatedness of cases within the largest MIRU-24 clusters was assessed using whole genome sequencing and phylogenetic analyses. Of 1841 culture-confirmed TB cases, 91.9% (1692/1841) had complete demographic and genotyping data. East-African Indian (474; 28.0%) and Beijing (470; 27.8%) lineage strains predominated. The overall rate of MIRU-24 clustering was 20.1% (340/1692) and was highest among Beijing lineage strains (35.7%; 168/470). One Beijing and three East-African Indian (EAI) clonal complexes were responsible for the majority of observed clusters. Whole genome sequencing of the 4 largest clusters (30 isolates) demonstrated diverse single nucleotide polymorphisms (SNPs) within identified clusters. All sequenced EAI strains and 70% of Beijing lineage strains clustered by MIRU-24 typing demonstrated distinct SNP profiles. The superior resolution provided by whole genome sequencing demonstrated limited M. tuberculosis transmission within NSW, even within identified MIRU-24 clusters. Routine whole genome sequencing could provide valuable public health guidance in low burden settings. PMID:27737005

Featured Image: New Detail in the Toothbrush Cluster

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-01-01

This spectacular composite (click here for the full image) reveals the galaxy cluster 1RXS J0603.3+4214, known as the Toothbrush cluster due to the shape of its most prominent radio relic. Featured in a recent publication led by Kamlesh Rajpurohit (Thuringian State Observatory, Germany), this image contains new Very Large Array (VLA) 1.5-GHz observations (red) showing the radio emission within the cluster. This is composited with a Chandra view of the X-ray emitting gas of the cluster (blue) and an optical image of the background from Subaru data. The new deep VLA data totaling 26 hours of observations provides a detailed look at the complex structure within the Toothbrush relic, revealing enigmatic filaments and twists (see below). This new data will help us to explore the possible merger history of this cluster, which is theorized to have caused the unusual shapes we see today. For more information, check out the original article linked below.High resolution VLA 12 GHz image of the Toothbrush showing the complex, often filamentary structures. [Rajpurohit et al. 2018]CitationK. Rajpurohit et al 2018 ApJ 852 65. doi:10.3847/1538-4357/aa9f13

Spectroscopic confirmation of the low-latitude object FSR 1716 as an old globular cluster

NASA Astrophysics Data System (ADS)

Koch, Andreas; Kunder, Andrea; Wojno, Jennifer

2017-09-01

Star clusters are invaluable tracers of the Galactic components and the discovery and characterization of low-mass stellar systems can be used to appraise their prevailing disruption mechanisms and time scales. However, owing to significant foreground contamination, high extinction, and still uncharted interfaces of the underlying Milky Way components, objects at low Galactic latitudes are notoriously difficult to characterize. Here, we present the first spectroscopic campaign to identify the chemodynamical properties of the low-latitude star cluster FSR 1716. While its photometric age and distance are far from settled, the presence of RR Lyrae variables indicates a rather old cluster variety. Using medium-resolution (R 10 600) calcium triplet (CaT) spectroscopy obtained with the wide-field, multi-fiber AAOmega instrument, we identified six member candidates with a mean velocity of -30 km s-1 and a velocity dispersion of 2.5 ± 0.9 km s-1. The latter value implies a dynamic mass of 1.3 × 104M⊙, typical of a low-mass globular cluster. Combined with our derived CaT metallicity of -1.38 ± 0.20 dex, this object is finally confirmed as an old, metal-poor globular cluster.

Galaxy Interactions, Tidal Debris, and the Origin of Intracluster Light in the Coma Cluster

NASA Astrophysics Data System (ADS)

Gregg, Michael

1999-07-01

We propose to obtain deep WFPC2 and parallel STIS images of low surface brightness tidal debris that we have recently discovered in the Coma cluster; the material is being stripped from its parent galaxy and added to the general cluster background. These images will enable direct study of the brightest blue and red supergiants, globular clusters, and star forming regions which may be present, or will place strong limits on the numbers of such objects and any recent star formation. We also propose similar observations of the parent spiral, NGC4911, in the core of Coma; it is losing its ISM to the hot cluster gas and as well as the low surface brightness tidal debris. By imaging this galaxy, we will get a high resolution look at the interaction between the galaxy and interstellar medium, as well as any ram-pressure induced star formation. The tidal features in Coma appear to be adding material to the background light and cD galaxy envelopes at a significant rate; determining the nature of the added stellar population and the interactions which produce it are critical to understanding the formation and evolution of cD galaxies and clusters.

Cluster Active Archive: lessons learnt

NASA Astrophysics Data System (ADS)

Laakso, H. E.; Perry, C. H.; Taylor, M. G.; Escoubet, C. P.; Masson, A.

2010-12-01

The ESA Cluster Active Archive (CAA) was opened to public in February 2006 after an initial three-year development phase. It provides access (both web GUI and command-line tool are available) to the calibrated full-resolution datasets of the four-satellite Cluster mission. The data archive is publicly accessible and suitable for science use and publication by the world-wide scientific community. There are more than 350 datasets from each spacecraft, including high-resolution magnetic and electric DC and AC fields as well as full 3-dimensional electron and ion distribution functions and moments from a few eV to hundreds of keV. The Cluster mission has been in operation since February 2001, and currently although the CAA can provide access to some recent observations, the ingestion of some other datasets can be delayed by a few years due to large and difficult calibration routines of aging detectors. The quality of the datasets is the central matter to the CAA. Having the same instrument on four spacecraft allows the cross-instrument comparisons and provide confidence on some of the instrumental calibration parameters. Furthermore it is highly important that many physical parameters are measured by more than one instrument which allow to perform extensive and continuous cross-calibration analyses. In addition some of the instruments can be regarded as absolute or reference measurements for other instruments. The CAA attempts to avoid as much as possible mission-specific acronyms and concepts and tends to use more generic terms in describing the datasets and their contents in order to ease the usage of the CAA data by “non-Cluster” scientists. Currently the CAA has more 1000 users and every month more than 150 different users log in the CAA for plotting and/or downloading observations. The users download about 1 TeraByte of data every month. The CAA has separated the graphical tool from the download tool because full-resolution datasets can be visualized in many ways and so there is no one-to-one correspondence between graphical products and full-resolution datasets. The CAA encourages users to contact the CAA team for all kind of issues whether it concerns the user interface, the content of the datasets, the quality of the observations or provision of new type of services. The CAA runs regular annual reviews on the data products and the user services in order to improve the quality and usability of the CAA system to the world-wide user community. The CAA is continuously being upgraded in terms of datasets and services.

Structure Refinement of Protein Low Resolution Models Using the GNEIMO Constrained Dynamics Method

PubMed Central

Park, In-Hee; Gangupomu, Vamshi; Wagner, Jeffrey; Jain, Abhinandan; Vaidehi, Nagara-jan

2012-01-01

The challenge in protein structure prediction using homology modeling is the lack of reliable methods to refine the low resolution homology models. Unconstrained all-atom molecular dynamics (MD) does not serve well for structure refinement due to its limited conformational search. We have developed and tested the constrained MD method, based on the Generalized Newton-Euler Inverse Mass Operator (GNEIMO) algorithm for protein structure refinement. In this method, the high-frequency degrees of freedom are replaced with hard holonomic constraints and a protein is modeled as a collection of rigid body clusters connected by flexible torsional hinges. This allows larger integration time steps and enhances the conformational search space. In this work, we have demonstrated the use of a constraint free GNEIMO method for protein structure refinement that starts from low-resolution decoy sets derived from homology methods. In the eight proteins with three decoys for each, we observed an improvement of ~2 Å in the RMSD to the known experimental structures of these proteins. The GNEIMO method also showed enrichment in the population density of native-like conformations. In addition, we demonstrated structural refinement using a “Freeze and Thaw” clustering scheme with the GNEIMO framework as a viable tool for enhancing localized conformational search. We have derived a robust protocol based on the GNEIMO replica exchange method for protein structure refinement that can be readily extended to other proteins and possibly applicable for high throughput protein structure refinement. PMID:22260550

Golgi sorting regulates organization and activity of GPI-proteins at apical membranes

PubMed Central

Tivodar, Simona; Formiggini, Fabio; Ossato, Giulia; Gratton, Enrico; Tramier, Marc; Coppey-Moisan, Maïté; Zurzolo, Chiara

2014-01-01

Here, we combined classical biochemistry with novel biophysical approaches to study with high spatial and temporal resolution the organization of GPI-anchored proteins (GPI-APs) at the plasma membrane of polarized epithelial cells. We show that in polarized MDCK cells, following sorting in the Golgi, each GPI-AP reaches the apical surface in homo-clusters. Golgi-derived homo-clusters are required for their subsequent plasma membrane organization into cholesterol-dependent hetero-clusters. By contrast, in non-polarized MDCK cells GPI-APs are delivered to the surface as monomers in an unpolarized manner and are not able to form hetero-clusters. We further demonstrate that this GPI-AP organization is regulated by the content of cholesterol in the Golgi apparatus and is required to maintain the functional state of the protein at the apical membrane. Thus, different from fibroblasts, in polarized epithelial cells a selective cholesterol-dependent sorting mechanism in the Golgi regulates both the organization and the function of GPI-APs at the apical surface. PMID:24681536

Red giants and yellow stragglers in the young open cluster NGC 2447

NASA Astrophysics Data System (ADS)

da Silveira, M. D.; Pereira, C. B.; Drake, N. A.

2018-06-01

In this work we analysed, using high-resolution spectroscopy, a sample of 12 single and 4 spectroscopic binary stars of the open cluster NGC 2447. For the single stars, we obtained atmospheric parameters and chemical abundances of Li, C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, Nd, Eu. Rotational velocities were obtained for all the stars. The abundances of the light elements and Eu and the rotational velocities were derived using spectral synthesis technique. We obtained a mean metallicity of [Fe/H] = -0.17 ± 0.05. We found that the abundances of all elements are similar to field giants and/or giants of open clusters, even for the s-process elements, which are enhanced as in other young open clusters. We show that the spectroscopic binaries NGC 2447-26, 38, and 42 are yellow-straggler stars, of which the primary is a giant star and the secondary a main-sequence A-type star.

Hydrodynamic fractionation of finite size gold nanoparticle clusters.

PubMed

Tsai, De-Hao; Cho, Tae Joon; DelRio, Frank W; Taurozzi, Julian; Zachariah, Michael R; Hackley, Vincent A

2011-06-15

We demonstrate a high-resolution in situ experimental method for performing simultaneous size classification and characterization of functional gold nanoparticle clusters (GNCs) based on asymmetric-flow field flow fractionation (AFFF). Field emission scanning electron microscopy, atomic force microscopy, multi-angle light scattering (MALS), and in situ ultraviolet-visible optical spectroscopy provide complementary data and imagery confirming the cluster state (e.g., dimer, trimer, tetramer), packing structure, and purity of fractionated populations. An orthogonal analysis of GNC size distributions is obtained using electrospray-differential mobility analysis (ES-DMA). We find a linear correlation between the normalized MALS intensity (measured during AFFF elution) and the corresponding number concentration (measured by ES-DMA), establishing the capacity for AFFF to quantify the absolute number concentration of GNCs. The results and corresponding methodology summarized here provide the proof of concept for general applications involving the formation, isolation, and in situ analysis of both functional and adventitious nanoparticle clusters of finite size. © 2011 American Chemical Society

Lithium Abundances in the Young Open Cluster IC 2602

NASA Technical Reports Server (NTRS)

Randich, S.; Aharpour, N.; Pallavicini, R.; Prosser, C. F.; Stauffer, J. R.

1997-01-01

We have obtained high-resolution spectra for 28 candidate late-type stars in the 30 Myr old cluster IC 2602. NLTE Li abundances have been derived from measured equivalent widths. The log n(Li) - T(sub eff) and log n(Li) - mass distributions for our sample stars have been compared with those of the Pleiades and alpha Persei. Our data show that F stars in the three clusters have the same lithium content, which corresponds to the initial content for Pop. I stars. G and early-K IC 2602 stars are, on average, somewhat more Li-rich than their counterparts in the two slightly older clusters. Finally, the latest-type IC 2602 stars are heavily Li depleted, with their Li content being as low as the lowest measured among the Pleiades. As in the Pleiades and alpha Per, a star-to-star scatter in lithium is observed among 30 Myr old late-K/early-K dwarfs in IC 2602, indicating that this spread develops in the pre-main sequence phases.

Evidence for Cluster Evolution from an Improved Measurement of the Velocity Dispersion and Morphological Fraction of Cluster 1324+3011 at z=0.76

NASA Astrophysics Data System (ADS)

Lubin, Lori M.; Oke, J. B.; Postman, Marc

2002-10-01

We have carried out additional spectroscopic observations in the field of cluster Cl 1324+3011 at z=0.76. Combined with the spectroscopy recently presented by Postman, Lubin, & Oke, we now have spectroscopically confirmed 47 cluster members. With this significant number of redshifts, we measure accurately the cluster velocity dispersion to be 1016+126-93 km s-1. The distribution of velocity offsets is consistent with a Gaussian, indicating no substantial velocity substructure. As previously noted for other optically selected clusters at redshifts of z>~0.5, a comparison between the X-ray luminosity (LX) and the velocity dispersion (σ) of Cl 1324+3011 implies that this cluster is underluminous in X-rays by a factor of ~3-40 when compared with the LX-σ relation for local and moderate-redshift clusters. We also examine the morphologies of those cluster members that have available high angular resolution imaging with the Hubble Space Telescope (HST). There are 22 spectroscopically confirmed cluster members within the HST field of view. Twelve of these are visually classified as early-type (elliptical or S0) galaxies, implying an early-type fraction of 0.55+0.17-0.14 in this cluster. This fraction is a factor of ~1.5 lower than that observed in nearby rich clusters. Confirming previous cluster studies, the results for cluster Cl 1324+3011, combined with morphological studies of other massive clusters at redshifts of 0<=z<~1, suggest that the galaxy population in massive clusters is strongly evolving with redshift. This evolution implies that early-type galaxies are forming out of the excess of late-type (spiral, irregular, and peculiar) galaxies over the ~7 Gyr timescale.

Influence of spectral resolution, spectral range and signal-to-noise ratio of Fourier transform infra-red spectra on identification of high explosive substances

NASA Astrophysics Data System (ADS)

Banas, Krzysztof; Banas, Agnieszka M.; Heussler, Sascha P.; Breese, Mark B. H.

2018-01-01

In the contemporary spectroscopy there is a trend to record spectra with the highest possible spectral resolution. This is clearly justified if the spectral features in the spectrum are very narrow (for example infra-red spectra of gas samples). However there is a plethora of samples (in the liquid and especially in the solid form) where there is a natural spectral peak broadening due to collisions and proximity predominately. Additionally there is a number of portable devices (spectrometers) with inherently restricted spectral resolution, spectral range or both, which are extremely useful in some field applications (archaeology, agriculture, food industry, cultural heritage, forensic science). In this paper the investigation of the influence of spectral resolution, spectral range and signal-to-noise ratio on the identification of high explosive substances by applying multivariate statistical methods on the Fourier transform infra-red spectral data sets is studied. All mathematical procedures on spectral data for dimension reduction, clustering and validation were implemented within R open source environment.

The Astro-H High Resolution Soft X-Ray Spectrometer

NASA Technical Reports Server (NTRS)

Kelley, Richard L.; Akamatsu, Hiroki; Azzarell, Phillip; Bialas, Tom; Boyce, Kevin R.; Brown, Gregory V.; Canavan, Edgar; Chiao, Meng P.; Costantini, Elisa; DiPirro, Michael J.;

The Astro-H high resolution soft x-ray spectrometer

NASA Astrophysics Data System (ADS)

Kelley, Richard L.; Akamatsu, Hiroki; Azzarello, Phillipp; Bialas, Tom; Boyce, Kevin R.; Brown, Gregory V.; Canavan, Edgar; Chiao, Meng P.; Costantini, Elisa; DiPirro, Michael J.; Eckart, Megan E.; Ezoe, Yuichiro; Fujimoto, Ryuichi; Haas, Daniel; den Herder, Jan-Willem; Hoshino, Akio; Ishikawa, Kumi; Ishisaki, Yoshitaka; Iyomoto, Naoko; Kilbourne, Caroline A.; Kimball, Mark O.; Kitamoto, Shunji; Konami, Saori; Koyama, Shu; Leutenegger, Maurice A.; McCammon, Dan; Mitsuda, Kazuhisa; Mitsuishi, Ikuyuki; Moseley, Harvey; Murakami, Hiroshi; Murakami, Masahide; Noda, Hirofumi; Ogawa, Mina; Ohashi, Takaya; Okamoto, Atsushi; Ota, Naomi; Paltani, Stéphane; Porter, F. S.; Sakai, Kazuhiro; Sato, Kosuke; Sato, Yohichi; Sawada, Makoto; Seta, Hiromi; Shinozaki, Keisuke; Shirron, Peter J.; Sneiderman, Gary A.; Sugita, Hiroyuki; Szymkowiak, Andrew E.; Takei, Yoh; Tamagawa, Toru; Tashiro, Makoto; Terada, Yukikatsu; Tsujimoto, Masahiro; de Vries, Cor P.; Yamada, Shinya; Yamasaki, Noriko Y.; Yatsu, Yoichi

2016-07-01

We present the overall design and performance of the Astro-H (Hitomi) Soft X-Ray Spectrometer (SXS). The instrument uses a 36-pixel array of x-ray microcalorimeters at the focus of a grazing-incidence x-ray mirror Soft X-Ray Telescope (SXT) for high-resolution spectroscopy of celestial x-ray sources. The instrument was designed to achieve an energy resolution better than 7 eV over the 0.3-12 keV energy range and operate for more than 3 years in orbit. The actual energy resolution of the instrument is 4-5 eV as demonstrated during extensive ground testing prior to launch and in orbit. The measured mass flow rate of the liquid helium cryogen and initial fill level at launch predict a lifetime of more than 4 years assuming steady mechanical cooler performance. Cryogen-free operation was successfully demonstrated prior to launch. The successful operation of the SXS in orbit, including the first observations of the velocity structure of the Perseus cluster of galaxies, demonstrates the viability and power of this technology as a tool for astrophysics.

Hubble space telescope observations of young star clusters in NGC-4038/4039, 'the antennae' galaxies

NASA Technical Reports Server (NTRS)

Whitmore, Bradley C.; Schweizer, Francois

1995-01-01

New, high-resolution images of the disks of NGC 4038/4039 obtained with the Wide Field Camera of the Hubble Space Telescope (HST) are presented. NGC 4038/4039, nicknamed The Antennae, is a prototypical example of a pair of colliding galaxies believed to be at an early stage of a merger. Down to the limiting magnitude of V approximately 23 mag, the HST images reveal a population of over 700 blue pointlike objects within the disks. The mean absolute magnitude of these objects is M(sub V) = -11 mag, with the brightest objects reaching M(sub V) approximately -15. Their mean apparent color indices ar U - V = -0.7 mag and V - 1 = 0.8 mag on the Johnson UVI passband system, while their mean indices corrected for internal reddening are (u - v)(sub 0) = -1.0 mag and (V - I(sub 0) = 0.5. Their mean effective radius, determined from slightly resolved images, is 18 pc (for H(sub 0) = 50 km/s /Mpc). Based on their luminosities and resolution, most of these objects cannot be individual stars, but are likely young compact star clusters. The brighter ones are similar to the objects found in NGC 1275 and NGC 7252, which appear to be young globular clusters formed during recent galazy mergers. Based on their U - V and V - I colors, the brightest, bluest clusters of NGC 4038/4039 appear to be less than 10 Myr old. Most of these bright clusters are relatively tightly clustered themselves, with typically a dozen individual clusters belonging to a complex identified as a giant H II region from ground-based observations. The cluster luminosity function (LF) is approximately a power law, phi(L)dL proportional to L(exp -1.78+/-0.05)dL, with no hint of a turnover at fainter magnitudes. This power-law shape agrees with the LF of Magellanic Cloud clusters and Galactic open clusters, but differs from the LF of old globular cluster systems that is typically Gaussian with a Full Width at Half Maximum (FWHM) of approximately 3 mag. Besides the blue clusters, we also find about a dozen extremely red objects with V - I greater than 3.0. The highest number density of these red objects is found in the SE quadrant, where star formation appears to be most recent. We propose that these objects may be very young star clusters still embedded in their placental dust cocoons.

Identifying microbially mediated transformations of DOC across season and tide from simultaneous changes in whole community gene expression and in mass spectra generated by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS)

NASA Astrophysics Data System (ADS)

Ballantyne, F.; Medeiros, P. M.; Moran, M. A.; Song, C.; Whitman, W. B.; Washington, B.; Yu, M.; Lee, J.

2017-12-01

Despite the advent of methods enabling high resolution characterization of metabolic activity and of organic matter, linking microbial metabolism to organic matter transformations remains a challenge. By sequencing metatranscriptomes and using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS) to characterize organic matter (OM) at the beginning and at the end of incubations of estuarine water across tide and season, we sought to link observed a changes in OM composition to microbial metabolism. We used linear models and K means clustering to identify clusters of genes that responded coherently across season, which accounted for most of the variability in gene expression, over tidal regime, which explained the majority of the remaining variation, and over time during the 24 hour incubations. We used an approach from the field of signal processing, that to our knowledge has not been used to analyze FTICR-MS data, to identify formulae of compounds that changed in concentration during the incubations. This approach, based on the discrete wavelet transform (DWT), allowed us to overcome some of the challenges associated with analyzing FTICR-MS data: variable ionization of organic compounds, signal suppression by high concentration compounds, and uncertainty about how to normalize changes across spectra. We were able to link clusters of metabolic and transporter genes to changes in OM composition, and uniquely identify genes based on their cross correlation with changes in FTICR mass spectra. Our approach for analyzing FTICR- MS data enables more robust inference about OM transformations, and linking high resolution changes in gene expression and in OM data during incubations represents an important step toward formulating models of microbial metabolism relevant for predicting biogeochemically relevant C fluxes.

Power spectrum for the small-scale Universe

NASA Astrophysics Data System (ADS)

Widrow, Lawrence M.; Elahi, Pascal J.; Thacker, Robert J.; Richardson, Mark; Scannapieco, Evan

2009-08-01

The first objects to arise in a cold dark matter (CDM) universe present a daunting challenge for models of structure formation. In the ultra small-scale limit, CDM structures form nearly simultaneously across a wide range of scales. Hierarchical clustering no longer provides a guiding principle for theoretical analyses and the computation time required to carry out credible simulations becomes prohibitively high. To gain insight into this problem, we perform high-resolution (N = 7203-15843) simulations of an Einstein-de Sitter cosmology where the initial power spectrum is P(k) ~ kn, with -2.5 <= n <= - 1. Self-similar scaling is established for n = -1 and -2 more convincingly than in previous, lower resolution simulations and for the first time, self-similar scaling is established for an n = -2.25 simulation. However, finite box-size effects induce departures from self-similar scaling in our n = -2.5 simulation. We compare our results with the predictions for the power spectrum from (one-loop) perturbation theory and demonstrate that the renormalization group approach suggested by McDonald improves perturbation theory's ability to predict the power spectrum in the quasi-linear regime. In the non-linear regime, our power spectra differ significantly from the widely used fitting formulae of Peacock & Dodds and Smith et al. and a new fitting formula is presented. Implications of our results for the stable clustering hypothesis versus halo model debate are discussed. Our power spectra are inconsistent with predictions of the stable clustering hypothesis in the high-k limit and lend credence to the halo model. Nevertheless, the fitting formula advocated in this paper is purely empirical and not derived from a specific formulation of the halo model.

SODIUM AND OXYGEN ABUNDANCES IN THE OPEN CLUSTER NGC 6791 FROM APOGEE H-BAND SPECTROSCOPY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cunha, Katia; Souto, Diogo; Smith, Verne V.

2015-01-10

The open cluster NGC 6791 is among the oldest, most massive, and metal-rich open clusters in the Galaxy. High-resolution H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) of 11 red giants in NGC 6791 are analyzed for their chemical abundances of iron, oxygen, and sodium. The abundances of these three elements are found to be homogeneous (with abundance dispersions at the level of ∼0.05-0.07 dex) in these cluster red giants, which span much of the red-giant branch (T {sub eff} ∼ 3500-4600 K), and include two red clump giants. From the infrared spectra, this cluster is confirmed to be amongmore » the most metal-rich clusters in the Galaxy (([Fe/H]) = 0.34 ± 0.06) and is found to have a roughly solar value of [O/Fe] and slightly enhanced [Na/Fe]. Our non-LTE calculations for the studied Na I lines in the APOGEE spectral region (16373.86 Å and 16388.85 Å) indicate only small departures from LTE (≤0.04 dex) for the parameter range and metallicity of the studied stars. The previously reported double population of cluster members with different Na abundances is not found among the studied sample.« less

Formation of metallic clusters in oxide insulators by means of ion beam mixing

NASA Astrophysics Data System (ADS)

Talut, G.; Potzger, K.; Mücklich, A.; Zhou, Shengqiang

2008-04-01

The intermixing and near-interface cluster formation of Pt and FePt thin films deposited on different oxide surfaces by means of Pt+ ion irradiation and subsequent annealing was investigated. Irradiated as well as postannealed samples were investigated using high resolution transmission electron microscopy. In MgO and Y :ZrO2 covered with Pt, crystalline clusters with mean sizes of 2 and 3.5nm were found after the Pt+ irradiations with 8×1015 and 2×1016cm-2 and subsequent annealing, respectively. In MgO samples covered with FePt, clusters with mean sizes of 1 and 2nm were found after the Pt+ irradiations with 8×1015 and 2×1016cm-2 and subsequent annealing, respectively. In Y :ZrO2 samples covered with FePt, clusters up to 5nm in size were found after the Pt+ irradiation with 2×1016cm-2 and subsequent annealing. In LaAlO3 the irradiation was accompanied by a full amorphization of the host matrix and appearance of embedded clusters of different sizes. The determination of the lattice constant and thus the kind of the clusters in samples covered by FePt was hindered due to strong deviation of the electron beam by the ferromagnetic FePt.

Distribution of cardiac sodium channels in clusters potentiates ephaptic interactions in the intercalated disc.

PubMed

Hichri, Echrak; Abriel, Hugues; Kucera, Jan P

2018-02-15

It has been proposed that ephaptic conduction, relying on interactions between the sodium (Na + ) current and the extracellular potential in intercalated discs, might contribute to cardiac conduction when gap junctional coupling is reduced, but this mechanism is still controversial. In intercalated discs, Na + channels form clusters near gap junction plaques, but the functional significance of these clusters has never been evaluated. In HEK cells expressing cardiac Na + channels, we show that restricting the extracellular space modulates the Na + current, as predicted by corresponding simulations accounting for ephaptic effects. In a high-resolution model of the intercalated disc, clusters of Na + channels that face each other across the intercellular cleft facilitate ephaptic impulse transmission when gap junctional coupling is reduced. Thus, our simulations reveal a functional role for the clustering of Na + channels in intercalated discs, and suggest that rearrangement of these clusters in disease may influence cardiac conduction. It has been proposed that ephaptic interactions in intercalated discs, mediated by extracellular potentials, contribute to cardiac impulse propagation when gap junctional coupling is reduced. However, experiments demonstrating ephaptic effects on the cardiac Na + current (I Na ) are scarce. Furthermore, Na + channels form clusters around gap junction plaques, but the electrophysiological significance of these clusters has never been investigated. In patch clamp experiments with HEK cells stably expressing human Na v 1.5 channels, we examined how restricting the extracellular space modulates I Na elicited by an activation protocol. In parallel, we developed a high-resolution computer model of the intercalated disc to investigate how the distribution of Na + channels influences ephaptic interactions. Approaching the HEK cells to a non-conducting obstacle always increased peak I Na at step potentials near the threshold of I Na activation and decreased peak I Na at step potentials far above threshold (7 cells, P = 0.0156, Wilcoxon signed rank test). These effects were consistent with corresponding control simulations with a uniform Na + channel distribution. In the intercalated disc computer model, redistributing the Na + channels into a central cluster of the disc potentiated ephaptic effects. Moreover, ephaptic impulse transmission from one cell to another was facilitated by clusters of Na + channels facing each other across the intercellular cleft when gap junctional coupling was reduced. In conclusion, our proof-of-principle experiments demonstrate that confining the extracellular space modulates cardiac I Na , and our simulations reveal the functional role of the aggregation of Na + channels in the perinexus. These findings highlight novel concepts in the physiology of cardiac excitation. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

UWB Tracking Algorithms: AOA and TDOA

NASA Technical Reports Server (NTRS)

Ni, Jianjun David; Arndt, D.; Ngo, P.; Gross, J.; Refford, Melinda

2006-01-01

Ultra-Wideband (UWB) tracking prototype systems are currently under development at NASA Johnson Space Center for various applications on space exploration. For long range applications, a two-cluster Angle of Arrival (AOA) tracking method is employed for implementation of the tracking system; for close-in applications, a Time Difference of Arrival (TDOA) positioning methodology is exploited. Both AOA and TDOA are chosen to utilize the achievable fine time resolution of UWB signals. This talk presents a brief introduction to AOA and TDOA methodologies. The theoretical analysis of these two algorithms reveal the affecting parameters impact on the tracking resolution. For the AOA algorithm, simulations show that a tracking resolution less than 0.5% of the range can be achieved with the current achievable time resolution of UWB signals. For the TDOA algorithm used in close-in applications, simulations show that the (sub-inch) high tracking resolution is achieved with a chosen tracking baseline configuration. The analytical and simulated results provide insightful guidance for the UWB tracking system design.

Ultra-diffuse cluster galaxies as key to the MOND cluster conundrum

NASA Astrophysics Data System (ADS)

Milgrom, Mordehai

2015-12-01

Modified Newtonian Dynamics (MOND) reduces greatly the mass discrepancy in clusters of galaxies,but does leave a global discrepancy of about a factor of 2 (epitomized by the structure of the Bullet Cluster). It has been proposed, within the minimalist and purist MOND, that clusters harbour some indigenous, yet undetected, cluster baryonic (dark) matter (CBDM), whose total amount is comparable with that of the observed hot gas. Koda et al. have recently identified more than a thousand ultra-diffuse, galaxy-like objects (UDGs) in the Coma cluster. These, they argue, require, within Newtonian dynamics, that they are much more massive than their observed stellar component. Here, I propound that some of the CBDM is internal to UDGs, which endows them with robustness. The rest of the CBDM objects formed in now-disrupted kin of the UDGs, and is dispersed in the intracluster medium. The discovery of cluster UDGs is not in itself a resolution of the MOND cluster conundrum, but it lends greater plausibility to CBDM as its resolution. Alternatively, if the UDGs are only now falling into Coma, their large size and very low surface brightness could result from the inflation due to the MOND, variable external-field effect (EFE). I also consider briefly solutions to the conundrum that invoke more elaborate extensions of purist MOND, e.g. that in clusters, the MOND constant takes up larger than canonical values of the MOND constant. Whatever solves the cluster conundrum within MOND might also naturally account for UDGs.

The Cluster-EAGLE project: velocity bias and the velocity dispersion-mass relation of cluster galaxies

NASA Astrophysics Data System (ADS)

Armitage, Thomas J.; Barnes, David J.; Kay, Scott T.; Bahé, Yannick M.; Dalla Vecchia, Claudio; Crain, Robert A.; Theuns, Tom

2018-03-01

We use the Cluster-EAGLE simulations to explore the velocity bias introduced when using galaxies, rather than dark matter particles, to estimate the velocity dispersion of a galaxy cluster, a property known to be tightly correlated with cluster mass. The simulations consist of 30 clusters spanning a mass range 14.0 ≤ log10(M200 c/M⊙) ≤ 15.4, with their sophisticated subgrid physics modelling and high numerical resolution (subkpc gravitational softening), making them ideal for this purpose. We find that selecting galaxies by their total mass results in a velocity dispersion that is 5-10 per cent higher than the dark matter particles. However, selecting galaxies by their stellar mass results in an almost unbiased (<5 per cent) estimator of the velocity dispersion. This result holds out to z = 1.5 and is relatively insensitive to the choice of cluster aperture, varying by less than 5 per cent between r500 c and r200 m. We show that the velocity bias is a function of the time spent by a galaxy inside the cluster environment. Selecting galaxies by their total mass results in a larger bias because a larger fraction of objects have only recently entered the cluster and these have a velocity bias above unity. Galaxies that entered more than 4 Gyr ago become progressively colder with time, as expected from dynamical friction. We conclude that velocity bias should not be a major issue when estimating cluster masses from kinematic methods.

Integrated Light Chemical Abundance Analyses of 7 M31 Outer Halo Globular Clusters from the Pan-Andromeda Archaeological Survey

NASA Astrophysics Data System (ADS)

Sakari, Charli; Venn, Kim; Mackey, Dougal; Shetrone, Matthew D.; Dotter, Aaron L.; Wallerstein, George

2015-01-01

Detailed chemical abundances of globular clusters provide insight into the formation and evolution of galaxies and their globular cluster systems. This talk presents detailed chemical abundances for seven M31 outer halo globular clusters (with projected radii greater than 30 kpc), as derived from high resolution integrated light spectra. Five of these clusters were recently discovered in the Pan-Andromeda Archaeological Survey (PAndAS). The integrated abundances show that 4 of these clusters are metal-poor ([Fe/H] < -1.5) while the other 3 are more metal-rich. The most metal-poor globular clusters are α-enhanced, though 3 of the 4 are possibly less α-enhanced than MW stars (at the 1σ level). Other chemical abundance ratios ([Ba/Eu], [Eu/Ca], and [Ni/Fe]) are consistent with origins in low mass dwarf galaxies (similar to Fornax). The most metal-rich cluster ([Fe/H] ~ -1) stands out as being chemically distinct from Milky Way field stars of the same metallicity---its chemical abundance ratios agree best with the stars and clusters in the Large Magellanic Cloud (LMC) and the Sagittarius dwarf spheroidal (Sgr) than with the Milky Way field stars. The other metal-rich clusters, H10 and H23, look similar to the LMC and Milky Way field stars in all abundance ratios. These results indicate that M31's outer halo is being at least partially built up by the accretion of dwarf satellites, in agreement with previous observations.

GLOBULAR CLUSTER ABUNDANCES FROM HIGH-RESOLUTION, INTEGRATED-LIGHT SPECTROSCOPY. II. EXPANDING THE METALLICITY RANGE FOR OLD CLUSTERS AND UPDATED ANALYSIS TECHNIQUES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colucci, Janet E.; Bernstein, Rebecca A.; McWilliam, Andrew

2017-01-10

We present abundances of globular clusters (GCs) in the Milky Way and Fornax from integrated-light (IL) spectra. Our goal is to evaluate the consistency of the IL analysis relative to standard abundance analysis for individual stars in those same clusters. This sample includes an updated analysis of seven clusters from our previous publications and results for five new clusters that expand the metallicity range over which our technique has been tested. We find that the [Fe/H] measured from IL spectra agrees to ∼0.1 dex for GCs with metallicities as high as [Fe/H] = −0.3, but the abundances measured for more metal-rich clustersmore » may be underestimated. In addition we systematically evaluate the accuracy of abundance ratios, [X/Fe], for Na i, Mg i, Al i, Si i, Ca i, Ti i, Ti ii, Sc ii, V i, Cr i, Mn i, Co i, Ni i, Cu i, Y ii, Zr i, Ba ii, La ii, Nd ii, and Eu ii. The elements for which the IL analysis gives results that are most similar to analysis of individual stellar spectra are Fe i, Ca i, Si i, Ni i, and Ba ii. The elements that show the greatest differences include Mg i and Zr i. Some elements show good agreement only over a limited range in metallicity. More stellar abundance data in these clusters would enable more complete evaluation of the IL results for other important elements.« less

A high throughput spectral image microscopy system

NASA Astrophysics Data System (ADS)

Gesley, M.; Puri, R.

2018-01-01

A high throughput spectral image microscopy system is configured for rapid detection of rare cells in large populations. To overcome flow cytometry rates and use of fluorophore tags, a system architecture integrates sample mechanical handling, signal processors, and optics in a non-confocal version of light absorption and scattering spectroscopic microscopy. Spectral images with native contrast do not require the use of exogeneous stain to render cells with submicron resolution. Structure may be characterized without restriction to cell clusters of differentiation.

C60 and U ion irradiation of Gd 2Ti xZr 2-xO 7 pyrochlore

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jiaming; Toulemonde, Marcel; Lang, Maik

2015-08-01

Gd 2Ti xZr 2-xO 7 (x = 0 to 2) pyrochlore was irradiated by 30 MeV C 60 clusters, which provide an extremely high ionizing energy density. Here, high-resolution transmission electron microscopy revealed a complex ion-track structure in Gd 2Ti 2O 7 and Gd 2TiZrO 7, consisting of an amorphous core and a shell of a disordered, defect-fluorite structure.

NGC 6067: a young and massive open cluster with high metallicity

NASA Astrophysics Data System (ADS)

Alonso-Santiago, J.; Negueruela, I.; Marco, A.; Tabernero, H. M.; González-Fernández, C.; Castro, N.

2017-08-01

NGC 6067 is a young open cluster hosting the largest population of evolved stars among known Milky Way clusters in the 50-150 Ma age range. It thus represents the best laboratory in our Galaxy to constrain the evolutionary tracks of 5-7 M⊙ stars. We have used high-resolution spectra of a large sample of bright cluster members (45), combined with archival photometry, to obtain accurate parameters for the cluster as well as stellar atmospheric parameters. We derive a distance of 1.78 ± 0.12 kpc, an age of 90 ± 20 Ma and a tidal radius of 14.8^{+6.8}_{-3.2} arcmin. We estimate an initial mass above 5700 M⊙, for a present-day evolved population of two Cepheids, two A supergiants and 12 red giants with masses ≈6 M⊙. We also determine chemical abundances of Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y and Ba for the red clump stars. We find a supersolar metallicity, [Fe/H] = +0.19 ± 0.05, and a homogeneous chemical composition, consistent with the Galactic metallicity gradient. The presence of a Li-rich red giant, star 276 with A(Li) = 2.41, is also detected. An overabundance of Ba is found, supporting the enhanced s-process. The ratio of yellow to red giants is much smaller than 1, in agreement with models with moderate overshooting, but the properties of the cluster Cepheids do not seem consistent with current Padova models for supersolar metallicity.

Remote sensing imagery classification using multi-objective gravitational search algorithm

NASA Astrophysics Data System (ADS)

Zhang, Aizhu; Sun, Genyun; Wang, Zhenjie

2016-10-01

Simultaneous optimization of different validity measures can capture different data characteristics of remote sensing imagery (RSI) and thereby achieving high quality classification results. In this paper, two conflicting cluster validity indices, the Xie-Beni (XB) index and the fuzzy C-means (FCM) (Jm) measure, are integrated with a diversity-enhanced and memory-based multi-objective gravitational search algorithm (DMMOGSA) to present a novel multi-objective optimization based RSI classification method. In this method, the Gabor filter method is firstly implemented to extract texture features of RSI. Then, the texture features are syncretized with the spectral features to construct the spatial-spectral feature space/set of the RSI. Afterwards, cluster of the spectral-spatial feature set is carried out on the basis of the proposed method. To be specific, cluster centers are randomly generated initially. After that, the cluster centers are updated and optimized adaptively by employing the DMMOGSA. Accordingly, a set of non-dominated cluster centers are obtained. Therefore, numbers of image classification results of RSI are produced and users can pick up the most promising one according to their problem requirements. To quantitatively and qualitatively validate the effectiveness of the proposed method, the proposed classification method was applied to classifier two aerial high-resolution remote sensing imageries. The obtained classification results are compared with that produced by two single cluster validity index based and two state-of-the-art multi-objective optimization algorithms based classification results. Comparison results show that the proposed method can achieve more accurate RSI classification.

Aptamer-recognized carbohydrates on the cell membrane revealed by super-resolution microscopy.

PubMed

Jing, Yingying; Cai, Mingjun; Xu, Haijiao; Zhou, Lulu; Yan, Qiuyan; Gao, Jing; Wang, Hongda

2018-04-26

Carbohydrates are one of the most important components on the cell membrane, which participate in various physiological activities, and their aberrant expression is a consequence of pathological changes. In previous studies, carbohydrate analysis basically relied on lectins. However, discrimination between lectins still exists due to their multivalent character. Furthermore, the structures obtained by carbohydrate-lectin crosslinking confuse our direct observation to some extent. Fortunately, the emergence of aptamers, which are smaller and more flexible, has provided us an unprecedented choice. Herein, an aptamer recognition method with high precise localization was developed for imaging membrane-bound N-acetylgalactosamine (GalNAc). By using direct stochastic optical reconstruction microscopy (dSTORM), we compared this aptamer recognition method with the lectin recognition method for visualizing the detailed structure of GalNAc at the nanometer scale. The results indicated that GalNAc forms irregular clusters on the cell membrane with a resolution of 23 ± 7 nm by aptamer recognition. Additionally, when treated with N-acetylgalactosidase, the aptamer-recognized GalNAc shows a more significant decrease in cluster size and localization density, thus verifying better specificity of aptamers than lectins. Collectively, our study suggests that aptamers can act as perfect substitutes for lectins in carbohydrate labeling, which will be of great potential value in the field of super-resolution fluorescence imaging.

FORS2/VLT survey of Milky Way globular clusters. II. Fe and Mg abundances of 51 Milky Way globular clusters on a homogeneous scale

NASA Astrophysics Data System (ADS)

Dias, B.; Barbuy, B.; Saviane, I.; Held, E. V.; Da Costa, G. S.; Ortolani, S.; Gullieuszik, M.; Vásquez, S.

2016-05-01

Context. Globular clusters trace the formation and evolution of the Milky Way and surrounding galaxies, and outline their chemical enrichment history. To accomplish these tasks it is important to have large samples of clusters with homogeneous data and analysis to derive kinematics, chemical abundances, ages and locations. Aims: We obtain homogeneous metallicities and α-element enhancement for 51 Galactic bulge, disc, and halo globular clusters that are among the most distant and/or highly reddened in the Galaxy's globular cluster system. We also provide membership selection based on stellar radial velocities and atmospheric parameters. The implications of our results are discussed. Methods: We observed R ~ 2000 spectra in the wavelength interval 456-586 nm for over 800 red giant stars in 51 Galactic globular clusters. We applied full spectrum fitting with the code ETOILE together with libraries of observed and synthetic spectra. We compared the mean abundances of all clusters with previous work and with field stars. We used the relation between mean metallicity and horizontal branch morphology defined by all clusters to select outliers for discussion. Results: [Fe/H], [Mg/Fe], and [α/Fe] were derived in a consistent way for almost one-third of all Galactic globular clusters. We find our metallicities are comparable to those derived from high-resolution data to within σ = 0.08 dex over the interval -2.5< [Fe/H] < 0.0. Furthermore, a comparison of previous metallicity scales with our values yields σ< 0.16 dex. We also find that the distribution of [Mg/Fe] and [α/Fe] with [Fe/H] for the 51 clusters follows the general trend exhibited by field stars. It is the first time that the following clusters have been included in a large sample of homogeneous stellar spectroscopic observations and metallicity derivation: BH 176, Djorg 2, Pal 10, NGC 6426, Lynga 7, and Terzan 8. In particular, only photometric metallicities were available previously for the first three clusters, and the available metallicity for NGC 6426 was based on integrated spectroscopy and photometry. Two other clusters, HP 1 and NGC 6558, are confirmed as candidates for the oldest globular clusters in the Milky Way. Conclusions: Stellar spectroscopy in the visible at R ~ 2000 for a large sample of globular clusters is a robust and efficient way to trace the chemical evolution of the host galaxy and to detect interesting objects for follow-up at higher resolution and with forthcoming giant telescopes. The technique used here can also be applied to globular cluster systems in nearby galaxies with current instruments and to distant galaxies with the advent of ELTs. Based on observations collected at the European Southern Observatory/Paranal, Chile, under programmes 68.B-0482(A), 69.D-0455(A), 71.D-0219(A), 077.D-0775(A), and 089.D-0493(B).Full Tables 1 and A.2 with the derived average parameters for the 758 red giant stars are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A9

Diffraction-limited Visible Light Images of Orion Trapezium Cluster with the Magellan Adaptive Secondary Adaptive Optics System (MagAO)

NASA Astrophysics Data System (ADS)

Close, L. M.; Males, J. R.; Morzinski, K.; Kopon, D.; Follette, K.; Rodigas, T. J.; Hinz, P.; Wu, Y.-L.; Puglisi, A.; Esposito, S.; Riccardi, A.; Pinna, E.; Xompero, M.; Briguglio, R.; Uomoto, A.; Hare, T.

2013-09-01

We utilized the new high-order (250-378 mode) Magellan Adaptive Optics system (MagAO) to obtain very high spatial resolution observations in "visible light" with MagAO's VisAO CCD camera. In the good-median seeing conditions of Magellan (0.''5-0.''7), we find MagAO delivers individual short exposure images as good as 19 mas optical resolution. Due to telescope vibrations, long exposure (60 s) r' (0.63 μm) images are slightly coarser at FWHM = 23-29 mas (Strehl ~28%) with bright (R < 9 mag) guide stars. These are the highest resolution filled-aperture images published to date. Images of the young (~1 Myr) Orion Trapezium θ1 Ori A, B, and C cluster members were obtained with VisAO. In particular, the 32 mas binary θ1 Ori C 1 C 2 was easily resolved in non-interferometric images for the first time. The relative positions of the bright trapezium binary stars were measured with ~0.6-5 mas accuracy. We are now sensitive to relative proper motions of just ~0.2 mas yr-1 (~0.4 km s-1 at 414 pc)—this is a ~2-10 × improvement in orbital velocity accuracy compared to previous efforts. For the first time, we see clear motion of the barycenter of θ1 Ori B 2 B 3 about θ1 Ori B 1. All five members of the θ1 Ori B system appear likely to be a gravitationally bound "mini cluster," but we find that not all the orbits can be both circular and co-planar. The lowest mass member of the θ1 Ori B system (B 4; mass ~0.2 M ⊙) has a very clearly detected motion (at 4.1 ± 1.3 km s-1 correlation = 99.9%) w.r.t. B 1. Previous work has suggested that B 4 and B 3 are on long-term unstable orbits and will be ejected from this "mini cluster." However, our new "baseline" model of the θ1 Ori B system suggests a more hierarchical system than previously thought, and so the ejection of B 4 may not occur for many orbits, and B 3 may be stable against ejection in the long-term. This "ejection" process of the lowest mass member of a "mini cluster" could play a major role in the formation of low-mass stars and brown dwarfs. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Combination of multivariate curve resolution and multivariate classification techniques for comprehensive high-performance liquid chromatography-diode array absorbance detection fingerprints analysis of Salvia reuterana extracts.

PubMed

Hakimzadeh, Neda; Parastar, Hadi; Fattahi, Mohammad

2014-01-24

In this study, multivariate curve resolution (MCR) and multivariate classification methods are proposed to develop a new chemometric strategy for comprehensive analysis of high-performance liquid chromatography-diode array absorbance detection (HPLC-DAD) fingerprints of sixty Salvia reuterana samples from five different geographical regions. Different chromatographic problems occurred during HPLC-DAD analysis of S. reuterana samples, such as baseline/background contribution and noise, low signal-to-noise ratio (S/N), asymmetric peaks, elution time shifts, and peak overlap are handled using the proposed strategy. In this way, chromatographic fingerprints of sixty samples are properly segmented to ten common chromatographic regions using local rank analysis and then, the corresponding segments are column-wise augmented for subsequent MCR analysis. Extended multivariate curve resolution-alternating least squares (MCR-ALS) is used to obtain pure component profiles in each segment. In general, thirty-one chemical components were resolved using MCR-ALS in sixty S. reuterana samples and the lack of fit (LOF) values of MCR-ALS models were below 10.0% in all cases. Pure spectral profiles are considered for identification of chemical components by comparing their resolved spectra with the standard ones and twenty-four components out of thirty-one components were identified. Additionally, pure elution profiles are used to obtain relative concentrations of chemical components in different samples for multivariate classification analysis by principal component analysis (PCA) and k-nearest neighbors (kNN). Inspection of the PCA score plot (explaining 76.1% of variance accounted for three PCs) showed that S. reuterana samples belong to four clusters. The degree of class separation (DCS) which quantifies the distance separating clusters in relation to the scatter within each cluster is calculated for four clusters and it was in the range of 1.6-5.8. These results are then confirmed by kNN. In addition, according to the PCA loading plot and kNN dendrogram of thirty-one variables, five chemical constituents of luteolin-7-o-glucoside, salvianolic acid D, rosmarinic acid, lithospermic acid and trijuganone A are identified as the most important variables (i.e., chemical markers) for clusters discrimination. Finally, the effect of different chemical markers on samples differentiation is investigated using counter-propagation artificial neural network (CP-ANN) method. It is concluded that the proposed strategy can be successfully applied for comprehensive analysis of chromatographic fingerprints of complex natural samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Centre-excised X-ray luminosity as an efficient mass proxy for future galaxy cluster surveys

DOE PAGES

Mantz, Adam B.; Allen, Steven W.; Morris, R. Glenn; ...

2017-10-02

The cosmological constraining power of modern galaxy cluster catalogues can be improved by obtaining low-scatter mass proxy measurements for even a small fraction of sources. In the context of large upcoming surveys that will reveal the cluster population down to the group scale and out to high redshifts, efficient strategies for obtaining such mass proxies will be valuable. Here in this work, we use high-quality weak-lensing and X-ray mass estimates for massive clusters in current X-ray-selected catalogues to revisit the scaling relations of the projected, centre-excised X-ray luminosity (L ce), which previous work suggests correlates tightly with total mass. Ourmore » data confirm that this is the case with Lce having an intrinsic scatter at fixed mass comparable to that of gas mass, temperature or YX. Compared to the other proxies, however, Lce is less susceptible to systematic uncertainties due to background modelling, and can be measured precisely with shorter exposures. This opens up the possibility of using L ce to estimate masses for large numbers of clusters discovered by new X-ray surveys (e.g. eROSITA) directly from the survey data, as well as for clusters discovered at other wavelengths with relatively short follow-up observations. We describe a simple procedure for making such estimates from X-ray surface brightness data, and comment on the spatial resolution required to apply this method as a function of cluster mass and redshift. Lastly, we also explore the potential impact of Chandra and XMM–Newton follow-up observations over the next decade on dark energy constraints from new cluster surveys.« less

Globular cluster x-ray sources

PubMed Central

Pooley, David

2010-01-01

Globular clusters and x-ray astronomy have a long and fruitful history. Uhuru and OSO-7 revealed highly luminous (> 1036 ergs-1) x-ray sources in globular clusters, and Einstein and ROSAT revealed a larger population of low-luminosity (< 1033 ergs-1) x-ray sources. It was realized early on that the high-luminosity sources were low-mass x-ray binaries in outburst and that they were orders of magnitude more abundant per unit mass in globular clusters than in the rest of the galaxy. However, the low-luminosity sources proved difficult to classify. Many ideas were put forth—low-mass x-ray binaries in quiescence (qLMXBs), cataclysmic variables (CVs), active main-sequence binaries (ABs), and millisecond pulsars (MSPs)—but secure identifications were scarce. In ROSAT observations of 55 clusters, about 25 low-luminosity sources were found. Chandra has now observed over 80 Galactic globular clusters, and these observations have revealed over 1,500 x-ray sources. The superb angular resolution has allowed for many counterpart identifications, providing clues to the nature of this population. It is a heterogeneous mix of qLMXBs, CVs, ABs, and MSPs, and it has been shown that the qLMXBs and CVs are both, in part, overabundant like the luminous LMXBs. The number of x-ray sources in a cluster correlates very well with its encounter frequency. This points to dynamical formation scenarios for the x-ray sources and shows them to be excellent tracers of the complicated internal dynamics. The relation between the encounter frequency and the number of x-ray sources has been used to suggest that we have misunderstood the dynamical states of globular clusters. PMID:20404204

Light and Heavy Element Abundance Variations in the Outer Halo Globular Cluster NGC 6229

NASA Astrophysics Data System (ADS)

Johnson, Christian I.; Caldwell, Nelson; Rich, R. Michael; Walker, Matthew G.

2017-10-01

NGC 6229 is a relatively massive outer halo globular cluster that is primarily known for exhibiting a peculiar bimodal horizontal branch morphology. Given the paucity of spectroscopic data on this cluster, we present a detailed chemical composition analysis of 11 red giant branch members based on high resolution (R ≈ 38,000), high S/N (>100) spectra obtained with the MMT-Hectochelle instrument. We find the cluster to have a mean heliocentric radial velocity of -{138.1}-1.0+1.0 {km} {{{s}}}-1, a small dispersion of {3.8}-0.7+1.0 {km} {{{s}}}-1, and a relatively low {(M/{L}{{V}})}⊙ ={0.82}-0.28+0.49. The cluster is moderately metal-poor with < [{Fe}/{{H}}]> =-1.13 dex and a modest dispersion of 0.06 dex. However, 18% (2/11) of the stars in our sample have strongly enhanced [La, Nd/Fe] ratios that are correlated with a small (˜0.05 dex) increase in [Fe/H]. NGC 6229 shares several chemical signatures with M75, NGC 1851, and the intermediate metallicity populations of ω Cen, which lead us to conclude that NGC 6229 is a lower mass iron-complex cluster. The light elements exhibit the classical (anti-)correlations that extend up to Si, but the cluster possesses a large gap in the O-Na plane that separates first and second generation stars. NGC 6229 also has unusually low [Na, Al/Fe] abundances that are consistent with an accretion origin. A comparison with M54 and other Sagittarius clusters suggests that NGC 6229 could also be the remnant core of a former dwarf spheroidal galaxy.

Centre-excised X-ray luminosity as an efficient mass proxy for future galaxy cluster surveys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mantz, Adam B.; Allen, Steven W.; Morris, R. Glenn

The cosmological constraining power of modern galaxy cluster catalogues can be improved by obtaining low-scatter mass proxy measurements for even a small fraction of sources. In the context of large upcoming surveys that will reveal the cluster population down to the group scale and out to high redshifts, efficient strategies for obtaining such mass proxies will be valuable. Here in this work, we use high-quality weak-lensing and X-ray mass estimates for massive clusters in current X-ray-selected catalogues to revisit the scaling relations of the projected, centre-excised X-ray luminosity (L ce), which previous work suggests correlates tightly with total mass. Ourmore » data confirm that this is the case with Lce having an intrinsic scatter at fixed mass comparable to that of gas mass, temperature or YX. Compared to the other proxies, however, Lce is less susceptible to systematic uncertainties due to background modelling, and can be measured precisely with shorter exposures. This opens up the possibility of using L ce to estimate masses for large numbers of clusters discovered by new X-ray surveys (e.g. eROSITA) directly from the survey data, as well as for clusters discovered at other wavelengths with relatively short follow-up observations. We describe a simple procedure for making such estimates from X-ray surface brightness data, and comment on the spatial resolution required to apply this method as a function of cluster mass and redshift. Lastly, we also explore the potential impact of Chandra and XMM–Newton follow-up observations over the next decade on dark energy constraints from new cluster surveys.« less

Globular Cluster Abundances from High-resolution, Integrated-light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques

NASA Astrophysics Data System (ADS)

Colucci, Janet E.; Bernstein, Rebecca A.; McWilliam, Andrew

2017-01-01

We present abundances of globular clusters (GCs) in the Milky Way and Fornax from integrated-light (IL) spectra. Our goal is to evaluate the consistency of the IL analysis relative to standard abundance analysis for individual stars in those same clusters. This sample includes an updated analysis of seven clusters from our previous publications and results for five new clusters that expand the metallicity range over which our technique has been tested. We find that the [Fe/H] measured from IL spectra agrees to ˜0.1 dex for GCs with metallicities as high as [Fe/H] = -0.3, but the abundances measured for more metal-rich clusters may be underestimated. In addition we systematically evaluate the accuracy of abundance ratios, [X/Fe], for Na I, Mg I, Al I, Si I, Ca I, Ti I, Ti II, Sc II, V I, Cr I, Mn I, Co I, Ni I, Cu I, Y II, Zr I, Ba II, La II, Nd II, and Eu II. The elements for which the IL analysis gives results that are most similar to analysis of individual stellar spectra are Fe I, Ca I, Si I, Ni I, and Ba II. The elements that show the greatest differences include Mg I and Zr I. Some elements show good agreement only over a limited range in metallicity. More stellar abundance data in these clusters would enable more complete evaluation of the IL results for other important elements. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Cluster galaxy dynamics and the effects of large-scale environment

NASA Astrophysics Data System (ADS)

White, Martin; Cohn, J. D.; Smit, Renske

2010-11-01

Advances in observational capabilities have ushered in a new era of multi-wavelength, multi-physics probes of galaxy clusters and ambitious surveys are compiling large samples of cluster candidates selected in different ways. We use a high-resolution N-body simulation to study how the influence of large-scale structure in and around clusters causes correlated signals in different physical probes and discuss some implications this has for multi-physics probes of clusters (e.g. richness, lensing, Compton distortion and velocity dispersion). We pay particular attention to velocity dispersions, matching galaxies to subhaloes which are explicitly tracked in the simulation. We find that not only do haloes persist as subhaloes when they fall into a larger host, but groups of subhaloes retain their identity for long periods within larger host haloes. The highly anisotropic nature of infall into massive clusters, and their triaxiality, translates into an anisotropic velocity ellipsoid: line-of-sight galaxy velocity dispersions for any individual halo show large variance depending on viewing angle. The orientation of the velocity ellipsoid is correlated with the large-scale structure, and thus velocity outliers correlate with outliers caused by projection in other probes. We quantify this orientation uncertainty and give illustrative examples. Such a large variance suggests that velocity dispersion estimators will work better in an ensemble sense than for any individual cluster, which may inform strategies for obtaining redshifts of cluster members. We similarly find that the ability of substructure indicators to find kinematic substructures is highly viewing angle dependent. While groups of subhaloes which merge with a larger host halo can retain their identity for many Gyr, they are only sporadically picked up by substructure indicators. We discuss the effects of correlated scatter on scaling relations estimated through stacking, both analytically and in the simulations, showing that the strong correlation of measures with mass and the large scatter in mass at fixed observable mitigate line-of-sight projections.

Cross Section High Resolution Imaging of Polymer-Based Materials

NASA Astrophysics Data System (ADS)

Delaportas, D.; Aden, P.; Muckle, C.; Yeates, S.; Treutlein, R.; Haq, S.; Alexandrou, I.

This paper describes a methodology for preparing cross sections of organic layers suitable for transmission electron microscopy (TEM) at high resolution. Our principal aim is to prepare samples that are tough enough to allow the slicing into sub-150 nm sections. We also need strong contrast at the organic layer area to make it identifiable during TEM. Our approach is to deposit organic layers on flexible substrates and prepare thin cross sections using ultra-microtomy. We sandwich the organic layer between two metal thin films in order to isolate it and improve contrast. Our methodology is used to study the microstructure of polymer/nanotube composites, allowing us to accurately measure the organic layer thickness, determine nanotube dispersion and assess the effect of nanotube clustering on film structural stability.

Lynx mission concept study

NASA Astrophysics Data System (ADS)

Vikhlinin, Alexey

2018-01-01

Lynx is an observatory-class mission, featuring high throughput, exquisite angular resolution over a substantial field of view, and high spectral resolution for point and extended X-ray sources. The design requirements provide a tremendous leap in capabilities relative to missions such as Chandra and Athena. Lynx will observe the dawn of supermassive black holes through detection of very faint X-ray sources in the early universe and will reveal the "invisible drivers" of galaxy and structure formation through observations of hot, diffuse baryons in and around the galaxies. Lynx will enable breakthroughs across all of astrophysics, ranging from detailed understanding of stellar activity including effects on habitability of associated planets to population statistics of neutron stars and black holes in the Local Group galaxies, to earliest groups and clusters of galaxies, and to cosmology

Investigation of point and extended defects in electron irradiated silicon—Dependence on the particle energy

NASA Astrophysics Data System (ADS)

Radu, R.; Pintilie, I.; Nistor, L. C.; Fretwurst, E.; Lindstroem, G.; Makarenko, L. F.

2015-04-01

This work is focusing on generation, time evolution, and impact on the electrical performance of silicon diodes impaired by radiation induced active defects. n-type silicon diodes had been irradiated with electrons ranging from 1.5 MeV to 27 MeV. It is shown that the formation of small clusters starts already after irradiation with high fluence of 1.5 MeV electrons. An increase of the introduction rates of both point defects and small clusters with increasing energy is seen, showing saturation for electron energies above ˜15 MeV. The changes in the leakage current at low irradiation fluence-values proved to be determined by the change in the configuration of the tri-vacancy (V3). Similar to V3, other cluster related defects are showing bistability indicating that they might be associated with larger vacancy clusters. The change of the space charge density with irradiation and with annealing time after irradiation is fully described by accounting for the radiation induced trapping centers. High resolution electron microscopy investigations correlated with the annealing experiments revealed changes in the spatial structure of the defects. Furthermore, it is shown that while the generation of point defects is well described by the classical Non Ionizing Energy Loss (NIEL), the formation of small defect clusters is better described by the "effective NIEL" using results from molecular dynamics simulations.

The CAnadian NIRISS Unbiased Cluster Survey (CANUCS)

NASA Astrophysics Data System (ADS)

Ravindranath, Swara; NIRISS GTO Team

2017-06-01

CANUCS GTO program is a JWST spectroscopy and imaging survey of five massive galaxy clusters and ten parallel fields using the NIRISS low-resolution grisms, NIRCam imaging and NIRSpec multi-object spectroscopy. The primary goal is to understand the evolution of low mass galaxies across cosmic time. The resolved emission line maps and line ratios for many galaxies, with some at resolution of 100pc via the magnification by gravitational lensing will enable determining the spatial distribution of star formation, dust and metals. Other science goals include the detection and characterization of galaxies within the reionization epoch, using multiply-imaged lensed galaxies to constrain cluster mass distributions and dark matter substructure, and understanding star-formation suppression in the most massive galaxy clusters. In this talk I will describe the science goals of the CANUCS program. The proposed prime and parallel observations will be presented with details of the implementation of the observation strategy using JWST proposal planning tools.

Locating the two black holes in NGC 6240.

PubMed

Max, Claire E; Canalizo, Gabriela; de Vries, Willem H

2007-06-29

Mergers play an important role in galaxy evolution and are key to understanding the correlation between central-black hole mass and host-galaxy properties. We used the new technology of adaptive optics at the Keck II telescope to observe NGC 6240, a merger between two disk galaxies. Our high-resolution near-infrared images, combined with radio and x-ray positions, revealed the location and environment of two central supermassive black holes. Each is at the center of a rotating stellar disk, surrounded by a cloud of young star clusters. The brightest of these young clusters lie in the plane of each disk, but surprisingly are seen only on the disks' receding side.

Astrophysics Meets Atomic Physics: Fe I Line Identifications and Templates for Old Stellar Populations from Warm and Hot Stellar UV Spectra

NASA Astrophysics Data System (ADS)

Peterson, Ruth

2017-08-01

Imaging surveys from the ultraviolet to the infrared are recording ever more distant astronomical sources. Needed to interpret them are high-resolution ultraviolet spectral templates at all metallicities for both old and intermediate-age stars, and the atomic physics data essential to model their spectra. To this end we are proposing new UV spectra of four warm and hot stars spanning a wide range of metallicity. These will provide observational templates of old and young metal-poor turnoff stars, and the laboratory source for the identification of thousands of lines of neutral iron that appear in stellar spectra but are not identified in laboratory spectra. By matching existing and new stellar spectra to calculations of energy levels, line wavelengths, and gf-values, Peterson & Kurucz (2015) and Peterson, Kurucz, & Ayres (2017) identified 124 Fe I levels with energies up to 8.4eV. These provided 3000 detectable Fe I lines from 1600A to 5.4mu, and yielded empirical gf-values for 640 of these. Here we propose high-resolution UV spectra reaching 1780A for the first time at the turnoff, to detect and identify the strongest Fe I lines at 1800 - 1850A. This should add 250 new Fe I levels. These spectra, plus one at lower resolution reaching 1620A, will also provide empirical UV templates for turnoff stars at high redshifts as well as low. This is essential to deriving age and metallicity independently for globular clusters and old galaxies out to z 3. It will also improve abundances of trace elements in metal-poor stars, constraining nucleosynthesis at early epochs and aiding the reconstruction of the populations of the Milky Way halo and of nearby globular clusters.

The Grism Lens-amplified Survey from Space (GLASS). X. Sub-kiloparsec Resolution Gas-phase Metallicity Maps at Cosmic Noon behind the Hubble Frontier Fields Cluster MACS1149.6+2223

NASA Astrophysics Data System (ADS)

Wang, Xin; Jones, Tucker A.; Treu, Tommaso; Morishita, Takahiro; Abramson, Louis E.; Brammer, Gabriel B.; Huang, Kuang-Han; Malkan, Matthew A.; Schmidt, Kasper B.; Fontana, Adriano; Grillo, Claudio; Henry, Alaina L.; Karman, Wouter; Kelly, Patrick L.; Mason, Charlotte A.; Mercurio, Amata; Rosati, Piero; Sharon, Keren; Trenti, Michele; Vulcani, Benedetta

2017-03-01

We combine deep Hubble Space Telescope grism spectroscopy with a new Bayesian method to derive maps of gas-phase metallicity for 10 star-forming galaxies at high redshift (1.2≲ z≲ 2.3). Exploiting lensing magnification by the foreground cluster MACS1149.6+2223, we reach sub-kiloparsec spatial resolution and push the limit of stellar mass associated with such high-z spatially resolved measurements below {10}8 {M}⊙ for the first time. Our maps exhibit diverse morphologies, indicative of various effects such as efficient radial mixing from tidal torques, rapid accretion of low-metallicity gas, and other physical processes that can affect the gas and metallicity distributions in individual galaxies. Based upon an exhaustive sample of all existing sub-kiloparesec resolution metallicity gradient measurements at high z, we find that predictions given by analytical chemical evolution models assuming a relatively extended star-formation profile in the early disk-formation phase can explain the majority of observed metallicity gradients, without involving galactic feedback or radial outflows. We observe a tentative correlation between stellar mass and metallicity gradients, consistent with the “downsizing” galaxy formation picture that more massive galaxies are more evolved into a later phase of disk growth, where they experience more coherent mass assembly at all radii and thus show shallower metallicity gradients. In addition to the spatially resolved analysis, we compile a sample of homogeneously cross-calibrated integrated metallicity measurements spanning three orders of magnitude in stellar mass at z ˜ 1.8. We use this sample to study the mass-metallicity relation (MZR) and find that the slope of the observed MZR can rule out the momentum-driven wind model at a 3σ confidence level.

Microwave spectroscopy of carbonyl sulfide isotopologues solvated with 2-5 para-hydrogen molecules

NASA Astrophysics Data System (ADS)

Raston, Paul L.; Knapp, Chrissy J.; Jäger, Wolfgang

2017-11-01

We report high resolution Fourier transform microwave spectra of (pH2)N-OC32S and (pH2)N-OC34S clusters in the size range from N = 2 to 5. Observation of the J = 1-0 and J = 2-1 transitions allowed for determination of the rotational (B) and quartic distortion (D) constants for each N. Comparison with theory (Paesani et al., 2003) reveals that the predicted B values are of good quality (all within 100 MHz of the actual values), while the predicted D values are an order of magnitude too high. Results from linear molecule Kraitchman analyses for clusters with N ≤ 5 are consistent with theoretical calculations which suggest that the initial pH2 density accumulates in a donut ring about the carbon-oxygen bond.

The Balloon Experimental Twin Telescope for Infrared Interferometry

NASA Technical Reports Server (NTRS)

Silverburg, Robert

2009-01-01

Astronomical studies at infrared wavelengths have dramatically improved our understanding of the universe, and observations with Spitzer, the upcoming Herschel mission, and SOFIA will continue to provide exciting new discoveries. The comparatively low spatial resolution of these missions, however, is insufficient to resolve the physical scales on which mid- to far-infrared emission arises, resulting in source and structure ambiguities that limit our ability to answer key science questions. Interferometry enables high angular resolution at these wavelengths. We have proposed a new high altitude balloon experiment, the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII). High altitude operation makes far-infrared (30- 300micron) observations possible, and BETTII's 8-meter baseline provides unprecedented angular resolution (approx. 0.5 arcsec) in this band. BETTII will use a double-Fourier instrument to simultaneously obtain both spatial and spectral information. The spatially resolved spectroscopy provided by BETTII will address key questions about the nature of disks in young cluster stars and active galactic nuclei and the envelopes of evolved stars. BETTII will also lay the groundwork for future space interferometers.

A DYNAMICAL STUDY OF SUSPECTED RUNAWAY STARS AS TRACES OF PAST SUPERNOVA EXPLOSIONS IN THE REGION OF THE SCORPIUS-CENTAURUS OB ASSOCIATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jilinski, E.; Ortega, V. G.; Drake, N. A.

2010-09-20

We address the question of identifying possible past supernovae events taking place in the region of the Scorpius-Centaurus (Sco-Cen) OB association based on stars proposed by Hoogerwerf et al. With this purpose, we obtained a time series of high-resolution spectra of six stars (HIP 42038, HIP 46950, HIP 48943, HIP 69491, HIP 76013, and HIP 82868) which, according to Hoogerwerf et al., may have been runaway stars with origins in the region of the Sco-Cen association. This also includes the nearby young open clusters IC 2391 and IC 2602. If confirmed, such supernovae events could, in principle, have played amore » role in triggering the formation of some small stellar groups thought to be associated with the Sco-Cen association. Our analysis shows that, except for HIP 48943, the remaining stars are spectroscopic binary systems. For HIP 46950 and HIP 69491, this was already noted by other authors. Our high-resolution spectra allowed us to obtain the radial velocities for all the stars which, combined with their proper motions and parallaxes from Hipparcos, provide a means to investigate, by retracing their orbits, if the Sco-Cen region was, in fact, the origin of these stars. We find that none of these systems originated in the Sco-Cen region. Exploring the possibility that the birthplace of the studied stars occurred in the clusters IC 2391 and IC 2602, we noticed that at the epoch of 2-3 Myr ago these clusters were at a distance comparable with their tidal radii.« less

OBSERVING CASCADES OF SOLAR BULLETS AT HIGH RESOLUTION. II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scullion, E.; Engvold, O.; Lin, Y.

High resolution observations from the Swedish 1-m Solar Telescope revealed bright, discrete, blob-like structures (which we refer to as solar bullets) in the Hα 656.28 nm line core that appear to propagate laterally across the solar atmosphere as clusters in active regions (ARs). These small-scale structures appear to be field aligned and many bullets become triggered simultaneously and traverse collectively as a cluster. Here, we conduct a follow-up study on these rapidly evolving structures with coincident observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly. With the co-aligned data sets, we reveal (a) an evolving multithermal structure in the bullet clustermore » ranging from chromospheric to at least transition region temperatures, (b) evidence for cascade-like behavior and corresponding bidirectional motions in bullets within the cluster, which indicate that there is a common source of the initial instability leading to bullet formation, and (c) a direct relationship between co-incident bullet velocities observed in Hα and He ii 30.4 nm and an inverse relationship with respect to bullet intensity in these channels. We find evidence supporting that bullets are typically composed of a cooler, higher density core detectable in Hα with a less dense, hotter, and fainter co-moving outer sheath. Bullets unequivocally demonstrate the finely structured nature of the AR corona. We have no clear evidence for bullets being associated with locally heated (or cooled), fast flowing plasma. Fast MHD pulses (such as solitons) could best describe the dynamic properties of bullets whereas the presence of a multithermal structure is new.« less

MAGNESIUM ISOTOPE RATIOS IN {omega} CENTAURI RED GIANTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Da Costa, G. S.; Norris, John E.; Yong, David

2013-05-20

We have used the high-resolution observations obtained at the Anglo-Australian Telescope with Ultra-High Resolution Facility (R {approx} 100,000) and at Gemini-S with b-HROS (R {approx} 150,000) to determine magnesium isotope ratios for seven {omega} Cen red giants that cover a range in iron abundance from [Fe/H] = -1.78 to -0.78 dex, and for two red giants in M4 (NGC 6121). The {omega} Cen stars sample both the ''primordial'' (i.e., O-rich, Na- and Al-poor) and the ''extreme'' (O-depleted, Na- and Al-rich) populations in the cluster. The primordial population stars in both {omega} Cen and M4 show ({sup 25}Mg, {sup 26}Mg)/{sup 24}Mgmore » isotopic ratios that are consistent with those found for the primordial population in other globular clusters with similar [Fe/H] values. The isotopic ratios for the {omega} Cen extreme stars are also consistent with those for extreme population stars in other clusters. The results for the extreme population stars studied indicate that the {sup 26}Mg/{sup 24}Mg ratio is highest at intermediate metallicities ([Fe/H] < -1.4 dex), and for the highest [Al/Fe] values. Further, the relative abundance of {sup 26}Mg in the extreme population stars is notably higher than that of {sup 25}Mg, in contrast to model predictions. The {sup 25}Mg/{sup 24}Mg isotopic ratio in fact does not show any obvious dependence on either [Fe/H] or [Al/Fe] nor, intriguingly, any obvious difference between the primordial and extreme population stars.« less

Absolute Effective Area of the Chandra High-Resolution Mirror Assembly

NASA Technical Reports Server (NTRS)

Schwartz, D. A.; David, L. P.; Donnelly, R. H.; Edgar, R. J.; Gaetz, T. J.; Jerius, D.; Juda, M.; Kellogg, E. M.; McNamara, B. R.; Dewey, D.

2000-01-01

The Chandra X-ray Observatory was launched in July 1999, and is returning exquisite sub-arcsecond x-ray images of star groups, supernova remnants, galaxies, quasars, and clusters of galaxies. In addition to being the premier X-ray observatory in terms of angular and spectral resolution, Chandra is the best calibrated X-ray facility ever flown. We discuss here the calibration of the effective area of the High Resolution Mirror Assembly. Because we do not know the absolute X-ray flux density of any celestial source, this must be based primarily on ground measurements and on modeling. In particular, we must remove the calibrated modeled responses of the detectors and gratings to obtain the mirror area. For celestial sources which may be assumed to have smoothly varying spectra, such as the Crab Nebula, we may verify the continuity of the area calibration as a function of energy. This is of significance in energy regions such as the Ir M-edges, or near the critical grazing angle cutoff of the various mirror shells.

[An improved low spectral distortion PCA fusion method].

PubMed

Peng, Shi; Zhang, Ai-Wu; Li, Han-Lun; Hu, Shao-Xing; Meng, Xian-Gang; Sun, Wei-Dong

2013-10-01

Aiming at the spectral distortion produced in PCA fusion process, the present paper proposes an improved low spectral distortion PCA fusion method. This method uses NCUT (normalized cut) image segmentation algorithm to make a complex hyperspectral remote sensing image into multiple sub-images for increasing the separability of samples, which can weaken the spectral distortions of traditional PCA fusion; Pixels similarity weighting matrix and masks were produced by using graph theory and clustering theory. These masks are used to cut the hyperspectral image and high-resolution image into some sub-region objects. All corresponding sub-region objects between the hyperspectral image and high-resolution image are fused by using PCA method, and all sub-regional integration results are spliced together to produce a new image. In the experiment, Hyperion hyperspectral data and Rapid Eye data were used. And the experiment result shows that the proposed method has the same ability to enhance spatial resolution and greater ability to improve spectral fidelity performance.

Determining SAFOD area microearthquake locations solely with the Pilot Hole seismic array data

NASA Astrophysics Data System (ADS)

Oye, Volker; Chavarria, J. Andres; Malin, Peter E.

2004-05-01

In August 2002, an array of 32 three-component geophones was installed in the San Andreas Fault Observatory at Depth (SAFOD) Pilot Hole (PH) at Parkfield, CA. As an independent test of surface-observation-based microearthquake locations, we have located such events using only data recorded on the PH array. We then compared these locations with locations from a combined set of PH and Parkfield High Resolution Seismic Network (HRSN) observations. We determined the uncertainties in the locations as they relate to errors in the travel time picks and the velocity model by the bootstrap method. Based on the PH and combined locations, we find that the ``C2'' cluster to the northeast of the PH has the smallest location uncertainties. Events in this cluster also have the most similar waveforms and largest magnitudes. This confirms earlier suggestions that the C2 cluster is a promising target for the SAFOD Main Hole.

Clustered Dynamics of Inhibitory Synapses and Dendritic Spines in the Adult Neocortex

PubMed Central

Chen, Jerry L.; Villa, Katherine L; Cha, Jae Won; So, Peter T.C.; Kubota, Yoshiyuki; Nedivi, Elly

2012-01-01

A key feature of the mammalian brain is its capacity to adapt in response to experience, in part by remodeling of synaptic connections between neurons. Excitatory synapse rearrangements have been monitored in vivo by observation of dendritic spine dynamics, but lack of a vital marker for inhibitory synapses has precluded their observation. Here, we simultaneously monitor in vivo inhibitory synapse and dendritic spine dynamics across the entire dendritic arbor of pyramidal neurons in the adult mammalian cortex using large volume high-resolution dual color two-photon microscopy. We find that inhibitory synapses on dendritic shafts and spines differ in their distribution across the arbor and in their remodeling kinetics during normal and altered sensory experience. Further, we find inhibitory synapse and dendritic spine remodeling to be spatially clustered, and that clustering is influenced by sensory input. Our findings provide in vivo evidence for local coordination of inhibitory and excitatory synaptic rearrangements. PMID:22542188

Variations in the magnetopause current layer

NASA Astrophysics Data System (ADS)

Laakso, H. E.; Middleton, H. R.

2017-12-01

We use multi-point observations from the Cluster spacecraft to investigate the variations in the magnetopause current layer. With help of the curlometer technique one can determine the magnetopause current and its variability. Most of the time the magnetopause location is moving back and forth, so during any given pass the current layer is crossed several times. We use such crossings to investigate the characteristics of the current layer as the solar wind pressure varies (and the magnetopause moves accordingly). In addition we take an advantage of the ambient electron measurements from the EDI experiment which have been calibrated against the PEACE electron spectrometer data. These data can be used to detect fast variations of 1 keV electrons at resolution of 1-100 ms. Overall, Cluster observations are highly complimentary to the MMS observations due to the polar orbit of the Cluster spacecraft which provide fast vertical profiles of the magnetopause current layer.

Large-scale atomistic calculations of clusters in intense x-ray pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Phay J.; Knight, Chris

Here, we present the methodology of our recently developed Monte-Carlo/ Molecular-Dynamics method for studying the fundamental ultrafast dynamics induced by high-fluence, high-intensity x-ray free electron laser (XFEL) pulses in clusters. The quantum nature of the initiating ionization process is accounted for by a Monte Carlo method to calculate probabilities of electronic transitions, including photo absorption, inner-shell relaxation, photon scattering, electron collision and recombination dynamics, and thus track the transient electronic configurations explicitly. The freed electrons and ions are followed by classical particle trajectories using a molecular dynamics algorithm. These calculations reveal the surprising role of electron-ion recombination processes that leadmore » to the development of nonuniform spatial charge density profiles in x-ray excited clusters over femtosecond timescales. In the high-intensity limit, it is important to include the recombination dynamics in the calculated scattering response even for a 2- fs pulse. We also demonstrate that our numerical codes and algorithms can make e!cient use of the computational power of massively parallel supercomputers to investigate the intense-field dynamics in systems with increasing complexity and size at the ultrafast timescale and in non-linear x-ray interaction regimes. In particular, picosecond trajectories of XFEL clusters with attosecond time resolution containing millions of particles can be e!ciently computed on upwards of 262,144 processes.« less

Large-scale atomistic calculations of clusters in intense x-ray pulses

DOE PAGES

Ho, Phay J.; Knight, Chris

2017-04-28

Here, we present the methodology of our recently developed Monte-Carlo/ Molecular-Dynamics method for studying the fundamental ultrafast dynamics induced by high-fluence, high-intensity x-ray free electron laser (XFEL) pulses in clusters. The quantum nature of the initiating ionization process is accounted for by a Monte Carlo method to calculate probabilities of electronic transitions, including photo absorption, inner-shell relaxation, photon scattering, electron collision and recombination dynamics, and thus track the transient electronic configurations explicitly. The freed electrons and ions are followed by classical particle trajectories using a molecular dynamics algorithm. These calculations reveal the surprising role of electron-ion recombination processes that leadmore » to the development of nonuniform spatial charge density profiles in x-ray excited clusters over femtosecond timescales. In the high-intensity limit, it is important to include the recombination dynamics in the calculated scattering response even for a 2- fs pulse. We also demonstrate that our numerical codes and algorithms can make e!cient use of the computational power of massively parallel supercomputers to investigate the intense-field dynamics in systems with increasing complexity and size at the ultrafast timescale and in non-linear x-ray interaction regimes. In particular, picosecond trajectories of XFEL clusters with attosecond time resolution containing millions of particles can be e!ciently computed on upwards of 262,144 processes.« less

Galaxy clusters in simulations of the local Universe: a matter of constraints

NASA Astrophysics Data System (ADS)

Sorce, Jenny G.; Tempel, Elmo

2018-06-01

To study the full formation and evolution history of galaxy clusters and their population, high-resolution simulations of the latter are flourishing. However, comparing observed clusters to the simulated ones on a one-to-one basis to refine the models and theories down to the details is non-trivial. The large variety of clusters limits the comparisons between observed and numerical clusters. Simulations resembling the local Universe down to the cluster scales permit pushing the limit. Simulated and observed clusters can be matched on a one-to-one basis for direct comparisons provided that clusters are well reproduced besides being in the proper large-scale environment. Comparing random and local Universe-like simulations obtained with differently grouped observational catalogues of peculiar velocities, this paper shows that the grouping scheme used to remove non-linear motions in the catalogues that constrain the simulations affects the quality of the numerical clusters. With a less aggressive grouping scheme - galaxies still falling on to clusters are preserved - combined with a bias minimization scheme, the mass of the dark matter haloes, simulacra for five local clusters - Virgo, Centaurus, Coma, Hydra, and Perseus - is increased by 39 per cent closing the gap with observational mass estimates. Simulacra are found on average in 89 per cent of the simulations, an increase of 5 per cent with respect to the previous grouping scheme. The only exception is Perseus. Since the Perseus-Pisces region is not well covered by the used peculiar velocity catalogue, the latest release lets us foresee a better simulacrum for Perseus in a near future.

Stars and their Environments at High-Resolution with IGRINS

NASA Astrophysics Data System (ADS)

Mace, Gregory; Jaffe, Daniel; Kaplan, Kyle; Kidder, Benjamin; Oh, Heeyoung; Sneden, Christopher; Afşar, Melike

2016-06-01

TheImmersion Grating Infrared Spectrometer (IGRINS) is a revolutionary instrument that exploits broad spectral coverage at high-resolution in the near-infrared. There are no moving parts in IGRINS and its high-throughput white-pupil design maximizes sensitivity. IGRINS on the 2.7 meter Harlan J. Smith Telescope at McDonald Observatory is nearly as sensitive as CRIRES at the 8 meter Very Large Telescope. However, IGRINS at R=45,000 has more than 30 times the spectral grasp of CRIRES. The use of an immersion grating facilitates a compact cryostat while providing simultaneous H and K band observations with complete wavelength coverage from 1.45 - 2.45 microns. Here we discuss details of instrument performance and summarize the application of IGRINS to stellar characterization, star formation in regions like Taurus and Ophiuchus, the interstellar medium, and photodissociation regions. IGRINS has the largest spectral grasp of any high-resolution, near-infrared spectrograph, allowing us to study star formation and evolution in unprecedented detail. With its fixed format and high sensitivity, IGRINS is a great survey instrument for star clusters, high signal-to-noise (SNR>300) studies of field stars, and for mapping the interstellar medium. As a prototype for GMTNIRS on the Giant Magellan Telescope, IGRINS represents the future of high-resolution spectroscopy. In the future IGRINS will be deployed to numerous facilities and will remain a versatile instrument for the community while producing a rich archive of uniform spectra.

Measurement of the spectral signature of small carbon clusters at near and far infrared wavelengths

NASA Technical Reports Server (NTRS)

Tarter, J.; Saykally, R.

1991-01-01

A significant percentage of the carbon inventory of the circumstellar and interstellar media may be in the form of large refractory molecules (or small grains) referred to as carbon clusters. At the small end, uneven numbers of carbon atoms seem to be preferred, whereas above 12 atoms, clusters containing an even number of carbon atoms appear to be preferred in laboratory chemistry. In the lab, the cluster C-60 appears to be a particularly stable form and has been nicknamed Bucky Balls because of its resemblance to a soccer ball and to geodesic domes designed by Buckminster Fuller. In order to investigate the prevalence of these clusters, and their relationship to the polycyclic aromatic hydrocarbons (PAHs) that have become the newest focus of IR astronomy, it is necessary to determine the spectroscopic characteristics of these clusters at near and far infrared wavelengths. Described here is the construction of a near to far IR laser magnetic resonance spectrometer that has been built at the University of California Berkeley in order to detect and characterize these spectra. The equipment produces carbon clusters by laser evaporation of a graphitic target. The clusters are then cooled in a supersonic expansion beam in order to simulate conditions in the interstellar medium (ISM). The expansion beam feeds into the spectrometer chamber and permits concentrations of clusters sufficiently high as to permit ultra-high resolution spectroscopy at near and far IR wavelengths. The first successful demonstration of this apparatus occurred last year when the laboratory studies permitted the observational detection of C-5 in the stellar outflow surrounding IRC+10216 in the near-IR. Current efforts focus on reducing the temperature of the supersonic expansion beam that transport the C clusters evaporated from a graphite target into the spectrometer down to temperatures as low as 1 K.

Short-term forecasting of individual household electricity loads with investigating impact of data resolution and forecast horizon

NASA Astrophysics Data System (ADS)

Yildiz, Baran; Bilbao, Jose I.; Dore, Jonathon; Sproul, Alistair B.

2018-05-01

Smart grid components such as smart home and battery energy management systems, high penetration of renewable energy systems, and demand response activities, require accurate electricity demand forecasts for the successful operation of the electricity distribution networks. For example, in order to optimize residential PV generation and electricity consumption and plan battery charge-discharge regimes by scheduling household appliances, forecasts need to target and be tailored to individual household electricity loads. The recent uptake of smart meters allows easier access to electricity readings at very fine resolutions; hence, it is possible to utilize this source of available data to create forecast models. In this paper, models which predominantly use smart meter data alongside with weather variables, or smart meter based models (SMBM), are implemented to forecast individual household loads. Well-known machine learning models such as artificial neural networks (ANN), support vector machines (SVM) and Least-Square SVM are implemented within the SMBM framework and their performance is compared. The analysed household stock consists of 14 households from the state of New South Wales, Australia, with at least a year worth of 5 min. resolution data. In order for the results to be comparable between different households, our study first investigates household load profiles according to their volatility and reveals the relationship between load standard deviation and forecast performance. The analysis extends previous research by evaluating forecasts over four different data resolution; 5, 15, 30 and 60 min, each resolution analysed for four different horizons; 1, 6, 12 and 24 h ahead. Both, data resolution and forecast horizon, proved to have significant impact on the forecast performance and the obtained results provide important insights for the operation of various smart grid applications. Finally, it is shown that the load profile of some households vary significantly across different days; as a result, providing a single model for the entire period may result in limited performance. By the use of a pre-clustering step, similar daily load profiles are grouped together according to their standard deviation, and instead of applying one SMBM for the entire data-set of a particular household, separate SMBMs are applied to each one of the clusters. This preliminary clustering step increases the complexity of the analysis however it results in significant improvements in forecast performance.

Application of the LEPS technique for Quantitative Precipitation Forecasting (QPF) in Southern Italy: a preliminary study

NASA Astrophysics Data System (ADS)

Federico, S.; Avolio, E.; Bellecci, C.; Colacino, M.; Walko, R. L.

2006-03-01

This paper reports preliminary results for a Limited area model Ensemble Prediction System (LEPS), based on RAMS (Regional Atmospheric Modelling System), for eight case studies of moderate-intense precipitation over Calabria, the southernmost tip of the Italian peninsula. LEPS aims to transfer the benefits of a probabilistic forecast from global to regional scales in countries where local orographic forcing is a key factor to force convection. To accomplish this task and to limit computational time in an operational implementation of LEPS, we perform a cluster analysis of ECMWF-EPS runs. Starting from the 51 members that form the ECMWF-EPS we generate five clusters. For each cluster a representative member is selected and used to provide initial and dynamic boundary conditions to RAMS, whose integrations generate LEPS. RAMS runs have 12-km horizontal resolution. To analyze the impact of enhanced horizontal resolution on quantitative precipitation forecasts, LEPS forecasts are compared to a full Brute Force (BF) ensemble. This ensemble is based on RAMS, has 36 km horizontal resolution and is generated by 51 members, nested in each ECMWF-EPS member. LEPS and BF results are compared subjectively and by objective scores. Subjective analysis is based on precipitation and probability maps of case studies whereas objective analysis is made by deterministic and probabilistic scores. Scores and maps are calculated by comparing ensemble precipitation forecasts against reports from the Calabria regional raingauge network. Results show that LEPS provided better rainfall predictions than BF for all case studies selected. This strongly suggests the importance of the enhanced horizontal resolution, compared to ensemble population, for Calabria for these cases. To further explore the impact of local physiographic features on QPF (Quantitative Precipitation Forecasting), LEPS results are also compared with a 6-km horizontal resolution deterministic forecast. Due to local and mesoscale forcing, the high resolution forecast (Hi-Res) has better performance compared to the ensemble mean for rainfall thresholds larger than 10mm but it tends to overestimate precipitation for lower amounts. This yields larger false alarms that have a detrimental effect on objective scores for lower thresholds. To exploit the advantages of a probabilistic forecast compared to a deterministic one, the relation between the ECMWF-EPS 700 hPa geopotential height spread and LEPS performance is analyzed. Results are promising even if additional studies are required.

Visualizing and Clustering Protein Similarity Networks: Sequences, Structures, and Functions.

PubMed

Mai, Te-Lun; Hu, Geng-Ming; Chen, Chi-Ming

2016-07-01

Research in the recent decade has demonstrated the usefulness of protein network knowledge in furthering the study of molecular evolution of proteins, understanding the robustness of cells to perturbation, and annotating new protein functions. In this study, we aimed to provide a general clustering approach to visualize the sequence-structure-function relationship of protein networks, and investigate possible causes for inconsistency in the protein classifications based on sequences, structures, and functions. Such visualization of protein networks could facilitate our understanding of the overall relationship among proteins and help researchers comprehend various protein databases. As a demonstration, we clustered 1437 enzymes by their sequences and structures using the minimum span clustering (MSC) method. The general structure of this protein network was delineated at two clustering resolutions, and the second level MSC clustering was found to be highly similar to existing enzyme classifications. The clustering of these enzymes based on sequence, structure, and function information is consistent with each other. For proteases, the Jaccard's similarity coefficient is 0.86 between sequence and function classifications, 0.82 between sequence and structure classifications, and 0.78 between structure and function classifications. From our clustering results, we discussed possible examples of divergent evolution and convergent evolution of enzymes. Our clustering approach provides a panoramic view of the sequence-structure-function network of proteins, helps visualize the relation between related proteins intuitively, and is useful in predicting the structure and function of newly determined protein sequences.

Structure of 2C-Methyl-D-erythritol-2,4-cyclodiphosphate Synthase from Shewanella oneidensis at 1.6 angstrom: Identification of Farnesyl pyrophosphate Trapped in a Hydrophobic Cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ni, Shuisong; Robinson, Howard; Marsing, Gregory C.

2004-11-01

1. Introduction Enzymes in the non-mevalonate pathway for isoprenoid synthesis have gained recent attention because of their potential value as targets for antibiotic drug development. 2C-methyl-D-erythritol-2,4 cyclophosphate (MECDP) synthase is the fifth enzyme in the seven enzyme non-mevalonate pathway for synthesis of isopentenyl diphosphate. Four groups have published structures of MECDP synthase at resolutions varying from 1.6Å to 2.8Å, either in the presence or absence of substrate from Escherichia coli (Richard et al., 2002; Kemp et al., 2002; Steinbacher et al., 2002) or from Thermus thermophilus (Kishida et al., 2003). Among these structures, the protein always exists as a homotrimermore » either with a crystallographic or a non-crystallographic three-fold symmetry axis and an active site formed in a cleft between adjacent monomers. While the overall shape of the proteins is highly similar among these structures, each of the four reported structures contain different combinations of metal ions in the active site including a Zn2+ ion only (Steinbacher et al., 2002), a Mn2+ ion only (Richard et al., 2002), Zn2+ and Mn2+ ions (Kemp et al., 2002) or two Mg2+ ions (Kishida et al., 2003). Furthermore, two of the structures are reported to contain a hydrophobic channel along the three-fold symmetry axis that is capped by a cluster of three arginine side chains (one from each monomer) at one end of the cavity and a cluster of three glutamic acid side chains (one from each monomer) at the other side of the cavity. In a 1.8Å resolution structure, Kemp et al. (2002) reported a sulfate ion coordinated to the arginine cap and solvent trapped in a hydrophobic cavity. In a lower 2.8Å resolution structure, Richard et al. (2002) concluded that geranyl diphosphate, GPP, was most likely trapped by the arginine cap and hydrophobic cavity (Richard et al., 2002), however, the low resolution of the data together with the presence of the crystallographic symmetry axis prohibited a definitive analysis of the identity and mode of binding of the bound molecule. Kishida et al. (2003) reported that no cavity existed in a 1.6Å structure of the SO3437 homolog from Thermus thermophilus, presumably due to tighter packing of the protein from the thermophilic organism. Steinbacher et al. (2002) make no description of a hydrophobic cavity in a lower resolution (2.5-3.2Å) of the Escherichia coli protein. Here, we report a high-resolution (1.6Å) structure of MECDP synthase from Shewanella oneidensis in the absence of substrate in the active site. We provide unambiguous data that confirms the presence of Zn2+ in one of the metal binding sites and observe what appears to be farnesyl diphosphate (FPP) bound in the hydrophobic cavity along the non-crystallographic three-fold symmetry axis of the homotrimer. The high-resolution structure clarifies the mode of binding of the pyrophosphate of FPP in the arginine cluster that caps the hydrophobic cavity.« less

Turbulence in the Intracluster Medium: XMM-Newton legacy

NASA Astrophysics Data System (ADS)

Pinto, C.; Fabian, A.; Sanders, J.; De Plaa, J.

2017-10-01

The kinematics structure of the Intracluster Medium (ICM) in clusters of galaxies is heir of their past evolution. AGN feedback, sloshing of gas within the potential well, and galaxy mergers are thought to generate turbulence of several hundred km/s into the ICM. Accurate measurements of velocity widths provide the means to understand the effects of these energetic phenomena onto the evolution of the clusters. In this talk I will review our recent measurements of turbulence using the high-resolution grating and microcalorimeter spectrometers on board XMM-Newton and Hitomi, respectively. Most recently, we have produced the largest XMM-Newton/RGS grating catalogue totalling about a hundred objects, which merge the recent CHEERS campaign and the efforts of the last decade as well as the newest observations of clusters and groups of galaxies. This catalogue includes all high-quality grating spectra publicly available by January 2017 and provides the XMM-Newton legacy for the future work. In this talk, I will discuss the first results with particular focus on the measurements of velocity broadening and the new constraints on turbulence.

Balloon-borne three-meter telescope for far-infrared and submillimeter astronomy

NASA Technical Reports Server (NTRS)

Fazio, G. G.

1985-01-01

Presented are scientific objectives, engineering analysis and design, and results of technology development for a Three-Meter Balloon-Borne Far-Infrared and Submillimeter Telescope. The scientific rationale is based on two crucial instrumental capabilities: high angular resolution which approaches eight arcseconds at one hundred micron wavelength, and high resolving power spectroscopy with good sensitivity throughout the telescope's 30-micron to 1-mm wavelength range. The high angular resolution will allow us to resolve and study in detail such objects as collapsing protostellar condensations in our own galaxy, clusters of protostars in the Magellanic clouds, giant molecular clouds in nearby galaxies, and spiral arms in distant galaxies. The large aperture of the telescope will permit sensitive spectral line measurements of molecules, atoms, and ions, which can be used to probe the physical, chemical, and dynamical conditions in a wide variety of objects.

Going Beyond Einstein with the Constellation-X Mission

NASA Technical Reports Server (NTRS)

White, Nicholas

2007-01-01

The Constellation-X mission will address the questions: "What happens to matter close to a black hole?" and "What is Dark Energy?" These questions are central to the NASA Beyond Einstein Program, where Constellation-X plays a central role. The mission will address these questions by using high throughput X-ray spectroscopy to observe the effects of strong gravity close to the event horizon of black holes, and to observe the formation and evolution of clusters of galaxies in order to precisely determine Cosmological parameters. To achieve these primary science goals requires a factor of 25-100 increase in sensitivity for high resolution X-ray spectroscopy.'The mission will also perform routine high-resolution X-ray spectroscopy of faint 2nd extended X-ray source populations. This will provide diagnostic information such as density, elemental abundances, velocity; and ionization state for a wide range of astrophysical problems, including new constraints on the Neutron Star equation of state.

High-Resolution Infrared Spectroscopy of Carbon-Sulfur Chains: II. C_5S and SC_5S

NASA Astrophysics Data System (ADS)

Thorwirth, Sven; Salomon, Thomas; Dudek, John B.

2016-06-01

Unbiased high-resolution infrared survey scans of the ablation products from carbon-sulfur targets in the 2100 to 2150 cm-1 regime reveal two bands previously not observed in the gas phase. On the basis of comparison against laboratory matrix-isolation work and new high-level quantum-chemical calculations these bands are attributed to the linear C_5S and SC_5S clusters. While polar C_5S was studied earlier using Fourier-transform microwave techniques, the present work marks the first gas-phase spectroscopic detection of SC_5S. H. Wang, J. Szczepanski, P. Brucat, and M. Vala 2005, Int. J. Quant. Chem. 102, 795 Y. Kasai, K. Obi, Y. Ohshima, Y. Hirahara, Y. Endo, K. Kawaguchi, and A. Murakami 1993, ApJ 410, L45 V. D. Gordon, M. C. McCarthy, A. J. Apponi, and P. Thaddeus 2001, ApJS 134, 311

Protoplanetary Disk Properties in the Orion Nebula Cluster: Initial Results from Deep, High-resolution ALMA Observations

NASA Astrophysics Data System (ADS)

Eisner, J. A.; Arce, H. G.; Ballering, N. P.; Bally, J.; Andrews, S. M.; Boyden, R. D.; Di Francesco, J.; Fang, M.; Johnstone, D.; Kim, J. S.; Mann, R. K.; Matthews, B.; Pascucci, I.; Ricci, L.; Sheehan, P. D.; Williams, J. P.

2018-06-01

We present Atacama Large Millimeter Array 850 μm continuum observations of the Orion Nebula Cluster that provide the highest angular resolution (∼0.″1 ≈ 40 au) and deepest sensitivity (∼0.1 mJy) of the region to date. We mosaicked a field containing ∼225 optical or near-IR-identified young stars, ∼60 of which are also optically identified “proplyds.” We detect continuum emission at 850 μm toward ∼80% of the proplyd sample, and ∼50% of the larger sample of previously identified cluster members. Detected objects have fluxes of ∼0.5–80 mJy. We remove submillimeter flux due to free–free emission in some objects, leaving a sample of sources detected in dust emission. Under standard assumptions of isothermal, optically thin disks, submillimeter fluxes correspond to dust masses of ∼0.5–80 Earth masses. We measure the distribution of disk sizes, and find that disks in this region are particularly compact. Such compact disks are likely to be significantly optically thick. The distributions of submillimeter flux and inferred disk size indicate smaller, lower-flux disks than in lower-density star-forming regions of similar age. Measured disk flux is correlated weakly with stellar mass, contrary to studies in other star-forming regions that found steeper correlations. We find a correlation between disk flux and distance from the massive star θ 1 Ori C, suggesting that disk properties in this region are influenced strongly by the rich cluster environment.

Mass distribution in galaxy clusters: the role of Active Galactic Nuclei feedback

NASA Astrophysics Data System (ADS)

Teyssier, Romain; Moore, Ben; Martizzi, Davide; Dubois, Yohan; Mayer, Lucio

2011-06-01

We use 1-kpc resolution cosmological Adaptive Mesh Refinement (AMR) simulations of a Virgo-like galaxy cluster to investigate the effect of feedback from supermassive black holes on the mass distribution of dark matter, gas and stars. We compared three different models: (i) a standard galaxy formation model featuring gas cooling, star formation and supernovae feedback, (ii) a 'quenching' model for which star formation is artificially suppressed in massive haloes and finally (iii) the recently proposed active galactic nucleus (AGN) feedback model of Booth and Schaye. Without AGN feedback (even in the quenching case), our simulated cluster suffers from a strong overcooling problem, with a stellar mass fraction significantly above observed values in M87. The baryon distribution is highly concentrated, resulting in a strong adiabatic contraction (AC) of dark matter. With AGN feedback, on the contrary, the stellar mass in the brightest cluster galaxy (BCG) lies below observational estimates and the overcooling problem disappears. The stellar mass of the BCG is seen to increase with increasing mass resolution, suggesting that our stellar masses converge to the correct value from below. The gas and total mass distributions are in better agreement with observations. We also find a slight deficit (˜10 per cent) of baryons at the virial radius, due to the combined effect of AGN-driven convective motions in the inner parts and shock waves in the outer regions, pushing gas to Mpc scales and beyond. This baryon deficit results in a slight adiabatic expansion of the dark matter distribution that can be explained quantitatively by AC theory.

MetMSLine: an automated and fully integrated pipeline for rapid processing of high-resolution LC-MS metabolomic datasets.

PubMed

Edmands, William M B; Barupal, Dinesh K; Scalbert, Augustin

2015-03-01

MetMSLine represents a complete collection of functions in the R programming language as an accessible GUI for biomarker discovery in large-scale liquid-chromatography high-resolution mass spectral datasets from acquisition through to final metabolite identification forming a backend to output from any peak-picking software such as XCMS. MetMSLine automatically creates subdirectories, data tables and relevant figures at the following steps: (i) signal smoothing, normalization, filtration and noise transformation (PreProc.QC.LSC.R); (ii) PCA and automatic outlier removal (Auto.PCA.R); (iii) automatic regression, biomarker selection, hierarchical clustering and cluster ion/artefact identification (Auto.MV.Regress.R); (iv) Biomarker-MS/MS fragmentation spectra matching and fragment/neutral loss annotation (Auto.MS.MS.match.R) and (v) semi-targeted metabolite identification based on a list of theoretical masses obtained from public databases (DBAnnotate.R). All source code and suggested parameters are available in an un-encapsulated layout on http://wmbedmands.github.io/MetMSLine/. Readme files and a synthetic dataset of both X-variables (simulated LC-MS data), Y-variables (simulated continuous variables) and metabolite theoretical masses are also available on our GitHub repository. © The Author 2014. Published by Oxford University Press.

Data Dependent Peak Model Based Spectrum Deconvolution for Analysis of High Resolution LC-MS Data

PubMed Central

2015-01-01

A data dependent peak model (DDPM) based spectrum deconvolution method was developed for analysis of high resolution LC-MS data. To construct the selected ion chromatogram (XIC), a clustering method, the density based spatial clustering of applications with noise (DBSCAN), is applied to all m/z values of an LC-MS data set to group the m/z values into each XIC. The DBSCAN constructs XICs without the need for a user defined m/z variation window. After the XIC construction, the peaks of molecular ions in each XIC are detected using both the first and the second derivative tests, followed by an optimized chromatographic peak model selection method for peak deconvolution. A total of six chromatographic peak models are considered, including Gaussian, log-normal, Poisson, gamma, exponentially modified Gaussian, and hybrid of exponential and Gaussian models. The abundant nonoverlapping peaks are chosen to find the optimal peak models that are both data- and retention-time-dependent. Analysis of 18 spiked-in LC-MS data demonstrates that the proposed DDPM spectrum deconvolution method outperforms the traditional method. On average, the DDPM approach not only detected 58 more chromatographic peaks from each of the testing LC-MS data but also improved the retention time and peak area 3% and 6%, respectively. PMID:24533635

MetMSLine: an automated and fully integrated pipeline for rapid processing of high-resolution LC–MS metabolomic datasets

PubMed Central

Edmands, William M. B.; Barupal, Dinesh K.; Scalbert, Augustin

2015-01-01

Summary: MetMSLine represents a complete collection of functions in the R programming language as an accessible GUI for biomarker discovery in large-scale liquid-chromatography high-resolution mass spectral datasets from acquisition through to final metabolite identification forming a backend to output from any peak-picking software such as XCMS. MetMSLine automatically creates subdirectories, data tables and relevant figures at the following steps: (i) signal smoothing, normalization, filtration and noise transformation (PreProc.QC.LSC.R); (ii) PCA and automatic outlier removal (Auto.PCA.R); (iii) automatic regression, biomarker selection, hierarchical clustering and cluster ion/artefact identification (Auto.MV.Regress.R); (iv) Biomarker—MS/MS fragmentation spectra matching and fragment/neutral loss annotation (Auto.MS.MS.match.R) and (v) semi-targeted metabolite identification based on a list of theoretical masses obtained from public databases (DBAnnotate.R). Availability and implementation: All source code and suggested parameters are available in an un-encapsulated layout on http://wmbedmands.github.io/MetMSLine/. Readme files and a synthetic dataset of both X-variables (simulated LC–MS data), Y-variables (simulated continuous variables) and metabolite theoretical masses are also available on our GitHub repository. Contact: ScalbertA@iarc.fr PMID:25348215

Observations of movement dynamics of flying insects using high resolution lidar.

PubMed

Kirkeby, Carsten; Wellenreuther, Maren; Brydegaard, Mikkel

2016-07-04

Insects are fundamental to ecosystem functioning and biodiversity, yet the study of insect movement, dispersal and activity patterns remains a challenge. Here we present results from a novel high resolution laser-radar (lidar) system for quantifying flying insect abundance recorded during one summer night in Sweden. We compare lidar recordings with data from a light trap deployed alongside the lidar. A total of 22808 insect were recorded, and the relative temporal quantities measured matched the quantities recorded with the light trap within a radius of 5 m. Lidar records showed that small insects (wing size <2.5 mm(2) in cross-section) moved across the field and clustered near the light trap around 22:00 local time, while larger insects (wing size >2.5 mm(2) in cross-section) were most abundant near the lidar beam before 22:00 and then moved towards the light trap between 22:00 and 23:30. We could distinguish three insect clusters based on morphology and found that two contained insects predominantly recorded above the field in the evening, whereas the third was formed by insects near the forest at around 21:30. Together our results demonstrate the capability of lidar for distinguishing different types of insect during flight and quantifying their movements.

Observations of movement dynamics of flying insects using high resolution lidar

PubMed Central

Kirkeby, Carsten; Wellenreuther, Maren; Brydegaard, Mikkel

2016-01-01

Insects are fundamental to ecosystem functioning and biodiversity, yet the study of insect movement, dispersal and activity patterns remains a challenge. Here we present results from a novel high resolution laser-radar (lidar) system for quantifying flying insect abundance recorded during one summer night in Sweden. We compare lidar recordings with data from a light trap deployed alongside the lidar. A total of 22808 insect were recorded, and the relative temporal quantities measured matched the quantities recorded with the light trap within a radius of 5 m. Lidar records showed that small insects (wing size <2.5 mm2 in cross-section) moved across the field and clustered near the light trap around 22:00 local time, while larger insects (wing size >2.5 mm2 in cross-section) were most abundant near the lidar beam before 22:00 and then moved towards the light trap between 22:00 and 23:30. We could distinguish three insect clusters based on morphology and found that two contained insects predominantly recorded above the field in the evening, whereas the third was formed by insects near the forest at around 21:30. Together our results demonstrate the capability of lidar for distinguishing different types of insect during flight and quantifying their movements. PMID:27375089

Modeling study of PM2.5 concentration change in Beijing-Tianjin-Hebei and Chengdu-Chongqing urban clusters

NASA Astrophysics Data System (ADS)

Wang, Y.; Chen, H.; Wu, Q.; Wang, Z.

2016-12-01

With the rapid economic development, air pollution is becoming more and more serious in China. Fine particulate matter (PM2.5) is one of major air pollution, affecting visibility and human health. In this study, a nested grid air quality model system (NAQPMS) was used to simulate PM2.5 during 2013-2015 in high resolution of 5km in China. Comparison with observations proved that NAQPMS was able to reproduce the temporal and spatial variation of pollutants in China, reasonably. The simulation showed that high levels of PM2.5 concentrated in the mid-eastern and Sichuan Basin, the concentration in the heaviest period was 120μg/m³ . This study focused on the Beijing-Tianjin-Hebei (BTH) and Chengdu-Chongqi urban clusters, the simulation was a little lower in Jing-Jin-Ji region, high concentration of PM2.5 concentrated in south of Hebei, and PM2.5 concentration in this region have gradually decreased over past three years, the best simulation result was 2014 in Beijing (R=0.75). However, the simulation was a bit higher in Chengdu-Chongqi urban cluster, high concentration concentrated in mid-eastern of Sichuan Basin, R increased obviously in 2015 (0.60). More detailed information and a possible cause for this discrepancy will be discussed.

Protostellar Outflows Mapped with ALMA and Techniques to Include Short Spacings

NASA Astrophysics Data System (ADS)

Plunkett, Adele

2018-01-01

Protostellar outflows are early signs of star formation, yet in cluster environments - common sites of star formation - their role and interaction with surrounding gas are complicated. Protostellar outflows are interesting and complex because they connect protostars (scales 10s au) to the surrounding gas environment (few pc), and their morphology constrains launching and/or accretion modes. A complete outflow study must use observing methods that recover several orders of magnitude of spatial scales, ideally with sub-arcsecond resolution and mapping over a few parsecs. ALMA provides high-resolution observations of outflows, and in some cases outflows have been mapped in clusters. Combining with observations using the Total Power array is possible, but challenging, and a large single dish telescope providing more overlap in uv space is advantageous. In this presentation I show protostellar outflows observed with ALMA using 12m, 7m, and To tal Power arrays. With a new CASA tool TP2VIS we create total power ``visibility'' data and perform joint imaging and deconvolution of interferometry and single dish data. TP2VIS will ultimately provide synergy between ALMA and AtLAST data.

Observing the real time formation of phosphine-ligated gold clusters by electrospray ionization mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ligare, Marshall R.; Johnson, Grant E.; Laskin, Julia

Early stages of the reduction and nucleation of solution-phase gold clusters are largely unknown. This is due, in part, to the high reaction rates and the complexity of the cluster synthesis process. Through the addition of a diphosphine ligand, 1-4,Bis(diphenylphosphino)butane (L4) to the gold precursor, chloro(triphenylphosphine) gold(I) (Au(PPh3)Cl), in methanol organometallic complexes of the type, [Au(L4)x(L4O)y(PPh3)z]+, are formed. These complexes lower the rate of reduction so that the reaction can be directly monitored from 1 min to over an hour using on-line electrospray ionization mass spectrometry (ESI-MS). Our results indicate that the formation of Au8(L4)42+, Au9(L4)4H2+ and Au10(L4)52+ cationic clustersmore » occurs through different reaction pathways that may be kinetically controlled either through the reducing agent concentration or the extent of oxidation of L4. Through comparison of selected ion chronograms our results indicate that Au2(L4)2H+ may be an intermediate in the formation of Au8(L4)42+and Au10(L4)52+ while a variety of chlorinated clusters are involved in the formation of Au9(L4)4H2+. Additionally, high-resolution mass spectrometry was employed to identify 53 gold containing species produced under highly oxidative conditions. New intermediate species are identified which help understand how different gold cluster nuclearities can be stabilized during the growth process.« less

A coarse to fine minutiae-based latent palmprint matching.

PubMed

Liu, Eryun; Jain, Anil K; Tian, Jie

2013-10-01

With the availability of live-scan palmprint technology, high resolution palmprint recognition has started to receive significant attention in forensics and law enforcement. In forensic applications, latent palmprints provide critical evidence as it is estimated that about 30 percent of the latents recovered at crime scenes are those of palms. Most of the available high-resolution palmprint matching algorithms essentially follow the minutiae-based fingerprint matching strategy. Considering the large number of minutiae (about 1,000 minutiae in a full palmprint compared to about 100 minutiae in a rolled fingerprint) and large area of foreground region in full palmprints, novel strategies need to be developed for efficient and robust latent palmprint matching. In this paper, a coarse to fine matching strategy based on minutiae clustering and minutiae match propagation is designed specifically for palmprint matching. To deal with the large number of minutiae, a local feature-based minutiae clustering algorithm is designed to cluster minutiae into several groups such that minutiae belonging to the same group have similar local characteristics. The coarse matching is then performed within each cluster to establish initial minutiae correspondences between two palmprints. Starting with each initial correspondence, a minutiae match propagation algorithm searches for mated minutiae in the full palmprint. The proposed palmprint matching algorithm has been evaluated on a latent-to-full palmprint database consisting of 446 latents and 12,489 background full prints. The matching results show a rank-1 identification accuracy of 79.4 percent, which is significantly higher than the 60.8 percent identification accuracy of a state-of-the-art latent palmprint matching algorithm on the same latent database. The average computation time of our algorithm for a single latent-to-full match is about 141 ms for genuine match and 50 ms for impostor match, on a Windows XP desktop system with 2.2-GHz CPU and 1.00-GB RAM. The computation time of our algorithm is an order of magnitude faster than a previously published state-of-the-art-algorithm.

Mass spectrometric imaging and laser desorption ionization (LDI) with ice as a matrix using femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Berry, Jamal Ihsan

The desorption of biomolecules from frozen aqueous solutions on metal substrates with femtosecond laser pulses is presented for the first time. Unlike previous studies using nanosecond pulses, this approach produces high quality mass spectra of biomolecules repeatedly and reproducibly. This novel technique allows analysis of biomolecules directly from their native frozen environments. The motivation for this technique stems from molecular dynamics computer simulations comparing nanosecond and picosecond heating of water overlayers frozen on Au substrates which demonstrate large water cluster formation and ejection upon substrate heating within ultrashort timescales. As the frozen aqueous matrix and analyte molecules are transparent at the wavelengths used, the laser energy is primarily absorbed by the substrate, causing rapid heating and explosive boiling of the ice overlayer, followed by the ejection of ice clusters and the entrained analyte molecule. Spectral characteristics at a relatively high fluence of 10 J/cm 2 reveal the presence of large molecular weight metal clusters when a gold substrate is employed, with smaller cluster species observed from frozen aqueous solutions on Ag, Cu, and Pb substrates. The presence of the metal clusters is indicative of an evaporative cooling mechanism which stabiles cluster ion formation and the ejection of biomolecules from frozen aqueous solutions. Solvation is necessary as the presence of metal clusters and biomolecular ion signals are not observed from bare metal substrates in absence of the frozen overlayer. The potential for mass spectrometric imaging with femtosecond LDI of frozen samples is also presented. The initial results for the characterization of peptides and peptoids linked to combinatorial beads frozen in ice and the assay of frozen brain tissue from the serotonin transporter gene knockout mouse via LDI imaging are discussed. Images of very good quality and resolution are obtained with 400 nm, 200 fs pulses at a fluence of 1.25 J/cm2 . An attractive feature of this technique is that images are acquired within minutes for large sample areas. Additionally, the images obtained with femtosecond laser desorption are high in lateral resolution with the laser capable of being focused to a spot size of 30 mum. Femtosecond laser desorption from ice is unique in that unlike matrix assisted laser desorption ionization mass spectrometry, it does not employ an organic UV absorbing matrix to desorb molecular ions. Instead, the laser energy is absorbed by the metal substrate causing explosive boiling and ejection of the frozen overlayer. This approach is significant in that femtosecond laser desorption possess the potential of analyzing and assaying biomolecules directly from their frozen native environments. This technique was developed to compliment existing ToF-SIMS imaging capability for analysis of tissue and cells, as well as other biological systems of interest.

Modeling and Testing Dark Energy and Gravity with Galaxy Cluster Data

NASA Astrophysics Data System (ADS)

Rapetti, David; Cataneo, Matteo; Heneka, Caroline; Mantz, Adam; Allen, Steven W.; Von Der Linden, Anja; Schmidt, Fabian; Lombriser, Lucas; Li, Baojiu; Applegate, Douglas; Kelly, Patrick; Morris, Glenn

2018-06-01

The abundance of galaxy clusters is a powerful probe to constrain the properties of dark energy and gravity at large scales. We employed a self-consistent analysis that includes survey, observable-mass scaling relations and weak gravitational lensing data to obtain constraints on f(R) gravity, which are an order of magnitude tighter than the best previously achieved, as well as on cold dark energy of negligible sound speed. The latter implies clustering of the dark energy fluid at all scales, allowing us to measure the effects of dark energy perturbations at cluster scales. For this study, we recalibrated the halo mass function using the following non-linear characteristic quantities: the spherical collapse threshold, the virial overdensity and an additional mass contribution for cold dark energy. We also presented a new modeling of the f(R) gravity halo mass function that incorporates novel corrections to capture key non-linear effects of the Chameleon screening mechanism, as found in high resolution N-body simulations. All these results permit us to predict, as I will also exemplify, and eventually obtain the next generation of cluster constraints on such models, and provide us with frameworks that can also be applied to other proposed dark energy and modified gravity models using cluster abundance observations.

Bottom-up strategies for the assembling of magnetic systems using nanoclusters

NASA Astrophysics Data System (ADS)

Dupuis, V.; Hillion, A.; Robert, A.; Loiselet, O.; Khadra, G.; Capiod, P.; Albin, C.; Boisron, O.; Le Roy, D.; Bardotti, L.; Tournus, F.; Tamion, A.

2018-05-01

In the frame of the 20th Anniversary of the Journal of Nanoparticle Research (JNR), our aim is to start from the historical context 20 years ago and to give some recent results and perspectives concerning nanomagnets prepared from clusters preformed in the gas phase using the low-energy cluster beam deposition (LECBD) technique. In this paper, we focus our attention on the typical case of Co clusters embedded in various matrices to study interface magnetic anisotropy and magnetic interactions as a function of volume concentrations, and on still current and perspectives through two examples of binary metallic 3d-5d TM (namely CoPt and FeAu) cluster assemblies to illustrate size-related and nanoalloy phenomena on magnetic properties in well-defined mass-selected clusters. The structural and magnetic properties of these cluster assemblies were investigated using various experimental techniques that include high-resolution transmission electron microscopy (HRTEM), superconducting quantum interference device (SQUID) magnetometry, and synchrotron techniques such as extended X-ray absorption fine structure (EXAFS) and X-ray magnetic circular dichroism (XMCD). Depending on the chemical nature of both NPs and matrix, we observe different magnetic responses compared to their bulk counterparts. In particular, we show how finite size effects (size reduction) enhance their magnetic moment and how specific relaxation in nanoalloys can impact their magnetic anisotropy.

Fundamental physics from future weak-lensing calibrated Sunyaev-Zel'dovich galaxy cluster counts

NASA Astrophysics Data System (ADS)

Madhavacheril, Mathew S.; Battaglia, Nicholas; Miyatake, Hironao

2017-11-01

Future high-resolution measurements of the cosmic microwave background (CMB) will produce catalogs of tens of thousands of galaxy clusters through the thermal Sunyaev-Zel'dovich (tSZ) effect. We forecast how well different configurations of a CMB Stage-4 experiment can constrain cosmological parameters, in particular, the amplitude of structure as a function of redshift σ8(z ) , the sum of neutrino masses Σ mν, and the dark energy equation of state w (z ). A key element of this effort is calibrating the tSZ scaling relation by measuring the lensing signal around clusters. We examine how the mass calibration from future optical surveys like the Large Synoptic Survey Telescope (LSST) compares with a purely internal calibration using lensing of the CMB itself. We find that, due to its high-redshift leverage, internal calibration gives constraints on cosmological parameters comparable to the optical calibration, and can be used as a cross-check of systematics in the optical measurement. We also show that in contrast to the constraints using the CMB lensing power spectrum, lensing-calibrated tSZ cluster counts can detect a minimal Σ mν at the 3 - 5 σ level even when the dark energy equation of state is freed up.

BLUE STRAGGLER EVOLUTION CAUGHT IN THE ACT IN THE LARGE MAGELLANIC CLOUD GLOBULAR CLUSTER HODGE 11

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Chengyuan; De Grijs, Richard; Liu Xiangkun

High-resolution Hubble Space Telescope imaging observations show that the radial distribution of the field-decontaminated sample of 162 'blue straggler' stars (BSs) in the 11.7{sup +0.2}{sub -0.1} Gyr old Large Magellanic Cloud cluster Hodge 11 exhibits a clear bimodality. In combination with their distinct loci in color-magnitude space, this offers new evidence in support of theoretical expectations that suggest different BS formation channels as a function of stellar density. In the cluster's color-magnitude diagram, the BSs in the inner 15'' (roughly corresponding to the cluster's core radius) are located more closely to the theoretical sequence resulting from stellar collisions, while thosemore » in the periphery (at radii between 85'' and 100'') are preferentially found in the region expected to contain objects formed through binary mass transfer or coalescence. In addition, the objects' distribution in color-magnitude space provides us with the rare opportunity in an extragalactic environment to quantify the evolution of the cluster's collisionally induced BS population and the likely period that has elapsed since their formation epoch, which we estimate to have occurred {approx}4-5 Gyr ago.« less

Shocks and cold fronts in merging and massive galaxy clusters: new detections with Chandra

NASA Astrophysics Data System (ADS)

Botteon, A.; Gastaldello, F.; Brunetti, G.

2018-06-01

A number of merging galaxy clusters show the presence of shocks and cold fronts, i.e. sharp discontinuities in surface brightness and temperature. The observation of these features requires an X-ray telescope with high spatial resolution like Chandra, and allows to study important aspects concerning the physics of the intracluster medium (ICM), such as its thermal conduction and viscosity, as well as to provide information on the physical conditions leading to the acceleration of cosmic rays and magnetic field amplification in the cluster environment. In this work we search for new discontinuities in 15 merging and massive clusters observed with Chandra by using different imaging and spectral techniques of X-ray observations. Our analysis led to the discovery of 22 edges: six shocks, eight cold fronts, and eight with uncertain origin. All the six shocks detected have M< 2 derived from density and temperature jumps. This work contributed to increase the number of discontinuities detected in clusters and shows the potential of combining diverse approaches aimed to identify edges in the ICM. A radio follow-up of the shocks discovered in this paper will be useful to study the connection between weak shocks and radio relics.

Identification of Clinical Phenotypes in Idiopathic Interstitial Pneumonia with Pulmonary Emphysema.

PubMed

Sato, Suguru; Tanino, Yoshinori; Misa, Kenichi; Fukuhara, Naoko; Nikaido, Takefumi; Uematsu, Manabu; Fukuhara, Atsuro; Wang, Xintao; Ishida, Takashi; Munakata, Mitsuru

2016-01-01

Objective Since the term "combined pulmonary fibrosis and emphysema" (CPFE) was first proposed, the co-existence of pulmonary fibrosis and pulmonary emphysema (PE) has drawn considerable attention. However, conflicting results on the clinical characteristics of patients with both pulmonary fibrosis and PE have been published because of the lack of an exact definition of CPFE. The goal of this study was thus to clarify the clinical characteristics and phenotypes of idiopathic interstitial pneumonia (IIP) with PE. Methods We retrospectively analyzed IIP patients who had been admitted to our hospital. Their chest high-resolution computed tomography images were classified into two groups according to the presence of PE. We then performed a cluster analysis to identify the phenotypes of IIP patients with PE. Results Forty-four (53.7%) out of 82 patients had at least mild emphysema in their bilateral lungs. The cluster analysis separated the IIP patients with PE into three clusters. The overall survival rate of one cluster that consisted of mainly idiopathic pulmonary fibrosis (IPF) patients was significantly worse than those of the other clusters. Conclusion Three different phenotypes can be identified in IIP patients with PE, and IPF with PE is a distinct clinical phenotype with a poor prognosis.

Conformation-dependent restraints for polynucleotides: I. Clustering of the geometry of the phosphodiester group

PubMed Central

Kowiel, Marcin; Brzezinski, Dariusz; Jaskolski, Mariusz

2016-01-01

The refinement of macromolecular structures is usually aided by prior stereochemical knowledge in the form of geometrical restraints. Such restraints are also used for the flexible sugar-phosphate backbones of nucleic acids. However, recent highly accurate structural studies of DNA suggest that the phosphate bond angles may have inadequate description in the existing stereochemical dictionaries. In this paper, we analyze the bonding deformations of the phosphodiester groups in the Cambridge Structural Database, cluster the studied fragments into six conformation-related categories and propose a revised set of restraints for the O-P-O bond angles and distances. The proposed restraints have been positively validated against data from the Nucleic Acid Database and an ultrahigh-resolution Z-DNA structure in the Protein Data Bank. Additionally, the manual classification of PO4 geometry is compared with geometrical clusters automatically discovered by machine learning methods. The machine learning cluster analysis provides useful insights and a practical example for general applications of clustering algorithms for automatic discovery of hidden patterns of molecular geometry. Finally, we describe the implementation and application of a public-domain web server for automatic generation of the proposed restraints. PMID:27521371

Physical properties and evolution of GMCs in the Galaxy and the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Onishi, Toshikazu

2015-08-01

Most stars are born as clusters in Giant Molecular Clouds (hereafter GMCs), and therefore the understanding of the evolution of GMCs in a galaxy is one of the key issues to investigate the evolution of the galaxy. The recent state-of-the-art radio telescopes have been enabling us to reveal the distribution of GMCs extensively in the Galaxy as well as in the nearby galaxies, and the physical properties and the evolution of the GMCs leading to cluster formations are actively being investigated. Here we present a review of studies of spatially resolved GMCs in the Galaxy and in the Large Magellanic Cloud (LMC), aiming at providing a template of GMC properties. For the Galactic GMCs, we will focus on the recent extensive survey of GMCs along the Galactic plane; the recent studies suggest cloud-cloud collision as mechanism of massive star formation. For the extra galactic GMCs, we will present recent high-resolution observations of GMCs in the LMC.The LMC is among the nearest star-forming galaxy (distance ~ 50kpc) and is almost face-on. From these aspects, it is becoming the most popular region for studying interstellar medium over an entire galaxy. For molecular gas, the NANTEN covered the entire LMC with a spatial resolution of 40 pc, revealing 272 molecular clouds whose mass ranges from ~104 to ~107 M⊙, which is the first uniform sample of GMCs in a single galaxy. Our Spitzer SAGE and Herschel HERITAGE surveys show that the interstellar medium has much smaller scale structures; full of filamentary and shell-like structures. In order to resolve the filamentary distributions and pre-stellar cores we definitely need to resolve clouds at sub-pc resolutions with ALMA and to cover regions of active cluster formation which are to be selected based on the Spitzer and Hershel data. Our ALMA targets in Cycle 1 and Cycle 2 include N159, which is the most intense and concentrated molecular cloud as shown by the brightest CO J=3-2 source in the LMC, and GMCs with different evolutionary stages. We present the maps of pre-stellar cores and linking filaments at sub-pc resolution and discuss the formation process of massive clusters.

Introducing the Japan Unified HIgh-Resolution Relocated Catalog for Earthquakes (JUICE) Project

NASA Astrophysics Data System (ADS)

Yano, T. E.; Takeda, T.; Shiomi, K.

2013-12-01

To understand the tectonic processes, seismogenic zones, and active fault evaluations, the precise location of earthquake hypocenters is necessary. Routinely determined hypocenters typically have uncertainties that can make seismically active areas appear more diffuse. These uncertainties influence the interpretation of what are active faults. Objective of this Japan Unified HIgh-resolution Relocated Catalog for Earthquakes (JUICE) project is to create a high-resolution earthquake relocated catalog for all of Japan. To initiate the project, we relocate hypocenters around Kanto-Tokai region. The network geometry, available phases, arrival-time reading accuracy, and knowledge of crustal structure control the accuracy of absolute hypocenter locations (Pavlis, 1986; Gomberg et al., 1990). We take advantage of having an excellent network operated by NIED Hi-net team. We use the high-quality data from this network for events from 2001 to the present. To initiate the JUICE project, we utilize more than 5,500,000 and 5,300,000 P and S phase arrival-time readings (catalog data) and waveforms for about 120,000 events between M0 and M6.5 from 2001 through 2012 in the Kanto and Tokai region. To reduce uncertainties, we apply the double-difference algorithm (hypoDD) by Waldhauser and Ellsworth (2000) to the data. To obtain the travel time differences for the pairs of earthquakes, we cross correlate the seismograms at the stations, which produces another data set -- cross-correlation data. In addition to the catalog phase data, we add 800,000 and 1,000,000 of P and S phase cross-correlations that are used to relocate hypocenters. We use Hi-net routine velocity structure (Ukawa et al., 1984) to estimate theoretical differential travel times. The newly relocated hypocenters show tighter clusters and lineaments compared to the routinely generated hypocenters. Figure 1 (a) shows the hypocenters in the Shizuoka region before relocation and (b) shows the hypocenters after relocation. Particularly, more compact clusters and lineaments clearly appear in the Shizuoka region after relocation. Significant changes are indicated in red circles and arrows for clusters and lineaments, respectively This relocated catalog will contribute to a better understanding of the depth of seismogenic zone and the mechanism for earthquakes. Because relocated hypocenters reflect the thickness of the seismogenic zone more accurately (Hauksson et al., 2012), they are more easily related to other data sets, such as geodetic, geological, gravity, and stress field measurements. We will continue expanding the area of study to relocate events all over Japan. We will apply 3D velocity model in future updated JUICE catalog to complete this project. Figure 1 (a): Map of hypocenters routinely determined by NIED Hi-net. (b): An example of hypocenters after relocations. Significant changes are indicated in red circles/arrows for clusters/lineaments.

Study of atmospheric dynamics and pollution in the coastal area of English Channel using clustering technique

NASA Astrophysics Data System (ADS)

Sokolov, Anton; Dmitriev, Egor; Delbarre, Hervé; Augustin, Patrick; Gengembre, Cyril; Fourmenten, Marc

2016-04-01

The problem of atmospheric contamination by principal air pollutants was considered in the industrialized coastal region of English Channel in Dunkirk influenced by north European metropolitan areas. MESO-NH nested models were used for the simulation of the local atmospheric dynamics and the online calculation of Lagrangian backward trajectories with 15-minute temporal resolution and the horizontal resolution down to 500 m. The one-month mesoscale numerical simulation was coupled with local pollution measurements of volatile organic components, particulate matter, ozone, sulphur dioxide and nitrogen oxides. Principal atmospheric pathways were determined by clustering technique applied to backward trajectories simulated. Six clusters were obtained which describe local atmospheric dynamics, four winds blowing through the English Channel, one coming from the south, and the biggest cluster with small wind speeds. This last cluster includes mostly sea breeze events. The analysis of meteorological data and pollution measurements allows relating the principal atmospheric pathways with local air contamination events. It was shown that contamination events are mostly connected with a channelling of pollution from local sources and low-turbulent states of the local atmosphere.

The INfrared Survey of Young Nebulous Clusters (IN-SYNC): Surveying the Dynamics and Star Formation Histories of Young Clusters with APOGEE

NASA Astrophysics Data System (ADS)

Covey, Kevin R.; Cottaar, Michiel; Foster, Jonathan B.; Da Rio, Nicola; Tan, Jonathan; Meyer, Michael; Nidever, David L.; Flaherty, Kevin M.; Arce, Hector G.; Rebull, Luisa M.; Chojnowski, S. Drew; Frinchaboy, Peter M.; Hearty, Fred R.; Majewski, Steven R.; Skrutskie, Michael F.; Stassun, Keivan; Wilson, John C.; Zasowski, Gail

2015-01-01

Young clusters are the most prolific sites of star formation in the Milky Way, but demographic studies indicate that relatively few of the Milky Way's stellar clusters persist as bound structures for 100 Myrs or longer. Uniform & precise measurements of the stellar populations and internal dynamics of these regions are difficult to obtain, however, particularly for extremely young clusters whose optical visibility is greatly hampered by their parental molecular cloud. The INfrared Survey of Young Nebulous Clusters (IN-SYNC), an SDSS-III ancillary science program, leverages the stability and multiplex capability of the APOGEE spectrograph to obtain high resolution spectra at near-infrared wavelengths, where photospheric emission is better able to penetrate the dusty shrouds that surround sites of active star formation. We summarize our recent measurements of the kinematics and stellar populations of IC 348 and NGC 1333, two young clusters in the Perseus Molecular Cloud, and of the members of the Orion Nebula Cluster (ONC) and L1641 filament in the Orion molecular complex. These measurements highlight the dynamically 'warm' environment within these young clusters, and suggest a range of stellar radii within these quasi-single-age populations. We close with a preview of plans for continuing this work as part of the APOGEE-2 science portfolio: self-consistent measurements of the kinematics and star formation histories for clusters spanning a range of initial conditions and ages will provide a opportunity to disentangle the mechanisms that drive the formation and dissolution of sites of active star formation.

Development of high resolution x-ray spectrometers for the investigation of bioinorganic chemistry in metalloproteins

NASA Astrophysics Data System (ADS)

Drury, Owen Byron

We have built an X-ray spectrometer for synchrotron-based high-resolution soft X-ray spectroscopy. The spectrometer uses four 9-pixel arrays of superconducting tunnel junctions (STJs) as sensors. They infer the energy of an absorbed X-ray from a temporary increase in tunneling current. The STJs are operated in a two-stage adiabatic demagnetization refrigerator (ADR) that uses liquid nitrogen and helium for precooling to 77 K and 4.2 K, and gallium gadolinium garnet and iron ammonium sulfate to attain a base temperature below 0.1 K. The sensors are held at the end of a 40-cm-long cold finger within ˜1 cm of a sample located inside the vacuum chamber of a synchrotron beam line end station. The spectrometer has an energy resolution between 10 eV and 20 eV FWHM below 1 keV, can be operated at rates up to ˜106 counts/s. STJ spectrometers are suited for chemical analysis of dilute samples by fluorescence-detected X-ray absorption spectroscopy (XAS) in cases where conventional germanium detectors do not have enough energy resolution. We have used this STJ spectrometer at the Advanced Light Source synchrotron for spectroscopy on the lower energy X-ray absorption edges of the elements Mo, S, Fe and N. These elements play an important role in biological nitrogen fixation at the metalloprotein nitrogenase, and we have examined if STJ spectrometers can be used to provide new insights into some of the open questions regarding the reaction mechanism of this protein. We have taken X-ray absorption near-edge spectra (XANES) and extended fine structure spectra (EXAFS) of an Fe 6N(CO)15-compound containing a single N atom inside a cluster of six Fe atoms, as postulated to exist inside the Fe-S cluster of the FeMo-cofactor (FeMo-co) in nitrogenase. The STJ detector has enabled the first-ever extended range EXAFS scans on nitrogen through the oxygen K-edge, enabling a comparison with N EXAFS on FeMo-co. We have taken iron L23-edge spectra of the Fe-S cluster in FeMo-co, which can be used to measure its oxidation state despite the very small chemical shifts. We also have taken spectra on the molybdenum M-edges and on the sulfur L-edges of inorganic model compounds.

No Evidence for Multiple Stellar Populations in the Low-mass Galactic Globular Cluster E 3

NASA Astrophysics Data System (ADS)

Salinas, Ricardo; Strader, Jay

2015-08-01

Multiple stellar populations are a widespread phenomenon among Galactic globular clusters. Even though the origin of the enriched material from which new generations of stars are produced remains unclear, it is likely that self-enrichment will be feasible only in clusters massive enough to retain this enriched material. We searched for multiple populations in the low mass (M˜ 1.4× {10}4 {M}⊙ ) globular cluster E3, analyzing SOAR/Goodman multi-object spectroscopy centered on the blue cyanogen (CN) absorption features of 23 red giant branch stars. We find that the CN abundance does not present the typical bimodal behavior seen in clusters hosting multistellar populations, but rather a unimodal distribution that indicates the presence of a genuine single stellar population, or a level of enrichment much lower than in clusters that show evidence for two populations from high-resolution spectroscopy. E3 would be the first bona fide Galactic old globular cluster where no sign of self-enrichment is found. Based on observations obtained at the Southern Astrophysical Research (SOAR) Telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the US National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

Clinical phenotypes and survival of pre-capillary pulmonary hypertension in systemic sclerosis.

PubMed

Launay, David; Montani, David; Hassoun, Paul M; Cottin, Vincent; Le Pavec, Jérôme; Clerson, Pierre; Sitbon, Olivier; Jaïs, Xavier; Savale, Laurent; Weatherald, Jason; Sobanski, Vincent; Mathai, Stephen C; Shafiq, Majid; Cordier, Jean-François; Hachulla, Eric; Simonneau, Gérald; Humbert, Marc

2018-01-01

Pre-capillary pulmonary hypertension (PH) in systemic sclerosis (SSc) is a heterogeneous condition with an overall bad prognosis. The objective of this study was to identify and characterize homogeneous phenotypes by a cluster analysis in SSc patients with PH. Patients were identified from two prospective cohorts from the US and France. Clinical, pulmonary function, high-resolution chest tomography, hemodynamic and survival data were extracted. We performed cluster analysis using the k-means method and compared survival between clusters using Cox regression analysis. Cluster analysis of 200 patients identified four homogenous phenotypes. Cluster C1 included patients with mild to moderate risk pulmonary arterial hypertension (PAH) with limited or no interstitial lung disease (ILD) and low DLCO with a 3-year survival of 81.5% (95% CI: 71.4-88.2). C2 had pre-capillary PH due to extensive ILD and worse 3-year survival compared to C1 (adjusted hazard ratio [HR] 3.14; 95% CI 1.66-5.94; p = 0.0004). C3 had severe PAH and a trend towards worse survival (HR 2.53; 95% CI 0.99-6.49; p = 0.052). Cluster C4 and C1 were similar with no difference in survival (HR 0.65; 95% CI 0.19-2.27, p = 0.507) but with a higher DLCO in C4. PH in SSc can be characterized into distinct clusters that differ in prognosis.

Identification of Reliable Components in Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS): a Data-Driven Approach across Metabolic Processes.

PubMed

Motegi, Hiromi; Tsuboi, Yuuri; Saga, Ayako; Kagami, Tomoko; Inoue, Maki; Toki, Hideaki; Minowa, Osamu; Noda, Tetsuo; Kikuchi, Jun

2015-11-04

There is an increasing need to use multivariate statistical methods for understanding biological functions, identifying the mechanisms of diseases, and exploring biomarkers. In addition to classical analyses such as hierarchical cluster analysis, principal component analysis, and partial least squares discriminant analysis, various multivariate strategies, including independent component analysis, non-negative matrix factorization, and multivariate curve resolution, have recently been proposed. However, determining the number of components is problematic. Despite the proposal of several different methods, no satisfactory approach has yet been reported. To resolve this problem, we implemented a new idea: classifying a component as "reliable" or "unreliable" based on the reproducibility of its appearance, regardless of the number of components in the calculation. Using the clustering method for classification, we applied this idea to multivariate curve resolution-alternating least squares (MCR-ALS). Comparisons between conventional and modified methods applied to proton nuclear magnetic resonance ((1)H-NMR) spectral datasets derived from known standard mixtures and biological mixtures (urine and feces of mice) revealed that more plausible results are obtained by the modified method. In particular, clusters containing little information were detected with reliability. This strategy, named "cluster-aided MCR-ALS," will facilitate the attainment of more reliable results in the metabolomics datasets.

Turbulence and vorticity in Galaxy clusters generated by structure formation

NASA Astrophysics Data System (ADS)

Vazza, F.; Jones, T. W.; Brüggen, M.; Brunetti, G.; Gheller, C.; Porter, D.; Ryu, D.

2017-01-01

Turbulence is a key ingredient for the evolution of the intracluster medium, whose properties can be predicted with high-resolution numerical simulations. We present initial results on the generation of solenoidal and compressive turbulence in the intracluster medium during the formation of a small-size cluster using highly resolved, non-radiative cosmological simulations, with a refined monitoring in time. In this first of a series of papers, we closely look at one simulated cluster whose formation was distinguished by a merger around z ˜ 0.3. We separate laminar gas motions, turbulence and shocks with dedicated filtering strategies and distinguish the solenoidal and compressive components of the gas flows using Hodge-Helmholtz decomposition. Solenoidal turbulence dominates the dissipation of turbulent motions (˜95 per cent) in the central cluster volume at all epochs. The dissipation via compressive modes is found to be more important (˜30 per cent of the total) only at large radii (≥0.5rvir) and close to merger events. We show that enstrophy (vorticity squared) is good proxy of solenoidal turbulence. All terms ruling the evolution of enstrophy (I.e. baroclinic, compressive, stretching and advective terms) are found to be significant, but in amounts that vary with time and location. Two important trends for the growth of enstrophy in our simulation are identified: first, enstrophy is continuously accreted into the cluster from the outside, and most of that accreted enstrophy is generated near the outer accretion shocks by baroclinic and compressive processes. Secondly, in the cluster interior vortex, stretching is dominant, although the other terms also contribute substantially.

Population clustering based on copy number variations detected from next generation sequencing data.

PubMed

Duan, Junbo; Zhang, Ji-Gang; Wan, Mingxi; Deng, Hong-Wen; Wang, Yu-Ping

2014-08-01

Copy number variations (CNVs) can be used as significant bio-markers and next generation sequencing (NGS) provides a high resolution detection of these CNVs. But how to extract features from CNVs and further apply them to genomic studies such as population clustering have become a big challenge. In this paper, we propose a novel method for population clustering based on CNVs from NGS. First, CNVs are extracted from each sample to form a feature matrix. Then, this feature matrix is decomposed into the source matrix and weight matrix with non-negative matrix factorization (NMF). The source matrix consists of common CNVs that are shared by all the samples from the same group, and the weight matrix indicates the corresponding level of CNVs from each sample. Therefore, using NMF of CNVs one can differentiate samples from different ethnic groups, i.e. population clustering. To validate the approach, we applied it to the analysis of both simulation data and two real data set from the 1000 Genomes Project. The results on simulation data demonstrate that the proposed method can recover the true common CNVs with high quality. The results on the first real data analysis show that the proposed method can cluster two family trio with different ancestries into two ethnic groups and the results on the second real data analysis show that the proposed method can be applied to the whole-genome with large sample size consisting of multiple groups. Both results demonstrate the potential of the proposed method for population clustering.

NGC 3312: A victim of ram pressure sweeping

NASA Technical Reports Server (NTRS)

Mcmahon, P. M.; Richter, O.-G.; Vangorkom, Jacqueline H.; Ferguson, H. C.

1990-01-01

Researchers are undertaking a volume limited survey of the Hydra I cluster in neutral hydrogen using the National Radio Astronomy Observatory's Very Large Array (VLA). The main purpose is to study the effects of a dense environment on the gaseous component of the galaxies. Observational evidence has been accumulating recently that ram pressure sweeping does occur in the centers of clusters, but it is possible that tidal interactions play a role as well. Results of high resolution HI imaging of NGC 3312, the large peculiar spiral near the cluster center are presented. Hydra I (= A1060) is the nearest rich cluster beyond Virgo and, as such, presents a unique opportunity to do a complete survey of a cluster. It is similar to the Virgo cluster in many of its general physical characteristics, such as size, x ray luminosity, velocity dispersion, and galaxy content (high spiral fraction). However, Hydra I appears to be more regular and relaxed. This is evident in the x ray distribution in its central region, which is radially symmetric and centered on the dominant galaxy, NGC 3311, a cD-like elliptical. The observed x ray luminosity implies a central gas density of 4.5 x 10 to the 3rd power cm(-3). Gallagher (1978) argued from optical images of NGC 3312 that this galaxy might be an ideal candidate to directly study effects of the ram pressure process; it might currently be undergoing stripping of its interstellar medium. The researchers' data are consistent with this suggestion, but other origins of the peculiar appearance cannot yet be ruled out.

Unsupervised Clustering of Subcellular Protein Expression Patterns in High-Throughput Microscopy Images Reveals Protein Complexes and Functional Relationships between Proteins

PubMed Central

Handfield, Louis-François; Chong, Yolanda T.; Simmons, Jibril; Andrews, Brenda J.; Moses, Alan M.

2013-01-01

Protein subcellular localization has been systematically characterized in budding yeast using fluorescently tagged proteins. Based on the fluorescence microscopy images, subcellular localization of many proteins can be classified automatically using supervised machine learning approaches that have been trained to recognize predefined image classes based on statistical features. Here, we present an unsupervised analysis of protein expression patterns in a set of high-resolution, high-throughput microscope images. Our analysis is based on 7 biologically interpretable features which are evaluated on automatically identified cells, and whose cell-stage dependency is captured by a continuous model for cell growth. We show that it is possible to identify most previously identified localization patterns in a cluster analysis based on these features and that similarities between the inferred expression patterns contain more information about protein function than can be explained by a previous manual categorization of subcellular localization. Furthermore, the inferred cell-stage associated to each fluorescence measurement allows us to visualize large groups of proteins entering the bud at specific stages of bud growth. These correspond to proteins localized to organelles, revealing that the organelles must be entering the bud in a stereotypical order. We also identify and organize a smaller group of proteins that show subtle differences in the way they move around the bud during growth. Our results suggest that biologically interpretable features based on explicit models of cell morphology will yield unprecedented power for pattern discovery in high-resolution, high-throughput microscopy images. PMID:23785265

Moderate-resolution spectral standards from lambda 5600 to lambda 9000

NASA Technical Reports Server (NTRS)

Allen, Lori E.; Strom, Karen M.

1995-01-01

We present a grid of stellar classification spectra of moderate resolution (R approximately 1500) in the range lambda lambda 5600-9000 A, compiled from high signal-to noise spectra of 275 stars, most in the open clusters Praesepe and M67. The grid covers dwarfs from types B8 through M5, giants from G8 through M7, and subgiants from F5 through K0. We catalog atomic and molecular absorption features useful for stellar classification, and demonstrate the use of luminosity-sensitive features to distinguish between late-type dwarf and giant stars. The entire database is made available in digital format on anonymous ftp and through the World Wide Web.

Ultrasonication-assisted synthesis of high aspect ratio gold nanowires on a graphene template and investigation of their growth mechanism.

PubMed

Xin, Wenbo; De Rosa, Igor M; Cao, Yang; Yin, Xunqian; Yu, Hang; Ye, Peiyi; Carlson, Larry; Yang, Jenn-Ming

2018-04-19

We report a facile synthesis of Au nanowires (AuNWs) with a high aspect ratio (l/D) of up to 5000 on a plasma activated graphene template with ultrasound assistance. We demonstrate that the ultrasonication induced symmetry breaking of Au clusters facilitates the growth of AuNWs from the embryonic stages. Furthermore, the growth mechanism of AuNWs is systematically investigated using high resolution electron transmission microscopy (HRTEM), which reveals the unique role of the defective graphene template in directing the growth of AuNWs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalessandro, E.; Lapenna, E.; Mucciarelli, A.

We used a combination of optical and near-UV Hubble Space Telescope photometry and FLAMES/ESO-VLT high-resolution spectroscopy to characterize the stellar content of the old and massive globular cluster (GC) NGC 121 in the Small Magellanic Cloud (SMC). We report on the detection of multiple stellar populations, the first case in the SMC stellar cluster system. This result enforces the emerging scenario in which the presence of multiple stellar populations is a distinctive-feature of old and massive GCs regardless of the environment, as far as the light-element distribution is concerned. We find that second-generation (SG) stars are more centrally concentrated thanmore » first-generation (FG) ones. More interestingly, at odds with what is typically observed in Galactic GCs, we find that NGC 121 is the only cluster so far to be dominated by FG stars that account for more than 65% of the total cluster mass. In the framework where GCs were born with 90%–95% of FG stars, this observational finding would suggest that either NGC 121 experienced a milder stellar mass-loss with respect to Galactic GCs or it formed a smaller fraction of SG stars.« less

Predawn plasma bubble cluster observed in Southeast Asia

NASA Astrophysics Data System (ADS)

Watthanasangmechai, Kornyanat; Yamamoto, Mamoru; Saito, Akinori; Tsunoda, Roland; Yokoyama, Tatsuhiro; Supnithi, Pornchai; Ishii, Mamoru; Yatini, Clara

2016-06-01

Predawn plasma bubble was detected as deep plasma depletion by GNU Radio Beacon Receiver (GRBR) network and in situ measurement onboard Defense Meteorological Satellite Program F15 (DMSPF15) satellite and was confirmed by sparse GPS network in Southeast Asia. In addition to the deep depletion, the GPS network revealed the coexisting submesoscale irregularities. A deep depletion is regarded as a primary bubble. Submesoscale irregularities are regarded as secondary bubbles. Primary bubble and secondary bubbles appeared together as a cluster with zonal wavelength of 50 km. An altitude of secondary bubbles happened to be lower than that of the primary bubble in the same cluster. The observed pattern of plasma bubble cluster is consistent with the simulation result of the recent high-resolution bubble (HIRB) model. This event is only a single event out of 76 satellite passes at nighttime during 3-25 March 2012 that significantly shows plasma depletion at plasma bubble wall. The inside structure of the primary bubble was clearly revealed from the in situ density data of DMSPF15 satellite and the ground-based GRBR total electron content.

Possible Very Distant or Optically Dark Cluster of Galaxies

NASA Technical Reports Server (NTRS)

Vikhlinin, Alexey; Mushotzky, Richard (Technical Monitor)

2003-01-01

The goal of this proposal was an XMM followup observation of the extended X-ray source detected in our ROSAT PSPC cluster survey. Approximately 95% of extended X-ray sources found in the ROSAT data were optically identified as clusters of galaxies. However, we failed to find any optical counterparts for C10952-0148. Two possibilities remained prior to the XMM observation: (1) This is was a very distant or optically dark cluster of galaxies, too faint in the optical, in which case XMM would easily detect extended X-ray emission and (2) this was a group of point-like sources, blurred to a single extended source in the ROSAT data, but easily resolvable by XMM due to a better energy resolution. The XMM data have settled the case --- C10952-0148 is a group of 7 relatively bright point sources located within 1 square arcmin. All but one source have no optical counterparts down to I=22. Potentially, this can be an interesting group of quasars at a high redshift. We are planning further optical and infrared followup of this system.

A US coordination Facility for the Spectrum-X-Gamma Observatory

NASA Technical Reports Server (NTRS)

Forman, W.; West, Donald (Technical Monitor)

2001-01-01

We have completed our efforts in support of the Spectrum X Gamma mission under a NASA grant. These activities have included direct support to the mission, developing unifying tools applicable to SXG and other X-ray astronomy missions, and X-ray astronomy research to maintain our understanding of the importance and relevance of SXG to the field. SXG provides: 1) Simultaneous Multiwavelength Capability; 2) Large Field of View High Resolution Imaging Spectroscopy; 3) Sensitive Polarimetry with SXRP (Stellar X-Ray Polarimeter). These capabilities will ensure the fulfillment of the following objectives: understanding the accretion dynamics and the importance of reprocessing, upscattering, and disk viscosity around black holes; studying cluster mergers; spatially resolving cluster cooling flows to detect cooling gas; detecting cool gas in cluster outskirts in absorption; mapping gas in filaments around clusters; finding the 'missing' baryons in the Universe; determining the activity history of the black hole in the Galactic Center of our own central black hole; determining pulsar beam geometry; searching for the Lense-Thirring effect in black hole sources; constraining emission mechanisms and accretion geometry in AGN.

Modified vegetation indices for Ganoderma disease detection in oil palm from field spectroradiometer data

NASA Astrophysics Data System (ADS)

Shafri, Helmi Z. M.; Anuar, M. Izzuddin; Saripan, M. Iqbal

2009-10-01

High resolution field spectroradiometers are important for spectral analysis and mobile inspection of vegetation disease. The biggest challenges in using this technology for automated vegetation disease detection are in spectral signatures pre-processing, band selection and generating reflectance indices to improve the ability of hyperspectral data for early detection of disease. In this paper, new indices for oil palm Ganoderma disease detection were generated using band ratio and different band combination techniques. Unsupervised clustering method was used to cluster the values of each class resultant from each index. The wellness of band combinations was assessed by using Optimum Index Factor (OIF) while cluster validation was executed using Average Silhouette Width (ASW). 11 modified reflectance indices were generated in this study and the indices were ranked according to the values of their ASW. These modified indices were also compared to several existing and new indices. The results showed that the combination of spectral values at 610.5nm and 738nm was the best for clustering the three classes of infection levels in the determination of the best spectral index for early detection of Ganoderma disease.

MC 2: Mapping the dark matter distribution of the “Toothbrush” cluster RX J0603.3+4214 with Hubble Space Telescope and Subaru weak lensing

DOE PAGES

Jee, M. James; Dawson, William A.; Stroe, Andra; ...

2016-02-01

The galaxy cluster RX J0603.3+4214 at z = 0:225 is one of the rarest clusters boasting an extremely large ( 2 Mpc) radio relic. Because of the remarkable morphology of the relic, the cluster is nicknamed the \\Toothbrush Cluster". Although the cluster's underlying mass distribution is one of the critical pieces of information needed to reconstruct the merger scenario responsible for the puzzling radio relic morphology, its proximity to the Galactic plane b 10 has imposed signi cant observational challenges. We present a high-resolution weak-lensing study of the cluster with Subaru/Suprime Cam and Hubble Space Telescope imaging data. Our massmore » reconstruction reveals that the cluster is composed of complicated dark matter substructures closely tracing the galaxy distribution, in contrast, however, with the relatively simple binary X-ray morphology. Nevertheless, we nd that the cluster mass is still dominated by the two most massive clumps aligned north-south with a 3:1 mass ratio (M 200 = 6:29 +2:24 -1:62 X 10 14M⊙ and 1:98 +1:24 -0:74 X 10 14M⊙ for the northern and southern clumps, respectively). The southern mass peak is 20 o set toward the south with respect to the corresponding X-ray peak, which has a \\bullet"-like morphology pointing south. Comparison of the current weak- lensing result with the X-ray, galaxy, and radio relic suggests that perhaps the dominant mechanism responsible for the observed relic may be a high-speed collision of the two most massive subclusters, although the peculiarity of the morphology necessitates involvement of additional subclusters. Careful numerical simulations should follow in order to obtain more complete understanding of the merger scenario utilizing all existing observations.« less

A High Angular Resolution Multiplicity Survey of the Open Clusters α Persei and Praesepe

NASA Astrophysics Data System (ADS)

Patience, J.; Ghez, A. M.; Reid, I. N.; Matthews, K.

2002-03-01

Two hundred forty-two members of the Praesepe and α Persei clusters have been surveyed with high angular resolution 2.2 μm speckle imaging on the 3 m Infrared Telescope Facility, the 5 m Hale, and the 10 m Keck telescopes, along with direct imaging using the near-infrared camera (NICMOS) aboard the Hubble Space Telescope. The observed stars range in spectral type from B (~5 Msolar) to early M (~0.5 Msolar), with the majority of the targets more massive than ~0.8 Msolar. The one quadruple and 39 binary systems detected encompass separations from 0.053" to 7.28" 28 of the systems are new detections, and there are nine candidate substellar companions. The results of the survey are used to test binary star formation and evolution scenarios and to investigate the effects of companion stars on X-ray emission and stellar rotation. The main results are as follows:1. Over the projected separation range of 26 to 581 AU and magnitude differences of ΔK<4.0 (comparable to mass ratios q=Msec/Mprim>0.25), the companion-star fraction (CSF) for α Per is 0.09+/-0.03, and that for Praesepe is 0.10+/-0.03. This fraction is consistent with the field G dwarf value, implying that there is not a systematic decline in multiplicity with age at these separations on timescales of a few times 107 yr. The combination of previous spectroscopic work and the current cluster survey results in a cluster binary separation distribution that peaks at 4+1-1.5 AU, a significantly smaller value than the peaks of both the field G dwarf and the nearby T Tauri distributions. If the field G dwarf distribution represents a superposition of distributions from the populations that contributed to the field, then the data imply that ~30% of field binaries formed in dark clouds like the nearby T Tauri stars and the remaining ~70% formed in denser regions.2. An exploration of the binary star properties reveals a cluster CSF that increases with decreasing target mass, and a cluster mass ratio distribution that rises more sharply for higher mass stars but is independent of binary separation. These observational trends are consistent with several models of capture in small clusters and simulations of accretion following fragmentation in a cluster environment. Other types of capture and fragmentation are either inconsistent with these data or currently lack testable predictions.3. Among the cluster A stars, there is a higher fraction of binaries in the subset with X-ray detections, consistent with the hypothesis that lower mass companions are the true source of X-ray emission.4. Finally, in the younger cluster α Per, the rotational velocities for solar-type binaries with separations less than 60 AU are significantly higher than those of wider systems. This suggests that companions may critically affect the rotational evolution of young stars.

Thermal and Non-thermal Nature of the Soft Excess Emission from Sersic 159-03 observed with XMM-Newton

NASA Technical Reports Server (NTRS)

Bonamente, Massimiliano; Lieu, Richard; Mittaz, Jonathan P. D.; Kaastra, Jelle S.; Nevalainen, Jukka

2005-01-01

Several nearby clusters exhibit an excess of soft X-ray radiation which cannot be attributed to the hot virialized intra-cluster medium. There is no consensus to date on the origin of the excess emission: it could be either of thermal origin, or due to an inverse Compton scattering of the cosmic microwave background. Using high resolution XMM-Newton data of Sersic 159-03 we first show that strong soft excess emission is detected out to a radial distance of 0.9 Mpc. The data are interpreted using the two viable models available, i.e., by invoking a warm reservoir of thermal gas, or relativistic electrons which are part of a cosmic ray population. The thermal model leads to a better goodness-of-fit, and the emitting warm gas must be high in mass and low in metallicity.

Crystallographic snapshots of sulfur insertion by lipoyl synthase

PubMed Central

McLaughlin, Martin I.; Lanz, Nicholas D.; Goldman, Peter J.; Lee, Kyung-Hoon; Booker, Squire J.; Drennan, Catherine L.

2016-01-01

Lipoyl synthase (LipA) catalyzes the insertion of two sulfur atoms at the unactivated C6 and C8 positions of a protein-bound octanoyl chain to produce the lipoyl cofactor. To activate its substrate for sulfur insertion, LipA uses a [4Fe-4S] cluster and S-adenosylmethionine (AdoMet) radical chemistry; the remainder of the reaction mechanism, especially the source of the sulfur, has been less clear. One controversial proposal involves the removal of sulfur from a second (auxiliary) [4Fe-4S] cluster on the enzyme, resulting in destruction of the cluster during each round of catalysis. Here, we present two high-resolution crystal structures of LipA from Mycobacterium tuberculosis: one in its resting state and one at an intermediate state during turnover. In the resting state, an auxiliary [4Fe-4S] cluster has an unusual serine ligation to one of the irons. After reaction with an octanoyllysine-containing 8-mer peptide substrate and 1 eq AdoMet, conditions that allow for the first sulfur insertion but not the second insertion, the serine ligand dissociates from the cluster, the iron ion is lost, and a sulfur atom that is still part of the cluster becomes covalently attached to C6 of the octanoyl substrate. This intermediate structure provides a clear picture of iron–sulfur cluster destruction in action, supporting the role of the auxiliary cluster as the sulfur source in the LipA reaction and describing a radical strategy for sulfur incorporation into completely unactivated substrates. PMID:27506792

Ion collision-induced chemistry in pure and mixed loosely bound clusters of coronene and C60 molecules.

PubMed

Domaracka, Alicja; Delaunay, Rudy; Mika, Arkadiusz; Gatchell, Michael; Zettergren, Henning; Cederquist, Henrik; Rousseau, Patrick; Huber, Bernd A

2018-05-23

Ionization, fragmentation and molecular growth have been studied in collisions of 22.5 keV He2+- or 3 keV Ar+-projectiles with pure loosely bound clusters of coronene (C24H12) molecules or with loosely bound mixed C60-C24H12 clusters by using mass spectrometry. The heavier and slower Ar+ projectiles induce prompt knockout-fragmentation - C- and/or H-losses - from individual molecules and highly efficient secondary molecular growth reactions before the clusters disintegrate on picosecond timescales. The lighter and faster He2+ projectiles have a higher charge and the main reactions are then ionization by ions that are not penetrating the clusters. This leads mostly to cluster fragmentation without molecular growth. However, here penetrating collisions may also lead to molecular growth but to a much smaller extent than with 3 keV Ar+. Here we present fragmentation and molecular growth mass distributions with 1 mass unit resolution, which reveals that the same numbers of C- and H-atoms often participate in the formation and breaking of covalent bonds inside the clusters. We find that masses close to those with integer numbers of intact coronene molecules, or with integer numbers of both intact coronene and C60 molecules, are formed where often one or several H-atoms are missing or have been added on. We also find that super-hydrogenated coronene is formed inside the clusters.

Cone-beam micro computed tomography dedicated to the breast.

PubMed

Sarno, Antonio; Mettivier, Giovanni; Di Lillo, Francesca; Cesarelli, Mario; Bifulco, Paolo; Russo, Paolo

2016-12-01

We developed a scanner for micro computed tomography dedicated to the breast (BµCT) with a high resolution flat-panel detector and a microfocus X-ray tube. We evaluated the system spatial resolution via the 3D modulation transfer function (MTF). In addition to conventional absorption-based X-ray imaging, such a prototype showed capabilities for propagation-based phase-contrast and related edge enhancement effects in 3D imaging. The system limiting spatial resolution is 6.2mm -1 (MTF at 10%) in the vertical direction and 3.8mm -1 in the radial direction, values which compare favorably with the spatial resolution reached by mini focus breast CT scanners of other groups. The BµCT scanner was able to detect both microcalcification clusters and masses in an anthropomorphic breast phantom at a dose comparable to that of two-view mammography. The use of a breast holder is proposed in order to have 1-2min long scan times without breast motion artifacts. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Combined readout of a triple-GEM detector

NASA Astrophysics Data System (ADS)

Antochi, V. C.; Baracchini, E.; Cavoto, G.; Di Marco, E.; Marafini, M.; Mazzitelli, G.; Pinci, D.; Renga, F.; Tomassini, S.; Voena, C.

2018-05-01

Optical readout of GEM based devices by means of high granularity and low noise CMOS sensors allows to obtain very interesting tracking performance. Space resolution of the order of tens of μm were measured on the GEM plane along with an energy resolution of 20%÷30%. The main limitation of CMOS sensors is represented by their poor information about time structure of the event. In this paper, the use of a concurrent light readout by means of a suitable photomultiplier and the acquisition of the electric signal induced on the GEM electrode are exploited to provide the necessary timing informations. The analysis of the PMT waveform allows a 3D reconstruction of each single clusters with a resolution on z of 100 μm. Moreover, from the PMT signals it is possible to obtain a fast reconstruction of the energy released within the detector with a resolution of the order of 25% even in the tens of keV range useful, for example, for triggering purpose.

Statistical Analysis of Small-Scale Magnetic Flux Emergence Patterns: A Useful Subsurface Diagnostic?

NASA Astrophysics Data System (ADS)

Lamb, Derek A.

2016-10-01

While sunspots follow a well-defined pattern of emergence in space and time, small-scale flux emergence is assumed to occur randomly at all times in the quiet Sun. HMI's full-disk coverage, high cadence, spatial resolution, and duty cycle allow us to probe that basic assumption. Some case studies of emergence suggest that temporal clustering on spatial scales of 50-150 Mm may occur. If clustering is present, it could serve as a diagnostic of large-scale subsurface magnetic field structures. We present the results of a manual survey of small-scale flux emergence events over a short time period, and a statistical analysis addressing the question of whether these events show spatio-temporal behavior that is anything other than random.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dhayal, Rajendra S.; Liao, Jian-Hong; Kahlal, Samia

An air- and moisture-stable nanoscale polyhydrido copper cluster [Cu 32(H) 20{S 2P(O i Pr) 2 } 12 ] (1 H) was synthesized and structurally characterized. The molecular structure of 1 H exhibits a hexacapped pseudo-rhombohedral core of 14 Cu atoms sandwiched between two nestlike triangular cupola fragments of (2x9) Cu atoms in an elongated triangular gyrobicupola polyhedron. The discrete Cu 32 cluster is stabilized by 12 dithiophosphate ligands and a record number of 20 hydride ligands, which were found by high-resolution neutron diffraction to exhibit tri-, tetra-, and pentacoordinated hydrides in capping and interstitial modes. We conclude that this resultmore » was further supported by a density functional theory investigation on the simplified model [Cu 32(H) 20(S 2PH 2) 12].« less

The influence of tropical cyclones on long-term riverine flooding; examples from tropical Australia

NASA Astrophysics Data System (ADS)

Nott, Jonathan

2018-02-01

Luminescence chronologies for two new slackwater flood deposit (SWD) sites (Broken River northeast Queensland and Ord River northwestern Western Australia) are presented and these along with other SWD chronologies from the same regions are compared with recently developed high resolution, isotope tropical cyclones (TC) records. Heightened TC activity occurred between 1400 and 1850 CE in Queensland and between 1500 and 1850 CE in Western Australia. A distinct clustering of flood events in northwest Western Australia during the period of enhanced TC activity suggests the two may be related. The SWD records in northeast Queensland do not cluster specifically during the period of heightened TC activity however several major floods do occur during this time suggesting that TCs may have been involved.

The uniformity and time-invariance of the intra-cluster metal distribution in galaxy clusters from the IllustrisTNG simulations

NASA Astrophysics Data System (ADS)

Vogelsberger, Mark; Marinacci, Federico; Torrey, Paul; Genel, Shy; Springel, Volker; Weinberger, Rainer; Pakmor, Rüdiger; Hernquist, Lars; Naiman, Jill; Pillepich, Annalisa; Nelson, Dylan

2018-02-01

The distribution of metals in the intra-cluster medium (ICM) encodes important information about the enrichment history and formation of galaxy clusters. Here, we explore the metal content of clusters in IllustrisTNG - a new suite of galaxy formation simulations building on the Illustris project. Our cluster sample contains 20 objects in TNG100 - a ˜(100 Mpc)3 volume simulation with 2 × 18203 resolution elements, and 370 objects in TNG300 - a ˜(300 Mpc)3 volume simulation with 2 × 25003 resolution elements. The z = 0 metallicity profiles agree with observations, and the enrichment history is consistent with observational data going beyond z ˜ 1, showing nearly no metallicity evolution. The abundance profiles vary only minimally within the cluster samples, especially in the outskirts with a relative scatter of ˜ 15 per cent. The average metallicity profile flattens towards the centre, where we find a logarithmic slope of -0.1 compared to -0.5 in the outskirts. Cool core clusters have more centrally peaked metallicity profiles (˜0.8 solar) compared to non-cool core systems (˜0.5 solar), similar to observational trends. Si/Fe and O/Fe radial profiles follow positive gradients. The outer abundance profiles do not evolve below z ˜ 2, whereas the inner profiles flatten towards z = 0. More than ˜ 80 per cent of the metals in the ICM have been accreted from the proto-cluster environment, which has been enriched to ˜0.1 solar already at z ˜ 2. We conclude that the intra-cluster metal distribution is uniform among our cluster sample, nearly time-invariant in the outskirts for more than 10 Gyr, and forms through a universal enrichment history.