Variation of the Surface to Bulk Contribution to Cluster Properties

2012 ◽  
pp. 939-954
Author(s):  
Antonis N. Andriotis ◽  
Zacharias G. Fthenakis ◽  
Madhu Menon
Keyword(s):  
Cluster Properties

Production and STEM examination of controlled-size silver clusters

1983 ◽  
Vol 41 ◽  
pp. 338-339
Author(s):  
M. A. Listvan ◽  
R. P. Andres
Keyword(s):  
Cluster Size ◽  
Metal Clusters ◽  
Experimental Parameter ◽  
Carbon Films ◽  
Metal Species ◽  
Silver Clusters ◽  
Free Jet ◽  
Size Dependent ◽  
Cluster Properties ◽  
Controllable Size

Knowledge of the function and structure of small metal clusters is one goal of research in catalysis. One important experimental parameter is cluster size. Ideally, one would like to produce metal clusters of regulated size in order to characterize size-dependent cluster properties.A source has been developed which is capable of producing microscopic metal clusters of controllable size (in the range 5-500 atoms) This source, the Multiple Expansion Cluster Source, with a Free Jet Deceleration Filter (MECS/FJDF) operates as follows. The bulk metal is heated in an oven to give controlled concentrations of monomer and dimer which were expanded sonically. These metal species were quenched and condensed in He and filtered to produce areosol particles of a controlled size as verified by mass spectrometer measurements. The clusters were caught on pre-mounted, clean carbon films. The grids were then transferred in air for microscopic examination. MECS/FJDF was used to produce two different sizes of silver clusters for this study: nominally Ag6 and Ag50.

scholarly journals Spike sorting with Gaussian mixture models

2018 ◽  
Author(s):  
Bryan C. Souza ◽  
Vítor Lopes-dos-Santos ◽  
João Bacelo ◽  
Adriano B. L. Tort
Keyword(s):  
Mixture Models ◽  
Principal Components ◽  
Gaussian Mixture Models ◽  
Gaussian Mixture ◽  
Spike Sorting ◽  
Main Challenge ◽  
Manual Adjustment ◽  
Cluster Properties ◽  
Spike Waveforms ◽  
Friendly Graphical User Interface

AbstractThe shape of extracellularly recorded action potentials is a product of several variables, such as the biophysical and anatomical properties of the neuron and the relative position of the electrode. This allows for isolating spikes of different neurons recorded in the same channel into clusters based on waveform features. However, correctly classifying spike waveforms into their underlying neuronal sources remains a main challenge. This process, called spike sorting, typically consists of two steps: (1) extracting relevant waveform features (e.g., height, width), and (2) clustering them into non-overlapping groups believed to correspond to different neurons. In this study, we explored the performance of Gaussian mixture models (GMMs) in these two steps. We extracted relevant waveform features using a combination of common techniques (e.g., principal components and wavelets) and GMM fitting parameters (e.g., standard deviations and peak distances). Then, we developed an approach to perform unsupervised clustering using GMMs, which estimates cluster properties in a data-driven way. Our results show that the proposed GMM-based framework outperforms previously established methods when using realistic simulations of extracellular spikes and actual extracellular recordings to evaluate sorting performance. We also discuss potentially better techniques for feature extraction than the widely used principal components. Finally, we provide a friendly graphical user interface in MATLAB to run our algorithm, which allows for manual adjustment of the automatic results.

Vapor-phase nucleation of n-pentane, n-hexane, and n-heptane: Critical cluster properties

2019 ◽  
Vol 151 (15) ◽  
pp. 154307 ◽  
Author(s):  
Kehinde E. Ogunronbi ◽  
Barbara E. Wyslouzil
Keyword(s):  
Vapor Phase ◽  
Critical Cluster ◽  
Cluster Properties ◽  
Phase Nucleation

scholarly journals Evolution of Compact Binary Populations in Globular Clusters: a Boltzmann Study

2007 ◽  
Vol 3 (S246) ◽  
pp. 246-250
Author(s):  
Sambaran Banerjee ◽  
Pranab Ghosh
Keyword(s):  
Globular Clusters ◽  
Orbital Evolution ◽  
Encounter Rate ◽  
X Ray ◽  
Compact Binary ◽  
Binary Formation ◽  
Cluster Properties ◽  
Star Binary ◽  
Dissociation Mechanisms ◽  
X Ray Binaries

AbstractWe explore a Boltzmann scheme for studying the evolution of compact binary populations in globular clusters. We include processes of compact binary formation by tidal capture and exchange encounters, binary destruction by exchange and dissociation mechanisms and binary hardening by encounters, gravitational radiation and magnetic braking, as also the orbital evolution during mass transfer, following Roche lobe contact. From the evolution of compact-binary population, we investigate the dependence of the model number of X-ray binaries NXB on two essential cluster properties, namely, the star-star and star-binary encounter-rate parameters Γ and γ (Verbunt parameters). We find that the values of NXB and their expected scaling with the Verbunt parameters are in good agreement with results from recent X-ray observations of Galactic globular clusters.

LOW DENSITY NUCLEAR MATTER IN FERMI ENERGY COLLISIONS

2010 ◽  
Vol 19 (08n09) ◽  
pp. 1513-1522
Author(s):  
L. QIN ◽  
K. HAGEL ◽  
R. WADA ◽  
Z. CHEN ◽  
M. HUANG ◽  
...  
Keyword(s):  
Effective Interaction ◽  
Cluster Formation ◽  
Heavy Ion ◽  
Alpha Particles ◽  
Low Density ◽  
Free Energies ◽  
Mass Fractions ◽  
Cluster Properties ◽  
Medium Modifications ◽  
Density Matter

Recent heavy ion reaction studies aimed at elucidating the properties of low density matter produced in near Fermi-energies are discussed. At the lowest densities and temperatures large alpha mass fractions are observed. The symmetry free energies derived from isoscaling analyses are far above those obtained in common effective interaction calculations, reflecting cluster formation, primarily of alpha particles, not included in such calculations. Theoretical modeling of these results requires the consideration of cluster formation and medium modifications of cluster properties.

Cluster Properties of Peptides on (100) Semiconductor Surfaces

Langmuir ◽  
2006 ◽  
Vol 22 (19) ◽  
pp. 8104-8108 ◽  
Author(s):  
Karsten Goede ◽  
Marius Grundmann ◽  
Kai Holland-Nell ◽  
Annette G. Beck-Sickinger
Keyword(s):  
Semiconductor Surfaces ◽  
Cluster Properties

scholarly journals Projection effects in galaxy cluster samples: insights from X-ray redshifts

2019 ◽  
Vol 626 ◽  
pp. A48 ◽  
Author(s):  
M. E. Ramos-Ceja ◽  
F. Pacaud ◽  
T. H. Reiprich ◽  
K. Migkas ◽  
L. Lovisari ◽  
...  
Keyword(s):  
Spatial Information ◽  
Galaxy Cluster ◽  
X Rays ◽  
X Ray ◽  
Cluster Sample ◽  
Global Cluster ◽  
Sky Survey ◽  
The Galaxy ◽  
Flux Measurements ◽  
Cluster Properties

Presently, the largest sample of galaxy clusters selected in X-rays comes from the ROSAT All-Sky Survey (RASS). Although there have been many interesting clusters discovered with the RASS data, the broad point spread function of the ROSAT satellite limits the attainable amount of spatial information for the detected objects. This leads to the discovery of new cluster features when a re-observation is performed with higher-resolution X-ray satellites. Here we present the results from XMM-Newton observations of three clusters: RXC J2306.6−1319, ZwCl 1665, and RXC J0034.6−0208, for which the observations reveal a double or triple system of extended components. These clusters belong to the extremely expanded HIghest X-ray FLUx Galaxy Cluster Sample (eeHIFLUGCS), which is a flux-limited cluster sample (fX, 500 ≥ 5 × 10−12 erg s−1 cm−2 in the 0.1−2.4 keV energy band). For each structure in each cluster, we determine the redshift with the X-ray spectrum and find that the components are not part of the same cluster. This is confirmed by an optical spectroscopic analysis of the galaxy members. Therefore, the total number of clusters is actually seven, rather than three. We derive global cluster properties of each extended component. We compare the measured properties to lower-redshift group samples, and find a good agreement. Our flux measurements reveal that only one component of the ZwCl 1665 cluster has a flux above the eeHIFLUGCS limit, while the other clusters will no longer be part of the sample. These examples demonstrate that cluster–cluster projections can bias X-ray cluster catalogues and that with high-resolution X-ray follow-up this bias can be corrected.

Machine-Learning Coupled Cluster Properties through a Density Tensor Representation

2020 ◽  
Vol 124 (23) ◽  
pp. 4861-4871 ◽  
Author(s):  
Benjamin G. Peyton ◽  
Connor Briggs ◽  
Ruhee D’Cunha ◽  
Johannes T. Margraf ◽  
T. Daniel Crawford
Keyword(s):  
Machine Learning ◽  
Coupled Cluster ◽  
Tensor Representation ◽  
Density Tensor ◽  
Cluster Properties

scholarly journals Population synthesis of black hole binary mergers from star clusters

2020 ◽  
Vol 492 (2) ◽  
pp. 2936-2954 ◽  
Author(s):  
Fabio Antonini ◽  
Mark Gieles
Keyword(s):  
Black Hole ◽  
Globular Clusters ◽  
Initial Conditions ◽  
Star Clusters ◽  
Population Synthesis ◽  
Wide Range ◽  
Binary Mergers ◽  
Cluster Properties ◽  
Black Hole Binary ◽  
Merger Rate

ABSTRACT Black hole (BH) binary mergers formed through dynamical interactions in dense star clusters are believed to be one of the main sources of gravitational waves (GWs) for Advanced LIGO and Virgo. Here, we present a fast numerical method for simulating the evolution of star clusters with BHs, including a model for the dynamical formation and merger of BH binaries. Our method is based on Hénon’s principle of balanced evolution, according to which the flow of energy within a cluster must be balanced by the energy production inside its core. Because the heat production in the core is powered by the BHs, one can then link the evolution of the cluster to the evolution of its BH population. This allows us to construct evolutionary tracks of the cluster properties including its BH population and its effect on the cluster and, at the same time, determine the merger rate of BH binaries as well as their eccentricity distributions. The model is publicly available and includes the effects of a BH mass spectrum, mass-loss due to stellar evolution, the ejection of BHs due to natal and dynamical kicks, and relativistic corrections during binary–single encounters. We validate our method using direct N-body simulations, and find it to be in excellent agreement with results from recent Monte Carlo models of globular clusters. This establishes our new method as a robust tool for the study of BH dynamics in star clusters and the modelling of GW sources produced in these systems. Finally, we compute the rate and eccentricity distributions of merging BH binaries for a wide range of cluster initial conditions, spanning more than two orders of magnitude in mass and radius.

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