Asymptotic equivalence of the shell-model and local-density descriptions of Coulombic systems confined by radially symmetric potentials in two and three dimensions

2013 ◽  
Vol 139 (11) ◽  
pp. 114109 ◽  
Author(s):  
Jerzy Cioslowski ◽  
Joanna Albin
Keyword(s):  
Shell Model ◽  
Local Density ◽  
Three Dimensions ◽  
Asymptotic Equivalence ◽  
Coulombic Systems

ELECTRONIC STRUCTURES OF HEAVY-METAL CLUSTERS

1996 ◽  
Vol 03 (01) ◽  
pp. 335-340
Author(s):  
Y. ISHII ◽  
N. WATARI ◽  
S. OHNISHI
Keyword(s):  
Shell Model ◽  
Electronic Structures ◽  
Density Functional ◽  
Local Density ◽  
Model Description ◽  
First Principle ◽  
Electronic Shell ◽  
Hexagonal Close Packed ◽  
The Stability ◽  
Doubly Charged

The electronic structures of small Hg and Pb clusters are studied by the first-principle calculations within the local density-functional approximation. It is found that the stable structure of Hg19 cluster is not polyicosahedral but hexagonal close-packed although the bonding nature is still atom-like with no significant sp-hybridization. The stability of a doubly charged Pb cluster is discussed in connection with the electronic shell-model description. We conclude that the stability of Pb clusters is determined by complicated correlation between the atomic and electronic structures, and the electronic shell model cannot be applied straightforwardly.

FINITE SIZE EFFECTS IN THE ELECTROMAGNETIC QUASI-ELASTIC RESPONSES OF NUCLEI

1994 ◽  
Vol 03 (02) ◽  
pp. 735-755 ◽  
Author(s):  
J.E. AMARO ◽  
A.M. LALLENA ◽  
G. CO’
Keyword(s):  
Shell Model ◽  
Size Effects ◽  
Local Density ◽  
Finite Size ◽  
Fermi Gas ◽  
Meson Exchange ◽  
Electromagnetic Excitation ◽  
Finite Size Effects ◽  
Elastic Responses ◽  
Meson Exchange Currents

The effects of the finite size of the nucleus in the electromagnetic excitation of the quasi-elastic peak have been studied by comparing the responses calculated for 12C and 40Ca with the Fermi gas and the shell model. The contribution of the Meson Exchange Currents has also been considered. We have investigated the possibility of improving the Fermi gas model with approximate estimations of the finite size effects. We found that the use of an effective Fermi momentum provides a better description of the shell model results than the Local Density Approximation.

scholarly journals 3D clustering analysis of super-resolution microscopy data by 3D Voronoi tessellations

2017 ◽  
Author(s):  
Leonid Andronov ◽  
Jonathan Michalon ◽  
Khalid Ouararhni ◽  
Igor Orlov ◽  
Ali Hamiche ◽  
...  
Keyword(s):  
Single Molecule ◽  
Local Density ◽  
3D Structure ◽  
Super Resolution ◽  
Three Dimensions ◽  
3D Analysis ◽  
Voronoi Tessellations ◽  
X Ray Crystallography ◽  
Cellular Context ◽  
Microscopy Data

AbstractSingle-molecule localization microscopy (SMLM) can play an important role in integrated structural biology approaches for example at the interface of cryo electron microscopy (cryo-EM), X-ray crystallography, NMR and fluorescence imaging to identify, localize and determine the 3D structure of cellular structures. While many tools exist for the 3D analysis and visualisation of crystal or cryo-EM structures little exists for 3D SMLM data which can provide fascinating insights but are particularly challenging to analyze in three dimensions especially in a dense cellular context. We developed 3DClusterViSu, a method based on 3D Voronoi tessellations that allows local density estimation, segmentation & quantification of 3D SMLM data and visualization of protein clusters within a 3D tool. We show its robust performance on microtubules and histone proteins H2B and CENP-A with distinct spatial distributions. 3DClusterViSu will favor multi-scale and multi-resolution synergies to allow integrating molecular and cellular levels in the analysis of macromolecular complexes.

scholarly journals Measure-Valued Branching Diffusions with Singular Interactions

1994 ◽  
Vol 46 (1) ◽  
pp. 120-168 ◽  
Author(s):  
Steven N. Evans ◽  
Edwin A. Perkins
Keyword(s):  
Existence And Uniqueness ◽  
Local Density ◽  
Contact Process ◽  
Martingale Problem ◽  
Three Dimensions ◽  
One Dimension ◽  
Martingale Measure ◽  
Brownian Motions ◽  
Five Dimensions ◽  
Super Brownian Motion

AbstractThe usual super-Brownian motion is a measure-valued process that arises as a high density limit of a system of branching Brownian particles in which the branching mechanism is critical. In this work we consider analogous processes that model the evolution of a system of two such populations in which there is inter-species competition or predation.We first consider a competition model in which inter-species collisions may result in casualties on both sides. Using a Girsanov approach, we obtain existence and uniqueness of the appropriate martingale problem in one dimension. In two and three dimensions we establish existence only. However, we do show that, in three dimensions, any solution will not be absolutely continuous with respect to the law of two independent super-Brownian motions. Although the supports of two independent super-Brownian motions collide in dimensions four and five, we show that there is no solution to the martingale problem in these cases.We next study a prédation model in which collisions only affect the "prey" species. Here we can show both existence and uniqueness in one, two and three dimensions. Again, there is no solution in four and five dimensions. As a tool for proving uniqueness, we obtain a representation of martingales for a super-process as stochastic integrals with respect to the related orthogonal martingale measure.We also obtain existence and uniqueness for a related single population model in one dimension in which particles are killed at a rate proportional to the local density. This model appears as a limit of a rescaled contact process as the range of interaction goes to infinity.

scholarly journals Probabilistic cosmic web classification using fast-generated training data

2020 ◽  
Vol 497 (4) ◽  
pp. 5041-5060
Author(s):  
Brandon Buncher ◽  
Matias Carrasco Kind
Keyword(s):  
Learning Algorithm ◽  
Local Density ◽  
Density Field ◽  
Training Data ◽  
Three Dimensions ◽  
Supervised Machine Learning ◽  
Data Generation ◽  
Data Set ◽  
Field Magnitude ◽  
Web Classification

ABSTRACT We present a novel method of robust probabilistic cosmic web particle classification in three dimensions using a supervised machine learning algorithm. Training data were generated using a simplified ΛCDM toy model with pre-determined algorithms for generating haloes, filaments, and voids. While this framework is not constrained by physical modelling, it can be generated substantially more quickly than an N-body simulation without loss in classification accuracy. For each particle in this data set, measurements were taken of the local density field magnitude and directionality. These measurements were used to train a random forest algorithm, which was used to assign class probabilities to each particle in a ΛCDM, dark matter-only N-body simulation with 2563 particles, as well as on another toy model data set. By comparing the trends in the ROC curves and other statistical metrics of the classes assigned to particles in each data set using different feature sets, we demonstrate that the combination of measurements of the local density field magnitude and directionality enables accurate and consistent classification of halo, filament, and void particles in varied environments. We also show that this combination of training features ensures that the construction of our toy model does not affect classification. The use of a fully supervised algorithm allows greater control over the information deemed important for classification, preventing issues arising from arbitrary hyperparameters and mode collapse in deep learning models. Due to the speed of training data generation, our method is highly scalable, making it particularly suited for classifying large data sets, including observed data.

High-resolution scanning electron microscopy (HRSEM) of mitochondria from various rat tissues

1988 ◽  
Vol 46 ◽  
pp. 14-15
Author(s):  
P.J. Lea ◽  
M.J. Hollenberg
Keyword(s):  
Electron Microscopy ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Rat Hepatocytes ◽  
Three Dimensions ◽  
Objective Lens ◽  
Rat Tissues ◽  
Thin Sections ◽  
Reconstruction Methods ◽  
Scanning Electron

Our current understanding of mitochondrial ultrastructure has been derived primarily from thin sections using transmission electron microscopy (TEM). This information has been extrapolated into three dimensions by artist's impressions (1) or serial sectioning techniques in combination with computer processing (2). The resolution of serial reconstruction methods is limited by section thickness whereas artist's impressions have obvious disadvantages.In contrast, the new techniques of HRSEM used in this study (3) offer the opportunity to view simultaneously both the internal and external structure of mitochondria directly in three dimensions and in detail.The tridimensional ultrastructure of mitochondria from rat hepatocytes, retinal (retinal pigment epithelium), renal (proximal convoluted tubule) and adrenal cortex cells were studied by HRSEM. The specimens were prepared by aldehyde-osmium fixation in combination with freeze cleavage followed by partial extraction of cytosol with a weak solution of osmium tetroxide (4). The specimens were examined with a Hitachi S-570 scanning electron microscope, resolution better than 30 nm, where the secondary electron detector is located in the column directly above the specimen inserted within the objective lens.

Inelastic Electron Scattering from Valence Electrons in Aluminum

1976 ◽  
Vol 34 ◽  
pp. 462-463
Author(s):  
P. E. Batson ◽  
C. H. Chen ◽  
J. Silcox
Keyword(s):  
Electron Scattering ◽  
Single Scattering ◽  
Three Dimensions ◽  
Inelastic Electron ◽  
Weak Beam ◽  
Scattering Spectrum ◽  
Valence Electrons ◽  
Diffraction Patterns ◽  
Electronic Scattering

We wish to report in this paper measurements of the inelastic scattering component due to the collective excitations (plasmons) and single particlehole excitations of the valence electrons in Al. Such scattering contributes to the diffuse electronic scattering seen in electron diffraction patterns and has recently been considered of significance in weak-beam images (see Gai and Howie) . A major problem in the determination of such scattering is the proper correction for multiple scattering. We outline here a procedure which we believe suitably deals with such problems and report the observed single scattering spectrum.In principle, one can use the procedure of Misell and Jones—suitably generalized to three dimensions (qx, qy and #x2206;E)--to derive single scattering profiles. However, such a computation becomes prohibitively large if applied in a brute force fashion since the quasi-elastic scattering (and associated multiple electronic scattering) extends to much larger angles than the multiple electronic scattering on its own.

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