Discovery of Most Stable Structures of Neutral and Anionic Phenylalanine through Automated Scanning of Tautomeric and Conformational Spaces

2013 ◽  
Vol 9 (10) ◽  
pp. 4374-4381 ◽  
Author(s):  
Zibo G. Keolopile ◽  
Maciej Gutowski ◽  
Maciej Haranczyk
Keyword(s):  
Automated Scanning ◽  
Conformational Spaces ◽  
Stable Structures

Cluster analysis for large data sets: applications to individual aerosol particles from the mid-pacific

1992 ◽  
Vol 50 (2) ◽  
pp. 1488-1489
Author(s):  
Thomas W. Shattuck ◽  
James R. Anderson ◽  
Neil W. Tindale ◽  
Peter R. Buseck
Keyword(s):  
Cluster Analysis ◽  
Chemical Reactivity ◽  
Large Data ◽  
Large Data Sets ◽  
Particle Analysis ◽  
Data Sets ◽  
Halogen Chemistry ◽  
Complete Study ◽  
Components Analysis ◽  
Automated Scanning

Individual particle analysis involves the study of tens of thousands of particles using automated scanning electron microscopy and elemental analysis by energy-dispersive, x-ray emission spectroscopy (EDS). EDS produces large data sets that must be analyzed using multi-variate statistical techniques. A complete study uses cluster analysis, discriminant analysis, and factor or principal components analysis (PCA). The three techniques are used in the study of particles sampled during the FeLine cruise to the mid-Pacific ocean in the summer of 1990. The mid-Pacific aerosol provides information on long range particle transport, iron deposition, sea salt ageing, and halogen chemistry.Aerosol particle data sets suffer from a number of difficulties for pattern recognition using cluster analysis. There is a great disparity in the number of observations per cluster and the range of the variables in each cluster. The variables are not normally distributed, they are subject to considerable experimental error, and many values are zero, because of finite detection limits. Many of the clusters show considerable overlap, because of natural variability, agglomeration, and chemical reactivity.

Gas-Phase Clustering of NO+ with H2S and H2O

2007 ◽  
Vol 72 (8) ◽  
pp. 1122-1138 ◽  
Author(s):  
Milan Uhlár ◽  
Ivan Černušák
Keyword(s):  
Hydrogen Bonds ◽  
Water Molecule ◽  
Gas Phase ◽  
Saddle Points ◽  
Solvent Molecule ◽  
Local Minima ◽  
Additional Water ◽  
Three Body ◽  
Rain Formation ◽  
Stable Structures

The complex NO+·H2S, which is assumed to be an intermediate in acid rain formation, exhibits thermodynamic stability of ∆Hº300 = -76 kJ mol-1, or ∆Gº300 = -47 kJ mol-1. Its further transformation via H-transfer is associated with rather high barriers. One of the conceivable routes to lower the energy of the transition state is the action of additional solvent molecule(s) that can mediate proton transfer. We have studied several NO+·H2S structures with one or two additional water molecule(s) and have found stable structures (local minima), intermediates and saddle points for the three-body NO+·H2S·H2O and four-body NO+·H2S·(H2O)2 clusters. The hydrogen bonds network in the four-body cluster plays a crucial role in its conversion to thionitrous acid.

Beryllium and Magnesium Metal Clusters: New Globally Stable Structures and G0W0 Calculations

2021 ◽  
Vol 125 (7) ◽  
pp. 1424-1435
Author(s):  
Sunila Bakhsh ◽  
Xiaohui Liu ◽  
Yanyong Wang ◽  
Lixin He ◽  
Xinguo Ren
Keyword(s):  
Metal Clusters ◽  
Magnesium Metal ◽  
Globally Stable ◽  
Stable Structures

scholarly journals Structural and Optical properties of Be, Mg and Ca nanorods and nanodisks

2021 ◽  
Author(s):  
Alexandros G. Chronis ◽  
Fotios Michos ◽  
Christos S Garoufalis ◽  
Michael M. Sigalas
Keyword(s):  
Optical Properties ◽  
Structural And Optical Properties ◽  
Electronic And Optical Properties ◽  
Different Shapes ◽  
Stable Structures

Nanorods and nanodisks of Be, Mg, and Ca with different shapes and sizes have been theoretically studied. Stable structures have been identified and their electronic and optical properties have been...

The Atomic Geometry of the Reconstructed (001) Surface of the Rutile Phase of SnO2

1989 ◽  
Vol 159 ◽  
Author(s):  
Charles B. Duke ◽  
Michael R. Thompson
Keyword(s):  
Energy Barrier ◽  
Tight Binding ◽  
Rutile Phase ◽  
Tetrahedral Coordination ◽  
Surface Geometry ◽  
Coordinate Surface ◽  
Rutile Structure ◽  
Reconstructed Surface ◽  
Distorted Tetrahedral Coordination ◽  
Stable Structures

AbstractThe tight-binding total energy formalism developed for tetrahedrally coordinated compound semiconductors has been extended to rutile-structure oxides and applied to calculate the surface atomic geometry and electronic structure of SnO2 (001). Two stable structures, separated by an energy barrier, are found. The first consists of slightly relaxed surface geometry with the top layer oxygen atoms relaxed outward by approximately 0.12A, and cations inward by 0.25A. The second geometry is a more massively reconstructed surface in which the four-coordinate surface Sn atoms attain highly distorted tetrahedral coordination.

scholarly journals Asymptotic Behavior of Stable Structures Made of Beams

2021 ◽  
Author(s):  
Georges Griso ◽  
Larysa Khilkova ◽  
Julia Orlik ◽  
Olena Sivak
Keyword(s):  
Asymptotic Behavior ◽  
Cross Section ◽  
Cross Sections ◽  
Linear Elasticity ◽  
Circular Cross Section ◽  
Linear Elasticity Theory ◽  
Linear Elastic ◽  
The Cross ◽  
Small Rotation ◽  
Stable Structures

AbstractIn this paper, we study the asymptotic behavior of an $\varepsilon $ ε -periodic 3D stable structure made of beams of circular cross-section of radius $r$ r when the periodicity parameter $\varepsilon $ ε and the ratio ${r/\varepsilon }$ r / ε simultaneously tend to 0. The analysis is performed within the frame of linear elasticity theory and it is based on the known decomposition of the beam displacements into a beam centerline displacement, a small rotation of the cross-sections and a warping (the deformation of the cross-sections). This decomposition allows to obtain Korn type inequalities. We introduce two unfolding operators, one for the homogenization of the set of beam centerlines and another for the dimension reduction of the beams. The limit homogenized problem is still a linear elastic, second order PDE.

scholarly journals Machine learning methodology for high throughput personalized neutron dose reconstruction in mixed neutron + photon exposures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Igor Shuryak ◽  
Helen C. Turner ◽  
Monica Pujol-Canadell ◽  
Jay R. Perrier ◽  
Guy Garty ◽  
...  
Keyword(s):  
Machine Learning ◽  
High Throughput ◽  
Mean Squared Error ◽  
Ex Vivo ◽  
Probability Distributions ◽  
Micronucleus Assay ◽  
Neutron Dose ◽  
Cell Probability ◽  
Scanning Imaging ◽  
Automated Scanning

AbstractWe implemented machine learning in the radiation biodosimetry field to quantitatively reconstruct neutron doses in mixed neutron + photon exposures, which are expected in improvised nuclear device detonations. Such individualized reconstructions are crucial for triage and treatment because neutrons are more biologically damaging than photons. We used a high-throughput micronucleus assay with automated scanning/imaging on lymphocytes from human blood ex-vivo irradiated with 44 different combinations of 0–4 Gy neutrons and 0–15 Gy photons (542 blood samples), which include reanalysis of past experiments. We developed several metrics that describe micronuclei/cell probability distributions in binucleated cells, and used them as predictors in random forest (RF) and XGboost machine learning analyses to reconstruct the neutron dose in each sample. The probability of “overfitting” was minimized by training both algorithms with repeated cross-validation on a randomly-selected subset of the data, and measuring performance on the rest. RF achieved the best performance. Mean R2 for actual vs. reconstructed neutron doses over 300 random training/testing splits was 0.869 (range 0.761 to 0.919) and root mean squared error was 0.239 (0.195 to 0.351) Gy. These results demonstrate the promising potential of machine learning to reconstruct the neutron dose component in clinically-relevant complex radiation exposure scenarios.

scholarly journals ℵ0-Categorical, ℵ0-stable structures

1985 ◽  
Vol 28 (2) ◽  
pp. 103-135 ◽  
Author(s):  
G. Cherlin ◽  
L. Harrington ◽  
A.H. Lachlan
Keyword(s):  
Stable Structures

Molecular Dynamic Simulation of Carbon Nanostructures Formation

2014 ◽  
Vol 1040 ◽  
pp. 92-96
Author(s):  
Denis A. Tatarnikov ◽  
Aleksey V. Godovykh
Keyword(s):  
Thermodynamic Properties ◽  
Molecular Dynamic Simulation ◽  
Molecular Dynamic ◽  
Dynamic Simulation ◽  
Carbon Nanostructures ◽  
Carbon Nanomaterials ◽  
Statistical Data ◽  
New Materials ◽  
Molecular Dynamic Simulation Study ◽  
Stable Structures

This paper is devoted to the study of stable structures of various carbon nanomaterials using molecular dynamic simulation, study of their properties and characteristics, as well as search for possible later use in nanoelectronics and nanomechanics. We develop programs for computation of the system of atoms at every step and visualization of that data, also we research of thermodynamic properties and conditions of formation of different carbon nanostructures, try to predict existence of new materials. Nowadays we have two separate programs: one for computation and one for visualization. We continue to collect statistical data, investigate behavior of the system under different conditions.

Cluster, Surface and Bulk Properties of ZnCd Binary Alloys: Molecular-Dynamics Simulations

2005 ◽  
Vol 502 ◽  
pp. 51-56 ◽  
Author(s):  
Sakir Erkoc
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Density Functional ◽  
Structural Features ◽  
Bulk Materials ◽  
Bulk Properties ◽  
Atom Clusters ◽  
Dynamics Simulations ◽  
Mixed Clusters ◽  
Stable Structures

The structural and electronic properties of isolated neutral ZnmCdn clusters for m+n £ 3 have been investigated by performing density functional theory calculations at B3LYP level. The optimum geometries, vibrational frequencies, electronic structures, and the possible dissosiation channels of the clusters considered have been obtained. An empirical many-body potential energy function (PEF), which comprices two- and three-body atomic interactions, has been developed to investigate the structural features and energetics of ZnmCdn (m+n=3,4) microclusters. The most stable structures were found to be triangular for the three-atom clusters and tetrahedral for the four-atom clusters. On the other hand, the structural features and energetics of Znn-mCdm (n=7,8) microclusters, and Zn50, Cd50, Zn25Cd25, Zn12Cd38, and Zn38Cd12 nanoparticles have been investigated by performing molecular-dynamics computer simulations using the developed PEF. The most stable structures were found to be compact and three-dimensional for all elemental and mixed clusters. An interesting structural feature of the mixed clusters is that Zn and Cd atoms do not mix in mixed clusters, they come together almost without mixing. Surface and bulk properties of Zn, Cd, and ZnCd systems have been investigated too by performing molecular-dynamics simulations using the developed PEF. Surface reconstruction and multilayer relaxation on clean surfaces, adatom on surface, substitutional atom on surface and bulk materials, and vacancy on surface and bulk materials have been studied extensively.

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