scholarly journals Positron annihilation and electron densities in organic liquids

1974 ◽  
Vol 27 (5) ◽  
pp. 1125 ◽  
Author(s):  
BJ Brown
Keyword(s):  
Positron Annihilation ◽  
Electron Density ◽  
Chain Length ◽  
Atomic Number ◽  
Aliphatic Hydrocarbons ◽  
Organic Liquids ◽  
Electron Densities ◽  
Effective Electron ◽  
Molecular Electron ◽  
Aromatic Systems

The effective electron density for positron annihilation in substituted aliphatic and aromatic liquid compounds has been determined. For the aliphatic hydrocarbons the molecular electron density Ne increases linearly with an increase in chain length and is equal to the sum of the partial electron densities of the substituent methyl (Ne(CH3) = 1.18) and methylene (Ne(CH2) = 1.28) groups.The values are approximately 10% lower for aromatic systems. The partial electron densities of substituted halogen atoms increase with atomic number and are: fluorine (9.3), chlorine (10.0), bromine (14.4) and iodine (23.0). For the aliphatic alcohols the partial Ne(OH) value decreases from 1.35 in methanol to 0.86 in octanol.

scholarly journals Investigation of Novel Composite Material Based on Extra-Heavy Concrete and Basalt Fiber for Gamma Radiation Protection Properties

2018 ◽  
pp. 52-58 ◽  
Author(s):  
І. Romanenko ◽  
M. Holiuk ◽  
A. Nosovsky ◽  
V. Hulik
Keyword(s):  
Composite Material ◽  
Gamma Radiation ◽  
Electron Density ◽  
Radiation Protection ◽  
Atomic Number ◽  
Gamma Ray ◽  
Basalt Fiber ◽  
Effective Atomic Number ◽  
Radiation Shielding ◽  
Effective Electron

The paper presents a new composite material for radiation protection based on extra-heavy concrete reinforced by basalt fiber. Basalt fiber is a new material for concrete reinforcement, which provides improved mechanical characteristics of concrete, reduces the level of microcracks and increases the durability of concrete. Within the scope of present work, the gamma-ray radiation protection properties of concrete reinforced with basalt fiber was modeled. Two types of extra-heavy concrete were used for this paper. The main gamma-ray attenuation coefficients such as mean atomic number, mean atomic mass, mean electron density, effective atomic number, effective electron density, Murty effective atomic number were analyzed with help of WinXCom software. It has been shown that the addition of basalt fiber to concrete does not impair its gamma-ray radiation shielding properties. With increasing the basalt fiber dosage in concrete, the radiation properties against gamma radiation are improved. This research was carried out with the financial support of the IAEA, within the terms and conditions of the Research Contract 20638 in the framework of the Coordinated Research Project (CRP) “Accelerator Driven Systems (ADS) Applications and use of Low-Enriched Uranium in ADS (T33002)” within the project “The Two-Zone Subcritical Systems with Fast and Thermal Neutron Spectra for Transmutation of Minor Actinides and Long-Lived Fission Products”.

scholarly journals Localizing electron density errors in density functional theory

2019 ◽  
Vol 21 (37) ◽  
pp. 20927-20938 ◽  
Author(s):  
Rubén Laplaza ◽  
Victor Polo ◽  
Julia Contreras-García
Keyword(s):  
Density Functional Theory ◽  
Electron Density ◽  
Quantum Chemical ◽  
Density Functional ◽  
Electron Densities ◽  
Functional Theory ◽  
Chemical Topology ◽  
Molecular Electron ◽  
Quantum Chemical Topology

The accuracy of different density functional approximations is assessed through the use of quantum chemical topology on molecular electron densities.

Effective electron density for free-positron annihilation in low-Z compounds

1967 ◽  
Vol 50 (2) ◽  
pp. 256-262 ◽  
Author(s):  
C. Bussolati ◽  
S. Cova ◽  
L. Zappa
Keyword(s):  
Positron Annihilation ◽  
Electron Density ◽  
Effective Electron ◽  
Free Positron

Study Total Atomic Cross-Sections, Effective Atomic Numbers, and Electron Densities for Palmitic Acid by Using Sources of Gamma Ray

2021 ◽  
Vol 19 (9) ◽  
pp. 152-158
Author(s):  
Mohammed Yahya Hadi ◽  
Ali Adil Turki Aldalawi ◽  
Karar Mahdi Talib
Keyword(s):  
Palmitic Acid ◽  
Attenuation Coefficient ◽  
Atomic Number ◽  
Gamma Ray ◽  
Effective Atomic Number ◽  
Mass Attenuation Coefficient ◽  
Electron Densities ◽  
Effective Electron ◽  
Total Electron ◽  
Mass Attenuation

The effective atomic number (Z effective), total atomic cross-section (б Total) electron density (N effective) have been Measured depending on the mass attenuation coefficient (μ/ρ). By using Gamma-ray radiation (γ), emitted from sources (57𝐶𝑜, 133𝐵𝑎, 22𝑁𝑎, 137𝐶𝑠, 54𝑀𝑛, 𝑎𝑛𝑑 60𝐶𝑜) with energies from (0.122, 0.356,0.511,0.662,0.84,1.17,1.275 𝑎𝑛𝑑 1.33𝑀𝑒𝑉) respectively. using the Sodium Iodide Scintillation Detectors NaI(Tl) at 662 keV and resolution about 8.2% have been measured the mass attenuation coefficients for the sample “Palmitic acid” it’s chemical formula C16H32O2. The data from the mass attenuation coefficient were then employed to study Z effective, N effective, and б total of the sample. In the presence of gamma-ray energy, it was discovered that the effective atomic number and effective electron densities first drop and they tend to remain nearly constant. The experimental values obtained by Z effective and N effective were in excellent agreement with the theoretical values. The theoretical data that is accessible is obtained from XCom, which is available online. The study's findings aid in understanding how (μ/ρ) values change when Zeff and Neff values vary in the case of H, C, and O based biological molecules such as fatty acids.

scholarly journals Measurement of Total Electronic Cross-Section, Total Atomic Cross-Section, Effective Atomic Numbers, Effective Electron Densities and Kerma for Some Br Compounds

2021 ◽  
Vol 2 (1) ◽  
pp. 024-029
Author(s):  
Tekerek Saniye ◽  
Küçükönder Adnan
Keyword(s):  
Electron Density ◽  
Attenuation Coefficient ◽  
Cross Section ◽  
Atomic Number ◽  
Gamma Ray ◽  
Effective Atomic Number ◽  
Mass Attenuation Coefficient ◽  
Transmission Method ◽  
Effective Electron ◽  
Mass Attenuation

The aim of this study is to calculate the experimental and theoretical the mass attenuation coefficient some Br compounds by using transmission method. Also using these values were determined the total electronic section, total atomic section, effective atomic number, effective electron density and Kerma. We performed the calculations of these values in attenuation by using direct excitation experimental geometry. The total attenuation cross sections of some halogene Br compounds were measured in a narrow beam good geometry using a high resolution Si(Li) detector in the energy with γ photons at 59.543 keV from Am-241 annular source. Theoretical mass attenuation coefficient values were computed from the XCOM data programme, based on mixture rule method. This study provide new insight into the literature since the values of effective atomic number, electron density and Kerma for some Br compounds have not been determined before. According to the results shown in mass attenuation coefficient, Zeff and Neff of Br compounds are closely associated with chemical structure. This research were undertaken to explore how Bromine compounds is gamma ray shielding material.

A Fundamental Relation of Molecular Informatics on the Information-Carrying Properties of Density Functions

2007 ◽  
Vol 72 (2) ◽  
pp. 153-163 ◽  
Author(s):  
Paul G. Mezey
Keyword(s):  
Electron Density ◽  
Complete Information ◽  
Molecular Shape ◽  
Density Theorem ◽  
Fundamental Relation ◽  
Electron Densities ◽  
Large Molecules ◽  
Topological Features ◽  
Fundamental Information ◽  
Molecular Electron

The molecular electron density carries the complete information about the molecule. This information is stored in the shape and more general topological features of molecular electron densities. A fundamental relation of molecular informatics, building on the Hohenberg-Kohn theorem, is the holographic electron density theorem: any nonzero volume part of a molecular electron density in a non-degenerate electronic ground state contains the complete information about all properties of the entire molecule. This fundamental feature of all molecules applies to all exhibited and also to all latent molecular properties, where latent properties are those not normally exhibited, only in response to some external stimulus. Recently it has become feasible to compute ab initio quality electron densities and approximate forces acting on individual nuclei in large molecules, even those beyond the thousand atom range, such as proteins. The newly expanded size range where reliable modelling methods can be also applied extends the role of detailed molecular shape analysis to macromolecules. In this context, it has become possible to study how the fundamental information-carrying properties of electron density take a newly recognized role influencing the predominance of specific nuclear conformations within the family of astronomically many potentially stable conformations of some macromolecules. Some special problems and results are discussed.

Understanding the molecular mechanism of the stereoselective conversion of N-trialkylsilyloxy nitronates into bicyclic isoxazoline derivatives

2021 ◽  
Author(s):  
Agnieszka Kącka-Zych ◽  
Radomir Jasinski
Keyword(s):  
Density Functional Theory ◽  
Molecular Mechanism ◽  
Electron Density ◽  
Density Functional ◽  
Dft Method ◽  
Functional Theory ◽  
Molecular Electron ◽  
Molecular Electron Density Theory

Conversion of N-trialkylsilyloxy nitronates into bicyclic isoxazoline derivatives has been explored using Density Functional Theory (DFT) method within the context of the Molecular Electron Density Theory (MEDT) at the B97XD(PCM)/6-311G(d,p)...

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