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Search Results: 1 - 10 of 190447 matches for " O. I. Obolensky "
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Rigorous treatment of electrostatics for spatially varying dielectrics based on energy minimization
O. I. Obolensky,T. P. Doerr,R. Ray,Yi-Kuo Yu
Physics , 2008, DOI: 10.1103/PhysRevE.79.041907
Abstract: A novel energy minimization formulation of electrostatics that allows computation of the electrostatic energy and forces to any desired accuracy in a system with arbitrary dielectric properties is presented. An integral equation for the scalar charge density is derived from an energy functional of the polarization vector field. This energy functional represents the true energy of the system even in non-equilibrium states. Arbitrary accuracy is achieved by solving the integral equation for the charge density via a series expansion in terms of the equation's kernel, which depends only on the geometry of the dielectrics. The streamlined formalism operates with volume charge distributions only, not resorting to introducing surface charges by hand. Therefore, it can be applied to any spatial variation of the dielectric susceptibility, which is of particular importance in applications to biomolecular systems. The simplicity of application of the formalism to real problems is shown with analytical and numerical examples.
Rearrangement of cluster structure during fission processes
A. G. Lyalin,O. I. Obolensky,A. V. Solov'yov,Il A. Solov'yov,W. Greiner
Physics , 2003, DOI: 10.1088/0953-4075/37/1/L02
Abstract: Results of molecular dynamics simulations of fission reactions $Na_{10}^{2+} \to Na_7^+ + Na_3^+$ and $Na_{18}^{2+} \to 2 Na_9^+$ are presented. Dependence of the fission barriers on isomer structure of the parent cluster is analyzed. It is demonstrated that the energy necessary for removing homothetic groups of atoms from the parent cluster is largely independent of the isomer form of the parent cluster. Importance of rearrangement of the cluster structure during the fission process is elucidated. This rearrangement may include transition to another isomer state of the parent cluster before actual separation of the daughter fragments begins and/or forming a "neck" between the separating fragments.
T-shaped dimer of coronene
O. I. Obolensky,V. V. Semenikhina,A. V. Solov'yov,W. Greiner
Physics , 2005,
Abstract: An evidence of importance of the T-shaped configuration of coronene dimer is presented. That is, the dimer's lowest energy configuration is not necessarily a stack, as it might had been expected a priori. This is a surprising result for dimer of such a large polycyclic aromatic hydrocarbon (PAH) as coronene. The energy of the T-shaped configuration at all considered levels of density functional theory (B3LYP,PBE/6-31+G(d),D95,cc-pVDZ,cc-pVTZ) was systematically lower than the energies of three plausible stack configurations. In order to get a better description of the van der Waals interaction,the density functional theory (DFT) results were adjusted by adding a phenomenological Lennard-Jones-type term into the total energy of the system. However, the van der Waals correction is somewhat arbitrary and its magnitude can not be rigorously justified. Depending on the choice of the parameters in the phenomenological term both the T-shaped and the parallel-displaced (PD) stack configurations can be the global energy minimum of the system. A simple model is proposed which is useful for qualitative understanding of possible geometries of the coronene dimer and larger coronene clusters. The model represents coronene dimer as two sets of charged rings interacting via Coulomb and Lennard-Jones potentials. The model provides an intuitively clear explanation why the T-shaped dimers can be of importance even for some of moderately large PAHs such as coronene and, may be, for circumcoronene.
Geometrical and statistical factors in fission of small metal clusters
O. I. Obolensky,A. G. Lyalin,A. V. Solov'yov,W. Greiner
Physics , 2005, DOI: 10.1103/PhysRevB.72.085433
Abstract: Fission of metastable charged univalent metal clusters has been studied on example of Na_{10}^{2+} and Na_{18}^{2+} clusters by means of density functional theory methods. Energetics of the process, i.e. dissociation energies and fission barriers, as well as its dynamics, i.e. fission pathways, have been analyzed. The dissociation energies and fission barriers have been calculated for the full range of fission channels for the Na_{10}^{2+} cluster. The impact of cluster structure on the fission process has been elucidated. The calculations show that the geometry of the smaller fragment and geometry of its immediate neighborhood in the larger fragment play a leading role in defining the fission barrier height. The present study demonstrates importance of rearrangement of the cluster structure during fission. It may include forming a neck between the two fragments or fissioning via another isomer state of the parent cluster; examples of such processes are given. For several low-lying isomers of Na_{10}^{2+} cluster the potential barriers for transitions between these isomer states are calculated and compared with the corresponding fission barriers. These data suggest that there is a competition between "direct" fission and fission going via intermediate isomer states of the parent cluster. An impact of the cluster geometry on the change of the system's entropy due to fission is also discussed.
Ion-induced electron production in tissue-like media and DNA damage mechanisms
E. Surdutovich,O. I. Obolensky,E. Scifoni,I. Pshenichnov,I. Mishustin,A. V. Solov'yov,W. Greiner
Physics , 2008, DOI: 10.1140/epjd/e2008-00207-y
Abstract: We propose an inclusive approach for calculating characteristics of secondary electrons produced by ions/protons in tissue-like media. This approach is based on an analysis of the projectile's interaction with the medium on the microscopic level. It allows us to obtain the energy spectrum and abundance of secondary electrons as functions of the projectile kinetic energy. The physical information obtained in this analysis is related to biological processes responsible for the irrepearable DNA damage induced by the projectile. In particular, we consider double strand breaks of DNA caused by secondary electrons and free radicals, and local heating in the ion's track. The heating may enhance the biological effectiveness of electron/free radical interactions with the DNA and may even be considered as an independent mechanism of DNA damage. Numerical estimates are performed for the case of carbon-ion beams. The obtained dose-depth curves are compared with results of the MCHIT model based on the GEANT4 toolkit.
3D Diffractive Focusing THz of In-Plane Surface Plasmon Polarition Waves  [PDF]
I. Minin, O. Minin
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.22017
Abstract: Demonstrated that analog of diffractive and refractive 3D optics in free space can be developed to manipulate surface waves such as surface plasmon polaritons (SPPs). It has been shown that an air-gap control of a floating dielectric block can generate the dynamic phase and amplitude modulation of the SPP transmission coefficient. Unlike conventional bulk optics, the nano-scale surface optics for SPP processing contains several unexpected and interesting features in addition to the physical features described. Dynamic plasmonic information processing on the nano-scale using air-gap control may be an effective mechanism for building a dynamic plasmonic information processing system.
Analysis of Factors Instigating Land Use Conflicts in Selected Forest Reserves of Ondo State, Nigeria  [PDF]
I. O. Azeez, O. J. Aluko
Journal of Environmental Protection (JEP) , 2019, DOI: 10.4236/jep.2019.105036
Abstract: Practice of agriculture and other none forestry uses in forest reserves often generates conflict owing to the former’s incompatibility with the latter. The need to identify the factors that triggers this conflict is germane to sustainable forest resources management. Thus, this paper report findings on various factors instigating land use conflicts in the high forest zone of Ondo state, Nigeria. Idanre and Oluwa forest reserves in the state were purposively selected for the study. Household counting was carried out in order to obtain a population in each settlement using participatory rural appraisal (PRA) technique. Fifty percent sampling intensity of individuals in settlements within and around the sites was used to select a total of 302 respondents for the study. Primary data were collected using both interview schedule guide and focus group discussion. Means, frequency counts and percentages were employed for descriptive analysis while factor analysis was used to identify the various factors instigating land use conflicts. Majority of the respondents were male (80.8%), married (86.1%), Yorubas (69.9%), farmers (69.6%) with a mean age of 43 ± 7.9 years. Boundary dispute (\"\"= 2.60), Resource control conflict (\"\"= 2.31), Inheritance conflict (\"\"= 2.11) as well as conflict between human/cultural and natural use (\"\"= 1.66) were the major types of conflicts identified in the study area. Four major factors that amplified the causes of land use conflicts in the forest reserves were: Cultural (settling land dispute cultural values between different ethnic group and access to land ownership); Economic (desperate for short term monetary gain , unpaid rent to landlords and unauthorised sale of common or collectively owned land); Social factors (increase in number of people and several people claiming the same land), and Political factors (breach of contract with government and changes in government policies on the use of forest).
Hydrocarbon Volumetric Analysis Using Seismic and Borehole Data over Umoru Field, Niger Delta-Nigeria  [PDF]
I. Aigbedion, H. O. Aigbedion
International Journal of Geosciences (IJG) , 2011, DOI: 10.4236/ijg.2011.22019
Abstract: Wireline signatures were used to identify hydrocarbon bearing sands and evaluate Petrophysical parameters for hydrocarbon pore volume determination. Well to seismic tie revealed that these reservoirs tied direct hydrocarbon indicators –bright and dim spots –on the seismic sections. Three hydrocarbon reservoir were delineated. Estimation of the volume of hydrocarbon in place revealed that reservoir A contained 1675091.54 ± 102 feet of gas in place, while reservoir B contained 163661.83 barrels ± 80 barrels and reservoir C contained 1739170.41 ± 102 cubic feet of gas.
Precipitation of Heavy Organics (Asphaltenes) from Crude Oil Residue Using Binary Mixtures of n-Alkanes  [PDF]
O. Achugasim, I. E. Ekpo
Advances in Chemical Engineering and Science (ACES) , 2015, DOI: 10.4236/aces.2015.51010
Abstract: Two solvent mixtures: n-pentane/n-hexane and n-heptane/n-octane at ten different percentage ratios were used to dissolve 2.5 g of vacuum distilled Anthan crude oil residue (500°C). The crude oil/n-alkane mixture in different conical flasks was stoppered, shaked mechanically and allowed to stand overnight. The resultant solution was subsequently filtered using a vacuum pump to afford the different weights of the residue (asphaltenes). The result of the weights of asphaltenes obtained at the different ratios of solvent mixtures showed that the highest amount of precipitate was obtained at 100% n-pentane solvent. Also there was a sharp increase in the amount of asphaltenes precipitated when the percentage ratio of n-pentane to n-hexane precipitant was 40:60 and when the ratio of n-heptane to n-octane precipitant was 30:70. A good understanding of the contribution of the different n-alkane solvents in the precipitation of asphaltenes is very necessary to flow assurance of crude oils in terms of solid precipitation.
Acinetobacter baumannii in Birds’ Feces: A Public Health Threat to Vegetables and Irrigation Farmers  [PDF]
M. Dahiru, O. I. Enabulele
Advances in Microbiology (AiM) , 2015, DOI: 10.4236/aim.2015.510072
Abstract: The rising trend of resistance in Acintobacter baumannii had in recent days become a public health care concern with most literature reported from samples collected from hospital environment. This research therefore, wishes to determine the occurrence of multidrug-resistant A. baumannii in birds’ droppings, associated with irrigated farms vegetables, for epidemiological update and future clinical forecast. Forty eight birds fecal samples were collected and processed for isolation and identification of A. baumannii on MacConkey agar and Microbact 24E (Oxoid), and tested against 10 commonly used antibiotics (quinolones, fluoroquinolones, aminoglycosides, sulfonamides). A. baumannii was isolated from 31.25% of samples and had shown more resistant to ceporex (100.00%) and to streptomycin with 80.00% and 90.00% for Jakara and Sharada farms’ fecal samples respectively; isolates were however sensitive to co-trimoxazole. Forty eight (46.67%) of the isolates were resistant to at least 6 drugs, with strong correlation between some drugs. By this result, wild birds’ fecal materials demonstrate high potential of A. baumannii carrying capacity and dissemination, and thus pose risk of contaminating vegetables, infecting human and transmitting resistance phenotype to other non-multidrug-resistant bacteria—a situation quite challenging to health care management and public health. And thus it further suggests for screening of additional probable contributing factors, so as to develop possible detailed transmission pathway and control strategies.
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