4,279 research outputs found
The mutual influence of Y⋯N and H⋯H interactions in XHY⋯NCH⋯HM complexes (X = F, Cl, Br; Y = S, Se; M = Li, Na, BeH, MgH): Tuning of the chalcogen bond by dihydrogen bond interaction
The equilibrium structures, interaction energies, and bonding properties of ternary XHY⋯NCH⋯HM complexes are studied by ab initio calculations, where X = F, Cl, Br, Y = S, Se, and M = Li, Na, BeH, MgH. The ab initio calculations are carried out at the MP2/aug-cc-pVTZ level. The results indicate that all optimized Y⋯N and H⋯H binding distances in the ternary complexes are smaller than the corresponding values in the binary systems. The calculated cooperative energies (Ecoop) are between -0.20 kcal/mol in BrHS⋯NCH⋯HBeH and -3.29 kcal/mol in FHSe⋯NCH⋯HNa. For a given Y and M, the estimated Ecoop values increase as X = F > Cl > Br. In addition, the selenium-bonded complexes exibit larger Ecoop values than those of the sulfur-bonded counterparts. The cooperativity between Y⋯N and H⋯H interactions is further analyzed by quantum theory of atoms in molecules and natural bond orbital methods. Cooperative effects make an increase in the J(Y-N) and J(H-H) spin-spin coupling constants of the ternary complexes with respect to the binary systems. © 2016 Published by NRC Research Press
Calculation of Spectral Darkening and Visibility Functions for Solar Oscillations
Calculations of spectral darkening and visibility functions for the
brightness oscillations of the Sun resulting from global solar oscillations are
presented. This has been done for a broad range of the visible and infrared
continuum spectrum. The procedure for the calculations of these functions
includes the numerical computation of depth-dependent derivatives of the
opacity caused by p modes in the photosphere. A radiative-transport code was
used for this purpose to get the disturbances of the opacities from temperature
and density fluctuations. The visibility and darkening functions are obtained
for adiabatic oscillations under the assumption that the temperature
disturbances are proportional to the undisturbed temperature of the
photosphere. The latter assumption is the only way to explore any opacity
effects since the eigenfunctions of p-mode oscillations have not been obtained
so far. This investigation reveals that opacity effects have to be taken into
account because they dominate the violet and infrared part of the spectrum.
Because of this dominance, the visibility functions are negative for those
parts of the spectrum. Furthermore, the darkening functions show a
wavelength-dependent change of sign for some wavelengths owing to these opacity
effects. However, the visibility and darkening functions under the assumptions
used contradict the observations of global p-mode oscillations, but it is
beyond doubt that the opacity effects influence the brightness fluctuations of
the Sun resulting from global oscillations
A New Look at Mode Conversion in a Stratified Isothermal Atmosphere
Recent numerical investigations of wave propagation near coronal magnetic
null points (McLaughlin and Hood: Astron. Astrophys. 459, 641,2006) have
indicated how a fast MHD wave partially converts into a slow MHD wave as the
disturbance passes from a low-beta plasma to a high-beta plasma. This is a
complex process and a clear understanding of the conversion mechanism requires
the detailed investigation of a simpler model. An investigation of mode
conversion in a stratified, isothermal atmosphere, with a uniform, vertical
magnetic field is carried out, both numerically and analytically. In contrast
to previous investigations of upward-propagating waves (Zhugzhda and Dzhalilov:
Astron. Astrophys. 112, 16, 1982a; Cally: Astrophys. J. 548, 473, 2001), this
paper studies the downward propagation of waves from a low-beta to high-beta
environment. A simple expression for the amplitude of the transmitted wave is
compared with the numerical solution.Comment: 14 pages, 6 figure
Rapid removal of phenol from aqueous solutions by AC_Fe3O4 nano-composite: Kinetics and equilibrium studies
Background and purpose: Phenol and its derivatives are used as raw material in many chemical, pharmaceutical and petrochemical industries. It is classified as priority pollutant, due to its high toxicity. In this study, the magnetic activated carbon nano-composite was used for quick removal of phenol. Materials and methods: The activated carbon was modified by magnetic nano-particles. Then physical properties of the adsorbent were investigated using BET, XRD and SEM. Afterwards, adsorption behavior of phenol onto the adsorbent was studied considering various parameters such as: pH, phenol concentration, contact time and adsorbent dosage. Also, the isotherms and adsorption kinetics model was studied. Results: BET analysis showed 10.25% decrease in the specific area of activated carbon after being amended by the Fe3O4 nano-particles. SEM and XRD confirmed the presence of Fe3O4 nanoparticles on the activated carbon. Optimum absorption points in this process were pH=8, contact time of 15 min and adsorbent dose 2 g/L. The Longmuir isotherm and pseudo-second-order kinetics were fitted to the data. The maximum adsorption capacity of phenol on AC_Fe3O4 was 84.033 mg/g. Conclusion: Creating magnetic properties on the activated carbon which has a high adsorption capacity of phenol could result in quick separation of phenol from aqueous solutions. Also, this adsorbent could be widely applied since it is inexpensive and simple to use. © 2015, Mazandaran University of Medical Sciences. All rights reserved
Modeling of the Influence of Energy Development on Different Branches of the National Economy
Within the Energy program, this paper contributes to the assessment, comparison. and evaluation of energy strategies, in particular the impact of the energy supply system on other branches of the economy. This impact is characterized by the demand for industrial products necessary for building and operating the energy supply system, the required putting into operation of industrial production capacities, capital investment in the energy supply system and related branches, and the direct and indirect expenses of limited domestic natural resources.
The dynamic model for treating all these characteristics was constructed at the Siberian Power Institute and modified at IIASA
Methods of Systems Analysis for Long-Term Energy Development
A constructive systems approach to long-term energy development forecasting (for 30 to 40 years) is elaborated and the main methods and mathematical models for implementing it are proposed. They are:
-- An intersector model and method for long-term forecasting of basic indices of economic growth and national economic estimation of energy development strategies;
-- An iterative scheme and optimization model for elaborating possible energy development strategies and comparison of tendencies in science and technology;
-- A statistical model for forecasting final energy demand based on existing dynamics of the main indices of economic growth.
These models and methods are tested on preliminary information
Mycosphaerella podagrariae - a necrotrophic phytopathogen forming a special cellular interaction with its host Aegopodium podagraria
We present a new kind of cellular interaction found between Mycosphaerella podagrariae and Aegopodium podagraria, which is remarkably different to the interaction type of the obligate biotrophic fungus Cymadothea trifolii, another member of the Mycosphaerellaceae (Capnodiales, Dothideomycetes, Ascomycota) which we have described earlier. Observations are based on both conventional and cryofixed material and show that some features of this particular interaction are better discernable after chemical fixation. We were also able to generate sequences for nuclear ribosomal DNA (complete SSU, 5.8 S and flanking ITS-regions, D1–D3 region of the LSU) confirming the position of M. podagrariae within Mycosphaerellacea
Electrochemical Process for Diazinon Removal from Aqueous Media: Design of Experiments, Optimization, and DLLME-GC-FID Method for Diazinon Determination
In the present study, electrochemical process was studied via removal of diazinon (O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate) as an insecticide/ acaricide organic case study. Influences of three operational parameters including initial ferrous ion concentration, initial hydrogen peroxide concentration, and initial diazinon concentration were measured and optimized in diazinon removal process. Response surface methodology (RSM) was used to design the experiments. The experimental data collected in a laboratory-scaled batch reactor equipped with four graphite bar electrodes as cathode and an aluminum sheet electrode as an anode. Quantitative analysis of diazinon was done with gas chromatography equipped with flame photometric detector. Disperse liquid–liquid microextraction was used prior to gas chromatography in order to extraction and preconcentration of diazinon from aqueous media to extraction phase. Acetone and chlorobenzene were used as disperser and extraction solvent, respectively. Maximum diazinon removal efficiency of 87% (0.85mg mass removal) in C0 of 2mg/L and 80% (120mg mass removal) in C0 of 300mg/L was achieved under different experimental conditions. The obtained experimental data were used for model building by RSM approach. Finally, optimization process was carried out using RSM algorithm. © 2015, King Fahd University of Petroleum & Minerals
On the Harmonic approximation for large Josephson junction coupling charge qubits
We revisit the harmonic approximation (HA) for a large Josephson junction
interacting with some charge qubits through the variational approach for the
quantum dynamics of the junction-qubit coupling system. By making use of
numerical calculation and analytical treatment, the conditions under which HA
works well can be precisely presented to control the parameters implementing
the two-qubit quantum logical gate through the couplings to the large junction
with harmonic oscillator (HO) Hamiltonian.Comment: 7 pages, 3 figure
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