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دسترسی آزاد مقاله
1 - Metallic and semi-conducting resistivity behaviour of La0.7Ca0.3−xKxMnO3 (x = 0.05, 0.1) manganites
Dinesh Varshney Neha DodiyaAbstractThe temperature dependence of electrical resistivity, ρ, of ceramic La0.7Ca0.3−xKxMnO3 (x = 0.05, 0.1) is investigated in metallic and semi-conducting phase. The metallic resistivity is attributed to be caused by electron–phonon, electron–electron and electron–m چکیده کاملAbstractThe temperature dependence of electrical resistivity, ρ, of ceramic La0.7Ca0.3−xKxMnO3 (x = 0.05, 0.1) is investigated in metallic and semi-conducting phase. The metallic resistivity is attributed to be caused by electron–phonon, electron–electron and electron–magnon scattering. Substitutions affect average mass and ionic radii of A–site resulting in an increase in Debye temperature θD attributed to hardening of lattice with K doping. The optical phonon modes shift gradually to lower mode frequencies leading to phonon softening. Estimated resistivity compared with reported metallic resistivity, accordingly ρdiff. = [ρexp. − {ρ0 + ρe−ph (=ρac + ρop)}], infers electron–electron and electron–magnon dependence over most of the temperature range. Semi-conducting nature is discussed with variable range hopping and small polaron conduction model. The decrease in activation energies and increase in density of states at the Fermi level with enhanced Ca doping is consistently explained by cationic disorder and Mn valence. پرونده مقاله -
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2 - Computational Design and Synthesis of Molecular Imprinted Polymers for solid-phase Extraction of Acyclovir
gholamali haghdoostHighly selective molecularly imprinted polymers (MIPs) for solid-phase extraction of acyclovir have been designed and prepared. In order to study the intermolecular interactions in the pre-polymerization mixture and to find a suitable functional monomer in MIP preparati چکیده کاملHighly selective molecularly imprinted polymers (MIPs) for solid-phase extraction of acyclovir have been designed and prepared. In order to study the intermolecular interactions in the pre-polymerization mixture and to find a suitable functional monomer in MIP preparation, a computational approach was developed. It was based on the comparison of the binding energy of the complexes between the template and functional monomers. The effect of the polymerization solvent was included using the polarizable continuum model. According to the theoretical calculation results, the MIP with acyclovir as template was prepared by precipitation polymerization method using acrylamide (AAM) as functional monomer and ethylene glycol dimethacrylate (EGDMA), as cross-linker in acetone. Having confirmed the results of computational method, three MIPs were synthesized with different functional monomers, i.e. acrylamide (AAM), allylamine (AA) and acrylonitrile (ACN), and then evaluated using LangmuirFreundlich (LF) isotherm. The results of this study have indicated the possibility of using computer aided design for rational selection of functional monomers and solvents capable of removal of acyclovir from contaminated fluids. پرونده مقاله -
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3 - AB Initio Calculations and IR Studies of Tautometric forms of Uracil and Cytosine and comparing results in different temperatures (25˚C, 37˚C and 40˚C).
M. Monajjemi R. Nikmaram F. Mollaamin Z. AziziIn this paper,the molecular geometry for three tautomers of uracil and four tautomers of cytosine has been analyzed. vibrational IR spectra of the tautomers were investigated at HF and B3LYP level using the AB initio 6-31G* and LANL2DZ basis sets from the program packag چکیده کاملIn this paper,the molecular geometry for three tautomers of uracil and four tautomers of cytosine has been analyzed. vibrational IR spectra of the tautomers were investigated at HF and B3LYP level using the AB initio 6-31G* and LANL2DZ basis sets from the program package Gaussian 98 (A.7 Public Domain version). The physico-chemical and biochemical properties of uracil and cytosine are one of the principal criteria for the selection of these compounds. Calculated results were compared with the corresponding experimental data if available. The harmonic wave numbers for the main tautomers of uracil (U1) and cytosine (C2) will compare at the 25ºC, 37ºC, and 40ºC. پرونده مقاله -
دسترسی آزاد مقاله
4 - Ab initio Study of Simple Mg-Ene Reactions of Propenyl Magnesium Halides and Ethylene (Type-I Intermolecular Reaction)
Elahe Rajaeian Avat (Arman) TaherpourThe insertion of an olefinic C=C bond into a metal-carbon bond is of potential interest as a preparativeroute to new products and as results of C-C coupling reactions to organic compounds. The allyl compoundsof Mg, react with an olefin by inversion of the allyl group vi چکیده کاملThe insertion of an olefinic C=C bond into a metal-carbon bond is of potential interest as a preparativeroute to new products and as results of C-C coupling reactions to organic compounds. The allyl compoundsof Mg, react with an olefin by inversion of the allyl group via a six center transition state. These precyclicreactions may be one of the most important classes of organic reactions. The reactions of C3H5MgX (X=F,Cl, Br, I) with ethylene will be discussed in light of computational studies using ab initio methods (RHF/6-31G*HRBF/6-31G* level). The investigation of the structural properties, theoretical thermodynamic andkinetic data i.e. ArG, AG# and rate constants of the reactions at 298°K will be presented. پرونده مقاله -
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5 - An Ab initio and chemical shielding tensors calculations for Nucleotide 5’-Monophosphates in the Gas phase
M. Monajemi M.A Seyed Sajjadi R. Sayyadi G. GhassemiStructural and magnetic properties of purine and pyrimidine nucleotides (CMP, UMP, dTMP, AMP, GMP, IMP) were studied at different levels of ab initio molecular orbital theory. These calculations were performed at the hartree-fock level and density functional B3LYP metho چکیده کاملStructural and magnetic properties of purine and pyrimidine nucleotides (CMP, UMP, dTMP, AMP, GMP, IMP) were studied at different levels of ab initio molecular orbital theory. These calculations were performed at the hartree-fock level and density functional B3LYP methods. Geometries were fully optimized by following Cs symmetry restrictions. The standard 6-31G** basis set which includes polarization and diffuse functions, was used for all the calculations. The gauge-invariant atomic atomic orbital (GIAO) method and the continuous-set-of-gauge-transformation (CSGT) procedure was employed to calculate atomic shielding tensors of the nucleotides using density theory at the B3LYP/6-31g** and HF/6-31g** level. The calculated chemical shifts were used to aid in assigning in the NMR spectra. پرونده مقاله -
دسترسی آزاد مقاله
6 - Ab Initio Study of Conformational and Configurational Properties of 1, 3- Diazacyclohepta-1, 2-diene and 1, 3-Diazacycloocta-1, 2-diene
Issa Yavari Vahideh Hadigheh-Rezvan Mohsen DadgarAb initio calculations at HF/6-31G* level of theory for geometry optimization and MP2/6-31G*//HF/6-31G* for a single point total energy calculation are reported for the importantenergy-minimum conformations and transition-state geometries of 1, 3-diazacyclohepta-1, 2-di چکیده کاملAb initio calculations at HF/6-31G* level of theory for geometry optimization and MP2/6-31G*//HF/6-31G* for a single point total energy calculation are reported for the importantenergy-minimum conformations and transition-state geometries of 1, 3-diazacyclohepta-1, 2-diene (2) and 1, 3-diazacycloocta-1, 2-diene (3). The C2 symmetric twist-chair (2-TC)conformation of 2 is calculated to be 7.4 kJ mol-1 more stable than the twist-boat (2-TB, C2)conformer. Interconversion of 2-TC and 2-TB conformations takes place by a relatively highenergy(58.2 kJ mol-1) transition state. The unsymmetrical chair (3-C) conformation of 3 iscalculated to be 6.6 kJ mol-1 more stable than the C2 symmetric twist-boat (3-TB) form. Thetransition state linking 3-C and 3-TB conformations is 40 kJ mol-1 above 3-C. Racemization of2-TC and 3-C conformations occures by cis-rotation and requires 77.9 and 83.5 kJ mol-1,respectively. پرونده مقاله -
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7 - Ab Initio Quantum Chemical Studies of 15N and 13C NMR Shielding Tensors in Serine and Complexes of Serine- nH2O: Investigation on Strength of the CαH…O Hydrogen bonding in the Amino Acid Residue.
M. Monajjemi T. Karimkeshteh F. MollaaminIn this paper, the hydrogen bonding (HB) effects on the NMR chemical shifts of selected atoms in serineand serine-nH2O complexes (from one to ten water molecules) have been investigated with quantummechanical calculations of the 15N and 13C tensors. Interaction with wat چکیده کاملIn this paper, the hydrogen bonding (HB) effects on the NMR chemical shifts of selected atoms in serineand serine-nH2O complexes (from one to ten water molecules) have been investigated with quantummechanical calculations of the 15N and 13C tensors. Interaction with water molecules causes importantchanges in geometry and electronic structure of serine.For the compound studied, the most important intermolecular interaction between serine and watermolecules employ different geometrical models of numerous N…H and C-H…O bonds in the crystallinestructures. These interactions have been approximated by explicitly adding the nearest neighbors into thecalculations.At present, quantum chemistry is almost universally applicable to the interpretation of physical andchemical properties of various compoundsChemical shift calculations, geometry optimization and energies have been performed with ab initiomethod at HF/6-31G* and HF/6-31G** levels with GIAO methods.There is strong evidence that intermolecular effects are important in determining the 15N chemical shiftsof free amino acid residue to assign principal axes of the tensors and some systematic trends appear fromthe analysis of the calculated values.Formation of each interaction (in ten orientations) results in a shift of the bridging hydrogen's chemicalshifts of N…H bond that indicate the most stabilized compound.The CαH…O bond plays an important role in the interactions of amino acids residue upon the structureand function of a protein.Despite the finding of numerous CαH…O contacts in proteins, major questions remain about theirimportance. Thus it is the strength of this binding that is of most importance in understanding the possiblefactor that the CαH…O H-bond may play in the folding of proteins.This paper represents comparison between theoretical and experimental values of NMR resonances, andcalculations of HF/6-31G** level produce results in better agreement with the experimental data. پرونده مقاله -
دسترسی آزاد مقاله
8 - Quantum Chemistry Study & Evaluation of Basis Set Effects on Prediction of Amino Acids Properties:
M. Monajjemi M. Karimkhan M. R. Gholami A. Ziglari K. Zare S. AfsharnezhadThe potential energy surface of gaseous glycine determined years ago in the ab initio B3LYP/6-311++G** calculations is composed of thirteen stable conformers. We performed the ab initiomolecular orbital calculations as the starting point to carry out a force field and n چکیده کاملThe potential energy surface of gaseous glycine determined years ago in the ab initio B3LYP/6-311++G** calculations is composed of thirteen stable conformers. We performed the ab initiomolecular orbital calculations as the starting point to carry out a force field and normal coordinatecalculation on the most stable conformer of non-zwitterionic glycine [conformer (I)]. Thecalculations were carried out at different levels of theory using two methods, namely, the Hartree-Fock (HF) and the Möller-Plesset second order perturbation (MP2) method (including electroncorrelation), and using the Pople’s basis sets, namely, STO-nG (n=2, 3 and 6), 3-21G, 6-21G, 6-31G, 6-311G and also cc-pVnZ to obtain HF limit. This different basis sets accompanied with thedifferent combinations of diffuse and polarization functions were used. Each level of theory, withno symmetry restrictions, did fully optimization of neutral glycine. The atomic chargedistributions were obtained using the Mulliken population analysis. The structural characteristicssuch as the total energies, the complete optimized geometrical parameters including bond lengths,normal and torsion angles, as well as dipole moments, rotational constants, atomic chargedistributions, vibrational frequencies and IR intensities of the equilibrium conformation of glycinein gas phase were calculated at a wide range of the levels of theory -as mentioned above- and theresults were compared together and with HF limit and the experimental data to examine thereliability of the applied basis sets and to introduce the most efficient ones. We also assayed howthe strength of internal H-bonds depended on the variant parameters of basis set via the calculatedatomic charges. پرونده مقاله -
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9 - An ab initio study of metalated CMP,UMP& dTMP at HF level:Bond energies and isotropic NMR shielding of atoms
M.A Seyed Sajjadi R. Sayadi G. Ghasem KH. KalatehThe interaction of Magnesium hydrate at the phosphate oxygen atom of the pyrimidine nucleotides (CMP,UMP,dTMP) were studied at the Hartree-Fock level Theory. We used LANL2DZ basis set for Mg and 6-31g* basis set for atoms.The basis set superposition error (BSSE) begins چکیده کاملThe interaction of Magnesium hydrate at the phosphate oxygen atom of the pyrimidine nucleotides (CMP,UMP,dTMP) were studied at the Hartree-Fock level Theory. We used LANL2DZ basis set for Mg and 6-31g* basis set for atoms.The basis set superposition error (BSSE) begins to converge for used Method/basis set. The gauge-invariant atomic orbital (GIAO) method and the continuous-set-of-gauge-transformation (CSGT) procedure were employed to calculate isotropic atomic shielding of the nucleotides using density functional theory at the B3LYP/6-31g** . These calculations yield molecular geometries in good agreement with available experimental data. پرونده مقاله -
دسترسی آزاد مقاله
10 - conformational properties and the anomeric effect study of phosphinanes
Javad Azizian Mahdieh Entezari Hossein Anaraki Ardakani Shahab ZomorodbakhshAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substitu چکیده کاملAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substituent can be seen by comparing the bond length in 2-chloro and 2- boromo substituented phosphinanes. The effect of anomeric effect have been effected on the bond length in 2-phosphinanes. پرونده مقاله -
دسترسی آزاد مقاله
11 - Theoretical study of conformational properties and the anomeric effect study of the 2- phosphinanes
Javad Azizian Hossein Anaraki Ardakani Shahab ZomorodbakhshAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substitu چکیده کاملAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substituent can be seen by comparing the bond length in 2-chloro and 2-boromo substituented phosphinanes. The effect of anomeric effect have been effected on the bond length in 2- phosphinanes. پرونده مقاله -
دسترسی آزاد مقاله
12 - Theoretical study of conformational properties and the anomeric effect study of the 2- phosphinanes
Javad Azizian Mahdieh Entezari Hossein Anaraki Ardakanib Shahab ZomorrodbakhshAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substitu چکیده کاملAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substituent can be seen by comparing the bond length in 2-chloro and 2-boromo substituented phosphinanes. The effect of anomeric effect have been effected on the bond length in 2- phosphinanes. پرونده مقاله -
دسترسی آزاد مقاله
13 - Theoretical insights into the encapsulation of anticancer Oxaliplatin drug into single walled carbon nanotubes
Mahyar Rezvani Iran Ahmadnezhad Masoud Darvish Ganji Maria FotukianThe present work was an attempt to evaluate the potentialities of using SWCNTs as nanovectors for drug delivery of anticancer drug Oxaliplatin. First-principles van der Waals density functional (vdW-DF) calculations are used to investigate the incorporation of oxaliplat چکیده کاملThe present work was an attempt to evaluate the potentialities of using SWCNTs as nanovectors for drug delivery of anticancer drug Oxaliplatin. First-principles van der Waals density functional (vdW-DF) calculations are used to investigate the incorporation of oxaliplatin inside the typical semiconducting and metallic single wall carbon nanotubes with various diameters (SWCNTs). Adsorption energy is calculated and the results show that oxaliplatin affinity for the semiconducting SWCNTs is stronger than that for the metallic counterparts. The obtained binding energies reveal that oxaliplatin prefers to be encapsulated into the semiconducting and metallic nanotubes with diameter of about 9 and 11 Å, respectively. We also found that vdW forces mainly contribute to the binding of selected drug molecule to SWCNTs. The study of the electronic structures and charge analysis indicate that no significant hybridization between the respective orbital takes place and the small interaction obtained quantitatively in terms of binding energies. Our findings afford not only a molecular insight into understanding of the interaction between oxaliplatin and SWCNTs but also may be instructive to relevant scientists who are attempt to develop effective methods for suitable nanovectors for drug delivery. پرونده مقاله
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