Transmission dynamics of novel coronavirus SARS-CoV-2 among healthcare workers,a case study in Iran

One of the main concerns during the COVID-19 pandemic was the protection of healthcare workers against the novel coronavirus. The critical role and vulnerability of healthcare workers during the COVID-19 pandemic leads us to derive a mathematical model to express the spread of coronavirus between the healthcare workers. In the first step, the SECIRH model is introduced, and then the mathematical equations are written. The proposed model includes eight state variables, i.e., Susceptible, Exposed, Carrier, Infected, Hospitalized, ICU admitted, Dead, and finally Recovered. In this model, the vaccination, protective equipment, and recruitment policy are considered as preventive actions. The formal confirmed data provided by the Iranian ministry of health is used to simulate the proposed model. The simulation results revealed that the proposed model has a high degree of consistency with the actual COVID-19 daily statistics. In addition, the roles of vaccination, protective equipment, and recruitment policy for the elimination of coronavirus among the healthcare workers are investigated. The results of this research help the policymakers to adopt the best decisions against the spread of coronavirus among healthcare workers.

     

Solvent Effect on The Equilibrium and Rate Constant of the Tautomeric Reaction in Nexium,Skelaxin, Aldara and Efavirenz Drugs: A Dft Study

Some drugs have two tautomeric structures in the liquid state and the tautomeric equilibrium is formed between these structures. The reaction rate and equilibrium constant of this reaction varies in different solvents. Thus, the determination of the appropriate solvent to separate tautomers is important. In this research, we used the DFT level of B3LYP and the 6-311++G** basis set to obtain the proper solvent for Nexium, Skelaxin, Aldara and Efavirenz drugs. All calculations were made above the melting point of the mentioned drugs, because these drugs are solid at room temperature. The solvent effect is included in the calculation utilizing the polarizable continuum model PCM. The transition state of the tautomeric reaction is determined using the quadratic synchronous transit (QST2) method. The geometry, energy, and dipole moment of transition states are analyzed in different solvent. The root mean square deviation (RMSD) analysis is performed to determine the degree of a structure deviation of tautomer 1 and tautomer 2 from the transition state in different solvents. It is found that the RMSD value for tatumer1 is higher than that for tautomer 2 in all studied drugs. The proper solvent for the separation of tautomers is determined from the analysis of thermodynamics and kinetics.     

Dft Study of the Structural and Electronic Properties of Conducting Oligo(<Emphasis Type="Italic">p</Emphasis>-Fluorophenylthiophene)

A comprehensive theoretical study on the conducting oligomeric systems is carried out in view of their potential application in electrochemical charge storage. Density functional theory (DFT) calculations are carried out on a series of oligomers made up of 3-(p-fluorophenyl)-thiophene (FPT) to estimate the geometric and electronic structures, conjugated lengths, bandwidths, and energetic properties of polymeric systems. The calculations are performed on the dimer up to octamer chains in the ground state and both pand n-doped phases. The results obtained show that the conjugated system in p- and n-doped oligo(FPT)s has a higher distance with more planar chains with respect to their neutral forms. The band gap energy between the frontier molecular orbitals decreases dramatically for both ionic states, and approaches a low limiting value with increasing oligomer length. The charge delocalization through the monomer rings along the backbone oligo(FPT)s reveals that the p- and n-doped states had more suitable properties, reflecting the electron and hole transport characteristics for conductivity, respectively. The calculated first excitation energies for oligo(FPT)s at the time-dependent B3LYP/6-31G(d,p) level of theory indicate that both doped oligomers have lower excitation energies, which display a red shift in their absorption spectra. For polymeric systems, the evolution of ionization potential, electron affinity, electron chemical potential, molecular hardness, and thermodynamic stability is made through the extrapolated oligomer ones.     

DFT study of molecular structure and electronic properties of fluoromethylpyrrole oligomers including di-, tri- and tetramer

Structural and electronic properties of oligomers including dimer, trimer and tetramer of fluoromethylpyrroles (FMPs), NC₄H₄-CH_nF_3−n with n = 0, 1, 2, 3, and their radical cations have been studied using DFT-B3LYP method with 6-31G(d, p) basis set. FMPs are proposed in this research as candidate monomers for conducting polymers with modified characteristics compared to polypyrrole and polymethylpyrrole. A preliminary study using a set of ab initio computations (HF) with medium basis set was carried out on di-, tri- and tetramer in order to investigate the stability of configuration of polymer chains for FMPs. The B3LYP/6-31G** optimized geometry and stereochemistry show that the selectivity of branching of the propagating polymer chain is affected by the characteristics of the substitutions of monomer and, therefore, the growth pattern of the polymer chain can be predicted upon characterization of different centers of the monomers. Also, the results of this study, including quinoid coefficients, orbital energy spacing, charge- and spin-density distributions and electric dipole moment vectors show that conducting polymers consisted of trifluoromethyl pyrrole (Py-CF₃), compared with the other FMPs, are the most favorable to be used as monomers for conducting polymer structural and electronic properties.     

Finite Order Batalin-Fradkin-Tyutin Method for Chiral Bosons in Non- Commutative Space

The recently improved finite order BFT Hamiltonian embedding method is applied to the two dimensional chiral bosons in non-commutative space. It is then systematically converted to a first class constraint model. Performing the momentum integrations, the corresponding fully gauge symmetry Lagrangian as well as its partition function in phase space are obtained.     

New aspects of quantization of the Jackiw–Pi model: field–antifield formalism and noncommutativity

The so‐called Jackiw–Pi (JP) model for massive vector fields is a three‐dimensional, gauge‐invariant and parity‐preserving model that was discussed in several contexts. In this paper we have discussed its quantum aspects through the introduction of Planck‐scale objects, i.e., via noncommutativity and the well‐known BV quantization. Namely, we have constructed the JP noncommutative space‐time version, we have provided the BV quantization of the commutative JP model and we have discussed its features. The noncommutativity has introduced interesting new objects in JP's Planck‐scale framework.

     

Finite Order Batalin-Fradkin-Tyutin Method for Chiral Bosons in Non-commutative Space

The recently improved finite order BFT Hamiltonian embedding method is applied to the two dimensional chiral bosons in non-commutative space. It is then systematically converted to a first class constraint model. Performing the momentum integrations, the corresponding fully gauge symmetry Lagrangian as well as its partition function in phase space are obtained.     

Molecular structure and electronic properties of a series of oligoalkylthiophenes: A theoretical investigation

Molecular geometries and electronic properties of 3-alkylthiophenes (ATs) and their oligomers (OATs) are studied by the density functional theory (DFT). Calculations are performed on the oligomers formed by n repeating units, where n ranges from 1 to 6, using the B3LYP/6-31G** level of theory. The results obtained show that the doped oligomers have more satisfactory structural and electronic characteristics for the conducting polymers. The conjugated system in the doped oligomers has more aromaticity, with expanded and planar chains. The calculated energy gap values between the frontal orbitals and also the ionization potential values for the oligomers indicate that with increase in the oligomer chain length, the conductive band gap decreases. Furthermore, our calculations suggest that an electron-donating alkyl substituent at position 3 of the thiophene ring plays an important role in the structural and electronic properties of the polymers.     

Indirect exchange interaction in Rashba-spin-orbit-coupled graphene nanoflakes

We study the indirect exchange interaction, named Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling, between localized magnetic impurities in graphene nanoflakes with zig-zag edges in the presence of the Rashba spin-orbit interaction (RSOI). We calculate the isotropic and anisotropic RKKY amplitudes by utilizing the tight-binding (TB) model. The RSOI, as a gate tunable variable, is responsible for changes of the RKKY amplitude. We conclude that there is not any switching of the magnetic order (from ferro- to antiferro-magnetic and vice versa) in such a system through the RSOI. The dependence of the RKKY amplitude on the positions of the magnetic impurities and the size of the system is studied. The symmetry breaking, which can occur due to the Rashba interaction, leads to spatial anisotropy in the RKKY amplitude and manifests as collinear and noncollinear terms. Our results show the possibility of control and manipulation of spin correlations in carbon spin-based nanodevices.