مجله شیمی فیزیک و شیمی نظری
سال:1393 | دوره: | شماره: |تعداد مقالات:6

The entanglement at zero-temperature is studied in a two-qubit XZ spin-1.2 chain model in an external magnetic field which is applied in the z direction. We have obtained an analytical relation for the effect of the external magnetic field on the concurrence. It is shown that the ground state of the system depends on the strength of exchange coupling. We have shown that the analytical relation of the concurrence is independent of Jz. It is shown that for Jz >0 the concurrence is depended on the critical value of the external magnetic field and it is changed at the critical external magnetic field. Also we have shown that for h <hc the concurrence is maximum (C=1) or states of the system are maximally entangled. For values of the field h>hc, the concurrence decreases by increasing the external magnetic field. For Jz <0, the concurrence decreases by increasing the external magnetic field.

The formation constants of the species formed in the systems H+ + cytidine 5’-monophosphate (CMP) and H+ + cytidine 5’-monophosphate + Tl (I) ion have been determined in aqueous solution in a wide pH range of 1.5 to 10.5 at 25oC and different ionic strengths ranging from 0.1 to 1.5 moldm-3 NaClO4, NaNO3, and NaCl using potentiometric-spectrophotometric technique. The composition of the complexes was specified and was shown that thallium ion forms mononuclear two 1:1 complexes with CMP. The general trend for the protonation constants of CMP and its complexes with thallium (I) are in the order of NaClO4>NaNO3>NaCl in different ionic media. The dependence of formation constants on ionic strength are described by a Debye-Huckel type equation and interpreted for the various supporting electrolytes.

A new kinetic spectrophotometic method for the determination of trace amount manganese (II) in Tea real samples has been described based on it s the catalytic effect on the oxidations of 1-(2-Pyridyl Azo) - 2 -Naphthol, (PAN), by potassium bromated in sulfuric acid. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance at 547.5 nm. Under the optimum conditions of 0.2 molL-1 sulfuric acid, 1.0×10-4 molL-1, 1- (2-PyridylAzo) -2- Naphthol, (PAN), 1mL of potassium bromate 0.11 mol L-1 at 35oC, calibration graph in the rang of 0.001-0.06 mg mL-1 manganese (II). Concentration was obtained with detection limit of 0.23 ng mL-1 by the fixed-time method of 4.5 min. The relative standard deviation for 0.05mg mL-1 manganese (II) is %90. No serious interference was identified. The applicability of the method was demonstrated by the determination of the manganese (II) in Water, Vegetables and blood samples.

Benzyl chloride and tin powder were used to prepare dibenzyltin dichloride according to a literature procedure. In this study, IR spectroscopy, HOMO-LUMO energy gap, NBO analysis, polarizability, some geometrical parameters, natural charge and electrical potential of atoms, global hardness, electronic chemical potential, global electrophilicity index, and molar volume of dibenzyltin dichloride were calculated. DFT calculations were performed at the B3LYP and B3PW91 methods with LanL2DZ basis set on the title compound. The title compound presents a total dipole moment of 4.2996 and 4.3235 Debye at the B3LYP and B3PW91 methods, respectively. Moreover, the HOMO- LUMO energy gap of 0.16988 and 0.17155 a.u. were obtained for the title compound using B3LYP and B3PW91 methods, respectively. The infrared spectrum of (C6H5CH2) 2SnCl2 was studied and analyzed. A good correlation was found between calculated and experimental data. Characteristic vibrational bands of the dibenzyltin dichloride associated with the Sn-C and Sn-Cl stretching vibrations were also identified.

P53 tumor suppressor gene, also known as “genome guardian” is mutated in more than half of all kind of cancers. In this study we have investigated the controls of environmental pH for P53 gene mutation in point of specific sequence which is prone to mutagenesis. The most probable cancerous mutations occur as point mutations in exons 5-8 of P53 gene. The 175th codon of P53 is the third most mutated codon in this gene. By experimental research, it is revealed that acidic pH raised the rate of cancer and mutation in 175 CGC codon of P53 gene. It to some extent is due to protonation of this three nucleotide codon. Mutation in this codon changes the encoding amino acid and subsequently produces a protein which has oncogenic features instead of tumor suppressor characteristics of original p53 protein. In current study, we perform investigation on the impact of protonation on stability of codon 175CGC in this gene. We used HyperChem software for answering to our mentioned goal above. Our results suggested a reliable answer about the effect of protonation on mentioned codon and its stability. From theoretical point of view, acidity can decrease the instability of this specific codon. Along with the experimental investigations, our results can to some extent elaborate acidic pH competency to cause mutation.

The solubility of KNO3 in the mixed solvent (water 85%+methanol 15%) were determined by using solvent evaporating method at different temperatures (25, 30, 40, 50, 60oC). In addition the equilibrium constant of ion pair formation, KIP, for K+NO3- ion-pair on the basis of Fuoss contact ion pair model was calculated. Upon choosing the extended Debye-Huckel model for estimating the mean activity coefficient of ions in the saturated solution and using the itteration calculations, we estimated the ion association contribution to the solubility of considered ionic compound in the mixed solvent at various temperatures. The value of thermodynamic solubility product constant, Ksp (th), ∆Hdiss, ∆Sdiss and ∆Gdiss of KNO3 in the mixed solvent (water 85%+methanol 15%) was calculated.