Journal of Physical and Theoretical Chemistry
Volume:11 Issue: 3, Autumn 2014

The entanglement at zero-temperature is studied in a two-qubit XZ spin-1/2 chain model in anexternal magnetic field which is applied in the z direction. We have obtained an analytical relation forthe effect of the external magnetic field on the concurrence. It is shown that the ground state of thesystem depends on the strength of exchange coupling. We have shown that the analytical relation ofthe concurrence is independent of Jz. It is shown that for Jz >0 the concurrence is depended on thecritical 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 aremaximally entangled. For values of the field h>hc, the concurrence decreases by increasing theexternal magnetic field. For Jz <0, the concurrence decreases by increasing the external magneticfield.

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 widepH range of 1.5 to 10.5 at 25 °C and different ionic strengths ranging from 0.1 to 1.5 moldm-3NaClO4, NaNO3, and NaCl using potentiometric-spectrophotometric technique. The composition ofthe complexes was specified and was shown that thallium ion forms mononuclear two 1:1 complexeswith 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 formationconstants on ionic strength are described by a Debye-Huckel type equation and interpreted for thevarious 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 μg 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 0.05μg 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 literatureprocedure. 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 dibenzyltindichloride were calculated. DFT calculations were performed at the B3LYP and B3PW91 methodswith LanL2DZ basis set on the title compound. The title compound presents a total dipole moment of4.2996 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 B3LYPand B3PW91 methods, respectively. The infrared spectrum of (C6H5CH2)2SnCl2 was studied andanalyzed. A good correlation was found between calculated and experimental data. Characteristicvibrational bands of the dibenzyltin dichloride associated with the Sn-C and Sn-Cl stretchingvibrations were also identified.

P53 tumor suppressor gene, also known as “genome guardian” is mutated in more than half of allkind of cancers. In this study we have investigated the controls of environmental pH for P53 genemutation in point of specific sequence which is prone to mutagenesis. The most probable cancerousmutations occur as point mutations in exons 5-8 of P53 gene. The 175th codon of P53 is the thirdmost mutated codon in this gene. By experimental research, it is revealed that acidic pH raised therate of cancer and mutation in 175 CGC codon of P53 gene. It to some extent is due to protonation ofthis three nucleotide codon. Mutation in this codon changes the encoding amino acid andsubsequently produces a protein which has oncogenic features instead of tumor suppressorcharacteristics of original p53 protein. In current study, we perform investigation on the impact ofprotonation on stability of codon 175CGC in this gene. We used HyperChem software for answeringto our mentioned goal above. Our results suggested a reliable answer about the effect of protonationon mentioned codon and its stability. From theoretical point of view, acidity can decrease theinstability of this specific codon. Along with the experimental investigations, our results can to someextent 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, 60 ;C). 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-Hückel 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), BHdiss, BSdiss and BGdiss of KNO3 in the mixed solvent (water 85%+methanol 15%) was calculated.