Biomedical subjects

Honggang Zhao

Publications and source records attributed to Honggang Zhao.

5 recordsLinked to original sources

PubMed2006

Predicting the phase behavior of nitrogen + n-alkanes for enhanced oil recovery from the SAFT-VR approach: examining the effect of the quadrupole moment.

The phase behavior of nitrogen + n-alkanes is studied within the framework of the statistical associating fluid theory for potentials of variable range (SAFT-VR). The effect of the quadrupole moment of nitrogen on the phase behavior is considered through an extension of the SAFT-VR equation that includes an additional contribution to the Helmholtz free energy due to quadrupolar interactions. A significant improvement in the description of the phase diagram of the binary mixtures of nitrogen with different n-alkanes is obtained with the new approach when compared to predictions from the original SAFT-VR EOS (i.e., without the quadrupolar term). The experimental value for the quadrupole moment of nitrogen is used in the new equation; thus, no additional parameters are employed. Given the nonideal nature of the binary mixtures, a binary interaction parameter is needed to describe the full-phase diagram and high-pressure critical lines of these systems; however, this can be fitted to a single system and successfully used to predict the phase behavior of other binary mixtures without additional fitting. Furthermore, only a single, transferable, cross-energy parameter is required when the quadrupolar term is considered, whereas a cross-range parameter is also needed with the original SAFT-VR approach. The inclusion of the quadrupolar term in the equation of state therefore reduces the need to use effective parameters by explicitly including at the molecular level interactions due to the quadrupole moment.

Journal Article↗

PubMed2006

Phase behavior of dipolar fluids from a modified statistical associating fluid theory for potentials of variable range.

A statistical associating fluid theory for potentials of variable range to model dipolar fluids is presented. The new theory, termed the SAFT-VR+D equation (the statistical associating fluid theory for potentials of variable range plus dipole), explicitly accounts for dipolar interactions and their effect on the structure of the fluid. This is achieved through the use of the generalized mean spherical approximation (GMSA) to describe a reference fluid of dipolar square-well segments. Isothermal-isobaric and Gibbs ensemble Monte Carlo simulations have been performed in order to test the new theoretical approach. Predictions for the thermodynamic properties and phase behavior of dipolar square-well monomer and chain fluids, in which one or more segments are dipolar, are considered and compared with new computer simulation data. The results show that the equation of state in general provides a good description of the phase behavior of dipolar monomer and chain fluids. Some deviations are seen between the simulation data and theoretical predictions for monomer fluids with large dipole moments and for molecules composed of segments with dipoles in different orientations. This is addressed through the replacement of the GMSA by the linearized exponential approximation.

Journal Article↗

PubMed2005

Predicting mixture phase equilibria and critical behavior using the SAFT-VRX approach.

The SAFT-VRX equation of state combines the SAFT-VR equation with a crossover function that smoothly transforms the classical equation into a nonanalytical form close to the critical point. By a combinination of the accuracy of the SAFT-VR approach away from the critical region with the asymptotic scaling behavior seen at the critical point of real fluids, the SAFT-VRX equation can accurately describe the global fluid phase diagram. In previous work, we demonstrated that the SAFT-VRX equation very accurately describes the pvT and phase behavior of both nonassociating and associating pure fluids, with a minimum of fitting to experimental data. Here, we present a generalized SAFT-VRX equation of state for binary mixtures that is found to accurately predict the vapor-liquid equilibrium and pvT behavior of the systems studied. In particular, we examine binary mixtures of n-alkanes and carbon dioxide + n-alkanes. The SAFT-VRX equation accurately describes not only the gas-liquid critical locus for these systems but also the vapor-liquid equilibrium phase diagrams and thermal properties in single-phase regions.

Journal Article↗

PubMed2004

Elevation of NMDAR after transplantation of neural stem cells.

Cognitive deficits could be alleviated by transplantation of neural stem cells in animals. Grafted cells may differentiate into neurons, thereby improving animal cognition. Alternatively, grafted cells may provide neurotrophic factors to modify neuronal functions and to alleviate cognitive deficits. To test which mechanism is underlying this recovery process, senescence-accelerated mice were transplanted with human neural stem cells into the hippocampus. The effect of cell transplantation was assessed in the Morris water maze. The survival and differentiation of grafted cells and the expression of NMDA receptors were examined. The data suggested that in addition to the neural differentiation of grafted neural stem cells, up-regulation of NMDA receptors after transplantation also contributed to the alleviation of cognitive deficits in this animal model.

Aging↗

PubMed2003

[Effects of cisplatin and sodium selenite on transformation and rRNA gene transcription activity of human T lymphocytes].

In order to investigate the effect of sodium selenite on the action of cisplatin inhibiting transformation of human T lymphocytes, explore the influence of cisplatin and sodium selenite on rRNA gene transcription activity of lymphocytes and to explore the relationship between transformation of T cells and rRNA gene transcription activity, cisplatin was administered to the culture of lymphocytes after incubation for 24 hours with three different dosages (0.05, 0.2, and 0.5 mg/L). The culture was also supplemented with sodium selenite (0.05 mg/L) at the beginning of the cell culture or at the same time as cisplatin was administered for different treatment. The slide specimens were prepared using cytogenetical method after the cells were cultured for 72 hours, and then, the changes of the transformation rate of T lymphocytes and frequencies of Ag-NORs that reflect rRNA gene transcription activity were investigated. The results showed that the rate of T lymphocyte transformation in the groups treated with both sodium selenite and cisplatin were significantly increased (p < 0.01) as compared with that in the groups without sodium selenite supplementation and suffering exposures to cisplatin alone at corresponding dose, up to or over the rate of negative control group. There were no significant differences in the ratios of lymphocyte transformation between the groups pre-treated by sodium selenite and the groups treated by both sodium selenite and cisplatin on the condition that the other treatments were the same. There were no remarkable differences (p > 0.05) in the frequencies of Ag-NOR and satellite association among the all groups. This study indicated that sodium selenite supplementation can preclude the inhibition of transformation of T lymphocytes in vitro by cisplatin, regardless the pre-treatment by sodium selenite or co-treatment with cisplatin.

Antineoplastic Agents↗