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Biomedical subjects

E Yurtsever

Publications and source records attributed to E Yurtsever.

10 recordsLinked to original sources
PubMed2006

Ionic dimers in He droplets: interaction potentials for Li2(+)-He,Na2(+)-He, and K2(+)-He and stability of the smaller clusters.

We present post Hartree-Fock calculations of the potential energy surfaces (PESs) for the ground electronic states of the three alkali dimer ions Li(2) (+),Na(2) (+), and K(2) (+) interacting with neutral helium. The calculations were carried out for the frozen molecular equilibrium geometries and for an extensive range of the remaining two Jacobi coordinates, R and theta, for which a total of about 1000 points is generated for each surface. The corresponding raw data were then fitted numerically to produce analytic expressions for the three PESs, which were in turn employed to evaluate the bound states of the three trimers for their J=0 configurations: The final spatial features of such bound states are also discussed in detail. The possible behavior of additional systems with more helium atoms surrounding the ionic dopants is gleaned from further calculations on the structural stability of aggregates with up to six He atoms. The validity of a sum-of-potential approximation to yield realistic total energies of the smaller cluster is briefly discussed vis-a-vis the results from many-body calculations.

Journal Article↗
PubMed2005

Finite-size effects in the dynamics and thermodynamics of two-dimensional Coulomb clusters.

The dynamics and thermodynamics of melting in two-dimensional Coulomb clusters is revisited using molecular dynamics and Monte Carlo simulations. Several parameters are considered, including the Lindemann index, the largest Lyapunov exponent, and the diffusion constant. In addition to the orientational and radial melting processes, isomerizations and complex size effects are seen to occur in a very similar way to atomic and molecular clusters. The results are discussed in terms of the energy landscape represented through disconnectivity graphs, with proper attention paid to the broken ergodicity problems in simulations. Clusters bound by 1/r3 and e(-kappar)/r forces, and heterogeneous clusters made of singly and doubly charged species, are also studied, as well as the evolution toward larger systems.

Journal Article↗
PubMed2004

Ab initio quantum dynamics with very weak van der Waals interactions: Structure and stability of small Li2(1Sigmag+)-(He)n clusters.

The potential energy surface (PES) for the interaction between Li2(1Sigmag+) and 4He has been computed using an accurate, post-Hartree-Fock quantum calculation for its ground electronic state. The orientational anisotropy of the forces and the interplay between repulsive and attractive effects within the PES are analyzed to extract information on the possible existence of bound states in the triatomic system. The structures of a few of the Li2(He)n small clusters are examined by comparing a classical approach with a full quantum one to generate bound configurations and to extract information on the possible spatial arrangements of the smaller clusters via à vis the location of the Li2 dopant. Some significant consequences on the Li2 behavior in larger clusters and droplets are drawn from the above findings.

Journal Article↗
PubMed2000

Rotationally induced transitions in small clusters.

The dynamics of an Ar6 cluster held together by Lennard-Jones forces is studied classically. The development of chaotic dynamics is mainly followed by a calculation of the maximum Lyapunov exponent (MLE). Initial momentum vectors are chosen from the eigenvectors of the Hessian of the potential energy so that rotating and nonrotating clusters can be studied systematically. It is found that the dependence of MLE on the total energy is considerably different for rotational and vibrational excitations. As the magnitude of the angular momentum increases, sharp transitions in MLE are observed. These transitions are explained in terms of the changes of the topology of the effective rovibrational potential energy surface and the dynamic equilibration between the global and local minima.

Journal Article↗
PubMed1999

Effect of tenoxicam on biochemical serum parameters of rats.

Tenoxicam is a nonsteroidal analgesic of the oxicam group, which possesses both antipyretic and anti-inflammatory characteristics. The use of tenoxicam has recently increased and it is reported in the literature that treatments lasting between a few weeks to three months caused increases in serum alanine transferase (ALT), aspartate transferase (AST), gamma glutamyl transferase (GGT) and bilirubin in humans. Toxic dose treatments to rats caused alterations in renal parameters. To verify these observations, various biochemical parameters were examined following administration of nontoxic doses of tenoxicam to rats. Rats were divided into three groups. One group received tenoxicam 0.6 mg/kg/day; the second group received 1.2 mg/kg/day i.p. The control group received normal saline i.p. At the end of 15 days, blood samples from the animals' hearts were taken for routine biochemical tests. No statistically significant changes were observed in serum urea, uric acid, creatinine, electrolytes, ALT, AST, total protein, bilirubin or glucose levels between the treatment groups and control groups. Increases in GGT levels were found to be statistically significant in both of the treatment groups compared with the control group.

Animals↗
PubMed1999

The in vivo effect of a Brassica oleracea var. capitata extract on Ehrlich ascites tumors of MUS musculus BALB/C mice.

An extract of Brassica oleracea var. capitata juice was prepared using petroleum ether, ether, ethanol and an Al2O3 column. The healing and tumor protecting effects of this extract were tested on Ehrlich ascites (EA) solid tumors of Mus musculus BALB/C mice. Complete disappearance of the tumors was observed in 54.5% of the animals in the experimental group (n = 22) which received 20 mg/day of the extract i.p. for 28 days. Regression of the tumors (27%), fixation of tumor size (4%) and an increase in tumor size (18%) were also recorded. Neither tumor size fixation nor regression was recorded in the control group which received physiological serum (0.5 ml/day). The healing effect was found to be related to the starting tumor size. The healed animals in the experimental group were followed for 6-7 months and no tumor recurrence was recorded. The protective effect of this extract on tumor formation was also tested. Experimental animals (n = 35) received 20 mg/day of the extract i.p. for 20 days. Physiological serum was administered to a control group (n = 30). Transplantation of solid tumors was performed on the 20th day and extract administration was discontinued. Transplantation success was recorded 20 days after transplantation. In the experimental group, only three out of 35 mice showed tumor development, whereas in the control group the number was 23 out of 35 mice. It was also observed that the extract prevented the development of liquid EA tumors. This extract was also found to be nontoxic. Brassica oleracea var. capitata had a healing effect as well as a protective effect on EA solid tumors of mice. These results are in agreement with our previous results obtained from a liquid Brassica oleracea var. acephala juice extract.

Animals↗