Variational Approach for the Effects of Periodic Modulations on the Spectrum of Massless Dirac Fermion

In the variational framework, we study the electronic energy spectrum of massless Dirac fermions of graphene subjected to one-dimensional oscillating magnetic and electrostatic fields centered around a constant uniform static magnetic field. We analyze the influence of the lateral periodic modulations in one direction, created by these oscillating electric and magnetic fields, on Dirac like Landau levels depending on amplitudes and periods of the field modulations. We compare our theoretical results with those found within the framework of non-degenerate perturbation theory. We found that the technique presented here yields energies lower than that obtained by the perturbation calculation, and thus gives more stable solutions for the electronic spectrum of massless Dirac fermion subjected to a magnetic field perpendicular to graphene layer under the influence of additional periodic potentials.Comment: 8 pages, 7 figure

Boundaries of Subcritical Coulomb Impurity Region in Gapped Graphene

The electronic energy spectrum of graphene electron subjected to a homogeneous magnetic field in the presence of a charged Coulomb impurity is studied analytically within two-dimensional Dirac-Weyl picture by using variational approach. The variational scheme we used is just based on utilizing the exact eigenstates of two-dimensional Dirac fermion in the presence of a uniform magnetic field as a basis for determining analytical energy eigenvalues in the presence of an attractive/repulsive charged Coulomb impurity. This approach allows us to determine under which conditions bound state solutions can or can not exist in gapped graphene in the presence of magnetic field. In addition, the effects of uniform magnetic field on the boundaries of subcritical Coulomb impurity region in the massless limit are also analyzed. Our analytical results show that the critical impurity strength decreases with increasing gap/mass parameter, and also that it increases with increasing magnetic field strength. In the massless limit, we investigate that the critical Coulomb coupling strength is independent of magnetic field, and its upper value for the ground-state energy is 0.752.Comment: 9 pages,10 figure

Assessment of plasma nitric oxide concentration and erythrocyte arginase activity in dairy cows with traumatic reticuloperitonitis

ΔΕΝ ΔΙΑΤΙΘΕΤΑΙ ΠΕΡΙΛΗΨΗThe aim of this study was to evaluate plasma nitric oxide (NO) concentrations, erythrocyte arginase (ARG) activity, plasma fibrinogen (Fb) and serum iron (Fe) levels and some biochemical parameters in dairy cows with traumatic reticuloperitonitis (TRP). The animal material of the study consisted of 14 Swiss Brown cows diagnosed with TRP (TRP group) between 4-8 years old brought to Firat University Animal Hospital Clinics and 14 healthy Swiss Brown cows (control group) aged 4-8 years obtained from dairy farms in different regions. Blood samples were taken from the vena jugularis of the animals. Concentrations of plasma NO, Fb, erythrocyte ARG activity, and some biochemical markers were determined after the serum and plasma of the receiving blood were separated. While the NO (318.9±5.8 vs. 270.3±9.6 μmol/L) concentrations of the TRP group were found to be significantly higher than the control group (P<0.001), the erythrocyte ARG activity (29.5±0.5 vs. 35.2±1.0 U/hb) was found to be higher in the control group (P<0.001). It was also observed that total protein (TP) (6.6±0.5 vs. 7.8±0.1 g/dL) (P<0.05) and Fb (914.3±68.6 vs. 265.4±19.8 mg/dL) (P<0.001) concentrations were higher in the TRP group, compared to the control group, while albumin (ALB) (1.9±0.2 vs. 3.1±0.1 g/dL) and Fe (47.00±5.29 vs.106.79±9.44 μg/dL) concentrations were significantly lower than the control group (P<0.001). In addition, a positive correlation was found between NO and Fb concentrations and between erythrocyte ARG activity and Fe concentrations. As a result, it was determined that NO concentrations were increased and erythrocyte ARG activity was not significant in dairy cows with TRP. In addition, increased plasma Fb concentration and decreased serum Fe concentration were determined in dairy cows with TRP. This study demonstrated that plasma NO, Fb and serum Fe concentrations in dairy cows with TRP may be useful markers for prognosis