Bilayer graphene Hall bar with a pn-junction

We investigate the magnetic field dependence of the Hall and the bend resistances for a ballistic Hall bar structure containing a pn-junction sculptured from a bilayer of graphene. The electric response is obtained using the billiard model and we investigate the cases of bilayer graphene with and without a band gap. Two different conduction regimes are possible: $i$) both sides of the junction have the same carrier type, and $ii$) one side of the junction is n-type while the other one is p-type. The first case shows Hall plateau-like features in the Hall resistance that fade away as the band gap opens. The second case exhibits a bend resistance that is asymmetric in magnetic field as a consequence of snake states along the pn-interface, where the maximum is shifted away from zero magnetic field

Graphene Hall bar with an asymmetric pn-junction

We investigated the magnetic field dependence of the Hall and the bend resistances in the ballistic regime for a single layer graphene Hall bar structure containing a pn-junction. When both regions are n-type the Hall resistance dominates and Hall type of plateaus are formed. These plateaus occur as a consequence of the restriction on the angle imposed by Snell's law allowing only electrons with a certain initial angles to transmit though the potential step. The size of the plateau and its position is determined by the position of the potential interface as well as the value of the applied potential. When the second region is p-type the bend resistance dominates which is asymmetric in field due to the presence of snake states. Changing the position of the pn-interface in the Hall bar strongly affects these states and therefore the bend resistance is also changed. Changing the applied potential we observe that the bend resistance exhibits a peak around the charge-neutrality point (CNP) which is independent of the position of the pn-interface, while the Hall resistance shows a sign reversal when the CNP is crossed, which is in very good agreement with a recent experiment [J. R. Williams et al., Phys. Rev. Lett. 107, 046602(2011)]

Spectroscopy of snake states using a graphene Hall bar

An approach to observe snake states in a graphene Hall bar containing a pn-junction is proposed. The magnetic field dependence of the bend resistance in a ballistic graphene Hall bar structure containing a tilted pn-junction oscillates as a function of applied magnetic field. We show that each oscillation is due to a specific snake state that moves along the pn-interface. Furthermore depending on the value of the magnetic field and applied potential we can control the lead in which the electrons will end up and hence control the response of the system

Ab initio description of nonlinear dynamics of coupled microdisk resonators with application to self-trapping dynamics

Ab initio approach is used to describe the time evolution of the amplitudes of whispering gallery modes in a system of coupled microdisk resonators with Kerr nonlinearity. It is shown that this system demonstrates a transition between Josephson-like nonlinear oscillations and self-trapping behavior. Manifestation of this transition in the dynamics of radiative losses is studied.Comment: 10 pages, 5 figures, accepted for publication in Phys. Rev.

Magnetic Kronig-Penney model for Dirac electrons in single-layer graphene

The properties of Dirac electrons in a magnetic superlattice (SL) on graphene consisting of very high and thin (delta-function) barriers are investigated. We obtain the energy spectrum analytically and study the transmission through a finite number of barriers. The results are contrasted with those for electrons described by the Schrodinger equation. In addition, a collimation of an incident beam of electrons is obtained along the direction perpendicular to that of the SL. We also highlight the analogy with optical media in which the refractive index varies in space.Comment: 21 pages, 13 figures, to appear in New Journal of Physic

Parámetros cinéticos y termodinámicos de la curcumina en aceites comestibles con diferentes grados de insaturación

The antioxidant activity of curcumin (0.02-0.1%) was evaluated in olive, sesame, and safflower oils at 373, 383, and 393 K. The results were examined in contrast to the effects of tocopherol (0.1%) and BHT (0.02%), so that the inhibitory function of curcumin was evaluated comparatively. The activation energy of oxidation was determined for olive (82.94 kJ·mol-1), sesame (77.39 kJ·mol-1) and safflower oils (74.42 kJ·mol-1). Adding curcumin (0.1%) enhanced the activation energy by 26.26, 26.64, and 38.81% in the case of olive, safflower, and sesame oils, respectively. Based on Gibbs free energy, curcumin functioned more effectively in olive oil at 373 K (growth coefficient: 1.52%), compared to the action of the other two antioxidants, namely tocopherol (1.43%) and BHT (1.39%). The efficiency of curcumin was lower in oils which had a higher degree of polyunsaturation due to the disproportionation of the hydrogen-donating mechanism and the rate of free-radical formation in these oils.La actividad antioxidante de la curcumina (0,02-0,1 %) se evaluó en aceites de oliva, sésamo y cártamo a 373, 383 y 393 K. Los resultados se contrastaron con los efectos del tocoferol (0,1 %) y del BHT (0,02%), por lo que se evaluó comparativamente la función inhibitoria de la curcumina. Se determinó la energía de activación de la oxidación para los aceites de oliva (82,94 kJ·mol-1), sésamo (77,39 kJ·mol-1) y cártamo (74,42 kJ·mol-1). La adición de curcumina (0,1 %) mejoró la energía de activación en un 26,26 %, 26,64 % y 38,81 % en el caso de los aceites de oliva, cártamo y sésamo, respectivamente. Según la energía libre de Gibbs, la curcumina funcionó de manera más eficaz en aceite de oliva a 373 K (coeficiente de crecimiento: 1,52 %), en comparación con la acción de los otros dos antioxidantes; es decir, tocoferol (1,43 %) y BHT (1,39 %). La eficiencia de la curcumina fue menor en los aceites que tenían un mayor grado de poliinsaturación debido a la desproporción del mecanismo de donación de hidrógeno y la tasa de formación de radicales libres en estos aceites

EFFECTS OF POLY-ALUMINUM CHLORIDE, STARCH , ALUM AND ROSIN ON THE ROSIN SIZING, STRENGTH AND MICROSCOPIC APPEARANCE OF PAPER PREPARED FROM OLD CORRUGATED CONTAINER (OCC) PULP

The influence of rosin (0.1-0.3%), alum (0.4-0.6%), polyaluminum chloride (0.3-0.7%), and starch (0.5-1.5%) in the making of paper from old corrugated container (OCC) pulp on the freeness, breaking length, tear index, and burst index of pulp and paper sheets was studied. Using a full factorial design to identify the optimum operating conditions, equations relating the dependent variables to the operational variables of the chemical additives were derived that reproduced the former with errors lower than 5%. Using a high starch (1.5%), high PAC (0.7%), low alum (0.4%), and low rosin (0.1%) combination led to pulp that was sufficient to obtain paper with good strength properties (breaking length 5720m; burst index: 3.1 kPam2g-1; tear index: 6.2mNm2/g; Cobb test: 94; fold endurance: 1.52) SEM analysis show increasing in bonding between fibers together at this level of additives. The influence of starch on Cobb test values was not significant

Climatic potential of sport tourism in Anzali-Rezvanshahr coastal belt, South-west of Caspian Sea, Iran

The goal of this research is to identify eco-tourist capabilities and to determine temporal and spatial suitable area in order to attract athletic tourism in the north of Iran from Anzali coast to Rezvanshahr. Investigation method in this research is deseriptive – analytic based on using attributive / library studies and due to existing capabilities in this region, the climatic rest area had been specified by performing Beicker and Olgay climogram method and had been dealt with studying the relation of climate with athletic coastal activities such as swimming, Aerial sports, football, parachuting and Athletics Track. Finally, regarding the results from above three methods, a communality was taken for more exact determination of human climatic rest area and suitable temporal area of performing athletic activities. The results had been indicated that in Anzali coastal belt to Rezvanshahr, June, July, August, and September are enjoying human rest climate where in Anzali shore June is suitable for Aerial sports and swimming. July and August are useful for swimming and September have temporate climate for football in Rezvanshahr shore. June and July are suitable for football and swimming. August have temporate climate for swimming and September is enjoy from an optimal condition for playing football and parachuting .So, regarding the results, we can engaged with optimal planning in order to attract naturalist and specially to attract athletic tourism

Magnetron sputtering technique for analyzing the influence of RF sputtering power on microstructural surface morphology of aluminum thin films deposited on SiO2/Si substrates

In this research, aluminum (Al) thin films were deposited on SiO2/Si substrates using RF magnetron sputtering technique for analyzing the influence of RF sputtering power on microstructural surface morphologies. Different sputtering RF powers (100–400 W) were employed to form Al thin films. The characteristics of deposited Al thin films are investigated using X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier-transforms infrared (FTIR) spectroscopy. The X-ray diffraction (XRD) results demonstrate that the deposited films in low sputtering power have amorphous nature. By increasing the sputtering power, crystallization is observed. AFM analysis results show that the RF power of 300 W is the optimum sputtering power to grow the smoothest Al thin films. FTIR results show that the varying RF power affect the chemical structure of the deposited films. The SEM results show that by increasing the sputtering power leads to the formation of isolated texture on the surface of substrate. In conclusion, RF power has a significant impact on the properties of deposited films, particularly crystallization and shape