Unidirectional Lasing Emerging from Frozen Light in Non-Reciprocal Cavities

We introduce a class of unidirectional lasing modes associated with the frozen mode regime of non-reciprocal slow-wave structures. Such asymmetric modes can only exist in cavities with broken time-reversal and space inversion symmetries. Their lasing frequency coincides with a spectral stationary inflection point of the underlying passive structure and is virtually independent of its size. These unidirectional lasers can be indispensable components of photonic integrated circuitry.Comment: 5 pages, 3 figure

Thermal stability of a special class of black hole solutions in F(R) gravity

In this paper, we work on the topological Lifshitz-like black hole solutions of a special class of vacuum $F(R)-$gravity that are static and spherically symmetric. We investigate geometric and thermodynamic properties of the solutions with due respect to the validity of the first law of thermodynamics. We examine the van der Waals like behavior for asymptotically AdS solutions with spherical horizon by studying the $P-v$, $G-T$ and $C_{Q,P}-r_{+}$ diagrams and find a consistent result. We also investigate the same behavior for hyperbolic horizon and interestingly find that the system under study can experience a phase transition with negative temperature.Comment: 14 pages with 7 captioned figures. Some additional notes are added. Accepted in EPJ

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

WAS FAIR FAIR TO U.S. CORN GROWERS? AN ANALYSIS OF THE PAYMENTS OFFERED TO CORN GROWERS UNDER THE 1996 FEDERAL AGRICULTURAL IMPROVEMENT AND REFORM ACT

The 1996 Farm Bill (FAIR) dramatically changed agricultural policy for producers of many commodities. A series of 7 annual decoupled payments replaced the deficiency-payment program. Option-pricing techniques are used to determine whether program benefits to corn producers are smaller or larger under the new program than the old.Agricultural and Food Policy,

Quasi-bound states of Schrodinger and Dirac electrons in magnetic quantum dot

The properties of a two-dimensional electron are investigated in the presence of a circular step magnetic field profile. Both electrons with parabolic dispersion as well as Dirac electrons with linear dispersion are studied. We found that in such a magnetic quantum dot no electrons can be confined. Nevertheless close to the Landau levels quasi-bound states can exist with a rather long life time.Comment: 9 pages, 10 figure

Roles of gibberellic acid and zinc sulphate in increasing size and weight of olive fruit

Olive trees (Olea europaea L. cv. Shengeh) were treated with gibberellic acid (GA3) at 0, 15, 30 and 45 ppm and zinc sulphate at 0, 0.25, 0.5 and 0.75% when fruit were at 70% of their final size in experiments carried out in 2007 season. The effect of GA3 and ZnSO4 treatments on yield and some variables related to fruit characteristics (fruit, pit and pulp weight, pulp/pit weight ratio, fruit length and diameter, pit length and diameter, fruit L/D ratio, pit L/D ratio fruit volume) was analyzed. Fruit weight was significantly increased most by concentrations of GA3 and ZnSO4 treatments with respect to control trees, due to an increase in fruit size. GA3 spray at the 30 ppm concentration was more effective in improving yield than spraying GA3 at other concentrations and control. Thus, these treatments accelerated fruit growth of olive, and also increased both fruit size and total yield per tree, allowing for an increase in its economic value. Use of 0.5% ZnSO4 + 30 ppm GA3 treatments was optimum for improvement of olive fruit yield