Optical Josephson oscillation achieved by two coupled exciton-polariton condensates.

Two coupled exciton-polariton condensates (EPCs) in a double-well photonic potential are suggested to form the optical Josephson oscillation (JO) whose dependences on the pump arrangement, the potential geometry, and the exciton-photon detuning are studied through the Gross-Pitaevskii equations. When the pump detuning is slightly positive with respect to the polariton energy and the phase difference between the two EPCs is near π/2 (both are controlled by the pump beams), the system demonstrates the optical JO. The optical JO tunneling strength (J) depends on the distance (d) and barrier (Λ) between the two wells, for which an empirical formula is fitted, i.e., J≈0.42exp⁡(-d Λ/18.4) with the energy and length units in meV and µm. Since the double-well potential adopted is general, this fitting relation can show a guidance in practice for designing the optical devices based on the optical JO.

Generation of optical vortices by exciton polaritons in pillar semiconductor microcavities.

We propose a scheme to generate optical vortices through exciting exciton polariton vortices by a Gaussian beam in a pillar microcavity. With coupled Gross-Piteavskii equations we find that the structure of the exciton polariton vortices and antivortices shows a strong dependence on the microcavity radius, pump geometry, and nonlinear exciton-exciton interaction. Due to the nonlinear exciton-exciton interaction the strong Gaussian beam cannot excite more exciton polariton vortices or antivortices with respect to the weak one. The calculation demonstrates that the weak Gaussian beam can excite vortex-antivortex pairs, vortices with high total orbital angular momentum, and superposition states of vortex and antivortex with high total opposite orbital angular momentum. The pump geometry for the Gaussian beam to excite these vortex structures is analyzed in detail, which shows a potential application for generating optical vortex beams.

Liver abscesses in dromedary camels: Pathological characteristics and aerobic bacterial aetiology.

The study was carried out at Nyala abattoirs, South Darfur State, Sudan during a period from 2009 to 2011. Slaughtered camels (822) were examined for pathological changes of liver abscesses and identification of the involved aerobic bacteria. Grossly, a total of 111 (13.5%) liver abscesses were recorded in different camel ages; 90 (81.1%) were less than seven years old and 21 (18.9%) were more than seven years old. Histopathology of sectioned tissues revealed necrotic abscesses with infiltration of inflammatory cells, hydropic degeneration with swelling of hepatocytes comprising the sinusoid and different size of vacuoles in the hepatic cells. Proliferation of bile ducts with fibrous tissue and infiltration of inflammatory cells was also recorded. Investigation of bacteria revealed 90 aerobic isolates; they were identified to 52 (57.8%) gram positive cocci, 20 (22.2%) gram positive rods and 18 (20.0%) gram negative rods. Staphylococcus spp. (41.1%), Corynebacterium spp. (17.9%) and Streptococcus spp. (13.3%) were the most frequently identified bacteria involved in liver abscesses of camels in the region. Further studies are required to assess the pathogenicity of bacterial isolates from camel livers. This is particularly important from a public health perspective, since some people of Sudan are known to consume raw camel liver.