Ceratocystis manginecans associated with a serious wilt disease of two native legume trees in Oman and Pakistan

A serious wilt disease has recently been found on Prosopis cineraria (Ghaf) in Oman and on Dalbergia sissoo (Shisham) in Pakistan. Disease symptoms on both these native, leguminous hosts include vascular discolouration and partial or complete wilt of affected trees. A species of Ceratocystis was consistently isolated from symptomatic material. Morphological comparisons and analyses of DNA sequence data of the ITS, β-tubulin, and EF 1-α gene regions showed that the Ceratocystis isolates obtained from both tree species represent C. manginecans. This is the same pathogen that is causing the devastating mango sudden decline disease in Oman and Pakistan. This is also the same pathogen that has been reported causing a wilting disease on Acacia mangium in Indonesia. Cross inoculation with C. manginecans isolates from P. cineraria, D. sissoo and mango showed that the fungus can cause disease on all three trees.Tree Protection Cooperative Programme (TPCP), University of Pretoria, South Africa, and the Ministry of Agriculture and Fisheries, Omanhttp://link.springer.com/journal/13313hb201

Organic copolymer lasing from single defect microcavity fabricated using laser patterning

Reducing the lasing threshold in optically pumped organic lasers is a necessary component of the drive to develop an organic laser diode, as this may help mitigate the losses associated with electrical contacts and charge injection. In this study we show how increasing the binaphthyl (BN) spacer content in polydioctylfluorene (PFO) decreases its amplified spontaneous emission threshold (ASE) through the suppression of intermolecular interactions. Using co-polymers with low lasing thresholds, we use a laser patterning technique to fabricate physical defects (having a diameter of ∼2.5 μm) within a vertical microcavity. Such defects create additional lateral confinement, with this approach allowing us to reduce the lasing threshold from 11 μJ cm−2 to 7 μJ cm−2 and increase cavity Q-factor from 495 (planar cavity) to 2300. The enhanced performance and the stack structure of the defect microcavity show it is a promising architecture for an electrically-pumped laser device

Polarization tuning of an H1 organic–inorganic nano-cavity

We investigate the optical properties of the dipole-like modes of an H1 nano-cavity consisting of a single missing airhole imbedded into a triangular two-dimensional silicon nitride (Si3N4) based photonic crystal coated with a red-fluorescent molecular dye. We modify the size and position of the first six neighboring airholes around the nano-cavity and demonstrate that this allows control over the energy and separation of two dipole-like optical modes (Mx and My). This allows us to produce either linearly polarized optical modes or an unpolarized optical mode composed of degenerate modes having orthogonal polarization. We confirm our findings using three-dimensional finite difference time domain calculations

Strong coupling in high-finesse organic semiconductor microcavities

We report the fabrication of high-finesse strongly coupled microcavities composed of a polystyrene film doped with the dye tetraphenyl-porphyrin zinc positioned between two high reflectivity dielectric mirrors. The bottom mirror was deposited by plasma enhanced chemical vapor deposition, and was composed of 11 lambda/4 thick (silicon oxide/silicon nitride) pairs. The organic layer was deposited on to this by spin coating. Finally, the top mirror was deposited by thermal evaporation and consisted of 12 lambda/4 thick (tellurium oxide/lithium fluoride) pairs. Such cavities are characterized by Q factors of between 440 and 620. Strong coupling was evidenced via white light reflectivity measurements. Due to the high cavity Q factor, a Rabi splitting of 135 meV at resonance was very clearly resolved. (C) 2003 American Institute of Physics

Ultra-fast polariton dynamics in an organic microcavity

We study an organic semiconductor microcavity operating in the strong-coupling regime using femtosecond pump-probe spectroscopy. By probing the photo-induced absorption bands, we characterize the time-dependent population densities of states in the two polariton branches. We found evidence of a scattering process from the upper-branch cavity polaritons to the exciton reservoir having a rate of (150 fs)-1. A slower process similarly populates lower-branch polaritons with a rate of around (3ps)-

Ultra-fast polariton dynamics in an organic microcavity

We study an organic semiconductor microcavity operating in the strong-coupling regime using femtosecond pump-probe spectroscopy. By probing the photo-induced absorption bands, we characterize the time-dependent population densities of states in the two polariton branches. We found evidence of a scattering process from the upper-branch cavity polaritons to the exciton reservoir having a rate of (150 fs)-1. A slower process similarly populates lower-branch polaritons with a rate of around (3ps)-