Selection rule for cavity configurations to generate cylindrical vector beams with low beam quality factor.

Considering the birefringence of the gain medium, we propose a selection rule for designing cavity configurations that enable the generation of radially and azimuthally polarized laser beams with a low beam quality factor, i.e., high beam quality. Using this rule, all stable regions can support cylindrical vector (CV) beams by using the position of the end mirror as the tuning parameter to vary the cavity configuration. Such cavity configurations tend to sustain the fundamental or lowest-order CV beam, and radially or azimuthally polarized beams can be obtained simply by varying the tuning parameter. Based on experimental measurements of the beam quality factor and polarization characteristics, we verified our analyses and simulations for a four-element laser system.

Seasonal changes in bacterial communities associated with healthy and diseased Porites coral in southern Taiwan.

We compared the bacterial communities associated with healthy scleractinian coral Porites sp. with those associated with coral infected with pink spot syndrome harvested during summer and winter from waters off the coast of southern Taiwan. Members of the bacterial community associated with the coral were characterized by means of denaturing gradient gel electrophoresis (DGGE) of a short region of the 16S rRNA gene and clone library analysis. Of 5 different areas of the 16S rRNA gene, we demonstrated that the V3 hypervariable region is most suited to represent the coral-associated bacterial community. The DNA sequences of 26 distinct bands extracted from DGGE gels and 269 sequences of the 16S rRNA gene from clone libraries were determined. We found that the communities present in diseased coral were more heterogeneous than the bacterial communities of uninfected coral. In addition, bacterial communities associated with coral harvested in the summer were more diverse than those associated with coral collected in winter, regardless of the health status of the coral. Our study suggested that the compositions of coral-associated bacteria communities are complex, and the population of bacteria varies greatly between seasons and in coral of differing health status.

Cerebral blood flow and apoptosis-associated factor with electroacupuncture in a traumatic brain injury rat model.

OBJECTIVE: Electroacupuncture (EA) has been widely used for treatment of stroke, but there is little information on the effect of EA on the neuroprotective function in traumatic brain injury (TBI). The aim of the present study was to investigate the protective effects and mechanisms of EA treatment in a TBI rat model. METHODS: Male Sprague-Dawley rats were randomly divided into four groups: sham operation, TBI control, TBI+EA treated for 30 min or TBI+EA treated for 60 min. The animals were treated with EA immediately after TBI. The EA was applied at acupuncture points GV20, GV26, LI4 and KI1 with a dense-dispersed wave, frequencies of 0.2 and 1 Hz, and amplitude of 1 mA for 30 or 60 min. Regional blood flow, cell infarction volume, extent of neuronal apoptosis, expression of cell apoptosis-associated factor transforming growth-interacting factor (TGIF) were studied, and functional outcome was assessed by running speed test. All tests except regional blood flow were performed 72 h after TBI onset. RESULTS: Immediately after TBI, compared with the TBI control groups, the regional blood flow was significantly increased by EA treatment for 60 min. Compared with the TBI controls 72 h after TBI, the TBI-induced run speed impairment, infarction volume, neuronal apoptosis and apoptosis-associated TGIF expression were significantly improved by EA treatment. CONCLUSIONS: The treatment of TBI in the acute stage with EA for 60 min could increase the regional blood flow and attenuate the levels of TGIF in the injured cortex, might lead to a decrease in neuronal apoptosis and cell infarction volume, and might represent one mechanism by which functional recovery may occur.