All-optical control of molecular fluorescence

We present a quantum electrodynamical procedure to demonstrate the all-optical control of molecular fluorescence. The effect is achieved on passage of an off-resonant laser beam through an optically activated system; the presence of a surface is not required. Following the derivation and analysis of the all-optical control mechanism, calculations are given to quantify the significant modification of spontaneous fluorescent emission with input laser irradiance. Specific results are given for molecules whose electronic spectra are dominated by transitions between three electronic levels, and suitable laser experimental methods are proposed. It is also shown that the phenomenon is sensitive to the handedness of circularly polarized throughput, producing a conferred form of optical activity

Status and distribution of Red-cockaded Woodpeckers and their habitat in southeastern Virginia

Intro and Objectives: For the first time in Virginia\u27s history, a Red-cockaded Woodpecker site has been purchased for long term management and protection. In addition, the site has been made ready to accommodate increasing population growth, through either productivity and recruitment, or outright translocation of birds from another source. Talks have also been underway to assess variable strategies for engaging private landowners in the business of Red-cockaded Woodpecker conservation. Therefore, a great priority has been placed on the need to assess the current status of the birds and their habitat as a first step toward moving the conservation of this species into the new millennium. It was with these issues in mind that this project evolved to undertake the challenge of reassessing the status of Red-cockaded woodpeckers and their habitat for the first time in 20 years. The project was designed to revisit the 1977/78 survey effort with slightly expanded coverage and decisively better survey tools. The current effort makes use of complete aerial photo and USGS topo coverage to comprehensively evaluate and survey ,where appropriate, relevant portions of the counties of Greensville, Southampton, Sussex, Prince George, Surry, and Isle of Wight, plus the cities of Suffolk, Chesapeake, and Virginia Beach. Only with a complete and current knowledge of the status and distribution of Red-cockaded Woodpeckers can any meaningful conservation effort begin to move forward. Objectives: 1. Identify and evaluate all accessible pine habitats capable of supporting Red-cockaded Woodpeckers (RCW) within the study area. 2. Map all currently suitable RCW habitats identified above, including a general description of stand size, speciation, condition, and age class. 3. Survey all sites identified above for evidence of past or present RCW occupancy. 4. Document numbers and status of Red-cockaded Woodpeckers and cavity trees at all sites where evidence of activity is found. 5. Document evidence observed of southern pine beetle or other infestations. 6. Through review of historic records and the activities described above, map and record all evidence of past and present RCW activity within the study area. 7. In addition, map and describe as above all habitats which appear likely to provide suitable trees for RCW cavity excavation within the next 20 years

Laser-controlled fluorescence in two-level systems

The ability to modify the character of fluorescent emission by a laser-controlled, optically nonlinear process has recently been shown theoretically feasible, and several possible applications have already been identified. In operation, a pulse of off-resonant probe laser beam, of sufficient intensity, is applied to a system exhibiting fluorescence, during the interval of excited- state decay following the initial excitation. The result is a rate of decay that can be controllably modified, the associated changes in fluorescence behavior affording new, chemically specific information. In this paper, a two-level emission model is employed in the further analysis of this all-optical process; the results should prove especially relevant to the analysis and imaging of physical systems employing fluorescent markers, these ranging from quantum dots to green fluorescence protein. Expressions are presented for the laser-controlled fluorescence anisotropy exhibited by samples in which the fluorophores are randomly oriented. It is also shown that, in systems with suitably configured electronic levels and symmetry properties, fluorescence emission can be produced from energy levels that would normally decay nonradiatively. © 2010 American Chemical Society