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

Developments in the Photonic Theory of Fluorescence

Conventional fluorescence commonly arises when excited molecules relax to their ground electronic state, and most of the surplus energy dissipates in the form of photon emission. The consolidation and full development of theory based on this concept has paved the way for the discovery of several mechanistic variants that can come into play with the involvement of laser input – most notably the phenomenon of multiphoton-induced fluorescence. However, other effects can become apparent when off-resonant laser input is applied during the lifetime of the initial excited state. Examples include a recently identified scheme for laser-controlled fluorescence. Other systems of interest are those in which fluorescence is emitted from a set of two or more coupled nanoemitters. This chapter develops a quantum theoretical outlook to identify and describe these processes, leading to a discussion of potential applications ranging from all-optical switching to the generation of optical vortices

Mechanism for optical enhancement and suppression of fluorescence

When fluorescence from electronically excited states follows the absorption of radiation, the emission spectrum is often a key to identification of the excited species. It now emerges that passing off-resonant laser light through such an electronically excited system may enhance or suppress the fluorescent emission. This report establishes the mechanism and theory for this optical control of spontaneous fluorescence, derived by quantum electrodynamical analysis. Experimental techniques to detect the enhanced signal are also proposed. © 2009 American Chemical Society

Triage of children with headache at the ED: a guideline implementation study

We present a multicenter validation of a modified Manchester Triage System (MTS) flowchart for pediatric patients who present with headache to the emergency department. A prospective observational study was conducted across 5 European pediatric emergency departments. The standard MTS headache flowchart and a modified MTS headache flowchart were tested in the participating centers, and results were compared with triage categories identified by either the physician at the end of the clinical examination or the reference classification matrix (RCM). Fifty-three patients were enrolled in the preimplementation phase and 112 in the postimplementation phase. When compared with physician's triage and RCM, the modified MTS flowchart demonstrated good sensitivity (79% and 70%, respectively), specificity (77% and 76%, respectively), and a high positive likelihood ratio (9.14 and 16.75, respectively) for the identification of low-risk children. Conclusions: Our modified headache flowchart is safe and reliable in pediatric emergency settings, especially for lower classes of urgency

Triage of children with headache at the ED: a guideline implementation study.

none18Abstract We present a multicenter validation of a modified Manchester Triage System (MTS) flowchart for pediatric patients who present with headache to the emergency department. A prospective observational study was conducted across 5 European pediatric emergency departments. The standard MTS headache flowchart and a modified MTS headache flowchart were tested in the participating centers, and results were compared with triage categories identified by either the physician at the end of the clinical examination or the reference classification matrix (RCM). Fifty-three patients were enrolled in the preimplementation phase and 112 in the postimplementation phase. When compared with physician's triage and RCM, the modified MTS flowchart demonstrated good sensitivity (79% and 70%, respectively), specificity (77% and 76%, respectively), and a high positive likelihood ratio (9.14 and 16.75, respectively) for the identification of low-risk children. Conclusions: Our modified headache flowchart is safe and reliable in pediatric emergency settings, especially for lower classes of urgency. (C) 2013 Elsevier Inc. All rights reserved.noneBalossini V;Zanin A;Alberti C;Freund Y;Decobert M;Tarantino A;La Rocca M;Lacroix L;Spiri D;Lejay E;Armoogum P;Wood C;Gervaix A;Zuccotti GV;Perilongo G;Bona G;Mercier JC;Titomanlio LBalossini, V; Zanin, A; Alberti, C; Freund, Y; Decobert, M; Tarantino, A; La Rocca, M; Lacroix, L; Spiri, D; Lejay, E; Armoogum, P; Wood, C; Gervaix, A; Zuccotti, Gv; Perilongo, Giorgio; Bona, G; Mercier, Jc; Titomanlio, L