SUDDEN POLARIZATION IN THE TWISTED, PHANTOM STATE OF TETRAPHENYLETHYLENE DETECTED BY TIME-RESOLVED MICROWAVE CONDUCTIVITY

Photoexcitation of the symmetrical molecules tetraphenylethylene and tetra-p-methoxyphenylethylene dissolved in saturated hydrocarbon solvents results in a transient increase in the dielectric loss of the solutions as monitored using the nanosecond time-resolved microwave conductivity (TRMC) technique. This provides direct evidence for the dipolar, or ''zwitterionic'', nature of the 1p* phantom state formed from S1 by rotation around the central carbon-carbon bond. Dipole relaxation occurs mainly by charge inversion between the two energetically equivalent zwitterionic configurations, Z+/-, on a timescale of several picoseconds. A minimum dipole moment of ca. 7.5 D for the individual Z+/- states is found. The fluorescence of TPE in alkane solvents has two decay components, one with a decay time less than 200 ps and a second with a decay time of 1.9 ns. The former (lambda(max) almost-equal-to 490 nm) is assigned to emission from the partially relaxed S1 state prior to twisting. The latter (lambda(max) almost-equal-to 540 nm) is assigned to emission from a small, ca. 1%, concentration of the relaxed S1 state in equilibrium with the 1p* state in saturated hydrocarbon solvent

Which screening strategy should be offered to women with BRCA1 or BRCA2 mutations? A simulation of comparative cost-effectiveness

<p>Background: There is no consensus on the most effective strategy (mammography or magnetic resonance imaging (MRI)) for screening women with BRCA1 or BRCA2 mutations. The effectiveness and cost-effectiveness of the Dutch, UK and US screening strategies, which involve mammography and MRI at different ages and intervals were evaluated in high-risk women with BRCA1 or BRCA2 mutations.</p><p>Methods: Into a validated simulation screening model, outcomes and cost parameters were integrated from published and cancer registry data. Main outcomes were life-years gained and incremental cost-effectiveness ratios. The simulation was situated in the Netherlands as well as in the United Kingdom, comparing the Dutch, UK and US strategies with the population screening as a reference. A discount rate of 3% was applied to both costs and health benefits.</p><p>Results: In terms of life-years gained, the strategies from least to most cost-effective were the UK, Dutch and US screening strategy, respectively. However, the differences were small. Applying the US strategy in the Netherlands, the costs were (sic)43 800 and 68 800 for an additional life-year gained for BRCA1 and BRCA2, respectively. At a threshold of (sic)20 000 per life-year gained, implementing the US strategy in the Netherlands has a very low probability of being cost-effective. Stepping back to the less-effective UK strategy would save relatively little in costs and results in life-years lost. When implementing the screening strategies in the United Kingdom, the Dutch, as well as the US screening strategy have a high probability of being cost-effective.</p><p>Conclusion: From a cost-effectiveness perspective, the Dutch screening strategy is preferred for screening high-risk women in the Netherlands as well as in the United Kingdom.</p>