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Most measurements of fluorescence lifetimes on the single-molecule level are carried out using avalanche photon diodes (APDs). These single-photon counters are inherently slow, and their response shows a strong dependence on photon energy, which can make reconvolution of the instrument response function (IRF) challenging. An ultrafast time resolution in single-molecule fluorescence is crucial, e.g., in determining donor lifetimes in donor–acceptor couples which undergo energy transfer, or in plasmonic antenna structures, where the radiative rate and non-radiative rates are enhanced. We introduce a femtosecond double-excitation (FeDEx) photon correlation technique, which measures the degree of photon antibunching as a function of time delay between two excitation pulses. In this boxcar integration, the time resolution of fluorescence transients is limited solely by the laser pulse length and is independent of the detector IRF. The versatility of the technique is demonstrated with a custom-made donor–acceptor complex with one donor and two acceptors and with single dye molecules positioned accurately between two gold nanoparticles using DNA origami. The latter structures show ∼75-fold radiative-rate enhancement and fluorescence lifetimes down to 19 ps, which is measured without the need for any reconvolution. With the potential of measuring subpicosecond fluorescence lifetimes, plasmonic antenna structures can now be optimized further.

After a short introduction into the application of organic barrier coatings for corrosion protection the expectable parameters of the tested materials are discussed and the principle limitations are shown. Electrochemical impedance spectroscopy (EIS) is an already well known and also widely used technique, here only a very fundamental approach will be given.

Summary Using transcranial real-time sonography, changes in the axial diameter of the third ventricle during manoeuvres, which increased intracranial pressure (ICP), were measured in 28 patients with moderate to severe head injury. The measurements were correlated with ICP measured by epidural pressure monitoring. We observed reductions in diameter ranging from 0.3 to 1.1 mm with rises in intracranial pressure of at least 5 mm in 22 patients of whom only one died. In 6 additional patients, no changes in diameter were seen, and 5 of the 6 died. We interprete that poor outcome as a measurable inability for the brain to expel cerebrospinal fluid into extracerebral compartments during increased ICP. Transcranial real-time sonography may provide additional information about intracranial cerebral fluid dynamics and compliance.

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