Picosecond spectroscopy of electronically excited singlet states in biphenylene

A photophys. properties of biphenylene-h8 and biphenylene-d8 in soln. at room temp. was investigated with picosecond absorption and fluorescence spectroscopy. The weak fluorescence with complex vibrational structure originates entirely from the S1 state. It decays monoexponentially with a lifetime of 240 +- 20 ps. Upon photoexcitation to S2 no emission attributable to the S2 state was obsd. Lifetime and quantum yield of fluorescence (FF = 2.3 * 10-4) are the same for biphenylene-h8 and for the completely deuterated compd., indicating the C-H vibrations are not involved in the major radiationless decay process of the S1 level, i.e. internal conversion (jIC > 0.99). This conclusion is supported by INDO/S CI calcns. where strong changes of the CC bond orders (particularly in the central C4 ring) with S0 -> S1 excitation are found. The time-resolved excited-state absorption, measured at several wavelengths, decays biexponentially with time consts. of 8 +- 3 and 250 +- 40 ps. Various interpretations of the 8 ps lifetime are discussed; the conclusion results that the 8 ps transient has to be assigned to the lifetime of the S2 state even though the emission expected for an allowed transition with such a long lifetime is not obsd. Strong S1 -> Sn and S2 -> Sn excited-state absorption is found as predicted by INDO/S calcns

Dynamic neurocognitive changes in interoception after heart transplant.

Heart-brain integration dynamics are critical for interoception (i.e. the sensing of body signals). In this unprecedented longitudinal study, we assessed neurocognitive markers of interoception in patients who underwent orthotopic heart transplants and matched healthy controls. Patients were assessed longitudinally before surgery (T1), a few months later (T2) and a year after (T3). We assessed behavioural (heartbeat detection) and electrophysiological (heartbeat evoked potential) markers of interoception. Heartbeat detection task revealed that pre-surgery (T1) interoception was similar between patients and controls. However, patients were outperformed by controls after heart transplant (T2), but no such differences were observed in the follow-up analysis (T3). Neurophysiologically, although heartbeat evoked potential analyses revealed no differences between groups before the surgery (T1), reduced amplitudes of this event-related potential were found for the patients in the two post-transplant stages (T2, T3). All these significant effects persisted after covariation with different cardiological measures. In sum, this study brings new insights into the adaptive properties of brain-heart pathways