Tree-ring-reconstructed summer temperatures from northwestern North America during the last nine centuries

Northwestern North America has one of the highest rates of recent temperature increase in the world, but the putative “divergence problem” in dendroclimatology potentially limits the ability of tree-ring proxy data at high latitudes to provide long-term context for current anthropogenic change. Here, summer temperatures are reconstructed from a Picea glauca maximum latewood density (MXD) chronology that shows a stable relationship to regional temperatures and spans most of the last millennium at the Firth River in northeastern Alaska. The warmest epoch in the last nine centuries is estimated to have occurred during the late twentieth century, with average temperatures over the last 30 yr of the reconstruction developed for this study [1973–2002 in the Common Era (CE)] approximately 1.3° ± 0.4°C warmer than the long-term preindustrial mean (1100–1850 CE), a change associated with rapid increases in greenhouse gases. Prior to the late twentieth century, multidecadal temperature fluctuations covary broadly with changes in natural radiative forcing. The findings presented here emphasize that tree-ring proxies can provide reliable indicators of temperature variability even in a rapidly warming climate.

Synchronization and desynchronization in epilepsy: controversies and hypotheses

Epilepsy has been historically seen as a functional brain disorder associated with excessive synchronization of large neuronal populations leading to a hypersynchronous state. Recent evidence showed that epileptiform phenomena, particularly seizures, result from complex interactions between neuronal networks characterized by heterogeneity of neuronal firing and dynamical evolution of synchronization. Desynchronization is often observed preceding seizures or during their early stages; in contrast, high levels of synchronization observed towards the end of seizures may facilitate termination. In this review we discuss cellular and network mechanisms responsible for such complex changes in synchronization. Recent work has identified cell-type-specific inhibitory and excitatory interactions, the dichotomy between neuronal firing and the non-local measurement of local field potentials distant to that firing, and the reflection of the neuronal dark matter problem in non-firing neurons active in seizures. These recent advances have challenged long-established views and are leading to a more rigorous and realistic understanding of the pathophysiology of epilepsy.

Localization of Epileptogenic Zone on Pre-surgical Intracranial EEG Recordings: Toward a Validation of Quantitative Signal Analysis Approaches

In patients diagnosed with pharmaco-resistant epilepsy, cerebral areas responsible for seizure generation can be defined by performing implantation of intracranial electrodes. The identification of the epileptogenic zone (EZ) is based on visual inspection of the intracranial electroencephalogram (IEEG) performed by highly qualified neurophysiologists. New computer-based quantitative EEG analyses have been developed in collaboration with the signal analysis community to expedite EZ detection. The aim of the present report is to compare different signal analysis approaches developed in four different European laboratories working in close collaboration with four European Epilepsy Centers. Computer-based signal analysis methods were retrospectively applied to IEEG recordings performed in four patients undergoing pre-surgical exploration of pharmaco-resistant epilepsy. The four methods elaborated by the different teams to identify the EZ are based either on frequency analysis, on nonlinear signal analysis, on connectivity measures or on statistical parametric mapping of epileptogenicity indices. All methods converge on the identification of EZ in patients that present with fast activity at seizure onset. When traditional visual inspection was not successful in detecting EZ on IEEG, the different signal analysis methods produced highly discordant results. Quantitative analysis of IEEG recordings complement clinical evaluation by contributing to the study of epileptogenic networks during seizures. We demonstrate that the degree of sensitivity of different computer-based methods to detect the EZ in respect to visual EEG inspection depends on the specific seizure pattern.

Laboratory observations and simulations of phase reddening

The visible reflectance spectrum of many Solar System bodies changes with changing viewing geometry for reasons not fully understood. It is often observed to redden (increasing spectral slope) with increasing solar phase angle, an effect known as phase reddening. Only once, in an observation of the martian surface by the Viking 1 lander, was reddening observed up to a certain phase angle with bluing beyond, making the reflectance ratio as a function of phase angle shaped like an arch. However, in laboratory experiments this arch-shape is frequently encountered. To investigate this, we measured the bidirectional reflectance of particulate samples of several common rock types in the 400–1000 nm wavelength range and performed ray-tracing simulations. We confirm the occurrence of the arch for surfaces that are forward scattering, i.e. are composed of semi-transparent particles and are smooth on the scale of the particles, and for which the reflectance increases from the lower to the higher wavelength in the reflectance ratio. The arch shape is reproduced by the simulations, which assume a smooth surface. However, surface roughness on the scale of the particles, such as the Hapke and van Horn (Hapke, B., van Horn, H. [1963]. J. Geophys. Res. 68, 4545–4570) fairy castles that can spontaneously form when sprinkling a fine powder, leads to monotonic reddening. A further consequence of this form of microscopic roughness (being indistinct without the use of a microscope) is a flattening of the disk function at visible wavelengths, i.e. Lommel–Seeliger-type scattering. The experiments further reveal monotonic reddening for reflectance ratios at near-IR wavelengths. The simulations fail to reproduce this particular reddening, and we suspect that it results from roughness on the surface of the particles. Given that the regolith of atmosphereless Solar System bodies is composed of small particles, our results indicate that the prevalence of monotonic reddening and Lommel–Seeliger-type scattering for these bodies results from microscopic roughness, both in the form of structures built by the particles and roughness on the surface of the particles themselves. It follows from the singular Viking 1 observation that the surface in front of the lander was composed of semi-transparent particles, and was smooth on the scale of the particle size.

Die Rolle des Benefit-Finding für die Qualität der Anpassung an das Leben nach dem Spitzensport

Die Lebensereignisforschung postuliert, dass die Anpassung an eine durch ein kritisches Ereignis veränderte Situation durch Benefit-Finding gefördert wird, indem Menschen Gewinnbringendes für ihr Leben erkennen (Filipp & Aymanns, 2010). Während in der frühen Forschung zum oft als kritisches Lebensereignis beschriebenen Karriereende im Spitzensport Benefit-Finding mitbedacht wurde, wird es in der aktuellen Forschung nur punktuell berücksichtigt (z.B. Curtis & Ennis, 1988, Wippert, 2011). Basierend auf dem Konzept Kritisches Lebensereignis (Filipp, 1995) untersucht die vorliegende Studie die Rolle des Benefit-Finding für die kurz-, mittel- und langfristige Qualität der Anpassung an das Karriereende. Methods: 290 Schweizer Spitzenathleten (Frauenanteil: 32.8%) aus 64 Sportarten wurden etwa 7.46 Jahre nach ihrem Karriereende mittels Fragebogen zum Benefit-Finding, Erleben des Karriereendes, zur Dauer und subjektiven Qualität der Anpassung an das Karriereende sowie zum psychischen Wohlbefinden befragt. Die Datenauswertung erfolgte mittels Strukturgleichungsmodellierung. Results: Das Modell zur Vorhersage der langfristigen Anpassungsqualität (psychische Wohlbefinden) an das Karriereende mit einer Varianzaufklärung von R2 = .26 passt recht gut zu den Daten (χ2 = 114.764, p ≤ .001, df = 56, CFI = .93, SRMR = .06, RMSEA = .06; AGFI = .91). Wie postuliert, hat das Ausmass von Benefit-Finding einen – über die kurz- und mittelfristige Anpassungsqualität (positive Emotionen, Anpassungsdauer und subjektive Anpassungsqualität) – vermittelten Effekt auf das psychische Wohlbefinden im Leben nach dem Spitzensport. Discussion/Conclusion: Das Konzept Kritisches Lebensereignis kristallisierte sich als zielführender Ansatz für die Analyse von zusammenwirkenden Faktoren hinsichtlich Qualität der Anpassung an das Leben nach dem Spitzensport heraus. Die Befunde indizieren, dass sportpsychologische Interventionen mit Fokus auf Benefit-Finding, zusammen mit anderen Elementen der gängigen Career-Assistance-Programme, kurzfristig für eine gelingende Transition und langfristig ein günstiges psychisches Wohlbefinden sinnvoll sind. References: Curtis, J. & Ennis, R. (1988). Negative consequences of leaving competitive sport? Comparative findings for former elite-level hockey players. Sociology of Sport Journal, 5, 87-106. Filipp, S.-H. (Hrsg.) (1995). Kritische Lebensereignisse (3. Aufl.). Weinheim: Beltz. Filipp, S.-H. & Aymanns, P. (2010). Kritische Lebensereignisse und Lebenskrisen. Vom Umgang mit den Schattenseiten des Lebens. Stuttgart: Kohlhammer. Wippert, P.-M. (2011). Kritische Lebensereignisse in Hochleistungsbiografien. Untersuchungen an Spitzensportlern, Tänzern und Musikern. Lengerich: Pabst.