Electrophysiological evidence for early perceptual facilitation and efficient categorization of self‐related stimuli during an Implicit Association Test measuring neuroticism

The Implicit Association Test (IAT) is a widely used latency‐based categorization task that indirectly measures the strength of automatic associations between target and attribute concepts. So far, little is known about the perceptual and cognitive processes underlying personality IATs. Thus, the present study examined event‐related potential indices during the execution of an IAT measuring neuroticism (N = 70). The IAT effect was strongly modulated by the P1 component indicating early facilitation of relevant visual input and by a P3b‐like late positive component reflecting the efficacy of stimulus categorization. Both components covaried, and larger amplitudes led to faster responses. The results suggest a relationship between early perceptual and semantic processes operating at a more automatic, implicit level and later decision‐related categorization of self‐relevant stimuli contributing to the IAT effect.     

Systematic determination of absolute absorption cross-section of individual carbon nanotubes

Optical absorption is the most fundamental optical property characterizing light–matter interactions in materials and can be most readily compared with theoretical predictions. However, determination of optical absorption cross-section of individual nanostructures is experimentally challenging due to the small extinction signal using conventional transmission measurements. Recently, dramatic increase of optical contrast from individual carbon nanotubes has been successfully achieved with a polarization-based homodyne microscope, where the scattered light wave from the nanostructure interferes with the optimized reference signal (the reflected/transmitted light). Here we demonstrate high-sensitivity absorption spectroscopy for individual single-walled carbon nanotubes by combining the polarization-based homodyne technique with broadband supercontinuum excitation in transmission configuration. To our knowledge, this is the first time that high-throughput and quantitative determination of nanotube absorption cross-section over broad spectral range at the single-tube level was performed for more than 50 individual chirality-defined single-walled nanotubes. Our data reveal chirality-dependent behaviors of exciton resonances in carbon nanotubes, where the exciton oscillator strength exhibits a universal scaling law with the nanotube diameter and the transition order. The exciton linewidth (characterizing the exciton lifetime) varies strongly in different nanotubes, and on average it increases linearly with the transition energy. In addition, we establish an empirical formula by extrapolating our data to predict the absorption cross-section spectrum for any given nanotube. The quantitative information of absorption cross-section in a broad spectral range and all nanotube species not only provides new insight into the unique photophysics in one-dimensional carbon nanotubes, but also enables absolute determination of optical quantum efficiencies in important photoluminescence and photovoltaic processes.Single-walled carbon nanotubes (SWNTs), a model one-dimensional nanomaterial system, constitute a rich family of structures (1). Each single-walled nanotube structure, uniquely defined by the chiral index (n,m), exhibits distinct electrical and optical properties (2–5). Quantitative information of SWNT absorption cross-section is highly desirable for understanding nanotube electronic structures, for evaluating quantum efficiency of nanotube photoluminescence (5, 6) and photocurrent (7–9), and for investigating the unique many-body effects in 1D systems (10–16). Despite its obvious importance, reliable experimental determination of nanotube absorption cross-section at the single-tube level is still challenging (17). Previous absorption measurements on ensemble nanotube samples only provide averaged behavior (18–20). Recent absorption studies of individual nanotubes, suffering from small absorption signals and/or slow laser-frequency scanning, cannot determine the absolute absorption cross-section and are limited in achievable spectral range (15, 21–23).We demonstrate here a high-sensitivity polarization-based homodyne method to measure nanotube absorption spectra. By manipulating the light polarization, we enhanced the nanotube-induced transmission contrast, ΔI/I, by two orders of magnitude, and this enhanced transmission contrast can be quantitatively related to nanotube absorption cross-section along and perpendicular to the nanotube axis. Using this polarization control together with supercontinuum laser source, we realized high-throughput and broadband absorption measurements at the single-tube level; combined with electron diffraction technique on the same tube, it enables absolute determination of absorption cross-sections of individual chirality-defined nanotubes, to our knowledge for the first time. We obtained quantitative absorption spectra of over 50 SWNTs of different chiralities, and established a phenomenological formula for absorption cross-sections of different nanotubes. The chirality-dependent nanotube absorption spectra reveal unique 1D photophysics in nanotubes, including a universal scaling behavior of exciton oscillator strength and of exciton resonance linewidth.     

Das EEG nach frontalen und frontobasalen Schädel-Hirn-Traumen

Zusammenfassung Untersucht wurden 88 Patienten mit frontalen und frontobasalen, mit einer Schädelfraktur einhergehenden Schädel-Hirn-Traumen (SHT). Die EEG-Veränderungen wurden nach Art und Häufigkeit im zeitlichen Albauf sowohl nach dem frischen Trauma wie auch in der Spätphase untersucht. Die Allgemeinveränderungen zeigten vornehmlich leichte bis mittelschwere Dysrhythmien, die häufig mit paroxysmalen Ausbrüchen verbunden waren. Die Herdbefunde waren vorwiegend temporal und erst an zweiter Stelle frontal lokalisiert. Alle pathologischen EEG zeigten eine gute Besserungstendenz, so daß in der Spätphase nur mehr selten und leichte Veränderungen vorhanden waren. Im Durchschnitt zeigten die EEG keinen Unterschied zu denen gedeckter, unkomplizierter SHT.Die Relationen zwischen dem EEG und der klinischen Form des SHT wurden statistisch berechnet. Bei klinischen Kopfprellungen überwogen die normalen und bei Hirnerschütterungen und noch mehr den Hirnkontusionen die pathologischen EEG. Dagegen war zwischen dem EEG und der Art der Fraktur keine Beziehung gegeben. Lediglich allein bei frontobasalen Frakturen mit Liquorrhoe fand sich ein signifikantes Überwiegen pathologischer EEG. Auch die in Herde und Dysrhythmien aufgegliederten EEG-Veränderungen ließen keine statistisch gesicherte Beziehung weder zur klinischen Form des SHT noch zur Art der Fraktur erkennen.Die frontale Gewalteinwirkung erschöpfte sich weitgehend in der Frakturierung frontaler Schädelknochen und führte meist zu einer nur geringen, elektrencephalographisch nachweisbaren Hirnschädigung. Die klinische Bedeutung des EEG liegt zwar nicht in der Diagnostik dieser Verletzungsart, sondern in der Feststellung von Schwere und Ausmaß der Hirnschädigung sowie der Erkennung von Komplikationen.

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The EEG after frontal and frontobasal skull and brain injury

Summary Eighty-eight patients with confirmed frontal and frontobasal lesions were examined. The EEG changes were investigated according to type and frequency both after recent trauma and in the later stages (Fig. 1). The general changes showed mainly slight (Fig. 2B) and only rarely severe, dysrhythmias (Fig. 3A) which, however, were frequently associated with paroxysmal outbursts. Focal findings were largely temporal and frontal in the second place (Fig. 2A). All pathological EEG changes showed a tendency to improvement, so that in the late phase they occurred rarely and less severe (Fig. 4). They showed no essential difference from the EEG of uncomplicated craniocerebral traumata.The relations between the EEG and the clinical form of craniocerebral trauma were examined. In contusions of the head the normal EEG was predominant. The pathological EEG was prominent with cerebral concussion and even more so with cerebral contusion. On the other hand, there was no relationship between the EEG and the type of fracture. A significant predominance of pathological EEG was found only in frontobasal fractures with rhinorrhoea. The EEG changes, classified as focal and dysrhythmic, show no statistically significant relationship either to the form of craniocerebral trauma or to the type of fracture.The effect of force coming form in front has apparently been used up chiefly in producing the frontal or frontobasal fractures, and leads to relatively slight cerebral damage. The clinical significance of the EEG does not actually lie in the diagnosis of these injuries, but, as always, in the establishment of the severity and extent of the cerebral lesion and the detection of complications.

Nach einem Vortrag, gehalten am Symposium über frontale und frontobasale Verletzungen, Wien, 27.–29. 6. 1974.     

External carotid pulse recordings in hypertrophic obstructive cardiomyopathy

External carotid pulse tracings were examined in 15 patients with hypertrophic obstructive cardiomyopathy (HOCM), the diagnosis being confirmed by catheterization of the left heart. Of 12 patients with intraventricular gradients at rest, 9 had a typical bifid pulse with midsystolic dipping. In one patient without a gradient at rest, midsystolic dipping occurred only in beats following extrasystoles (Brockenbrough phenomenon). The upstroke of the pulse wave was rapid in all the patients, a finding that distinguishes them from patients with valvular aortic stenosis. There was a correlation between the length of the left ventricular ejection time and the intraventricular gradient (r = 0.71) but as more than half the patients had normal or shortened ejection times, the diagnosis of HOCM cannot be based on measurements of this parameter. It is concluded that carotid pulse registrations are of considerable diagnostic value in patients suspected of having HOCM. As the pulse changes are correlated to the degree of left ventricular outflow obstruction, it is suggested that repeated pulse tracings may be used as a means for controlling the degree of obstruction once the diagnosis has been established in the individual patient.