MEG alpha activity decrease reflects destabilization of multistable percepts

Multistable stimuli offer the possibility to investigate visual awareness, since they evoke spontaneous alternations between different perceptual interpretations of the same stimulus and, therefore, allow to dissociate perceptual from stimulus-driven mechanisms. In the present study, we used an ambiguous motion paradigm and compared endogenous reversals of perceived motion direction which occur spontaneously during constant ambiguous stimulation with exogenous reversals that were induced externally by changes of stimulation. Contrasting the two conditions allowed to investigate processes that trigger endogenous reversals, since the related activity should be absent in the exogenous reversal condition. We employed ambiguous dot patterns which can easily be transformed to present two stable motion directions in order to induce exogenous pattern reversals. Whole-head MEG was recorded from 10 subjects. We analyzed event-related fields (ERFs) and oscillatory activity in the alpha and gamma ranges. The results showed P300-like slow waves in response to both endogenous and exogenous reversals reflecting the conscious recognition of pattern reversals. Analyses in the gamma-band did not reveal any significant modulations. The alpha activity showed different time courses for endogenous and exogenous reversals. While the exogenous alpha activity decreased in temporal relation to the pattern reversal, the endogenous alpha activity displayed a continuous decrease starting in the time interval preceding the reversal. This time course of the endogenous alpha activity is consistent with a bottom-up approach to figure reversals, since it reflects a process of destabilization of the actual percept until a switch of visual awareness occurs

A Maturity Assessment Framework for Conversational AI Development Platforms

Conversational Artificial Intelligence (AI) systems have recently sky-rocketed in popularity and are now used in many applications, from car assistants to customer support. The development of conversational AI systems is supported by a large variety of software platforms, all with similar goals, but different focus points and functionalities. A systematic foundation for classifying conversational AI platforms is currently lacking. We propose a framework for assessing the maturity level of conversational AI development platforms. Our framework is based on a systematic literature review, in which we extracted common and distinguishing features of various open-source and commercial (or in-house) platforms. Inspired by language reference frameworks, we identify different maturity levels that a conversational AI development platform may exhibit in understanding and responding to user inputs. Our framework can guide organizations in selecting a conversational AI development platform according to their needs, as well as helping researchers and platform developers improving the maturity of their platforms.Comment: 10 pages, 10 figures. Accepted for publication at SAC 2021: ACM/SIGAPP Symposium On Applied Computin

The response of a neutral atom to a strong laser field probed by transient absorption near the ionisation threshold

We present transient absorption spectra of an extreme ultraviolet attosecond pulse train in helium dressed by an 800 nm laser field with intensity ranging from $2times10^{12}$ W/cm$^2$ to $2times10^{14}$ W/cm$^2$. The energy range probed spans 16-42 eV, straddling the first ionisation energy of helium (24.59 eV). By changing the relative polarisation of the dressing field with respect to the attosecond pulse train polarisation we observe a large change in the modulation of the absorption reflecting the vectorial response to the dressing field. With parallel polarized dressing and probing fields, we observe significant modulations with periods of one half and one quarter of the dressing field period. With perpendicularly polarized dressing and probing fields, the modulations of the harmonics above the ionisation threshold are significantly suppressed. A full-dimensionality solution of the single-atom time-dependent Schr odinger equation obtained using the recently developed ab-initio time-dependent B-spline ADC method reproduce some of our observations

Optical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopy

Optically driven spin transport is the fastest and most efficient process to manipulate macroscopic magnetization as it does not rely on secondary mechanisms to dissipate angular momentum. In the present work, we show that such an optical inter-site spin transfer (OISTR) from Pt to Co emerges as a dominant mechanism governing the ultrafast magnetization dynamics of a CoPt alloy. To demonstrate this, we perform a joint theoretical and experimental investigation to determine the transient changes of the helicity dependent absorption in the extreme ultraviolet spectral range. We show that the helicity dependent absorption is directly related to changes of the transient spin-split density of states, allowing us to link the origin of OISTR to the available minority states above the Fermi level. This makes OISTR a general phenomenon in optical manipulation of multi-component magnetic systems

Measurement of sulfur L2,3 and carbon K edge XANES in a polythiophene film using a high harmonic supercontinuum

We use a high harmonic generated supercontinuum in the soft X-ray region to measure X-ray absorption near edge structure (XANES) spectra in polythiophene (poly(3-hexylthiophene)) films at multiple absorption edges. A few-cycle carrier-envelope phase-stable laser pulse centered at 1800 nm was used to generate a stable soft X-ray supercontinuum, with amplitude gating limiting the generated pulse duration to a single optical half-cycle. We report a quantitative transmission measurement of the sulfur L2,3 edge over the range 160-200 eV and the carbon K edge from 280 to 330 eV. These spectra show all the features previously reported in the XANES spectra of polythiophene, but for the first time they are measured with a source that has an approximately 1 fs pulse duration. This study opens the door to measurements that can fully time-resolve the photoexcited electronic dynamics in these systems

Transient magnetic gratings on the nanometer scale

Laser-driven non-local electron dynamics in ultrathin magnetic samples on a sub-10 nm length scale is a key process in ultrafast magnetism. However, the experimental access has been challenging due to the nanoscopic and femtosecond nature of such transport processes. Here, we present a scattering-based experiment relying on a laser-induced electro- and magneto-optical grating in a Co/Pd ferromagnetic multilayer as a new technique to investigate non-local magnetization dynamics on nanometer length and femtosecond timescales. We induce a spatially modulated excitation pattern using tailored Al near-field masks with varying periodicities on a nanometer length scale and measure the first four diffraction orders in an x-ray scattering experiment with magnetic circular dichroism contrast at the free-electron laser facility FERMI, Trieste. The design of the periodic excitation mask leads to a strongly enhanced and characteristic transient scattering response allowing for sub-wavelength in-plane sensitivity for magnetic structures. In conjunction with scattering simulations, the experiment allows us to infer that a potential ultrafast lateral expansion of the initially excited regions of the magnetic film mediated by hot-electron transport and spin transport remains confined to below three nanometers

Aerodynamic Shape Optimization of a Blended-Wing-Body Aircraft

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106465/1/AIAA2013-283.pd

Ultrastructural changes of the intracellular surfactant pool in a rat model of lung transplantation-related events

<p>Abstract</p> <p>Background</p> <p>Ischemia/reperfusion (I/R) injury, involved in primary graft dysfunction following lung transplantation, leads to inactivation of intra-alveolar surfactant which facilitates injury of the blood-air barrier. The alveolar epithelial type II cells (AE2 cells) synthesize, store and secrete surfactant; thus, an intracellular surfactant pool stored in lamellar bodies (Lb) can be distinguished from the intra-alveolar surfactant pool. The aim of this study was to investigate ultrastructural alterations of the intracellular surfactant pool in a model, mimicking transplantation-related procedures including flush perfusion, cold ischemia and reperfusion combined with mechanical ventilation.</p> <p>Methods</p> <p>Using design-based stereology at the light and electron microscopic level, number, surface area and mean volume of AE2 cells as well as number, size and total volume of Lb were determined in a group subjected to transplantation-related procedures including both I/R injury and mechanical ventilation (I/R group) and a control group.</p> <p>Results</p> <p>After I/R injury, the mean number of Lb per AE2 cell was significantly reduced compared to the control group, accompanied by a significant increase in the luminal surface area per AE2 cell in the I/R group. This increase in the luminal surface area correlated with the decrease in surface area of Lb per AE2. The number-weighted mean volume of Lb in the I/R group showed a tendency to increase.</p> <p>Conclusion</p> <p>We suggest that in this animal model the reduction of the number of Lb per AE2 cell is most likely due to stimulated exocytosis of Lb into the alveolar space. The loss of Lb is partly compensated by an increased size of Lb thus maintaining total volume of Lb per AE2 cell and lung. This mechanism counteracts at least in part the inactivation of the intra-alveolar surfactant.</p

Active behaviour during early development shapes glucocorticoid reactivity

TGlucocorticoids are the final effectors of the stress axis, with numerous targets in the central nervous system and the periphery. They are essential for adaptation, yet currently it is unclear how early life events program the glucocorticoid response to stress. Here we provide evidence that involuntary swimming at early developmental stages can reconfigure the cortisol response to homotypic and heterotypic stress in larval zebrafish (Danio rerio), also reducing startle reactivity and increasing spontaneous activity as well as energy efficiency during active behaviour. Collectively, these data identify a role of the genetically malleable zebrafish for linking early life stress with glucocorticoid function in later life

Exogenous surfactant application in a rat lung ischemia reperfusion injury model: effects on edema formation and alveolar type II cells

<p>Abstract</p> <p>Background</p> <p>Prophylactic exogenous surfactant therapy is a promising way to attenuate the ischemia and reperfusion (I/R) injury associated with lung transplantation and thereby to decrease the clinical occurrence of acute lung injury and acute respiratory distress syndrome. However, there is little information on the mode by which exogenous surfactant attenuates I/R injury of the lung. We hypothesized that exogenous surfactant may act by limiting pulmonary edema formation and by enhancing alveolar type II cell and lamellar body preservation. Therefore, we investigated the effect of exogenous surfactant therapy on the formation of pulmonary edema in different lung compartments and on the ultrastructure of the surfactant producing alveolar epithelial type II cells.</p> <p>Methods</p> <p>Rats were randomly assigned to a control, Celsior (CE) or Celsior + surfactant (CE+S) group (n = 5 each). In both Celsior groups, the lungs were flush-perfused with Celsior and subsequently exposed to 4 h of extracorporeal ischemia at 4°C and 50 min of reperfusion at 37°C. The CE+S group received an intratracheal bolus of a modified natural bovine surfactant at a dosage of 50 mg/kg body weight before flush perfusion. After reperfusion (Celsior groups) or immediately after sacrifice (Control), the lungs were fixed by vascular perfusion and processed for light and electron microscopy. Stereology was used to quantify edematous changes as well as alterations of the alveolar epithelial type II cells.</p> <p>Results</p> <p>Surfactant treatment decreased the intraalveolar edema formation (mean (coefficient of variation): CE: 160 mm³(0.61) vs. CE+S: 4 mm³(0.75); p < 0.05) and the development of atelectases (CE: 342 mm³(0.90) vs. CE+S: 0 mm³; p < 0.05) but led to a higher degree of peribronchovascular edema (CE: 89 mm³(0.39) vs. CE+S: 268 mm³(0.43); p < 0.05). Alveolar type II cells were similarly swollen in CE (423 μm³(0.10)) and CE+S (481 μm³(0.10)) compared with controls (323 μm³(0.07); p < 0.05 vs. CE and CE+S). The number of lamellar bodies was increased and the mean lamellar body volume was decreased in both CE groups compared with the control group (p < 0.05).</p> <p>Conclusion</p> <p>Intratracheal surfactant application before I/R significantly reduces the intraalveolar edema formation and development of atelectases but leads to an increased development of peribronchovascular edema. Morphological changes of alveolar type II cells due to I/R are not affected by surfactant treatment. The beneficial effects of exogenous surfactant therapy are related to the intraalveolar activity of the exogenous surfactant.</p