Explore the vast range of titles available.

Animal psychophysics can generate rich behavioral datasets, often comprised of many 1000s of trials for an individual subject. Gradient-boosted models are a promising machine learning approach for analyzing such data, partly due to the tools that allow users to gain insight into how the model makes predictions. We trained ferrets to report a target word’s presence, timing, and lateralization within a stream of consecutively presented non-target words. To assess the animals’ ability to generalize across pitch, we manipulated the fundamental frequency (F0) of the speech stimuli across trials, and to assess the contribution of pitch to streaming, we roved the F0 from word token to token. We then implemented gradient-boosted regression and decision trees on the trial outcome and reaction time data to understand the behavioral factors behind the ferrets’ decision-making. We visualized model contributions by implementing SHAPs feature importance and partial dependency plots. While ferrets could accurately perform the task across all pitch-shifted conditions, our models reveal subtle effects of shifting F0 on performance, with within-trial pitch shifting elevating false alarms and extending reaction times. Our models identified a subset of non-target words that animals commonly false alarmed to. Follow-up analysis demonstrated that the spectrotemporal similarity of target and non-target words rather than similarity in duration or amplitude waveform was the strongest predictor of the likelihood of false alarming. Finally, we compared the results with those obtained with traditional mixed effects models, revealing equivalent or better performance for the gradient-boosted models over these approaches.

The KATRIN (Karlsruhe Tritium Neutrino) experiment investigates the energetic endpoint of the tritium beta-decay spectrum to determine the effective mass of the electron anti-neutrino. The collaboration has reported a first mass measurement result at this TAUP-2019 conference. The TRISTAN project aims at detecting a keV-sterile neutrino signature by measuring the entire tritium beta-decay spectrum with an upgraded KATRIN system. One of the greatest challenges is to handle the high signal rates generated by the strong activity of the KATRIN tritium source while maintaining a good energy resolution. Therefore, a novel multi-pixel silicon drift detector and read-out system are being designed to handle rates of about 100 Mcps with an energy resolution better than 300 eV (FWHM). This report presents succinctly the KATRIN experiment, the TRISTAN project, then the results of the first 7-pixels prototype measurement campaign and finally describes the construction of the first TRISTAN module composed of 166 SDD-pixels as well as its implementation in KATRIN experiment.

Expose is a multi-user instrument for astrobiological and astrochemical experiments in space. Installed at the outer surface of the International Space Station, it enables investigators to study the impact of the open space environment on biological and biochemical test samples. Two Expose missions have been completed so far, designated as Expose-E (Rabbow et al. 2012) and Expose-R (Rabbow et al. this issue). One of the space-unique environmental factors offered by Expose is full-spectrum, ultraviolet (UV)-rich electromagnetic radiation from the Sun. This paper describes and analyses how on Expose-R, access of the test samples to Solar radiation degraded during space exposure in an unpredicted way. Several windows in front of the Sun-exposed test samples acquired a brown shade, resulting in a reduced transparency in visible light, UV and vacuum UV (VUV). Post-flight investigations revealed the discolouration to be caused by a homogenous film of cross-linked organic polymers at the inside of the windows. The chemical signature varied per sample carrier. No such films were found on windows from sealed, pressurized compartments, or on windows that had been kept out of the Sun. This suggests that volatile compounds originating from the interior of the Expose facility were cross-linked and photo-fixed by Solar irradiation at the rear side of the windows. The origin of the volatiles was not fully identified; most probably there was a variety of sources involved including the biological test samples, adhesives, plastics and printed circuit boards. The outer surface of the windows (pointing into space) was chemically impacted as well, with a probable effect on the transparency in VUV. The reported analysis of the window contamination on Expose-R is expected to help the interpretation of the scientific results and offers possibilities to mitigate this problem on future missions – in particular Expose-R2, the direct successor of Expose-R.

The green, unicellular flagellate Euglena gracilis orientates itself in the water column by means of external stimuli such as light and gravity. Although much is known about photo-orientation, we know little about gravity-dependent orientation of microorganisms. Here we show that gravitactic orientation is strongly impaired by an increase in the density of the surrounding medium, by inhibitors of stretch-sensitive ion channels and by the disturbance of membrane potentials.

The effects of the calcium sequester EGTA on gravitactic orientation and membrane potential changes in the unicellular flagellate Euglena gracilis were investigated during a recent parabolic-flight experiment aboard of an Airbus A300. In the course of a flight parabola, an acceleration profile is achieved which yields subsequently about 20 s of hypergravity (1.8 g n), about 20 s of microgravity, and another 20 s of hypergravity phases. The movement behavior of the cells was investigated with real-time, computer-based image analysis. Membrane potential changes were detected with a newly developed photometer which measures absorption changes of the membrane potential-sensitive probe oxonol VI. To test whether the data obtained by the oxonol device were reliable, the signal of non-oxonol-labelled cells was recorded. In these samples, no absorption shift was detected. Changes of the oxonol VI signals indicate that the cells depolarize during acceleration (very obvious in the step from microgravity to hypergravity) and slightly hyperpolarize in microgravity, which can possibly be explained with the action of Ca-ATPases. These signals (mainly the depolarization) were significantly suppressed in the presence of EGTA (5 mM). Gravitaxis in parallel was also inhibited after addition of EGTA. Initially, negative gravitaxis was inverted into a positive one. Later, gravitaxis was almost undetectable.

The effects of solar irradiance on the photosynthesis of the marine angiosperm Posidonia oceanica L. Delile were investigated by means of pulse amplitude-modulated (PAM) fluorescence in the Natural Park of Cabo de Gata-Nijar, southern Spain. The study was conducted in 2 different seasons, summer (September 1996) and winter (February 1997). Daily variation in the effective quantum yield ( Delta F/F sub(m)') was determined in plants growing at 2.5 m and in plants transferred from 15 m to 0.5 and 2.5 m depth. Three different experimental designs were conducted: (1) Incubation of shoots under 3 different solar radiation treatments using cut-off UV filters: full solar radiation (PAR + UV-A + UV-B), solar radiation without UV-B (PAR + UV-A) and solar radiation without UV (PAR); (2) short-term exposure (30 min) to high solar irradiance (photoinhibitory phase) under all treatments followed by transfer of the plants to low irradiance for 4 h (recovery phase); (3) Preincubation of plants for 4 d under the 3 cited treatments followed by short-term exposure (30 min) to high solar irradiance under PAR + UV-A + UV-B, PAR + UV-A and PAR. A significant decrease in Delta F/F sub(m)' occurred from dawn to noon (18% in September and only 6% in February), followed by total recovery during the afternoon in both seasons. The highest decrease in Delta F/F sub(m)' occurred in shoots illuminated with PAR + UV-A radiation. This decrease was more pronounced in winter than in summer, and was substantially higher in plants transferred from deep (15 m) to shallow water than in plants harvested at 2.5 m. Moreover, the recovery in the afternoon was higher in plants incubated at 2.5 m than in those transferred from 15 m to shallow waters. In the second set of experiments, short exposure (30 min) of plants collected from 2.5 m confirmed that inhibition under PAR + UV-A was higher than under PAR + UV-A + UV-B. In general, full recovery after exposure to high solar irradiance (PAR + UVA + UV-B) occurred only in PAR-treated plants in September. Finally, when shoots of P. oceanica were preincubated for 4 d under PAR, PAR + UV-A or PAR + UV-A + UV-B and then submitted to full solar irradiance at the water surface, the greatest reduction in Delta F/F sub(m)' was seen in plants grown under PAR, while the lowest occurred in PAR + UV-A + UV-B pretreated plants in both seasons. Recovery was higher in PAR + UV-A + UV-B pretreated plants. UV solar irradiance also affected both maximal electron transport rate (ETR) and the initial slope of the ETR-irradiance curves. P. oceanica seems to be well acclimated to high solar irradiance, showing a high capacity for recovery. Solar UV-B might be involved in the impairment and recovery of photosynthesis, since removal of UV-B promoted higher inhibition by solar irradiance. The absence of UV under high PAR for several days resulted in a partial loss of the capacity for photoprotection. We conclude that UV radiation could act in the natural habitat as a trigger for the induction of photoprotective mechanisms against high solar irradiance. The ecological implication of the beneficial role of UV-B in well-acclimated marine plants to high irradiance is discussed.

ABSTRACT We report here the draft genome sequence of a novel Xenophilus species cultured from the skin of a southern leopard frog (Rana sphenocephala). Compared to previously sequenced bacterial genomes, our novel isolate showed the most significant homology with Xenophilus azovorans. The assembled genome is 3,978,285 bp, with 3,704 predicted genes and one predicted plasmid.

Transmembrane signaling by bacterial chemoreceptors is thought to involve conformational changes within a stable homodimer. We investigated the functional consequences of constraining movement between pairs of helices in the four-helix structure of the transmembrane domain of chemoreceptor Trg. Using a family of cysteine-containing receptors, we identified oxidation treatments for intact cells that catalyzed essentially complete sulfhydryl cross-linking at selected positions and yet left flagellar and sensory functions largely unperturbed. Constraining movement by cross-links between subunits had little effect on tactic response, but constraining movement between transmembrane segments of the monomer drastically reduced function. We deduce that transmembrane signaling requires substantial movement between transmembrane helices of a monomer but not between interacting helices across the interface between subunits.

Euglena gracilis, a unicellular freshwater protist exhibits different photomovement responses, such as phototaxis (oriented movement toward or away from the light source) and photophobic (abrupt turn in response to a rapid increase [step-up] or decrease [step-down] in the light fluence rate) responses. Photoactivated adenylyl cyclase (PAC) has been isolated from whole-cell preparations and identified by RNA interference (RNAi) to be the photoreceptor for step-up photophobic responses but not for step-down photophobic responses (M. Iseki, S. Matsunaga, A. Murakami, K. Ohno, K. Shiga, C. Yoshida, M. Sugai, T. Takahashi, T. Hori, M. Watanabe [2002] Nature 415: 1047-1051). The present study shows that knockdown of PAC by RNAi also effectively suppresses both positive and negative phototaxis, indicating for the first time that PAC or a PAC homolog is also the photoreceptor for photoorientation of wild-type E. gracilis. Recovery from RNAi occurred earlier for step-up photophobic responses than for positive and negative phototaxis. In addition, we investigated several phototaxis mutant strains of E. gracilis with different cytological features regarding the stigma and paraxonemal body (PAB; believed to be the location for the phototaxis photoreceptor) as well as Astasia longa, a close relative of E. gracilis. All of the E. gracilis mutant strains had PAC mRNAs, whereas in A. longa, a different but similar mRNA was found and designated AlPAC. Consistently, all of these strains showed no phototaxis but performed step-up photophobic responses, which were suppressed by RNAi of the PAC mRNA. The fact that some of these strains possess a cytologically altered or no PAB demonstrates that at least in these strains, the PAC photoreceptor responsible for the step-up photophobic responses is not located in the PAB.

Anandamide is an endogenous ligand for central cannabinoid receptors and is released after neuronal depolarization. Anandamide increased protein tyrosine phosphorylation in rat hippocampal slices and neurons in culture. The action of anandamide resulted from the inhibition of adenylyl cyclase and cyclic adenosine 3′,5′-monophosphate-dependent protein kinase. One of the proteins phosphorylated in response to anandamide was an isoform of pp125-focal adhesion kinase (FAK+) expressed preferentially in neurons. Focal adhesion kinase is a tyrosine kinase involved in the interactions between the integrins and actin-based cytoskeleton. Thus, anandamide may exert neurotrophic effects and play a role in synaptic plasticity.