948 research outputs found
Die tribologischen Eigenschaften Silicium-basierter Keramiken in Isooctan unter BerĂŒcksichtigung der UmgebungsatmosphĂ€re
Im Rahmen dieser Arbeit wurden die tribologischen Eigenschaften von selbstgepaartem Siliciumcarbid (SSiC) und Siliciumnitrid (SiâNâ) unter dem Einfluss verschiedener AtmosphĂ€ren (feuchte Luft, trockene Luft und trockener Stickstoff) charakterisiert, wobei die WirkflĂ€chen der Keramiken zu jeder Zeit der Experimente durch Einsatz eines Tauchbades vollstĂ€ndig von Isooctan bedeckt waren. Die Versuche wurden allesamt in einer konformen Pellet Platte Konfiguration (KontaktflĂ€che nominell: â 9,5 mm) durchgefĂŒhrt und es wurden eine reversierende Gleitbewegung mit HublĂ€nge s = 5 mm, Hubfrequenzen von f = 2,5 bis 20 Hz und eine Normalkraft von Fâ = 200 N gewĂ€hlt.
Die Ergebnisse zeigen, dass die chemischen EinflĂŒsse aus der Umgebung trotz des Tauchbades signifikante Effekte auf das Reibungs- und VerschleiĂverhalten der beiden keramischen Werkstoffe haben. Im Falle des SSiC fĂŒhrte eine AtmosphĂ€re aus feuchter Luft zu unruhigen ReibzahlverlĂ€ufen mit kurzzeitigen ReibzahlĂŒberhöhungen und generell höheren Reibwerten als in trockener Luft oder StickstoffatmosphĂ€re. FĂŒr SiâNâ Ă€uĂerte sich der Einfluss ĂŒberwiegend in verĂ€nderten VerschleiĂbetrĂ€gen und entstehenden OberflĂ€chentopographien, hierbei fĂŒhrte Feuchtigkeit zur Bildung inselartiger, sauerstoffreicher Bereiche auf den KontaktflĂ€chen. Durch den Einsatz kleinster Mengen einer grenzflĂ€chenaktiven Substanz (AOT) konnten Reib- und VerschleiĂverhalten beider Keramiken auf ein nĂ€herungsweise einheitliches Niveau gebracht werden.
Zudem konnte nachgewiesen werden, dass fĂŒr selbstgepaartes SSiC in Kombination mit Isooctan ein Ăbergang des Tribosystems in die flĂŒssige SupraschmierfĂ€higkeit mit Reibwerten von ” < 0,003 trotz reversierender Gleitbewegung eintritt. ErklĂ€rungsansĂ€tze in der Literatur fĂŒr diesen Zustand in wĂ€ssrigen Medien stĂŒtzen sich hĂ€ufig auf elektrochemische, Ionen-basierte OberflĂ€cheneffekte, welche vor dem Hintergrund des verwendeten Isooctans nicht anwendbar sind. Die plausibelste Ursache fĂŒr die verschwindend geringe Reibung ist ein oberflĂ€chentrennender Film aus Isooctan
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SpectralNET â an application for spectral graph analysis and visualization
BACKGROUND: Graph theory provides a computational framework for modeling a variety of datasets including those emerging from genomics, proteomics, and chemical genetics. Networks of genes, proteins, small molecules, or other objects of study can be represented as graphs of nodes (vertices) and interactions (edges) that can carry different weights. SpectralNET is a flexible application for analyzing and visualizing these biological and chemical networks. RESULTS: Available both as a standalone .NET executable and as an ASP.NET web application, SpectralNET was designed specifically with the analysis of graph-theoretic metrics in mind, a computational task not easily accessible using currently available applications. Users can choose either to upload a network for analysis using a variety of input formats, or to have SpectralNET generate an idealized random network for comparison to a real-world dataset. Whichever graph-generation method is used, SpectralNET displays detailed information about each connected component of the graph, including graphs of degree distribution, clustering coefficient by degree, and average distance by degree. In addition, extensive information about the selected vertex is shown, including degree, clustering coefficient, various distance metrics, and the corresponding components of the adjacency, Laplacian, and normalized Laplacian eigenvectors. SpectralNET also displays several graph visualizations, including a linear dimensionality reduction for uploaded datasets (Principal Components Analysis) and a non-linear dimensionality reduction that provides an elegant view of global graph structure (Laplacian eigenvectors). CONCLUSION: SpectralNET provides an easily accessible means of analyzing graph-theoretic metrics for data modeling and dimensionality reduction. SpectralNET is publicly available as both a .NET application and an ASP.NET web application from . Source code is available upon request
Nature Of Transition Circumstellar Disks. I. The Ophiuchus Molecular Cloud
We have obtained millimeter-wavelength photometry, high-resolution optical spectroscopy, and adaptive optics near-infrared imaging for a sample of 26 Spitzer-selected transition circumstellar disks. All of our targets are located in the Ophiuchus molecular cloud (d similar to 125 pc) and have spectral energy distributions (SEDs) suggesting the presence of inner opacity holes. We use these ground-based data to estimate the disk mass, multiplicity, and accretion rate for each object in our sample in order to investigate the mechanisms potentially responsible for their inner holes. We find that transition disks are a heterogeneous group of objects, with disk masses ranging from <0.6 to 40 M(JUP) and accretion rates ranging from <10(-11) to 10(-7) M(circle dot) yr(-1), but most tend to have much lower masses and accretion rates than "full disks" (i.e., disks without opacity holes). Eight of our targets have stellar companions: six of them are binaries and the other two are triple systems. In four cases, the stellar companions are close enough to suspect they are responsible for the inferred inner holes. We find that nine of our 26 targets have low disk mass (<2.5 M(JUP)) and negligible accretion (<10(-11) M(circle dot) yr(-1)), and are thus consistent with photoevaporating (or photoevaporated) disks. Four of these nine non-accreting objects have fractional disk luminosities <10(-3) and could already be in a debris disk stage. Seventeen of our transition disks are accreting. Thirteen of these accreting objects are consistent with grain growth. The remaining four accreting objects have SEDs suggesting the presence of sharp inner holes, and thus are excellent candidates for harboring giant planets.NASA 1224608, 1230782, 1230779, 1407FONDECYT 1061199Basal CATA PFB 06/09ALMA FUND 31070021ALMA-Conicyt FUND 31060010National Science Foundation AST0-808144Spitzer Space Telescope Legacy Science ProgramAstronom
B-mode ultrasound assessment of pupillary function: feasibility, reliability and normal values
PURPOSE: To evaluate B-mode ultrasound as a novel method for the examination of pupillary function and to provide normal values for the pupillary reflex as assessed by B-mode ultrasound. METHODS: 100 subjects (49 female, 51 male, mean [range] age 51 [18-80 years]) with no history of ophthalmologic disease, no clinically detectable pupillary defects, and corrected visual acuity >= 0.8 were included in this prospective observational study. B-mode ultrasound was performed with the subjects eyes closed using an Esaote-Mylab25 system according to current guidelines for orbital insonation. A standardized light stimulus was applied. RESULTS: The mean +/- standard deviation left and right pupillary diameters (PD) at rest were 4.7 +/- 0.8 and 4.5 +/- 0.8 mm. Following an ipsilateral light stimulus (Lstim), left and right constricted PD were 2.8 +/- 0.6 and 2.7 +/- 0.6 mm. Following a contralateral Lstim, left and right constricted PD were 2.7 +/- 0.6 and 2.6 +/- 0.5 mm. Left and right pupillary constriction time (PCT) following ipsilateral Lstim were 970 +/- 261.6 and 967 +/- 220 ms. Left and right PCT following a contralateral Lstim were 993.8 +/- 192.6 and 963 +/- 189.4 ms. Patient age was inversely correlated with PD at rest and with PD after ipsilateral and contralateral Lstim (all p<0.001), but not with PCT. CONCLUSIONS: B-mode ultrasound is a simple, rapid and objective method for the quantitative assessment of pupillary function, which may prove useful in a variety of settings where eyelid retraction is impeded or an infrared pupillometry device is unavailable
Managing FAIR Tribological Data Using Kadi4Mat
The ever-increasing amount of data generated from experiments and simulations in engineering sciences is relying more and more on data science applications to generate new knowledge. Comprehensive metadata descriptions and a suitable research data infrastructure are essential prerequisites for these tasks. Experimental tribology, in particular, presents some unique challenges in this regard due to the interdisciplinary nature of the field and the lack of existing standards. In this work, we demonstrate the versatility of the open source research data infrastructure Kadi4Mat by managing and producing FAIR tribological data. As a showcase example, a tribological experiment is conducted by an experimental group with a focus on comprehensiveness. The result is a FAIR data package containing all produced data as well as machine- and user-readable metadata. The close collaboration between tribologists and software developers shows a practical bottom-up approach and how such infrastructures are an essential part of our FAIR digital future
No evidence for retinal damage evolving from reduced retinal blood flow in carotid artery disease
Introduction. Carotid artery disease (CAD) comprising high-grade internal carotid artery stenosis (CAS) or carotid artery occlusion (CAO) may lead to ipsilateral impaired cerebral blood flow and reduced retinal blood supply. Objective. To examine the influence of chronic CAD on retinal blood flow, retinal morphology, and visual function. Methods. Patients with unilateral CAS â„ 50% (ECST criteria) or CAO were grouped according to the grade of the stenosis and to the flow direction of the ophthalmic artery (OA). Retinal perfusion was measured by transorbital duplex ultrasound, assessing central retinal artery (CRA) blood flow velocities. In addition, optic nerve and optic nerve sheath diameter were measured. Optical coherence tomography (OCT) was performed to study retinal morphology. Visual function was assessed using high- and low-contrast visual paradigms. Results. Twenty-seven patients were enrolled. Eyes with CAS â„ 80%/CAO and retrograde OA blood flow showed a significant reduction in CRA peak systolic velocity (no-CAD side: 0.130 ± 0.035âm/s, CAS/CAO side: 0.098 ± 0.028; p = 0.005; n = 12). OCT, optic nerve thicknesses, and visual functional parameters did not show a significant difference. Conclusion. Despite assessable hemodynamic effects, chronic high-grade CAD does not lead to gaugeable morphological or functional changes of the retina
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A randomised phase I study of etrolizumab (rhuMAb ÎČ7) in moderate to severe ulcerative colitis.
ObjectiveEtrolizumab (rhuMAb ÎČ7, anti-ÎČ7, PRO145223) is a humanised monoclonal antibody targeting the ÎČ7 subunit of the heterodimeric integrins α4ÎČ7 and αEÎČ7, which are implicated in leucocyte migration and retention in ulcerative colitis (UC). This randomised phase I study evaluated the safety and pharmacology of etrolizumab in patients with moderate to severe UC.DesignIn the single ascending dose (SAD) stage, etrolizumab (0.3, 1.0, 3.0, 10 mg/kg intravenous, 3.0 mg/kg subcutaneous (SC) or placebo) was administered 4:1 (n=25) in each cohort. In the multiple dose (MD) stage, new patients received monthly etrolizumab (0.5 mg/kg SC (n=4), 1.5 mg/kg SC (n=5), 3.0 mg/kg SC (n=4), 4.0 mg/kg intravenous (n=5)) or placebo (n=5). The pharmacokinetics was studied and Mayo Clinic Score evaluated at baseline, day 29 (SAD), and days 43 and 71 (MD).ResultsIn the SAD stage, there were no dose limiting toxicities, infusion or injection site reactions. Two impaired wound healing serious adverse events occurred in two patients receiving etrolizumab. In the MD stage, there were no dose limiting toxicities, and no infusion or injection site reactions. Headache was the most common adverse event, occurring more often in etrolizumab patients. Antietrolizumab antibodies were detected in two subjects. The duration of ÎČ7 receptor full occupancy was dose related. A clinical response was observed in 12/18 patients, and clinical remission in 3/18 patients treated with etrolizumab in the MD stage, compared with 4/5 and 1/5 placebo patients, respectively.ConclusionEtrolizumab is well tolerated in moderate to severe UC. Further investigation is warranted
Influence of Ionic Conductances on Spike Timing Reliability of Cortical Neurons for Suprathreshold Rhythmic Inputs
Spike timing reliability of neuronal responses depends on the frequency content of the input. We investigate how intrinsic properties of cortical neurons affect spike timing reliability in response to rhythmic inputs of suprathreshold mean. Analyzing reliability of conductance-based cortical model neurons on the basis of a correlation measure, we show two aspects of how ionic conductances influence spike timing reliability. First, they set the preferred frequency for spike timing reliability, which in accordance with the resonance effect of spike timing reliability is well approximated by the firing rate of a neuron in response to the DC component in the input. We demonstrate that a slow potassium current can modulate the spike timing frequency preference over a broad range of frequencies. This result is confirmed experimentally by dynamic-clamp recordings from rat prefrontal cortical neurons in vitro. Second, we provide evidence that ionic conductances also influence spike timing beyond changes in preferred frequency. Cells with the same DC firing rate exhibit more reliable spike timing at the preferred frequency and its harmonics if the slow potassium current is larger and its kinetics are faster, whereas a larger persistent sodium current impairs reliability. We predict that potassium channels are an efficient target for neuromodulators that can tune spike timing reliability to a given rhythmic input
The Origin of Line Emission in Massive z~2.3 Galaxies: Evidence for Cosmic Downsizing of AGN Host Galaxies
Using the Gemini Near-InfraRed Spectrograph (GNIRS), we have assembled a
complete sample of 20 K-selected galaxies at 2.0<z<2.7 with high quality
near-infrared spectra. As described in a previous paper, 9 of these 20 galaxies
have strongly suppressed star formation and no detected emission lines. The
present paper concerns the 11 galaxies with detected Halpha emission, and
studies the origin of the line emission using the GNIRS spectra and follow-up
observations with SINFONI on the VLT. Based on their [NII]/Halpha ratios, the
spatial extent of the line emission and several other diagnostics, we infer
that four of the eleven emission-line galaxies host narrow line active galactic
nuclei (AGNs). The AGN host galaxies have stellar populations ranging from
evolved to star-forming. Combining our sample with a UV-selected galaxy sample
at the same redshift that spans a broader range in stellar mass, we find that
black-hole accretion is more effective at the high-mass end of the galaxy
distribution (~2.9x10^11 Msun) at z~2.3. Furthermore, by comparing our results
with SDSS data, we show that the AGN activity in massive galaxies has decreased
significantly between z~2.3 and z~0. AGNs with similar normalized accretion
rates as those detected in our K-selected galaxies reside in less massive
galaxies (~4.0x10^10 Msun) at low redshift. This is direct evidence for
downsizing of AGN host galaxies. Finally, we speculate that the typical stellar
mass-scale of the actively accreting AGN host galaxies, both at low and at high
redshift, might be similar to the mass-scale at which star-forming galaxies
seem to transform into red, passive systems.Comment: Accepted for publication in the Astrophysical Journa
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