Ultra-high performance alkali activated material with silica fume and nanosilica

Based on the principles of ultra-high performance concrete a cement free, alkali-activated system was optimized in order to enhance the strength and durability. This system is based on a ground granulated blast furnace slag and the activator is a combination of potassium water-glass and potassium hydroxide. Furthermore, inorganic fines were used for enhancing the packing density. As aggregates, quartz sand (0-2 mm) and quartz powder are added. The rheological properties could be improved by adding a certain amount of silica fume. A water/binder ratio of 0.25 was realized using a certain mixing procedure on a high-intensity mixer. The compressive strength reaches 150 MPa after 14 days, which lies in the range of an ultra-high performance concrete. The rheology was measured by using a rotation rheometer depending on time and silica fume content. Different silica fumes were tested in order to vary the grain sized distribution and the chemical composition. Beneath silica fume with a d50-value of 2 µm also nanosilica with a d50 value of 0.2 µm was tested in terms of gaining higher strength and durability and as well in terms to enhance the rheological properties. The silica fume could be substituted by nanosilica, which proofs that the improving rheology is not only due to the ball bearing effect of silica fume. The microstructure of the hardened AAM was investigated using SEM, FTIR, XRD and MIP. Please click Additional Files below to see the full abstract

Audio Segmentation for Robust Real-Time Speech Recognition Based on Neural Networks

Speech that contains multimedia content can pose a serious challenge for real-time automatic speech recognition (ASR) for two reasons: (1) The ASR produces meaningless output, hurting the readability of the transcript. (2) The search space of the ASR is blown up when multimedia content is encountered, resulting in large delays that compromise real-time requirements. This paper introduces a segmenter that aims to remove these problems by detecting music and noise segments in real-time and replacing them with silence. We propose a two step approach, consisting of frame classification and smoothing. First, a classifier detects speech and multimedia on the frame level. In the second step the smoothing algorithm considers the temporal context to prevent rapid class fluctuations. We investigate in frame classification and smoothing settings to obtain an appealing accuracy-latency-tradeoff. The proposed segmenter yields increases the transcript quality of an ASR system by removing on average 39 % of the errors caused by non-speech in the audio stream, while maintaining a real-time applicable delay of 270 milliseconds

Aufklärung der Interaktionen von Enterococcus faecalis mit dem angeborenen Immunsystem

Enterococcus faecalis has emerged as the third most common cause of life-threatening bacterial nosocomial infections in the US and in Europe. The knowledge of how enterococci interact with the host immune system is still very limited. The aim of this thesis was to explore the role of so far neglected sentinel cells of the innate immune system like mast cells (MC) and dendritic cells (DC). Also the endothelial barrier represents an important first counterpart with major immunomodulatory functions in the response to E. faecalis infections. Here it could be shown that MCs have a protective and critical role in the control of E. faecalis growth based on extracellular processes; first, by the formation of so called mast cells extracellular traps (MCETs) and second by the release of pre-stored antimicrobial peptides like the cathelicidin LL-37, which could be confirmed as the antimicrobial agent responsible to induce cell wall stress and vesicle formation on the surface of E. faecalis. Furthermore the importance of the TLR/MyD88 signaling pathway in the response of MCs to E. faecalis was confirmed using MyD88 or TLR2 deficient MCs. In comparison to MCs, DCs actively phagocytize and kill E. faecalis and create an inflammatory milieu consisting of immunomodulatory molecules like IL-12, KC or MIP-2 underlining the modulatory function of these cells. The TLR/MyD88 pathway could also be determined to be important for DC maturation and the release of mediators underlining the key role of this pattern recognition receptor-mediated pathway in the immune response to enterococci. Entering the blood stream, E. faecalis faces the endothelial barrier. Endothelial cells are an essential source of cytokine and chemokine production during bacterial infection and additionally, it is involved in a process called leukocyte extravasation which is mediated by the expression of endothelial surface receptors like E-selectin, ICAM-1 and VCAM-1. This study provided for the first time evidence, that E. faecalis is able to interfere with this pathway and therefore blocking the adhesion and transmigration of leukocytes through the endothelial barrier into deeper tissue. Moreover, a diminished IL-8 response indicates the ability for E. faecalis to manipulate the responses of the endothelial barrier. Taken together this work is shedding light on the complex interplay between E. faecalis and the host innate immune response.Enterococcus faecalis Infektionen haben sich in den USA und Europa zur dritt häufigsten Ursache für lebensbedrohliche bakterielle Infektionen in Krankenhäusern entwickelt. Ein zentrales Problem stellt dabei die Ansammlung von Resistenzen gegen viele klinisch verwendete Antibiotika dar. Das Wissen über die Interaktionen von Enterokokken mit dem Wirtsimmunsystem ist nach wie vor sehr unzureichend. Zielsetzung dieser Arbeit war es daher, zu untersuchen, welche Rolle wichtige, aber bisher wenig untersuchte Zellen der angeborenen Wirtsimmunabwehr wie Mastzellen (MCs), Dendritische Zellen (DCs) sowie das Endothel, als erste Effektorzellen mit entscheidenden immunmodulatorischen Funktionen, im Infektionsverlauf von E. faecalis spielen. Es konnte gezeigt werden, das MCs des Wachstums von E. faecalis kontrollieren und dabei auf extrazelluläre Prozesse, wiedie Freisetzung von sogenannten „mast cell extracellular traps“ (MCETs) oder von gespeicherten antimikrobiellen Peptiden, wie zum Beispiel des Cathelicidin LL-37, zurückgreifen. Auch konnte durch Versuche an MyD88 und TLR2 defizienten MCs die Bedeutung des TLR2/MyD88-Signalweg in diesen Zellen während einer Infektion mit E. faecalis charakterisiert werden. Anders als MCs sind DCs in der Lage, aktiv E. faecalis zu phagozytieren und intrazellulär abzutöten. Zudem erzeugen sie ein Milieu bestehend aus wichtigen immunmodulatorischen Zytokinen wie IL-12, KC oder MIP-2 und haben damit eine wichtige modulatorische Funktion.Auch hier spielt der TLR/MyD88 Signalweg für die Induktion der Zellreifung und die Freisetzung von Zytokinen und Chemokinen eine zentrale Rolle. Beim Eintriitt in den Blutkreislauf interagiert E. faecalis mit der Endothelzelle-Barriere. Endothelzellen stellen eine wesentliche Quelle für Mediatoren bei bakteriellen Infektionen dar. Neben dieser Funktion wird auch die sogenannte Leukozyten-Extravasation, durch das Endothel in Form der Expression von Oberflächenrezeptoren wie E-Selektin, ICAM-1 und VCAM-1 vermittelt. Diese Studie liefert zum ersten Mal den Nachweis, dass E. faecalis mit diesen Signalwegen wechselwirkt und damit die Adhäsion und Transmigration von Leukozyten durch die Endothelschranke blockiert. Auch die Fähigkeit von E. faecalis die IL-8 Antwort des Endothels zu beeinflussen deutet auf die Fähigkeit dieses Bakteriums hin, die Endothelbarriere zu beeinflussen. Zusammengefasst beleuchtet diese Studie das komplexe Zusammenspiel von E. faecalis mit Teilen des angeborenen Immunsystems

Reproducing the CO-to-H₂ conversion factor in cosmological simulations of Milky-Way-mass galaxies

We present models of CO(1–0) emission from Milky-Way-mass galaxies at redshift zero in the FIRE-2 cosmological zoom-in simulations. We calculate the molecular abundances by post-processing the simulations with an equilibrium chemistry solver while accounting for the effects of local sources, and determine the emergent CO(1–0) emission using a line radiative transfer code. We find that the results depend strongly on the shielding length assumed, which, in our models, sets the attenuation of the incident UV radiation field. At the resolution of these simulations, commonly used choices for the shielding length, such as the Jeans length, result in CO abundances that are too high at a given H₂ abundance. We find that a model with a distribution of shielding lengths, which has a median shielding length of ∼3 pc in cold gas (T < 300 K) for both CO and H₂, is able to reproduce both the observed CO(1–0) luminosity and inferred CO-to-H₂ conversion factor at a given star formation rate compared with observations. We suggest that this short shielding length can be thought of as a subgrid model, which controls the amount of radiation that penetrates giant molecular clouds

Corrosion Inhibition in Acidic Environments: Key Interfacial Insights with Photoelectron Spectroscopy

In many engineering scenarios, surface-active organic species are added to acidic solutions to inhibit the corrosion of metallic components. Given suitable selection, such corrosion inhibitors are highly effective, preventing significant degradation even in highly aggressive environments. Nevertheless, there are still considerable gaps in fundamental knowledge of corrosion inhibitor functionality, severely restricting rational development. Here, we demonstrate the capability of X-ray photoelectron spectroscopy (XPS), supported by ab initio modelling, for revealing key details of inhibited substrates. Attention is focussed on the corrosion inhibition of carbon steel through the addition of an exemplar imidazoline-based corrosion inhibitor (OMID) to aqueous solutions of both HCl and H2SO4. Most notably, it is demonstrated that interfacial chemistry varies with the identity of the acid. High resolution Fe 2p, O 1s, N 1s, and Cl 2p XPS spectra, acquired from well-inhibited carbon steel in 1 M HCl, show that there are two different singly protonated OMID species bound directly to the metallic carbon steel substrate. In sharp contrast, in 0.01 M H2SO4, OMID adsorbs onto an ultra-thin surface film, composed primarily of a ferric sulfate (Fe2(SO4)3)-like phase. Such insight is essential to efforts to develop a mechanistic description of corrosion inhibitor functionality, as well as knowledge-based identification of next generation corrosion inhibitors

Dark Matter Halo Mergers I: Dependence on Environment & Redshift Evolution

This paper presents a study of the specific merger rate as a function of group membership, local environment, and redshift in a very large, $500h^{-1} Mpc$, cosmological N-body simulation, the \textit{Millennium Simulation}. The goal is to provide environmental diagnostics of major merger populations in order to test simulations against observations and provide further constraints on major merger driven galaxy evolution scenarios. A halo sample is defined using the maximum circular velocity, which is both well defined for subhalos and closely correlated with galaxy luminosity. Subhalos, including the precursors of major mergers, are severely tidally stripped. Major mergers between subhalos are therefore extremely rare. Tidal stripping also suppresses dynamical friction, resulting in long major merger time scales when the more massive halo does not host other subhalos. In contrast, when other subhalos are present major merger time scales are several times shorter. This enhancement is likely due to inelastic unbound collisions between subhalos. Following these results, we predict that major mergers in group environments are dominated by mergers involving the central galaxy, that the specific merger rate is suppressed in groups, and that the frequency of fainter companions is enhanced for mergers and their remnants. We also observe an `assembly bias' in the major merger rate in that mergers of galaxy-like halos are slightly suppressed in overdense environments while mergers of group-like halos are slightly enhanced. A dynamical explanation for this trend is advanced which calls on both tidal effects and interactions between bound halos beyond the virial radii of locally dynamically dominant halos.Comment: 44 pages, 8 figures, Preprint Submitted to Ap