Screening and further investigations on promising bi-functional catalysts for metal–air batteries with an aqueous alkaline electrolyte

A wide range catalyst screening with noble metal and oxide catalysts for a metal–air battery with an aqueous alkaline electrolyte was carried out. Suitable catalysts reduce overpotentials during the charge and discharge process, and therefore improve the round-trip efficiency of the battery. In this case, the electrodes will be used as optimized cathodes for a future lithium–air battery with an aqueous alkaline electrolyte. Oxide catalysts were synthesized via atmospheric plasma spraying. The screening showed that IrO₂, RuO₂, La_0.6Ca_0.4Co₃, Mn₃O₄, and Co₃O₄ are promising bi-functional catalysts. Considering the high price for the noble metal catalysts further investigations of the oxide catalysts were carried out to analyze their electrochemical behavior at varied temperatures, molarities, and in case of La_1?x Ca _x CoO₃ a varying calcium content. Additionally all catalysts were tested in a longterm test to proof cyclability at varied molarities. Further investigations showed that Co₃O₄ seems to be the most promising bi-functional catalyst of the tested oxide catalysts. Furthermore, it was shown that a calcium content of x = 0.4 in LCCO has the best performance.     

Leichte Dachschalen aus Carbonbeton

Light‐weight precast shell elements made of textile reinforced concrete: production, experimental investigations and application potential For single curved barrel‐vault shells made of textile reinforced concrete (TRC) a manufacturing process has been developed that comprises the production of the precast parts as well as tailored solutions for transport and mounting of the filigree shells at the construction site. Furthermore, the load‐bearing capacity of the shells could be verified experimentally using large‐scale tests of prototypes. Saw cuts document the high production quality of the precast parts.The developed methods were successfully applied within the research project by constructing a large‐scale roof structure consisting of five barrel‐vault shells. The cross‐sectional thickness of the 10 m2 large elements amounts to only 2 cm emphasizing the high strength and application potential of TRC.     

Natural Threat – Tornadoes

Counting only the month of May 2015 about 20 tornadoes developed in Germany. At least three of them reached tornado category F3 destroying villages, e.g. [ 15 ]. About 50 people were injured and the insurance companies recorded about 100 Mio. Euros insured loss. Press media headlined: Tornadoes in Germany – the underestimated threat? The forecasting of extreme weather conditions in Germany due to climate change is still very uncertain. The design codes in Germany do not consider tornado actions. Thus, they are still considered catastrophic events. But owners ask experts whether their home can actually be protected. In the USA tornado actions are defined in codes for critical infrastructure. Because of the frequency and intensity of tornadoes, people in the USA have experiences with such events. This article introduces the phenomena of extreme winds, defines actions generated by extreme winds, explains building vulnerabilities, and gives some guidelines on how to protect buildings. Because of lack of research in Germany concerning protection of structures against tornado actions, we benefit from the expertise in the USA. This article is aimed at sensitize for the tornado threat from an engineering point of view, showing related problems, and hopefully initiate research in the future. Naturgefahr Tornados Allein im Mai 2015 ereigneten sich fast 20 Tornados in Deutschland, von denen zumindest drei die Tornado‐Kategorie F3 erreichten und ganze Ortschaften verwüsteten, z.B. [ 15 ]. Etwa 50 Menschen wurden verletzt, der Sachschaden ging in die 100 Mio. Euro. Die Medien titelten: Tornados in Deutschland – eine unterschätzte Gefahr? Tatsächlich sind die Vorhersagen der Experten vor dem Hintergrund der Klimaänderung derzeit noch sehr unklar. Hauseigentümer fragen Architekten und Bauingenieure, ob man sich vor Tornados schützen kann. Die die Einwirkungen regelnden Normen (DIN 1055, EC 1 (DIN EN 1991‐1‐1)) in Deutschland behandeln den Lastfall Tornado bisher nicht. Insofern sind die Einwirkungen aus Tornado als Katastrophenlastfall einzustufen. In den USA sind Tornado‐Einwirkungen für kritische Infrastrukturen geregelt. Sie behandeln die Winddrücke und die Einwirkungen aus herum fliegenden Objekten. Als Folge von Tornados fällt häufig der Strom aus mit all den spezifischen weiteren Folgen. Der Beitrag führt in die Problematik des Naturphänomens “Tornado” ein, beschreibt anhand der amerikanischen Vorschriften die zu erwartenden Einwirkungen und behandelt Schwachstellen‐Analysen sowie bauliche Lösungen für unterschiedliche Tornado‐Kategorien. Eine Risiko‐Betrachtung dient als Grundlage zur Erweiterung der Normen um den Lastfall “Tornado”. Gerade technische Anlagen und bauliche Anlagen der kritischen Infrastruktur bedürfen einer Risiko‐Bewertung zu Sicherung der Resilienz. Da es in Deutschland bisher keine Forschungen zum baulichen Schutz vor Tornado‐Einwirkungen gibt, ist es zweckmäßig, sich in Ländern Rat zu holen, in denen Tornados ständig auftreten. Dieser Beitrag soll vom Ingenieurstandpunkt aus sensibilisieren, Probleme aufzeigen und zu Forschungen anregen.     

Linearly tunable quadrature oscillator derived from LC Colpitts structure using voltage differencing transconductance amplifier and adjustable current amplifier

The paper deals with an interesting oscillator solution derived from LC Colpitts circuit structure. Electronically controllable current gain of the current amplifier is utilized for driving of oscillation condition together with two transconductances in frame of voltage differencing transconductance amplifier for adjusting of frequency of oscillation. In the proposed structure these elements replace common bipolar transistor and metal coil. Designed circuit offers important advantages, i.e. absence of metal coil, quadrature outputs, amplitudes of generated signals independent of tuning process, linear electronic control of oscillation frequency (independent of oscillation condition). Implementation of circuit for amplitude stabilization and automatic control of oscillation condition for designed circuit is simple. These benefits are not available in classical LC Colpitts structures or in many well-known third-order oscillators. The theoretical conclusions are supported by experiments with behavioral representation employing commercially available devices and also by simulations using CMOS model.     

Photocatalytic degradation of benzenesulfonate on colloidal titanium dioxide

Titanium dioxide-mediated photocatalyzed degradation of benzenesulfonate (BS) was investigated by monitoring chemical oxygen demand (COD), total organic carbon (TOC) content, sulfate concentration, pH as well as the absorption and emission spectral changes in both argon-saturated and aerated systems. Liquid chromatography-mass spectrometry analysis was utilized for the detection of intermediates formed during the irradiation in the UVA range (λ_max = 350 nm). The results obtained by these analytical techniques indicate that the initial step of degradation is hydroxylation of the starting surfactant, resulting in the production of hydroxy- and dihydroxybenzenesulfonates. These reactions were accompanied by desulfonation, which increases [H⁺] in both argon-saturated and aerated systems. In accordance with our previous theoretical calculations, the formation of ortho- and meta-hydroxylated derivatives is favored in the first step. The main product of the further oxygenation of these derivatives was 2,5-dihydroxy-benzesulfonate. No decay of the hydroxy species occurred during the 8-h irradiation in the absence of dissolved oxygen. In the aerated system much more efficient desulfonation and hydroxylation, moreover, a significant decrease of TOC took place at the initial stage. Further hydroxylation led to cleavage of the aromatic system, due to the formation of polyhydroxy derivatives, followed by ring fission, resulting in the production of aldehydes and carboxylic acids. Total mineralization was achieved by the end of the 8-h photocatalysis. It has been proved that in this photocatalytic procedure the presence of dissolved oxygen is necessary for the cleavage of the aromatic ring because hydroxyl radicals photochemically formed in the deaerated system too alone are not able to break the C-C bonds.     

Multiplexed immunohistochemical detection of tumor markers in breast cancer tissue using laser ablation inductively coupled plasma mass spectrometry

We optimized multiplexed immunohistochemistry (IHC) on breast cancer tissue. Up to 20 tumor markers are routinely evaluated for one patient, and thus, a common analysis results in a series of time consuming staining procedures. As an alternative, we used lanthanides for labeling of primary antibodies, which are applied in IHC. Laser ablation (LA) ICPMS was elaborated as a detection tool for multiplexed IHC of tissue sections. In this study, we optimized sample preparation steps and LA ICPMS parameters to achieve a sufficient signal-to-background ratio. The results prove the high selectivity of applied antibodies, which was sustained after labeling. Up to three tumor markers (Her 2, CK 7, and MUC 1) were detected simultaneously in a single multiplex analysis of a 5 μm thin breast cancer tissue at a laser spot size of 200 μm. Furthermore, the LA ICPMS results indicate a significantly higher expression level of MUC 1 compared to Her 2 and CK 7, which was not obvious from the conventionally stained tissue sections.     

Simulation of fatigue failure in composite axial compressor blades

Centrifugal forces are generated by a spinning impeller, of magnitudes that create large stresses. Aerodynamic forces are also imparted on an impeller blade, which varies with time and position. These two forces play different roles during compressor events. Damage accumulated from these events results in the fatigue failure of impeller material and structure. Therefore, it is important to design an impeller against dynamic and fatigue failure. The finite element method has been used in the study of impeller fracture mechanics and is regarded as an important tool in the design and analysis of material and structures.     

Tailoring the near-surface composition profiles of pressure-sensitive adhesive films and the resulting mechanical properties

We present a possibility of tailoring the near-surface composition profiles of pressure sensitive adhesive (PSA) films by an exposure to atmospheres of different relative humidities (RHs). The statistical copolymer P(EHA-stat-20MMA) with a majority of ethylhexylacrylate (EHA) and a minority of methylmethacrylate (MMA), being cast from a toluene based solution, is chosen as a model system. The near-surface composition profile is probed with X-ray reflectivity. All probed samples show an enrichment of PMMA at the sample surface; however, the near-surface PMMA content strongly increases with increasing RH. The influence of the RH on the composition profile is present down to a depth of 50 nm. Therefore the surface tensions being derived from contact angle measurements do not show any measurable humidity dependence. In contrast, in a mechanical tack test with a smooth punch surface, a strong influence is probed. This observation can be explained by considering the integrated PMMA content over an appropriate near-surface region and the resulting impact on the cavitation process.