Does modality play a role? Visual‐verbal cognitive style and multimedia learning

The study presented in this paper aimed to examine the effect of visual and verbal cognitive style on learning from different types of visualization and modalities of explanatory text. Learning materials in the form of either computer‐based animation or a series of static pictures with written or spoken explanations were presented to 197 students. We found that a more developed visual cognitive style was related to a better learning outcome, when learning from a combination of static pictures and written text. Higher developed visualizers achieved poorer learning outcomes when learning with an animation and written text. The results are partially in line with an ability‐as‐compensator effect and the expertise reversal effect. Additionally, we found a modality effect as the versions with spoken text provided better results on learning outcome than the versions with written text regardless of the prominence of visual cognitive style. No significant interaction effects were found regarding verbal cognitive style.     

Dynamic force microscopy imaging of native membranes

We employed magnetic ACmode atomic force microscopy (MACmode AFM) as a novel dynamic force microscopy method to image surfaces of biological membranes in their native environments. The lateral resolution achieved under optimized imaging conditions was in the nanometer range, even when the sample was only weakly attached to the support. Purple membranes (PM) from Halobacterium salinarum were used as a test standard for topographical imaging. The hexagonal arrangement of the bacteriorhodopsin trimers on the cytoplasmic side of PM was resolved with 1.5nm lateral accuracy, a resolution similar to images obtained in contact and tapping-mode AFM. Human rhinovirus 2 (HRV2) particles were attached to mica surfaces via nonspecific interactions. The capsid structure and 2nm sized protein loops of HRV2 were routinely obtained without any displacement of the virus. Globular and filamentous structures on living and fixed endothelial cells were observed with a resolution of 5-20nm. These examples show that MACmode AFM is a favorable method in studying the topography of soft and weakly attached biological samples with high resolution under physiological conditions.     

Limits of DPUI application associated with the number of particles within actinide aerosols

Dose per unit intake (DPUI) of radionuclides is obtained using International Commission on Radiological Protection (ICRP) models. After inhalation exposure, the first model calculates the fraction of activity deposited within the different regions of the respiratory tract, assuming that the aerosol contains an infinite number of particles. Using default parameters for workers, an exposure to one annual limit of intake (ALI) corresponds to an aerosol of 239PuO2 containing approximately 1 x 10(6) particles. To reach such an exposure, very low particle number might be involved especially for compounds having a high specific activity. This study provides examples of exposures to actinide aerosols for which the number of particles is too low for a standard application of the ICRP model. These examples, which involve physical studies of aerosols collected at the workplace and interpretation of bioassay data, show that the number of particles of the aerosol can be the main limit for the application of DPUI after inhalation exposure.     

Deposition and Characteristics of Submicrometer-Structured Thermal Barrier Coatings by Suspension Plasma Spraying

In the field of thermal barrier coatings (TBCs) for gas turbines, suspension plasma sprayed (SPS) submicrometer-structured coatings often show unique mechanical, thermal, and optical properties compared to conventional atmospheric plasma sprayed ones. They have thus the potential of providing increased TBC performances under severe thermo-mechanical loading. Experimental results showed the capability of SPS to obtain yttria stabilized zirconia coatings with very fine porosity and high density of vertical segmentation cracks, yielding high strain tolerance, and low Young??s modulus. The evolution of the coating microstructure and properties during thermal cycling test at very high surface temperature (1400?°C) in our burner rigs and under isothermal annealing was investigated. Results showed that, while segmentation cracks survive, sintering occurs quickly during the first hours of exposure, leading to pore coarsening and stiffening of the coating. In-situ measurements at 1400?°C of the elastic modulus were performed to investigate in more detail the sintering-related stiffening.     

Quantification of structural and material failure mechanisms across different length scales: from instability to brittle-ductile transitions

Structures may fail due to a myriad of different causes. Often, distinction is made between structural and material failure, that means a structure can fail, while the material is still intact (this is the case in so-called stability loss), or the material fails, which, as consequence, may lead to structural failure. The material behavior may turn out difficult to be mathematically guessed at the macro-level. On the other hand, a lot may be known about the chemistry or the microstructure of the material of interest. Herein, we aim at categorizing different scenarios which in the end provoke structural failure, discussing various cases investigated during the last five years, at the Institute for Mechanics of Materials and Structures of Vienna University of Technology: A well-chosen eigenvalue problem shows considerable potential for categorizing stability loss. We then turn to complex composite materials with a hierarchical organization, where a single constituent dominates the overall quasi-brittle failure of the material, such as lignin in wood and wood products, or the cement–water reaction products (shortly called hydrates) in cement-based materials. The picture changes if the first inelastically behaving constituent is related to ductile load carrying, then the loads within the microstructure are re-distributed before the overall material fails: this turns out to be the case in bone. Finally, due to highly confined multiaxial stress states, the elastic portion of the overall energy invested into the material may become negligible—and then yield design analysis employed on material volumes gives an idea of the highly ductile behavior of complex confined materials, such as asphalt. What integrates all the reported cases is the high capacity of mature mathematical and mechanical formulations to reveal the intricate, yet decipherable nature of the (continuum) mechanics of materials and structures.     

Micromechanical Explanation of Elasticity and Strength of Gypsum: From Elongated Anisotropic Crystals to Isotropic Porous Polycrystals

Gypsum is made up of interlocked and elongated crystals. The random nature of its morphology suggests to resort to homogenization of random media to investigate its mechanical properties from the scale of the single crystals upwards. Unfortunately, the usual homogenization schemes fail to quantitatively predict the influence of the porosity on the effective Young’s modulus of gypsum. This is clearly due to the inability of such approaches to take into account the elongated nature of the crystals. A modification of the classical self-consistent scheme is proposed. It is validated against elastic characteristics computed by finite element analyses, and also against experiments on real dried gypsum samples (with empty pores). Finally, a strength model based on brittle failure is presented. The whole strength domain in the space of macroscopic principal stresses is derived. The comparison to experimental data in both simple tension and simple compression is remarkably good.     

Suspension Plasma Spraying: Process Characteristics and Applications

Suspension plasma spraying (SPS) offers the manufacture of unique microstructures which are not possible with conventional powdery feedstock. Due to the considerably smaller size of the droplets and also the further fragmentation of these in the plasma jet, the attainable microstructural features like splat and pore sizes can be downsized to the nanometer range. Our present understanding of the deposition process including injection, suspension plasma plume interaction, and deposition will be outlined. The drawn conclusions are based on analysis of the coating microstructures in combination with particle temperature and velocity measurements as well as enthalpy probe investigations. The last measurements with the water cooled stagnation probe gives valuable information on the interaction of the carrier fluid with the plasma plume. Meanwhile, different areas of application of SPS coatings are known. In this paper, the focus will be on coatings for energy systems. Thermal barrier coatings (TBCs) for modern gas turbines are one important application field. SPS coatings offer the manufacture of strain-tolerant, segmented TBCs with low thermal conductivity. In addition, highly reflective coatings, which reduce the thermal load of the parts from radiation, can be produced. Further applications of SPS coatings as cathode layers in solid oxide fuel cells (SOFC) and for photovoltaic (PV) applications will be presented.     

Acoustical and Poromechanical Characterisation of Titanium Scaffolds for Biomedical Applications

Abstract:  Biocompatible materials are designed so as to mimic biological materials such as bone as closely as possible. As regards the mechanical aspect of bone replacement materials, a certain stiffness and strength are mandatory to effectively carry the loads imposed on the skeleton. In this paper, porous titanium with different porosities, produced on the basis of metal powder and space holder components, is investigated as bone replacement material. For the determination of mechanical properties, i.e. strength of dense and porous titanium samples, two kinds of experiments were performed – uniaxial and triaxial tests. The triaxial tests were of poromechanical nature, i.e. oil was employed to induce the same pressure both at the lateral surfaces of the cylindrical samples and inside the pores. The stiffness properties were revealed by acoustic (ultrasonic) tests. Different frequencies give access to different stiffness components (stiffness tensor components related to high-frequency-induced bulk waves versus Young's moduli related to low-frequency-induced bar waves), at different observation scales; namely, the observation scale the dense titanium with around 100  μ m characteristic length (characterised through the high frequencies) versus that of the porous material with a few millimetres of characteristic length (characterised through the low frequencies). Finally, the experimental results were used to develop and validate a poro-micromechanical model for porous titanium, which quantifies material stiffness and strength from its porosity and (in the case of the aforementioned triaxial tests) its pore pressurisation state.     

Bestandsaufnahme zum Vorkommen von Lysinoalanin in milcheiwei?haltigen Lebensmitteln

Zusammenfassung Mit einer verbesserten Analysen-methode wurde in ca. 350 milcheiweißhaltigen Lebensmittelproben des Handels Lysinoalanin (LAL) spezifisch und quantitativ bestimmt. Das Gros der Proben stammte aus dem mitteleuropäischen Raum. In Rohmilch und pasteurisierten Milchprodukten war LAL nicht nachweisbar. UHT-Produkte (Milch, Milcherzeugnisse, Sahne) enthielten in der Regel kaum LAL, Erzeugnisse mit 60 ppm LAL im Protein waren nachweislich stärker wärmebelastet worden als allgemein üblich. Ungezuckerte Kondensmilch enthielt durchschnittlich 150 bis 250 ppm LAL, in gezuckerter Kondensmilch wurde LAL meist nur in Spuren bis etwa 40 ppm gefunden. Autoklavierte Flüssigprodukte wie Sterilmilch, Kaffeesahne und vor allem Babymilch-Formulakost wiesen 200–1160 ppm LAL im Eiweiß auf, wodurch zum Teil intensive Eiweißschädigung indiziert wurde. Die große Schwankungsbreite im LAL-Gehalt dieser Produktgruppe war in erster Linie auf unterschiedliche Temperaturbelastungen und Erhitzungszeiten zurückzuführen. Die Herstellung von Milch- und Molkenpulver, Säure- und Labcasein, Käse und Käseprodukten, sowie Baby-Milchformulanahrung in Pulverform führte zu keiner nennenswerten LAL-Bildung. Caseinate und Kopräzipitate zeigten stark streuende Werte von 0 bis 1530 ppm LAL im Eiweiß. Caseinate, die mit Carbonat- und Citratsalzen oder durch vorsichtige stufenweise Zugabe von Natronlauge unter ständiger pH-Kontrolle (pH < 8) aufgeschlossen wurden, enthielten maximal 250 ppm LAL im Eiweiß. Direkte Zugabe von Natronlauge und Temperaturen über 100 °C führen zu hohen LAL-Werten. Zahlreiche untersuchte Lebensmittel mit Milcheiweißzusatz (z. B. Schlagcremepulver, Kaffeeweißer, Desserteremepulver) zeigten stark differierende LAL-Mengen von 0 bis 1300 ppm, hoher LAL-Gehalt ist dabei in der Regel auf die Verwendung stark alkalibehandelter Caseinate zurückzuführen. In diätetischen Eiweißkonzentraten (z. B. Formuladiät), die granuliertes Casein-oder Molkeneiweiß enthielten, wurden LAL-Mengen bis zu 1 180 ppm gefunden. Einige Schaumproteine auf der Basis von partiell alkalihydrolysiertem Milcheiweiß wiesen extrem hohe LAL-Mengen bis zu 53 000 ppm auf und enthielten zum Teil auch freies LAL. In allen anderen Lebensmitteln kommt LAL anscheinend nur proteingebunden vor.

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Study on the occurrence of lysinoalanine in food which contain milk proteins

Summary In 350 commercial samples of food and food ingredients containing milk protein lysinoalanine (LAL) was determined by an improved method. Most of the samples originated from the central European market. LAL was not detectable in fresh milk and pasteurized milk products. Ultra-High-Temperature(UHT)-products (milk, mixed milk and cream) generally did not contain LAL, samples with 60 ppm LAL i.p. (i.p. = in the protein) evidently had been heat treated to a greater extent than usual. In unsweetened evaporated and condensed milk LAL was present at an average of 150 ppm to 250 ppm i.p., whereas in most sweetened condensed milk samples there were only from traces up to 40 ppm LAL. Autoclave sterilized products such as sterilized milk, coffee cream and above all liquid infant milk formulas contained 200 to 1,160 ppm LAL i.p., the higher levels indicating intensive protein damage. The wide range of LAL in these samples was attributed to the diverse heat treatment — both in temperature and time. The production of powdered milk and whey, acid and rennet casein, cheese and cheese products as well as powdered infant milk formulas induced no appreciable LAL formation. LAL-levels in caseinates and coprecipitates diverged widely (0–1,530 ppm LAL i.p.). Conversion of casein curd into caseinate dispersion by carbonate and citrate salts or by a careful and gradual addition of hydroxide led to maximum LAL-levels of 250 ppm i.p. High LAL values resulted from direct addition of hydroxide and temperatures above 100 °C. In numerous food samples containing milk protein as an ingredient (e.g. whipped topping mix, coffee creamer, dessert cream) the degree of LAL varied from 0 to 1,300 ppm i.p.; the high values were attributed to the use of strong alkali treated cascinates. In dietetic protein concentrates (e.g. formula diet) containing granulated casein or whey protein LAL was found in relatively large amounts up to 1,180 ppm i.p. Some whipping agents from partially alkali hydrolyzed milk protein showed extremely high levels of LAL up to 53,000 ppm i.p. and some of the samples contained also free LAL. In all other kinds of food LAL seems to be exclusively present as protein-bound LAL.