Effects of processing on texture,internal stresses and mechanical properties during the pulsed electrodeposition of nanocrystalline and ultrafine-grained nickel

The mechanical properties of nanocrystalline and ultrafine-grained metals strongly depend on grain size, grain boundary segregation, texture and internal stresses. In this paper a thorough systematic analysis is given on the influence of different pulsed electrodeposition processing parameters and grain refiners on the grain size, texture and segregation of Ni and thus on internal stresses. The grain refiner content of the electrolyte, mainly the saccharin content, and the pulse parameters on- and off-time as well as the pulse current density were varied systematically. The combination of different methods of stress and texture analysis allows, among other things, a careful discussion of the influence of saccharin on stress and texture development. Massive tensile specimens were produced with different grain sizes and deformed in incremental load tests. These tests clearly demonstrate the strong effect of the production process on the deformation behavior under constant load.     

Sila-haloperidol, a silicon analogue of the dopamine (D2) receptor antagonist haloperidol: synthesis, pharmacological properties, and metabolic fate

Haloperidol (1 a), a dopamine (D(2)) receptor antagonist, is in clinical use as an antipsychotic agent. Carbon/silicon exchange (sila-substitution) at the 4-position of the piperidine ring of 1 a (R(3)COH --> R(3)SiOH) leads to sila-haloperidol (1 b). Sila-haloperidol was synthesized in a new multistep synthesis, starting from tetramethoxysilane and taking advantage of the properties of the 2,4,6-trimethoxyphenyl unit as a unique protecting group for silicon. The pharmacological profiles of the C/Si analogues 1 a and 1 b were studied in competitive receptor binding assays at D(1)-D(5), sigma(1), and sigma(2) receptors. Sila-haloperidol (1 b) exhibits significantly different receptor subtype selectivities from haloperidol (1 a) at both receptor families. The C/Si analogues 1 a and 1 b were also studied for 1) their physicochemical properties (log D, pK(a), solubility in HBSS buffer (pH 7.4)), 2) their permeability in a human Caco-2 model, 3) their pharmacokinetic profiles in human and rat liver microsomes, and 4) their inhibition of the five major cytochrome P450 isoforms. In addition, the major in vitro metabolites of sila-haloperidol (1 b) in human liver microsomes were identified using mass-spectrometric techniques. Due to the special chemical properties of silicon, the metabolic fates of the C/Si analogues 1 a and 1 b are totally different.     

Compared imbibitions of ordinary and high performance concrete with null or positive water pressure head

A method to simultaneously measure the moisture diffusion coefficient, D_θ, of unsaturated concrete, and the saturated concrete hydraulic conductivity, K_l, was developed for cylindrical specimens placed on a container filled with water that could be maintained at a given hydraulic pressure. Ordinary Portland cement Concrete (OPC) with a moderate and High Performance Concrete (HPC) with a low water to cement ratio were tested. The time dependent distribution of water content in the specimens was measured using a non-intrusive method based on gamma-ray attenuation. The measurements were conducted with varying hydraulic head (positive or null). Boltzmann's transformation was used to analyze the experimental results obtained at different hydraulic pressures and the difference between the null (or atmospheric) and positive pressure results is used to accurately determine K_l and also D_θ . This paper will present the results obtained using this original method, possible interpretations and future research.     

Analysis of the Influence of Processing Conditions on the Supramolecular Structure and Antioxidant Distribution in PP‐Pipes Using Infrared Microscopy

The supramolecular structure in pipe walls of isotactic PP‐R is a function of compound composition and processing parameters, which both influence the mechanical properties of the pipes. µFTIR shows a gradient of the crystallinity across the pipe wall, with a lower‐crystalline outer layer, and a higher‐crystalline core layer. The rate of extrusion has an influence on the thickness of the outer layer. The nucleating effect on the morphological profile throughout the pipe wall can be visualised. µFTIR shows a homogeneous distribution of the primary antioxidant in the pipe wall. Both the spectral crystallinity and the antioxidant concentration distribution are calculated.

     

Optimized Characterization of Thermoelectric Generators for Automotive Application

New developments in the field of thermoelectric materials bring the prospect of consumer devices for recovery of some of the waste heat from internal combustion engines closer to reality. Efficiency improvements are expected due to the development of high-temperature thermoelectric generators (TEG). In contrast to already established radioisotope thermoelectric generators, the temperature difference in automotive systems is not constant, and this imposes a set of specific requirements on the TEG system components. In particular, the behavior of the TEGs and interface materials used to link the heat flow from the heat source through the TEG to the heat sink must be examined. Due to the usage patterns of automobiles, the TEG will be subject to cyclic thermal loads, which leads to module degradation. Additionally, the automotive TEG will be exposed to an inhomogeneous temperature distribution, leading to inhomogeneous mechanical loads and reduced system efficiency. Therefore, a characterization rig is required to allow determination of the electrical, thermal, and mechanical properties of such high-temperature TEG systems. This paper describes a measurement setup using controlled adjustment of cold-side and warm-side temperatures as well as controlled feed-in of electrical power for evaluation of TEGs for application in vehicles with combustion engines. The temperature profile in the setup can be varied to simulate any vehicle usage pattern, such as the European standard driving cycle, allowing the power yield of the TEGs to be evaluated for the chosen cycle. The spatially resolved temperature distribution of a TEG system can be examined by thermal imaging. Hotspots or cracks on thermocouples of the TEGs and the thermal resistance of thermal interface materials can also be examined using this technology. The construction of the setup is briefly explained, followed by detailed discussion of the experimental results.     

Microscopic oxygen imaging based on fluorescein bleaching efficiency measurements

Photobleaching of the fluorophore fluorescein in an aqueous solution is dependent on the oxygen concentration. Therefore, the time‐dependent bleaching behavior can be used to measure of dissolved oxygen concentrations. The method can be combined with epi‐fluorescence microscopy. The molecular states of the fluorophore can be expressed by a three‐state energy model. This leads to a set of differential equations which describe the photobleaching behavior of fluorescein. The numerical solution of these equations shows that in a conventional wide‐field fluorescence microscope, the fluorescence of fluorescein will fade out faster at low than at high oxygen concentration. Further simulation showed that a simple ratio function of different time‐points during a fluorescence decay recorded during photobleaching could be used to describe oxygen concentrations in an aqueous solution. By careful choice of dye concentration and excitation light intensity the sensitivity in the oxygen concentration range of interest can be optimized. In the simulations, the estimation of oxygen concentration by the ratio function was very little affected by the pH value in the range of pH 6.5–8.5. Filming the fluorescence decay by a charge‐coupled‐device (ccd) camera mounted on a fluorescence microscope allowed a pixelwise estimation of the ratio function in a microscopic image. Use of a microsensor and oxygen‐consuming bacteria in a sample chamber enabled the calibration of the system for quantification of absolute oxygen concentrations. The method was demonstrated on nitrifying biofilms growing on snail and mussel shells, showing clear effects of metabolic activity on oxygen concentrations. Microsc. Res. Tech. 77:341–347, 2014. © 2014 Wiley Periodicals, Inc.     

Adsorption of Collagen Nanofibrils on Rough TiO2: A Molecular Dynamics Study

Classical molecular dynamics simulations of tropocollagen molecules on rough titania surfaces are presented. On the basis of plane rutile (100), two models for surface roughness have been adopted: (1 × 3) microfacets with dimensions of less than 14 Å had only minor influence on the adsorption of a triple helical structure with a diameter of about 16 Å. After increasing the roughness by terraces, steric hindrance of helix binding was observed. A model for telopeptide capping of the collagen triple helices was developed. The highly flexible telopeptide structures mediated adsorption on the surface and inserted into grooves of both surface models. The telopeptide β‐turn motifs at the C‐terminus of the tropocollagen interact with specific receptor regions of the triple helices. This intermolecular process seems to be entropy driven and may be the first step of assembling helices to ordered fibrils. Interaction between telopeptide and triple helix seems to be in competition with the rather enthalpy controlled surface adsorption of single collagen molecules.     

TiO2 coating of high surface area silica gel by chemical vapor deposition of TiCl4 in a fluidized-bed reactor

TiO2 was deposited on high surface area porous silica gel (400 m2g(-1)) in a fluidized bed reactor. Chemical vapor deposition was employed for the coating under vacuum conditions with TiCl4 as precursor. Nitrogen physisorption, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy were applied to characterize the obtained TiO2-SiO2 composites with different Ti loadings up to 5 wt%. Only a slight decrease in the specific surface area was detected at low Ti loadings. At a Ti loading of 2 wt%, TiO2 was found to be highly dispersed on the SiO2 surface likely in form of a thin film. At higher Ti loadings, two weak reflections corresponding to anatase TiO2 were observed in the diffraction patterns indicating the presence of crystalline bulk TiO2. High resolution XPS clearly distinguished two types of Ti species, i.e., Ti-O-Si at the interface and Ti-O-Ti in bulk TiO2. The presence of polymeric TiOx species at low Ti loadings was confirmed by a blue shift in the UV-vis spectra as compared to bulk TiO2. All these results point to a strong interaction between the TiO2 deposit and the porous SiO2 substrate especially at low Ti loadings.     

Questionnaire Design: Carry‐Over Effects of Overall Acceptance Question Placement and Pre‐evaluation Instructions on Overall Acceptance Scores in Central Location Tests

Question placement and usage of pre‐evaluation instructions (PEI) in questionnaires for food sensory analysis may bias consumers’ scores via carry‐over effects. Data from consumer sensory panels previously conducted at a central location, spanning 11 years and covering a broad range of food product categories, were compiled. Overall acceptance (OA) question placement was studied with categories designated as first (the first evaluation question following demographic questions), after nongustation questions (immediately following questions that do not require panelists to taste the product), and later (following all other hedonic and just‐about‐right [JAR] questions, but occasionally before ranking, open‐ended comments, and/or intent to purchase questions). Each panel was categorized as having or not having PEI in the questionnaire; PEI are instructions that appear immediately before the first evaluation question and show panelists all attributes they will evaluate before receiving test samples. Postpanel surveys were administered regarding the self‐reported effect of PEI on panelists’ evaluation experience. OA scores were analyzed and compared (1) between OA question placement categories and (2) between panels with and without PEI. For most product categories, OA scores tended to be lower when asked later in the questionnaire, suggesting evidence of a carry‐over effect. Usage of PEI increased OA scores by 0.10 of a 9‐point hedonic scale point, which is not practically significant. Postpanel survey data showed that presence of PEI typically improved the panelists’ experience. Using PEI does not appear to introduce a meaningful carry‐over effect.