Influence of priming time and primer’s concentrations on bovine enamel bond strengths

This study investigated the effects of priming time (5, 30 or 60?s), 10-MDP (10-methacryloyloxydecyl dihydrogen phosphate)-containing primer’s concentrations (0.5, 1, 5, 10 and 20% (w/w)) and two neutral primers (5% (w/w) of 10-MDP-Na or EDTA-2Na) on bovine enamel microtensile bond strength (μTBS) using a novel prime-and-rinse approach. After priming, the enamel surfaces were thoroughly water-sprayed and dried before resin composite was placed. There was a significant influence of primer’s concentrations and priming time on bovine enamel μTBS when 10-MDP-containing primers were used (p?<?0.001), revealing the optimal priming time (30?s) and the best combination (priming with 20% of 10-MDP for 30?s). The prime-and-rinse approach might be an innovative supplement to contemporary dental adhesive procedures. The neutral primer (5% of 10-MDP-Na) produced moderate enamel μTBS on highly polished enamel surfaces, while another neutral primer (5% of EDTA-2Na) failed, suggesting that chemical bonding of 10-MDP to enamel hydroxyapatite crystallites could yield detectable bond strengths on smooth enamel surfaces.     

Cobalt-Containing Hyperbranched Poly(silylenearylene)s

A group of hyperbranched poly(silylenearylene)s are synthesized by homopolycyclotrimerizations of A₂-type silylenediynes. The polymers can be readily metallized by complexations of their periphery triple bonds with cobalt octacarbonyls Co₂(CO)₈. Pyrolysis of these organometallic polymers gives magnetic ceramics in good yields. Analyses by SEM, TEM, XPS, EDX, and XRD demonstrate that the ceramics comprise ferromagnetic Co and paramagnetic Co₂Si nanocrystallites wrapped by carboneous shell. The ceramics show high magnetic susceptibilities (M _s up to ~50 emu/g) and near-zero coercivity (H _c down to ~0.14 kOe), suggesting that they are good soft magnetic materials with low hysteresis loss. This article was to be included in the March issue of Volume 19, which was dedicated to Professor Takakazu Yamamoto. The journal editors sincerely apologize for the omission and delay in publication for which the authors and the guest editor bare no responsibility. M. Zeldin and A. S. Abd-El-Aziz, Editors.     

Critical review of models for H2-permeation through polymers with focus on the differential pressure method

To reduce loss of hydrogen in storage vessels with high energy-to-weight-ratio, new materials, especially polymers, have to be developed as barrier materials. Very established methods for characterization of barrier materials with permeation measurements are the time-lag and flow rate method along with the differential pressure method, which resembles the nature of hydrogen vessel systems very well. Long measurement durations are necessary to gain suitable measurement data for these evaluation methods, and often restrictive conditions have to be fullfilled. For these reasons, common models for hydrogen permeation through single-layer and multi-layer membranes, as well as models for hydrogen gas properties were collected and reviewed. Using current computer power together with these models can reduce measurement time for characterization of the barrier properties of materials, while additional information about the quality of the measurement results is obtained.     

科帕卡格拉纳建筑 奥地利维亚纳

正科帕卡格拉纳位于新多瑙河12.5公里处,毗邻Reichsbrücke大桥。出于同旧有设计保持协调性考虑,力求能让大楼融入当地环境,迎合自身功能性需要,GERNER GERNER PLUS团队充分考虑现有周边环境,对大楼重新规划设计。新的设计突显建筑的特殊性和重要性,面向河流的立面是科帕卡格拉纳大楼最重要的部分,所以设计的重点也放在了这里。现有的城市中轴线是一个参照物,为了视觉上和氛围上形成一体化城市的感     

Modeling Firm and Market Dynamics: A Flexible Model Reproducing Existing Stylized Facts on Firm Growth

This paper presents a model of firm and market dynamics that is able to reproduce the empirically observed patterns on firm growth and its statistical characteristics. It goes beyond the existing firm models by reproducing all stylized facts established in the literature. Furthermore, the model is flexible in the sense that various parameter settings are identified that reproduce the stylized facts. We identify and discuss different ranges of the model’s parameters that allow for adapting the model to certain industries and life-cycle stages.     

Untersuchung von lokalen Schichtdickenverteilungen in Fluiden mithilfe der Nahinfrarot‐Bildanalyse

An online image analysis method to determine the film thickness in fluids by use of pulsed near infrared LEDs and an NIR camera was developed. This technique offers the possibility to monitor moving fluid layers. In this work the possibilities and limits of the used apparatus are demonstrated with the application example of measurement of the fluid film thickness distribution of water and glycerol in a falling film.     

Experimental and numerical analysis of the influence of cable tray arrangements on the resulting mass loss rate and fire spreading

In the context of industrial buildings and power plants, electrical installations and cable trays represent a main fuel load and a potential initial fire source due to possible short circuits or comparable malfunction. Furthermore, a fire can spread from one tray to additional trays mounted above and/or horizontally on one tray. Because of the high significance of cable fires, several research projects have been carried out, investigating the fire behaviour of cables from small‐scale tests, eg, the cone calorimeter, up to large‐scale tests, analysing complete cable tray constructions. The goal of the work presented in this paper is the extension of the knowledge regarding the influence of geometrical parameters like the packing density and tray distance on the burning behaviour and fire spread of cable tray installations. The results are considered, together with test results from the literature, to quantify the main physical parameters describing the burning behaviour. In a next step, the general applicability of these parameters as input data for the parametrization of the source term of numerical simulations is shown. The test results show that the burning behaviour and the fire spreading highly depend on the cable arrangement of the cables on the cable tray, in combination with other boundary conditions. By applying the results as input for a fire simulation, the mass loss rate is considered appropriately.     

Large Area Thick Films of PVDF‐TrFE and Relaxor‐Ceramics for Piezo‐ and Pyroelectric Applications

Wearable electronics, sensors, and energy harvesting devices are gaining an ever increasing importance in consumer products. Their success is, however, contingent on the availability of flexible and cost‐effective functional materials. The present paper presents an up‐scaled processing route for 0–3 thick film composites of the ferroelectric polymer polyvinylidenefluoride‐trifluoroethylene and a relaxor ceramic. Different compositions are investigated for pyro‐ and piezoelectric applications. Various samples are produced via tape casting and spin‐coating as freestanding and supported films of up to 600 × 200 mm² and on 150 mm silicon wafers, respectively. The samples are characterized in terms of thickness and roughness reproducibility, mechanical properties, and impedance. It is shown that good reproducibility and quality of the films can be realized. Depending on the application targeted (pyroelectric or piezoelectric), specific compositions together with the suitable poling process are presented. For instance, a composite with 24 vol% ceramic shows highest pyroelectric properties together with lowest piezoelectric thickness coefficient (d₃₃) when poled for pyroelectric applications. On the other hand, a composite with 50 vol% ceramic exhibits a d₃₃ of 100 pm V^?1 that is unsurpassed for this type of composites. These properties are advantageous in a large variety of applications, including wearable devices.     

Time-resolved photoelectron spectroscopy to probe ultrafast charge transfer and electron dynamics in solid surface systems and at metal-molecule interfaces

Photoelectron spectroscopy (PES) is a versatile tool, which provides insight into electronic structure and dynamics in condensed matter, surfaces, interfaces and molecules. The history of PES is briefly outlined and illustrated by current developments in the field of time-resolved PES. Our group's research is mostly aimed at studying ultrafast processes and associated lifetimes related to electronic excitation at solid surfaces.