Stability and structures of the CFCC-TmC phases: A first-principles study

The η-M₆C, γ-M₂₃C₆, and π-M₁₁C₂ phases (M = Cr, Mn and Fe) have complex cubic lattices with lattice parameters of approximately 1.0 nm. They belong to the CFCC-TmC family (complex face-centered cubic transition metal carbides), display a rich variety of crystal structures, and play in important role in iron alloys and steels. Here we show that first-principles calculations predict high stability for the γ-M₂₃C₆ and η-M₆C phases, and instability for the π-M₁₁C₂ phases, taking into account various compositional and structural possibilities. The calculations also show a wide variety in magnetic properties. The Cr-containing phases were found to be non-magnetic and the Fe-phases to be ferromagnetic, while the Mn-containing phases were found to be either ferrimagnetic or non-magnetic. Details of the local atomic structures, and the formation and stability of these precipitates in alloys are discussed.     

Superprotonic KH(PO3H)–SiO2 composite electrolyte for intermediate temperature fuel cells

Novel thin film composite electrolyte membranes, prepared by dispersion of nano-sized SiO₂ particles in the solid acid compound KH(PO₃H), can be operated under both oxidizing and reducing conditions. Long-term stable proton conductivity is observed at 140 °C, i.e., slightly above the superprotonic phase transition temperature of KH(PO₃H), under conditions of relatively low humidification (pH₂O ≈ 0.02 atm).     

水冷型和风冷型日晒色牢度试验机

日晒色牢度试验机自诞生以来，经历了转鼓式风冷、转鼓式水冷和平板式风冷三个时期。该文重点分析了风冷和水冷机型的优缺点，并结合日晒色牢度测试的常用标准和实际应用情况，就风冷和水冷机型对检测结果的影响和不同机型之间检测结果的可比性问题，进行了讨论。     

Checking Finite Traces Using Alternating Automata

Alternating automata have been commonly used as a basis for static verification of reactive systems. In this paper we show how alternating automata can be used in runtime verification. We present three algorithms to check at runtime whether a reactive program satisfies a temporal specification, expressed by a linear-time temporal logic formula. The three methods start from the same alternating automaton but traverse the automaton in different ways: depth-first, breadth-first, and backwards, respectively. We then show how an extension of these algorithms, that collects statistical data while verifying the execution trace, can be used for a more detailed analysis of the runtime behavior. All three methods have been implemented and experimental results are presented.     

Does individual or collaborative self-debriefing better enhance learning from games?

The primary aim of this study is to find out whether use of different self-debriefing modes affects learning from a game. In self-debriefing participants are led to reflect upon their game experiences by a set of debriefing questions. Two conditions were compared: Individual and Collaborative self-debriefing. The 45 participants first played the game of Lemonade Tycoon Deluxe, were tested for knowledge and self-debriefed in pairs or alone. Then they played the game once more and were tested again. Game scores increased significantly from the first to the second round of gameplay to an equal degree in both conditions. Knowledge scores of participants in individual self-debriefing increased significantly more than those of participants in the Collaborative condition. The study shows that game-based learning can be effectively scaffolded with self-debriefing. Future studies might investigate whether the type of self-debriefing differentially affects game motivation. In addition, attention to the role of feedback is called for.     

Centrifugal Casting of Tubular Perovskite Membranes

Dense tubular membranes were produced by centrifugal casting of an aqueous suspension, containing powder particles of the mixed-conducting perovskite La_0.5Sr_0.5CoO_3−δ and a dispersant. The resulting green bodies were dried and sintered to produce tubes with a maximum length of 12 cm, having a relative density higher than 92%. The particle morphology, the amount of dispersant and its burnout appeared to influence the quality of the final product. Oxygen permeation measurements were conducted in the temperature range 850°–950°C in Air/He gradients. Results were found to be consistent with data reported for disk-type membranes.     

Possibilities and impossibilities of magnetic nanoparticle use in the control of infectious biofilms

Targeting of chemotherapeutics towards a tumor site by magnetic nanocarriers is considered promising in tumor-control. Magnetic nanoparticles are also considered for use in infection-control as a new means to prevent antimicrobial resistance from becoming the number one cause of death by the year 2050. To this end, magnetic nanoparticles can either be loaded with an antimicrobial for use as a delivery vehicle or modified to acquire intrinsic antimicrobial properties. Magnetic nanoparticles can also be used for the local generation of heat to kill infectious microorganisms. Although appealing for tumor-and infectioncontrol, injection in the blood circulation may yield reticuloendothelial uptake and physical obstruction in organs that yield reduced targeting efficiency. This can be prevented with suitable surface modification. However, precise techniques to direct magnetic nanoparticles towards a target site are lacking. The problem of precise targeting is aggravated in infection-control due to the micrometer-size of infectious biofilms, as opposed to targeting of nanoparticles towards centimeter-sized tumors. This review aims to identify possibilities and impossibilities of magnetic targeting of nanoparticles for infection-control. We first review targeting techniques and the spatial resolution they can achieve as well as surface-chemical modifications of magnetic nanoparticles to enhance their targeting efficiency and antimicrobial efficacy.It is concluded that targeting problems encountered in tumor-control using magnetic nanoparticles, are neglected in most studies on their potential application in infection-control. Currently biofilm targeting by smart, self-adaptive and pH-responsive, antimicrobial nanocarriers for instance, seems easier to achieve than magnetic targeting. This leads to the conclusion that magnetic targeting of nanoparticles for the control of micrometer-sized infectious biofilms may be less promising than initially expected.However, using propulsion rather than precise targeting of magnetic nanoparticles in a magnetic field to traverse through infectious-biofilms can create artificial channels for enhanced antibiotic transport.This is identified as a more feasible, innovative application of magnetic nanoparticles in infection-control than precise targeting and distribution of magnetic nanoparticles over the depth of a biofilm.     

Thermally induced structural and morphological changes of CdSe/CdS octapods

Branched nanostructures are of great interest because of their promising optical and electronic properties. For successful and reliable integration in applications such as photovoltaic devices, the thermal stability of the nanostructures is of major importance. Here the different domains (CdSe cores, CdS pods) of the heterogeneous octapods are shown to have different thermal stabilities, and heating is shown to induce specific shape changes. The octapods are heated from room temperature to 700 °C, and investigated using (analytical and tomographic) transmission electron microscopy (TEM). At low annealing temperatures, pure Cd segregates in droplets at the outside of the octapods, indicating non-stochiometric composition of the octapods. Furthermore, the tips of the pods lose their faceting and become rounded. Further heating to temperatures just below the sublimation temperature induces growth of the zinc blende core at the expense of the wurtzite pods. At higher temperatures, (500-700 °C), sublimation of the octapods is observed in real time in the TEM. Three-dimensional tomographic reconstructions reveal that the four pods pointing into the vacuum have a lower thermal stability than the four pods that are in contact with the support.     

Axisymmetric non-Newtonian drops treated with a boundary integral method

A boundary integral method for the simulation of the time-dependent deformation of axisymmetric Newtonian or non-Newtonian drops suspended in a Newtonian fluid subjected to an axisymmetric flow field is developed. The boundary integral formulation for Stokes flow is used and the non-Newtonian stress is treated as a source term which yields an extra integral over the domain of the drop. By transforming the integral representation for the velocity to cylindrical coordinates we can reduce the dimension of the computational problem. The integral equation for the velocity remains of the same form as in Cartesian coordinates, and the Green's functions are transformed explicitly to cylindrical coordinates. Besides a numerical validation of the method we present simulation results for a Newtonian drop and a drop consisting of an Oldroyd-B fluid. The results for the Newtonian drop are consistent with results from the literature. The deformation process of the non-Newtonian drop for small capillary numbers appears to be governed by two relaxation times.