Investigation of High-Temperature Slag/Copper/Spinel Interactions

Metallurgical and Materials Transactions B - An important cause for the mechanical entrainment of copper droplets in slags during primary and secondary copper production is their interaction with...     

Use of neutron radiography and tomography to visualize the autonomous crack sealing efficiency in cementitious materials

Penetration of moisture into building materials is at the origin of several damage mechanisms. In the case of cement-based materials crack formation is a common problem and highly accelerates the ingress of water and aggressive substances. Crack repair may be needed, however, repair works are expensive and in some cases cracks are even not accessible. Therefore, in this research we aim at autonomous crack sealing. Upon crack appearance, damage is sealed autonomously by the release of encapsulated agents. Visualization of the water uptake by means of neutron radiography for samples with manually and autonomously sealed cracks showed that in both cases ingress of water into the crack can be prevented depending on the type of agent. The efficiency of three different agents was examined and it was shown that the use of polyurethane or a water repellent agent were most promising. Neutron tomography scans demonstrated that poor results were obtained when encapsulated methyl methacrylate was used, since one component of the agent hardened inside the capsules before crack appearance. From the results we can conclude that autonomous sealing of cracks is feasible and that neutron radiography and tomography are suitable non-destructive test techniques to visualize the autonomous crack sealing efficiency.     

Analytical and finite element models of the thermal behavior for lead-free soldering processes in electronic assembly

The development of a simplified analytical model to describe the thermal history of a printed circuit board assembly (PCA) during convective reflow soldering is discussed in this paper. Verification of the assumptions was done by Finite Element Modeling, as well as comparison with experimental measured temperature profiles. The important parameter determining how fast a component heats up is the so called time constant which describes the time needed for the component to reach the set temperature. Comparison between finite element model-based estimations and measured values for three different components, CCGA, PBGA and μBGA, has been made and a reasonable agreement has been obtained.     

Monitoring the setting of concrete containing blast-furnace slag by measuring the ultrasonic p-wave velocity

Ultrasonic transmission measurements allow the continuous monitoring of the setting of both mortar and concrete samples, which is important to determine for instance the formwork removal time. However, aspects such as the cause of the low initial velocity, the relation between the velocity and the setting times and the effect of cement type or cement replacing additives are still under discussion. Therefore, different concrete compositions with blast-furnace slag were tested by traditional as well as ultrasonic measurements.The ultrasonic method gives a more complete picture of the setting. The change of ultrasonic velocity in time is sensitive to the differences in setting behaviour of the tested mixtures. The initial setting seems to correspond with the inflection point of the velocity-vs.-time graphs and the final setting with the point at which the velocity increase levels off.     

Performance assessment of electrospun nanofibers for filter applications

The aim of this study was to evaluate the use of nanofiber microfiltration membranes, spun by an innovative electrospinning technique, in water filtration applications. As such, this study bridges between developments in electrospinning techniques for the production of flat sheet membranes and the application of these membranes in water filtration. Three different applications were examined. First, the use of the membrane (functionalized or non-functionalized) for the removal of pathogens was investigated. Second the electrospun flat sheet membranes were applied in a lab scale submerged membrane bioreactor (MBR). Third, the electrospun membranes were applied as stand-alone filter for water treatment. Next to these applications, physical properties such as clean water permeability (CWP) and strength were also examined. The test showed that the electrospun membranes can be used for water filtration applications, but that further research is necessary towards irreversible fouling properties and level of functionalisation.     

A single bioavailability model can accurately predict Ni toxicity to green microalgae in soft and hard surface waters

The major research questions addressed in this study were (i) whether green microalgae living in soft water (operationally defined water hardness <10 mg CaCO₃/L) are intrinsically more sensitive to Ni than green microalgae living in hard water (operationally defined water hardness >25 mg CaCO₃/L), and (ii) whether a single bioavailability model can be used to predict the effect of water hardness on the toxicity of Ni to green microalgae in both soft and hard water. Algal growth inhibition tests were conducted with clones of 10 different species collected in soft and hard water lakes in Sweden. Soft water algae were tested in a ‘soft’ and a ‘moderately hard’ test medium (nominal water hardness = 6.25 and 16.3 mg CaCO₃/L, respectively), whereas hard water algae were tested in a ‘moderately hard’ and a ‘hard’ test medium (nominal water hardness = 16.3 and 43.4 mg CaCO₃/L, respectively). The results from the growth inhibition tests in the ‘moderately hard’ test medium revealed no significant sensitivity differences between the soft and the hard water algae used in this study. Increasing water hardness significantly reduced Ni toxicity to both soft and hard water algae. Because it has previously been demonstrated that Ca does not significantly protect the unicellular green alga Pseudokirchneriella subcapitata against Ni toxicity, it was assumed that the protective effect of water hardness can be ascribed to Mg alone. The log K_MgBL (= 5.5) was calculated to be identical for the soft and the hard water algae used in this study. A single bioavailability model can therefore be used to predict Ni toxicity to green microalgae in soft and hard surface waters as a function of water hardness.     

(+)-Catechin Attenuates Multiple Atherosclerosis-Associated Processes In Vitro,Modulates Disease-Associated Risk Factors in C57BL/6J Mice and Reduces Atherogenesis in LDL Receptor Deficient Mice by Inhibiting Inflammation and Increasing Markers of Plaque Stability

Scope

A prospective study of 34492 participants shows an inverse association between (+)-catechin intake and coronary heart disease. The effects of (+)-catechin on atherosclerosis and associated risk factors are poorly understood and are investigated.

Methods and results

(+)-Catechin attenuates reactive oxygen species production in human macrophages, endothelial cells and vascular smooth muscle cells, chemokine-driven monocytic migration, and proliferation of human macrophages and their expression of several pro-atherogenic genes. (+)-Catechin also improves oxidized LDL-mediated mitochondrial membrane depolarization in endothelial cells and attenuates growth factor-induced smooth muscle cell migration. In C57BL/6J mice fed high fat diet (HFD) for 3 weeks, (+)-catechin attenuates plasma levels of triacylglycerol and interleukin (IL)-1β and IL-2, produces anti-atherogenic changes in liver gene expression, and reduces levels of white blood cells, myeloid-derived suppressor cells, Lin⁻ Sca⁺ c-Kit⁺ cells, and common lymphoid progenitor cells within the bone marrow. In LDL receptor deficient mice fed HFD for 12 weeks, (+)-catechin attenuates atherosclerotic plaque burden and inflammation with reduced macrophage content and increased markers of plaque stability; smooth muscle cell and collagen content.

Conclusion

This study provides novel, detailed insights into the cardio-protective actions of (+)-catechin together with underlying molecular mechanisms and supports further assessments of its beneficial effects in human trials.     

Engineered Platelet-Derived Growth Factor-Releasing Hydrogels Promote Fetal Membrane Healing In Vivo

Fetoscopic interventions to treat fetal anomalies are currently performed for a variety of conditions. Depending on the procedure, preterm rupture of the fetal membranes (FMs) happens in around 30% of the cases, potentially leading to preterm birth and fetal morbidity and mortality. Here, the capacity of modular transglutaminase crosslinked poly(ethylene glycol) (TG-PEG) hydrogels that release platelet-derived growth factor (PDGF)-BB to promote FM healing is described. In vitro, such growth factor-loaded hydrogels are able to stimulate amniotic cell migration and proliferation. When applied in vivo, these TG-PEG hydrogels tightly seal the FM and uterus defects created by a fetoscope and remain stable for 10 days. The migration of healing-related cells into such hydrogels in the myometrium, endometrium, and FM areas is only possible in soft TG-PEG hydrogels. Importantly, bioengineered hydrogels releasing PDGF-BB promote recruitment of host cells from the myometrium and the endometrium, and to a lesser extent from FM areas. In such hydrogels, the potent proliferation and matrix production of the recruited cells at the site of treatment into the biomaterial initiates a robust early healing response. PDGF-BB-loaded TG-PEG hydrogels hold great promise for the treatment of fetoscopy-induced FM defects and for the prevention of preterm birth.     

Reaction and thermal behavior of vitrimer-like polyhydroxy esters based on polyethylene glycol diglycidyl ether

Vitrimers-like polyhydroxy esters networks were thermally synthesized from mixtures of the diepoxide monomer diglycidyl ether polyethyleneglycol (DGEPEG), citric (CA), and sebacic acids (SA), using zinc acetate in proportions of 1 to –5 mol%. as catalyst for bond exchange reactions. Reaction of DGEPEG with the acids is exothermic with enthalpy up to 326 J/g and takes place even without any catalyst. The progress of the reaction is reduced as the content of SA is increased in the formulations, but reaction enthalpy in mixtures containing 1% of Zn catalyst is higher than those with 5%mol Zn. These polyhydroxy esters networks are rubber-like materials with T_g varying from −24 to −43°C, with formulations containing SA showing the lowest T_g values. The presence of ester and hydroxyl groups and Zn catalyst in the polymers give rise to exchange reactions similar to those shown by vitrimers. However, the increase in Zn concentration from 1% to 5%, arouses a loss of thermal stability of these materials.     

An image acquisition system for real-time seam tracking

Process planning is a function that establishes the technological requirements necessary to convert a part from its raw material to the finished form. Generally, the result of process planning is delivered to the workshop to guide the manufacturing process in the form of process plan. However, a part always has multi alternative process plans for the processing means and techniques are not unique, therefore, optimization and selection of process plans is an important task of flexible process planning. In this paper, the flexibility of process planning and the AND/OR network adopted to represent the flexibility of process plans were described, and a mathematical model for the optimization of flexible process planning based on the AND/OR network was established. On this basis, a new heuristic method, called cross-entropy (CE) approach, was proposed to optimize flexible process planning. In order to facilitate the implementation of the CE-based approach, the new sample representation and probability distribution parameter were introduced; meanwhile, the new sample generation mechanism was presented and the updating expression of probability distribution parameter was deduced. Case studies, used for comparing this approach with genetic algorithm (GA) and genetic programming (GP)-based approach, were discussed to indicate the performance and adaptability of the proposed CE-based approach in terms of the solution quality and computational efficiency of the algorithm. The results show that the CE-based approach is effective for the optimization research of flexible process planning.