Asymmetric One‐Pot Conjugate Addition of Grignard Reagents to α,β‐Unsaturated Compounds Followed by Reaction with Carbenium Ions

Asymmetric catalytic multistep reactions enable the formation of structurally complex compounds from simple starting materials. Enantioselective Cu‐catalyzed 1,4‐additions of Grignard reagents to Michael acceptors form reactive chiral enolates. We show here that these chiral enolates react in a one‐pot fashion with naked carbenium ions, such as tropylium, 1,3‐benzodithiolium, and dianisylmethylium ions. The corresponding products were obtained in good yields, with enantioselectivities up to 96% ee and high diastereomeric purities.

     

Modeling of temperature field and grain growth of a dual phase steel DP980 in direct diode laser heat treatment

The temperature field due to heating from a high-powered direct diode laser is calculated first by using an experiment-based finite element model. The Monte Carlo method is applied, which uses the calculated temperature history as thermal loading to obtain the grain growth in the heat-affected zone (HAZ) of dual phase steel DP980. The martensite decomposition in the heat treatment is considered to be a function of the scanning speed. Numerical results demonstrate that the increased scanning speed of the laser beam under laser power of 2 kW decreases the temperature gradient in the HAZ, resulting in finer martensite grains and a smaller percentage of martensite decomposition in the HAZ. This is in good agreement with the experimental data.     

Cooking oils and fat waste collection infrastructure planning: a regional-level outline

Clean Technologies and Environmental Policy - Among the current trends in waste management and circular economy is the involvement of new fractions of waste for sorting and collection. One of them...     

Metallization‒induced recombination losses of bifacial silicon solar cells

In this study, we investigate the metallization‒induced recombination losses of high efficiency bifacial n‒type and p‒type crystalline Si solar cells. From the experimental data, we found that the most efficiency limiting parameter by the screen‒printed metallization is the open‒circuit voltage (V_OC) of the cells. We investigated the mechanism responsible for this loss by varying the metallization fraction on either side of the cell and determined the local enhancement in the dark saturation current density beneath the metal contacts (J_0(met)). Under optimum fabrication conditions, the J_0(met) at metal‒p⁺ (boron) emitter interfaces was found to be significantly higher compared with the values obtained for metal‒n⁺ emitters. A two‒dimensional simulation model was used to get further insight into the recombination mechanism leading to these V_OC losses. The model assumes that metal contacts penetrate (or etch) into the diffused region following the firing process and depassivate the interface. Applying this model to our n‒type solar cells with a boron p⁺ emitter, we demonstrated that the simple loss of passivated area beneath the metal contact cannot explain the degradation observed in the V_OC of the cell without considering a significant etching or metal penetration into the emitter region. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental and numerical modelling comparison of thermal performance of expanded polystyrene and corrugated plastic packaging for fresh fish

Experiments were carried out to compare the thermal performance of wholesale fresh fish boxes made of corrugated plastic (CP) and expanded polystyrene (EPS). Free standing boxes containing whole, fresh fillets were exposed to dynamic thermal loads. The chilling effect of frozen ice packs was studied by including them in some of the boxes. The frozen ice packs proved efficient for protecting fresh fish fillets against temperature abuse. Furthermore, the results show that the insulating performance of EPS is significantly better than the insulating capacity of CP. Maximum fish temperature of 16.1 °C (CP) and 11.0 °C (EPS) were recorded inside the thermally abused boxes without ice packs, initially at 1.9 to 2.1 °C and stored for 6.1 h at a mean ambient temperature of 19.4 °C. The fish temperature distributions during thermal abuse were studied with a numerical model for both packaging types, applying effective thermal properties of the sandwich-structured CP box. The purpose of the model was to cost effectively improve the packaging design. A satisfactory agreement between numerical results and experimental results was obtained.     

Analysis of miR-9-5p,miR-124-3p,miR-21-5p,miR-138-5p,and miR-1-3p in Glioblastoma Cell Lines and Extracellular Vesicles

Glioblastoma (GBM), the most common primary brain tumor, is a complex and extremely aggressive disease. Despite recent advances in molecular biology, there is a lack of biomarkers, which would improve GBM’s diagnosis, prognosis, and therapy. Here, we analyzed by qPCR the expression levels of a set of miRNAs in GBM and lower-grade glioma human tissue samples and performed a survival analysis in silico. We then determined the expression of same miRNAs and their selected target mRNAs in small extracellular vesicles (sEVs) of GBM cell lines. We showed that the expression of miR-21-5p was significantly increased in GBM tissue compared to lower-grade glioma and reference brain tissue, while miR-124-3p and miR-138-5p were overexpressed in reference brain tissue compared to GBM. We also demonstrated that miR-9-5p and miR-124-3p were overexpressed in the sEVs of GBM stem cell lines (NCH421k or NCH644, respectively) compared to the sEVs of all other GBM cell lines and astrocytes. VIM mRNA, a target of miR-124-3p and miR-138-5p, was overexpressed in the sEVs of U251 and U87 GBM cell lines compared to the sEVs of GBM stem cell line and also astrocytes. Our results suggest VIM mRNA, miR-9-5p miRNA, and miR-124-3p miRNA could serve as biomarkers of the sEVs of GBM cells.     

Numerical modelling of temperature fluctuations of chilled and superchilled cod fillets packaged in expanded polystyrene boxes stored on pallets under dynamic temperature conditions

Temperature variations in cod fillets packaged in four levels of EPS boxes stored on pallets under thermal load were studied numerically and experimentally. In the experiment the fillet temperature along with environmental temperature were monitored at 39 positions on the pallets during 9-h dynamic temperature storage between 7 and 23 °C. A three-dimensional time-dependent heat transfer model was developed using the ANSYS FLUENT Computational Fluid Dynamics (CFD) software. The overall mean absolute error of the model was 0.3 °C and the maximum error obtained at a single position over the whole period was 2.4 °C. The model was further developed in order to simulate temperature evolution inside a fully loaded, 12-level pallet under the same dynamic temperature conditions as a four-level pallet studied before. The mean temperature after 9-h thermal load was 1.0 °C lower in the 12-level pallet but the maximum temperature evolution was similar in both pallets. Finally, the model was used to investigate the temperature-maintaining effect of superchilling fish before the thermal load.     

The Fracture of Concrete due to Erosive Wear by High Velocity Water Flow

Wear and erosion of concrete structures by high velocity water flow is a basic aspect of the durability of marine and water constructions. The mechanism of concrete failure in such constructions is not well understood. Using high velocity water jets for simulating the loading, the authors observed the general behavior of the material during failure and investigated the influence of water velocity and exposure time. The results show that the interface between hardened cement paste and aggregate grains plays the main role in the fracture process. The basic mechanism of material failure is the generation and propagation of cracks at this interface. It is found that a critical loading intensity, which is characterized by a threshold velocity and a threshold exposure time, must be achieved in order to induce the erosion process. Through mass removal measurements, a mathematical relation between both parameters and the erosion intensity is found. Using a computer program for simulating the hydrodynamics inside a crack, the water pressure and flow velocities in a model crack were calculated.