The Relation between Calcium Sequestering Capacity and Oxidation Degree of Dicarboxy-Starch and Dicarboxy-Inulin

The objective of this study was to establish the relation between the calcium sequestering capacity (SC) of dicarboxy-starch and that of dicarboxy-inulin, and the oxidation degree of these products. An S-type curve is obtained when plotting the SC of oxidized starch versus the degree of oxidation. By contrast the sequestering capacity of dicarboxy-inulin increases linearly with the degree of oxidation. The difference in behaviour of these materials can be attributed to the fact that upon starch oxidation the favourable oxydiacetate structure is obtained only after substantial conversion, whereas in inulin this structure is obtained immediately and is present in each oxidized fructose unit.     

Synthesis of Alkyl Fructosides

The anomeric alkylation of D-fructose is efficiently catalyzed by mild acid catalysts. Degradation of fructose is negligible under the conditions applied.     

自由之鸟与牢笼:二战后十年间荷兰建筑期刊考

本文追溯了二战后十年间《建造周刊》《论坛》《天主教建筑期刊》等重要期刊的创立(重建)与发展的历史,管窥战后荷兰专业建筑期刊业的全貌。文章讨论了展现在战后荷兰建筑期刊中的多元思想——米拉斯所代表的中间路线,J·B·巴克马、J·H·凡·登·布鲁克、A·E·凡·艾克代表的新一代先锋思潮,J·朗普雷·莫里哀领导下的战后传统主义,巴克马对"自由"的解读等。本文是一篇呈现荷兰战后建筑界思想发展驱动力与思想交锋的文章。     

Coordination‐Assisted Bioorthogonal Chemistry: Orthogonal Tetrazine Ligation with Vinylboronic Acid and a Strained Alkene

Bioorthogonal chemistry can be used for the selective modification of biomolecules without interfering with any other functionality that might be present. Recent developments in the field include orthogonal bioorthogonal reactions to modify multiple biomolecules simultaneously. During our research, we observed that the reaction rates for the bioorthogonal inverse‐electron‐demand Diels–Alder (iEDDA) reactions between nonstrained vinylboronic acids (VBAs) and dipyridyl‐s‐tetrazines were exceptionally higher than those between VBAs and tetrazines bearing a methyl or phenyl substituent. As VBAs are mild Lewis acids, we hypothesised that coordination of the pyridyl nitrogen atom to the boronic acid promoted tetrazine ligation. Herein, we explore the molecular basis and scope of VBA–tetrazine ligation in more detail and benefit from its unique reactivity in the simultaneous orthogonal tetrazine labelling of two proteins modified with VBA and norbornene, a widely used strained alkene. We further show that the two orthogonal iEDDA reactions can be performed in living cells by labelling the proteasome by using a nonselective probe equipped with a VBA and a subunit‐selective VBA bearing a norbornene moiety.     

Heat transfer effects in nano-aluminum combustion at high temperatures

Recent measurements of nano-aluminum combustion in which burning time and peak particle temperature are measured simultaneously have suggested that heat transfer models currently used for burning nanoparticles may significantly overestimate heat losses during combustion. By applying conventional non-continuum heat transfer correlations to burning nano-aluminum particles, the observed peak temperatures, which greatly exceed the ambient temperature, should only be observable if the burning time were very short, of the order of 1 μs, whereas the observed burning time is two orders of magnitude larger. These observations can be reconciled if the energy accommodation coefficient for these conditions is of the order of 0.005, which is the value suggested by Altman, instead of approximately unity, which is the common assumption. Experimental data obtained in the heterogeneous shock tube under a wide array of conditions are compared with basic heat transfer models, and the agreement of both peak temperature values and emission intensity traces for low energy accommodation coefficients supports the hypothesis of Altman and co-workers.     

Sugarcane bagasse cellulose/HDPE composites obtained by extrusion

Natural fibers used in this study were both pre-treated and modified residues from sugarcane bagasse. Polymer of high density polyethylene (HDPE) was employed as matrix in to composites, which were produced by mixing high density polyethylene with cellulose (10%) and Cell/ZrO₂·nH₂O (10%), using an extruder and hydraulic press. Tensile tests showed that the Cell/ZrO₂·nH₂O (10%)/HDPE composites present better tensile strength than cellulose (10%)/HDPE composites. Cellulose agglomerations were responsible for poor adhesion between fiber and matrix in cellulose (10%)/HDPE composites. HDPE/natural fibers composites showed also lower tensile strength in comparison to the polymer. The increase in Young’s modulus is associated to fibers reinforcement. SEM analysis showed that the cellulose fibers insertion in the matrix caused an increase of defects, which were reduced when modified cellulose fibers were used.     

The Effect of Ketone Defects on the Charge Transport and Charge Recombination in Polyfluorenes

The effect of on‐chain ketone defects on the charge transport of the polyfluorene derivative poly(9,9‐dioctylfluorene) (PFO) is investigated. Using MoO₃ as ohmic hole contact, the hole transport in a pristine PFO diode is observed to be limited by space‐charge, whereas fluorenone contaminated PFO (PFO‐F) is shown to be trap limited by the occurrence of an exponential trap distribution with a trap depth of 0.18 eV. The electron transport in PFO is also observed to be trap limited, but in order to describe the electron transport of PFO‐F, an additional trap level with a depth of 0.46 eV must be introduced. The obtained energy levels of the fluorenone trapping sites are in close agreement with cyclic voltammetry (CV) measurements reported in literature. As a result, the fluorenone defects are shown to simultaneously act as hole‐ and electron trap. Moreover, through ideality factor measurements, the green emission associated with these defects is observed to originate from trap‐assisted recombination.     

The effects of asymmetrical cold rolling on kinetics,grain size and texture in IF steels

Asymmetrical rolling is a promising way to achieve high rolling reductions and potentially grain refinement. However in steels the effect of asymmetrical rolling is not thoroughly quantified. In this paper the impact of cold asymmetrical rolling obtained by changing the roll velocity ratio (from 1.1 to 1.45) on the deformation and recrystallization features has been finely investigated by Electron Back-Scattering Diffraction in a Scanning Electron Microscope. In the investigated conditions (with low thickness reduction), it is found that asymmetrical rolling induces grain refinement and more homogeneous gamma fiber texture.