Towards a Fundamental Understanding of the Improved Electrochemical Performance of Silicon–Carbon Composites

Silicon–carbon composites consisting of Si particles embedded in a dense and non‐porous carbon matrix are prepared by the pyrolysis of intimate mixtures of poly(vinyl chloride) (PVC) and Si powder at 900 °C under a flow of N₂. In contrast to bare micrometer‐sized (1–10 μm) and nanometer‐sized (10–100 nm) Si powders, which show poor cycling behavior with almost no capacity remaining after 15 cycles, the texture of the composite is seen to greatly enhance the reversibility of the alloying reaction of Si with Li. For instance, a capacity of ca. 1000 mA h g^–1 is achieved for 20 cycles (0–2.0 V vs. Li⁺/Li) for a silicon–carbon composite containing nanometer‐sized Si particles. We also demonstrate that a mild manual grinding treatment degrades the cycling performance of the composites to levels as low as the parent Si, even though free Si is not released. The electrochemical measurements in conjunction with Raman spectroscopy data indicate that a huge stress is exerted on the Si domains by the in situ formed carbon. This carbon‐induced stress is found to disappear during the milling of the composites, indicating that the carbon‐induced pressure, along with the accompanying improvement in electrical connectivity, are the key parameters for the improved cycling behavior of Si versus Li.     

Effect of the nonenzymatic glycosylation of high density lipoprotein-3 on the cholesterol ester transfer protein activity

This study examines the relationship between high density lipoprotein-3 (HDL-3) glycation and cholesteryl ester transfer mediated by cholesteryl ester transfer protein (CETP). HDL-3 were glycated with various glucose concentrations (0–200 mM) for 3 d at 37°C with sodium cyanoborohydride as reducing agent and antioxidants. About 47% of the lysine residues were glycated in the presence of 200 mM glucose, resulting in an increase in the cholesterol ester (CE) transfer of about 30%. Apparent kinetic parameters [expressed as maximal transfer (appT _max) and CE concentration at half of T _max (appK _H)] of CETP activity with glycated HDL-3 showed conflicting and paradoxical data: an increase in CETP activity associated with a decrease of CETP affinity. These alterations were not due to a change in HDL-3 lipid and protein composition nor to a peroxidative process but were associated with an increase in HDL-3 electronegativity and a decrease of HDL-3 fluidity. This study suggests that glycation modifies the apolipoprotein’s conformation and solvation which are major determinants of interfacial properties of HDL-3. These modifications in turn affect CETP reactivity.     

Characterization of meso-scale mechanical properties of Longmaxi shale using grid microindentation experiments

Mechanical properties,such as the hardness H,Young's modulus E,creep modulus C,and fracture toughness Kc,are essential parameters in the design of hydraulic fracturing systems for prospective shale gas formations.In this study,a practical methodology is presented for obtaining these properties through microindentation experiments combined with quantitative observations of the mineralogical phases using X-ray diffraction(XRD),scanning electron microscopy(SEM) with backscattered electron(BSE)imaging,and energy-dispersive X-ray spectroscopy(EDS) analyses.We apply this method in the case of three types of Longmaxi shales with different mineralogies(i.e.carbonate-,clay-,and quartz-rich,respectively),which allows us to determine the characteristic indentation depth,h_c=8-10 μm,beyond which the mechanical response of the carbonate-rich shale is homogeneous and independent of its complex heterogeneous microstructure.Moreover,exploiting the results of a large number of indentation tests,we demonstrate that the indentation modulus M of the shale increases as a power-law of hardness H,and its creep modulus C increases linearly with H.We also compute the fracture toughness Kc from the indentation data by assuming a perfectly plastic behavior of the sample.Our results are in good agreement with independent measurements of Kc determined by microscratch tests.Finally,further tests on quartz-and clay-rich samples of the Longmaxi shale suggest further variations in the samples' mechanical properties depending on their burial conditions and the mechanical properties of their dominant mineral phases.     

Carnobacterium maltaromaticum: Identification,isolation tools,ecology and technological aspects in dairy products

Carnobacterium species constitute a genus of Lactic Acid Bacteria (LAB) present in different ecological niches. The aim of this article is to summarize the knowledge about Carnobacterium maltaromaticum species at different microbiological levels such as taxonomy, isolation and identification, ecology, technological aspects and safety in dairy products. Works published during the last decade concerning C. maltaromaticum have shown that this non-starter LAB (NSLAB) could present major interests in dairy product technology. Four reasons can be mentioned: i) it can grow in milk during the ripening period with no competition with starter LAB, ii) this species synthesizes different flavouring compounds e.g., 3-methylbutanal, iii) it can inhibit the growth of foodborne pathogens as Listeria monocytogenes due to its ability to produce bacteriocins, iv) it has never been reported to be involved in human diseases as no cases of human infection have been directly linked to the consumption of dairy products containing this species.     

Multi-Material 3D Microprinting of Magnetically Deformable Biocompatible Structures

Two-photon polymerization (2PP) allows precise 3D printing at the micrometer scale, and by associating it with magnetic materials, the creation of remotely actuatable micro-structures. Such structures attract a growing interest for biomedical applications, thanks to their size and to the biocompatibility of some photoresist materials. Gelatin methacryloyl (Gel-MA) is one such material, and can be used to create physiological scaffolds for cell culture. Here, the physico-chemical properties of two resins are exploited, the first being a silica-based hybrid polymer, the OrmoComp, and the second a Gel-MA-based hydrogel. A 2PP manufacturing protocol is defined and designed to print both materials in succession as a single structure, which is then linked to a neodymium-iron-boron (NdFeB) magnetic bead for actuation. By this combination, a magnetically deformable 3D culture substrate is created to study cells in an environment that mimics soft, curved, and dynamic properties of tissues in vivo. The structure is actuated via an external magnetic field and bends back and forth along its longest axis. Lastly, preliminary cell culture trials are conducted showing the proliferation of cells on the structures.