Porous functionalized polymers enable generating and transporting hyperpolarized mixtures of metabolites

Hyperpolarization by dissolution dynamic nuclear polarization (dDNP) has enabled promising applications in spectroscopy and imaging, but remains poorly widespread due to experimental complexity. Broad democratization of dDNP could be realized by remote preparation and distribution of hyperpolarized samples from dedicated facilities. Here we show the synthesis of hyperpolarizing polymers (HYPOPs) that can generate radical- and contaminant-free hyperpolarized samples within minutes with lifetimes exceeding hours in the solid state. HYPOPs feature tunable macroporous porosity, with porous volumes up to 80% and concentration of nitroxide radicals grafted in the bulk matrix up to 285 μmol g−1. Analytes can be efficiently impregnated as aqueous/alcoholic solutions and hyperpolarized up to P(13C) = 25% within 8 min, through the combination of 1H spin diffusion and 1H → 13C cross polarization. Solutions of 13C-analytes of biological interest hyperpolarized in HYPOPs display a very long solid-state 13C relaxation times of 5.7 h at 3.8 K, thus prefiguring transportation over long distances.

Phonon Scattering and Suppression of Bipolar Effect in MgO/VO2 Nanoparticle Dispersed p-Type Bi0.5Sb1.5Te3 Composites

Bismuth-Telluride-based compounds are unique materials for thermoelectric cooling applications. Because Bi2Te3 is a narrow gap semiconductor, the bipolar diffusion effect is a critical issue to enhance thermoelectric performance. Here, we report the significant reduction of thermal conductivity by decreasing lattice and bipolar thermal conductivity in extrinsic phase mixing of MgO and VO2 nanoparticles in Bi0.5Sb1.5Te3 (BST) bulk matrix. When we separate the thermal conductivity by electronic κel, lattice κlat, and bipolar κbi thermal conductivities, all the contributions in thermal conductivities are decreased with increasing the concentration of oxide particle distribution, indicating the effective phonon scattering with an asymmetric scattering of carriers. The reduction of thermal conductivity affects the improvement of the ZT values. Even though significant carrier filtering effect is not observed in the oxide bulk composites due to micro-meter size agglomeration of particles, the interface between oxide and bulk matrix scatters carriers giving rise to the increase of the Seebeck coefficient and electrical resistivity. Therefore, we suggest the extrinsic phase mixing of nanoparticles decreases lattice and bipolar thermal conductivity, resulting in the enhancement of thermoelectric performance over a wide temperature range.

Feeding the team: Analysis of a Spratt’s dog cake from Antarctica

The use of Spratt’s dog cakes is well documented in the diaries and reminiscences of many early Antarctic expedition members. Commercially produced dog food was promoted by the likes of Spratt’s as an advanced form of animal nutrition and would have been of interest to expedition planners who were already concerned with the nutritional requirements of expedition members. An approximately 100-year-old dog cake recovered from Antarctica was compared by chemical analysis and spectroscopic methods with a series of model dog cakes and a commercial dog biscuit to determine the composition and calorific content. The presence of bone fragments within the dog cake was confirmed, whereas starch in the bulk matrix of the sample was consistent with being a mixture of wheat and oat flour, while only minimal fat or oil was present. Calorific content, while insufficient compared to a modern feed for high-performance dogs, would nonetheless have been a valuable addition to the use of dried or frozen whole meat such as seal, fish, or pemmican and contributed additional energy compared to meat alone.

Comparative study of sucrose plasticised bioplastic derivatives with selected petro-plastics

The major setback with most bioplastics is their inherent inability to compete with Petro-plastics in terms of high production cost, and there poor mechanical properties like low tensile strength and percentage extension. This study explore the availability and affordability of mango starch as raw material for bioplastic production and compared some of its mechanical properties with High density Polyethylene (HDPE), Low density polyethylene (LDPE), polyvinyl chloride (PVC), and Polyurethane (PU). Mango starch was used to synthesize bioplastic derivatives, with variable levels of sucrose as plasticiser, aqueous HCl concentration and Carboxymethyl cellulose (CMC) as additive and the mechanical properties of the derived biofilms was measured and compared with the selected Petro-plastics films. It was observed that B1 thermoplastic derivatives have the higher young modulus of 5.658 GPa than that obtained for PVC (4.682 GPa), and PU (3.771 GPa) but show no significant difference and significantly higher than that of HDPE (0.049 GPa), and LDPE (0.063 GPa) (p < 0.05). B2 and B3 indicated a young modulus that is significantly lower than PU and PVC, but showed a young modulus that is higher than LDPE and HDPE with no significant difference (p < 0.05). The FTIR spectra indicate that hydrogen bond was formed in the bulk matrix of the bioplastic derivatives at a band region of 3600 -600 cm-1 wavenumber with broad discrete peaks. Keywords: Petro-plastics; Bioplastics; Mechanical Properties; Plasticization; Mango Starch

The Effect of Soaking on Segregation and Primary-Carbide Dissolution in Ingot-Cast Bearing Steel

In this work, segregation in the cast and hot worked structure, as well as the effects of soaking on macro and micro segregation, in hypereutectoid bearing steel produced by ingot casting were studied. Samples were selected from ingots that where either as cast or soaked for twenty hours. Two similar bearing steel grades were used for this investigation. For the as cast ingot, samples were selected from both A-segregation channel regions and the matrix region. Samples were also selected from hot-worked bars originating from ingots that had been soaked for four hours or twenty hours. Micro and macro examinations of the microstructures were conducted and compared. In addition, a segregation analysis of the substitutional solute elements was performed using EDX equipment mounted on a Scanning Electron Microscope (SEM). EMPA mapping of the composition pattern in the bulk, as well as the carbides, was conducted. Precipitation of M3C, M2C, and M6C was observed. The carbides at A-segregation channels were found to have a different morphology to those precipitated in the bulk matrix. After soaking at 1200 °C for 4 h, all the primary carbides are dissolved.

Influence of Interfacial Transition Zone on Local and Overall Fracture Response of Cementitious Composites

Mechanical fracture properties of interfacial transition zone (ITZ) of fine-grained composite based on cement matrix with different types – basalt, granite, marble and amphibolite – of rock inclusion were studied. Specimens with the initial stress concentrator were tested in standard three-point bending configuration. Fracture surfaces were examined with light and electron microscopes. Local ITZ response was characterized by nanoindentation in the vicinity of rock inclusions. Local elasticity, hardness and viscous properties were assessed. It has been shown that the ITZ is mechanically weaker compared to the bulk matrix in the region of ca. 0–20 μm from the inclusion for all specimen’s types. It exhibits gradual increase of elastic modulus and hardness, which can be approximately expressed by a power law. On the other hand, the creep in ITZ was found to be higher compared to the bulk matrix. The results of nanoindentation measurements are in a good agreement with overall mechanical properties, fracture response and microstructure measurements done by scanning electron microscopy.

Stray Current Induced Corrosion Control in Reinforced Concrete by Addition of Carbon Fiber and Silica Fume

ABSTRACTStray current arising from direct current electrified traction systems and then circulating in reinforced concrete near railways is known to induce corrosion on embedded steel reinforcement. The present paper will review the principles of stray current induced corrosion in reinforced concrete, which is relatively uncommon but with significant impact in practice.Within one of the approaches to ease this kind of specific corrosion in reinforced concrete, carbon fibres (CF) can be added to enhance the conductivity of concrete, subsequently reduce the stray current density and/or direct the stray current dissipation in a desired manner. The side effects (such as increasing the bulk matrix porosity) caused by CF, which can in turn reduce the general corrosion resistance of reinforced concrete, will be compensated by adding silica fume (SF). The combination of CF and SF can be a potentially feasible and original application to reduce the risk of stray current induced corrosion in reinforced concrete, without obvious negative side effects.