Distribution of carbon contamination in MgAl2O4 spinel occurring during spark-plasma-sintering (SPS) processing: I – Effect of heating rate and post-annealing

Carbon contamination from the carbon paper/dies during spark-plasma-sintering (SPS) processing was examined in the MgAl₂O₄ spinel. The carbon contamination sensitively changes with the heating rate during the SPS processing. At the high heating rate of 100 °C/min, the carbon contamination having organized structures occurred over almost the entire area from the surface to deep inside the SPSed spinel disk. In contrast, at the slow heating rate of 10 °C/min, the carbon contamination having disordered structures occurred only around the surface area. The carbon phases transform into high pressure CO/CO₂ gases by post-annealing in air and lead to pore formation along the grain junctions. The pore formation significantly occurs at the high heating rate due to the large amount of the contaminant carbon phases. This suggests that if once the carbon contamination was formed in the materials, it is very difficult to remove the carbon phases from the materials.     

Transport of oxygen and carbon dioxide through polycarbonate membrane

Sorption equilibria and permeation rates for oxygen and carbon dioxide in polycarbonate membrane were measured at different temperature between 30 and 60°C and at pressures up to 2.5 MPa. The pressure dependence of mean permeability coefficient to oxygen obeyed the conventional dual-mode mobility model, whereas that to carbon dioxide followed a modified dual-mode mobility model with concentration-dependent diffusivities, as that of polystyrene to the same gas did.     

Sustained photobiological hydrogen production in the presence of N2 by nitrogenase mutants of the heterocyst-forming cyanobacterium Anabaena

Heterocyst-forming cells of the cyanobacterium Anabaena sp. strain PCC 7120 ΔHup, lacking an uptake hydrogenase, photobiologically produce H₂ by nitrogenase. Under N₂-rich atmosphere, the nitrogenase activity declines in a rather short time due to the sufficiency of combined nitrogen. From the parental ΔHup strain, site-directed double-crossover variants, dc-Q193S and dc-R284H, were created with amino acid substitutions presumed to be located in the vicinity of the FeMo-cofactor of nitrogenase. Unlike the case for the ΔHup strain, H₂ production activities of the variants were not decreased by the presence of high concentrations of N₂ and they continuously produced H₂ over 21 days with occasional headspace gas replacement. This property of N₂ insensitivity is a potentially useful strategy for reducing the cost of the culture gas in future practical applications of sustainable biofuel production. This Anabaena strain has only the Mo-containing nitrogenase which reduces acetylene to ethylene, but the dc-Q193S variant also produced ethane at low but measurable rates along with greater rates of ethylene production.     

Development of biobased microwave absorbing composites with various magnetic metals and carbons

The preparation and characterization of a biobased electromagnetic absorbing composites derived from natural lacquer as a renewable resource with microwave‐absorption fillers, including Ni–Zn ferrite and carbonyl iron (CI) as magnetic metals and soot and carbon nanotube (CNT) as carbon materials, were investigated in terms of the gel content, hardness, drying properties, and electromagnetic absorption properties. Interestingly, composites with ferrite and CI contained up to 320 and 550 wt %, respectively, of these compounds. This quite high loading capacity of the metal fillers in a natural‐lacquer base could have been due to the high compatibility between the filler and the natural lacquer; this indicated that the natural lacquer worked as a binder for these metals. The morphology of the biobased composite was characterized by scanning electron microscopy. The electromagnetic absorption properties of composites were characterized in the frequency range from 0.05 and 20 GHz by the reflection loss (RL) measurement method in terms of the kind of fillers and filler loading. The natural lacquer did not affect the absorption properties of the fillers. Biobased composites showed over 99% electromagnetic absorption in the frequency range 3.0–4.0 GHz for 280 wt % ferrite and 8.9–9.7 GHz for 200 wt % CI. Conversely, 10 and 20 wt % soot exhibited good performance (RL < ?20 dB) between 16.5 and 17.3 and between 8.8 and 9.2 GHz, respectively. The areas with RL values of less than ?20 dB of the CNT composites were 10.4–11.0 GHz for 5 wt % and 14.6–15.2 GHz for 10 wt %. Hence, natural lacquer can be used as a binder material for electromagnetic absorption composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44131.     

Calcitonin gene-related peptide (CGRP)-containing nerve fibers in bone tissue and their involvement in bone remodeling

Bone remodeling is a process of bone renewal accomplished by osteoclastic bone resorption and osteoblastic bone formation. These two activities are regulated by systemic hormones and by local cytokines and growth factors. Moreover, the nervous system and certain neuropeptides seem to be involved in regulation of bone remodeling. In this paper, we focus on the distribution of CGRP-containing nerve fibers and their dynamics, and discuss the role of these fibers as a possible mechanism for nervous system involvement in regulation of bone remodeling. CGRP-immunoreactive nerve fibers are widely distributed in bone tissue, such as periosteum and bone marrow, and show apparent regional distribution with different densities. They are often associated with blood vessels and show a beaded appearance. The wide distribution of CGRP-immunoreactive nerve fibers in bone tissue and the changes in distribution during bone development and regeneration suggest the involvement of these fibers in bone remodeling. The effect of CGRP on bone remodeling could partly be through its action on blood vessels, thereby regulating local blood flow. Moreover, in vitro biochemical data and the localization of CGRP-immunoreactive nerve fibers in the vicinity of bone cells suggest that they are directly involved in local regulation of bone remodeling by elevating the concentration of CGRP in the microenvironment around bone cells, especially during bone growth or repair.     

Numerical prediction of fraction of eutectic phase in Sn−Ag−Cu soldring using the phase-field method

A combination of macroscale solidification simulation and phase-field calculation is employed to predict the volume fraction of the eutectic phase in Sn-4.0 mass% Ag-XCu solder alloys (X=0.5–1.1 mass%). The solidification simulation incorporates the cooling rate in the phase-field simulation. We assume the residual liquid solidifies as eutectic phase when the driving force for the nucleation of Cu₆Sn₅ amounts to a critical value, which is determined based on the experimental data. Though the calculation results depend on the experimental data, the obtained fractions are about 40% for 0.5 mass% Cu and more than 90% for 1.1 mass% Cu alloy, which shows good agreement with the experimental data.     

Short-term algal toxicity test based on phosphate uptake

In order to develop a short-term algal toxicity test, the growth of and the phosphate uptake by the green alga Selenastrum capricornutum during batch culture were observed. In the control medium, S. capricornutum took up phosphate earlier than it grew. It was also observed that the phosphate uptake was inhibited by the presence of a toxicant. From these results, phosphate uptake was considered as one of the useful effect parameters for a short-term algal toxicity test. As the removal rate of phosphate from the medium is a function of the amount of algal cell initially inoculated, the test period is variable. The relationship between the amount of inoculation and phosphate uptake was examined and the test conditions suitable for a 3-h toxicity test were established as one example. According to this test procedure, the inhibitory effect of some toxicants on the phosphate uptake was determined. For comparison, a conventional algal assay based on algal growth was also performed. The EC50s for both tests were close. This indicated that the algal toxicity test method proposed in this paper would be useful for the uses where rapidity is required.     

Fourier synthesis image reconstruction by use of one-dimensional position-sensitive detectors

An improvement of Fourier synthesis optics for hard x-ray imaging is described, and the basic performance of the new optics is confirmed through numerical simulations. The original concept of the Fourier synthesis imager utilizes nonposition-sensitive hard x-ray detectors coupled to individual bigrid modulation collimators. The improved concept employs a one-dimensional position-sensitive detector (such as a CdTe strip detector) instead of the second grid layer of each bigrid modulation collimator. This improves the imaging performance in several respects over the original design. One performance improvement is a two-fold increase in the average transmission, from 1/4 to 1/2. The second merit is that both the sine and cosine components can be derived from a single grid-detector module, and hence the number of imaging modules can be halved. Furthermore, it provides information along the depth direction simultaneously. This in turn enables a three-dimensional imaging hard x-ray microscope for medical diagnostics, incorporating radioactive tracers. A conceptual design of such a microscope is presented, designed to provide a field of view of 4 mm and a spatial resolution of 400 microm.     

Defective bone remodelling in osteoprotegerin-deficient mice

Previous studies have reported enhanced osteoclastogenesis, increased bone resorption and osteoporosis in osteoprotegerin (OPG)-deficient mice. In the present study, we show that the tibial epiphyses contain abundant, thin trabeculae lined with numerous osteoclasts and cuboidal osteoblasts. The increase in osteoblasts and osteoclasts was associated with a dramatic increase in calcein labelling of the mineralization fronts and replacement of much of the intertrabecular marrow with numerous alkaline phosphatase-positive preosteoblasts. Furthermore, the discrete, linear cement lines seen in wild-type mice were replaced by a randomly oriented meshwork of cement lines that were stained intensely for tartrate-resistant acid phosphatase and osteopontin in the OPG-/- mice. These indices of accelerated bone remodelling in mutant bone were associated with irregular trabecular surfaces, a disorganized collagen matrix interspersed with amorphous ground substance and numerous fissures between old and new bone. In total, these observations indicate that enhanced osteoclastic activity in OPG-/- epiphyses led to a coupled increase in osteoblast differentiation and activity and an increase in bone remodelling. The high bone turnover, disorganized matrix and impaired attachment of new to old bone in the cement lines in OPG-/- mice appear to cause bone fragility.     

Characterisation of optically driven microstructures for manipulating single DNA molecules under a fluorescence microscope

Optical tweezers are powerful tools for manipulating single DNA molecules using fluorescence microscopy, particularly in nanotechnology‐based DNA analysis. We previously proposed a manipulation technique using microstructures driven by optical tweezers that allows the handling of single giant DNA molecules of millimetre length that cannot be manipulated by conventional techniques. To further develop this technique, the authors characterised the microstructures quantitatively from the view point of fabrication and efficiency of DNA manipulation under a fluorescence microscope. The success rate and precision of the fabrications were evaluated. The results indicate that the microstructures are obtained in an aqueous solution with a precision ∼50 nm at concentrations in the order of 10⁶ particles/ml. The visibility of these microstructures under a fluorescence microscope was also characterised, along with the elucidation of the fabrication parameters needed to fine tune visibility. Manipulating yeast chromosomal DNA molecules with the microstructures illustrated the relationship between the efficiency of manipulation and the geometrical shape of the microstructure. This report provides the guidelines for designing microstructures used in single DNA molecule analysis based on on‐site DNA manipulation, and is expected to broaden the applications of this technique in the future.Inspec keywords: DNA, molecular biophysics, fluorescence, optical microscopy, radiation pressure, biological techniquesOther keywords: optically driven microstructures, single DNA molecule analysis, fluorescence microscopy, optical tweezers, nanotechnology‐based DNA analysis, manipulation technique, aqueous solution, fine tune visibility, yeast chromosomal DNA molecules, geometrical shape, on‐site DNA manipulation