Changes in S-allyl cysteine contents and physicochemical properties of black garlic during heat treatment

This study aimed to investigate the effects of temperature on the black garlic manufacturing process. The moisture content, pH, browning intensity, S-allyl cysteine (SAC) content and antioxidant activity, including DPPH radical scavenging activity and reducing power, were determined. The moisture content of garlic gradually decreased throughout the heating process. The rate of moisture removal was higher at high temperatures compared with low temperatures. The pH also decreased more significantly in garlic heated at high temperatures. The browning intensity increased with increasing temperature. The SAC contents of black garlic were significantly different according to heating temperature; the garlic samples heated at a low temperature had a higher SAC contents. Antioxidant activity, as determined by the DPPH radical scavenging activity and reducing power, increased when the garlic was exposed to higher temperatures.     

Update on optimized purification and characterization of natural milk allergens

Highly purified allergens namely cow's milk alpha-lactalbumin (ALA). (Bos d 4), beta-lactoglobulin (BLG) (Bos d 5) and casein (Bos d 8) and goat's milk casein were prepared from the raw milk from a single animal with a known genetic background. Consequently the natural isoforms are limited, constant and characterized. Purification included selective precipitations and chromatographical steps. Characterization of structure and allergenic activity assessment of milk allergens were carried out using physicochemical and immunochemical methods. Taken together data demonstrated the absence of impurities and of contamination by other milk allergens in each preparation. NMR and circular dichroism analyses confirmed the native conformation and proper folding of ALA and BLG and the expected absence of folding of bovine and caprine casein. Enzyme immuno assays confirmed the native conformation of BLG and the purity and immunoreactivity of all the proteins. The allergenic activity, e. g. the IgE binding capacity, of purified proteins was identical as that of those proteins when present in milk. The purified proteins also demonstrated the ability to provoke the degranulation of humanized rat basophilic leukaemia cells. All the data thus confirm the purity, identity, structural conformation and functionality of the prepared milk allergens.     

Constituents isolated from Glehnia littoralis suppress proliferations of human cancer cells and MMP expression in HT1080 cells

Crude extract and solvent-partitioned fraction of Glehnia littoralis were found to possess different anti-proliferative effects against AGS, HT1080 and U937 human cancer cells. The crude extracts and solvent fractions dose-dependently inhibited cell proliferation. Especially, n-hexane and 85% aqueous MeOH fractions exhibited comparatively higher anti-proliferative effects and reduced expressions of Bcl-2, COX-2 and iNOS genes. Systematic separation of all solvent fractions by chromatographic methods led to the isolation of three glucopyranosides, four furanocoumarins and two polyacetylenic alcohols. All the nine compounds were evaluated for their inhibitory effects against both proliferation of human cancer cells and expressions of MMP-2 and -9 in HT1080 cells. Two polyacetylenic alcohols exerted the highest inhibitory activity against both human cancer cell lines, and MMP-2 and -9. These results suggest that G. littoralis may possibly be used as a valuable chemopreventive agent or food supplement for reducing cancer risk.     

High thermal conductivity of spark plasma sintered silicon carbide ceramics with yttria and scandia

A fully dense SiC ceramic with a room‐temperature thermal conductivity of 262 W·(m·K)^?1 was obtained via spark plasma sintering β‐SiC powder containing 0.79 vol% Y₂O₃‐Sc₂O₃. High‐resolution transmission electron microscopy revealed two different SiC‐SiC boundaries, that is, amorphous and clean boundaries, in addition to a fully crystallized junction phase. A high thermal conductivity was attributed to a low lattice oxygen content and the presence of clean SiC‐SiC boundaries.     

Low-bandgap copolymers consisting of 2,1,3-benzoselenadiazole and carbazole derivatives with thiophene or selenophene π-bridges

Two donor–acceptor-type alternating copolymers consisting of 2,1,3-benzoselenadiazole and carbazole derivatives with thiophene or selenophene π-bridges were synthesized by Suzuki cross-coupling polymerization, and their optical, electrochemical, and photovoltaic properties were compared. The selenophene π-bridged copolymer (PCz-DSeBSe) exhibited a smaller band-gap (1.82 eV) than the thiophene-bridged polymer (PCz-DTBSe; 1.89 eV). PCz-DSeBSe also showed a deeper highest occupied molecular orbital energy level (−5.36 eV) than PCz-DTBSe (−5.20 eV). Moreover, the PCz-DSeBSe thin film showed higher crystallinity and hole mobility than the PCz-DTBSe thin film. Organic photovoltaic devices were fabricated using the polymers as the donors and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) as the acceptor. The device using PCz-DSeBSe showed a higher open circuit voltage (V_oc), short circuit current density (J_sc), and power conversion efficiency (PCE) than that using PCz-DTBSe. The fabricated indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/PCz-DSeBSe:PC₇₁BM/LiF/Al device showed the maximum PCE of 2.88% with a J_sc of 7.87 mA/cm², an V_oc of 0.80 V, and a fill factor of 0.50 under AM 1.5G irradiation (100 mW/cm²).     

Simultaneous quantification of free fatty acids,free sterols,squalene, and acylglycerol molecular species in palm oil by high-temperature gas chromatography-flame ionization detection

This paper discusses a rapid GC-FID technique for the simultaneous quantitative analysis of FFA, MAG, DAG, TAG, sterols, and squalene in vegetable oils, with special reference to palm oil. The FFA content determined had a lower SE compared with a conventional titrimetric method. Squalene and individual sterols, consisting of β-sitosterol, stigmasterol, campesterol, and cholesterol, were accurately quantified without any losses. This was achieved through elimination of tedious conventional sample pretreatments, such as saponification and preparative TLC. With this technique, the separation of individual MAG, consisting of 16∶0, 18∶0, and 18∶1 FA, and the DAG species, consisting of the 1,2(2,3)- and 1,3-positions, was sufficient to enable their quantification. This technique enabled the TAG to be determined according to their carbon numbers in the range of C₄₄ to C₅₆. Comparisons were made with conventional methods, and the results were in good agreement with those reported in the literature.     

Aeroacoustic characteristics and noise reduction of a centrifugal fan for a vacuum cleaner

The aeroacoustic characteristics of a centrifugal fan for a vacuum cleaner and its noise reduction method are studied in this paper. The major noise source of a vacuum cleaner is the centrifugal fan. The impeller of the fan rotates at over 3000 rpm, and generates very high-level noise. It was revealed that the dominant noise source is the aerodynamic interaction between the rotating impeller and stationary diffuser. The directivity of acoustic pressure showed that most of the noise propagates backward direction of the fan-motor assembly. In order to reduce the high tonal sound generated from the aerodynamic interaction, unevenly pitched impeller and diffuser, and tapered impeller designs were proposed and experiments were performed. Uneven pitch design of the impeller changes the sound quality while the overall sound power level (SPL) and the performance remains similar. The effect of the tapered design of impeller was evaluated. The trailing edge of the tapered fan is inclined. This reduces the flow interaction between the rotating impeller and the stationary diffuser because of some phase shifts. The static efficiency of the new impeller design is slightly lower than the previous design. However, the overall SPL is reduced by about 4 dB(A). The SPL of the fundamental blade passing frequency (BPF) is reduced by about 6 dB(A) and the 2^nd BPF is reduced about 20 dB(A). The vacuum cleaner with the tapered impeller design produces lower noise level than the previous one, and the strong tonal sound was dramatically reduced.     

Evaluation of system codes for analyzing naturally circulating gas loop

Steady-state natural circulation data obtained in a 7 m-tall experimental loop with carbon dioxide and nitrogen are presented in this paper. The loop was originally designed to encompass operating range of a prototype gas-cooled fast reactor passive decay heat removal system, but the results and conclusions are applicable to any natural circulation loop operating in regimes having buoyancy and acceleration parameters within the ranges validated in this loop. Natural circulation steady-state data are compared to numerical predictions by two system analysis codes: GAMMA and RELAP5-3D. GAMMA is a computational tool for predicting various transients which can potentially occur in a gas-cooled reactor. The code has a capability of analyzing multi-dimensional multi-component mixtures and includes models for friction, heat transfer, chemical reaction, and multi-component molecular diffusion. Natural circulation data with two gases show that the loop operates in the deteriorated turbulent heat transfer (DTHT) regime which exhibits substantially reduced heat transfer coefficients compared to the forced turbulent flow. The GAMMA code with an original heat transfer package predicted conservative results in terms of peak wall temperature. However, the estimated peak location did not successfully match the data. Even though GAMMA's original heat transfer package included mixed-convection regime, which is a part of the DTHT regime, the results showed that the original heat transfer package could not reproduce the data with sufficient accuracy. After implementing a recently developed correlation and corresponding heat transfer regime map into GAMMA to cover the whole range of the DTHT regime, we obtained better agreement with the data. RELAP5-3D results are discussed in parallel.     

Thermal hydraulic performance analysis of the printed circuit heat exchanger using a helium test facility and CFD simulations

The thermal-hydraulic performance of the PCHE was investigated using the KAIST helium test loop. Experiments were performed in the helium laminar region with 350 < Re < 1200. The hot/cold side inlet conditions were 25–550 °C/25–100 °C over the operating pressure of 1.5–1.9 MPa, respectively. Mass flow rates were controlled in the range of 40–100 kg/h. Pressure drop and temperature difference were measured at the inlet and outlet of the hot and cold sides. A global Fanning factor correlation and a global Nusselt number correlation were proposed using information only at the inlet and outlet of the hot and cold sides. A three-dimensional (3-D) numerical simulation was performed using FLUENT, a commercial computational fluid dynamics (CFD) code, to compare simulation results to the KAIST helium test data and to obtain the local Nusselt number in the PCHE. CFD predictions showed good agreement with experimental data. A local pitch-averaged Nusselt number correlation was proposed using local temperature, pressure, surface heat fluxes, and properties provided by CFD simulations. The system analysis code, GAMMA, was also utilized to identify which correlation was more applicable for system analysis. It turns out that the proposed local pitch-averaged Nusselt number correlation from CFD simulations is more appropriate than the global Nusselt number correlation developed from experimental data.     

Permeability differences based on three-dimensional geometrical information of void spaces

In this study,the permeabilities of Berea and Otway sandstones were measured under different confining pressures,and porosity was investigated through mercury intrusion porosimetry(MIP).The total porosities of the Berea and Otway sandstones were approximately 17.4%and 25%,respectively.Pore size distributions of each sandstone were almost the same,but the pores in the Otway sandstone were slightly narrower.However,the permeability of the Otway sandstone was smaller than that of the Berea sandstone by one order of magnitude.Three-dimensional(3D)void geometry and geometrical properties of the void spaces relevant to flow were compared to obtain the relation between the permeability differences and porosities of the two sandstones.The 3D geometrical analysis using microfocus X-ray computed tomography(CT)was performed,and the pore geometries of both sandstones were compared using the 3D medial axis(3DMA)method.Pore and throat radii,pore coordination number,tortuosity,number of connecting paths,connecting path volume,and other factors were determined using 3DMA.The Otway sandstone was characterized by a small effective throat/pore radius ratio.Based on the fluid flow mechanism,the lower effective throat/pore radius ratio results in a lower permeability induced by the fluid energy loss,which means that the 3D geometrical shape of void spaces affects the permeability value.