Odor Threshold of Some Pyrazines

Odor thresholds of 46 pyrazines in water were investigated. Pyrazines examined were 15 alkylpyrazines, 1 phenylpyrazine, 10 alkoxypyrazines, 6 phenoxypyrazines, 3 phenylthiopyrazines, and 11 alkylthiopyrazines. Alkoxypyrazine exhibited the lowest odor threshold among the pyrazine derivatives tested. Odor thresholds of the pyrazines varied from 0.00001 ppm [2-methoxy-3-methyl-5-(2-methylbutyl)pyrazine] to 6.00 ppm (5-isopentyl-2,3-dimethyl-pyrazine).     

A Half-Embryo Test for Identification of Gamma-Irradiated Grapefruit

Whole grapefruit were exposed to 5, 15, 30, 50, and 100 krad doses of gamma-radiation. Seeds were removed and half-embryos, consisting of one cotyledon and embryo axis, dissected from the surrounding tissue. Nonirradiated half-embryos germinated faster than intact or partially dissected (outer seed coat removed) seeds. Shoot elongation was also quicker, occurring within 6 days. Irradiated half-embryos over 15 krad doses showed markedly reduced root growth and shoot elongation was almost totally retarded. Differences between irradiated and nonirradiated half-embryo were not affected when variety, harvest date, and fruit storage conditions were varied. This test could thus discriminate between irradiated and non irradiated grapefruit.     

Improvement of the Half-embryo Test for Detection of Gamma-irradiated Grapefruit and Its Application to Irradiated Oranges and Lemons

The duration of the half-embryo test used for identification of gamma-irradiated grapefruit was shortened by increasing germination temperature to 35°C. Maximum shooting percentages were reached within 3 days. Gibberellin application reduced the required incubation time to 2 days. Half-embryos extracted from irradiated orange and lemon gave similar results to those of grapefruit. This half-embryo test is proposed as an identification method for irradiated citrus. Assessment can be made after 3 to 4 days when shooting percentage is greater than 50%.     

Introduction of High Pressure to Food Processing: Preferential Proteolysis of β-Lactoglobulin in Milk Whey

Various proteins were subjected to thermolysin digestion at 2000 atm. Casein and soy protein were extensively digested at both atmospheric and high pressures, but the tetrameric proteins alcohol dehydrogenase and hemoglobin and the monomeric protein β-lactoglobulin were degraded only upon pressurization. Globular proteins with many disulfide bonds (RNase A, lysozyme, and α-lactalbumin) resisted the proteolysis at both pressures. These observations led to the preferential digestion of β-lactoglobulin in cow's milk whey, thus simulating human milk protein. The versatility of pressure-induced proteolysis in food processing is also proposed.     

Mechanical Properties on Ni3 Al Intermetallic Compound-SiC Composite Material Generated by SHS Method

0 Introduction The Ni3 Al intermetallic compound is of great interest because of its corrosion-resistance, and high melting point. However, it is difficult to make the intermetallic compound using the ordinary method.     

Ultra-High-Speed Performance of Ball Bearings and Annular Seals in Liquid Hydrogen at Up to 3 Million DN (120,000 rpm)©

The ultra-high-speed performance of a hybrid ceramic 25-mm-bore ball bearing, as well as that of floating-ring seals with a sealing diameter of 30 mm, was determined in liquid hydrogen at speeds to 120,000 rpm, 3 million DN, under thrust loads to 3,140 N and sealed pressures to 1.7 MPaG. The bearings had Si₃N₄ balls and a single outer land-guided retainer. The hybrid ceramic bearing exhibited excellent performance at high load, contrasting with the seized all-steel bearing; however, the ceramic balls developed superficial micro-cracks due to frictional heating. Effective cooling of the bearing was achieved by increasing the jet speed through the nozzles. The bearing power loss drastically increased with increasing speed and cooling flow rate. The critical load capacity without bearing damage was also evaluated. Furthermore, the sealing performance of the one-ring seal was superior to that of the two-ring seal in preventing the sealing ring seizure against the runner.     

Study on Mechanism of Hydrogen Generation from Lubricants

To establish fundamental countermeasures for hydrogen embrittlement that occurs to several kinds of bearings, the mechanism of hydrogen generation from lubricants was studied. Sliding tests were conducted, and the amount of hydrogen generated from several kinds of lubricants during sliding was measured. It is concluded that the lubricant is decomposed and hydrogen is generated through a catalytic reaction with the fresh steel surface. The amount of hydrogen generated from each lubricant depends on its lubricity, not on its chemical structure. It is also confirmed that the lubricant with the larger wear brings more generated hydrogen into steel. Based on the above mechanism of hydrogen generation, methods of inhibiting hydrogen brittle flaking with additives were investigated. It is clarified that the addition of corrosion inhibitors that form a passive state film on the steel surface effectively inhibits generation of hydrogen from lubricants and penetration of hydrogen into steel.

     

A Low‐Speed,High‐Torque Motor Drive Using a Modular Multilevel Cascade Converter Based on Triple‐Star Bridge Cells (MMCC‐TSBC)

This paper provides an experiment‐based discussion on a modular multilevel cascade converter based on triple‐star bridge cells (MMCC‐TSBC) for a low‐speed high‐torque motor drive. The TSBC is a direct ac‐to‐ac power converter capable of achieving bidirectional power flow as well as drawing and feeding three‐phase sinusoidal input (supply‐side) and output (motor‐side) currents with any power factor at both sides. This paper discusses active dc‐capacitor‐voltage control applied to the low‐speed, high‐torque motor drive. A specially designed downscaled system combining a 320‐V, 38‐Hz, 6‐pole, 15‐kW induction motor with a 400‐V, 15‐kW TSBC is constructed and tested to confirm the validity of the motor drive. Experimental waveforms obtained from the downscaled system confirm stable operation with the rated load torque across a range from a standstill to the rated speed, including satisfactory start‐up performance.     

Internal Stresses and Microcrack Formation Caused by Drying in Hardened Cement Pastes

The shrinkage stresses due to drying and the differences of volume changes and rigidities between the two phases of dense Ca(OH), crystals and porous C-S-H gel are estimated. High tensile stresses are calculated around the Ca(OH), crystals at a relatively high humidity. It is also shown by a calculation on the basis of some assumptions that the shrinkage stresses may cause microcracks which drastically increase permeability.