Comparison of 80-keV D+ Ion Implantation with Thermal D2 Doping in Silica by FTIR and ESR Spectroscopy

Behavior of deuterium atoms in fused silica, which were implanted by 80-keV D⁺ (D₂⁺, D₃⁺) ions or doped thermally by D₂ (or D₂O), was studied by infrared Fourier transform spectroscopy (FTIR) and by ESR spectroscopy. When 80-keV deuteron ions are implanted into fused silica, OD bonds are formed. The OD bonds are also formed by thermal doping with D₂ or D₂O. When the deuterated silica is γ-ray irradiated at 77 K, D atoms are formed by rupture of the OD bonds. The efficiency of the OD bond rupture in the deuteron-implanted silica is much less than that in the D₂-doped silica. It is concluded from the results of thermal annealing that the low efficiency of the OD bond rupture in the deuteron-implanted silica is due to the radiation damage accompanying the implantation process. However, the decay rate and detrapping energy of deuterium atoms, once formed in the silica, are similar in both cases.     

Modified age replacement policies

Modified age replacement policies, where a system is not always as good as new after each maintenance, are discussed. The expected total discounted cost for an infinite time-span, introducing some costs and a continuous type discount rate is applied as a criterion of optimality, and the optimum policies minimizing this cost are obtained. It is shown that, under certain conditions, there exists a finite and unique optimum policy. Relations to the existing publications are also shown.     

Selective O–H Bond Cleavage in the Radiolysis of Quartz

Cleavage of the O–H bond in quartz was studied by Fourier transform infrared spectroscopy and ESR spectroscopy. When quartz single crystals and fused silica glass are γ-irradiated at 77 K, hydrogen atoms are produced by rupture of O–H bonds. The initial efficiency of O–H bond cleavage in quartz single crystals, i.e. the initial yield of H atoms, was three times as great as that in fused silica glass, although the concentration of O–H bonds in quartz single crystals (70 ppm) is much lower than that in fused silica glass (4000 ppm). The efficiency of O–H bond cleavage in quartz single crystals indicates that energy transfer from the irradiated single crystal to the O–H bonds takes place effectively at 77 K. The efficiency of O–H bond cleavage decreases with increasing γ-ray dose, i.e. with increasing amounts of radiation-induced defects in quartz single crystals. When the radiation-induced defects are removed by annealing the irradiated quartz single crystal at 773 K, the O–H bonds are ruptured again as effectively as for a fresh quartz single crystal. The distance of the energy transfer, estimated by a target model, is ∼15 nm.     

KINETICS OF BIOETHANOL PRODUCTION FROM WHEAT MILLING BY-PRODUCTS

An overview of the potential application of wheat milling by‐products as substrate for bioethanol production is presented. In order to select a suitable microorganism, model fermentations were conducted using glucose and dry baker's yeast. The overall ethanol yield was nearly stable (ca. 0.35 g/g), independent of mash glucose concentration; mashes with 100 g glucose/L resulted in an overall ethanol productivity of 3.48 g/L·h. Slurries containing low‐grade wheat flour (LG) (100, 200 or 300 g/L) were used for simultaneous saccharification and fermentation (SSF) with Zymomonas mobilis. Fermentation performance was evaluated based on ethanol concentration (P), productivity (Q_v), yield (Y_P/S), production rate (Q_p) and glucose consumption rate (Q_s). Mashes containing 200 g LG/L produced about 52 g ethanol/L, with Q_vof 2.17 g/L·h. Based on the relatively high fermentation rate of LG, reaching peak ethanol productivity within ca. 9 h of SSF, considerable savings on fermentation time was achieved. Using Z. mobilis for LG fermentation, P was about 30% higher than that obtained with Saccharomyces cerevisiae.     

Kinetic Behavior of H and D Atoms in γ-Irradiated SiO2 as Studied by ESR Spectroscopy

The decay of hydrogen atoms, produced by γ irradiation of fused silica and quartz, was studied by ESR spectroscopy. The decay of H atoms in silica cannot be explained by a secondorder kinetics nor by a simple first-order kinetics. Also, the decay is not composed of several first-order processes with different activation energies. The data for the decay of H atoms can be described by a first-order kinetic equation with a timedependent rate constant of the form k(t) = Bt ^α−1, where B and α are constants. The decay kinetics of D atoms in deuterated fused silica and H atoms in a single crystal of quartz are also explained by use of the time-dependent rate constant. The apparent activation energies for the decay of H and D atoms in the silica are 15 to 16 kJ/mol and 14 to 15 kJ/mol, respectively. The decay rates for D and H atoms in the silica are similar.     

Robust network structures for conserving total activity in Boolean networks

One of the typical properties of biological systems is the law of conservation of mass, that is, the property that the mass must remain constant over time in a closed chemical reaction system. However, it is known that Boolean networks, which are a promising model of biological networks, do not always represent the conservation law. This paper thus addresses a kind of conservation law as a generic property of Boolean networks. In particular, we consider the problem of finding network structures on which, for any Boolean operation on nodes, the number of active nodes, i.e., nodes whose state is one, is constant over time. As a solution to the problem, we focus on the strongly-connected network structures and present a necessary and sufficient condition.     

Optimal maintenance policies with lead times and repair

Maintenance policies with lead times and repair are discussed. We first discuss ordering policy with repair and refer to inspection-ordering policy. In each policy, as a criterion of optimality, we apply cost effectiveness which balances system effectiveness and cost, and obtain the optimal policies. It is shown that, under certain conditions, there exists a finite and unique optimal policy.     

Circle condition and stability margin of the optimal regulator for systems with delays

Robustness properties of the optimal regulator for systems with delays in the state are characterized: first, a Nyquist stability criterion is developed and the circle condition of the optimal regulator is derived. On the basis of these results, the stability margin of the optimal regulator is evaluated as by Lehtomaki el al. (1981), and it is shown finally that the stability margin is equal to that in the finite-dimensional case     

DIRECT MEASUREMENT OF LIP PRESSURE WHEN INGESTING SEMI-LIQUID FOOD

A spoon sensor to measure lip pressure when slurping liquid food was developed. Several sheet‐type sensors of 3 mm diameter were aligned along the back‐center line of the bowl of a spoon, at intervals of 5 mm and the lip pressure was evaluated while average adults ingested five samples of semi‐liquid foods with varying viscosities. Samples with greater viscosity required correspondingly greater lip pressure and maximum force, as well as a greater impulse or time integral of the force detected by a single sensor. The sum of the force, the impulse, duration and velocity using pressure data from a sequence of four sensors were calculated. Thicker samples required greater force and impulse, and longer duration, but lower velocity. The test subjects slurped semi‐liquid foods differently, adapting to viscosity. Mechanoreceptors in the lips may play an important role in the discrimination of food viscosity.     

Identification of Low Molecular Weight Peptides in Gouda-type Cheese and Evidence for the Formation of These Peptides from 23 N-terminal Residues of αsl-casein by Proteinases of Streptococcus cremoris H61

Water-soluble extracts from Gouda-type cheese in a 0.05M sodium citrate buffer at pH 4.0 were fractionated by high-pressure liquid chromatography (HPLC) before and after ripening for 1, 2, and 3 months. Three major peptides were isolated from each sample of extract, but size of the peaks increased with ripening period. The amino acid compositions of these peptides were similar to fragments of αsl-casein, i.e., αsl-CN(fl-9), αsl-CN(fl-13) and αsl-CN(fl-14). αsl-CN(fl-23) was hydrolyzed by cellular proteases of Streptococcus cremoris H61; seven main peptides including αsl-CN(fl-9), αsl-CN(fl-13) and αsl-CN(fl-14) were isolated and characterized by HPLC. This suggests that hydrolysis of αsl-CN(fl-23) by lactic acid bacterial proteinase is one of the main pathways of αsl-casein degradation during Gouda-type cheese ripening.