冰结构蛋白对湿面筋蛋白冻藏稳定性的影响

研究冬小麦冰结构蛋白(ISP)对湿面筋蛋白冻藏稳定性的影响。采用差示扫描量热仪、动态流变仪、扫描电子显微镜分别研究空白湿面筋蛋白(未添加ISP)和添加ISP 的湿面筋蛋白冻藏不同时间后可冻结水含量、流变学特性及超微结构的变化。结果表明：1)随着冻藏时间延长,湿面筋蛋白可冻结水含量逐渐增大;冻藏时间相同时,添加ISP 湿面筋蛋白的融化焓小于空白湿面筋蛋白。2)湿面筋蛋白的弹性模量、黏性模量和蠕变均随冻藏时间的延长而降低;冻藏时间相同时,含ISP 湿面筋蛋白的蠕变明显小于空白湿面筋蛋白的相应参数。3)湿面筋蛋白网络经过冻藏后,不规则的孔洞更大,引入ISP 后,冰晶形成的不规则孔洞相对于空白湿面筋蛋白更加细小和均匀。说明ISP 能够通过减少湿面筋蛋白体系中的可冻结水含量,抑制冰晶形成和重结晶,从而减小冻藏过程中湿面筋蛋白网络遭受的破坏。     

Parametric control of structural responses using an optimal passive tuned mass damper under stationary Gaussian white noise excitations

In this study, the structural control strategy utilizing a passive tuned mass damper (TMD) system as a seismic damping device is outlined, highlighting the parametric optimization approach for displacement and acceleration control. The theory of stationary random processes and complex frequency response functions are explained and adopted. For the vibration control of an undamped structure, the optimal parameters of a TMD, such as the optimal tuning frequency and optimal damping ratio, to stationary Gaussian white noise acceleration are investigated by using a parametric optimization procedure. For damped structures, a numerical searching technique is used to obtain the optimal parameters of the TMD, and then the explicit formulae for these optimal parameters are derived through a sequence of curve-fitting schemes. Using these specified optimal parameters, several different controlled responses are examined, and then the displacement and acceleration based control effectiveness indices of the TMD are examined from the view point of RMS values. From the viewpoint of the RMS values of displacement and acceleration, the optimal TMDs adopted in this study shows clear performance improvements for the simplified model examined, and this means that the effective optimization of the TMD has a good potential as a customized target response-based structural strategy.     

Effects of the integrity of silicon thin films on the electrical characteristics of thin dielectric ONO film

Capacitors with two kinds of lower electrodes were fabricated and their effects evaluated on the electrical characteristics of oxide–nitride–oxide (ONO) film. One of the electrodes was made of amorphous silicon film chemically deposited using a gas mixture of Si2H6–PH3; the other was made of poly-Si film deposited by SiH4 decomposition and doped by As+ ion implantation. The ONO thin dielectric layer was composed of natural oxide, CVD silicon nitride and thermal oxide formed on the silicon nitride. The capacitance, the leakage current, the dielectric breakdown field and the time-dependent dielectric breakdown (TDDB) were tested to evaluate the electrical properties of the capacitors. The leakage current and the dielectric breakdown voltage showed similar values between the two capacitors, whereas the TDDB under negative bias showed a great difference. This indicates that, with respect to electrical properties, the integrity of the oxide grown on the in situ P-doped amorphous silicon is better than the oxide grown on the As+ ion-implanted poly-Si. What is more, phosphorus in the amorphous silicon did not lead to any problems with junction depth, even after post heat treatment at 950°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

High temperature strength and oxidation behaviour of hot-pressed silicon nitride-disilicate ceramics

Twelve different silicon nitride-disilicate ceramics have been fabricated by hot-pressing Si3N4 with the oxides of Y, Yb, Ho, Dy, Er, Sm, Ce, Lu, La, Pr, Gd, and Sc that are used as sintering additives. The high temperature strength and oxidation behaviour of the hot-pressed ceramics were investigated and correlated with the cationic radii of the oxide additives. The flexural strength at 1200°C increased, from 666 MPa for Si3N4-La2Si2O7 to 965 MPa for Si3N4-Sc2Si2O7 which is correlated with a decreasing cationic radius of the oxide additive. The weight gain during oxidation at 1400°C for 192 h in air decreased, from 0.8732 mg cm-2 for a Si3N4-Sm2Si2O7 ceramic to 0.1089 mg cm-2 for a Si3N4-Sc2Si2O7 ceramic, which is a function of the decreasing cationic radius of the oxide additive. This revised version was published online in November 2006 with corrections to the Cover Date.     

Evaluation of SDS-PAGE Method for Estimating Protein Digestibility

In a new technique digestibility of unheated and autoclaved soy protein concentrate (SPC) samples was determined in vitro by SDS-PAGE. Results were compared with those determined by the pH drop method and with apparent in vivo digestibility in rats. Results of the pH drop method correlated more highly (r = 0.95) with apparent in vivo digestibility than SDS-PAGE results (r=0.92). However, the SDS-PAGE technique had two advantages: it allowed estimation of the molecular weight(s) of polypeptides/peptides remaining in protein hydrolyzates and from densitometric analysis, visualization of the process of protein digestion.     

RECOVERY OF FISH BONE FROM HOKI (JOHNIUS BELENGERI) FRAME USING A PROTEOLYTIC ENZYME ISOLATED FROM MACKEREL INTESTINE

A new enzymatic treatment procedure was devised to recover and further utilize fish bones from processing which are normally discarded. This procedure includes the use of an enzyme preparation isolated from raw mackerel intestine by acetone precipitation. The caseinolytic activity of mackerel intestine crude enzyme (MICE) was approximately 0.58 U/mg protein, which was comparable to those of trypsin and α‐chymotrypsin, or even higher than those of papain and Aspergillus saitoi protease. The optimum pH, temperature and enzyme/substrate ratio of MICE for hydrolysis of protein with hoki (Johnius belengeri) frames were determined to be pH 9.0, 40C and 1:100 (w/w). When the hoki frame was treated by MICE for 6 h under the optimum reaction conditions, the yield of bone recovery was approximately 90%. Compared to Alcalase, trypsin, α‐chymotrypsin and Neutrase, the yield of bone recovery using MICE was higher. These results suggest that MICE may be utilized for bone recovery from fish frame.     

Effect of Grain Growth on Pore Coalescence During the Liquid-Phase Sintering of MgO-CaMgSiO4 Systems

During the liquid-phase sintering of MgO-CaMgSiO₄ systems in N₂ atmosphere, the total porosity and the average pore size increase while the number of pores decreases. The negligible permeability of entrapped nitrogen through the liquid matrix and the observed linear relationship between the number of pores and that of the MgO grains suggest that the pores coalesce as a consequence of grain growth during sintering. An analysis of the balance between the pressure of the entrapped N₂ gas and the capillary pressure shows that pore coalescence in turn causes the observed porosity increase. When Fe₂O₃ or Cr₂O₃ is added to MgO-CaMgSiO₄, the pore size and the total porosity become larger or smaller, because the grain growth is accelerated or retarded, respectively.     

CHANGES IN RHEOLOGICAL PROPERTIES OF HYDROXYPROPYL POTATO STARCH PASTES DURING FREEZE-THAW TREATMENTS II. EFFECT OF MOLAR SUBSTITUTION AND CROSS-LINKING

The effects of molar substitution (M.S.) and cross-linking on the freeze-thaw stability of hydroxypropyl potato starch pastes were studied by following the changes in the rheological behaviour during heat treatment of the thawed starch pastes, and by determination of syneresis. In addition, differential scanning calorimetry (DSC) was used to investigate the thermal transition properties of the starch pastes that exhibited syneresis. With increasing M.S., the changes in both complex modulus (G*) and phase angle (δ) indicative of destabilization, and starch paste syneresis were delayed with regard to the number of freeze-thaw cycles. When a starch paste showed a peak in G*, related to syneresis, it also showed a thermal transition peak in the DSC measurements. The enthalpy value decreased with increasing M.S., and it appeared to be related to the extent of syneresis and the magnitude of the peak in G*. Comparison of the rheological behaviour of hydroxypropyl potato starch pastes and hydroxypropyl and cross-linked potato starch pastes, suggested that the former were gradually transformed into coarsely aggregated structures while the latter became diluted starch dispersions, due to shrinkage of swollen starch granules and their disruption.