EFFECT OF ALKALI METAL IONS ON THE RHEOLOGICAL PROPERTIES OF κ-CARRAGEENAN AND AGAROSE GELS

Stress relaxation and dynamic measurements were carried out on κ-carrageenan and agarose gels to examine the effect of alkali metal ions. The elastic modulus of κ-carrageenan gels increase remarkably by adding alkali metal ions Li⁺, Na⁺, K⁺, Cs⁺. This was explained as follows: the electrostatic repulsion of sulfate groups in κ-carrageenan gels are prevented by the shielding action of the alkali metal ions stabilizing the double helical structure of κ-carrageenan gels. The increase of the modulus was in the order: Cs⁺ > K⁺≫ Na⁺ > Li⁺. The difference between these two groups (Cs⁺, K⁺) and (Na⁺, Li⁺) is that the former group belongs to the structure disordering ions while the latter group belongs to the structure ordering ions. Thus, the former group prevents the repulsion of sulfate groups more directly than the latter. Agarose gel, which lacks sulfate groups, is not influenced so much by adding the alkali metal ions.     

Glass-ceramic from sewage sludge ash

Glass-ceramic was produced by adding limestone to sewage sludge incinerated ash. Black glass was produced by melting a blended ash batch at 1450°C. For nucleation, this glass was reheated at 800°C for 1 h, and reheated at 1100°C for 2 h to form glass-ceramic. The main components of sewage sludge incinerated ash are SiO2 and Al2O3. Because small amounts of Fe2O3, sulfur and carbon are included, the addition of limestone alone can generate the crystal nucleant, FeS, to form anorthite (CaO·Al2O3·2SiO2) crystal. The glass-ceramic showed superior characteristics of high strength and acid resistance for use in construction materials. This revised version was published online in November 2006 with corrections to the Cover Date.     

COMPARATIVE STUDY OF TEXTURE TERMS: ENGLISH,FRENCH, JAPANESE AND CHINESE

ABSTRACT

Texture vocabularies in English, French, Japanese and Chinese languages are examined, and their characteristics are described. It wasconfirmed that most frequently used texture vocabularies concern with the mechanical and geometrical properties, and are used to describe solid‐like foods rather than liquid‐like foods. It was also shown that in all the languages, the terms used by texture experts and consumers are different. Complete agreement was not recognized even among texture experts, although it is expected that the validation of most fundamental terms could be reached through discussions. Further detailed comparison is now in progress.

PRACTICAL APPLICATIONS

In the globalization age, it is becoming more and more important to understand different languages representing texture of foods. Therefore, it is useful to compare the texture terms in different languages both for academic researchers and workers in the trade and industries.     

Sugar and Cyclitol Determination in Vegetables by HPLC Using Postcolumn Fluorescent Derivatization

Nonreducing sugars such as sucrose, raffinose, myo-inositol, pinitol and galactinol were separated on a polyamine-bonded polymer gel (NH₂ type) column using acetonitrile-water as mobile phase. Sugars in the eluate were detected by periodate oxidation and the subsequent derivation of guanidine to fluorescent compounds. Detection limits were: sucrose 2.5, D-glucose 2.5 and pinitol 4 ng. This highly sensitive method was more accurate and rapid for determining sugar contents in immature soybean seeds, sweet corn kernels and chinese mustard leaves than the conventional method using refractive index detection. Also, this method reduced the injection volumes of extracts to the column and allowed to lengthen the column life.     

RHEOLOGICAL PROPERTIES OF AQUEOUS AGAROSE-GELATIN GELS

Melting temperatures were determined for 1-5% agarose gels, 7.5-40% gelatin gels and mixed gels of different concentrations of the two hydro-colloids. The dynamic viscoclastic constants were also quantified at 0.05 HZ for mixed gels containing 0.5% agarose and 2.5–20% gelatin.
In single component gels, the melting temperature increased with hydrocolloid concentration. The melting temperature of gelatin gels was lower than that of agarose gels (22–31°C vs 69–80°C) and less concentration dependent. The melting temperature of mixed gels was more similar to that of agarose gels at low (2.5–6.25%) gelatin concentrations and more similar to that of gelatin gels at high (7.5–20%) gelatin concentrations. The storage modulus decreased with increasing temperature indicating that the thermal rupturing of the noncovalent crosslinks in the gels was stronger than the entropic behavior of the network. The temperature dependence of the storage modulus and of the dynamic viscosity increased with gelatin concentration. Based on these results and on the determination of the activation energy it is concluded that, in mixed agarose/gelatin gels, the two species form individual networks which interfere with one another at high concentrations.     

放射防护体系的演进

建立在线性无阈假设上的现行辐射防护体系对工作人员和公众成员所受剂量的最小化具有很大的贡献。然而,因为线性无阈意味着不管剂量多么小辐射总是有害的,所以已经引起人们的“辐射恐惧”并因过度审管而造成资源的浪费。作者重温了辐射健康效应的研究结果,包括对辐射工作人员的重大流行病学研究。发现在低于目前最大剂量限值(工作人员：50 mSv／y,公众成员：5 mSv／y)的辐射照射情形下没有明显的有害健康效应的证据,而二十世纪后半叶这些限值在全世界被广泛采用。既然DNA修复、细胞凋亡、适应性反等生物防预机理的存在得到了公认,那么线性假设就不能说成是“科学的”。越来越多的证据表明存在着辐射危险的阈效应。为了解决低剂量问题。在新的放射防护体系中应当引入“实际的”阈值或“事实上的安全剂量”概念。“实际的”阈值可定义为某一剂量水平,低于此剂量水平就不会诱发可观察到的放射所致的癌症或遗传效应。除了医疗目的有意照射以外,如果工作人员和公众成员从受照中得不到利益,则辐射照射应当保持在“实际的”阈值之下。假设目前的剂量限值低于“实际的”阈值且没有“辐射损害”,那么对于职业照射和公众照射就不需要“正当性”和“最优化(ALARA)”原则。这样一来,允许以对社会的利益抵销对个人的辐射损害的“正当性”伦理学问题也就能够得到解决。而且,用健康和安全换取经济利益的“最优化”的伦理问题也可以得到解决。只有通过引入“实际的”阈值概念的方法才能使辐射防护体系建立在面向个人的理念上,并且满足21世纪伦理学的平等原则。     

低温烧结用PZT粉体水热合成

水热合成了低温烧结用PZT粉体,合成时添加Fe∧ 2,Bi∧ 3,Cu∧ 2等离子化合物,生成粉体中外加微量Ba（Cu0.5W0.5）O3,经X-ray,SEM,TG-DTA及比表面积的测定,表明当反应介质为4mol/L NaOH,时间2h,反应温度200℃时,合成的粉体中PZT微晶子已大量生成。PZT陶瓷在850℃温度下烧成,密度可达理论值98%,并对其压电性能进行了测定,结果证实,微量烧结助剂的添加除有效地降低烧结温度外,使Qm值提高,而Kp值有所下降。     

New acoustic system for continuous measurement of river discharge and water temperature

In many cases,river discharge is indirectly estimated from water level or streamflow velocity near the water surface.However,these methods have limited applicability.In this study,an innovative system,the fluvial acoustic tomography system(FATS),was used for continuous discharge measurement.Transducers with a central frequency of 30 kHz were installed diagonally across the river.The system's significant functions include accurate measurement of the travel time of the transmission signal using a GPS clock and the attainment of a high signal-to-noise ratio as a result of modulation of the signal by the 10th order M-sequence.In addition,FATS is small and lightweight,and its power consumption is low.Operating in unsteady streamflow,FATS successfully measured the cross-sectional average velocity.The agreement between FATS and acoustic Doppler current profilers(ADCPs)on water discharge was satisfactory.Moreover,the temporal variation of the cross-sectional average temperature deduced from the sound speed of FATS was similar to that measured by a temperature sensor near the bank.