加速器质谱测量129I方法的改进

在筑波大学的12UD串列加速器上开发了一套改进的129I加速器质谱(AMS)测量方法,包括在120°磁铁后安装了一副自行设计制作有静电偏转板,有效改善了对127I束流和129I计数的测量;采用97MoO2分子导航束稳定加速器端电压,加速器的端电压能稳定在几天内不超过0.1%,结合二次剥离,取得了满意的测量效果.用该方法测得AgI试剂样品的本底水平为7.83×10-13.对129I/127I比值范围为(4.92～0.28)×10-10的一系列样品的测量不确定度在7%以下,准确度较前有所提高.     

Thermal Expansion and Chemical Durability of Phosphate Glasses

The thermal expansion coefficient and aqueous dissolution rate were measured for alkali phosphate glasses containing a third and fourth component. For a given series, both properties increased monotonically as the radii of the alkali ions increased. The observed expansion coefficients were in the range 99 to 286 × 10⁻⁷°C⁻¹. A small mixed-alkali effect was observed for both properties.     

Conjugation and H ∞ control of discrete-time systems

We establish conjugation notion in discrete-time systems, first introduced into the H ^∞ control theory of continuous-time systems by Kimura (1989). In discrete-time systems, conjugation is a very elementary operation on rational transfer functions that replaces some of their poles by their reflections with respect to the unit circle. With the aid of J-lossless conjugation conjugation by a J.lossless system), it is shown that the parametrization of sub-optimal solutions of H ^∞ model-matching problems is reduced to a Lyapunov-type equation. The parametrization of all solutions is given in an extremely simple way. It is further proved that the J-lossless conjugation of the H ^∞ model-matching problem is a natural state-space representation of classical interpolation in discrete-time systems.     

A LRT Control Method Using Sensor Information in Distribution Systems with a Large Amount of PVs and EVs

It is of prime importance to maintain voltage profile within the proper range in distribution systems with a large amount of photovoltaics and electric vehicles (EVs). In particular, there is a possibility that line drop compensation (LDC) logic, which is utilized for the control of load ratio tap transformer (LRT) does not work properly when reverse power flow is included partially. Hence, in this paper, we have developed a new LRT control method based on the sensor information supposing that some section switchgears with sensors are introduced in the future distribution systems. Specifically, the extreme value of voltage profile is estimated by convergence calculation in the section between the section switchgear with sensor and LRT. Moreover, the voltage at the end node can be estimated by LDC method using sensor information of section switchgear. The proposed method was tested using a distribution system model and its effectiveness was shown.     

ADDUCT FORMATION OF β-DIKETONATO LANTHANOIDS(III) WITH CARBOXYLIC ACIDS HAVING HYDROXYL AND METHOXYL GROUPS

Adduct formation of 2-thenoyltrifluoroacetonato(tta) lantha-num(III), europium(III), and ytterbium(I II) with α-pheny 1 1 actic, α-methoxy phenyl acetic, salicylic, and o-methoxy benzoic acids in chloroform has been studied by solvent extraction technique. It has been found that 1anthanoid(111) chelates form more stable adducts with these carboxylic acids in the sequence: Yb(tta)₃ < Eu(tta) ₃ < La(tta) ₃. The adduct formation constants as well as the separation factors obtained as the ratio of the constants between a pair of metals are the largest for α-phenyl lactic acid among these acids. The characteristics with α-phenyl 1actic acid would be caused by the action as bidentate unlike benzoic acid derivatives which work as monodentates owing to the internal complexa-tion through hydrogen bonding.     

α-HYDROXYCARBOXYLIC ACID AS ADDUCT FORMING LIGAND FOR EXTRACTION OF LANTHANIDE(III)

Lanthanide(lII) chelates with 1,1,1 -trif luoro-5,5-dimethyl-2,4-hexanedione form adducts with benzilic acid, an a-hydroxycar-boxylic acid, in chloroform. The order of. the adduct formation constants in magnitude is: La^m> Eu^m> Yb^m although it is known that the stability constant of lanthanide(III) complexes with α-hydroxycarboxylic acids in aqueous solutions increases with increasing atomic number.     

Limonoids in Pummelos [Citrus grandis (L.) Osbeck]

Juice and seeds from 16 cultivars of mature pummelo fruits were analyzed for limonoid content. Pummelo juice contained an average of 18 ppm limonin and 29 ppm total limonoid glucosides. Compared to other juices, ptmnnelo contained very high concentrations of limonin and very low concentrations of limonoid glucosides. Limonin, nomilin, obacunone and trace amounts of deacetyhromilin were found in pummelo seeds. The 17–β-D-glucopyranoside derivatives (glucosides) of nomilin, nomilinic acid and obacunone were also present. Total limonoid aglycone concentration in the seeds ranged from 773 ppm to 9,900 ppm and total limonoid glucosides ranged from 130 ppm to 1,912 ppm.     

Further Studies on the Roles of the Head and Tall Regions of the Myosin Molecule in Heat-induced Gelation

Heat induced gelation properties of the two proteolytic fragments of myosin, heavy (HMM) and light meromyosin (LMM), were studied by rigidity measurement in a band type viscometer and by a direct examination using a scanning electron microscope. A heat induced network forming ability for both LMM and HMM was found in 0.6M KCl at a pH 6.0. LMM produced gels corresponding to a reversible helix-coil transition at temperatures ranging from 40–70°C, with little evidence of aggregation as assessed from a turbidity change of the system. Contrary, HMM associated irreversibly producing a gel with increased rigidity at pH 5.0 and a salt concentration of 0.1 M. Oxidation of SH-groups appeared to be involved only in HMM and not in LMM gelation process.     

Relative Roles of the Head and Tail Portions of the Molecule in Heat-Induced Gelation of Myosin

Myosin molecules are cleaved by chymotrypsin digestion into two fragments: subfragment 1, which originates from the globular heads of myosin, and the myosin rod, which originates from the helical tail of the myosin molecule. The heat-induced gelation of these subfragments was compared to that of intact myosin by measuring rigidity, turbidity, and other physico-chemical characteristics of each system. Two features of the heat-induced gelation of myosin, aggregation and three-dimensional network formation were found to be imparted by the subfragment 1 and the rod, respectively. The former involves disulfide exchange and the latter relates to conformational changes arising from a partially irreversible helix-coil transition during heating. Possible relationships are suggested between these physicochemical changes of the myosin head and tail regions upon heating and the heat-induced gelation of myosin.