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Effects of thyroid dysfunction on the secretory ability of thyroid C cells (parafollicular cells) were studied in rats. The rats born to mothers thyroidectomized on day 5 of gestation (Tx-F1) were found to have an increased serum thyroxine level and a decreased basal level of serum calcitonin. The calcitonin secretory response to gastrin related peptide (gastrin) was normal in these rats. Neonatal treatment of rats with 0.5 or 2 μg of thyroxine from 2 to 10 days of age (neoT4) resulted in a marked hypothyroid state in adulthood. They showed a significant decrease in the basal serum calcitonin levels and in the calcitonin response to gastrin stimulation. The rats in both groups showed a significant retardation in the body growth and the growth retardation was much greater in the neoT4 rats than in the Tx-F1 rats. The results suggest that the thyroid function alone or together with the thyrotrope function in the pituitary during the fetal life and neonatal period in the rat is important for the functional development of thyroid C cells.

A study on the radiation resistance of two types of ethylene-styrene copolymers, random and graft, is described. It is shown that the random copolymer is highly resistant to gamma -rays in the aspects of carbonyl group formation, gel formation, and elongation. It shows even better resistance when proper additives are compounded in. The tensile strength of the graft copolymer did not show a decrease under gamma -irradiation even at a high dose of 10 MGy. >

Erbium-doped silica optical fibers were irradiated by γ-rays, and their loss-increasing characteristics were analyzed. The loss is mainly induced by Er2+ created by the reduction of Er3+. It does not show a simple dependence on the Er3+ concentration. The loss increase is described by the sum of several saturating exponential terms and one linear term, which can be derived from the yield equation of E ′γ centers or other species induced from precursors by hole trapping. It is considered that hole trapping supplies electrons to induce the reduction, and plays an important role in the loss increase.

Irradiation of sodium allylsulfonate in aqueous solution at high pressure (up to 9000 kg/cm/sup 2/) gave a deliquescent white powder which is insoluble in organic solvent. The product was addition polymer of allylsulfonate from the high-resolution NMR and infrared spectra. The rate of polymerization was proportional to the third and second powers of monomer concentration in the initial and later stages, respectively. From the high dependence of the rate on monomer concentration, the reaction was deduced to proceed in an associated monomer or micelle. The rate of polymerization was increased by addition of sodium chloride. The G value for monomer consumption was about 10/sup 4/ at high pressure, which suggests that the degradative chain transfer is not important in the polymerization. Overall activation volumes were -7 and -5 ml/mole in the initial and later stages, respectively.

The effect of the specific surface area of silica gels on the radiation-induced polymerization of styrene adsorbed on silica gel was studied by ESR. The same radicals were generated on the silica gels regardless of the specific surface area, but the stability of the radicals at room temperature depended on the specific surface area. This means that the decay of the radicals proceeded mainly on the surface of the silica gel. Almost all the radicals generated by irradiation were initially in the bulk of the silica gel and migrated from the interior to the surface of the gel. When styrene monomer was adsorbed on the surface of the silica gel, the silica gel radicals interacted with the monomer and initiated polymerization and then generated polymer. The rate of migration of the silica gel radical was rather fast in the case of silica gel with a large specific surface area. Thus, the polymerization behavior of styrene adsorbed on silica gel greatly depended on the specific surface area of the gel.

The types of free radicals produced in the water-accessible regions of cellulose I and cellulose II fibers by γ-irradiation in nitrogen atmosphere at room temperature were studied by ESR spectroscopy. The ESR spectra of the irradiated cellulose I and II change by contacting the fibers with water, and after immersion in water the spectral shape depends on the orientation of the fiber axes to the magnetic field. These spectra are probably related to the free radicals generated in the highly ordered regions inaccessible to water in irradiated cellulosic fibers. The ESR spectrum of free radicals generated in decrystallized cellulose after irradiation consists of a singlet and a doublet. When the ESR spectra of free radicals formed in the highly ordered regions of cellulose I and II and the singlet and the doublet are combined in adequate ratio, the constructed spectra are similar to those of the radicals scavenged by water in the irradiated cellulose I and II fibers. From these facts, the spectra due to the free radicals in the water-accessible regions in irradiated cellulose I and II are considered to consist of the singlet and the doublet formed by free radicals in the typical amorphous regions and the spectra of other types of radicals generated in the semicrystalline regions.

The effect of amount of monomer on radiation-induced polymerization of styrene adsorbed on silica gel was investigated with the monomer amounting from less than monolayer adsorption to more than the equilibrium adsorption. The rate of graft polymerization and the molecular weight of the polymer changed with the amount of monomer adsorbed on silica gel. Maximum grafting efficiency was obtained at monolayer adsorption. The molecular weight of graft polymer was higher than that of homopolymer in both radical and cationic polymerizations, and the ratio in molecular weight of graft polymer to that of homopolymer tends to be unity with increasing amount of adsorbed monomer. These results can mainly be explained in terms of the number of initiating species (radical and cation) that change in relation to the amount of adsorbed monomer. Propagation and termination change with amount of adsorbed monomer in relation to the molecular mobility of adsorbed monomer. A very high-molecular-weight graft polymer is formed only with a small amount of adsorbed monomer in the initial stage. The grafting percent with a large amount of adsorbed monomer increased after most of the monomer has been polymerized. Secondary effect of radiation on the graft and homopolymers due to energy transfer from silica gel is suggested from the complicated phenomena in the later stage of the reaction.

The effect of dose rate on the rate of polymerization and molecular weight distribution of radiation-induced polymerization of styrene adsorbed on silica gel was studied in a wide dose rate range of 4.4 × 104 to 3 × 108 rad/hr by γ rays of 60Co and electron beams with a Cockcroft-Walton-type accelerator. Dose rate dependence on the initial rate of polymerization was about 1 below 3 × 107 rad/hr, and it decreased gradually at high dose rates. Throughout the dose rate range, graft polymerizations and homopolymerizations by cationic and radical mechanisms proceeded simultaneously. Dose rate dependence of the cationic polymerization was 1 below 3 × 107 rad/hr, while dose rate dependence of the radical polymerization was 0.65 below 3 × 107 rad/hr. At high dose rates, molecular weight and fraction of graft polymer decreased, and fraction of cationic polymerization increased. A very high-molecular-weight graft polymer was formed above 4.4 × 105 rad/hr at the initial stage of the polymerization. The dose rate dependence of this polymerization was larger than 1 and decreased with increase in dose rate. The polymerization seems to be related to an excitation of monomer or growing chain.

The types of free radicals formed by γ-irradiation in cellulose I and II were studied. The ESR spectra obtained with the γ-irradiated cellulose I and II were changed by contacting the fibers with water, and also the spectra for these fibers after immersion in water were varied by orientations of fiber axes to the magnetic field. These spectra seem to be related to the free radicals generated in the highly ordered regions inaccessible to water in irradiated cellulosic fibers. And the spectral differences between cellulose I and II may be due to the differences in the molecular conformation in the crystal lattices. As a model of typical amorphous regions in cellulose, decrystallized cellulose was prepared. The ESR spectrum of irradiated decrystallized cellulose was simple. When the sample was contacted with moisture, the ESR spectrum changed to a narrow singlet, which gradually decreased the intensity until the spectrum completely disappeared. By subtracting the spectrum of free radicals remaining in decrystallized cellulose after contacting with moisture from the spectrum of decrystal-lized cellulose, it was found that the types of free radicals formed in the decrystallized cellulose consisted of the overlap of narrow singlet (line width 8G, g-value 2.0050) and doublet (splitting 10G, g-value 2.0045) spectra. The singlet spectrum is attributed to alkoxyl radical formed by the rupture of glycosidic linkage at C1 or C4 position, and the doublet spectrum is ascribed to the radical formed by hydrogen abstraction from C1 position. When the ESR spectra of free radicals formed in the highly ordered regions of the irradiated cellulose I and II were added to the spectra of the singlet and doublet in adequate ratio, the constructed spectra were similar to the spectra of free radicals scavenged by water in cellulose I and II. From these facts the spectra generated by free radicals in the amorphous regions accessible to water in the irradiated cellulose I and II are considered to be composed of the ringlet and doublet formed by free radicals in the typical amorphous regions, and the spectra of other types of radicals, which are similar to the spectra for free radicals formed in crystal regions inaccessible to water. It is considered that the radicals are generated mainly in the typical amorphous regions in cellulose, since the contribution of the doublet spectrum is great in these constructed spectra for both cellulose I and II.

The types of free radicals formed in decrystallized cellulose prepared from cellulose I and II after γ-irradiation in nitrogen atmosphere at room temperature were studied by ESR spectroscopy. X-Ray diffraction revealed that decrystallized cellulose I and II have the same microstructure. The ESR spectra obtained with the γ-irradiated decrystallized samples are simple. By contacting the irradiated sample with moisture in nitrogen atmosphere, the ESR spectrum changed to a narrow singlet, which gradually decreased in intensity until the spectrum completely disappeared. It was found that the types of free radicals generated in the decrystallized cellulose by γ-irradiation consist of the overlap of singlet and doublet. The singlet spectrum is mainly attributed to alkoxyl radical formed by the rupture of glycosidic linkage at the C 1 or C 4 position, and the doublet spectrum is ascribed to radical formed by hydrogen abstraction from the C 1 position in cellulose molecule.

Radiation degradation of cellulose fibers was investigated by gel permeation chromatography (GPC). Scoured cotton of Mexican variety (cellulose I), Polynosic rayon (cellulose II), and their microcrystalline celluloses obtained by hydrolysis of the original fibers were irradiated by Co-60 ..gamma..-rays under vacuum or humid conditions. The irradiated samples were then nitrated under nondegradative conditions. The molecular weights and molecular weight distributions were measured by GPC using tetrahydrofuran as solvent. The relationship between molecular weight and elution count was obtained with cellulose trinitrate standards fractionated by preparative GPC. The degree of polymerization of the fibers decreased with increasing irradiation dose, but their microcrystalline celluloses were only slightly degraded by irradiation, especially in microcrystalline cellulose from cellulose I. Degradation of the fibers irradiated under humid conditions was less than that irradiated under vacuum. It was found that the G-values for main-chain scission for the irradiated cellulose I, cellulose II, microcrystalline cellulose I, and microcrystalline cellulose II were 2.8, 2.9, less than 1, and 2.9, respectively, but the G-value for main-chain scission for the irradiated cellulose II was increased to 11.2 at irradiation doses above 3 Mrad. Consequently, it is inferred that cellulose molecules in the amorphous regions are degraded more readily, and themore » well-aligned molecules in crystalline regions are not as easily degraded by irradiation.« less

これまでグラフト重合生成物のグラフト率の決定は, (W-W0)/W0×100 (%) で定義される重量増加率で行なわれてきた (ここでWはグラフトした後の重量, W0はグラフト前の重量)。しかし, この方法は実験室的規模では適用可能であるが, パイロット, または工業装置で得られた製品の重量を正確に測定することは困難であり, 適用できないことから, 間接的にグラフト率を測定する必要が生じる。主鎖, または側鎖がアクリロニトリルなどのような特定元素を含んだポリマーである場合, この特定元素の分析からグラフト率が決定できるが, スチレンセルロース系ではこの方法もまた不適当である。そこでスチレングラフトレーヨンのグラフト率とともに変化する種々の性質から, 間接的にグラフト率を決定する方法を検討した。赤外線吸収強度比, 比重, 吸湿率などについて調べた結果, 赤外法, 比重法は試料の量がわずかで, 正確に再現性よくグラフト率が決定できることがわかった。赤外法では重量増加率0～120%程度, 比重法でもやはりこの範囲できれいな曲線が得られ, グラフト率にして1～2%の誤差で測定できる。赤外法をベンチスケールの装置での製品のグラフト率の分布の測定に応用した例を示す。以上の方法のほかにも, グラフト率とともに変化することが予想される二三の性質, 吸水性, 染料の染着性, 誘電率などについても若干検討を行なった結果, いずれの場合にも試料の前処理がむずかしいため, 期待された結果は得られなかった。

ポリ塩化ビニル繊維の熱酌性質を向上させるため,種々の試みが行なわれている。桜田らはポリ塩化ビニル繊維にアクリ獄ニトリルのグラフト重合を行ない,耐熱性が著しく向上することを報告している。本報告では放射線同時照射法により,ポリ塩化ビニル繊維にアクリロニトリルをグラフト重合させる反応について,線量率の影響を検討した。照射は未延伸のポリ塩化ビニル繊維をアクリロニトリルモノマーとn-ヘキサンとの1:1の混含液中に浸漬した状態で行ない,線源としては低線量率(104～106rad/hr)を得るため60℃を用い,高線量率(107～10grad/hr)を得るため電子線加速器を用いた。その結果,次の点が明らかになった。(1)低線量率でも高線量率でも容易に100%程度のグラフト率が得られるが,特に高線量率の場合2～3分の短い反応時間で達成される。(2)グラフト重合反応の初期速度は低線量率では線量率の1次に比例し,高線量率では線量率の増加とともに0.3次から0次へと変化する。(3)グラフト重合反応の初期速度の温度依存性は小さい。(4)グラフト重合反応の後重合効果は非常に小さい。(5)グラフト効率は高線量率で反応を行なった方が高い。(6)雰囲気の影響は反応のごく初期にのみ観測される。