ABSTRACT:Contact angles of water droplet on regenerated cellulose films as an index of wettability were positively correlated with the orientation of (1-10) crystal planes and crystallinity. Because hydroxyl groups of cellulose are located at the equatorial positions of glucopyranose rings, corresponding to the surface of (1-10) crystal planes, the hydrophilicity of the (1-10) surface is expected to be very high. It is natural, therefore, that higher planar orientation of (1-10) planes and crystallinity lead to higher density of hydroxyl groups on the surface of regenerated cellulose films resulting in higher wettability. In contrast, hydrogen atoms are located at the axial positions of the glucopyranose rings, corresponding to the surface of (110) planes. Thus, the (110) surface is expected to be hydrophobic, and the surface energy obtained by computer simulations was far lower than that of the (1-10) surface. This suggests that cellulose with complementary properties, i.e., hydrophobicity, may be created by structural controls such as reversing the planar orientation from (1-

Superconducting triplet quadrupoles (STQs) with large apertures and high field-gradients are employed for the in-flight radioactive-isotope (RI) beam separator BigRIPS at RIKEN. It consists of fourteen STQs and six room-temperature dipoles. The use of the STQs makes it possible to achieve important features of the BigRIPS separator: large acceptances and a large magnetic rigidity, allowing efficient production of RI beams. The BigRIPS separator is presently under construction and assembly as a major installation in the RIKEN RI-beam factory project, and the commissioning is scheduled in early 2007. In this paper we present the status and overview of the BigRIPS separator, emphasizing the STQs and their liquid-helium cryogenic systems.Index Terms-Accelerator magnets, in-flight RI-beam separator, liquid-helium cryogenic system, particle beam focusing superconducting magnets.

A scheme for spot scanning using 11C beams has been developed in order to form and verify a three-dimensionally conformal irradiation field for cancer radiotherapy. By selecting the momentum spread of a 11C beam, we could considerably decrease the distal falloff of the irradiation field, thus conserving the beam quality. To estimate and optimize the dose distribution in the irradiation field, it is essential to evaluate the precise dose distribution of spot beams. The coupling of the lateral dose and depth-dose distributions originating from a wide momentum spread should be taken into account to calculate the dose distribution of 11C beams. The reconstructed dose distribution of the irradiation field was in good agreement with the experimental results, i.e., within ±0.2%. An irradiation field of 35×35×43 mm3 was optimized and spot scanning using 11C beams was carried out. The flatness was within ±2.3% with an error of 1% in the detector resolution.

ABSTRACT:A new type of hydrogel, transparent cellulose hydrogel (TCG), is the aqueous dispersion of cellulose nanofibers (microfibrils) 10 nm in width and several hundreds nanometers in extended fiber length, and shows unique rheological properties leading to unique applications. The rheological properties of TCG, especially their dependences on temperature were investigated through the spin-spin relaxation time (T 2 ) analysis in 1 H NMR for water in the systems. Viscosity under low shear stress and T 2 of water (being very short for T 2 value) were proved to be constant in a wide range of temperature (ca. 30-80 C). These results may be explained by two considerations that network in TCG gradually grows with increasing temperature but collapses by adding weak shear stress and that TCG gel has large amount of bound water. It was also confirmed that the ionic strength such as pH and NaCl concentration sensitively influences on rheological parameters. With increasing ionic strength, the network formation and the successive aggregation of microfibrils occur and both should be interpreted in terms of the electrostatic interaction between negative charge on a cellulose surface and cationic aqueous layer around it (i.e., electric double layer). [DOI 10.1295/polymj.36.684] KEY WORDS Cellulose / Hydrogel / Nanofiber / Microfibril / Rheology / Spin-Spin Relaxation Time / Network / We have already found a preparation method of a new type of hydrogel, transparent cellulose hydrogel (TCG, Figure 1a), an aqueous dispersion of cellulose microfibrils (degree of polymerization: ca. 40) having low crystallinity with about 10-15 nm in diameter and several hundred nanometers in extended length ( Figure 1b) and reported the results for its characterization and properties. 1,2 This new nanomaterial was prepared by downsizing by chemical (hydrolysis reaction) 3 and mechanical (smashing by a ultra high pressure homogenizer) techniques. Resultant cellulose microfibrils in TCG are flexible fibrous particles, i.e., ''nanofibers'', having nano-size diameter (Figure 1b) and show strong attractive interaction based on hydrogen bonding between hydroxyl groups localized densely on their surfaces, leading to quite unique rheological properties. In view of the application, four major unique properties of TCG are pointed out 2 as follows: 1) Rheological properties such as very high viscosity under the low share stress, a large thixotropic character and low fluctuation of rheological parameters in the range of ambient temperature to the higher temperature region, 2) Formation of transparent coating film on substrate materials by drying, 3) Formation of cellulose microspheres having average particle size of less than 5 mm by spray drying, and 4) Stabilizing ability as an additive for aqueous suspension systems such as aqueous dispersion of inorganic particles (SiO 2 , TiO 2 , . . ., etc.) and O/W type emulsion (also as an emulsifier).Especially from an industrially applicable aspect, we discovered that TCG is a gel which can be sprayed by only ...

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