Scintillators for Alpha and Neutron Radiations Synthesized by Room Temperature Sol–Gel Processing

Solid-state scintillating materials were synthesized by the co-doping of sol–gel components with neutron absorbers [⁶Li and ¹⁰B], organic fluorescence sensitizers such as salicylic acid and 2,5-diphenyloxazole (PPO) and activator 1,4-bis-2-(5-phenyloxazolyl)-benzene (POPOP). The room-temperature sol–gel process through the addition of organic polymers is the key to the successful entrapment of the organic sensitizers and activator in inorganic matrixes. These transparent or translucent sol–gel scintillators were evaluated for alpha radiation and neutron detections.     

Distribution of macropores in silica particles prepared by using multiple emulsions

The distribution of macropores in silica particles prepared by the hydrolysis and condensation of TEOS in a hexane/water/decyl alcohol (O(1)/W/O(2)) multiple emulsion was investigated. To stabilize the emulsion structure, hydroxypropyl cellulose (HPC) was added into the O(2) phase and polyethylene glycol (PEG) was added into the water phase. Without HPC, the particles have an irregular shape and hardly have particulate forms. As the concentration of HPC increases, the shape of particles becomes more and more spherical and the size decreases. The size of silica particles was varied from 5 to 1 microm as the concentration of HPC increased from 0.5 to 0.7 wt%. The number and size of the macropores in silica particles were affected by PEG polymer concentration. With the variation in the concentration of PEG, macropores in silica particles were located at the surface of or inside the particles. At high concentrations of PEG, the macropores in particles were located inside the particles, but at low concentrations of PEG the macropores were located at the surfaces of particles. Interestingly, the particles of dimpled surfaces were formed when the molar ratio of water to TEOS (R(w)) was 4.0 and the concentrations of PEG and HPC were 2.0 and 0.7 wt% respectively. The surface areas of dimpled silica particles and completely spherical particles, measured by the BET method, were 409 and 433 m(2)/g respectively.     

Monodisperse oligofluorenes with keto defect as models to investigate the origin of green emission from polyfluorenes: synthesis, self-assembly, and photophysical properties

Oligofluorenes (a trimer, pentamer, and heptamer) with one fluorenone unit in the center (OFnK: n=3, 5, or 7) were synthesized and used as models to understand the origin of the low-energy emission band in the photoluminescence and electroluminescence spectra of some polyfluorenes. All compounds form glasses with T(g) at 30 degrees C (OF3 K), 50 degrees C (OF5 K) and 57 degrees C (OF7 K). Oligomers OF5 K and OF7 K exhibit smectic liquid crystal phases that undergo transition to isotropic melts at 107 and 205 degrees C, respectively. Oligomer OF5 K could be obtained in form of single crystals. The X-ray structure analysis revealed the helical nature of the molecule and a helix reversal defect located at the central fluorenone unit. The packing pattern precludes formation of excimers. Electrochemical properties were investigated by cyclic voltammetry. The ionization potential (I(p)) and electron affinity (E(a)) were calculated from these data. Studies of the photophysical properties of OFnK in solution and thin film by steady-state and time-resolved fluorescence spectroscopic measurements suggest efficient funneling of excitation energy from the photoexcited fluorene segments to the low-energy fluorenone sites by both intra- and intermolecular hopping events whereby they give rise to green emission. Intermolecular energy transfer was investigated by using a model system composed of a highly defect free polyfluorene PF2/6 doped by OFnK. F?rster-type energy transfer takes place from PF2/6 to OFnK. The energy-transfer efficiency increases predictably with increasing concentration of OFnK.     

Trp-Lys-Tyr-Met-Val-Met stimulates phagocytosis via phospho-lipase D-dependent signaling in mouse dendritic cells

Dendritic cells (DCs) play a key role in activating the immune response against invading pathogens as well as dying cells or tumors. Although the immune response can be initiated by the phagocytic activity by DCs, the molecular mechanism involved in this process has not been fully investigated. Trp-Lys-Tyr-Met-Val-Met-NH(2) (WKYMVM) stimulates the activation of phospholipase D (PLD) via Ca(2+) increase and protein kinase C activation in mouse DC cell line, DC2.4. WKYMVM stimulates the phagocytic activity, which is inhibited in the presence of N-butanol but not t-butanol in DC2.4 cells. Furthermore, the addition of phosphatidic acid, an enzymatic product of PLD activity, enhanced the phagocytic activity in DC2.4 cells. Since at least two of formyl peptide receptor (FPR) family (FPR1 and FPR2) are expressed in DC2.4 as well as in mouse bone marrow-derived dendritic cells, this study suggests that the activation of FPR family by WKYMVM stimulates the PLD activity resulting in phagocytic activity in DC2.4 cells.     

In vitro and in vivo degradation behaviors of synthetic absorbable bicomponent monofilament suture prepared with poly(p-dioxanone) and its copolymer

A synthetic absorbable bicomponent monofilament suture (MonoFlex), composed of poly(p-dioxanone) and its copolymer, was prepared by a conjugate spinning method, and its degradation behavior was investigated in vitro and in vivo. MonoFlex degraded by hydrolysis, and retained approximately 55% of its original strength after four weeks of incubation in PBS at 37 °C. About 70% of the original strength was maintained after four weeks of implantation in rats, and the suture material was completely absorbed after 180-210 days post-implantation in rats. No remarkable tissue reactions were observed during degradation, and foreign body reactions were similar to those of commercially available suture materials composed of poly(p-dioxanone). This study to monitor the degradation behavior of monofilament sutures in vitro as well as in vivo may be useful in the development of novel suture materials for extended wound support.     

Four new saponins from the starfish Certonardoa semiregularis

Four new saponins, designated as certonardosides K-N (1-3, 5), were isolated, along with culcitoside C(6) (4), from the brine shrimp active fraction of the starfish Certonardoa semiregularis. The structures were determined on the basis of spectral analysis and chemical derivatization. These compounds were evaluated for cytotoxicity and antibacterial activity.     

Organization of branched rod-coil molecules into a 3-D tetragonally perforated lamellar mesophase

Tetramerization of coil-rod-coil ABC triblock copolymers to a tetrabranched molecule induces an unusual 3-D tetragonally perforated layered liquid crystalline phase as an intermediate structure between 1-D lamellar and 2-D hexagonal columnar phases.     

Biodegradable aliphatic polyester ionomers

A series of polyester-based ionomers containing dimethyl 5-sulfoisophthalate sodium salt (DMSI) with up to 5 mol-% diacid units was synthesized by two-step polycondensation. Furthermore a polylactic acid (PLA) was modified by introducing poly(ethylene-co-methacrylic acid) ionomers with different ion groups, such as Na, Li, and Zn, using the melt blending method. This review examines the effect of the ionic group on the dynamic mechanical properties, melt rheology, crystallization behavior, degradation behavior, and biocompatibility with human dermal cells, as well as the nucleating effect of poly(ethylene-co-methacrylic acid) ionomer in PLA.     

Cesium release during high-temperature pre-treatment of fuel fragments with a burn-up of 61 GWd/tU

The electrolytic reduction process in pyroprocessing of used fuel requires that fuel fragments be pre-treated to remove cesium and iodine. The effect of high temperatures and fuel fragment size on release of cesium was investigated over 10 h at a temperature of 1300–1400 °C for fuel fragments with an O/U ratio of 2.2. Re-fragmentation of the original fragments was observed as changes in cesium release count rates as fuel was heated from 484 to 1329 °C. The release of cesium is highly dependent on the size of fuel fragments and most of the cesium is released as the temperature is held at the maximum target value.