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Recent studies indicate that l-glutamate (l-Glu), abundant in many foods, is a stimulator of gastric vagal afferent nerves. The aim of the present study was to examine the possibility that l-Glu supplementation of a protein-rich liquid diet may prevent the incidence of diarrhoea during repetitive intra-gastric tube feeding. The gastric vagal afferent nerve recording of rats indicated that intra-gastric administration of a protein-rich liquid diet supplemented with 0·5 % monosodium glutamate enhanced the basal afferent activities seen with the protein-rich diet alone. The examination of the faeces showed that the addition of monosodium glutamate to the liquid diet significantly prevented the incidence of diarrhoea induced by repetitive gastric feeding. In conclusion, supplementation of an enteral liquid diet with free l-Glu may ameliorate diarrhoea during intra-gastric tube feeding by sending visceral glutamate information from the stomach to the brain.
We prepare Nd-Bi codoped zeolites by a method consisting of a simple ion-exchange process and subsequent high-temperature annealing. The emission covers the range of 970∼1450 nm, corresponding to the electronic transitions of Nd3+ ions and Bi-related active centers (BiRAC), respectively. The introduction of Bi distinctly broadens the excitation band of Nd3+ in the visible region, and the lifetime of Nd3+ reaches as long as 354 μs. In the zeolite matrix, Bi ions exist as BiRAC and Bi oxide agglomerates. The former one act as a sensitizer of Nd3+ ions, and the latter one act as a blockage to avoid the quenching effect of coordinated water, which enable Nd3+ ions to show efficient near-infrared (NIR) emission even the zeolites contain large amount of coordinated water. The excellent optical and structural properties make these NIR emitting nanoparticles promising in application as laser materials and biological probes.
Photoluminescence (PL) of SiO2 films co-doped with Si nanocrystals (nc-Si) and Er was studied. The average size of nc-Si was changed in a wide range in order to tune the exciton energy of nc-Si to the energy separations between the discrete electronic states of Er3+. PL from exciton recombination in nc-Si and the intra-4f shell transition of Er3+ were observed simultaneously. At low temperatures, periodic features were observed in the PL spectrum of nc-Si. The period agreed well with the optical phonon energy of Si. The appearance of the phonon structures implies that nc-Si which satisfy the energy conservation rule during the energy transfer process can resonantly excite Er3+. The effects of the quantum confinement of excitons in nc-Si on the energy transfer process are discussed.
Effects of impurity (P and B) doping on the photoluminescence (PL) properties of Si nanocrystals (nc-Si) in SiO2 thin films are studied. It is shown that with increasing P concentration, PL intensity first increases and then decreases. In the P concentration range where PL intensity increases, quenching of the defect-related PL is observed, suggesting that dangling-bond defects are passivated by P doping. On the other hand, in the range where PL intensity decreases, optical absorptiondue to the intravalley transitions of free electrons generated by P doping appears. The generation of free electrons andthe resultant three-body Auger recombination of electron-hole pairs is considered to be responsible for theobserved PL quenching. In the case of B doping, the behavior is much different. With increasing B concentration, PL intensity decreases monotonously. By combining the results obtained for P and B doped samples, theeffects of donor and acceptor impurities on the PL properties of nc-Si are discussed.
Growth of perturbations and fragmentation of isothermal sheet-like clouds are computed three dimensionally. An initial cloud is a self-gravitating equilibrium gas layer with small fluctuations, which have the form ei(kxk+kyy). The simulations of models with various values of kx and ky are performed.
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