The temperature dependence of the dielectric constant and dissipation in potassium dihydrogen phosphate ͑KDP͒, its deuterated compound ͑DKDP͒, triglycine sulfate ͑TGS͒, and TGS doped with ␣-alanine ͑LATGS͒ has been studied at various frequencies. It is found that the relaxation time of domain freezing in KDP and DKDP in the kHz range can be described by the Vogel-Fulcher relation. Evidence of domain freezing in TGS is presented through an analysis of relaxation time related to domain walls and a comparison between TGS and LATGS. Studies of internal friction and compliance show preliminary evidence of domain freezing in CuAlZnNi alloy. A domain-freezing model is proposed based upon the collective pinning of randomly distributed pinning centers to domain walls. Some key experiments related to domain freezing, such as ͑1͒ the Vogel-Fulcher relation for relaxation time; ͑2͒ the size effect of domain freezing; ͑3͒ two kinds of relaxation in low-and high-frequency ranges, respectively; and ͑4͒ the dependence of T F on defect density and applied field, etc., are explained. ͓S0163-1829͑97͒01323-4͔

Background: Despite titanium (Ti) implants have been commonly used in the medical device field due to their superior biocompatibility, implant-associated bacterial infection remains a major clinical complication. Nanosilver, an effective antibacterial agent against a wide spectrum of bacterial strains, with a low-resistance potential, has attracted much interest too. Incorporation of nanosilver on Ti implants may be a promising approach to prevent biofilm formation. Purpose: The objective of the study was to investigate the antibacterial effects and osteoinductive properties of nanosilver/poly (dl-lactic-co-glycolic acid)-coated titanium (NSPTi). Methods: Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and the Gramnegative opportunistic pathogen Pseudomonas aeruginosa (PAO-1) were used to evaluate the antibacterial activity of NSPTi implants through the analysis of bacterial colonization in vitro and in vivo. Furthermore, we examined the osteoinductive potential of NSPTi implants by investigating the proliferation and differentiation of MC3T3-E1 preosteoblast cells. In vivo, the osteoinductive properties of NSPTi implants were assessed by radiographic evaluation, H&E staining, and Masson's trichrome staining. Results: In vitro, bacterial adhesion to the 2% NSPTi was significantly inhibited and ,1% of adhered bacteria survived after 24 hours. In vitro, the average colony-forming units (CFU)/g ratios in the 2% NSPTi with 10 3 CFU MRSA and PAO-1 were 1.50±0.68 and 1.75±0.6, respectively. In the uncoated Ti groups, the ratios were 1.03±0.82×10 3 and 0.94±0.49×10 3 , respectively. These results demonstrated that NSPTi implants had prominent antibacterial properties. Proliferation of MC3T3-E1 cells on the 2% NSPTi sample was 1.51, 1.78, and 2.22 times that on the uncoated Ti control after 3, 5, and 7 days' incubation, respectively. Furthermore, NSPTi implants promoted the maturation and differentiation of MC3T3-E1 cells. In vivo, NSPTi accelerated the formation of new bone while suppressing bacterial survival. Conclusion: NSPTi implants have simultaneous antibacterial and osteoinductive activities and therefore have the potential in clinical applications.

Domain freezing is observed for the first time in triglycine sulphate. A new domain freezing model is proposed based upon the collective-pinning of random distributing pinning centers to DW's, and Vogel-Fulcher relation, which describes the relaxation during the process of domain freezing successfully, is deduced.

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