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In this paper, Φ25 mm lanthanum bromide scintillation crystals with 5%Ce3+ and different Sr2+ doping concentrations (0.1%, 0.3%, 0.5% in molar ratio) were successfully grown by spontaneous nucleation vertical Bridgman method. X-ray excited emission spectra, transmission spectra and pulse height spectra of these crystals were measured. Results show that, the emission spectra waveform of LaBr3:Ce crystals with different Sr2+ doping concentrations is basically consistent under X-ray excitation, and the emission peak shows a significant red shift compared with that of sample without Sr2+ doping. With the increase of Sr2+ doping concentration, the emission peak of LaBr3:Ce,Sr crystal shows a slight red shift. There is no obvious absorption peak range from 350 to 800 nm of LaBr3:Ce,Sr crystals with different Sr2+ doping concentrations. Compared with LaBr3:Ce crystals, transmittance of 0.3% and 0.5% Sr2+ doped LaBr3:Ce crystals decrease. In addition, with the increase of Sr2+ doping concentration, the energy resolution of the crystal increases correspondingly. LaBr3:Ce,0.5% Sr crystal has the highest energy resolution of 2. 99%@662 keV. The energy resolution of the encapsulated LaBr3:Ce,0.5%Sr crystal with size of Φ25 mm x 25 mm is 2.93%@662 keV. [ABSTRACT FROM AUTHOR]

Objective: To construct antimicrobial peptides with potent antimicrobial activity, low cytotoxicity and efficient killing rate of Streptococcus mutans for prevention and treatment of dental caries., Methods: We exploited the existing design strategies to modify reutericin 6 or gassericin A produced by Lactobacillus species in the oral cavity based on their cationicity, amphipathicity and α -helical structure. We examined their antimicrobial activities using bacterial susceptibility assay, their cytotoxicity through cytotoxicity assay and their killing rate of Streptococcus mutans with time-kill assay. We further evaluated the candidate derivatives for their killing rate against Streptococcus mutans , their antimicrobial activity against different oral pathogens and the development of drug resistance., Results: We constructed 6 AT-1 derivatives, among which AT-7 showed an MIC of 3.3 μmol/L against Streptococcus mutans , Porphyromonas gingivalis and Actinomyces viscosus with a killing rate of 88.7% against Streptococcus mutans within 5 min. We did not obtain de novo strains of Streptococcus mutans resistant to AT- 7 after induction for 10 passages., Conclusions: Hydrophobicity and imperfect amphipathic structure are two key parameters that define the antimicrobial potency of the antimicrobial peptides. The imperfectly amphipathic peptide AT-7 shows the potential for clinical application in dental caries treatment.