Photoluminescence Stokes shift and exciton fine structure in CdTe nanocrystals

The photoluminescence spectra of spherical CdTe nanocrystals with zincblende structure are studied by size-selective spectroscopic techniques. We observe a resonant Stokes shift of 15 meV when the excitation laser energy is tuned to the red side of the absorption band at 2.236 eV. The experimental data are analyzed within a symmetry-based tight-binding theory of the exciton spectrum, which is first shown to account for the size dependence of the fundamental gap reported previously in the literature. The theoretical Stokes shift presented as a function of the gap shows a good agreement with the experimental data, indicating that the measured Stokes shift indeed arises from the electron-hole exchange interaction.Comment: 8 pages, 4 figures, LaTe

Contaminated water delivery as a simple and effective method of experimental Salmonella infection

AimIn most infectious disease models, it is assumed that gavage needle infection is the most reliable means of pathogen delivery to the GI tract. However, this methodology can cause esophageal tearing and induces stress in experimental animals, both of which have the potential to impact early infection and the subsequent immune response.Materials & methodsC57BL/6 mice were orally infected with virulent Salmonella Typhimurium SL1344 either by intragastric gavage preceded by sodium bicarbonate, or by contamination of drinking water.ResultsWe demonstrate that water contamination delivery of Salmonella is equivalent to gavage inoculation in providing a consistent model of infection. Furthermore, exposure of mice to contaminated drinking water for as little as 4 h allowed maximal mucosal and systemic infection, suggesting an abbreviated window exists for natural intestinal entry.ConclusionTogether, these data question the need for gavage delivery for infection with oral pathogens