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A letter to the editor is presented about the storage conditions for photographic materials.

Objective: To investigate the efficacy of silver diamine fluoride (SDF) with 5% fluoride varnish (FV) in treating cavitated caries in young children and to explore the association between SDF treatment and oral-health-related quality of life (OHRQoL)., Methods: Children with active dentinal caries in primary teeth underwent treatment with 38% SDF and 5% FV at baseline and 4 months later. Treated lesions were assessed 4 and 8 months after baseline. Child-level analysis focused on classifying SDF treatment as completely successful if all of a child's treated lesions were arrested or incompletely successful if at least 1 lesion was not arrested. The Early Childhood Oral Health Impact Scale questionnaire was completed at second and third visits. Statistical analyses included descriptive and bivariate methods. A p value ≤ 0.05 was considered significant., Results: This pilot study enrolled 40 children with 239 caries lesions; mean age 40.2 ± 14.9 months and 45% male. Lesion arrest rates after 1 and 2 applications of SDF were 74.1% and 96.2%, respectively. Children who reportedly brushed twice daily were more likely to be in the completely successful group compared with those who brushed less (p = 0.006). Those in the completely successful group had a significantly lower mean baseline dmft score than those in the incompletely successful group (p = 0.048). No significant difference in OHRQoL was observed between the 2 groups., Conclusions: SDF with 5% FV is an effective approach to the management of early childhood caries; more than 1 application is recommended, along with regular follow up of patients and twice daily brushing. OHRQoL was not found to be affected by the level of success of SDF treatment.

Employing several nematic liquid crystal mixtures, we investigate how the thermo-optic response of nonlinear birefringent soft-matter affects the propagation of light beams and the features of self-induced waveguides. We address the formation of optical spatial solitons and the control of their trajectories versus temperature, comparing the measurements with the expectations based on a simplified model, showing an excellent agreement. Moreover, in a guest⁻host mixture with an absorbing dye dopant, we study the competition between reorientational and thermal nonlinearities, demonstrating that the two processes can be adjusted independently in order to tune the soliton properties, i.e., trajectory and confinement strength. Our results are an important contribution to better comprehend the role played by material properties on linear and nonlinear beam propagation, as well as their exploitation for signal processing and addressing.

We investigate nonlinear optical propagation of continuous-wave (CW) beams in bulk nematic liquid crystals. We thoroughly analyze the competing roles of reorientational and thermal nonlinearity with reference to self-focusing/defocusing and, eventually, the formation of nonlinear diffraction-free wavepackets, the so-called spatial optical solitons. To this extent we refer to dye-doped nematic liquid crystals in planar cells excited by a single CW beam in the highly nonlocal limit. To adjust the relative weight between the two nonlinear responses, we employ two distinct wavelengths, inside and outside the absorption band of the dye, respectively. Different concentrations of the dye are considered in order to enhance the thermal effect. The theoretical analysis is complemented by numerical simulations in the highly nonlocal approximation based on a semi-analytic approach. Theoretical results are finally compared to experimental results in the Nematic Liquid Crystals (NLC) 4-trans-4'-n-hexylcyclohexylisothiocyanatobenzene (6CHBT) doped with Sudan Blue dye.

In this article we present a new all-optical method to measure elastic constants connected with twist and bend deformations. The method is based on the optical Freedericksz threshold effect induced by the linearly polarized electro-magnetic wave. In the experiment elastic constants are measured of commonly used liquid crystals 6CHBT and E7 and two new nematic mixtures with low birefringence. The proposed method is neither very sensitive on the variation of cell thickness, beam waist or the power of a light beam nor does it need any special design of a liquid crystal cell. The experimental results are in good agreement with the values obtain by other methods based on an electro-optical effect.