Real-Time Feedback of the Applied Light-Curing Technique and Its Impact on Degree of Conversion of Composite Restorations—A Study with Undergraduate Dental Students

The objective of this study was to investigate the effect of individual instructions and training of dental students on the amount of applied light irradiance before and after training using a patient simulator with integrated visual feedback. Furthermore, the effect on the degree of conversion of composite restorations placed by the dental students was assessed. Forty-two dental students, split into two groups, light-cured a simulated restoration in tooth 27 of a dental patient simulator for 20 s. The irradiance (mW/cm2) received by the detector was measured in real-time before and after individual instructions and training, and the energy delivered (J/cm2) was calculated for each student. The degree of conversion at the bottom of incrementally placed composite restorations prior to individual instructions (group 1) and after individual instructions (group 2) was assessed using Fourier-transform infrared (FTIR) spectroscopy. The irradiance and degree of conversion measurements were re-assessed after all students received individual instructions. Data were analyzed using Wilcoxon signed-rank test and Mann–Whitney U-test at an overall level of significance of ⍺ = 0.05. A significant increase (p < 0.001) in applied light irradiance could be observed after individual instructions for both groups, with notably reduced data scattering. However, no significant difference was detected for the degree of conversion of placed composite restorations before or after instruction and training. Neither gender nor age of the dental students affected the obtained results. Consistent light energy delivered by dental students could be achieved through individual instructions and training with a patient simulator, also leading to less scattered irradiance results. However, the improved light-curing performance after the training did not affect the degree of conversion of the placed class II composite restorations.

An algal-bacterial symbiotic system of carbon fixation using formate as a carbon source

Algae are an attractive option for CO2 sequestration due to their natural ability to simultaneously fix CO2 and accumulate algal biomass for value-added products. However, the commercial implementation of such technology for efficient capture of CO2 from fossil-derived flue gases is not a reality yet due to several major challenges, such as low gas-liquid mass transport efficiency and relatively high light irradiance demand of algal growth. This study explored an algal-bacterial symbiotic system to utilize formate, a potential intermediate liquid compound of CO2, as carbon source to support microbial growth. The algal-bacterial assemblage, after an adaptive evolution using the formate medium, demonstrated a new route to assimilate CO2 without using high pH cultivations and promote biomass production under low light irradiance condition. The formate based culture system not only resolves CO2 mass transfer limitation, but also expels algae grazers in non-sterilized cultivation conditions. Continuous cultivation of the assemblage on formate led to a carbon capture efficiency of 90% with biomass concentration of 0.92 g/L and biomass productivity of 0.31 g/L/day, which is significantly better than the control cultivation on saturated CO2. In addition, isotope tracing and microbial community analysis offer new insights into formate metabolism and algal-bacterial symbiosis under light and carbon conditions. This study demonstrates a promising route of using electrochemical-derived formate to support algal biorefining.

Leaf elongation response to blue light is mediated by stomatal-induced variations in plant transpiration in Festuca arundinacea

Reduced blue light irradiance is known to enhance leaf elongation rate (LER) in grasses but the mechanisms involved have not yet been elucidated. We investigated if leaf elongation response to reduced blue light could be mediated by stomatal induced variations of plant transpiration. Two experiments were carried out on tall fescue in order to monitor LER and transpiration under reduced blue light irradiance. Additionally, LER dynamics were compared to those observed in the response to VPD-induced variations of transpiration. Finally, we developed a model of water flow within a tiller to simulate the observed short-time response of LER to various transpiration regimes. LER dramatically increased in response to blue light reduction and then reached new steady states, which remained higher than the control. Reduced blue light triggered a simultaneous stomatal closure which induced an immediate decrease of leaf transpiration. The hydraulic model of leaf elongation accurately predicted the LER response to blue light and VPD, resulting from an increase in the growth-induced water potential gradient in the leaf growth zone. Our results suggest that the blue light signal is sensed by stomata of expanded leaves and transduced to the leaf growth zone through the hydraulic architecture of the tiller.

Light regulating metabolic responses of Cyanobium sp. (Cyanobacteria)

Cyanobacteria are an important group of microorganisms of significant economic interest due to, for ex- ample, the antioxidant capacity of their metabolites. Cyanobium sp. LEGE 06113 is a marine cyanobacterium poorly studied, but with promising future applications. The aim of this study was to optimize the light conditions (both source and irradiance) and nutrient (N and P) concentration for Cyanobium sp. production as a source of high-valued com- pounds. The optimization of the processing parameters was performed using two different light sources (fluorescent and low-pressure sodium lamp), four irradiances (50, 100, 200 and 300 μmol photons m–2 s–1) and two variations of BG11 medium (BG11 and BG11+, with the second containing double amounts of phosphates and nitrates). The effects of the three factors were evaluated on the biomass production, photosynthetic activity, biochemical composition and antioxidant capacity. A synergistic effect between the light source, light intensity, and medium was observed for all measured parameters, with the greatest impact of light irradiance on the metabolism of Cyanobium sp. The combination of the SOX lamp, BG11+ medium, and a light irradiance of 200 μmol photons m–2 s–1 was optimal for the cultivation of Cyanobium sp. This work reports the tools for the production of Cyanobium sp. as a source of high-value products, thus increasing its biotechnological potentials.