Accuracy of Irradiance and Power of Light-Curing Units Measured With Handheld or Laboratory Grade Radiometers

This study measured and compared exitance irradiance and power of 4 commercial dental light-curing units (LCU) (Elipar S10, Elipar DeepCure-S, Corded VALO and Bluephase Style) using different types of radiometers. The devices used to analyze the LCU were classified as either handheld analog (Henry Schein, Spring, Demetron 100A, Demetron 100B and Demetron 200), handheld digital (Bluephase 1, Bluephase II, Coltolux, CureRite and Hilux), or laboratory instruments (Thermopile and Integrating Sphere). The laboratory instruments and the Bluephase II radiometer were also used to measure the LCU’s power (mW). The LCU’s were activated for 20 s (n=5). Data were analyzed using Kruskal-Wallis and Student-Newman-Keuls multiple comparison test (a=0.05). Among the LCU, the laboratory instruments presented different irradiance values, except for Corded VALO. The Coltolux and Hilux radiometers measured greater irradiance values compared to the laboratory instruments for the four LCUs tested. Within a given LCU, handheld analog units measured lower irradiance values, compared to handheld digital and laboratory instruments, except using the Spring radiometer for the Elipar S10 LCU. None of the handheld radiometers were able to measure similar irradiance values compared to laboratory instruments, except for Elipar S10 when comparing Bluephase 1 and Thermopile. Regarding power measurement, Bluephase II always presented the lowest values compared to the laboratory instruments. These findings suggest that the handheld radiometers utilized by practitioners (analog or digital) exhibit a wide range of irradiance values and may show lower outcomes compared to laboratory based instruments.

Stability of the Light Output, Oral Cavity Tip Accessibility in Posterior Region and Emission Spectrum of Light-Curing Units

SUMMARYObjectives: This study evaluated the light output from six light-emitting diode dental curing lights after 25 consecutive light exposures without recharging the battery, tip accessibility in the posterior region, and light beam spread from light-curing units.Methods: Irradiance, spectral peak, and radiant exposure were measured with the battery fully charged (Bluephase Style, ESPE Cordless, Elipar S10, Demi Ultra, Valo Cordless, and Radii-Cal) and monitored for 25 light exposures (each lasting 10 seconds). The tip diameter was measured to identify the beam size and the ability of the six light-curing units to irradiate all areas of the lower second molar in the standard output setting.Results: Four curing lights delivered a single peak wavelength from 454 to 462 nm, and two (Bluephase Style and Valo Cordless) delivered multiple emission peaks (at 410 and 458 nm and 400, 450, and 460 nm, respectively). The irradiance and radiant exposure always decreased after 25 exposures by 2% to 8%, depending on the light unit; however, only ESPE Cordless, Valo Cordless, and Radii-Cal presented a statistical difference between the first and the last exposure. The tip diameter ranged from 6.77 mm to 9.40 mm. The Radii-Cal delivered the lowest radiant exposure and irradiance. This light was also unable to access all the teeth with the tip parallel to the occlusal surface of the tooth.Conclusion: Not all of the blue-emitting lights deliver the same emission spectra, and some curing lights delivered a lower irradiance (as much as 8% lower) after the 25th exposure.

Growth characteristics of selected thermophilic strains of cyanobacteria using crossed gradients of temperature and light

Growth requirements of 10 possibly thermophilic strains of cyanobacteria were compared under a wide spectrum of light and temperature conditions (7–80Wm−2, 12–40°C). The strains were isolated from different localities: six of thermal springs in Slovakia (4 from Piešťany, 2 from Sklené Teplice), one from thermal waters in Rupite, Bulgaria, 2 strains from a hypersaline lake Chott-el-Djerid, Tunisia, and one strain from the tropical island of Cebu, Philippines. Although the crossed gradient unit allowed only sub-optimal temperature range with respect to thermophile definition, i.e. optimum temperature above 45°C, there were difference among the strains. The most thermophilic and high-light tolerant strain was Synechococcus bigranulatus strain Lukavsky 2005/66, with a peak above 45°C; the second was Chroococcidiopsis thermalis strain Hindák 2008/9, and Isocystis sp. strain Hindák 2006/1. The temperature requirements of other strains were similar; the least thermophilic were both Slovakian strains of the genus Hapalosiphon. Growth was not limited below 80 W m−2, except for H. fontinalis strain Hindák 2008/3, which prefers lower irradiance. Hapalosiphon delicatulus strain Hindák 2007/20, isolated from a bark tree on the tropical island of Cebu was rather mesophilic than thermophilic and shade-preferring. The CCA revealed that the ecologically similar strains originated from the same or nearby localities. There were no significant correlations between temperature optima in culture and in nature. Bulgarian and Tunisian strains preferred higher irradiances.

Ecosystem metabolism in a temporary Mediterranean marsh (Doñana National Park, SW Spain)

The metabolic balance of the open waters supporting submerged macrophytes of the Doñana marsh (SW Spain) was investigated in spring, when community production is highest. The marsh community (benthic + pelagic) was net autotrophic with net community production rates averaging 0.61 g C m−2 d−1, and gross production rates exceeding community respiration rates by, on average, 43%. Net community production increased greatly with increasing irradiance, with the threshold irradiance for communities to become net autotrophic ranging from 42 to 255 μE m−2 s−1, with net heterotrophic at lower irradiance. Examination of the contributions of the benthic and the pelagic compartments showed the pelagic compartment to be strongly heterotrophic (average P/R ratio = 0.27), indicating that the metabolism of the pelagic compartment is highly subsidised by excess organic carbon produced in the strongly autotrophic benthic compartment (average P/R = 1.58).

What is the influence of ordinary epidermal cells and stomata on the leaf plasticity of coffee plants grown under full-sun and shady conditions?

Stomata are crucial in land plant productivity and survival. In general, with lower irradiance, stomatal and epidermal cell frequency per unit leaf area decreases, whereas guard-cell length or width increases. Nevertheless, the stomatal index is accepted as remaining constant. The aim of this paper to study the influence of ordinary epidermal cells and stomata on leaf plasticity and the influence of these characteristics on stomata density, index, and sizes, in the total number of stomata, as well as the detailed distribution of stomata on a leaf blade. As a result, a highly significant positive correlation (R²a = 0.767 p < 0.001) between stomatal index and stomatal density, and with ordinary epidermal cell density (R²a = 0.500 p < 0.05), and a highly negative correlation between stomatal index and ordinary epidermal cell area (R²a = -0.571 p < 0.001), were obtained. However in no instance was the correlation between stomatal index or stomatal density and stomatal dimensions taken into consideration. The study also indicated that in coffee, the stomatal index was 19.09% in shaded leaves and 20.08% in full-sun leaves. In this sense, variations in the stomatal index by irradiance, its causes and the consequences on plant physiology were discussed.

Photosynthesis and water-use efficiency of seedlings from northern Australian monsoon forest, savanna and swamp habitats grown in a common garden

Islands of monsoon rainforest and Melaleuca swamp punctuate vast tracts of savanna in monsoonal northern Australia. Seedlings of species from each of these habitat associations were grown in a common garden. Monsoon forest species had higher specific leaf area, lower photosynthetic capacity and lower photosynthetic light compensation points, and required lower irradiance to achieve 50% of light-saturated photosynthesis compared with savanna or swamp species. These traits probably contribute towards greater shade tolerance beneath dense monsoon-forest canopies, whereas savanna and swamp canopies are relatively open. Swamp species, especially two Melaleuca species, had high stomatal conductance and small CO2 drawdown during photosynthesis, and more negative leaf δ13C, compared with monsoon forest and savanna species. Higher stomatal conductance increases carbon uptake during photosynthesis and a high transpiration rate would increase transport of nutrients to absorbing surfaces in the root by mass flow. Thus, a strategy of high transpiration and low water-use efficiency appears to be favoured in swamp species compared with monsoon-forest and savanna species. Instantaneous measurements of the ratio of intercellular to ambient CO2 concentrations (ci/ca) explained 81% of variation in leaf δ13C across 44 species sampled in this and other studies, suggesting that leaf δ13C generally provides a robust proxy for comparisons of ci/ca, even when applied across species.

Influence of Daily Light Period and Irradiance on Yield and Leaf Elemental Concentration of Hydroponically Grown Sweetpotato

Growth chamber experiments were conducted to evaluate the effect of irradiance and daily light period on storage root yield and leaf elemental concentration of two sweetpotato cultivars grown hydroponically by use of the nutrient film technique (NFT). Stem cuttings (15 cm) of cv. Whatley/Loretan and Georgia Jet were grown in NFT channels (0.15 × 0.15 × 1.2 m) in reach-in growth chambers under light period/irradiance combinations of 18 h: 300 μmol·m−2·s−1 or 9 h: 600 μmol·m−2·s−1 photosynthetic photon flux. Temperature was 28/22 °C light/dark with a relative humidity of 70% ± 5%. Storage root and foliage yields were greater in both cultivars exposed to a longer daily light period and lower irradiance. The main effect of cultivar indicated that storage root yield was significantly greater among plants of ‘Whatley/Loretan’ compared with that of ‘Georgia Jet’, whereas foliage yield was similar between cultivars. Leaves of plants grown under longer daily light period and lower irradiance had significantly lower concentrations of all elements, nitrogen, phosphorus, potassium, calcium, magnesium, manganese, iron, calcium, boron, and zinc, except for calcium, manganese, and boron. There were no significant differences in leaf elemental concentration between cultivars. Thus, a longer daily light and lower irradiance enhanced biomass production of sweetpotato but reduced leaf elemental concentration probably because of a “dilution” effect.

Degree of Conversion and Contraction Stress Development of a Resin Composite Irradiated Using Halogen and LED at Two C-factor Levels

Clinical Relevance Curing methods using lower irradiance levels were shown to be effective in reducing the rate of stress generation without compromising the conversion of the restorative composite. Higher C-factor was shown to enhance the stress rate and amount of stress generated.