Maximum Light Levels Research Articles

A Cross-Sectional Study of Circadian Stimulus in Swedish Radiographers' Light Environment.

Background: Timely light exposure is a vital aspect to achieve better sleep and well-being. As there are risks with a disturbed circadian rhythm and benefits with light settings that stimulate the rhythm, the circadian effective light, circadian stimulus (CS), for radiographers was examined. Aim: The aim of the study was to compare radiographers' light environment on the workstations, at a university hospital in Southern Sweden in the form of CS and relate that to recommendations published by the Swedish Environmental Protection Agency. Method: A cross-sectional method has been applied. The measurements for CS were collected in all labs in the radiology department in the middle of January. Result: A total of 804 measures were evenly collected resulting in a median for the 19 labs, where the observed median for all labs was 0.091 CS which is significantly lower than the recommended value of 0.3 CS (p < .001). Comparing work light settings with maximum light levels in the brightest and darkest labs showed a significant difference (p < .001). Conclusion: The CS values in the labs, at the radiology department at a university hospital in Southern Sweden, do not reach the recommended values of circadian stimulus published by the Swedish Environmental Protection Agency when the radiographers themselves set the light. There is a potential for improvement as a significant difference could be seen between the chosen level of light and the maximum possible level of light.

PHOTOSYNTHESIS OF INDIAN WOODOATS IN CENTRAL TEXAS WOODLANDS

Abstract Measurements of photosynthetic rates were made on leaves of Chasmanthium latifolium (Michx.) Yates, Indian woodoats (Poaceae / Gramineae–Grass family). Plants were in the understory of Juniperus ashei/Quercus fusiformis (Ashe juniper/live oak) woodlands in central Texas. Density was low for C. latifolium in the woodlands where it was found. External light level (PFD, photosynthetic-flux density) at midday in the open, above the canopy, on a cloudless day was 1897 ± 21 μmol/m2/s (mean ± SE). Below the canopy, light level was 203 ± 28 μmol/m2/s. Leaves were exposed to light levels from zero to 2000 μmol/m2/s using a Li Cor 6400 photosynthetic meter. Photosynthetic rates were measured and used to generate light response curves. Leaf maximum photosynthetic rate (Amax) was 12.92 ± 0.50 μmol CO2/m2/s. Dark respiration was 0.08 ± 0.09 μmol CO2/m2/s. Light saturation was 1027 ± 42 μmol/m2/s or 54% of the midday maximum light level. The light compensation point was 6 ± 2 μmol/m2/s or 0.32% of the midday light level in the open, above the canopy. Thus, C. latifolium had a positive carbon uptake at very low light levels below canopies where it is usually found. Chasmanthium latifolium was able to fix carbon at light levels almost 10 times lower than some C4 grasses. Light levels below the canopy were 80% below the light saturation point of C. latifolium, which means the plants were fixing carbon at less than their Amax. However, for part of the day, if plants were in light gaps, gas exchange rates would be near the maximum rates measured.

Predicting HDR Cinema Requirements from HDR Home Master Statistics

The high-dynamic-range (HDR) home video format launched several years ago has been adopted by the industry such that HDR Home Masters are created for most new release titles and released for home video distribution using ultrahigh-definition Blu-ray and digital formats. Mastering titles in HDR Cinema is the next logical evolution toward higher quality content and is thus greatly anticipated. However, mastering for HDR Cinema is still experimental due to the wide variety of potential HDR Cinema display technologies and their unique dynamic range characteristics. Determining the required dynamic range for HDR Cinema Masters is thus of great interest. In this paper, we propose an estimation of two properties of the dynamic range required for HDR Cinema Masters based on two different data sets. The first data set corresponds to the dynamic range statistics and cumulative distribution function of 41 Warner Bros. HDR Home Masters. Analyzing this data set indicates that the maximum light level of a frame (the peak luminance value) is directly related Average Light Level (FALL). In other words, there is a maximum contrast between the intensity of the highlights in an image and the average intensity of the image. The second data set is composed of matching mastered grades for standard dynamic range (SDR) cinema (Digital Cinema Initiative), Enhanced Dynamic Range Cinema (Dolby Cinema theatrical release), and HDR Home formats. Paired matching of content is useful to derive a translation between grades. By performing a cross-analysis between SDR and Enhanced Dynamic Range (EDR) Cinema content, we estimate a trend on the evolution of the FALL statistic when a higher dynamic range is provided. A second cross-analysis between HDR Home and EDR Cinema characterize the translation of midtones between small screens with surround illumination to big screens in a dark-viewing environment. Using the different analysis, we predict two optimized properties of the dynamic range needed to represent most future HDR Cinema mastered content.

PRODUCTIVITY OF THE GREENHOUSE TOMATO CULTURE IN THE LONG TURNOVER IN THE NORTH

The data on the greenhouse tomato culture productivity in the long turnover (February November) without application of artificial light are presented. The plants were grown using small-volume hydroponic technology on mineral wool in the industrial greenhouse of LLC "Prigorodny" (Syktyvkar, 61° 40′35″N, 50° 48′35″E). Tomato seeds (hybrid Starbuck F1) were sown in early December 2016. The seedlings were illuminated for 19 h daily with the high-pressure sodiumvapor reflector lamps (HPSV-400W / REFLUX) with an installed power of 130 W/m2. In early February 2017 plants at the age of 4245 days were transferred to the greenhouse and grown at density of 2 plants per square meter under natural lighting conditions. The dependence between the light intensity at leaf level and the natural light entering the greenhouse was studied. In spring sunny days, the light intensity at the level of the upper leaves did not exceed the 450500 μmol quanta/m2s, and in cloudy weather was 2-3 times lower. It was found that the saturation of leaf CO2-uptake by light took place at intensity of 800-1000 μmol quanta/m2s. The leaves formed under light deficiency had lowered photosynthetic activity (near 3 μmol СО2/m2s). The maximal productivity of tomato culture was observed during maximum light levels and sunny period (June-July). The average value of tomato productivity was about 34 kg/m2. The data show the possibility of producing commercial tomato yield in the first light zone without artificial lighting, which significantly reduces production costs.

Sound and Light Levels Are Similarly Disruptive in ICU and non-ICU Wards.

To compare ambient sound and light levels, including SLCs, in ICU and non-ICU environments. Observational study. Tertiary-care hospital. Sound measurements of 0.5 Hz were analyzed to provide average hourly sound levels, sound peaks, and SLCs =17.5 decibels (dB). For light data, measurements taken at 2-minute intervals provided average and maximum light levels. The ICU rooms were louder than non-ICU wards; hourly averages ranged from 56.1 ± 1.3 dB to 60.3 ± 1.7 dB in the ICU, 47.3 ± 3.7 dB to 55.1 ± 3.7 dB on the telemetry floor, and 44.6 ± 2.1 dB to 53.7 ± 3.6 dB on the general ward. However, SLCs = 17.5 dB were not statistically different (ICU, 203.9 ± 28.8 times; non-ICU, 270.9 ± 39.5; P = 0.11). In both ICU and non-ICU wards, average daytime light levels were <250 lux, and peak light levels occurred in the afternoon and early evening. Quieter, non-ICU wards have as many SLCs as ICUs do, which has implications for quality improvement measurements. Efforts to further reduce average noise levels might be counterproductive. Light levels in the hospital (ICU and non-ICU) may not be optimal for maintenance of a normal circadian rhythm for most people.

Studi evaluasi Pencahayaan Alami Pada Gedung Kuliah Bersama Iii Universitas Muhammadiyah Malang

In Gedung Kuliah Bersama (GKB) III at University Muhammadiyah of Malang, at the first floor with a low-level of illumination should be used for audio-visual rooms or meeting, or it’s not used to read, write a long time (often), and for a thorough job, so it does not require a high level of illumination, because the majority of rooms on the first floor level of 30 lux illumination only and the maximum light level is only about 300 lux at the window. On the second floor with office functions majors and computer labs are appropriate to the level of illumination most of the rooms reached 200 lux, at the window level to 500 lux maximum lighting. Lecture room on 3 and 4 floors have a very high level of illumination, on the third floor reached 120-240 lux in the most of the rooms and around the window to 1200 lux, the uneven illumination very disturbing visual comfort of user room. On the fourth floor most of the rooms have lighting levels of 200-400 lux and 1800 lux maximum reached around the windows.Key Words: Lighting levels or level of illumination, GKB ( Gedung Kuliah Bersama )

Seasonal coupling and de‐coupling of net calcification rates from coral reef metabolism and carbonate chemistry at Ningaloo Reef, Western Australia

Rates of net production, net calcification, and nutrient uptake were measured in a coral‐dominated reef flat community on Ningaloo Reef in northwestern Australia under seasonally minimum and maximum light levels. Daily integrated light decreased twofold while water temperatures remained relatively constant increasing by only 1°C on average from summer to winter. Rates of daily community gross primary production (GPP) were only 33% ± 9% higher in summer than in winter (1400 ± 70 versus 1050 ± 60 mmol C m−2 d−1), far less than the twofold seasonal changes reported for most shallow reef communities. Rates of daily community net calcification (Gnet) were not significantly different between seasons (190 ± 40 mmol CaCO3 m−2 d−1 in summer versus 200 ± 10 mmol CaCO3 m−2 d−1 in winter). The average rate of total nitrogen uptake (dissolved + particulate) was also not significantly different between summer and winter (8.3 ± 3.8 versus 6.6 ± 3.4 mmol N m−2 d−1, respectively), despite evidence of sporadically high nitrate uptake in both seasons. In summer, rates of hourly net calcification (gnet) were linearly correlated with diurnal changes in net production, pH, and aragonite saturation state (Ωar); and were mostly correlated with light except at mid‐day under heavy cloud cover. However, in winter,gnet was independent of diurnal changes in light, net production, pH, and Ωar indicating that the reef flat community had possibly reached a threshold above which rates of net calcification were insensitive to diurnal changes in their environment.

Daylight savings time (DST) transition: The effect on serious or fatal road traffic collision related injuries

Introduction: It has been suggested that the transition phases of implementing daylight saving time (DST) may impact on serious or fatal injuries sustained as the result of road traffic collision (RTC). The aim of this study is to explore the effects of transitions into and out of daylight saving time on the incidence of such injuries. Results: Out of 55,826 incidents in England and Wales, TARN returned 1296 incidents meeting the above time criteria, of which 282 involved a fatality. Overall, there were more crashes in autumn (845, 65.2%) comparing to spring period (451, 34.8%), with the majority occurring around sunset (1057, 81.5%). RTC related injuries at the onset of DST in spring showed a significant increase up to 14 days post-time change (P = 0.029), with the majority of the increase occurring at sunset. The highest increases occurred within the fatal incidents group (P = 0.0019) and affected mainly the pedestrian subgroup (P = 0.013). Changes in the incidence of injuries around the change back to Greenwich Mean Time (GMT) in autumn did not reach significance. Conclusion: The use of DST over the period studied was associated with rise in RTC related injury figures up to two weeks following the spring time transition. These findings inform the continuing clock changes debate. The introduction of 2-h time change may result in detrimental effects on RTC related injuries. Keywords: Daylight saving time; Road traffic collision injuries; Pedestrians; Fatal crashes Method: This is a retrospective comparative observational study of 11-year of data submitted prospectively to the Trauma Audit Research Network (TARN) between 1996 and 2006. Data for 4 weeks before and after time transition in spring and autumn of each year was collected. The time periods selected reflect those hours with maximum light level changes due to time alterations (2-h around sunrise and 4-h around sunset). Travellers outside those hours are unlikely to be affected by the changes.

Influence of Gap Size and Position within Gaps on Light Levels

The previous studies have reported maximum light levels at different positions within gaps but many of these studies are based on gaps of different size. The objective of this study is to evaluate the influence of gap size and position within gap on light distribution in gaps and under the canopy north of gaps in a mixedwood temperate forest. For three gap sizes, with gap widths ranging between 0.5 and 1.5 times the height of the surrounding stand, light was measured at different positions along the north-south axis in each gap using two different techniques (hemispherical photographs and instantaneous measurements). In small gaps, the position with the most light was close to the northern edge although not under the canopy north of the gap. For both methods, the position with the highest light level shifted from the north towards the center of gaps as gap size increased which clarifies some of the variability in light measurements previously observed in gap studies. Higher light levels in the northern part of small and medium gaps compared to the southern portion could allow management of a mixture of species with intolerant species in the northern portions of gaps and tolerant species to the south.

Modeling the changing spot features of SW Lacertae: A three year study

In the present study, the activity of the eclipsing binary of the W UMa-type system SW Lac is examined by analysing the new BV photoelectric observations obtained in 2001, 2002 and 2003 at the Ankara University Observatory. During this period, the seasonal light curves show significant differences and asymmetries. A simultaneous analysis of the light curves is made using Djurašević's inverse-problem method. To explain the light-curve asymmetries and the different maximum light levels in the seasonal light curves we used a Roche model that involved regions containing spots on the components. The analysis shows that SW Lac is in an overcontact configuration with a relatively high degree of overcontact 31%. The Roche model with spotted areas on the more massive and cooler component yields a good fit of the observations for the whole set of the seasonal light curves, without any changes of the basic system parameters. This indicates that the complex nature of the light-curve variations during the examined period can be explained by the changes of spotted areas on the cooler component, which cover a significant part of the stellar surface.

Loss of quantum yield in extremely low light.

It has generally been assumed that the photosynthetic quantum yield of all C3 plants is essentially the same for all unstressed leaves at the same temperature and CO2 and O2 concentrations. However, some recent work by H.C. Timm et al. (2002, Trees 16:47-62) has shown that quantum yield can be reduced for some time after leaves have been exposed to darkness. To investigate under what light conditions quantum yield can be reduced, we carried out a number of experiments on leaves of a partial-shade (unlit greenhouse)-grown Coleus blumei Benth. hybrid. We found that after leaves had been exposed to complete darkness, quantum yield was reduced by about 60%. Only very low light levels were needed for quantum yield to be fully restored, with 5 micromol quanta m(-2) s(-1) being sufficient for 85% of the quantum yield of fully induced leaves to be achieved. Leaves regained higher quantum yields upon exposure to higher light levels with an estimated time constant of 130 s. It was concluded that the loss of quantum yield would be quantitatively important only for leaves growing in very dense understoreys where maximum light levels might not exceed 5 micromol quanta m(-2) s(-1) even in the middle of the day. Most leaves, even in understorey conditions, do, however, experience light levels in excess of 5 micromol quanta m(-2) s(-1) over periods where they obtain most of their carbon so that the loss of quantum yield would affect total carbon gain of those leaves only marginally.

A Phytotron for Plant Stress Research: How Far Can Artificial Lighting Compare to Natural Sunlight?

Plants have adapted very efficiently to their natural light habitat. Artificial plant illumination, therefore, requires careful design. Not only the quantity of radiation per area or volume (intensity) but also the spectral quality has to match seasonal and diurnal variations of natural global radiation as close as possible. The GSF Research Center has developed a phytotron system especially devoted to plant stress research, where these requirements are of particular importance. The phytotron consists of seven closed chambers (4 walk-in size chambers, two medium and one small sun simulator). Our contribution oudines the basic design of the lighting and presents spectral data. A good approximation of terrestrial global radiation is achieved if several commercially available lamp types are combined and adequate filters are applied to reject unwanted infrared and harmful ultraviolet radiation. A programmable switch control for the individual lamp banks allows a variation of both spectrum and intensity of the illumination. Spectroradiometric measurements show that the maximum level of illumination in the small and in the medium size chambers can compete both in spectral distribution and in intensity with outdoor global radiation for solar elevations up to 60°. The maximum light level available inside the large walk-in chambers reaches an irradiance corresponding to solar elevation of 50°. The UV-B: UV-A: PAR ratio, which mirrors the spectral balance of plant lighting, can be adjusted to values following the diurnal variation of natural global radiation.

Relationship between pH and the availability of dissolved inorganic nitrogen in the zooxanthella-giant clam symbiosis

Giant clams of the family Tridacnidae live in symbiosis with intercellular dinoflagellates of the genus Symbiodinium, often referred to by the trivial name “zooxanthellae.” Intact clams take up both ammonium and nitrate when they are offered separately. When zooxanthellae were removed from the mantle and incubated in hemolymph, they took up ammonium, and they took up nitrate when ammonium concentrations were low enough (< 1 PM) not to inhibit uptake. The pH of hemolymph collected from the venous sinuses (immediately below the mantle tissue where most of the zooxanthellae reside) varied on a diel cycle, with highest values (-8.1) measured during the middle of the day and lowest (-7.2) detected at night. Zooxanthellae are probably responsible for the alkalization of the hemolymph since the increase in pH is coincident with maximum light levels and photosynthesis. Natural concentrations of ammonium in the hemolymph of freshly collected clams were inversely correlated with pH, with highest values detected at night when pH was lowest. Rates of diffusion of ammonia from seawater (pH 8.1) into animal compartments of lower pH were proportional to the pH differential. Diffusion of ammonia over a pH gradient, with diel variation in pH, may act to regulate availability of nitrogen to the algal symbionts in all zooxanthellae symbioses, including reef corals, thereby controlling the timing and rate of algal division.

Minimum spectral light requirements and maximum light levels for long-term germling growth of several red algae from different water depths and a green alga

Spores and germlings of six red algal species were cultivated for 15 weeks in coloured light fields at low intensities. The photon fluence rates at which growth exceeded growth in dark-kept controls were, in green light, 0·1 μmol m−2s−1 in Audouinella daviesii, 0.5 μmol m−2s−1 in Halarachnion ligulatum, Pterothamnion plumula, Chondrus crispus and Plumaria elegans, and 1·0 μmol m−2s−1 in Ceramium rubrum. In blue or red light, at least 1·0 μmol m−2s−1 was required for germling growth in these species, except for P. elegans which required 0·5 μmol m−2s−1 in blue light. The advantage of green light for growth was particularly evident in A. daviesii which formed no more than two cells in darkness and in photon fluence rates up to 1 μmol m−2s−1 of blue or red, but one further cell after 15 weeks at 0·1 μmol m−2s−1 in green. Germling growth of the green alga Ulva pseudocurvata required at least 3 μmol m−2s−1 in green, but only 1·0 μmol m−2s−1 in blue or red light. White fluorescent light levels permitting growth in red algae were higher than those in green light and equal to minimum requirements in blue or red light in the majority of species investigated. Settled spores of H. ligulatum and the green alga Chaetomorpha melagonium survived for at least 1 year in darkness, whereas spores of C. crispus survived only 39 weeks and those of 11 other red algae and U. pseudocurvata survived 26 weeks or less. Light saturation and light inhibition of growth occurred at higher photon fluence rates in the lower eulittoral species Ceramium rubrum, C. crispus and U. pseudocurvata (saturation, 200–300 μmol m−2s−1; inhibition, 300–500 μmol m−2s−1) than in the strictly sublittoral species H. ligulatum and P. plumula (saturation, 10–20 μmol m−2s−1; inhibition, 50–100 μmol m−2s−1).

Dusk and Dawn Effect on Spruce Photosynthesis. Comparative Studies of Long Term IR-CO2-Analyses of Whole Plants and Short Term 14CO2-Incorporation in Detached Leaves

Summary Two methods were used for measuring photosynthesis in spruce plants exposed to different light and twilight periods: (1) Long-term experiments were performed on whole plants in an open system, using an IR-CO 2 -gas analyser over a period of ten days. (2) Short-term experiments with 14 CO 2 -incorporation during 23 s. were carried out with detached pieces of leaves. With the long-term method, a plateau in photosynthetic rate was reached one hour after the onset of maximum light. With the short-term method, a decline in photosynthetic rate was attained shortly after exposure to maximum light level. Possible explanations for these differences are discussed. With both methods, a close relationship was observed between light levels and photosynthetic rates, independent of the duration of twilight.