Pineal response types in the frog's brain under white light exposure

1979 ◽  
Vol 36 (1) ◽  
Author(s):  
J. Cadusseau ◽  
F. Gaillard ◽  
G. Galand
Keyword(s):  
White Light ◽  
Light Exposure

scholarly journals Light, Alertness, and Alerting Effects of White Light: A Literature Overview

2018 ◽  
Vol 33 (6) ◽  
pp. 589-601 ◽  
Author(s):  
Renske Lok ◽  
Karin C. H. J. Smolders ◽  
Domien G. M. Beersma ◽  
Yvonne A. W. de Kort
Keyword(s):  
White Light ◽  
Light Exposure ◽  
Neural Mechanisms ◽  
Dependent Manner ◽  
Experimental Paradigm ◽  
Research Paradigms ◽  
Lighting Conditions ◽  
Literature Overview ◽  
Dose Dependent ◽  
As Effects

Light is known to elicit non–image-forming responses, such as effects on alertness. This has been reported especially during light exposure at night. Nighttime results might not be translatable to the day. This article aims to provide an overview of (1) neural mechanisms regulating alertness, (2) ways of measuring and quantifying alertness, and (3) the current literature specifically regarding effects of different intensities of white light on various measures and correlates of alertness during the daytime. In general, the present literature provides inconclusive results on alerting effects of the intensity of white light during daytime, particularly for objective measures and correlates of alertness. However, the various research paradigms employed in earlier studies differed substantially, and most studies tested only a limited set of lighting conditions. Therefore, the alerting potential of exposure to more intense white light should be investigated in a systematic, dose-dependent manner with multiple correlates of alertness and within one experimental paradigm over the course of day.

scholarly journals Photoradiation models for the clinical ex vivo treatment of autologous bone marrow grafts

Blood ◽  
1987 ◽  
Vol 70 (2) ◽  
pp. 484-489
Author(s):  
J Atzpodien ◽  
SC Gulati ◽  
A Strife ◽  
BD Clarkson
Keyword(s):  
Bone Marrow ◽  
Tumor Cells ◽  
White Light ◽  
Ex Vivo ◽  
Light Exposure ◽  
B Cell Lymphoma ◽  
Autologous Bone Marrow ◽  
Neoplastic Cells ◽  
Drug Concentrations ◽  
Autologous Bone

To assess the potential of photoradiation therapy for the in vitro purging of residual tumor cells from autologous bone marrow (BM) transplants, we studied normal marrow and tumor cell clonogenicity in response to different light-activated compounds by using the fluorescent dyes dihematoporphyrin ether (DHE) and merocyanine-540 (MC- 540). After photoradiation of cells with white light, both DHE and MC- 540 showed high cytocidal activity toward lymphoid and myeloid neoplastic cells but had a significantly lesser effect on normal granulocyte-macrophage (CFU-GM), erythroid (BFU-E), and mixed colony- forming (CFU-GEMM) progenitor cells. Acute promyelocytic leukemia (HL- 60), non-B, non-T, CALLA-positive acute lymphoblastic leukemia (Reh), and diffuse histocytic B cell lymphoma (SK-DHL-2) cell lines were exposed to different drug concentrations in combination with white light at a constant illumination rate of 50,000 lux. With DHE doses varying from 2.0 to 2.5 micrograms/mL and MC-540 concentrations of 15 to 20 micrograms/mL, clonogenic tumor cells could be reduced by more than 4 logs when treated alone or in mixtures with normal irradiated human marrow cells. However, preferential cytotoxicity towards neoplastic cells was highly dependent on the mode of light activation. MC-540 had no substantial effect on malignant lymphoid (SK-DHL-2) and myeloid (HL-60) cells and on normal marrow myeloid (CFU-GM) precursors when drug incubation was performed in the dark and followed by light exposure of washed cells. Equal doses of MC-540 (15 to 20 micrograms/mL) could preferentially eliminate tumor cells under conditions of simultaneous light and drug treatment (30 minutes at 37 degrees C). When using DHE (2.5 micrograms/mL), 29.3%, 46.8%, and 27.5% of normal marrow CFU-GM, BFU-E, and CFU-GEMM, respectively, were spared after sequential drug and light exposure of cells, whereas simultaneous treatment reduced both normal (CFU-GM) and neoplastic cells below the limits of detection. In summary, our results indicate the usefulness of various photoradiation models for the ex vivo treatment of leukemic and lymphomatous bone marrow autografts.

scholarly journals Circadian Potency Spectrum with Extended Exposure to Polychromatic White LED Light under Workplace Conditions

2020 ◽  
Vol 35 (4) ◽  
pp. 405-415 ◽  
Author(s):  
Martin Moore-Ede ◽  
Anneke Heitmann ◽  
Rainer Guttkuhn
Keyword(s):  
Spectral Sensitivity ◽  
White Light ◽  
Light Exposure ◽  
Human Subjects ◽  
Light Sources ◽  
Led Light ◽  
Light Spectra ◽  
Timing System ◽  
Circadian Timing System ◽  
Spectral Sensitivity Curve

Electric light has enabled humans to conquer the night, but light exposure at night can disrupt the circadian timing system and is associated with a diverse range of health disorders. To provide adequate lighting for visual tasks without disrupting the human circadian timing system, a precise definition of circadian spectral sensitivity is required. Prior attempts to define the circadian spectral sensitivity curve have used short (≤90-min) monochromatic light exposures in dark-adapted human subjects or in vitro dark-adapted isolated retina or melanopsin. Several lines of evidence suggest that these dark-adapted circadian spectral sensitivity curves, in addition to 430- to 499-nm (blue) wavelength sensitivity, may include transient 400- to 429-nm (violet) and 500- to 560-nm (green) components mediated by cone- and rod-originated extrinsic inputs to intrinsically photosensitive retinal ganglion cells (ipRGCs), which decay over the first 2 h of extended light exposure. To test the hypothesis that the human circadian spectral sensitivity in light-adapted conditions may have a narrower, predominantly blue, sensitivity, we used 12-h continuous exposures of light-adapted healthy human subjects to 6 polychromatic white light-emitting diode (LED) light sources with diverse spectral power distributions at recommended workplace levels of illumination (540 lux) to determine their effect on the area under curve of the overnight (2000–0800 h) salivary melatonin. We derived a narrow steady-state human Circadian Potency spectral sensitivity curve with a peak at 477 nm and a full-width half-maximum of 438 to 493 nm. This light-adapted Circadian Potency spectral sensitivity permits the development of spectrally engineered LED light sources to minimize circadian disruption and address the health risks of light exposure at night in our 24/7 society, by alternating between daytime circadian stimulatory white light spectra and nocturnal circadian protective white light spectra.

Degradation Behavior of a-Si:H Pin Solar Cells With Intentionally O-Contaminated i-Layers

1987 ◽  
Vol 95 ◽  
Author(s):  
W. Krühler ◽  
E. Gonzel
Keyword(s):  
Solar Cells ◽  
Electrical Properties ◽  
Glow Discharge ◽  
White Light ◽  
Light Exposure ◽  
Degradation Behavior ◽  
Initial Value ◽  
Glow Discharge Deposition

AbstractThe discussion about the influence of oxygen on the degradation be-havior of a-Si:H pin solar cells is now as before controversial. Therefore, we prepared a-Si:H pin solar cells having different amounts of O contami-nation in the i-layer by adding O2 gas to the silane gas during the glow-discharge deposition of the i-layer. The admixture of O2 gas was in the 0 ppm to 1000 ppm range resulting in an O concentration in the i-layer of 1.10190/cm3 to 3.1020 0/cm3 determined by SIMS measurements. Then we inves-tigated the long-term degradation behavior of these cells, exposing them for about 270 h to white light of 100 mW/cm2 intensity. During the first 20 h the cell efficiencies dropped relatively fast to about 80 % of the initial value and then more slowly to about 60 % after 270 h. The degradation of the cells may be slightly different during the first 20 h, but this has nothing to do with the O concentration. The normalized efficiency values meet all at the 60 % level after the long-term light exposure for 270 h. We there-fore conclude that the degradation behavior of pin a-Si:H solar cells after long-term exposure is not dependent on the O concentration in the range investigated. At O concentrations higher than about 5.1020 cm−3, the den-sity of states increases rapidly and the electrical properties of the solar cells deteriorate, making it difficult to clarify the true influence of oxygen on the degradation behavior.

scholarly journals Does Bright Light Counteract the Post-lunch Dip in Subjective States and Cognitive Performance Among Undergraduate Students?

2021 ◽  
Vol 9 ◽  
Author(s):  
Ying Zhou ◽  
Qingwei Chen ◽  
Xue Luo ◽  
Le Li ◽  
Taotao Ru ◽  
...  
Keyword(s):  
Working Memory ◽  
Undergraduate Students ◽  
White Light ◽  
Light Exposure ◽  
Negative Mood ◽  
Bright Light ◽  
Impaired Performance ◽  
Early Afternoon ◽  
And Performance ◽  
Bright Blue

The post-lunch dip in alertness and performance was widely experienced during the early afternoon. Taking a short nap was documented as a practical strategy for habitual nappers to counteract the decline of alertness and performance. Yet, it remains unknown whether bright light exposure in the early afternoon working hours could alleviate the performance deficits caused by a post-lunch nap loss for habitual nappers. Seventeen undergraduate students who had a long-term habit of taking a post-lunch nap were assigned to three interventions: (1) a short nap + normal indoor light (100 lx, 4,000 K at eye level); (2) no nap + normal indoor light, and (3) no nap + blue-enriched bright light (1,000 lx, 6,500 K at eye level), in which subjective alertness (Karolinska Sleepiness Scale, KSS), mood (Positive and Negative Affect Schedule, PANAS), and task performance in sustained attention (psychomotor vigilance test, PVT), response inhibition (go/no-go task), and working memory (paced visual serial addition test, PVSAT) were measured. Results showed that a post-lunch nap deprivation significantly increased subjective sleepiness and negative mood and impaired performance in PVT and PVSAT, while exposure to bright blue-enriched white light vs. normal indoor light in the early afternoon significantly relieved such negative effects on mood, sleepiness, and performance in PVSAT; subjective positive mood and performance in PVT and go/no-go task remained unaffected with light intervention. These findings suggested that bright blue-enriched white light exposure could be a potential strategy for those who are suffering from drowsiness and low working memory following a habitual midday nap loss.

scholarly journals Chronobiological Factors Related to Sleep and Neuropsychiatric Symptoms in Persons Living With Dementia

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. 436-437
Author(s):  
Nancy Hodgson ◽  
Fanghong Dong
Keyword(s):  
Circadian Rhythm ◽  
White Light ◽  
Salivary Cortisol ◽  
Light Exposure ◽  
Neuropsychiatric Symptoms ◽  
Clear Understanding ◽  
Diurnal Cortisol ◽  
Endogenous Factors ◽  
Subjective Sleep ◽  
Rhythm Pattern

Abstract Circadian rhythm disturbances (CRD) are commonly seen in people living with dementia. A clear understanding of the role of CRD in dementia etiology will be beneficial by exploring the exogenous factors (externally influence the duration of sleep hours, such as light/dark cycles) and endogenous factors (internal biological rhythm, such as diurnal cortisol pattern). This symposium will apply a chronobiological approach to study exogenous and endogenous factors that influence circadian rhythm and their effects on sleep and neuropsychiatric symptoms in persons living with dementia (PLWD). Four paper presentations will use secondary data analysis of data from the Healthy Patterns Clinical Trial (NCT03682185), a randomized controlled trial of a home-based activity intervention designed to improve circadian rhythm disorders in PLWD. We will first describe the circadian rhythm pattern reflected by endogenous factors (salivary cortisol), then examine salivary cortisol (endogenous) and white light intensity (exogenous) and on subjective sleep and neuropsychiatric symptoms (including depression) in PLWD, respectively. In session 1, we will present cortisol diurnal rhythm pattern in PLWD using a cross-sectional design. In session 2, we will discuss the relationship between salivary cortisol indicators and depressive symptoms. In session 3, we focus on the association between diurnal cortisol slope and neuropsychiatric symptoms using the baseline data. In session 4, we describe the association between evening white light exposure and subjective sleep. The discussant will describe how these findings build on our understanding the nature of circadian rhythm disturbance in dementia and inform future research and treatment approaches.

Photoinduced changes in amorphous selenium

2014 ◽  
Vol 92 (7/8) ◽  
pp. 663-666 ◽  
Author(s):  
F. Djefaflia ◽  
C. Mebarkia ◽  
A. Hafdallah ◽  
M.L. Benkhedir ◽  
A. Belfedal
Keyword(s):  
Thin Films ◽  
White Light ◽  
Room Temperature ◽  
Light Exposure ◽  
Red Light ◽  
Amorphous Selenium ◽  
Corning Glass ◽  
Visible Transmittance ◽  
Photoinduced Changes ◽  
Photoinduced Phenomena

Photoinduced phenomena in thin films of amorphous selenium (a-Se) have been a subject of intensive researches so far. Thin films of a-Se were deposited on corning glass by thermal evaporation, with several thicknesses. The influence of light exposure, with different colors (blue or red or natural white light), on the optical and structural properties of a-Se thin films was carried out by using ultraviolet–visible transmittance spectroscopy. It was found that the gap of the samples illuminated with blue and natural white light at room temperature shifts to lower energies. This photodarkening is stable at room temperature and is irreversible even after several days. On the other hand the photodarkening in the samples illuminated with red light is much smaller than that for samples illuminated with blue and natural white light. The photodarkening is accompanied by an increase in the refractive index. These results are discussed with results, previously obtained, about the photoinduced changes of the negative-U centers in, T– and T+, studied using time-of-flight (TOF) traces recorded on samples prepared in the same conditions. These TOF measurements show that the defect level T– at 0.4 eV above the valence band edge shifts to 0.5 eV under illumination with white light at room temperature. This effect is not seen if the illumination is done at 35 °C. These phenomena are attributed to nanocrystallization in the a-Se films.

scholarly journals Microstructural Study of Two-Dimensional Organic-Inorganic Hybrid Perovskite Nanosheet Degradation under Illumination

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 722 ◽  
Author(s):  
Lingfang Nie ◽  
Xiaoxing Ke ◽  
Manling Sui
Keyword(s):  
White Light ◽  
Uv Light ◽  
Light Exposure ◽  
Optoelectronic Devices ◽  
Two Dimensional ◽  
Inorganic Hybrid ◽  
Hybrid Perovskite ◽  
Transmission Electron ◽  
New Perspective ◽  
Photo Stability

Two-dimensional (2D) organic-inorganic hybrid perovskite materials have received substantial attention because of their exceptional optoelectronic properties. Although the applications of 2D perovskite nanosheets are promising in various optoelectronic devices, which all face harsh working conditions of light exposure, little is known about the photo-stability and degradation mechanisms of these 2D perovskite nanosheets. In this work, degradation of (C4H9NH3)2PbBr4 (BA2PbBr4) nanosheets when exposed to ultraviolet (UV) light and white light is explored. The morphology, optical properties, and microstructure of the nanosheets, under different conditions of light exposure, was studied in detail. UV light is more destructive compared to white light, which both led to a nanosheet breakdown. A combination of transmission electron microscopy (TEM) imaging and electron diffraction revealed that the organic moieties are most sensitive to light exposure and partial disorder toward complete disorder takes place during light exposure. Moreover, excessive light exposure further causes a [PbBr6]4− octahedron tilt and re-ordering within the perovskite structure. This study could enrich the understanding of 2D perovskite nanosheets and their photostability, offer a new perspective in interpreting the light–perovskite interaction, and further help the design of robust and light-tunable 2D perovskite-based optoelectronic devices.

Photoconductivity of Pharma-Grade ZnO under UVA and White Light Exposure

2015 ◽  
Vol 1108 ◽  
pp. 73-78
Author(s):  
Ling Chuo Ann ◽  
Shahrom Mahmud ◽  
Siti Khadijah Mohd Bakhori ◽  
Amna Sirelkhatim
Keyword(s):  
Electron Microscopy ◽  
White Light ◽  
Light Exposure ◽  
Atomic Ratio ◽  
Surface Conductivity ◽  
Light Illumination ◽  
Long Wavelength ◽  
Transmission Electron ◽  
Zno Crystal ◽  
Zno Powder

In this study, we investigated the photoconductivity of pharma-grade zinc oxide (ZnO) which was excited under ultraviolet - long wavelength (UVA) and white light illumination. The morphological structures of ZnO were studied using field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The ZnO sample was composed of micro/nanorods, slabs, tripods, tetrapods and irregular-shaped particles. The energy-dispersive X-ray spectroscopy (EDS) result revealed the high purity of ZnO, with the relative O/Zn atomic ratio lower than 1. The absorption spectrum of ZnO suspension was performed using UV-Visible spectroscopy. ZnO sample exhibited strong absorption at 387 nm, corresponding to optical bandgap of 3.23 eV. The ZnO powder was converted into pellets to study its photoconductivity under different intensity of UVA (0.5-2.0 mW/cm-2) and white light exposure (200-1000 lux) from conventional fluorescent lamp. The significant increase in surface conductivity of the ZnO pellets could be due to UVA illumination that produces photo-generated charge carriers on the surface of ZnO pellet. There was a small persistency of current flow after the UVA exposure was terminated. Under the white light exposure, the surface conductivity was slightly higher than that of dark condition. This is probably due to the small amount of defects, particularly oxygen vacancies and zinc interstitials that produce some light-generated charges on the ZnO crystal structures. The white light exposure may cause the excitation of electrons from the defects energy level to the conduction band, this being the underlying cause for the increase in the conductivity. ZnO pellet exhibited a dramatic enhancement of photoconductivity under UVA illumination if compared with small improvement of photoconductivity under white light exposure.

scholarly journals Transcriptomic analyses of cacao flavonoids produced in photobioreactors

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Adriana M. Gallego ◽  
Luisa F. Rojas ◽  
Wilmar G. Valencia ◽  
Lucía Atehortúa ◽  
Aura I. Urrea ◽  
...  
Keyword(s):  
Blue Light ◽  
White Light ◽  
Stress Responses ◽  
Large Scale ◽  
Light Exposure ◽  
Expression Patterns ◽  
Flavonoid Biosynthesis ◽  
Plant Secondary Metabolite ◽  
Two Component

Abstract Background Theobroma cacao is a major source of flavonoids such as catechins and their monomers proanthocyanidins (PAs), widely studied for their potential benefits in cardiovascular diseases. Light has been shown to promote plant secondary metabolite production in vitro. In this study, cacao cells cultured in 7.5 L stirred tank photobioreactors (STPs) were exposed to a change of white to blue LED lights for 28 days (d). Results Transcriptomic analyses were performed in three time points comparing changing expression patterns, after cell exposure to white light (d0-VS-d14), after a shift from white to blue light (d14-VS-d15), and after an extended period of blue light for the following 15 days (d15-VS-d28). Under white light, there was enrichment in metabolic pathways associated with cell growth (carbon, glycolysis, and amino acid biosynthesis) accompanied by a significant increase in the PAs content. In the shift to blue light, further increase in PAs content was observed concomitantly with the significant expression of TWO-COMPONENT RESPONSE REGULATOR genes involved in the early stress responses via circadian clock and hormone pathways. Under blue light exposure, we observed a depletion of PAs content associated with ROS-mediated stress pathways. Conclusions Light effects on large-scale cell cultures in photobioreactors are complex and pleiotropic; however, we have been able to identify key regulatory players upstream cacao flavonoid biosynthesis in STPs, including TWO-COMPONENT SYSTEM and ROS-signaling genes. The crosstalk between flavonoid biosynthesis and regulatory networks led to understand the dynamics of flavonoid production and degradation in response to light-driven ROS signals. This can be used to optimize the time, and the yield of in vitro targeted metabolites in large-scale culture systems.

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