Light is the main source of energy for the primary process that sustains life on our planet, known as photosynthesis. Photosynthesis is the strategy adopted by many living organisms for capturing and ...incorporating energy, and it is under this context that light is primarily experienced, explored, and exploited. Plants perceive information from the ambient environment and communicate with other organisms using light. They have developed a plethora of photoreceptors that permit this communication with the surrounding environment. Additionally, the physical properties of light, such as the spectral quality, irradiance, intensity, and photoperiod, play an integral role in the morphogenesis, growth, and metabolism of many biochemical pathways in plants.To facilitate photosynthesis in controlled environments, light‐emitting diodes (LEDs) have been shown to offer interesting prospects for use in plant lighting designs in controlled-environment agriculture (greenhouses) and growth chambers for in vitro cultures. In high-technology greenhouses (for instance, vertical agriculture), artificial light may assume both assimilative (optimizing photosynthetic efficiency) and control functionality (guiding growth and development or the synthesis and accumulation of plant metabolites). In vitro cultures are regulated by different factors, and among them, light is the most important.
The positive refractive index of conventional optical lenses means that they need curved surfaces to form an image, whereas a negative index of refraction allows a flat slab of a material to behave ...as a lens and focus electromagnetic waves to produce a real image.
Abstract
Introduction
Blue-blocking glasses are increasingly used as an intervention for jet-lag and other situations where an individual wishes to promote a “dark” signal despite the presence of ...ambient light. However, most studies on blue-blockers are done under controlled laboratory settings using emissions generated from electric light sources. The present study evaluated the performance of commercially available blue-blockers under daytime sunlight conditions.
Methods
A calibrated spectroradiometer (Ocean Insight), cosine corrector, optic fiber, and software package were used to measure the absolute irradiance (uW/cm^2/nm) available midday in a standardized location that received direct sunlight. Thirty-one commercially available blue-blockers were individually placed in front of the cosine corrector and intensity was measured and analyzed. Each lens was tested for its ability to block visible light, as well as light within the 440-530nm range. Lenses were evaluated individually and grouped by lens type: red-tinted lenses (RTL), orange-tinted lenses (ORL), orange-tinted lenses with blue reflectivity (OBL), brown-tinted lenses (BTL), yellow-tinted lenses (YTL), and clear lenses with blue reflectivity (RBL).
Results
Across the full spectrum, RTL blocked 66% of the light, OTL blocked 60%, OBL blocked 43%, BTL blocked 56%, YTL blocked 28%, and RBL blocked 20%. When the range was restricted to 440-530nm, RTL blocked 99%, OTL blocked 96%, OBL blocked 90%, BTL blocked 66%, YTL blocked 38%, and RBL blocked 17% of the light. Variation across lens types was significant for the full spectrum (one-way ANOVA, p < 0.0001) as well as the 440-530nm range (one-way ANOVA, p < 0.0001). Individual lenses showed variability in performance, though this variability was smaller than the between-group differences.
Conclusion
Under daylight conditions, red and orange lenses (RTL, OTL, and OBL) blocked at least 90% of the light in the 440-530nm range. Notably, RBL lenses restricted the most short-wavelength light as a proportion of the total light blocked. These data suggest that RTL, OTL, and OBL are effective at blocking the most circadian photosensitive components of daylight at the cost of reducing total illumination.
Support (if any)
R01MD011600, R01DA051321
Plasmonic nanostructures ensure the reception and harvesting of visible lights for novel photonic applications. In this area, plasmonic crystalline nanodomains decorated on the surface of ...two-dimensional (2D) semiconductor materials represent a new class of hybrid nanostructures. These plasmonic nanodomains activate supplementary mechanisms at material heterointerfaces, enabling the transfer of photogenerated charge carriers from plasmonic antennae into adjacent 2D semiconductors and therefore activate a wide range of visible-light assisted applications. Here, the controlled growth of crystalline plasmonic nanodomains on 2D Gasub.2Osub.3 nanosheets was achieved by sonochemical-assisted synthesis. In this technique, Ag and Se nanodomains grew on 2D surface oxide films of gallium-based alloy. The multiple contribution of plasmonic nanodomains enabled the visible-light-assisted hot-electron generation at 2D plasmonic hybrid interfaces, and therefore considerably altered the photonic properties of the 2D Gasub.2Osub.3 nanosheets. Specifically, the multiple contribution of semiconductor-plasmonic hybrid 2D heterointerfaces enabled efficient COsub.2 conversion through combined photocatalysis and triboelectric-activated catalysis. The solar-powered acoustic-activated conversion approach of the present study enabled us to achieve the COsub.2 conversion efficiency of more than 94% in the reaction chambers containing 2D Gasub.2Osub.3-Ag nanosheets.
Dark photon production via [Formula omitted] Wong, Xiaorui; Huang, Yongsheng
The European physical journal. C, Particles and fields,
05/2021, Letnik:
81, Številka:
5
Journal Article
Recenzirano
The dark photon is a new gauge boson which arises from an extra Formula omitted gauge symmetry. In this paper, a novel dark photon production mechanism based on MeV-scale Formula omitted- Formula ...omitted collider is considered: Formula omitted. With the aid of PACKAGE-X, differential cross section of Formula omitted is obtained, as a function of the kinetic mixing parameter Formula omitted and dark photon mass Formula omitted. Taking the light-by-light scattering as background, the constraints on the dark photon parameter space for different time intervals in a MeV-scale Formula omitted- Formula omitted collider are also given.
Abstract
Introduction
Blue wavelength light is an effective treatment for delayed sleep phase syndrome, seasonal affective disorder and bipolar depression. The role of blue light in regulating ...melatonin production has been extensively studied, but other potential neurophysiological effects remain poorly understood. Some studies have suggested that daily blue light exposure may modulate functional brain responses within the amygdala and prefrontal cortex (PFC), potentially explaining blue light’s antidepressant effect. In this study we investigated the effects of a single 30-minute session of blue light exposure on functional resting state connectivity between the amygdala and PFC.
Methods
Twenty-nine healthy 18–32 year olds were randomly assigned to either receive 30 minutes of blue (n=17) or non-blue (amber) light (n=12) exposure followed by a 7-minute resting state scan. Pre- and post light exposure, participants completed the Positive and Negative Affect Scale, as a measure of state affect.
Results
Individuals who received blue versus amber light showed greater positive connectivity between the right amygdala and the left dorsolateral prefrontal cortex (DLPFC) (x=-24, y=46, z=18, k=90, volume p-FDR corrected, p<0.001). Increased amygdala-DLFC connectivity correlated with greater decreases in negative mood for the blue (ρ=-.55, p=0.03), but not the amber group. Using Granger Causality, we found that the directionality of information flow between these two areas was bidirectional (p<0.0025).
Conclusion
Blue light exposure appears to facilitate greater information flow between the amygdala and the DLPFC at rest, potentially enhancing cognitive processes that regulate arousal and mood. As blue light exposure has been shown to enhance attention and learning, using blue light exposure during practice of emotional regulation strategies, such as reappraisal, may further increase the beneficial effects of blue light on mood. In order to use blue light exposure in a more targeted manner for sleep and mood disorders, further research into the underlying neurophysiological mechanisms is needed.
Support
This research was supported by a USAMRAA grant to WDSK (W81XWH-14-1-0571) as well as by an Arizona Health Education Centers (AHEC) Research Grant to AA.
Abstract
Introduction
Light exposure has powerful effects on the circadian timing of sleep and wake, primarily through the regulation of the secretion of melatonin. However, it is becoming clear that ...light has additional alerting effects beyond its primary effect on the circadian system. Exposure to light, particularly blue-wavelength light, has been shown to acutely increase brain activation, alertness, and some elementary aspects of cognitive performance such as working memory and emotional anticipation during the day. Whether blue light exposure can have longer-lasting effects on brain activation and performance during more complex cognitive control tasks up to 30-minutes after light cessation is unknown.
Methods
In a sample of 30 healthy adults, we examined the effects of a single 30-minute exposure to either blue (n=14) or amber placebo (n=16) light on subsequent brain activation and performance during the Multi-Source Interference Task (MSIT) measured a half-hour after light cessation using functional magnetic resonance imaging. Mean activation in all regions showing increased task-related activation (i.e., Task Positive Network; TPN) and regions showing decreased activation (i.e., Default Mode Network; DMN) at p<.001 (FWE corrected) was extracted separately for each network in SPM12 and compared between light conditions.
Results
Performance metrics for the MSIT, including accuracy, response time, and cognitive throughput, did not differ between the blue and amber conditions, suggesting that performance was sustained equally between light conditions. However, brain activation within the TPN to the interference condition of the MSIT was significantly lower (p=.024) in the blue relative to the amber condition, with no group differences observed for suppression of the DMN.
Conclusion
Compared to amber, a single exposure to blue light was associated with enhanced neural efficiency a half-hour later as demonstrated by reduced TPN activation to achieve the same level of cognitive performance. Blue light may be an effective method for optimizing neurocognitive performance under some conditions.
Support
US Army Medical Research and Materiel Command: W81XWH-14-1-0571
Mimicking the intelligence of biological organisms in artificial systems to design smart actuators that act autonomously in response to constant environmental stimuli is crucial to the construction ...of intelligent biomimetic robots and devices, but remains a great challenge. Here, a light‐driven autonomous carbon‐nanotube‐based bimorph actuator is developed through an elaborate structural design. This curled droplet‐shaped actuator can be simply driven by constant white light irradiation, self‐propelled by a light‐mechanical negative feedback loop created by light‐driven actuation, time delay in the photothermal response along the actuator, and good elasticity from the curled structure, performing a continuously self‐oscillating motion in a wavelike fashion, which mimics the human sit‐up motion. Moreover, this autonomous self‐oscillating motion can be further tuned by controlling the intensity and direction of the incident light. The autonomous actuator with continuous wavelike oscillating motion shows immense potential in light‐driven biomimetic soft robots and optical‐energy‐harvesting devices. Furthermore, a self‐locomotive artificial snake with phototaxis is constructed, which autonomously and continuously crawls toward the light source in a wave‐propagating manner under constant light irradiation. This snake can be placed on a substrate made of triboelectric materials to realize continuous electric output when exposed to constant light illumination.
A curled droplet‐shaped carbon‐nanotube‐based autonomous actuator is designed, producing a continuous self‐oscillating motion in a wavelike fashion under constant light irradiation, similar to the sit‐up motion. This actuator can autonomously and continuously crawl toward the light source in a wave‐propagating manner, showing phototactic self‐locomotion. Moreover, after being placed on a triboelectric substrate, it generates continuous electric output under constant light irradiation.
In this work, cuprous oxide (Cusub.2O) thin films were prepared using a simplistic sputtering technique. The films were grown on both traditional fluorine-doped tin oxide (FTO) and Ti-metallic ...substrates. X-ray diffraction applied for investigation of the crystal structure proved that the Cusub.2O layer acquires the cubic structure with a (111) main peak at 2θ of 36.46°. The optical absorption and transmission were detected through the utilization of a UV-Vis spectrophotometer, and the optical bandgap for the Cusub.2O layer was determined to be ~2.15 eV using Tauc’s equation. XPS and scanning electron microscopy were also performed for chemical structure and morphological investigation, respectively. The optoelectronic behaviors for the prepared samples were carried out using a Keithley source meter; the photocurrent density was measured in a range of applied voltage between −1 and 1 volt under the illumination of a xenon lamp with a power density of 100 mWcmsup.−2. External quantum efficiency, sensitivity, responsivity, and detectivity were computed using proprietary models based on the experimental data.
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