Bio-inspired ultra dark nanoparticles for lasing and water desalination

Traditional light source modelling is concerned with specific types of light sources, the two most common of which are point sources and daylight. Little attempt has been made, however, to relate different types of sources to each other. For example, how may the lighting from an overcast sky be compared to that from a lamp? Having a theoretical framework to compare different types of light sources is important for computer vision, in particular for understanding shading and shadow cues. A vision system needs to take account of the light source in order to interpret these cues. In this paper, we present a framework for comparing types of light sources which is based on a dimensional analysis of the set of light rays in a free space. Specifically, we introduce a 4-D light source hypercube in which the different types of sources may be embedded and compared. We also present a novel definition for light sources which generalizes the standard definition of a source as an emitter.

Nighttime light emissions are increasing in most countries worldwide, but which types of lighting are responsible for the increase remains unknown. Also unknown is what fraction of outdoor light emissions and associated energy use are due to public light sources (i.e. streetlights) or various types of private light sources (e.g. advertising). Here we show that it is possible to measure the contribution of street lighting to nighttime satellite imagery using ‘smart city’ lighting infrastructure. The city of Tucson, USA, intentionally altered its streetlight output over 10 days, and we examined the change in emissions observed by satellite. We find that streetlights operated by the city are responsible for only 13% of the total radiance (in the 500–900 nm band) observed from Tucson from space after midnight (95% confidence interval 10–16%). If Tucson did not dim their streetlights after midnight, the contribution would be 18% (95% confidence interval 15–23%). When streetlights operated by other actors are included, the best estimates rise to 16% and 21%, respectively. Existing energy and lighting policy related to the sustainability of outdoor light use has mainly focused on street lighting. These results suggest an urgent need for consideration of other types of light sources in outdoor lighting policy.

A reference light source employing scintillations in air

Broadband perfect absorbers are of great importance for various applications such as stealth technologies, thermal photovoltaic cells, optical communication, photodetection, and photovoltaic devices. However, they are often made by lithographic techniques with high cost and complexity, which hinders their practical applications. The design of broadband and ultrahigh absorber at low cost and ease in fabrication is still a big challenge in the field of optics. Here, an all‐solution‐processed plasmonic perfect absorber is proposed and demonstrated by incorporating Mxene Ti3C2Tx (Tx = F, O or OH) and gold nanoparticles (NPs) in metal–insulator–metal configuration. The absorption of the designed plasmonic absorber can reach up to 99% with polarization‐ and angle‐independence in a broad range of wavelengths from ultraviolet to near‐infrared region. This ultrahigh and broadband absorbance is attributed to the synergy of plasmon resonance, magnetic resonance, and cavity effect between gold NPs layer and Mxene film, which is further corroborated by simulations of the finite element method for both random and patterned orientation of the gold nanoparticles. The excellent optical property together with the easy fabrication method paves the way for preparing photon‐absorbing nanostructures in photocatalysis and solar photovoltaics.

Spektrochemische analysen mit einer glimmentladungslampe als lichtquelle—I: Elektrische eigenschaften, probenabbau und spektraler charakter

A non-contact colour correction system on mobile display under various light sources

In this paper, we propose a terahertz bifunctional absorber with broadband and dual-band absorbing properties based on a hybrid graphene-vanadium dioxide (VO2) metamaterial configuration. When VO2 is in the insulating state and the Fermi energy of graphene is set to 0.8 eV, the designed device behaves as a tunable perfect dual-band absorber. The operating bandwidth and magnitude of the dual-band spectrum can be continuously adjusted by changing the Fermi energy of graphene. When VO2 is changed from insulator to metal, the designed system can be regarded as a broadband absorber, it has a broad absorption band in the range of 1.45-4.37 THz, and the corresponding absorptance is more than 90%. The simulation results indicate that the absorptance can be dynamically changed from 17% to 99% by adjusting the conductivity of the VO2 when the Fermi energy of graphene is fixed at 0.01 eV. Besides, both dual absorption spectrum and broad absorption spectrum maintain a strong polarization-independent characteristic and operate well at wide incident angles. Furthermore, we have introduced the interference theory to explain the physical mechanism of the absorption from an optical method. Therefore, our designed system can be applied in many promising fields like cloaking and switch.

The authors use goniophotometer to experimentally measure the light flux distribution of a wall-mounted luminaire with a luminous light bulb, a direct-replacement light-emitting diode (LED) lamp, and a three-dimensional LED module with a heat pipe-based cooling system. The change dynamics of integral characteristics of the light flux is determined. The stabilized light flux for different types of light sources at different power supply voltages is measured. The obtained experimental data are used to calculate the luminous efficacy of the luminaire with the direct-replacement lamps and to determine its dependence on the supply voltage. The thermal conditions for using LEDs in direct-replacement lamps and in lamps with an original cooling system based on heat pipes are also determined. Cite this article as: Pekur DV, Sorokin VM, Nikolaenko YE. Features of Wall-Mounted Luminaires with Different Types of Light Sources. Electrica, 2021; 21(1): 32-40

Picolinate binds to the anionic semiquinoid form of D-amino acid oxidase (DAO), and the complex formed has a broad absorption band in the long-wavelength region extending beyond 800 nm, which is reminiscent of a charge transfer interaction. The binding has a stoichiometry of 1:1 with respect to the enzyme. The dissociation constant at 25 degrees C was 30 microM at pH 7.0. The pH dependence (pH 7.0-8.3) of the dissociation constant indicates that one proton is associated with the complex formation, and suggests that picolinate able to bind to the anionic semiquinoid enzyme is in the cationic form protonated at the nitrogen atom. By adding dithionite to the oxidized DAO solution containing pyruvate and various amines, a similar anionic semiquinoid DAO complex having a broad long-wavelength absorption band, appeared. Resonance Raman spectra with excitation at 623.8 nm of the anionic semiquinoid DAO complex formed in the presence of pyruvate and methylamine indicate that the complex consists of the anionic semiquinoid DAO and N-methyl-alpha-iminopropionate produced from pyruvate and methylamine, and that the imino group must be protonated. This supports the proposal that the presence of a positively charged group in the vicinity of flavin is required for the stabilization of the anionic semiquinoid flavin. The results also suggest that the broad absorption band is derived from the charge transfer interaction between the anionic semiquinoid flavin and the imino acid, in which the flavin C(4a)-N(5) locus and the locus containing (Formula: see text) of the amino acid are important for the interaction.(ABSTRACT TRUNCATED AT 250 WORDS)

In order to obtain new, more efficient laser materials for diode laser-pumped lasers, the laser host materials with broad absorption bands are very important. This paper reports the structure and spectral properties of Nd3+ : KBaGd(MoO4)3 crystal. KBaGd(MoO4)3 crystallizes in the monoclinic system with space groupC2/c. The structure analysis shows that KBaGd(MoO4)3 crystal has a disordered structure. The investigation of the spectral properties of Nd3+ : KBaGd(MoO4)3 crystals shows that it exhibits broad absorption and emission bands, which are caused by the disordered structure of the KBaGd(MoO4)3 crystal. The broad absorption band is very suitable for diode laser pumping. To sum up the spectral properties of Nd3+ : KBaGd(MoO4)3 crystal, it may be regarded as a potential solid-state laser material for diode laser pumping.

To understand the effects of the terminal substituent at the diimine ligand on the photophysics of heteroleptic cationic Ir(III) complexes and to obtain Ir(III) complexes with extended ground-state absorption to the near-IR region while retaining the long-lived and broadly absorbing triplet excited state, we synthesized three heteroleptic cationic iridium(III) complexes bearing cyclometalating 1-phenylisoquinoline (C^N) ligands and substituted 6,6'-bis(7-R-fluoren-2-yl)-2,2'-biquinoline (N^N) ligand (R = H, NO2, or NPh2). The photophysics of these complexes was systematically investigated via spectroscopic methods and time-dependent density functional theory. All complexes possess strong ligand-localized 1π,π* transitions mixed with ligand-to-ligand charge transfer (1LLCT)/metal-to-ligand charge transfer (1MLCT) transitions below 400 nm, and a broad and featureless absorption band above 400 nm that arises from the N^N ligand-localized 1π,π*/1ILCT (intraligand charge transfer) transitions as well as the very weak 1,3LLCT/1,3MLCT transitions at longer wavelengths. The electron-withdrawing NO2 substituent on the N^N ligand leads to a blue-shift of the 1π,π*/1ILCT absorption band, while the electron-donating NPh2 substituent causes a pronounced red-shift of this band. The unsubstituted and NO2-substituted complexes (complexes 1 and 2, respectively) are moderately emissive at room temperature (RT) in solution as well as at 77 K in the glassy matrix, while the NPh2-substituted complex (3) is weakly emissive at RT, but the emission becomes much brighter at 77 K. Complexes 1 and 2 show very broad and strong triplet excited-state absorption from 460 to 800 nm with moderately long lifetimes, while complex 3 exhibits weak but broad absorption bands from 384 to 800 nm with a longer lifetime than those of 1 and 2. The nonlinear transmission experiment manifests that complexes 1 and 2 are strong reverse saturable absorbers (RSA) at 532 nm, while 3 shows weaker RSA at this wavelength. These results clearly demonstrate that it is feasible to tune the ground-state and excited-state properties of the Ir(III) complexes via the terminal substituents at the diimine ligand. By introducing the fluoren-2-yl groups to the 2,2'-biquinoline ligand to extend the diimine ligand π-conjugation, we can obtain Ir(III) complexes with reasonably long-lived and strongly absorbing triplet excited state while red-shifting their 1,3LLCT/1,3MLCT absorption band into the near-IR region. These features are critical in developing visible to near-IR broadband reverse saturable absorbers.

Background: Salvia miltiorrhiza Bunge has been used in traditional medicine. The type of light source has an effect on the growth properties and composition of functional compounds in plants. In this study, we analyzed the effects of different artificial light sources on the growth characteristics as well as antioxidant and antimicrobial activities of S. miltiorrhiza.<BR>Methods and Results: Seedlings of S. miltiorrhiza were grown under various artificial light sources, including fluorescent light (FL), light emitting diode (LED), and microwave electrodeless light (MEL), for 8 weeks. Growth characteristics were the best in plants treated with MEL. DPPH scavenging activity of the shoot was more pronounced with the FL treatments, while the roots were more active in plants grown under single wavelength lights (i.e., blue and red LEDs). Among the different light source treatments, the blue LED resulted in a higher total phenolic content in the plants. Furthermore, growing plants growth under the red LED enhanced their total flavonoid content. Notably, the antimicrobial properties of plants varied significantly between light source treatments in this study. Except for E. coli, all the tested microorganisms were susceptible to the plant extracts.<BR>Conclusions: The type of light source may be an important parameter for the enhancement of plant growth and functional compounds in S. miltiorrhiza.

In this paper, a new model of multi-layer metamaterial perfect absorber (MPA) in the terahertz region has been introduced. This model is similar to the classic absorber model, ie the three traditional layers of metal-dielectric-metal. The difference is that the middle layer has changed in height and consists of 3 separate layers with the same material. Therefore, the middle layer of the proposed structure is metamaterial. Numerical results of the simulation show that the absorption rate of the perfect absorber at 6.86 THz is 99.99%. Also, by changing the width of the two middle layer columns w, a dual-band perfect absorber with an average absorption rate of 97.18% is obtained at frequencies of 4.24 THz and 6.86 THz. A significant advantage of this paper over other works is that this absorber is adjustable, in addition to obtaining a nearly perfect dual-band absorber with a narrow-band peak by adjusting the parameters and also a nearly broad-band absorber can also be obtained by changing the parameters without re-manufacturing the structure. We believe that the proposed absorber has potential in filtering, detection and imaging.

Light-emitting diodes (LEDs) became an important home-lighting device. Due to the property of high efficiency LED lighting sources, thus we expected to apply high efficiency LED lighting to improve or enhance our lighting environment. The purpose of this study is to design LED ceiling lightings layout based on evaluating human’s physiological responses and subjective feelings, where the experiments were conducted in the office-like laboratory. We had four experimental combinations included two Correlated Color Temperature (CCT) and two different types of lighting sources (lower Blue-value and high-efficiency). Two different types of lighting sources, one was that the lower Blue-value lighting sources was equipped at the center of the device, the other was that high-efficiency equipped around the lower Blue-value lighting source. Six participants were recruited in this study to perform sheet, laptop-typing, and tablet-searching tasks under the four experimental combinations. In addition to working performance measures, heart rate, Galvanic Skin Response (GSR), eyes blink duration, blink time, and critical fusion frequency (CFF) values were measured as well. The results showed that CCT 4,000 K-high efficiency lightings design would affect human’s physiological alert and stress. Thus we suggested the CCT 4,000 K-high efficiency participants had lower Tablet-searching error rate higher physiological alert and less eye fatigue.

The fidelity of color perception under various lighting conditions is crucial in lighting quality assessment. Traditional color rendering metrics, like the Total Color Rendering Index (CRI or Ra) developed by the Commision Internationale l’Eclairage (CIE) in 1964, provide an average measure of color fidelity across a limited set of color samples but do not capture individual color variations. This metric, while widely used, has limitations in predicting color fidelity, especially for specific colors or applications where precise color rendition (such as in skin tones, food items, or particular-colored objects) is essential. That is, this traditional method of evaluating color rendering has a number of limitations, such as using only eight test colors, which is insufficient for a wide range of sources and does not take into account new types of light sources, such as modern LEDs. With the advent of solid-state lighting, especially LEDs, the limitations of CRI became more pronounced, leading to calls for improved metrics. In response, the Society of Lighting Engineers of North America (IESNA) proposed the Color Fidelity Index (Rf), incorporating 99 uniformly distributed color samples and a refined color space to better predict visual color perception. And the color saturation index (Rg). These methods use modern color spaces, such as CIE CAM02-UCS, to increase the accuracy of the work. That is why modern approaches to assessing color rendering will allow us to take into account various types of light sources, including LED ones, ensure the accuracy of transmission where colors are critical and create standards for harmonizing lighting in different industries. The development of these metric systems helps to create better quality light sources and increase the comfort of human color perception. A calculation method was applied, which is determining the deviation of each test color from the reference one under standard lighting and averaging the deviations to obtain the final index. This article explores the fidelity of color indices, compares the efficacy of Ra and Rf metrics, and analyzes their application across various lighting sources, providing insights into the future of color rendering standards.