The power of healthy daytime lighting in indoor settings:melanopic lighting advances and office applications

This white paper discusses the latest scientific insights on how light affects people’s sleep, health and well-being. It also provides some initial guidance and recommendations for the application of melanopic lighting in indoor environments.With the recent insight that light plays a much bigger role than vision only, two new quantities have been defined to specify the lighting environment with respect to its ability to support health and well-being aspects [39]:The effectiveness of a lighting condition to activate melanopsin-based photoreception and drive ipRGC responses can be expressed in terms of the absolute quantity melanopic equivalent daylight illuminance (melanopic EDI). During daytime the guideline for melanopic EDI is: the more, the better, although this should not supersede existing guidelines [12]. Based on a comprehensive analysis of the sensitivity of human non-visual responses to retinal light exposure Brown et al. [11] recommend a minimum melanopic EDI of 250 lx at the eye for daytime indoor environments (measured in the vertical plane at ~1.2 m height) as to promote optimal physical and mental health and performance.The melanopic daylight efficacy ratio (melanopic DER) is a dimensionless relative quantity that describes a spectral characteristic of a light source and expresses the melanopic activation of a (test) light source as compared to a reference light source that emits a daylight spectrum (D65) and produces the same photopic illuminance as the test light. For instance, a test light with a melanopic DER of 1.25 or 0.75, has a melanopic activation (per lumen) that is 25% more or less as compared to daylight D65, respectivelyNote: the melanopic equivalent daylight illluminance (lx) (Melanopic EDI) equals the product of the amount of light (photopic illuminance in lx) that falls on the eye and the melanopic DER: melanopic EDI = illuminance * melanopic DE

Alignment of rod-shaped gold particles by electric fields

The electro-optical response of colloidal dispersions of rod-shaped gold particles is studied for various aspect ratios (2.6 < L/d < 49; d = 15 nm) by monitoring the absorbance spectra in the visible wavelength regime. The absorbance spectra strongly depend on the degree of orientational order of the rods and the direction of the polarization of the incident light with respect to the applied electric field. From the change in absorbance of the transverse resonance the electro-optical effect is deduced: at low electric field strengths a linear dependence on the squared electric field strength is observed, and at sufficiently high electric field strengths saturation occurs. This is in agreement with electro-optical theory. With increasing length, the anisotropy in electric polarizability increases from 6.10-30 F.m2 to 12.10-30 F.2. It is found that the anisotropy in electric polarizability depends on the square root of the particle length

Increasing the viewing angle of multidomain LCDs by using patterned retarders

The increase in viewing angle of multidomain liquid crystal displays (LCD) using patterned retarders was discussed. The twisted nematic (TN) LCDs were the most commonly used LCD in the high volume electronic industry. The contrast in the multi-domain TN LCD was reduced under large polar viewing angles

Synthesis of non-spherical gold nanoparticles

Non-spherical gold nanoparticles such as rods (short, long) (1,2), wires, cubes (3), nanocages (4), (multi-)concentric shells (5), triangular prisms (6-7), as well as other more exotic structures such as hollow tubes, capsules (6), even branched nanocrystals (8-9) have garnered significant research attention in the past few years..