A MgWO₄ PHOTOCONVERTER‐BASED PERSONNEL UV‐B DOSIMETER*

Abstract

Design, construction, and testing of a photoelectronic UV-B personnel dosimeter whose optical system and thus wavelength and angular response match closely the Robertson-Berger sunburn ultraviolet meter is described. Erythema1 irradiance is sensed by a MgWO, fluor, and cumulative exposure is stored in digital form by custom-built hybrid microcircuits for readout through a microcomputer at a central station or a field display unit. Sensitivity and exposure storage capacity are designed to provide research-standard precision in measurements of a few hours to 5 2 months duration, and a high level of temperature stability has been achieved. The dosimeter's compactness, rugged and waterproof construction, and wide dynamic range make it applicable to laboratory and environmental photobiology research as well as in skin cancer epidemiology studies.

UV‐cured cellulose nanofiber composites with moisture durable oxygen barrier properties

“…Note that there was no visible degradation of the cellulosic materials under these UV exposure conditions (no discoloration). While general mechanisms for the photodegradation of cellulose molecules through free radical formation are well documented, 37,38 no relevant quantitative data could be found in the literature for the specific case of cellulose nanofibrils and the study of NFC photo-degradation is beyond the scope of this work.…”

The fluorescence of dihydroxyphenylalanine: the effects of protonation‐deprotonation

“…Oxidation of some amino acid residues in proteinaceous materials can alter the 'natural' or base colour of the substrate and can also affect the dye uptake of the material. Particularly susceptible to oxidation reactions are the aromatic amino acids, tryptophan and tyrosine, which contribute to yellowing and darkening of commercially important structural proteins such as keratin (wool) and collagen (animal skins) [1][2][3]. Both tryptophan and tyrosine, together with a number of their oxidation products, exhibit fluorescence [1][2][3][4][5][6][7][8].…”

“…Particularly susceptible to oxidation reactions are the aromatic amino acids, tryptophan and tyrosine, which contribute to yellowing and darkening of commercially important structural proteins such as keratin (wool) and collagen (animal skins) [1][2][3]. Both tryptophan and tyrosine, together with a number of their oxidation products, exhibit fluorescence [1][2][3][4][5][6][7][8]. Indeed, fluorescence spectroscopy has been used to advantage to demonstrate oxidation/ weathering of wool and to establish the nature of some of the oxidative reactions occurring in the fibre [5][6][7].…”

“…This includes establishing how the molecular environment, such as pH and the nature of neighbouring chemical groups, affects the fluorescence spectra and yields. Considerable attention has been paid to the fluorescence of tryptophan and its oxidation products because this aromatic amino acid dominates the emission from the proteins in which it is present [1,2].…”