Having good information about fluorescence lifetime standards is essential for anyone performing lifetime experiments. Using lifetime standards in fluorescence spectroscopy is often regarded as a straightforward process, however, many earlier reports are limited in terms of lifetime concentration dependency, solvents and other technical aspects. We have investigated the suitability of the fluorescent dyes rhodamine B, coumarin 6, and lucifer yellow as lifetime standards, especially to be used with two-photon excitation measurements in the time-domain. We measured absorption and emission spectra for the fluorophores to determine which wavelengths we should use for the excitation and an appropriate detector range. We also measured lifetimes for different concentrations, ranging from 10−2– 10−6 M, in both water, ethanol and methanol solutions. We observed that rhodamine B lifetimes depend strongly on concentration. Coumarin 6 provided the most stable lifetimes, with a negligible dependency on concentration and solvent. Lucifer yellow lifetimes were also found to depend little with concentration. Finally, we found that a mix of two fluorophores (rhodamine B/coumarin 6, rhodamine B/lucifer yellow, and coumarin 6/lucifer yellow) all yielded very similar lifetimes from a double-exponential decay as the separate lifetimes measured from a single-exponential decay. All lifetime measurements were made using two-photon excitation and obtaining lifetime data in the time-domain using time-correlated single-photon counting.

Frette Ø, Erga SR, Hamre B, Aure J, Stamnes JJ. 2004. Seasonal variability in inherent optical properties in a western Norwegian fjord. Sarsia 89:276-291. SARSIAWe present measured seasonal variations in the inherent optical properties (the absorption and scattering coefficients) of water in a deep silled fjord (Samnangerfjorden) in western Norway. These were based on measurements taken at monthly intervals during an annual cycle. The measurements also include concentrations of chlorophyll a and yellow substance, which were assumed to dominate the behaviour of the absorption and scattering coefficients. The stations were at three fixed locations, one being placed in the innermost part of the fjord where there is little mixing of fjord water with water from the coastal current. The other two stations were placed at different distances from the mouth of the fjord, so that the water masses are characterized by different amounts of mixing between fjord water and coastal current water. Our data set shows how the absorption and scattering coefficients vary in a Norwegian fjord during an annual cycle, and how they depend on the concentrations of chlorophyll a and yellow substance. Values of the absorption coefficient at 412 nm varied between 0.1 and 2.0 m À1 , and scattering coefficients were also found to vary within this range. Little variation over the spectral range was found for the scattering coefficients, but the absorption coefficient had larger spectral variations. The chlorophyll a concentrations varied from 0.01 to 6.3 mg m À3 , and the concentration of yellow substance, as expressed by its absorption coefficient at 310 nm, was within the range 0.7-7.8 m À1 .

We investigated the ultraviolet radiation (UVR) transmission properties of Norwegian oceanic, coastal and fjord waters, and how they influence the primary production and vertical distribution of phytoplankton. Values of the 1% UVR attenuation depth and diffuse attenuation coefficients (K d ) in the Greenland and Norwegian Seas (GNS), in the coastal waters of south-western Norway (SWN) and in the Samnanger fjord (SAF) are presented. Maximum penetration of UVR in the GNS was confirmed by K d (320) = 0.25 m -1 , and mimimum penetration in the SAF, by K d (320) = 9 m -1 . In the GNS, K d and chlorophyll a (chl a) were closely correlated, while coloured dissolved organic matter (CDOM) was the main contributor to ultraviolet (UV) attenuation in the SAF. Also, in SWN waters, CDOM was more important than chl a for UV attenuation, but less important than in SAF waters. In GNS and SAF waters the average vertical distribution of chl a had its maximum in the upper 10 and 7.5 m of the water column, respectively, while in SWN waters it had its maximum at 20 m. The depths with the highest photosynthetic rates per unit volume decreased successively from the oceanic waters of the GNS via the coastal waters of the SWN to the fjord waters of the SAF. Under similar PAR intensities, however, the water column photosynthetic efficiency (integrated carbon assimilation/chl a ratio) was highest in SWN waters. Maximum and mean percentage potential for inhibition of the estimated (from PAR and UV) primary production due to UVR at a depth of 5 m were 11 and 4.3% in the GNS, 3.2 and 0.9% in the SWN and 0.5 and 0.1% in the SAF. The UVR potential for inhibition was significant down to a depth of 10 m in the GNS, down to a depth of 5 m in the waters of the SWN, while it was seldom found deeper than 3 m in the SAF. These variations could be ascribed to differences in CDOM concentrations and mixed-layer depths. The optical properties of the investigated water masses were found to be highly influenced by the circulation patterns. KEY WORDS: UV transmission · Norwegian waters · Phytoplankton · Primary production Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 305: 2005 total ozone has been observed at middle and high latitudes in the Northern Hemisphere during the last decades (Stolarski et al. 1992, Jokela et al. 1993, Varotsos et al. 1998, Dahlback 2002. According to Austin et al. (1992), Bjørn et al. (1998) and Hessen (2002), this tendency is expected to continue in the 21st century. In addition, there is a tendency towards more rapid depletion of the ozone layer over Scandinavia than over most other geographical regions at corresponding latitudes. In contrast to the antarctic ozone hole, which occurs regularly both on a spatial and a temporal scale (Hofmann et al. 1992, Davidson & van der Heijden 2000, the arctic ozone hole seems to occur irregularly (Stamnes et al. 1988, Jokela et al. 1993). The radiation levels within both the visible and the UV bands decrease with increasing la...

The full Mueller matrix for a Spectralon white reflectance standard was measured in the incidence plane, to obtain the polarization state of the scattered light for different angles of illumination. The experimental setup was a Mueller matrix ellipsometer, by which measurements were performed for scattering angles measured relative to the normal of the Spectralon surface from -90° to 90° sampled at every 2.5° for an illumination wavelength of 532 nm. Previously, the polarization of light scattered from Spectralon white reflectance standards was measured only for four of the elements of the Muller matrix. As in previous investigations, the reflection properties of the Spectralon white reflectance standard was found to be close to those of a Lambertian surface for small scattering and illumination angles. At large scattering and illumination angles, all elements of the Mueller matrix were found to deviate from those of a Lambertian surface. A simple empirical model with only two parameters, was developed, and used to simulate the measured results with fairly good accuracy.

We used size distributions of volume equivalent spherical particles with complex refractive index to model the inherent optical properties (IOPs) in four different layers of human skin at ten different wavelengths in the visible and near-infrared spectral bands. For each layer, we first computed the size-averaged absorption coefficient, scattering coefficient, and asymmetry factor for the collection of particles in a host medium using Mie theory and compared these IOPs in each layer with those obtained from a bio-optical model (BOM). This procedure was repeated, using an optimization scheme, until satisfactory agreement was obtained between the IOPs obtained from the particle size distribution and those given by the BOM. The size distribution as well as the complex refractive index of the particles, obtained from this modeling exercise, can be used to compute the phase matrix, which is an essential input to model polarized light transport in human skin tissue.