Characterization of fresh PM deposits on calcareous stone surfaces: Seasonality, source apportionment and soiling potential.

Particulate matter (PM) pollution is one of the major threats to cultural heritage outdoors. It has been recently implied that organic aerosols will prevail over inorganic carbon particulates in the future, changing the main mechanisms of damage caused by poor air quality to calcareous heritage in particular. We studied fresh particulate deposits on marble and limestone surfaces exposed to urban air in sheltered and unsheltered configurations.

Analysis of the polarized IR reflectance spectra of the monoclinic α-oxalic acid dihydrate.

In contrast to the extensive molecular and crystal structure investigations on oxalic acid dihydrate (CHO·2HO, α-POX) and its deuterated analogues (α-DOX), stands the absence of a complete vibrational spectra analysis. Such analysis is desirable in view of the proton dynamics in α-POX crystals. In this communication we report the room temperature polarized IR reflectance spectra of a single crystal of α-POX recorded from the ac crystal plane, and from the plane containing the b-crystallographic axis, with polarization along the axis.

Relation between colour- and phase changes of a leuco dye-based thermochromic composite.

Reversible colour change of leuco dye-based composites is in general closely related to their phase change, thus the two phenomena should occur at around the same temperature and should be influenced similarly. However, spatial confinement of the analysed sample affects the change in colour differently compared to its phase transition and the most pronounced effects can be observed during cooling. The bulk composite is coloured while still liquid and the colour hysteresis does not exhibit a loop.

Goniospectrometric space curve for coatings with special effect pigments: erratum.

In the original publication [Appl. Opt.55, 122 (2016)APOPAI0003-693510.

Goniospectrometric space: identifiable presentation of spectral goniometric data for complex diffractive samples.

Optical security takes advantage of complex gonioapparent effects of diffractive samples having strong angular and spectral dependence of reflected light. However, resolving the full angular and spectral properties of these kinds of targets might be a tremendous task. Preferably, one would like to measure a more limited number of illumination-viewing directions, using a multiangle goniometer, and still reveal the complex and unique properties of the target.

Goniospectrometric space curve for coatings with special effect pigments.

Advanced application of eye-catching effects occurring in coatings with special effect pigments requires controlling their appearance. For this purpose, angular dependent reflectance must be analyzed in terms of the used flakes and their distribution inside the coating; it is important to know the size of the surface area they cover, and the position and precision of their orientation. These properties were varied using our numerical model, which gave an angular dependent reflectance factor for each set of coating parameters.

White LED compared with other light sources: age-dependent photobiological effects and parameters for evaluation.

Ergonomic science at work and living places should appraise human factors concerning the photobiological effects of lighting. Thorough knowledge on this subject has been gained in the past; however, few attempts have been made to propose suitable evaluation parameters. The blue light hazard and its influence on melatonin secretion in age-dependent observers is considered in this paper and parameters for its evaluation are proposed.

Evaluation of complex gonioapparent samples using a bidirectional spectrometer.

Many applications use gonioapparent targets whose appearance depends on irradiation and viewing angles; the strongest effects are provided by light diffraction. These targets, optically variable devices (OVDs), are used in both security and authentication applications. This study introduces a bidirectional spectrometer, which enables to analyze samples with most complex angular and spectral properties.

High-performance lighting evaluated by photobiological parameters.

The human reception of light includes image-forming and non-image-forming effects which are triggered by spectral distribution and intensity of light. Ideal lighting is similar to daylight, which could be evaluated by spectral or chromaticity match. LED-based and CFL-based lighting were analyzed here, proposed according to spectral and chromaticity match, respectively.

Goniospectrophotometric space curves of diffraction gratings and their applicability as appearance fingerprints.

The bidirectional reflectance distribution functions of diffraction gratings were calculated by applying diffraction theory and transformed into goniospectrophotometric space curves. Gratings with parallel sinusoidal grooves having periods of 1-3.5 μm and amplitudes below 0.

Suitability of goniospectrophotometric space curves as appearance fingerprints.

Goniospectrophotometric space curves were obtained by summation of spatially under-sampled bidirectional reflectance distribution function over all directions and repeating this for all wavelengths in the visible spectral region. This gives a 3D goniospectrophotometric curve called an xDNA graph. Systematic analysis applying 19 measurement geometries confirms existence of characteristic shapes of the graph for all optically similar samples.

Optical properties of exfoliated MoS2 coaxial nanotubes - analogues of graphene.

We report on the first exfoliation of MoS2 coaxial nanotubes. The single-layer flakes, as the result of exfoliation, represent the transition metal dichalcogenides' analogue of graphene. They show a very low degree of restacking in comparison with exfoliation of MoS2 plate-like crystals.

Dispersion analysis of polarized bulk reflectance spectra of potassium hydrogen succinate monocrystal.

Reflectance spectra may show very different and interesting shapes. The most interesting may be connected to Evans holes. Model calculations to reproduce this effect were done applying model dielectric function functions.

Optical behaviour of copper phthalocyanine preparations for inkjet inks.

The present study investigates the preparation of the copper phthalocyanine pigment for inkjet printing inks. The pigment particle size distribution was measured with laser diffraction at different times of wet milling. Simultaneously, the absorbance spectra in a visible-near infrared spectral region of the corresponding diluted pigment dispersions were measured.

Color rendering properties of interior lighting influenced by a switchable window.

Switchable windows are being installed into modern buildings. We report on how the variable transmittance of gasochromic and electrochromic switchable windows changes the color rendering properties of the daylight passing through these windows. We present a series of color rendering examples.

Infrared reflection-absorption spectra of metal-effect coatings.

The results of studies of infrared reflection-absorption spectra of metal-effect coatings are presented in this paper. Such coatings consist of metallic flakes that are dispersed in a polymer binder. The spectra show two distinct phenomena.