Design of online practical lessons in colorimetry

Applied colorimetry is an important module in the program of the elective subject "Colour Science: industrial applications”. This course is taught in the Optics and Optometry Degree and it has been used as a testing for the application of new teaching and assessment techniques consistent with the new European Higher Education Area. In particular, the main objective was to reduce the attendance to lessons and encourage the individual and collective work of students. The reason for this approach is based on the idea that students are able to work at their own learning pace. Within this dynamic work, we propose online lab practice based on Excel templates that our research group has developed ad-hoc for different aspects of colorimetry, such as conversion to different colour spaces, calculation of perceptual descriptors (hue, saturation, lightness), calculation of colour differences, colour matching dyes, etc. The practice presented in this paper is focused on the learning of colour differences. The session is based on a specific Excel template to compute the colour differences and to plot different graphs with these colour differences defined at different colour spaces: CIE ΔE, CIE ΔE94 and the CIELAB colour space. This template is implemented on a website what works by addressing the student work at a proper and organized way. The aim was to unify all the student work from a website, therefore the student is able to learn in an autonomous and sequential way and in his own pace. To achieve this purpose, all the tools, links and documents are collected for each different proposed activity to achieve guided specific objectives. In the context of educational innovation, this type of website is normally called WebQuest. The design of a WebQuest is established according to the criteria of usability and simplicity. There are great advantages of using WebQuests versus the toolbox “Campus Virtual” available in the University of Alicante. The Campus Virtual is an unfriendly environment for this specific purpose as the activities are organized in different sectors depending on whether the activity is a discussion, an activity, a self-assessment or the download of materials. With this separation, it is more difficult that the student follows an organized sequence. However, our WebQuest provides a more intuitive graphical environment, and besides, all the tasks and resources needed to complete them are grouped and organized according to a linear sequence. In this way, the student guided learning is optimized. Furthermore, with this simplification, the student focuses on learning and not to waste resources. Finally, this tool has a wide set of potential applications: online courses of colorimetry applied for postgraduate students, Open Course Ware, etc.

Circumstellar emission in Be/X-ray binaries of the Magellanic Clouds and the Milky Way

Aims. We study the optical and near-infrared colour excesses produced by circumstellar emission in a sample of Be/X-ray binaries. Our main goals are exploring whether previously published relations, valid for isolated Be stars, are applicable to Be/X-ray binaries and computing the distance to these systems after correcting for the effects of the circumstellar contamination. Methods. Simultaneous UBVRI photometry and spectra in the 3500−7000 Å spectral range were obtained for 11 optical counterparts to Be/X-ray binaries in the LMC, 5 in the SMC and 12 in the Milky Way. As a measure of the amount of circumstellar emission we used the Hα equivalent width corrected for photospheric absorption. Results. We find a linear relationship between the strength of the Hα emission line and the component of E(B − V) originating from the circumstellar disk. This relationship is valid for stars with emission lines weaker than EW ≈ −15   Å. Beyond this point, the circumstellar contribution to E(B − V) saturates at a value ≈0.17   mag. A similar relationship is found for the (V − I) near infrared colour excess, albeit with a steeper slope and saturation level. The circumstellar excess in (B − V) is found to be about five times higher for Be/X-ray binaries than for isolated Be stars with the same equivalent width EW(Hα), implying significant differences in the physical properties of their circumstellar envelopes. The distance to Be/X-ray binaries (with non-shell Be star companions) can only be correctly estimated by taking into account the excess emission in the V band produced by free-free and free-bound transitions in the circumstellar envelope. We provide a simple method to determine the distances that includes this effect.

Colour morphotypes of Elysia timida (Sacoglossa, Gastropoda) are determined by light acclimation in food algae

Elysia timida (Risso, 1818) colonizing the shallow waters of the Mar Menor Lagoon (Spain) exhibit a brown and a green morph. It was hypothesised that these morphs were the result of feeding preferentially on brown and green algae, respectively. E. timida and its potential food sources, Acetabularia acetabulum (Chlorophyta) and Halopteris filicina (Heterokontophyta) were collected by snorkelling during April 2010. Photosynthetic pigments were analysed by HPLC, photo-physiological parameters were estimated by PAM fluorometry and body colour was characterized by spectral reflectance. Digital photography was used to count the number and area of red spots (small red dots on the slug’s surface) on the parapodia of the 2 morphs. In the laboratory, green E. timida was fed with A. acetabulum cultured under 2 light treatments (high light, 600 µmol E m−2 s−1 and low light, 40 µmol E m−2 s−1), and digital photography was used to monitor colour alterations in E. timida. Spectral reflectance confirmed the colour differences, but both morphs showed a pigment composition similar to the green alga A. acetabulum and showed none of the pigments present in the brown alga H. filicina, neither immediately after collection of the slugs in situ, nor after the feeding experiment. A. acetabulum grown under high light intensity changed from green to brown colour and E. timida changed to brown colour when fed with high-light acclimated A. acetabulum. Thus, E. timida colour differences could not be attributed to feeding on different algae groups but was likely the result of feeding on A. acetabulum growing under different light intensities.

An improved procedure for obtaining and maintaining well characterized partial water saturation states on concrete samples to be used for mass transport tests

A conditioning procedure is proposed allowing to install into the concrete specimens any selected value of water saturation degree with homogeneous moisture distribution. This is achieved within the least time and the minimum alteration of the concrete specimens. The protocol has the following steps: obtaining basic drying data at 50 °C (water absorption capacity and drying curves); unidirectional drying of the specimens at 50 °C until reaching the target saturation degree values; redistribution phase in closed containers at 50 °C (with measurement of the quasi-equilibrium relative humidities); storage into controlled environment chambers until and during mass transport tests, if necessary. A water transport model is used to derive transport parameters of the tested materials from the drying data, i.e., relative permeabilities and apparent water diffusion coefficients. The model also allows calculating moisture profiles during isothermal drying and redistribution phases, thus allowing optimization of the redistribution times for obtaining homogeneous moisture distributions.

Colour changes by laser irradiation of reddish building limestones

We have used X-ray photoelectron spectroscopy (XPS) as a novel method to investigate the causes of colour changes in a reddish limestone under irradiation by a Q-switched Nd:YAG 1064 nm laser. We irradiated clean dry and wet surfaces of Pidramuelle Roja, a building stone frequently used in the Asturian heritage, at fluences ranging from 0.12 to 1.47 J cm−2. We measured the colour coordinates and undertook XPS analysis of the state of oxidation of iron both before and after irradiation. Visible colour changes and potential aesthetic damage occurred on dry surfaces from a fluence of 0.31 J cm−2, with the stone showing a greening effect and very intense darkening. The colour change on dry surfaces was considerably higher than on wet surfaces, which at the highest fluence (1.47 J cm−2) was also above the human visual detection threshold. The use of XPS demonstrated that the change in colour (chroma and hue) is associated with a reduction in the iron oxidation state on dry surfaces during laser irradiation. This points out to a potential routinary use of XPS to analyse causes of colour changes during laser cleaning in other types of coloured building stones.