Physics Department

Biological tissues have individual optical properties that may be used as an identity card. The refractive index in particular, which can be measured directly, is very significant for the improvement or development of optical technologies in clinical practice. With the objective of verifying if healthy and pathological tissues can be discriminated from refractive index measurements, we have studied human colorectal mucosa. By using the total internal reflection method to measure the refractive index from healthy and pathological colorectal mucosa tissues at different wavelengths, it was possible to calculate the dispersion curves for both types of tissues. It was observed a decaying refractive index with wavelength, both for healthy and pathological tissues, which were fitted with curves described by Cornu's equation for wavelengths between ultraviolet and near-infrared range. Experimental results show higher refractive index values for the pathological mucosa for all wavelengths. By performing measurements at wavelengths near 850 nm, we have detected non-monotonic behavior for the refractive index of both healthy and pathological tissues. Such abnormal wavelength dependence is evidence of lipids in both tissues. The acquired experimental data demonstrated that it is possible to discriminate between healthy and pathological tissues from refractive index measurements. Similar studies can be made for different biological tissues. By using lasers with different wavelengths it might be possible to identify other tissue components.

It is known that the fibrous structure of muscle causes light scattering. This phenomenon occurs due to the refractive index discontinuities located between muscle fibers and interstitial fluid. To study the possibility of reducing light scattering inside muscle, we consider its spectral transmittance evolution during an immersion treatment with an optical clearing solution containing ethanol, glycerol, and distilled water. Our methodology consists of registering spectral transmittance of muscle samples while immersed in that solution. With the spectral data collected, we represent the transmittance evolution for some wavelengths during the treatment applied. Additionally, we study the variations that the treatment has caused on the samples regarding tissue refractive index and mass. By analyzing microscopic photographs of tissue cross section, we can also verify changes in the internal arrangement of muscle fibers caused by the immersion treatment. Due to a mathematical model that we develop, we can explain the variations observed in the studied parameters and estimate the amount of optical clearing agent that has diffused into the tissue samples during the immersion treatment. At the end of the study, we observe and explain the improvement in tissue spectral transmittance, which is approximately 65% after 20 min.

The main purpose of this research was to create a portable equipment capable of measuring colour and turbidity during production of port wine. Actually, human, chemical and colour analysis are performed in key production stages for quality control. Several wine transformation processes are done without any kind of control. By using a ÿbre optic illuminator with a tungsten/halogen light source and a small spectrometer with ÿbre optic input, it was possible to perform angular measurements in wine samples. We have adapted these optical devices with a specially designed mechanical equipment which allows the passage of the wine during production. The spectral measurements were acquired in four diierent angular positions in a bypass of the mechanical support. This way we could determine colour coordinates and spectral transmittance and turbidity for three stages of a Ruby production. The entire equipment assembly had been previously calibrated in terms of colour and turbidity determination. The obtained results are in agreement with wine transformations between measurements, showing a small variation in colour and a high diminishing in spectral turbidity when ÿltration was performed. Transmittance has also increased after ÿltration turning the wine more limpid as it should be for human appreciation.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright a b s t r a c t Complete optical characterization of biological tissue is desirable to develop clinical methods using optical technologies. Particularly, to develop optical clearing methods in biological tissues, it is necessary to know the composition of the tissue, the percentage of each constituent and corresponding refractive indexes. To obtain such information for rat muscle, we used a simple method to characterize tissue constituents for both content percentage and refractive index. The study consisted on measuring mass with a precision weighting scale and the refractive index with an Abbe refractometer during tissue dehydration. With the collected data, we used a theoretical model to calculate the refractive index and percentage for both interstitial fluid and solid part of the rat muscle. The results obtained are in good agreement with data published by other authors, and were considered of vital information for the optical clearing studies that we planned to perform.

Biological tissues have individual optical properties that may be used as an identity card. The refractive index in particular, which can be measured directly, is very significant for the improvement or development of optical technologies in clinical practice. With the objective of verifying if healthy and pathological tissues can be discriminated from refractive index measurements, we have studied human colorectal mucosa. By using the total internal reflection method to measure the refractive index from healthy and pathological colorectal mucosa tissues at different wavelengths, it was possible to calculate the dispersion curves for both types of tissues. It was observed a decaying refractive index with wavelength, both for healthy and pathological tissues, which were fitted with curves described by Cornu's equation for wavelengths between ultraviolet and near-infrared range. Experimental results show higher refractive index values for the pathological mucosa for all wavelengths. By performing measurements at wavelengths near 850 nm, we have detected non-monotonic behavior for the refractive index of both healthy and pathological tissues. Such abnormal wavelength dependence is evidence of lipids in both tissues. The acquired experimental data demonstrated that it is possible to discriminate between healthy and pathological tissues from refractive index measurements. Similar studies can be made for different biological tissues. By using lasers with different wavelengths it might be possible to identify other tissue components.

Skeletal muscle dispersion and optical clearing kinetics were studied experimentally to
prove the existence of the refractive index (RI) matching mechanism of optical clearing.
Sample thickness and collimated transmittance spectra were measured during treatments with glucose (40%) and ethylene glycol (99%) solutions and used to obtain the time dependence of the RI of tissue fluids basing on the proposed theoretical model.
Calculated results demonstrated an increase of RI of tissue fluids and consequently
proved the occurrence of the RI matching mechanism. The RI increase was observed for
the wavelength range between 400 and 1000 nm and for the two probing molecules
explored. We found that for 30 min-treatment with 40%-glucose and 99%-ethylene
glycol, RI of sarcoplasm plus interstitial fluid was increased at 800 nm from 1.328 to
1.348 and from 1.328 to 1.369, respectively.

Informal Learning plays an important role in everyone's life and yet we often are unaware of it. The need to keep track of the knowledge acquired through informal learning is increasing as its sources become increasingly diverse. This paper presents a study on a tool developed to help keeping track of learners’ informal learning, both within academic and professional contexts, This tool, developed within the European Commission funded TRAILER project, will further integrate the improvements suggested by users during the piloting phase. The two studied contexts were similar regarding the importance and perception of Informal Learning, but differed concerning tool usage. The overall idea of managing one’s informal learning was well accepted and welcomed, which validated the emerging need for a tool with this purpose.

The evolution of new technology and its increasing use, has for some years been making the existence of informal learning more and more transparent, especially among young and older adults in both Higher Education and workplace contexts. However, the nature of formal and non-formal, coursebased, approaches to learning has made it hard to accommodate these informal processes satisfactorily. The project aims to facilitate first the identification by the learner (as the last responsible of the learning process), and then the recognition by the institution, in dialogue with the learner, of this learning. To do so a methodology and a technological framework to support it have been implemented. This project have been tested in several context and it is possible to say that an informal learning dialogue between learners and people in chargé of the institutions is possible.

People do not learn only in formal educational institutions, but also throughout their lives, from their experiences, conversations, observations of others, exploration of the Internet, meetings and conferences, and chance encounters etc. However this informal and non-formal learning can easily remain largely invisible, making it hard for peers and employers to recognize or act upon it. The TRAILER project aims to make this learning visible so that it can benefit both the individual and the organization. The proposed demonstration will show a software solution that (i) helps the learners to capture, organize and classify a wide range of 'informal' learning taking place in their lives, and (ii) assists the organization in recognizing this learning and use it to help managing human resources (benefiting both parts). This software tool has recently been used in two phases of pilot studies, which have run in four different European countries.