Feature Extraction and Machine Learning for the Classification of Brazilian Savannah Pollen Grains.

The classification of pollen species and types is an important task in many areas like forensic palynology, archaeological palynology and melissopalynology. This paper presents the first annotated image dataset for the Brazilian Savannah pollen types that can be used to train and test computer vision based automatic pollen classifiers. A first baseline human and computer performance for this dataset has been established using 805 pollen images of 23 pollen types. In order to access the computer performance, a combination of three feature extractors and four machine learning techniques has been implemented, fine tuned and tested. The results of these tests are also presented in this paper.

Evaluation of the superficial characteristics of articular cartilage using evanescent waves in the friction tests with intermittent sliding and loading.

Articular cartilage plays an important role in the lubrication of synovial joints because of its peculiar characteristics. In this work, the frictional and superficial characteristics of articular cartilage were evaluated simultaneously during intermittent sliding and loading. The apparatus used for the analysis of the articular surface was based on the evanescent waves, where a laser light was reflected at the interface between a prism and a specimen of articular cartilage. Friction forces were measured due to the sliding of specimens on the prism. Images of reflected light were analyzed and attenuation of the reflectance was associated with the presence of collagen fibers near the interface, which interacted with the evanescent waves because of the high refractive index of these fibers. Specimens were tested in the intervals of 5.5 min with an interruption of 10 and 30 s in the sliding and loading. Results indicated a decrease in the both friction coefficient and attenuation of reflectance after the unloading. The level of reduction of the friction as well as of the attenuation of reflectance increased as the time of unloading increased. Decrease of friction after unloading was related to the decrease of collagen contents, or increase in water contents, at the articular surface, which was observed through the decrease of the attenuation of reflectance. Results indicated that the increase in the water content at the articular surface and the rehydration ability of articular cartilage after unloading could be responsible for the maintenance of friction in low levels.

Evaluation of the effect of collagen network degradation on the frictional characteristics of articular cartilage using a simultaneous analysis of the contact condition.

BACKGROUND: Superficial conditions and integrity of collagen network play an important role on the lubrication performance of articular cartilage. In this work, a technique based on the evanescent waves is used for the evaluation of contact condition during friction tests. METHODS: The frictional and superficial characteristics of the normal and degraded articular cartilages with high and low concentration of collagenase were evaluated. The optical apparatus was set in order to decrease the intensity of a light reflected at the interface between a prism and specimens when collagen fibers are found near the interface. FINDINGS: For all conditions, an increase in the attenuation of reflectance as the friction coefficient increases was observed with reasonable correlation. For the specimens degraded with collagenase, low friction and reduced attenuation of reflectance were observed at the beginning of sliding followed by a gradual increase in both friction and attenuation of reflectance. In comparison to the degraded specimens, normal specimens presented high friction at beginning and low friction at the end of test. INTERPRETATION: The superficial conditions and the presence of water at the articular surface play an important role in the lubrication of synovial joints. The ability to retain water for degraded specimens is impaired due to the loss of proteoglycan observed in the histological sections and hence, their low friction observed at the beginning of the test is not sustained for a long time. The use of evanescent waves demonstrated to be very useful in the analysis of the contact condition of articular cartilage.