Layer-by-Layer Investigation of Ultrastructures and Biomechanics of Human Cornea

The cornea is an avascular, innervated, and transparent tissue composed of five layers: the epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium. It is located in the outermost fraction of the eyeball and is responsible for the refraction of two-thirds of light and protection from external mechanical damage. Although several studies have been done on the cornea on the macroscopic scale, there is a lack of studies on the micro-nanoscopic scale, especially an analysis evaluating the cornea layer by layer. In this study, atomic force microscopy (AFM) was employed to assess four layers that form the cornea, analyzing: adhesion, stiffness, and roughness. The results showed microvilli in the epithelial and endothelial layers, pores in the basement membrane, and collagen fibers in the Stroma. These data increase the knowledge about the human cornea layers’ ultrastructures and adds new information about its biophysical properties.     

Is autonomic control of the heart rate at rest altered by detraining? A study of heart rate variability in professional soccer players after the pretraining period and after the preparatory period for competitions

The aim of this study was to assess the influence of detraining and training on the autonomic control of heart rate (HR), using time and frequency (spectral analysis) domain components of heart rate variability. Sixteen professional football players (26.7 +/- 3.8 years; 74.9 +/- 4.1 kg; 177 +/- 6.3 cm) were analysed at the end of a 1 month holiday (detraining) and after a 6 week training period (training). HR was recorded over 15 minutes with Holter equipment. The athletes rested in a supine position, in a quiet place and all test were performed between 8 and 10 AM. The subjects were requested to refrain from meals or caffeine for 12 hours before testing. In spite of the high intensity of the training period, there was no significant change in results from detraining condition to training condition. These results can have two possible explanations: (i) the high level of cardiovascular capacity in the detraining trial originated by the recreative physical activity that the players underwent during their holidays, and/or (ii) the training period was not long enough to promote any relevant effect on the autonomic control of HR.     

A recurrent neural network architecture to model physical activity energy expenditure in older people

Data Mining and Knowledge Discovery - Through the quantification of physical activity energy expenditure (PAEE), health care monitoring has the potential to stimulate vital and healthy ageing,...     

Evaluating the antioxidant capacity of wines: a laccase-based biosensor approach

Polyphenolic compounds present in wine have a high antioxidant capacity providing a protective effect on human health. There is a worldwide agreement on this assertion. However, there is no agreement on the method of assessing the antioxidant capacity of wines. The purpose of this study was to emphasize the ability of the laccase-based biosensor developed by our group to evaluate the antioxidant capacity of several types of wine in relation to their polyphenolic content. The values of total antioxidant activity of the investigated wine samples were well correlated with the corresponding bioelectrochemical polyphenol-estimated values, the correlation coefficient obtained being r = 0.9795 (p < 0.05). The linear relationship between total antioxidant activity and bioelectrochemical polyphenol index determined by laccase-based biosensor enabled the calculation of the TEAC (Trolox Equivalent Antioxidant Capacity) of a wine from its bioelectrochemical polyphenol index.     

Corrosion aspects of metallic implants — An overview

The ability to replace or augment diseased body parts totally or partially has improved both the quality and life span of human population. The decline in surgical risks during recent decades has encouraged the development of more complex procedures for prosthetic implantation. Additionally, a variety of extracorporeal devices, such as the heart, lung and blood dialysis machines are used routinely, but these prosthetic elements have several limitations. Hence, research projects are currently underway to overcome the limitations of synthetic materials by developing formulations with varying properties, such as asymptomatic, long‐term function in the human physiological environment, etc., to meet the needs of biomedical surgeons. This review focuses on the several biomaterials corrosion and its measures to prevent corrosion.     

Geometry, the Measure of the World

This study considers the relationship between the approach to urban planning in Portugal up to the eighteenth century, and the effective process of urbanisation, from both a theoretical and practical perspective. Portuguese urban layout does not develop as a set of random shapes but rather arises from structured thinking by “urban makers” who are firmly grounded in the subject of geometry. Being able to measure the universe and codify it in drawings was one of the major scientific accomplishments of the age of Portuguese discoveries in the sixteenth century and the acquisition of such knowledge demanded a unique ability for abstraction which could not have simply emerged out of nothing. Portugal’s investment in the training of skilled professionals is made evident in treatises, manuals, dissertations, and cartography and iconography works. The interpretation of the ideas of Order and Space in urban design evolved through history in parallel with the evolution of philosophical and scientific thought. In fact, urban space is associated the search of the laws of the nature and the intelligibility of the cosmos.     

The oxidation of Fe?Nb alloys in 1 atm of pure oxygen at 600–800°C

The corrosion of two Fe-Nb alloys containing 15 and 30 wt% Nb has been studied at 600–800°C under 1 atm of pure oxygen. The reaction followed the parabolic rate law to a reasonable approximation with rate constants much lower than for the oxidation of pure iron under the same conditions. Internal oxidation and depletion of niobium in the alloy have never been observed. The external scales were composed of a matrix of Fe₂O₃ containing a dispersion of double Fe-Nb oxide, while FeO and Fe₃O₄ were not observed. The oxidation behavior of these alloys is interpreted with reference to an approximate phase diagram of the ternary system Fe? Nb? O, taking into account the effects of the low solubility of niobium in the base metals and of the presence of two metal phases in the alloy.     

Study of a Nitinol Stent Deployed into Anatomically Accurate Artery Geometry and Subjected to Realistic Service Loading

Realistic simulation of a stent in service loading is necessary for the design of Nitinol stents. This type of analysis is complicated by several issues: artery geometry and material properties are largely unknown and may vary from person to person; the loading on the stent is due to interactions between pulsatile blood flow, the artery, and stent. This study addresses the first issue by obtaining realistic artery geometry from magnetic resonance imaging (MRI) scans of a patient in the fetal and supine positions, and comparing deformation of the stent deployed into the two different artery configurations. The second issue is addressed by investigating two different methods of applying service loading. The first method applies sinusoidal pressure waves directly to the artery wall. The second method considers the effect of blood flow within the artery by performing a fluid-structure interaction (FSI) simulation. Simulation of expansion, annealing, crimping, and deployment of a Nitinol stent into the two artery configurations was performed using Abaqus. Following the deployment, sinusoidal pressure pulses, emulating systolic and diastolic blood pressures, were applied to the inner surface of the artery. To simulate the effect of blood within the artery, the coupled Eulerian-Lagrangian method in Abaqus was used. The blood was modeled as a partially filled Eulerian domain, whose material boundary contacted the Lagrangian artery. Transient inlet velocity and outlet pressure conditions were applied to the Eulerian domain to simulate blood flow. Since fatigue life calculations are important for the design of Nitinol stents, the maximum principal strains at the diastolic pressure troughs and the difference between the maximum principal strains at diastolic and systolic pressure were investigated for five cycles. Different maximum principal strains resulted for the different artery geometries (fetal or supine), while the difference between maximum principal strains was similar. For the simulations including the effect of blood flow, the maximum principal strains at the diastolic pressure troughs were somewhat higher than the simulations in which pressure was directly applied to the artery. In conclusion, this study established and compared various methods of improving the service loading in the simulation of Nitinol stents, specifically including anatomically correct artery geometry and the effect of blood flow.