Light pollution: Assessment of sky glow on two dark sky regions of Portugal.

Artificial light at night (ALAN), producing light pollution (LP), is not a matter restricted to astronomy anymore. Light is part of modern societies and, as a consequence, the natural cycle day-night (bright-dark) has been interrupted in a large segment of the global population. There is increasing evidence that exposure to certain types of light at night and beyond threshold levels may produce hazardous effects to humans and the environment. The concept of "dark skies reserves" is a step forward in order to preserve the night sky and a means of enhancing public awareness of the problem of spread of light pollution worldwide. The aim of this study was to assess the skyglow at two sites in Portugal, the Peneda-Gerês National Park (PNPG) and the region now known as Dark Sky Alqueva Reserve. The latter site was classified as a "Starlight Tourism Destination" by the Starlight Foundation (the first in the world to achieve this classification) following a series of night sky measurements in situ described herein. The measurements at PNPG also contributed to the new set of regulations concerning light pollution at this national park. This study presents the first in situ systematic measurements of night sky brightness, showing that at the two sites the skies are mostly in levels 3 to 4 of the Bortle 9-level scale (with level 1 being the best achievable). The results indicate that the sources of light pollution and skyglow can be attributed predominantly to contamination from nearby urban regions.

Study and characterization of the crest module design: A 3D finite element analysis.

STATEMENT OF PROBLEM: The importance of the crest module design in the cortical bone region triggered a need to understand its geometry and its influence on stress management and bone stimulation. PURPOSE: The purpose of this study was to determine the effect of different crest module designs in the cortical bone region in terms of critical stress distribution and bone stimulation. MATERIAL AND METHODS: Several 3-dimensional finite element analyses were conducted of a mandibular cross section with osseointegrated dental implants. For the numerical models, different crest module designs (cylindrical, divergent, convergent, and cup shaped) were analyzed. An average value of a maximum occlusal load of 250 N was applied to each dental implant design, 30 degrees from the top surface. The concentration and distribution patterns of principal and maximum shear stresses and strains were obtained and analyzed. RESULTS: According to the comparative finite element analyses, the most pathologic stress and strain peaks around the implant collar in the cortical bone region were found in divergent crest modules with angles 14 degrees or larger. Nevertheless, the highest physiologic peaks of passive bone stimulation through compression, and the lowest tensile and shear stresses and strains in the cortical bone region were promoted by extended divergent crest module designs. CONCLUSIONS: A slightly divergent and smooth crest module design extended to the cancellous bone increases the surface area available. This results in the dissipation of critical stresses expressed around the collar of the cortical bone region, not only promoting a higher bone-implant contact area and a physiologic bone stimulation but also boosting a healthy and strong bone-implant interface.

Differential Expression of miRNAs in Amyotrophic Lateral Sclerosis Patients.

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease that affects nerve cells in the brain and spinal cord, causing loss of muscle control, muscle atrophy and in later stages, death. Diagnosis has an average delay of 1 year after symptoms onset, which impairs early management. The identification of a specific disease biomarker could help decrease the diagnostic delay. MicroRNA (miRNA) expression levels have been proposed as ALS biomarkers, and altered function has been reported in ALS pathogenesis. The aim of this study was to assess the differential expression of plasma miRNAs in ALS patients and two control populations (healthy controls and ALS-mimic disorders). For that, 16 samples from each group were pooled, and then 1008 miRNAs were assessed through reverse transcription-quantitative polymerase chain reaction (RT-qPCR). From these, ten candidate miRNAs were selected and validated in 35 ALS patients, 16 ALS-mimic disorders controls and 15 healthy controls. We also assessed the same miRNAs in two different time points of disease progression. Although we were unable to determine a miRNA signature to use as disease or condition marker, we found that miR-7-2-3p, miR-26a-1-3p, miR-224-5p and miR-206 are good study candidates to understand the pathophysiology of ALS.

Quasi-static and dynamic properties of the intervertebral disc: experimental study and model parameter determination for the porcine lumbar motion segment.

PURPOSE: The study of axial loading is essential to determine the properties of intervertebral disc. The objectives of this work are (1) to quantify the mechanical properties of porcine lumbar intervertebral discs under static and cyclic compressive loading, and (2) to determine the parameters of a five-parameter rheological model for porcine and compare them with those obtained for human lumbar intervertebral discs. METHODS: Thus, the porcine lumbar motion segments were subjected to quasi-static and dynamic compression tests. The quasi-static tests were used to obtain the static stiffness coefficient at different strain rates, while the data from the cyclic compressive tests were used to both determine the dynamic stiffness coefficient and to be fitted in a 5-parameter model, in order to simulate the creep response of the porcine intervertebral discs. RESULTS: The results demonstrated that dynamic stiffness coefficient of porcine discs is between four and ten times higher than the static stiffness coefficient, depending on load applied. The parameters of the rheological model suggested a low permeability of nucleus and endplate during the fast response of porcine discs. In addition, the fast response in terms of displacement is four times higher than those documented for human discs. CONCLUSIONS: This study revealed that care must be taken on the comparison between porcine and human discs, since they present different behaviour under quasi-static and dynamic compressive loading.