140 research outputs found
Experimental validation of a current-source converter with reduced dc-link operating as shunt active power filter
Nowadays, the majority of electronic equipment behaves as nonlinear loads, introducing power quality problems into the
power grid, namely, current harmonics and low power factor. These problems contribute to reduce the efficiency of the
power grid and can cause malfunctioning of sensitive loads connected to the power grid. Therefore, it is important to develop
power electronics solutions capable to mitigate these power quality problems. In this context, this paper presents a novel
single-phase shunt active power filter (SAPF) based on a current-source converter, where the key differencing factor, when
compared with the conventional approach, is the reduced dc-link. As the proposed topology requires a reduced dc-link, it
represents a relevant advantage, requiring a less bulky inductance in the dc-link, reducing the losses, cost, and volume. The
proposed SAPF with reduced dc-link is introduced in detail along the paper, and a comprehensive comparison with the
conventional SAPF is established based on computer simulations. Besides, an experimental validation is carried out with a
developed laboratory prototype, validating the main advantages of the proposed SAPF with reduced dc-link.This work has been supported by FCT – Fundação para a Ciência e
Tecnologia with-in the Project Scope: UIDB/00319/2020. This work
has been supported by the FCT Project newERA4GRIDs
PTDC/EEI-EEE/30283/2017 and the FCT Project
QUALITY4POWER PTDC/EEI-EEE/28813/2017, and by. Mr.
Luis A. M. Barros is supported by the doctoral scholarship
PD/BD/143006/2018 granted by the Portuguese FCT foundation
Impact of Physical Exercise on Melanoma Hallmarks: Current Status of Preclinical and Clinical Research
In recent years, accumulating evidence from preclinical and clinical studies consistently indicated that physical activity/exercise plays a crucial role in reducing the incidence and recurrence of various malignancies, by exerting a beneficial modulation of cancer hallmarks. moreover, physical activity is suggested to attenuate certain adverse effects of anticancer therapy, including the reduction of cardiovascular toxicity and symptoms related to depression and anxiety, among others, while preserving muscular strength. In the case of melanoma, the relationship with physical activity has been critically debated. historically, several cohort studies and meta-analyses reported a positive association between physical activity/exercise and melanoma risk. this association was primarily attributed to outdoor activities that may expose the skin to UV radiation, a well-known risk factor for melanocyte transformation. However, more recent evidence does not support such association and recognizes physical activity/exercise role in both melanoma prevention and progression. nevertheless, sun protection is recommended during outdoor training to minimize UV radiation exposure. this narrative review summarizes preclinical and clinical data about physical activity effects on melanoma hallmarks. Specifically, experimental evidence is reported concerning (i) invasion and metastasis, (ii) reprogramming of energy metabolism, (iii) angiogenesis, (iv) resistance to cell death, (v) evasion from immune destruction, and (vi) tumor-promoting inflammation
End-of-day dryness, corneal sensitivity and blink rate in contact lens wearers
Purpose: To study the relationship among the variables intensity ofthe end-of-day (EOD) dryness, corneal
sensitivity and blink rate in soft contact lens (CL) wearers.
Methods: Thirty-eight soft CL wearers (25 women and 13 men; mean age 27.1 ± 7.2 years) were enrolled.
EOD dryness was assessed using a scale of 0–5 (0, none to 5, very intense). Mechanical and thermal (heat
and cold) sensitivity were measured using a Belmonte’s gas esthesiometer. The blink rate was recorded
using a video camera while subjects were wearing a hydrogel CL and watching a film for 90 min in a
controlled environmental chamber.
Results: A significant inverse correlation was found between EOD dryness and mechanical sensitivity
(r: −0.39; p = 0.02); however, there were no significant correlations between EOD dryness and thermal
sensitivity. A significant (r: 0.56; p < 0.001) correlation also was observed between EOD dryness and blink
rate, but no correlations were found between blink rate and mechanical or thermal sensitivity.
Conclusions: CL wearers with higher corneal sensitivity to mechanical stimulation reported more EOD
dryness with habitual CL wear. Moreover, subjects reporting more EOD dryness had an increased blink
rates during wear of a standard CL type. The increased blink rate could act to improve the ocular surface
environment and relieve symptom
Insights into corrosion behaviour of uncoated Mg alloys for biomedical applications in different aqueous media
MgCa and MgGd series of alloys are often reported as promising candidates for biomedical
applications. In the present study, cytotoxicity and corrosion behavior of Mg1Ca and
Mg10Gd alloys in different electrolytes (NaCl, PBS, MEM) have been investigated in order to
make a direct comparison and understand the mechanisms behind their performance.
Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were
employed to analyze corrosion processes depending on media composition, whereas X-Ray
diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate crystalline
structure, phase composition and surface morphology of the corroded substrates after
immersion in the different electrolytes. Moreover, cytotoxicity of the Mg alloys was
assessed using the WST-1 reduction and lactate dehydrogenase (LDH) release assays in
L929 mouse fibroblasts. The electrochemical results showed that Mg1Ca has a lower
degradation rate when compared to Mg10Gd, due to the lower microgalvanic effects and
the presence of Ca as an alloying element. Furthermore, the corrosion activity is reduced in
MEM, for both alloys, when compared to NaCl and PBS. The cytotoxicity assays revealed
that Mg10Gd was cytotoxic in all the conditions tested, while the toxicity of Mg1Ca was
low. Overall, these findings show that Mg1Ca alloy presents a higher corrosion resistance
and biocompatibility and is a promising material to be used in biomedical implants.This work was financed by Portugal 2020 through European
Regional Development Fund (ERDF) in the frame of Operational
Competitiveness and Internationalization Programme (POCI),
in the scope of the project MAGICOAT POCI-01-0145-FEDER016597/PTDC/CTM-BIO/2170/2014 and in the scope of the project CICECO - Aveiro Institute of Materials, UIDB/50011/2020 &
UIDP/50011/2020, financed by national funds through
the Portuguese Foundation for Science and Technology/
MCTES. Furthermore, thanks are due to Portuguese Foundation
for Science and Technology/MCTES for the financial support
through national funds to EPI Unit (UIDB/04750/2020).info:eu-repo/semantics/publishedVersio
Nonperturbative Yukawa theory at finite density and temperature
In-medium Yukawa theory is part of the thermodynamics of the Standard Model
of particle physics and is one of the main building blocks of most effective
field theories of fermionic systems. By computing its pressure we investigate
the nonperturbative thermodynamics at finite temperature and density using the
optimized perturbation theory (OPT) framework. Our calculations are valid for
arbitrary fermion and scalar masses, temperature, chemical potential, and not
restricted to weak coupling. The model is considered in the presence as well as
in the absence of condensates. Comparison with nonperturbative results shows
that second order perturbation theory (PT) fails in the first case but performs
rather well when condensates are absent, even at high-temperature regimes.Comment: 18 pages, 15 figures; v2: references added, improved discussion in
the Conclusions, matches published versio
Development and characterization of PHB-HV based 3D scaffolds for a tissue engineering and cell-therapy combinatorial approach for spinal cord Injury regeneration
Spinal cord injury (SCI) leads to devastating neurological deficits. Several tissue engineering (TE)-
based approaches have been investigated for repairing this condition. Poly (3-hydroxybutyrateco-
3-hydroxyvalerate) (PHB-HV) is found to be particularly attractive for TE applications due to
its properties, such as biodegradability, biocompatibility, thermoplasticity and piezoelectricity.
Hence, this report addresses the development and characterization of PHB-HV-based 3D
scaffolds, produced by freeze-drying, aimed to SCI treatment. The obtained scaffolds reveal an
anisotropic morphology with a fully interconnected
network of pores. In vitro studies demonstrate
a lack of cytotoxic effect of PHB-HV
scaffolds. Direct contact assays also reveal their
ability to support the culture of CNS-derived cells
and mesenchymal-like stem cells from different
sources. Finally, histocompatibility studies show
that PHB-HV scaffolds are well tolerated by the
host tissue, and do not negatively impact the left
hindlimb locomotor function recovery. Therefore
results herein presented suggest that PHB-HV
scaffolds may be suitable for SCI treatment.This study was supported by the Portuguese Foundation for Science and Technology (FCT; Grant no PTDC/SAU-BMA/114059/2009; PEst-C/SAU/LA0001/2013-2014 and RNEM-REDE/1506/REM/2005) and Foundation Calouste Gulbenkian, under the scope of the Gulbenkian Program to Support Cutting Edge Research in Life Sciences (A.J.S.). This work was also partially supported by the European FP7 Project Find and Bind (NMP4-SL-2009-229292). The authors would like to thank Miguel Carvalho, Fabio Teixeira, and Filipa Campos for their collaboration in in vivo experiments
Avaliação da origem de variações fenotípicas da manga 'Keitt' cultivada em São Paulo com base em marcadores RAPD.
bitstream/CPAC-2009/26861/1/p2005_52.pd
Integrated analysis of climate, soil, topography and vegetative growth in Iberian viticultural regions
The Iberian viticultural regions are convened according to the Denomination of Origin (DO) and present different climates, soils, topography and management practices. All these elements influence the vegetative growth of different varieties throughout the peninsula, and are tied to grape quality and wine type. In the current study, an integrated analysis of climate, soil, topography and vegetative growth was performed for the Iberian DO regions, using state-of-the-art datasets. For climatic assessment, a categorized index, accounting for phenological/thermal development, water availability and grape ripening conditions was computed. Soil textural classes were established to distinguish soil types. Elevation and aspect (orientation) were also taken into account, as the leading topographic elements. A spectral vegetation index was used to assess grapevine vegetative growth and an integrated analysis of all variables was performed. The results showed that the integrated climate-soil-topography influence on vine performance is evident. Most Iberian vineyards are grown in temperate dry climates with loamy soils, presenting low vegetative growth. Vineyards in temperate humid conditions tend to show higher vegetative growth. Conversely, in cooler/warmer climates, lower vigour vineyards prevail and other factors, such as soil type and precipitation acquire more important roles in driving vigour. Vines in prevailing loamy soils are grown over a wide climatic diversity, suggesting that precipitation is the primary factor influencing vigour. The present assessment of terroir characteristics allows direct comparison among wine regions and may have great value to viticulturists, particularly under a changing climate
Aspiração de corpo estranho por menores de 15 anos: experiência de um centro de referência do Brasil
Vitamin D-related polymorphisms and vitamin D levels as risk biomarkers of COVID-19 disease severity
© The Author(s) 2021. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Vitamin D is a fundamental regulator of host defences by activating genes related to innate and adaptive immunity. Previous research shows a correlation between the levels of vitamin D in patients infected with SARS-CoV-2 and the degree of disease severity. This work investigates the impact of the genetic background related to vitamin D pathways on COVID-19 severity. For the first time, the Portuguese population was characterized regarding the prevalence of high impact variants in genes associated with the vitamin D pathways. This study enrolled 517 patients admitted to two tertiary Portuguese hospitals. The serum concentration of 25 (OH)D, was measured in the hospital at the time of patient admission. Genetic variants, 18 variants, in the genes AMDHD1, CYP2R1, CYP24A1, DHCR7, GC, SEC23A, and VDR were analysed. The results show that polymorphisms in the vitamin D binding protein encoded by the GC gene are related to the infection severity (p = 0.005). There is an association between vitamin D polygenic risk score and the serum concentration of 25 (OH)D (p = 0.04). There is an association between 25 (OH)D levels and the survival and fatal outcomes (p = 1.5e-4). The Portuguese population has a higher prevalence of the DHCR7 RS12785878 variant when compared with its prevalence in the European population (19% versus 10%). This study shows a genetic susceptibility for vitamin D deficiency that might explain higher severity degrees in COVID-19 patients. These results reinforce the relevance of personalized strategies in the context of viral diseases.This project was supported by the “Fundação para a Ciência e Tecnologia”, program “Research 4 Covid-19 Apoio especial a projetos de implementação rápida para soluções inovadoras de resposta à pandemia de COVID-19”. It was also partially supported by each institution.info:eu-repo/semantics/publishedVersio
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