Optimization of zirconia surface textured designs using Nd:Yag laser for biomedical applications

The development of surface textured designs has influence in primary stability of surgically placed implants since a textured surface allows to firmer mechanical link to the surrounding tissue. Laser technology has been investigated to develop new surface designs on green zirconia compacts by cold pressing. Nd:Yag laser were used to produce several strategies and different laser parameters (laser power, speed and laser passages) were tested to evaluate their impact on cavities geometry and depth. The surface texture designs were analysed by Scanning Electron Microscopy (SEM) and regular geometries such as cavities or pillars were observed. The distance between lines have a strong impact on texturing quality and should be combined with optimum power and speed conditions. Regarding the optimized conditions, several surface textured patterns were created in both green and sintered zirconia compacts. This study allowed to conclude that only some texturing strategies are suitable to obtain high quality surface textured patterns. Otherwise, the remaining strategies are potential solutions for obtaining high quality machined structures (laser does not machine cavities but crosses the entire bulk). High strength zirconia scaffolds were machined by laser and CNC machining technologies and the two promising technologies were compared.This work is supported by FCT (Fundação para a Ciência e a Tecnologia) through the grant SFRH/BD/148031/2019, the project UIDB/04436/2020 and UIDP/04436/2020

Quasi-static compressive properties of aluminium foams with functionally graded properties

This paper presents experimental results of compressive behavior of aluminium alloy metal foams with controlled pore morphology. Different types of metal foams were analyzed, having uniform cell structure with different pore size and gradient variation of cellular structure along length. The test samples were manufactured by lost-wax casting using 3D printed components for internal structure definition. Results for stiffness and energy absorption were obtained and compared on weight efficiency basis. The results are analyzed regarding the efficiency of the different cell structures and its suitability for energy absorbing application in components subjected to impact or compression loading.(undefined

Correlated color temperature preferred by observers for illumination of artistic paintings

The visual effects of lighting on art paintings is an important aspect that should be considered by museum curators. The aim of this work was to determine the correlated color temperature (CCT) of daylight illumination preferred by observers when appreciating art paintings. Hyperspectral images of 11 oil paintings were collected at the museum, and the appearance of the paintings under daylight illuminants with CCT from 25,000 K to 3600 K was computed. In a psychophysical experiment using precise CRT reproductions of the paintings, observers had to adjust the CCT of the illuminant such that it produced the best visual impression. It was found that the distribution of observers' preferences had a maximum at a CCT of about 5100 K and that this value did not depend on whether the observers were undergraduate students or museum visitors or on the degree of adaptation to the color of the illumination. These results suggest that observers prefer a more bluishwhite light than that normally used in museums. © 2008 Optical Society of America.Centro de Física of Minho University in Braga, Portugal, by the Fundação para a Ciência e a Tecnologia (grant POCI/EAT/55416/ 2004) and by MultiOpticas Unipessoal, Lda. We are grate- ful to the Museu Nogueira da Silva in Braga, Portugal, for access to the paintings and facilities, to Maria Carolina V. P. Leite, Maria H. Regalo, and Carlos A. L. C. Corais for adviceinfo:eu-repo/semantics/publishedVersio

Chromatic diversity index : an approach based on natural scenes

Common descriptors of light quality fail to predict the chromatic diversity produced by the same illuminant in different contexts such as images of natural scenes. The aim of this paper was to introduce a new index, capable of predicting illuminant-induced variations in the chromatic diversity off natural scenes. The spectral reflectance of each pixel of 50 images of natural scenes obtained using a hyperspectral imaging and the spectral reflectance of 1264 Munsell surfaces were converted into the CIELAB color space for each of the 55 illuminants and 5 light sources. The CIELAB volume was estimated by the convex hull method. The number of discernible colors was estimated by segmenting the CIELAB color volume into unitary cubes and by counting the number of non-empty cubes. High correlation was found between the CIELAB volume occupied by the Munsell surfaces, the number of discernible colors and C1LEAB color volume of the colors of natural scenes. These results seem to indicate that a new illuminant chromatic diversity index based on natural scenes could be defined using the CIELAB volume of the Munsell surfaces.(undefined)info:eu-repo/semantics/publishedVersio

Compressive properties and energy absorption of metal-polymer hybrid cellular structures,

This study presents experimental results on the mechanical behavior of aluminum alloy cellular structures filled with Polypropylene or ABS. Two types of base cell geometries were analyzed, having uniform cell structure and with a dual-size cell arrangement seeking optimized mechanical properties. The structures were manufactured by lost-wax casting using 3D printed components for internal structure definition. The polymer fill was introduced through a process of temperature assisted impregnation in a specially developed tool. Results for stiffness and energy absorption were obtained and compared on weight efficiency basis. The results are indicative of higher efficiency of the dual-size structures having PP/ABS filling that may be considered for energy absorption parts in compressive loading.This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDP/04077/2020

Colour rendering of indoor lighting with CIE illuminants and white LEDs for normal and colour deficient observers

DraftThe goal of this work was to evaluate the colour rendering of indoor lighting with CIE illuminants and white LEDs by estimating the chromatic diversity produced for normal and colour deficient observers. Reflectance spectra of a collection of scenes made of objects typically found indoors were obtained with hyperspectral imaging. Chromatic diversity was computed for 55 CIE illuminants and five LED light sources by estimating the number of different colours perceived in the scenes analysed. A considerable variation in chromatic diversity was found across illuminants, with the best producing about 50% more colours than the worst. For normal observers, the best illuminant was CIE FL3.8 which produced about 8% more colours than CIE illuminant A and D 65 ; for colour deficient observers, the best illuminants varied with the type of deficiency. When the number of colours produced with a specific illuminant was compared against its colour rendering index (CRI) and gamut area index (GAI), weak correlations were obtained. Together, these results suggest that normal and colour deficient observers may benefit from a careful choice of the illuminant, and this choice may not necessarily be based only on the CRI or GAI. © 2010 The Authors, Ophthalmic and Physiological Optics © 2010 The College of Optometrists.Centro de Física of Minho University, Braga, Portugal, and by the Fundação para a Ciência e a Tecnologia (grant POSC/EEA-SRI/57554/2004). João M.M. Linhares was supported by grant SFRH/BD/35874/2007, Paulo E.R. Felgueiras by grant SFRH/BD/44698/2008 and Paulo D. Pinto by grant SFRH/BD/49112/2008info:eu-repo/semantics/publishedVersio

Review on current limits and potentialities of technologies for biomedical ceramic scaffolds production

First published: 14 September 2020Osseointegration is defined by a stable and functional union between bone and a surface of a material. This phenomenon is influenced by the geometric and surface characteristics of the part where the bone cells will attach. A wide variety of studies proves that ceramic materials are strong competitors against conventional metals in the scope of bone tissue engineering. Ceramic scaffolds, porous structures that allow bone ingrowth, have been studied to enhance the osseointegration phenomenon. Geometric and dimensional parameters of the scaffold have influence in its performance as mechanical and structural supporter of bone growth. However, these parameters are conditioned by the manufacturing process by which these scaffolds are obtained. Several studies focusing on the production process of ceramic scaffolds have been developed, using 3D printing, stereolithography, selective laser sintering, green machining, robocasting, and others. The main purpose of this work is to evaluate and compare the different manufacturing processes by which ceramic scaffolds can be produced. This comparison addresses scaffold parameters like pore size, pore shape, porosity percentage, roughness, and so forth. Additionally, the different materials used in different manufacturing processes are also mentioned and discussed given its influence on a successful osseointegration while simultaneously displaying adequate mechanical properties. After making a screening on the available ceramic scaffolds manufacturing processes, several examples are presented, proving the potential of each of these manufacturing process for a given scaffold geometry.Fundação para a Ciência e a Tecnologia, Grant/ Award Number: UIDB/04436/2020; UIDP/04436/2020; SFRH/BPD/112111/2015; PTDC/EMS-TEC/5422/2014; NORTE-01- 0145-FEDER-000018-HAMaBICo; POCI-01- 0145-FEDER-03049

Hardware-software extensions to a softcore processor for FPGA-based adaptive PID control

Embedded Systems were traditionally implemented as a microprocessor surrounded by on-board peripherals, specifically assembled for a given application. Several Commercial Off-The Shelf solutions already provide a variety of on-chip custom modules, which allow a higher performance, smaller power consumption solution for a variety of applications. The advent of Field Programmable Gate Arrays (FPGA) allowed custom chips to be designed on a per-application basis, with fine-grain control over hardware/software partitioning. This paper presents a case study about the integration of an adaptive control system on a softcore processor. An MRAC-PID custom hardware module was developed and implemented on FPGA, taking advantage of the extensibility capabilities of the utilized softcore. Results demonstrate how software to hardware migration can accelerate system performance and maximize application parallelism.Fundação para a Ciência e a Tecnologia (FCT

Brazilian Flora 2020: Leveraging the power of a collaborative scientific network

International audienceThe shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora

Delayed colorectal cancer care during covid-19 pandemic (decor-19). Global perspective from an international survey

Background The widespread nature of coronavirus disease 2019 (COVID-19) has been unprecedented. We sought to analyze its global impact with a survey on colorectal cancer (CRC) care during the pandemic. Methods The impact of COVID-19 on preoperative assessment, elective surgery, and postoperative management of CRC patients was explored by a 35-item survey, which was distributed worldwide to members of surgical societies with an interest in CRC care. Respondents were divided into two comparator groups: 1) ‘delay’ group: CRC care affected by the pandemic; 2) ‘no delay’ group: unaltered CRC practice. Results A total of 1,051 respondents from 84 countries completed the survey. No substantial differences in demographics were found between the ‘delay’ (745, 70.9%) and ‘no delay’ (306, 29.1%) groups. Suspension of multidisciplinary team meetings, staff members quarantined or relocated to COVID-19 units, units fully dedicated to COVID-19 care, personal protective equipment not readily available were factors significantly associated to delays in endoscopy, radiology, surgery, histopathology and prolonged chemoradiation therapy-to-surgery intervals. In the ‘delay’ group, 48.9% of respondents reported a change in the initial surgical plan and 26.3% reported a shift from elective to urgent operations. Recovery of CRC care was associated with the status of the outbreak. Practicing in COVID-free units, no change in operative slots and staff members not relocated to COVID-19 units were statistically associated with unaltered CRC care in the ‘no delay’ group, while the geographical distribution was not. Conclusions Global changes in diagnostic and therapeutic CRC practices were evident. Changes were associated with differences in health-care delivery systems, hospital’s preparedness, resources availability, and local COVID-19 prevalence rather than geographical factors. Strategic planning is required to optimize CRC care