158 research outputs found
Formation energy and interaction of point defects in two-dimensional colloidal crystals
The manipulation of individual colloidal particles using optical tweezers has
allowed vacancies to be created in two-dimensional (2d) colloidal crystals,
with unprecedented possibility of real-time monitoring the dynamics of such
defects (Nature {\bf 413}, 147 (2001)). In this Letter, we employ molecular
dynamics (MD) simulations to calculate the formation energy of single defects
and the binding energy between pairs of defects in a 2d colloidal crystal. In
the light of our results, experimental observations of vacancies could be
explained and then compared to simulation results for the interstitial defects.
We see a remarkable similarity between our results for a 2d colloidal crystal
and the 2d Wigner crystal (Phys. Rev. Lett. {\bf 86}, 492 (2001)). The results
show that the formation energy to create a single interstitial is
lower than that of the vacancy. Because the pair binding energies of the
defects are strongly attractive for short distances, the ground state should
correspond to bound pairs with the interstitial bound pairs being the most
probable.Comment: 5 pages, 2 figure
Biodegradable wet-spun fibers modified with antimicrobial agents for potential applications in biomedical engineering
Wet-spinning is a non-solvent induced phase inversion technique that allows the
production of continuous polymeric microfibers, with a uniform morphology, based on the
principle of precipitation. It allows the production of 3D fibrous constructs with an intricated
architecture that facilitates cell infiltration, something that is very limited in electrospun
nanofibrous mats, thus increasing its interest in biomedicine. Wet-spun scaffolds are also more
easily processed and can be loaded with a variety of biomolecules of interest. Antimicrobial
agents that display a broad spectrum of activity against bacteria, fungi and viruses have been
combined with such constructs demonstrating great potential to fight infections. In the present
work, we explore the use of wet-spinning to process both natural and synthetic biodegradable
polymers in the form of microfibers, and the necessary processes to modify their surface to
increase their antimicrobial profile. The synergistic potential of specialized biomolecules within
wet-spun fibrous architectures are also highlighted.Authors acknowledge the Foundation for Science and Technology (FCT) of Portugal for funding the
projects PTDC/CTM-TEX/28074/2017 (POCI-01-0145-FEDER-028074) and UID/CTM/00264/2020
from 2C2T
Combinatory action of chitosan-based blended films and loaded cajeput oil against Staphylococcus aureus and Pseudomonas aeruginosa-mediated infections
Chronic wounds (CW) have numerous entry ways for pathogen invasion and prosperity,
damaging host tissue and hindering tissue remodeling. Essential oils exert quick and efficient antimicrobial
(AM) action, unlikely to induce bacterial resistance. Cajeput oil (CJO) has strong AM
properties, namely against Staphylococcus aureus and Pseudomonas aeruginosa. Chitosan (CS) is a natural
and biodegradable cationic polysaccharide, also widely known for its AM features. CS and
poly(vinyl alcohol) (PVA) films were prepared (ratio 30/70; 9 wt%) by solvent casting and phase
inversion method. Films’ thermal stability and chemical composition data reinforce polymer blending.
Films were supplemented with 1 and 10 wt% of CJO in relation to total polymeric mass. Loaded
films were 23 and 57% thicker, respectively, than the unloaded films. Degree of swelling and porosity
also increased, particularly with 10 wt% CJO. AM testing revealed that CS films alone were effective
against both bacteria, eradicating all P. aeruginosa within the hour (*** p < 0.001). Still, loaded
CS/PVA films showed improved AM traits, being significantly more efficient than unloaded films
right after 2 h of contact. This study is the first proof of concept that CJO can be dispersed into
CS/PVA films and show bactericidal effects, particularly against P. aeruginosa, this way opening new
avenues for CW therapeutics.Authors acknowledge the Portuguese Foundation for Science and Technology
(FCT), FEDER funds by means of Portugal 2020 Competitive Factors Operational Program (POCI)
and the Portuguese Government (OE) for funding the project PEPTEX with reference PTDC/CTMTEX/28074/2017 (POCI-01-0145-FEDER-028074). Authors also acknowledge project
UID/CTM/00264/2020 of Centre for Textile Science and Technology (2C2T), funded by national
funds through FCT/MCTES
Sodium alginate/polycaprolactone co-axial wet-spun microfibers modified with N-carboxymethyl chitosan and the peptide AAPV for Staphylococcus aureus and human neutrophil elastase inhibition in potential chronic wound scenarios
In chronic wound (CW) scenarios, Staphylococcus aureus-induced infections are very prevalent. This leads to abnormal inflammatory processes, in which proteolytic enzymes, such as human neutrophil elastase (HNE), become highly expressed. Alanine-Alanine-Proline-Valine (AAPV) is an antimicrobial tetrapeptide capable of suppressing the HNE activity, restoring its expression to standard rates. Here, we proposed the incorporation of the peptide AAPV within an innovative co-axial drug delivery system, in which the peptide liberation was controlled by N-carboxymethyl chitosan (NCMC) solubilization, a pH-sensitive antimicrobial polymer effective against Staphylococcus aureus. The microfibers' core was composed of polycaprolactone (PCL), a mechanically resilient polymer, and AAPV, while the shell was made of the highly hydrated and absorbent sodium alginate (SA) and NCMC, responsive to neutral-basic pH (characteristic of CW). NCMC was loaded at twice its minimum bactericidal concentration (6.144Â mg/mL) against S. aureus, while AAPV was loaded at its maximum inhibitory concentration against HNE (50Â ÎĽg/mL), and the production of fibers with a core-shell structure, in which all components could be detected (directly or indirectly), was confirmed. Core-shell fibers were characterized as flexible and mechanically resilient, and structurally stable after 28-days of immersion in physiological-like environments. Time-kill kinetics evaluations revealed the effective action of NCMC against S. aureus, while elastase inhibitory activity examinations proved the ability of AAPV to reduce HNE levels. Cell biology testing confirmed the safety of the engineered fiber system for human tissue contact, with fibroblast-like cells and human keratinocytes maintaining their morphology while in contact with the produced fibers. Data confirmed the engineered drug delivery platform as potentially effective for applications in CW care.Authors acknowledge the Portuguese Foundation for Science and Technology (FCT), FEDER funds by means of Portugal 2020 Competitive Factors Operational Program (POCI) and the Portuguese Government
(OE) for funding the project PEPTEX with reference PTDC/CTMTEX/28074/2017 (POCI-01-0145-FEDER-028074). Authors also acknowledge project UIDP/00264/2020 of 2C2T and UID/QUI/00686/2020 of CQ, funded by national funds through FCT/MCTES. C.S.M. and H.P.F. also acknowledge FCT for PhD funding via scholarship 2020.08547.BD and for auxiliary researcher contract via 2021.02720.CEEIND, respectively
Tomato seedling production in substrate containing coconut fiber and mushroom culture waste AB S TR ACT
Tomato seedling production in substrate containing coconut fiber and mushroom culture waste Revista Brasileira de CiĂŞncias Agrárias, vol. 3, nĂşm. 3, julio-septiembre, 2008, pp. 237-241 Universidade Federal Rural de Pernambuco Pernambuco, Brasil Tomato seedling production in substrate containing coconut fiber and mushroom culture waste AB S TR ACT The objective of this research was to evaluate the ratio of coconut fiber and mushroom culture waste in the tomato seedling production. A greenhouse experiment was carried out in the randomized block experimental design, with seven treatments and four replications: T1 -Commercial Substrate Hortimix®; T2 -0% coconut fiber dry matter (CF) + 100% dry matter of mushroom culture waste (MW); T3 -20% (CF) + 80% (MW); T4 -40% (CF) + 60% (MW); T5 -60% (CF) + 40% (MW); T6 -80% (CF) + 20% (MW); T7 -100% (CF) + 0% (MW). Stem diameter, seedling height, emergence speed, germination percentage, shoot and root fresh matter and shoot and root dry matter were evaluated. It was evidenced, for all the studied characteristics, with exception of the speed of germination-aid seedling emergence and of the germination percentage, significant differences between substrate containing coconut fiber and mushroom culture residue and the commercial substratum, the best results presented by the last one. The increase in the proportion of mushroom residue in relation to the coconut fiber provided tomato seedling with better characteristics than the others. Key words: organic substrate, recycling, organic manure, germination Produção de mudas de tomate em substrato contendo fibra de coco e resĂduo de cultivo de cogumelo RES UMO Visou-se, com o presente trabalho, avaliar proporções de fibra de coco e de resĂduo proveniente do cultivo de cogumelo como substratos para a produção de mudas de tomate. O experimento foi conduzido em casa de vegetação, tendo-se utilizado o delineamento em blocos inteiramente casualizados, com sete tratamentos e quatro repetições: T 1 -Substrato comercial Hortimix ® ; T 2 -0% matĂ©ria seca de fibra de coco (FC) + 100% matĂ©ria seca de resĂduo proveniente do cultivo de cogumelo (RC); T 3 -20% FC + 80% RC; T 4 -40% FC + 60% RC; T 5 -60% + 40% RC; T 6 -80% FC + 20% RC; T 7 -100% FC + 0% RC. Avaliaram-se o diâmetro do caule, a altura da planta, o Ăndice de velocidade de emergĂŞncia, a percentagem de germinação, a matĂ©ria fresca da parte aĂ©rea e da raiz, e a matĂ©ria seca da parte aĂ©rea e da raiz. Constataram-se, para todas as caracterĂsticas estudadas, com exceção do Ăndice de velocidade emergĂŞncia e da percentagem de germinação, diferenças significativas entre os substratos contendo fibra de coco e resĂduo do cultivo de cogumelo e o substrato comercial, em que este Ăşltimo apresentou os melhores resultados. O aumento da proporção de resĂduo de cogumelo em relação Ă fibra de coco proporcionou a produção de mudas com melhores caracterĂsticas que as demais
Bioeconomic efficiency of lamb finishing production systems.
Abstract: This study aimed to evaluate the production performance, quantitative carcass characteristics, and economic viability of lambs of genetic group Pantaneiro finished under four production systems: 1) Stockpiled Brachiaria brizantha cv piatĂŁ pasture; 2) Consortium of sorghum intercropped with Brachiaria brizantha cv piatĂŁ; 3) Feedlot based on sorghum silage and 2% body weight energyprotein supplementation, 4) Feedlot based on sorghum silage and 4% body weight energy-protein supplementation. Were used one hundred Pantaneiro lambs with an average body weight of 17.85 ± 2.50 kg and at 70 ± 15 days of age, approximately. The average final body weight and total body weight gain of the animals finished on the consortium of sorghum intercropped with Brachiaria brizantha cv piatĂŁ were higher than those obtained with feedlot based on sorghum silage and 2% body weight energy-protein supplementation. However, when this system were compared with sorghum silage and 4% body weight energy-protein supplementation, these characteristics did not differ (P > 0.05). Hot and cold carcass weights were lower when animals were fed sorghum silage and 2% body weight energyprotein supplementation as compared with the animals finished on the other systems. The greatest hot (48.20%) and cold (45.83%) carcass yields were observed in animals finished on sorghum silage and 4% body weight energy-protein supplementation. For the carcass compactness index, animals that received sorghum silage and 4% body weight energy-protein supplementation obtained higher values than those observed for 2% of supplementation. The economic evaluation showed a great return for the finishing systems, except for sorghum silage and 4% body weight energy-protein supplementation, and concluded that finishing lambs in a crop-livestock integration system presented a higher benefit/cost ratio (1.61). Therefore, based on the conditions under which this study was conducted, the croplivestock integration is the most viable system for finishing lambs. [EficiĂŞncia bioeconĂ´mica de sistemas de terminação de cordeiros]. Resumo: Avaliou-se o desempenho produtivo, caracterĂsticas quantitativas das carcaças e viabilidade econĂ´mica de cordeiros do grupamento genĂ©tico Pantaneiro, terminados em quatro sistemas de produção: 1) Pastagem vedada de Brachiaria brizantha cv piatĂŁ; 2) Pastagem de Brachiaria brizantha cv piatĂŁ em plantio consorciado com sorgo; 3) Confinamento a base de silagem de sorgo e suplementação energĂ©ticoproteica fornecida na proporção de 2% do peso corporal; 4) Confinamento a base de silagem de sorgo e suplementação energĂ©tico-proteica fornecida na proporção de 4% do peso corporal. Foram utilizados cem cordeiros Pantaneiros com peso mĂ©dio de 17,85 ± 2,50 kg e 70 ± 15 dias de idade, aproximadamente. O peso corporal mĂ©dio final e o ganho de peso corporal total dos animais terminados em consĂłrcio de sorgo com Brachiaria brizantha cv piatĂŁ foram superiores aos obtidos com o confinamento a base de silagem de sorgo e suplementação energĂ©tico-proteica na razĂŁo de 2% do peso corporal. No entanto, quando comparados com o confinamento a base de silagem de sorgo e suplementação energĂ©tico-proteica na razĂŁo de 4% do peso corporal, essas caracterĂsticas nĂŁo diferiram (P > 0,05). Os pesos de carcaça quente e fria foram inferiores para os animais alimentados com silagem de sorgo e suplementação energĂ©tica-proteica na razĂŁo de 2% do peso corporal em comparação com os animais terminados nos outros sistemas. Os maiores rendimentos de carcaça quente (48,20%) e fria (45,83%) foram observados nos animais terminados com silagem de sorgo e suplementação energĂ©tico-proteica na razĂŁo de 4% do peso corporal. Para o Ăndice de compacidade da carcaça, os animais que receberam silagem de sorgo e 4% de suplementação energĂ©tico-proteica com relação ao peso corporal obtiveram valores maiores do que os observados com 2% de suplementação. A avaliação econĂ´mica mostrou que houve um Ăłtimo retorno econĂ´mico para os sistemas de terminação, exceto para o sistema de terminação com pasto vedado, e concluiu que a terminação de cordeiros em integração lavoura pecuária relação de benefĂcio/custo superior (1,61). Portanto, baseado nas condições em que foi conduzido o estudo, a integração lavoura pecuária apresenta-se como o sistema mais viável para terminação de cordeiros
Reducing the effects of Low Albedo of asphalt materials incorporating Polyethylene Glycol (PEG) 1000, 2000 and 4000 as Phase Change Materials (PCM)
Albedo plays a vital role in urban microclimates. Civil engineering structures usually absorb a high amount of energy in form of heat, for example asphalt pavements, which have a low albedo, thus contributing to the Urban Heat Island (UHI) effects. Modifying the physical characteristics of asphalt pavements, including reflectance and thermal properties, can help mitigate UHI. The literature points out that one alternative to thermoregulating asphalt materials is the incorporation of phase change materials. Thus, the main goal of this research is to present a systematic review regarding the effectiveness of the incorporation of polyethylene glycol (PEG) 1000, 2000 and 4000 as Phase Change Material (PCM) in asphalt materials. The results showed that incorporating PEG into asphalt materials can regulate heat storage, promoting stability and reducing UHI effects. PEG2000 was more frequently used. PEGs can reduce between of 3.5 and 4.2ÂşC of the asphalt materials when compared to the conventional ones.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of
the Strategic Funding UIDB/04650/2020 and the projectsMicroCoolPav project EXPL/EQU-EQU/1110/2021, and
NanoAir project PTDC/FISMAC/6606/2020
Coaxial fibres incorporated with phase change materials for thermoregulation applications
Nowadays, the growing concern about improving thermal comfort in different structures (textiles, buildings, and pavements, among others) has stimulated research into phase change materials (PCMs). The direct incorporation of PCMs into composite materials can cause mechanical impacts. Therefore, this study focuses on the design of phase change coaxial fibres (PCFs), using commercial cellulose acetate (CA) or recycled CA obtained from cotton fabrics (CAt) as the sheath and polyethylene glycol (PEG) 2000 as the core, via the wet spinning method; the fibres vary in molecular weight, concentration and ejection velocity. The fibres were assessed for their optical, chemical, thermal, and mechanical properties. The presence of PEG2000 is confirmed in the core of the fibres. Thermal analyses revealed a mass loss at high temperatures, attributable to the presence of PEG2000. Notably, the fibres with CA (Mn 30,000) showed superior thermal and mechanical performance. The melting point of PEG2000 incorporated into these PCFs coincided with the melting point of pure PEG2000 (about 55 °C), with a slight deviation, indicating that PCFs were obtained. Finally, the results point to the application of the fibres in civil engineering materials requiring a phase change between 50 and 60 °C, providing promising prospects for their use in applications requiring thermoregulatory properties.This research was funded by the Portuguese Foundation for Science and Technology (FCT) under the projects MicroCoolPav EXPL/EQUEQU/1110/2021 and NanoAir PTDC/FISMAC/6606/2020 (https://doi.org/10.54499/PTDC/FIS-MAC/6606/2020) and within the framework of Strategic Funding UIDB/04650/2020, UIDB/04029/2020 (https://doi.org/10.54499/UIDB/04029/2020) and UID/QUI/0686/2020. I.R.S. and H.P.F. would like to thank FCT for their funding contracts 2022.00763.CEECIND (https://doi.org/10.54499/2022.00763.CEECIND/CP1718/CT0006) and 2021.02720.CEECIND (https://doi.org/10.54499/DL57/2016/CP1377/CT0098)
Advancements in phase change materials in asphalt pavements for mitigation of urban heat island effect: bibliometric analysis and systematic review
This research presents a dual-pronged bibliometric and systematic review of the
integration of phase change materials (PCMs) in asphalt pavements to counteract the urban heat
island (UHI) effect. The bibliometric approach discerns the evolution of PCM-inclusion asphalt
research, highlighting a marked rise in the number of publications between 2019 and 2022. Notably,
Chang’an University in China has emerged as a leading contributor. The systematic review
addresses key questions like optimal PCM types for UHI effect mitigation, strategies for PCM
leakage prevention in asphalt, and effects on mechanical properties. The findings identify
polyethylene glycols (PEGs), especially PEG2000 and PEG4000, as prevailing PCMs due to their
wide phase-change temperature range and significant enthalpy during phase transitions. While
including PCMs can modify asphalt’s mechanical attributes, such mixtures typically stay within
performance norms. This review emphasises the potential of PCMs in urban heat management and
the need for further research to achieve optimal thermal and mechanical balanceThis research was partially funded by the Portuguese Foundation for Science and
Technology (FCT) under the framework of the projects MicroCoolPav EXPL/EQU-EQU/1110/2021,
NanoAir PTDC/FIS-MAC/6606/2020, UIDB/04650/2020, and UIDB/04029/2020. This research was
also supported by the doctoral Grant PRT/BD/154269/2022 financed by the FCT, and with funds
from POR Norte-Portugal 2020 and State Budget, under MIT Portugal Program. I.R.S. would like to
acknowledge the FCT for funding (2022.00763.CEECIND). V.C.B. acknowledges the Fundação
Cearense de Apoio ao Desenvolvimento CientĂfico e TecnolĂłgico (Funcap), MLC-0191-
00144.01.00/22 (Edital Mulheres na CiĂŞncia), and the National Council for Scientific and
Technological Development (CNPq), Process 404978/2021-5—Call CNPq/MCTI/FNDCT N°
18/2021—Faixa B—Consolidated Groups
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