1,721,089 research outputs found
Enhancing the thermal conductivity and shape stability of phase-change composites using diatomite and graphene nanoplates for thermal energy storage
No full textThe effects of mixing diatomite and graphene nanoplatelets (GNP) with xylitol were examined in this study. Form stability and thermal conductivity were also evaluated. According to the experimental results, the PCM composites exhibited a thermal conductivity of 0.403 W/mK. Melting and solidification points were determined by differential scanning calorimetry (DSC) to be 89.0 °C and 36.5 °C, respectively. To maximize the thermal characteristics of the PCM, the response surface methodology (RSM) was utilized to create prediction models for thermal conductivity based on the mass fractions of diatomite and GNP. These findings highlight the importance of understanding how the introduction of nanoparticles affects thermal properties. The prospective use of PCM in thermal energy storage is enhanced by its higher solidification enthalpy, noteworthy thermal stability, and insights into the impacts of diatomite and GNP
Potential use of kraft and organosolv lignins as a natural additive for healthcare products
Full text linkWOS: 000440243600050The growing interest in substituting synthetic products coming from non-renewable sources with products from biomass has focused attention on the lignin biopolymer. Its high availability, low price and properties make the development of new and valuable uses for lignin interesting, thus improving the economic and environmental aspects of the biomass conversion. To achieve this objective, the potential use of industrial kraft and organosolv lignins as antioxidants, antimicrobials and sunscreen products has been evaluated. The results of a detailed antibacterial and antifungal study demonstrated the high potential of kraft lignins against a variety of foodborne and human pathogenic microorganisms. Moreover, both organosolv and kraft lignins presented an effective protection factor (SPF values from 10-20), demonstrating their effectiveness as natural additives for the sun lotion market. In addition, lignin samples presented high antioxidant capacity compared to butylated hydroxytoluene (BHT), one common commercial antioxidant industrially used. Therefore, the development of innovative applications of lignins as a commodity for the chemical, pharmaceutical or cosmetic industries could expand their possible uses in the market giving new added values to lignin.University of the Basque Country [PIF 13/050]; Basque Government [IT1008-16]The authors are grateful for the financial support received from the University of the Basque Country (doctoral grant of Ms Gordobil Grant No. PIF 13/050) and to the Basque Government (scholarship of young researchers training and project IT1008-16)
Antifungal cellulose by capsaicin surface grafting
No full textCellulose is one of the most abundant materials in nature. Besides its biological function, cellulose can be extracted from the cell wall and used in several industrial applications. Thus, it can be used in papers, pharmaceuticals, food, cosmetics and innovative materials such as nanocomposites, packaging, coatings and dispersion technology. With the aim of extending cellulose applications and producing so-called “smart” materials, new functionality can be introduced by physical or chemical modifications. Taking into account that capsaicin, the active component of chili peppers, is an excellent antifungal agent, a potential new material could be obtained by chemical reaction between this active compound and cellulose. In this work, capsaicin grafting onto cellulose using polycarboxylic acid as linking agent is proposed. The reaction occurrence was corroborated by Fourier transform infrared spectroscopy and UV–Vis spectrophotometry in reflectance mode. Modified cellulose with <2 wt% of capsaicin shows a strong change in antifungal activity with respect to the unmodified one. This activity was evaluated by the fungal growth inhibition test with two different fungi, Trametes versicolor and Gloeophyllum trabeum. Modified cellulose samples showed a high percentage of fungal growth inhibition, demonstrating the success of the cellulose modification and high antifungal power of the grafting molecule.Fil: Martini, Raquel Evangelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahia Blanca. Planta Piloto de Ingeniería Química (I). Grupo Vinculado al Plapiqui - Investigación y Desarrollo en Tecnología Química; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Serrano, Luis. Universidad del País Vasco; EspañaFil: Barbosa, Silvia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Labidi, Jalel. Universidad del País Vasco; Españ
Enhancing the thermal transfer properties of phase change material for thermal energy storage by impregnating hybrid nanoparticles within copper foams
No full textA phase-change material (PCM) is recommended for thermal energy storage. However, conventional PCMs suffer from poor thermal conductivity. To solve this problem, this study presented different compositions to improve PCM thermal conductivity. The effects of the average specific surface of metal foams and the weight percentage of metal foams and hybrid nanoparticles on the phase-change materials' thermal characteristics were investigated. The findings demonstrate that thermal performance of the PCM composite is noticeably better than that of pure PCM and increasing the weight content of foam metal and hybrid nanoparticles leads to an increase in thermal conductivity of 37.7% for the same type of copper. The results also reveal that thermal conductivity performance increases as the amount of metal foam and hybrid nanoparticles increases. The average specific surface value of 1600 m2/m3 shows better thermal properties compared with other average specific surface values. Moreover, the heat capacity is affected by the increase in the content of metal foam. Many drawbacks have been found in using foam metal in PCM preparation, mainly the fixed shapes of metal foams compared with the formability nature of the PCM, which effects the shapes of the PCM composites and thus limits its use in applications with limited size. This novel approach to improving PCM's thermal behaviour may be applied to the creation of thermal energy storage devices with predetermined characteristics
Development of Bioactive Paper by Capsaicin Derivative Grafting Onto Cellulose
No full textIn this chapter the capsaicin derivative grafting onto cellulose ispresented as an alternative to obtain bioactive papers. First, grafting of nonivamide (capsaicin derivative) onto cellulose fibers using polycarboxylicacid as linking agent is discussed. The effect of different reaction variables(namely, time, temperature, and catalyst amount), on reaction occurrenceand efficacy is analyzed. From this data, the optimal reaction conditionsare selected and then grafting reaction is applied to commercial paper sheets. Final properties like antioxidant, insect repellent, and antimicrobialactivity, as well as mechanical properties of the modified paper are presentedand discussed.Fil: Muratore, Florencia. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; ArgentinaFil: Goñi, Maria Laura. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; ArgentinaFil: Serrano, Luis. Universidad de Córdoba; EspañaFil: Labidi, Jalel. Universidad del País Vasco; EspañaFil: Barbosa, Silvia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Martini, Raquel Evangelina. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; Argentin
Biological, mechanical, optical and physicochemical properties of natural chitin films obtained from the dorsal pronotum and the wing of cockroach
No full textWOS: 000396955500019PubMed: 28267493In previous studies, chitin-based films were produced from chitin nanofibers in dust form and fully characterized. However, chitin films naturally present.in many organisms have not been isolated and characterized. Herein, structurally intact chitin films were successfully extracted from the dorsal pronoturn and the wing of cockroach. Despite using the same extraction procedure, important differences were observed. Especially, hydrophobicity, transparency, antifungal and antibacterial biofilm activities of wing chitin film were recorded notably higher than those of chitin film from the dorsal pronotum. However, better mechanical properties were observed for chitin film from the dorsal pronotum. Notably, among the tested bacteria, two common pathogens could not form biofilms on the surface of the films. This study clearly demonstrated natural chitin films obtained from an insect can provide a new perspective to chitin-based applications where chitin films with high thermal stability, transparency, resistance to bacterial biofilm formation and antifungal activity are needed
Antioxidant and biocide behaviour of lignin fractions from apple tree pruning residues
No full textDifferent lignin fractions were obtained from apple tree pruning residues following different isolation processes (autohydrolysis, organosolv with ethanol and acetic acid, and soda processes) and acid hydrolysis purification to obtain the acid insoluble lignin fractions. All the obtained lignin samples were characterised for chemical composition, chemical structure (by ATR-IR, NMR and Pyr-GC/MS analyses), molecular weight distribution (by GPC), total phenolic content, antioxidant power and antimicrobial activity towards a typical food and environment contaminant (Aspergillus niger) and a food processing yeast (Saccharomyces cerevisiae). The results showed different chemical composition and structure for the lignin samples, in particular for the soda lignin characterised by a higher hemicellulose and inorganic matter content. The acid hydrolysis was effective in removing hemicellulose but partially modified the lignin structure. The total phenolic content was the lowest for the soda lignin, the highest for the autohydrolysis lignin and was generally reduced after acid hydrolysis. However, the specific antioxidant capacity (in relation to the phenolic content) was higher for the organosolv lignin samples and was not reduced by acid hydrolysis (with exception for the soda lignin). Addition of lignin samples in the culturing media of A. niger, delayed the growth and brought to colonies with different morphological aspects. On the contrary, the lignin samples showed a clear inhibitory effect on S. cerevisiae growth
La rectification-inverse : modélisation et applications aux thermotransformateurs et thermofrigopompes
No full textNot availableLe principe de la rectification-inverse repose sur la possibilité de récupération du travail de séparation, fourni précédemment dans une séparation effectuée par rectification directe (=distillation fractionnée). Il s'agit en somme d'une opération de mélangeage de deux corps pouvant se prêter à de telles opérations. L'association d'une colonne de rectification directe et d'une colonne de rectification-inverse constitue une pompe à chaleur d'un nouveau type, qui présente de nombreux avantages: la possibilité d'utiliser n'importe quel couple, même les mélanges idéaux, ce qui constitue une révolution dans le domaine des pompes à chaleur à absorption ou les mélanges utilisés jusqu'à présent étaient limites à quelques uns et présentaient souvent des inconvénients dus à leurs propriétés physico-chimiques; l'utilisation d'un appareillage classique conçue pour les opérations unitaires du génie chimique; les pompes à chaleur fonctionnant selon le principe de la rectification-inverse, sont caractérisées par un fonctionnement proche de la réversibilité, ce qui améliore leurs performances. Dans cette étude, nous développons, dans le premier chapitre, les bases thermodynamiques du principe de la rectification-inverse et les différents modes de couplage d'une colonne de rectification-inverse et d'une colonne de rectification directe. Le second chapitre est consacré à la simulation du fonctionnement de différentes structures de mélangeur, tandis que le chapitre suivant est une validation expérimentale des résultats de la simulatio
Drug release system based on nanocrystalline cellulose membranes.
No full textCellulose is an abundant natural polymer and materials from renewable sources has motivated a number of studies because it is eco-friendly. On the other hand, the drug release technology represents one of the boundaries of science, involving different multidisciplinary aspects and contributing to the advancement of human health. This work aimed the development of a drug release system based on nanocrystalline cellulose (CNC), derived from a renewable resource. For this, the nanocelulose was obtained from flax and characterized by different techniques, such as: X-Ray Diffraction, Atomic Force Microscopy, Zeta Potential, Fourier Transform Infrared Spectroscopy (FT-IR), Magnetic Resonance Nuclear, among others. Subsequently, through the insertion of drug chlorhexidine into the suspension of cellulose nanocrystals a membrane was formed. The obtained membranes were characterized by Infrared Spectroscopy with Fourier Transform (FT-IR), Nuclear Magnetic Resonance, Scanning Electron Microscopy and Atomic Force Microscopy. The evaluation of the rate of drug release was performed using the Ultraviolet–visible spectroscopy technique. Antibacterial activity (S. aureus) and cytotoxicity (L929 fibroblasts) were evaluated and the results demonstrated that cellulose nanocrystals membranes are efficient drug delivery systems.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESA celulose é um dos polímeros naturais mais abundantes na Terra e a utilização de materiais oriundos de fontes renováveis vem despertando o interesse de inúmeras pesquisas pelo seu apelo ecológico. Por outro lado, a tecnologia de liberação de fármacos representa uma das fronteiras da ciência, envolvendo diferentes aspectos multidisciplinares e contribuindo para o avanço da saúde humana. Desta maneira, este trabalho visou o desenvolvimento de um sistema de liberação de fármaco a base de celulose nanocristalina (CNC) oriunda de recurso renovável. Para isto, a nanocelulose foi obtida a partir do linho e caracterizada por diferentes técnicas, tais como: Difração de Raios-x, Microscopia de Força Atômica, Potencial Zeta, Espectroscopia no Infravermelho com Transformada de Fourier (FT-IR), Ressonância Magnética Nuclear, entre outras. Posteriormente, por meio da inserção do fármaco clorexidina na suspensão de nanocristais de celulose formou-se uma membrana. As membranas obtidas foram caracterizadas por Espectroscopia no Infravermelho com Transformada de Fourier (FT-IR), Ressonância Magnética Nuclear, Microscopia Eletrônica de Varredura e Microscopia de Força Atômica. A avaliação da taxa de liberação do fármaco foi realizada por meio da técnica Espectroscopia de luz ultravioleta-visível (UV-vis). A atividade antibacteriana (S. aureus) e a citotoxicidade (fibroblastos L929) foram avaliadas e os resultados demonstraram que as membranas de nanocristais de celulose são eficientes sistemas de liberação de fármaco
La rectification-inverse : modélisation et applications aux thermotransformateurs et thermofrigopompes
No full textNot availableLe principe de la rectification-inverse repose sur la possibilité de récupération du travail de séparation, fourni précédemment dans une séparation effectuée par rectification directe (=distillation fractionnée). Il s'agit en somme d'une opération de mélangeage de deux corps pouvant se prêter à de telles opérations. L'association d'une colonne de rectification directe et d'une colonne de rectification-inverse constitue une pompe à chaleur d'un nouveau type, qui présente de nombreux avantages: la possibilité d'utiliser n'importe quel couple, même les mélanges idéaux, ce qui constitue une révolution dans le domaine des pompes à chaleur à absorption ou les mélanges utilisés jusqu'à présent étaient limites à quelques uns et présentaient souvent des inconvénients dus à leurs propriétés physico-chimiques; l'utilisation d'un appareillage classique conçue pour les opérations unitaires du génie chimique; les pompes à chaleur fonctionnant selon le principe de la rectification-inverse, sont caractérisées par un fonctionnement proche de la réversibilité, ce qui améliore leurs performances. Dans cette étude, nous développons, dans le premier chapitre, les bases thermodynamiques du principe de la rectification-inverse et les différents modes de couplage d'une colonne de rectification-inverse et d'une colonne de rectification directe. Le second chapitre est consacré à la simulation du fonctionnement de différentes structures de mélangeur, tandis que le chapitre suivant est une validation expérimentale des résultats de la simulatio
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