1,720,959 research outputs found
Encapsulation of hexanal in Calcium based squaric acid metal organic frameworks UTSA-280
No full textVerschillende poreuze stoffen zijn de afgelopen jaren onderzocht voor diverse toepassingen. Metal organic frameworks (MOF's) zijn een uitgebreide familie van poreuze materialen, die worden gevormd door metaalionen te combineren met organische linkers om complexe driedimensionale structuren te vormen. De poriën kunnen specifiek worden ontworpen om actieve moleculen in op te slaan, die nadien op gecontroleerde wijze worden vrijgezet om zo bv. de houdbaarheid van voedsel te verlengen. Deze studie beoogt het synthetiseren van een calcium kwadraatzuur MOF, ook bekend als UTSA-280, door middel van een mechanisch-chemisch syntheseproces. Hierbij wordt ook de haalbaarheid van calcium als vervanger van traditionele transitiemetalen in MOF’s onderzocht. Hexanal, een vluchtige antimicrobiële verbinding, wordt geïntegreerd in UTSA-280-kristallen via een dampdiffusieproces. Voor en na de hexanal encapsulatie, worden de gesynthetiseerde UTSA-280-kristallen gekarakteriseerd met behulp van X-stralen diffractie (XRD), Fourier transform infrarood spectroscopie (FTIR), thermogravimetrische analyse (TGA), differentiële scanning calorimetrie (DSC) en scanning elektronenmicroscopie (SEM). XRD-patronen, FTIR-spectra en SEM-beelden bewijzen dat de UTSA-280-kristallen succesvol zijn gesynthetiseerd. FTIR-, TGA- en DSC-analyses bevestigen dat de inkapseling succesvol was, waarbij TGA aantoont dat UTSA-280 ongeveer ~20 wt% hexanal kan opslaan
Encapsulation of hexanal in Calcium based squaric acid metal organic frameworks UTSA-280
No full textVerschillende poreuze stoffen zijn de afgelopen jaren onderzocht voor diverse toepassingen. Metal organic frameworks (MOF's) zijn een uitgebreide familie van poreuze materialen, die worden gevormd door metaalionen te combineren met organische linkers om complexe driedimensionale structuren te vormen. De poriën kunnen specifiek worden ontworpen om actieve moleculen in op te slaan, die nadien op gecontroleerde wijze worden vrijgezet om zo bv. de houdbaarheid van voedsel te verlengen. Deze studie beoogt het synthetiseren van een calcium kwadraatzuur MOF, ook bekend als UTSA-280, door middel van een mechanisch-chemisch syntheseproces. Hierbij wordt ook de haalbaarheid van calcium als vervanger van traditionele transitiemetalen in MOF’s onderzocht. Hexanal, een vluchtige antimicrobiële verbinding, wordt geïntegreerd in UTSA-280-kristallen via een dampdiffusieproces. Voor en na de hexanal encapsulatie, worden de gesynthetiseerde UTSA-280-kristallen gekarakteriseerd met behulp van X-stralen diffractie (XRD), Fourier transform infrarood spectroscopie (FTIR), thermogravimetrische analyse (TGA), differentiële scanning calorimetrie (DSC) en scanning elektronenmicroscopie (SEM). XRD-patronen, FTIR-spectra en SEM-beelden bewijzen dat de UTSA-280-kristallen succesvol zijn gesynthetiseerd. FTIR-, TGA- en DSC-analyses bevestigen dat de inkapseling succesvol was, waarbij TGA aantoont dat UTSA-280 ongeveer ~20 wt% hexanal kan opslaan
Encapsulation of hexanal in Ca squarte MOF for active packaging
No full textVarious high surface area porous materials have been widely researched for active food applications. Metal organic frameworks (MOFs), a vast family of porous compounds, have been derived by combining metal ions with organic linkers to form complex 3D structures. Pores present in these structures can be engineered to encapsulate active molecular species and control their release kinetics in the headspace of a product package system for shelflife extension. This work focuses on synthesizing calcium squarate acid MOF, also known as UTSA-280 using mechano-chemical synthesis process. Hexanal, a volatile antimicrobial compound, was encapsulated in UTSA-280 crystals via vapor diffusion process. The synthesized crystals were characterized before and after hexanal encapsulation using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). XRD patterns, FTIR and SEM images indicate that the UTSA-280 crystals were successfully synthesized. FTIR, TGA and DSC analyses conclude that encapsulation was successful, with TGA showing that approximately ~20 wt% hexanal was encapsulated in the UTSA-280 structure
Encapsulation of hexanal in Ca squarte MOF for active packaging
No full textVarious high surface area porous materials have been widely researched for active food applications. Metal organic frameworks (MOFs), a vast family of porous compounds, have been derived by combining metal ions with organic linkers to form complex 3D structures. Pores present in these structures can be engineered to encapsulate active molecular species and control their release kinetics in the headspace of a product package system for shelflife extension. This work focuses on synthesizing calcium squarate acid MOF, also known as UTSA-280 using mechano-chemical synthesis process. Hexanal, a volatile antimicrobial compound, was encapsulated in UTSA-280 crystals via vapor diffusion process. The synthesized crystals were characterized before and after hexanal encapsulation using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). XRD patterns, FTIR and SEM images indicate that the UTSA-280 crystals were successfully synthesized. FTIR, TGA and DSC analyses conclude that encapsulation was successful, with TGA showing that approximately ~20 wt% hexanal was encapsulated in the UTSA-280 structure
Mechanochemical synthesis of Calcium-Squarate MOF and encapsulation of hexanal
No full textPorous high surface area supramolecules have been widely researched for controlled delivery and chemical stabilization of active molecular species. Metal-organic frameworks (MOFs), a vast category of high surface area microporous compounds, can be tailored to encapsulate specific active molecules, and control their release kinetics in the headspace of a product-package system for treatment and shelf-life extension of various agricultural produce. Hexanal has been widely reported to reduce post-harvest losses due to its antimicrobial, antifungal, ethylene-modulating, and phospholipase D (PLD) inhibiting characteristics. In this work, we synthesized Calcium-Squarate MOF by a quick simple mechanochemical process using bioderived linkers and non-toxic endogenous cations. We herein report the encapsulation of hexanal in Ca-Squarate MOF, and probe the strength of non-covalent host-guest interactions of hexanal encapsulated in the pores. The synthesized MOF crystals were characterized by thermal analysis, infrared spectroscopy, and diffraction studies. We observed approximately 20% encapsulation of hexanal by weight using thermo-gravimetric analysis. The infrared spectroscopy and simulation study supported the formation of hydrogen bonds between H atoms of hexanal and O atoms of the Ca-Squarate MOF with the strongest binding affinity of -3.81 kcal mol-1. Crystals maintained their porous structure and microscale morphologies post-encapsulation, as observed using X-ray diffraction and scanning electron microscopy. These results are encouraging for the potential use of hexanal encapsulated MOFs in active packaging applications.The authors would like to thank Hasselt University for sponsoring Tuur Bollen’s internship within the framework of generic scholarships 2023-2024 to conduct this research work at California Polytechnic State Universit
A lab approach to Simulate the Effects of Thermoforming on the Gas Permeability of Commercial Multilayers
No full textIn the search for sustainable food packaging, critical reflection on the choice, combination and quantity of (bio)materials for specific applications is becoming increasingly important to prevent food waste. Our previous research has shown the combined effects of material thinning and polymer reorientation on the gas permeability of thermoformed multilayer trays. This study aims to investigate the feasibility of simulating the thermoforming process by heating and deforming (bio)plastic multilayers in a lab scale set-up to determine the maximum thinning and the associated gas permeability properties.
First, thermal and tensile properties of commercial PE/EVOH/PE and ecovio®/G-Polymer/ecovio multilayer films (~85 µm) are characterized. Next, tensile testing at selected temperatures is applied to determine the maximum stretch, based on the elongation at break. Then, hot stretching of 70x60 mm2-films in machine and/or cross direction (MD, CD, MD+CD) or 45°, is done in an oven at optimal temperature by applying maximum gravity without breaking the multilayer. The microscopical thickness resulting from these situations is compared with the thinning in the bottom, walls and corners of thermoformed trays. The results show that thinning of both films is proportional to an increase in the water vapor transmission rate (WVTR), with the PE-layers providing a better water vapor barrier than the ecovio-layers. In contrast, the oxygen transmission rate (OTR) is not proportional to thinning of the total film, nor the thickness of the barrier layer. Here, polymer reorientation comes into play, even resulting in improved oxygen permeability coefficients as compared to the base films.
We conclude that this approach can support the optimization of thermoforming processes by determining the maximal stretch of the individual layers while safeguarding the gas barrier properties of the final packaging, e.g. in thermoformed fiber-based trays
A lab approach to Simulate the Effects of Thermoforming on the Gas Permeability of Commercial Multilayers
No full textIn the search for sustainable food packaging, critical reflection on the choice, combination and quantity of (bio)materials for specific applications is becoming increasingly important to prevent food waste. Our previous research has shown the combined effects of material thinning and polymer reorientation on the gas permeability of thermoformed multilayer trays. This study aims to investigate the feasibility of simulating the thermoforming process by heating and deforming (bio)plastic multilayers in a lab scale set-up to determine the maximum thinning and the associated gas permeability properties.
First, thermal and tensile properties of commercial PE/EVOH/PE and ecovio®/G-Polymer/ecovio multilayer films (~85 µm) are characterized. Next, tensile testing at selected temperatures is applied to determine the maximum stretch, based on the elongation at break. Then, hot stretching of 70x60 mm2-films in machine and/or cross direction (MD, CD, MD+CD) or 45°, is done in an oven at optimal temperature by applying maximum gravity without breaking the multilayer. The microscopical thickness resulting from these situations is compared with the thinning in the bottom, walls and corners of thermoformed trays. The results show that thinning of both films is proportional to an increase in the water vapor transmission rate (WVTR), with the PE-layers providing a better water vapor barrier than the ecovio-layers. In contrast, the oxygen transmission rate (OTR) is not proportional to thinning of the total film, nor the thickness of the barrier layer. Here, polymer reorientation comes into play, even resulting in improved oxygen permeability coefficients as compared to the base films.
We conclude that this approach can support the optimization of thermoforming processes by determining the maximal stretch of the individual layers while safeguarding the gas barrier properties of the final packaging, e.g. in thermoformed fiber-based trays
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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