scholarly journals Effect of Photoinitiator on Precursory Stability and Curing Depth of Thiol-Ene Clickable Gelatin

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1877
Author(s):  
Kai-Hung Yang ◽  
Gabriella Lindberg ◽  
Bram Soliman ◽  
Khoon Lim ◽  
Tim Woodfield ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Visible Light ◽  
Rheological Properties ◽  
Swelling Ratio ◽  
Sodium Persulfate ◽  
Photo Polymerization ◽  
Gelation Kinetics ◽  
The Stability ◽  
Over Time

Recent advances highlight the potential of photopolymerizable allylated gelatin (GelAGE) as a versatile hydrogel with highly tailorable properties. It is, however, unknown how different photoinitiating system affects the stability, gelation kinetics and curing depth of GelAGE. In this study, sol fraction, mass swelling ratio, mechanical properties, rheological properties, and curing depth were evaluated as a function of time with three photo-initiating systems: Irgacure 2959 (Ig2959; 320–500 nm), lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP; 320–500 nm), and ruthenium/sodium persulfate (Ru/SPS; 400–500 nm). Results demonstrated that GelAGE precursory solutions mixed with either Ig2959 or LAP remained stable over time while the Ru/SPS system enabled the onset of controllable redox polymerization without irradiation during pre-incubation. Photo-polymerization using the Ru/SPS system was significantly faster (<5 s) compared to both Ig2959 (70 s) and LAP (50 s). Plus, The Ru/SPS system was capable of polymerizing a thick construct (8.88 ± 0.94 mm), while Ig2959 (1.62 ± 0.49 mm) initiated hydrogels displayed poor penetration depth with LAP (7.38 ± 2.13 mm) in between. These results thus support the use of the visible light based Ru/SPS photo-initiator for constructs requiring rapid gelation and a good curing depth while Ig2959 or LAP can be applied for photo-polymerization of GelAGE materials requiring long-term incubation prior to application if UV is not a concern.

Activity networks and the temporality of urban space: the case of a cul-de-sac square

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ahlam Ammar Sharif
Keyword(s):  
Urban Space ◽  
Actor Network Theory ◽  
Ethnographic Study ◽  
Urban Change ◽  
Content Type ◽  
Activity Networks ◽  
Nuanced Understanding ◽  
The Stability ◽  
Over Time

PurposeThis study draws on recent actor-network theory (ANT) literature to provide a nuanced understanding of the effect of time on activity networks in urban spaces. It investigates the role of time in multiplying these networks and producing urban change, which is limited in similar ANT-related research.Design/methodology/approachThis ethnographic study of a cul-de-sac square within a housing project in the suburb of Dahiyat Al-Hussein in Amman, Jordan, documents the changes in its activity networks when comparing the 1990s with 2019. Data were collected through interviews and site observations covering the two time periods to investigate the different activities that occurred constantly over time, which reflect the temporal network stabilisation within the square.FindingsThe findings demonstrate the profound effect time has on the stability of activity networks related to playing, observing, walking, vending and their interrelations. Their overlaps and conflicts with each other and with other networks in the space were observed. Unpacking the stability of activity networks and their interrelations demonstrates the change in their actor relations and temporalities over time. This is significant in understanding urban change.Originality/valueThe study investigates the importance of time in recognising and extending the multiplicity of urban activities, which suggests new ways of understanding urban change. This exploration highlights new possibilities for creating more adaptable spaces according to residents' long-term needs.

scholarly journals Time-Stability Dispersion of MWCNTs for the Improvement of Mechanical Properties of Portland Cement Specimens

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4149
Author(s):  
Laura M. Echeverry-Cardona ◽  
Natalia Álzate ◽  
Elisabeth Restrepo-Parra ◽  
Rogelio Ospina ◽  
Jorge H. Quintero-Orozco
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Raman Spectroscopy ◽  
Portland Cement ◽  
Time Stability ◽  
Cement Pastes ◽  
Multi Wall Carbon Nanotubes ◽  
Vis Spectroscopy ◽  
The Stability ◽  
Over Time

This study shows the energy optimization and stabilization in the time of solutions composed of H2O + TX-100 + Multi-Wall Carbon Nanotubes (MWCNTs), used to improve the mechanical properties of Portland cement pastes. For developing this research, sonication energies at 90, 190, 290, 340, 390, 440, 490 and 590 J/g are applied to a colloidal substance (MWCNTs/TX-100 + H2O) with a molarity of 10 mM. Raman spectroscopy analyses showed that, for energies greater than 440 J/g, there are ruptures and fragmentation of the MWCNTs; meanwhile at energies below 390 J/g, better dispersions are obtained. The stability of the dispersion over time was evaluated over 13 weeks using UV-vis spectroscopy and Zeta Potential. With the most relevant data collected, sonication energies of 190, 390 and 490 J/g, at 10 mM were selected at the first and the fourth week of storage to obtain Portland cement specimens. Finally, we found an improvement of the mechanical properties of the samples built with Portland cement and solutions stored for one and four weeks; it can be concluded that the MWCNTs improved the hydration period.

scholarly journals New crosslinkers for electrospun chitosan fibre mats. I. Chemical analysis

2012 ◽  
Vol 9 (75) ◽  
pp. 2551-2562 ◽  
Author(s):  
Marjorie S. Austero ◽  
Amalie E. Donius ◽  
Ulrike G. K. Wegst ◽  
Caroline L. Schauer
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Mechanical Stability ◽  
Dissolution Tests ◽  
Natural Polysaccharide ◽  
Biomedical Field ◽  
The Stability ◽  
Scanning Electron

Chitosan (CS), the deacetylated form of chitin, the second most abundant, natural polysaccharide, is attractive for applications in the biomedical field because of its biocompatibility and resorption rates, which are higher than chitin. Crosslinking improves chemical and mechanical stability of CS. Here, we report the successful utilization of a new set of crosslinkers for electrospun CS. Genipin, hexamethylene-1,6-diaminocarboxysulphonate (HDACS) and epichlorohydrin (ECH) have not been previously explored for crosslinking of electrospun CS. In this first part of a two-part publication, we report the morphology, determined by field emission scanning electron microscopy (FESEM), and chemical interactions, determined by Fourier transform infrared microscopy, respectively. FESEM revealed that CS could successfully be electrospun from trifluoroacetic acid with genipin, HDACS and ECH added to the solution. Diameters were 267 ± 199 nm, 644 ± 359 nm and 896 ± 435 nm for CS–genipin, CS–HDACS and CS–ECH, respectively. Short- (15 min) and long-term (72 h) dissolution tests (T 600 ) were performed in acidic, neutral and basic pHs (3, 7 and 12). Post-spinning activation by heat and base to enhance crosslinking of CS–HDACS and CS–ECH decreased the fibre diameters and improved the stability. In the second part of this publication, we report the mechanical properties of the fibres.

scholarly journals Stability Evaluation of DMT and Harmala Alkaloids in Ayahuasca Tea Samples

Molecules ◽  
2020 ◽  
Vol 25 (9) ◽  
pp. 2072 ◽  
Author(s):  
Gabriela de Oliveira Silveira ◽  
Rafael Guimarães dos Santos ◽  
Felipe Rebello Lourenço ◽  
Giordano Novak Rossi ◽  
Jaime Hallak ◽  
...  
Keyword(s):  
Therapeutic Potential ◽  
Stability Evaluation ◽  
Glass Containers ◽  
Chromatography Tandem Mass Spectrometry ◽  
Liquid Chromatography Tandem Mass ◽  
Harmala Alkaloids ◽  
Health Disorders ◽  
The Stability ◽  
Over Time

Ayahuasca tea is a hallucinogenic beverage used for religious purposes in Brazil and many other countries that has therapeutic potential in the treatment of some mental health disorders. In the context of psychedelic research, quantification of the tea’s main alkaloids prior to its administration in animal or human studies is essential. For this reason, this study aims to provide information regarding the stability of the main ayahuasca alkaloids (dimethyltryptamine, DMT; harmine, HRM; tetrahydroharmine, THH; harmaline, HRL) in three different conditions: (1) A year stored in a refrigerator either in plastic or glass containers, (2) seven days at 37 °C to reproduce usual mail transportation, and (3) after three freeze–thaw cycles. Samples were quantified after a dilute-and-shoot procedure using liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS). There was no significant degradation of DMT concentration over time in all tested conditions. Harmala alkaloids (THH, HRL, and HRM) showed important variations after long-term and high-temperature storages. Although DMT has proven to be stable in all studied conditions, the harmala alkaloids revealed intense degradation and even concentration increment. This may be caused by degradation, alkaloid inter-conversion, and leaching from tea precipitate material. Therefore, ayahuasca quantification before administration in controlled sets is mandatory.

COMPLEX DEFLOCCULENT BASED ON SODA, LIQUID GLASS AND OXYETHYLIDENEDIPHOSPHONIC ACID IN CERAMIC CASTING TECHNOLOGY

2020 ◽  
Vol 63 (7) ◽  
pp. 31-40
Author(s):  
Mikhail F. Butman ◽  
Natalya V. Filatova ◽  
Galina P. Kozlovskaya
Keyword(s):  
Mechanical Properties ◽  
Rheological Properties ◽  
Liquid Glass ◽  
Rheological Parameters ◽  
Hydrate Shell ◽  
Complex Additive ◽  
Wide Range ◽  
The Stability ◽  
Newtonian Systems ◽  
Full Factorial

Here are discussed some results to use oxyethylidenediphosphonic acid (OEDPA) and various additives as a deflocculant composition for controlling the rheological properties of a ceramic suspension. According to the results of determining thixotropy, it was found that a complex thinner based on soda and OEDPA is the most effective. It is desirable to replace a portion of the soda with liquid glass. By the full factorial experiment method, it was established the optimal composition of the components of the complex thinner. The proposed thinner is highly effective in a wide range of OEDPA, soda, and liquid glass concentrations. The resulting suspensions have stable, high structural–mechanical properties. A mathematical model describing the effect of the composition of the thinner on the viscosity and thixotropy of the suspension is presented. The effect of the diluent on the mechanical properties of the molded dried and fired samples was determined. The addition of OEDPA to the thinner significantly lowers the rheological parameters and the rheological properties of the suspensions approach the rheological properties of Newtonian systems. It was found that OEDPA lowers the mass buildup rate, which can be increased by lowering the moisture content in the suspension, which makes it possible to increase the post-casting and -drying density of the samples. The introduction of this additive leads to an increase in the hydrate shell around the clayey particle and an increase in the stability of the suspension, but the increase in the ζ - potential in comparison with the production additive is very small. The mechanism of action of a complex additive is proposed, including ion-exchange, complexation and chemisorption. An increase in the strength and density of dry and calcinated clay samples as well as a decrease in the shrinkage and porosity are observed. The complex additive makes it possible to optimize the technology at the stages of casting slip and to decrease the number of parts rejected during molding, drying and firing.

scholarly journals Functionality of Beech Bark in Adhesive Mixtures Used in Plywood and Its Effect on the Stability Associated with Material Systems

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1298 ◽  
Author(s):  
Roman Réh ◽  
Rastislav Igaz ◽  
Ľuboš Krišťák ◽  
Ivan Ružiak ◽  
Milada Gajtanska ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Urea Formaldehyde ◽  
Wood Processing ◽  
Material Systems ◽  
Adhesive Mixtures ◽  
The Common ◽  
The Stability ◽  
Heating Up

The results of research into utilizing grinded beech bark in order to substitute commonly used fillers in urea formaldehyde (UF) adhesive mixtures to bond plywood are presented in the present study. Four test groups of plywood with various adhesive mixtures were manufactured under laboratory conditions and used for experimentation. Plywood made using the same technology, with the common filler (technical flour), was used as a reference material. Three different concentrations of grinded beech bark were used. The thermal conductivity of the fillers used, viscosity and its time dependence, homogeneity and the dispersion performance of fillers were evaluated in the analysis of adhesive mixture. The time necessary for heating up the material during the pressing process was a further tested parameter. The produced plywood was analyzed in terms of its modulus of elasticity, bending strength, perpendicular tensile strength and free formaldehyde emissions. Following the research results, beech bark can be characterized as an ecologically friendly alternative to technical flour, shortening the time of pressing by up to 27%. At the same time, in terms of the statistics, the mechanical properties and stability of the material changed insignificantly, and the formaldehyde emissions reduced significantly, by up to 74%. The utilization of bark was in compliance with long-term sustainability, resulting in a decrease in the environmental impact of waste generated during the wood processing.

scholarly journals Temporal stability of primate scent samples

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Alice C. Poirier ◽  
John S. Waterhouse ◽  
Jacob C. Dunn ◽  
Andrew C. Smith
Keyword(s):  
Chemical Composition ◽  
Room Temperature ◽  
Solid Phase ◽  
Temporal Stability ◽  
Gas Chromatography Mass Spectrometry ◽  
Headspace Gas ◽  
The Stability ◽  
Natural Decay ◽  
Over Time

AbstractA common recommendation in the field of animal chemosignaling is to store and transport scent samples frozen, since they are likely to change with time and degrade due to bacterial activity inside the sample containers and the loss of the most volatile compounds. However, we still ignore the exact pattern of change or degradation for these types of samples. Here we experimentally tested the stability of primate scent samples during analytical procedures. For this purpose, we used swabs of naturally deposited glandular secretions from captive tamarins (Neotropical primates) analyzed by headspace gas chromatography-mass spectrometry. We successively extracted the samples by solid-phase microextraction, while controlling for the delay between extractions, and compared the number of compounds detected in the samples under each condition. We found that compounds were lost and transformed over time inside the sample vials. Such natural decay of scent signals is likely to contribute to the long term information transmitted. We found no evidence that long delays at room temperature affected sample chemical composition more than short delays. Nonetheless, we showed that repeated extraction of a sample increased the loss of compounds. The changes in sample chemical composition observed over time in this experiment support standard recommendation to avoid storing samples for long periods at room temperature and to extract each sample only once, in order to ensure optimum results.

A Study on the Differences of Mechanical Properties between CH4 and CO2 Hydrate-Bearing Sediments

2013 ◽  
Vol 353-356 ◽  
pp. 1240-1244 ◽  
Author(s):  
Yuan Luo ◽  
Yong Chen Song ◽  
Wei Guo Liu ◽  
Jia Fei Zhao ◽  
Yun Fei Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Gas Hydrate ◽  
Triaxial Compression ◽  
Triaxial Tests ◽  
Long Term Storage ◽  
Replacement Method ◽  
Three Stages ◽  
The Stability ◽  
Hydrate Bearing Sediments

The CH4-CO2replacement method to recover CH4from hydrate-bearing sediments has received great attention because it enables the long term storage of CO2and is expected to maintain the stability of gas hydrate-bearing sediments. This paper extends our previous study of the stability of CH4hydrate-bearing sediments to CO2hydrate-bearing sediments to evaluate the safety of the CH4-CO2replacement method. Low temperature, high pressure triaxial compression apparatus was used to measure the mechanical properties of CO2hydrate-bearing sediments. The triaxial tests results for CH4and CO2hydrate-bearing sediments were then compared. It was found that the failure mode of both the CO2and CH4hydrate-bearing sediments was a bulging deformation at mid-height on the samples. Moreover, the stress-strain curves of both the CO2and CH4hydrate-bearing sediments appear to be hyperbolic in shape, and could be divided into three stages: the quasi-elastic stage, the hardening stage and the yield stage. However, the strength of the CO2hydrate-bearing sediments was approximately 15% larger than that of the CH4hydrate-bearing sediments under the same conditions. The results imply that the stability of gas hydrate-bearing sediments could be maintained using the CH4-CO2replacement method to recover CH4from these sediments.

scholarly journals Long-Term Stability of Cortisol Production and Metabolism Throughout Adolescence: Longitudinal Twin Study

2020 ◽  
Vol 23 (1) ◽  
pp. 33-38 ◽  
Author(s):  
Britt J. van Keulen ◽  
Conor V. Dolan ◽  
Ruth Andrew ◽  
Brian R. Walker ◽  
Hilleke E. Hulshoff Pol ◽  
...  
Keyword(s):  
Hpa Axis ◽  
Excretion Rate ◽  
Term Stability ◽  
Long Term Stability ◽  
Cortisol Metabolism ◽  
The Stability ◽  
Longitudinal Twin Study ◽  
Hpa Axis Activity ◽  
Over Time

AbstractLife-course experiences have been postulated to program hypothalamus–pituitary–adrenal (HPA) axis activity, suggesting that HPA axis activity is, at least partially, stable over time. Yet, there is paucity of data on the long-term stability of cortisol production and metabolism. We performed a prospective follow-up study in twins recruited from a nationwide register to estimate the stability of cortisol production and metabolism over time, and the contribution of genetic and environmental factors to this stability. In total, 218 healthy mono- and dizygotic twins were included. At the ages of 9, 12 and 17 years, morning urine samples were collected for assessment (by gas chromatography-tandem mass spectrometry) of cortisol metabolites, enabling the calculation of cortisol metabolite excretion rate and cortisol metabolism activity. Our results showed a low stability for both cortisol metabolite excretion rate (with correlations <.20) and cortisol metabolism activity indices (with correlations of .25 to .46 between 9 and 12 years, −.02 to .15 between 12 and 17 years and .09 to .28 between 9 and 17 years). Because of the low stability over time, genetic and environmental contributions to this stability were difficult to assess, although it seemed to be mostly determined by genetic factors. The low stability in both cortisol production and metabolism between ages 9 and 17 years reflects the dynamic nature of the HPA axis.

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