scholarly journals Porous Phantoms Mimicking Tissues—Investigation of Optical Parameters Stability Over Time

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 423
Author(s):  
Paulina Listewnik ◽  
Monika Ronowska ◽  
Michał Wąsowicz ◽  
Valery V. Tuchin ◽  
Małgorzata Szczerska
Keyword(s):  
Optical Measurement ◽  
Measuring System ◽  
Integrating Sphere ◽  
Optical Parameters ◽  
Coherent Light ◽  
Multiple Series ◽  
Lung Phantom ◽  
The Stability ◽  
Over Time

Optical phantoms are used to validate optical measurement methods. The stability of their optical parameters over time allows them to be used and stored over long-term periods, while maintaining their optical parameters. The aim of the presented research was to investigate the stability of fabricated porous phantoms, which can be used as a lung phantom in optical system. Measurements were performed in multiple series with an interval of 6 months, recreating the same conditions and using the same measuring system consisting of an integrating sphere, a coherent light source with a wavelength of 635 nm and a detector. Scattering and absorption parameters were determined on the basis of the measured reflectance and transmittance. The tested samples were made of silicone and glycerol in various proportions.

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 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.

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.

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.

Studying the Stayers: the Stable Population of Long Melford, Suffolk, over Two Hundred Years

2015 ◽  
pp. 9-28
Author(s):  
Lyn Boothman
Keyword(s):  
Stable Population ◽  
Population Movement ◽  
Single Adults ◽  
Population Reconstruction ◽  
The Stability ◽  
Local Family ◽  
Over Time

Studies of population movement are more common than those focusing on the long-term inhabitants of a settlement. This article, based on data from a population reconstruction, examines long-term and inter-generational stability amongst couples resident in Long Melford, Suffolk, both those with local family links and those who migrated from elsewhere. The study focuses on three periods: 1661–91, 1753–83 and 1831–61 and finds that the proportion of couples who met the stability indicators increased over time; overall the proportion of wives who met the criteria increased more than that of husbands. A comparison of the children of these couples is used to relate stability amongst the couples and their children and to highlight issues relating to assessing the stability of single adults.

scholarly journals Separation of Gases by Membranes: The Effects of Pollutants on the Stability of Membranes

2017 ◽  
Vol 45 (1) ◽  
pp. 5-8
Author(s):  
Nándor Nemestóthy
Keyword(s):  
Polymer Membranes ◽  
Measuring System ◽  
Nitrogen Gas ◽  
Long Term Stability ◽  
Separation Membranes ◽  
Gas Separation Membranes ◽  
Separation Of Gases ◽  
Multichannel Measuring ◽  
The Stability

Abstract The long-term stability of membranes is determined mainly by their sensitivity to pollutants. Their stability was tested using a novel, multichannel measuring system, which is based on pressure differences. This measuring system is suitable to determine the changes in permeability of polymer membranes. The damaging effects of H2S, BTX and n-dodecane were investigated in terms of polyimide gas separation membranes using nitrogen gas.

On the Robustness of Solution Strategy Classifications

2010 ◽  
Vol 31 (2) ◽  
pp. 68-73 ◽  
Author(s):  
María José Contreras ◽  
Víctor J. Rubio ◽  
Daniel Peña ◽  
José Santacreu
Keyword(s):  
Individual Differences ◽  
Study Strategies ◽  
Solution Strategy ◽  
Specific Test ◽  
Spatial Tasks ◽  
The Stability ◽  
Strategy Changes ◽  
Over Time

Individual differences in performance when solving spatial tasks can be partly explained by differences in the strategies used. Two main difficulties arise when studying such strategies: the identification of the strategy itself and the stability of the strategy over time. In the present study strategies were separated into three categories: segmented (analytic), holistic-feedback dependent, and holistic-planned, according to the procedure described by Peña, Contreras, Shih, and Santacreu (2008) . A group of individuals were evaluated twice on a 1-year test-retest basis. During the 1-year interval between tests, the participants were not able to prepare for the specific test used in this study or similar ones. It was found that 60% of the individuals kept the same strategy throughout the tests. When strategy changes did occur, they were usually due to a better strategy. These results prove the robustness of using strategy-based procedures for studying individual differences in spatial tasks.

On the Stability of Evaluative Conditioning Effects

2013 ◽  
Vol 44 (6) ◽  
pp. 380-389 ◽  
Author(s):  
Sabine Förderer ◽  
Christian Unkelbach
Keyword(s):  
Evaluative Conditioning ◽  
Indirect Measures ◽  
The Stability ◽  
Over Time

Evaluative conditioning (EC) refers to valence changes in neutral stimuli (CSs) through repeated pairing with liked or disliked stimuli (USs). The present study examined the stability of EC effects in the course of 1 week. We investigated how this stability depends on memory for US valence and US identity. We also investigated whether CSs evaluations occurring immediately after conditioning (i.e., evaluative consolidation) are necessary for stable EC effects. Participants showed stable EC effects on direct and indirect measures, independent of evaluations immediately after conditioning. EC effects depended on memory for US valence but not for US identity. And although memory decreased significantly over time, EC effects remained stable. These data suggest that evaluative consolidation is not necessary, and that conditioned preferences and attitudes might persist even when people do not remember the concrete source anymore.

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