scholarly journals The properties and performance of a pH-responsive functionalised nanoparticle

2014 ◽  
Vol 175 ◽  
pp. 171-187 ◽  
Author(s):  
Sandra Ast ◽  
Peter J. Rutledge ◽  
Matthew H. Todd
Keyword(s):  
Exchange Process ◽  
Ph Responsive ◽  
Disulfide Exchange ◽  
Emission Maximum ◽  
Fluorescence Measurements ◽  
And Performance ◽  
The Stability ◽  
Ph Range ◽  
Naphthalimide Dye ◽  
Over Time

We report fluorescence measurements of three quantum dots (QDs) of different sizes functionalised with the same pH responsive naphthalimide dye. QD size strongly influences energy transfer between dye and dot. Using QDs with an emission maximum of 570 nm gives rise to an interesting transfer of energy from dye to dot, while QDs with an emission maximum at 670 nm give unexpected enhancement of the dye emission. Titrations of QDs with the dye provide a means to establish the loading and hence an approximation of the surface dye density, which varies in proportion to QD size. Quenching effects are observed beyond the loading limit, and may indicate non-specific interactions between the excess dye and the nanoparticle. Attachment of the dye to the QD core is achieved by a thiol/disulfide exchange process that has been interrogated with Raman spectroscopy. The stability of these QD–dye conjugates over time and across a physiological pH range has been investigated to provide an assessment of their performance and robustness.

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.

scholarly journals Stabilization and Release of Palm Tocotrienol Emulsion Fabricated Using pH-Sensitive Calcium Carbonate

Foods ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 358
Author(s):  
Phui Yee Tan ◽  
Beng Ti Tey ◽  
Eng Seng Chan ◽  
Oi Ming Lai ◽  
Hon Weng Chang ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Droplet Size ◽  
Entrapment Efficiency ◽  
Ph Sensitive ◽  
Emulsion System ◽  
Ph Responsive ◽  
Small Droplet ◽  
Homogenization Time ◽  
Oil In Water ◽  
Ph Range

Calcium carbonate (CaCO3) has been utilized as a pH-responsive component in various products. In this present work, palm tocotrienols-rich fraction (TRF) was successfully entrapped in a self-assembled oil-in-water (O/W) emulsion system by using CaCO3 as the stabilizer. The emulsion droplet size, viscosity and tocotrienols entrapment efficiency (EE) were strongly affected by varying the processing (homogenization speed and time) and formulation (CaCO3 and TRF concentrations) parameters. Our findings indicated that the combination of 5000 rpm homogenization speed, 15 min homogenization time, 0.75% CaCO3 concentration and 2% TRF concentration resulted in a high EE of tocotrienols (92.59–99.16%) and small droplet size (18.83 ± 1.36 µm). The resulting emulsion system readily released the entrapped tocotrienols across the pH range tested (pH 1–9); with relatively the highest release observed at pH 3. The current study presents a potential pH-sensitive emulsion system for the entrapment and delivery of palm tocotrienols.

scholarly journals A pH-Responsive Foam Formulated with PAA/Gemini 12-2-12 Complexes

2021 ◽  
Vol 5 (3) ◽  
pp. 37
Author(s):  
Hernán Martinelli ◽  
Claudia Domínguez ◽  
Marcos Fernández Leyes ◽  
Sergio Moya ◽  
Hernán Ritacco
Keyword(s):  
Surface Tension ◽  
Dynamic Surface Tension ◽  
Foam Formation ◽  
Ph Responsive ◽  
Dynamic Surface ◽  
X Ray ◽  
Equilibrium Surface Tension ◽  
Potential Applications ◽  
The Stability ◽  
Air Interfaces

In the search for responsive complexes with potential applications in the formulation of smart dispersed systems such as foams, we hypothesized that a pH-responsive system could be formulated with polyacrylic acid (PAA) mixed with a cationic surfactant, Gemini 12-2-12 (G12). We studied PAA-G12 complexes at liquid–air interfaces by equilibrium and dynamic surface tension, surface rheology, and X-ray reflectometry (XRR). We found that complexes adsorb at the interfaces synergistically, lowering the equilibrium surface tension at surfactant concentrations well below the critical micelle concentration (cmc) of the surfactant. We studied the stability of foams formulated with the complexes as a function of pH. The foams respond reversibly to pH changes: at pH 3.5, they are very stable; at pH > 6, the complexes do not form foams at all. The data presented here demonstrate that foam formation and its pH responsiveness are due to interfacial dynamics.

scholarly journals Steady-state $$\dot{V}{\text{O}}_{2}$$ above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners

2021 ◽  
Author(s):  
Rebekah J. Nixon ◽  
Sascha H. Kranen ◽  
Anni Vanhatalo ◽  
Andrew M. Jones
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Lactate Concentration ◽  
Practical Interest ◽  
Blood Lactate Concentration ◽  
Distance Runners ◽  
Severe Intensity ◽  
The Stability ◽  
Trained Runners ◽  
Over Time

AbstractThe metabolic boundary separating the heavy-intensity and severe-intensity exercise domains is of scientific and practical interest but there is controversy concerning whether the maximal lactate steady state (MLSS) or critical power (synonymous with critical speed, CS) better represents this boundary. We measured the running speeds at MLSS and CS and investigated their ability to discriminate speeds at which $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 was stable over time from speeds at which a steady-state $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 could not be established. Ten well-trained male distance runners completed 9–12 constant-speed treadmill tests, including 3–5 runs of up to 30-min duration for the assessment of MLSS and at least 4 runs performed to the limit of tolerance for assessment of CS. The running speeds at CS and MLSS were significantly different (16.4 ± 1.3 vs. 15.2 ± 0.9 km/h, respectively; P < 0.001). Blood lactate concentration was higher and increased with time at a speed 0.5 km/h higher than MLSS compared to MLSS (P < 0.01); however, pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 did not change significantly between 10 and 30 min at either MLSS or MLSS + 0.5 km/h. In contrast, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 increased significantly over time and reached $$\dot{V}{\text{O}}_{2\,\,\max }$$ V ˙ O 2 max at end-exercise at a speed ~ 0.4 km/h above CS (P < 0.05) but remained stable at a speed ~ 0.5 km/h below CS. The stability of $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 at a speed exceeding MLSS suggests that MLSS underestimates the maximal metabolic steady state. These results indicate that CS more closely represents the maximal metabolic steady state when the latter is appropriately defined according to the ability to stabilise pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 .

scholarly journals An Investigation of the Physical and Electrical Properties of Knitted Electrodes When Subjected to Multi-Axial Compression and Abrasion

Proceedings ◽  
2021 ◽  
Vol 68 (1) ◽  
pp. 2
Author(s):  
Arash M. Shahidi ◽  
Theodore Hughes-Riley ◽  
Carlos Oliveira ◽  
Tilak Dias
Keyword(s):  
Heart Rate ◽  
Electrical Properties ◽  
Applied Load ◽  
Pressure Sensors ◽  
Electrical Performance ◽  
Electronic Textiles ◽  
Heart Rate Monitors ◽  
Mechanical Loads ◽  
And Performance ◽  
Over Time

Knitted electrodes are a key component to many electronic textiles including sensing devices, such as pressure sensors and heart rate monitors; therefore, it is essential to assess the electrical performance of these knitted electrodes under different mechanical loads to understand their performance during use. The electrical properties of the electrodes could change while deforming, due to an applied load, which could occur in the uniaxial direction (while stretched) or multiaxial direction (while compressed). The properties and performance of the electrodes could also change over time when rubbed against another surface due to the frictional force and generated heat. This work investigates the behavior of a knitted electrode under different loading conditions and after multiple abrasion cycles.

scholarly journals Analytical Modeling and Design of Novel Conical Halbach Permanent Magnet Couplings for Underwater Propulsion

2021 ◽  
Vol 9 (3) ◽  
pp. 290
Author(s):  
Yukai Li ◽  
Yuli Hu ◽  
Youguang Guo ◽  
Baowei Song ◽  
Zhaoyong Mao
Keyword(s):  
Permanent Magnet ◽  
Analytical Calculation ◽  
Underwater Propulsion ◽  
Conical Structure ◽  
Torque Analysis ◽  
Dynamic Seal ◽  
And Performance ◽  
The Stability ◽  
Propulsion Unit ◽  
Force Calculation

Permanent magnet couplings can convert a dynamic seal into a static seal, thereby greatly improving the stability of the underwater propulsion unit. In order to make full use of the tail space and improve the transmitted torque capability, a conical Halbach permanent magnet coupling (C-HPMC) is proposed in this paper. The C-HPMC combines multiple cylindrical HPMCs with different sizes into an approximately conical structure. Compared with the conical permanent magnet couplings in our previous work, the novel C-HPMC has better torque performance and is easy to process. The analytical calculation method of transmitted torque of C-HPMC is proposed on the basis of torque calculation of the three common types of HPMCs. The accuracy of the torque calculation of the three HPMCs is verified, and the torque performance of the three HPMCSs of different sizes is compared and discussed. The “optimal type selection” method is proposed and applied in the design of C-HPMC. Finally, on the basis of torque analysis calculation and axial force calculation, a complete flowchart of the design and performance analysis of C-HPMC is described.

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.

Recovery from memory failure when recalling a memorized performance: The role of musical structure and performance cues

2021 ◽  
pp. 102986492110254
Author(s):  
Roger Chaffin ◽  
Jane Ginsborg ◽  
James Dixon ◽  
Alexander P. Demos
Keyword(s):  
Vocal Music ◽  
Musical Structure ◽  
Public Performance ◽  
Memory Failure ◽  
And Performance ◽  
Written Recall ◽  
Performance Gains ◽  
Over Time

To perform reliably and confidently from memory, musicians must able to recover from mistakes and memory failures. We describe how an experienced singer (the second author) recovered from mistakes and gaps in recall as she periodically recalled the score of a piece of vocal music that she had memorized for public performance, writing out the music six times over a five-year period following the performance. Five years after the performance, the singer was still able to recall two-thirds of the piece. When she made mistakes, she recovered and went on, leaving gaps in her written recall that lengthened over time. We determined where in the piece gaps started ( losses) and ended ( gains), and compared them with the locations of structural beats (starts of sections and phrases) and performance cues ( PCs) that the singer reported using as mental landmarks to keep track of her progress through the piece during the sung, public performance. Gains occurred on structural beats where there was a PC; losses occurred on structural beats without a PC. As the singer’s memory faded over time, she increasingly forgot phrases that did not start with a PC and recovered at the starts of phrases that did. Our study shows how PCs enable musicians to recover from memory failures.

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