Physico-chemical properties of ionic-liquid water mixtures

In order for Ionic Liquids (ILs) to be utilized to their full potential, it is necessary to have a complete understanding of their physical properties, including phase transitions temperatures1. We have previously reported into the extent of structuring of ILs using photochromic molecular probes, and investigated the appropriate IL water content to yield hydrated IL systems for analysis of polarity and to create environments suitable for effective enzyme activity 1,2,3. In this study we investigated interactions in hydrated ILs containing variable hydrophobic and hydrophilic regions through optical and thermal analysis. The enthalpies and phase transitions of the systems were compared, between the temperature range -50°C to +30°C for the ILs with varying degrees of hydration. Reichardtʼs dye was used as a molecular probe to monitor changes in interactions in the ILs as a function of temperature. Comparisons were made between ILs and for ILs with varying degrees of hydration. Spectroscopic studies were performed using Perkin Elmer UV-Visible Spectrometer and phase transitions monitored using a Perkin Elmer Differential Scanning Calorimeter. The ILs examined are; Trihexyltetradecylphosphonium Chloride [P6,6,6,14 Cl] Tributyl-tetradecylphosphonium Chloride, [P4,4,4,14 Cl], 1-Ethyl-methyl-3-imidazolium-ethyl Sulfate [Emim][EtSO4] and Trihexyltetradecylphosphonium Dicyanamide [P6,6,6,14 DCA]. 1. Robert Byrne, Simon Coleman, Simon Gallagher, and Dermot Diamond. Designer Molecular Probes for Phosphonium Ionic Liquids. Physical Chemistry Chemical Physics, 2010. 2. Kyoko Fujita, Douglas R. MacFarlane, Maria Forsyth, Masahiro Yoshizawa-Fujita, Kenichi Murata,† Nobuhumi Nakamura, and Hiroyuki Ohno*,Solubility and Stability of Cytochrome c in Hydrated Ionic Liquids: Effect of Oxo Acid Residues and Kosmotropicity, 2007. 3. SergeiV.DzyubaandRichardA.Bartsch,Expandingthepolarityrange of ionic liquids, Tetrehedron Letters, 2002

Reverse Derivative Categories

The reverse derivative is a fundamental operation in machine learning and automatic differentiation. This paper gives a direct axiomatization of a category with a reverse derivative operation, in a similar style to that given by Cartesian differential categories for a forward derivative. Intriguingly, a category with a reverse derivative also has a forward derivative, but the converse is not true. In fact, we show explicitly what a forward derivative is missing: a reverse derivative is equivalent to a forward derivative with a dagger structure on its subcategory of linear maps. Furthermore, we show that these linear maps form an additively enriched category with dagger biproducts.Comment: Extended version of paper to appear at CSL 202

Poly(ionic liquid) based dual responsive smart hydrogels

Poly(ionic liquid)s (PILs) are a subclass of ionic liquid that feature polymerizable groups either in the cation, the anion or both. Applications of these materials include solid ion conductors, CO2 absorption and energy storage. Furthermore, a branch of PILs feature lower critical solution temperature (LCST) behaviour, making them suitable for the synthesis of temperature responsive materials. The aim of this study was to synthesize thermo-responsive crosslinked PIL hydrogels based on phosphonium PILs. Moreover, taking into account that these PIL hydrogels consist of polyelectrolyte chains, the effect of added salt was also investigated

Photo-responsive semi-interpetrating network hydrogels based on poly(ionic liquids) and a poly(N-Isopropylacrylamide-Spiropyran-Acrylic Acid) copolymer

Poly(ionic liquids) are a subclass of ionic liquids that feature polymerizable groups in either the anion, the cation or both. They are used as a building block for a wide range of materials which can be used for a broad spectrum of applications, including conducting materials in solar cells, lithium rechargeable batteries, actuators and other electrochemical devices [1]. Poly(N-isopropylacrylamide) (pNiPAAm) is known to exhibit a lower critical solution temperature (LCST) in an aqueous medium [2]. By incorporating other co-monomers in the pNiPAAm network, such as spiropyran (SPA) photochromic units, materials which exhibit are both thermo- and photo-responsive can be synthesized [3]. By crosslinking a poly(ionic liquid), such as tributylhexylphosphonium 3-sulfopropylacrylate (PSPA), in the presence of a linear poly(N-isopropylacrylamide-co-spiropyran-co-acrylic acid) (pNiPAAm-SPA-AA) copolymer, a semi-interpenetrating network (sIPN) was synthesized. The following research focuses on the synthesis of and characterization of linear (pNiPAAm-SPA-AA) and its incorporation in a sIPN. The photo-induced shrinking of the resulting sIPN was characterized in the presence of deionized water and NaCl solutions of different concentrations

Mechanical Resistance of Cracked Dam Mass Concrete Repaired by Grouting: An Experimental Study

RÉSUMÉ Pour évaluer le module de rupture et la résistance au cisaillement du béton de masse réparé par injection de coulis, six spécimens de 400 x 400 x 1250 mm en béton avec des agrégats de taille maximale de 100 mm ont été testés suivant la norme ASTM C78 et avec une configuration de chargement favorisant de grandes contraintes de cisaillement le long d'un plan de rupture vertical. L'essai de la norme ASTM C78 a été effectué sur tous les échantillons non-fissurés et sur les échantillons réparés (deux spécimens à réparation simple et deux à réparations multiples en utilisant deux coulis d'injection microfins avec un ratio eau/ciment (e/c) de 1,0 et 0,5 respectivement. L'essai de cisaillement a été effectué sur deux spécimens à réparation simple et deux spécimens à réparations multiples, injectés dans les deux cas avec les deux mélanges de coulis. Une résistance à la traction indirecte moyenne de 2,8 MPa a été obtenue pour les échantillons vierges. Cette valeur a été diminuée à 1 MPa et 0,5 MPa pour les échantillons réparés à l'aide du coulis avec rapport e/c égal à 0,5 et 1,0 respectivement, quel que soit le nombre de réparations. La résistance au cisaillement des spécimens est affectée à la fois par le rapport e/c du coulis d‟injection et par de la largeur des fissures réparées.----------ABSTRACT To evaluate the modulus of rupture and the shear strength of mass concrete repaired by grout injection, six 400 x 400 x 1250 mm concrete specimens with a maximum aggregate size of 100 mm were tested following ASTM C78 and a loading configuration promoting large shear stresses along a vertical failure plane. ASTM C78 was done on the all virgin specimens and on repaired specimens (two repaired once and two repaired multiple times) using two different micro fine injection grout mixes with water cement ratio (w/c) of 1.0 and 0.5. The shear test was done on two single repaired and two multiple repaired specimens; with both grout mixes. Average indirect tensile strength of 2.8 MPa was obtained for virgin specimens. This value was reduced to 1 MPa and 0.5 MPa for specimens repaired using grout with a w/c ratio respectively equal to 0.5 and 1.0 regardless of the number of repairs. The shear strength of the specimens is affected by both the injection grouts w/c ratio and the repaired crack width

Semi-interpenetrating network photo-responsive hydrogels containing poly(ionic liquid)s

Poly(ionic liquid)s are a subclass of ionic liquids that feature polymerizable groups in either the anion, the cation or both. They are used as building blocks for a wide range of materials which can be used for a broad spectrum of applications, including conducting materials in solar cells, lithium rechargeable batteries, actuators and other electrochemical devices [1]. Poly(N-isopropylacrylamide) (pNiPAAm) is known to exhibit a lower critical solution temperature (LCST) in an aqueous medium [2]. By incorporating other co-monomers in the pNiPAAm network, such as spiropyran (SPA) photochromic units, materials which are both thermo- and photo-responsive can be synthesized [3]. By crosslinking a poly(ionic liquid), such as tributylhexylphosphonium 3-sulfopropylacrylate (PSPA), in the presence of linear poly(N-isopropylacrylamide-co-spiropyran-co-acrylic acid) (pNiPAAm-SPA-AA) copolymer, a semi-interpenetrating network (sIPN) was synthesized. The following research focuses on the synthesis and characterization of linear (pNiPAAm-SPA-AA) and its incorporation in a sIPN. A series of sIPN hydrogels have been synthesized, each having a different concentration of the (pNiPAAm-SPA-AA) linear copolymer, and their photo-response was analyzed in deionized water and in a series of NaCl solutions (0.5 wt%, 1 wt% and 5 wt%). For the sIPNs containing 100%, 200%, 300% and 400% w/w linear copolymer, the total area contraction after 30 min white light irradiation in deionized water was ≈3%, ≈6%, ≈10% and ≈13%. In conclusion, a linear p(NiPAAm-SPA-AA) copolymer was synthesized and incorporated in a crosslinked PSPA matrix to create photo-responsive sIPNs with finely tuned photo-actuation properties. References: [1] J. Yuan, D. Mecerreyes, M. Antonietti, Prog. Polym. Sci., 2013, 38, 1009-1036. [2] C. Boutris, E. G. Chatzi, C. Kiparissides, Polymer, 38 (1997) 2567-2570. [3] K. Sumaru, M. Kameda, T. Kanamori, T. Shinbo, Macromolecules, 37 (2004) 4949-4955

Committed to burnout: An investigation into the relationship between sport commitment and athlete burnout in Gaelic games players

This study examined the relationship between sports commitment, outlined in the hierarchical Sport Commitment Model, and athlete burnout in men and women playing Gaelic games, for the first time. These athletes experience a number of unique challenges, including playing with numerous teams simultaneously, significant personal commitment despite their amateur status, and the societal and cultural importance of their sports. This study also involved piloting a novel commitment measure of ‘team importance’ for team-sport athletes. Two-hundred-and-one male and female Gaelic games players completed the Sports Commitment Questionnaire, team importance measure and Athlete Burnout Questionnaire. Hierarchical Multiple Regression analyses revealed a negative relationship between sport enjoyment, social support (emotional) and desire to excel and particular burnout components; a positive relationship between other priorities and personal investments and particular burnout components; and enthusiastic commitment was associated with lower burnout, while constrained commitment was linked to higher burnout. The team importance measure was also found to be a reliable and valid measure of sports commitment. These findings provide important insight into how sports commitment can contribute to, or guard against, burnout in male and female athletes