EPR Sensing of a Cation Species by Aza-Crown Ethers Incorporating a Persistent Nitroxidic Radical Unit

New nitroxides based on aza-crown ethers were prepared and employed as selective sensors for the detection of inorganic and organic cations by EPR analysis of the corresponding host-guest complexes. The nitroxide unit behaves as a sensitive probe for a number of alkali and alkaline earth metal cations affording EPR spectra differing in the value of nitrogen hyperfine constants and in the appearance of splitted signals due to the non-zero nuclear spin of some metal cation upon complexation. Owing to the remarkable EPR spectral differences between the host and the corresponding cation complex the new macrocycles are likely to act as multitasking tools to recognize several cationic species. EPR behaviour of the larger nitroxide azacrown 1(center dot) when acting as a wheel in a radical synthetic bistable [2]rotaxane containing both secondary dialkylammonium and 1,2-bis(pyridinium) molecular stations, was also investigated. Reversible movements of the macrocycle between the two recognition sites in the rotaxane were promptly revealed by EPR, which shows significant changes either in nitrogen coupling constant values (a(N)) or in the spectral shape in the two rotaxane co-conformations

Commoning Design and Designing Commons

This workshop explores the relevance of the notion of commons as an objective, and commoning as a way of doing and being for design. We invite the PD community to reflect on ways in which these concepts help us critically protect and support sustainable futures for communities of humans and non-humans. How can participatory design remain open to multiple ways of sharing and different worldviews? What would it mean for the participatory design community in terms of challenging established notions such as participation, facilitation, empowerment, to name but a few? How can participatory design contribute further to theoretical elaboration and activist practices?</p

2-Cyano-2-phenylpropanoic Acid Triggers the Back and Forth Motions of an Acid-Base-Operated Paramagnetic Molecular Switch

The back and forth motions of a crown-ether based wheel along the axis of a bistable rotaxane are triggered by the decarboxylation of 2-cyano-2-phenylpropanoic acid and detected by the oscillation of the EPR nitrogen splitting of a dialkyl nitroxide function mounted within the macrocyclic ring. When the p-Cl derivative of the acid is used, back and forth motions are accelerated. Conversely, with p-CH3 and p-OCH3 derivatives, the back motion is strongly inhibited by the insurgence of collateral radical reactions

2-Cyano-2-phenylpropanoic acid triggers the back and forth motions of an acid-base-operated paramagnetic molecular switch

The back and forth motions of a crown-ether based wheel along the axis of a bistable rotaxane are triggered by the decarboxylation of 2-cyano-2-phenylpropanoic acid and detected by the oscillation of the EPR nitrogen splitting of a dialkyl nitroxide function mounted within the macrocyclic ring. When the p-Cl derivative of the acid is used, back and forth motions are accelerated. Conversely, with p-CH3 and p-OCH3 derivatives, the back motion is strongly inhibited by the insurgence of collateral radical reactions

An in vitro study on the adhesion of quartz fiber posts to radicular dentin

Purpose: To evaluate in vitro the bond strength at the adhesive interface between a quartz fiber post, different adhesive systems, and different composite cements. Materials and Methods: Thirty extracted single-rooted teeth were endodontically treated and divided into three groups (n = 10). Quartz fiber posts (DT Light-Post) were cemented with the following materials: group I: Prime & Bond NT + Self Cure Activator, and Calibra as luting cement; group II: Prime & Bond NT + Self Cure Activator, and UniFil Core; group III: UniFil Bond in combination with Unifil Core. The specimens were processed for the push-out test to evaluate bond strength at the root dentin-cement-post interface. They were sectioned along the long axis of the post into 1-mm-thick slices. A total of 60 sections was obtained from group I. Group II provided 67 slices, while group III provided 69. Loading was performed at a crosshead speed of 0.5 mm/min until the post segment was dislodged from the root section. Results: There was no statistically significant difference between the three experimental groups. The mean bond strength obtained for group I was 9.81 ± 5.40 MPa. For group II it was 12.06 ± 6.25 MPa, and 9.80 ± 5.01 MPa for group III. Conclusion: All the materials tested were similar in terms of providing satisfactory bond strength when used for luting fiber posts. However, Unifil Core may be advantageous since it can also be used as a core buildup material, which simplifies the clinical procedures. Keywords: dental adhesives, resin cements, fiber posts, bond strength, push-out test

An in vitro study on the adhesion of quartz fiber posts to radicular dentin

Purpose: To evaluate in vitro the bond strength at the adhesive interface between a quartz fiber post, different adhe- sive systems, and different composite cements. Materials and Methods: Thirty extracted single-rooted teeth were endodontically treated and divided into three groups (n = 10). Quartz fiber posts (DT Light-Post) were cemented with the following materials: group I: Prime & Bond NT + Self Cure Activator, and Calibra as luting cement; group II: Prime & Bond NT + Self Cure Activator, and UniFil Core; group III: UniFil Bond in combination with Unifil Core. The specimens were processed for the push-out test to evaluate bond strength at the root dentin-cement-post interface. They were sectioned along the long axis of the post into 1-mm-thick slices. A total of 60 sections was obtained from group I. Group II provided 67 slices, while group III provided 69. Load- ing was performed at a crosshead speed of 0.5 mm/min until the post segment was dislodged from the root section. Results: There was no statistically significant difference between the three experimental groups. The mean bond strength obtained for group I was 9.81 ± 5.40 MPa. For group II it was 12.06 ± 6.25 MPa, and 9.80 ± 5.01 MPa for group III. Conclusion: All the materials tested were similar in terms of providing satisfactory bond strength when used for luting fiber posts. However, Unifil Core may be advantageous since it can also be used as a core buildup material, which sim- plifies the clinical procedures