Complete Set of Elastic Moduli of a Spin-Crossover Solid: Spin-State Dependence and Mechanical Actuation.

Molecular spin crossover complexes are promising candidates for mechanical actuation purposes. The relationships between their crystal structure and mechanical properties remain, however, not well understood. In this study, combining high pressure synchrotron X-ray diffraction, nuclear inelastic scattering, and micromechanical measurements, we assessed the effective macroscopic bulk modulus ( B = 11.5 ± 1.5 GPa), Young's modulus ( Y = 10.9 ± 1.0 GPa), and Poisson's ratio (ν = 0.34 ± 0.04) of the spin crossover complex [FeII(HB(tz)3)2] (tz = 1,2,4-triazol-1-yl). Crystal structure analysis revealed a pronounced anisotropy of the lattice compressibility, which was correlated with the difference in spacing between the molecules as well as by the distribution of the stiffest C-H···N interactions in different crystallographic directions. Switching the molecules from the low spin to the high spin state leads to a remarkable drop of the Young's modulus to 7.1 ± 0.5 GPa both in bulk and thin film samples. The results highlight the application potential of these films in terms of strain (ε = -0.17 ± 0.05%), recoverable stress (σ = -21 ± 1 MPa), and work density ( W/V = 15 ± 6 mJ/cm3).

A Bistable Microelectromechanical System Actuated by Spin-Crossover Molecules.

We report on a bistable MEMS device actuated by spin-crossover molecules. The device consists of a freestanding silicon microcantilever with an integrated piezoresistive detection system, which was coated with a 140 nm thick film of the [Fe(HB(tz)3 )2 ] (tz=1,2,4-triazol-1-yl) molecular spin-crossover complex. Switching from the low-spin to the high-spin state of the ferrous ions at 338 K led to a reversible upward bending of the cantilever in agreement with the change in the lattice parameters of the complex. The strong mechanical coupling was also evidenced by the decrease of approximately 66 Hz in the resonance frequency in the high-spin state as well as by the drop in the quality factor around the spin transition.

Current Switching Coupled to Molecular Spin-States in Large-Area Junctions.

The fabrication of large-area vertical junctions with a molecular spin-crossover complex displaying concerted changes of spin degrees of freedom and charge-transport properties is reported. Fabricated devices allow spin-state switching in the spin-crossover layer to be triggered and probed by optical means, while detecting associated changes in electrical resistance in the junctions.

In Situ AFM Imaging of Microstructural Changes Associated with The Spin Transition in [Fe(Htrz)2(Trz)](Bf4) Nanoparticles.

Topographic images of [Fe(Htrz)2(trz)](BF4) nanoparticles were acquired across the first-order spin transition using variable-temperature atomic force microscopy (AFM) in amplitude modulation mode. These studies revealed a complex morphology of the particles consisting of aggregates of small nanocrystals, which expand, separate and re-aggregate due to the mechanical stress during the spin-state switching events. Both reversible (prompt or slow recovery) and irreversible effects (fatigue) on the particle morphology were evidenced and correlated with the spin crossover properties.

Adecuación de los alimentos grasos envasados a la normativa de rotulación nutricional argentina / No disponible

Objetivo: Constatar la adecuación actual del rotulado de losalimentos grasos envasados en la República Argentina a partirde la obligatoriedad del rotulado nutricional en las etiquetasde los alimentos, vigente a partir de 1 de agosto de 2006.Método: Se analizaron 95 etiquetas de 7 grupos de alimentosgrasos más consumidos en Argentina, estudiándose la presentaciónde la información obligatoria en el rótulo, según lo queestablece el Capítulo V del Código Alimentario Argentino.Resultados: El 74% de las etiquetas de los alimentos grasospresentaron datos relativos a la información obligatoriamenteestablecida. La declaración de nutrientes fue correctamenteaportada por el 75% de los alimentos que presentaron el rotuladonutricional en sus etiquetas. El 48% de los alimentos presentaroninformación nutricional complementaria u opcional, pero tansólo el 22% de los mismos cumplió con la legislación vigente.Los alimentos que menos cumplieron la normativa de rotuladonutricional fueron los aceites y los rocíos vegetales.Conclusiones: El etiquetado de los alimentos grasos envasadosen Argentina cumplió mayoritariamente con la información obligatoriaestablecida, excepto en lo que se refiere a la presentacióndel rotulado nutricional. Se recomienda extremar la vigilanciadel cumplimiento de la reglamentación, así como incrementarel nivel de educación nutricional de los consumidores(AU)

Aims: To assess the adequacy of packed fatty food labelsto the mandatory nutritional labelling in Argentina, since ithas been forced in August 1st 2006.Method: The present study analyzed 95 labels comprising7 different fatty foods most consumed in Argentina. Mandatoryinformation on labels, according to the Chapter V ofArgentinean Alimentary Code, has been studied.Results: Mandatory information has been provided by 74%of the fatty food labels. Right nutritional information wasjust provided by 75% of those foods that showed nutritionallabelling. Complementary nutritional information (optional)was provided by 48% of foods, but just 22% of foods fulfilledthe food labelling regulation. The highest defaults wereobserved in vegetable oils and vegetable oil sprays.Conclusions: The mandatory labelling according to theArgentinean food labelling regulation was highly fulfilled byfatty foods, excluding the nutritional labelling. To observe thecompliance of nutritional labelling regulation in Argentina,as well as to increase the nutritional education of consumersis recommended(AU)