Hamiltonian Formulation and Order Reduction for Nonlinear Splines in the Euclidean 3-Space

The authors use the procedure developed in [9] to develop a Hamiltonian structure into the variational problem given by the integral of the squared curvature on the spatial curves. The solutions of that problem are the elasticae or nonlinear splines. The symmetry of the problem under rigid motions is then used to reduce the Euler–Lagrange equations to a firstorder dynamical system

Variational first-order quasilinear equations.

The systems of first-order quasilinear partial differential equations defined on the 1-jet bundle of a fibred manifold which come from a variational problem defined by an affine Lagrangian are characterized by means of the Hamilton-Cartan formalism and the theory of formal integrability

Sublimable complexes with spin switching: Chemical design, processing as thin films and integration in graphene-based devices

Among the different types of switchable molecular compounds, sublimable Fe(II) SCO molecules provide a suitable platform to develop smart devices that respond to external stimuli. Here we report the synthesis, crystallographic structure and magnetic properties of three new neutral Fe(II) SCO molecules belonging to the {Fe[H2B(pz)2]2(L)} family with bidentate-alpha-diimine ligands L = 3-(pyridin-2-yl)-[1,2,3]triazolo[1,5-a]pyridine (tzpy), 5,5,6,6-tetrahydro-4H,4H-2,2-bi(1,3-thiazine) (btz) and 4,4,5,5-tetrahydro-2,2-bithiazole (bt) (1, 2 and 3, respectively), as well as two solvated forms of 1 and 3. All three desolvated compounds present thermal- and light-induced SCO transitions with different degrees of cooperativity and effectiveness. Furthermore, 1 and 2 are demonstrated to be sublimable under HV conditions affording homogeneous thin films 200 nm thick (TF1 and TF2) that retain the chemical integrity of the original molecules regardless the deposition surface. The SCO behaviour of the films is characterized by XAS technique revealing the partial retainment of both thermal- and light-induced spin transitions, yet losing the cooperativity. Finally, SCO/2D horizontal hybrid devices based on CVD-graphene are produced using these films. Being the first ones of this type utilizing molecules of {Fe[H2B(pz)2]2(L)} family, with L = tzpy and btz, the devices have allowed the successful detection of the thermal SCO transition through the electric properties of the CVD-graphene.Comment: 20 pages, 8 figure

Electrical sensing of the thermal and light induced spin transition in robust contactless spin-crossover/graphene hybrid devices

Hybrid devices based on spin-crossover (SCO)/2D heterostructures grant a highly sensitive platform to detect the spin transition in the molecular SCO component and tune the properties of the 2D material. However, the fragility of the SCO materials upon thermal treatment, light irradiation or contact with surfaces and the methodologies used for their processing have limited their applicability. Here, we report an easily processable and robust SCO/2D hybrid device with outstanding performance based on the sublimable SCO [Fe(Pyrz)2] molecule deposited over CVD-graphene, which is fully compatible with electronics industry protocols. Thus, a novel methodology based on growing an elusive polymorph of [Fe(Pyrz)2] (tetragonal phase) over graphene is developed that allows us to electrically detect a fast and effective light-induced spin transition in the devices (~50% yield in 5 minutes). Such performance can be enhanced even more when a flexible polymeric layer of PMMA is inserted in between the two active components in a contactless configuration, reaching a ~100 % yield in 5 minutes.Comment: 25 pages, 5 figure

Electrical sensing of the thermal and light induced spin transition in robust contactless spin-crossover/graphene hybrid devices

Hybrid devices based on spin-crossover (SCO)/2D heterostructures grant a highly sensitive platform to detect the spin transition in the molecular SCO component and tune the properties of the 2D material. However, the fragility of the SCO materials upon thermal treatment, light irradiation or contact with surfaces and the methodologies used for their processing have limited their applicability. Here, we report an easily processable and robust SCO/2D hybrid device with outstanding performance based on the sublimable SCO [Fe(Pyrz)2] molecule deposited over CVD-graphene, which is fully compatible with electronics industry protocols. Thus, a novel methodology based on growing an elusive polymorph of [Fe(Pyrz)2] (tetragonal phase) over graphene is developed that allows us to electrically detect a fast and effective light-induced spin transition in the devices (~50% yield in 5 minutes). Such performance can be enhanced even more when a flexible polymeric layer of PMMA is inserted in between the two active components in a contactless configuration, reaching a ~100 % yield in 5 minutes

Design and processing as ultrathin films of a sublimable Iron(II) spin crossover material exhibiting efficient and fast light-induced spin transition

Materials based on spin crossover (SCO) molecules have centred the attention in Molecular Magnetism for more than forty years as they provide unique examples of multifunctional and stimuli-responsive materials, which can be then integrated into electronic devices to exploit their molecular bistability. This process often requires the preparation of thermally stable SCO molecules that can sublime and remain intact in contact with surfaces. However, the number of robust sublimable SCO molecules is still very scarce. Here we report a novel example of this kind. It is based on a neutral iron (II) coordination complex formulated as [FeII(neoim)2], where neoimH is the ionogenic ligand 2-(1H-imidazol-2-yl)-9-methyl-1,10-phenanthroline. In the first part a comprehensive study, which covers the synthesis and magneto-structural characterization of the [FeII(neoim)2] complex as a bulk microcrystalline material, is reported. Then, in the second part we investigate the suitability of this material to form thin films through high vacuum (HV) sublimation. Finally, the retainment of all present SCO capabilities in the bulk when the material is processed is thoroughly studied by means of X-ray absorption spectroscopy. In particular, a very efficient and fast light-induced spin transition (LIESST effect) has been observed, even for ultrathin films of 15 nm.Comment: 27 pages, 2 schemes, 5 figures, 1 tabl

Sublimable complexes with spin switching: chemical design, processing as thin films and integration in graphene-based devices

Entre los diferentes tipos de compuestos moleculares conmutables, las moléculas SCO de Fe( II ) sublimables proporcionan una plataforma adecuada para desarrollar dispositivos inteligentes que respondan a estímulos externos. En este documento, presentamos la síntesis, la estructura cristalográfica y las propiedades magnéticas de tres nuevas moléculas neutras de Fe( II ) SCO pertenecientes a la familia {Fe[H 2 B(pz) 2 ] 2 (L)} con ligandos bidentado-α-diimina L = 3-(piridin-2-il)-[1,2,3]triazolo[1,5- a ]piridina (tzpy), 5,5′,6,6′-tetrahidro-4 H ,4′ H - 2,2′-bi(1,3-tiazina) (btz) y 4,4′,5,5′-tetrahidro-2,2′-bitiazol (bt) ( 1 , 2 y 3, respectivamente), así como dos formas solvatadas de 1 y 3 . Los tres compuestos desolvatados presentan transiciones de SCO inducidas por calor y luz con diferentes grados de cooperatividad y efectividad. Además, se ha demostrado que 1 y 2 son sublimables en condiciones HV, lo que proporciona películas delgadas homogéneas de 200 nm de espesor ( TF1 y TF2) que conservan la integridad química de las moléculas originales independientemente de la superficie de depósito. El comportamiento SCO de las películas se caracteriza por la técnica XAS que revela la retención parcial de las transiciones de espín inducidas por la luz y el calor, pero pierde la cooperatividad. Finalmente, los dispositivos híbridos horizontales SCO/2D basados ​​en CVD-grafeno se producen utilizando estas películas. Siendo los primeros de este tipo utilizando moléculas de la familia {Fe[H 2 B(pz) 2 ] 2 (L)}, con L = tzpy y btz, los dispositivos han permitido la detección exitosa de la transición térmica SCO a través de la Propiedades eléctricas del CVD-grafeno.Among the different types of switchable molecular compounds, sublimable Fe(II) SCO molecules provide a suitable platform to develop smart devices that respond to external stimuli. Herein, we report the synthesis, crystallographic structure and magnetic properties of three new neutral Fe(II) SCO molecules belonging to the {Fe[H2B(pz)2]2(L)} family with bidentate-α-diimine ligands L = 3-(pyridin-2-yl)-[1,2,3]triazolo[1,5-a]pyridine (tzpy), 5,5′,6,6′-tetrahydro-4H,4′H-2,2′-bi(1,3-thiazine) (btz) and 4,4′,5,5′-tetrahydro-2,2′-bithiazole (bt) (1, 2 and 3, respectively), as well as two solvated forms of 1 and 3. All three desolvated compounds present thermal- and light-induced SCO transitions with different degrees of cooperativity and effectiveness. Furthermore, 1 and 2 are demonstrated to be sublimable under HV conditions, affording homogeneous thin films 200 nm thick (TF1 and TF2) that retain the chemical integrity of the original molecules regardless of the deposition surface. The SCO behaviour of the films is characterized by the XAS technique revealing the partial retainment of both thermal- and light-induced spin transitions, yet losing the cooperativity. Finally, SCO/2D horizontal hybrid devices based on CVD-graphene are produced using these films. Being the first ones of this type utilizing molecules of the {Fe[H2B(pz)2]2(L)} family, with L = tzpy and btz, the devices have allowed the successful detection of the thermal SCO transition through the electric properties of CVD-graphene

The mersade (European Union) project: testing procedures and environmental impact for the safe storage of liquid mercury in the Almadén district, Spain.

The MERSADE Project (LIFE--European Union) tested the Las Cuevas decommissioned mining complex (Almadén mercury district, Spain) as a potential site for the installation of a future European prototype safe deposit of surplus mercury from industrial activities. We here present the results of a baseline study on the distribution of mercury in soils and air in the Las Cuevas complex and surrounding areas, and show the results of a plume contamination model using the ISC-AERMOD software. Despite restoration works carried out in 2004, the Las Cuevas complex can still be regarded as hotspot of mercury contamination, with large anomalies above 800 microg g(-1) Hg (soils) and 300 ng Hg m(-3) (air). In the case of soils, high, and persistent concentrations above 26 microg g(-1) Hg extend well beyond the complex perimeter for more than 2 km. These concentrations are about three orders of magnitude above world baselines. The same applies to mercury in air, with high concentrations above 300 ng Hg m(-3) inside the perimeter, which nonetheless fade away in a few hundred meters. Air contamination modelling (Hg gas) predicts formation of a NW-SE oriented narrow plume extending for a few hundred meters from the complex perimeter. The geographic isolation of Las Cuevas and its mining past make the complex an ideal site for mercury stocking. The only potential environmental hazards are the raising of livestock only a few hundred meters away from the complex and flash floods