Driving rate effects in avalanche-mediated, first-order phase transitions

We have studied the driving rate and temperature dependence of the power-law exponents that characterize the avalanche distribution in first-order phase transitions. Measurements of acoustic emission in structural transitions in Cu-Zn-Al and Cu-Al-Ni are presented. We show how the observed behaviour emerges within a general framework of competing time scales of avalanche relaxation, driving rate, and thermal fluctuations. We have confirmed our findings by numerical simulations of a prototype model.Comment: 4 pages, 3 figure

Training-induced criticality in martensites

We propose an explanation for the self-organization towards criticality observed in martensites during the cyclic process known as `training'. The scale-free behavior originates from the interplay between the reversible phase transformation and the concurrent activity of lattice defects. The basis of the model is a continuous dynamical system on a rugged energy landscape, which in the quasi-static limit reduces to a sandpile automaton. We reproduce all the principal observations in thermally driven martensites, including power-law statistics, hysteresis shakedown, asymmetric signal shapes, and correlated disorder.Comment: 5 pages, 4 figure

Acoustic emission across the magnetostructural transition of the giant magnetocaloric Gd5Si2Ge2 compound

We report on the existence of acoustic emission during the paramagnetic-monoclinic to ferromagnetic-orthorhombic magnetostructural phase transition in the giant magnetocaloric Gd5Si2Ge2 compound. The transition kinetics have been analyzed from the detected acoustic signals. It is shown that this transition proceeds by avalanches between metastable states.Comment: 5 pages, 4 figure

Driving-induced crossover: from classical criticality to self-organized criticality

We propose a spin model with quenched disorder which exhibits in slow driving two drastically different types of critical nonequilibrium steady states. One of them corresponds to classical criticality requiring fine-tuning of the disorder. The other is a self-organized criticality which is insensitive to disorder. The crossover between the two types of criticality is determined by the mode of driving. As one moves from "soft" to "hard" driving the universality class of the critical point changes from a classical order-disorder to a quenched Edwards-Wilkinson universality class. The model is viewed as prototypical for a broad class of physical phenomena ranging from magnetism to earthquakes.Comment: 4 pages, 4 figure

Quality More Than Quantity: The Use of Carbohydrates in High-Fat Diets to Tackle Obesity in Growing Rats

This research was supported by funds provided by the Abbott Laboratories S.A.Childhood obesity prevention is important to avoid obesity and its comorbidities into adulthood. Although the energy density of food has been considered a main obesogenic factor, a focus on food quality rather that the quantity of the different macronutrients is needed. Therefore, this study investigates the effects of changing the quality of carbohydrates from rapidly to slowly digestible carbohydrates on metabolic abnormalities and its impact on obesity in growing rats fed a high-fat diet (HFD). Growing rats were fed on HFD containing carbohydrates with different digestion rates: a HFD containing rapid-digesting carbohydrates (OBE group) or slow-digesting carbohydrates (ISR group), for 4 weeks and the effect on the metabolism and signaling pathways were analyzed in different tissues. Animals from OBE group presented an overweight/obese phenotype with a higher body weight gain and greater accumulation of fat in adipose tissue and liver. This state was associated with an increase of HOMA index, serum diacylglycerols and triacylglycerides, insulin, leptin, and pro-inflammatory cytokines. In contrast, the change of carbohydrate profile in the diet to one based on slow digestible prevented the obesity-related adverse effects. In adipose tissue, GLUT4 was increased and UCPs and PPARg were decreased in ISR group respect to OBE group. In liver, GLUT2, FAS, and SRBP1 were lower in ISR group than OBE group. In muscle, an increase of glycogen, GLUT4, AMPK, and Akt were observed in comparison to OBE group. In conclusion, this study demonstrates that the replacement of rapidly digestible carbohydrates for slowly digestible carbohydrates within a highfat diet promoted a protective effect against the development of obesity and its associated comorbidities.Abbott Laboratories S.A

Single chain variable fragment fused to maltose binding protein: a modular nanocarrier platform for the targeted delivery of antitumorals

This work was supported by grants CTQ2014-55474-C2-1-R, CTQ2014-55474-C2-2-R and CTQ2017-86125-P from the Ministerio Economia, Industria y Competitividad (co-financed by FEDER funds). SP is supported by a FPU fellowship (FPU17/ 04749). We acknowledge the University of Granada (Spain) cell culture, animal and microscopy central facilities (CIC-UGR).The use of the specific binding properties of monoclonal antibody fragments such as single-chain variable fragments (ScFv) for the selective delivery of antitumor therapeutics for cancer cells is attractive due to their smaller size, low immunogenicity, and low-cost production. Although covalent strategies for the preparation of such ScFv-based therapeutic conjugates are prevalent, this approach is not straightforward, as it requires prior chemical activation and/or modification of both the ScFv and the therapeutics for the application of robust chemistries. A non-covalent alternative based on ScFv fused to maltose-binding protein (MBP) acting as a binding adapter is proposed for active targeted delivery. MBP-ScFv proves to be a valuable modular platform to synergistically bind maltose-derivatized therapeutic cargos through the MBP, while preserving the targeting competences provided by the ScFv. The methodology has been tested by using a mutated maltose-binding protein (MBP I334W) with an enhanced affinity toward maltose and an ScFv coding sequence toward the human epidermal growth factor receptor 2 (HER2). Non-covalent binding complexes of the resulting MBP-ScFv fusion protein with diverse maltosylated therapeutic cargos (a near-infrared dye, a maltosylated supramolecular beta-cyclodextrin container for doxorubicin, and non-viral polyplex gene vector) were easily prepared and characterized. In vitro and in vivo assays using cell lines that express or not the HER2 epitope, and mice xenografts of HER2 expressing cells demonstrated the capability and versatility of MBP-ScFv for diagnosis, imaging, and drug and plasmid active targeted tumor delivery. Remarkably, the modularity of the MBP-ScFv platform allows the flexible interchange of both the cargos and the coding sequence for the ScFv, allowing ad hoc solutions in targeting delivery without any further optimization since the MBP acts as a pivotal element.Ministerio Economia, Industria y Competitividad - FEDER funds CTQ2014-55474-C2-1-R CTQ2014-55474-C2-2-R CTQ2017-86125-PSpanish Government FPU17/0474

CiTiEs (Ciudades: Tiempo + Espacio) Diseño e implementación de materiales didácticos para la enseñanza virtual del Patrimonio cultural de Madrid a través de la flipped classroom

Se han diseñado e implementado materiales digitales para la Educación patrimonial de Madrid, dirigidos a estudiantes de varias asignaturas. Para su utilización, se ha utilizado preferentemente el "aula invertida" (flipped classroom), adaptándose a las circunstancias excepcionales del curso académico 2020-21

CiTiEs (Ciudades: Tiempo + Espacio). Implementación de itinerarios didácticos para la enseñanza virtual y presencial del Patrimonio cultural de Madrid a través del aprendizaje cooperativo

Retomando los itinerarios didácticos diseñados en un PID anterior (2019/20, nº 363), se implementarán materiales digitales para la Educación patrimonial de Madrid. Se utilizarán técnicas de aprendizaje cooperativo y recursos para la enseñanza virtual.Depto. de Didáctica de las Ciencias Experimentales , Sociales y MatemáticasFac. de EducaciónFALSEsubmitte

Experimentos y modelos en sistemas que presentan transiciones de fase de primer orden con dinámica de avalanchas

[spa] En esta tesis se han estudiado algunos aspectos de sistemas que presentan transiciones de fase. Para ello se ha empleado tanto un enfoque experimental como teórico. En particular, se han investigado algunas transiciones de fase de primer orden que tienen lugar con una dinámica de avalanchas. Tal dinámica se observa en numerosas transiciones de fase (efecto Barkhausen en sistemas magnéticos o transición martensítica en sólidos) en que los efectos de las fluctuaciones térmicas no son muy importantes. La tesis se estructura básicamente en tres partes. La primera (capítulos 1 y 2) es una introducción a diversos aspectos generales que son importantes para el resto de la tesis. En el capítulo 1 se hace una introducción general de las transiciones de fase más comunes y también de aquellas en que los efectos del desorden presente son importantes. Esto lleva de forma natural a la definición del concepto de avalancha. Dentro de este mismo capítulo se dedica un apartado a conceptos generales de la transición martensítica ya que es una de las transiciones que se ha estudiado experimentalmente en esta tesis. El capítulo 2 introduce algunos conceptos fundamentales sobre el comportamiento de los sistemas que se encuentran cerca de una transición de fase de segundo orden. En dicho capítulo se introduce el Grupo de Renormalización y los métodos de escalado de tamaño finito que son importantes para analizar los resultados de nuestras simulaciones numéricas. En la segunda parte (capítulos 3-5) se presentan los resultados teóricos de la tesis. En primer lugar, en el capítulo 3 se estudia el efecto de las fluctuaciones térmicas en las transiciones de primer orden y se establece en qué condiciones se puede considerar que las fluctuaciones no son relevantes en la transición (transiciones atérmicas). En los dos capítulos siguientes (capítulos 4 y 5) se presenta un análisis extenso de las propiedades de las avalanchas observadas en el modelo de Ising con campos aleatorios en condiciones atérmicas. En la tercera parte de la tesis (capítulos 6-10) se estudian diversos aspectos relacionados con la cinética de las transiciones estructurales en estado sólido (básicamente la transición martensítica en aleaciones con memoria de forma). Antes de presentar los resultados experimentales propiamente dichos, en el capítulo 6 se describen las técnicas experimentales utilizadas, haciendo especial hincapié en la emisión acústica ya que ésta es la técnica que más se ha utilizado en nuestro caso para caracterizar las transiciones estructurales. Tras esta descripción introductoria, en el capítulo 7 se analiza, sobre la base de los modelos propuestos en el capítulo 3, el efecto de las fluctuaciones térmicas en la transición martensítica en aleaciones con memoria de forma. En el capítulo siguiente se estudia el efecto del ciclado térmico en la transición martensítica en el mismo tipo de aleaciones. En el capítulo 9 se analiza cuál es el efecto del ritmo al que se inducen las transiciones de fase de primer orden sobre las avalanchas que se observan. En este mismo capítulo se analiza también el efecto que tienen las fluctuaciones térmicas sobre dichas avalanchas. Finalmente, en el capítulo 10, se presentan los resultados de un estudio sobre la cinética de las transiciones martensítica y premartensítica que se observan en aleaciones de Ni-Mn-Ga. Como conclusión general de la tesis, podríamos decir que los resultados obtenidos han aclarado algunos aspectos de las transiciones de fase de primer orden y han permitido entender algunas propiedades de dichas transiciones con mayor profundidad.[eng] OF THE THESIS This thesis have been devoted to study some aspects of systems exhibiting phase transitions. In particular, we have focused our analysis on those systems in which the transition involves an avalanche dynamics (some magnitudes evolve in a discontinuous way during the phase transition). Such a dynamics has been observed to occur in several phase transitions (Barkhausen effect in magnetic systems or martensitic transition in solids) in which thermal fluctuations does not play a relevant role. The analyzed issues in this thesis can be classified into two groups: study of the kinetics of structural phase transitions (mainly martensitic transition in shape memory alloys) and analysis of first-order phase transitions in disordered systems. Concerning the study of the structural phase transitions, we have analyzed (i) the effect of thermal fluctuations, (ii) the effect of thermal cycling, and (iii) the driving rate effects on the observed avalanches. Our results indicate that (i) thermally activated effects are difficult to observe under certain conditions, (ii) thermal cycling induces a learning process towards a reproducible behaviour, and (iii) the exponents characterizing the power-law distributions in first-order phase transitions show a non-monotonous dependence with the driving rate. Concerning the study of disordered systems, we have analysed in a detailed way the behaviour of the random field Ising model obeying a metastable dynamics (athermal and adiabatic) when an external applied field changes. We have performed numerical simulations to study the model and the obtained data have been analysed in terms of sophisticated finite-size scaling hypothesis. The studied model shows a disorder-induced continuous phase transition on the metastable phase diagram. Our study has allowed for a better understanding of several aspects of this model as, for example, the geometrical properties of the avalanches in the thermodynamic limit and the identification of the order parameter