First order transitions by conduction calorimetry: Application to deuterated potassium dihydrogen phosphate ferroelastic crystal under uniaxial pressure

The specific heat c and the heat power W exchanged by a Deuterated Potassium Dihydrogen Phosphate ferroelectric-ferroelastic crystal have been measured simultaneously for both decreasing and increasing temperature at a low constant rate (0.06 K/h) between 175 and 240 K. The measurements were carried out under controlled uniaxial stresses of 0.3 and 4.5±0.1 bar applied to face (110). At Tt=207.9 K, a first order transition is produced with anomalous specific heat behavior in the interval where the transition heat appears. This anomalous behavior is explained in terms of the temperature variation of the heat power during the transition. During cooling, the transition occurs with coexistence of phases, while during heating it seems that metastable states are reached. Excluding data affected by the transition heat, the specific heat behavior agrees with the predictions of a 2-4-6 Landau potential in the range of 4–15 K below Tt while logarithmic behavior is obtained in the range from Tt to 1 K below Tt. Data obtained under 0.3 and 4.5 bar uniaxial stresses exhibit the same behavior.Dirección General de Investigación Científica y Técnica. Gobierno de España-PB91-60

Phase coexistence in highly deuterated ferroelectric triglycine selenate: Landau description

The phase transition in a 90% deuterated sample of TGSe has been investigated by calorimetric and dielectric measurements. As a consequence of the presence of an internal crack in the sample, the transition takes place in two stages separated by an interval where the paraelectric and the ferroelectric phases coexist without latent heat contribution. From the latent heat, the specific heat excess and the Curie law for the dielectric constant, it is shown that the transition follows a 2-4-6 Landau potential, whose coefficients are determined. This potential describes completely all the data, including those corresponding to the coexistence interval.Dirección General de Investigación Científica y Técnica (DGICYT) FIS2005-0244

Deuteration effect on tricritical phase transition of triglycine selenate: Calorimetric and dielectric measurements analyzed in the framework of Landau theory

The ferroelectric phase transition of three single crystals of TGSe1−x DTGSex has been described by using specific heat, latent heat, and dielectric permittivity measurements. Pure, half-deuterated, and highly-deuterated TGSe single crystals were analyzed. Transition temperature and latent heat increase with increasing deuteration. Irrespective of the degree of deuteration, a 2-4-6 Landau model is suitable to describe the phase transition. The fourth-rank prefactor in Landau potential is found to be very sensitive to deuteration while the second-rank and the sixth-rank prefactors smoothly change with composition. The pyroelectric figure of merit for these materials has also been derived from the theoretical model.Gobierno de España-FIS2006-0404

Scale-invariant avalanche dynamics in the temperature-driven martensitic transition of a Cu-Al-Be single crystal

We have combined high sensitivity, extra-low differential temperature scanning rate calorimetry, and acoustic emission (AE) measurements to study avalanches during the cubic ↔ 18R martensitic transition of a Cu-Al-Be single crystalline shape memory alloy. Both AE and calorimetry corroborate a good power-law behavior for cooling with an exponent ε 1.6. For heating, a slope is observed in the maximum likelihood curves, which confirms that our data are affected by an exponential cutoff. An effective energy exponent, ε ∼ 1.85, and a cutoff, λ −1 = 0.115(38)E-3 aJ, were determined by fits of power-laws with exponential damping. The long tail observed in the low-temperature region by calorimetric measurements suggests the existence of significant elastic effects that constrain the progress of the transformation at low temperatures. While thermodynamic features such as transformation enthalpy and entropy are those expected for Cu-based shape-memory alloys undergoing a cubic ↔ 18R transition, the critical behavior deviates from the corresponding behavior expected from this symmetry change. These deviations are a consequence of the elastic hardening induced by the interplay of the transformation with dislocation jamming, which has the effect of effectively reducing the number of pathways connecting the parent and martensitic phaseMinisterio de Ciencia,Innovación y Universidades (MAT2016-75823-R)Engineering and Physical Sciences Research Council (EP/P024904/1

La enseñanza problémica y el desarrollo del razonamiento en la disciplina Informática Médica

Introducción: En el proceso de enseñanza aprendizaje de la disciplina Informática Médica es necesario utilizar métodos de enseñanza dirigidos a la comprensión consciente de los diferentes contenidos y al desarrollo del razonamiento en los estudiantes. Los métodos de la enseñanza problémica estén dirigidos a estimular y desarrollar los procesos lógicos del pensamiento, por lo que se requiere la utilización de los mismos.Objetivo: Diseñar acciones para la utilización de la enseñanza problémica en el proceso de enseñanza aprendizaje de la disciplina Informática Médica.Método: Se realizó una investigación de desarrollo en la Facultad de Ciencias Médicas de Holguín, de septiembre a diciembre del 2017. Se aplicaron métodos teóricos para fundamentar el problema. Se utilizaron métodos del nivel teórico, así como el análisis de documentos de diferentes informes. Dentro de los métodos empíricos se utilizó la observación y la encuesta.Resultados: Se expone la esencia de los métodos problémicos: la exposición problémica, la búsqueda parcial, la conversación heurística y el método investigativo. Se propone un conjunto de acciones para utilizar los métodos de la enseñanza problémica en el proceso de enseñanza aprendizaje de la disciplina Informática Médica.Conclusiones: Para lograr que los estudiantes adquieran formas adecuadas de razonamiento en la solución de situaciones de salud se requiere el empleo de métodos activos de apropiación del conocimiento, que permitan que el estudiante alcance niveles de asimilación productivos.Palabras claves: enseñanza problémica; proceso de enseñanza aprendizaje; razonamiento; Informática Médica.</p

Memory effect in triglycine sulfate induced by a transverse electric field: specific heat measurement

The influence of a transverse electric field on the specific heat of triglycine sulfate (TGS) has been studied. The specific heat of TGS has been measured on heating the sample from the ferroelectric to the paraelectric phase after prolonged application of transverse electric field (i.e. perpendicular to the ferroelectric axis). It is shown that the specific heat of TGS can 'remember' the temperature T(s) at which the transverse field was previously applied.España, Gobierno de España IS-2006-0404

Dynamic heat flux experiments in Cu67.64Zn 16.71Al15.65: Separating the time scales of fast and ultra-slow kinetic processes in martensitic transformations

Crackling noise and avalanches during the martensite phase transformation of Cu67.64Zn16.71Al15.65 were investigated. Heat flux measurements with extremely slow heating rates of 0.005 Kh -1 allowed sufficient separation between the continuous background and the avalanche jerks. The jerk enthalpy is below 3 of the total transformation enthalpy. The crackling noise follows power law behavior with an energy exponent near ε=1.8. The jerks are almost uncorrelated with approximately a Poisson distribution of the waiting times between jerks. Quantitative analysis showed a scaling behavior with p(wt) ∼ wt (γ-1)exp(-wt/τ)n with γ=0.7 and n ≈ 1.Ministerio de Educación y Ciencia FIS2006-0404

Long-Term in vivo Evaluation of Orthotypical and Heterotypical Bioengineered Human Corneas

Purpose: Human cornea substitutes generated by tissue engineering currently require limbal stem cells for the generation of orthotypical epithelial cell cultures. We recently reported that bioengineered corneas can be fabricated in vitro from a heterotypical source obtained from Wharton’s jelly in the human umbilical cord (HWJSC). Methods: Here, we generated a partial thickness cornea model based on plastic compression nanostructured fibrin-agarose biomaterials with cornea epithelial cells on top, as an orthotypical model (HOC), or with HWJSC, as a heterotypical model (HHC), and determined their potential in vivo usefulness by implantation in an animal model. Results: No major side effects were seen 3 and 12 months after implantation of either bioengineered partial cornea model in rabbit corneas. Clinical results determined by slit lamp and optical coherence tomography were positive after 12 months. Histological and immunohistochemical findings demonstrated that in vitro HOC and HHC had moderate levels of stromal and epithelial cell marker expression, whereas in vivo grafted corneas were more similar to control corneas. Conclusion: These results suggest that both models are potentially useful to treat diseases requiring anterior cornea replacement, and that HHC may be an efficient alternative to the use of HOC which circumvents the need to generate cornea epithelial cell cultures.Spanish Plan Nacional de Investigacion Cientifica, Desarrollo e Innovacion Tecnologica (I CD Ci) from the Spanish Ministry of Science and Innovation: Instituto de Salud Carlos III FIS PI17/0391 FIS PI14/0955European Union (EU)Spanish Plan Nacional de Investigacion Cientifica, Desarrollo e Innovacion Tecnologica (I CD Ci) from the Spanish Ministry of Science and Innovation: Ministry of Science, Innovation and Universities of Spain PGC2018-101904-A-I00 RTC-2017-6696-

Substitute therapy of the sclera. Identification of the patologies and methodologies in the University Hospital of Granada (2014-2019)

Introducción: La esclera es un tejido avascular compuesto por tejido conectivo denso cuya función principal es proteger las estructuras intraoculares. Existen diversas patologías que ponen en riesgo la integridad de dicho tejido y, en consecuencia, pueden provocar terribles secuelas con un pronóstico nefasto. El tratamiento sustitutivo forma parte de la terapia de dicha patología, siendo el injerto de esclerótica cadáver una opción biocompatible y biomimética a valorar. El injerto de esclerótica de cadáver es un tejido de fácil acceso y con buenos resultados post-quirúrgicos por lo que no solo es usado en el ámbito de la patología escleral, sino que también es utilizado para cirugía de oculoplástica, glaucoma o de retina. No obstante, el peligro de transmisión de priones o el déficit de suministro en algunos países hacen que este tejido sea suplantado por otros tejidos o técnicas quirúrgicas. Métodos: Los objetivos de este estudio son identificar la patología esclerótica susceptible de terapia sustitutiva en los últimos 5 años en el complejo hospitalario universitario de Granada, identificar los métodos empleados como terapéutica sustitutiva en dicha patología y evaluar la práctica de dicha terapia en el contexto de la bibliografía existente al respecto. Para ello, se aplicó un diseño retrospectivo en el que se realizó una búsqueda en los archivos de la unidad de documentación clínica del Hospital Clínico San Cecilio y Hospital Virgen de las Nieves, de los cuales se obtuvieron 9 casos clínicos. Resultados: Entre los 9 casos clínicos, solo 4 fueron sometidos a tratamiento quirúrgico, y de estos, 3 de ellos a terapia sustitutiva por membrana amniótica o injerto escleral. En los 5 casos restantes no se llevó a cabo ninguna técnica quirúrgica, no obstante, podría ser de gran valor el uso del refuerzo con injerto de esclerótica en los casos con escleromalacia para evitar complicaciones futuras. La esclerótica procedente de cadáver se postula como una opción con unos resultados prometedores; sin embargo, las líneas de investigación actuales apuestan por el desarrollo de un sustituto basado en las ventajas de la fibrina agarosa que supla los puntos negativos del tejido donante.Introduction: The sclera is an avascular tissue composed of dense connective tissue whose main function is to protect intraocular structures. There are several pathologies that jeopardize the integrity of this tissue and, consequently, can cause terrible consequences with a dire prognosis. Substitute treatment is part of the therapy of this pathology, with the donor sclera graft being a biocompatible and biomimetic option to be evaluated. The donor sclera graft is an easily accessible tissue with good post-surgical results, so it is not only used in the field of scleral pathology, but also used for oculoplastic, glaucoma or retinal surgery. However, the danger of prion transmission or the supply deficit in some countries causes that, other tissues or surgical techniques supplant this tissue. Methods: The objectives of this study are to identify the sclerotic pathology susceptible of replacement therapy in the last 5 years in the university hospital of Granada, identify the methods used as a replacement therapy in this pathology and evaluate the practice of such therapy. A retrospective design was applied and a search was made in the archives of the clinical documentation unit of the San Cecilio Clinical Hospital and Virgen de las Nieves Hospital. There were 9 clinical cases found. Results: Among the nine clinical cases, only 4 were subjected to surgical treatment, and of these, three of them for replacement therapy of donor sclera or amniotic membrane. In the remaining 5 cases did not carry out any surgical technique, however, it could be of great value using reinforcement sclera graft in cases with scleromalacia to avoid further complications. Sclera from cadaver is postulated as an option with promising results; however, current research committed to the development of a substitute based on the advantages of fibrin agarose that mitigates the negative points of the donor tissue