Guía básica para el muestreo y preparado de huesos actuales y fósiles para estudios histológicos

The study of bone microstructure of fossil vertebrates (i.e., paleohistology) has demonstrated to be a very important source of paleobiological information. Paleohistological studies are based on the standardized analysis of petrographic thin sections. Although the development of new technologies (e.g., microtomography) have provided non-destructive procedures for the study the fossil tissues, thin sections are still the main source of information in paleohistology. In this contribution, we provide a detailed protocol for sampling and thin-sectioning preparation of bone tissue from both fossil and extant vertebrates. We describe the most common procedures for sampling and also some particularities related to variations in equipment and sampling techniques. The main goal of this contribution is to offer an alternative protocol for research teams of recent formation and/or with limited funding.El estudio de la microestructura ósea de vertebrados fósiles (i.e., paleohistología) ha demostrado ser una importante fuente de información paleobiológica. Los estudios paleohistológicos están basados en análisis estandarizados de secciones delgadas petrográficas. A pesar de que el desarrollo de nuevas tecnologías (e.g., microtomografía) ha proporcionado procedimientos no destructivos para el estudio de tejidos fósiles, las secciones delgadas continúan siendo la principal fuente de información paleohistológica. En esta contribución, proporcionamos un protocolo detallado para el muestreo y preparación de secciones delgadas de huesos de vertebrados tanto fósiles como vivientes. Se describen los procedimientos más comunes para la obtención de las muestras y se plantean diferencias particulares, las cuales están relacionadas con las variaciones del equipamiento y las técnicas de muestreo. El objetivo principal de esta contribución es proveer un protocolo alternativo para laboratorios en formación y/o con financiamiento limitado.Fil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; ArgentinaFil: Pereyra, Maria Eugenia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garrone, Mariana Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Ponce, Denis Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; ArgentinaFil: Navarro, Tamara Giselle. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; ArgentinaFil: González, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Militello, Mariano. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Luna, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Jannello, Juan. University of Cape Town; Sudáfric

Adquisición de imágenes en tres dimensiones mediante escaneo de superficie en paleontología de vertebrados: revisión de técnicas principales

Three-dimensional (3D) surface scanning includes techniques of image acquisition and image processing. Among the former, hardware devices (e.g., portable and non-portable scanners, camera) capture images from the target, whereas image processing is conducted via specialized software, in which acquired images are processed to merge them into a single 3D surface model. Image surface scanning comprises a wide variety of devices which incorporate different image acquisition techniques, all of them with potential high standards results. We describe four different scanning devices and techniques commonly used in vertebrate paleontology in order to compare them in terms of pros and cons, considering different variables, such as scanning time, post-processing time, costs and image resolution. The decision on which device to choose will depend on the budget available, the portability as well as the nature of the fossil material being analyzed (e.g., size, weight, accessibility). In the light of this, photogrammetry constitutes the image surface technique which fulfills these requirements, having the best cost-benefit relationship.El escaneo de superficie incluye técnicas de adquisición de imágenes y su procesamiento. La adquisición se lleva a cabo a través de diferentes dispositivos (e.g., escáneres portables y fijos, cámaras) que capturan imágenes del objetivo, mientras que el procesamiento se realiza a través de software especializado en el cual las imágenes adquiridas son procesadas para fusionarlas en una imagen simple en tres dimensiones. El escaneo en 3D en paleontología de vertebrados incluye una gran variedad de dispositivos que incorporan diferentes técnicas de adquisición de imágenes, los cuales son descriptos y comparados aquí, en términos de sus ventajas y desventajas, considerando el tiempo de escaneo y post-procesamiento, costos y calidad de imagen. La decisión de qué dispositivo elegir dependerá, principalmente, del presupuesto, la transportabilidad y de la naturaleza del material fósil a ser escaneado (e.g., tamaño, peso, accesibilidad). En este sentido, la fotogrametría constituye la técnica de escaneo de superficie que posee la mejor relación costo-beneficio.Facultad de Ciencias Naturales y Muse

Guía básica para el muestreo y preparado de huesos actuales y fósiles para estudios histológicos

The study of bone microstructure of fossil vertebrates (i.e. paleohistology) has demonstrated to be a very important source of paleobiological information. Paleohistological studies are based on the standardized analysis of petrographic thin sections. Although the development of new technologies (e.g. microtomography) have provided non-destructive procedures for the study the fossil tissues, thin sections are still the main information source in paleohistology. In this contribution, we provide a detailed protocol for sampling and thin sectioning preparation of bone tissue from both fossil and extant vertebrates. We describe the most common procedures for sample obtainment and also some particular differences, which are related to variations in the equipment and sampling techniques. The main objective of this contribution is to offer an alternative protocol for laboratories in formation and/or with limited funding.El estudio de la microestructura ósea de vertebrados fósiles (i.e., paleohistología) ha demostrado ser una importante fuente de información paleobiológica. Los estudios paleohistológicos están basados en análisis estandarizados de secciones delgadas petrográficas. A pesar de que el desarrollo de nuevas tecnologías (e.g., microtomografía) ha proporcionado procedimientos no destructivos para el estudio de tejidos fósiles, las secciones delgadas continúan siendo la principal fuente de información paleohistológica. En esta contribución, proporcionamos un protocolo detallado para el muestreo y preparación de secciones delgadas de huesos de vertebrados tanto fósiles como vivientes. Se describen los procedimientos más comunes para la obtención de las muestras y se plantean diferencias particulares, las cuales están relacionadas con las variaciones del equipamiento y las técnicas de muestreo. El objetivo principal de esta contribución es proveer un protocolo alternativo para laboratorios en formación y/o con financiamiento limitado.Facultad de Ciencias Naturales y MuseoConsejo Nacional de Investigaciones Científicas y Técnica

The role of ETG modes in JET-ILW pedestals with varying levels of power and fuelling

We present the results of GENE gyrokinetic calculations based on a series of JET-ITER-like-wall (ILW) type I ELMy H-mode discharges operating with similar experimental inputs but at different levels of power and gas fuelling. We show that turbulence due to electron-temperature-gradient (ETGs) modes produces a significant amount of heat flux in four JET-ILW discharges, and, when combined with neoclassical simulations, is able to reproduce the experimental heat flux for the two low gas pulses. The simulations plausibly reproduce the high-gas heat fluxes as well, although power balance analysis is complicated by short ELM cycles. By independently varying the normalised temperature gradients (omega(T)(e)) and normalised density gradients (omega(ne )) around their experimental values, we demonstrate that it is the ratio of these two quantities eta(e) = omega(Te)/omega(ne) that determines the location of the peak in the ETG growth rate and heat flux spectra. The heat flux increases rapidly as eta(e) increases above the experimental point, suggesting that ETGs limit the temperature gradient in these pulses. When quantities are normalised using the minor radius, only increases in omega(Te) produce appreciable increases in the ETG growth rates, as well as the largest increases in turbulent heat flux which follow scalings similar to that of critical balance theory. However, when the heat flux is normalised to the electron gyro-Bohm heat flux using the temperature gradient scale length L-Te, it follows a linear trend in correspondence with previous work by different authors

Spectroscopic camera analysis of the roles of molecularly assisted reaction chains during detachment in JET L-mode plasmas

The roles of the molecularly assisted ionization (MAI), recombination (MAR) and dissociation (MAD) reaction chains with respect to the purely atomic ionization and recombination processes were studied experimentally during detachment in low-confinement mode (L-mode) plasmas in JET with the help of experimentally inferred divertor plasma and neutral conditions, extracted previously from filtered camera observations of deuterium Balmer emission, and the reaction coefficients provided by the ADAS, AMJUEL and H2VIBR atomic and molecular databases. The direct contribution of MAI and MAR in the outer divertor particle balance was found to be inferior to the electron-atom ionization (EAI) and electron-ion recombination (EIR). Near the outer strike point, a strong atom source due to the D+2-driven MAD was, however, observed to correlate with the onset of detachment at outer strike point temperatures of Te,osp = 0.9-2.0 eV via increased plasma-neutral interactions before the increasing dominance of EIR at Te,osp < 0.9 eV, followed by increasing degree of detachment. The analysis was supported by predictions from EDGE2D-EIRENE simulations which were in qualitative agreement with the experimental observations

Shattered pellet injection experiments at JET in support of the ITER disruption mitigation system design

A series of experiments have been executed at JET to assess the efficacy of the newly installed shattered pellet injection (SPI) system in mitigating the effects of disruptions. Issues, important for the ITER disruption mitigation system, such as thermal load mitigation, avoidance of runaway electron (RE) formation, radiation asymmetries during thermal quench mitigation, electromagnetic load control and RE energy dissipation have been addressed over a large parameter range. The efficiency of the mitigation has been examined for the various SPI injection strategies. The paper summarises the results from these JET SPI experiments and discusses their implications for the ITER disruption mitigation scheme

New H-mode regimes with small ELMs and high thermal confinement in the Joint European Torus

New H-mode regimes with high confinement, low core impurity accumulation, and small edge-localized mode perturbations have been obtained in magnetically confined plasmas at the Joint European Torus tokamak. Such regimes are achieved by means of optimized particle fueling conditions at high input power, current, and magnetic field, which lead to a self-organized state with a strong increase in rotation and ion temperature and a decrease in the edge density. An interplay between core and edge plasma regions leads to reduced turbulence levels and outward impurity convection. These results pave the way to an attractive alternative to the standard plasmas considered for fusion energy generation in a tokamak with a metallic wall environment such as the ones expected in ITER.& nbsp;Published under an exclusive license by AIP Publishing

Overview of JET results for optimising ITER operation

The JET 2019–2020 scientific and technological programme exploited the results of years of concerted scientific and engineering work, including the ITER-like wall (ILW: Be wall and W divertor) installed in 2010, improved diagnostic capabilities now fully available, a major neutral beam injection upgrade providing record power in 2019–2020, and tested the technical and procedural preparation for safe operation with tritium. Research along three complementary axes yielded a wealth of new results. Firstly, the JET plasma programme delivered scenarios suitable for high fusion power and alpha particle (α) physics in the coming D–T campaign (DTE2), with record sustained neutron rates, as well as plasmas for clarifying the impact of isotope mass on plasma core, edge and plasma-wall interactions, and for ITER pre-fusion power operation. The efficacy of the newly installed shattered pellet injector for mitigating disruption forces and runaway electrons was demonstrated. Secondly, research on the consequences of long-term exposure to JET-ILW plasma was completed, with emphasis on wall damage and fuel retention, and with analyses of wall materials and dust particles that will help validate assumptions and codes for design and operation of ITER and DEMO. Thirdly, the nuclear technology programme aiming to deliver maximum technological return from operations in D, T and D–T benefited from the highest D–D neutron yield in years, securing results for validating radiation transport and activation codes, and nuclear data for ITER

Testing a prediction model for the H-mode density pedestal against JET-ILW pedestals

The neutral ionisation model proposed by Groebner et al (2002 Phys. Plasmas 9 2134) to determine the plasma density profile in the H-mode pedestal, is extended to include charge exchange processes in the pedestal stimulated by the ideas of Mahdavi et al (2003 Phys. Plasmas 10 3984). The model is then tested against JET H-mode pedestal data, both in a 'standalone' version using experimental temperature profiles and also by incorporating it in the Europed version of EPED. The model is able to predict the density pedestal over a wide range of conditions with good accuracy. It is also able to predict the experimentally observed isotope effect on the density pedestal that eludes simpler neutral ionization models

Peripheral temperature gradient screening of high-Z impurities in optimised 'hybrid' scenario H-mode plasmas in JET-ILW

Screening of high-Z (W) impurities from the confined plasma by the temperature gradient at the plasma periphery of fusion-grade H-mode plasmas has been demonstrated in the JET-ILW (ITER-like wall) tokamak. Through careful optimisation of the hybrid-scenario, deuterium plasmas with sufficient heating power (greater than or similar to 32 MW), high enough ion temperature gradients at the H-mode pedestal top can be achieved for the collisional, neo-classical convection of the W impurities to be directed outwards, expelling them from the confined plasma. Measurements of the W impurity fluxes between and during edge-localised modes (ELMs) based on fast bolometry measurements show that in such plasmas there is a net efflux (loss) between ELMs but that ELMs often allow some W back into the confined plasma. Provided steady, high-power heating is maintained, this mechanism allows such plasmas to sustain high performance, with an average D-D neutron rate of similar to 3.2 x 10(16) s(-1) over a period of similar to 3 s, after an initial overshoot (equivalent to a D-T fusion power of similar to 9.4 MW), without an uncontrolled rise in W impurity radiation, giving added confidence that impurity screening by the pedestal may also occur in ITER, as has previously been predicted (Dux et al 2017 Nucl. Mater. Energy 12 28-35)