Brief communication: Estimating the ice thickness of the Müller Ice Cap using an inversion of the shallow ice approximation

The Müller Ice Cap will soon set the scene for a new drilling project. Therefore, ice thickness estimates are necessary for planning since thickness measurements of the ice cap are sparse. Here, two models are presented and compared, i) a simple inversion of the shallow ice approximation (SIA inversion) by the use of a single radar line in combination with the glacier outline, surface slope, and elevation, and ii) an iterative inverse method using the Parallel Ice Sheet Model (PISM). The two methods mostly agree about a good drill site candidate. However, the new semi-empirical SIA inversion is insensitive to mass balance, computationally fast, and provides better fits.

The Structure of Interrogative Sentences with a Nominal Subject in the French Language in a Diachronic Aspect

The article is focused on the study of interrogative sentences with a nominal subject in the French language in terms of structural criteria in a diachronic aspect. The purpose of this study is to reveal the features of the so-called complex inversion in interrogative sentences. Special attention is paid to terminological problems. Pronominal reprise is recognized by the authors as the most correct term for an interrogative construction with a nominal subject duplicated by a personal pronoun. The lack of uniformity in terminology indicates a multidimensional nature of the inversion phenomenon in the French language. For instance, in addition to interrogative sentences, it can be used in other contexts: in simple declarative sentences after certain adverbs, in subordinate clauses after some conjunctions, in exclamatory sentences, etc. The authors highlight and describe the characteristic features of interrogative sentences with a nominal subject in terms of diachrony. Pronominal reprise appears in interrogative constructions as early as in the 16th century, mainly in general questions, subsequently extending to special questions. In the 16th – 17th centuries, the subject did not regularly precede the verb; the same applied to interrogative words, which could be placed both to the left and to the right of the subject. In sentences with a nominal subject, reprise was not the only possible structural option. The following were also used: direct word order, construction question word + est-ce que, and simple inversion. The authors come to the conclusion that pronominal reprise had finally replaced simple inversion of the nominal subject in general questions in French by the end of the 17th century.

Cambios generados por la COVID-19 en la práctica formativa e investigativa en Trabajo Social: oportunidades, dilemas y retos para la investigación social

Introducción. Este artículo presenta los resultados de una investigación que tuvo como objetivo analizar las condiciones que docentes y estudiantes de Trabajo Social tuvieron para realizar investigaciones científicas o trabajos de fin de carrera durante la crisis de la COVID-19. Se asumió la perspectiva comprensivista de las ciencias sociales, desde autores que debaten la racionalidad técnico-instrumental y que plantean, en contraposición, la necesidad de una racionalidad práctico-reflexiva tanto en la práctica profesional como en la formación en Trabajo Social. Los autores llamados a dialogar proceden de la Filosofía, la Sociología y el Trabajo Social, con posturas frente los conceptos de “saber práctico”, “proceso reflexivo”, “reflexividad” y “conocimiento en la acción”. Metodología. El diseño metodológico se sustentó en una lectura emic de la realidad. Se utilizó una muestra aleatoria simple por conveniencia, a partir de criterios muestrales como: ubicación geográfica, cargo ocupado en las universidades y experiencia en investigación. Como técnicas se utilizaron la revisión documental, para el análisis de 42 proyectos de tesis, y la entrevista semiestructurada a siete (7) académicos-investigadores —de cuatro (4) países de América Latina— y a once (11) estudiantes que cumplían con: encontrarse en el semestre de fin de carrera, pertenecer a una universidad de la ciudad de Guayaquil y estar investigando temas relacionados con la pandemia. Resultados. Teniendo en cuenta cuatro dimensiones: el contexto, la práctica investigativa y la producción científica de docentes, la tutoría de la producción académica de los estudiantes de fin de carrera y la formación investigativa en Trabajo Social, se hicieron evidentes las alteraciones en las voces de lo que implicó la pandemia en la cotidianidad para quienes estaban realizando algún proyecto de investigación o formando nuevos investigadores. Las dinámicas personales producto del virus han redireccionado y, sobre todo, producido aprendizajes que nutren la posibilidad de describir, explicar y comprender nuevas dinámicas para formar y producir conocimiento. Discusión y conclusiones. Se plantean nuevos retos o dilemas para la investigación en Trabajo Social, en tanto que la pandemia —como hecho sociohistórico y bio-psico-social— evidenció que las desigualdades y las vulnerabilidades sociales no necesariamente están solo en el plano de la materialidad física o de tener los recursos tecnológicos a disposición (un computador, un celular, internet, servicio de energía); esto, si acaso, modificará los presupuestos en las investigaciones para dotar de estas materialidades a las personas vinculadas. Además, existen en otro plano: el subjetivo, en el cual la cultura, el territorio, la clase o el género, entre otros, determinan vulneraciones más complejas que en el mundo simbólico al que pertenecen y no es posible resolverlas con una simple inversión material o tecnológica.

An Analytical Solution for Pressure-Induced Deformation of Anisotropic Multilayered Subsurface

We present a generalized Geertsma solution that can consider any number of finite-thickness layers in the subsurface whose mechanical properties are different from layer to layer. In addition, each layer can be assumed either isotropic or anisotropic. The accuracy of the generalized solution is validated against a numerical reference solution. The generalized Geertsma solution is further extended by a linear superposition framework that enables a response simulation due to an arbitrarily-distributed non-uniform pressure anomaly. The linear superposition approach is tested and validated by solving a realistic synthetic model based on the In Salah CO2 storage model and compared with a full 3D finite element solution. Finally, by means of a simple inversion exercise (based on the linear superposition approach), we learn that the stiffnesses of cap rock and reservoir are the most influencing parameter on the inversion result for a given layering geometry, suggesting that it is very important to estimate high-confidence mechanical properties of both cap rock and reservoir.

Rotational sensor on a volcano: New insights from Etna, Italy

<p>Rotational seismology is an emerging field of seismology with rotational sensors such as blueSeis-3A as portable devices. We deployed one of these rotational sensors on Etna volcano from August to September 2019 in the middle of a 26 stations broadband seismic array and a fibre-optic cable deployed for Distributed Acoustic Sensing (DAS). We, therefore, recorded continuously the full seismic wavefield using a 6C station (rotational sensor co-located with a broadband seismometer) for 30 days.</p><p>We will present an overview of our work on the rotational data in combination with a broadband seismometer. We will (i) compare the translational with rotational data and show how they complement each other, (ii) calculate back azimuths using only a 6C station or using merely the horizontal components of the rotational sensor, (iii) determine Love and Rayleigh wave velocities from the rotation rate and (iv) perform a simple inversion for the shallow velocity structure below the station, and finally (v) discuss the usefulness of such a sensor in a volcanic environment and (vi) highlight what new it would bring to volcano-related research.</p>

Deducing Crystallization Sequence of Magmas from Spatial Distribution of Crystals in Rocks

The order of crystallization of minerals from melt is of prime importance for an understanding of magma fractionation and chemical differentiation from the magma chamber to the planetary scale. Determination of the crystallization sequence based on petrographic observations, however, is often ambiguous; especially in multiply saturated, nearly eutectic felsic melts. This paper presents a novel approach to estimate the order of crystallization of minerals in igneous systems based on a quantitative study of their spatial distributions. Statistical modelling of crystallization demonstrates that later crystallizing mineral phases are generally more clustered. A simple inversion model is then derived to calculate the crystallization sequence and the volume fraction of older minerals present in the system at the onset of crystallization of a later (younger) phase. Application of the model to a sample of equigranular granodiorite (Fichtelgebirge granite batholith, Germany) indicates that plagioclase was the first liquidus phase. It was followed by biotite, K-feldspar, and quartz at 41, 48, and 63 vol. % crystallized, respectively, which is in qualitative agreement with experimental phase equilibria results for moderately hydrous granitic melts. If phase equilibria for a given composition are known or assumed, the crystallization sequence thus constrains the intensive variables (e.g., water content) and their evolution during magma solidification. The model thus provides a novel and independent approach to reconstruct the magma crystallization path that would be inaccessible by other methods.

Generation of DC, AC, and Second-Harmonic Spin Currents by Electromagnetic Fields in an Inversion-Asymmetric Antiferromagnet

Manipulating spin currents in magnetic insulators is a key technology in spintronics. We theoretically study a simple inversion-asymmetric model of quantum antiferromagnets, where both the exchange interaction and the magnetic field are staggered. We calculate spin currents generated by external electric and magnetic fields by using a quantum master equation. We show that an ac electric field with amplitude E 0 leads, through exchange-interaction modulation, to the dc and second-order harmonic spin currents proportional to E 0 2 . We also show that dc and ac staggered magnetic fields B 0 generate the dc and ac spin currents proportional to B 0 , respectively. We elucidate the mechanism by an exactly solvable model, and thereby propose the ways of spin current manipulation by electromagnetic fields.

On the Use of Focused Incident Near-Field Beams in Microwave Imaging

We consider the use of focused incident near-field (NF) beams to interrogate the object of interest (OI) in NF microwave imaging (MWI). To this end, we first discuss how focused NF beams can be advantageously utilized to suppress scattering effects from the neighbouring objects whose unknown dielectric properties are not of interest (i.e., undesired scatterers). We then discuss how this approach can also be helpful in reducing the required measured data points to perform imaging. Driven by the relation between the electromagnetic inverse source and inverse scattering problems, our approach emphasizes the importance of tailoring the induced contrast sources in the imaging domain through the utilized incident NF beams. To demonstrate this idea, we consider two recently-proposed NF beams, and simulate them for imaging applications. The first one is a subwavelength focused NF beam generated by a passive NF plate, and the other is a Bessel beam generated by a leaky radial waveguide. Simple imaging examples are considered to explore the potential advantages of this approach, in particular, toward mainly seeing the object of interest, and not the unknown undesired scatterers. The scope of this paper is limited to homogeneous dielectric objects for which the induced total field distributions in the interrogated objects are similar to the incident field distributions (e.g., those that satisfy the Born approximation). Simple inversion results for focused and non-focused beams are presented accompanied by discussions comparing the achieved reconstructed values.