Waiting in Irregularity: how young Moroccans in southern Spain navigate temporal bordering processes produced by the Spanish migration law

[Abstract] El Ejido, in southern Spain, constitutes the densest surface for agroindustry, where manual work is done mainly by migrants. It is a microcosm that particularly encapsulates social problems, struggles, and (state) violence. The thesis exposes practices of temporal bordering, by analysing the role of migration laws, through the lens of waiting. The ‘arraigo social’ is a regulation mechanism, conditioned on a previous three years' irregular stay in the country. Through ethnographic observations and narrative interviews, this paper asks about the function of waiting and how it is experienced and encountered by the people living through this time. To this end, it maps its connections with exploitation of labour, negotiation of belonging and the exertion of state violence. I argue the function is to keep migrants in a situation of a ‘inclusive exclusion’, tantamount to ‘capitalist exploitation’. As through their irregularised stay and the need for an employment contract, they face employers with an extreme power imbalance.[Resumen] El Ejido, en el sur de España, constituye la superficie más densa de la agroindustria, donde el trabajo manual lo realizan principalmente los inmigrantes. Se trata de un microcosmos que encapsula especialmente los problemas sociales, las luchas y la violencia (estatal). La tesis expone prácticas de temporal bordering, analizando el papel de las leyes migratorias, a través de la mirada de la espera. El ‘arraigo social’ es un mecanismo de regulación, condicionado a una estancia irregular previa de tres años en el país. Por medio de observaciones etnográficas y entrevistas narrativas, este trabajo se pregunta acerca de la función de la espera y de cómo es experimentada y enfrentada por las personas que viven este tiempo. Para ello, analiza sus conexiones con la explotación del trabajo, la negociación de la pertenencia y el ejercicio de la violencia estatal. Sostengo que la función es mantener a los inmigrantes en una situación de ‘exclusión incluida’, equivalente a la ‘explotación capitalista’. Ya que a través de su estancia irregular y la necesidad de un contrato de trabajo, se afrentan a empleadores con un desequilibrio de poder extremo.Traballo fin de mestrado (UDC.SOC). Políticas sociais e intervención sociocomunitaria. Curso 2021/202

Lorentz force evaluation: novel forward solution and inverse methods

The development of new materials, as well as the increasing standards for quality and safety, require high-resolution, nondestructive evaluation methods for manufacturing and maintenance. In a novel method, referred to as Lorentz force evaluation, a permanent magnet is moved relative to a conducting specimen. Owing to this movement, eddy currents are induced inside the conductor. The interaction of the eddy currents with the magnetic field leads to the Lorentz force acting on the conductor. A force of the same magnitude but in opposite direction acts on the permanent magnet, where it is measured. In the presence of a defect, the eddy currents are perturbed. Consequently, the Lorentz force components are also perturbed. The defect properties are determined from the measured Lorentz force components by solving an ill-posed inverse problem. The thesis aims to develop a novel forward solution, compare different forward solutions, develop new inverse calculation methods and create a method for improving defect depth estimation for Lorentz force evaluation. Further, a qualitative comparison to classical eddy current evaluation was realized. The existing forward solutions in Lorentz force evaluation: approximate forward solution and the computational more demanding extended area approach were compared regarding their defect reconstruction performance. A goal function scanning method was used as inverse method in order to directly compare the influence of both forward solutions on the defect reconstruction result avoiding the bias of tuning parameters of the inverse methods. The use of the extended area approach as forward solution yielded more accurate defect depth and extensions estimations compared to the approximate forward solution. However, both forward solutions are limited to defects of regular geometry. Thus, a novel forward solution referred to as single voxel approach was developed. It is based on the superposition of force perturbation signals of small elementary defects. For numerical simulations of various defect sizes, depths and shapes, the novel forward solution showed the smallest deviation in comparison to the other two existing forward solutions. To reconstruct the defect properties, a minimum norm estimation with elastic net regularization was applied to Lorentz force measurement data of an aluminum specimen. The rationale of using the elastic net regularization is given by the a priori knowledge of a non-conducting defect surrounded by a conductor with constant conductivity. The widely used Tikhonov-Phillips-regularization was applied for comparison purposes. With both regularization methods reproducible and correct depth and adequate size estimations were obtained. The same inverse methods have been applied for defect reconstruction of eddy current evaluation measurements of an aluminum specimen. The reconstructed defects where blurred and less stable for deep lying defects in comparison to the Lorentz force evaluation. Conversely, with the eddy current evaluation, the reconstruction of more complex shaped defects was possible. As another inverse method, the adapted Landweber iteration was introduced for Lorentz force evaluation. The Landweber iteration has been selected due to promising imaging results in the field of electrical capacitance tomography. An adapted Landweber iteration yielded adequate defect size estimations. The positions of deep lying defects were estimated above the correct ones. The Lorentz force evaluation is characterized by the difficulty that a small defect close to the specimen surface and a larger and deeper defect generate similar force perturbation signals. This aggravates the estimation of the correct defect depth. A novel principle, referred to as velocity dependent Lorentz force evaluation, was introduced to support the defect depth estimation. The Lorentz force perturbation signals are evaluated at a high velocity (10 m/s) relative to a low velocity (0.1 m/s). Amplitude changes and signal shifts are used to determine the defect depth incorporating the motion-evoked skin effect. The general feasibility of this novel method has been shown for simulated data.Die Entwicklung neuer Materialien sowie die ansteigenden Anforderungen an Qualität und Sicherheit erfordern die Entwicklung hochauflösender, zerstörungsfreier Werkstoffevaluierungsverfahren für die Produktion und Wartung. Im neuen Lorentzkraftevaluierungsverfahren wird ein Permanentmagnet relativ zu einem elektrisch leitenden Prüfkörper bewegt. Aufgrund der Bewegung werden Wirbelströme im Prüfkörper induziert. Die Wechselwirkung der Wirbelströme mit dem Magnetfeld führt zur Lorentzkraft, welche auf den Prüfkörper wirkt. Eine Kraft derselben Größe aber in entgegengesetzte Richtung wirkt auf den Permanentmagneten, wo sie gemessen wird. Bei Vorliegen eines Defekts sind die Wirbelstromverteilung und entsprechend die Lorentzkraft verändert. Die Defekteigenschaften werden aus den gemessenen Lorentzkraftkomponenten mittels der Lösung eines schlecht gestellten inversen Problems bestimmt. Die Ziele der Dissertation umfassen die Entwicklung einer neuen Vorwärtslösung, den Vergleich verschiedener Vorwärtslösungen, die Entwicklung neuer inverser Verfahren sowie die Erarbeitung einer Methode zur verbesserten Defekttiefenbestimmung für die Lorentzkraftevaluierung. Des Weiteren wurde ein qualitativer Vergleich mit der klassischen Wirbelstromevaluierung umgesetzt. Die existierenden Vorwärtslösungen für die Lorentzkraftevaluierung: „Approximate Forward Solution“ und „Extended Area Approach“ wurden hinsichtlich der Defektrekonstruktionsgüte verglichen. Es wurde ein Zielfunktionsscanningverfahren angewandt um den Einfluss der beiden Vorwärtslösungen direkt zu vergleichen. Damit wurde eine Verzerrung durch die sonst notwendige Parameterwahl bei inversen Methoden vermieden. Die Verwendung der Vorwärtslösung „Extended Area Approach“ erzielte genauere Schätzungen der Defekttiefe und -abmessungen im Vergleich zur „Approximate Forward Solution“. Die beiden Vorwärtslösungen sind jedoch auf Defekte mit gleichmäßiger Geometrie beschränkt. Aus diesem Grund wurde die neue Vorwärtslösung „Single Voxel Approach“ entwickelt. Sie basiert auf der Superposition von Kraftveränderungssignalen von kleinen elementaren Defekten. Bei numerischen Simulationen mit Defekten verschiedener Größen, Tiefen und Formen zeigte der „Single Voxel Approach“ die geringste Abweichung im Vergleich zu den beiden existierenden Vorwärtslösungen. Eine Minimum-Norm-Schätzung mit Elastic-Net-Regularisierung wurde auf die Lorentzkraftmessdaten eines Aluminiumprüfkörpers zur Rekonstruktion der Defekteigenschaften angewandt. Die Motivation zur Nutzung der Elastic-Net-Regularisierung stammt aus dem a priori Wissen, dass ein nicht-leitender Defekt von einem Prüfstück mit konstanter Leitfähigkeit umgeben ist. Die weit verbreitete Tikhonov-Phillips-Regularisierung wurde zu Vergleichszwecken angewandt. Mit beiden Regularisierungsmethoden konnte reproduzierbar eine korrekte Defekttiefenschätzung und eine adäquate Größenschätzung erzielt werden. Dasselbe inverse Verfahren wurde für die Defektrekonstruktion aus Wirbelstromevaluierungsmessdaten eines Aluminiumprüfkörpers angewandt. Die Defektrekonstruktionsergebnisse stellten sich für tiefer liegende Defekte verschwommen und weniger stabil im Vergleich zur Lorentzkraftevaluierung dar. Im Gegensatz war mit der Wirbelstromevaluierung die Rekonstruktion komplexerer Defektgeometrien möglich. Als weitere inverse Methode, wurde die adaptierte Landweber-Iteration für die Lorentzkraftevaluierung eingeführt. Die Landweber-Iteration wurde ausgewählt, da sich im Bereich der elektrischen Kapazitätstomographie vielversprechende Rekonstruktionsergebnisse gezeigt haben. Die adaptierte Landweber-Iteration erzielte adäquate Defektgrößenschätzungen. Die Position von tief liegenden Defekten wurde zu hoch rekonstruiert. Die Lorentzkraftevaluierung ist gekennzeichnet durch die Schwierigkeit, dass ein kleiner Defekt nahe der Prüfkörperoberfläche und ein größerer tiefer liegender Defekt ähnliche Kraftveränderungssignale zeigen. Das erschwert die Bestimmung der korrekten Defekttiefe. Das neue Prinzip der geschwindigkeitsabhängigen Lorentzkraftevaluierung wurde eingeführt um die Defekttiefenbestimmung zu unterstützen. Die Lorentzkraftveränderungssignale werden bei einer hohen Geschwindigkeit (10m/s) relativ zu den Signalen bei einer niedrigen Geschwindigkeit (0.1 m/s) ausgewertet. Amplitudenveränderungen und Signalverschiebungen werden genutzt um die Defekttiefe zu bestimmen. Dabei wird der bewegungsinduzierte Skineffekt ausgenutzt. Die Plausibilität dieser neuen Methode wurde für Simulationsdaten gezeigt

Perception thresholds and qualitative perceptions for electrocutaneous stimulation

Our long-term goal is the development of a wearable warning system that uses electrocutaneous stimulation. To find appropriate stimulation parameters and electrode configurations, we investigate perception amplitude thresholds and qualitative perceptions of electrocutaneous stimulation for varying pulse widths, electrode sizes, and electrode positions. The upper right arm was stimulated in 81 healthy volunteers with biphasic rectangular current pulses varying between 20 and 2000 μs. We determined perception, attention, and intolerance thresholds and the corresponding qualitative perceptions for 8 electrode pairs distributed around the upper arm. For a pulse width of 150 μs, we find median values of 3.5, 6.9, and 13.8 mA for perception, attention, and intolerance thresholds, respectively. All thresholds decrease with increasing pulse width. Lateral electrode positions have higher intolerance thresholds than medial electrode positions, but perception and attention threshold are not significantly different across electrode positions. Electrode size between 15 × 15 mm2 and 40 × 40 mm2 has no significant influence on the thresholds. Knocking is the prevailing perception for perception and attention thresholds while mostly muscle twitching, pinching, and stinging are reported at the intolerance threshold. Biphasic stimulation pulse widths between 150 μs and 250 μs are suitable for electric warning wearables. Within the given practical limits at the upper arm, electrode size, inter-electrode distance, and electrode position are flexible parameters of electric warning wearables. Our investigations provide the basis for electric warning wearables

Evaluation of spatio-temporal electrocutaneous warning signals

Acoustic or visual warning signals for workers in hazardous situations might fail under loud and/or lowvisibility work situations. A warning system that uses electrocutaneous stimulation can overcome this problem. The aim of this pilot study was to find spatio-temporal stimulation patterns for appropriate electrical warning. Eight electrode pairs were attached to the upper right arm of 16 participants. The stimulation was conducted with bi-phasic rectangular pulses of 150 μs and an amplitude of up to 25 mA. Pulse intervals that generate a single pulse, pulsating, vibrating, and continuous perception as well as varying spatial patterns (e.g. alternating between electrode pairs or circumferentially around the arm) were investigated and evaluated with regard to alertness, discomfort, and urgency. The pilot study revealed that a stimulation signal that generates a vibrating perception and is applied as a circumferential signal around the arm showed the highest values of alertness and is therefore considered a potential warning pattern for future studies with larger study groups

The SH2 Domain Regulates c-Abl Kinase Activation by a Cyclin-Like Mechanism and Remodulation of the Hinge Motion

Regulation of the c-Abl (ABL1) tyrosine kinase is important because of its role in cellular signaling, and its relevance in the leukemiogenic counterpart (BCR-ABL). Both auto-inhibition and full activation of c-Abl are regulated by the interaction of the catalytic domain with the Src Homology 2 (SH2) domain. The mechanism by which this interaction enhances catalysis is not known. We combined computational simulations with mutagenesis and functional analysis to find that the SH2 domain conveys both local and global effects on the dynamics of the catalytic domain. Locally, it regulates the flexibility of the αC helix in a fashion reminiscent of cyclins in cyclin-dependent kinases, reorienting catalytically important motifs. At a more global level, SH2 binding redirects the hinge motion of the N and C lobes and changes the conformational equilibrium of the activation loop. The complex network of subtle structural shifts that link the SH2 domain with the activation loop and the active site may be partially conserved with other SH2-domain containing kinases and therefore offer additional parameters for the design of conformation-specific inhibitors

Interaction of β-Sheet Folds with a Gold Surface

The adsorption of proteins on inorganic surfaces is of fundamental biological importance. Further, biomedical and nanotechnological applications increasingly use interfaces between inorganic material and polypeptides. Yet, the underlying adsorption mechanism of polypeptides on surfaces is not well understood and experimentally difficult to analyze. Therefore, we investigate here the interactions of polypeptides with a gold(111) surface using computational molecular dynamics (MD) simulations with a polarizable gold model in explicit water. Our focus in this paper is the investigation of the interaction of polypeptides with β-sheet folds. First, we concentrate on a β-sheet forming model peptide. Second, we investigate the interactions of two domains with high β-sheet content of the biologically important extracellular matrix protein fibronectin (FN). We find that adsorption occurs in a stepwise mechanism both for the model peptide and the protein. The positively charged amino acid Arg facilitates the initial contact formation between protein and gold surface. Our results suggest that an effective gold-binding surface patch is overall uncharged, but contains Arg for contact initiation. The polypeptides do not unfold on the gold surface within the simulation time. However, for the two FN domains, the relative domain-domain orientation changes. The observation of a very fast and strong adsorption indicates that in a biological matrix, no bare gold surfaces will be present. Hence, the bioactivity of gold surfaces (like bare gold nanoparticles) will critically depend on the history of particle administration and the proteins present during initial contact between gold and biological material. Further, gold particles may act as seeds for protein aggregation. Structural re-organization and protein aggregation are potentially of immunological importance