Testing climate synchronicity between Scotland and Romania since the last glacial maximum

This thesis develops a chronology of ice retreat in the Monadhliath Mountains (Scotland) and Rodna Mountains (Romania) during the late Pleistocene using glacial geomorphology and surface exposure dating with cosmogenic 10Be. In the Monadhliath Mountains, 10Be exposure ages indicate deglaciation of the Last Devensian ice sheet at 15.1 ka (n = 2). Boulders from moraines in three Monadhliath cirques yielded exposure ages between 11.8 ka and 9.8 ka (470 – 600 m), suggesting that a Late Glacial readvance occurred during the Younger Dryas stadial (n = 9). The limited extent of these YD glaciers in the Monadhliath Mountains is explained in terms of the drier climate experienced by the eastern part of the Central Highland ice cap, but also in terms of local factors such as topography and snow blow. The resulting glacial reconstruction largely confirms that a SW to NE precipitation gradient dominated Scotland during the Younger Dryas. In the Romanian Carpathians, located at the southern periphery of the NW European ice sheet, there was only limited coverage of ice, mostly at higher elevations in the form of mountain glaciers. Field evidence suggests that during the last local maximum glaciation ice reached lower elevations than previously suggested in the Rodna Mountains. Glacially transported boulders were abandoned at 37.2 – 26.6 ka (n = 4) at an elevation of ~900 m. Glacial erratics and bedrock samples (n = 27) provide a consistent chronology for deglaciation during the Lateglacial, suggesting that ice retreated towards higher ground between 18.3 – 13.2 ka (1100 – 1800 m altitude). Final deglaciation took place at 12.5 - 11.2 ka (n = 9). These new chronologies are compared to other climate archives in Europe and the climatic oscillations recorded in the North Atlantic region. This analysis increases our understanding of past atmospheric circulation across Europe, and gives insights into the climatic forcing mechanisms during the last maximum extent of ice sheets and glaciers. During the last glacial episodes, the pattern of climate cooling from the western high latitudes towards the eastern mid latitudes was complicated, triggering different responses in local climates that appear to have been out of phase with the broader north-western European trend. Located in the NW Europe, Scotland was influenced by the wetter and colder conditions from the Atlantic which led to the expansion of the British Ice sheet during the global Last Glacial Maximum (LGM). However, smaller ice masses located further southwards and south-eastwards of the European ice sheet responded faster to the climatic oscillations in the North Atlantic region. During the LGM, the southward repositioning of the Polar Front and the presence of the ice sheet changed the atmospheric circulation across Europe. There was limited supply of moisture to the Rodna Mountains, especially because of blocking by the eastern Siberian high pressure system, and the glaciers experienced a slow retreat in a very cold and dry environment. However, a more synchronous Younger Dryas is likely to have occurred due to a more northern position of the Polar Front. This allowed for stronger wet and cold westerly winds to reach most of Europe at the same time

On some apllications of Lie Algebroids in Geometry and Physics

El objetivo de esta tesis es el estudio de algunas aplicaciones de la teoría de algebroides de Lie, un concepto que generaliza tanto al de álgebra de Lie como al de fibrado vectorial, en problemas matemáticos y físicos concretos. La estructura de algebroide de Lie ha sido ya utilizada en distintos campos como mecánica, topología algebraica, geometría algebraica y geometría diferencial. En el primer capítulo hemos introducido esta noción, presentado unos ejemplos de ello y unas de sus propiedades que van a ser útiles en los siguientes capítulos. Un concepto fundamental para la parte matemática de nuestro trabajo es el del campo de Jacobi, que en la geometría Riemanniana puede ser interpretado como el campo vectorial variacional asociado a una familia 1-paramétrica de geodésicas. En esta parte, uno de nuestros resultados principales es la generalización de dicha noción a la de sección de Jacobi asociada a una ecuación diferencial de segundo orden (denominada sode) definida en un algebroide de Lie, que está acompañada de la generalización de la ecuación de Jacobi que la satisfacen estas secciones de Jacobi. Para ello hemos introducido el concepto de derivada dinámica covariante y el del endomorfismo de Jacobi asociados a una sode en este caso general. Una referencia importante relacionada con estos asuntos es. A continuación hemos considerado el caso de un algebroide de Lie Riemanniano. Hemos recordado brevemente la noción de la conexión Levi-Civita asociada a la métrica de Riemann, su correspondiente spray geodésico y hemos hallado las fórmulas de variación de la funcional de energía. Hemos utilizado nuestra teoría por el caso de una sode definida en un algebroide de Lie Riemanniano, donde el sode es el spray geodésico asociado a la conexión de Levi-Civita. En este caso, hemos mostrado que la derivada covariante asociada a la conexión Levi-Civita es la derivada covariante dinámica asociada al spray geodésico correspondiente a esta conexión, y hemos hallado la relación existente entre el endomorfismo Jacobi asociado a este spray y el tensor de la curvatura de la conexión Levi-Civita. Con estas observaciones, a través de la forma que lleva la segunda variación calculada anteriormente, se ha reencontrado, tal como en el caso de la Geometría Riemnniana, la relación que hay entre las secciones de Jacobi y los problemas de minimización de la energía. En final, hemos definido el concepto de puntos conjugados y hemos demostrado que si a largo de una curva integral del spray geodésico no hay puntos conjugados, entonces esta minimiza la funcional energía del sistema cuyas soluciones son dadas de este mismo spray. En la parte relativa a las aplicaciones físicas nos hemos centrado nuestra atención sobre el teorema de virial, mostrando que admite una generalización al marco de algebroides de Lie. El teorema de virial para una función virial,-una función acotada en un intervalo de tiempo-, afirma que su promedio sobre un tal intervalo es cero. En casos particulares, como consecuencia, en el teorema de virial aparecen relaciones entre los promedios temporales de cantidades, como, por ejemplo, de la energía cinética del sistema con la de la energía potencial del sistema. Originalmente introducido de Clausius en el campo de la mecánica clásica estadística, el teorema de virial se ha mostrado de gran utilidad también en otras distintas ramas de la física. Tiene una amplia aplicabilidad en sistemas dinámicos y termodinámicos, sistemas con velocidad dependiente de fuerzas y en sistemas viscosos. Aunque el teorema de virial ofrece menos información que las propias soluciones de las ecuaciones de movimiento, es mas simple de aplicar y puede ofrecer información sobre sistemas cuyo análisis completo puede ser complicado. Se ha probado recientemente que los teoremas de tipo virial son válidos también para espacios de configuración distintos al espacio real n-dimensional. Fue estudiado haciendo uso del formalismo simpléctico tanto en el caso Hamiltoniano como en el Lagrangiano. En la parte de aplicaciones en física, hemos comenzado con el formalismo Lagrangiano, y escrito intrínsecamente y en coordinadas locales el teorema de virial para un sistema Lagrangiano de tipo mecánico en una variedad de Riemann. Casos particulares importantes estudiados son el de una función virial afin asociada con un campo vectorial en la variedad de configuración, los de funciones viriales asociadas con campos Killing, homotéticos, y conformes Killing. Los campos vectoriales conformes de Killing y en particular los campos vectoriales homoteticos han sido relevantes en muchos problemas en física y particularmente en la geometría espacio-tiempo. Cada uno de estos casos particulares ha sido ilustrado por medio de un ejemplo. Después hemos estudiado en el marco geométrico del teorema de virial en términos de cuasi velocidades en el caso Lagrangiano dando así una interpretación geométrica del formalismo de Boltzmann del teorema de virial, trasladable en cuasi-momenta al caso Hamiltoniano, dando así una interpretación geométrica del teorema de virial en el formalismo de Poincaré. Esto nos ha preparado el camino para proponer una generalización del teorema de virial para sistemas mecánicos en Lie algebroides, usando los métodos geométricos de la mecánica Lagrangiana y Hamiltoniana en la prologación de un algebroide de Lie en el caso Lagrangiano, respectivo de su dual en el caso Hamiltonianao, con respecto al Lie algebroide inicial, dos casos particulares de algebroides de Lie simplécticos. Esta nueva generalización del teorema del virial y en particular el caso de la formulación en términos de cuasi-velocidades nos permite utilizarlo para sistemas mecánicos con ligaduras no holónomas. El oscilador armónico noholonómico, el trineo de Chapygin, y el sistema de Suslov, son ejemplos que hemos usado para ilustrar la teoría de los sistemas no holónomos.The main purpose of our work is to present applications of the Lie algebroid structure in both mathematical and physical context. In the first chapter we have introduced the notion of Lie algebroid, presenting a number of examples, and we have presented some useful properties that we used later on. One of our principal results in the mathematical part was to give a generalization of the notion of Jacobi fields corresponding to sode on manifolds and on Lie algebroids. We have done that considering a new take on a first order variational equation on a manifold. We also generalized the Jacobi equation for this generalized cases of Jacobi fields associated to sode. For that we had to generalize the non-linear connection and the Jacobi endomorphism to the context of Lie algebroid. We used this theory in the particular instance of a geodesic spray on a Riemannian Lie algebroid. For this case we have shown that an integral curve of it has no conjugate points along it if and only if it minimizes the energy functional of the system whose solution are given by the geodesic spray. To exemplify the theorem we considered the space of skew-symmetric matrices of dimension 3 who has a Lie algebroid structure. In Chapter 4, for the physical counterpart, we analyzed the virial theorem in the first place for mechanical systems and nonholonomic systems on the tangent bundle, and afterwards, for unconstrained and nonholonomic systems on Lie algebroids. We could prove that a virial like theorem holds for systems on Lie algebroids, fact that will allow us to obtain information about the time average of the action of the dynamical section upon the virial function for more systems than before due to the wide range of systems that can be described with the help of a Lie algebroid structure. Also in this chapter we have presented in detail instances of this theorem through some examples. We find interesting for further investigation to see if the minimizing theorem presented here takes place for any Lagrangian, not necessarily a Riemannian one and for the other topology. Precisely see in what conditions the result holds when we look for the geodesic to be a strong minimum for the energy functional

Gender differences in tourism behaviour in the European Union

Given its increasing role in today´s societal and economic realities, tourism is seen more and more as a discursive area and a successful channel for transmitting gender equality issues. The purpose of this article was to examine the differences regarding gender gaps in tourist behaviour between core-members and the latest accession states in the European Union We used the number of trips, overnight stays, and the values for travel expenditures from Eurostat database as indicators to study the participation of men and women in tourism for both leisure and professional purposes. The results indicated small or almost non-existent differences between the core-members of the European Union and the latest accession states regarding gender gaps in tourism; however, both groups manifested an under representation of women in professional or business tourism as well as smaller values of expenditures overall for women. The results seemed to indicate the existence of a “glass ceiling”, despite the overall progress made in the gender equality area

Electric Cell-Substrate Impedance Sensing of Cellular Effects under Hypoxic Conditions and Carbonic Anhydrase Inhibition

Tumor hypoxia provides a dynamic environment for the cancer cells to thrive and metastasize. Evaluation of cell growth, cell-cell, and cell surface interactions in hypoxic conditions is therefore highly needed in the establishment of treatment options. Electric cell-substrate impedance sensing (ECIS) has been traditionally used in the evaluation of cellular platforms as a real-time, label-free impedance-based method to study the activities of cells grown in tissue cultures, but its application for hypoxic environments is seldom reported. We present real-time evaluation of hypoxia-induced bioeffects with a focus on hypoxic pH regulation of tumor environment. To this end, multiparametric real-time bioanalytical platform using electrical impedance spectroscopy (EIS) and human colon cancer HT-29 cells is advanced. A time series of EIS data enables monitoring with high temporal resolution the alterations occurring within the cell layer, especially at the cell-substrate level. We reveal the dynamic changes of cellular processes during hypoxic conditions and in response to application of acetazolamide (AZA), a carbonic anhydrase inhibitor. Optical evaluation and pH assessment complemented the electrical analysis towards establishing a pattern of cellular changes. The proposed bioanalytical platform indicates wide applicability towards evaluation of bioeffects of hypoxia at cellular level

Electrochemical push-pull probe: from scanning electrochemical microscopy (SECM) to multimodal altering of cell microenvironment

To understand biological processes at the cellular level, a general approach is to alter the cells’ environment and to study their chemical responses. Herein, we present the implementation of an electrochemical push-pull probe, which combines a microfluidic system with a microelectrode, as a tool for locally altering the microenvironment of few adherent living cells by working in two different perturbation modes, namely electrochemical (i.e. electrochemical generation of a chemical effector compound) and microfluidic (i.e. infusion of a chemical effector compound from the pushing microchannel, while aspirating it through the pulling channel thereby focusing the flow between the channels). The effect of several parameters such as flow rate, working distance and probe inclination angle on the affected area of adherently growing cells was investigated both theoretically and experimentally. As a proof of concept, localized fluorescent labeling and pH changes were purposely introduced to validate the probe as a tool for studying adherent cancer cells through the control over the chemical composition of the extracellular space with high spatiotemporal resolution. A very good agreement between experimental and simulated results showed for instance, that the electrochemical perturbation mode enables to affect precisely only few living cells localized in a high-density cell culture

Primary intramedullary spinal cord non-Hodgkin lymphoma: Case report and review of the literature

Introduction: Primary intramedullary spinal cord lymphomas are extremely rare, occurring mainly in immune compromised patients. Case report: We report a case of a 43 years old patient admitted with spinal cord compression. Spinal MRI revealed two thoracic intramedullary tumours. The patients underwent surgery and we performed resection of both primary intramedullary tumours, with favourable neurological outcome. The histopathologic exam was non-Hodgkin lymphoma. The patient underwent adjuvant radiotherapy. Two months later the patient presented thoracic and cerebellar drop metastases, confirmed histopathologically. Conclusions: The diagnosis of primary intramedullary spinal lymphoma must be kept in mind in patients with myelopathy. Surgery is needed to provide histopathological samples for positive diagnosis and spinal decompression. Primary intramedullary spinal lymphomas have a propensity to disseminate along the neuraxis

Racial differences in systemic sclerosis disease presentation: a European Scleroderma Trials and Research group study

Objectives. Racial factors play a significant role in SSc. We evaluated differences in SSc presentations between white patients (WP), Asian patients (AP) and black patients (BP) and analysed the effects of geographical locations.Methods. SSc characteristics of patients from the EUSTAR cohort were cross-sectionally compared across racial groups using survival and multiple logistic regression analyses.Results. The study included 9162 WP, 341 AP and 181 BP. AP developed the first non-RP feature faster than WP but slower than BP. AP were less frequently anti-centromere (ACA; odds ratio (OR) = 0.4, P < 0.001) and more frequently anti-topoisomerase-I autoantibodies (ATA) positive (OR = 1.2, P = 0.068), while BP were less likely to be ACA and ATA positive than were WP [OR(ACA) = 0.3, P < 0.001; OR(ATA) = 0.5, P = 0.020]. AP had less often (OR = 0.7, P = 0.06) and BP more often (OR = 2.7, P < 0.001) diffuse skin involvement than had WP.AP and BP were more likely to have pulmonary hypertension [OR(AP) = 2.6, P < 0.001; OR(BP) = 2.7, P = 0.03 vs WP] and a reduced forced vital capacity [OR(AP) = 2.5, P < 0.001; OR(BP) = 2.4, P < 0.004] than were WP. AP more often had an impaired diffusing capacity of the lung than had BP and WP [OR(AP vs BP) = 1.9, P = 0.038; OR(AP vs WP) = 2.4, P < 0.001]. After RP onset, AP and BP had a higher hazard to die than had WP [hazard ratio (HR) (AP) = 1.6, P = 0.011; HR(BP) = 2.1, P < 0.001].Conclusion. Compared with WP, and mostly independent of geographical location, AP have a faster and earlier disease onset with high prevalences of ATA, pulmonary hypertension and forced vital capacity impairment and higher mortality. BP had the fastest disease onset, a high prevalence of diffuse skin involvement and nominally the highest mortality

Gate circuits in the algebra of transients


We study simulation of gate circuits in the infinite algebra of transients recently introduced by Brzozowski and Ésik. A transient is a word consisting of alternating 0s and 1s; it represents a changing signal. In the algebra of transients, gates process transients instead of 0s and 1s. Simulation in this algebra is capable of counting signal changes and detecting hazards. We study two simulation algorithms: a general one that works with any initial state, and a special one that applies only if the initial state is stable. We show that the two algorithms agree in the stable case. We also show that the general algorithm is insensitive to the removal of state variables that are not feedback variables. We prove the sufficiency of simulation: all signal changes occurring in binary analysis are predicted by the general algorithm. Finally, we show that simulation can be more pessimistic than binary analysis, if wire delays are not taken into account. We propose a circuit model that we conjecture to be sufficient for proving the equivalence of simulation and binary analysis for feedback-free circuits.

Revealing alteration of membrane structures during ischema using impedance spectroscopy

Alterations of membrane structure and function are essential characteristics of cells undergoing ischemia. Noninvasive monitoring of tissue alterations during ischemia and the estimation of the reversibility domain (corresponding to organ capability to fully recover its functions after shifting back to normal blood perfusion) are important for biomedical applications allowing better time management during surgical interventions, especially in organ transplantation. Due to it’s capability to reveal inhomogeneities, as well as it’s noninvasive character, impedance spectroscopy was used for continuous monitoring of the progression of excised tissue samples during ischemia. We have developed a fast, noninvasive, automated method for quantitative analysis of impedance spectra of tissue samples, capable of revealing, through characteristic parameters (dispersion amplitudes, time constants and distribution parameters) membrane based microscopic processes like the closure ofgap-junctions (a characteristic of the early alterations of ischemic tissues in the reversibility phase). Microscopic and equivalent circuit modeling was used to probe the effect of closure of cell connections and of changes in electrical properties of cell constituents on impedance spectra. We have developed a normalizing procedure emphasizing the pattern of ischemic alterations and enabling the comparison of different data sets