Estudios más allá de la línea de goteo de neutrones usando reacciones (p,2p) cuasi-libres : el caso del ¹³Be

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, leída el 03-07-2015El objetivo de este trabajo es estudiar la estructura de capas del 13Be, un núcleo no-ligado rico en neutrones utilizando una reacción (p, 2p) de knockout. Este tipo de estructuras nucleares no-ligadas son objeto de interés debido a que permiten estudiar los límites de la fuerza nuclear donde aún es capaz de formar estructuras observables con ciertas combinaciones de protones y neutrones, y también porque son buenos laboratorios donde probar los modelos teóricos de las interacciones entre un nucleón y el núcleo. Con este objetivo realizamos un experimento en el acelerador de iones pesados GSI, donde núcleos de 14B a energías del orden de 490 MeV/u se hicieron incidir sobre un blanco de CH2, produciendo 13Be. Este tipo de núcleos sin ningún estado ligado, tienen una vida media extremadamente corta, del orden de los 10-21 s, por lo que no se pueden medir directamente sino que hay que buscar los restos de su desintegración, en este caso: 12Be y un neutrón. Un complejo sistema de detectores de la Colaboración R3B ha permitido estudiar todos los productos de reacción. Los detectores disponibles para el trabajo experimental eran: un sistema para identificar los isótopos entrantes formado por detectores de centelleo y semiconductor, una esfera de detectores de centelleo para rayos gamma y protones alrededor del blanco, una serie de detectores de silicio antes y después del mismo y un electroimán de muy alta aceptancia y potencia para separar los productos de la reacción con carga y dirigirlos hacia los detectores de fibras y centelleo para detectar, en este caso, los núcleos de 12Be, y un detector de neutrones de gran eficiencia. Este trabajo detalla todas las técnicas utilizadas para producir los núcleos de interés, así como para calibrar los más de 9 conjuntos de detectores utilizados, pero el núcleo del trabajo consiste en el análisis de los datos obtenidos, encontrando los que permiten reconstruir la energía relativa de los componentes del 13Be : 12Be + n, utilizando la técnica de la masa invariante. El espectro de energía relativa muestra un conjunto de resonancias que han sido analizadas para obtener sus valores medios, anchuras y el momento angular del estado resonante correspondiente. Para obtener un resultado más limpio de contaminación, se ha verificado la producción de la reacción nuclear mediante la búsqueda de los dos protones que son emitidos en la misma con un ángulo de apertura de aproximadamente 82 grados. Para poder entender por completo los resultados también se han buscado los rayos gamma de la desexcitación de dos de los estados del núcleo hijo: 12Be, encontrándose uno de energía 2.1 MeV en coincidencia. Esto permite fijar las resonancias del espectro de energías del 13Be a sus valores reales, puesto que el método de la masa invariante es insensible a la energía que queda almacenada en los estados excitados de los núcleos. Este trabajo, a pesar de la baja estadística disponible y de la poca resolución energética, ha conseguido resolver una estructura de capas para un núcleo muy exótico como el 13Be, con tres estados, un estado s a 0.3 MeV por encima del estado fundamental del 12Be, un estado d a 2.20 MeV y otro estado a 3.05 MeV que puede ser s o d. Además se propone también, aunque no se puede confirmar por falta de estadística suficiente, un cuarto estado a 0.95 MeV. Este es el primer experimento que, buscando este núcleo, verifica la producción de la reacción (p, 2p) de knockout, y es el segundo que ha podido contar con medidas de los rayos gamma emitidos tras la reacción, que es un detalle clave para poder completar el análisis con el método utilizadoFac. de Ciencias FísicasTRUEunpu

Wie es zur Wirtschafts-, Währungs- und Sozialunion kam : Wirtschaftliche Voraussetzungen und politische Vorbedingungen

Es gab, so verkünden seit nunmehr zwei Jahrzehnten die bundesdeutschen Medien, zum Zeitpunkt und zur Art und Weise, wie die Wirtschafts- und Währungsunion vollzogen wurde, keine Alternative. «Ich kenne keine ernsthafte Betrachtung, wie man es hätte anders machen können», äußerte sich der Chefunterhändler des Einigungsvertrages Wolfgang Schäuble in einem Interview im «Neuen Deutschland» im Mai 2009. Bezogen auf jene programmatischen Konzepte, die die Währungsunion im Transformationsprozess der DDR-Wirtschaft bzw. im Einigungsprozess anders platzieren wollten, stimmt Schäubles Aussage offensichtlich nicht. Doch siegte mit dem «Stichwortkonzept: Schritte zur deutschen Wirtschaftseinheit » das bessere Programm? Welche Motive hatten Kanzler Kohl bzw. Finanzminister Waigel die Währungsunion an den Beginn des wirtschaftpolitischen Transformationsprozesses in der DDR zu setzen? Glaubten beide wirklich, sich für das bessere, d. h. für die DDR-Bürger und für das Zusammenwachsen von DDR und BRD günstigere Konzept entschieden zu haben? Warum verweigerten sie sich so vehement jedem Vorschlag ausgewiesener Experten, die Transformation von der Planwirtschaft zur Marktwirtschaft in Ostdeutschland über mehrere Jahre statt über einige Monate zu vollziehen? Vermutlich ging es dem Bundeskanzler nur um eins – um den Machterhalt. Nur als «Kanzler der Einheit», hatte er alle Chancen im Herbst 1990 die anstehenden Bundestagswahlen zu gewinnen. So hat er das natürlich in seinen Memoiren nicht formuliert

An idea for the future proton detection of (p,2p) reactions with the (RB)-B-3 set-up at FAIR

5 págs.; 6 figs.; 1 tab.; FAIRNESS 2014; Open Access funded by Creative Commons Atribution Licence 3.0The R3B Collaboration has a long experience in probing exotic nuclei via quasi-free scattering reactions. To continue these studies a new array capable of detecting protons and gamma rays of high energy is currently being developed, the CALIFA (R3B CALorimeter for In Flight γ arrays and high energy charged pArticles). This contribution reports on the current solution for the forward Endcap of the CALIFA detector and on the latest test results.This work was partly financed by the Spanish Research Funding Agency CICYT under Project FPA2012-32443. Further Guillermo Ribeiro acknowledges his FPI-MICINN grant.Peer Reviewe

Transport across two interacting quantum dots: Bulk Kondo, Kondo box, and molecular regimes

We analyze the transport properties of a double quantum dot device with both dots coupled to perfect conducting leads and to a finite chain of N noninteracting sites connecting both of them. The interdot chain strongly influences the transport across the system and the local density of states of the dots. We study the case of a small number of sites, so that Kondo box effects are present, varying the coupling between the dots and the chain. For odd N and small coupling between the interdot chain and the dots, a state with two coexisting Kondo regimes develops: the bulk Kondo due to the quantum dots connected to leads and the one produced by the screening of the quantum dot spins by the spin in the finite chain at the Fermi level. As the coupling to the interdot chain increases, there is a crossover to a molecular Kondo effect, due to the screening of the molecule (formed by the finite chain and the quantum dots) spin by the leads. For even N the two Kondo temperatures regime does not develop and the physics is dominated by the usual competition between Kondo and antiferromagnetism between the quantum dots. We finally study how the transport properties are affected as N is increased. For the study we used exact multiconfigurational Lanczos calculations and finite-U slave-boson mean-field theory at T=0. The results obtained with both methods describe qualitatively and also quantitatively the same physics.We acknowledge financial support from the Brazilian agencies FAPERJ (CNE) and CNPq, the Spanish MCYT (Grants No. FIS2009-10325 and No. FIS2012-35880), CONICET (Argentina), Universidad de Alicante, and PUC–Rio de Janeiro

Totally Spin-Polarized Currents in an Interferometer with Spin–Orbit Coupling and the Absence of Magnetic Field Effects

The paper studies the electronic current in a one-dimensional lead under the effect of spin–orbit coupling and its injection into a metallic conductor through two contacts, forming a closed loop. When an external potential is applied, the time reversal symmetry is broken and the wave vector k of the circulating electrons that contribute to the current is spin-dependent. As the wave function phase depends upon the vector k, the closed path in the circuit produces spin-dependent current interference. This creates a physical scenario in which a spin-polarized current emerges, even in the absence of external magnetic fields or magnetic materials. It is possible to find points in the system’s parameter space and, depending upon its geometry, the value of the Fermi energy and the spin–orbit intensities, for which the electronic states participating in the current have only one spin, creating a high and totally spin-polarized conductance. For a potential of a few tens of meV, it is possible to obtain a spin-polarized current of the order of μA. The properties of the obtained electronic current qualify the proposed device as a potentially important tool for spintronics applications.V.L. and G.C. acknowledge financial support from the Generalitat Valenciana through grants references Prometeo/2021/017 and MFA/2022/045. V.L. acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación, PID2019-109539GB. G.C. acknowledges financial support from the Spanish Ministry of Education and Science, PID2019-109539GB-C41 and PID2019-106114GB-I00. E.V.A. acknowledges financial support from the Brazilian Agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), process number 306000/2017-2

Terra dos dinossauros: la construcción e implementación del turismo paleontológico en el barrio rural de Peirópolis, Uberaba (MG, Brasil)

Con el fin de generar un tipo de turismo determinado en una localidad es necesario seleccionar ciertos elementos (patrimonio local, recursos naturales, entre otros) para ofrecerlos como atractivos. En el caso del barrio rural de Peirópolis, ubicado en el municipio de Uberaba (Minas Gerais, Brasil), se seleccionó su patrimonio paleontológico para generar un turismo paleontológico. Los objetivos de este trabajo es analizar los procesos de patrimonialización y turistificación que se produjeron en Peirópolis. A través de diferentes técnicas (observación participante, entrevistas semiestructuradas, consulta de diversas fuentes gráficas y bibliográficas) se presentan los resultados de la investigación: la construcción social e implantación de un turismo paleontológico, una apropiación territorial del turismo, construcción de lugar turístico. Todos estos procesos y acciones llevaron a transformar la identidad del barrio rural de Peirópolis.In order to generate a specific type of tourism in a locality, it is necessary to select certain elements (local Heritage, natural resources, among others) to offer as touristic attractions. In the case of the rural neighborhood of Peirópolis, located in Uberaba district (Minas Gerais, Brazil), its paleontological Heritage was selected to generate a paleontological tourism. The objectives of this paper are to analyze the Heritage and Touristification processes in Peirópolis. Through different techniques (participant observation, semi-structure interviews, and analyses of different types of sources), the result of the research are presented: the social construction and implementation of a paleontological tourism, tourism territorial appropriation, and, the construction of a touristic place in Peirópolis. All these processes and actions transformed the rural neighborhood identity of Peirópolis.Fil: Perez Winter, Cecilia Verena. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Instituto de Ciencias Antropológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martinelli, Agustín Guillermo. Universidad de Uberaba. Centro de Pesquisas Paleontológicas Llewellyn Ivor Price. Complexo Cultural e Científico de Peirópolis; BrasilFil: Ribeiro Borges, Luiz Carlos. Universidade Federal do Rio de Janeiro; Brasi

Cellular proliferation dynamics during regeneration in Syllis malaquini (Syllidae, Annelida)

BACKGROUND: In syllids (Annelida, Syllidae), the regenerative blastema was subject of many studies in the mid and late XX(th) century. This work on syllid regeneration showed that the blastema is developed by a process of dedifferentiation of cells near the wound, followed by their proliferation and redifferentiation (cells differentiate to the original cell type) or, in some specific cases, transdifferentiation (cells differentiate to a cell type different from the original). Up to date, participation of stem cells or pre-existing proliferative cells in the blastema development has never been observed in syllids. This study provides the first comprehensive description of Syllis malaquini’s regenerative capacity, including data on the cellular proliferation dynamics by using an EdU/BrdU labelling approach, in order to trace proliferative cells (S-phase cells) present before and after operation. RESULTS: Syllis malaquini can restore the anterior and posterior body from different cutting levels under experimental conditions, even from midbody fragments. Our results on cellular proliferation showed that S-phase cells present in the body before bisection do not significantly contribute to blastema development. However, in some specimens cut at the level of the proventricle, cells in S-phase located in the digestive tube before bisection participated in regeneration. Also, our results showed that nucleus shape allows to distinguish different types of blastemal cells as forming specific tissues. Additionally, simultaneous and sequential addition of segments seem to occur in anterior regeneration, while only sequential addition was observed in posterior regeneration. Remarkably, in contrast with previous studies in syllids, sexual reproduction was not induced during anterior regeneration of amputees lacking the proventricle, a foregut organ widely known to be involved in the stolonization control. CONCLUSIONS: Our findings led us to consider that although dedifferentiation and redifferentiation might be more common, proliferative cells present before injury can be involved in regenerative processes in syllids, at least in some cases. Also, we provide data for comparative studies on resegmentation as a process that differs between anterior and posterior regeneration; and on the controversial role of the proventricle in the reproduction of different syllid lineages. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12983-021-00396-y

Kondo Effect in Distorted Titanium Phthalocyanine Molecules Adsorbed on a Cu(110) Metallic Surface

In this work, we study the quantum transition taking place when titanium phthalocyanine molecules are adsorbed on a copper’s surface. Submitted to thermal annealing, depending on the way in which the molecule is adsorbed, this system can be characterized by a Kondo ground state, giving rise to a zero bias peak in the differential conductance. To clarify this new property, derived from the annealing process, we propose a model Hamiltonian that describes the essential physics involved. We show that the Kondo ground state appears as a consequence of the broken symmetry introduced by the annealing. It is not due to an increase of the molecule–substrate interactions but to the modification of the intermolecular lobe orbital matrix elements. This rearrangement rules the entrance of charge into the molecule and provides the conditions for the establishment of the Kondo state. Our results for the differential conductance, corresponding to the electronic current between a STM tip and one of the molecular lobes, agree with the experimental differential conductance measurements. It presents an Abrikosov–Suhl–Kondo resonance at the Fermi level for the configuration where the molecule is distorted. The results obtained within the model we propose, when compared with the experiments, give quantitative support to our interpretation.V.L. and G.C. acknowledge a financial support from the Generalitat Valenciana through grant reference Prometeo/2021/017. V.L. acknowledges a financial support from the Spanish Ministerio de Ciencia e Innovación, PID2019-109539GB-C41. G.C. acknowledges a financial support from the Spanish Ministry of Education and Science, PID2019-109539GB-C41, PID2019-106114GB-I00, and from the Generalitat Valenciana MFA/2022/045. E.V.A. acknowledges financial support from the Brazilian Agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), process number 307644/2022-7

A new herrerasaurid dinosaur record from southern BrazilL (Upper Triassic) and its faunal association

The Predebon Site, located in São João do Polêsine, Quarta Colônia region (Rio Grande do Sul, Brazil) has a Triassic fauna, including footprints and traces of small vertebrates and abundant remains of rhynchosaurs. This fauna is typical of the Hyperodapedon Assemblage Zone, which is correlated to the late Carnian Ischigualasto Formation (Ischigualasto-Villa Unión Basin) in Argentina. The present study records new fossil remains for the Predebon Site collected in 2001 that consists of two dorsal and two sacral vertebrae referred to the same individual (MCN-PV 10344), and two isolated, serrated blade-shaped teeth (MCN-PV 10425 and 10426). The trunk vertebrae were identified as between 11th and 15th. The sacral vertebrae are fully fused, with no indication of another fused vertebral element, not even signs suggestive of dorsosacral and caudosacral vertebrae, also because the ilia are not preserved. The general characteristics observed are: (i) lateral fossa in the vertebral body; (ii) concave ventral face of the vertebral body; (iii) neural spine high and wide at the top, subquadrangular in shape, in both dorsal and sacral vertebrae; (iv) infrapre - and infrapostzygapophyseal ridges on the dorsals; (v) presence of hyposphene and hypantrum; and (vi) first sacral vertebra larger than the second, with transverse processes and broad sacral ribs, triangular in shape in dorsal view. This set of features in the vertebral elements i s sim ilar to tha t present in Herrerasaurus ischigualastensis from the Ischigualasto Formation and allows us to consider MCN-PV 10344 as a member of the Herrerasauridae clade. It differs from Staurikosaurus pricei, which has three smaller and more slender sacral vertebrae and a low neural spine without subquadrangular platform at the top, and from Gnathovorax cabreirai, which has subrectangular platforms, slightly more elongated anteroposteriorly, suggesting the presence of a new herrerasaurid morphotype. The two isolated, serrated blade -shaped teeth were attributed to Archosauriformes indet., because this morphotype is observed in several groups within this clade.Fil: Silva, Fernanda Oliveira da. Universidade Federal do Rio Grande do Sul; BrasilFil: Martinelli, Agustín Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Ferigolo, Jorge. Museu de Ciências Naturais do Rio Grande do Sul; BrasilFil: Ribeiro, Ana Maria. Museu de Ciências Naturais do Rio Grande do Sul; Brasi