Theoretical analysis of hidden photon searches in high-precision experiments

Although the Standard Model of particle physics (SM) provides an extremely successful description of the ordinary matter, one knows from astronomical observations that it accounts only for around 5% of the total energy density of the Universe, whereas around 30% are contributed by the dark matter. Motivated by anomalies in cosmic ray observations and by attempts to solve questions of the SM like the (g-2)_mu discrepancy, proposed U(1) extensions of the SM gauge group have raised attention in recent years. In the considered U(1) extensions a new, light messenger particle, the hidden photon, couples to the hidden sector as well as to the electromagnetic current of the SM by kinetic mixing. This allows for a search for this particle in laboratory experiments exploring the electromagnetic interaction. Various experimental programs have been started to search for hidden photons, such as in electron-scattering experiments, which are a versatile tool to explore various physics phenomena. One approach is the dedicated search in fixed-target experiments at modest energies as performed at MAMI or at JLAB. In these experiments the scattering of an electron beam off a hadronic target e+(A,Z)->e+(A,Z)+l^+l^- is investigated and a search for a very narrow resonance in the invariant mass distribution of the lepton pair is performed. This requires an accurate understanding of the theoretical basis of the underlying processes. For this purpose it is demonstrated in the first part of this work, in which way the hidden photon can be motivated from existing puzzles encountered at the precision frontier of the SM. The main part of this thesis deals with the analysis of the theoretical framework for electron scattering fixed-target experiments searching for hidden photons. As a first step, the cross section for the bremsstrahlung emission of hidden photons in such experiments is studied. Based on these results, the applicability of the Weizsäcker-Williams approximation to calculate the signal cross section of the process, which is widely used to design such experimental setups, is investigated. In a next step, the reaction e+(A,Z)->e+(A,Z)+l^+l^- is analyzed as signal and background process in order to describe existing data obtained by the A1 experiment at MAMI with the aim to give accurate predictions of exclusion limits for the hidden photon parameter space. Finally, the derived methods are used to find predictions for future experiments, e.g., at MESA or at JLAB, allowing for a comprehensive study of the discovery potential of the complementary experiments. In the last part, a feasibility study for probing the hidden photon model by rare kaon decays is performed. For this purpose, invisible as well as visible decays of the hidden photon are considered within different classes of models. This allows one to find bounds for the parameter space from existing data and to estimate the reach of future experiments.

The coevolution of cooperation and dispersal in social groups and its implications for the emergence of multicellularity

Background Recent work on the complexity of life highlights the roles played by evolutionary forces at different levels of individuality. One of the central puzzles in explaining transitions in individuality for entities ranging from complex cells, to multicellular organisms and societies, is how different autonomous units relinquish control over their functions to others in the group. In addition to the necessity of reducing conflict over effecting specialized tasks, differentiating groups must control the exploitation of the commons, or else be out-competed by more fit groups. Results We propose that two forms of conflict – access to resources within groups and representation in germ line – may be resolved in tandem through individual and group-level selective effects. Specifically, we employ an optimization model to show the conditions under which different within-group social behaviors (cooperators producing a public good or cheaters exploiting the public good) may be selected to disperse, thereby not affecting the commons and functioning as germ line. We find that partial or complete dispersal specialization of cheaters is a general outcome. The propensity for cheaters to disperse is highest with intermediate benefit:cost ratios of cooperative acts and with high relatedness. An examination of a range of real biological systems tends to support our theory, although additional study is required to provide robust tests. Conclusion We suggest that trait linkage between dispersal and cheating should be operative regardless of whether groups ever achieve higher levels of individuality, because individual selection will always tend to increase exploitation, and stronger group structure will tend to increase overall cooperation through kin selected benefits. Cheater specialization as dispersers offers simultaneous solutions to the evolution of cooperation in social groups and the origin of specialization of germ and soma in multicellular organisms.

Der mittelfristige Einfluss von Feedback auf die Leistung von Mastery oder Performance motivierten Personen

In vielen Situationen bekommen Personen beim Lernen neuer Aufgaben in einer ersten Phase Feedback, doch in einer zweiten Phase arbeiten sie ohne Feedback. Bislang gibt es einige Befunde zu der Auswirkung eines Feedbacks auf die unmittelbare Leistung, nicht jedoch auf die mittelfristige Leistung in einer Phase ohne Feedback. Es ist zu erwarten, dass die Form der Leistungsmotivation hier eine entscheidende Rolle spielt. Für Personen, die das Ziel haben, besser zu sein als andere, kann ein negatives Feedback eine Bedrohung des Selbstwertes darstellen und daher demotivieren. Mittelfristig sollte jedoch die Bedrohung des Selbstwertes abnehmen. Daher ist zu erwarten, dass Feedback mittelfristig die Leistung steigert. Für Personen, die das Ziel haben, ihre Kenntnisse zu verbessern, stellt ein negatives Feedback keine Bedrohung des Selbstwertes da. Daher sollte sich Feedback anfänglich positiv auf die Leistung auswirken. Diese Personen lieben jedoch das Gefühl, sich Kenntnisse selbst zu erarbeitet zu haben. Feedback verdirbt den Spass am selbstständigen Explorieren und Lösungen finden. Feedback sollte daher - nach einer anfänglichen Leistungssteigerung- mittelfristig zu einer Verringerung der Leistung führen. Wir zeigen in einer Studie in der Tangram Puzzles gelöst wurden, dass beide Prozesse stattfinden.

Interaction of small molecules with specific immune receptors: the p-i concept and its consequences

Drugs may stimulate the immune system by forming stable new antigenic complexes consisting of the drug or drug metabolite which is covalently bound to a protein or peptide (hapten-carrier complex). Both, B- and T-cell immunity may arise, the latter directed to hapten modified peptides presented by HLA molecules. Beside this immunological stimulation, drugs can also stimulate the immune system through binding by non-covalent bonds to proteins like immune receptors. This so-called “pharmacological interaction with immune receptors” concept (“p-i concept”) may occur with HLA or TCR molecules themselves (p-i HLA or p-i TCR), and not the immunogenic peptide. It is a type of “off-target” activity of the drug on immune receptors, but more complex as various cell types, cell interactions and functionally different T cells are involved. In this review the conditions which lead to activation of T cells by p-i are discussed: important factors for a functional consequence of drug binding is the location of binding (p-i HLA or p-i TCR); the exact site within these immune receptors; the affinity of binding and the finding that p-i HLA can stimulate the immune system like an allo-allele. The p-i concept is able to solve some puzzles of drug hypersensitivity reactions and are a basis to better treat and potentially avoid drug hypersensitivity reactions. Moreover, the p-i concept shows that in contrast to previous beliefs small molecules do interact with immune receptors with functional consequence. But these interactions are not based on “immune recognition”, are at odds with some immunological concepts, but may nevertheless open new possibilities to understand and even treat immune reactions

GENETIC ANALYSIS OF THE HIPPO PATHWAY IN MOUSE LIVER

Cancer therapy and tumor treatment remain unsolved puzzles. Genetic screening for tumor suppressor genes in Drosophila revealed the Hippo-signaling pathway as a kinase cascade consisting of five core components. Disrupting the pathway by deleting the main component genes breaks the balance of cell proliferation and apoptosis and results in epithelial tissue tumorigenesis. The pathway is therefore believed to be a tumor suppressor pathway. However, a corresponding role in mammals is yet to be determined. Our lab began to investigate the tumor suppression function of the potent mammalian Hippo pathway by putting floxed alleles into the mouse genome flanking the functional-domain-expressing exons in each component (Mst1, Mst2, Sav1, Lats1 and Lats2). These mice were then crossed with different cre-mouse lines to generate conditional knockout mice. Results indicate a ubiquitous tumor suppression function of these components, predominantly in the liver. A further liver specific analysis of the deletion mutation of these components, as well as the Yap/Taz double deletion mutation, reveals essential roles of the Hippo pathway in regulating hepatic quiescence and embryonic liver development. One of the key cellular mechanisms for the Hippo pathway’s involvement in these liver biological events is likely its cell cycle regulation function. Our work will help to develop potential therapeutic approaches for liver cancer.

Política de sensibilización ambiental

Uno de los objetivos del Programa de Ordenamiento y Protección de los Recursos Naturales de la Costa Atlántica de Río Negro es promover experiencias innovadoras, vinculadas a la protección del patrimonio natural y cultural del litoral costero rionegrino. Dentro de este marco, el objetivo general es establecer las bases para un desarrollo sustentable. Esto no es posible, si no se acompaña de una fuerte sensibilización ambiental dirigida a diferentes sectores sociales respecto de los valores que representa este ecosistema costero, actividad desarrollada en el marco del Proyecto Desarrollo de una Política de Sensibilización ambiental. La implementación de una estrategia de Educación Ambiental que permita generar en la comunidad una mayor capacidad para comprender el ambiente y que contribuyan a valorar el patrimonio natural y cultural, es el eje fundamental para alcanzar el desarrollo sustentable de la región. Es por ello que se plantea el objetivo de generar una política integral de sensibilización ambiental que permita incluir la temática ambiental en los diferentes sectores sociales y modalidades del sistema educativo. Para lograrlo se realiza el Primer Seminario Taller sobre Diseño de una Política de Capacitación y Sensibilización Ambiental, que es el primer paso que permitió generar las bases de una propuesta de una Política Integral de Sensibilización Ambiental. Posteriormente se realiza una encuesta dirigida a la comunidad en general y a docentes en la que se propone analizar cada una de las problemáticas ambientales reconocidas a la luz de cuatro variables: muy grave, grave, leve y no conoce/no contesta. No fue intención realizar un análisis profundo y detallado de las variables sino resaltar grandes rasgos que permitan establecer comparaciones para su ordenamiento y tratamiento. También la se realiza un Curso para Docentes que brinda el marco propicio para la Formulación e Implementación de una Política de Sensibilización Ambiental. Otra actividad es la organización de un concurso anual "Conozcamos Nuestras Costas" dirigido a la comunidad educativa, en el que participaron activamente 430 alumnos pertenecientes a las tres localidades costeras. Se elabora y distribuye materiales de sensibilización ambiental elaborados luego de un trabajo de diagnóstico, recopilación de información y material fotográfico. El mismo se organizó en sets de 10 juegos cada uno (rompecabezas, libro de imágenes, memotest, entre otros), cuyo contenido es de flora y fauna, áreas de mayor sensibilidad ecológica y los principios de conservación. Por último se realiza un Taller para la Cooperación en la Prevención y Mitigación de Impactos Ambientales en la Costa Atlántica. Como resultado de este taller se obtuvo una Red de Alerta y Comunicación, que contribuya a la formalización y fortalecimiento de la ya existente. La creación de un Centro de un Coordinación Ambiental (CCA) que tendría su sede en la Dirección de Defensa Civil.

Los enigmas en El libro de los cuentos de Rafael Boira

El libro de los cuentos, de Rafael Boira, fue uno de los muchos que se publicaron como esparcimiento en el siglo xix. Es una recopilación de composiciones jocosas menores, en prosa, salvo algunas en verso; entre éstas hay más de un centenar de enigmas o adivinanzas en quintillas cuya autoría no nos reveló. El autor de las adivinanzas es Cristóbal Pérez de Herrera (1618). Aunque como autor generalmente es original, copia o imita algunas adivinanzas preexistentes en la tradición oral o culta. Boira copió de manera literal muchas adivinanzas de este autor, aunque escribió otras con alteraciones, mayores o menores, quizás por recordarlas de memoria. "Las enigmas", de Pérez de Herrera, fueron muy divulgados anónimamente: pasaron a la tradición escrita pero también se recogieron, y aún es así hoy en día, de modo oral. Lo cierto es que también están ya presentes en la tradición oral algunas versiones tal como Boira las alteró. Incuestionablemente, los enigmas cultos han pasado a la tradición oral en el ámbito de la cultura hispana. Herrera y Boira son dos marcas en este camino de popularización

Los enigmas en El libro de los cuentos de Rafael Boira

El libro de los cuentos, de Rafael Boira, fue uno de los muchos que se publicaron como esparcimiento en el siglo xix. Es una recopilación de composiciones jocosas menores, en prosa, salvo algunas en verso; entre éstas hay más de un centenar de enigmas o adivinanzas en quintillas cuya autoría no nos reveló. El autor de las adivinanzas es Cristóbal Pérez de Herrera (1618). Aunque como autor generalmente es original, copia o imita algunas adivinanzas preexistentes en la tradición oral o culta. Boira copió de manera literal muchas adivinanzas de este autor, aunque escribió otras con alteraciones, mayores o menores, quizás por recordarlas de memoria. "Las enigmas", de Pérez de Herrera, fueron muy divulgados anónimamente: pasaron a la tradición escrita pero también se recogieron, y aún es así hoy en día, de modo oral. Lo cierto es que también están ya presentes en la tradición oral algunas versiones tal como Boira las alteró. Incuestionablemente, los enigmas cultos han pasado a la tradición oral en el ámbito de la cultura hispana. Herrera y Boira son dos marcas en este camino de popularización

Los enigmas en El libro de los cuentos de Rafael Boira

El libro de los cuentos, de Rafael Boira, fue uno de los muchos que se publicaron como esparcimiento en el siglo xix. Es una recopilación de composiciones jocosas menores, en prosa, salvo algunas en verso; entre éstas hay más de un centenar de enigmas o adivinanzas en quintillas cuya autoría no nos reveló. El autor de las adivinanzas es Cristóbal Pérez de Herrera (1618). Aunque como autor generalmente es original, copia o imita algunas adivinanzas preexistentes en la tradición oral o culta. Boira copió de manera literal muchas adivinanzas de este autor, aunque escribió otras con alteraciones, mayores o menores, quizás por recordarlas de memoria. "Las enigmas", de Pérez de Herrera, fueron muy divulgados anónimamente: pasaron a la tradición escrita pero también se recogieron, y aún es así hoy en día, de modo oral. Lo cierto es que también están ya presentes en la tradición oral algunas versiones tal como Boira las alteró. Incuestionablemente, los enigmas cultos han pasado a la tradición oral en el ámbito de la cultura hispana. Herrera y Boira son dos marcas en este camino de popularización

Can ends justify the means?: Telomeres and the mechanisms of replicative senescence and immortalization in mammalian cells

Finite replicative lifespan, or senescence, of mammalian cells in culture is a phenomenon that has generated much curiosity since its description. The obvious significance of senescence to organismal aging and the development of cancer has engendered a long-lasting and lively debate about its mechanisms. Recent discoveries concerning the phenotypes of telomerase knockout mice, the consequences of telomerase reexpression in somatic cells, and genes that regulate senescence have provided striking molecular insights but also have uncovered important new questions. The objective of this review is to reconcile old observations with new molecular details and to focus attention on the key remaining puzzles.

Enabling, empowering, inspiring: research and mentorship through the years*

The interrelationship between research and mentorship in an association such as the Medical Library Association (MLA) is revealed through the contributions of individuals and significant association activities in support of research. Research is vital to the well-being and ultimate survival of health sciences librarianship and is not an ivory tower academic activity. Mentorship plays a critical role in setting a standard and model for those individuals who want to be involved in research and, ultimately, for the preparation of the next generation of health sciences librarians. Research and mentorship are discussed in the context of personal experiences, scholarship, and problem solving in a practice environment. Through research and mentorship, we are enabled to enhance our services and programs, empowered to look beyond our own operations for information puzzles to be solved, and inspired to serve society by improving health.

Conscious recollection and the human hippocampal formation: evidence from positron emission tomography.

We used positron emission tomography (PET) to examine the role of the hippocampal formation in implicit and explicit memory. Human volunteers studied a list of familiar words, and then they either provided the first word that came to mind in response to three-letter cues (implicit memory) or tried to recall studied words in response to the same cues (explicit memory). There was no evidence of hippocampal activation in association with implicit memory. However, priming effects on the implicit memory test were associated with decreased activity in extrastriate visual cortex. On the explicit memory test, subjects recalled many target words in one condition and recalled few words in a second condition, despite trying to remember them. Comparisons between the two conditions showed that blood-flow increases in the hippocampal formation are specifically associated with the conscious recollection of studied words, whereas blood-flow increases in frontal regions are associated with efforts to retrieve target words. Our results help to clarify some puzzles concerning the role of the hippocampal formation in human memory.

El bienestar en España: una perspectiva de largo plazo, 1850-1991

Los historiadores económicos han estimado tradicionalmente el bienestar en términos de renta por persona. Durante la última década se han publicado, sin embargo, diversos trabajos que utilizan otros indicadores. Siguiendo esta línea de investigación, el artículo contrasta cuatro indicadores del bienestar en España (renta per capita, índice de Desarrollo Humano, Índice Físico de Calidad de Vida y estatura), dos de los cuales son inéditos (IDH e IFCV). Los resultados complican el objeto de estudio, pero sirven para proponer algunas hipótesis que deben ser ratificadas o desmentidas por futuras investigaciones.

The Legal Construction of Membership: Nationality Law in Germany and the United States. CES Germany & Europe Working Papers No. 00.5, 2000

The argument of this paper is that several empirical puzzles in the citizenship literature are rooted in the failure to distinguish between the mainly legal concept of nationality and the broader, political concept of citizenship. Using this distinction, the paper analysis the evolution of German and American nationality laws over the last 200 years. The historical development of both legal structures shows strong communalities. With the emergence of the modern system of nation states, the attribution of nationality to newborn children is ascribed either via the principle of descent or place of birth. With regard to the naturalization of adults, there is an increasing ethnization of law, which means that the increasing complexities of naturalization criteria are more and more structured along ethnic ideas. Although every nation building process shows some elements of ethnic self-description, it is difficult to use the legal principles of ius sanguinis and ius soli as indicators of ethnic or non-ethnic modes of community building.

The developmental control of size in insects

The mechanisms that control the sizes of a body and its many parts remain among the great puzzles in developmental biology. Why do animals grow to a species-specific body size, and how is the relative growth of their body parts controlled to so they grow to the right size, and in the correct proportion with body size, giving an animal its species-characteristic shape? Control of size must involve mechanisms that somehow assess some aspect of size and are upstream of mechanisms that regulate growth. These mechanisms are now beginning to be understood in the insects, in particular in Manduca sexta and Drosophila melanogaster. The control of size requires control of the rate of growth and control of the cessation of growth. Growth is controlled by genetic and environmental factors. Insulin and ecdysone, their receptors, and intracellular signaling pathways are the principal genetic regulators of growth. The secretion of these growth hormones, in turn, is controlled by complex interactions of other endocrine and molecular mechanisms, by environmental factors such as nutrition, and by the physiological mechanisms that sense body size. Although the general mechanisms of growth regulation appear to be widely shared, the mechanisms that regulate final size can be quite diverse.