Unusual manganese enrichment in the Mesoarchean Mozaan Group, Pongola Supergroup, South Africa

An unusual sediment-hosted manganese deposit is described from the Mesoarchean Mozaan Group, Pongola Supergroup, South Africa. MnO contents up to 15 wt.% were observed in marine clastic and chemical sedimentary rocks. Mn enrichment is interpreted to have resulted from the hydrothermal alteration of manganiferous shale and BIF parent rocks, the primary MnO contents of which are as high as 8.5 wt.%. A detailed mineralogical and petrographic study shows that these parent rocks are characterized by manganoan siderite, ferroan rhodochrosite and other Mn-Fe-rich mineral phases, such as kutnohorite and Fe-Mn-chlorite. Their hypogene alteration gave rise to a diversification of mineral assemblages where ferroan tephroite, calcian rhodochrosite, rhodochrosite, pyrochroite, pyrophanite, cronstedtite, manganoan Fe-rich chlorite and manganoan phlogopite partially or totally replaced the previous mineral assemblage. Thermodynamic modeling performed on chlorite phases associated with the described mineral assemblages illustrates a decrease of average crystallization temperatures from ca. 310 °C during early metamorphic stages to ca. 250 °C during a hydrothermal stage. Mineral transformation processes were thus related to retrograde metamorphism and/or hydrothermal alteration post-dating metamorphism and gave rise to progressive Mn enrichment from unaltered parent to altered rocks. The timing of hypogene alteration was constrained by 40Ar/39Ar dating to between about 1500 and 1100 Ma ago, reflecting tectonic processes associated with the Namaqua-Natal orogeny along the southern Kaapvaal Craton margin. Manganiferous shale and BIF of the Mozaan Group may represent the oldest known examples of primary sedimentary Mn deposition, related to oxidation of dissolved Mn(II) by free oxygen in a shallow marine environment. Oxygenic photosynthesis would have acted as a first-order control during Mn precipitation. This hypothesis opens a new perspective for better constraining secular evolution of sediment-hosted mineral deposits linked to oxygen levels in the atmosphere-hydrosphere system during the Archean Eon

Valoración de salud mental en formación de profesores en dos universidades chilenas

This study analyzed the evaluation of professors of pedagogy and directors programs, about the importance of mental health in vocational training, and factors that might influence this valuation. The methodology includes participation of 17 academicians (professors and belonging to the managerial staff) of two universities in southern Chile. A survey with closed and open questions, and in-depth interviews were used to collect information. Data was analyzed using content analysis. The results show that teachers have, mostly, a high personal assessment of the topic ( = 2.8, between 0 and 3). There is, on the other hand, an ambivalent valuation on the part of the institutions; a lack of knowledge and a low conceptual and procedural proficiency of pedagogues, and a low priority as a competence in their training (59% of participants are not aware of the existence of any programs or courses related to this subject). The ambivalence in institutions, its importance as competence in teachers’ training and the consistency with the low priority given to the subject in public policies are discussed.El estudio analizó la valoración de docentes universitarios de pedagogía y directores de carrera respecto a la importancia de la salud mental en la formación profesional analizando, además, los factores que podrían influir en dicha valoración. Dentro de la metodología utilizada se consideró la participación de 17 académicos (docentes y directivos) formadores de profesores de dos instituciones universitarias del sur de Chile. Para la recolección de información se utilizó una encuesta con preguntas cerradas y abiertas y entrevistas en profundidad; se analizó la información mediante análisis de contenido. Los resultados muestran que los docentes tienen, en su mayoría, una alta valoración personal del tema ( = 2.8, entre 0 y 3), existiendo una valoración ambivalente por parte de las instituciones; bajo conocimiento y dominio conceptual y procedimental, de los pedagogos, y baja prioridad como competencia en su formación (59% desconoce la existencia de asignaturas o programas en la carrera). Se discute acerca de la ambivalencia que presentaría en las instituciones, su importancia como competencia en la formación docente y la consistencia con la escasa importancia dada, en general, al tema a nivel de política pública.El estudio analizó la valoración de docentes universitarios de pedagogía y directores de carrera respecto a la importancia de la salud mental en la formación profesional analizando, además, los factores que podrían influir en dicha valoración. Dentro de la metodología utilizada se consideró la participación de 17 académicos (docentes y directivos) formadores de profesores de dos instituciones universitarias del sur de Chile. Para la recolección de información se utilizó una encuesta con preguntas cerradas y abiertas y entrevistas en profundidad; se analizó la información mediante análisis de contenido. Los resultados muestran que los docentes tienen, en su mayoría, una alta valoración personal del tema ( = 2.8, entre 0 y 3), existiendo una valoración ambivalente por parte de las instituciones; bajo conocimiento y dominio conceptual y procedimental, de los pedagogos, y baja prioridad como competencia en su formación (59% desconoce la existencia de asignaturas o programas en la carrera). Se discute acerca de la ambivalencia que presentaría en las instituciones, su importancia como competencia en la formación docente y la consistencia con la escasa importancia dada, en general, al tema a nivel de política pública

Bosonization as Duality

We show that bosonization in two dimensions can be derived as a special case of the duality transformations that have recently been used to good effect in string theory. This allows the construction of the bosonic counterpart of any fermionic theory simply by `following your nose' using the standard duality transformation rules. We work through the bosonization of the Dirac fermion, the massive and massless Thirring models, and a fermion on a cylindrical spacetime as illustrative examples.Comment: plain TeX, 21 page

Flavour and polarisation in heavy neutrino production at e+ e- colliders

We analyse l W nu production at ILC, paying special attention to the role of the final lepton flavour and beam polarisation in the search for a new heavy neutrino N. We show that a sizeable coupling to the electron V_eN ~ 10^-2 is necessary to have an observable signal in any of the channels, despite the fact that the signal may be more visible in muon or tau final states. The non-observation of a heavy neutrino at ILC will improve the present upper bound on its mixing with the electron by more than one order of magnitude, V_eN < 0.007 for m_N between 200 and 400 GeV.Comment: 17 pages, 5 PS figures. References added. To be published in PL

Bosonization in Higher Dimensions

Using the recently discovered connection between bosonization and duality transformations (hep-th/9401105 and hep-th/9403173), we give an explicit path-integral representation for the bosonization of a massive fermion coupled to a U(1) gauge potential (such as electromagnetism) in d space (D=d+1 spacetime) dimensions. The bosonic theory is described by a rank d-1 antisymmetric Kalb-Ramond-type gauge potential. We construct the bosonized lagrangian explicitly in the limit of large fermion mass. We find that the resulting action is local for d=2 (and given by a Chern-Simons action), but nonlocal for d larger than 3. By coupling to a statistical Chern-Simons field for d=2, we obtain a bosonized formulation of anyons. The bosonic theory may be further dualized to a theory involving purely scalars, for any d, and we show this to be governed by a higher-derivative lagrangian for which the scalar decouples from the U(1) gauge potential.Comment: (We had omitted some references and had misspelled `aficionados') plain TeX, 11 pages, McGill-94/33, NEIP-94-006, OSLO-TP 10-9

Relation between metacognitive strategies, motivation to think, and critical thinking skills

Critical thinking is a complex reasoning skill, and even though it is hard to reach a consensus on its definition, there is agreement on it being an eminently cognitive skill. It is strongly related with reflective and metacognitive skills, as well as attitudinal or motivational aspects, although no model has yet been able to integrate these three elements. We present herein the preliminary results of a study seeking to establish these relations, in a sample of Chilean university students. 435 students from three universities participated, of which 88 were men, 333 were women, and 14 did not indicate their gender. Their ages ranges between 18 and 51 years old (M = 21, SD = 3.09). Three instruments were applied, one to measure metacognitive strategies, one to measure motivation to critical thinking, and a third to measure critical thinking skills. The relation was analyzed via structural equations. The results show a positive, strong, and significant relation between metacognition and motivation to think. However, only a weak significant relation was observed between motivation to think and critical thinking, and no direct relation was found between metacognition and critical thinking. We hypothesize a significant but moderate relation between the variables, where metacognition influences motivation to think, which in turn influences critical thinking skills. Factors are discussed which could negatively affect the studied relations, as well as the importance of generating integrated models between the three variables, as they would show a theoretical and empirical link

ArgoNeuT and the Neutrino-Argon Charged Current Quasi-Elastic Cross Section

ArgoNeuT, a Liquid Argon Time Projection Chamber in the NuMI beamline at Fermilab, has recently collected thousands of neutrino and anti-neutrino events between 0.1 and 10 GeV. The experiment will, among other things, measure the cross section of the neutrino and anti-neutrino Charged Current Quasi-Elastic interaction and analyze the vertex activity associated with such events. These topics are discussed along with ArgoNeuT's automated reconstruction software, currently capable of fully reconstructing the muon and finding the event vertex in neutrino interactions.Comment: 6 pages, 4 figures, presented at the International Nuclear Physics Conference, Vancouver, Canada, July 4-9, 2010, to be published in Journal of Physics: Conference Series (JPCS

Possible Origin of Fermion Chirality and Gut Structure From Extra Dimensions

The fundamental chiral nature of the observed quarks and leptons and the emergence of the gauge group itself are most puzzling aspects of the standard model. Starting from general considerations of topological properties of gauge field configurations in higher space-time dimensions, it is shown that the existence of non-trivial structures in ten dimensions would determine a class of models corresponding to a grand unified GUT structure with complex fermion representations with respect to $SU(3)_C \otimes SU(2)_L \otimes U(1)_Y$. The discussion is carried out within the framework of string theories with characteristic energy scales below the Planck mass. Avoidance of topological obstructions upon continuous deformation of field configurations leads to global chiral symmetry breaking of the underlying fundamental theory, imposes rigorous restrictions on the structure of the vacuum and space-time itself and determines uniquely the gauge structure and matter content.Comment: final version to appear in Phys. Rev.

Paz es entender lo que somos: prácticas socioculturales de paz en Quibdó

This paper presents the research findings of the project Socio-cultural Practices of Peace in Quibdó (Prácticas socioculturales de paz en Quibdó), which aims to contribute to understanding peacebuilding out of the daily life of communities from the capital of Chocó. A contextualized analysis of Quibdó is proposed regarding peacebuilding from cultural practices. This qualitative research study unfolds a hermeneutic phenomenological methodology. The information analysis was carried out by triangulating information, with primary and secondary sources, through ten semi-structured, in-depth interviews. The axial and categorical coding was carried out using the ATLAS.ti software, version 7.5. The study found that the recognition of peace from a territorial approach based on daily cultural practices allows both resignification of memory and appropriation of social environment, historical memory and non-violence. The study concludes that socio-cultural practices of peace make it possible to demonstrate the vindication of the "Afro" and the "Chocoano", thus recognizing the need to integrate aspects such as gender, ethnicity and social commitment in coexistence with others.El artículo presenta los resultados de investigación del proyecto «Prácticas socioculturales de paz en Quibdó», que busca contribuir a la comprensión de la construcción de paz desde la cotidianidad de las comunidades de la capital del Chocó. Se plantea un análisis contextualizado de Quibdó frente a la construcción de paz desde las prácticas culturales. El enfoque es cualitativo, desde una metodología hermenéutico-fenomenológica. El análisis de la información se realizó a partir de la triangulación de información con fuentes primarias y secundarias a través de diez entrevistas semiestructuradas a profundidad. La codificación axial y categorial se realizó mediante el software ATLAS.ti, versión 7.5. Se encontró que el reconocimiento de la paz desde un enfoque territorial a partir de prácticas culturales cotidianas permite la resignificación de la memoria y la apropiación del entorno social, la memoria histórica y la no violencia. Se concluye que las prácticas socioculturales de paz permiten evidenciar la reivindicación de lo «afro» y lo «chocoano», reconociendo la necesidad de integrar aspectos como el género, lo étnico y el compromiso social en coexistencia con los otros

Overview of Plasma Lens Experiments and Recent Results at SPARC_LAB

Beam injection and extraction from a plasma module is still one of the crucial aspects to solve in order to produce high quality electron beams with a plasma accelerator. Proper matching conditions require to focus the incoming high brightness beam down to few microns size and to capture a high divergent beam at the exit without loss of beam quality. Plasma-based lenses have proven to provide focusing gradients of the order of kT/m with radially symmetric focusing thus promising compact and affordable alternative to permanent magnets in the design of transport lines. In this paper an overview of recent experiments and future perspectives of plasma lenses is reported