Age Determination of a Granite Gneiss from the Precambrian Basement of Scioto County, Ohio

Author Institution: Department of Geology and Mineralogy, The Ohio State University, Columbus, Ohio 43210 and Ohio Division of Geological Survey, Columbus, Ohio 43212Biotite and potassium feldspar from a specimen of granite gneiss from the Precambrian basement of Scioto County (Permit No. 212, Greenup Quadrangle of Green Township) have been dated by the Rb-Sr method. The model dates, calculated relative to an assumed initial 87Sr/86Sr ratio of 0.7040, are 898±40 million years (biotite) and 1242±46 million years (potassium feldspar). The dates are discordant, which suggests that the minerals gained or lost rubidium and/or strontium during an episode of metamorphism. The age of the metamorphism is estimated as 840=t42 million years, assuming that both minerals were isotopically re-equilibrated and had the same 87Sr/86Sr ratio of 0.7178± 0.0026. The model date of the biotite agrees with previous age determinations of basement rocks from Ohio and confirms the interpretation that the Grenville Province of the Canadian Precambrian Shield extends southward into Ohio

Middle Carboniferous crustal melting in the Variscan Belt: New insights from U-Th-Pbtot. monazite and U-Pb zircon ages of the Montagne Noire Axial Zone (southern French Massif Central)

International audienceIn France, the Devonian-Carboniferous Variscan orogeny developed at the expense of continental crust belonging to the northern margin of Gondwana. A Visean-Serpukhovian crustal melting has been recently documented in several massifs. However, in the Montagne Noire of the Variscan French Massif Central, which is the largest area involved in this partial melting episode, the age of migmatization was not clearly settled. Eleven U-Th-Pbtot. ages on monazite and three U-Pb ages on associated zircon are reported from migmatites (La Salvetat, Ourtigas), anatectic granitoids (Laouzas, Montalet) and post-migmatitic granites (Anglès, Vialais, Soulié) from the Montagne Noire Axial Zone are presented here for the first time. Migmatization and emplacement of anatectic granitoids took place around 333-326Ma (Visean) and late granitoids emplaced around 325-318Ma (Serpukhovian). Inherited zircons and monazite date the orthogneiss source rock of the Late Visean melts between 560Ma and 480Ma. In migmatites and anatectic granites, inherited crystals dominate the zircon populations. The migmatitization is the middle crust expression of a pervasive Visean crustal melting event also represented by the "Tufs anthracifères" volcanism in the northern Massif Central. This crustal melting is widespread in the French Variscan belt, though it is restricted to the upper plate of the collision belt. A mantle input appears as a likely mechanism to release the heat necessary to trigger the melting of the Variscan middle crust at a continental scale

6D Frictional Contact for Rigid Bodies

International audienceWe present a new approach to modeling contact between rigid objects that augments an individual Coulomb friction point-contact model with rolling and spinning friction constraints. Starting from the intersection volume, we compute a contact normal from the volume gradient. We compute a contact position from the first moment of the intersection volume, and approximate the extent of the contact patch from the second moment of the intersection volume. By incorporating knowledge of the contact patch into a point contact Coulomb friction formulation, we produce a 6D constraint that provides appropriate limits on torques to accommodate displacement of the center of pressure within the contact patch, while also providing a rotational torque due to dry friction to resist spinning. A collection of examples demonstrate the power and benefits of this simple formulation

Une affaire de spécialistes ?

Partant du travail d’inventaire et de documentation des collections zoologiques des muséums de Clermont-Ferrand et de Bordeaux, cette contribution montre comment l’assistance de naturalistes spécialisés dans ces domaines, et extérieurs aux établissements, est indispensable pour valider les données de biodiversité de ces collections et valoriser leur intérêt scientifique

Visions et divisions à l’université

Comment les universitaires parlent-ils de leur travail ? Comment décrivent-ils leurs tâches et comment celles-ci s’agencent-elles ? L’article met en discussion les résultats principaux d’un rapport de recherche publié en 2005. Celui-ci s’interroge sur les pratiques et les catégories de perception des enseignants-chercheurs face à l’accroissement des tâches administratives, au développement des formations professionnelles et à la massification des publics étudiants, ces transformations semblant devoir se traduire par le recul de la place de la recherche dans l’économie générale du métier.How do university professors speak about their work? How do they describe their tasks and how do these tasks combine ? This paper discusses the main results of a research report published in 2005. This report wonders about the practices and categories of perception of teachers- researchers faced with the increase of administrative tasks, the development of professional training and the massification of student audiences. These changes seem to involve a decline of the place of research in the general organisation of the profession.¿Cómo hablan los universitarios de su trabajo ? ¿Cómo describen sus tareas ? y ¿cómo se agencian éstas ? El artículo pone en discusión los principales resultados de una relación de investigación publicada en 2005. Ésta se interroga sobre las prácticas y las categorías de percepción de los docentes-investigadores frente al aumento de las tareas administrativas, al desarrollo de las formaciones profesionales y a la masificación de los públicos estudiantiles, al parecer estas transformaciones se traducirían por la regresión del lugar de la investigación en la economía general del oficio.Wie sprechen die Akademiker von ihrer Arbeit ? Wie beschreiben sie ihre Tätigkeiten und wie passen diese zusammen ? Der Artikel zeigt die Hauptergebnisse eines 2005 veröffentlichen Forschungsberichts. Dieser analysiert die Tätigkeiten und die Wahrnehmungskategorien der Lehrer-Forscher der Zunahme der Verwaltungsaufgaben, der Entwicklung der Berufsausbildungen und der Vermassung der Studenten gegenüber. Dabei verursachen diese Verwandlungen anscheinend den Rückgang der Forschung im Beruf

Palaeomagnetic constraints from granodioritic plutons (Jiaodong Peninsula): New insights on Late Mesozoic continental extension in eastern Asia.

International audienceMechanism and kinematics of the Late Mesozoic continental extension event of eastern Asia are still debated. In order to better constrain its evolution, two granodioritic plutons of the Jiaodong Peninsula have been chosen as targets for a time-constrained palaeomagnetic study. Indeed, plutons are devoid of visible deformation, did not experience rotation along horizontal axis and are precisely dated by U/Pb and 40Ar/39Ar methods. Multidomain (MD) magnetite has been identified as the principal magnetic remanent carrier. The interpolation of existing and new U/Pb and 40Ar/39Ar ages revealed that characteristic remanent magnetisation was acquired in a narrow range of 116 ± 2 Ma. Twenty out of 27 sites present stable magnetic directions calculated from high-temperature or high-coercive components. The observations of the solo normal magnetic polarity for this palaeomagnetic collection and of the magnetic remanent age consistent with the Cretaceous Normal Superchron (CNS) argue that the characteristic magnetic remanence may be considered as primary. Detailed field observations of the intrusive relationship between the plutons and country rocks and Anisotropy of Magnetic Susceptibility (AMS) study reveal the absence of the subsequent deformation of plutons, or rigid rotation of plutons along a horizontal axis. Two palaeomagnetic poles have been therefore calculated from these plutons. Among 12 out 15 Cretaceous palaeomagnetic poles, including the two new poles provided by this study, from the Jiaodong Peninsula and on both sides of Tan-Lu and Muping-Jimo faults are statistically consistent. As a result, the Jiaodong Peninsula behaved as a rigid block as internal deformation appears negligible. The remaining three derived poles are probably due to the secular variation or/and the vicinity of fault zones near of the palaeomagnetic sampling site. Thus, they can not be applied to the peninsula-scaled tectonics. Comparison of these time52 constrained Cretaceous palaeomagnetic results of the Jiaodong Peninsula with those of North China Block (NCB) indicate that the Jiaodong Peninsula was rigidly attached to NCB since, 3 at least, the Cretaceous as residual difference is clearly insignificant with respect to the error brackets. These new palaeomagnetic results confirm that the relative clockwise (CW) rotation of Eastern Liaoning-Korea Block (ELKB) with respect to NCB does not affect the Jiaodong Peninsula as a rigid block, nevertheless, some tectonic structures have been reactivated since Cenozoic and local rotations could be produced. This palaeomagnetic study reveals that the Late Mesozoic extension in Eastern Asia is heterogeneously expressed in time and space. The complete understanding of the mechanism(s) of this extensional event needs further multidisciplinary investigations

Virtual reality gaming elevates heart rate but not energy expenditure compared to conventional exercise in adult males

Virtual reality using head-mounted displays (HMD) could provide enhanced physical load during active gaming (AG) compared to traditional displays. We aimed to compare the physical load elicited by conventional exercise and AG with an HMD. We measured energy expenditure (EE) and heart rate (HR) in nine healthy men (age: 27 ± 5 years) performing three testing components in a randomised order: walking at 6 km/h (W6), AG, and AG with an additional constraint (AGW; wrist-worn weights). Although we found that HR was not significantly different between W6 and the two modes of AG, actual energy expenditure was consistently lower in AG and AGW compared to W6. We observed that playing AG with wrist-worn weights could be used as a means of increasing energy expenditure only at maximum game level, but ineffective otherwise. Our findings indicate that AG in an HMD may not provide a sufficient stimulus to meet recommended physical activity levels despite increased psychophysiological load. The differential outcomes of measures of HR and EE indicates that HR should not be used as an indicator of EE in AG. Yet, adding a simple constraint (wrist-worn weights) proved to be a simple and effective measure to increase EE during AG

Recurrence Quantification Analysis and Principal Components in the Detection of Short Complex Signals

Recurrence plots were introduced to help aid the detection of signals in complicated data series. This effort was furthered by the quantification of recurrence plot elements. We now demonstrate the utility of combining recurrence quantification analysis with principal components analysis to allow for a probabilistic evaluation for the presence of deterministic signals in relatively short data lengths.Comment: 10 pages, 3 figures; Elsevier preprint, elsart style; programs used for analysis available for download at http://homepages.luc.edu/~cwebbe

Shape and topology optimization considering anisotropic features induced by additive manufacturing processes

International audienceThis article considers the modelling of the effective properties of the constituent material of structures fabricated by additive manufacturing technologies; the influence of these properties on the design optimization process is analyzed, and the opportunities that they offer in this context are investigated. On the one hand, emphasizing on the case where the particular material extrusion techniques are used for the construction, we propose a model for the anisotropic material properties of shapes depending on the (user-defined) trajectory followed by the machine tool during the assembly of their $2d$ layers. On the other hand, we take advantage of the potential of additive manufacturing technologies for constructing very small features: we consider the optimization of the infill region of a shape with given external contour with the goal to improve at the same time its lightness and its robustness. The optimized and constraint functionals of the domain involved in the shape optimization problems in both contexts are rigorously analyzed, notably by relying on the notion of signed distance function. Eventually, several numerical experiments are conducted in two dimensions to illustrate the main points of the study

PARENTESCO E ETNICIDADE: trajetória de uma liderança quilombola no sertão de Pernambuco

Neste artigo, analisaremos como uma liderança comunitária do Sítio Feijão e Posse (em Mirandiba, sertão de Pernambuco) dá materialidade a intervenções públicas ligadas a categoria quilombola (como categoria identitária, jurídica e administrativa). Tendo como referência as práticas e representações dos comunitários e da própria liderança, faremos umretrato ambivalente dessa pessoa, que, para alguns, age a favor de seu grupo de parentesco restrito, e, para outros, age a favor dos quilombolas em geral. Nosso enfoque empírico no “mundo de vida” dos atores locais é inspirado pela antropologia da ação pública e das políticas públicas, a qual e studa, geralmente em contextos africanos, o “entrelaçamento de lógicas sociais” observado localmente em intervenções incialmente induzidas pelo poder público. Diante da complexidade das dinâmicas observadas, é preciso, em nossa visão, uma abordagem que não se restringe a etnicidade, noção de base em vários estudos sobre comunidades quilombolas.&nbsp