Discovery of photospheric argon in very hot central stars of planetary nebulae and white dwarfs

We report the first discovery of argon in hot evolved stars and white dwarfs. We have identified the ArVII 1063.55A line in some of the hottest known (Teff=95000-110000 K) central stars of planetary nebulae and (pre-) white dwarfs of various spectral type. We determine the argon abundance and compare it to theoretical predictions from stellar evolution theory as well as from diffusion calculations. We analyze high-resolution spectra taken with the Far Ultraviolet Spectroscopic Explorer. We use non-LTE line-blanketed model atmospheres and perform line-formation calculations to compute synthetic argon line profiles. We find a solar argon abundance in the H-rich central star NGC1360 and in the H-deficient PG1159 star PG1424+535. This confirms stellar evolution modeling that predicts that the argon abundance remains almost unaffected by nucleosynthesis. For the DAO-type central star NGC7293 and the hot DA white dwarfs PG0948+534 and REJ1738+669 we find argon abundances that are up to three orders of magnitude smaller than predictions of calculations assuming equilibrium of radiative levitation and gravitational settling. For the hot DO white dwarf PG1034+001 the theoretical overprediction amounts to one dex. Our results confirm predictions from stellar nucleosynthesis calculations for the argon abundance in AGB stars. The argon abundance found in hot white dwarfs, however, is another drastic example that the current state of equilibrium theory for trace elements fails to explain the observations quantitatively.Comment: Accepted for publication in A&

Onset of giant planet migration before 4480 million years ago

Immediately after their formation, the terrestrial planets experienced intense impact bombardment by comets, leftover planetesimals from primary accretion, and asteroids. This temporal interval in solar system evolution, termed late accretion, thermally and chemically modified solid planetary surfaces and may have impeded the emergence of life on the Hadean Earth. The sources and tempo of late accretion are, however, vague. Here, we present a timeline that relates variably retentive radiometric ages from asteroidal meteorites, to new dynamical models of late accretion that invokes giant planet migration. Reconciliation of the geochronological data with dynamical models shows that giant planet migration immediately leads to an intense 30 Myr influx of comets to the entire solar system. The absence of whole-sale crustal reset ages after 4450 Ma for the most resilient chronometers from Earth, Moon, Mars, Vesta and various meteorite parent bodies confines the onset of giant planet migration to no later than ca. 4480 Ma. Waning impacts from planetesimals, asteroids (and a minor cometary component) continue to strike the inner planets through a protracted monotonic decline in impactor flux; this is in agreement with predictions from crater chronology. Amended global 3-D thermal analytical bombardment models derived from our new impact mass-production functions show that persistent niches for prebiotic chemistry on the early Hadean Earth could endure late accretion for at least the last 4400 Myr.Comment: Main text: 46564 characters with spaces/7549 words Tables: 3 Figures:7 References: 11

Separability criterion and inseparable mixed states with positive partial transposition

It is shown that any separable state on Hilbert space ${\cal H}={\cal H}_1\otimes{\cal H}_2$, can be written as a convex combination of N pure product states with $N\leq (dim{\cal H})^2$. Then a new separability criterion for mixed states in terms of range of density matrix is obtained. It is used in construction of inseparable mixed states with positive partial transposition in the case of $3\times 3$ and $2\times 4$ systems. The states represent an entanglement which is hidden in a more subtle way than it has been known so far.Comment: It is improved and extended version of the former manuscript, in particular the theorem concerning finite decomposition of separable states has been included, 14 pages, RevTe

Competition and bistability of ordered undulations and undulation chaos in inclined layer convection

Experimental and theoretical investigations of undulation patterns in high-pressure, inclined layer gas convection at a Prandtl number near unity are reported. Particular focus is given to the competition between the spatiotemporal chaotic state of undulation chaos and stationary patterns of ordered undulations. In experiments a competition and bistability between the two states is observed, with ordered undulations most prevalent at higher Rayleigh number. The spectral pattern entropy, spatial correlation lengths, and defect statistics are used to characterize the competing states. The experiments are complemented by a theoretical analysis of the Oberbeck-Boussinesq equations. The stability region of the ordered undulation as a function of their wavevectors and the Rayleigh number is obtained with Galerkin techniques. In addition, direct numerical simulations are used to investigate the spatiotemporal dynamics. In the simulations both ordered undulations and undulation chaos were observed dependent on initial conditions. Experiment and theory are found to agree well.Comment: Reduced-resolution figure

The Networked Recluse

The image is so well known it is practically iconic: The reclusive poet, feminine and fragile, weaving verse of beguiling complexity from the room in which she kept herself sequestered from the world. The Belle of Amherst, the distinctive American voice, the singer of the soul’s mysteries: Emily Dickinson. Yet that image scarcely captures the fullness and vitality of Dickinson’s life, most notably her many connections—to family, to friends, to correspondents, to the literary tastemakers of her day, even to the unnamed, and perhaps unknowable, “Master” to whom she addressed three of her most breathtaking works of prose. Through an exploration of a relatively small group of items from Dickinson’s vast literary remains, this volume—an accompaniment to an exhibition on Dickinson mounted at The Morgan Library & Museum in New York—demonstrates the complex ways in which these often humble objects came into conversation with other people, places, and events in the poet’s life. Seeing the network of connections and influences that shaped Dickinson’s life presents us with a different understanding of this most enigmatic yet elegiac poet in American letters, and allows us more fully to appreciate both her uniqueness and her humanity. The materials collected here make clear that the story of Dickinson’s manuscripts, her life, and her work is still unfolding. While the image of Dickinson as the reclusive poet dressed only in white remains a popular myth, details of Dickinson’s life continue to emerge. Several items included both in the exhibit and in this volume were not known to exist until the present century. The scrap of biographical intelligence recorded by Sarah Tuthill in a Mount Holyoke catalogue, or the concern about Dickinson’s salvation expressed by Abby Wood in a private letter to Abiah Root, were acquired by Amherst College in the last fifteen years. What additional pieces of evidence remain to be uncovered and identified in the attics and basements of New England? Published to accompany The Morgan Library & Museum’s pathbreaking exhibit I’m Nobody! Who are You? The Life and Poetry of Emily Dickinson—part of a series of exhibits at the Morgan celebrating and exploring the creative lives of significant women authors—The Networked Recluse offers the reader an account of the exhibit itself, together with a series of contributions by curators, scholars of Dickinson, and poets whose own work her words have influenced

O "USO" COMO FUNDAMENTO DE DESCRIÇÃO DA LÍNGUA NAS GRAMÁTICAS CASTELHANAS DE NEBRIJA E BELLO

À luz da História das Ideias Linguísticas, este estudo observa duas importantes gramáticas do castelhano: Gramática de la lengua castellana (1492), de autoria de Antonio de Nebrija, e a Gramática de la lengua castellana destinada al uso de los americanos (1847), de Andrés Bello, e propõe uma reflexão sobre a noção de “uso”, estabelecendo possíveis aproximações e distanciamentos. Reparamos que o “uso” é o critério tomado pelos dois gramáticos para definir a língua a ser descrita. Essa constatação nos suscita inquietações, como: Que “uso” é esse? O que esse “uso” determina no que se refere à língua? Que língua é essa que passa a ser descrita pelos gramáticos nas duas obras? Observamos os títulos, os prólogos e as noções preliminares das gramáticas na tentativa de compreender a dimensão que essa noção de “uso” ganha para os referidos autores. Concluímos que apresenta nuances diferentes

As representações do sujeito professor no manual didático de língua espanhola: uma leitura enunciativa

The present text presents the results of a study on the representation of teacher identity in Spanish-language didactic books. The theoretical frame employed is the Enunciative theory by Benveniste, particularly the notion of subjectivity in language. We analyzed the written enunciation in a teacher’s manual and the teacher’s oral enunciation through the observation, recording and transcription of 4 hours of class. Among other aspects the category of person was analyzed. Our departing point was the interactive relation between I-you in the classroom, which allows the constitution of interactive subjects in language. We checked two working hypotheses: if the teacher follows closely the discourse of the manual he/she presents him/herself as a repeater of someone else’s discourse. If he/she does not repeat the manual, he/she then appears as the subject of his/her enunciation. We concluded that the teacher presented him/herself as a mediator between the book and the students, adopting his/her own discourse, but that the teacher and the students were dependent on the discourse in the book.Este texto presenta los resultados de un estudio sobre la representación la subjetividad del profesor en el libro didáctico de lengua española. El referencial teórico utilizado es la teoría de la enunciación de Benveniste, específicamente la noción de subjetividad en el lenguaje. Hicimos el análisis de la enunciación escrita del manual y de la enunciación oral del profesor, mediante observación, grabación y transcripción de cuatro horas de clase. Analizamos la categoría de persona, entre otros aspectos. Partimos de la relación interactiva yo-tú, en el aula, lo que permitió la constitución de esos sujetos en el lenguaje. Trabajamos con dos hipótesis: si el profesor profiere fielmente el discurso del manual, se representa como un repetidor del discurso ajeno; si no lo repite, se muestra como sujeto de su enunciación. Concluimos que el profesor se representa como un mediador entre el libro y los alumnos, adoptando un discurso propio; pero, observamos que profesor y alumnos son dependientes del discurso del libro.Ce texte présente les résultats d’une étude sur la représentation de la subjectivité du professeur dans le livre didactique de langue espagnole. Le référentiel théorique employé est la théorie de l’énonciation de Benveniste, surtout la notion de subjectivité dans le langage. On a fait l’analyse de l’énonciation écrite du manuel et de l’énonciation orale du professeur à travers l’observation, l’enregistrement et la transcription de quatre heures de cours. On a analysé la catégorie de personne parmi d’autres aspects. On est partis de la relation interactive je-tu, dans la salle de classe, ce qui a permis la constitution de ces sujets dans le langage. On a travaillé avec deux hypothèses: si le professeur profère fidèlement le discours du manuel, il est représenté comme le répétiteur du discours d’autrui; s’il ne le répète pas, il se montre comme sujet de son énonciation. On a conclu que le professeur est représenté comme un médiateur entre le livre et les élèves, adoptant un discours propre, mais on a observé que le professeur et les élèves dépendent du discours du livre.Este texto apresenta os resultados de um estudo sobre a representação da subjetividade do professor no livro didático de língua espanhola. O referencial teórico utilizado é a teoria da enunciação de Benveniste, especificamente a noção de subjetividade na linguagem. Fizemos a análise da enunciação escrita do manual e da enunciação oral do professor mediante observação, gravação e transcrição de quatro horas/aula. Analisamos a categoria de pessoa, dentre outros aspectos. Partimos da relação interativa eu-tu, na sala de aula, o que permitiu a constituição desses sujeitos na linguagem. Trabalhamos com duas hipóteses: se o professor profere fielmente o discurso do manual, representa-se como um repetidor do discurso alheio; se não o repete, mostra-se como sujeito da sua enunciação. Concluímos que o professor se representa como um mediador entre o livro e os alunos, adotando um discurso próprio, mas observamos que professor e alunos são dependentes do discurso do livro

Os estudos da enunciação e a formação do professor de línguas

Este trabalho apresenta algumas reflexões a respeito de como os estudos da enunciação, principalmente da teoria da subjetividade de Émile Benveniste, podem contribuir para a formação de professores de línguas (estrangeiras). Acreditamos que noções de língua/linguagem, subjetividade e sentido podem ajudar a esses profissionais na sua prática pedagógica. O presente estudo justifica-se principalmente pela busca constante de leituras e atitudes que venham a continuar a formação profissional, reforçando a formação reflexiva de professores de línguas. “A primeira condição para que um ser possa assumir um ato comprometido está em ser capaz de agir e refletir.” (Freire, 1983:16)

Presence and Localization of Pro-and Mature Forms of Biglycan and Decorin in Human Costal Cartilage Derived from Chest Wall Deformities

Costal cartilage is a type of hyaline cartilage that forms rod-like structures that connect the ribs to the sternum. The most common chest wall deformities, pectus excavatum and pectus carinatum involved efective costal cartilage resulting in sternal displacement. Costal cartilage is not widely studied leaving little insight into possible factors involved in the pathogenesis of these pectus deformities. This study focused on the presence and distribution of two important regulators of collagen fibrillogenesis and organization, biglycan and decorin. Immunohistochemical analysis of transverse cross sections of normal and deformed costal cartilage revealed that biglycan and decorin mainly localized in the territorial matrix except for prodecorin which was only found within chondrocytes. Western blot analysis of whole protein extracts demonstrated the presence of both pro and mature forms of biglycan and mature decorin in patients and controls. In normal costal cartilage of different ages, the mature form of decorin was absent in a fetal sample whereas mature biglycan was weakly expressed, suggestive that mature biglycan may play a role in early costal cartilage development. Further studies are needed to determine the functional differences between the pro- and mature forms of biglycan and decorin both in age and disease