Detailed Spectral Analysis of the Type Ib Supernova 1999dn. Paper I: Hydrogen-free Models

We present spectral fits to five epochs of the typical Type Ib supernova 1999dn using the generalized, non-LTE, stellar atmospheres code PHOENIX. Our goal is threefold: to determine basic physical properties of the supernova ejecta, such as velocity, temperature, and density gradients; to reproduce He I absorption lines by invoking non-thermal excitation; and, to investigate possible spectral signatures of hydrogen, especially a feature around 6200 Angstrom, which has been attributed to high velocity $H_\alpha$. Our models assume an atmosphere with uniform composition devoid of any hydrogen. Our model spectra fit the observed spectra well, successfully reproducing most of the features, including the prominent He I absorptions. The most plausible alternative to $H_\alpha$ as the source of the 6200 Angstrom feature is a blend of Fe II and Si II lines, which can be made stronger to fit the observed feature better by increasing the metallicity of the ejecta. High-metallicity models fit well at early epochs, but not as well as solar-metallicity models after maximum light. While this blend of metal lines is a reasonable explanation of the source of the 6200 Angstrom feature, it is still important to investigate hydrogen as the source; therefore, a second paper will present models that include a thin shell of hydrogen around the main composition structure.Comment: 24 pages, 11 figures, 2 tables, submitted to Ap

Occupational Therapy’s Role in Early Language Development of Babies and Young Children

Occupational therapy practitioners in their interactions with babies, young children and their families, can be change-agents who promote rich language environments as a foundation to social interactions, social participation and academic successes. OTPs may be the sole provider working with a family or may reinforce with families the plan of care developed by speech-language pathologists (SLP) or early intervention teachers. The first step for OTPs is deeper knowledge of the importance of early language exposure, social interaction and participation development in young children and approaches that promotes rich language environments

Future Requirements and Applications for Orbital Transfer Vehicles

The capability of the Space Shuttle will be enhanced by use of the high-energy Centaur to provide payload transfer to higher orbits (geosynchronous, etc.) and for planetary escape missions. Future orbital transfer vehicles (OTV) requirements for NASA, military, and commercial exploitation of space will require improvements and technological developments such as increased performance, increased reliability, and increased mission versatility. Eventual OTV space basing should offer further cost reductions through vehicle reuse, freedom from Shuttle constraints, and possible STS propellant recovery. This paper summarizes Centaur characteristics, performance, and program status and presents future considerations for orbital transfer vehicles into the Space Station era, including their capabilities, operational requirements, and the technology developments required to make them a reality

Searching for Hydrogen in Type Ib Supernovae

We present synthetic spectral fits of the typical Type Ib SN 1999dn and the Hydrogen Rich Ib SN 2000H using the generalized non-local thermodynamic equilibrium stellar atmospheres code \phx. We fit model spectra to five epochs of SN 1999dn ranging from ten days pre-maximum light to 17 days post-maximum light and the two earliest epochs of SN 2000H available, maximum light and six days post-maximum. Our goal is to investigate the possibility of hydrogen in Type Ib Supernovae (SNe Ib), specifically a feature around 6200\AA\ which has previously been attributed to high velocity H-alpha. In earlier work on SN 1999dn we found the most plausible alternative to H-alpha to be a blend of Si II and Fe II lines which can be adjusted to fit by increasing the metallicity. Our models are simple; they assume a powerlaw density profile with radius, homologous expansion, and solar compositions. The helium core is produced by burning 4H --> He in order to conserve nucleon number. For models with hydrogen the outer skin of the model consists of a shell of solar composition. The hydrogen mass of the standard solar composition shell is M_H less than about 0.001 times the mass of the sun in SN 1999dn and M_H less than about 0.2 times the mass of the sun for SN 2000H. Our models fit the observed spectra reasonably well, successfully reproducing most features including the characteristic He I absorptions. The hydrogen feature in SN 1999dn is clear, but much more pronounced in SN 2000H. We discuss a possible evolutionary scenario that accounts for the dichotomy in the hydrogen shell mass between these two supernovae.Comment: 20 pages, 11 figures, ApJ, in pres

The Cape Porcupine Complex, northern mainland Nova Scotia – no longer a geological orphan

The Cape Porcupine Complex west of the Strait of Canso in northern mainland Nova Scotia consists of mainly fault-bounded units of metasedimentary, metavolcanic, and granitoid rocks. A previously reported U-Pb (zircon) age of 610 ± 3 Ma from syenogranite combined with petrological characteristics indicates that some of the granitic rocks and possibly an associated body of leucodiorite are Late Neoproterozoic. In contrast, alkali-feldspar granite from a more extensive suite of quartz alkali-feldspar syenite/alkali-feldspar syenite, alkali-feldspar granite/syenogranite, and quartz alkali-feldspar leucosyenite with A-type characteristics yielded an early Ordovician age of 478 ± 3 Ma. Similar A-type chemical characteristics suggest that the metavolcanic unit may be the extrusive equivalent of the Ordovician suite.Similarities in age and petrological characteristics indicate that the Cape Porcupine Complex is linked to rock units in the Antigonish Highlands. The ca. 610 Ma granitic rocks are likely related to plutonic and volcanic rocks of similar age in the Antigonish Highlands interpreted to have formed at a continental margin subduction zone. In contrast the A-type syenitic and metavolcanic rocks are probably related to the compositionally similar West Barneys River plutonic suite and younger volcanic rocks formed in an extensional regime. Such rocks do not occur in adjacent Ganderia or Avalonia in Cape Breton Island or southern New Brunswick, further demonstrating the regional significance of the Canso Fault in tectonic reconstructions.RÉSUMÉSitué à l’ouest du détroit de Canso au nord de la partie continentale de la Nouvelle-Écosse, le complexe du cap Porcupine se compose principalement d’unités rocheuses métasédimentaires, métavolcaniques et de granitoïdes limitées par des failles. Une datation réalisée précédemment par la méthode U-Pb sur zircon et qui a établi un âge de 610 ± 3 Ma à partir du syénogranite et des caractéristiques pétrologiques indique qu’une partie des roches de granite et vraisemblablement un corps connexe de leucodiorite sont du Néoprotérozoïque tardif. Par contraste, du granite de feldspath alcalin d’une succession plus importante de syénite de feldspath alcalin quartzeux/syénite de feldspath alcalin, de granite de feldspath alcalin/syénogranite, et de leucosyénite de feldspath alcalin quartzeux présentant des caractéristiques de type A a produit un âge de l’Ordovicien précoce, soit environ 478 ± 3 Ma. Ces caractéristiques chimiques de type A analogues portent à croire que l’unité métavolcanique pourrait être l’équivalent extrusif de la succession de l’Ordovicien.Les similitudes de datation et les caractéristiques pétrologiques indiquent que le complexe du cap Porcupine est relié aux unités rocheuses des hautes-terres d’Antigonish. L’âge du granite, d’environ 640 Ma, se rapporterait vraisemblablement aux roches plutoniques et volcaniques de la même époque observées dans les hautes-terres d’Antigonish, dont on suppose qu’elles ont été formées dans une zone de subduction de la marge continentale. Par contraste, les roches métavolcaniques et syénitiques de type A sont probablement reliées par la similitude de leur composition au cortège plutonique et aux roches volcaniques plus jeunes de la rivière Barneys Ouest formées dans un milieu de distension. Ces roches ne sont pas présentes dans la partie adjacente de Ganderia ou d’Avalonia sur l’île du Cap-Breton ou dans le sud du Nouveau-Brunswick, ce qui tendrait à souligner encore plus l’importance régionale de la faille de Canso dans les reconstructions tectoniques.[Traduit par la redaction

Orbital Instabilities in a Triaxial Cusp Potential

This paper constructs an analytic form for a triaxial potential that describes the dynamics of a wide variety of astrophysical systems, including the inner portions of dark matter halos, the central regions of galactic bulges, and young embedded star clusters. Specifically, this potential results from a density profile of the form $\rho (m) \propto m^{-1}$, where the radial coordinate is generalized to triaxial form so that $m^2 = x^2/a^2 + y^2/b^2 + z^2/c^2$. Using the resulting analytic form of the potential, and the corresponding force laws, we construct orbit solutions and show that a robust orbit instability exists in these systems. For orbits initially confined to any of the three principal planes, the motion in the perpendicular direction can be unstable. We discuss the range of parameter space for which these orbits are unstable, find the growth rates and saturation levels of the instability, and develop a set of analytic model equations that elucidate the essential physics of the instability mechanism. This orbit instability has a large number of astrophysical implications and applications, including understanding the formation of dark matter halos, the structure of galactic bulges, the survival of tidal streams, and the early evolution of embedded star clusters.Comment: 50 pages, accepted for publication in Ap

Field relations, age, and tectonic setting of metamorphic and plutonic rocks in the Creignish Hills – North Mountain area, southwestern Cape Breton Island, Nova Scotia, Canada

 The Creignish Hills and North Mountain areas of southwestern Cape Breton Island consist mostly of Neoproterozoic rocks typical of the Ganderian Bras d’Or terrane. U-Pb ages presented here for detrital zircon in the Blues Brook Formation of the Creignish Hills confirm a depositional age no greater than about 600 Ma. Although it is possible that some components of the formation are much older, similarities in rock types and field relations suggest that this is not the case. It is likely that the equivalent Malagawatch Formation of the North Mountain area, as well as high-grade metasedimentary rocks of the Melford Formation and Chuggin Road complex in the Creignish Hills and Lime Hill gneiss complex in the North Mountain area, represent the same or stratigraphically equivalent units as the Blues Brook Formation. The minimum ages of all of these units are constrained by cross-cutting syn- and post-tectonic plutons with ages mostly between 565 and 550 Ma, indicating that sediments were deposited, regionally metamorphosed, deformed, and intruded by plutons in less than 40–50 million years. The assemblage of pelitic, psammitic, and carbonate rocks indicates that a passive margin in a tropical climate was quickly changed to an active Andean-type continental margin in which voluminous calcalkaline dioritic to granitic plutons were emplaced. This sedimentary and tectonic history is characteristic of the Bras d’Or terrane and is shared by its likely correlative, the Brookville terrane in southern New Brunswick.

Serum Dioxin, Testosterone, and Subsequent Risk of Benign Prostatic Hyperplasia: A Prospective Cohort Study of Air Force Veterans

BACKGROUND: Operation Ranch Hand veterans were involved in spraying herbicides, including Agent Orange, during the Vietnam War in 1962–1971; Agent Orange was contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). It has been hypothesized that dioxins may be partially responsible for an increase of male reproductive tract disorders such as testicular cancer, cryptorchidism, and hypospadias. OBJECTIVES: In this study, our objective was to assess the effect of serum TCDD concentration on the risk of development of benign prostatic hyperplasia (BPH) and on serum testosterone levels. METHODS: This study was a longitudinal, prospective cohort study made up of U.S. Air Force veterans involved in Operation Ranch Hand. Other Air Force veterans who did not spray herbicides were included as comparisons. BPH was determined by medical record review and by medical examinations conducted during the study. Data were available for 971 Ranch Hand and 1,266 comparison veterans. We investigated the relationship between BPH and serum TCDD level using the Cox proportional hazards models adjusted for testosterone levels, body mass index (BMI), and the percentage change in BMI per year. RESULTS: In univariate and multivariate analyses, the risk of BPH decreased with increasing serum TCDD in the comparison group. The multivariate risk ratio for BPH in the comparison group was 0.84 (95% confidence interval, 0.73–0.98). Excluding men with prostate cancer, inflammatory or other prostatic diseases did not substantially alter the association. Serum testosterone levels were inversely associated with serum TCDD levels in both Ranch Hand and comparison groups. CONCLUSIONS: TCDD exposure at general population levels is associated with a decreasing risk of BPH with higher exposure levels. TCDD exposure is also negatively associated with serum testosterone levels

Proton Motive Force-Dependent Hoechst 33342 Transport by the ABC Transporter LmrA of Lactococcus lactis

The fluorescent compound Hoechst 33342 is a substrate for many multidrug resistance (MDR) transporters and is widely used to characterize their transport activity. We have constructed mutants of the adenosine triphosphate (ATP) binding cassette (ABC)-type MDR transporter LmrA of Lactococcus lactis that are defective in ATP hydrolysis. These mutants and wild-type LmrA exhibited an atypical behavior in the Hoechst 33342 transport assay. In membrane vesicles, Hoechst 33342 transport was shown to be independent of the ATPase activity of LmrA, and it was not inhibited by orthovanadate but sensitive to uncouplers that collapse the proton gradient and to N,N'-dicyclohexylcarbodiimide, an inhibitor of the F0F1-ATPase. In contrast, transport of Hoechst 33342 by the homologous, heterodimeric MDR transporter LmrCD showed a normal ATP dependence and was insensitive to uncouplers of the proton gradient. With intact cells, expression of LmrA resulted in an increased rate of Hoechst 33342 influx while LmrCD caused a decrease in the rate of Hoechst 33342 influx. Cellular toxicity assays using a triple knockout strain, i.e., L. lactis ΔlmrA ΔlmrCD, demonstrate that expression of LmrCD protects cells against the growth inhibitory effects of Hoechst 33342, while in the presence of LmrA, cells are more susceptible to Hoechst 33342. Our data demonstrate that the LmrA-mediated Hoechst 33342 transport in membrane vesicles is influenced by the transmembrane pH gradient due to a pH-dependent partitioning of Hoechst 33342 into the membrane.