Spectroscopy of new brown dwarf members of rho Ophiuchi and an updated initial mass function

To investigate the universality hypothesis of the initial mass function in the substellar regime, the population of the rho Ophiuchi molecular cloud is analysed by including a new sample of low-mass spectroscopically confirmed members. To that end, we have conducted a large spectroscopic follow-up of young substellar candidates uncovered in our previous photometric survey. The spectral types and extinction were derived for a newly found population of substellar objects, and its masses estimated by comparison to evolutionary models. A thoroughly literature search was conducted to provide an up-to-date census of the cluster, which was then used to derive the luminosity and mass functions, as well as the ratio of brown dwarfs to stars in the cluster. These results were then compared to other young clusters. It is shown that the study of the substellar population of the rho Ophiuchi molecular cloud is hampered only by the high extinction in the cluster ruling out an apparent paucity of brown dwarfs. The discovery of 16 new members of rho Ophiuchi, 13 of them in the substellar regime, reveals the low-mass end of its population and shows the success of our photometric candidate selection with the WIRCam survey. The study of the brown dwarf population of the cluster reveals a high disk fraction of 76 (+5-8)%. Taking the characteristic peak mass of the derived mass function and the ratio of brown dwarfs to stars into account, we conclude that the mass function of rho Ophiuchi is similar to other nearby young clusters.Comment: Accepted to A&A (30 December 2011); v2 includes language editin

Clinical faculty associates serving as hybrid teacher educators: Personal and professional impacts

BackgroundUniversity supervisors in teacher education assume a complex and demanding role, which is essential to the development of prospective teachers, but is often underappreciated or ignored.AimThis descriptive study was designed to explore former clinical faculty associates’ (CFAs’) perceptions of the challenges and opportunities inherent in their work as CFAs, and the influence of this experience on their future professional work.Materials and methodsUsing survey research methodology, followed by selected individual interviews, this paper focuses on the experiences of CFAs, highly respected PK-6 teachers employed by the university for 2–3 years to serve as university supervisors.Results and conclusionAlthough participants reported facing several professional and personal challenges as CFAs, they also described opportunities to participate in a wide variety of professional experiences that positively impacted their future work. Furthermore, most reported feeling the CFA experience was professionally renewing and brought opportunities to build strong personal and professional relationships that cross institutional boundaries

Molecular Outflows Identified in the FCRAO CO Survey of the Taurus Molecular Cloud

The 100 square degree FCRAO CO survey of the Taurus molecular cloud provides an excellent opportunity to undertake an unbiased survey of a large, nearby, molecular cloud complex for molecular outflow activity. Our study provides information on the extent, energetics and frequency of outflows in this region, which are then used to assess the impact of outflows on the parent molecular cloud. The search identified 20 outflows in the Taurus region, 8 of which were previously unknown. Both $^{12}$CO and $^{13}$CO data cubes from the Taurus molecular map were used, and dynamical properties of the outflows are derived. Even for previously known outflows, our large-scale maps indicate that many of the outflows are much larger than previously suspected, with eight of the flows (40%) being more than a parsec long. The mass, momentum and kinetic energy from the 20 outflows are compared to the repository of turbulent energy in Taurus. Comparing the energy deposition rate from outflows to the dissipation rate of turbulence, we conclude that outflows by themselves cannot sustain the observed turbulence seen in the entire cloud. However, when the impact of outflows is studied in selected regions of Taurus, it is seen that locally, outflows can provide a significant source of turbulence and feedback. Five of the eight newly discovered outflows have no known associated stellar source, indicating that they may be embedded Class 0 sources. In Taurus, 30% of Class I sources and 12% of Flat spectrum sources from the Spitzer YSO catalogue have outflows, while 75% of known Class 0 objects have outflows. Overall, the paucity of outflows in Taurus compared to the embedded population of Class I and Flat Spectrum YSOs indicate that molecular outflows are a short-lived stage marking the youngest phase of protostellar life.Comment: Accepted for publication in MNRAS; 28 pages, 60 figures, 5 tables. For full abstract, see pape

Does Reduced IGF-1R Signaling in Igf1r+/− Mice Alter Aging?

Mutations in insulin/IGF-1 signaling pathway have been shown to lead to increased longevity in various invertebrate models. Therefore, the effect of the haplo- insufficiency of the IGF-1 receptor (Igf1r+/−) on longevity/aging was evaluated in C57Bl/6 mice using rigorous criteria where lifespan and end-of-life pathology were measured under optimal husbandry conditions using large sample sizes. Igf1r+/− mice exhibited reductions in IGF-1 receptor levels and the activation of Akt by IGF-1, with no compensatory increases in serum IGF-1 or tissue IGF-1 mRNA levels, indicating that the Igf1r+/− mice show reduced IGF-1 signaling. Aged male, but not female Igf1r+/− mice were glucose intolerant, and both genders developed insulin resistance as they aged. Female, but not male Igf1r+/− mice survived longer than wild type mice after lethal paraquat and diquat exposure, and female Igf1r+/− mice also exhibited less diquat-induced liver damage. However, no significant difference between the lifespans of the male Igf1r+/− and wild type mice was observed; and the mean lifespan of the Igf1r+/− females was increased only slightly (less than 5%) compared to wild type mice. A comprehensive pathological analysis showed no significant difference in end-of-life pathological lesions between the Igf1r+/− and wild type mice. These data show that the Igf1r+/− mouse is not a model of increased longevity and delayed aging as predicted by invertebrate models with mutations in the insulin/IGF-1 signaling pathway

Design Methods for the Control of Restrained Shrinkage Cracking

Cracking in concrete bridge decks can result in increased susceptibility to deterioration. As cracks provide direct routes for the ingress of deleterious elements to the reinforcement and superstructure, cracking can lead to reduced service lives for bridge structures. Several factors affect the extent of cracks which develop in bridge decks; however, relatively few are within the control of the designer. The objective of this research was to evaluate the influence of design parameters on the performance of bridge decks with respect to cracking and to develop simple design tools that are appropriate for both steel and nonmetallic reinforcement. This research was conducted in two phases. The first phase consisted of a field investigation of four bridges which incorporated different design elements to determine the in-service performance of bridge decks. Bridges were instrumented, monitored, and crack mapped. In the second phase of the research, a simple, finite element model was developed and calibrated against data from the field investigation and laboratory studies conducted by others. A parametric study was then conducted using this method to evaluate the effects of a range of design variables on the resistance to crack formation and the width of cracks that subsequently formed. Based on the results of the parametric study, it was determined that the amount and spacing of reinforcement in the deck directly influenced the extent of cracking that developed. It is recommended that the amount of reinforcement provided be sufficient to prevent localized yielding at cracks in the case of steel reinforcement and to prevent fatigue failure when FRP reinforcement is considered. Simple design equations are provided for the amount and spacing of reinforcement for both steel and FRP reinforcement to control cracking in bridge deck