Searching for old neutron stars with ROSAT. II. Soft X-ray sources in galactic dark clouds

This is the second in a series of three papers constraining the number of detectable old neutron stars in the Galaxy. Here, I present the statistical analysis of a sample of X-ray sources coincident with areas of dark clouds in the Galactic plane. I compare this sample with all sources in the ROSAT All-Sky Survey bright source catalog within 20° of the Galactic plane. I present the results of an identification program of a subset of sources that are compatible with a soft, thermal X-ray spectrum and an effective source temperature of less than 70 eV. The three brightest sources in this sample form an intriguing subgroup. One of them is a previously identified candidate for an accreting neutron star. I identify the other two sources with hot white dwarf stars. I find no new accreting neutron star candidate in this sample. Based on this result, I derive an upper limit to the space density of accreting neutron stars in fields of Galactic dark clouds of ~ 2 sr^(-1) at a count rate > 0.05 s^(-1)

Descaling Injury Impairs the Osmoregulatory Ability of Atlantic Salmon Smolts Entering Seawater

The effect of descaling injury on the osmoregulatory ability of hatchery Atlantic salmon Salmo salar smolts in seawater was investigated. Experimental series were initiated during early, middle, and late periods of the spring smolt migration (April 25, May 11, and May 31, respectively). For each time series, descaled smolts (subjected to descaling on 10% of the body surface area) and control smolts (held out of water for 15 s) were transferred to seawater at 0, 1, 3, or 7 d posttreatment. After fish were held in 35% seawater for 24 h, gill and blood samples were collected and analyzed for Na(+),K(+)-ATPase activity and plasma osmolyte levels. Based on gill Na(+),K(+)-ATPase activity, the three series spanned the period from early smolting (increasing activity) to de-smolting (decreasing activity). In each series, descaled fish transferred to seawater at 0 and 1 d posttreatment had greater plasma osmolality than control fish; descaled fish transferred to seawater at 3 d posttreatment did not differ from controls. The greatest perturbation in osmolality (70 milliosmoles) was observed at the peak of smolting (middle series), whereas lesser increases were seen for early and late-series smolts. The observed osmotic perturbations in descaled fish would probably reduce performance and decrease survival during smolt migration

Searching for old neutron stars with ROSAT. I. Soft X-ray sources in molecular clouds at high galactic latitude

This is the first in a series of three papers aiming to put strong observational constraints on the number of old accreting neutron stars in the Galaxy. Old neutron stars have been predicted to be visible as soft X-ray sources. The brightest sources are expected where the density of the interstellar medium is high. I present an X-ray survey of a complete sample of molecular clouds at high galactic latitudes based on the ROSAT All-Sky Survey. I detect 89 sources inside the projected contours of the molecular clouds and report on a comprehensive identification program. For all sources I searched astronomical catalogs and created finding charts. I also observed all sources at radio frequencies, most of them at 1.4 GHz and at 8 GHz. For sources with bright counterparts, optical spectra are presented. For fainter sources, optical CCD images are shown. Of all sources, 54 are securely identified and for the majority of the remaining sources likely identifications are given. I find no candidate for an old accreting neutron star in this sample. From this survey I derive an upper limit to the neutron star density of 50 sr^(-1) at a ROSAT count rate of 0.012 s^(-1)

Searching for old neutron stars with ROSAT. II. Soft X-ray sources in galactic dark clouds

This is the second in a series of three papers constraining the number of detectable old neutron stars in the Galaxy. Here, I present the statistical analysis of a sample of X-ray sources coincident with areas of dark clouds in the Galactic plane. I compare this sample with all sources in the ROSAT All-Sky Survey bright source catalog within 20° of the Galactic plane. I present the results of an identification program of a subset of sources that are compatible with a soft, thermal X-ray spectrum and an effective source temperature of less than 70 eV. The three brightest sources in this sample form an intriguing subgroup. One of them is a previously identified candidate for an accreting neutron star. I identify the other two sources with hot white dwarf stars. I find no new accreting neutron star candidate in this sample. Based on this result, I derive an upper limit to the space density of accreting neutron stars in fields of Galactic dark clouds of ~ 2 sr^(-1) at a count rate > 0.05 s^(-1)

ENERGETIC COSTS AND STRATEGIES OF POST‐JUVENAL MOLT IN AN EQUATORIAL BIRD, THE RUFOUS‐COLLARED SPARROW (ZONOTRICHIA CAPENSIS)

Abstract  ∙ Many tropical birds have slow‐paced life history strategies, exhibiting lower metabolic rates, reduced annual investment in reproduction, and longer lifespans relative to birds at higher latitudes. Life history strategies have been relatively well documented in adult individuals in the tropics, but we know comparatively little about the immature life history stage. Here we examine strategies of feather replacement (molt) and fattening in immature Rufous‐collared Sparrows (Zonotrichia capensis) in a high elevation equatorial population, following a parallel, previous study on an arctic congener, the White‐crowned Sparrow (Zonotrichia leucophrys gambelii). In captivity, Rufous‐ collared Sparrows incurred energetic costs of experimentally induced feather growth, similar to those previously described for Zonotrichia at higher latitudes. In contrast, free‐ranging immature Rufous‐collared Sparrows in natural molt had fat stores that declined over time, opposite to patterns evident in arctic Zonotrichia that fatten before migration. Equatorial birds in good condition molted more heavily (controlling for fat stores), suggesting that body condition limits the intensity of molt. Heavily molting equatorial sparrows also had lower amounts of fat (controlling for body condition), suggesting a trade‐off between allocation of resources to fat stores versus feather growth. Molt progressed slowly in Rufous‐collared Sparrows relative to previously described patterns in their arctic congener, which is concordant with a slower pace‐of‐life syndrome in tropical, as compared with high latitude, birds. Resumen ∙ Costos energéticos y estrategias de muda post‐juvenil en un ave ecuatorial, el Chingolo (Zonotrichia capensis) Muchas especies de aves tropicales presentan historias de vida lenta, exhibiendo bajas tasas metabólicas, esfuerzo reproductivo anual reducido, y mayor longevidad que las especies que habitan en latitudes más altas. La variación en historia de vida en especies tropicales ha sido bien documentada para individuos adultos, pero sabemos comparativa‐ mente poco de los individuos inmaduros. Aquí estudiamos las estrategias de muda y deposición de grasa en individuos inmaduros de Chingolo (Zonotrichia capensis) en una población ecuatorial de altura y comparamos los resultados con un estudio similar realizado en una población ártica del congénere Chingolo Coroniblanco (Zonotrichia leucophrys gambelii). En cautiverio, individuos juveniles de Z. capensis incurrieron costos energéticos debidos a la muda inducida, similar lo encontrado en Z. leucophrys gambelii. En contraste, Z. capensis inmaduros mudando en libertad presentaron depósitos de grasa que disminuyeron a lo largo del tiempo, lo opuesto a Z. l. gambelii, que deposita más grasa antes de migrar. Z. capensis inmaduros en buen estado nutricional (controlando por diferencias en deposición de grasa) mudaron de manera más intensa, lo que sugiere que el estado nutricional limita la muda. Individuos inmaduros de Z. capensis mudando de manera intensa presentaron menor cantidad de grasa depositada (controlando por diferencias en estado nutricional), lo que sugiere un balance entre la deposición de grasa y la muda. La muda fue más lenta en la población ecuatorial de Z. capensis comparado con la de Z. l. gambelii, lo que concuerda con lo esperado debido a la historia de vida más lenta en aves tropicales

The Arts as a Teaching Tool and the Power of Collaboration and Co-teaching

Over the last seventeen years, an arts education initiative has transformed the dynamics of an isolated rural school into a model for rural arts access. Three teachers from Copper Basin High School began an avalanche of possibilities in 1997 when the Annenberg Rural Challenge Grant provided funding to begin a new era in a small rural school. Isolated by geographical boundaries and stifled by economical hardships since the closing of the copper mines in 1988, something had to be done. After a series of teacher in-services for visual strategies (using art as a teaching tool reflective of Gardner\u27s Multiple Intelligences), followed with collaborations between teachers and art consultants, students were led to a deeper understanding through problem solving, critical thinking, and creative explorations. After this experiment proved successful, in a grassroots self-supporting survival move, a non-profit organization was established and grants were obtained to continue and expand the work. In 2004, an unexpected corporate partnership with Glenn Springs Holdings, Inc. was established to provide funding and support to develop the Copper Basin Learning Center. This session examines the path that led to the Learning Center, challenges faced along the way, and what works in the program and why. There is a lot of talk on the educational forefront today concerning moving from STEM to STEAM, with the arts being a significant component. Discussion will include dispelling basic assumptions and developing a workable plan of action for incorporating the arts in the school curriculum

Denotational semantics as a foundation for cost recurrence extraction for functional languages

A standard informal method for analyzing the asymptotic complexity of a program is to extract a recurrence that describes its cost in terms of the size of its input, and then to compute a closed-form upper bound on that recurrence. We give a formal account of that method for functional programs in a higher-order language with let-polymorphism The method consists of two phases. In the first phase, a monadic translation is performed to extract a cost-annotated version of the original program. In the second phase, the extracted program is interpreted in a model. The key feature of this second phase is that different models describe different notions of size. This plays out specifically for values of inductive type, where different notions of size may be appropriate depending on the analysis, and for polymorphic functions, where we show that the notion of size for a polymorphic function can be described formally as the data that is common to the notions of size of its instances. We give several examples of different models that formally justify various informal cost analyses to show the applicability of our approach.Comment: Revisions, mainly to clarify the goal of this paper and to place it in context of related work. Also many minor revision