164 research outputs found
A reduced set of moves on one-vertex ribbon graphs coming from links
Every link in R^3 can be represented by a one-vertex ribbon graph. We prove a
Markov type theorem on this subset of link diagrams.Comment: 14 pages, 15 figure
Star Formation in the Gulf of Mexico
We present an optical/infrared study of the dense molecular cloud, L935,
dubbed "The Gulf of Mexico", which separates the North America and the Pelican
nebulae, and we demonstrate that this area is a very active star forming
region. A wide-field imaging study with interference filters has revealed 35
new Herbig-Haro objects in the Gulf of Mexico. A grism survey has identified 41
Halpha emission-line stars, 30 of them new. A small cluster of partly embedded
pre-main sequence stars is located around the known LkHalpha 185-189 group of
stars, which includes the recently erupting FUor HBC 722.Comment: Submitted to A&A, 14 pages, 18 figure
A Reduced Set of Moves on One-Vertex Ribbon Graphs Coming from Links
Every link in R3 can be represented by a one-vertex ribbon graph. We prove a Markov type theorem on this subset of link diagrams
Lactation and neonatal nutrition: defining and refining the critical questions.
This paper resulted from a conference entitled "Lactation and Milk: Defining and refining the critical questions" held at the University of Colorado School of Medicine from January 18-20, 2012. The mission of the conference was to identify unresolved questions and set future goals for research into human milk composition, mammary development and lactation. We first outline the unanswered questions regarding the composition of human milk (Section I) and the mechanisms by which milk components affect neonatal development, growth and health and recommend models for future research. Emerging questions about how milk components affect cognitive development and behavioral phenotype of the offspring are presented in Section II. In Section III we outline the important unanswered questions about regulation of mammary gland development, the heritability of defects, the effects of maternal nutrition, disease, metabolic status, and therapeutic drugs upon the subsequent lactation. Questions surrounding breastfeeding practice are also highlighted. In Section IV we describe the specific nutritional challenges faced by three different populations, namely preterm infants, infants born to obese mothers who may or may not have gestational diabetes, and infants born to undernourished mothers. The recognition that multidisciplinary training is critical to advancing the field led us to formulate specific training recommendations in Section V. Our recommendations for research emphasis are summarized in Section VI. In sum, we present a roadmap for multidisciplinary research into all aspects of human lactation, milk and its role in infant nutrition for the next decade and beyond
The VISCACHA survey -- V. Rejuvenating three faint SMC clusters
We present the analysis of three faint clusters of the Small Magellanic Cloud
RZ82, HW42 and RZ158. We employed the SOAR telescope instrument SAM with
adaptive optics, allowing us to reach to V~23-24 mag, unprecedentedly, a depth
sufficient to measure ages of up to about 10-12Gyr. All three clusters are
resolved to their centres, and the resulting colour-magnitude diagrams (CMDs)
allow us to derive ages of 3.9, 2.6, and 4.8Gyr respectively. These results are
significantly younger than previous determinations (7.1, 5.0, and 8.3Gyr,
respectively), based on integrated photometry or shallower CMDs. We rule out
older ages for these clusters based on deep photometry and statistical
isochrone fitting. We also estimate metallicities for the three clusters of
[Fe/H]=-0.68, -0.57 and -0.90, respectively. These updated ages and
metallicities are in good agreement with the age-metallicity relation for the
bulk of SMC clusters. Total cluster masses ranging from ~7-11x10^3Mo were
estimated from integrated flux, consistent with masses estimated for other SMC
clusters of similar ages. These results reduce the number of SMC clusters known
to be older than about 5 Gyr and highlight the need of deep and spatially
resolved photometry to determine accurate ages for older, low-luminosity SMC
star clusters.Comment: Accepted for publication as MNRAS letter, 5 pages, 5 figure
The VISCACHA survey -- VII. Assembly history of the Magellanic Bridge and SMC Wing from star clusters
The formation scenario of the Magellanic Bridge during an encounter between
the Large and Small Magellanic Clouds Myr ago, as proposed by
-body models, would be imprinted in the chemical enrichment and kinematics
of its stars, and sites of ongoing star formation along its extension. We
present an analysis of 33 Bridge star clusters using photometry obtained with
the SOAR 4-m telescope equipped with adaptive optics for the VISCACHA survey.
We performed a membership selection and derived self-consistent ages,
metallicities, distances and reddening values via statistical isochrone
fitting, as well as tidal radii and integrated masses from structure analysis.
Two groups are clearly detected: 13 well-studied clusters older than the
Bridge, with Gyr and dex; and 15 clusters with
dex, probably formed in-situ. The old
clusters follow the overall age and metallicity gradients of the SMC, whereas
the younger ones are uniformly distributed along the Bridge. The main results
are as follows: we derive ages and metallicities for the first time for 9
and 18 clusters, respectively; we detect two metallicity dips in the
age-metallicity relation of the Bridge at Myr and Gyr ago
for the first time, possibly chemical signatures of the formation of the Bridge
and Magellanic Stream; we estimate a minimum stellar mass for the
Bridge of ; we confirm that all the young
Bridge clusters at are metal-rich dex.Comment: 15 pages, 13 figures + appendix. Accepted for publication in MNRA
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