14,391 research outputs found
The Hetu'u Global Network: Measuring the Distance to the Sun Using the June 5th/6th Transit of Venus
In the spirit of historic astronomical endeavors, we invited school groups
across the globe to collaborate in a solar distance measurement using the rare
June 5/6th transit of Venus. In total, we recruited 19 school groups spread
over 6 continents and 10 countries to participate in our Hetu'u Global Network.
Applying the methods of French astronomer Joseph-Nicolas Delisle, we used
individual second and third Venus-Sun contact times to calculate the distance
to the Sun. Ten of the sites in our network had amiable weather; 8 of which
measured second contact and 5 of which measured third contact leading to
consistent solar distance measurements of 152+/-30 million km and 163+/-30
million km respectively. The distance to the Sun at the time of the transit was
152.25 million km; therefore, our measurements are also consistent within
1sigma of the known value. The goal of our international school group network
was to inspire the next generation of scientists using the excitement and
accessibility of a rare astronomical event. In the process, we connected
hundreds of participating students representing a diverse, multi-cultural group
with differing political, economic, and racial backgrounds.Comment: 19 pages; 7 Figures; 1 Table; Accepted for publication in Astronomy
Education Review (AER) For more information see
http://www.das.uchile.cl/~drodrigu/easter/index_en.htm
Involvement of Park and Recreation Professionals in Pedestrian Plans
Professionals from many different disciplines are finding innovative ways to work together to increase physical activity to help create healthier communities. One process that can provide a focal point for promoting physical activity by park and recreation professionals, land use and transportation planners, public health practitioners, and other stakeholders is the development and implementation of pedestrian plans. A pedestrian plan is a public document that lays out a community’s vision for future pedestrian activity, identifies the actions required to realize that vision, ties actions to funding sources, and describes implementation and use. The purpose of this study was to explore whether park and recreation professionals were involved in creating pedestrian plans and how park and recreation elements were represented in these plans. To answer this, we identified, collected, and conducted a content analysis of all pedestrian plans in North Carolina. Among the 41 regional, county, and municipal pedestrian plans, park and recreation professionals were mentioned in the plan 56% of the time. Seventy-one percent (n=29) had a vision statement; however, among those only five vision statements mentioned parks or recreation. In all five cases, when a plan contained a vision statement that mentioned parks or recreation, there was a park and recreation member involved in the development of the plan. A higher percent of plans with a park and recreation professional involved were more likely to list parks in their land use analysis (74% vs. 67%). Park master plans were mentioned in the pedestrian plans 29% of the time; however, a lower percent of plans with a park and recreational professional involved mentioned a park master plan (26% vs. 33%). Given the potential importance of pedestrian plans in creating connections for pedestrians, park and recreation professionals are encouraged to become involved in the pedestrian planning process if they are not already. Parks can offer opportunities for residents of diverse ages and cultures to come together to socialize and engage in health-promoting activities. Integrating a park and recreation perspective into a more comprehensive planning process can enhance access to parks, inform programs, support multiple community goals, facilitate efficient use of resources, and promote partnerships for greater sustainabilit
Unbiased mm-wave Line Surveys of TW Hya and V4046 Sgr: The Enhanced C2H and CN Abundances of Evolved Protoplanetary Disks
We have conducted the first comprehensive mm-wave molecular emission line
surveys of the evolved circumstellar disks orbiting the nearby T Tauri stars TW
Hya and V4046 Sgr AB. Both disks are known to retain significant residual
gaseous components, despite the advanced ages of their host stars. Our unbiased
broad-band radio spectral surveys of the TW Hya and V4046 Sgr disks were
performed with the Atacama Pathfinder Experiment (APEX) 12 meter telescope and
are intended to yield a complete census of bright molecular emission lines in
the range 275-357 GHz (1.1-0.85 mm). We find that lines of 12CO, 13CO, HCN, CN,
and C2H, all of which lie in the higher-frequency range, constitute the
strongest molecular emission from both disks in the spectral region surveyed.
The molecule C2H is detected here for the first time in both disks, as is CS in
the TW Hya disk. The survey results also include the first measurements of the
full suite of hyperfine transitions of CN N=3-2 and C2H N=4-3 in both disks.
Modeling of these CN and C2H hyperfine complexes in the spectrum of TW Hya
indicates that the emission from both species is optically thick and may
originate from very cold disk regions. It furthermore appears that the
fractional abundances of CN and C2H are significantly enhanced in these evolved
protoplanetary disks relative to the fractional abundances of the same
molecules in the environments of deeply embedded protostars.Comment: 29 pages, 6 figures; to appear in Vol. 791 of The Astrophysical
Journa
Time-Series Ensemble Photometry and the Search for Variable Stars in the Open Cluster M11
This work presents the first large-scale photometric variability survey of
the intermediate age (~200 Myr) open cluster M11. Thirteen nights of data over
two observing seasons were analyzed (using crowded field and ensemble
photometry techniques) to obtain high relative precision photometry. In this
study we focus on the detection of candidate member variable stars for
follow-up studies. A total of 39 variable stars were detected and can be
categorized as follows: 1 irregular (probably pulsating) variable, 6 delta
Scuti variables, 14 detached eclipsing binary systems, 17 W UMa variables, and
1 unidentified/candidate variable. While previous proper motion studies allow
for cluster membership determination for the brightest stars, we find that
membership determination is significantly hampered below V=15,R=15.5 by the
large population of field stars overlapping the cluster MS. Of the brightest
detected variables that have a high likelihood of cluster membership, we find
five systems where further work could help constrain theoretical stellar
models, including one potential W UMa member of this young cluster.Comment: 38 pages, 13 figures, accepted for December 2005 AJ, high-resolution
version available upon reques
Correction of Optical Aberrations in Elliptic Neutron Guides
Modern, nonlinear ballistic neutron guides are an attractive concept in
neutron beam delivery and instrumentation, because they offer increased
performance over straight or linearly tapered guides. However, like other
ballistic geometries they have the potential to create significantly
non-trivial instrumental resolution functions. We address the source of the
most prominent optical aberration, namely coma, and we show that for extended
sources the off-axis rays have a different focal length from on-axis rays,
leading to multiple reflections in the guide system. We illustrate how the
interplay between coma, sources of finite size, and mirrors with non-perfect
reflectivity can therefore conspire to produce uneven distributions in the
neutron beam divergence, the source of complicated resolution functions. To
solve these problems, we propose a hybrid elliptic-parabolic guide geometry.
Using this new kind of neutron guide shape, it is possible to condition the
neutron beam and remove almost all of the aberrations, whilst providing the
same performance in beam current as a standard elliptic neutron guide. We
highlight the positive implications for a number of neutron scattering
instrument types that this new shape can bring.Comment: Presented at NOP2010 Conference in Alpe d'Huez, France, in March 201
Transcriptome analysis of bacteriophage communities in periodontal health and disease.
BackgroundThe role of viruses as members of the human microbiome has gained broader attention with the discovery that human body surfaces are inhabited by sizeable viral communities. The majority of the viruses identified in these communities have been bacteriophages that predate upon cellular microbiota rather than the human host. Phages have the capacity to lyse their hosts or provide them with selective advantages through lysogenic conversion, which could help determine the structure of co-existing bacterial communities. Because conditions such as periodontitis are associated with altered bacterial biota, phage mediated perturbations of bacterial communities have been hypothesized to play a role in promoting periodontal disease. Oral phage communities also differ significantly between periodontal health and disease, but the gene expression of oral phage communities has not been previously examined.ResultsHere, we provide the first report of gene expression profiles from the oral bacteriophage community using RNA sequencing, and find that oral phages are more highly expressed in subjects with relative periodontal health. While lysins were highly expressed, the high proportion of integrases expressed suggests that prophages may account for a considerable proportion of oral phage gene expression. Many of the transcriptome reads matched phages found in the oral cavities of the subjects studied, indicating that phages may account for a substantial proportion of oral gene expression. Reads homologous to siphoviruses that infect Firmicutes were amongst the most prevalent transcriptome reads identified in both periodontal health and disease. Some genes from the phage lytic module were significantly more highly expressed in subjects with periodontal disease, suggesting that periodontitis may favor the expression of some lytic phages.ConclusionsAs we explore the contributions of viruses to the human microbiome, the data presented here suggest varying expression of bacteriophage communities in oral health and disease
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