2,313 research outputs found
Specification for wide channel bandwidth one-inch video tape
Standards and controls are established for the procurement of wide channel bandwidth one inch video magnetic recording tapes for Very Long Base Interferometer (VLBI) system applications. The Magnetic Tape Certification Facility (MTCF) currently maintains three specifications for the Quality Products List (QPL) and acceptance testing of magnetic tapes. NASA-TM-79724 is used for the QPL and acceptance testing of new analog tapes; NASA-TM-80599 is used for QPL and acceptance testing of new digital tapes; and NASA-TM-100702 is used for the QPL and acceptance testing of new IBM/IBM compatible 3480 magnetic tape cartridges. This specification will be used for the QPL and acceptance testing of new wide channel bandwidth one inch video magnetic recording tapes. The one inch video tapes used by the Jet Propulsion Lab., the Deep Space Network and the Haystack Observatory will be covered by this specification. These NASA stations will use the video tapes for their VLBI system applications. The VLBI system is used for the tracking of quasars and the support of interplanetary exploration
Sequential sampling of junction trees for decomposable graphs
The junction-tree representation provides an attractive structural property
for organizing a decomposable graph. In this study, we present a novel
stochastic algorithm, which we call the junction-tree expander, for sequential
sampling of junction trees for decomposable graphs. We show that recursive
application of the junction-tree expander, expanding incrementally the
underlying graph with one vertex at a time, has full support on the space of
junction trees with any given number of underlying vertices. A direct
application of our suggested algorithm is demonstrated in a sequential Monte
Carlo setting designed for sampling from distributions on spaces of
decomposable graphs, where the junction-tree expander can be effectively
employed as proposal kernel; see the companion paper Olsson et al. 2019 [16]. A
numerical study illustrates the utility of our approach by two examples: in the
first one, how the junction-tree expander can be incorporated successfully into
a particle Gibbs sampler for Bayesian structure learning in decomposable
graphical models; in the second one, we provide an unbiased estimator of the
number of decomposable graphs for a given number of vertices. All the methods
proposed in the paper are implemented in the Python library trilearn.Comment: 31 pages, 7 figure
Resolution of a paradox: Hummingbird flight at high elevation does not come without a cost
Flight at high elevation is energetically demanding because of parallel reductions in air density and oxygen availability. The hovering flight of hummingbirds is one of the most energetically expensive forms of animal locomotion, but hummingbirds are nonetheless abundant at high elevations throughout the Americas. Two mechanisms enhance aerodynamic performance in high-elevation hummingbirds: increase in wing size and wing stroke amplitude during hovering. How do these changes in morphology, kinematics, and physical properties of air combine to influence the aerodynamic power requirements of flight across elevations? Here, we present data on the flight performance of 43 Andean hummingbird species as well as a 76-taxon multilocus molecular phylogeny that served as the historical framework for comparative analyses. Along a 4,000-m elevational transect, hummingbird body mass increased systematically, placing further aerodynamic demands on high-elevation taxa. However, we found that the minimum power requirements for hovering flight remain constant with respect to elevation because hummingbirds compensate sufficiently through increases in wing size and stroke amplitude. Thus, high-elevation hummingbirds are not limited in their capacity for hovering flight despite the challenges imposed by hypobaric environments. Other flight modes including vertical ascent and fast forward flight are more mechanically and energetically demanding, and we accordingly also tested for the maximum power available to hummingbirds by using a load-lifting assay. In contrast to hovering, excess power availability decreased substantially across elevations, thereby reducing the biomechanical potential for more complex flight such as competitive and escape maneuvers
A novel interdigitated capacitor based biosensor for detection of cardiovascular risk marker
C-reactive protein (CRP) is a potential biomarker whose elevated levels in humans determine cardiovascular disease risk and inflammation. In this study, we have developed a novel capacitive biosensor for detection of CRP-antigen using capacitor with interdigitated gold (GID) electrodes on nanocrystalline diamond (NCD) surface. The NCD surface served as a dielectric layer between the gold electrodes. GID-surface was functionalized by antibodies and the immobilization was confirmed by Fourier transform spectroscopy (FT-IR) and contact angle measurements. The CRP-antigen detection was performed by capacitive/dielectric-constant measurements. The relaxation time and polarizability constants were estimated using Cole-Cole model. Our results showed that the relaxation time constant (tau) of only CRP-antibody was within 10(-16)-10(-13) s, which was increased to 10(-11) s after the incubation with CRP-antigen, suggesting that the CRP-antigen was captured by the antibodies on GID-surface. In addition, polarizability constant(m) of CRP was also increased upon incubation with increasing concentration of CRP-antigen. Our results showed that the response of GID-NCD-based capacitive biosensor for CRP-antigen was dependent on both concentration (25-800 ng/ml) as well as frequency (50-350 MHz). Furthermore, using optimized conditions, the GID-NCD based capacitive biosensor developed in this study can potentially be used for detection of elevated levels of protein risk markers in suspected subjects for early diagnosis of disease
TWO-SPIRIT STORIES: LEARNING TO NAVIGATE MULTIPLE FORMS OF OPPRESSIONS AND ESTABLISHING A PRACTICE OF WAHKOWTOWIN
In 2011, Equality for Gays and Lesbians Everywhere (EGALE) published the following study, Every Class in Every school . The study, first of its kind in Canada focused on gathering high school students’ perspectives around homophobia, biphobia, and transphobia. One of the recommendations from this study was that future research needed to be done around the experiences of Two-spirit youth (Every Class in Every school, 2011). This recommendation brings attention to the unique experiences that Two-spirit youth and/or Queer Indigenous people may have, particularly around their interconnected identities (Wilson, 1996). It has been expressed that if the only forms oppression that go noticed are singular we soon only begin to represent those who are fortunate enough to possess a simple and uncomplicated oppression (Kumashiro, 2002). This thesis focused on four Indigenous undergraduate and one Indigenous graduate students’ narratives around how they navigate their multiple forms of oppression while attending universities in Saskatchewan.
The Cree concept of Wahkohtowin shaped the mixed qualitative nature of this study. A combination of an Indigenous research methodology with an anti-oppressive lens, and a voice-centered relational method of data gathering and analysis were used. The perceptions that participants shared in this research were heavily influenced by their varied relationships with their families, partners, teachers, Elders, and communities. A key finding that emerged was the notion of teaching others through their lived experiences and this was perceived to be an advantage of navigating homophobia, transphobia, sexism, and racism. Implications for enhancing education and policy are provided. Include themes that educators can explore when teaching Two-spirit issues. Highlight the ways policies can change to reflect a safe and nurturing environment for Two-spirit students in levels of education that are not exclusive to post-secondary
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