4,115 research outputs found
Description of an experimental (hydrogen peroxide) rocket system and its use in measuring aileron and rudder effectiveness of a light airplane
A hydrogen peroxide fueled rocket system, which is to be used as a research tool in flight studies of stall and spin maneuvers, was installed on a light, four place general aviation airplane. The pilot controlled rocket system produces moments about either the roll or the yaw body axis to augment or oppose the aerodynamic forces and inertial moments acting on the airplane during various flight maneuvers, including the spin. These controlled moments of a known magnitude can be used in various ways to help analyze and interpret the importance of the various factors which influence airplane maneuvers. The rocket system and its installation in the airplane are described, and the results of flight rests used to measure rudder and aileron effectiveness at airspeeds above the stall are presented. These tests also serve to demonstrate the operational readiness of the rocket system for future research operations
A statistical method for revealing form-function relations in biological networks
Over the past decade, a number of researchers in systems biology have sought
to relate the function of biological systems to their network-level
descriptions -- lists of the most important players and the pairwise
interactions between them. Both for large networks (in which statistical
analysis is often framed in terms of the abundance of repeated small subgraphs)
and for small networks which can be analyzed in greater detail (or even
synthesized in vivo and subjected to experiment), revealing the relationship
between the topology of small subgraphs and their biological function has been
a central goal. We here seek to pose this revelation as a statistical task,
illustrated using a particular setup which has been constructed experimentally
and for which parameterized models of transcriptional regulation have been
studied extensively. The question "how does function follow form" is here
mathematized by identifying which topological attributes correlate with the
diverse possible information-processing tasks which a transcriptional
regulatory network can realize. The resulting method reveals one form-function
relationship which had earlier been predicted based on analytic results, and
reveals a second for which we can provide an analytic interpretation. Resulting
source code is distributed via http://formfunction.sourceforge.net.Comment: To appear in Proc. Natl. Acad. Sci. USA. 17 pages, 9 figures, 2
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Statistical competencies for medical research learners: What is fundamental?
IntroductionIt is increasingly essential for medical researchers to be literate in statistics, but the requisite degree of literacy is not the same for every statistical competency in translational research. Statistical competency can range from 'fundamental' (necessary for all) to 'specialized' (necessary for only some). In this study, we determine the degree to which each competency is fundamental or specialized.MethodsWe surveyed members of 4 professional organizations, targeting doctorally trained biostatisticians and epidemiologists who taught statistics to medical research learners in the past 5 years. Respondents rated 24 educational competencies on a 5-point Likert scale anchored by 'fundamental' and 'specialized.'ResultsThere were 112 responses. Nineteen of 24 competencies were fundamental. The competencies considered most fundamental were assessing sources of bias and variation (95%), recognizing one's own limits with regard to statistics (93%), identifying the strengths, and limitations of study designs (93%). The least endorsed items were meta-analysis (34%) and stopping rules (18%).ConclusionWe have identified the statistical competencies needed by all medical researchers. These competencies should be considered when designing statistical curricula for medical researchers and should inform which topics are taught in graduate programs and evidence-based medicine courses where learners need to read and understand the medical research literature
Late-time evolution of the Yang-Mills field in the spherically symmetric gravitational collapse
We investigate the late-time evolution of the Yang-Mills field in the
self-gravitating backgrounds: Schwarzschild and Reissner-Nordstr\"om
spacetimes. The late-time power-law tails develop in the three asymptotic
regions: the future timelike infinity, the future null infinity and the black
hole horizon. In these two backgrounds, however, the late-time evolution has
quantitative and qualitative differences. In the Schwarzschild black hole
background, the late-time tails of the Yang-Mills field are the same as those
of the neutral massless scalar field with multipole moment l=1. The late-time
evolution is dominated by the spacetime curvature. When the background is the
Reissner-Nordstr\"om black hole, the late-time tails have not only a smaller
power-law exponent, but also an oscillatory factor. The late-time evolution is
dominated by the self-interacting term of the Yang-Mills field. The cause
responsible for the differences is revealed.Comment: Revtex, 14 pages, no figure
Building blocks of a black hole
What is the nature of the energy spectrum of a black hole ? The algebraic
approach to black hole quantization requires the horizon area eigenvalues to be
equally spaced. As stressed long ago by by Mukhanov, such eigenvalues must be
exponentially degenerate with respect to the area quantum number if one is to
understand black hole entropy as reflecting degeneracy of the observable
states. Here we construct the black hole states by means of a pair of "creation
operators" subject to a particular simple algebra, a slight generalization of
that for the harmonic oscillator. We then prove rigorously that the n-th area
eigenvalue is exactly 2 raised to the n-fold degenerate. Thus black hole
entropy qua logarithm of the number of states for fixed horizon area comes out
proportional to that area.Comment: PhysRevTeX, 14 page
No Scalar Hair Theorem for a Charged Spherical Black Hole
This paper consolidates noscalar hair theorem for a charged spherically
symmetric black hole in four dimension in general relativity as well as in all
scalar tensor theories, both minimally and nonminimally coupled, when the
effective Newtonian constant of gravity is positive. However, there is an
exception when the matter field itself is coupled to the scalar field, such as
in dilaton gravity.Comment: 13 pages, Latex format, some minor corrections are made, accepted for
publication in Physical Review
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