146,903 research outputs found
Effects of internal fluctuations on the spreading of Hantavirus
We study the spread of Hantavirus over a host population of deer mice using a
population dynamics model. We show that taking into account the internal
fluctuations in the mouse population due to its discrete character strongly
alters the behaviour of the system. In addition to the familiar transition
present in the deterministic model, the inclusion of internal fluctuations
leads to the emergence of an additional deterministically hidden transition. We
determine parameter values that lead to maximal propagation of the disease, and
discuss some implications for disease prevention policies
Absolute reliability and concurrent validity of hand held dynamometry and isokinetic dynamometry in the hip, knee and ankle joint: Systematic review and meta-analysis
Indexación: Scopus.The purpose of the study is to establish absolute reliability and concurrent validity between hand-held dynamometers (HHDs) and isokinetic dynamometers (IDs) in lower extremity peak torque assessment. Medline, Embase, CINAHL databases were searched for studies related to psychometric properties in muscle dynamometry. Studies considering standard error of measurement SEM (%) or limit of agreement LOA (%) expressed as percentage of the mean, were considered to establish absolute reliability while studies using intra-class correlation coefficient (ICC) were considered to establish concurrent validity between dynamometers. In total, 17 studies were included in the meta-analysis. The COSMIN checklist classified them between fair and poor. Using HHDs, knee extension LOA (%) was 33.59%, 95% confidence interval (CI) 23.91 to 43.26 and ankle plantar flexion LOA (%) was 48.87%, CI 35.19 to 62.56. Using IDs, hip adduction and extension; knee flexion and extension; and ankle dorsiflexion showed LOA (%) under 15%. Lower hip, knee, and ankle LOA (%) were obtained using an ID compared to HHD. ICC between devices ranged between 0.62, CI (0.37 to 0.87) for ankle dorsiflexion to 0.94, IC (0.91to 0.98) for hip adduction. Very high correlation were found for hip adductors and hip flexors and moderate correlations for knee flexors/extensors and ankle plantar/dorsiflexors.https://www.degruyter.com/view/j/med.2017.12.issue-1/med-2017-0052/med-2017-0052.xm
Cluster Origin of Triple Star HD 188753 and its Planet
The recent discovery by M. Konacki of a ``hot Jupiter'' in the hierarchical
triple star system HD 188753 challenges established theories of giant-planet
formation. If the orbital geometry of the triple has not changed since the
birth of the planet, then a disk around the planetary host star would probably
have been too compact and too hot for a Jovian planet to form by the
core-accretion model or gravitational collapse. This paradox is resolved if the
star was initially either single or had a much more distant companion. It is
suggested here that a close multi-star dynamical encounter transformed this
initial state into the observed triple, an idea that follows naturally if HD
188753 formed in a moderately dense stellar system--perhaps an open
cluster--that has since dissolved. Three distinct types of encounters are
investigated. The most robust scenario involves an initially single planetary
host star that changes places with the outlying member of a pre-existing
hierarchical triple.Comment: Accepted by ApJL; minor changes from origina
EPR before EPR: a 1930 Einstein-Bohr thought experiment revisited
In 1930 Einstein argued against consistency of the time-energy uncertainty
relation by discussing a thought experiment involving a measurement of mass of
the box which emitted a photon. Bohr seemingly triumphed over Einstein by
arguing that the Einstein's own general theory of relativity saves the
consistency of quantum mechanics. We revisit this thought experiment from a
modern point of view at a level suitable for undergraduate readership and find
that neither Einstein nor Bohr was right. Instead, this thought experiment
should be thought of as an early example of a system demonstrating nonlocal
"EPR" quantum correlations, five years before the famous
Einstein-Podolsky-Rosen paper.Comment: 11 pages, revised, accepted for publication in Eur. J. Phy
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