129 research outputs found
Skeletal Immaturity, Rostral Sparing, and Disparate Hip Morphologies as Biomechanical Causes for Legg-Calve-Perthesâ Disease
Legg-CalvĂ©-Perthesâ (Perthesâ) disease is a developmental disease of the hip joint that may result
in numerous short and long term problems. The aetiology of the disease remains largely unknown, but
the mechanism is believed to be vascular and/or biomechanical in nature. There are several anatomical
characteristics that tend to be prevalent in children with Perthesâ disease, namely: skeletal immaturity,
reduced height and rostral sparing. We present an overview of the literature, summarising the current
understanding of the pathogenesis, particularly related to how the formation of the vasculature to the
femoral epiphysis places children aged 5-8 at a higher risk for Perthesâ disease, how skeletal immaturity
and rostral sparing could increase the probability of developing Perthesâ disease, and how animal
models have aided our understanding of the disease. In doing so, we also explore why Perthesâ disease
is correlated to latitude, with populations at higher latitudes having higher incidence rates than
populations closer to the Equator. Finally, we present five hypotheses detailing how Perthesâ disease
could have a biomechanical cause
A Weyl-Dirac Cosmological Model with DM and DE
In the Weyl-Dirac (W-D) framework a spatially closed cosmological model is
considered. It is assumed that the space-time of the universe has a chaotic
Weylian microstructure but is described on a large scale by Riemannian
geometry. Locally fields of the Weyl connection vector act as creators of
massive bosons having spin 1. It is suggested that these bosons, called
weylons, provide most of the dark matter in the universe. At the beginning the
universe is a spherically symmetric geometric entity without matter. Primary
matter is created by Dirac's gauge function very close to the beginning. In the
early epoch, when the temperature of the universe achieves its maximum,
chaotically oriented Weyl vector fields being localized in micro-cells create
weylons. In the dust dominated period Dirac's gauge function is giving rise to
dark energy, the latter causing the cosmic acceleration at present. This
oscillatory universe has an initial radius identical to the Plank length =
1.616 exp (-33) cm, at present the cosmic scale factor is 3.21 exp (28) cm,
while its maximum value is 8.54 exp (28) cm. All forms of matter are created by
geometrically based functions of the W-D theory.Comment: 25 pages. Submitted to GR
Estudo dos cortes da carcaça de cordeiros Santa InĂȘs puros e cruzas Santa InĂȘs com Texel, Ile de France e BergamĂĄcia
Serum progesterone concentration and conception rate of beef cows supplemented with ground corn after a fixed-time artificial insemination protocol
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