2,374 research outputs found
Residual strength of equine bone is not reduced by intense fatigue loading: Implications for stress fracture
Fatigue or stress fractures are an important clinical problem in humans as well as racehorses. An important question in this context is, when a bone experiences. fa!igue damage ~uring e~treme use, how much is it weakened compared to its original state? Since there are very ltmtted data on thts quesuon and stress fractures are common in racehorses, we sought to determine the effect of fatigue loading on the monotonic l:trength of equine cortical bone. Beams were machined from the dorsal, medial and lateral cortices of the third metacarpal bones of six thoroughbred racehorses. Beams from left and right bones were assigned to control and fatigue groups. respectively (N- 18 each). The fatigue group was cyclicully loaded in three-point bending at 2Hz for 100,000 cycles at 0- 5000 microstrain while submerged in saline at 37°C. These beams. as well as those in the control group. were then monotonically loaded to failure in three-point bending. The monotonic load-deflection curves were analyzed for differences using three-factor (fatigue loading, ~natotni~ region. and horse)_ analysis o_f variance .. The mean failure load was 3% less in the fatigue group, but thts reduction was only margmally stgmficant. Netther elastic modulus nor yield strength was significantly affected by the fatigue loading. The principal effects of fatigue loading were on post-yield behavior (yield being based on a 0.02% offset criter!on). The work don~ and the load increase between yield and failure were both significantly reduced. All the vanables except post-yteld deflecuon were significantly affected by anatomic region. In summary, loading equivalent to a lifetime of racing does not significantly weaken equine cortical bone ex vivo. The clinical implication of this may be that the biological repair of fatigue damage can actually contribute to stress fracture if pressed too far
Irradiation of the secondary star in X-ray Nova Scorpii 1994 (=GRO J1655--40)
We have obtained intermediate resolution optical spectra of the black-hole
candidate Nova Sco 1994 in June 1996, when the source was in an X-ray/optical
active state (R~15.05). We measure the radial velocity curve of the secondary
star and obtain a semi-amplitude of 279+/-10 km/s; a value which is 30 per cent
larger than the value obtained when the source is in quiescence. Our large
value for K_2 is consistent with 60 +9,-7 per cent of the secondary star's
surface being heated; compared to 35 per cent, which is what one would expect
if only the inner face of the secondary star were irradiated. Effects such as
irradiation-induced flows on the secondary star may be important in explaining
the observed large value for K_2.Comment: 5 pages, 2 figures, accepted by MNRA
The Mental and Physical Health of Mothers of Children with Special Health Care Needs in the United States
OBJECTIVE: To determine the prevalence of poor mental and physical health among mothers of children with special health care needs (CSHCN) and to determine the association between maternal health and the child\u27s number of special health care needs (SHCN) and severity of ability limitation.
METHODS: We used the combined 2016-2018 National Survey of Children\u27s Health Dataset of 102,341 children ages 0-17 including 23,280 CSHCN. We used regression models to examine the associations of a child\u27s number of SHCN and ability limitations with maternal health.
RESULTS: Twice as many mothers of CSHCN had poor mental and physical health compared to non-CSHCN (mental 10.3% vs. 4.0%, pâ\u3câ.001; physical 11.9% vs 5.0%, pâ\u3câ.001). In regression models, increased number of SHCN and severity of activity limitations were associated with significantly increased odds of poor maternal health.
CONCLUSIONS FOR PRACTICE: Mothers of CSHCN have worse health compared to mothers of non-CSHCN, especially those who experience social disadvantage and those with children with complex SHCN or severe ability limitations. Interventions to improve the health of these particularly vulnerable caregivers of CSHCN are warranted
Protective Role for Properdin in Progression of Experimental Murine Atherosclerosis
Genetic, dietary and immune factors contribute to the pathogenesis of atherosclerosis in humans and mice. Complement activation is an integral part of the innate immune defence but also shapes cellular responses and influences directly triglyceride synthesis. Deficiency of Factor B of the alternative pathway (AP) of complement is beneficial in LDLRâ/â mice fed a high fat diet. The serum glycoprotein properdin is a key positive regulator of the AP but has not been studied in experimental atherosclerosis. Atherosclerosis was assessed after feeding low fat (LFD) or high fat (HFD) Western type diets to newly generated LDLRâ/â ProperdinKO (LDLRâ/âPKO) and LDLRâ/âPWT mice. Lipids, lymphocytes and monocytes were similar among genotypes, genders and diets. Complement C3, but not C3adesarg, levels were enhanced in LDLRâ/âPKO mice regardless of diet type or gender. Non-esterified fatty acids (NEFA) were decreased in male LDLRâ/âPKO fed a HFD compared with controls. All mice showed significant atherosclerotic burden in aortae and at aortic roots but male LDLRâ/â mice fed a LFD were affected to the greatest extent by the absence of properdin. The protective effect of properdin expression was overwhelmed in both genders of LDLRâ/âmice when fed a HFD. We conclude that properdin plays an unexpectedly beneficial role in the development and progression of early atherosclerotic lesions
Empirical validation of the UNAIDS Spectrum model for subnational HIV estimates: case-study of children and adults in Manicaland, Zimbabwe
Background: More cost-effective HIV control may be achieved by targeting geographical areas with high infection rates. The AIDS Impact model of Spectrum â used routinely to produce national HIV estimates â could provide the required subnational estimates but is rarely validated with empirical data, even at a national level. Design: The validity of the Spectrum model estimates were compared to empirical estimates. Methods: Antenatal surveillance and population survey data from a population HIV cohort study in Manicaland, east Zimbabwe, were input into Spectrum 5.441 to create a simulation representative of the cohort population. Model and empirical estimates were compared for key demographic and epidemiological outcomes. Alternative scenarios for data availability were examined and sensitivity analyses were conducted for model assumptions considered important for subnational estimates. Results: Spectrum estimates generally agreed with observed data but HIV incidence estimates were higher than empirical estimates while estimates of early age all-cause adult mortality were lower. Child HIV prevalence estimates matched well with the survey prevalence among children. Estimated paternal orphanhood was lower than empirical estimates. Including observations from earlier in the epidemic did not improve the HIV incidence model fit. Migration had little effect on observed discrepancies - possibly because the model ignores differences in HIV prevalence between migrants and residents. Conclusions: The Spectrum model, using subnational surveillance and population data, provided reasonable subnational estimates although some discrepancies were noted. Differences in HIV prevalence between migrants and residents may need to be captured in the model if applied to subnational epidemics
An atlas of line profile studies for SU UMa type cataclysmic variables
We present H-alpha line-profile analyses for the seven SU UMa type dwarf
novae AK Cnc, WX Cet, AQ Eri, VW Hyi, RZ Leo, TU Men, and HS Vir. All data sets
are treated in the same manner, applying a sequence of techniques for each
system. The basic ingredients of this sequence are the diagnostic diagram to
determine the zero point of the orbital phase, and Doppler tomography to
visualise the emission distribution. We furthermore introduce a new qualitative
way of to evaluate the Doppler fit, by comparing the line profile of the
reconstructed with the original spectrum in the form of the V/R plot. We
present the results of the analysis in the compact form of an atlas, allowing a
direct comparison of the emission distribution in our targets. Although most of
the data sets were not taken with the intention of a line-profile analysis, we
obtain significant results and are able to indicate the type of the additional
emission in these systems. Our objects should have in principle very similar
physical properties, i.e. they cover only a small range in orbital periods,
mass ratios, and mass-transfer rates. Nevertheless, we find a large variety of
phenomena both with respect to the individual systems and also within
individual data sets of the same object. This includes `canonical' additional
emission components from the secondary star and the bright spot, but also
emission from the leading side of the accretion disc.Comment: 20 pages, 25 figures, accepted for publication in A&A, figures have
been diminished in size and qualit
New results on GP Com
We present high resolution optical and UV spectra of the 46 min orbital
period, helium binary, GP Com. Our data contains simultaneous photometric
correction which confirms the flaring behaviour observed in previous optical
and UV data. In this system all lines show a triple peaked structure where the
outer two peaks are associated with the accretion disc around the compact
object. The main aim of this paper is to constrain the origin of the central
peak, also called ``central spike''. We find that the central spike contributes
to the flare spectra indicating that its origin is probably the compact object.
We also detect that the central spike moves with orbital phase following an
S-wave pattern. The radial velocity semiamplitude of the S-wave is ~10 km/s
indicating that its origin is near the centre of mass of the system, which in
this case lies very close to the white dwarf. Our resolution is higher than
that of previous data which allows us to resolve structure in the central peak
of the line. The central spike in three of the HeI lines shows another peak
blueshifted with respect to the main peak. We propose that one of the peaks is
a neutral helium forbidden transition excited in a high electron density
region. This forbidden transition is associated with the permitted one (the
stronger peak in two of the lines). The presence of a high electron density
region again favours the white dwarf as their origin.Comment: 14 pages, 16 figures. Accepted for publication in A&
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