713 research outputs found
Causes of failure of ceramic-on-ceramic and metal-on-metal hip arthroplasties.
BACKGROUND: Few large series of hard bearing surfaces have reported on reasons for early failure. A number of unique mechanisms of failure, including fracture, squeaking, and adverse tissue reactions, have been reported with these hard bearing surfaces. However, the incidence varies among the published studies.
QUESTIONS/PURPOSES: To confirm the incidences, we identified the etiologies of early failures of hard-on-hard bearing surfaces for ceramic-on-ceramic and metal-on-metal THAs.
METHODS: We retrospectively reviewed records of 2907 THAs with hard-on-hard bearing surfaces implanted between 1996 and 2009; 1697 (58%) had ceramic-on-ceramic and 1210 (42%) had metal-on-metal bearing surfaces. We recorded bearing-related complications and compared them to nonspecific reasons for revision THA. The minimum followup of the ceramic-on-ceramic and metal-on-metal cohorts was 6 months (mean, 48 months; range, 6-97 months) and 24 months (mean, 60 months; range, 24-178 months), respectively.
RESULTS: The overall revision rate for ceramic-on-ceramic THA was 2.2% (38 of 1697), with aseptic loosening accounting for 55% of revisions (femur or acetabulum). The bearing accounted for 13% of the revisions in the ceramic-on-ceramic THA cohort. The overall metal-on-metal revision rate was 5.4% (65 of 1210), 17 involving adverse tissue reactions related to the metal-on-metal bearing surface (17 of 1210, 1.4% of cases; 17 of 65, 26% of revisions).
CONCLUSIONS: Twenty-six percent of the revisions from metal-on-metal and 13% of ceramic-on ceramic were bearing related. The overall short- to medium-term revision rate was 2.2% and 5.4% for ceramic-on-ceramic and metal-on-metal, respectively. The most common etiology of failure was loosening of the femoral or acetabular components.
LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of level of evidence
Decreased Incidence of Periprosthetic Joint Infection in Total Hip Arthroplasty with Use of Topical Vancomycin
Background: Periprosthetic joint infections following total hip arthroplasty (THA) can cause significant patient morbidity and carry with them a substantial cost burden to the healthcare system. The purpose of this study was to assess whether the addition of topical vancomycin decreased the incidence of superficial and deep infections after primary total hip arthroplasty?
Methods: We performed a retrospective analysis of patients who underwent primary THA with (1070 hips) and without (815 hips) the use of topical vancomycin. Records were reviewed to determine incidence of PJI. Infections were categorized as deep or superficial. Medical comorbidity data was evaluated for known risk factors including diabetes, rheumatoid arthritis, and BMI. Records were further reviewed to determine surgical approach used and bacterial cause of PJI.
Results: The overall incidence of infection in the control group was 1.47% (12 hips) and significantly decreased to 0.47% (5 hips) with the addition of topical vancomycin (p=0.022). Deep infections also decreased from 0.86% (7 hips) in the control group to 0.09% (1 hip) in the vancomycin group (p=0.011). There was no difference in BMI or percent of patients with diabetes between groups. In all patients, regardless of vancomycin use, the incidence of infection in the direct lateral approach was higher (2.04%, 9 hips) than the anterior approach (0.055%, 8 hips) (p=0.004).
Conclusions: We found a lower incidence of periprosthetic joint infection after THA with the addition of topical vancomycin. We also found a decreased incidence of infection in patients who had surgery through an anterior approach compared with those who had a direct lateral approach
Cross-sectional associations between sleep duration, sedentary time, physical activity, and adiposity indicators among Canadian preschool-aged children using compositional analyses
Abstract Background Sleep duration, sedentary behaviour, and physical activity are three co-dependent behaviours that fall on the movement/non-movement intensity continuum. Compositional data analyses provide an appropriate method for analyzing the association between co-dependent movement behaviour data and health indicators. The objectives of this study were to examine: (1) the combined associations of the composition of time spent in sleep, sedentary behaviour, light-intensity physical activity (LPA), and moderate- to vigorous-intensity physical activity (MVPA) with adiposity indicators; and (2) the association of the time spent in sleep, sedentary behaviour, LPA, or MVPA with adiposity indicators relative to the time spent in the other behaviours in a representative sample of Canadian preschool-aged children. Methods Participants were 552 children aged 3 to 4 years from cycles 2 and 3 of the Canadian Health Measures Survey. Sedentary time, LPA, and MVPA were measured with Actical accelerometers (Philips Respironics, Bend, OR USA), and sleep duration was parental reported. Adiposity indicators included waist circumference (WC) and body mass index (BMI) z-scores based on World Health Organization growth standards. Compositional data analyses were used to examine the cross-sectional associations. Results The composition of movement behaviours was significantly associated with BMI z-scores (p = 0.006) but not with WC (p = 0.718). Further, the time spent in sleep (BMI z-score: γ sleep = −0.72; p = 0.138; WC: γ sleep = −1.95; p = 0.285), sedentary behaviour (BMI z-score: γ SB = 0.19; p = 0.624; WC: γ SB = 0.87; p = 0.614), LPA (BMI z-score: γ LPA = 0.62; p = 0.213, WC: γ LPA = 0.23; p = 0.902), or MVPA (BMI z-score: γ MVPA = −0.09; p = 0.733, WC: γ MVPA = 0.08; p = 0.288) relative to the other behaviours was not significantly associated with the adiposity indicators. Conclusions This study is the first to use compositional analyses when examining associations of co-dependent sleep duration, sedentary time, and physical activity behaviours with adiposity indicators in preschool-aged children. The overall composition of movement behaviours appears important for healthy BMI z-scores in preschool-aged children. Future research is needed to determine the optimal movement behaviour composition that should be promoted in this age group
Optical properties of structurally-relaxed Si/SiO superlattices: the role of bonding at interfaces
We have constructed microscopic, structurally-relaxed atomistic models of
Si/SiO superlattices. The structural distortion and oxidation-state
characteristics of the interface Si atoms are examined in detail. The role
played by the interface Si suboxides in raising the band gap and producing
dispersionless energy bands is established. The suboxide atoms are shown to
generate an abrupt interface layer about 1.60 \AA thick. Bandstructure and
optical-absorption calculations at the Fermi Golden rule level are used to
demonstrate that increasing confinement leads to (a) direct bandgaps (b) a blue
shift in the spectrum, and (c) an enhancement of the absorption intensity in
the threshold-energy region. Some aspects of this behaviour appear not only in
the symmetry direction associated with the superlattice axis, but also in the
orthogonal plane directions. We conclude that, in contrast to Si/Ge, Si/SiO
superlattices show clear optical enhancement and a shift of the optical
spectrum into the region useful for many opto-electronic applications.Comment: 11 pages, 10 figures (submitted to Phys. Rev. B
Longitudinal double spin asymmetries in single hadron quasi-real photoproduction at high
We measured the longitudinal double spin asymmetries for single
hadron muo-production off protons and deuterons at photon virtuality <
1(GeV/) for transverse hadron momenta in the range 0.7
GeV/ to 4 GeV/ . They were determined using COMPASS data taken
with a polarised muon beam of 160 GeV/ or 200 GeV/ impinging on
polarised or targets. The experimental
asymmetries are compared to next-to-leading order pQCD calculations, and are
sensitive to the gluon polarisation inside the nucleon in the range
of the nucleon momentum fraction carried by gluons
Interplay among transversity induced asymmetries in hadron leptoproduction
In the fragmentation of a transversely polarized quark several left-right
asymmetries are possible for the hadrons in the jet. When only one unpolarized
hadron is selected, it exhibits an azimuthal modulation known as Collins
effect. When a pair of oppositely charged hadrons is observed, three
asymmetries can be considered, a di-hadron asymmetry and two single hadron
asymmetries. In lepton deep inelastic scattering on transversely polarized
nucleons all these asymmetries are coupled with the transversity distribution.
From the high statistics COMPASS data on oppositely charged hadron-pair
production we have investigated for the first time the dependence of these
three asymmetries on the difference of the azimuthal angles of the two hadrons.
The similarity of transversity induced single and di-hadron asymmetries is
discussed. A new analysis of the data allows to establish quantitative
relationships among them, providing for the first time strong experimental
indication that the underlying fragmentation mechanisms are all driven by a
common physical process.Comment: 6 figure
Interplay among transversity induced asymmetries in hadron leptoproduction
In the fragmentation of a transversely polarized quark several left-right
asymmetries are possible for the hadrons in the jet. When only one unpolarized
hadron is selected, it exhibits an azimuthal modulation known as Collins
effect. When a pair of oppositely charged hadrons is observed, three
asymmetries can be considered, a di-hadron asymmetry and two single hadron
asymmetries. In lepton deep inelastic scattering on transversely polarized
nucleons all these asymmetries are coupled with the transversity distribution.
From the high statistics COMPASS data on oppositely charged hadron-pair
production we have investigated for the first time the dependence of these
three asymmetries on the difference of the azimuthal angles of the two hadrons.
The similarity of transversity induced single and di-hadron asymmetries is
discussed. A new analysis of the data allows to establish quantitative
relationships among them, providing for the first time strong experimental
indication that the underlying fragmentation mechanisms are all driven by a
common physical process.Comment: 6 figure
Leading-order determination of the gluon polarisation from semi-inclusive deep inelastic scattering data
Using a novel analysis technique, the gluon polarisation in the nucleon is
re-evaluated using the longitudinal double-spin asymmetry measured in the cross
section of semi-inclusive single-hadron muoproduction with photon virtuality
. The data were obtained by the COMPASS experiment at
CERN using a 160 GeV/ polarised muon beam impinging on a polarised LiD
target. By analysing the full range in hadron transverse momentum ,
the different -dependences of the underlying processes are separated
using a neural-network approach. In the absence of pQCD calculations at
next-to-leading order in the selected kinematic domain, the gluon polarisation
is evaluated at leading order in pQCD at a hard scale of . It is determined in three intervals
of the nucleon momentum fraction carried by gluons, , covering the
range ~ and does not exhibit a significant
dependence on . The average over the three intervals, at
, suggests that the gluon polarisation
is positive in the measured range.Comment: 14 pages, 6 figure
Information flows at inter-team boundaries in agile information systems development
Agile software development methods are being used on larger projects thus the study of inter-team communication are becoming an important topic of interest for researchers. This research addresses inter-team communication by exploring the tools and three different boundaries, inter-team, team and customers, and geographically separated teams. In this research, we gathered data from semi-structured face-to-face interviews which were analyzed following the grounded theory approach. Our study reveals consensus from different teams on the importance of virtual Kanban boards. Also, some teams members tend to adapt to other teams’ preferred communication tool. We observed challenges around interdependent user stories among the different teams and highlighted the problems that rise at the different boundaries.
Keywords: agile information system development • inter-team communication • agile team boundary • communication • agile methods • cooperating agile team
The Spin Structure Function of the Proton and a Test of the Bjorken Sum Rule
New results for the double spin asymmetry and the proton
longitudinal spin structure function are presented. They were
obtained by the COMPASS collaboration using polarised 200 GeV muons scattered
off a longitudinally polarised NH target. The data were collected in 2011
and complement those recorded in 2007 at 160\,GeV, in particular at lower
values of . They improve the statistical precision of by
about a factor of two in the region . A next-to-leading order
QCD fit to the world data is performed. It leads to a new determination
of the quark spin contribution to the nucleon spin, ranging
from 0.26 to 0.36, and to a re-evaluation of the first moment of .
The uncertainty of is mostly due to the large uncertainty in
the present determinations of the gluon helicity distribution. A new evaluation
of the Bjorken sum rule based on the COMPASS results for the non-singlet
structure function yields as ratio of the axial and
vector coupling constants , which validates the sum rule to an accuracy of about
9\%.Comment: 19 pages, 8 figures and table
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