675 research outputs found
Non-Bogomolny SU(N) BPS Monopoles
For N>2 we present static monopole solutions of the second order SU(N) BPS
Yang-Mills-Higgs equations which are not solutions of the first order Bogomolny
equations. These spherically symmetric solutions may be interpreted as monopole
anti-monopole configurations and their construction involves harmonic maps into
complex projective spaces.Comment: 14 pages, 1 figur
Monopoles from Rational Maps
The moduli space of charge k SU(2) BPS monopoles is diffeomorphic to the
moduli space of degree k rational maps between Riemann spheres. In this note we
describe a numerical algorithm to compute the monopole fields and energy
density from the rational map. The results for some symmetric examples are
presented.Comment: 8 pages, 2 figures. To appear in Phys. Lett.
Solitons, Links and Knots
Using numerical simulations of the full nonlinear equations of motion we
investigate topological solitons of a modified O(3) sigma model in three space
dimensions, in which the solitons are stabilized by the Hopf charge. We find
that for solitons up to charge five the solutions have the structure of closed
strings, which become increasingly twisted as the charge increases. However,
for higher charge the solutions are more exotic and comprise linked loops and
knots. We discuss the structure and formation of these solitons and demonstrate
that the key property responsible for producing such a rich variety of solitons
is that of string reconnection.Comment: 24 pages plus 14 figures in GIF forma
Instanton Moduli and Topological Soliton Dynamics
It has been proposed by Atiyah and Manton that the dynamics of Skyrmions may
be approximated by motion on a finite dimensional manifold obtained from the
moduli space of SU(2) Yang-Mills instantons. Motivated by this work we describe
how similar results exist for other soliton and instanton systems. We describe
in detail two examples for the approximation of the infinite dimensional
dynamics of sine-Gordon solitons by finite dimensional dynamics on a manifold
obtained from instanton moduli. In the first example we use the moduli space of
CP1 instantons and in the second example we use the moduli space of SU(2)
Yang-Mills instantons. The metric and potential functions on these manifolds
are constructed and the resulting dynamics is compared with the explicit exact
soliton solutions of the sine-Gordon theory.Comment: uuencoded tex file, 27 pages including 4 figures, requires phyzzx
macro. DAMTP 94-5
Multi-soliton dynamics in the Skyrme model
We exhibit the dynamical scattering of multi-solitons in the Skyrme model for
configurations with charge two, three and four. First, we construct maximally
attractive configurations from a simple profile function and the product
ansatz. Then using a sophisticated numerical algorithm, initially
well-separated skyrmions in approximately symmetric configurations are shown to
scatter through the known minimum energy configurations. These scattering
events illustrate a number of similarities to BPS monopole configurations of
the same charge. A simple modification of the dynamics to a dissipative regime,
allows us to compute the minimal energy skyrmions for baryon numbers one to
four to within a few percent.Comment: latex, 10 pages, plus 5 figures (as gif files
Seiberg-Witten theory, monopole spectral curves and affine Toda solitons
Using Seiberg-Witten theory it is known that the dynamics of N=2
supersymmetric SU(n) Yang-Mills theory is determined by a Riemann surface. In
particular the mass formula for BPS states is given by the periods of a special
differential on this surface. In this note we point out that the surface can be
obtained from the quotient of a symmetric n-monopole spectral curve by its
symmetry group. Known results about the Seiberg-Witten curves then implies that
these monopoles are related to the Toda lattice. We make this relation explicit
via the ADHMN construction. Furthermore, in the simplest case, that of two
SU(2) monopoles, we find that the general two monopole solution is generated by
an affine Toda soliton solution of the imaginary coupled theory.Comment: uuencoded latex, 15 pages, 1 figure. To appear in Physics Letters
Q-ball Dynamics
We investigate the dynamics of Q-balls in one, two and three space
dimensions, using numerical simulations of the full nonlinear equations of
motion. We find that the dynamics of Q-balls is extremely complex, involving
processes such as charge transfer and Q-ball fission. We present results of
simulations which illustrate the salient features of 2-Q-ball interactions and
give qualitative arguments to explain them in terms of the evolution of the
time-dependent phases.Comment: 37 pages, including figure
Total hip replacement for the treatment of end stage arthritis of the hip : a systematic review and meta-analysis
Background: Evolvements in the design, fixation methods, size, and bearing surface of implants for total hip replacement (THR) have led to a variety of options for healthcare professionals to consider. The need to determine the most optimal combinations of THR implant is warranted. This systematic review evaluated the clinical effectiveness of different types of THR used for the treatment of end stage arthritis of the hip.
Methods: A comprehensive literature search was undertaken in major health databases. Randomised controlled trials (RCTs) and systematic reviews published from 2008 onwards comparing different types of primary THR in patients with end stage arthritis of the hip were included.
Results: Fourteen RCTs and five systematic reviews were included. Patients experienced significant post-THR improvements in Harris Hip scores, but this did not differ between impact types. There was a reduced risk of implant dislocation after receiving a larger femoral head size (36 mm vs. 28 mm; RR = 0.17, 95% CI: 0.04, 0.78) or cemented cup (vs. cementless cup; pooled odds ratio: 0.34, 95% CI: 0.13, 0.89). Recipients of cross-linked vs. conventional polyethylene cup liners experienced reduced femoral head penetration and revision. There was no impact of femoral stem fixation and cup shell design on implant survival rates. Evidence on mortality and complications (aseptic loosening, femoral fracture) was inconclusive.
Conclusions: The majority of evidence was inconclusive due to poor reporting, missing data, or uncertainty in treatment estimates. The findings warrant cautious interpretation given the risk of bias (blinding, attrition), methodological limitations (small sample size, low event counts, short follow-up), and poor reporting. Long-term pragmatic RCTs are needed to allow for more definitive conclusions. Authors are encouraged to specify the minimal clinically important difference and power calculation for their primary outcome(s) as well CONSORT, PRISMA and STROBE guidelines to ensure better reporting and more reliable production and assessment of evidence
Inactivity/sleep in two wild free-roaming African elephant matriarchs - Does large body size make elephants the shortest mammalian sleepers?
The current study provides details of sleep (or inactivity) in two wild, free-roaming African elephant matriarchs studied in their natural habitat with remote monitoring using an actiwatch subcutaneously implanted in the trunk, a standard elephant collar equipped with a GPS system and gyroscope, and a portable weather station. We found that these two elephants were polyphasic sleepers, had an average daily total sleep time of 2 h, mostly between 02:00 and 06:00, and displayed the shortest daily sleep time of any mammal recorded to date. Moreover, these two elephants exhibited both standing and recumbent sleep, but only exhibited recumbent sleep every third or fourth day, potentially limiting their ability to enter REM sleep on a daily basis. In addition, we observed on five occasions that the elephants went without sleep for up to 46 h and traversed around 30 km in 10 h, possibly due to disturbances such as potential predation or poaching events, or a bull elephant in musth. They exhibited no form of sleep rebound following a night without sleep. Environmental conditions, especially ambient air temperature and relative humidity, analysed as wet-bulb globe temperature, reliably predict sleep onset and offset times. The elephants selected novel sleep sites each night and the amount of activity between sleep periods did not affect the amount of sleep. A number of similarities and differences to studies of elephant sleep in captivity are noted, and specific factors shaping sleep architecture in elephants, on various temporal scales, are discussed
Belimumab : a technological advance for systemic lupus erythematosus patients? Report of a systematic review and meta-analysis
Objectives: To undertake a systematic review and meta-analysis to investigate clinical effectiveness of belimumab for patients with systemic lupus erythematosus (SLE) and antinuclear and/or anti-double-stranded DNA (dsDNA) autoantibodies.
Methods: We searched eight electronic databases and reference lists for randomised controlled trials (RCTs) of belimumab against placebo or best supportive care. Quality assessment and random effects meta-analysis were undertaken.
Design: A meta-analysis of RCTs.
Participants: 2133 SLE patients.
Primary and secondary outcome measures: SLE Responder Index (SRI) at week 52.
Results: Three double-blind placebo-controlled RCTs (L02, BLISS-52 BLISS-76) investigated 2133 SLE patients. BLISS-52 and BLISS-76 trials recruited patients with antinuclear and/or anti-dsDNA autoantibodies and demonstrated belimumab effectiveness for the SRI at week 52. Ethnicity and geographical location of participants varied considerably between BLISS trials. Although tests for statistical heterogeneity were negative, BLISS-52 results were systematically more favourable for all measured outcomes. Meta-analysis of pooled 52-week SRI BLISS results showed benefit for belimumab (OR 1.63, 95% CI 1.27 to 2.09). By week 76, the primary SRI outcome in BLISS-76 was not statistically significant (OR 1.31, 95% CI 0.919 to 1.855)
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