1,971 research outputs found
Active multilayer mirrors for reflectance tuning at extreme ultraviolet (EUV) wavelengths
We propose an active multilayer mirror structure for EUV wavelengths
which can be adjusted to compensate for reflectance changes. The multilayer structure tunes the reflectance via an integrated piezoelectric layer that can change its dimension due to an externally applied voltage. Here, we present design and optimization of the mirror structure for maximum reflectance tuning. In addition, we present preliminary results showing that the deposition of piezoelectric thin films with the requisite layer smoothness and crystal structure are possible. Finally, polarization switching of the smoothest piezoelectric film is presented
Is there a role for prophylactic mesh in abdominal wall closure after emergency laparotomy? A systematic review and meta-analysis
Background
Incisional hernias are a common complication of emergency laparotomy and are associated with significant morbidity. Recent studies have found a reduction in incisional hernias when mesh is placed prophylactically during abdominal closure in elective laparotomies. This systematic review will assess the safety and efficacy of prophylactic mesh placement in emergency laparotomy.
Methods
A systematic review was performed according to the PROSPERO registered protocol (CRD42018109283). Papers were dual screened for eligibility, and included when a comparison was made between closure with prophylactic mesh and closure with a standard technique, reported using a comparative design (i.e. case–control, cohort or randomised trial), where the primary outcome was incisional hernia. Bias was assessed using the Cochrane risk of bias in non-randomised studies tool. A meta-analysis of incisional hernia rate was performed to estimate risk ratio using a random effects model (Mantel–Haenszel approach).
Results
332 studies were screened for eligibility, 29 full texts were reviewed and 2 non-randomised studies were included. Both studies were biased due to confounding factors, as closure technique was based on patient risk factors for incisional hernia. Both studies found significantly fewer incisional hernias in the mesh groups [3.2% vs 28.6% (p < 0.001) and 5.9% vs 33.3% (p = 0.0001)]. A meta-analysis of incisional hernia risk favoured prophylactic mesh closure [risk ratio 0.15 (95% CI 0.6–0.35, p < 0.001)]. Neither study found an association between mesh and infection or enterocutaneous fistula.
Conclusion
This review found that there are limited data to assess the effect or safety profile of prophylactic mesh in the emergency laparotomy setting. The current data cannot reliably assess the use of mesh due to confounding factors, and a randomised controlled trial is required to address this important clinical question
Monopole Solutions in AdS Space
We find monopole solutions for a spontaneously broken SU(2)-Higgs system
coupled to gravity in asymptotically anti-de Sitter space. We present new
analytic and numerical results discussing,in particular, how the gravitational
instability of self-gravitating monopoles depends on the value of the
cosmological constant.Comment: 14 pages, 4 figures, Latex fil
Comments on the U(2) Noncommutative Instanton
We discuss the 't Hoof ansatz for instanton solutions in noncommutative U(2)
Yang-Mills theory. We show that the extension of the ansatz leading to singular
solutions in the commutative case, yields to non self-dual (or self-antidual)
configurations in noncommutative space-time. A proposal leading to selfdual
solutions with Q=1 topological charge (the equivalent of the regular BPST
ansatz) can be engineered, but in that case the gauge field and the curvature
are not Hermitian (although the resulting Lagrangian is real).Comment: Latex file, no figure
K\"{a}hler-Einstein metrics on strictly pseudoconvex domains
The metrics of S. Y. Cheng and S.-T. Yau are considered on a strictly
pseudoconvex domains in a complex manifold. Such a manifold carries a complete
K\"{a}hler-Einstein metric if and only if its canonical bundle is positive. We
consider the restricted case in which the CR structure on is
normal. In this case M must be a domain in a resolution of the Sasaki cone over
. We give a condition on a normal CR manifold which it cannot
satisfy if it is a CR infinity of a K\"{a}hler-Einstein manifold. We are able
to mostly determine those normal CR 3-manifolds which can be CR infinities.
Many examples are given of K\"{a}hler-Einstein strictly pseudoconvex manifolds
on bundles and resolutions.Comment: 30 pages, 1 figure, couple corrections, improved a couple example
Conjectures for Large N Superconformal N=4 Chiral Primary Four Point Functions
An expression for the four point function for half-BPS operators belonging to
the [0,p,0] SU(4) representation in N=4 superconformal theories at strong
coupling in the large N limit is suggested for any p. It is expressed in terms
of the four point integrals defined by integration over AdS_5 and agrees with,
and was motivated by, results for p=2,3,4 obtained via the AdS/CFT
correspondence. Using crossing symmetry and unitarity, the detailed form is
dictated by the requirement that at large N the contribution of long multiplets
with twist less than 2p, which do not have anomalous dimensions, should cancel
corresponding free field contributions.Comment: 50 pages, 1 figure, uses harvmac, version 2 extra reference, minor
change
Stability of Subsequent-to-Leading-Logarithm Corrections to the Effective Potential for Radiative Electroweak Symmetry Breaking
We demonstrate the stability under subsequent-to-leading logarithm
corrections of the quartic scalar-field coupling constant and the
running Higgs boson mass obtained from the (initially massless) effective
potential for radiatively broken electroweak symmetry in the
single-Higgs-Doublet Standard Model. Such subsequent-to-leading logarithm
contributions are systematically extracted from the renormalization group
equation considered beyond one-loop order. We show to be the dominant
coupling constant of the effective potential for the radiatively broken case of
electroweak symmetry. We demonstrate the stability of and the running
Higgs boson mass through five orders of successively subleading logarithmic
corrections to the scalar-field-theory projection of the effective potential
for which all coupling constants except the dominant coupling constant
are disregarded. We present a full next-to-leading logarithm
potential in the three dominant Standard Model coupling constants
(-quark-Yukawa, , and ) from these coupling constants'
contribution to two loop - and -functions. Finally, we
demonstrate the manifest order-by-order stability of the physical Higgs boson
mass in the 220-231 GeV range. In particular, we obtain a 231 GeV physical
Higgs boson mass inclusive of the -quark-Yukawa and coupling
constants to next-to-leading logarithm order, and inclusive of the smaller
gauge coupling constants to leading logarithm order.Comment: 21 pages, latex2e, 2 eps figures embedded in latex file. Updated
version contains expanded analysis in Section
Superconformal Indices for Orbifold Chern-Simons Theories
We calculate the superconformal indices of recently discovered
three-dimensional N=4,5 Chern-Simons-matter theories and compare them with the
corresponding indices of supergravity on AdS4 times orbifolds of S7. We find
perfect agreement in the large N and large k limit, provided that the twisted
sector contributions at the fixed loci of the orbifolds are properly taken into
account. We also discuss the index for the so-called "dual ABJM" proposal.Comment: 27 pages, 1 figure; v2. reference added, minor correction
Bogomol'nyi Bounds and the Supersymmetric Born-Infeld Theory
We study N=2 supersymmetric Born-Infeld-Higgs theory in 3 dimensions and
derive Bogomol'nyi relations in its bosonic sector. A peculiar coupling between
the Higgs and the gauge field (with dynamics determined by the Born-Infeld
action) is forced by supersymmetry. The resulting equations coincide with those
arising in the Maxwell-Higgs model. Concerning Bogomol'nyi bounds for the
vortex energy, they are derived from the N=2 supersymmetry algebra.Comment: 24 pages, Latex fil
Some Systematics of the Coupling Constant Dependence of N=4 Yang-Mills
The operator, O_\tau, that generates infinitesimal changes of the coupling
constant in N=4 Yang-Mills sits in the same supermultiplet as the
superconformal currents. We show how superconformal current Ward identities
determine a class of terms in the operator product expansion of O_\tau with any
other operator. In certain cases, this leads to constraints on the coupling
dependence of correlation functions in N=4 Yang-Mills. As an application, we
demonstrate the exact non-renormalization of two and certain three-point
correlation functions of BPS operators.Comment: 56 pages, LaTeX; amended and expanded arguments, added reference
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