201 research outputs found
Drinfeld-Twisted Supersymmetry and Non-Anticommutative Superspace
We extend the analysis of hep-th/0408069 on a Lorentz invariant
interpretation of noncommutative spacetime to field theories on
non-anticommutative superspace with half the supersymmetries broken. By
defining a Drinfeld-twisted Hopf superalgebra, it is shown that one can restore
twisted supersymmetry and therefore obtain a twisted version of the chiral
rings along with certain Ward-Takahashi identities. Moreover, we argue that the
representation content of theories on the deformed superspace is identical to
that of their undeformed cousins and comment on the consequences of our
analysis concerning non-renormalization theorems.Comment: 1+17 pages; typos fixed, minor correction
Optilene, a new non-absorbable monofilament is safe and effective for CABG anastomosis. OPTICABG - A prospective international, multi-centric, cohort study
Introduction: Coronary artery bypass grafting (CABG) is performed to improve quality of life and to reduce cardiac-related mortality and morbidity in patients with coronary artery disease (CAD). The aim of the present observational study was to assess the performance of a new suture material (Optilene) for anastomosis construction in CABG surgery using a routine clinical procedure. Performance was assessed using the incidence of major adverse cardiac and cerebrovascular events (MACCE). Methods: The study was designed as an international, multi-centre, prospective cohort study to evaluate the safety and efficacy of a new non-absorbable monofilament for CABG surgery compared to data published in a previous meta-analysis. Optilene suture was used to create the distal and proximal coronary artery anastomoses. The primary endpoint was the cumulative MACCE rate up to discharge. Secondary parameters were intraoperative handling of the suture material and QoL up to 3 months after surgery. Patients were examined 30 days and 3 months postoperatively. Results: In total, 199 patients were enrolled in 3 centres in Europe. The cumulative CABG adverse event rate up to the day of discharge was 3%, in contrast to the 8.46% given by the data generated by Nalysnyk et al. A t-test showed that our CABG rate was significantly lower. QoL significantly increased from preoperatively until 3 months after surgery. Ease of handling the suture material was rated as very good. Conclusion: Optilene suture material represents a safe and effective alternative to existing sutures used in CABG surgery for anastomosis construction
N=1/2 Super Yang-Mills Theory on Euclidean AdS2xS2
We study D-branes in the background of Euclidean AdS2xS2 with a graviphoton
field turned on. As the background is not Ricci flat, the graviphoton field
must have both self-dual and antiself-dual parts. This, in general, will break
all the supersymmetries on the brane. However, we show that there exists a
limit for which one can restore half of the supersymmetries. Further, we show
that in this limit, the N=1/2 SYM Lagrangian on flat space can be lifted on to
the Euclidean AdS2xS2 preserving the same amount of supersymmetries as in the
flat case. We observe that without the C-dependent terms present in the action
this lift is not possible.Comment: 12 pages, latex file; v2: minor corrections, references adde
Does the type of suture technique affect the fluid-dynamic performance of bioprostheses implanted in small aortic roots? Results from an in vitro study.
Background: The in vivo hemodynamic performance of a bioprosthesis implanted in an aortic position is affected by the characteristics of the prosthesis and the sizing strategy adopted. Recently, it has been hypothesized that the type of suture used to implant the prosthesis might influence hemodynamics.
Methods: Bioprostheses with labeled sizes of 19 mm and 21 mm were implanted in 2 groups of 5 porcine aortic roots, with native annuli of 19 mm and 21 mm, by means of 2 different suture techniques: simple interrupted and noneverting mattress with pledgets. The aortic roots were tested in an in vitro mock loop. The stroke volume imposed by the mock loop was set at 40 mL, and was increased by steps of 15 mL until a stroke volume of 100 mL was attained. Main fluid-dynamic parameters were analyzed.
Results: At each level of stroke volume, ie, 40 mL, 55 mL, 70 mL, 85 mL, and 100 mL, the mean and peak pressure drops were significantly greater with the noneverting mattress suture with pledgets than with the simple interrupted suture. The effective orifice area behaved accordingly, being significantly smaller in the former case.
Conclusions: Our data show that the type of suture technique can influence bioprosthesis performance and that it is reasonable to assume that this is especially true in small annuli (<= 21 mm). Thus, to optimize prosthesis performance and reduce the incidence of patient-prosthesis mismatch, the role of the suture technique should not be disregarded
Moduli stabilization with Fayet-Iliopoulos uplift
In the recent years, phenomenological models of moduli stabilization were
proposed, where the dynamics of the stabilization is essentially
supersymmetric, whereas an O'Rafearthaigh supersymmetry breaking sector is
responsible for the "uplift" of the cosmological constant to zero. We
investigate the case where the uplift is provided by a Fayet-Iliopoulos sector.
We find that in this case the modulus contribution to supersymmetry breaking is
larger than in the previous models. A first consequence of this class of
constructions is for gauginos, which are heavier compared to previous models.
In some of our explicit examples, due to a non-standard gauge-mediation type
negative contribution to scalars masses, the whole superpartner spectrum can be
efficiently compressed at low-energy. This provides an original phenomenology
testable at the LHC, in particular sleptons are generically heavier than the
squarks.Comment: 29 pages, 2 figure
Nonanticommutative Deformation of N=4 SYM Theory: The Myers Effect and Vacuum States
We propose a deformation of SYM theoery induced by
nonanticommutative star product. The deformation introduces new bosonic terms
which we identify with the corresponding Myers terms of a stack of D3-branes in
the presence of a five-form RR flux. We take this as an indication that the
deformed lagrangian describes D3-branes in such a background. The vacuum states
of the theory are also examined. In a specific case where the U(1) part of the
gauge field is nonvanishing the (anti)holomorphic transverse coordinates of the
brane sit on a fuzzy two sphere. For a supersymmetric vacuum the
antiholomorphic coordinates must necessarily commute. However, we also
encounter non-supersymmetric vacua for which the antiholomorphic coordinates do
not commute.Comment: 14 pages, minor changes, refs. adde
Strong Reduction of the Effective Radiation Length in an Axially Oriented Scintillator Crystal
We measured a considerable increase of the emitted radiation by 120 GeV/c electrons in an axially oriented lead tungstate scintillator crystal, if compared to the case in which the sample was not aligned with the beam direction. This enhancement resulted from the interaction of particles with the strong crystalline electromagnetic field. The data collected at the external lines of the CERN Super Proton Synchrotron were critically compared to Monte Carlo simulations based on the Baier-Katkov quasiclassical method, highlighting a reduction of the scintillator radiation length by a factor of 5 in the case of beam alignment with the [001] crystal axes. The observed effect opens the way to the realization of compact electromagnetic calorimeters or detectors based on oriented scintillator crystals in which the amount of material can be strongly reduced with respect to the state of the art. These devices could have relevant applications in fixed-target experiments, as well as in satellite-borne γ telescopes
Gauge Theory on Noncommutative Supersphere from Supermatrix Model
We construct a supermatrix model which has a classical solution representing
the noncommutative (fuzzy) two-supersphere. Expanding supermatrices around the
classical background, we obtain a gauge theory on a noncommutative superspace
on sphere. This theory has supersymmetry and gauge
symmetry. We also discuss a commutative limit of the model keeping radius of
the supersphere fixed.Comment: 16 pages, Latex, typos corrected, references adde
Hard X-ray stereographic microscopy for single-shot differential phase imaging
The characterisation of fast phenomena at the microscopic scale is required for the understanding of catastrophic responses of materials to loads and shocks, the processing of materials by optical or mechanical means, the processes involved in many key technologies such as additive manufacturing and microfluidics, and the mixing of fuels in combustion. Such processes are usually stochastic in nature and occur within the opaque interior volumes of materials or samples, with complex dynamics that evolve in all three dimensions at speeds exceeding many meters per second. There is therefore a need for the ability to record three-dimensional X-ray movies of irreversible processes with resolutions of micrometers and frame rates of microseconds. Here we demonstrate a method to achieve this by recording a stereo phase-contrast image pair in a single exposure. The two images are combined computationally to reconstruct a 3D model of the object. The method is extendable to more than two simultaneous views. When combined with megahertz pulse trains of X-ray free-electron lasers (XFELs) it will be possible to create movies able to resolve 3D trajectories with velocities of kilometers per second
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