ABSTRACT
Using combined data from the Relativistic Heavy Ion and Large Hadron Colliders, we constrain the shear and bulk viscosities of quark-gluon plasma (QGP) at temperatures of â¼150-350 MeV. We use Bayesian inference to translate experimental and theoretical uncertainties into probabilistic constraints for the viscosities. With Bayesian model averaging we propagate an estimate of the model uncertainty generated by the transition from hydrodynamics to hadron transport in the plasma's final evolution stage, providing the most reliable phenomenological constraints to date on the QGP viscosities.
ABSTRACT
We report on the first lattice calculation of the QCD phase transition using chiral fermions with physical quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm)(3) and (11 fm)(3) and temperatures between 139 and 196 MeV. Each temperature is calculated at a single lattice spacing corresponding to a temporal Euclidean extent of N(t) = 8. The disconnected chiral susceptibility, χ(disc) shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability near the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD "phase transition" is not first order but a continuous crossover for m(π) = 135 MeV. The peak location determines a pseudocritical temperature T(c) = 155(1)(8) MeV, in agreement with earlier staggered fermion results. However, the peak height is 50% greater than that suggested by previous staggered results. Chiral SU(2)(L) × SU(2)(R) symmetry is fully restored above 164 MeV, but anomalous U(1)(A) symmetry breaking is nonzero above T(c) and vanishes as T is increased to 196 MeV.
ABSTRACT
BACKGROUND: In this study, we assessed the feasibility of laser-assisted tissue welding as a means of fixing mesh prostheses to the peritoneum. We then tested the initial tensile strength of the bonds. METHODS: Fresh porcine peritoneal coupons were lap-joint bonded with laser-activated solder. Anesthetized New Zealand white rabbits and Yorkshire pigs also underwent laparotomy. Vicryl mesh (2.0 x 1.0 cm) was attached to the peritoneum using a laser system (1.43 mu, 2.5 W, 60 degrees C), solder formulations and configurations, and a 1 cm2 bond area. Control segments were affixed with 4.8-mm staples. After the animals were killed, the segments were excised en bloc. Tensile strength assessment was conducted by measuring peak force breaking strength. RESULTS: The strength of the solder bonds were similar in all groups (range, 261.5 +/- 170.3-465.3 +/- 288.2 g/cm2) and were not statistically different from the controls (215.8 +/- 117.8 g/cm2). CONCLUSIONS: These values are similar to the 200-500 g/cm2 acute strengths reported for sutured or stapled peritoneal closure. Mesh fixation by solder is feasible, and further development of this technology is warranted.