Calculation of W b bbar Production via Double Parton Scattering at the LHC

We investigate the potential to observe double parton scattering at the Large Hadron Collider in p p -> W b bbar X -> l nu b bbar X at 7 TeV. Our analysis tests the efficacy of several kinematic variables in isolating the double parton process of interest from the single parton process and relevant backgrounds for the first 10 inverse fb of integrated luminosity. These variables are constructed to expose the independent nature of the two subprocesses in double parton scattering, pp -> l nu X and pp -> b bbar X. We use next-to-leading order perturbative predictions for the double parton and single parton scattering components of W b bbar and for the pertinent backgrounds. The next-to-leading order contributions are important for a proper description of some of the observables we compute. We find that the double parton process can be identified and measured with significance S/sqrt(B) ~ 10, provided the double parton scattering effective cross section sigma_{eff} ~ 12 mb.Comment: 21 pages, 9 figures; v2: improved presentation and figures, version published in Phys. Rev.

Area-Suction Boundary-Layer Control as Applied to the Trailing-Edge Flaps of a 35 Degree Swept-Wing Airplane

A wind-tunnel investigation was made to determine the effects on the aerodynamic characteristics of a 35 degree swept-wing airplane of applying area-suction boundary-layer control to the trailing-edge flaps. Flight tests of a similar airplane were then conducted to determine the effect of boundary-layer control in the handling qualities and operation of the airplane, particularly during landing. The wind-tunnel and flight tests indicated that area suction applied to the trailing-edge flaps produced significant increases in flap lift increment. Although the flap boundary-layer control reduced the stall speed only slightly, a reduction in minimum comfortable approach speed of about 12 knots was obtained

Quantum theory of optical temporal phase and instantaneous frequency. II. Continuous time limit and state-variable approach to phase-locked loop design

We consider the continuous-time version of our recently proposed quantum theory of optical temporal phase and instantaneous frequency [Tsang, Shapiro, and Lloyd, Phys. Rev. A 78, 053820 (2008)]. Using a state-variable approach to estimation, we design homodyne phase-locked loops that can measure the temporal phase with quantum-limited accuracy. We show that post-processing can further improve the estimation performance, if delay is allowed in the estimation. We also investigate the fundamental uncertainties in the simultaneous estimation of harmonic-oscillator position and momentum via continuous optical phase measurements from the classical estimation theory perspective. In the case of delayed estimation, we find that the inferred uncertainty product can drop below that allowed by the Heisenberg uncertainty relation. Although this result seems counter-intuitive, we argue that it does not violate any basic principle of quantum mechanics.Comment: 11 pages, 6 figures, v2: accepted by PR

Overutilization of magnetic resonance imaging in the diagnosis and treatment of moderate to severe osteoarthritis

Advanced imaging is a major driver of health care expenditures. Magnetic resonance imaging provides advantages over radiography because of its ability to visualize soft tissues within the knee joint. The clinical relevance of these findings in osteoarthritis, however, is not well understood. For example, MRI can detect meniscal tears, but these are frequent findings in patients with osteoarthritis, with no difference in prevalence among those with and without symptoms. In addition to concerns about excessive cost, it is possible that patients may undergo unnecessary procedures due to MRI findings. A randomized placebo-controlled trial showed no benefit of arthroscopy for osteoarthritis. Our goal was to examine how prevalent this practice is at this institution, and to examine the characteristics of physicians who ordered these MRIs. Our hypothesis is that many providers order MRI for evaluation of osteoarthritis before referring to an orthopedic surgeon, and that providers with higher levels of training are less likely to order these unnecessary MRIs