Specific Heat of Disordered 3^{3}He

Porous aerogel is a source of elastic scattering in superfluid 3He and modifies the properties of the superfluid, suppressing the transition temperature and order parameter. The specific heat jumps for the B-phase of superfluid 3He in aerogel have been measured as a function of pressure and interpreted using the homogeneous and inhomogeneous isotropic scattering models. The specific heat jumps for other p-wave states are estimated for comparison.Comment: Manuscript prepared for LT 2

Measuring Which-Path Information with Coupled Electronic Mach-Zehnder Interferometers

We theoretically investigate a generalized "which-path" measurement on an electronic Mach-Zehnder Interferometer (MZI) implemented via Coulomb coupling to a second electronic MZI acting as a detector. The use of contextual values, or generalized eigenvalues, enables the precise construction of which-path operator averages that are valid for any measurement strength from the available drain currents. The form of the contextual values provides direct physical insight about the measurement being performed, providing information about the correlation strength between system and detector, the measurement inefficiency, and the proper background removal. We find that the detector interferometer must display maximal wave-like behavior to optimally measure the particle-like which-path information in the system interferometer, demonstrating wave-particle complementarity between the system and detector. We also find that the degree of quantum erasure that can be achieved by conditioning on a specific detector drain is directly related to the ambiguity of the measurement. Finally, conditioning the which-path averages on a particular system drain using the zero frequency cross-correlations produces conditioned averages that can become anomalously large due to quantum interference; the weak coupling limit of these conditioned averages can produce both weak values and detector-dependent semi-weak values.Comment: 17 pages, 12 figures, published version including appendi

Fermi Surface of Cr1−x_{1-x}Vx_x across the Quantum Critical Point

We have measured de Haas-van Alphen oscillations of Cr$_{1-x}$V$_x$, $0 \le x \le 0.05$, at high fields for samples on both sides of the quantum critical point at $x_c=0.035$. For all samples we observe only those oscillations associated with a single small hole band with magnetic breakdown orbits of the reconstructed Fermi surface evident for $x<x_c$. The absence of oscillations from Fermi surface sheets most responsible for the spin density wave (SDW) in Cr for $x>x_c$ is further evidence for strong fluctuation scattering of these charge carriers well into the paramagnetic regime. We find no significant mass enhancement of the carriers in the single observed band at any $x$. An anomalous field dependence of the dHvA signal for our $x=0.035$ crystal at particular orientations of the magnetic field is identified as due to magnetic breakdown that we speculate results from a field induced SDW transition at high fields.Comment: 8 pages with 7 figure

Pressure Distribution Over the Palm Region During Forward Falls on the Outstretched Hands

Falls on the outstretched hands are the cause of over 90% of wrist fractures, yet little is known about bone loading during this event. We tested how the magnitude and distribution of pressure over the palm region during a forward fall is affected by foam padding (simulating a glove) and arm configuration, and by the faller’s body mass index (BMI) and thickness of soft tissues over the palm region. Thirteen young women with high (n=7) or low (n=6) BMI participated in a “torso release experiment” that simulated falling on both outstretched hands with the arm inclined either at 20° or 40° from the vertical. Trials were acquired with and without a 5 mm thick foam pad secured to the palm. Outcome variables were the magnitude and location of peak pressure (d, θ) with respect to the scaphoid, total impact force, and integrated force applied to three concentric areas, including “danger zone” of 2.5 cm radius centered at the scaphoid. Soft tissue thickness over the palm was measured by ultrasound. The 5 mm foam pad reduced peak pressure, and peak force to the danger zone, by 83% and 13%, respectively. Peak pressure was 77% higher in high BMI when compared with low BMI participants. Soft tissue thickness over the palm correlated positively with distance (d) (R=0.79, p=0.001) and force applied outside the danger zone (R=0.76, p=0.002), but did not correlate with BMI (R=0.43, p=0.14). The location of peak pressure was shunted 4 mm further from the scaphoid at 20° than that of 40° falls (d=25 mm (SD 8), θ= −9° (SD 17) in the 20° falls versus d=21 mm (SD 8), θ= −5° (SD 24) in the 40° falls). Peak force to the entire palm was 11% greater in 20° compared with 40° falls. These results indicate that even a 5 mm thick foam layer protects against wrist injury, by attenuating peak pressure over the palm during forward falls. Increased soft tissue thickness shunts force away from the scaphoid. However, soft tissue thickness is not predicted by BMI, and peak pressures are greater in high individuals than that of low BMI individuals. These results contribute to our understanding of the mechanics and prevention of wrist and hand injuries during falls