2,637 research outputs found
Efficacy of crustal superfluid neutrons in pulsar glitch models
In order to assess the ability of purely crust-driven glitch models to match
the observed glitch activity in the Vela pulsar, we conduct a systematic
analysis of the dependence of the fractional moment of inertia of the inner
crustal neutrons on the stiffness of the nuclear symmetry energy at saturation
density . We take into account both crustal entrainment and the fact that
only a fraction of the core neutrons may couple to the crust on the
glitch-rise timescale. We use a set of consistently-generated crust and core
compositions and equations-of-state which are fit to results of low-density
pure neutron matter calculations. When entrainment is included at the level
suggested by recent microscopic calculations and the core is fully coupled to
the crust, the model is only able to account for the Vela glitch activity for a
1.4 star if the equation of state is particularly stiff MeV.
However, an uncertainty of about 10\% in the crust-core transition density and
pressure allows for the Vela glitch activity to be marginally accounted for in
the range MeV consistent with a range of experimental results.
Alternatively, only a small amount of core neutrons need be involved. If less
than 50\% of the core neutrons are coupled to the crust during the glitch, we
can also account for the Vela glitch activity using crustal neutrons alone for
EOSs consistent with the inferred range of . We also explore the possibility
of Vela being a high-mass neutron star, and of crustal entrainment being
reduced or enhanced relative to its currently predicted values.Comment: 10 pages, 6 figure
ASSESSING THE ECONOMICS OF FOOD SAFETY ACTIVITIES: STUDIES OF BEEF SLAUGHTER AND MEAT PROCESSING
Food Consumption/Nutrition/Food Safety,
On-Orbit Measurement of the Superconductive Transition Temperatures of YBa2Cu3O(7-x) Thick Films
Thick film superconductors were integrated into hybrid circuits and tested in the Materials In Devices As Superconductors (MIDAS) spaceflight experiment which operated autonomously aboard the MIR space station for 90 days. MIDAS was designed to cool the circuits from 300 to 75K, maintain the temperature at 75K for 28 days, and warm the circuits back to 300K. This cycle was performed a total of three times, during which the superconductive transition temperature was measured during each cool-down and warm-up portion of the experiment. All of the thick films used in this experiment exhibited superconductive transition temperatures of approximately 87K, and no significant differences in the resistance versus temperature properties of the materials were observed among the data collected during pre-flight, flight, and post-flight operations
Preparation and Properties of High-T(sub c) Bi-Pb-Sr-Ca-Cu-O Thick Film Superconductors on YSZ Substrates
An evaluation of four firing profiles was performed to determine the optimum processing conditions for producing high-T(sub c) Bi-Pb-Sr-Ca-Cu-O thick films on yttria-stabilized zirconia substrates. Using these four profiles, the effects of sintering temperatures of 830-850 C and soak times of 0.5 to 12 hours were examined. In this study, T-c, zero values of 100 K were obtained using a firing profile in which the films were sintered for 1.5 to 2 hours at 840 to 845 C and then quenched to room temperature. X-ray diffraction analyses of these specimens confirmed the presence of the high-T(sub c) phase. Films which were similarly fired and furnace cooled from the peak processing temperature exhibited a two-step superconductive transition to zero resistance, with T-c,zero values ranging from 85 to 92 K. The other firing profiles evaluated in this investigation yielded specimens which either exhibited critical transition temperatures below 90 K or did not exhibit a superconductive transition above 77 K
- …