258 research outputs found
Applications of Tethers in Space, Volume 2
Topics discussed include tethered satellites, tether deployment, satellite systems, science applications, electrodynamic interactions, transportation applications, artificial gravity, constellations, and technology and testing
Applications of Tethers in Space, Volume 1
The tethered satellite system is described including tether fundamentals. Applications of very long tethers in space to a broad spectrum of future space missions are explored. Topics covered include: science, transportation, constellations, artificial gravity, technology and test, and electrodynamic interactions. Recommendations to NASA are included
Dynamical Coulomb blockade of multiple Andreev reflections
We analyze the dynamical Coulomb blockade of multiple Andreev reflections
(MAR) in a superconducting quantum point contact coupled to a macroscopic
impedance. We find that at very low transmission the blockade scales as
with , where is the bias voltage and is the
superconducting gap, as it would correspond to the occurrence of "shots" of
charge . For higher transmission the blockade is reduced both due to Pauli
principle and to elastic renormalization of the MAR probability, and for
certain voltage regions it may even become an "antiblockade", i.e. the current
is enhanced due to the coupling with the electromagnetic environment.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Let
Experimental Test of the Dynamical Coulomb Blockade Theory for Short Coherent Conductors
We observed the recently predicted quantum suppression of dynamical Coulomb
blockade on short coherent conductors by measuring the conductance of a quantum
point contact embedded in a tunable on-chip circuit. Taking advantage of the
circuit modularity we measured most parameters used by the theory. This allowed
us to perform a reliable and quantitative experimental test of the theory.
Dynamical Coulomb blockade corrections, probed up to the second conductance
plateau of the quantum point contact, are found to be accurately normalized by
the same Fano factor as quantum shot noise, in excellent agreement with the
theoretical predictions.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
Direct link between Coulomb blockade and shot noise in a quantum coherent structure
We analyze the current-voltage characteristic of a quantum conduction channel
coupled to an electromagnetic environment of arbitrary frequency-dependent
impedance. In the weak blockade regime the correction to the ohmic behavior is
directly related to the channel current fluctuations vanishing at perfect
transmission in the same way as shot noise. This relation can be generalized to
describe the environmental Coulomb blockade in a generic mesoscopic conductor
coupled to an external impedance, as the response of the latter to the current
fluctuations in the former.Comment: 12 pages, 2 figures, submitted to Phys. Rev. Let
Using analytic morphomics to describe body composition associated with post‐kidney transplantation diabetes mellitus
BackgroundBetter risk assessment tools are needed to predict post‐transplantation diabetes mellitus (PTDM). Using analytic morphomic measurements from computed tomography (CT) scans, we aimed to identify specific measures of body composition associated with PTDM.MethodsWe retrospectively reviewed 99 non‐diabetic kidney transplant recipients who received pre‐transplant CT scans at a single institution between 1/2005 and 5/2014. Analytic morphomic techniques were used to measure abdominal adiposity, abdominal size, and psoas muscle area and density, standardized by gender. We measured the associations of these morphomic factors with PTDM.ResultsOne‐year incidence of PTDM was 18%. The morphomic factors significantly associated with PTDM included visceral fat area (OR=1.84 per standard deviation increase, P=.020), body depth (OR=1.79, P=.035), and total body area (OR=1.67, P=.049). Clinical factors significantly associated with PTDM included African American race (OR=3.01, P=.044), hypertension (OR=2.97, P=.041), and dialysis vintage (OR=1.24 per year on dialysis, P=.048). Body mass index was not associated with PTDM (OR=1.05, P=.188). On multivariate modeling, visceral fat area was an independent predictor of PTDM (OR=1.91, P=.035).ConclusionsAnalytic morphomics can identify pre‐transplant measurements of body composition that are predictive of PTDM in kidney transplant recipients. Pre‐transplant imaging contains a wealth of underutilized data that may inform PTDM prevention strategies.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138207/1/ctr13040.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138207/2/ctr13040_am.pd
Subharmonic Shapiro steps and assisted tunneling in superconducting point contacts
We analyze the current in a superconducting point contact of arbitrary
transmission in the presence of a microwave radiation. The interplay between
the ac Josephson current and the microwave signal gives rise to Shapiro steps
at voltages V = (m/n) \hbar \omega_r/2e, where n,m are integer numbers and
\omega_r is the radiation frequency. The subharmonic steps (n different from 1)
are a consequence of the ocurrence of multiple Andreev reflections (MAR) and
provide an unambiguous signature of the peculiar ac Josephson effect at high
transmission. Moreover, the dc current exhibits a rich subgap structure due to
photon-assisted MARs.Comment: Revtex, 4 pages, 4 figure
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