308 research outputs found
Time-Resolved Detection of Individual Electrons in a Quantum Dot
We present measurements on a quantum dot and a nearby, capacitively coupled,
quantum point contact used as a charge detector. With the dot being weakly
coupled to only a single reservoir, the transfer of individual electrons onto
and off the dot can be observed in real time in the current signal from the
quantum point contact. From these time-dependent traces, the quantum mechanical
coupling between dot and reservoir can be extracted quantitatively. A similar
analysis allows the determination of the occupation probability of the dot
states.Comment: 3 pages, 3 figure
Finite bias charge detection in a quantum dot
We present finite bias measurements on a quantum dot coupled capacitively to
a quantum point contact used as a charge detector. The transconductance signal
measured in the quantum point contact at finite dot bias shows structure which
allows us to determine the time-averaged charge on the dot in the non-blockaded
regime and to estimate the coupling of the dot to the leads.Comment: 6 pages, 4 figure
Dynamic water routing using a predictor-corrector method with sediment routing
Submitted to Bureau of Reclamation, U.S. Dept. of the Interior.September 1982.Bibliography: pages 61-63.Project no. B-228-COLO
Cotunneling-mediated transport through excited states in the Coulomb blockade regime
We present finite bias transport measurements on a few-electron quantum dot.
In the Coulomb blockade regime, strong signatures of inelastic cotunneling
occur which can directly be assigned to excited states observed in the
non-blockaded regime. In addition, we observe structures related to sequential
tunneling through the dot, occuring after it has been excited by an inelastic
cotunneling process. We explain our findings using transport calculations
within the real-time Green's function approach, including diagrams up to fourth
order in the tunneling matrix elements.Comment: 4 pages, 3 figure
MacDowell-Mansouri gravity and Cartan geometry
The geometric content of the MacDowell-Mansouri formulation of general
relativity is best understood in terms of Cartan geometry. In particular,
Cartan geometry gives clear geometric meaning to the MacDowell-Mansouri trick
of combining the Levi-Civita connection and coframe field, or soldering form,
into a single physical field. The Cartan perspective allows us to view physical
spacetime as tangentially approximated by an arbitrary homogeneous "model
spacetime", including not only the flat Minkowski model, as is implicitly used
in standard general relativity, but also de Sitter, anti de Sitter, or other
models. A "Cartan connection" gives a prescription for parallel transport from
one "tangent model spacetime" to another, along any path, giving a natural
interpretation of the MacDowell-Mansouri connection as "rolling" the model
spacetime along physical spacetime. I explain Cartan geometry, and "Cartan
gauge theory", in which the gauge field is replaced by a Cartan connection. In
particular, I discuss MacDowell-Mansouri gravity, as well as its more recent
reformulation in terms of BF theory, in the context of Cartan geometry.Comment: 34 pages, 5 figures. v2: many clarifications, typos correcte
Examining the referral of patients with elevated blood pressure to health resources in an under-resourced community in South Africa
BackgroundLow-and-middle income countries face a disproportionate burden of non-communicable diseases (NCDs) that threaten to overwhelm under-resourced health systems. Community health workers (CHWs) can promote NCD prevention, reach patients, and connect them to local community health resources; however, little has been done to examine how referrals to these resources are utilized by community members. The purpose of this study is to examine the use of referrals to community-based health resources and investigate the factors influencing patient utilization of referrals connecting them to appropriate health resources for elevated blood pressure (BP).MethodsCHWs conducted home visits, which included BP screening and brief counseling, with community members in Soweto, South Africa. Participants with elevated (systolic BP: 121–139/ diastolic BP: 81–89 mmHg) or high (≥ 140/90 mmHg) BP were referred to either a local, community-based physical activity (PA) program managed by a non-governmental organization or local health clinics. The number of participants that received and utilized their referrals was tracked. Follow-up interviews were conducted with individuals given a referral who: (1) went to the PA program, (2) did not go to the PA program, (3) went to a clinic, and (4) did not go to a clinic. Interviews were transcribed and analyzed to identify common themes and differences between groups regarding their decisions to utilize the referrals.ResultsCHWs visited 1056 homes, with 1001 community members consenting to the screening; 29.2% (n = 292) of adults were classified as having optimal BP (≤120/80 mmHg), 35.8% (n = 359) had elevated BP, and 35.0% (n = 350) had high BP. One hundred and seventy-three participants accepted a referral to the PA program with 46 (26.6%) enrolling. Five themes emerged from the interviews: (1) prior knowledge and thoughts on BP, (2) psychosocial factors associated with BP control, (3) perception about receiving the referral, (4) contextual factors influencing referral utilization, and (5) perceived benefits of utilizing the referral.ConclusionCHWs can successfully increase community members’ access to health resources by providing appropriate referrals. However, greater attention needs to address community members’ barriers and hesitancy to utilize health resources
Effect of Ta 2 O 5 , Nb 2 O 5 , and HfO 2 Alloying on the Transformability of Y 2 O 3 -Stabilized Tetragonal ZrO 2
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65528/1/j.1151-2916.1990.tb05100.x.pd
Fibrous Monolithic Ceramics: III, Mechanical Properties and Oxidation Behavior of the Silicon Carbide/Boron Nitride System
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66176/1/j.1151-2916.1994.tb05399.x.pd
Free energy and molecular dynamics calculations for the cubic-tetragonal phase transition in zirconia
The high-temperature cubic-tetragonal phase transition of pure stoichiometric
zirconia is studied by molecular dynamics (MD) simulations and within the
framework of the Landau theory of phase transformations. The interatomic forces
are calculated using an empirical, self-consistent, orthogonal tight-binding
(SC-TB) model, which includes atomic polarizabilities up to the quadrupolar
level. A first set of standard MD calculations shows that, on increasing
temperature, one particular vibrational frequency softens. The temperature
evolution of the free energy surfaces around the phase transition is then
studied with a second set of calculations. These combine the thermodynamic
integration technique with constrained MD simulations. The results seem to
support the thesis of a second-order phase transition but with unusual, very
anharmonic behaviour above the transition temperature
Measurement of Longitudinal Spin Transfer to Lambda Hyperons in Deep-Inelastic Lepton Scattering
Spin transfer in deep-inelastic Lambda electroproduction has been studied
with the HERMES detector using the 27.6 GeV polarized positron beam in the HERA
storage ring. For an average fractional energy transfer = 0.45, the
longitudinal spin transfer from the virtual photon to the Lambda has been
extracted. The spin transfer along the Lambda momentum direction is found to be
0.11 +/- 0.17 (stat) +/- 0.03 (sys); similar values are found for other
possible choices for the longitudinal spin direction of the Lambda. This result
is the most precise value obtained to date from deep-inelastic scattering with
charged lepton beams, and is sensitive to polarized up quark fragmentation to
hyperon states. The experimental result is found to be in general agreement
with various models of the Lambda spin content, and is consistent with the
assumption of helicity conservation in the fragmentation process.Comment: 8 pages, 3 figures; new version has an expanded discussion and small
format change
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