1,940 research outputs found
Power Doppler sonography in tenosynovitis: significance of the peritendinous hypoechoic rim.
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135464/1/jum1998172103.pd
Prototype finline-coupled TES bolometers for CLOVER
CLOVER is an experiment which aims to detect the signature of gravitational
waves from inflation by measuring the B-mode polarization of the cosmic
microwave background. CLOVER consists of three telescopes operating at 97, 150,
and 220 GHz. The 97-GHz telescope has 160 feedhorns in its focal plane while
the 150 and 220-GHz telescopes have 256 horns each. The horns are arranged in a
hexagonal array and feed a polarimeter which uses finline-coupled TES
bolometers as detectors. To detect the two polarizations the 97-GHz telescope
has 320 detectors while the 150 and 220-GHz telescopes have 512 detectors each.
To achieve the target NEPs (1.5, 2.5, and 4.5x10^-17 W/rtHz) the detectors are
cooled to 100 mK for the 97 and 150-GHz polarimeters and 230 mK for the 220-GHz
polarimeter. Each detector is fabricated as a single chip to ensure a 100%
operational focal plane. The detectors are contained in linear modules made of
copper which form split-block waveguides. The detector modules contain 16 or 20
detectors each for compatibility with the hexagonal arrays of horns in the
telescopes' focal planes. Each detector module contains a time-division SQUID
multiplexer to read out the detectors. Further amplification of the multiplexed
signals is provided by SQUID series arrays. The first prototype detectors for
CLOVER operate with a bath temperature of 230 mK and are used to validate the
detector design as well as the polarimeter technology. We describe the design
of the CLOVER detectors, detector blocks, and readout, and present preliminary
measurements of the prototype detectors performance.Comment: 4 pages, 6 figures; to appear in the Proceedings of the 17th
International Symposium on Space Terahertz Technology, held 10-12 May 2006 in
Pari
Coherent population transfer in a chain of tunnel coupled quantum dots
We consider the dynamics of a single electron in a chain of tunnel coupled
quantum dots, exploring the formal analogies of this system with some of the
laser-driven multilevel atomic or molecular systems studied by Bruce W. Shore
and collaborators over the last 30 years. In particular, we describe two
regimes for achieving complete coherent transfer of population in such a
multistate system. In the first regime, by carefully arranging the coupling
strengths, the flow of population between the states of the system can be made
periodic in time. In the second regime, by employing a "counterintuitive"
sequence of couplings, the coherent population trapping eigenstate of the
system can be rotated from the initial to the final desired state, which is an
equivalent of the STIRAP technique for atoms or molecules. Our results may be
useful in future quantum computation schemes
Coherent Resonant Tunneling Through an Artificial Molecule
Coherent resonant tunneling through an artificial molecule of quantum dots in
an inhomogeneous magnetic field is investigated using an extended Hubbard
model. Both the multiterminal conductance of an array of quantum dots and the
persistent current of a quantum dot molecule embedded in an Aharanov-Bohm ring
are calculated. The conductance and persistent current are calculated
analytically for the case of a double quantum dot and numerically for larger
arrays using a multi-terminal Breit-Wigner type formula, which allows for the
explicit inclusion of inelastic processes. Cotunneling corrections to the
persistent current are also investigated, and it is shown that the sign of the
persistent current on resonance may be used to determine the spin quantum
numbers of the ground state and low-lying excited states of an artificial
molecule. An inhomogeneous magnetic field is found to strongly suppress
transport due to pinning of the spin-density-wave ground state of the system,
and giant magnetoresistance is predicted to result from the ferromagnetic
transition induced by a uniform external magnetic field.Comment: 23 pages, 12 figure
Charge Transfer Induced Persistent Current and Capacitance Oscillations
The transfer of charge between different regions of a phase-coherent
mesoscopic sample is investigated. Charge transfer from a side branch quantum
dot into a ring changes the persistent current through a sequence of plateaus
of diamagnetic and paramagnetic states. In contrast, a quantum dot embedded in
a ring exhibits sharp resonances in the persistent current, whose sign is
independent of the number of electrons in the dot if the total number of
electrons in the system is even. It is shown that such a mesoscopic system can
be polarized appreciably not only by the application of an external voltage,
but also via an Aharonov-Bohm flux.Comment: 4 pages, REVTEX 3.0, 2 postscript figure
Hemorrhage from varices in hepaticojejunostomy in the fifth and tenth year after surgery for hepatic hilar bile duct cancer: a case report
We report a case of a 64-year-old female patient who underwent a right lobectomy of the liver (including total resection of the caudate lobe), dissection of the group 2 lymph nodes, left hepaticojejunostomy (Roux-en-Y fashion), and reconstruction of the portal vein (end-to-end anastomosis between the main portal vein and the left portal branch) for treatment of hepatic hilar bile duct cancer in 1996. In 2001, the anastomotic site of the hepaticojejunostomy was dissected and re-anastomosed due to gastrointestinal bleeding caused by variceal rupture in the jejunal loop. In 2006, splenectomy was performed for recurrence of gastrointestinal bleeding due to another variceal rupture in the jejunal loop. Portal venography performed perioperatively showed a decrease in portal blood flow into the liver via the jejunal varices and an increase in portal blood flow into the liver via the left gastric vein. She had two jejunal variceal ruptures at five-year intervals after extrahepatic portal obstruction and underwent successful treatments
Correlation and symmetry effects in transport through an artificial molecule
Spectral weights and current-voltage characteristics of an artificial
diatomic molecule are calculated, considering cases where the dots connected in
series are in general different. The spectral weights allow us to understand
the effects of correlations, their connection with selection rules for
transport, and the role of excited states in the experimental conductance
spectra of these coupled double dot systems (DDS). An extended Hubbard
Hamiltonian with varying interdot tunneling strength is used as a model,
incorporating quantum confinement in the DDS, interdot tunneling as well as
intra- and interdot Coulomb interactions. We find that interdot tunneling
values determine to a great extent the resulting eigenstates and corresponding
spectral weights. Details of the state correlations strongly suppress most of
the possible conduction channels, giving rise to effective selection rules for
conductance through the molecule. Most states are found to make insignificant
contributions to the total current for finite biases. We find also that the
symmetry of the structure is reflected in the I-V characteristics, and is in
qualitative agreement with experiment.Comment: 25 figure files - REVTEX - submitted to PR
AC-conductance of a quantum wire with electron-electron interaction
The complex ac-response of a quasi-one dimensional electron system in the
one-band approximation with an interaction potential of finite range is
investigated. It is shown that linear response is exact for this model. The
influence of the screening of the electric field is discussed. The complex
absorptive conductance is analyzed in terms of resistive, capacitive and
inductive behaviors.Comment: 13 pages, REVTeX, 7 eps figures, to appear in Phys. Rev.
Assessing the Long Term Impact of Phosphorus Fertilization on Phosphorus Loadings Using AnnAGNPS
High phosphorus (P) loss from agricultural fields has been an environmental concern because of potential water quality problems in streams and lakes. To better understand the process of P loss and evaluate the effects of different phosphorus fertilization rates on phosphorus losses, the USDA Annualized AGricultural Non-Point Source (AnnAGNPS) pollutant loading model was applied to the Ohio Upper Auglaize watershed, located in the southern portion of the Maumee River Basin. In this study, the AnnAGNPS model was calibrated using USGS monitored data; and then the effects of different phosphorus fertilization rates on phosphorus loadings were assessed. It was found that P loadings increase as fertilization rate increases, and long term higher P application would lead to much higher P loadings to the watershed outlet. The P loadings to the watershed outlet have a dramatic change after some time with higher P application rate. This dramatic change of P loading to the watershed outlet indicates that a “critical point” may exist in the soil at which soil P loss to water changes dramatically. Simulations with different initial soil P contents showed that the higher the initial soil P content is, the less time it takes to reach the “critical point” where P loadings to the watershed outlet increases dramatically. More research needs to be done to understand the processes involved in the transfer of P between the various stable, active and labile states in the soil to ensure that the model simulations are accurate. This finding may be useful in setting up future P application and management guidelines
Electron transport through double quantum dots
Electron transport experiments on two lateral quantum dots coupled in series
are reviewed. An introduction to the charge stability diagram is given in terms
of the electrochemical potentials of both dots. Resonant tunneling experiments
show that the double dot geometry allows for an accurate determination of the
intrinsic lifetime of discrete energy states in quantum dots. The evolution of
discrete energy levels in magnetic field is studied. The resolution allows to
resolve avoided crossings in the spectrum of a quantum dot. With microwave
spectroscopy it is possible to probe the transition from ionic bonding (for
weak inter-dot tunnel coupling) to covalent bonding (for strong inter-dot
tunnel coupling) in a double dot artificial molecule. This review on the
present experimental status of double quantum dot studies is motivated by their
relevance for realizing solid state quantum bits.Comment: 32 pages, 31 figure
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