40,469 research outputs found
150°C amorphous silicon thin-film transistor technology for polyimide substrates
We have developed a 150°C technology for amorphous silicon thin-film transistors (a-Si:H TFTs) on polyimide substrates deposited by plasma enhanced chemical vapor deposition. The silicon nitride gate dielectric and the a-Si:H channel material were tailored to provide the least leakage current and midgap defect density, respectively. In addition, we conducted experiments on the TFT structure and fabrication with the aim of obtaining high electron mobility. TFTs with back-channel etch and channel-passivated structures were fabricated on glass or 51 μm thick polyimide foil. The a-Si:H TFTs have an on/off current ratio of ∼10 7 and an electron mobility of ∼0.7 cm 2/V s
The evidence of quasi-free positronium state in GiPS-AMOC spectra of glycerol
We present the results of processing of Age-Momentum Correlation (AMOC)
spectra that were measured for glycerol by the Gamma-induced positron
spectroscopy (GiPS) facility. Our research has shown that the shape of
experimental s(t) curve cannot be explained without introduction of the
intermediate state of positronium (Ps), called quasi-free Ps. This state yields
the wide Doppler line near zero lifetimes. We discuss the possible properties
of this intermediate Ps state from the viewpoint of developed model. The amount
of annihilation events produced by quasi-free Ps is estimated to be less than
5% of total annihilations. In the proposed model, quasi-free Ps serves as a
precursor for trapped Ps of para- and ortho-states
The Exchange Gate in Solid State Spin Quantum Computation: The Applicability of the Heisenberg Model
Solid state quantum computing proposals rely on adiabatic operations of the
exchange gate among localized spins in nanostructures. We study corrections to
the Heisenberg interaction between lateral semiconductor quantum dots in an
external magnetic field. Using exact diagonalization we obtain the regime of
validity of the adiabatic approximation. We also find qualitative corrections
to the Heisenberg model at high magnetic fields and in looped arrays of spins.
Looped geometries of localized spins generate flux dependent, multi-spin terms
which go beyond the basic Heisenberg model.Comment: 13 pages, 8 figure
Symmetric Rotating Wave Approximation for the Generalized Single-Mode Spin-Boson System
The single-mode spin-boson model exhibits behavior not included in the
rotating wave approximation (RWA) in the ultra and deep-strong coupling
regimes, where counter-rotating contributions become important. We introduce a
symmetric rotating wave approximation that treats rotating and counter-rotating
terms equally, preserves the invariances of the Hamiltonian with respect to its
parameters, and reproduces several qualitative features of the spin-boson
spectrum not present in the original rotating wave approximation both
off-resonance and at deep strong coupling. The symmetric rotating wave
approximation allows for the treatment of certain ultra and deep-strong
coupling regimes with similar accuracy and mathematical simplicity as does the
RWA in the weak coupling regime. Additionally, we symmetrize the generalized
form of the rotating wave approximation to obtain the same qualitative
correspondence with the addition of improved quantitative agreement with the
exact numerical results. The method is readily extended to higher accuracy if
needed. Finally, we introduce the two-photon parity operator for the two-photon
Rabi Hamiltonian and obtain its generalized symmetric rotating wave
approximation. The existence of this operator reveals a parity symmetry similar
to that in the Rabi Hamiltonian as well as another symmetry that is unique to
the two-photon case, providing insight into the mathematical structure of the
two-photon spectrum, significantly simplifying the numerics, and revealing some
interesting dynamical properties.Comment: 11 pages, 5 figure
The Evolution of Shocks in Blazar Jets
We consider the shock structures that can arise in blazar jets as a
consequence of variations in the jet flow velocity. There are two possible
cases: (1) A double shock system consisting of both a forward and reverse shock
(2) A single shock (either forward or reverse) together with a rarefaction
wave. These possibilities depend upon the relative velocity of the two
different sections of jet. Using previously calculated spherical models for
estimates of the magnetic field and electron number density of the emission
region in the TeV blazar Markarian 501, we show that this region is in the form
of a thin disk, in the plasma rest frame. It is possible to reconcile spectral
and pair opacity constraints for MKN 501 for Doppler factors in the range of
10--20. This is easiest if the corrections for TeV absorption by the infrared
background are not as large as implied by recent models.Comment: 19 pages, 8 figures, accepted for publication in PASA, 19, No.1, AGN
Variability across the Electromagnetic Spectru
Primary Chondroblastic Osteosarcoma of the Lung
Purpose. Primary extra-osseous osteosarcomas are uncommon
lesions, and those originating within the lung are especially rare, with few case reports
existing in the literature
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