39,379 research outputs found
A dc-coupled noninverting one-shot Patent
Transistorized dc-coupled multivibrator with noninverted output signa
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Wannier–Koopmans method calculations for transition metal oxide band gaps
The widely used density functional theory (DFT) has a major drawback of underestimating the band gaps of materials. Wannier–Koopmans method (WKM) was recently developed for band gap calculations with accuracy on a par with more complicated methods. WKM has been tested for main group covalent semiconductors, alkali halides, 2D materials, and organic crystals. Here we apply the WKM to another interesting type of material system: the transition metal (TM) oxides. TM oxides can be classified as either with d0 or d10 closed shell occupancy or partially occupied open shell configuration, and the latter is known to be strongly correlated Mott insulators. We found that, while WKM provides adequate band gaps for the d0 and d10 TM oxides, it fails to provide correct band gaps for the group with partially occupied d states. This issue is also found in other mean-field approaches like the GW calculations. We believe that the problem comes from a strong interaction between the occupied and unoccupied d-state Wannier functions in a partially occupied d-state system. We also found that, for pseudopotential calculations including deep core levels, it is necessary to remove the electron densities of these deep core levels in the Hartree and exchange–correlation energy functional when calculating the WKM correction parameters for the d-state Wannier functions
Estimating factor models for multivariate volatilities : an innovation expansion method
We introduce an innovation expansion method for estimation of factor models for conditional variance (volatility) of a multivariate time series. We estimate the factor loading space and the number of factors by a stepwise optimization algorithm on expanding the "white noise space". Simulation and a real data example are given for illustration
Reactively sputtered RuO2 diffusion barriers
The thermal stability of reactively sputtered RuO2 films is investigated from the point of view of their application as diffusion barriers in silicon contact metallizations with an Al overlayer. Backscattering spectra of Si/RuO2/Al samples and electrical measurements on shallow junction diodes with Si/TiSi2.3/RuO2/Al contacts both show that RuO2 films are effective diffusion barriers between Al and Si for 30-min annealing at temperatures as high as 600°C
Exact isovector pairing in a shell-model framework: Role of proton-neutron correlations in isobaric analog states
We utilize a nuclear shell model Hamiltonian with only two adjustable
parameters to generate, for the first time, exact solutions for pairing
correlations for light to medium-mass nuclei, including the challenging
proton-neutron pairs, while also identifying the primary physics involved. In
addition to single-particle energy and Coulomb potential terms, the shell model
Hamiltonian consists of an isovector pairing interaction and an average
proton-neutron isoscalar interaction, where the term describes the
average interaction between non-paired protons and neutrons. This Hamiltonian
is exactly solvable, where, utilizing 3 to 7 single-particle energy levels, we
reproduce experimental data for 0 state energies for isotopes with mass
through exceptionally well including isotopes from He to Ge.
Additionally, we isolate effects due to like-particle and proton-neutron
pairing, provide estimates for the total and proton-neutron pairing gaps, and
reproduce (neutron) = (proton) irregularity. These results provide a
further understanding for the key role of proton-neutron pairing correlations
in nuclei, which is especially important for waiting-point nuclei on the
rp-path of nucleosynthesis.Comment: 10 pages, 4 figure
Microscopic origin of the next generation fractional quantum Hall effect
Most of the fractions observed to date belong to the sequences and , and integers, understood as the familiar
{\em integral} quantum Hall effect of composite fermions. These sequences fail
to accommodate, however, many fractions such as and 5/13, discovered
recently in ultra-high mobility samples at very low temperatures. We show that
these "next generation" fractional quantum Hall states are accurately described
as the {\em fractional} quantum Hall effect of composite fermions
Donor species complement after liver xenotransplantation: The mechanism of protection from hyperacute rejection
Hamster hearts transplanted into stable rat recipients of hamster livers (OLT rats) were hyperacutely rejected after transfer with unaltered rat antihamster hyperimmune serum (HS). This was followed by immediate liver xenograft rejection in 4 of 5 rats. In contrast, simple heat inactivation of the rat HS resulted in prolonged survival of hamster hearts to 25 days without deterioration effect in the liver xenografts. This effect was species-specific because third-party mouse heart grafts in OLT rats were hyperacutely rejected in minutes if either active or heat inactivated antimouse HS was given. In cytotoxicity experiments, the complement in OLT serum produced weak lysis of hamster lymphocytes, while efficiently doing so with mouse cell targets. Because normal hamster serum caused no lysis at all of hamster target cells, the residual low-grade lysis of OLT serum was possibly being mediated by extrahepatic sources of rat C. In conclusion, the homology of C and target cells represents a mechanism of protection that the liver confers to other organs, and that is most easily seen in xenografts but may be allospecifically operational with allografts as well within the limits of MHC restriction. © 1994 by Williams and Wilkins
New Anisotropic Behavior of Quantum Hall Resistance in (110) GaAs Heterostructures at mK Temperatures and Fractional Filling Factors
Transport experiments in high mobility (110) GaAs heterostructures have been
performed at very low temperatures 8 mK. At higher Landau-Levels we observe a
transport anisotropy that bears some similarity with what is already seen at
half-odd-integer filling on (001) oriented substrates. In addition we report
the first observation of transport anisotropies within the lowest Landau-Level.
This remarkable new anisotropy is independent of the current direction and
depends on the polarity of the magnetic field.Comment: 3 Pages, 4 figures, Latex, uses elsart.cls and physart.cls, to be
published in Physica E Added reference, made contact configuration more clea
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